Wenson Chang

Gale-Shapley-algorithm based resource allocation scheme for device-to-device communications underlaying downlink cellular networks

Device-to-Device (D2D) communications underlaying cellular networks can improve the network capacity and spectrum efficiency by sharing the cellular resources in the direct-transmission mode. However, the stringent interference between D2D and cellular systems can seriously repress the overall performance improvement. In this paper, we aim to solve this dilemma by applying the concept of differentiated priority into the resources sharing problem between the D2D pairs and cellular users. Firstly, we modified the conventional partial time-frequency resource allocation scheme to let each D2D pair select its sharing comrades, i.e. the cellular users, based on its own preference list such that less amount of mutually interference can be incurred. Secondly, the differentiated priority scheme is furthered implemented into the cellular users, i.e. the so-called bipartite differentiated priority. Then, the association problem between the D2D pairs and cellular users is solved by using the Gale-Shapley algorithm. The simulation results show that the proposed schemes can greatly enhance the system stability and capacity, while accommodating more D2D pairs.

A Novel Cluster Head Reselection and Edge Sub-Clustering Lifetime Prolongation Scheme for Modern Sensor Networks

In the wireless sensor network (WSN), how to efficiently utilize the energy of each sensor node is the key to prolong the network lifetime. The balance of energy consumption among the nodes located at different areas, e.g. the central and edge areas, also plays another important role in the scenario of lifetime prolongation. Thus, the energy efficiency of the whole network can be severely reduced if the geography of network topology is ignored in the cluster head (CH) selection. To our best knowledge, the geography effect of Poison point process (PPP) has not yet been investigated in the existing cluster head (CH) selection algorithm. In this paper, considering the PPP geography effect, the weighted residual energy and distance (WRED) algorithm is proposed to favor the nodes positioned near the cluster center with more energy in the CH selection. On top of this algorithm, the edge sub-clustering (ESC) scheme is further developed to alleviate the effect of non- uniform node distribution on the edge. Additionally, without reforming the clusters and sub-clusters, frame-by-frame CH and sub-CH reselection is also designed to reinforce the effectiveness of the proposed WRED and ESC schemes. In this fashion, not only the energy conservation but also the balance of energy consumption can be significantly improved, which can contribute to longer network lifetime and lower outage probability.

On the Performance of the DNPS-Based Relay Networks under Masquerading Attack

In the relay networks, two typical issues of physical layer security are selfishness and garbling. As a matter of fact, a certain nontypical but severely harmful misbehavior can also remove the cooperative diversity gain. Here, we coin the masquerading attack to indicate this kind of misbehavior. A masquerade relay can always pretend to be the best one to forward signals and, in consequence, deprive the others of the opportunities to cooperate. To the best of our knowledge, the impact of the masquerading attack has not yet been fully investigated. In this paper, multiple masquerade relays with random masquerading behavior are taken into account. Also, the complete channel effects, including the effects of the flat Rayleigh fading, log-normal shadowing, and path loss, are considered such that the geographical effects of the network topology can be completely captured. At last, the impact of the masquerade relays are evaluated in terms of the outage probability and end-to-end capacity.

ERA Cooperative Sensing with Differentiated Sensing Period and Retreat Scheme in Cognitive Radio

During the past dozen years, numerous approaches have been proposed to enhance the efficiency of the cooperative spectrum sensing (CSS) for the cognitive radio (CR) systems. Reducing the signaling overheads and energy consumption during the reporting period are the main targets of these works. In this paper, we propose an efficient reporting and accumulating (ERA) scheme to jointly improve the sensing and reporting efficiency. However, owing to individually reducing the sensing period for each secondary user (SU), the undesired collisions can be incurred while reporting the local decisions. To alleviate the collision problem, a Gaussian retreat (GR) scheme is developed. As verified by the simulation results, higher energy efficiency and spectrum utilization can be achieved. Moreover, the miss-detection probability can become negligible by using the GR scheme.

Partial Overlapped Time-Shifted Pilots for Massive MIMO Systems

This letter proposes a partial-time-shifted pilot scheme to find a better tradeoff between the user accommodation and orthogonality of pilots for the massive multiple-input multiple-output system. To this end, the pilot symbols rather than the pilot sequences are applied. In addition, the neighboring cells are allowed to transmit the pilot signals using the overlapped symbol periods. Despite the stronger interference, the larger user accommodation as well as the near-far effect incurred by using the pilot symbols can contribute to the higher sum transmission rates for both the uplink and downlink cases.

Efficient load-aware vertical handoff for HetNet with poisson-point-process distributed traffics

Nowadays, the emerging hyper-dense heterogeneous network (HetNet) is an effective solution to building an easy-access wireless communication environment. In the hyper-dense HetNet, however, the inescapable handoff procedure is the key to its success. An effective handoff algorithm can not only achieve the goal of load-balancing but also enhance the overall system capacity. In this paper, we proposed an efficient load-aware vertical handoff (VHO) algorithm for HetNets. With the aid of the system load information from the neighboring cells, the computational complexity during the VHO procedure can be significantly reduced. Moreover, by effectively off-loading the cells with relatively light traffic loads (i.e. non-worst conditioned cells), the dropping rate can be significantly reduced. Most importantly, the user and the overall system capacity can be greatly enhanced as well.

Effects of non-uniform quantisation on the interference mitigation using multi-cell multiple-input and multiple-output-coordinated beamforming

In recent years, coordinated beamforming (CBF) has attracted considerable attention because of its effectiveness in intercell interference (ICI) mitigation. To facilitate the operations of CBF for the frequency-division duplex mode, efficient channel state information (CSI) exchanges through backhaul links are necessary. In previous studies, uniform quantisation of CSI has been generally assumed in feedback schemes. Statistically, however, uniform quantisation may not be optimal from the viewpoint of the ICI in CBF, which is mainly caused by the quantisation error (QE). This study proposes a low-complexity cumulative distribution function (CDF)-based non-uniform quantisation method with a limited number of feedback bits for applying more quantisation levels to represent feedback CSI, which occurs with higher probability. This is because a more accurate representation of frequent CSI can lead to a lower QE for reducing the ICI level in most cases. To prove the effectiveness of the proposed CDF-based quantisation scheme, the ICI in the considered two-cell CBF scenario was analysed using several feedback bits. The simulation results proved the higher transmission rate, particularly in cases with fewer feedback bits.