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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 39772 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Ashtiani, Farid
- Abstract:
- OFDMA multi-hop cellular network (MCN) is the topic of a wide range of research today. In this thesis, we analyse this type of networks, regarding shadowing status, mobility patterns and different service requirements. In the multi-hop (MH) scenario, six fixed relays are set up in each cell, which split the cell into seven subcells. For mobility modeling, each subcell is split into several sub-regions. Mobile nodes are able to maintain at each sub-region with a random time distribution and migrate from it to one of its neighboring sub-regions. We also consider three types of services requiring specific number of subcarriers with specific BERs. The set of subcarriers is distributed among subcells for MS (mobile set)-RS (relay station) and MS-BS (base station) links as well as RS-BS links, in a specific manner. We model the network with two tiers of queuing networks. The first tier network is a closed multi-class Jackson queuing network with sub-regions as its nodes and acquires spatial distribution and shadowing status distribution of a typical customer in each subcell. In the second tier network we model the whole cellular network as an open multi-class Jackson queuing network with subcells as its nodes and it results in users' terrific distribution in the whole considered area. For simplifying the analysis, subcells are approximated with M/M/ queue nodes in the second tier network. This approximation can model blocking and dropping of entering users with different service requirements without involving too much complexity. Solving the two tiers of networks simultaneously, interference and SINR distribution functions and then average throughput are acquired. Results are obtained for two cases, with using a simple adaptive modulation and coding (AMC) mechanism and without it. Average blocking and dropping probabilities and average number of used subcarriers in the target cell, are also attained. An OFDMA single-hop cellular network (SCN) is analysed in the same way and results are compared with the multi-hop case. The comparison concludes that throughput improvement while reducing blocking and dropping probabilities, specially in crowded networks, are the advantages of applying fixed relays in the infrastructure of the cellular network
- Keywords:
- Throughput ; Frequency Hopping Code Division Multiple Access (FH-CDMA) ; Queueing Network ; Multi-hop Cellular Network ; Blocking Probability ; Dropping Probability
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