Wireless Communication Systems, Multi-dimensional Constellation Modulation Method

Diversity is an effective means to combat fading in wireless communication systems. When several replicas of the same information are available, a receiver combines them to increase the received signal-to-noise ratio (SNR) to improve the system performance. Moreover, if each replica experiences uncorrelated fading, diversity order can be increased.Time diversity, frequency diversity and space diversity are three kinds of diversities which have been researched widely. But these diversity technologies need additional power or bandwidth to be realized. In single antenna systems, signal space diversity (SSD) has been introduced as an alternative scheme to achieve an additional diversity gain. The SSD involves interleaving over coordinates and employs a signal constellation rotation. SSD is quite different from the three kinds of diversities mentioned above. Diversity gain of SSD is obtained from the modulation part of system and it need no additional resource, but the complexity of the receiver is the barrier of the application of SSD. With the present of some decoding methods for SSD, SSD has been widely used in different kinds of communication systems, so it is meaningful to research it.Although the work of SSD fundamental theory almost has been solved, the application of SSD has not received attention enough. Specially, the research of the application of SSD in MIMO and OFDM is far from adequacy, both of which are the key technologies in the next generation of wireless communication system. The research work of SSD will be started as following:Summary of the fundamental theory of SSD is finished in detail in this paper and the structure of rotation matrix is explained in the view of lattice and number theory. The appliance of SSD in PSK is studied and the problem of"zero signal"is explained by strict mathematic speculation.A new method of expanding SISO system with SSD to MIMO system is presented. A lot of work in this topic is available but the complexity of the system in these works is too high or the performance of the system is not so good. The method in this paper is very simple and it is proved by simulation that the rate of system is arisen to N times to the original SISO system (N is the number of transmitting and receiving antenna) and the performance of SISO system is reserved.Precoded OFDM and vector OFDM both of which are special OFDM system are introduced simply. There exist many research results on these two OFDM systems. Optimization of VOFDM is completed and the performance of VOFDM is improved when exists spectral nulls in channel. Simulation shows that in some kinds of channels, BER=10-2, OVOFDM brings gains of 4dB and 3dB to VOFDM, respectively.For resolving the bad effect of spectral nulls in channel on OFDM system, we study the application of SSD in OFDM system. By grouping carriers, it is possible to use SSD in it. Through the simulations, we proof that SSD-OFDM bring the performance improvement for OFDM system. The performance of VOFDM and SSD-OFDM is compared in simulation and the advantage of SSD-OFDM is obvious.The research of the application of SSD in MIMO and OFDM system can be used some other complicated communication system, such as MIMO-OFDM system and cooperation system, etc.