Traditional Backoff Research Articles

A distributed multichannel MAC protocol for rendezvous establishment in cognitive radio ad hoc networks

Rendezvous in cognitive radio ad-hoc networks is an essential step for a pair of unknown cognitive radio (CR) users to initiate a communication. Most of the existing studies address rendezvous problems as a design of a search strategy to meet on the same channel at the same time. However, in a multi-user environment, a rendezvous cannot guarantee even if two users are on the same channel at the same time due to channel contention and the multi-channel hidden node problem. To overcome problems, we propose a novel cognitive radio rendezvous (CR-RDV) protocol by integrating the rendezvous and medium access control (MAC) issues. We modify the traditional backoff strategy based on remaining transmission time and packet length to avoid the concurrent transmission with the primary users (PUs). Moreover, an additional sensing period is introduced immediately after the RTS packet to solve the blocking problem in the multi-user environment. The proposed CR-RDV protocol is analysed based on the modified Bianchi model and an absorbing Markov chain model to capture the multi-user and rendezvous channel contention. Through extensive simulations, we show that the proposed CR-RDV protocol outperforms the existing methods with respect to throughput, delay, and packet dropping.

Energy aware medium access control for CPS-based wireless networks

Cyber physical systems CPSs are an emerging area of research. Medium access control MAC plays a major role in improving the performance of a wireless system involved in CPS. In this paper, we try to refine the process of MAC to increase the performance level of CPS-based wireless networks. Though CPS is a combination of different networks, an attempt had been made to create flexibility in the traditional backoff mechanism. We have implemented an energy efficient backoff methodology called as energy hashed virtual backoff algorithm EHVBA for a CPS-based wireless networks. This algorithm uses energy as one of the parameters in the existing VBA-CS to increase the CPS's efficacy. However there is a need to bring adaptability to the conventional backoff process in wireless networks. The proposed approach is compared with the similar existing approach in a heterogeneous network's environment. Components like MAC efficiency and energy consumption are elevated to a certain percentage comparatively with existing procedure.

Efficient Medium Access Control for Cyber–Physical Systems With Heterogeneous Networks

A cyber-physical system (CPS) consists of a group of interlinked networked objects. CPSs are characteristically different from the traditional internetworked systems (e.g., Internet) due to the operating environment and their applications, which impose high reliability constraints on them. One of the fundamental considerations for enabling this technology is the medium access control (MAC). The traditional IEEE 802.11-based MAC layer solutions need to be revamped. In order to increase the efficiency of data transmission, we introduce a new approach, which argues the replacement of the traditional backoff algorithm of 802.11. The proposed approach attempts to address some of the obligations posed by CPS networks. At the core of the proposed solution is the introduction of the adaptability factor to the traditional backoff procedure, which can help CPS networks operate under diverse environmental conditions. In order to survive the high degrees of dynamism of these networks, each of the nodes is equipped with a learning automaton, which adapts to the changing environment and provides the node with the most optimized value. The consistent outperformance of the proposed approach when compared with similar existing approaches under different simulation scenarios exhibits its efficacy. The critical parameters, such as packet delivery ratio and delay, are improved by up to 40% and 27%, respectively, over the traditional protocols.

Complexity-Effective Contention Management with Dynamic Backoff for Transactional Memory Systems

Reducing memory access conflicts is a crucial part of the design of Transactional Memory (TM) systems since the number of running threads increases and long latency transactions gradually appear: without an efficient contention management, there will be repeated aborts and wasteful rollback operations. In this paper, we present a dynamic backoff control algorithm developed for complexity-effective and distributed contention management in Hardware Transactional Memory (HTM) systems. Our approach aims at controlling the restarting intervals of aborted transactions, and can be easily applied to the various TM systems. To this end, we have profiled the applications of the STAMP benchmark suite and have identified those “problem” transactions which repeatedly cause aborts in the applications with the attendant high contention rate. The proposed algorithm alleviates the impact of these repeated aborts by dynamically adjusting the initial exponent value of the traditional backoff approach. In addition, the proposed scheme decreases the number of wasted cycles down to 82% on average compared to the baseline TM system. Our design has been integrated in LogTM-SE where we observed an average performance improvement of 18%.

CSMA/CA‐based medium access control for indoor millimeter wave networks

AbstractMillimeter wave (mmWave) communication is a promising technology to support high‐rate (e.g., multi‐Gbps) multimedia applications because of its large available bandwidth. Multipacket reception is one of the important capabilities of mmWave networks to capture a few packets simultaneously. This capability has the potential to improve medium access control layer performance. Because of the severe propagation loss in mmWave band, traditional backoff mechanisms in carrier sensing multiple access/collision avoidance (CSMA/CA) designed for narrowband systems can result not only in unfairness but also in significant throughput reduction. This paper proposes a novel backoff mechanism in CSMA/CA by giving a higher transmission probability to the node with a transmission failure than that with a transmission success, aiming to improve the system throughput. The transmission probability is adjusted by changing the contention window size according to the congestion status of each node and the whole network. The analysis demonstrates the effectiveness of the proposed backoff mechanism on reducing transmission collisions and increasing network throughput. Extensive simulations show that the proposed backoff mechanism can efficiently utilize network resources and significantly improve the network performance on system throughput and fairness. Copyright © 2014 John Wiley & Sons, Ltd.