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 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

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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

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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