Analysis of Priority R-ALOHA (PR-ALOHA) protocol

摘要

With the exception of required time synchronization, the Reservation-ALOHA (R-ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR-ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay-sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR-ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR-ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R-ALOHA is also carried out. Modeling and simulation results of PR-ALOHA show that PR-ALOHA improves the performance of high-priority traffic with limited effect on normal network traffic. Thus, PR-ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright (c) 2013 John Wiley & Sons, Ltd.