Energy Saving Mechanisms Of Base Station With QoS Guaranteeing

With the development of mobile Internet, the traffic demands of wireless appli-cations increase explosively. At the same time, the kinds of service and QoS (Qual-ity of Service) requirements become diverse. To satisfy traffic demand and improve the capacity of network, the designment of next generation network should consider the transmission technology and network architecture. Advanced physical technolo-gies such as OFDM and MIMO result in more energy cost while improving the spectral efficiency(SE). Densification deployment requires more number of sites and makes the network interference limited and decrease the energy efficiency(EE). To reduce the en-ergy consumption and carbon emission, BSs need energy saving design.This thesis starts from the characterization parameters of QoS and finds that delay is the most important effect factor of QoS. We group the wireless applications into delay constraint traffic and delay tolerant traffic and design energy efficient schedular for these two kinds of traffic with delay providing from link level. In addition, we propose a two-level schedular with QoS guaranteeing and energy saving for the practical cellular networks. When the traffic load is low, BSs can coordinate the micro sleep subframes to minimize interference and improve EE. All these works consider practical power model. There are no optimal solutions for most of the cases because the power function is discontinuous.Firstly, we study the energy efficient scheduling policies for delay constraint ser-vice. We focus on how to minimize the total energy consumption when transmit the non-causal independent arriving and delay constraint packets. Using the quasiconvex optimization theory, we propose an optimal rate adaptive and sleep control algorithm with low complexity. Then, based on the results, we propose a heuristic online schedul-ing algorithm for the causal Poisson arriving process. In addition, we consider the scheduling policy for fading channel in which the transmitter should send pilot signal to estimate the channel state and this process is not only time consuming but also energy consuming. The original optimization problem is NP-Hard and we propose a subopti-mal scheduling algorithm consisting three parts:a time-dependent weighted sum of a delay associated term, an opportunistic term and a practical energy consumption related term.Then, we also study the energy efficient transmission scheme for delay tolerant traffic. For the single channel, we propose two sleep strategies and deduce the closed form of energy consumption with the M/G/1queueing theory. Then we propose an optimal iterative algorithm using biconvex optimization theory and Lagrangian method. For the multi channel multi user scenario, we deduce the average and variance of user’s delay for the ARQ process. With the constraint of average delay, we propose a heuristic resource allocation algorithm based on the traffic statistical information and channel state information.In the end, we study the multi BSs cooperative subframe-level sleeping strategy with QoS guaranteeing for the practical cellular networks. We propose a two-level schedular model and use the linear control theory to design the upper level schedu-lar which segments the packets into multiple small ones and transmit each one over different frames. The lower level schedular is used for the energy efficient resource allocation. For the scenario with single BS and single user, we formulate the prob-lem as a mix integer programming problem to minimize the energy consumption while satisfying average data rate requirement. We relax the integer of sleep subframes to a continuous variable and use convex theory to demonstrate the existence of a unique globally optimal resource allocation solution and develop an iterative algorithm to ob-tain it. For the scenario with single BS and multiple users, we use the property of time sharing condition for multiple channel system to obtain the optimal sleep subframes for the BS. Then we allocate the power and subchannel for each user using the traditional Marginal Adaption problem. For the multiple BSs system, each BS allocates the re-source independently based on the channel state and interference level of the last frame. Then the BSs coordinate sleep subframes with each other as orthogonal as possible to reduce interference and improve the energy efficiency of network.