Investigation On The Wireless Channel Resource Management In Hierarchical Cellular Systems

As the mobile communication services grow rapidly, the conflict between frequency resources and subscriber's demand is getting more seriously. With the increasing demand of data communications, data calls and voice calls start competing the limited channel resources. Recent research indicates that Hierarchical Cellular System (HCS) can increase the channel utilization and reduce the handoff rate effectively. For the data packet transmission, by using the packet De-Allocation scheme, the data service can be enhanced without degrading noticeably the voice service. Therefore, this thesis will focus on the following three key issues related to channel allocations in HCS, i.e. (1) channel allocation scheme for voice calls in HCS, which includes call bi-directional overflow strategy for HCS with arbitrary layers, new layer selection velocity threshold determination scheme for HCS, call bi-directional overflow scheme with channel borrowing in each layer of HCS; (2) channel allocation scheme for GSM/GPRS network, including general analysis model of dynamical channel allocation scheme for voice/data services in GSM/GPRS, performance analysis and comparison of several channel De-Allocation schemes, channel De-Allocation scheme with released channel reallocation, channel De-Allocation with released channel reallocation for both voice calls and packets calls, a new approximate analysis method for multiple traffic and multiple priorities in communication systems; (3) analysis and design of micro/macro channel allocation schemes allowing the sharing of both voice calls and data calls in HCS.The main research work and contributions of the thesis include the following aspects:1. Based on the analysis of the existing channel allocation schemes in macro/micro cellular system, an analytical model for channel allocation scheme with call bi-directional overflow in an HCS with arbitrary layers is proposed, together with the general theoretical analysis and performance evaluation due to the overflow in different layers.2. By analyzing the velocity threshold of layer selection in HCS, a new velocity threshold based on the service unsatisfaction is proposed. Through the velocity threshold, it is possible to achieve the maximum service satisfaction which is a function of the macro/micro service unsatisfaction, under certain call arrival rate and appropriate channel allocation.3. Of those existing channel allocation schemes in HCS, an important fact is that only the call overflowing strategy is considered, and no channel borrowing is investigated, as is the case in the single layer system. In this thesis, a new channel allocation scheme for HCS by considering both call bi-directional overflowing and channel borrowing is presented. Our results show that the blocking probability of the new scheme is much smaller than that of the FCA scheme with only call bi-directional overflowing.4. Different from the existing dynamical resource allocation (DRA) schemes in GSM/GPRS network which normally uses specific fixed parameters, this thesis proposes a general analysis model for DRA in GSM/GPRS networks, and a new strategy named DMCDRA which can dynamically adjust the minimum number of channels a packet can occupy. Our results show that, under different packets call arrival rate, the performance can be enhanced by changing the minimum number of channels a packet call can occupy.5. Based on the investigation of selecting the De-Allocation candidate and suitable time in GSM/GPRS network, this thesis proposes a few De-Allocation schemes for selecting candidate, i.e. selecting from the richest packet, from the poorest packet, from the oldest packet, from the young packet, and from the random packet. In addition, two strategies, i.e. priority De-Allocation and De-Allocation on demand, are discussed, together with the combination of how and when to select candidates. Simulation results show that the selection of De-Allocation candidate randomly with De-Allocation on demand is better because of its low complexity and better performances.6. Concerning the released channels which are not re-allocated immediately in the existing De-Allocation scheme in GSM/GPRS, this thesis proposes a new channel allocation scheme named DA_DRA_MCP which can re-allocate the released channels to packets calls promptly. Simulation results show that the...