| In order to respond to the increases in the number of users and demand for highdata rate, the next generation wireless mobile network tends to be heterogeneous.Oneoperator may run several different networks, such as macro base stations of GSM,WCDMA, LTE system as well as small cells deployed around them, and then acomplex heterogeneous network is formed. Although such a heterogeneous network inwhich a large area of overlapping coverage is able to solve the deep coverage of thenetwork to ensure the user’s quality of service, the emergence of a large number ofvarious small cells (such as Fmetocell Picocell Relay node) to networks will result inhuge energy consumption and a certain degree of waste of resources. Thereforeincreasing the resource utilization of heterogeneous networks seems imperative.The distribution of future mobile traffic presents unbalanced in time and spacedomain. In some region resource is tense and lead to overload blocking, while in someother part resource is too idle and the resource utilization is relatively low. The overallnetwork resources can not achive effective allocation and utilization. In order toimprove the resource utilization of heterogeneous networks, this paper presents anenergy-efficient Relay deployment algorithm and a time domain multi-cell cooperativeSleep-Compensation mechanism; we also provide a theoretical analytical model usingqueuing theory to verify the effectness of sleep-mode in improving the system energy-efficiency. The main results and contributions are summarized as follows:1. We investigate energy-efficient relay deployment by determining the optimalnumber and location of relays in next generation cellular networks. We establish amathematic model for analyzing energy efficiency measured by ‘Joule per bit’ in relayaided cellular networks, where the pathloss status related to the cell traffic busy level isconsidered. We conduct intensive simulation experiments based on the model withrealistic broadband channel propagation conditions. Our findings suggest thatintroducing appropriate number of relay nodes with proper locations into the cellularsystem can improve system energy efficiency without compromising systemthroughput. 2. We propose a cooperative sleep-mode strategy for heterogeneous mobilenetworks where several small cells supply the overlapping coverage, and provide amathematical model for analyzing the performance of the strategy. Specifically, wedevelop a cooperative sleep-mode mechanism, which is implemented by an Adaptivesleep-mode mechanism (ASM) algorithm. We then use E/M/1and E/M/n queuingmodel to analyze the energy efficiency of our proposed algorithm. Our model takes intoaccount the traffic density and system transmission capacity. We also conduct intensivesimulation experiments based on the model with realistic broadband channelpropagation conditions, to verify advantages of the cooperative sleep mode forimproving network energy efficiency and demonstrate the effectiveness of ouranalytical model.3. In order to further improve the system transmission performance of the basestation dormancy mechanism. We propose a Cell Sleep-Compensation (CSC)mechanism. The basic idea of the CSC mechanism is that most of small cells deployedin the hotspot can operate sleep-mode mecanism and one intermediate deployed smallcell acts as compensation cell, providing coverage compensation. Cell compensationcan ensure that the user’s transmission performance of small cells with sleep-mode,while allowing as many as possible small cells in the sleep cycle as long as possible.This paper provides a CSC mechanism and CSC algorithm, relative to the pure celldormancy mechanisms, CSC mechanism balance spectrum efficiency and energyefficiency optimization and is in line with the needs of future mobile networks... |
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