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Title: Resource allocation for cooperative broadcasting in W-CDMA networks
Author: Imran, M. A.
ISNI:       0000 0004 2737 4918
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2007
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Cooperative broadcasting is a capacity-approaching transmission strategy over a broadcast channel like the downlink of Wideband Code Division Multiple Access (W-CDMA) mobile networks. The W-CDMA codes on downlink are rendered nonorthogonal due to multipath and the simultaneous transmissions interfere with each other. The system capacity is interference limited and the strongest interference is caused by the transmissions to the users at the cell edge. This thesis focuses on the resource allocation for the communication link from the basestation to the user at the cell boundary, to increase the overall system capacity using cooperative broadcasting. Focusing on the link between the user at the cell edge and the base station, multiple W-CDMA channels are used for this link to distribute the available power over these channels. This leads to a larger number of simultaneous transmissions with reduced Signal to Noise and Interference Ratio (SNIR) on each channel. The reduced SNIR on each channel can be improved by symbol repetition with random phasor rotations and adding the multiple received copies. The decrease in SNIR tends to reduce the capacity but the stronger effect of increase in number of parallel channels provides an overall capacity improvement. A capacity upper-bound is identified that depends on the system dimensions. A proposed receiver operation extends the system dimension (by a factor of 2), increases the capacity upper-bound and improves other performance criteria. Optimum discrete loading of parallel channels is shown to achieve performance close to the capacity upper-bound. As the transmissions to the user at the cell boundary appear as interference for many other users who intend to decode this interference for cancellation purpose, error free reception at multiple receiving ends is required. Retransmission on failures is not feasible and the decoder complexity must be kept low. We propose a packet parity coding scheme and corresponding iterative decoding arrangement that achieves this with (around 1 dB) smaller gap value compared with Turbo coding scheme. The multiple packet detectors, identified in this thesis, further reduce the packet error floors.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available