Channel Assignment in Multihop Cellular Networks

Recently, several work related to channel assignment for MCN-type systems were reported. Wu et al proposed diverting traffic from the congested cells to the non-congested cells (Wu et al., 2001; Wu et al., 2004), which is achieved by relaying traffic through unlicensed frequency band, such as the industrial, scientific and medical (ISM) band. For iCAR (Wu et al., 2001; Wu et al., 2004), ad hoc relay stations (ARSs), either being fixed (Wu et al., 2001) or mobile (Wu et al., 2004), are deployed for balancing traffic. The communication link between a mobile station (MS) and an ARS is established using the ISM band. Similarly, UCAN is used to increase the system throughput through relaying using the ISM band (Luo et al., 2003). None of the above papers describes how to select and allocate the relay channels for each hop in detail. An ad hoc GSM (A-GSM) protocol was proposed in (Aggelou & Tafazolli, 2001) using the cellular frequency band for RSs to cover dead spots and increase the capacity. Aggelou and Tafazolli (Aggelou & Tafazolli, 2001) investigated the concept of A-GSM, which includes AGSM network components, protocol architecture, and handover procedure to allow a MS to perform GSM-to-A-GSM and A-GSM-to-A-GSM handovers. The GSM-to-GSM connection uses the resource from the BS. The A-GSM-to-GSM connection routes through the RS and uses the resource from that RS. The coordinating of the allocation of resources of a relay node is controlled by a resource manager. However, it did not clearly address how the resources are allocated to the BS and RSs. It also did not address the channel assignment method for each type of connection. In addition, the analysis for a single GSM cell is done in (Aggelou & Tafazolli, 2001) so that the co-channel interference, which is one of the major issues in channel assignment in cellular networks, is not considered. Similarly, the MCN in (Hsu & Lin, 2002) assumes to use cellular frequency for relaying, whereas no clear description on how to allocate a channel to a MS for cellular or ad hoc mode is included.