Resource Management with Limited Capability of Fixed Relay Station in Multi-Hop Cellular Networks

The purpose of this chapter is to develop a resource management technique to utilize resource efficiently in multi-hop cellular networks. Multi-hop cellular networks have been proposed as a way to enhance throughput and extend coverage (Cho & Haas, 2004). This enhancement can in general be achieved by deploying relay stations in conventional cellular networks. The advantage of multi-hop networks arises from the reduction in the overall path loss achieved by using a relay station between a base station and a mobile station. Moreover, deeply shadowed mobile stations can be supported by using relay stations to bypass obstacles. Even though the multi-hop transmission has advantages, it also carries a penalty: the need for additional resources to transmit data in multi-hop manner (for example, in two-hop transmission, two time slots or frequency channels for the base station-relay station link and the relay station-mobile station link) (Lee et al., 2008). Hence, this penalty of multi-hop transmission is represented by ‘worms’, which devour resources (Ju et al., 2009). The trade-offs associated with the multi-hop networks make it difficult to assess their overall performance. For mobile stations with quality-of-service (QoS) requirements guaranteed by single-hop transmission with few resources, multi-hop transmission could end up wasting additional resources through multiple hops, even though it may provide higher end-to-end data rates. In other words, a higher end-to-end data rate does not guarantee higher efficiency in resource utilization. Hence, the amount of resources required to guarantee QoS should be considered when assessing multi-hop transmission performance and the performance can be different depending on a mobile station. In addition, the infrastructure cost increases almost linearly with the equipment capability (Johansson et al., 2004), and it is impossible to change the capability of the installed equipment flexibly according to the change of the required capability. Hence, a relay station has the limited and determined capability. Due to the limited capability, some of mobile stations cannot transmit in multi-hop if all capability of relay station has been already fully used for the other mobile stations. Hence, the resource management for assigning the 17