Link Budgeting - Motorola White Paper

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LINK BUDGETS AND ASSOCIATED PLANNING CONSIDERATIONS

RF Planning

WP2003-010-2 September 15, 2004

Motorola General Business Information iDEN Technical Publications White Paper

Table of Contents Introduction ................................................................................................................................. 6

EBTS Transmit Combing ............................................................................................................ 7

GEN4 Duplex/Hybrid .............................................................................................................. 7

Cavity Combining.................................................................................................................... 8

Auto-Tune Combiners.......................................................................................................... 9

Peak Power Considerations ..................................................................................................... 9

EBTS Receiver Configuration................................................................................................... 11

Receiver Reference Point....................................................................................................... 11

System Gain ....................................................................................................................... 12

Receive Sensitivity ................................................................................................................ 13

Faded Receiver Sensitivity................................................................................................. 13

Site Noise and Reuse Interference ..................................................................................... 15

Tower Top Amplifiers ........................................................................................................... 16

TTA Sensitivity and Gain .................................................................................................. 16

Hybrid/Duplex/Tower Top Amplifier ................................................................................ 17

Receive Antenna Diversity Gain ........................................................................................... 18

Enhanced Receiver............................................................................................................. 19

Subsciber Unit Considerations .................................................................................................. 20

General Specifications ........................................................................................................... 20

Antenna Performance ............................................................................................................ 21

Car Kits .............................................................................................................................. 22

Vehicle Losses ................................................................................................................... 22

Building Losses.................................................................................................................. 23

Reference Link Budgets (Noise Limited Case) ......................................................................... 24

Single Base Radio: Hybrid Combining ................................................................................. 24

Single Base Radio: Cavity Combining .................................................................................. 26

Quad Base Radio ................................................................................................................... 26

Estimates of Cell Radius........................................................................................................ 28

Power Control ........................................................................................................................ 29

September 15, 2004 Page 2 of 59 WP2003-010-2

Motorola General Business Information iDEN Technical Publications White Paper Power Control Constant ..................................................................................................... 30

Subscriber Unit Transmit Power ........................................................................................ 32

Cell Pti Max ....................................................................................................................... 33

900 MHz Considerations ....................................................................................................... 33

RFDS Requirements........................................................................................................... 33

Frequency Planning Concepts ................................................................................................... 34

Reuse Factor (K).................................................................................................................... 35

Reuse Patterns........................................................................................................................ 35

Omni-Directional ............................................................................................................... 36

Directional (Sectored) ........................................................................................................ 37

Cell Placement ................................................................................................................... 39

Color Code and Color Code Extension.................................................................................. 40

PCCH Offset .......................................................................................................................... 40

Quad BR Considerations ....................................................................................................... 41

Adjacent Channel Interference........................................................................................... 42

Sample Channel Assignments with Quad BRs .................................................................. 43

Cellular Interference .............................................................................................................. 44

Capacity Planning...................................................................................................................... 45

Call Model ............................................................................................................................. 45

Traffic Distribution ................................................................................................................ 46

Traffic Mix ......................................................................................................................... 47

Capacity Rules ....................................................................................................................... 48

Primary / Secondary Control Channels.............................................................................. 48

Dedicated Control Channels............................................................................................... 48

Packet Channel................................................................................................................... 49

RF Congestion Relief ......................................................................................................... 49

Split 3:1 Channels.................................................................................................................. 50

Impact of the FNE �Split 3:1 Preferred� Algorithm on Channel Assignments.................. 51

Determining Cell Resources for a Given Traffic Load.......................................................... 53

Calculating Erlangs from a Call Model.............................................................................. 53

Calculating Required Traffic Channels from Erlangs........................................................ 54



List of Tables Table 1: GEN4 RFDS Base Radio Capacity..............................................................................................7 Table 2: Typical Duplex/Hybrid Combiner Insertion Losses ....................................................................8 Table 3: Typical Cavity Combiner Insertion Losses (dB per channel) ......................................................8 Table 4: Receive Antenna Diversity ........................................................................................................18 Table 5: Measured SQE Improvements ...................................................................................................19 Table 6: Subscriber Transmit Power........................................................................................................20 Table 7: Faded Receive Sensitivity Specification @ 20 dB C/N.............................................................20 Table 8: Typical Retractable Antenna Performance ................................................................................21 Table 9: Typical Fixed Antenna Performance .........................................................................................21 Table 10: Car Kit Antenna Performance..................................................................................................22 Table 11: Typical In-Vehicle Losses .......................................................................................................22 Table 12: Building Loss...........................................................................................................................23 Table 13: Downlink RSSI Thresholds @ 20 dB C/N ..............................................................................24 Table 14: 3-Way Hybrid / Duplexed Combiner Link Budget..................................................................25 Table 15: 3-Way Hybrid/Duplexed w/Tower Top Amp..........................................................................25 Table 16: 10 Channel Cavity w/Tower Top Amp....................................................................................26 Table 17: Duplexed Quad BR: 4 Carriers Equipped with no Combining................................................27 Table 18: 800/900 MHz Quad BR Transmit Power.................................................................................27 Table 19: PCC and Desired_Pri for Various Interference Levels ............................................................31 Table 20: 12-cell Channel Assignment ....................................................................................................37 Table 21: 7 Site-3 Sector Channel Assignments (Sector 1) .....................................................................38 Table 22: 7 Site-3 Sector Channel Assignments (Sector 2) .....................................................................38 Table 23: 7 Site-3 Sector Channel Assignments (Sector 3) .....................................................................38 Table 24: Adjacent Channel Statistics .....................................................................................................42 Table 25: 9-Cell / 3-Sector Reuse Pattern w/ Quads (Sector 1)...............................................................43 Table 26: 9-Cell / 3-Sector Reuse Pattern w/ Quads (Sector 2)...............................................................43 Table 27: 9-Cell / 3-Sector Reuse Pattern w/ Quads (Sector 3)...............................................................43 Table 28: Cellular and iDEN Operating Frequencies ..............................................................................44 Table 29: Call Model Definitions ............................................................................................................46 Table 30: EBTS Configuration Mix.........................................................................................................46 Table 31: Typical Subscriber Service Percentages ..................................................................................46 Table 32: EBTS Carrier Capacity Rules ..................................................................................................48 Table 33: DCCH Allocation.....................................................................................................................49 Table 34: RF Congestion Relief Capacity Gains .....................................................................................49 Table 35: Percentage of Calls Assigned Full 3:1 .....................................................................................53 Table 36: Example Call Model ................................................................................................................54 Table 37: Standard Grade of Service Assumptions .................................................................................54



List of Figures Figure 1: Cavity/TTA Two Rack Expanded EBTS -4 Ant - 10 BR EBTS................................................9 Figure 2: Rx Reference Point...................................................................................................................11 Figure 3: Noise Limited Faded Receiver Sensitivity ...............................................................................13 Figure 4: Interference Limited Faded Receiver Sensitivity .....................................................................15 Figure 5: Duplexed Tower Top Amplifier System Block Diagram.........................................................17 Figure 6: Estimated Cell Radius using the HATA Propagation Model ...................................................28 Figure 7: SU Power Control Flow Chart..................................................................................................29 Figure 8: RxTxGain Example (without TTA)..........................................................................................31 Figure 9: RxTxGain Example (with TTA)...............................................................................................32 Figure 10: 800/900 MHz RFDS to Diplexer Integrated Block Diagram .................................................34 Figure 11: Reuse Distance (D/R Ratio)....................................................................................................35 Figure 12: Frequency Reuse Pattern Performance...................................................................................36 Figure 13: 12 Cell Omni Reuse Pattern (K=12).......................................................................................36 Figure 14: 7 Site - 3 Sector Reuse Pattern (K=7).....................................................................................37 Figure 15: Example PCCH Offset............................................................................................................40 Figure 16: PCCH Offset Overlaid on the Color Code Reuse...................................................................41 Figure 17: Quad BR Contiguous Channel Requirement ..........................................................................41 Figure 18: Adjacent Channel Interference ...............................................................................................42 Figure 19: 800 MHz Spectrum Layout ....................................................................................................44 Figure 20: Split 3:1 Channels...................................................................................................................50 Figure 21: Percent of Split 3:1 Calls Assign Full 3:1 Channels...............................................................52 Figure 22: Split 3:1 Erlang Gain with 3:1 Preferred ................................................................................52



Introduction The link budget is a fundamental aspect of RF planning as it defines the required coverage contours, based on equipment specifications and configuration, for a given reliability and quality requirements. Incorrect assumptions and calculations will typically lead to undesirable system performance issues.

One goal of the link budget is to determine RF levels required to provide a balanced path, i.e. the path loss is equal for both uplink and downlink. The maximum allowable path loss will define cell contours, for a given lognormal fade margin equating to desired coverage and cell edge reliability percentages.

NOTE: Topographical and environmental factors, in addition to antenna height and frequency, are significant factors for determining the actual coverage for a given pathloss.

The general recommendation is for a balanced inbound and outbound RF system design. However, there are some cases where the outbound could be set approximately 2 dB higher, to an unbalanced condition, if interference conditions permit. In many cases, uplink diversity gains from the Enhanced Receiver feature and potentially from signal decorrelation gain will tend to offset the outbound imbalance.

This paper provides basic guidelines for standard RFDS configurations, for which reference link budgets have been provided, to highlight key assumptions. Information has been broken out for the EBTS transmit and receive paths as well as for typically subscriber unit performance. Additionally, guidance is provided on frequency reuse and resultant interference issue as well as standard capacity planning methodology.



EBTS Transmit Combining Under normal circumstances, it is desirable to minimize the number of antennas required for a particular EBTS configuration while maintaining the desired transmit power. A single antenna must serve multiple BRs/Carriers, which is achieved through the combining the associated transmit signals. Additionally, both transmit and receive paths may be served by a single antenna through the use of duplexers.

Currently, there are two different transmit combining techniques available for iDEN:

• Hybrid: The standard GEN4 RFDS employs hybrid combining with duplexers, where frequency agility is traded for higher insertion loss than a cavity solution.

• Cavity combining tends to be used either to maximize transmit power or for improved sideband noise filtering to reduce potential interference into other systems. Typically a Tower Top Amplifier (TTA) is deployed to compensate for increased downlink power, offered by the lower insertion loss. However, it is important to remember that a TTA will increase tower loading and degrade the overall receiver interference immunity of the EBTS.

For cavity solutions, the use of duplexers is not standard thus a separate transmit antenna may be required.

GEN4 Duplex/Hybrid The current GEN4 hybrid RFDS system comprises a main (primary) rack and multiple expansion (secondary) racks each allowing a maximum of 6 BRs to be equipped. The following table highlights the maximum BRs supported by a single EBTS controller (ACG):

ACG Platform Omni Sector Sector Site Total iSCII 20 201 24 iSCIII 20 20 36

Table 1: GEN4 RFDS Base Radio Capacity

It should be noted that one can physically equip greater than 24 BRs on a site controlled by an iSCII; however collisions on the single Ethernet loop will cause site instability. It is not recommended to exceed the iSCII recommended Carrier/BR limit.

There are a number of hybrid combining schemes available, as indicated by the information with Table 2; however, by default, a GEN4 RFDS is equipped with a Dual three-way combiner deck. A second stage of combining is offered by a Triple two-way combiner (without isolators) to enable 6 BRs to be combined onto a single antenna port. It is important that only one stage of isolators be used to minimize potential transmit intermodulation (IM) related performance degradation.

1 As of SR9.6, the number of BRs/Carriers supported per sector was increased from 12 to 20.


Motorola General Business Information iDEN Technical Publications White Paper The number of ports on the hybrid combiner determines the Insertion loss. The following table presents the total RFDS combining, cable and duplexer loss for the standard hybrid combining options:

Combining Scheme BRs per Antenna Maximum Insertion Loss (dB) Typical Insertion Loss (dB) 3 Way 1-3 -8.5 -7.5 4 Way 4 -10.45 -9.2 6 Way 5-6 -12.5 -11.1

Table 2: Typical Duplex/Hybrid Combiner Insertion Losses

If a non-duplexed TTA is used on a Hybrid/Duplexed RFDS, an additional one dB of Insertion Loss must be added.

For Quad BR deployments, the recommended combining scheme is a little different from a single BR. It is recommended that the Quad BR be connected directly to the duplexer assembly to maximize the available top of rack power. The Quad is designed such that path balance is achieved, for a four carrier configuration, without combining. If it is required that a Quad by combined with hybrids, the Triple two-Way combiner (without isolators) should be used.

Recommended hybrid combining options are presented in the most current version of iDEN white paper WP2003-018.

Cavity Combining The cavity combiner system typically provides less insertion loss and improved sideband noise filtering than the standard hybrid/duplex RFDS. Tower Top Amplifiers can be used to improve the inbound signal as separate transmit antennas are used in this configuration.

Up to ten channels can be combined using two five-port cavity combiners. The associated insertion losses, shown in Table 3, indicate typical values for various frequency spacing. All channels should be adjusted in the combiner so that all output levels are consistent for the EBTS.

Spacing 2 Ch 3 Ch 4 Ch 5 Ch 6 Ch 7 Ch 8 Ch 9 Ch 10 Ch 250kHz 4.2 4.6 4.6 4.7 5.3 5.3 5.6 5.6 5.8 500kHz 3.5 3.8 3.8 3.9 4.5 4.5 4.8 4.8 5.0 1MHz 3.2 3.4 3.4 3.5 4.1 4.1 4.4 4.4 4.6

Table 3: Typical Cavity Combiner Insertion Losses (dB per channel)


Motorola General Business Information iDEN Technical Publications White Paper The following diagram presents an example cavity combiner configuration:

BR1 - BR5 in 1st RF cabinetBR6 - BR10 in 2nd RF cabinet

2 Ch to 5 Ch Expandable CavityCombiner

10 ChannelPhasingHarness

TripleTTA

Rx2 Rx3Rx1 Rx4 Rx5

Primary RMC

Rx2 Rx3Rx1 Rx4 Rx5

Primary RMC

Rx2 Rx3Rx1 Rx4 Rx5

Primary RMC

Divider/Splitter

Rx6 Rx7 Rx10Rx9Rx8

Divider/Splitter

Rx6 Rx7 Rx10Rx9Rx8

Divider/Splitter

Rx6 Rx7 Rx10Rx9Rx8

Tx2 Tx3 Tx4Tx1 Tx5

Tx6 Tx7 Tx8 Tx9 Tx10 Figure 1: Cavity/TTA Two Rack Expanded EBTS -4 Ant - 10 BR EBTS

NOTE: Please refer to Volume 3 of the EBTS Product Manual for information on cavity combiner RFDS cabinets.

Auto-Tune Combiners

It is recognized that auto-tuned cavity combiners are deployed in many markets. An auto-tuned cavity combiner will typically go into a �park� mode when the BR stops transmitting on the tuned frequency. When transmission resumes, there is a period during which the combiner must retune itself for that frequency. The probable result of this procedure is that slots and data are lost. To avoid this, the operator must disable the Reduced EBTS Power Consumption feature on BRs connected to auto-tune combiners that exhibit this performance characteristic.

Peak Power Considerations In general, the number of BRs/Carriers served by a single antenna is a function of the required ERP over the combining losses as well as the peak power rating of the antenna it self.

The RFDS is designed such that recommended combining schemes will provide sufficient top of rack power for a balanced link budget. As such, the limiting factor will tend to be the peak power rating of the antenna system, which includes cables, connectors, and the antenna itself.

For example; consider an RFDS where three transmitters each with 70 W (48.5 dBm) of output power are summed together in a hybrid/duplexer configuration with a total loss of -8.5 dB.


Motorola General Business Information iDEN Technical Publications White Paper The resultant peak power is determine as follows:

1. Calculate the top of rack power per carrier:

PA Power (48.5 dBm) � RFDS Loss (8.5 dB) = 40 dBm

2. Apply peak to average ratio:

Top of Rack Power (40 dBm) + Peak to Average Ratio (9.7 dB) = 49.7 dBm

3. Calculate total power in Volts:

Per carrier peak power = 49.7 dBm = 93.93 Watts

Volts into a 50 Ohm transmission system = √ (93.93 × 50) = 68.5 Volts

Total peak voltage = 68.5 × 3 = 205.6 Volts

4. Calculate total peak instantaneous power:

(205.6) 2 ÷ 50 = 845.3 Watts

NOTE: The total power in Volts is true ONLY if the transmission line is properly terminated. If the line is accidentally left disconnected or is shorted out anywhere along its length, and the connector happens to be located at a maximum in the resulting standing wave pattern, the peak voltage could double.



EBTS Receiver Configuration The RFDS utilizes a Receive Multi-Coupler (RMC) to distribute each receive branch to all BRs within the sector, the operation of which is discussed within Volume 3 of the EBTS Hardware Manual (68P80801E35).

For the purposes of link budget planning one need only be concerned with the receiver (Rx) reference point.

Receiver Reference Point The EBTS is designed such that all RF measurements, made by the BR, are adjusted to the Rx reference point.

TX Reference Point

RX Reference Point

Arbitrary point in far ¼eld

FNE

Gtx

Grx

TX antenna

RX antenna

RFDS Antenna

Port

Base Radio

RF Distribution

System (RFDS)

Figure 2: Rx Reference Point

The Rx reference point must be taken into consideration when choosing between the two basic RFDS receive configurations employed by the iDEN EBTS:

Without Top Tower Amplifier: The Rx reference point equates to the top of the rack.

With Tower Top Amplifier: The Rx reference point is the TTA receive antenna port.

Arbitrary point in far field



System Gain

By default the BR will adjust received signal measurements by -8.5dB to determine �top of rack� signal levels, i.e. the default Rx reference point. This is to offset the amplification, known as �System Gain�, provided by the GEN4 RFDS receive multicoupler (RMC).

If the Rx reference point changes, the system gain must be adjusted accordingly. In the case of a TTA, it is recommended that the System Gain not exceed 12 dB. An in-line attenuator, known as a branch attenuator, is used to maintain an acceptable System Gain.

Additionally, the operator must adjust the RxTxGain parameter to achieve optimum sensitivity without significantly degrading the third order intercept performance, and consequently, protection against IM (intermodulation) generated interference. As a result, iDEN most often specifies receive sensitivity at the �top of the rack� rather than at the base radio receiver port.

Please refer to the section Reference Link Budgets (Noise Limited Case) for additional information on System Gain and RxTxGain adjustments.



Receive Sensitivity Receiver sensitivity is a function of the thermal noise floor, receiver noise figure, site interference/noise, and design C/N. The Static Receiver Sensitivity of the Base Radio is quoted, in Volume 2 of the EBTS Hardware Manual, as -108 dBm for 8% BER. Applying such a specification is not appropriate for RF system design in a faded environment. Rather, one must use a Faded Receive Sensitivity number and account for (co-channel) interference.

Faded Receiver Sensitivity

Assuming no interference, or more correctly the interference level is much less than the noise, the system is said to be noise limited and the equipment noise floor for a standard GEN4 RFDS is approximately -124.5 dBm. This is calculated as follows:

Equipment Noise Floor (N) = Thermal Noise Floor (kTB) + Cascaded Noise Figure (NF)

= -131.5 + 7

= -124.5 dBm

Where:

Thermal Noise Floor = 10 * log (Boltzman�s Constant * Temperature (°K) * Bandwidth)

To allow the system to operate at an acceptable quality and to account for fading, a design margin (CF/N) must be added to the Equipment Noise Floor value to provide a Faded Receiver Sensitivity value. This is represented (not to scale) in the following diagram:

Thermal Noise Floor (kTB)

Static Receiver Sensitivity

NoiseFigure (NF)

Equipment Noise Floor (N)

Faded Receiver SensitivityRayleigh

Fade Margin

CS/NCF/N

Figure 3: Noise Limited Faded Receiver Sensitivity


Motorola General Business Information iDEN Technical Publications White Paper The recommended minimum CF/N, commonly referred to as C/N, values are as follows:

• For systems operating 3:1 VSELP or New 6:1 AMBE+2 Interconnect service, it is recommended that the minimum C/N be at least 20 dB or 3% BER. This equates to a faded receiver sensitivity number of -104.5 dBm, i.e. -124.5 + 20. This is the typical deployment scenario and hence the 20 dB C/N value is used throughout this and other documents.

• For systems operating Dispatch only, the C/N requirements may be relaxed to 18 dB or 3.5% BER. This equates to a faded receiver sensitivity number of -106.5 dBm, i.e. -124.5 + 18

• For systems operating 6:1 VSELP Interconnect services, it is recommended that the minimum design margin be increased to 25 dB. This equates to a faded receiver sensitivity number of -99.5 dBm, i.e. -124.5 + 25

However, if interference is introduced into the system, the equipment noise floor will be degraded. In this instance, the value of N will be adjusted by the interference (I) to produce a resultant Interference + Noise (I+N) value, i.e. a degraded, or increased, noise floor. This may be calculated via a power sum of I and N, as follows:

Interference + Noise (I+N) = 10 * LOG(10^(N/10) + 10^(I/10))

As an example; assume N = -124.5 dBm and I = -120 dBm, the resultant I+N value would be:

I + N = 10 * LOG(10^(-124.5/10) + 10^(-120/10))

I + N = -118.7 dBm

To maintain the same level of quality as for the noise limited case, the same design margin is required. The typical 20 dB CF/N design margin has now become 20 dB CF/(I+N) hence, for the example I+N calculation, the Faded Receiver Sensitivity has been degraded from -104.5 dBm to -98.7 dBm due to the presence of interference. This is represented (not to scale) in the following diagram.



Thermal Noise Floor (kTB)

NoiseFigure (NF)

Equipment Noise Floor (N)

Total Interference + Noise (I+N)

Interference (I)

Faded Receiver Sensitivity:Interference Limited

Design margin:CF/(I+N)

Design margin:CF/N

Faded Receiver Sensitivity:Noise Limited

Impact ofInterference

Figure 4: Interference Limited Faded Receiver Sensitivity

It is critical to understand the level of interference during the initial design since degrade receiver performance will impact coverage reliability and hence quality. One must remember to examine both paths since uplink interference will degrade the EBTS receiver performance but downlink interference will degrade the SU receiver performance.

Site Noise and Reuse Interference

Several tests conducted in June of 1995, throughout various areas in the Chicago area, at 850 MHz have demonstrated that the noise level encountered is typically a few dB below the thermal noise floor of -131.5dBm. In general, such empirical studies within congested and non-congested areas have shown that site noise may range from -130 dBm in a very dense urban environment to -135 dBm in a rural environment.

Frequency reuse, discussed later in this document, will introduce co-channel interference, which has the potential to degrade the effective receive sensitivity and must be accounted for within the link budget. Typically, the level of co-channel interference will be between -110 dBm and -136 dBm. However, the reuse pattern employed, site locations relative to an idea grid and environment will ultimately determine the level of interference experienced. As such, the key to successful frequency planning is controlling the level of interference to maintain quality.

For example; using a 7-cell, 3-sector reuse pattern, the offered cell edge C/I could range between 17 to 21 dB depending upon cell size; building density; and terrain. The effect on receive sensitivity could be up to a 6dB degradation. Increasing the reuse pattern would improve the effective receive sensitivity. A cell with a cell radius of five miles would allow the use of a 7/3 sector with minimal receiver degradation of less than 1dB. This same reuse pattern with one mile radius cells could experience a degradation of up to 6dB.


Motorola General Business Information iDEN Technical Publications White Paper Tower Top Amplifiers A standard tower top amplifier (TTA) comprises; a pre-selector filter; a 20 dB directional coupler; a Low Noise Amplifier (LNA); a DC block; and an impulse suppressor per branch. The combination of these devices can provide significant improvement in uplink system performance.

The TTA and multicoupler, when acting together as a system, essentially eliminate the losses between the antenna port and receiver. The only line loss uncompensated for is that connecting the pre-amplifier and the antenna. The maximum losses that can be compensated for are limited by the gain of the amplifier and system noise figure. Care should be taken to adjust the various system gains to improve receiver sensitivity without unduly sacrificing intermodulation susceptibility. Therefore, it is recommended to limit the overall gain setting to keep the third order IM intercept (IP3) around four dB, which would put the overall system gain (from antenna to BR port) in the area of 12 dB.

TTA Sensitivity and Gain

Sensitivity is measured for the TTA case at the antenna input, due to the cascading of active and passive elements. It should be noted that in order to compare sensitivities for TTA and non-TTA scenarios, the non-TTA sensitivity must now be measured at the antenna input, figuring in all losses between the EBTS cabinet and the antenna.

The sensitivity used should be determined by considering the noise figure. The typical receiver sensitivity value for this application is -105.1 dBm @ 20 dB C/N using 11.8 dB system gain. If a particular C/N level is required, keep in mind that the amplifier system amplifies the noise and the desired signal. Thus, if ambient noise is higher than (or close to) the system sensitivity, then the C/N level desired may no longer exist. For example; if 22 dB C/N faded sensitivity is required, the engineer must ensure that the design sensitivity is 22 dB above the ambient noise.

Careful consideration should be given to the noise environment at the site where a TTA is to be located. The impact of amplifier gain on total performance is limited where there is considerable site noise. Large increases in amplifier gain do not necessarily guarantee large increase in system performance and too much gain can actually be harmful. Typically, the amplifier gain is adjusted to compensate for the loss of the receive transmission line, with a maximum gain of 8.5 dB between the antenna and the input of the base radio receiver. As a rule, the tower top amplifier gain can be raised up to 12 dB at less noisy sites, typically at higher rural or suburban/rural sites.

NOTE: A TTA will not improve performance significantly at lower (antenna height) or noisier sites. In these cases, less gain may possibly prove more beneficial.


Motorola General Business Information iDEN Technical Publications White Paper Hybrid/Duplex/Tower Top Amplifier

Integrating a TTA into the receive side of a duplexer and mounting the device in a small enclosure at the top of a tower allows the designer to derive the benefits of the TTA while using one transmission line per receive branch for both transmit and receive.

DuplexedTTA

Power &Alarms

Duplexer

TransmitCombiner

Base RadioReceiveMulticoupler

Surge Protector

DC Injector

Attenuator

Test Port

Figure 5: Duplexed Tower Top Amplifier System Block Diagram

The duplexed TTA is used in conjunction with a duplexed RFDS and performs a similar function to a standard TTA. B-band filtering and ultimate receive selectivity filtering are determined by the RFDS duplexer. The duplexed TTA has a single transmit filter and two receive filters. One receive filter is duplexed with the transmit filter at the antenna port. A second receive filter is duplexed to the transmit filter at the input/output port. A low noise amplifier (LNA) and test port coupler are inserted in series between the two receive filters.

Additionally, this configuration requires fixed attenuators for adjusting the total gain of the amplifier. The correct amount of attenuation, termed Branch Equalization, required for a given installation is determined by adding all the gains and losses in the receive side of the antenna network and RFDS and achieving the desired amount of System Gain.



Receive Antenna Diversity Gain The iDEN system offers antenna diversity in order to help improve the uplink signal. The method employed is maximal ratio combined diversity. This is a technique that co-phases the signals from multiple sources, scales their magnitudes, and sums them so that the maximum instantaneous signal to noise ratio is achieved. Systems employing this method of combining benefit in two ways:

1. Provided that the noise and/or interference are non-correlated on the branches, an aperture gain is obtained because the maximal ratio combining co-phases and adds the antennas� signals.

For example, for a two-branch system with equal branch powers and correlated fading, the aperture gain = 10 * log10 (2) = 3 dB:

For a 3-branch system, the aperture gain = 10 * log10 (3) = 4.7dB.

2. A gain is obtained when the fading is de-correlated between different branches. As the fading becomes less correlated the fading statistics of the amplitude of the combined signal are improved and the deep fades occur less often.

NOTE: In the absence of fading, the diversity improvement cannot be greater than the aperture gain.

Different antenna configurations offer different levels of performance when used with maximal ratio combining. A space diversity antenna system (antennas in the same horizontal plane), which is Motorola�s recommendation, has equal branch powers and variable branch correlations, and as such maximal ratio combined systems using this configuration generally benefit fully from aperture gain and to some degree from fading gain.

Depending upon the horizontal antenna spacing, antenna height and multi-path fading, tests have shown that an additional gain of up to 1.5 dB can be added to the aperture gain. This would occur in the optimal conditions with spacing between antennas of 1.5 ft. - 2.5 ft per mile from the site. Practical spacing is usually on the order of 10 ft, so for high antenna heights getting this amount of additional gain will be difficult.

Typically suburban and rural sites may yield fading de-correlation gains of about 0.5 dB. Nevertheless, the additional uplink gain that diversity provides is critical to iDEN performance and Motorola recommends that three branch diversity be utilized at all sites.

Configuration Two Branch Three Branch Aperture Gain 3.0 dB 4.7 dB

Correlation Gain 1.5 dB 1.5 dB Total Possible Gain 4.5 dB 6.2 dB

Table 4: Receive Antenna Diversity


Motorola General Business Information iDEN Technical Publications White Paper As a rule of thumb, Motorola recommends that aperture gain alone be used for link budget calculations, since the de-correlation gain is variable and in many cases may be 0 dB. However, in urban and dense urban environments it is reasonable to assume that de-correlation will be present.

Enhanced Receiver

The SR9.6 Enhanced Receiver feature, also known as �Smart Antenna�, incorporates a diversity-combining scheme that improves uplink coverage by reducing interference. This feature is implemented as a layer to the Base Radio DSP in contrast to an externally based antenna system. Embedded within the solution are; post-combiner SQE algorithms, predictive software for handover and new call assignments. Enhanced Receiver is active on all BRs with an EBRC (Quad and GEN2 BR) operating SR9.6 or greater.

The RF system benefit will increase as more Enhanced Receiver capable BRs are deployed in a cell. For a mixed cell with both legacy and Enhanced Receiver BRs, no degradation will occur. In cells with inbound interference, traffic will tend to migrate toward the Enhanced Receiver BRs since the uplink INI, on unassigned channels, will likely be lower. Also, these BRs will initiate fewer handovers because of improved inbound SQE. The actual interference reduction capabilities of Enhanced Receiver depend on a number of factors, as listed below.

• The number of antenna elements in the array

• Enhanced Receiver requires at least two branches; with three branches provide better performance than two.

• The number of interfering signals

• The relative interference and noise levels

• The spatial aspects, including azimuths and inter-branch correlations

• Enhanced Receiver performs better with higher azimuth separation between desired and interfering signals and with more correlation between diversity branches.

• The relative delays of the desired and interfering signals

I+N I/N Average SQE Improvement

-117 dBm 14 dB 7.25 dB -119 dBm 12 dB 5.75 dB -121 dBm 10 dB 5.00 dB -123 dBm 8 dB 3.50 dB -125 dBm 6 dB 2.50 dB

Table 5: Measured SQE Improvements

NOTE: If a system is noise limited, or if only a single receiver branch is deployed, no improvement is possible.



Subscriber Unit Considerations This section presents typical subscriber unit information relevant to the RF design link budget. For Control Station information, please refer to the iDEN manual �Control Station Applications Planning and Installation� (68P80801B70-O).

General Specifications Typically, for a link budget discussion, one is most concerned with the available transmit power and the receiver performance. The specifications of typical iDEN subscriber products are provided below:

Radio Type Transmit Power (Pti) Standard Portable 600 mW / 28 dBm Rugged Portable 600 mW / 28 dBm

Mobile 3 W / 35 dBm Table 6: Subscriber Transmit Power

NOTE: All current portable subscriber units have a 34 dB transmit power range, i.e. +28 dBm to �6 dBm, which is �cutback� (attenuated) in 1 dB increments. Older models, e.g. LINGO, have 5 dB power control steps.

The faded voice sensitivity of the iDEN subscriber products is shown below, for a C/N level of 20 dB, which approximates to a three percent Bit Error Rate (BER).

SU Type Sensitivity Standard Portable -101.0 dBm Standard Mobile -103.5 dBm

Table 7: Faded Receive Sensitivity Specification @ 20 dB C/N

NOTE: Under typical conditions, the SU will tend to lose registration with the system (red light) around the 12 dB C/I2 level, however additional C/I is required for initial registration (16 dB) and mobility.

2 C/I is a generic term. For a noise limited system this will equate to C/N but for an Interference limited system, C/I will equate to C/(I+N).



Antenna Performance It is common for vendors to separately quote an antenna gain value and a body loss value within a link budget. However, for iDEN subscriber units, Motorola has performed controlled testing to determine the overall antenna performance, during the various modes of operation. The result of such testing is a composite value representing both antenna gain and body loss. A summary of typical results from these empirical measurements is presented in this section.

The standard portable SU has a retractable antenna; however the unit is not intended for operation with the antenna collapsed. The following antenna performance numbers represent mean measurements, with adjustments for the standard deviations found during the tests.

Placement Ant. Extended Ant. Collapsed Dispatch at Face -4.6 dBd -8.4 dBd

Interconnect at Ear -8.0 dBd -14.6 dBd Standby on Hip -5.5 dBd -7.6 dBd

Table 8: Typical Retractable Antenna Performance

Ruggedized subscriber units are typically equipped with a fixed �stub� antenna, which tends to have improved performance characteristics over a retractable antenna. The following antenna performance numbers represent mean measurements with adjustments for the standard deviations found during the tests:

Placement Fixed Antenna Dispatch at Face -3.1 dBd

Interconnect at Ear -8.3 dBd Dispatch on Hip -14.0 dBd

Table 9: Typical Fixed Antenna Performance

NOTE: Antenna performance will vary by subscriber platform and model type (monolith or clam shell). The numbers presented are typical, not guaranteed.



Car Kits

Portable subscriber units can be used with a �Car Kit� to couple the antenna, through an adapter, to an external glass or roof mounted antenna. The improvement in performance over the portable being used in car is approximately 4 to 6dB. However, the additional loss through this device is 3dB, which is then added to the vehicle antenna gain and associated cable performance values listed below.

Item Gain Antenna Gain -1.0 dBd

Coax Cable Loss 2.3 dB Table 10: Car Kit Antenna Performance

Vehicle Losses

While portable antenna performance, in most cases, tends to typify that experienced in the anechoic chamber this is not the case for portables operating in vehicles. A unique in-vehicle chamber effect, combined with antenna position and multipath fading, allows the RF energy to be reflected in such as manner that the resulting performance equalizes antenna radiation differences. The result is that all portables tend to perform about the same when used inside a vehicle.

Several independent tests have demonstrated that the typical loss due to use of an iDEN portable in vehicle is approximately -13 dBd, while used in operating position such as interconnect at the ear. When used in the dispatch position, testing reflected the radio being angled so as to allow the driver clear vision of the road. Compared to the direct vertical position used in the anechoic chamber resulted in some additional loss. Therefore, based upon this a recommended value of -10.5 dBd should be used.

Category Typical Portable Typical Car/Port Ant Loss - Dispatch 10.5 dB

Typical Car/Port Ant Loss - Interconnect 13 dB Table 11: Typical In-Vehicle Losses



Building Losses

Portable antenna operation within a building tends to closely follow the antenna performance experienced in the anechoic chamber. Typical suburban in-building losses are generally assumed to be 15dB but the actual mean and standard deviation will vary with building size, density and construction; width of the streets and angle of arrival. .

The following table breakouts out typical losses for different building classifications.

Category Mean Loss Standard Deviation Typical Loss 15 dB 6 dB

Light Building 4-6 dB 4 dB Medium Building 11 dB 6 dB

Large Building 18 dB 6 dB Table 12: Building Loss

IMPORTANT: Specific building losses must be determined by testing performance both outside and inside the building, taking many measurements for each condition and using this difference as the building loss.



Reference Link Budgets (Noise Limited Case) The link budgets presented in this section define typical signal thresholds, at 20 dB C/N, for multiple combining scenarios with; GEN4 RFDS cabinets; 800 MHz 70 W legacy BRs; 800 MHz Quad BRs, 900 MHz Quad BRs. It is not required to redefined design C/N values for Split 3:1 channel formats used with the New 6:1 Interconnect feature. These templates are only valid for standard RFDS configurations and assume typical antenna performance of a standard subscriber unit.

The following table presents the downlink RSSI design thresholds for the link budgets in this section:

Category Contour RSSI On-street threshold with no margin -93 dBm On-street threshold, w/ 6 dB lognormal fade margin -87 dBm In-car threshold, w/ 6 dB lognormal fade margin -82 dBm In-building threshold, w/ 6 dB lognormal fade margin -72 dBm

Table 13: Downlink RSSI Thresholds @ 20 dB C/N

NOTE: The effects of interference may cause the effective faded EBTS receive sensitivity to degraded hence these contour RSSI values may change.

Single Base Radio: Hybrid Combining This section provides standard link budgets for the GEN4 RFDS, with hybrid combining and specification receiver sensitivity at 20 dB C/N. It is assumed that, in all cases, a balanced path is desired.


Motorola General Business Information iDEN Technical Publications White Paper Element

Maximum PA Output: 70.0 W 48.5 dBm 0.6 W 27.8 dBmCombiner & Duplexer (incl.cables & connectors): -8.5 dB 40.0 dBm 0.0 dB 27.8 dBm

Bottom Jumper & Connector: -0.7 dB 39.3 dBm 0.0 dB 27.8 dBmLightning Arrestor: -0.1 dB 39.2 dBm 0.0 dB 27.8 dBm

Transmission Cable and Connectors: -2.1 dB 37.1 dBm 0.0 dB 27.8 dBmTop Jumper & Connector: -0.2 dB 36.9 dBm 0.0 dB 27.8 dBm

Transmit Antenna: 10.0 dBd 46.9dBm -8.0 dBd 19.8dBmResultant ERP: 46.9dBm 19.8dBm

Receiver Sensitivity @ 20dB C/(I+N) -101.0 dBm -104.5 dBmDiversity Gain: 0.0 dB -101.0 dBm 4.7 dB -109.2 dBm

Receive Antenna: -8.0 dBd -93.0 dBm 10.0 dBd -119.2 dBmTop Jumper & Connector: 0.0 dB -93.0 dBm -0.2 dB -119.0 dBm

Transmission Cable and Connectors: 0.0 dB -93.0 dBm -2.1 dB -117.0 dBmLightning Arrestor: 0.0 dB -93.0 dBm -0.1 dB -116.9 dBm

Bottom Jumper & Connector: 0.0 dB -93.0 dBm -0.7 dB -116.2 dBmEffective Receiver Sensitivity -93.0 dBm -116.2 dBm

Maximum Path Loss 139.9 dB 136.0 dBPath Imbalance 4.0 dB Base Hot

Adjusted EBTS ERP for Balanced Path 43.0 dBm 20 WPA Setting for Balanced Path 44.5 dBm 28 W

Downlink Uplink

Table 14: 3-Way Hybrid / Duplexed Combiner Link Budget

For a TTA design the system gain is adjusted to be 11.8 dB. In this instance the RxTxGain parameter must be modified accordingly. This is reflected in the following link budgets:

ElementMaximum PA Output: 70.0 W 48.5 dBm 0.6 W 27.8 dBm

Combiner & Duplexer (incl.cables & connectors): -8.5 dB 40.0 dBm 0.0 dB 27.8 dBmBottom Jumper & Connector: -0.7 dB 39.3 dBm 0.0 dB 27.8 dBm

Lightning Arrestor: -0.1 dB 39.2 dBm 0.0 dB 27.8 dBmTransmission Cable and Connectors: -2.1 dB 37.1 dBm 0.0 dB 27.8 dBm

Top Jumper & Connector: -0.2 dB 36.9 dBm 0.0 dB 27.8 dBmTransmit Antenna: 10.0 dBd 46.9dBm -8.0 dBd 19.8dBm

Resultant ERP: 46.9dBm 19.8dBm

Receiver Sensitivity @ 20dB C/(I+N): -101.0 dBm -105.1 dBmDiversity Gain: 0.0 dB -101.0 dBm 4.7 dB -109.8 dBm


Transmission Cable and Connectors: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBmLightning Arrestor: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBm

Bottom Jumper & Connector: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBmEffective Receiver Sensitivity -93.0 dBm -119.6 dBm



Downlink Uplink

Table 15: 3-Way Hybrid/Duplexed w/Tower Top Amp



Single Base Radio: Cavity Combining For a cavity combining solution, a TTA is used to balance the uplink path due to the lower insertion loss offered by cavity combiners over hybrids. A typical cavity link budget is as follows:

ElementMaximum PA Output: 70.0 W 48.5 dBm 0.6 W 27.8 dBm

Combiner & Duplexer (incl.cables & connectors): -5.8 dB 42.7 dBm 0.0 dB 27.8 dBmBottom Jumper & Connector: -0.7 dB 42.0 dBm 0.0 dB 27.8 dBm

Lightning Arrestor: -0.1 dB 41.9 dBm 0.0 dB 27.8 dBmTransmission Cable and Connectors: -2.1 dB 39.8 dBm 0.0 dB 27.8 dBm

Top Jumper & Connector: -0.2 dB 39.6 dBm 0.0 dB 27.8 dBmTransmit Antenna: 10.0 dBd 49.6dBm -8.0 dBd 19.8dBm

Resultant ERP: 49.6dBm 19.8dBm

Receiver Sensitivity @ 20dB C/(I+N): -101.0 dBm -105.1 dBmDiversity Gain: 0.0 dB -101.0 dBm 4.7 dB -109.8 dBm


Transmission Cable and Connectors: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBmLightning Arrestor: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBm

Bottom Jumper & Connector: 0.0 dB -93.0 dBm 0.0 dB -119.6 dBmEffective Receiver Sensitivity -93.0 dBm -119.6 dBm


Downlink Uplink

Adjusted EBTS ERP for Balanced Path 46.4 dBm 44 WPA Setting for Balanced Path 45.3 dBm 34 W Table 16: 10 Channel Cavity w/Tower Top Amp

Quad Base Radio The link budget shown in the following table is for an 800 MHz or 900 MHz Quad BR, equipped with 4 carriers, directly connected to a duplexer, i.e. no combining.


Motorola General Business Information iDEN Technical Publications White Paper Element

Maximum PA Output: 10.5 W 40.2 dBm 0.6 W 27.8 dBmCombiner & Duplexer (incl.cables & connectors): -1.5 dB 38.7 dBm 0.0 dB 27.8 dBm

Bottom Jumper & Connector: -0.7 dB 38.0 dBm 0.0 dB 27.8 dBmLightning Arrestor: -0.1 dB 37.9 dBm 0.0 dB 27.8 dBm

Transmission Cable and Connectors: -2.5 dB 35.5 dBm 0.0 dB 27.8 dBmTop Jumper & Connector: -0.2 dB 35.3 dBm 0.0 dB 27.8 dBm

Transmit Antenna: 10.0 dBd 45.3dBm -8.0 dBd 19.8dBmm

mmmmmmmm

ot

Downlink Uplink

Transmit ERP: 45.3dBm 19.8dB

Receiver Sensitivity @ 20dB C/(I+N): -101.0 dBm -101.0 dBm -104.5 dBm -104.5 dBDiversity Gain: 0.0 dB -101.0 dBm 4.7 dB -109.2 dB

Receive Antenna: -8.0 dBd -93.0 dBm 10.0 dBd -119.2 dBTop Jumper & Connector: 0.0 dB -93.0 dBm -0.2 dB -119.0 dB

Transmission Cable and Connectors: 0.0 dB -93.0 dBm -2.5 dB -116.6 dBLightning Arrestor: 0.0 dB -93.0 dBm -0.1 dB -116.5 dB

Bottom Jumper & Connector: 0.0 dB -93.0 dBm -0.7 dB -115.8 dBEffective Receiver Sensitivity: -93.0 dBm -115.8 dB

Maximum Path Loss 138.3 dB 135.6 dBPath Imbalance 2.7 dB Base H


Table 17: Duplexed Quad BR: 4 Carriers Equipped with no Combining

If 800 MHz and 900 MHz BRs are sharing the same antenna system, additional losses need to be added for the diplexer equipment. The typical combined insertion and cable loss for the diplexer is 0.75 dB.

For reference, the following table presents the transmit power ranges for the Quad BR:

Carriers Maximum PA Power Minimum PA Power 1 52.0 W 47.2 dBm 5.0W 37.0dBm 2 26.0 W 44.1 dBm 2.5W 34.0dBm 3 16.1 W 42.1 dBm 1.7W 32.3dBm 4 10.5 W 40.2 dBm 1.3W 31.1dBm

Table 18: 800/900 MHz Quad BR Transmit Power

Based on the values presented in, the default 3-way hybrid combining option will cause a Quad BR equipped with four carriers to be downlink limited by 3.5 dB. If implemented this will degrade the coverage reliability and hence system quality for coverage limited designs.



Estimates of Cell Radius From the maximum allowable path loss, calculated within the link budget, an estimated cell radius may be determined. Typically, the HATA propagation model is initially used to provide an estimation of distance within specific environments, e.g. urban or suburban, for a given pathloss value, antenna height and frequency.

The following chart provides the estimated cell radius across the standard environmental classifications for a wide range of base antenna heights. For this example, a pathloss value of 130dB (including a 6 dB lognormal fade margin) was assumed.

Cell Radius vs. Base Antenna Height

12.00

14.00

16.00

18.00

m)

0.00

2.00

4.00

6.00

8.00

10.00

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Base Antenna Height (m)

Cel

l Rad

ius

(k

Dense Urban (km) Urban (km) Suburban (km) Rural (km)

Figure 6: Estimated Cell Radius using the HATA Propagation Model

IMPORTANT: This data is intended to offer the reader guidance and does not guarantee RF coverage and/or satisfactory system performance at the distances indicated. The HATA model provides an estimation of distance, based on defined inputs. An RF prediction tool utilizing terrain and clutter data will provide improved accuracy, however neither can replace actual field measurements.



Power Control Parameters associated with power control, correlate to the link budget and overall RF system design. For good system performance, it is required to correctly define the system design threshold and hence the power control parameters.

The iDEN technology employs an open loop power control algorithm, in the SU, based on FNE parameters (transmitted on the BCCH of the serving cell) and SU measurements. This algorithm is summarized in the following flow chart (Figure 7: SU Power Control Flow Chart):

Measure ReceivePower (RSSI /

Pro)

Calculate cutbackrequired using serving

cell's PCC

(Max SU pwr - (PCC-Pro))

Is cutback outof range?

Set Pti

(28dBm to -6dBmw/ 1dB resolution)

Set to minimum ormaximum as

applicable

(0 to 34dB)

System InformationMessage 1 transmitted on

BCCH provides PCC

NO

YES

Figure 7: SU Power Control Flow Chart

To summarize; the SU applies the Power Control Constant (PCC) offset, of the serving cell, to the measured receive power (Pro) and determines the appropriate attenuation (cutback) of the maximum transmit power. The resultant SU transmit power is referred to as Pti (Power Transmit Inbound).

NOTE: The cutback level of the SU can be viewed via a drive test tool since it is reported in the �Normal Mode Summary� message.



Power Control Constant

This section provides further information on power control parameters, which correlate with a link budget discussion. Also reference the most current version of WP2003-007 (Configurable RF Parameters).

The Power Control Constant (PCC) is a function the RF design and is determined as follows:

PCC = Pto + Desired_Pri - RxTxGain

Equation 1: Power Control Constant

Where:

Pto: Determined by the balanced path link budget measured at the EBTS antenna connector (Tx Reference Point).

Pto = PA Power � sum (Combiner Insertion Loss, Duplexer Loss, Internal Cable & Connector Loss)

Desired_Pri: Typically -88dBm +/- the effects of interference, site noise, cable loss and TTA referenced to the antenna connector (Rx Reference Point). This parameter is actually determined from PCC, Pto and RxTxGain as shown later in this section.

RxTxGain: Grx - Gtx

Where:

Gtx: Transmit Antenna Gain (dBd) + Total Transmission Line Loss + TTA duplexer loss

Grx: Receive Antenna Gain (dBd) + Total Transmission Line Loss + TTA gain + Branch attenuator loss + (RFDS gain new - 8.5dB)

The desired receive power level (Desired_Pri) is normally approximately -88dBm for a standard GEN4 hybrid/duplex RFDS and will be approximately -81 to -85dBm with a TTA, which is a good balance between operation with minimal frequency reuse and reasonable signal levels for coverage. This value is based on maintaining 36 dB (C/I+N) at the reference point and includes the effects of site noise and reuse interference. The following table can be used as a reference for a hybrid/duplex configuration in areas with varying levels of uplink interference, typically due to co-channel.



Uplink Interference Level I+N Threshold Desired_Pri Pto PCC None, 3 Branch -134 dBm -88 dBm 36 dBm -44 dB None, 2 Branch -132 dBm -88 dBm 36 dBm -52 dB None, 1 Branch -129 dBm -88 dBm 36 dBm -52 dB

Low -125 dBm -86 dBm 36 dBm -50 dB Moderate -120 dBm -83 dBm 36 dBm -47 dB

High -115 dBm -79 dBm 36 dBm -43 dB Very High -110 dBm -74 dBm 36 dBm -38 dB

Extremely High -105 dBm -69 dBm 36 dBm -33 dB Table 19: PCC and Desired_Pri for Various Interference Levels

Generally, a small change either raising or lowering the PCC will not affect system performance; however a change of 6dB or more could have a detrimental effect. It should also be noted that the EBTS top of rack transmit power (Pto) must be adjusted to accommodate the design conditions for whatever subscriber coverage level the system has been designed to, mobile or portable.

Notes on Receiver-Transmitter Gain (RxTxGain) The RxTxGain is defined as the gain delta, in dB, between the RFDS receive and transmit paths, i.e. from the BR to the respective reference point. As such, this parameter defines the adjustment to default signal measurements made by the BR. An inappropriate setting will cause the BR to make incorrect measurements impacting power control and handover decisions. Poor system performance will result.

For a standard GEN4 RFDS, the typical value for RxTxGain is 0dB since the Tx and Rx cabling, connector and antenna gains/loses are the same. This is based on an assumed system gain of 8.5dB for a standard GEN4 RFDS.

System Gain is defined as the effective gain between the Rx reference point (antenna cable port) and the Base Radio, i.e. the gain through the Receive Multicoupler. The BR will, by design, adjust measured signals by 8.5dB to determine the Rx reference point value (top of rack for non-TTA configurations).

GRx = Ant Gain + Cbl & Con + TTA & Filter + Branch Attn + RFDS= 10.00 dB + -3.00 dB + 0.00 dB + 0.00 dB 0.00 dB= 7.00 dB

GTx = Ant Gain + Cbl & Con + TTA Dupl= 10.00 dB + -3.00 dB + 0.00 dB= 7.00 dB

RxTxGain = GRx - GTx

= 7.00 dB - 7.00 dB= 0.00 dB

Figure 8: RxTxGain Example (without TTA)


Motorola General Business Information iDEN Technical Publications White Paper When using a tower top amplifier, receive line insertion losses (including coax, lightning suppresser, jumper cables, and connectors between the antenna and the multicoupler) are compensated for. In this case the Rx Gain will effectively be greater than the Tx Gain, hence the RxTxGain parameter would need to be greater than 0.

GRx = Ant Gain + Cbl & Con + TTA & Filter + Branch Attn + RFDS= 10.00 dB + -3.00 dB + 15.50 dB + -10.09 dB 0.00 dB= 12.41 dB

GTx = Ant Gain + Cbl & Con + TTA Dupl= 10.00 dB + -3.00 dB + -1.00 dB= 6.00 dB

RxTxGain = GRx - GTx

= 12.41 dB - 6.00 dB= 6.41 dB

Figure 9: RxTxGain Example (with TTA)

Subscriber Unit Transmit Power

The transmit power of the SU, known as Pti (Power Transmitted Inbound), is defined as follows:

Pti = PCC - Pro

Equation 2: Subscriber Transmit Power

As an example; assuming a Pro of -75dBm and a PCC of -53dB, the subscriber transmit power required would be about 22dBm. In reality the SU determines the amount of power to attenuate (cutback) from the maximum available SU transmit power. Within drive test logs the amount of cutback is typically the only indication of subscriber transmit power.

Cutback is the attenuation applied to the maximum Pti, typically 28dBm, in 1dB steps. As such, for the same example the Pti of 22dBm will equate to 6dB of cutback, which is calculated as follows:

Cutback = Max SU Power – (PCC – Pro)

Equation 3: Subscriber Cutback

Typically, there are 34 cutback steps correlating to the 28dBm to �6dBm transmit power range of a standard SU.



Cell Pti Max

�Cell Pti Max� equates to the maximum power a subscriber is allowed to transmit within a particular cell. The default setting is two (37dBm) to allow for high powered SU, such as mobiles and control stations. However, for a portable design, this parameter should be adjusted to five (28dBm) to control any potential uplink interference from higher powered SUs.

900 MHz Considerations For 800/900 MHz dual band operation changes to the iDEN RF subsystem are required with the rest of the infrastructure being common to 800 MHz and 900 MHz operations.

• The 900 MHz band can only be configured on a 900 MHz Quad BR. The ACG will not allow older 900 MHz single BRs to be configured on an 800/900 MHz dual band site. The ACG will ignore the BR registration and send an alarm to the OMC-R.

• Any Bi-Directional Amplifier associated with a 900 MHz EBTS must be upgraded to support the 900MHz frequency band.

The 900MHz carriers only provide 3:1 interconnect services: telephone calls; circuit switched data calls, handovers, and short message services (during 3:1 telephone calls). Legacy and Multiple PCHs are not allowed on 900 MHz BR; however for SR12, a Separate WiDEN PCH may be configured at 900 MHz.

RFDS Requirements

To have the 800/900 MHz Dual Band Interconnect Service feature available the following equipment is required:

• 900 MHz Quad BR(s)

• Diplexer equipment

• 900 MHz RF Distribution System


Motorola General Business Information iDEN Technical Publications White Paper The following diagram illustrates the integration of 800 MHz and 900 MHz RFDS cabinets, if a dual band antenna is to be used.

800MHzRFDS

900MHzRFDS

Combiner

Duplexer Duplexer

Diplexer

Combiner

800MHz In

900MHz In

Ant Out

Tx In Ant Out Tx In Ant Out

Figure 10: 800/900 MHz RFDS to Diplexer Integrated Block Diagram

This configuration requires the use of a diplexer unit that can be mounted horizontally within the cabinet or vertically on the cabinet�s rear rails. The additional loss of the diplexer must be accounted for within the link budget calculations to achieve correct transmit power setting for a balanced path.

Frequency Planning Concepts The cellular concept is based on the principle of controlling of interference between cells assigned the same frequency. Designing to an optimal frequency reuse will maximize system capacity while maintaining acceptable quality levels. The system operator must consider many factors when implementing a frequency re-use scheme, however the following points should be high on any list:

• Interference protection of the pattern • A simple method of growth • The additional number of subscribers that can be served by a new cell, or conversely,

the number of cells required to serve a given population

An appropriate re-use pattern will help to balance coverage and interference, as well as enabling future system development with minimum disturbance to the system. Closer re-use of frequencies increases the utilization of the allocated spectrum and as a direct consequence allows for greater subscriber densities to be realized. This must be weighed against the increased level of interference.

NOTE: It is recommended that frequency planning be such that TCH carriers have equal or better quality than PCCH carriers to minimize poor handover performance.


Motorola General Business Information iDEN Technical Publications White Paper Reuse Factor (K) The minimum sustainable C/I ratio will determine the reuse distance. The distance between cells reusing the same frequency is critical and a greater reuse pattern will provide for more physical separation between the reuse sites and hence lower levels of potentially interfering signals.

The reuse distance (D) is determined by; the radius of the cell (R); and the cell pattern used through the D = √3K*R relationship. Note that K3 is the cell pattern defined by the number of sites in the reuse cluster. This relationship is also referred to as the D/R ratio.

Cell R

adius

(R)

Reuse Distance (D)

Figure 11: Reuse Distance (D/R Ratio)

As an example; if one assumed a 12 cell Omni reuse pattern, the D = 6R. Alternatively, if one used a 7 cell, 3 sector reuse pattern D=4.6R.

Reuse Patterns When designing a system co-channel interference, as well as site noise, must be taken into consideration. As previously eluded, the amount of co-channel interference is defined by the choice of the frequency reuse pattern made during the initial system layout.

NOTE: The actual C/I achieved by a reuse pattern is dependent upon site acquisition, terrain and clutter.

3 The reuse factor K may also referred to as N, as in N cell reuse.


Motorola General Business Information iDEN Technical Publications White Paper The following chart highlights the C/I performance obtained from various reuse patterns, based on the use of a cell radius of approximately 3.5 miles and 100 ft. antenna height.

C/I REQUIREMENT FOR 90% RELIABILITY S = 6.5 dB

-5 dB 0 dB

1 Cell

Omni (-

5.7 dB)

Sectors

(2.7 d

B)

ni (5.6

dB)

Sectors

(7.8 d

B)

(8.3

dB)

tors (12

.4 dB)

Sectors

(12.5

dB)

(14.2

dB)

rs (15

.0 dB)

ctors

(16.7

dB)

(17.1

dB)

Sectors

(19.4

dB)

ni (20.8

dB)

Sectors

(20.8

dB)

Sectors

(24.1

dB)

Sectors

(24.9

dB)

Cell O

mni (25.0

dB)

12 C

ell / 3

Sectors

(27.8

dB)

+5 dB +10 dB +15 dB +20 dB +25 dB

1 Cell

/ 3

3 Cell

Om

1 Cell

/ 6

4 Cell

Omni

2 Cell

/ 6 Sec

3 Cell

/ 3

7 Cell

Omni

4 Cell

/ 3 Sec

to

3 Cell

/ 6 Se

9 Cell

Omni

4 Cell

/ 6

12 C

ell O

m

7 Cell

/ 3

9 Cell

/ 3

7 Cell

/ 6

16

Figure 12: Frequency Reuse Pattern Performance

Omni-Directional

An omni-directional antenna configuration provides the most basic reuse scheme. Such configurations are typically recommended for rural locations. A 20 dB C/N design level allows for a 12-cell reuse pattern to be deployed, under ideal conditions. A standard 12-cell omni reuse pattern is shown below:

I

A

B

C

G

H

F

D

L K

J

E

J

H

Reuse Distance Figure 13: 12 Cell Omni Reuse Pattern (K=12)

The primary advantage of an omni site is trunking efficiency, since all traffic channels are available to all users, within the coverage area. Trunking efficiency impacts the amount of hardware required to support a given number of subscribers at a given call model. However, interference can present more of a problem since an omni-directional antenna radiates and receives signals equally throughout the 360° horizontal plane, which means a site has the potential to cause and receive multiple interferers in all directions.


Motorola General Business Information iDEN Technical Publications White Paper Each cell, within the reuse cluster, is provisioned with a unique set of frequencies, known as a channel set or frequency group. For K=12, number of channel sets equates to the number of cells within the reuse cluster, in this case 12. The assignment of frequencies to these 12 channel sets is highlighted in the following table.

A B C D E F G H I J K L 1 2 3 4 5 6 7 8 9 10 11 12

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

Table 20: 12-cell Channel Assignment

As can be seen, a total of 96 frequencies would be required to enable 8 carriers per cell.

Directional (Sectored)

The use of a directional antenna configuration is standard practice for high subscriber density urban environments due to the advantages it offers from the control of the RF coverage area. For a design level of 20dB C/N, a 7cell - 3sector reuse pattern is the most efficient theoretically allowed.

G1

G2G3

A1

A2A3

B1B3

C1

C2C3

F1

F2F3

E1

E2E3

D1

D2D3

G2

B2

G3G1

Reuse Distance Figure 14: 7 Site - 3 Sector Reuse Pattern (K=7)


Motorola General Business Information iDEN Technical Publications White Paper By controlling the RF coverage, it is possible to create high signal strength areas, required for effective in-building penetration and hand portable coverage. This controlled coverage, aided by the high front to back ratio characteristics of a directional antenna, leads to higher interference rejection characteristics, which allows more efficient use of the available spectrum by improved frequency re-use patterns.

As with the omni design, each cell/sector within the reuse cluster is provisioned with a unique set of frequencies. For sectored K=7, the number of channel sets equates to the number of cells within the reuse cluster multiplied by the number of sector per site, in this case 7 * 3 = 21. The assignment of frequencies, to these channel sets, is highlighted in the following tables.

A1 B1 C1 D1 E1 F1 G1 1 2 3 4 5 6 7

22 23 24 25 26 27 28 43 44 45 46 47 48 49 64 65 66 67 68 69 70 85 86 87 88 89 90 91

106 107 108 109 110 111 112 127 128 129 130 131 132 133 148 149 150 151 152 153 154

Table 21: 7 Site-3 Sector Channel Assignments (Sector 1)

A2 B2 C2 D2 E2 F2 G2 8 9 10 11 12 13 14

29 30 31 32 33 34 35 50 51 52 53 54 55 56 71 72 73 74 75 76 77 92 93 94 95 96 97 98

113 114 115 116 117 118 119 134 135 136 137 138 139 140 155 156 157 158 159 160 161


A3 B3 C3 D3 E3 F3 G3 15 16 17 18 19 20 21 36 37 38 39 40 41 42 57 58 59 60 61 62 63 78 79 80 81 82 83 84 99 100 101 102 103 104 105

120 121 122 123 124 125 126 141 142 143 144 145 146 147 162 163 164 165 166 167 168


As can be seen, a total of 168 frequencies would be required to enable 8 carriers per cell, which equates to 24 per site.


Motorola General Business Information iDEN Technical Publications White Paper Cell Placement

In practice, finding ideal site locations is often not possible thus an alternative frequency reuse factor may need to be employed. The most common alternative three sector reuse plans are 9-cell and 12-cell.

In general, as long as the positioning of new sites follows the hexagonal grid pattern, the minimum D/R ratio between all cells using the same frequency will be maintained and the permissible C/I ratio will not be exceeded throughout the system. In the real world, practical designs will locate some reuse sites closer together while other reuse sites may be located further apart. The effects of frequency reuse will reduce the C/I ratio in some areas producing increased interference.

Frequency interference studies should be performed, using planning tools, to predict the amount of interference and the resulting loss of coverage reliability.



Color Code and Color Code Extension The purpose of color code is to allow a subscriber to differentiate between selecting the desired channel versus an undesired channel sharing the same frequency, utilizing a signal quality measurement that accurately accounts for co-channel interference. This differentiation is required to allow frequency re-use in the system.

There are 16 color-codes available that, when used with a cell reuse plan, are acceptable for most areas. For Split 3:1 channel formats, 6 color code extensions may be assigned to inbound channels to increase this number to 96.

PCCH Offset By default the PCCH occurs on Slot 0 of the DCAP frame. However, it is possible to change this assignment, via the PCCH Offset parameter, to increase re-use distances.

For example; within a frequency re-use plan the closest co-channel co-color code cell can be assigned a PCCH Offset = 1, rather than 0.

Slot offset 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5

Desired cell

Co-co cell

Slot offset 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5

Desired cell

Co-co cell

Figure 15: Example PCCH Offset

The recommended deployment of PCCH Offsets is shown in the following diagram where the PCCH Offset plan is overlaid onto the color code re-use.

CC=1

CC=1

CC=2

CC=3

CC=4CC=5

CC=6

CC=7

PCCH_offset = 0

CC=12

CC=10

CC=11

CC=12

CC=13

CC=14

CC=15

CC=8CC=9

CC=16

CC=13

CC=1

CC=1

PCCH_offset = 1

CC=1

PCCH_offset = 3PCCH _offset = 2

PCCH_offset = 4

CC=11


Motorola General Business Information iDEN Technical Publications White Paper Figure 16: PCCH Offset Overlaid on the Color Code Reuse

Quad BR Considerations Frequency assignment / spectrum requirements for the Quad BR must follow the following guidelines:

All four 25 kHz channels must be within a contiguous 100 kHz block to meet FCC spurious emissions requirements

Frequency allocation is flexible anywhere in the available spectrum

Blocks of 1, 2, 3, or 4 contiguous channels can be used for multi-carrier operation Use of non-contiguous channels poses a problem with adjacent channel interference on another Operator�s channel.

AAUAA

A = AcceptableU = Un-Acceptable

AAUAA

AAUAA

A = AcceptableU = Un-Acceptable

Figure 17: Quad BR Contiguous Channel Requirement



Adjacent Channel Interference

Traditionally, adjacent channel interference was avoided through appropriate frequency planning measures, which prevents the configuration of adjacent carriers in the same or adjacent cells. However, the Quad BR now requires the configuration of adjacent frequencies. The resulting potential for adjacent channel interference occurs when the sidebands of a transmitting subscriber, with a strong signal, interfere with the weaker signal of another MS, perhaps transmitting from a greater distance, on an adjacent frequency.

Desired signal

Thermal noise floor

Interference

Adjacent Channel Signal

Receive passband

Figure 18: Adjacent Channel Interference

This type of interference was significantly reduced by equipping the MS with a wider range of power control (34 dB) so that when close to the EBTS, the signal level in to the point where its sideband amplitude is sufficiently low in amplitude to avoid interference with subscriber transmissions on adjacent frequencies. This change was implemented in late 1997.

The following statistics are provided for Quad BRs (reference WP2003-011).

Statistics Name Description ADJACENT_CHANNEL_INTERFERENCE_COUNT

Number of slots with uplink SQE <15dB and where adjacent channel interference from other quad BR carriers is the likely source.

ADJACENT_CHANNEL_INTERFERENCE_CHECK

Number of slots checked for poor uplink SQE where adjacent channel interference from other quad BR carriers is the likely source.

Table 24: Adjacent Channel Statistics

With knowledge of such interference, the operator may be able to reduce the dynamic range of signal levels, and therefore interference effects. This may be accomplished through antenna placement (height, down-tilt) and, in some cases, through choice of antenna type.


Motorola General Business Information iDEN Technical Publications White Paper Sample Channel Assignments with Quad BRs

The following tables provide simplified channel assignments for a 9-cell/3-sector frequency re-use pattern for Quad BRs equipped with 3 channels. It is a general recommendation that, for control channel flexibility, the PCCH and redundant PCCH be assigned to single (legacy or GEN2) BRs.

A1 B1 C1 D1 E1 F1 G1 H1 I1 PCCH 1 2 3 4 5 6 7 8 9

Redundant PCCH 28 29 30 31 32 33 34 35 36 55 58 61 64 67 70 73 76 79 56 59 62 65 68 71 74 77 80 3 Channel Quad 57 60 63 66 69 72 75 78 81

136 139 142 145 148 151 154 157 160 137 140 143 146 149 152 155 158 161 3 Channel Quad 138 141 144 147 150 153 156 159 162

Table 25: 9-Cell / 3-Sector Reuse Pattern w/ Quads (Sector 1)

A2 B2 C2 D2 E2 F2 G2 H2 I2 PCCH 10 11 12 13 14 15 16 17 18

Redundant PCCH 37 38 39 40 41 42 43 44 45 82 85 88 91 94 97 100 103 106 83 86 89 92 95 98 101 104 107 3 Channel Quad 84 87 90 93 96 99 102 105 108

163 166 169 172 175 178 181 184 187 164 167 170 173 176 179 182 185 188 3 Channel Quad 165 168 171 174 177 180 183 186 189


A3 B3 C3 D3 E3 F3 G3 H3 I3 PCCH 19 20 21 22 23 24 25 26 27

Redundant PCCH 46 47 48 49 50 51 52 53 54 109 112 115 118 121 124 127 130 133 110 113 116 119 122 125 128 131 134 3 Channel Quad 111 114 117 120 123 126 129 132 135 190 193 196 199 202 205 208 211 214 191 194 197 200 203 206 209 212 215 3 Channel Quad 192 195 198 201 204 207 210 213 216


NOTE: The frequency assignments are presented as an example and do not reflect any actual frequency allocations and site capacity requirements.



Cellular Interference The proximity of the 800 MHz, as well as the 900 MHz, spectrum used by iDEN and cellular may cause adjacent Channel interference and Intermodulation products. Typically in these instances antenna orientation and proximity is a key factor. Coordination between operators may be necessary to mitigate such potential interference issues.

816861

824821

Contiguous SMR CellularA & B

InterleavedILT/IB/ SMR

PS

806

GC

809.750

Interleaved ILT/IB/ SMR

Public Safety


Public SafetyContiguous SMR

851 854.750 861

GC

866 869

CellularA & B

PS

Cell Site TxSubscriber Rx851 – 866 MHz

Cell Site RxSubscriber Tx806 – 821 MHz

816861

824821

Contiguous SMR CellularA & B

InterleavedILT/IB/ SMR

PS

806

GC

809.750


Public Safety


Public SafetyContiguous SMR

851 854.750 861

GC

866 869

CellularA & B

PS

Cell Site TxSubscriber Rx851 – 866 MHz

Cell Site RxSubscriber Tx806 – 821 MHz

Figure 19: 800 MHz Spectrum Layout

For reference, the cellular and iDEN frequency bands are as follows:

Band Spectrum Allocation (MHz)

Base Transmit (MHz)

Base Receive (MHz)

iDEN 800MHz 16 851 to 865 806 to 821 iDEN 800MHz Extended 5 865 to 869 821 to 825

Cellular A″ 1 869 to 870 824 to 825 Cellular A 10 870 to 880 825 to 835 Cellular B 10 880 to 890 835 to 845 Cellular A′ 1.5 890 to 891.5 845 to 846.5 Cellular B′ 2.5 891.5 to 894 846.5 to 849

iDEN 900MHz 5 935 to 940 896 to 901 Table 28: Cellular and iDEN Operating Frequencies

From the table the other key relationships are:

The extended Cellular B receive band (B′) is separated from the iDEN 800 MHz transmit band by 2 MHz. This results in receiver degradation, typically due to sideband noise emissions and IM, at the cellular BTS.

The extended Cellular B transmit band (B′) is separated from the iDEN 900 MHz receive band by 2 MHz. This results in receiver degradation, typically due to sideband noise emissions and IM, at the iDEN EBTS.



NOTE: The GEN4 duplexer incorporates a notch filter to reduce iDEN transmitter sideband emissions into the Cellular B band by 50dB, however additional filtering may be required in some cases.

Capacity Planning The goal of capacity planning is to determine the appropriate resources to serve a given load. As such, this section provides an introduction to the planning of radio channel resources at the EBTS, to meet specific traffic requirements.

Call Model The call model, also known as a traffic profile or traffic model, uses average values for key events to describe average busy hour subscriber traffic on a system. This information allows the configuration and system design teams to correctly size the Fixed Network Equipment (FNE) and the associated links.

There are multiple subscriber traffic groups that contribute, as follows:

! Dispatch only subscribers

! Interconnect only subscribers

! Multi-service subscribers, i.e. interconnect and dispatch capable.

! Split 3:1 (AMBE++) Capable SUs

NOTE: Packet Data usage may also be an input, however it is common to assume a nominal minimum packet channel size, e.g. the i12 equivalent of a 3:1 channel.

The following are definitions of the various fields that make up the call model:

Item Definition Dispatch Call Rate The average number attempts per dispatch capable subscriber during the busy

hour. Dispatch Hold Time The average call duration, in seconds, typically for the busy hour. The duration

includes dispatch hang time. Dispatch Illuminations

The average number of servers used in the dispatch calls.

Dispatch Erlangs per Call

The average number of Erlangs used by a dispatch capable subscriber in the busy hour. This value is calculated as follows: ((Dispatch Call Rate * Dispatch Hold Time) * Dispatch Illuminations) / 3600 seconds

Interconnect Call Rate The average number of call attempts per interconnect capable subscriber in the busy hour. Mobile originated and mobile terminated call attempts are counted separately.

Interconnect Hold The average call duration, in seconds in the busy hour.


Motorola General Business Information iDEN Technical Publications White Paper Item Definition

Time Interconnect Illuminations

This is defined always as one.

Interconnect Erlangs per Call

The average number of Erlangs used by an interconnect capable subscriber in the busy hour. This value is calculated as follows: (Interconnect Call Rate * Interconnect Hold Time) / 3600 seconds

Table 29: Call Model Definitions

Traffic Distribution For budgetary system designs, it is typically assumed that the projected subscriber base will be evenly distributed across the network since the exact nature of the subscriber distribution is not known. In reality the traffic/subscriber distribution is not uniform hence EBTS capacity needs to be determined based on actual requirements or market demographics. Knowing the subscriber distribution, especially for each service, will enable the network operator to correctly equip cells with sufficient resources to accommodate the expected traffic load.

If one wishes to account for non-uniform traffic distribution, the 80/20 �rule of thumb� may be applied to the percentage of the traffic carried by a given percentage of sites. In most systems, a large number of sites are deployed for coverage rather than capacity purposes. However, a low significance may be assigned to these coverage sites for capacity planning purposes.

NOTE: One can assume that 80% of the traffic is served by 60% of the sites.

Assumptions may also be made as to the EBTS configuration mix deployed and the type of services for which subscribers provisioned and capable of. Suggested values for these metrics are showing in the following tables:

EBTS Configuration Percentage of Total Omni 15%

2-Sector / Highway 10% 3-Sector 75%

Table 30: EBTS Configuration Mix

Service Type Subscriber/Call Mix Dispatch Only Subscribers 5%

Interconnect Only Subscribers 5% Multi-Service Subscribers 90%

AMBE++ Interconnect Capable (SR10.5) Market Dependent Table 31: Typical Subscriber Service Percentages


Motorola General Business Information iDEN Technical Publications White Paper Traffic Mix

The split in traffic between dispatch and interconnect services must be identified. For many markets 60% to 70% of the carried Erlangs are from Interconnect service, as such if the service traffic mix is unknown, a 65% Interconnect to 35% Dispatch mix is suggested.

For an existing system, statistics may be used to determine Dispatch usage and corresponding Interconnect traffic demands. This relationship can be used to determine the split of RF resources between Interconnect and Dispatch services.

The formula to calculate the Dispatch traffic percentage is expressed as follows:

D = Dispatch Erlangs / (Dispatch Erlangs + Interconnect Erlangs)

Equation 4: Estimated Dispatch Traffic Percentage

Where:

• Dispatch Erlangs = dis_i6_tch_c_secs / 360,0004

• Interconnect Erlangs = (i3_tch_c_secs + tel_i6_tch_c_secs + s3_tch_c_secs) /360,000

Alternatively, if one wishes to calculate the ratio of servers, the following formula may be used:

D = Dispatch Servers / (Dispatch Servers + (NBR*6 - C – (i12PCH / 2) - Dispatch Servers) / 2)

Equation 5: Estimated Dispatch Server Percentage

Where:

• Dispatch Servers = ErlangCtrunk (dis_i6_tch_c_secs / 360,000, 5% GOS5)

NOTE: It should be noted that percentage of Dispatch Erlangs and the percentage of Dispatch Servers will not be the same since fraction servers cannot be allocated.

In all cases, it is recommended that the statistical data points selected are representative of typical traffic patterns. In this regard, taking an average of the peak dispatch demand over multiple weeks is a common methodology employed. However, the traffic mix obtained from PM statistics is itself an average and within that time period the actual traffic mix will vary. This variance may result in a greater demand than assumed; as such a traffic mix range may be more appropriate. 4 360,000 is the number of centiseconds in 1 hour. If one is using 30minute PM statistics the denominator should be changed to 180,000 5 5% GOS for Erlang C is the standard blocking clear rate planning rule for Dispatch services. Lower values, such as 4%, may be used with the understanding that a lower GOS requires a larger server pool for a given traffic demand.


Motorola General Business Information iDEN Technical Publications White Paper Capacity Rules For this document, we are concerned with the capacity of the EBTS rather than other network elements. The following table highlights the number of carriers that may be equipped, based upon the site controller version.

Hybrid Combining RFDS (GEN4) Cavity Combining RFDS ACG Platform Omni Sector Site Site

iSCII 20 20 24 20 iSCIII 20 20 36 20

Table 32: EBTS Carrier Capacity Rules

Primary / Secondary Control Channels

Each cell must have a PCCH, on a Band 1 (standard 800 MHz) frequency, which is typically configured as a 6:1 interleave when more than two carriers are equipped. Additionally, up to 4 Secondary Control Channels (SCCH) may be equipped per cell as required.

! The PCCH comprises the Broadcast (BCCH), the Common/Paging (CCCH) and the Random Access (RACH) control channels.

! An SCCH has Common/Paging (CCCH) and the Random Access (RACH) control channels. The number of SCCHs is dependent upon the volume of control channel traffic. Typically, a cell will require at least 1 SCCH when traffic demands are greater than 8 carriers.

! The P/SCCH may be interleaved as either 12:1 or 6:1 depending upon the number of BRs equipped within the cell.

Dedicated Control Channels

DCCHs are used for Interconnect call setup; Interconnect location updates, SMS pages, VMS notifications and initial registration. The number of DCCH required will impact the number of available traffic channels at any given time. The goal is to provide a balance between control and traffic channel capacity. The DCA algorithm performs this task; however it is limited by the correct parameter settings, which will vary depending upon the traffic mix.


Motorola General Business Information iDEN Technical Publications White Paper The following table highlights the relationship between potential 6:1 slots and DCCH requirements. Note that the minimum DCCH (min12) values have been determined from simulation results.

6:1 Slots (TCH)

Number of Carriers

Minimum DCCH

Total 6:1 Slots

Number of Carriers

Minimum DCCH

<= 6 1 1 <= 42 7 4 <=12 2 1 <= 48 8 4 <= 18 3 2 <= 54 9 6 <= 24 4 2 <= 60 10 6 <= 30 5 4 <= 66 11 8 <= 36 6 4 <= 72 12 8

Table 33: DCCH Allocation

Please refer to the most current version of iDEN white paper WP2001-20: DCA Optimization for further details.

Packet Channel

Packet channel (PCH) resources are initially defined by a minimum PCH bandwidth allocation (TPMS) per cell. This typically equates to an I3 equivalent channel being reserved for the PCH, however an entire carrier or multiple carriers may be reserved on sites depending on demand. It is recommended to start with the default allocation and monitor PCH performance metrics (reference the most current version of WP2003-011) to determine when additional bandwidth is required.

For Multiple Packet Channels and WiDEN, it is typically assumed that the minimum packet channel size would be greater than a single 25 kHz carrier, i.e. the Legacy PCH limit. Depending upon the implementation of MPCH and WiDEN the packet channel may be a fixed size. Please refer to PRO-FID-020 and PRO-FID-078 for more details on these features.

RF Congestion Relief

The RF Congestion Relief feature, introduced in SR9.8, provides RF capacity improvements where sufficient (> 20%) cell coverage overlap is provided. To account for capacity uplift, when dimensioning cell resources, the following table can be referenced:

Environment Typical RF Congestion Relief Uplift Rural 0-5%

Suburban 10-15% Urban 15-20%

Dense Urban 20-25%+ Table 34: RF Congestion Relief Capacity Gains

These gains are translated to a reduction of call setup blocking over what can be calculated with Erlang lookup tables due to averaging within the busy hour, i.e. a given load is supported by fewer servers at a given GOS.


Motorola General Business Information iDEN Technical Publications White Paper Split 3:1 Channels The SR10.5 New 6:1 Interconnect Services feature offers improved RF capacity through the use of Split 3:1 channels utilizing a 4400bps AMBE+2 vocoder. It is important not to confuse the feature name (New 6:1) with the interleave type. A Split 3:1 channel is literally the division of an existing 3:1 channel interleave into two sub-slots thus maintaining an acceptable delay. This is not the same as the original (old) VSELP 6:1 Interconnect.

The Split 3:1 Channel concept is presented in the following diagram:

Figure 20: Split 3:1 Channels

As the penetration of Split 3:1 capable subscriber units increase, so allocation of RF resources will become more efficient and closer to the capacity offered by a true 6:1 interleave. However, this is not a linear relationship but the capacity improvement may be estimated, as follows:

i3RES = (((NBR * 6) – (i12PCH / 2) - C) / ((2 – Split %) + (D / (1-D)))

Equation 6: Interconnect Servers at Traffic Mix (i3RES) with Split 3:1

Where:

i3RES = Number of offered 3:1 Interconnect servers at traffic mix

NBR = Base Radio (BR) / Carrier count, whichever is larger.

i12PCH = Maximum i12 resources available to packet data service. Depending upon the deployment of packet data this could be the configured TPMS (Total Packet Channel Minimum Size) or the maximum packet channel size.

C = i6 servers required for Control Channels (P/SCCH, DCCH)

This may be estimated as 10% of available i6 servers: C = (NBR * 6) * 0.1

D = Dispatch Server Mix. Reference Equation 5.


Motorola General Business Information iDEN Technical Publications White Paper Impact of the FNE “Split 3:1 Preferred” Algorithm on Channel Assignments

SR11 introduces the �3:1 Preferred�6 algorithm within the ACG, which provides the option to limit the allocation of Split 3:1 channels, for subscribers with a Bearer Capability setting of �3:1 ONLY�, to times when the cell reaches a defined capacity level. A Split 3:1 capable SU with a Bearer Capability setting of �3:1 Preferred� will always be assigned its primary interleave, i.e. a Split 3:1 channel. If the primary interleave is unavailable a secondary interleave will be offered. This will be a VSELP 6:1 interleaved channel.

The algorithm utilizes the existing methodology within RF Congestion Relief to determine the available cell capacity as follows:

available_ic_capacity = number of unassigned I3 channels on non - PCH carriers using primary band + the number of I3 channels in holdbacks on PCH carriers � I3 channels used to satisfy I6 and I12 minimums

The ACG will use a new factory tunable parameter, splitThreshold, as a defined offset to the RF Congestion Relief (CR) threshold to determine when to start allocating Split 3:1 call requests Split 3:1 channels rather than Full 3:1 channels.

The following check is made by the ACG when a Split 3:1 call request is received, assuming that the SU is set for 3:1 Only:

• If the available_ic_capacity <= (crThreshold + splitThreshold) assign Split 3:1 channel

• If channel not available, queue for Split 3:1 channel

• Else assign full 3:1 channel

6 The 3:1 Preferred feature referenced is at the ACG level and should not be confused with the 3:1 Preferred setting in the SU, which allows a the FNE to allocate a Full 6:1 channel interleave if a Full 3:1 is not available.


Motorola General Business Information iDEN Technical Publications White Paper The result is that a variable percentage of Split 3:1 call requests will be served by Full 3:1 channels. This will be a function of cell parameters, loading and the mix of interconnect to dispatch. The following chart provides simulation data for a 65/35 traffic mix with 25% Split 3:1 penetration:

% Split 3:1 Calls assigned to Full 3:1

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

99 3 2 1 0

Split 3:1 Threshold

% s

plit

3:1

calls

ass

igne

d to

full

3:1

low traffic load

moderate traffic load

2% blocking

Figure 21: Percent of Split 3:1 Calls Assign Full 3:1 Channels

If one assumes a splitThreshold of zero and 2% blocking, simulations show that approximately 50% of all Split 3:1 call requests will be served by Full 3:1 channel interleaves. As can be seen, as the blocking level decreased, the number of requests served by Full 3:1 channels increases.

The following chart highlights the impact this scenario would have on the capacity gain offered by Split 3:1.

Split 3:1 Capacity Gain (Erlangs)Typical 18 BR Site (6 BRs per Cell)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Split 3:1 Penetration

Perc

ent G

ain

Split 3:1 Gain Split 3:1 Gain w / splitThreshold=0 Split 3:1 Gain w / splitThreshold=1

Figure 22: Split 3:1 Erlang Gain with 3:1 Preferred


Motorola General Business Information iDEN Technical Publications White Paper Once can see that as the SplitThreshold parameter is increased fewer calls are assigned Split 3:1 channels.

The following table provides a summary of simulation results for different threshold settings and penetration rates.

Penetration Rate 10% 25% 50% splitThreshold=1 50% 46% 44% splitThreshold=2 33% 32% 29% splitThreshold=3 20% 20% 17% splitThreshold=4 13% 11% 8%

Table 35: Percentage of Calls Assigned Full 3:1

Determining Cell Resources for a Given Traffic Load With any RF/EBTS capacity planning exercise, the traffic load in Erlangs needs to be provided or calculated. There are a number of ways to calculate the required resources per cell, for a given traffic load, based upon initial information.

Calculating Erlangs from a Call Model

Given a call model, the following formula may be used to determine the Erlangs per subscriber: or per call:

Erlangs per Subscriber/Call = (Call Hold Time * BHCA * Illumination) / 3600

Equation 7: Converting a Call Model to Erlangs

A call model may also be presented as Minutes of Use (MOU) per service per month. This is translated to Erlangs based on a predefined number of days of use per month and the percentage of the daily traffic expected in the busy hour, as follows:

Erlangs per Subscriber/Call = ((MOU / 25.6 days per month) * 8% of traffic in busy hour) / 60

Equation 8: Converting Minutes of Use to Erlangs


Motorola General Business Information iDEN Technical Publications White Paper The following table presents an example Interconnect and Dispatch busy hour call model.

Interconnect Dispatch Busy Hour Call Attempts 0.85 0.6 Call Hold Time (seconds) 110 35 Cell Illumination (number of cells) 1 2.057

Resultant Erlangs per Subscriber/Call 0.0260 0.0120 OR

Minutes of Use per Month 500 230 Resultant Erlangs per Subscriber/Call 0.0260 0.0120

Table 36: Example Call Model

Calculating Required Traffic Channels from Erlangs

In order to calculate the required TCH resources for a cell, the total Erlangs for the cell must be defined. This would require knowledge of the call volume or subscriber count per cell. It is also necessary to define the blocking rate / Grade of Service (GOS) and appropriate Erlang lookup tables to be used.

Service G.O.S. Erlang Table Interconnect 2% B

Dispatch 5% C Table 37: Standard Grade of Service Assumptions

From this information the number of traffic channels (TCH) may be determined, via Erlang lookup tables, separately for Interconnect and Dispatch services.

Interconnect Servers The following equation presents the standard method of calculating Interconnect servers:

ICi3servers = ErlangBtrunk (Interconnect Erlangs per Cell, 2% GOS)

Equation 9: Erlang B Lookup to Determine Interconnect TCH

NOTE: Erlang B assumes that blocked calls are cleared, however Interconnect call attempts can be queued for a maximum of 10 seconds on a DCCH. Due to the short queue time the use of Erlang C, is not warranted. The use of Engset is an alternative.

7 The dispatch cell illumination factor is a combination of private and group calls. As group calls increase the cell illumination factor will increase from the minimum of 2.


Motorola General Business Information iDEN Technical Publications White Paper By way of an example, one can determine the required server pool (ICi3servers), using Equation 9, assuming that a cell must carry, say, 10 Erlangs of Interconnect traffic. Here, an Erlang B lookup on 10 Erlangs at 2% GOS would offer 16.48 servers. Obviously, one must round to a whole integer so let�s say 17 * I3 interleaves are required. A key point is that I3 interleaves require two RF timeslots, as such 17 * i3 servers equates to 34 RF timeslots, or 5.5 BRs.

The introduction of the Split 3:1 channel format with New 6:1 Interconnect subscribers will result in an added layer of complexity with the capacity planning process. For SR10.5 systems, with New 6:1 enabled, a simplistic approach to adjusting EBTS resources is to assume that the required number of Interconnect TCHs is reduced by the percentage of Split 3:1 channel assignments, as follows:

Adjusted_ICi3servers = ICi3servers * (1 – (Split3:1%/2))

Equation 10: Adjusting Interconnect Servers for Split 3:1 Channel Usage

Using the previous example, one may adjust the 16.48 servers to determine the actual number of TCHs required for a given penetration. Remember that a Split 3:1 channel requires an I3 interleave, or an open sub-slot on a previously split 3:1 interleave. A common error is to assume a 6:1 interleave because the feature name is �New 6:1 Interconnect Services�. The �New 6:1� simply refers to the bandwidth required for a single call, not the physical channel requirements.

Assuming that the Split 3:1 call volume is 25% of the total one can use Equation 10: Adjusting Interconnect Servers for Split 3:1 Channel Usage as follows:

Adjusted TCH = 16.48 * (1 � 25%/2) = 14.42 servers

Rounded up, this comes to 15 * I3 interleaves or 30 RF timeslots / 4.95 BRs.

Dispatch Servers Dispatch servers are i6 interleaves and present significantly less confusion that Interconnect, with the exception of �old� VSELP 6:1. The server calculation is as follows:

Di6servers = ErlangCtrunk (Dispatch Erlangs per Cell, 5% GOS)

Equation 11: Erlang C Lookup to Determine Dispatch TCH

NOTE: The Erlang C table determines resources based on blocked calls being queued, rather than cleared. The FNE could queue dispatch call requests for an infinite time, however the default queue time implemented is actually 35 seconds.


Motorola General Business Information iDEN Technical Publications White Paper To illustrate the use of Equation 11: Erlang C Lookup to Determine Dispatch TCH one can again use a simple example:

Assume that a cell must carry a total of 5 dispatch Erlangs, an Erlang C lookup at 5% GOS would offer 9.45 servers, rounded up to 10. Note that one i6 dispatch server requires a single RF timeslot, thus 10 timeslots equates to 1.6 BRs.

Base Radios The number of BRs required is dependent upon the Interconnect and Dispatch server requirements as well as the BR type deployed. It becomes much simpler to think in terms of 25 kHz carriers and then worry about BRs counts later.

The number of 25 kHz carriers required may be expressed as follows:

NumCarriers = (((i12PCH / 2) + ((Adjusted_ICi3servers * 2) + Dservers) / 0.9) / 6

Equation 12: Interconnect and Dispatch RF Carrier Requirements

Here it is assumed that 10% overhead is required for control channels, i.e. P/SCCH and DCCH. The i12PCH will equate to the TPMS parameter setting for busy hour calculations.



Revision History Version Date Author Description

1.0 4/7/03 John Critchley Original issue

2.0 06/04/04 John Critchley Periodic Update.

Capacity planning notes for Split 3:1 channels used by the SR10.5 �New 6:1 Interconnect Services� feature.

Notes on SR11 ACG 3:1 Preferred Algorithm.



Contact Information For assistance please contact your Motorola Regional Customer Network Resolution Center (CNRC) at:

iDEN/Harmony Products:

US/Canada

+1-800-499-6477

International

Brazil: +0-800-891-5895 Mexico: +001-800-499-6477 Peru: +0-800-52-121 Colombia: +01-800-700-1614 Argentina: +0-800-666-1559 China: +10-800-130-0617 Singapore: +800-1301-285 Philippines: +1-800-1-116-0119 Korea: +00-308-13-1358 All other International locations: +1-847-761-7149

World-wide Web Additional information can be found at:

iDEN:

https://mynetworksupport.motorola.com/


https://mynetworksupport.motorola.com/

MOTOROLA and the Stylized M logo are registered in the U.S. Patent and Trademark Office. All other product or service names are the property of their respective owners © Motorola, Inc. 2004.

September 15, 2004

Documents

Link Budgeting - Motorola White Paper