MIMO Techniques For Emerging Wireless Communications

The Multiple-Input Multiple-Output (MIMO) and beamforming technique are vital issues in emerging wireless communication as the number of user and the demand of capacity increase rapidly. MIMO technology takes advantage of different diversity scheme which can remarkably improve the spectral efficiency, the channel capacity and the data transmission rates. The V-BLAST space-time coding is an important method to obtain the required capacity in MIMO channels by spatial multiplexing that provides superior spectral effectiveness in fading channel. Furthermore, a smart antenna (beamforming) technique is able to increase the subscriber capacity and decrease the interference. These techniques are fruitful to raise capacity, interference cancellation, congestion control management and user load management.To the emerging wireless communication systems, this dissertation aims to further research the MIMO and beamforming techniques by using the space-time coding and network coding methods, and some innovations have been achieved. The proposed solution can effectively increase the system capacity, improve the spectral efficiency and enhance the performance of interference suppression.In this dissertation, the key innovations are as follows:(1) A multi-user MIMO scheme with zoom beamforming and load balancing performances is proposed. The existing schemes focus on multi-layer transmissions for multi-user without load balancing. While, the wireless communication system performances, such as energy consumption, time and data processing delay, are degraded. Whereas, the proposed load management scheme is based on beamforming layer zoom (in/out) technique, and the multiple users are handled by single beamforming transmission. Meanwhile, taking the load balancing issue into consideration, the proposed scheme is an efficient way to increase throughput, reduce the congestion and enhance data rates in wireless communications within the same energy consumption.(2) An efficient Long Term Evolution (LTE) uplink transmission scheme is proposed. In general, the reference signals and the demodulation signals are transmit, respectively, which will cause many constraints, such as interferences between layers and reference signal symbols, delay increasing and overall throughput reducing of the LTE uplink transmission. In present research, the channel characteristics are estimated based on the uplink reference signal and a LTE uplink transmission scheme is proposed by integrating the signaling information of Demodulation Reference Signal (DM-RS) as the Single Value Sounding Reference Signal (SV-SRS) from the signaling symbols of Sounding Reference Signal (SRS). In this scheme, the reserve capacity of the DM-RS is used for uplink data, thus the overall capacity of the uplink is increased. Besides, this scheme can suppress the symbols & channel interference and reduces the Bit Error Rate (BER) of LTE uplink system.(3) A comparative study of the diversity gain and coding gain in MIMO system is carried out. The heavy demands of wireless networks bring higher requirements for data transmission rate, transmission range and power of the wireless devices. By using the space-time coding method, a thorough comparison of coding gain with the diversity gain is discussed for 4x2 and 4x4 MIMO systems. The diversity gain is achieved by the Orthogonal Space-Time Coding (OSTBC) and the coding gain adopts the Turbo Code (TC) rates 1/2 and 3/4 encoding scheme. The performance of comparison results indicate that the combination of diversity gain with coding gain has a productive influence on data rate and multi user handling performances for the MIMO system.(4) Based on Physical-layer Network Coding (PNC), a novel MIMO scheme is proposed by combining the Vertical-Bell Laboratories Layered Space-Time (V-BLAST) with the PNC. In order to enhance the reliability of data transmission with the help of diversity gain, V-BLAST and PNC is combined in the multi-user MIMO scheme and redundancy is introduced to avoid the data packets retransmissions at the upper layer. This scheme improves the throughput and performance of wireless communication system.(5) To the 3D beamforming transmission, a feedback path based Self-Interference (SI) mitigation method in the Co-frequency and Co-Time Full Duplex (CCFD) system is proposed. The 3D beamforming network has dimensional diversity that it transmits data according to the user-specified horizontal and vertical sectorization and tilt beamforming. Commonly,3D beamforming transceiver transmission is based on half duplex either Frequency Division Duplex (FDD) or Time Division Duplexing (TDD) strategy that consumes extra spectrum and energy. Therefore, a feedback path based self-interference mitigation method in CCFD for the coordinated 3D beamforming transmissions scheme is considered to improve the overall system performance for energy and spectrum efficiencies.The performance analysis and numerical results demonstrate that all the proposed strategies outperform the existing approaches in terms of higher capacity, interference suppression and better energy consumptions in the emerging wireless communication.