Yuxin Cheng

Cell selection in two-tier femtocell networks using Q-learning algorithm

Next-generation wireless networks will generate a heterogeneous network with micro base station (MBS) and femtocells where cell selection becomes crucial for balancing the utilization of the whole network. In this paper, we investigate cell selection problem in a two-tier femtocell network that contains a MBS and several femtocells with open/closed access methods and coverage areas. The selection process among groups of users in different service areas is formulated as a dynamic evolutionary game. In order to achieve an equilibrium, we present the Q-learning algorithm that can help distributed individual users adapt the situation and make cell selection decisions independently. With their own knowledge of the past, the users can learn to achieve the equilibrium without a centralized controller to gather other users information. Finally, simulation results present the convergence and effectiveness of the proposed algorithm.

Distributed Joint Cluster Formation and Resource Allocation Scheme for Cooperative Data Collection in Virtual MIMO-Based M2M Networks

An efficient data collection scheme plays an important role for the real-time intelligent monitoring in many machine-to-machine (M2M) networks. In this paper, a distributed joint cluster formation and resource allocation scheme for data collection in cluster-based M2M networks is proposed. Specifically, in order to utilize the advantages of cooperation, we first propose a hierarchical transmission model which contains two communication phases. In the first phase, the intracluster information sharing is carried out by all the nodes within the same cluster. Then these nodes transmit the total information to the BS cooperatively with virtual-MIMO (VMIMO) protocol in the second phase. To grasp the properties and advantages of this cooperative transmission strategy, the theoretical analysis results are provided. The key issue in this system is to form the clusters and allocate resources efficiently. Since the optimization problem on this issue is an NP-hard problem, a feasible joint scheme for the cluster formation and resource allocation is proposed in this paper, which is carried out via coalition formation game with a distributed algorithm. This scheme can reduce the complexity while keeping an attractive performance. Simulation results show the properties of the proposed scheme and its advantages when comparing with the noncooperative scheme for the data collection in a practical scenario.

A Non-adjacent Feed Selection Method for Beamforming Performance Enhancement for Multi-beam Satellite Antenna

In recent years, user-centered beamforming systems have attracted increasing interest in the study of multi-beam satellite communication systems. In order to ensure service quality, the beam directivity of targets should have enough flexibility to bear the randomness of user locations. In this paper, a non-adjacent feed selection method is proposed to minimize the mean square error of beamforming and provide enough flexibility of the beam directivity at the same time.

Dynamic Transmission Mode Selection and Resource Sharing Schemes for M2M Communications in Cellular Networks

Direct Device-to-Device (D2D) communications is showing promising advantages on supporting machine-to-machine (M2M) communications in cellular networks. In this paper, a dynamic transmission mode selection and a corresponding resource sharing strategy are proposed to enhance the average Quality of Service (QoS) performance of the hybrid networks. Specifically, the machine nodes can choose either cellular mode or D2D mode according to the power efficiency. And then, three kinds of service, the machine nodes in cellular mode, machine nodes in D2D mode and common UEs in cellular network can be formed. If the traffic load grows heavier, an efficient resource allocation strategy should be employed to guarantee the network QoS performance. To address this problem, a dynamic resource sharing strategy is proposed for this kind of hybrid network with the purpose of minimizing the largest waiting time of different types of service. To grasp the properties and advantages of the proposed strategies, the performance of the system is analyzed theoretically, such as the average waiting service number and the blocking probability. Simulation results shows that the proposed transmission mode selection and dynamic resource sharing schemes are efficient from the view of the QoS performance in the whole network.

Frequency Resource Sharing and Allocation Scheme Based on Coalition Formation Game in Hybrid D2D-Cellular Network

A distributed cooperation scheme on frequency resource sharing is proposed to improve the quality of service (QoS) in device-to-device (D2D) communications underlaying cellular networks. Specifically, we formulate the resource allocation problem as a coalition formation game with transferable utility, in which all users have the incentive to cooperate with some others and form a competitive group to maximize the probability of obtaining their favorite spectrum resources. Taking the cost for coalition formation into account, such as the path loss for data sharing, we prove that the core of the proposed game is empty, which shows the impossibility of grand coalition. Hence, we propose a distributed merge-and-split based coalition formation algorithm based on a new defined Max-Coalition order to effectively solve the coalition game. Compared with the exhaustive search, our algorithm has much lower computer complexity. In addition, we prove that stability and convergence of the proposed algorithm using the concept of a defection function. Finally, the simulation results show that the proposed scheme achieves a suboptimal performance in terms of network sum rate compared with the centralized optimal resource allocation scheme obtained via exhaustive search.

Multi-Beam Collaborative Joint Detection for TD-SCDMA Compatible Mobile Satellite Communications System

Multi-user detection can improve the performance of TD-SCDMA compatible mobile satellite communication system. This paper focuses on the technique of multi-beam collaborative joint detection. Based on the multi-beam joint detection technique in mobile terrestrial communication system, theadjacent beam assisted single-beam joint detection scheme is realized in the satellite system firstly. Then two new multi-beam collaborative joint detection schemes are proposed which are multi-beam collaborative joint detection and multi-beam joint detection combination. Both schemes estimate the signal in target beam cell according to the received signal in target beam cell and its adjacent beam cells. Theoretical analysis and simulationshow thatthe proposed scheme has better performance than the single-beam joint detection and the adjacent beam assisted single-beam joint detection.

A Non Cyclic Prefixed MIMO-OFDM Scheme in Mobile Satellite Broadcasting Systems

In this paper, we propose a non-cyclic prefixed multiple-input multiple-output orthogonal frequency division multiplexing (non-CP MIMO-OFDM) transmission scheme using polarization antenna diversity based on a recursive algorithm of joint channel and data detection for mobile satellite broadcasting systems under frequency selective fading channel. Unlike the traditional cyclic prefixed MIMO-OFDM scheme, the transmitted block in the proposed scheme is designed that pilot sequence and OFDM symbols have been arranged alternately without any cyclic prefix (CP) at the head of each OFDM symbol. Moreover, a recursive algorithm of joint channel estimation and data detection based on interference cancellation is proposed for user terminals. Simulation results show that the proposed system achieves lower bit error rate (BER) and higher information data rate than the traditional cyclic prefixed MIMO-OFDM system with least square (LS) or iterative LS channel estimation algorithm.