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Effects of Call Arrival Rate and Effects of Call Arrival Rate and Mobility on Network Throughput Mobility on Network Throughput in Multi-Cell CDMAin Multi-Cell CDMA
Manju Hegde, Robert Akl, Paul Min
Washington University
St. Louis, Missouri USA
OutlineOutline
CDMA Capacity and Inter-cell Effects Feasible Region Mobility Model and Blocking Net Revenue Implied Costs Effects of Mobility Maximization of Subscribers Maximization of Revenue Shaping Feasible Region
Probability of OutageProbability of Outage
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Probability of OutageProbability of Outage
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Gaussian ApproximationGaussian Approximation
We approximate the Poisson by a Gaussian variable with the same mean and variance:
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Probability of Outage for Multiple CellsProbability of Outage for Multiple Cells
Nine Cell NetworkNine Cell Network
Probability of Outage For Each CellProbability of Outage For Each Cell
Inter-Cell InterferenceInter-Cell Interference
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Soft HandoffSoft Handoff
User is permitted to be in soft handoff to its two nearest cells.
Soft HandoffSoft Handoff
(c)region
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(c)region
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(a)region
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Inter-Cell Interference FactorInter-Cell Interference Factor
Kji : per user inter-cell interference factor from cell j to cell i
nj users in cell j produce an amount of interference in cell i equal to njKji
Feasible RegionFeasible Region
Total Offered TrafficTotal Offered Traffic
New call arrival process to cell i is Poisson.
Total offered traffic to cell i is:
Handoff RateHandoff Rate
Probability of State Probability of State nn
Fixed PointFixed Point
Net Revenue Net Revenue WW
Revenue generated by accepting a new call
Cost of a forced termination
Implied CostsImplied Costs
Find derivative of W wrt new call arrival rate
Capture knockon effect of increases in an arrival rate
Maximize net revenue for a given blocking probability vector
Three Cell NetworkThree Cell Network
Low Mobility
qii 0.26
qij 0.02
High Mobility
qii 0.00
qij 0.15
Blocking in Cell 3Blocking in Cell 3
Normalized Arrival RateNormalized Arrival Rate
Net Revenue W=1 C=2Net Revenue W=1 C=2
Net Revenue W=1 C=10Net Revenue W=1 C=10
Optimization of SubscribersOptimization of Subscribers
Best Scenario:
Optimization of SubscribersOptimization of Subscribers
Worst Scenario:
For all values of the arrival rates summing to S, the
blocking probabilities do not exceed the threshold.
Maximized SubscribersMaximized Subscribers
Optimization of Net RevenueOptimization of Net Revenue
Maximized Net RevenueMaximized Net Revenue
Shaping Feasible RegionShaping Feasible Region
Increases capacity
Fine tune the nominal power of the users through PCF
PCF defined for each cell
PCF is a design tool to maximize the capacity of the entire network
Power Compensation FactorPower Compensation Factor
Interference is linear in PCF
Allows us to reshape the Feasible Region.
Equal Number of UsersEqual Number of Users
Implied CostImplied Cost
*2
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Shaping with PCFShaping with PCF
Two Cell NetworkTwo Cell Network
qii 0.04
qij 0.26
Mobility
Feasible RegionFeasible Region
Shaped Feasible RegionShaped Feasible Region
Maximized SubscribersMaximized Subscribers
Maximized Net RevenueMaximized Net Revenue
ConclusionsConclusions
For a given network topology we calculate:
– Inter-cell and intra-cell interference and Feasible Region
– Maximized net revenue
– Maximized subscriber capacity
– Effects of Mobility
Shape feasible region to increase maximized net revenue and subscriber capacity
Future WorkFuture Work
Design Problem: given a user demand distribution, what are the optimal location and coverage of Base Stations to:
– Maximize Net Revenue
– Maximize Subscriber Capacity