Duzhong Zhang

A service-oriented spectrum allocation algorithm using enhanced PSO for cognitive wireless networks

Because of the increasing growth of spectrum utilization in wireless networks, dynamic spectrum allocation (DSA) using cognitive radio has recently attracted attention. DSA provides a promising communication paradigm to relieve the bottleneck that arises in the spectrum utilization of wireless networks. In a cognitive wireless network, deficient matching between user demands and spectrum resources can result in communication deterioration; however, superfluous matching can lead to inefficient spectrum utilization. In this study, a service-oriented, multi-attribute normalization model is developed that considers user demands and spectrum characteristics. Based on this model, a service-oriented DSA, which applies the graph coloring problem (GCP) and an enhanced particle swarm optimization (PSO) method, is proposed to efficiently satisfy user service demands and achieve better utilization and fairness rewards. The simulation results demonstrate that the algorithm satisfies the requirements for accurate spectrum allocations in cognitive wireless networks and performs better with respect to iteration efficiency and utilization rewards than the existing algorithms.

Ecology-Based Coexistence Mechanism in Heterogeneous Cognitive Radio Networks

Recently, tremendous utilization of wireless networks has led to sever scarcity of radio spectrum resources. TV White Spaces (TVWSs) as novel bands enabling Cognitive Radio (CR) technology to improve spectrum resources utilization, have attracted significant standardisation efforts such as IEEE 802.11af, IEEE 802.16h and 802.22. As these heterogeneous networks may operate on the same channels of TVWSs, network coexistence problem cannot be avoided and is particularly challenging given the heterogeneous MAC/PHY layer protocols and operation parameters (e.g., tx power) employed in coexisting networks. In this paper, we develop a coexistence mechanism called ecological Species Competition based HEterogeneous networks coexistence MEchanism (SCHEME). Inspired by ecology based species competition model, SCHEME uses an ecological spectrum allocation method to assign available spectrums. Through both theoretical and simulation analysis, we demonstrate that SCHEME can achieve stable and fair spectrum allocation among coexisting networks.

Empirical analysis of ZigBee and WiFi coexistence

In design and manufacturing, the heterogeneous network is applied. So the coexistence of different networks is the trend and bottleneck, especially the manual interference and coexistence between the typical WiFi and ZigBee. In this paper, a set of experiments have been done to observe the node-to-node ZigBee communication performance in all of 16 channels under the WiFi interference in the actual laboratory. The USRP N210 devices are used to send and receive 1000 ZigBee packets under the almost fixed and busy WiFi environment once a time. The WiFi interference depends on the actual laboratory radio environment. And We change the transmit power, communication channels and communication distance respectively. And we record the packet loss rate and the packet error rate at the receiver relevantly. Then, the diagrams are given out. Through the analysis of the data, the relationship between the ZigBee communication performance and the parameters is concluded. Finally, the conclusion is given out-what are the best parameters for ZigBee to achieve assured high communication performance under the currently WiFi interference.

QoE Based Spectrum Allocation Optimization Using Bees Algorithm in Cognitive Radio Networks

Cognitive Radio is a promising technology for addressing the spectrum scarce since the growing number of wireless applications. Most of recent researches about spectrum allocation based on users’ demands are channel allocation which may not effectively use spectrum holes and meanwhile, users’ satisfactions are not fully matched. To satisfy users’ demand better, Quality of Experience (QoE), which numerically describes users’ satisfaction, is used to evaluate the spectrum allocation result; Bees algorithm is used to facilitate QoE based spectrum allocation optimization, so as to maximize the users’ overall QoE while ensuring user’s fairness by dynamically allocating free bandwidth to users according to their QoE requirements; Considering the network circumstance, a network model considering the Primary Users’(PU) activity, Secondary Users’(SU) diversity, spectrum characters is proposed for the QoE based spectrum optimization to adapt to network states. Evaluation performances show that the proposed spectrum allocation method outperforms the existing channel allocation methods.

Multi-layer based multi-path routing algorithm for maximizing spectrum availability

Last 2 decades have witnessed the spectrum resources scarcity which is caused by wireless networks’ ubiquitous applications. To utilize the rare spectrum resources more efficiently, Cognitive Radio (CR) technology has been developed as a promising scheme. However, in CR networks, a novel NP-Hard disjoint multi-path routing problem has been encountered due to the Primary Users’ (PUs’) random movements. To settle this problem, we present a Spectrum History Matrix mechanism to define long-term spectrum sensing information on time-spectrum level such that spectrum availability and communication efficiency can be quantized in CR networks. To lessen the possibility for an active PU to interrupt all paths simultaneously, a sub-optimal Multi-layer based Multi-path Routing Algorithm (MMRA) is provided to determine how to route multiple paths which are not under the same PUs’ interference ranges. Through theoretical and simulation analyses, MMRA can not only settle the disjoint multi-path routing problem in polynomial time complexity, but also maximize communication efficiency.

Survey on coexistence of heterogeneous wireless networks in 2.4 GHz and TV white spaces

Given the unprecedentedly dense deployment of wireless networks due to the proliferation of inexpensive, widely available wireless devices in the limited spectrum bands, many of these wireless networks should operate at least partially overlapped or even on the same spectrum band. Incompatible communication pattern of different networks with different applications (e.g. Internet of Things, wireless sensor networks and individual wireless communication) would cause serious wireless networks coexistence problem. For the representative, two bands, 2.4 GHz industrial, scientific and medical band and the TV white spaces, effective signalling protocols, as well as radio resource allocation mechanisms could achieve an efficient and fair utilization of spectrum. In this survey, we report and analyse the recent technical advance and development of coexistence protocols. Aiming at tracing the latest developments in this field, we attempt to deliver a comprehensive coverage on existing literatures with a proper technical depth to introduce the design idea and philosophy and analyse the pros and cons of each surveyed coexistence solution. We also discuss a number of important and relevant research challenges that have not been addressed in the existing literatures and that deserve further research attention and investigation.

On-demand ecology-inspired spectrum allocation mechanism for heterogeneous cognitive radio networks

As increasing number of cognitive radio network (CRN) standards are developed in TV White Spaces band with incompatible communication patterns, heterogeneous CRNs coexistence problem could not be avoided. However, most solutions on this problem have not considered CRNs’ actual data transmission demands and weighted fairness simultaneously. Therefore, we would like to introduce a novel On-demand ecological Species Competition based HEterogeneous networks coexistence MEchanism (O-SCHEME) in this paper. Inspired by ecology species competition model, O-SCHEME utilizes an ecology based spectrum allocation mechanism for guaranteeing heterogeneous CRNs’ spectrum shares weighted fairness. And by employing CRNs’ communication spectrum requirement constraints, actual data transmission needs could be satisfied without wasted communication resources. Through both theoretical and simulation analyses, we demonstrate that O-SCHEME can achieve stable and fair spectrum allocations among coexisting networks with high communication efficiency.

An adaptive hybrid ARQ method for coexistence of ZigBee and WiFi

With the rapid development of modern communication technology, all kinds of radio technologies emerge endlessly. As different wireless networks share the same spectrum, coexistence of the heterogeneous networks becomes a challenging problem, especially the coexistence between ZigBee and WiFi. Much research has been done to solve this problem, and some coexistence methods have been proposed, such as the spectrum allocation, power control and so on. However, the proposed methods are either too complex to implement or need additional hardware cost. This paper proposes an easy and feasible method called AHA for ZigBee. The method modifies the current FEC coding method and additionally colligates energy sensing and adaptive retransmission. By implementing the method on ZigBee using USRP N210 devices, it is demonstrated that AHA effectively improves the communication performance of ZigBee under WiFi interference.