%0 Journal Article
%T Investigation on Mutual Contention Bandwidth Request Mechanisms in Two-Hop Relay Network with ITU-R Path Loss Models
%A Rajesh Anbazhagan
%A Nakkeeran Rangaswamy
%J ISRN Communications and Networking
%D 2013
%R 10.1155/2013/417132
%X 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. 1. Introduction Broadband wireless technologies with worldwide interoperability for microwave access (WiMAX) networks are gaining tremendous attention due to the increasing consumer demands. WiMAX is envisioned to provide high-speed data rate to last mile and last inch customers. In recent years, mobile WiMAX has emerged to support high-speed data rate to customers at vehicular speed. The IEEE 802.16j task group has been formed to extend the scope of single hop WiMAX network (IEEE 802.16e) in terms of capacity (throughput) and coverage [1]. In WiMAX relay network, the stations of interest are base station (BS), relay station (RS), and mobile station (MS). Based on the number of hops between BS and MS, the WiMAX networks may be classified into two types, namely, single hop network and multihop network. Further, the architecture modes supported by the WiMAX standard are as follows: point-to-point (PP), point-to-multipoint (PMP), and mesh modes. In a single hop network, the MS communicate directly with the BS, and hence the network follows PP (between BSs) or PMP architecture [2, 3]. In multihop network, the MS may not be in a position to communicate directly with the BS and involve multiple hops to establish the connectivity. One or more RS are involved to establish
%U http://www.hindawi.com/journals/isrn.communications.networking/2013/417132/