Traditional cellular networks provide a centralized wireless networking paradigm within the wireless domain with the help of fixed infrastructure nodes such as Base Stations (BSs). On the other hand, Ad hoc wireless networks provide a fully distributed wireless networking scheme with no dependency on fixed infrastructure nodes. Recent studies show that the use of multihop wireless relaying in the presence of infrastructure based nodes improves system capacity of wireless networks. In this paper, we consider three recent wireless network architectures that combine the multihop relaying with infrastructure support – namely Integrated Cellular and Ad hoc Relaying (iCAR) system, Hybrid Wireless Network (HWN) architecture, and Multihop Cellular Networks (MCNs), for a detailed qualitative and quantitative performance evaluation. MCNs use multihop relaying by the Mobile Stations (MSs) controlled by the BS. iCAR uses fixed Ad hoc Relay Stations (ARSs) placed at the boundaries to relay excess traffic from a hot cell to cooler neighbor cells. HWN dynamically switches its mode of operation between a centralized Cellular mode and a distributed Ad hoc mode based on the throughput achieved. An interesting observation derived from these studies is that, none of these architectures is superior to the rest, rather each one performs better in certain conditions. MCN is found to be performing better than the other two architectures in terms of throughput, under normal traffic conditions. At very high node densities, the variable power control employed in HWN architecture is found to be having a superior impact on the throughput. The mobility of relay stations significantly influences the call dropping probability and control overhead of the system and hence at high mobility iCAR which uses fixed ARSs is found to be performing better.

Multi-hop cellular architectures are being explored for use in future fourth generation (4G) cellular networks. This paper is a step towards identifying desirable features of such multi-hop architectures. Towards this end, we compare two network architectures which have been proposed to improve the throughput of packet data cellular networks viz. the hybrid wireless network (HWN) architecture proposed by Hsieh and Sivakumar (see Proc. ACM SIGMETRICS 2001, Cambridge, MA, USA, June 2001) and the multi-hop cellular network (MCN) architecture proposed Lin and Hsu (see Proc. IEEE INFOCOM 2000, Tel-Aviv, Israel, March 2000) and by Ananthapadmanabha, Manoj and Siva Ram Murthy (see IEEE PIMRC 2001, San Diego, USA, October 2001). We extend the HWN architecture (proposed only for operation over a single cell by Hsieh and Sivakumar) to multiple cells. We present an analysis of the MCN architecture to gain additional insights into its operation. We also present simulations to highlight the strengths and weaknesses of the two architectures. Based on these simulations, we suggest modifications to improve the performance of both architectures. We identify issues relating in general to the inclusion of ad hoc features (multiple hops) into cellular architectures.

We have considered the problem of providing greater throughput in cellular networks. We propose a novel cellular architecture, RT-MuPAC, that supports greater throughput compared to conventional cellular architectures. RTMuPAC (Real-time Multi-power Architecture for Cellular Networks) is based on two fundamental features not present in today's cellular networks: usage of multiple hops and power control (power control is used only in a limited way to reduce interference and save battery energy for the mobile nodes in today's cellular networks). These features, we believe, will become increasingly important in next generation cellular systems as heterogeneous networks will operate in synergy. We also provide an analytical treatment of RT-MuPAC to support its superior performance. We show using detailed simulations that RT-MuPAC is indeed a significant improvement over conventional networks. We also discuss possible enhancements to the basic architecture in order to counter specific issues. RT-MuPAC can evolve from the existing infrastructure and offer advantages to both the service provider and the users. RT-MuPAC also serves as a proof of concept for the use of multi-hop architectures in cellular networks.