Tingrui Pei

A throughput aware with collision-free MAC for wireless LANs

创新点本文结合CSMA/CA与TDMA思想的方式,通过利用节点在网络中能感知到其他节点成功传输的特点,使节点选取在上一个虚拟TDMA周期中是第i个成功发送数据的顺序作为在当前虚拟TDMA周期中的发送顺序。由于同一时隙有且仅有一个成功传输的节点,那么所有成功传输的节点都有一个独立的时隙来发送数据,未成功的节点则随机选取剩余的时隙中某一个再次发送数据。这样成功节点间的数据发送不会相互干扰,未成功节点也不会影响到成功节点的传输。并且在一个虚拟TDMA周期中,当所有节点都能成功发送一次数据时就能一直延续下去,实现免碰撞从而获得高吞吐量。

Generalized analytical expressions for end-to-end throughput of IEEE 802.11 string-topology multi-hop networks

Abstract It is an effective approach for comprehending network performance is to develop a mathematical model because complex relationship between system parameters and performance can be obtained explicitly. This paper presents generalized analytical expressions for end-to-end throughput of IEEE 802.11 string-topology multi-hop networks. For obtaining expressions, a relationship between the durations of the backoff-timer (BT) decrements and frame transmission is expressed by integrating modified Bianchi’s Markov-chain model and airtime expression. Additionally, the buffer queueing of each node is expressed by applying the queueing theory. The analytical expressions obtained in this paper provide end-to-end throughput for any hop number, any frame length, and any offered load, including most of analytical expressions presented in previous papers. The analytical results agree with simulation results quantitatively, which shows the verifications of the analytical expressions.

Energy-efficient selection of cluster headers in wireless sensor networks

Clustering is vital for lengthening the lives of resource-constrained wireless sensor nodes. In this work, we propose a cluster-based energy-efficient router placement scheme for wireless sensor networks, where the K-means algorithm is used to select the initial cluster headers and then a cluster header with sufficient battery energy is selected within each cluster. The performance of the proposed scheme was evaluated in terms of the energy consumption, end-to-end delay, and packet loss. Our simulation results using the OPNET simulator revealed that the energy consumption of our proposed scheme was better than that of the low-energy adaptive clustering hierarchy, which is known to be an energy-efficient clustering mechanism. Furthermore, our scheme outperformed low-energy adaptive clustering hierarchy in terms of the end-to-end delay, throughput, and packet loss rate.

Quality assessment of streaming services in mobile devices

Recently, mobile broadcast services such as DMB, multimedia streaming services and IPTV, caused rapid increase of multimedia services sent over the Internet. It is important to define, measure and evaluate the elements related to the quality of providing the services over the Internet. In this paper, we propose multimedia quality measurement model that evaluates the quality of multimedia from consumers point of view. We selected some parameters that affect the quality of multimedia on application level as well as network level, and then use these parameters to create multiple altered versions of an original video. All videos are then uploaded to YouTube, the popular streaming site. Then each video is viewed by a subject using multiple devices. For each video and device, subjects give Mean Opinion Score (MOS) rating. Then we determined the influence of parameters on videos and devices.

Overlapping Community Detection by Local Community Gravitation in Social Networks

In this paper, a simple but efficient method of overlapping community detection is presented using local community gravitation in social networks. Given a high-quality, non-overlapping partition generated by existing methods, this proposed method identifies the overlapping nodes from their surrounding partitioned communities according to their local community gravitation, with low computational complexity. Our experiments on synthetic networks and real-world networks demonstrate that the proposed algorithm is better than other algorithms in terms of the general quality.

A Graph-Based Multi-hop Cooperative MIMO Scheme for Heterogeneous WSN

A Graph-based multi-hop cooperative MIMO transmission scheme (GM-MIMO) aimed at optimizing the network lifetime and saving energy for heterogeneous wireless sensor networks (WSN) is proposed. In GM-MIMO, clusters are established based on geographical position. Graph theory is applied to find an optimal forwarding path. For taking the presence of node heterogeneity into consideration, GM-MIMO obtains maximum network lifetime. Simulation results show that GM-MIMO makes a significant performance improvement in terms of network lifetime and survival rate of nodes.