Self-Management in Chaotic Wireless Deployments

A. Akella, G. Judd, S. Seshan, P. Steenkiste

Carnegie Mellon University

Outline

• INTRODUCTION• IMPACT ON END-USER PERFORMANCE• TRANSMISSION POWER AND RATE

SELECTION• PERFORMANCE EVALUATION• CONCLUSION

INTRODUCTION• Chaotic Wireless Networks

– Unolanned– Unmanaged

• Suffer from– serious contention– poor performance– security problems

INTRODUCTION

• To improve end-user performance– Automatically manage the transmission power l

evels– Transmissions rates of APs and clients.

INTRODUCTION

• Power control algorithm called– Power-controlled Estimated Rate Fallback (PE

RF)

IMPACT ON END-USER PERFORMANCE

• Simulation GloMoSim Topology

IMPACT ON END-USER PERFORMANCE

• Simulation assumptions ：– Each node on the map is an AP

– Each AP has D clients with 1 ≤ D ≤3

– Clients are within 1 meter from their AP and they don’t move

– All APs transmit on channel 6

– All APs use fixed power level of 15dBm

– All APs transmit at fixed rate 2Mbps

– RTC/CTS is turned off (default settings)

IMPACT ON END-USER PERFORMANCE

• http with thinking time by Poisson distribution with mean equal to 5s or 20s

• Comb-ftpi, i clients run FTP transmission

• Results:– HTTP ： 83.3 Kbps for 5s 24.5 Kbps for 20s– FTP ： 0.89 Mbps for 300s

IMPACT ON END-USER PERFORMANCE

IMPACT ON END-USER PERFORMANCE

IMPACT ON END-USER PERFORMANCE

• Two simple mechanisms on mitigating interference– Use an optimal static allocation of non-

overlapping channels– Reduce the transmit power levels

IMPACT ON END-USER PERFORMANCE

• Non-overlapping channel assignment

IMPACT ON END-USER PERFORMANCE

Three non-overlapping channels 1 6 11 Only channel 6

IMPACT ON END-USER PERFORMANCE

IMPACT ON END-USER PERFORMANCE

• Transmit power control

IMPACT ON END-USER PERFORMANCE

• Managing power control and using static allocation of non-overlapping channels can reduce the impact of interference on performance

TRANSMISSION POWER AND RATE SELECTION

• PARF: Power-controlled Auto Rate Fallback– Based on ARF

• It Attempts to elect the best transmission rate

– adding low power states above the highest rate state.

– Power is repeatedly reduced until • the lowest level is • the transmission failed threshold is reached

TRANSMISSION POWER AND RATE SELECTION

• PERF: Power-controlled Estimated Rate Fallback– Based on ERF(SNR+ERF):

• It uses path loss information to estimate the SNR with which each transmission will be received

– The transmission power is reduced to estimatedSNR = decisionThreshold + powerMargin

PERFORMANCE EVALUATION

PERFORMANCE EVALUATION

=>

CONCLUSION

• Power control and rate adaptation can reduce interference

• Reduce power as long as transmission rate was unaffected.