Abstract
The performance of two-hop contention based bandwidth request (BR) mechanism for WiMAX relay networks is investigated under ITU-R path loss models. In conventional WiMAX systems, the mobile stations (MS) update their contention window irrespective of their transmission failures. Those systems update their contention window on collision and due to channel error or unavailability of bandwidth. Further, these failure models have been suggested for single hop networks. The failure model in two-hop systems becomes complex since it may include additional failure events such as improper detection of codes and channel error due to varying path loss. Interestingly, these failure events (collision, channel error, unavailability of bandwidth, and improper detection of codes) do not occur evenly for both hops of a link. Hence, to set the contention window effectively, unique failure models are developed by considering the characteristics of BR mechanism and hop at which the BR is performed. In the proposed system, the two-hop BR is carried out with all combinations of message and code bandwidth request schemes. Among them, the message-code BR mechanism performs better under suburban fixed and outdoor to indoor or pedestrian environment, and code-code BR scheme performs better for vehicular environment.
Highlights
Broadband wireless technologies with worldwide interoperability for microwave access (WiMAX) networks are gaining tremendous attention due to the increasing consumer demands
It should be noted that the increase in simulation time is in conjunction with the increase in the number of stations that participate in the bandwidth request mechanism
With the CC based bandwidth request (BR), the throughput is improved by 4.18%, the connection delay is reduced by 21.9%, and the queuing delay is reduced by 33.35% compared to Outdoor to indoor and pedestrian
Summary
Broadband wireless technologies with worldwide interoperability for microwave access (WiMAX) networks are gaining tremendous attention due to the increasing consumer demands. The contention based bandwidth request (BR) mechanisms in WiMAX networks are classified into message BR and code division multiple access (CDMA) or code BR [11]. There always exists a tradeoff between message and CDMA BR with single hop networks The former suffers from low contention efficiency and high access delay amid low signaling overhead with increase in the number of stations. Many works have been carried out with contention based BR in single hop networks, no work has been cited in the literature to evaluate the performance over two-hop WiMAX relay networks.
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