Wu Muqing

Design and Realization of a Novel Multi-path Load-Balancing Routing Protocol in Ad Hoc Network

A load-balancing scheme has a significant effect on the performance of the multi-path routing protocol, especially in an ad hoc network environment. In order to analyze the effect on the distribution of input traffic among multiple paths in AODV-MP (Ad Hoc On-Demand Distance Vector Routing with Multi-Path), first of all, we give the essence of the AODV-MP, and then we design and realize a load-balancing algorithm based on AODV-MP made up of independent nodes, which source node distributes packets reasonably in the several paths according to the load state of the network. Finally we will employ OPNET to simulate the Multi-path routing protocol with load-balancing algorithm. Results of the simulation show that the load-balancing protocol can alleviate the congestion, decrease the end-to-end delay and increase the packet delivery ratio and throughput, thus the performance of multi-path routing protocol can be improved consequently.

Opportunistic cooperative routing in multi-radio multi-channel wireless sensor networks

Interference and unreliability of wireless transmissions limit the throughput of wireless sensor networks. Multi-radio multi-channel technology shows its prospect to significantly improve the network capacity by reducing co-channel interference, and opportunistic cooperative offers a great chance to cope with the unreliability of wireless transmissions. In this paper, we present a multi-radio multi-channel opportunistic cooperative routing (MMOCR) protocol to improve the network throughput. Different from the traditional routing protocols, MMOCR chooses some opportunistic forwarding nodes on the channel with the least interference. The cumulative interference strength (CIS) is proposed to quantify different channel conditions, and a receiver-oriented mechanism to avoid the deafness problem. Packets are collaborative forwarded in accordance with the priorities of forwarding candidate nodes and a slotted acknowledgement is used to guarantee packet delivery and reduce duplication. We finally compare MMOCR with traditional opportunistic routing and deterministic routing protocols, the results show the proposed routing strategy achieves a better performance, especially in terms of the network throughput and packet delivery radio.

An Adaptive LS-SVM Based Differential Evolution Algorithm

Differential Evolution (DE) is featured by its simple parameter control; genetic operation and fine robustness. However, DE yet still has difficulty with complex functions in continuous space due to its searching blindness and inefficiency from time to time. An adaptive DE algorithm based on LS-SVM (Least Square Support Vector Machine) is proposed in this paper. The key genetic operators such as differential mutation and crossover are modified; Adaptive population evolution guiding strategy based on LS-SVM n-best training set approximation and optimization is designed; With applying condition analyzed, the procedure and complexity of the LS-SVM based evolution guiding strategy is summarized. The comparative results of the proposed DE with traditional one based on various standard test functions effectively demonstrate the high accuracy and efficiency of the proposed approach for continuous multi-modal optimization.

Lifetime-based greedy caching approach for content-centric networking

In Content-centric Networking (CCN), in-network caching can enhance content delivery at a global scale without requiring special infrastructure. In this paper, we propose a lifetime-based greedy caching approach (LBGC) which involves both caching decision and cache replacement. Contents are preferred to be stored in nodes with high betweenness centrality, and only expired cache items can be replaced by new arrival contents, which differs from least recently used (LRU) strategy and guarantees the caching of popular contents. Simulation results indicate that LBGC can improve the cache hit ratio and reduce average hops to get content items compared with other caching approaches.

The approach of the New Downlink Control Information Design for Transmission Mode 10

In this paper, we proposed the addition of 2 new bits in Downlink Control Information (DCI) format 2D used for Transmission Mode 10 in 3GPP LTE-A specification. This New Downlink Control Information Design with two new bits extends the Downlink Demodulation Reference Signal (DMRS) so that the Physical Downlink Shared Channel (PDSCH) shall be processed and mapped to Resource Elements (RE) mapping and Quasi-Co-Location (QCL) parameter for a User Equipment UE. The new design was analyzed for Multi-user MIMO (MU-MIMO) and Coordinated Multi-point Transmission (CoMP) techniques. The analysis and simulation results indicate that DCI format 2D with the additional bits used with the CIF field are beneficial for both MU-MIMO and CoMP.

A two-dimensional integrated channel model for train-ground communications

The increasing interest drawn to LTE system requires the analysis of train-ground communication channel. By the approval of the Ministry of Railways of China, extensive and practical measurements are performed on Harbin-Dalian railway with a speed up to 370 km/h. Both large-scale and small-scale fading characteristics are specified. Firstly, path loss and shadowing effect are evaluated based on the hierarchical two-hop network structure. Compared with classical models, the proposed channel model is more applicable in the special via duct scenarios. Channel characteristics, such as channel impulse response, power delay profile, K-factor, delay spread and Doppler spectrum are parameterized and reported. The in-depth analysis of these statistical channel data is from the perspectives of geographical position and relative antenna height. In particular, a new stage-wise K-factor model is investigated and developed. Combined with the cumulative distribution function of the RMS delay spread and the number of paths, they illustrate the distance-dependent and antenna height-dependent variances of the channel. Finally, the two-dimensional integrated channel models are first proposed to give a comprehensive description of broadband mobile channel in high-speed railway scenario. All these informative results promote the evaluation and verification of broadband communication system on High-Speed Railway.

Small worlds in multi-channel wireless networks: An analytical approach

By utilizing the multi-channel technology and small world properties, the average path length of a wireless network can be reduced drastically, leading to a significant improvement of network performance. It has been proven that, by upgrading a fraction of nodes into the high-level nodes with multi interfaces and higher transmission powers, small world effect can be introduced owing to the shortcuts created by the high-level nodes. However, it is difficult to control the small world properties in wireless networks by adjusting the rewiring probability. This work, in particular, investigates the relationship between the network parameters and the equivalent rewiring probability by building an analytical model. Two parameters, communication range multiplier γ and upgrading ratio ρ, are defined to describe this relationship concisely. Simulation results indicate that when γ and ρ are within the optimal ranges, compared with single interface, performance of the double-channel wireless network can be improved by 90%, without introducing any additional mechanisms.

A small world-based energy-efficient mechanism in wireless ad hoc networks

By utilizing the multi-channel technology and small world properties, the average path length of a wireless network can be reduced drastically, leading to a significant improvement of network performance. By upgrading a fraction of nodes into the high-level nodes with multi interfaces and higher transmission powers, small world effect can be introduced owing to the short-cuts created by the high-level nodes. This work, in particular, investigates the relationship between the network parameters and the equivalent rewiring probability in wireless networks. Based on an analytical model, small world energy-efficient mechanism (SWEE) is proposed. Focusing on the additional energy cost consumed by shortcuts and high-level nodes, the main idea of SWEE is to create small world effect with as few shortcuts as possible by allowing a fraction of the potential high-level nodes to degrade themselves into regular nodes. Simulation results show that, compared with the distributed channel allocation mechanism without small-world effect, SWEE can reduce end-to-end delay and energy cost by 40% and 25% respectively.

Mathematical Modeling and Analysis Methodology for Opportunistic Routing in Wireless Multihop Networks

Modeling the forwarding feature and analyzing the performance theoretically for opportunistic routing in wireless multihop network are of great challenge. To address this issue, a generalized geometric distribution (GGD) is firstly proposed. Based on the GGD, the forwarding probability between any two forwarding candidates could be calculated and it can be proved that the successful delivery rate after several transmissions of forwarding candidates is irrelevant to the priority rule. Then, a discrete-time queuing model is proposed to analyze mean end-to-end delay (MED) of a regular opportunistic routing with the knowledge of the forwarding probability. By deriving the steady-state joint generating function of the queue length distribution, MED for directly connected networks and some special cases of nondirectly connected networks could be ultimately determined. Besides, an approximation approach is proposed to assess MED for the general cases in the nondirectly connected networks. By comparing with a large number of simulation results, the rationality of the analysis is validated. Both the analysis and simulation results show that MED varies with the number of forwarding candidates, especially when it comes to connected networks; MED increases more rapidly than that in nondirectly connected networks with the increase of the number of forwarding candidates.

Reclaiming the Efficiency of Opportunistic Routing in Wireless Multi-Hop Networks

Opportunistic routing (OR) is an effective way to guarantee transmission reliability in wireless multi-hop networks. However, little research focuses on transmission efficiency. Thus, an analytical model based on open queuing network with Markov chains was proposed to evaluate the efficiency. By analyzing two typical ORs, we find duplicate transmission and collision avoidance overhead are the root reasons behind inefficiency. Therefore, a new scheme called dual priority cooperative opportunistic routing (DPCOR) was proposed. In DPCOR, forwarding candidates are configured with dual priority, which enables the network to classify forwarding candidates more effectively so as to reduce the back-off time and obtain more diversity gain. Theoretical analysis and simulation results show DPCOR achieves significant performance improvement with less time overhead compared with traditional routings and typical ORs.