Research On Technologies For Future Wireless Communication System

Spectrum efficiency and reliability are ultimate targets of wireless communication system design. Advanced signal detection technologies are employed to improve error correction performance. Furthermore, because of the channel fading, diversity techniques should be used to improve the reliability of wireless transmission. Effective multiplexing and multi-access techniques should also be used to gain higher spectrum efficiency. In this thesis, several techniques are discussed, including optimal detection structure of digital modulation system, effective optimal and near-optimal detection algorithm, and space transfer diversity in frequency selective channel, overlapped multiplexing implemented by OVTDM, OVCDM, and overlapped multi access implemented by OVCDMA, interference alignment.Whiten filter receiver, the optimal detection structure of digital modulation system, is discussed at first. An improved whiten filter based on matrix decomposition is proposed. Compared with the original whiten filter based on polynomial factorization, the new design can be applied to time-varied channels. Second, closest lattice point question, a very important question in communication, is discussed. To solve this question, sphere decoding algorithm (PDA) and probability data assisted algorithm (PDA) are introduced. An enhanced SDA is proposed. Using constant amplitude property new SDA is applicable to overloaded system. A new form PDA is also proposed. It is equal to the original PDA but do not need inverse of channel correlation matrix. Transfer diversity design in frequency-selective channel is next discussed. There are two criterions in space-time coding design. First one shows that full diversity can be obtained if error matrix is always of full rank. Second one shows how to maximize coding gain. Under the guidance of these two criterions, several space-time coding scheme used applied to flat fading channel are modified to frequency-selective channel. A transfer diversity scheme based on zero correlation window (ZCW) code is proposed. It is equivalent to the space-time block coding but with lower complexity. A thread layer space-time coding scheme which is suitable for frequency-selective channel is proposed. It is a full diversity full multiplexing (FDFM) space-time code and can switch between diversity and multiplexing freely.Theoretical research of overlapped time division multiplexing (OVTDM) is the next topic. After fundamental introduction of OVTDM, Several theoretical question of OVTDM, like the power spectrum density of OVTDM, channel capacity of OVTDM, is answered. The research of capacity of OVTDM shows that by waveform overlapping OVTDM can achieve higher capacity than Nyquist system. When overlapping factor is greater than the product of shaping pulse bandwidth and shaping pulse ISI-free sampling interval, capacity of OVTDM is equal to the capacity of waveform channel capacity which is the upper bound of all digital modulation channels.Fast detection algorithm of overlapped code division multiplexing (OVCDM) is discussed. After fundamental introduction of OVCDM, Concatenate OVCDM is discussed. A parallel detection structure is proposed to reduce complexity of concatenate OVCDM detection. Next topic is the system design of overlapped code division multi-access (OVCDMA). OVCDMA uses ZCW code and its shift as address code. Optimal receiver of OVCDMA and several question of OVCDMA are discussed. At last interference alignment (IA) technology is discussed.