Real Time Traffic Balancing in Cellular Network by Multi-Criteria Handoff Algorithm Using Fuzzy Logic

Abstract

Cellular systems are extremely popular. These are the systems that ignited the wireless revolution. Cellular systems provide duplex voice and data communication with regional and national coverage. The basic premise behind cellular system design is frequency reuse pattern, which exploits the fact that signal power falls off with distance to re-use the same frequency spectrum at spatially separated locations. Cellular systems’ frequency band is a very limited resource, even after applying multiple access methods and aggressive frequency re-use, mobile service providers still face the challenge of over-congestion due to growing size and demand. The degree of Traffic Channel (TCH) congestion in the network results in large number of TCH blocking which greatly affects negatively the subscriber satisfaction and revenue of a mobile service provider. The available congestion relief methodologies such as cell splitting, microcells and expanding frequency bands depend on time and cost factors for implementation. Network parameters are manually adjusted to obtain a high level of network performance. There are many parameters for solving uneven load distribution in the cluster. Some of them are transmitter power, Cell Bar Quality (CBQ), Half-Rate, RXLEV-ACCESS-MIN, Timing Advance (TA) and Handoff threshold and among others. All the above techniques of load balancing are not self-adaptive in the sense that every time congestion occurred in the network either of the above methods has to be manually applied. xiv In an effort to address the above challenges, this research presents a design and implementation of a fuzzy multi-criteria handoff algorithm based on signal strength, pathloss, traffic load of BTS and Signal to Noise Ratio (SNR). The algorithm balances traffic in all the neighboring BTSs at any time and enhances the performance of the cellular system by selecting the best network segment. This was achieved by multi-criteria handoff algorithm using fuzzy logic. The proposed algorithm has been tested using data from wireless propagation models based on straight line mobility between two BTSs in suburban area. Simulation results show the MS in the region between 2000m to 7000m dynamically swing between BTS I and J depending the load on the BTSs. The coverage area of a BTS can dynamically be expand towards a nearby loaded cell or shrunk towards cell center for a loaded sector. Therefore, this mechanism activates a handoff procedure to shift some traffic of a loaded cell towards a lightly loaded cell thereby increase the resource utilization. In case of low load scenarios, the coverage area of a BTS is presumed to be virtually widened to cover up to the partial serving area of neighboring BTS. This helps a highly loaded neighboring BTS.