The Future Mobile Communication System More High Spectrum Efficiency Transmission Technology Research

The thesis conducts research on high spectral efficiency communication technologies in cellular mobile systems.The capacity of traditional coded modulation schemes is bounded away from the Shannon limit due to fixed channel symbol set. Overlapped code division multiplexing (OvCDM) output Gaussian distributed channel symbols through overlapping several independent coded streams. The thesis proves that random time-varying OvCDM is capacity achievable with increased constraint length. A novel simplified OvCDM (S-OvCDM) scheme is devised to reduce the receiver complexity while its performance maintained. In Rayleigh fading channels, OvCDM system has a high error floor. In order to solve this problem, an interleaved code doping scheme is devised. Another scheme that concate-nates OvCDM and high rate outer code is designed to improve its frame error rate performance in urban macro channels. Through the observation of OvCD-M output symbol set, the thesis constructs a36-point constellation to replace normal64QAM. Under proper code rate and labeling strategy, the new constel-lation could even outperform64QAM in bit error rate due to increased distance between constellation points. Furthermore, fewer constellation points would lead to lower peak to average power ratio.The frequency shift transmit diversity and cyclic delay diversity schemes in LTE both relies on Turbo code to achieve the spatial diversity gain. How-ever, in high spectral efficiency system, the free distance of Turbo code is very small and thus could not achieve the diversity gain. A novel scheme based on position permutation is designed to solve the problem. The scheme could be further generalized to a new kind of space time code, space time interleaving code. It could be used in multi-path channels and achieve full spatial diversi-ty, full frequency diversity gain without any rate loss. Furthermore, the em- bedded interleavers facilitate design of iterative receivers which largely reduce the implementation complexity. Fast detection algorithms in highly correlated multiple antenna systems is also studied in the thesis. Due to the equivalence between high spectral efficiency OvFDM system and highly correlated MIMO system, the fast detection algorithms of the latter could be applied to reduce the complexity of OvFDM receiver.In order to study inter-cell interference suppression, the channel capaci-ty of cellular system is analyzed case by case. Without cooperation between cells, the interference is processed as pure noise. It is proved that with normal interference randomization technique, the cell edge spectral efficiency of full frequency reuse system is higher than that of the system with lower frequency reuse factor. If the interference channel coefficients could be gained through cell cooperation, the degrees of freedom of the cellular system could be very close to the system without any interference. If there is real time cooperat-ed signal processing between cells, then the strong interference between cells could even boost the cell edge spectral efficiency. Based on these analysis, an overlapped interleaving division multiplexing (OvIDM) system is designed to suppress strong interference from other cells. Combined with interference alignment, OvIDM system could be further improved in spectral efficiency. Fi-nally, a multi-cell joint scheduling strategy is given for OvIDM system and its simplified iterative version is devised.System level simulation and hardware simulation platforms are useful for performance evaluation. The way to construct such platforms are discussed based on two platforms designed by the author.