Multihop Relay-Enhanced WiMAX Networks

Abstract

The demand for high speed data service has been increasing dramatically since the Internet has become a part of people’s lives. Most broadband wireless service providers have boosted data service rates by adopting recently developed technologies such as OFDM, MIMO, and smart antennas. However, in practice there are still problems such as coverage holes due to shadowing, and poor signal to interference and noise ratio (SINR) for the subscriber stations (SSs) that are far away from the base station (BS). A simple solution for this problem is to add more BSs, but it is a very inefficient solution especially when there are few SSs to be served (e.g., in rural areas.) As an alternative to adding BSs, deploying low-cost relay stations (RSs) provides a cost-effective way to overcome the above problem (RSs are a simplified version of a full BS resulting in with lower upfront cost than BS; additionally, RSs do not require backhaul connections, thus reducing operating costs). The WiMAX specification was amended (802.16j, 2009) to includemultihop relays, an extensionwhich has gainedmuch attention and proved to be an attractive technology for the next-generation of wireless communications. Furthermore, the currently evolving Long Term-Evolution Advanced (LTE-A) standard considers multihop relaying as an essential feature (3GPP, 2009). In this chapter, we study the effect of using RSs on both capacity and coverage enhancements.