Design and Analysis of Medium Access Protocol: Throughput and Short-Term Fairness Perspective

Abstract

We consider a simple MAC protocol, called the renewal access protocol (RAP), that adopts all of the legacy 802.11 standard but the backoff stage feature. To meet two objectives in the design of the RAP-optimal throughput and high short-term fairness-we develop a mathematical model of the RAP and rigorously analyze the performance of the RAP. First, we show that the throughput performance of the RAP depends only on the expectation of the selection distribution where the backoff counter is selected, provided that the number of terminals is fixed, which is in accordance with a well-known result. Second, with the help of renewal and reliability theories, we analyze the short-term fairness of the RAP. We also show that if the RAP has a selection distribution of the New Better than Used in Expectation (NBUE) type, the RAP can guarantee high short-term fairness. Third, we construct a special binomial distribution that is obviously of the NBUE type that can achieve high short-term fairness as well as optimal throughput when used as the selection distribution of the RAP. Furthermore, by the Poisson approximation for binomial distributions, we propose to use in practice a Poisson distribution corresponding to the special binomial distribution. Numerical and simulation results are provided to validate our analysis.

Delay analysis and optimality of the renewal access protocol

“…In the above, E [B s ] and E [B c ] are the average lengths of time periods for a successful packet transmission and a collided packet transmission, respectively. They are derived in the same way as given in Bianchi (2000), Bianchi et al (1996) as follows: It is shown in Kim and Hwang (2015) that throughput T in (2) is a strictly convex function of τ . Since τ depends only on μ, we conclude that the network throughput performance depends only on the first moment (expectation) of the selection distribution, which is in accordance with well-known results in earlier works, e.g., Kumar et al (2007).…”

“…To consider the fairness of the protocol itself, we assume that there are no hidden or exposed terminals and each terminal transmits packets of the same size. The analysis in short-term fairness in Kim and Hwang (2015) is summarized below. We will use the same notations as given below in the delay analysis.…”

“…In order to meet the three criteria, we propose a simple MAC protocol, called the renewal access protocol (RAP) (Kim and Hwang 2015). In the RAP, each terminal having a packet selects a new backoff counter value based on a so-called selection distribution and transmits its packet whenever the backoff counter value becomes zero as in the IEEE 802.11 DCF.…”

“…Note that the RAP allows any distribution as its selection distribution. It is shown in Kim and Hwang (2015) that, if a Poisson distribution is used as the selection distribution, then the resulting RAP achieves high short-term fairness as well as optimal throughput, which are briefly reviewed in Sect. 2.…”

“…In this section, as a preliminary, we review the renewal access protocol (RAP) which is proposed and analyzed in Kim and Hwang (2015). The RAP is a simplified version of the IEEE 802.11 DCF in the sense that it has only one parameter, called the backoff counter.…”