Laixian Peng

Neighbor discovery in three-dimensional mobile ad hoc networks with directional antennas

In this paper, we consider the problem of neighbor discover in three-dimensional wireless mobile ad hoc networks with directional antennas. A directional neighbor discovery algorithm named Limited Random Algorithm(LRA) is proposed in the paper. The difference between LRA and previous researches that assume no prior knowledge of neighbors, is that LRA takes advantage of the approximate location information of neighbors obtained from global positioning system (GPS) or any other similar technologies, which is not exact but fuzzy. LRA is applied to neighbor discovery process between high-speed aircraft and low-speed ships in the Airborne-sea ad hoc networks (ASNETs). We investigate the influence of the fuzzy degree, speed of nodes and distance between nodes on the performance of LRA. Analysis and simulation show that the performance of this algorithm is sensitive to the value of beta which denotes the pitch of aircraft and ship. In the end, future possibilities to ameliorate LRA are discussed.

RR-LQD: A novel scheduling algorithm for CICQ switching fabrics

CICQ(Combined Input-Crosspoint Queued) is a switch fabric with buffers in crosspoints, which brings its nice distributed parallel scheduling property with no internal speedup required. In order to adjust to the nonuniform traffic in the network environment, a novel round-robin scheduling algorithm by using the longest queue detecting (RR-LQD) is proposed. The simulation results show that the RR-LQD can achieve 100% throughput and delay performance close to LQF-RR under various uniform and non-uniform traffics. In addition, the time complexity of RR-LQD is O(1) for hardware implementation. The implementation feasibility of RR-LQD is shown by an FPGA-based design in this paper.

An All-to-All-Broadcast Oriented MAC Protocol Using Directional Antennas in Ad Hoc Networks

In order to share information among all nodes, an all-to-all-broadcast scheme is needed for situation awareness networks. For this type of distributed sensor network, a directional antenna array, called multi-beam adaptive array (MBAA) is proposed to improve the transmission range and reject the interference. In this paper, an all-to-all-broadcast oriented MAC protocol is designed based on receiver-oriented multiple access (ROMA) protocol, which is an efficient MAC protocol exploiting the multi-beam forming capability of MBAA antennas but not designed for the information sharing. For all-to-all-broadcast scheme, the proposed protocol inserts two mini-slots for communication pairs to exchange control information, which helps to decrease the redundant data transmission and quicken the rate of information sharing. The performance of the proposed protocol is studied by the simulations. Compared with the original ROMA protocol, the proposed protocol shows a high performance in all-to-all-broadcast, which proves that the method can be an efficient way for similar MAC protocols to utilize all-to-all-broadcast scheme.

A Unitary Precoder for Optimizing Spectrum and PAPR Characteristic of OFDMA Signal

In this paper, a unitary precoder is proposed to suppress the out-of-subband (OOSB) spectral leakage and reduce the peak-to-average-power-ratio (PAPR) for DFT-based orthogonal frequency division multiple access uplink signal. The optimum precoder is developed by solving a multi-objective optimization problem and a method which includes two steps is presented. First, employ eigenvalue decomposition to design the precoder with minimizing OOSB power radiation. Then search for the optimum permutation of columns to reduce the PAPR sufficiently. Besides, an iterative decoding algorithm for the proposed precoder is designed to improve the system performance on bit-error-rate (BER). Simulations show that the proposed precoding and decoding method offers significant performance advantages of spectral leakage suppression, PAPR reduction, and BER improvement at the same time.

An all-to-all broadcast protocol for variable packet sizes using directional antennas

All-to-all broadcast, which means that every node in the network has its own data packet to share among the other nodes, plays a significant role in some applications, such as situation awareness and cooperative engagement. However, current studies in the TDMA (Time Division Multiple Access) manner mainly focus on the fixed size model, which assumes that all data packets can be successfully transmitted within a time slot. Restricted by the transmission rate and limited lengths of a time slot, this assumption is surely unsuitable for practical applications in which the packet size can be variable. To address this issue, we propose an all-to-all broadcast protocol for variable packet sizes (ABVP), which employs the multi-beam adaptive array (MBAA) as well as two redundant transmission eliminating mechanisms. The simulation results show that, compared with the existing packet scheduling algorithm the Delay Aware scheduling (DAS), the proposed protocol can make an effective schedule for variable packet sizes which diminishes the delay to at most 60% for accomplishing all-to-all broadcast.

A fuzzy service matching algorithm based on Bloom filter

With the development of the Web service, enhancing the capabilities of the current Web service search engines with effective and efficient techniques for Web service retrieval and selection becomes an important issue. This paper presents a novel service matching degree assessment method based on Bloom filter. Facilitated by this method, an algorithm that supports service fuzzy matching has been proposed. The main idea of this algorithm is using Bloom filter to describe the service and request, and assessing the similarity of service and request by the similarity of Bloom filter vectors. Experimental and theoretical results show that this algorithm can support service fuzzy matching by simple algebraic operations on Bloom filter. The evaluation accuracy rate is beyond 95%.

A novel windowing scheme to suppress spectral sidelobes for OFDMA system

Orthogonal frequency division multiplexing access (OFDMA) inherently suffers from large spectral sidelobes, which will lead to interference between users and can not be ignored. In this paper, in order to suppress spectral sidelobes, we propose a novel windowing scheme. The derivation of the optimum window function is based on the solution of an optimization problem. It aims to minimize in-band-out-of-subband (IBOSB) power radiation. An algorithm named GSSO is designed to approximate the optimum window function. The simulation results show that with a lower roll-off factor (2.5%) the proposed windowing scheme can significantly improve the performance of spectral sidelobes suppression.

Study on Routing Protocol in Airborne-Sea Ad Hoc Networks with Directional Antennas

In this paper, we propose a directional routing protocol for airborne-sea ad hoc networks (ASNETs). Directional antennas have the potential to provide a fundamental breakthrough in ad hoc network capacity, connectivity, and covertness because they have great advantages such as high spatial reuse and range extension. ASNETs is a special ad hoc network which include two kinds nodes, namely aircraft and ship. To fully exploit the benefits of directional antennas in ASNETs, a Node-Avoided Directional Routing (NADR) protocol is to be considered. The main feature of NADR is that route request packets is always transmitted by those less load nodes. That is why NADR can effectively balance the load of node. Preliminary simulation results are found to be very promising, the performance of NADR is better than DSR and DRP in terms of the packet delivery ratio and throughput. Introduction Wireless ad hoc networks, particularly, mobile ad hoc networks such as airborne ad hoc networks (AANETs) [1] and vehicular ad hoc networks (VANETs) [2] have been experiencing a modernization that make a significant change in human life. One can define the wireless ad hoc network as dynamic network because it is a group of communications devices or nodes that communicate with each other without fixed topology and without pre-determined organization. In this paper, we mainly research Airborne-sea ad hoc networks (ASNETs) which will support the military battleground to preserve some information among the aircrafts and ships. Most of the existing works [3] [4] on wireless ad hoc networks assume the use of omni-directional antennas at the physical layer that radiate or receive power equally well in all directions. With omni-directional antennas, the distribution of energy in all directions other than just the intended direction generates unnecessary interference to other nodes thereby considerably reduces network capacity. On the contrary, with directional antennas or smart antennas [5] both transmission range and spatial reuse can be substantially enhanced by having nodes concentrate transmitted energy only towards their destination’s direction, thereby achieving higher signal to noise ratio and reducing multipath components. There are a few studies of routing protocols using directional antennas. Directional Routing Protocol (DRP) [6] is an on-demand directional routing protocol which is specifically tuned to the underlying directional antennas. DRP attempts to alleviate some of the inherent drawbacks involved in directional communications while

A max-group coloring-based gossiping mechanism using double-face phased array radar for wireless multi-hop networks

Gossiping (all-to-all broadcast) plays an important role in network communication. There are many studies of gossiping trying to reduce the transmission energy consumption and time consumption. Nevertheless, with wide applications of double-face phased array radar in military and other special fields, a specific gossiping mechanism for this model is needed. In this paper, we consider the gossiping with double-face phased array radar model and global topology model. Then a maxgroup coloring-based gossiping mechanism for wireless multi-hop networks is proposed. The mechanism introduces virtual nodes and virtual links in the topology generating process, and takes the idea of coloring. In addition, a direction selecting mechanism is proposed for improving the performance of the gossiping process. Finally, the simulations show that the proposed mechanism could reduce time consumption significantly.

Neighbor Discovery in Wireless Network with Double-Face Phased Array Radar

As one of the important steps in the process of self-organization of wireless ad hoc networks, neighbor discovery has substantial influence on the network performance. Especially in the modern warfare environment, the time consumption of neighbor discovery is very important for holding the battlefield situation. In this paper, we address the problem of neighbor discovery in ad hoc network with double-face phased array radar. And we take advantage of double-face phased array radar to improve the efficiency of neighbor discovery. Unlike former researches on single beam directional antenna, double beam directional antenna is introduced to our system. However, the direction of the antenna has been limited to two exclusive ranges due to the structure of double-face phased array radar. Obviously, the performance of the system which is in half duplex working mode can be better than the same one using single beam antenna. Thus we compare our system with the one using single beam antenna which is in full duplex mode. The experiential results show that the performance of neighbor discovery using double-face phased array radar in half duplex working mode is about 5 times better than the one using single beam directional antenna in full duplex working mode with the same algorithm.