Effective Carrier Sensing in CSMA Networks under Cumulative Interference

TL;DR

This paper introduces a safe carrier-sensing range for CSMA networks under cumulative interference, proposes the Incremental-Power Carrier-Sensing mechanism to implement it, and demonstrates its advantages over traditional power threshold methods.

Contribution

It defines a new safe carrier-sensing range under realistic interference models and proposes the IPCS mechanism to realize it effectively.

Findings

Safe carrier-sensing range is larger under cumulative interference.

IPCS can distinguish power increments from concurrent transmitters.

IPCS enables interference-safe transmissions in CSMA networks.

Abstract

This paper proposes and investigates the concept of a safe carrier-sensing range that can guarantee interference safe (also termed hidden-node-free) transmissions in CSMA networks under the cumulative interference model. Compared with the safe carrier-sensing range under the commonly assumed but less realistic pairwise interference model, we show that the safe carrier-sensing range required under the cumulative interference model is larger by a constant multiplicative factor. The concept of a safe carrier-sensing range, although amenable to elegant analytical results, is inherently not compatible with the conventional power threshold carrier-sensing mechanism (e.g., that used in IEEE 802.11). Specifically, the absolute power sensed by a node in the conventional mechanism does not contain enough information for it to derive its distances from other concurrent transmitter nodes. We show that, fortunately, a carrier-sensing mechanism called Incremental-Power Carrier-Sensing (IPCS) can realize the carrier-sensing range concept in a simple way. Instead of monitoring the absolute detected power, the IPCS mechanism monitors every increment in the detected power. This means that IPCS can separate the detected power of every concurrent transmitter, and map the power profile to the required distance information.