Xi Luan

Evolutionary game based access class barring for machine-to-machine communications

Machine-to-machine (M2M) communication faces the most critical challenge that when a massive number of MTC devices perform random access, there will be severe congestions. 3GPP developed a network coordinated random access stabilization scheme known as the access class barring(ACB) to deal with the problem in LTE-Advanced. However, MTC devices in overlapped areas still suffer severe access delays due to the noncooperation and individual setting of ACB factor among BSs. We propose evolutionary game based ACB algorithm to help MTC devices alleviate congestions and thus eliminate substantial defects in the ordinary ACB. Finally, the performance of the evolutionary game based ACB algorithm is analysed, and simulation results show the convergence and effectiveness of the proposed algorithm.

An interleaver scheme for TD-SCDMA compatible GEO satellite communication system

A three-layer interleaver scheme, which is added into TD-SCDMA specification for the compatibility with satellite environment, is proposed for 3G mobile satellite communication systems. Simulation results for satellite channel are presented, which demonstrate that the third interleaver can improve the system performance significantly and satisfy the demands. The proposed interleaver design also provides the theory basis for researching upper layer protocol and transplanting TD-SCDMA specification to satellite environment.

Source nodes power optimization in energy harvesting two-way relay networks

In this paper, we investigate the outage performance for the two-way relaying model in which a half-duplex energy harvesting relay assists in the bi-directional communication of two source nodes. Closed form results for the outage probability of two-way relaying networks has been introduced and corrected in the scenario of an energy harvesting relay. We then consider the relationship between source nodes power allocation, relay energy harvesting efficiency and outage probability. The two source nodes share the limited total power, to minimize the outage probability, we derive closed form results for the source nodes power allocation with fixed relay energy harvesting efficiency. Simulation results are provided to confirm the analytical results.

Selection of sub-carrier bandwidth in OFDM based mobile satellite communication

In mobile satellite communication systems, Doppler shift is caused by the movement of both unified equipment and satellite, and differs from that in terrestrial mobile communication. Therefore, in OFDM based mobile satellite communication systems, the selection of sub-carrier bandwidth should be different. In this paper, the characteristic of Doppler shift in the satellite communication is analyzed, and then a formula is represented to explain the influence on the theoretical system capacity from sub-carrier bandwidth with specific Doppler shift. Using the formula, this paper gives a practicable means to select the optimal sub-carrier bandwidth, and obtains the optimal range of sub-carrier bandwidth in GEO and LEO circumstances through the simulation.

Hybrid cooperation for machine-to-machine data collection in hierarchical smart building networks

Machine-to-machine (M2M) communication plays an important role in various kinds of intelligent networks. In this study, a hybrid cooperation scheme for data collection in hierarchical smart building networks (SBN) is proposed under the framework of M2M communications. The hierarchical network structure means that the data collection process is carried out via multi-layer communications. In the first layer, smart metres organise themselves into clusters and send information to the cluster-heads. Then all cluster-heads forward the received information to the base station automatically in the second layer. In particular, the roles of cluster-head can be acted by either fixed nodes or user terminals in the building, and this endow a hybrid cooperation mode to the data collection process. To construct the network structure and utilise the resources efficiently, the authors first provide some theoretical analysis on the influence of network structure and bandwidth constraints. Then a distributed scheme for joint structure formation and subband allocation is proposed based on coalitional game theory. Furthermore, for the feasibility of this scheme in practical applications, some improvements of the proposed scheme have also been made at last. The advantages of the proposed scheme are verified by simulation results.

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.

Superimposed training and channel estimation for two-way relay networks

In this paper, the superimposed training strategy is introduced into the OFDM modulated amplify-and-forward (AF) two-way relay network (TWRN) to simplify the channel estimation at the destination, and the closed-form Bayesian Cramér-Rao lower bound (CRLB) is derived for the estimation of block-fading frequency-selective channels, which is used to guide the optimal training design. Through the superposition of an additional training vector at the relay under certain power allocation scheme, the separated channel information can be obtained directly at the destination. The Bayesian CRLB is derived for the random channel parameters, and orthogonal training vectors from the two source nodes are required to keep the Bayesian CRLB practical, due to the self-interference in the TWRN. A set of training vectors obtained from the minimization of the Bayesian CRLB are applied in a specific suboptimal channel estimation algorithm, and the mean-square error (MSE) performance is provided to verify the Bayesian CRLB results.

Propagation delays computation in GEO multi-beam satellite communications system

In order to overcome delay-sensitive shortcoming of satellite communications system based on Time Division Duplex mode, a scheme of acquiring propagation delay of any place within a spot beam is proposed. It is accurately calculated by space geometric model according to the satellite position ranging results by three calibration stations. Based on actual system parameters in China, the influence on radio frame design and synchronization problem by using midpoint propagation delay as synchronization reference time instead of average propagation delay is analyzed. The result shows that this approximation can not only reduce the computational complexity, but also ensure the adaptability of TD-SCDMA radio frame structure in GEO satellite communications system.

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.

Content distribution in vehicular networks using coalitional graph game

The popular content distribution (PCD) problem in Vehicular Ad-hoc Networks (VANETs) is considered. We model this problem as a coalitional graph game in which the on-board units (OBUs) try to form a peer-to-peer (P2P) network where one OBU transmits files to multi OBUs but receives from only one OBU each time, to complete the data dissemination efficiently. In this game, the OBUs engage in bilateral negotiations which result in a bilaterally agreement of forming a directed link among OBUs. Once the network is constructed, the OBUs will transmit the content pieces to each other. We study this game under a form of myopic dynamics which is carried out by each OBU in a distributed way. Furthermore, the network formed in this game is a pairwise stable network. Simulation results show that the proposed approach performs better comparing with the non-cooperative case.