Collision-Minimizing CSMA and Its Applications to Wireless Sensor Networks

Abstract

Abstract-Recent research in sensor networks, wireless location systems, and power-saving in ad hoc networks suggests that some applications' wireless traffic be modeled as an event-driven workload: a workload where many nodes send traffic at the time of an event, not all reports of the event are needed by higher level protocols and applications, and events occur infrequently relative to the time needed to deliver all required event reports. We identify several applications that motivate the event-driven workload and propose a protocol that is optimal for this workload.Our proposed protocol, named CSMA , is nonpersistent carrier sense multiple access (CSMA) with a carefully chosen nonuniform probability distribution that nodes use to randomly select contention slots. We show that CSMA is optimal in the sense that is the unique probability distribution that minimizes collisions between contending stations. CSMA has knowledge of . We conclude with an exploration of how could be used to build a more practical medium access control protocol via a probability distribution with no knowledge of that approximates .Index Terms-Carrier sense multiple access (CSMA), medium access control (MAC), nonpersistent, performance, poisson process, sensor networks.

A Low Latency MAC Scheme for Event-Driven Wireless Sensor Networks

“…SIFT guarantees successful transmission of R out of N packet (each sensor detects an event and sends one packet) with the shortest delay where N is the number of nodes which detected the event. Based on the same principle, CSMA/p* [10] is proposed where p* is also a non-uniform distribution in order to minimize latency. However, the main objective of this proposal is to reduce the collision but not to reduce the transmission latency for event-driven wireless sensor networks.…”

Performance Evaluation of Non-persistent CSMA as Anti-collision Protocol for Active RFID Tags

“…As said in Section 1, we propose the use of CSMA with the optimal probability distribution (p * ) for the selection of CSMA contention micro-slots derived in [9]. This distribution maximises the probability of success when N stations become simultaneously backlogged, but depends on the number of slots in use (K) and the number of nodes (N ) contending.…”

“…Since the latter is usually unknown (also in RFID), an approximation is also provided, the Sift distribution, which not only keeps close to the optimal for a wide range of its configuration parameters but it is also scalable. The authors of reference [9] discuss different applications in wireless sensor networks, but RFID is not mentioned. In this paper we show that RFID is a major field of application of this optimised distribution.…”

“…The probability of success π p (N ) when N nodes select a contention microslot using probability distribution p, where p r is the probability each contender independently picks slot r, is [9]:…”

“…As we will show, if micro-slots are selected uniformly (the classical approach), the identification of tags does not have to be more efficient than a framed slotted ALOHA. However, an optimised distribution for the selection of CSMA contention micro-slots has been proposed for Wireless Sensor Networks [9]. This distribution minimises the probability of collision when N stations become simultaneously backlogged, which is exactly the main problem of RFID identification.…”