Research On Theory And Methods Of Energy-Efficient Resources Management In Wireless Networks

Green wireless communication is considered as the most promising method for reducing the increasing energy consumption, which has been researched extensively and intensively recently. Wireless resources includes BS density, transmit power and frequency bandwidth. As an effective method to improve the energy efficiency of wireless network, energy-efficient resources management of wireless networks has rapidity become a hot issue in green communications. The heterogeneous network is a new trend of wireless network development, which including the complementary low-power nodes providing very high data rates in hotspot region and the traditional macro nodes providing wide-area coverage in non-hotspot region. Such new architecture can reduce the increasing power consumption of network while meet the increasing data rates and the seamless connection of traffic demands. Our research mainly includes the analysis the heterogeneity of traffic demands in the time/spatial/content dimensions, the quantitative relationship between the energy-efficient resources management and energy efficiency of wireless network, the influence on the heterogeneity of traffic demands and thus provides necessary theoretical support to apply this energy-efficient resources management in next generation wireless networks. In this dissertation, we present a quantitative model for heterogeneity of traffic demands. Based on this model, the energy-efficient two-tier deployment and configuration is proposed to adapt the heterogeneity of traffic demands in the spatial dimension, where the base station (BS) density, BS transmit power and frequency bandwidth are taken into account. We present closed-form formulas which establish the quantitative relationship between heterogeneity of traffic demands and energy-efficient network resources allocation. In order to adapt the heterogeneity of traffic demands in the time dimension, we further present three energy-efficient control strategies of micro BSs, including micro BS sleep control, coverage expansion control and coverage shrinking control. Last we propose three energy-efficient multicast schemes in order to adapt the heterogeneity of traffic demands in the content dimension, which can potentially lead to significant power savings. The main study points are shown as follows.1. Quantitative model for heterogeneity of traffic demandsThe existing traffic models are unable to characterize the heterogeneity of traffic demands and thus we develop the quantitative model for heterogeneity of traffic demands in the time/spatial/content dimensions. First, we propose a traffic heterogeneity curve to describe the heterogeneity phenomena of traffic demands and then define a traffic heterogeneity coefficient to quantitative characterize the heterogeneity of traffic demands. Secondly, we calculate the traffic heterogeneity coefficient for several classic heterogeneity probability distributions. Last, we derive the traffic heterogeneity coefficient for the scenario where the traffic demands are non-uniformly distributed in hotspot regions and non-hotspot regions. This research can be regarded as the improvements for the traditional study of heterogeneity of traffic demands and provides theoretical support for the analysis and utilizing heterogeneity of traffic demands in the rest of paper.2. Research on theoretical relationship between energy efficiency, resources and heterogeneity of traffic demandsTraditional theoretical analysis of energy efficiency of wireless network is unable to consider the impact of heterogeneity of traffic demands. We first develop the heterogeneous networks model including both macro BSs and micro BSs and drive the expressions for outage probability, average spatial rate and network energy efficiency, which shows the diffidence energy efficiency of point-to-point transmit and that of networks. These expressions includes the BS density, BS transmit power and frequency bandwidth and thus very flexible in different scenarios. Furthermore, we analyze the impact of different degree of heterogeneity of traffic demands on energy efficiency of wireless network and resource and prove the significant potential of energy-efficient resource management in saving network energy consumption.3. Research on energy-efficient resource allocation networks for spatial heterogeneity of traffic demandsTraditional energy-efficient resource allocation is unable to consider the impact of heterogeneity of traffic demands. Based on the proposed quantitative model for heterogeneity of traffic demands, we develop the optimal BS transmit power and BS density configuration for wireless networks. Secondly, we design the optimal bandwidth allocation strategies for fractional frequency reuse and carrier aggregation scenarios. The micro BSs can use the frequency band for hotspot regions coverage which is not suitable for macro BSs in wide-area coverage. This technique needs lower transmit power and will not generate the interference to the users severing by macro BS and further prove the significant feasibility of energy-efficient resource management in saving network energy consumption and thus can be directly deployed in real wireless networks.4. Research on energy-efficient BS sleep control, coverage expansion and shrinking control networks for time heterogeneity of traffic demandsTraditional BS sleep control, coverage expansion and shrinking control are not precisely designed because lack of heterogeneity of traffic demands. In order to meet the fluctuation of traffic demands in time dimension, we develop the BS sleep control strategy based on the heterogeneity of traffic demands. Due to the energy ineffective BS coverage for hotspot regions, we proposed the BS coverage expansion and shrinking control. This technique can further decrease the power consumption of BS while guaranteeing the Quality of Service (QoS) and the seamless connectivity of traffic demands.5. Research on energy-efficient BS unicast and multicast mode control networks for content heterogeneity of traffic demandsIn recent years, the widespread requirement of wide-band multimedia communication, especially Video-on-Demand, has led to rapidly rising energy consumption and wireless network resource. The heterogeneity of traffic demands in the time/spatial/content dimensions means a large number of users request the same traffic within short time interval thus the transmission technique can aggregate the traffic demands for the same content of traffic can significantly improve the energy efficiency of wireless network. We propose an energy-efficient transmission scheme where in each time-window the transmitter analyzes the similarity of users’traffic requests and the similar traffics will be transmitted by multicast mode while the other traffics will be transmitted using unicast mode. Secondly we extent this scheme to adept the multi-cell and multi-antenna scenario which can aggregate more traffic demands for the same content and provide higher multicast data rate. Last, in order to overcome the transmit delay in previous two schemes, we propose an energy-efficient multicast scheme with patching stream which enable the transmitter to deliver both patching streams through unicast transmission guaranteeing the real-time demand and shared streams through multicast transmission guaranteeing high energy efficiency.