| The future mobile communication system is characterized with its high spectral efficiency even in high speed environment. Based on the GZCW (Group Zero Correlation Window) spreading codes and the theory of MIMO, Professor Daoben Li provided a famous theory system on the design of generalized, parallel, group zero correlation window spreading codes, with the elements of which being random, i.e. GPRGZCW. The most attractive character is its super high spectral efficiency. This theory on one hand enlarges its elements from the numeric one to those random ones on the description of time, space and frequency. With the proper design, these elements not only broaden the freedom of design on spreading codes, which means there could be more spreading codes available in the system, but also can provide gains of diversity, which would improve system performance. On the other hand, with allocating more parallel sub-channels within one group and introducing the controllable interference between these sub-channels, it can improve system spectral efficiency greatly, which can satisfy the requirements of the future mobile communications. This theory not only enriches the content of the theory on spreading codes design, but also shows the right way for the future mobile communications.Based on this theory, my thesis focuses on the design of the proper spreading codes that are with high spectral efficiency and diversity gain at the transmitter. And the low complexity, good performance receiver also interests me, which means the better MCD (Multi-Code Detector) that is fit for those special codes. What is more, I have also payed much attention to the methods of channel estimation, which plays an important role in the mobile communication system.1. In the following, we give a sufficient discussion of space-time GZCW. Based on the system with two transmitters, how to get more transmitting diversity gains and how to improve spectral efficiency are studied. We altogether compare the performance, capacity of four schemes. The results show that our space-time GZCW surely provides much higher spectral efficiency than the LS-MIMO system, and with the proper design, system performance can also be improved. Besides, a new method for LAS-MIMO which would be close to the upper bound of MIMO system capacity is provided.2. In chapter 3, based on the space-time system, we focus on the MCD. Firstly, we provide the ZF method on chip level and symbol level respectively, and the one on chip level performs better. As it for SIC, we provide a new method that can simplify the SIC process while the performance degrades little. When MLD is employed, we provide a rule that can be used to judge how the design of space-time spreading codes will perform.3. Channel estimation plays a very important role in mobile communication system. In LAS-CDMA, the most often used channel estimation methods are continuous pilots and linear interpolation method. As for continuous pilots method, because of the IFW of spreading codes for data symbol and pilot symbol, the main error comes from the noise. Based on this, we provide a new channel estimation method which combines continuous pilot methods with regression to suppress the noise degradation. The results show that it will provide 2dB gain and will perform as well as the ideal channel estimation does. As for the linear interpolation methods, after analyzing, it is found that for the same interpolation... |
