Time: Tuesday, July 22, 2003, 10:00 - 11:00 a.m.

Place: Room 4359, Mackenzie Building, Carleton University

Refreshments will be served starting 9:45 a.m.

Part I

The 4th generation (4G) of mobile communication systems will develop toward the direction of large capacity, high speed and multimedia transmissions. In these systems, the frequency resource will be further limited and the requirement to the reliability for the transmission will be higher and higher. Therefore how to find a kind of novel coded modulation scheme not only with power efficiency but also with frequency efficiency is of important significance. Since there is the special and serious fast fading interference in mobile fading channels it is really a tough problem for a long time for the researchers working in this area to find a designing metric for an optimal coded modulation scheme. The designing metric is very different from that used in AWGN channels and is with both power and frequency efficiency in the same time. Multilevel coded modulation with multistage decoding (MLC/MSD) should be an efficient way to solve this problem. In this talk we will focus on the following problems in the designing of an optimal MLC/MSD coded modulation scheme in Rayleigh fading channels: optimal non-Euclidean metric, reasonable choice for code rate according to the channel capacity rule, different mapping and set partitioning strategies, different decoding methods and so on. For the first time, we propose a non-Euclidean metric in designing an optimal MLC/MSD system applied to independent Rayleigh fading channels, that is the Channel Capacity Rule and Block Partitioning (BP) strategy together. Using this new metric makes us getting thoroughly rid of the former and old design metric used in AWGN channels in which the Euclidean distance is the main and optimal metric in design. The performance of a MLC/MSD scheme is studied in AWGN and Rayleigh fading channels respectively, in which the MLC/MSD scheme is constructed by combining BCH codes with 8ASK modulation strategy. The channel capacities of 8ASK modulation with three different set partitioning strategies: Ungerboeck partitioning (UP), Block partitioning (BP) and Mixed partitioning (MP) are calculated in independent Rayleigh fading channel based on the calculation results of the channel capacities got in AWGN channel. The channel capacity rule is used to the designing for an optimal MLC/MSD system in Rayleigh fading channels. The important feature of robustness of BP set patitioning strategy in both AWGN and Rayleigh fading channels is presented and proved by our theoretical analysis and computer simulations. We also have compared the performance of two different decoding methods usually used in MLC scheme which are called Multistage Decoding (MSD) and Parallel Decoding Level (PDL) in AWGN and Rayleigh fading channels respectively for a large range of BCH code length. Based on above theoretical analysis and computer simulation results a novel 8PSK MLC/MSD multilevel coded modulation scheme used in AWGN channels with better performance is proposed which is 0.5 dB better than the scheme proposed by Dr. Imai in 1977. For Rayleigh fading channels we present another novel 8ASK MLC/MSD multilevel coded modulation scheme used in independent Rayleigh fading channels. The results show that the novel 8ASK MLC/MSD scheme can obtain 21.5 dB code gain which is more than the scheme of uncoded 4ASK modulation when the component code length n in MLC is equal to 127. 23 dB code gain can be got when the component code length n is equal to 255.

Part II

Based on the basic concepts and discussions in Part I, a brief summary on the new developments of multilevel coding is given in this part: 1. Using Turbo codes and LDPC codes instead of BCH or convolutional codes in MLC/MSD systems; 2. Proposed a new "rotation metric" in order to answer why BP is better than UP in Rayleigh fading channel; 3. Pursue higher frequency efficiency in the structure of MLC --- MLC with 16QAM (4 levels) and MLC with 64QAM (6 levels); 4. The application of MLC in the frequency selective fading channel; 5. Joint MLC with OFDM for higher speed multimedia transmission in the 4G environment; 6. Adaptive MLC scheme.

Part III

A brief introduction for my research group including: our research directions, our interesting areas, our on-going projects and our publications in recent years.

Back to the Systems and Computer Engineering Page

Questions and comments regarding this site? webweavers@sce.carleton.ca