GaMa : An Evolutionary Algorithmic Approach for the Design of Mesh-Based Radio Access Networks Samik Ghosh, Preetam Ghosh, Kalyan Basu, Sajal K. Das Center for Research in Wireless Mobility and Networking (CReWMaN) Department of Computer Science and Engineering The University of Texas at Arlington {sghosh, ghosh, basu, das}@cse.uta.edu Abstract Wireless mesh based access networks are destined to play a pivotal role in next generation broadband systems. With the proliferation of mesh networks, a key issue for network designers is the design of an optimal mesh topology which minimizes cost while maintaining carrier-class features. In this paper, we formulate the design of an optimal mesh, taking network deployment cost, topological properties and carrier-grade reliability into account. Next, we present a Genetic Algorithm based algorithm (GaMa) for mesh topol- ogy design. We show that GaMa is capable of determining a generic mesh topology with carrier-class network features. The performance of the algorithm is compared with exist- ing mesh topologies and gives improved results without the constraints of maintaining a regular topology. 1. Introduction The future generations of wireless communication sys- tems are envisioned to provide bandwidth-intensive, data- oriented services to mobile users. New radio interfaces are being defined and research challenges identified in the design and architecture of such next generation wireless systems [12]. One of the fundamental areas of change is the radio ac- cess network, which provides the vital link for backhauling user traffic and control signals to the backbone network and contributes to a large portion of service provider costs. In existing networks, this access network is a hierarchical tree/star based network interconnecting the base stations to the Base Station Controllers (BSC)s (known as Radio Network Controller (RNC) in 3G), which are connected to the Mobile Switching Centers (MSCs)(Fig. 1). The inter- connecting links are traditionally highly reliable (99.999%) time division multiplexing (TDM) circuits over T1/E1 links, leased fiber optics or microwave links. Although, existing RAN models are capable of support- ing current voice-centric traffic requirements, they are not optimized to support high-speed micro-cellular networks of the future. The high data-rate services of future networks will result in reduced cell footprints and increased network traffic [12]. The radio backhaul will need to evolve to sup- port the new cell-sites and their offered loads. As next generation access networks will cater to heterogeneous net- works (Fig. 2), they also need to be highly scalable, flexible and dynamically reconfigurable. Future wireless users will demand the same carrier-class reliability features enjoyed in the traditional circuit-switched domain. Thus, the under- lying principle in the design of access networks should be to provide carrier-class reliability for the whole gamut of applications and services at low system costs. In the light of the above-mentioned characteristics, the ra- dio access network design problem has to be revisited - both in topology as well as transmission technologies. While high capacity fiber-optics links can provide carrier-class re- liable services for the backhaul, these solutions can be pro- hibitively costly given the dynamic nature of future access networks. Free Space Optical (FSO) links (Optical Wire- less), 60 Ghz millimeterWave have been studied in recent literature as alternative access technologies [1], [4], which are capable for providing high capacity at low system costs. These technologies have specific characteristics, like line- of-sight requirements and weather-dependant link availabil- ity in case of optical wireless, which have to be taken into account for their effective deployment. New interconnec- tion topologies for the access network have been studied in [16]. In [12], a ring-based cluster-cellular horizontal topol- ogy has been suggested for interconnecting the base stations, using distributed BS control and short, high-speed wireless links. Apart from the general topology issues,[10],[13] have focussed on the access network optimization problem on an underlying hierarchical tree architecture - clustering of base Proceedings of the IEEE Conference on Local Computer Networks 30th Anniversary (LCN’05) 0-7695-2421-4/05 $20.00 © 2005 IEEE