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The CDMA is a broadband single frequency cellular system that maintains resource balance dynamically, mainly by power control. A repeater in the network may serve for enhancement of coverage or capacity. It interacts with the network paramters. Analysis is provided herein.
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Repeaters in CDMA network
• Dr. Joseph Shapira
PROPRIETARY AND CONFIDENTIAL1
Parameters affecting capacity• Power (FL) limit• Effect - Blocking• Measure - Power-per-user, blocking rate• Interference (RL) limit• Measure – noise rise ( may have an access limit set by the
system)• Effect - Access failures, dropped calls, coverage reduction
(“breathing”)• Measure – (RL) access failures/ dropped calls rates• Excess SHO• Draws power from multiple cells – limits FL power• Increases overhead communications• Draws channel cards
PROPRIETARY AND CONFIDENTIAL2
Capacity Measurements• Measure – Power per WC (Power per user).• This is an average measurement, that assumes the
same user distribution and data flow per user.• P/WC is sensitive to coverage, and has to be corrected
for change of coverage, if channel changes are measured (diversity)
• Pilot power allocation % affects TCH power and capacity
• Measure - Blocking rate• A valid measure only for full load (saturation)• Disrupted by anti-saturation means (e.g. AOC)• Noise Rise – (may have a limit by the system)
PROPRIETARY AND CONFIDENTIAL3
CDMA optimization parameters
•Improve the channel – reduce Eb/Nt required margin
– Receive diversity– Transmit diversity
•Reduce link loss variations– Distributed antennas– Repeaters
•Reduce SHO overhead– Increase the transmission-
loss slope– Balance FWD and RVS links– Access Control
•Balance the loads– Intersector – Intercell
•Optimize the service •Dynamic optimization is the next frontier
PROPRIETARY AND CONFIDENTIAL4
Time Delay Transmit Diversity (TDTD)
PROPRIETARY AND CONFIDENTIAL5
Residential area
70% increase in capacity
(2.3 dB gain)
Performance Comparison - Sector 21Z
-0.1
0.4
0.9
1.4
1.9
2.4
2.9
3.4
3.9
4.4
4.9
200 300 400 500 600 700 800
Minutes of Use
P b
lock
ing
[%
]
w/o TDTD
w TDTD - Before Tilt
Performance Comparison - Sector 21X
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
700 900 1100 1300 1500 1700 1900
Minutes of Use
P b
loc
kin
g
[%]
w/o TDTD
w TDTD
Highway traffic
25% increase in capacity
( 1 dB gain)
Blocking probability
2%
2%
Indoors Penetration enhancementby a repeater across-the-street, with
Transmit Diversity plus TTLNA
PROPRIETARY AND CONFIDENTIAL6
-10 -5 0 5 10 15 20 250
0.5
1
1.5
2
2.5
3
-25 -20 -15 -10 -5 0 5 10 150
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
RSSI {with TD – w/o TD } [dB] Distribution Handset Tx Power {with TD – w/o TD} [dB] Distribution
-4dB5dB
Network Optimization/ Capacity Maximization Process
•Improve the channel – reduce Eb/Io required margin
– Receive diversity– Transmit diversity
•Reduce link loss variations– Distributed access– Repeaters
•Reduce SHO overhead– Increase the transmission-
loss slope– Balance FWD and RVS links– Access Control
•Balance the loads– Intersector – Intercell
•Optimize the service •Dynamic optimization is the next frontier
PROPRIETARY AND CONFIDENTIAL7
Network Optimization/ Capacity Maximization Process
•Improve the channel – reduce Eb/Io required margin
– Receive diversity– Transmit diversity
•Reduce link loss variations– Distributed antennas– Repeaters
•Reduce SHO overhead– Antenna control– Balance FWD and RVS links– Access Control
•Balance the loads– Intersector – Intercell
•Optimize service •Dynamic optimization is the next frontier
PROPRIETARY AND CONFIDENTIAL8
Number of Sectors involved in a callA Major Metropolitan Market, US
PROPRIETARY AND CONFIDENTIAL9
Site # X Site # Y
2.12.2
1.5
3.4
2.3
2.2
Power Inefficiency factor
PROPRIETARY AND CONFIDENTIAL10
Site # X Site # Y
[Simple+2*CTrfCode+ChnSrHO+2.25*CTrfCode+ChnSHO] / [Simple+CTrfCode+ChnSrHO+CTrfCode+ChnSHO]
20 - 30%
Network Optimization/ Capacity Maximization Process
•Improve the channel – reduce Eb/Io required margin
– Receive diversity– Transmit diversity
•Reduce link loss variations– Distributed antennas– Repeaters
•Reduce SHO overhead– Increase the transmission-
loss slope– Balance FWD and RVS links– Access Control
•Balance the loads– Intersector – Intercell
•Optimize service •Dynamic optimization is the next frontier
PROPRIETARY AND CONFIDENTIAL11
Network Optimization/ Capacity Maximization Process
•Improve the channel – reduce Eb/Io required margin
– Receive diversity– Transmit diversity
•Reduce link loss variations– Distributed antennas– Repeaters
•Reduce SHO overhead– Increase the transmission-
loss slope– Balance FWD and RVS links– Access Control
•Balance the loads– Intersector – Intercell
•Optimize service •Dynamic optimization is the next frontier
PROPRIETARY AND CONFIDENTIAL12
The Smart ClusterAdd-On Dynamic Optimization
Cluster size - 10 to 15 cells
PROPRIETARY AND CONFIDENTIAL13
SensorsOptimization
Effectors
Communication Communication
Objectives
Mobile unitsBTS RF stateRepeatersAntenna stateSwitch – performance parameters
RET and RBC AntennasRepeater gainBTS pilot levelNeighbor listSearch window
Additional parameters
Repeater usage for Maximizing Capacity
1. Hot spots2. Indoor illumination from outdoor3. Indoor distribution (DAS)4. Increase transmission slope/ reduce SHO5. Load balancing6. Add diversity
PROPRIETARY AND CONFIDENTIAL14
Types of Repeaters
1. Embedded2. Border extension3. Remote4. Cascaded
PROPRIETARY AND CONFIDENTIAL15
RR3
D3
D2
1
2
3
RR2
RR1
D1 RCRR3
D3
D2
1
2
3
RR2
RR1
D1 RC
Forward Link
•Relays all donor transmission ( plus other interfering sources)
•No automatic balancing RVS/FWD•Has to be controlled for coverage (gain) and saturation (AMLC)•Reduces RSU (repeater-served-users) per-user power•Increases PiCH/TCH ratio for RSU (TCH is power-controlled)
RFDFF GTy
PROPRIETARY AND CONFIDENTIAL16
Impact of Repeaters on the Network - FL
• Net gain (yF) determines coverage
• Excess gain causes oscillations/spurii• AMLC reduces coverage, causes imbalance and reduces capacity• Amplifying other sources may lead to AMLC• Instability of the BS-Repeater (BSR) link (e.g. directive antenna nodding,
fiber loss change with temperature, etc.) changes coverage• Overlap with donor’s coverage adds multiple fingers to the MS receiver,
introduces interference (excess fingers) and diversity• Repeater delay requires broadening of the search window (significant in
fiber and selective repeaters)
PROPRIETARY AND CONFIDENTIAL17
Impact of repeater on network - RL
•Effective cell noise factor
•Repeater adds RL noise•Reduces donors’ coverage, • or donor’s capacity.•Trade-off repeater coverage• vs. donor coverage/ capacity
RCCE yFFF
PROPRIETARY AND CONFIDENTIAL18
RCCE yFFF
GRR
FR
GBFB
BTS Repeater
Tr
n
TD
RC RR
Tc
RC0
m
GRR
FR
GBFB
BTS Repeater
Tr
n
TD
RC RR
Tc
RC0
m
RL Impact of repeater on network – cont.
• No Rx diversity – increases MTX and BTS load, and reduces coverage
• Loads the donor noise and reduces its coverage and/ or capacity
• Overlap introduces diversity. Excess fingers introduce interference
• Change in BSR link gain causes change in coverage for both repeater and donor
• Imbalance FL-RL (excess offset) causes the P.C. open loop to be noisy, and loss of capacity. Imbalance exceeding about close loop range breaks the P.C. loop and drops RSUs
PROPRIETARY AND CONFIDENTIAL19
Fixed Coverage vs. Fixed Capacity
• A Excess noise rise for fixed capacity (loss of coverage)
• B Loss of capacity for fixed noise rise• A B
PROPRIETARY AND CONFIDENTIAL20
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-10 -8 -6 -4 -2 0 2 4 6 8
Apparent repeater noise figure
Do
no
r ca
pac
ity
rela
tive
to
no
min
al
(max
. lo
ad f
acto
r vs
. no
min
al)
8
9
10
11
12
13
14
15
16
17
18
-10 -8 -6 -4 -2 0 2 4 6 8
Apparent repeater noise figure
No
ise
rise
[d
B]
Coverage of repeaters
• Embedded Border Remote
PROPRIETARY AND CONFIDENTIAL21
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
Distance from BTS (normalized)
Prs
/Ps
[dB
]
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
0.46
0.52
0.58
0.64 0.
7
0.76
0.82
0.88
0.94
1
1.06
1.12
1.18
1.24 1.
3
Distance from BTS (normalized)
Prs
/Ps
[dB
]
-15.00
-13.00
-11.00
-9.00
-7.00
-5.00
-3.00
-1.00
1.00
3.00
5.00
Distance from BTS (normalized)
Prs
/Ps
[dB
]Cell border
Repeater Controls
• Gain, RL• Power, RL• Gain, FL• Power, FL• AMLC – Automatic Level Control• Frequency filtering• Switching (advanced option)• BS-Repeater Link Gain• Antenna controls
PROPRIETARY AND CONFIDENTIAL22
Basic Repeaters
• Definition: Fixed frequency band/selective, fixed gain independent in FWD/RVS, has maximum power protection (e.g. AMLC), provides alarms and monitoring, no AISG provisioning (maybe external), no diversities, simple RF F1-F1 (no dedicated conduit), no watermarking, no multi-hop, includes a wireless modem
• Parameters: FWD Gain, RVS Gain, RVS Tx Power, FWD Power, AMLC Level and Status, Wireless Modem parameters forwarding (Ec/Io, RSSI, FER, Tx PWR)
• Optimization: Setting procedures (FWD, RVS, Noise Rise, Pilot PWR %, balancing), search window, neighbor list
• Parameters such as # carriers, traffic load, carriers' loading, BTS allowed shrinkage, enter into setting and optimization as constraints
• Incorporate repeaters in the optimization tool with shared BTS-Repeater coverage, combined traffic, macro-diversity and interference, all above setting considerations.
PROPRIETARY AND CONFIDENTIAL23
Advanced Repeaters
1. Repeater performance2. Enhanced performance3. Enhanced features4. Network Parameters Readout
PROPRIETARY AND CONFIDENTIAL24
Advanced Repeaters
Repeater performance1. Stability2. Robustness3. Installation – parameter setting4. Alarm functions5. Link balancing 6. Traffic, coverage, overhead
PROPRIETARY AND CONFIDENTIAL25
Enhanced performance
• Interference cancellation1. Adaptive angular interference cancellation
(adaptive donor antenna)Filter-out other donors or interfering sources
2. Adaptive feedback cancellationReduces coupling between donor and service antennas, allowing for tighter installation on the tower
PROPRIETARY AND CONFIDENTIAL26
Enhanced features
1. Frequency filtersInter-systems and sub-bands
2. Antenna control (RET/ RBC)Control of repeater service antenna
3. Diversity FWD/RVS True or pseudo-diversity (PSD/TDD)
4. Multi-carrier/ multi functionMulti-systems with separate controls
5. BTS-Repeater (backhaul) link stabilization
PROPRIETARY AND CONFIDENTIAL27
Network Parameters Readout
1. Traffic load through repeaterLimited effectiveness. The noise rise is affected by the total donor+repeater load
2. Tagging repeater – “Water-marking” RSUsFrequency or delay modulation of repeater RL. Requires detection by BTS
3. Wireless Modem parameters’ monitoring4. Switch parameters pre-filtering and processing
PROPRIETARY AND CONFIDENTIAL28
Cascaded (multi-hop) repeaters• Repeaters are cascaded to increase coverage1. Along roads • maximal area/ length2. Within an area/ campus • mixed large/ small areas3. Within buildings• limited area, complex coverage • Distribution (backhaul):• Star• Cascade
PROPRIETARY AND CONFIDENTIAL29
Star/ Cascade
• Star• Each repeater may be controlled independently• The aggregate apparent noise factor counts. Optimal
setting – same net gain to each. • Cascade• The gain setting of each repeater influence the rest of
the chain. The coverage is successively smaller. Optimal setting – same net gain (y) to all repeaters but the first (preferably y=1). Control the chain by the net gain of the first.
PROPRIETARY AND CONFIDENTIAL30
RCR1 R2 R3 R4
Total range
RCR1 R2 R3 R4
Total range
Setting
• Roads/ area• Maximizes for y=1. Repeaters and donor are planned
and optimized together.
• Indoors• Low net gain (y <<1). Small coverage. Minor impact on
donor coverage. Loosely interdependent optimization of donor and repeater chain.
PROPRIETARY AND CONFIDENTIAL31
Network planning with repeaters
• Optimizing the repeaters’ location and their parameters’ setting is crucial for any further control and optimization of the network.
• Major parameters:• Repeater RL/FL power, gain, dynamic range (per
location and purpose)• Repeater location• height, beam-width, direction and tilt of dservice
antenna• Backhaul link
PROPRIETARY AND CONFIDENTIAL32
Optimization with Repeaters• Change repeater coverage vs. donor coverage
– Hot spot – Repeater coverage should exceed high density area– Border – affects pilot pollution/ SHO extent– Remote – rural coverage vs. core coverage
• Change repeater antenna orientation/ tilt– Hot spot – controls overlap with donor (capacity, performance)– Border – controls pilot pollution/ SHO extent– Remote – controls Repeater coverage area
• Frequency Filters and service antenna control– Controls load distribution/ service destination
• Switch– Switch off dormant coverage and reduce noise
PROPRIETARY AND CONFIDENTIAL33
Enhancement Tools CDMA wireless modem in the repeater
1. Reports repeater status2. Relays commands to the repeater3. Automatic FL/RL links balancing
By reading the offset parameter of the modem P.C. and controlling repeater gains
4. Location • (e.g. by differentiating time-of-flight to
modem and to subscriber)5. Identifies PNs through repeater
Support reduction of interference from other sources
PROPRIETARY AND CONFIDENTIAL34
Thank you• Contact• Dr. Joseph Shapira• Comm&Sens Ltd• +972 4 8251653• +972 54 6607088• Jshapira@comm-and-
sens.com
PROPRIETARY AND CONFIDENTIAL35