iCAR: An Integrated Cellular and Ad-hoc Relaying System
Ever increasing data traffic and limited capacity are major causes for congestion in current cellular systems. Adding to the problem of limited capacity in existing wireless systems is the presence of unbalanced traffic. Specifically, some cells may be heavily congested (called hot spots), while the other cells still have available DCH's. In other words, even though the traffic load doesn't reach the maximum capacity of the entire system, call blocking and dropping may occur due to localized congestion. Since the locations of hot spots vary from time to time (e.g. downtown areas in Monday morning, or amusement parks in Sunday afternoon), it's difficult, if not impossible, to provide the guarantee of a sufficient amount of resources in each cell in an cost-effective way. Other problems in cellular systems include the presence of shadows where MH's cannot receive strong enough signals, and the need for MH's to transmit at high power when they are farther away from base stations thus limiting their battery life.
In this work, we study the important problem of how to evolve from the existing, heavily-invested cellular infrastructure to wireless systems that scale well with the number of mobile hosts. We propose to integrate the cellular infrastructure with modern Ad-hoc relaying technologies to achieve dynamic load balancing among different cells in a cost-effective way. The basic idea of the proposed iCAR (integrated Cellular and Ad-hoc Relay) system is to place a number of Ad-hoc Relay Stations} (or ARS) at strategic locations, which can be used to relay signals between MH's and base stations. By using ARS's, it's possible to divert traffic in one (possibly congested) cell to another (non-congested) cell. This helps circumvent congestion, and make it possible to maintain (or hand-off) calls involving MH's (especially a high-priority call) that are moving into a congested cell, or to accept new call requests involving MH's that are in a congested cell. Other benefits include enhanced coverage and reliability (or fault-tolerance) of the system, and potential improvement in MHs' battery life and transmission rate.
Acknowledgment and Disclaimer: This material is based upon work supported by the National Science Foundation under Grant No. NSF/ITR ANI-0082916. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
