7/28/2019 Enhancement and optimal utilization of CDMA2000 network
1/43
1
Enhancement and
Optimal Utilization ofCDMA2000 Networks
Dr. Joseph ShapiraAlexander Chair Professor
IIT Madras
President, Comm&[email protected]
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
2/43
2
When the Tire meets the Road..
Only then you feel the ride.
Nothing is more true for cellular systems.
Performance shows up only in large-scale
field deployment.
15 years of CDMA, and there are yet
lessons to learn.
Packet CDMA will teach yet more lessons
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
3/43
3
Channel Impulse
response ina developed suburban
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
4/43
4
CDMA Cellular
Reverse Link Forward link
Capacity limit Interference Power
Coverage limit Users power BTS power
Power control Controlled by aggregate
interference to the BTS
Controlled by
interference to the MS
Cell boundary Shrinks when loaded Expands when loaded
Responds to aggregate interference
No frequency planning and structured (hexagon) grids
Local environment and traffic density affects optimization
Forward and reverse links are not symmetrical
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
5/43
5
CDMA outperforms
when optimized over all parameters
Reduce SHO overhead
Increase the transmission-loss slope
Balance up and down links Access Control
Balance the loads
Intersector
Intercell
Optimize the service
Dynamic optimization isthe next frontier
Improve the channel
reduce Eb/Nt required
margin
Receive diversity
Transmit diversity
Reduce link loss variations
Distributed antennas Repeaters
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
6/43
6
Diversity Gain
Signal fading below threshold increases theBit Error Rate (BER)
Correlated fading: gain 3 dB
Threshold
Rx Diversity
MS
SDiversity gain is the rise of the average signal
level for the same BER (for the same fraction of
time below the threshold)
Uncorrelated fading: gain 7 dB
(at 1% FER)
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
7/43
7
Cumulative Distribution Function (CDF)
for Diversity Combining
Single Branch
Diversity Gain (dB)
Signal [dB]
CDF
10%
100%
Prob. Signal 10 dB
Open, Line of SightSingle ray high Rician
Eb/Io -> 3 dB
Developed Suburban.
Long delay multipathEb/Io = 5 dB
Loss of orthogonality
Half of the power is lost if no EIRP
shaping is applied
Activity Eb/Nt EIRP
(dB)a1 (=1/3) 10 10/3
a2 (=1/3) 3 2/3
a3 (=1/3) 5 3/3
Total EIRP 15/3
(required )
Total EIRP 30/3
(available)
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
25/43
25
Distributed Load Balancing
Intersector Hot Spot Repeater
Intercell Hot Spot
Repeater
Remote sector
BTS hotellingremote cells
Links:
F1/F2Microwave
Fiber Optics
Free Space Optics
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
26/43
26
Network Optimization/ Capacity
Maximization Process
Reduce SHO overhead
Increase the transmission-loss slope
Balance up and down links Access Control
Balance the loads
Intersector
Intercell
Optimize service
Dynamic optimization isthe next frontier
Improve the channel
reduce Eb/Io required
margin
Receive diversity
Transmit diversity
Reduce link loss variations
Distributed antennas
Repeaters
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
27/43
27
The Smart ClusterAdd-On Dynamic Optimization
Cluster size - 10 to 15 cells
Sensors
Optimization
Effectors
Communication Communication
Objectives
Mobile units
BTS RF state
Repeaters
Antenna state
Switchperformance parameters
RET and RBC Antennas
Repeater gainBTS pilot level
Neighbor list
Search window
Additional parameters
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
28/43
28
3GThe cost of High Data Rate
Frequency
(band-width)
Time
(duration)
Power(signal-to-noise
and interference)
BIT
3G cellularBandwidth is fixed
CostHigher Eb/Nt needed
Higher modulation constellation,
Reduction of code protection
Protection by ARQ and Scheduling
The cost - latency
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
29/43
29
DIGITAL MODULATION
Signal constellationA trade-off between spectral efficiency
(bits/Hz), and interference immunity
Cellular systems use2 and 4 state modulation.
Higher state8 PSK, 16 QAM
require high Eb/Nt.
The service has a shorter range
Im
Re
BPSK
Im
Re
QPSKIm
Re
16 QAM
Im
Re
8 PSK
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
30/43
30
Signal constellation -sensitivity to noise
BPSK,QPSK
Higher spectral efficiency goes with higher
sensitivity to co-channel interference (requires
higher Eb/Nt)
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
31/43
31
3GServices and Constraints
Service Rate Session Latency ErrorTolerance
Voice Low Long Low High
PTT Low Long High Very High
SMS Low Short High Med
Large files High Long High Very Low
Video/games Med Long Low Med
Means
Circuit switched Packet switched - Scheduling:
Code Division Time Division
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
32/43
32
IS 95 and 1xEV DO Fwd Link
Structure
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
33/43
33
Forward vs Reverse
Forward link (FL) efficiency depends on Tx power per bit
Large variation of FL efficiency between MS and over time
DO, DV, and HSDPA all take advantage of short-term goodchannel condition by fast MS feedback
RL efficiency depends on the Rx power per bit
Schedule-to-Tx-when-channel-is-above-average reduces theinterference to other BSs statistically.
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
34/43
34
C/I vs non-orthogonal multipath
-15
-10
-5
0
5
10
15
0.
05
0.
15
0.
25
0.
35
0.
45
0.
55
0.
65
0.
75
0.
85
0.
95
1.
05
1.
15
r/R
C/I[dB]
al=.99 al=.95 al=.7 al=.5
a=.99
a=.95
a=.7
a=.5
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
35/43
FORWARD LINK Eb/Nt vs. Distance(The Geometry factor G)
Distance from BS (in cell radius units)
Relative Eb / I0 [dB]
Load full .75 .5 .25
Non Orthogonal InterferenceOther cells loaded 50%
-10
0
10
20
30
40
50
60
70
80
0.05
0.15
0.25
0.35
0.45
0.55
0.65
0.75
0.85
0.95
1.05
1.15
1.25
1.35
Distance from BS
Eb
Orthogonal Interference
(noise limited)
Orthogonality and Diversity govern Eb/Nt
35
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
36/43
36
Time Division Duplexing/
Scheduling For moving MSthe channel fluctuates
The peaks exceed the average by typical 3dB.
The signal does not peak simultaneously for different MSs.
The scheduler allocates time slots to the user with the best
channel, thus getting max data rate
Many users activity offers more opportunities for signal
peaks to the scheduler and increase the throughput.. This is
user diversity.
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
37/43
37
Radio Resource Management
3G sacrifices capacity for service versatility
Mixture of different Eb/Nt requirements and packet
schedulingVariance in Power Control
Soft HandOff common to allVariance in boundary and
link balance.
Dynamic control is desired for optimizing capacity,coverage and quality
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
38/43
38
Congestion Control
Limits the traffic in the cell within desired quality
Means:
PowerAdmission Control
Load control
Packet Scheduler
Antenna Tilt / Orientation/ Pattern Change
- impacts all other means
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
39/43
39
Coverage Transformation
Antennas above the scenery(suburban environment)
The dominant parameter is angle
The angular spread grows as theantenna is lower
Antennas below the roof level
The dominant parameter is the
locationThe array manifold is squeezedinto a narrow coverage area.Multiple reflections areattenuated.
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
40/43
40
Summary
The cellular CDMA systems achieves superior performance
and capacitywhen optimized against traffic and
environmentlocally and globally.
Initial planning and deployment need optimization to reflect
the actual traffic and environment, and their changes.
The advent of wide range of services on one platform adds
dynamics and variance to the network balance. Dynamic
optimization will be most advantageous.
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
41/43
41
Summary (2)
Most of the Radio Resources are controlled at the RF
access level and allow for low BTS-intervention.
The meaningful locality in a CDMA network is a cluster of
10 to 15 cells. This is the optimization subject.
Smart antenna is a local solution. Smart cluster is a
network solution.
Dynamic optimization of Smart clusters is the eventual
goal.
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
42/43
Reference
CDMA Radio with Repeaters
Joseph Shapira
Shmuel Miller
SPRINGER, 2007ISBN 978-0-387-26329-8
42
7/28/2019 Enhancement and optimal utilization of CDMA2000 network
43/43
Thank You