Upload
ankurinfo
View
48
Download
4
Embed Size (px)
Citation preview
GPRS/EDGE FUNDAMENTALS
Prepared by Naveen Bhartiya 1
BSC
GGSN
IP/MPLS/IPoATM -
Applicatio
n Servers
(co -
located
2G
SGSN BTS
HLR/ AC/ EIR
TCSM
TC
MSC/VLR
Abis Gb BSC BSC
GGSN GGSN
- backbone
Application Servers
2G
SGSN
2G
SGSN BTS
HLR/ AC/ EIR
HLR/ AC/ EIR
TCSM
TC
MSC/VLR
Gn Gi
Gs
RF interface
• Coverage
•C/I
• Capacity
• Traffic volume
• Mobility
MS/Client parameters
• GPRS/EDGE capability and release
•Multislot support
Abis interface
• EDAP size / dimensioning
• # of E1/T1s
• GPRS/EDGE traffic
Gb interface
• Bearer size
• IP v.s. FR
• Dimensioning
BTS
• GPRS territory
• BTS HW considerations (TRX & BB-card)
• BTS SW (EPCR)
BSS
• PCU variant & dimensioning
• PCU strategy in mixed configuration
• BSS SW and features
SGSN
• Unit capacity (PAPU etc.)
• BSS Gb Flow control
RF
Server
• load
• settings (Linux/Win)
HLR
• QoS profile
• GPRS settings
(E)GPRS Optimization – Network Element and Configuration Assessment
2 Prepared by Naveen Bhartiya
General Packet Radio Service (GPRS) & Enhanced data rate for GPRS evolution(EDGE)
• GPRS uses a packet-mode technique to transfer high-speed and low-speed data and signaling in an efficient manner.
• GPRS optimizes the use of network and radio resources
• GPRS is designed to support from intermittent and bursty data transfers through to occasional transmission of large volumes of data.
• GPRS uses GMSK Modulation Scheme.
Prepared by Naveen Bhartiya 3
• Enhanced Data rates for GSM Evolution (EDGE) (also known as Enhanced GPRS (EGPRS) is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM.
• EDGE is the radio technology that allows operators to increase both data speeds and throughout capacity 3 times over GPRS.
• EDGE uses both GMSK and 8-PSK Modulation Scheme.
• EDGE produces a 3-bit word for every change in carrier phase. This effectively triples the gross data rate offered by GSM. EDGE. like GPRS uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel. and thus the bit rate and robustness of data transmission.
Prepared by Naveen Bhartiya 4
DEVICES
Class –A - Operates GPRS and other GSM services simultaneously. Class – B - Monitors control channels for GPRS and other GSM services simultaneously. but operates one set of services at a time. Class – C - Are connected to either GPRS service or GSM service. Must be switched manually between one or the other service.
GPRS Mobile Station(MS) modes of operation
Prepared by Naveen Bhartiya 5
Multislot Class Downlink TS Uplink TS Active TS
1 1 1 2
2 2 1 3
3 2 2 3
4 3 1 4
5 2 2 4
6 3 2 4
7 3 3 4
8 4 1 5
9 3 2 5
10 4 2 5
11 4 3 5
12 4 4 5
30 5 1 6
31 5 2 6
32 5 3 6
33 5 4 6
34 5 5 6
Multislot Classes for GPRS/EGPRS
• The multislot class determines the speed of data transfer available in the Uplink and Downlink directions. • A multislot allocation is represented as. for example. 5+2. The first number is the number of downlink timeslots and the second is the number of uplink timeslots allocated for use by the mobile station. • A commonly used value is class 10 for many GPRS/EGPRS mobiles which uses a maximum of 4 timeslots in downlink direction and 2 timeslots in uplink direction. However simultaneously a maximum number of 5 simultaneous timeslots can be used in both uplink and downlink. The network will automatically configure the for either 3+2 or 4+1 operation depending on the nature of data transfer.
Under the best reception conditions. i.e. when the best EDGE modulation and coding scheme can be used. 5
timeslots can carry a bandwidth of 5*59.2 Kbit/s = 296 Kbit/s. In uplink direction. 3 timeslots can carry a bandwidth of 3*59.2 Kbit/s = 177.6 Kbit/s.
Prepared by Naveen Bhartiya 6
Prepared by Naveen Bhartiya 7
RF
Modulation schemes in GPRS/EDGE
• GPRS system is using GMSK (Gaussian Minimum Shift Keying). a constant-envelope modulation scheme. The advantage of the constant envelope modulation is that it allows the transmitter power amplifiers to be operated in a non-linear (saturated) mode. offering high power efficiency. The saturation means that even if the input signal level is increased. no increment will be seen in the output power. as shown.
• 8-PSK. in the form used in EDGE. has a varying envelope. see the lower part. It means that the amplifier must be operated in the linear region in case of 8-PSK since distortion is to be avoided.(There is an additional 22.5 deg rotation to avoid zero crossing.)
Prepared by Naveen Bhartiya 8
Modulation schemes in GPRS/EDGE
• In GMSK each bit is represented by one symbol. • In 8-PSK transmitted symbols are one of the eight sinusoids which have same amplitude and phase but differ in phase. The digital data are combined in group of 3 Bits. Thus there are 8 possible combinations starting from (0.0.0) to (1.1.1). • Each of the 3-bit patterns is then matched to one of 8-PSK Symbols. The Mapping is done in such way that there is a single bit difference between adjacent symbols. It ensures that if a symbol is received in error as an adjacent symbol only one of the bits will be in error.
(0,0,1)
(1,0,1)
(d(3k),d(3k+1),d(3k+2))=
(0,0,0) (0,1,0)
(0,1,1)
(1,1,1)
(1,1,0)
(1,0,0)
• 8-PSK (Phase Shift Keying) has been selected as the new modulation added in EGPRS
• 3 bits per symbol
• 22.5° offset to avoid origin crossing (called 3/8-8-PSK)
• Symbol rate and burst length identical to those of GMSK
• Non-constant envelope high requirements for linearity of the power amplifier
Prepared by Naveen Bhartiya 9
Coding schemes in GPRS
• GPRS provides four coding schemes: CS-1. CS-2 .CS-3. CS-4.
CS - 1 CS - 2 CS - 3 CS - 4
Increasing data throughput rates
Increasing protection against errors
Coding Scheme
Payload (bits) per RLC block
Data Rate (kbit/s)
CS1 181 9.05
CS2 268 13.4
CS3 312 15.6
CS4 428 21.4
Nokia GPRS PCU
Nokia GPRS PCU2
Dat
a
Erro
r C
orr
ecti
on
More Data =
Less Error Correction
• CS1 & CS2 – Implemented in all Nokia BTS without HW change
• CS1 & CS4 – S11.5 (with PCU2) and UltraSite BTS SW CX4.1 CD1 (Talk does not support CS3 and CS4)
Prepared by Naveen Bhartiya 10
CS-1 CS-2 CS-3
57 57 57 57 57 57 57 57
456 bits
MAC
USF BCS +4
puncturing
rate a/b convolutional coding
CS-1 CS-2 CS-3 RLC/MAC Block Size: 181 268 312 Block Check Sequence: 40 16 16 Precoded USF: 3 6 6 1/2 ~2/3 ~3/4 length: 456 588 676 0 132 220 Data rate (kbit/s): 9.05 13.4 15.6
interleaving
MAC
USF BCS
RLC/MAC Block Size: 428 BCS Size: 16 Precoded USF: 12 Data rate (Kbit/s): 21.4
CS-4
20 ms
Coding schemes in GPRS
Prepared by Naveen Bhartiya 11
Coding schemes in EDGE
DOCUMENTTYPE 1 (1)
TypeUnitOrDepartmentHere TypeYourNameHere TypeDateHere
Scheme Code rate Header Code rate
Modulation RLC blocks per Radio
Block (20ms)
Raw Data within one Radio Block
Family BCS Tail payloa
d
HCS Data rate kbit/s
MCS-9 1.0 0.36
8PSK
2 2x592 A 2x12 2x6
8
59.2
MCS-8 0.92 0.36 8PSK 2 2x544 A 54.4
MCS-7 0.76 0.36 2 2x448 B 44.8
MCS-6 0.49 1/3 1 592 A
12
6
29.6
MCS-5 0.37 1/3 1 448 B 22.4
MCS-4 1.0 0.53
GMSK
1 352 C 17.6
MCS-3 0.80 0.53 1 296
A 14.8
MCS-2 0.66 0.53 1 224 B 11.2
MCS-1 0.53 0.53 1 176 C 8.8
• EDGE provides nine coding schemes: MCS-1 till MCS-9.
Prepared by Naveen Bhartiya 12
Coding scheme
CS-1
CS-2
CS-3
CS-4
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
Bit rate (Kbps)
9.05
13.4
15.6
21.4
8.8
11.2
14.8
17.6
22.4
29.6
44.8
54.4
59.2
Abis PCM allocation (fixed + pool/slave)
GPRS and EDGE
EDGE
• Higher data rates don’t fit in 16 Kbit/s channels
• GPRS CS-2 requires 1 slave when EDGE activated (TRX/BTS)
• 32. 48. 64 or 80 Kbit/s Abis links per RTSL needed
Retrans.
EDGE and GPRS – Master / Slave Channel Usage
13 Prepared by Naveen Bhartiya
The LA algorithm measures the signal quality for each TBF in terms of the received signal quality (RXQUAL). RXQUAL is measured for each received RLC block. which makes it a more accurate estimate than BLER. The PCU determines the average BLER value separately for each BTS by continuously collecting statistics from all the connections in the territory in question. Based on the estimates. the LA algorithm determines which coding scheme will give the best performance. The new LA algorithm can be used in both RLC acknowledged and un-acknowledged modes in both uplink and downlink direction. Link Adaptation algorithm for PCU1 The GPRS Link Adaptation (LA) algorithm selects the optimum channel coding scheme (CS-1 or CS-2) for a particular RLC connection and is based on detecting the occurred RLC block errors and calculating the block error rate (BLER). Link Adaptation algorithm for PCU2 A new Link Adaptation algorithm is introduced with PCU2. which replaces the previous GPRS LA algorithm and covers the following coding schemes: • CS-1 and CS-2 if CS-3 and CS-4 support is disabled in the territory in question • CS-1. CS-2. CS-3. and CS-4 if CS-3 and CS-4 support is enabled in the territory .
GPRS Link Adaptation
14 Prepared by Naveen Bhartiya
The task of the LA algorithm is to select the optimal MCS for each radio condition to maximize RLC/MAC data rate. so the LA algorithm is used to adapt to situations where signal strength and or C/I level is low and changing slowly with time. Ideal LA would follow the envelope of the throughput of different MCSs. The PCU selects the data block and additionally selects the MCS depending on radio link quality and amount of available dynamic Abis channels. LA is done independently for each UL and DL TBF on RLC/MAC block level. but the LA algorithm is same for uplink and downlink . The MCS selection is not the same in case of initial transmission and retransmission. LA algorithm works differently for RLC acknowledged mode and unacknowledged mode. -In Acknowledged mode. the algorithm is designed to optimize channel throughput in different radio conditions. -In Unacknowledged mode. the algorithm tries to keep below a specified Block Error Rate (BLER) limit.
EGPRS Link Adaptation
15 Prepared by Naveen Bhartiya
Prepared by Naveen Bhartiya 16
Logical Channels
Prepared by Naveen Bhartiya 17
Logical Channels
Common Control channel(CCH) are bidirectional , point-to multipoint ,signaling channels that are used to establish dedicated channels. Packet Broadcast control channel (PBCCH): is a downlink-only channel for broadcasting packet data (GPRS) specific system information messages to all GPRS enabled MS in cell. Packet paging channel(PPCH) : is a downlink only paging channel used to page the MS prior to downlink packet transfer. Packet access grant channel(PAGCH) : is a downlink only channel used for resource assignment during the packet transfer establishment phase. Packet random access channel(PRACH) : is an uplink only channel , which MS uses for uplink traffic channel request and for obtaining the Timing advance. Packet data traffic channel(PDTCH) is reserved for GPRS packet data transfer. Packet associated control channel(PACCH) : is a bi-directional signaling channel dedicated for a certain MS . Packet timing advance control channel(PTCCH) : is used in uplink direction for the transmission of random access bursts to estimate the timing advance for one mobile
Temporary Block Flow (TBF): • Physical connection where multiple mobile stations can share one or more traffic channels – each
MS has own TFI • The traffic channel is dedicated to one mobile station at a time (one mobile station is transmitting
or receiving at a time) • Is a one-way session for packet data transfer between MS and BSC (PCU) • Uses either uplink or downlink but not both (except for associated signaling) • Can use one or more TSLs Comparison with circuit-switched: • normally one connection uses both the uplink and the downlink timeslot(s) for traffic In two-way data transfer: • uplink and downlink data are sent in separate TBFs - as below
BSC
Uplink TBF (+ PACCH for downlink TBF)
Downlink TBF (+ PACCH for uplink TBF)
PACCH (Packet Associated Control Channel): Similar to GSM CSW SACCH
Temporary Block Flow
Prepared by Naveen Bhartiya
Prepared by Naveen Bhartiya
Timeslot sharing by TBF
• Territory method is used to divide the CS and PS resources
– Timeslots within a cell are dynamically divided into the CS and (E)GPRS territories.
– Number of consecutive traffic timeslots in (E)GPRS territory are reserved (or initially available) for (E)GPRS traffic. the remaining timeslots are available for GSM voice .
– The dynamic variation of the territory boundary are controlled by territory parameters.
– The system is able to adapt to different load levels and traffic proportions. offering an optimized performance under a variety of load conditions.
– The PS territory can contain dedicated. default and additional capacity
• Dedicated capacity: number of timeslots are allocated to (E)GPRS on a permanent basis i.e. are always configured for (E)GPRS and cannot be used by the circuit switched traffic. This ensures that the (E)GPRS capacity is always available in a cell
• Default capacity: the (E)GPRS territory is an area that always is included in the instantaneous (E)GPRS territory. provided that the current CS traffic levels permit this
• Additional capacity= Additional (E)GPRS capacity means the extra time slots beyond the default capacity which are assigned due to a load demand.
(E)GPRS Resource Allocation
20 Prepared by Naveen Bhartiya
TRX 1
TRX 2
BCCH SD TS TS TS TS TS TS
TS TS TS TS TS TS TS TS
Circuit Switched Territory
Packet Switched Territory
Territory border moves based on Circuit Switched and GPRS traffic load
Default GPRS Capacity
CDEF Dedicated GPRS Capacity
CDED
TS TS
Additional GPRS territory
TS TS
Max GPRS
CapacityCMAX
Territory Method in (E)GPRS
21 Prepared by Naveen Bhartiya
TRX 1
TRX 2
= (E)GPRS Territory = CSW Territory
Case 1:
- Many (E)GPRS users
- Low CS traffic
TRX 1
TRX 2
Case 2:
- High CS traffic
- (E)GPRS user have
to take the ‘rest’
TRX 1
TRX 2
Case 3:
- No (E)GPRS user
- Zero CS traffic Default capacity
Dedicated capacity
Territory Method Load Examples
22 Prepared by Naveen Bhartiya
One 64 kbit/s (8 bits) channel in PCM frame is called timeslot (TSL)
One 16 kbit/s (2bits) channel timeslot is Sub-TSL PCM frame has 32 (E1) or 26 (E1) TSLs
One Radio timeslot corresponds one 16 kbit/s Sub-TSL (BCCH. TCH/F etc.) and one TRX takes two TSLs from Abis
0 MCB LCB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18 TCH 0 TCH 1 TCH 2 TCH 3
19 TCH 4 TCH 5 TCH 6 TCH 7
20
21
22
23
24
25 TRXsig
26
27 BCFsig
28
29
30
31 Q1-management
One TRX has dedicated TRXsig of 16. 32 or 64 kbit/s
One BCF has dedicated BCFsig (16 or 64 kbit/s) for O&M
TRX1
Q1-management needed if TRS management under BSC
MCB/LCB required if loop topology is used
Abis
BTS BSC
Abis Basic Concepts – PCM frame (E1)
Prepared by Naveen Bhartiya
• The resources for signaling and voice are fixed.
• Dynamic Abis pool (DAP) for data
– Predefined size 1-12 PCM TSL per DAP (24 with Flexi EDGE BTS possible). Typically used range from 4 to 8 TSL.
– DAP can be shared by several TRXs in the same BCF (and same E1/T1)
– DAP + TRXsig + TCHs have to be in same PCM
– UL and DL EDAP is used independently
– DAP schedule rounds for each active Radio Block (20 ms)
– Different users/RTSLs can use same EDAP Sub-TSL
TRX1
TRX2
TRX3
EGPRS
pool
0 1 2 3 4 TCH 0 TCH 1 TCH 2 TCH 3 5 TCH 4 TCH 5 TCH 6 TCH 7 6 TCH 0 TCH 1 TCH 2 TCH 3 7 TCH 4 TCH 5 TCH 6 TCH 7 8 TCH 0 TCH 1 TCH 2 TCH 3 9 TCH 4 TCH 5 TCH 6 TCH 7
10 11 12 13 14 15 EDAP EDAP EDAP EDAP 16 EDAP EDAP EDAP EDAP 17 EDAP EDAP EDAP EDAP 18 EDAP EDAP EDAP EDAP 19 EDAP EDAP EDAP EDAP 20 EDAP EDAP EDAP EDAP 21 EDAP EDAP EDAP EDAP 22 EDAP EDAP EDAP EDAP 23 24 25 TRXsig1 TRXsig2
26 TRXsig3
27 BCFsig
28 29 30
31
(E)GPRS Dynamic Abis Pool – EDAP Introduction
Prepared by Naveen Bhartiya
Prepared by Naveen Bhartiya 25
Packet Abis means introduction of a new transport concept:
• Abis frames conveying traffic and signaling information between BTS and BSC are subject to packetization process prior to sending them to the transmission path as a result of packetization the incoming TRAU/PCU/LAPD frames are converted to new (Packet Abis specific) formats which are encapsulated and form IP packets eventually transmitted over Abis . • Bandwidth is pooled for all types of traffic (no dedicated allocation anymore) e.g. PS data traffic can utilize all bandwidth available.
Benefits of Packet Abis : • Bandwidth Savings in terms of E1 saving. • Reduction in congestion due to EDAP as bandwidth is pooled for all types of traffic. • Reduction in PCU Utilization as resource allocation are dynamic and not hardcoded. • Improvement in Latency.
Packet Abis Solution
Prepared by Naveen Bhartiya 26
BSS
• The PCU is the BSC plug-in unit that controls the (E)GPRS radio resources, receives and transmits PCU frames to the BTSs and Frame Relay (or IP packets) to the SGSN
• It handles both the Gb interface and RLC/MAC protocols in the BSS and acts as the key unit in the following procedures:
– (E)GPRS radio resource allocation and management
– (E)GPRS radio connection establishment and management
– Data transfer
– (Modulation and) Coding scheme selection
– PCU statistics
• The first generation PCUs (PCU or PCU1) are optimized to meet (E)GPRS requirements, i.e. non real time solutions (QoS classes "Background" and "Interactive“). EGPRS, NCCR, NACC are supported by both PCUs.
• The second generation PCU (PCU2) is a high capacity embedded plug-in unit that provides additional (E)GPRS processing power and extended functionality from BSS11.5 onwards. Second Generation PCUs have a new architecture.
• There are 3 PCU2 plug-in unit variants for the different NSN GSM/EDGE BSC variants:
• PCU2-U: BSCi and BSC2i
• PCU2-D: BSC3i 660, BSC3i 1000 and BSC3i 2000
• PCU2-E for BSC3i versions including the Flexi BSC
Packet Control Unit – PCU (Introduction)
27 Prepared by Naveen Bhartiya
• PCU types and capacity limits
• The relations between PCU and BSC types as well as the connectivity limits of BTSs, TRXs, TSLs, Abis and Gb TSLs are shown in the table:
PCU type PCU PCU-S PCU-T PCU-B PCU2-U PCU2-D PCU2-E**
BSCi type BSCi, BSC2i BSCi, BSC2i BSCi, BSC2i BSC3i BSC2i BSC3i BSC3i
#logical PCU per PIU 1 1 1 2 1 2 1
#Abis/BTS/TRX/RTSL/Gb per logical PCU 256 / 064 / 128 / 128 / 32* 256 / 064 / 128 / 128 / 32* 256 / 064 / 128 / 256 / 32* 256 / 064 / 128 / 256 / 32* 256 / 128 / 256 / 256 / 32* 256 / 128 / 256 / 256 / 32* 1024 / 384 / 1024 / 1024 / 128*
CPU/memory 166MHz / 128MB 200MHz / 128MB 300MHz / 256MB 300MHz / 256MB 450MHz / 256MB 450MHz / 256MB 1.33GHz / 1GB
* Maximum capacity of one FR link is 31 PCM TSL (31 x 64 kbps) in case of Gb over IP value gives the maximum processing capacity of one logical PCU (example 32 means 32 x 64kbps = 2048 kbps) * Each BCSU (Base Control Signaling Unit) can be equipped with
1-2 PCU for BSCi, BSC2i and BSC3i 660* 1-5 PCU for BSC3i 1000/2000* and Flexi BSC
Packet Control Unit (PCU) - Variants and Connectivity Limits
28 Prepared by Naveen Bhartiya
Prepared by Naveen Bhartiya 29
Packet Control Unit (PCU) Dimensioning
Consider site with 3+3+3 configuration : Dedicated TSLS(CDED) – 2+2+2 = 6 TSL Default TSLS(CDEF) – 2+2+2 = 6 TSL EDAP – 3 64 Kbps TSLS = 12 TSL 16 Kbps CMAX – 100% Considering additional 30% TSLS (((9*8)-6)*0.3) – 20 TSLS based on CMAX With 85% PCU loading and PCU2D we can have 217 TSLS Thus we can map 5 sites (44*5= 220 TSLS) in 1 NSEI or logical PCU
• With PCU2 Pooling feature the operator can easily take a new PCU PIU into use in live BSC
• PCU2 Pooling feature introduces the Packet Service Entity (PSE) concept. PSE is a logical concept, which covers several PCU PIUs in BSC. All PCUs in PSE are serving the same NSE
• When the operator adds a new PCU into PSE, the system automatically configures Gb interface to new PCU and then allocates DAPs and Segments to new PCU based on each Segment’s (E)GPRS load. The operator does not need to do any changes to the logical network configuration in BSC and either in SGSN
PCU2 Pooling – Introduction
Benefits for the customer:
• Easy way to increase (E)GPRS capacity in the network, in BSC. All PCUs are effectively in use • Savings in configuration costs (no modification to logical network configuration in the BSC and
neither in the SGSN)
• Abis and Gb resources are shared more efficiently and dynamically between PCUs in NSE
• (E)GPRS load is shared dynamically between PCUs within the PSE when the operator adds a new PCU into the PSE or reallocates PSE configuration
• Instead of configuring multiple NSEI we configured single NSEI and mapped all PCU IP’s to that NSEI
• Post PCU Pooling Gb traffic doesn't come NS-VCI wise but is generated based on PCU IP.
• The Gb interface is the interface between the BSS and the Serving GPRS Support Node (SGSN)
• It allows the exchange of signaling information and user data between one
– Packet Control Unit (PCU) or PSE (Packet Service Entity) at the BSS side and one
– Packet Processing Unit (PAPU) at the SGSN side
• Each PCU/PSE has its own separate Gb interface to the SGSN. Many users share the same physical resource. Resources are given to a user upon activity (sending/receiving)
• Signaling and user data are sent in the same transmission plane and no dedicated physical resources are required to be allocated for signaling purposes .
• Access rates per user may vary without restriction from zero data to the maximum possible line rate.
• One Gb interface can be implemented using the Frame Relay or IP.
Gb Interface - Introduction
31 Prepared by Naveen Bhartiya
Paging
UL TBF for MS location
Packet Control Ack (for TA)
Packet Polling
Packet Downlink Assignment
Data / Signalling
Ack / Nack
Packet Channel Request
Packet Paging Response (LLC Frame)
BTS
RACH
AGCH
PDTCH
PACCH
PACCH
PACCH
PCH
Immediate Assignment for UL TBF
Immediate Assignment for DL TBF AGCH
PDTCH
PACCH
PACCH
Establishing a DL TBF and Sending Data
32 Prepared by Naveen Bhartiya
TFI2
TFI5
TFI3
TFI2 BTS
The TFI included in the Downlink RLC Block header indicates which Mobile will open the RLC Block associated with its TBF
RLC Data Block
Multiple Mobiles and Downlink Transmission
33 Prepared by Naveen Bhartiya
Packet Channel Request
Immediate Assignment for UL TBF
UL Data
Signaling + Ack/Nack
Final UL Data
Final Ack/Nack
Packet control Ack
RACH
AGCH
PDTCH
PACCH
PDTCH
PACCH
PACCH
BTS
Establishing an UL TBF and Sending Data
34 Prepared by Naveen Bhartiya
• Several mobiles can share one timeslot
• Maximum of 7 Mobiles are queued in the Uplink
• Mobile transmissions controlled by USF (Uplink State Flag) sent on DL (dynamic allocation)
TS 1
TS 2
TS 3
Uplink State Flag
• Mobile with correct USF will transmit in following Uplink block
• Timeslot selected to give maximum throughput
New MS
Multiple Mobiles and Uplink Transmission
35 Prepared by Naveen Bhartiya
USF = 1
USF = 2
USF = 3
USF = 3
BTS
RLC Data Block
The USF included in the Downlink RLC Block header identifies which Mobile will transmit in the following Uplink RLC Block
Multiple Mobiles and Uplink Transmission
36 Prepared by Naveen Bhartiya
Prepared by Naveen Bhartiya 37
Packet Data Protocol stack
3G RAN Data Fundamentals
Sections:
WCDMA Overview
Architecture and Call Flow
RAN Dimensioning
Concept of LA, RA and URA
WCDMA Overview
• Multiple Access Technology for 3G is wideband CDMA (WCDMA) – All Cells Use Same Carrier Frequency
– Spreading Codes are used to separate Cells and Users
– Signal Bandwidth is 3.84 MHz
• Multiple carriers can be used to increase capacity
• Inter-System Functionality to support mobility between GSM and WCDMA
• Initial version of 3G is known as Release 99
• HSDPA in Downlink and HSUPA in Uplink are newer versions supporting higher data rates with the help of Fast Link Adaptation, Effective Power Control and Higher order Modulation and Coding Schemes.
WCDMA Benefits
Wideband CDMA is the Access Technology of UMTS. It offers some
key benefits against GSM systems.
• Soft Handover
– Make before Break Connection, unlike GSM. Provides greater reliability.
• Processing Gain
– Basic CDMA benefit => the wider the transmitted bandwidth compared to the
user data rate the less power is needed for the transmission
• Advanced Radio Resource Management (RRM)
– RRM will control call admission and packet scheduling and all RRM building
blocks are closely related to each other
• Multipath Signal Processing
– Combines power for increased signal integrity => RAKE receiver
Soft Handover Soft Handover provides greater reliability to the links. It works as follows:
• UE is simultaneously connected to 2 to 3 cells during soft handover
• Soft Handover is performed based on UE Cell Pilot Power measurements and
Handover thresholds set by radio network planning parameters.
• Soft Handover consumes both base station and transmission resources.
Concept of Spreading – The Processing Gain
CDMA uses a concept of “spreading” the actual Information signal, which can be of different
bandwidth, over a final bandwidth of 3.84 Mchips /sec. This makes it more robust and less
prone to external noise, which generally is narrow band and can affect only a portion of the
spread signal. This gain in robustness is termed as Processing Gain.
So, more the extent of spreading, less would be the actual data rate and more would be the
processing gain. Mathematically, processing gain is represented as:
Processing Gain (dB) = 10* log (W/R). where W= Final Bandwidth, which is 3.84 Mcps and
R = The actual Information Rate.
Extent of spreading depends upon the multiplication factor used to increase the bandwidth.
This is known as the spreading Factor and is explained further in the next slide
Bits, Chips and The Spreading Factor
• Spreading is done by multiplying the Baseband signal with a specific spreading
sequence. In the example about, each bit is multiplied by 8 chips to generate a
spread signal.
• So, the spreading factor of the spreading code is 8.
• At the receiver’s side, the spread signal, when multiplied with the same spreading
code results in the original signal. This is known as “De-spreading”.
Concept of Code Tree
C0(0)
=[1]
C2(1)=[1-
1]
C2(0)=[11
]
C4(0)=[11
11]
C4(1)=[11-
1-1]
C4(2)=[1-
11-1]
C4(3)=[1-1-
11]
C8(0)=[11111
111]
C8(1)=[1111-1-1-
1-1]
C8(2)=[11-1-111-
1-1]
C8(3)=[11-1-1-1-111]
C8(0)=[1-11-11-
11-1]
C8(5)=[1-11-1-11-
11]
C8(6)=[1-1-111-1-
11]
C8(7)=[1-1-11-
111-1]
C16(0)=[....
........] C16(1)=[....
........]
C16(15)=[..
.........]
C16(14)=[..
.........]
C16(13=[...
........]
C16(12)=[..
.........]
C16(11)=[.....
......]
C16(10)=[....
.......]
C16(9)=[....
........]
C16(8)=[....
........]
C16(7)=[....
........]
C16(6)=[....
........]
C16(5)=[....
........]
C16(4)=[....
........]
C16(3)=[....
........]
C16(2)=[....
........]
• Channelization Codes used to spread
information signal.
• These codes are orthogonal to each
other.
• Spreading provides gain in the form of
robustness and is known as Processing
gain
• More the spreading, less the data rate.
• Lower SF codes are used to generate
higher SF codes, which result into a
code tree.
• If a lower SF code is being used, the
codes in the branches below it are
blocked.
• Channelization codes are used to
distinguish between users. SF=1 SF=4 SF=2 SF=8…
Modulation & Coding Schemes Used
WCDMA offers 3 Modulation schemes viz. QPSK, 16 QAM and 64 QAM. It supports
adaptive modulation, meaning the modulation to be used is selected based on the
capability of the User Equipment, as well as the RF conditions that it is in. Each
Modulation has its own benefits and limitations.
QPSK:
• Known as Quadrature Phase Shift Keying
• 2 Bits per Symbol
• Can support double the data rate of BPSK with
same bandwidth
• Is more robust in nature as compared to 16 QAM
and 64 QAM Constellation
Diagram of
QPSK
Modulation & Coding Schemes Used contd..
16 QAM:
• Known as Quadrature Amplitude Modulation
• Combines Phase Shifting with Amplitude Modulation to
support more data rates.
• For example symbols 0011 and 0001 have same phase but
different amplitude. Similarly symbols 0000 and 1000 have
different phase but same amplitude.
• Provides 4 bits per Symbol
• Is not as robust as QPSK. Needs better RF conditions, i.e. a
better SNR.
64 QAM:
• Higher order Modulation using combination of PSK and
Amplitude Modulation like 16 QAM
• Provides 6 bits per symbol and hence can support quite
higher data rates.
• Needs very good RF conditions as it is more prone to errors
than 16QAM or QPSK
•Next slide provides details of theoretical Data rates in 3G
using these Modulation Schemes with different coding
rates.
Constellation
Diagram of
16QAM
3G Data Rates
Bandwidth Spreading Factor Channel Symbol Rate (Ksps) Channel Bit Rate with QPSK(kbps)
3840000 512 7.5 15
3840000 256 15 30
3840000 128 30 60
3840000 64 60 120
3840000 32 120 240
3840000 16 240 480
3840000 8 480 960
3840000 4 960 1920
Release 99:
HSDPA
Bandwidth Spreading Factor Channel Symbol Rate
(Ksps) Modulation Coding Rate Channel Bit Rate (kbps) Rate with 5 Codes(kbps)
Rate with 10 Codes(kbps)
Rate with 15 Codes(kbps)
3840000 16 240 QPSK 1/4 120 600 1200 1800
3840000 16 240 QPSK 2/4 240 1200 2400 3600
3840000 16 240 QPSK 3/4 360 1800 3600 5400
3840000 16 240 16QAM 2/4 480 2400 4800 7200
3840000 16 240 16QAM 3/4 720 3600 7200 10800
3840000 16 240 16QAM 4/4 960 4800 9600 14400
3840000 16 240 64QAM - 1440 7200 14400 21600 HSDPA +
Bandwidth Coding Rate 1xSF4 (kbps) 2xSF4(kbps) 2xSF2(kbps) 2xSF2 + 2xSF4(Mbps)
3840000 1/2 960 1920 3840 2.88
3840000 3/4 960 1920 3840 4.32
3840000 4/4 960 1920 3840 5.76
HSUPA
HSDPA UE Categories
3GPP
ReleaseCategory
Max No. of HS-
DSCH codesModulation Coding Rate
Max Data
Rate (Mbps)
Release 5 1 5 16-QAM 0.76 1.2
Release 5 2 5 16-QAM 0.76 1.2
Release 5 3 5 16-QAM 0.76 1.8
Release 5 4 5 16-QAM 0.76 1.8
Release 5 5 5 16-QAM 0.76 3.6
Release 5 6 5 16-QAM 0.76 3.6
Release 5 7 10 16-QAM 0.75 7.2
Release 5 8 10 16-QAM 0.76 7.2
Release 5 9 15 16-QAM 0.7 10.1
Release 5 10 15 16-QAM 0.97 14
Release 5 11 5 QPSK 0.76 0.9
Release 5 12 5 QPSK 0.76 1.8
Release 7 13 15 64-QAM 0.82 17.6
Release 7 14 15 64-QAM 0.98 21.1
Sections:
WCDMA Overview
Architecture and Call Flow
RAN Dimensioning
Concept of LA, RA and URA
3G Network Architecture
GSM /GPRS BSS
BTS
BSC
PCU
SS
7
SCP
SMS
SCE
PSTN/other PLMN
Internet,
Intranet
MSC/VLR GMSC
HLR/AUC
SGSN
CG BG
GGSN
PS backbone
Other PLMN
CS domain
PS domain
NodeB
RNC
UTRAN
Iu-CS
Iu-PS
A
Gb
3G System introduces some new Network Elements viz Radio Network
Controller (RNC) and Node-B. Combined together it is known as UMTS
Terrestrial Radio Access Network.
3G Call Setup Phases
Setup
Complete
Access
Complete
Active
Complete
Setup Access Active
Att
em
pts
Setup failures (blocking)
Access failures
Acce
ss
Active
Release
Active
Failures
RRC Drop
Success
Phase:
RRC and RAB phases Call Setup divided into 3 phases:
1. Setup Phase: Resource is reserved by the
“System”
2. Access Phase: UE confirms the Setup back to
the “System”
3. Active Phase: Ready for communication
These 3 phases are applicable to both RRC and
RAB stage
RRC is about radio connection, the owner of
which is RAN
RAB is about the actual Bearer, which is owned
by the Core Network.
RRC Connection Setup and Access and Active Phase
BTS UE RNC CN
RRC: RRC connection Request
RRC: RRC connection Setup
RRC SETUP phase
(Resource Reservation in RNC, BTS, Transport)
RRC ACCESS phase
(RNC waits for Reply from UE)
RRC: RRC connection Setup Complete
RR
C S
etu
p tim
e
RRC: Initial Direct Transfer
RANAP: Initial UE Message
RANAP: Iu Release Command
UE-CN Signalling
(E.g. RAB Establishment and Release)
RRC: RRC connection Release
RRC: RRC connection Release Complete
Release RRC resources in RNC, BTS,
Transport
RRC ACTIVE phase
RAB Setup & Access and Active Phases
RAB Reconfiguration Actions
(Reconfigure RAB resources in RNC, BTS, Transport)
BTS UE RNC CN
RRC: Radio Bearer Setup
RAB SETUP phase
(Resource Reservation in RNC, BTS,
Transport)
RAB ACCESS phase
(RNC waits for Reply from UE)
RRC: RB Setup Complete
RA
B S
etu
p tim
e
RRC: RB Reconfiguration
RANAP: RAB Assignment Response
RANAP: RAB Assignment Response
Release RAB resources in RNC, BTS,
Transmission
RRC Connection Active Phase, UE-CN Signalling
RANAP: RAB Assignment Request
RANAP: RAB Assignment Response
RAB ACTIVE phase
(User Plane Data Transfer)
RANAP: RAB Assignment Request with IE: RAB reconfiguration
RRC: Radio Bearer Release
RRC: RB Reconfiguration Complete
RANAP: RAB Assignment Request with IE: RAB Release
RRC: Radio Bearer Release Complete
RA
B H
old
ing
Tim
e
UMTS QoS Classes When RAB is being setup, the core network (CN) provides to RNC bearer attributes like:
Traffic QoS class, Maximum bit rate, Guaranteed bit rate, Residual BER, Transfer delay
and so on.
There are four different QoS classes defined for UMTS
• Conversational Class
Conversational RT
Preserve Time variation between information entities of the stream
Conversation pattern (stringent and low delay)
Voice falls under Conversational Class
• Streaming Class
Streaming RT
Preserve Time variation between information entities of the stream
Streaming Video falls under Streaming Class
UMTS QoS Classes contd..
• Interactive Class
Interactive Best Effort
Request Response Pattern
Preserve Payload Content
Web Browsing falls under Interactive Class
• Background Class
Background Best Effort
Destination is not expecting the data within a certain time
Preserve Payload
Background Download of emails falls under Background Class
Key Interfaces
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub Iub Iub Iub
The UTRAN consists of a set of Radio Network Subsystems connected to the Core Network through
the Iu.
A RNS consists of a Radio Network Controller and one or more Node Bs. A Node B is connected to
the RNC through the IuB interface.
Inside the UTRAN, the RNCs of the Radio Network Subsystems can be interconnected together
through the IuR. Iu(s) and IuR are logical interfaces. IuR can be conveyed over direct physical
connection between RNCs or virtual networks using any suitable transport network.
Key Interfaces contd..
IuB Interface:
• Logical Interface between NodeB and RNC
• Manages Transport Resources
• Handles Logical O&M of the NodeB
• Manages traffic of Common & Dedicated Channels
IuR Interface:
• Logical Interface between two RNCs
• Manages Transport Network
• Manages traffic of Dedicated Channels and reporting Measurements
Iu Interface: Logical Interface between RAN and Core Network. Responsible for establishing ,
maintaining and releasing RABs. Also responsible for performing handovers and serving RNC
relocations. Paging is also handled by Iu interface. It has two instances:
• Iu-CS Interface:
Between RAN and Circuit Switched domain in the Core Network
Carries communication between RAN & MSC and also UE & MSC
• Iu-PS Interface:
Between RAN and Circuit Switched domain in the Core Network
Carries communication between RAN & SGSN and also UE & SGSN
Sections:
WCDMA Overview
Architecture and Call Flow
RAN Dimensioning
Concept of LA, RA and URA
Radio Dimensioning Data Flow
Radio Dimensioning follows the process as shown in the flow chart below, which is
based on both Coverage and Capacity Requirements.
Capacity Dimensioning of Node-B ,RNC and the interface between them, i.e. IuB
is covered in subsequent slides
Node-B Overview
Specifications: •Up to 3 RF Modules per system Module
• Up to 2 System Modules
• 1 Tx sub module per System Module
• Up to 2 AC/DC Power Modules
• Optional Outdoor Cabinet
Main functions of RF Module:
• Antenna Filtering
• Power Amplification (Transmitter)
• Low Noise Amplification (Receiver)
• Combiner (Carriers)
Node-B Dimensioning
System Module
No. of RF Modules
HW Support for No. of Cells CCH
Max HW CE Capacity
Max SW Capacity (traffic)
Total Max SW Capacity with 2 SM
FSMB 3 6 240 240 480
FSMC 3 6 250 180 360
FSMD 3 12 500 396 792
Channel Elements of a Node-B reside inside the System Module. So, Capacity
Dimensioning from a HW point of view is done considering the CE capacity of a
System Module, which has three variants
Number of Channel Elements Required during a call depend upon the RAB type.
Following slide provides the details.
RAB wise CE Requirements RAB Traffic
Class CS/PS Max
rates for each RAB
SF UL SF DL CEs UL CEs DL
AMR Speech Conversational CS 12.2 64 128 1 1
AMR Speech Conversational CS 7.95 64 128 1 1
AMR Speech Conversational CS 5.9 64 128 1 1
AMR Speech Conversational CS 4.75 64 128 1 1
AMR Speech Conversational CS 12.65 64 128 1 1
AMR Speech Conversational CS 8.85 64 128 1 1
AMR Speech Conversational CS 6.65 64 128 1 1
Packet INT / BG PS 16 64 128 1 1
Packet INT / BG PS 32 32 64 2 2
Packet INT / BG PS 64 16 32 4 4
Packet INT / BG PS 128 8 16 4 4
Packet INT / BG PS 256 4 8 8 8
Packet INT / BG PS 384 4 8 16 16
UDI Conversational CS 64 16 32 4 4
Streaming Streaming CS 57.6 16 32 4 4
Streaming Streaming CS 14.4 64 128 1 1
RNC: Overview
Radio Network Controller performs the following Key Functions:
• Radio Resource Management
• Telecom
• Transmission and Transport
• O&M
• WCDMA Radio Resource Management can be broken down into following functions:
Resource Manager
Admission Control
Load Control
Power Control
Handover Control
Packet Scheduler
• Telecom Functions can be broken into:
Security Functions: Integrity Checking, Ciphering
User Plane Processing towards CS and PS (e.g. Management of RABs)
Radio Network Layer Control Processing
Service Area Broadcast
Location Services
RNC Dimensioning RNC Capacity is licensed as:
• IuB PS Data Throughput
• AMR Capacity
• Number of carriers, BTS or cells
Generally RNC Dimensioning is done considering the factors as given in the below
flowchart.
RNC Model NodeB Equipped
Capacity IuB Throughput Capacity (Mbps)
AMR erlangs Capacity (Erl)
MODEL3 900 900 11700
MODEL3 900 900 11700
MODEL2 600 600 7800
IuB Dimensioning - ATM
• Each Tellabs 8660 caters 50% of the total NodeBs
• MSP 1+1 between STM cards in RNC, Tellabs and ALU MUXs
• All STM cards have optical STM1 interfaces
• Each NodeB connected to 4 E1s (17960 cps) to Tellabs 8660.
• 15 NodeBs (60 E1s) on one ch. STM-1 link to Tellabs.
• Tellabs – RNC interface are overbooked with 19 - 25 NodeBs on 1 VC4 link to RNC.
• In RU10/RU20, Overbooking is supported only for UBR+ VPs carrying NRT traffic.
IuB Dimensioning – Dual IuB Ethernet
• Each Tellabs 8660 caters 50% of the total NodeBs • 2N redundancy for NPGE cards • Each GE Module has 8 x 1000 opt. interfaces • ELP redundancy for GE modules b/w RNC and Tellabs.
• Each Dual IuB NodeB is planned with 17Mbps Ethernet bandwidth for HSPA and R99 traffic.
• All RT traffics along with Signaling & DCN are kept on ATM.
• All Dual IuB sites have HSPA fallback feature enabled
Sections:
WCDMA Overview
Architecture and Call Flow
RAN Dimensioning
Concept of LA, RA and URA
Location Area & Routing Area
• Location Area (LA) and Routing Area (RA) are used by the Core Network to track UEs
• LA are used by CS Domain whereas RA are used by PS Domain
• The main CS Service States are CS-Detached, CS Idle and CS-Connected
• The main PS Service States are PS-Detached, PS-Idle and PS-Connected
Location Areas:
• A UE in CS Idle Mode does not have to update the CS Core of its location when
moving within an LA.
• LA consists of one or more RNCs connected to the same CN, i.e. MSC / VLR.
• The mapping between a LA and its associated RNCs is handled by the
MSC/VLR
• The mapping between LA and its Cells is handled by the RNC.
• A LA is identified using a Location Area Identity
Routing Areas:
• A UE in PS Idle Mode does not have to update the PS Core of its location when moving
within an RA.
• RA consists of one or more RNCs connected to the same CN, i.e. SGSN.
• A RA is always contained within a single LA.
• The mapping between a RA and its associated RNCs is handled by the SGSN
• The mapping between a RA and its cells is handled by the RNC
• A RA is identified using a Routing Area Identity
UTRAN Registration Area
• RU 10 onwards, RNC supports URA_PCH State
• The purpose of this state is to decrease the cell update signaling due to cell reselection
, which saves RNC and UE resources
• When the UE is in Cell_FACH or Cell_PCH state, its location is known at the cell level.
Cell updates are sent by the UE when Cell reselection occurs.
• If too many cell updates are received in a pre-defined window, the UE is ordered to
transfer to URA_PCH state in order to reduce cell update signaling between the UE and
the RNC.
• In URA_PCH state, UE sends the URA update to RNC after reselection to new URA.
• Planning of URA involves a balance between paging load and signaling load. Large
URA would increase the signaling load whereas small URA will lead to frequent URA
updates which increases signaling load as well as UE power consumption.
THANKS
Prepared by Naveen Bhartiya 71