Resource Allocation And SWIPT For Cooperative Relaying Wireless Networks

Modern communication technology has experienced significant revolution from ana-log to digital, from fixed to mobile, and from low speed to high speed in the past decades. Recently, the huge energy consumption and carbon emissions of the information and communication technology (ICT) have attracted enough attention along with its rapid de-velopment. It is hoped that the power consumption could be decreased while the users’ Quality of Service (QoS) are guaranteed to restrain the carbon population. On the other hand, wireless communications are suitable for many critical applications such as sen-sors in hazardous environment or implanted medical devices. Those wireless devices can neither be connected to power grid nor replaced or recharged batteries frequently, which makes the devices’lifetime limited to the battery capacity. Thus, it is of great importance to power the wireless energy-constrained devices with continuous and stable energy over the air without disruption to the use.For the above-mentioned problems, this thesis does the following work. Firstly, by designing the effective protocols and doing the resource allocation combined with network coding (NC) to reduce the power consumption of relay cooperative networks. Secondly, the emerging simultaneous wireless information and power transfer (SWIPT) technology is applied to enable the energy-constrained devices to harvest energy from the radio frequency (RF) signals in the surrounding environment, and use the harvested en-ergy for the subsequent information transmission, which can extend the devices’lifetime and improve the communication performance. The main contributions are summarized as follows:(1) The resource allocation and relaying deployment are investigated in a two-way transmission aware multi-user cellular network to minimize the average transmis-sion power of mobile stations (MSs). Firstly, an efficient bandwidth allocation method and a transmission strategy combined with network coding (NC) are pro-posed, based on which, an optimization problem is formulated to minimize the average transmission power of MSs. Secondly, as the optimization problem is non-convex, a genetic algorithm (GA) based algorithm is presented by jointly consider-ing the MSs’transmission strategy and the relays station (RS) positions. Thirdly, in order to improve the system spectral efficiency (SE), the influences of different frequency reuse type on MS’s transmission power and system SE under different number of relays are also discussed. Numerical results show that the proposed NC cooperation relaying scheme can extend MSs’battery life at least6%more than traditional decode-and-forward (DF) method.(2) The outage performance is investigated in a two-way relaying system employing SWIFT combined with digital NC. Firstly, by considering two practical receivers, i.e. power splitting (PS) and time switching (TS) receivers, two protocols named power splitting-based network coding relaying (PSNCR) and time switching-based network coding relaying (TSNCR) are proposed respectively to enable the ener-gy harvesting (EH) and information processing at the relay without power supply. Secondly, for both proposed protocols, the explicit expressions and the approximate expressions in high signal-to-noise ratio (SNR) of the system outage probability are theoretically derived. Then, in order to achieve the minimal outage performance of the system, an outage minimal optimization problem is formulated and a corre-sponding optimization algorithm is designed to get the optimal system deployment parameters. Besides, the optimal region of system parameters is also presented. Numerical results show that the SWIPT combined with NC can greatly decreased the system outage probability. It can also be observed that the relay position great-ly affects the system performance, where relatively worse outage performance is achieved when the relay is placed in the middle of the two sources. This is the first time to observe such a phenomena in EH two-way relay systems.(3) The outage performance is studied in a multiuser transmission system with an EH cooperative relay. Firstly, by considering analog NC relaying cooperation, two pro-tocols named PS cooperative multiuser transmission (PSCMT) and TS cooperative multiuser transmission (TSCMT) protocols are proposed respectively to enable the simultaneously EH and information processing at the relay by applying PS and TS receivers. Secondly, for both proposed protocols, the system outage performance is studied, and the closed-form expressions as well as the approximate expressions in high SNR of the system outage probability are theoretically derived. Thirdly, based on the analytical outage probability, the effects of system configuration parameters on the system outage performance are discussed. Extensive numerical results show that the two proposed protocols can achieve better outage performance than the traditional non-cooperative system. Moreover, due to the fact that the energy used by the relay is harvested from the RF signals in communication networks, our pro- posed protocols can improve the system outage performance without consuming extra energy.(4) Extending the SWIPT to the MIMO-OFDM relaying system and exploring the sys-tem achievable rate limit. Firstly, by considering TS and PS receivers, two cooper-ative protocols named TS-based DF relaying (TSDFR) and PS-based DF relaying (PSDFR) protocol are proposed respectively to enable the simultaneous informa-tion processing and energy harvesting at the relay. Secondly, in order to explore the system performance limit, the system achievable rate is theoretically analyzed, based on which, two optimization problems for the proposed protocols are formu-lated to maximize the system achievable rate. Since the problems are non-convex and difficult to solve, the problems are decoupled into different sub-problems ac-cording to the receiver performance. After getting some explicit results of sub-problems theoretically, an Augmented Lagrangian Penalty Function (ALPF) based algorithm are designed to jointly optimize multiple deployment parameters to max-imize the system achievable rate. Numerical results show that, PSDFR outperforms TSDFR to achieve higher achievable rate in such a MIMO-OFDM relaying system. It can also be observed that the relay position greatly affects the system perfor-mance of both protocols, and relatively worse achievable rate is achieved when the relay is placed in the middle of the source and the destination.