Interference Mitigation And Resource Scheduling For60GHz Wireless System

In the past years, with the improvement of the fourth generation (4G) cellular mobile communication system standards for International Mobile Telecommunications-Advanced (IMT-Advanced), very high spectrum efficiency can be achieved in these standards, for an example, up to30bit/s/Hz. However, current wireless communication systems, operating at traditional low cellular carrier bands (e.g.450MHz-3GHz), can only support limited transmission data rate, which is not able to satisfy the growing data traffic requirements.60GHz wireless communication with up to7-9GHz bandwidth can provide multi-Gbps wireless data rate, even employing the low spectrum efficiency technologies. However, there are still some challenges to restrict its applications in60GHz millimeter-wave wireless communication, for examples, high propagation loss, interference in beamforming process and multi-link user-intensive scenarios, and resource scheduling for relay assisted transmission system are investigated.Firstly, beam squint and interference caused by IEEE802.15.3c codebook in60G Hz millimeter-wave communication are analyzed. To minimize the beam squint, three codebook design schemes are proposed for different implementation complexity and performance requirements, namely, phase adjustment scheme based on IEEE802.15.3c codebook, single phase adjustment scheme and main response axis (MRA) alignment codebook design scheme. Compared with3c codebook, all these three codebook schemes can suppress beam squint and interference, improve spatial multiplexing efficiency and system capacity. The first two schemes have an appropriate performance to beam squint suppress, and the second scheme only requires a1/M(M stands for the number of antennas) phase shifters than the first scheme. The direction of MRA can be adjusted and aligned exactly in different frequencies by the third scheme, higher array antenna gain with a lower side lobe level (SLL) can be achieved. The growth rate of system capacity is up to26.3%with the third scheme, but it requires more phase shifters.In a user-intensive multi-link60GHz wireless transmission scenario, interference between different links will result decrease of system capacity, and even the high-rate transmission cannot be achieved as promised by60GHz networks. A maximum sum-rate algorithm based on the IA (Interference Alignment) is proposed, which employs joint transmission and IA according to the different channel state information (CSI). Maximum sum-rate of the system can be achieved by the proposed algorithm. In addition, we investigate the performance of IA with limited feedback and CSI delay. Compared to the rate with perfect CSI, a rate loss upper bound is obtained by analytical derivation. Furthermore, we show that if the time delay and signal to noise ratio (SNR) satisfy a certain relationship, the system rate loss can maintain a constant value, and with SNR increasement optimal transmission degrees of freedom (DoF) can be obtained.Thirdly, since high penetration loss in60GHz millimeter, wireless communication becomes sensitive with the surrounding environment, and the capacity of link will decrease significantly. In order to improve system throughput, an idle user or access point (AP) can be selected as a relay node for dual-hop transmission. Based on performance analyze of the relay assist dual-hop transmission, a closed form outage probability (OP) solutions is derived. To minimize the OP for relay position selection, the objective task is formulated as a minimization problem, and it can be obtained numerically. Simulation results show that, comparing with the conventional relay transmission, the proposed scheme can reduce the outage probability, and the system throughput can be improved25%.60GHz millimeter-wave enables multi-Gbps wireless data communications at the expense of high energy consumption. The optimization the energy-efficiency resource allocation with required system throughput is studied in a two-hop60GHz relaying system. Single relay assisted transmission scheme is proved that can achieve optimal energy-efficient in physical layer network coding (PNC) based relay system. The closed form subcarrier and power allocation solutions are obtained by analyzing Karush-Kuhn-Tucker (KKT) conditions. Based on the derived solution, a novel optimal energy-efficient single relay selection (RS) and power allocation (PA) is proposed. The energy-efficient optimality of the derived scheme is demonstrated as compared to PNC with equal rate power allocation (ER-PA), as well as three-stage time division broadcast (TDBC). The proposed scheme can significantly improve system energy-efficiency, energy consumption is only36%of the TDBC scheme.The main research contributions of interference mitigation and resource scheduling for60GHz wireless system are four-fold. The all of the three proposed codebook schemes which are designed for different implementation complexity can suppress interference and improve the spatial multiplexing efficiency. In multi-link scenario, the proposed maximum system capacity interference alignment scheme can effectively suppress interference, enhance network capacity. Based on the research of idle user as a potential relay node for dual-hop transmission, it can provide method in optimal relay selection and system enhancement. The proposed energy-efficiency resource management scheme can improve system energy efficiency significantly, as well as effectively supporting for massive data transmission in mobile terminals.