On using the ad-hoc network model in cellular packet data networks
Proceedings of the 3rd ACM international symposium on Mobile ad hoc networking & computing - MobiHoc '02
While several approaches have been proposed in literature for improving the performance of wireless packet data networks, a recent class of approaches has focused on improving the underlying wireless network model itself. Several of such approaches have shown that using peer-to-peer communication, a mode of communication used typically in ad-hoc wireless networks, can result in performance improvement in terms of both throughput and energy consumption. However, the true impact of using the
... c network model in wireless packet data networks has neither been comprehensively studied, nor characterized. In this paper, we investigate the benefits of using an ad-hoc network model in cellular wireless packet data networks. We find that while the ad-hoc network model has significantly better spatial reuse characteristics, the improved spatial reuse does not translate into better throughput performance. Furthermore, although considerable improvement is seen in energy consumption performance, we observe that using the ad-hoc network model as-is might actually degrade the throughput performance of the network. We identify and discuss the reasons behind these observations. Finally, using the insights gained through our performance evaluations, we discuss strawman versions of three techniques which when used in tandem with the ad-hoc network model result in better throughput, energy consumption, fairness, and mobility-resilience characteristics. Through our simulation results, we motivate that using the ad-hoc network model in conventional wireless packet data networks is a promising approach when the network model is complemented with appropriate mechanisms. base-stations communicate with mobile-stations directly, and the mobile-stations operate in a purely peer agnostic fashion. The fundamental element of the proposed alternative network models is thus the adoption of the peer-to-peer mode of communication in cellular packet data networks to improve performance. In  , the authors propose an approach called ad-hoc GSM (A-GSM), wherein mobile-stations participate in relaying to improve coverage and robustness against radio link failures. The approach uses received signal strength as the parameter in the decision process to switch from direct base-station communications to mobilestation relays. In opportunity driven multiple access (ODMA) , a scheme considered under the 3G endeavor, the high data rate coverage of the cell is increased at the boundaries by allowing mobilestations inside the original high data rate coverage area to act as relays for mobile-stations outside. In  , the authors propose an integrated cellular and ad-hoc relay (iCAR) approach wherein special mobile relays are placed between cells to relay traffic from an overloaded cell to a relatively under-loaded cell and therein achieve load balancing. In the mobile-assisted data forwarding (MADF) approach , a similar relaying scheme is proposed to reduce delay. In , the proposed model called multi-hop cellular networks (MCN) uses multi-hop relays for the mobile-stations to reach the base-station while reducing the transmission power of the mobilestations and the base-station. MCN is shown to improve throughput performance when sources and destinations co-exist in a single wireless cell without mobility. In  , a simple hybrid model is proposed wherein mobile-stations are used for multi-hop relays, and the base-station coordinates the network topology by directing the power adaptation at the mobile-stations. Although the purpose is to maximize spatial reuse and reduce network partitions, the model is evaluated only for the scenario in which all sources and destinations are co-located within the same cell. Despite the fact that peer-to-peer communication is used in these proposed models, the true impact of using such a communication model is yet to be comprehensively understood. In this paper, we investigate the benefits of using peer-to-peer communication 1 in cellular packet data networks. We evaluate the use of peer-to-peer communication along a variety of performance metrics, and conclude that while the better spatial reuse characteristics of peer-topeer communication results in better throughput per unit power, it does not translate into better performance in terms of throughput. On the contrary, we demonstrate that using peer-to-peer communication on an as-is basis can result in degraded throughput. We identify and discuss the reasons behind these observations. We then discuss three approaches that in tandem translate the spatial reuse benefits of peer-to-peer communication into better performance in terms of throughput, throughput per unit power, fair service allocation and mobility-resilience. Using strawman realizations of the three approaches, we show the performance enhancements that can be achieved and hence motivate further investigation along these lines. Thus, the contributions of this paper are twofold: • We show that using peer-to-peer communication on an as-is basis has its benefits in terms of throughput per unit power, but results in degradation of throughput. Moreover, we demonstrate that peer-to-peer communication exhibits unfair service allocation and is more vulnerable to mobility induced performance degradation.