Weixia Zou

On the Efficient Beam-Forming Training for 60GHz Wireless Personal Area Networks

In this article, we suggest an efficient beam switching technique for the emerging 60GHz wireless personal area networks. Given the pre-specified beam codebooks, the beam switching process, aiming to identify the best beam-pair for data transmissions, is formulated as a global optimization problem in a two-dimension plane that is formed by the potential beam pattern index. As the analytical gradient information of the objective reward function is practically unavailable, Rosenbrock numerical algorithm is properly adopted to implement beam searching, by implicitly approaching and exploiting the gradient descent direction through the numerical pattern-search mechanic. In order to enhance search performance, furthermore, a novel initialization process is presented to provide the feasible initial solution for Rosenbrock search. Inspired by the appealing conception of small-region dividing and conquering, this pre-search algorithm can efficiently reduce the search scope and hence improve the success probability. The developed beam switching technique, i.e. an initialization process followed by Rosenbrock search, exhibits a much lower complexity than the current state-of-the-art strategies. It is demonstrated from both theoretical analysis and numerical experiments that, compared with the existing popular methods, the required protocol overhead of the new beam-training procedure can be significantly reduced, accompanying the power consumption of 60GHz devices.

On the distributed cooperative spectrum sensing for cognitive radio

Cognitive radio can increase spectrum utilization and avoid interference to licensed users by spectrum sensing. However limitation exists in local spectrum sensing by single cognitive radio node. Although several methods of cooperative spectrum sensing schemes are proposed, they were not checked under different SNR levels. Based on the investigation of the cooperation between CR nodes of different SNR levels, we propose the neighbor exchange of spectrum sensing information scheme aims at comprehensive thinking on increasing spectrum utilization, decreasing the interference to primary licensee and also the traffic load in whole networks.

Priority-based adaptive timeslot allocation scheme for wireless body area network

In recent years, Wireless Body Area Network (W-BAN) is attracting more and more attentions with its various applications like the medical and CE application. And these applications present diverse quality of service (QoS) requirements, so it is necessary to design a medium access control (MAC) protocol to support differentiated services for various traffics coexisting in WBAN. Addressing this problem, in this paper, a new scheme named priority-based adaptive timeslot allocation (PTA) scheme is proposed to differentiate the QoS for the priority classified data in WBAN. Simulation is constructed to testify the efficiency of the PTA scheme compared to IEEE 802.15.4 protocol, and the results show that the PTA scheme provides the better QoS for the higher priority data, and also, performs better performance in terms of the average transmission time and energy consumption efficiency.

A Novel Spectrum Adaptive UWB Pulse: Application in Cognitive Radio

In consideration of the overcrowded spectrum resource, it is of great importance to study the combination of the cognitive radio (CR) and ultra wideband impulse radio (UWB- IR). In the cognitive UWB scene, the UWB pulse is supposed to constantly change its spectrum according to the state of the primary users to mitigate the potential interference to these vulnerale wireless systems. Meanwhile, the frequency utilization of the UWB pulse still eagerly requires improvement to guarantee their transmission reliability. In this paper, we propose a novel UWB pulse based on the neural network, and its simple implementation has also been presented. The frequency utilization of our designed UWB pulse can surpass any other existing UWB signals when no primary user is working around. Based on spectrum sensing information, our designed UWB pulse can adaptively alter its output spectrum to effectively avoid interference to the primary users. We also demonstrate that the proposed UWB pulse is much more suitable for the FCC emission limit than the ECC emission limit.

Analysis on Coexistence of Ultra Wideband with OFDM-Based Communication Systems

Considering the potential interference of ultrawideband (UWB) on OFDM-based wireless communication systems, this paper studies coexistence issue between UWB with both impulse radio (IR) and multiband (MB) modulation and IEEE802.11n, WiMAX, and LTE downlink systems, using physical layer modeling strategy. According to the physical characteristics of UWB and the victim systems, entire physical layer models are set up. Based on the requirements of bit error rate (BER) and receiver sensitivity of the three victim systems, the emission limits of UWB are respectively obtained. Compared with a method based on interference to noise ratio (I/N) criteria, this method reflects the effect of the actual systems, so the conclusion can provide the reference to formulating the frequency spectrum of UWB within the operating frequency bands of the victim systems. Besides, we also reveal that IR-UWB should be more strictly regulated compared with MB-OFDM because of its time domain characteristic.

Detection Fusion by Hierarchy Rule for Cognitive Radio

Cooperation between cognitive radio nodes is indispensable in order to mitigate the sensitivity requirement on individual radio and increase the reliability of spectrum sensing. Normally the fusion network is in parallel configuration and the conventional fusion rules are the k out of N rules because of their simplicity to manage. When the detection nodes are similar with each other i.e. their observations are from same probability distribution, the k out of N rules can make improvement to detection performance since they are equivalent to Neyman-Pearson criteria in this case. However the detection performance decreases greatly when the detection nodes are dissimilar due to fading and shadowing of radio channels especially when most of them are at low SNR states. The hierarchy fusion scheme we proposed in this paper incorporates both parallel and serial configuration and classifies detection nodes into different groups by their SNR levels. The receiver operating characteristic (ROC) of hierarchy fusion rule shows that the detection efficiency and reliability can be increased no matter the detection nodes are similar or dissimilar.

Cluster Based Dynamic Routing on Powerline Carrier Network

Topology of power line carrier network (PLCN) is complex, fast changeable and its channel is time-variant. To enhance the availability and effectiveness of network communication, a cluster based dynamic routing algorithm (CBDR) is proposed in the paper. The algorithm adopts clustering based on root tree and local traversal in order to construct and maintain the dynamic routes according to trees topology, uncertain nodes and the characteristics of power line carrier network, it also adjusts effective communication distance to simplify route. The simulation shows that CBDR using in PLCN is available, it reduces network construction time and maintains the routes effectively. It makes routes of PLCN stabile and flexible. At last the conclusion is made for the further study.

A Multi-Tier Clustering Strategy for Wireless Sensor Network Longevity Using Cultural-Based Multiobjective Particle Swarm Optimization

In this paper, we propose a novel multi-tier clustering strategy using cultural-based multiobjective particle swarm optimization (Cultural-MOPSO) for maximizing the longevity of wireless sensor networks. We take into account the distribution of surviving nodes and define three objective functions based on multi-tier cluster hierarchy to fully evaluate every clusterhead election. Simulation results demonstrate that our proposed strategy can achieve energy-efficient multi-tier cluster hierarchy and outperform two other PSO-based clustering schemes in terms of a new metric of network longevity.

Improving spectrum sensing by counting rules for cognitive radio

Spectrum sensing is crucial for the success of cognitive radio because it will guarantee service improvement to unlicensed users and avoidance of interference to licensed users. However this new radio functionality will place severe sensitivity requirement on individual radio. Local decision fusion as a low complexity method can improve the detection performance by simply increasing the number of times of observation and decision. This paper analyses fusion rules of local decision and deduces their properties and conditions under the assumption that all the decisions are independent and follow the same probability distributions. These properties and conditions can be used to increase the detection probability and to lower the false alarm probability. Finally computation examples show that the performance of local detector can be optimal when choosing appropriate decision number and fusion rule.

An Active Congestion Help Mechanism in Wireless Sensor Network

Many-to-one transport results in congestion in wireless sensor networks (WSNs). This is due to the sudden impulse of information flowing to a single destination by single branch. More attention has been paid to congestion control in WSN, but most research works in the past were apt to handle it by controlling output sending rate, and seldom sought solutions on utilizing the idle resources of non-congestion branch. In this paper, an Active Congestion Help (ACOH) mechanism is designed to find and build an auxiliary routing when congestion. For fairness and flow balancing, Adaptive Flow Allocation algorithm (AF) is designed to distribute flow as adaptive proportion between the main routing and the auxiliary. AF is considering the transmitting-receiving rate of congestive and auxiliary node, and quickly converges to a fair and efficient proportion. In ACOH, a simple backpressure is used to handle the data flow which exceeds the maximum throughput. Simulation results validate the effectiveness of our ACOH.