Data Forwarding in Wireless Relay Networks

Abstract

Broadband wireless communication has brought users a number of multimedia services for years. As wireless broadband markets mature, system operators face new problems. First, system capacity is bounded by finite radio resources. Second, service providers increasing spend on network deployments and services provisions. With limited radio resource and increased costs, operators have no choice but to force users to pay higher rates to preserve the same service quality than they had several years ago. The expectation is that these problems are solved by introducing relay station (RS) into traditional wireless systems. The relaying technology has proven to be a feasible technology to expand system capacity and reduce deployment costs simultaneously. One of the most popular technologies is cooperative communications that boost network throughput significantly by improving the radio quality for transmission and reception (Nosratinia et al., 2004); (Mohr, 2005); (Doppler et al., 2007). Numerical results (Soldani & Dixit, 2008) showed the cost saving benefits when conventional communication networks adopt relay functionality. From this, a commercial cellular system can save more than 56 % on capital expenditures when RSs are deployed. RS is a wireless communication station that provides relay services for receiving and forwarding radio signals between two stations. In a cellular system, RS is in charge of receiving, decoding, and forwarding data between the Base Station (BS) and the Subscriber Stations (SSs). During the relaying, RS provides additional features to assist data transmissions. For example, (Tao et al., 2007) proposed a novel data forwarding scheme in this environment. The novel data forwarding scheme improved the transmission efficiency by approximately 66 %. Although data relay shows superior performances in throughput enhancements and cost savings. Multi-hop relaying introduces new issues that impact overall performance. To indicate a routing path in multi-hop circumstances, additional control information should be introduced. The routing indication design for multiple radio links introduces new overhead and may impact transmission efficiency during relay. Imprecise indications may waste RS computation and storage since it does not know what it shall relay and where to forward. Moreover, there may be a case that data destined to others are received by the RS that is not in charge. Imprecise relay indication will not only increase overheads but also lead RS to use its processor and storage inefficiently. In other words, data forwarding with ambiguous control information would increase RS complexity and buffer storage unnecessarily. During