| Device-to-Device (D2D) communication is an important proximity communication technology, which has been in standard process of LTE-Advanced system and it is a key technology for the future hybrid networks. Wih the development of mobile internet, the cellular network is not able to meet the requirements for the furture localizing applications and D2D technology comes to an important complement for it.D2D communication in cellular spectrum supported by a cellular infrastructure holds the promise of three types of gains. First, the D2D transmission can save half resource due to a single link rather than using both uplink and downlink resource when communicating via base station in the traditional cellular transmission. Second, the proximity of user equipment (UE) in the D2D communication may allow for extremely high bit rates, low delays and low power consumption. Finally, D2D communication can reuse the radio resource of cellular in underlay mode, which can further improve the spectrum efficiency by spatial multiplexing. Additionally, D2D communications may extend the cellular coverage and facilitate new types of wireless peer-to-peer services.In this issue, we study the hybrid networks of D2D communication underlaying cellular system from three aspects with target of solving key problems in D2D communication and optimizing the performance of D2D transmission. The main contribution of this paper shows as follows:Firstly, we have studied the network capacity of D2D transmission. In this paper, we model the hybrid network of cellular and D2D communication with random geometry theory and optimize the D2D capacity with guarantee of cellular user’s QoS (quality of service). The main innovations in this paper show as follows:in the first, we make the sum-capacity of hybrid networks reach maximum by scheduling users according to the optimal transmission mode proportion. Then we extend the D2D user sharing single band with cellular user to the multi-bands scenario. By proper allocating D2D user and transmit power over multi-bands, we propose the upper bound of sum capacity of D2D transmission on multi-bands. Finally, we analyze the transmission capacity of D2D communication assisted by mobile relay based on stochastic geometry for the first time and present some results for it.Secondly, we have analyzed and solved the wide-band spectrum sensing problem faced by D2D users in the communication. In our study, we build a wide-band sampling spectrum model and design a detection method with target of minimizing the whole detection error, which overall consider the false detection probability and false alarm probability. And we also take the specification of detection and false alarm probability into account and provide the trade-off between watching time and detection performance. Besides, we discuss about the effect of noise uncertainty on the detection performance and obtain the minimum length of watching period when the peak noise uncertainty is given. Based on former results, we propose a noise-estimation and signal-detection joint iteration algorithm, which is able to evaluate the noise power during detection and the simulations demonstrate the reliability of the method over different scenarios.Thirdly, we have studied the resource management in the hybrid networks. Comparing with present work, the main contribution shows as follows:at first we provide a mode selection criterion based on the limited location information, which provides the theory support for the present study based on the simulation. Then we analyze the effect of cooperation between cellular and D2D links on the sum capacity of two links. Finally, we set up an optimization problem with target of maximizing D2D network capacity and solve it through Lagrangian dual method. The optimal D2D user allocation over multi-bands is derived first and then we provide an interactive method for both optimal user and power allocation over multi-bands. The simulation results demonstrate the efficiency and reliability of the algorithm. |
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