International Journal of Computer Applications (0975 – 8887) Volume 61– No.10, January 2013 11 Optimal Channel Allocation with Hot-Spot Technique in Wireless Network Smriti Dubey Department of Computer Science and Engineering Sati College, Vidisha (M.P) ABSTRACT In wireless mobile communication systems, proper channel allocation scheme is required. Due to the limitation of available frequency spectrum, channels must be reused as much as possible to increase system capacity. Complication arises in channel allocation, when more than one cell become “hot-spot” in the network of one BSC. The cells become “hot-spot” when bandwidth resources currently available in those cells are not sufficient to sustain any more call. In hybrid channel allocation, cells send a multilevel hot-spot notification to the dynamic pool of BSC on each channel request that cannot be satisfied locally at the base station. Proportional to the current hot-spot level of the cell, this hot-spot notification will request more than one channel to assign to the requesting cell. Severe complication arises, when not even one channel available in the dynamic pool of BSC in order to assign to requesting cells. This is the situation, when call starts dropping or blocking. This paper presents a new scheme in which BSC will fetch those ideal channels, which are borrowed to requesting cell from the dynamic pool in the time of hot spot but become ideal in the temporary pool of BTS for some period of time. BTS make use of these channels in order to sustain new incoming call .The proposed algorithm in this paper will reduce the call dropping probability comparatively more than the simple hybrid channel allocation algorithm. Keywords: hybrid channel allocation, hot-spot, blocking probability, handover 1. INTRODUCTION Due to increased urge to use the wireless communication in a satisfied way, a promised quality of service is required to manage incoming new calls and handoff more efficiently [2]. In radio resource management for wireless network, proper channel allocation scheme are required to allocate bandwidth for communication channels to base stations, access points and terminal equipment. Call refusal rate or Call drop rate is the main evaluation parameter, when talking about channel allocation scheme i.e. the ratio between numbers of drop calls to the total number of calls. For the given technique Call drop rate can be measured in erlang, where 1 erlang= 1 ongoing call per second. In [5&6] different channel allocation algorithms are used to allocate channels. As in [1-3], Following are the three major categories for assigning channels to cells. Fig .1 Channel Allocation Strategies FIXED CHANNEL ALLOCATION (FCA): In FCA, according to predetermined traffic demand and co- channel interference constraints, a fixed number of channels are assigned to each cell. [1] FCA is very simple but this scheme is difficult to survive in changing traffic conditions and user distributions. Over the whole service area if traffic varies from cell to cell, FCA could not attain a high efficiency of total channel usage. DCA strategy has been proposed, in order to overcome the problems of FCA. DYNAMIC CHANNEL ALLOCATION (DCA): In DCA, channels are not allocated to cells permanently. For every call request base station request channel from BSC. According to the duration of the calls, channels are assigned temporarily for use in cells. The channel is returned back and kept in the central pool, after the call is over. In order to avoid co-channel interference, any channel that is in use in one cell can only be reassigned to another cell simultaneously if the distance between those two cells is larger than the minimum reuse distance. DCA needs many transceivers for each base station. Behave well in low load but behave worse than FCA in heavy load. HCA strategy has been proposed, in order to overcome the problems of DCA. DCA schemes are suggested for TDMA/FDMA based cellular systems such as GSM, but are currently not used in any products. HYBRID CHANNEL ALLOCATION (HCA): The third category of channel allocation is hybrid channel allocation; it is hybrid of fixed and dynamic channel allocation algorithm. Channels in HCA are divided into two disjoint sets- First is fixed set: set of channel which is assigned to each cell on FCA basis. Second is dynamic set: set which are kept in a central pool of BSC for dynamic assignment.