Study of Advanced Techniques in High Speed Wireless Transmissions

This dissertation, "Study of Advanced Techniques in High Speed Wireless Transmissions" by Yuanliang, Huang, 黃源良, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled "Study of Advanced Techniques in High Speed Wireless Transmissions" Submitted by Huang Yuanliang for the degree of Doctor of Philosophy at The University of Hong Kong in February 2006 Future wireless communication systems aim to provide extremely high speed data transmission. Several advanced techniques are investigated in this thesis, to solve challenging technical problems in broadband wireless communication systems, such as the impulse radio ultra wideband (IR-UWB) communication systems, the coded layered space-time-frequency (LSTF) architectures in orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) multiplexing systems, and the low-density parity-check (LDPC) codes. In Chapter 2, a novel acquisition scheme with two-stage serial search noncoherent correlator for time hopping (TH) IR-UWB is proposed. The new two-stage acquisition scheme gets chip timing synchronization, and aligns phase of the local time-hopping code in two stages successively. With the aid of the flow-graph approach, analytical expressions are derived for the mean acquisition time and the probability of acquisition. Numerical results based on a slow fading channel show that the novel two-stage acquisition method can offer much shorter mean acquisition time or much higher probability of acquisition than that of the conventional acquisition. In order to achieve the available spatial, temporal and frequency diversity, and also make the system implementation cost-effective for high speed OFDM MIMO multiplexing, in Chapter 3 a novel LSTF architecture is proposed with each independent codeword being threaded in the three-dimensional space-time-frequency transmission resource array. Channel estimation based on a time-multiplexed pilot channel is employed. List sphere detection is used as the detector, and the irregular LDPC code is chosen as the channel code. Computer simulation shows that the proposed LSTF architecture can significantly outperform the LSTF (i.e., LSTF-b) in which each independent codeword is associated with a dedicated antenna, and can obtain almost the same performance as the LSTF (i.e., LSTF-a) where coding is applied across the whole information stream. Due to its structure of multiple parallel lower-speed encoders/decoders with shorter codeword length, the proposed LSTF architecture can be much more easily implemented than the LSTF-a. Moreover, pilot-aided channel estimation is important to the system performance and the percentage of the pilot channel energy in one packet should be in the range of 16% to 24% to provide near optimum performance. With the iterative receiver structure consisting of the minimum-mean-square-error soft- interference-cancellation (MMSE-SIC) detectors and soft-in soft-output (SISO) maximum a posteriori (MAP) convolutional decoders with time-multiplexed pilot-aided channel estimation, system performances of the three LSTF architectures are investigated in Chapter 4. Simulation results show that the proposed LSTF architecture can considerably outperform the LSTF-b, and obtain almost the same performance as the LSTF-a. Moreover, four iterations in the joint MMSE-SIC detectors and MAP decoders are sufficient to achieve stable performance, and the pilot channel energy in one packet should be in the range of 16% to 24% to provide near optimum performance. DOI: 10.5353/th_b3682465 Subjects: W