Wen Xiangming

Research on the modulation and coding scheme in LTE TDD wireless network

In accordance with the channel status information, modulation and coding method can be changed adaptively to enhance the throughput in Long Term Evolution Time Division Duplexing (LTE TDD) system. With the scheme of Exponential Effective SNR Mapping (EESM) and Mutual Information Effective SNR Mapping (MIESM), two Adaptive modulation and coding mechanisms are proposed in this paper. Simulation results show that the performance on network throughput can be improved effectively both in the ideal channel and multi-path channel environment.

Video quality assessment based on Fast Structural Similarity index algorithm

Objective quality measures play important roles in fast image and video quality assessment (VQA). In the paper, a Fast Structural Similarity (FSSIM) index algorithm, which modifies Structural Similarity (SSIM) to achieve a high speed of execution, is used to assess the quality of real-time video application. The experimental results show that the FSSIM index algorithm not only has competitive performance with normal SSIM for assessing video quality, but also has much lower computational complexity.

SWN: An SDN based framework for carrier grade Wi-Fi networks

With the rapid growth of mobile data traffic and vast traffic offloaded from cellular network, Wi-Fi has been considered as an essential component to cope with the tremendous growth of mobile data traffic. Although operators have deployed a lot of carrier grade Wi-Fi networks, but there are still a multitude of arrears for nowadays Wi-Fi networks, such as supporting seamless handover between APs, automatic network access and unified authentication, etc. In this paper, we propose an SDN based carrier grade Wi-Fi network framework, namely SWN. The key conceptual contribution of SWN is a principled refactoring of Wi-Fi networks into control and data planes. The control plane has a centralized global view of the whole network, can perceive the underlying network state by network situation awareness (NAS) technique, and bundles the perceived information and network management operations into northbound Application Programming Interface (API) for upper applications. In the data plane, we construct software access point (SAP) to abstract the connection between user equipment (UE) and access point (AP). Network operators can design network applications by utilizing these APIs and the SAP abstraction to configure and manage the whole network, which makes carrier grade Wi-Fi networks more flexible, user-friendly, and scalable.

Using complex network theory in the Internet engineering

In the next generation network engineering research, network simulation and modelling is very important. The ongoing GNEI, FP7 plan and so on, needs to experiment and simulate the future network. Premise is that the model of network is correct. If the topology model of network is not consistent with the actual network, the conclusion is not correct. Internet network has some characteristics as Hierarchy, Power law distribution, Rich-club property, Disassortative, Self-similarity, Robust yet fragile and others. The complex network theory is a mathematical method to reveal the network scale features. Through the method to establish the network topology will have more match framework with the actual network. This paper analyzed the Waxman model and the BA model based on the distribution of power law. Simulation result shows that the scale-free network has more realistic characteristics of the Internet.

A concept-based approach to video semantic analysis and coding

We propose a concept-based approach to video semantic analysis and coding for video retrieval. The proposed approach is aimed at bridging of the gap between the low-level video features and high level of semantics of video and providing a convenient and efficient way to create semantic descriptions and retrieve video. In the paper, we built an ontology model of the video semantic objects and described the basic relations (part-of, kind-of, instance-of and attribute-of) among these concepts. According to the human concept response of video, we propose a scalable video encoding. Compared to feature-based indexing and retrieval, the proposed concept -based coding presents better results in several kinds of videos.

A Video Retrieval Algorithm Based on Affective Features

One important but often overlooked aspect of human interpretation of multimedia data is the affective information. Affective labels of video content can be extracted automatically from multimedia data streams. These can then be used for content-based retrieval and browsing. In this paper we propose an approach to retrieve the video clips which are similar to the given query in emotion from the video database. We adopt fuzzy representation of video emotion to bridge the semantic gap. Then, we use the cosine measure to compute the similarity between the query video clip and each video clip in database. Ten video clips in database with the highest similarity are output and submitted to the user. And our experiment indicates that the algorithm works well.

Service-oriented network performance evaluation framework based on LA-FAHP

Abstract Since the different characteristics of various network services determine that their requirements for network are also disparate, the performance of one network varies according to the services running on it. However, most of previous network performance evaluation (NPE) researches conduct evaluations based on the network parameters, but without considering from the perspective of specific service running on the network. In view of this issue, a novel service-oriented NPE framework is proposed. First, the characteristics discrepancy among different types of services are investigated. Next, in order to conduct comprehensive evaluation of multiple services, an enhanced low-complexity adaptive (LA)-fuzzy analytical hierarchy process (FAHP) is introduced; meanwhile by applying the experts-construct-directly (ECD) algorithm proposed later, the consistency check required in previous studies can be omitted, thereby significantly reducing the computation complexity and assessment workload for experts. Then, in accordance with the features of each service, corrections are made to their respective membership functions, thus making the proposed LA-FAHP adaptive to various service evaluation scenarios. The subsequent comparison with other NPE methods well proves the effectiveness and high sensitivity of proposed framework, and the analysis verifies the low computation complexity of the proposed algorithms as well.

A human-centered object-oriented framework for semantic video analysis

Semantic video analysis and retrieval is an important way to deal with massive video data. To solve the shortcomings of video analysis directly based on low-level features, this paper presents a video analysis framework based on human subjective affections, the framework according to the impact on object human subjective affection. First, object-oriented model is established, based on object-oriented thinking, we analysis the basic characteristics of the object, and apply it to the video analysis process. Second, we form a video object library, and sort the objects in the library according to their effect on human visual system, and analysis video using it. Lastly we design an interface for retrieving the video analysis. The frame address shortcomings the method directly based on the low-level features effectively, to avoid video noise and other minor objects on the video analysis results. To make the results more in line with the subjective human affections, so that Search more accurately, to better meet human needs.

A Method Based on Cross-layer Design to Solve Cooperation Problem in Wireless Ad Hoc Network

An ad hoc network is a collection of wireless mobile terminals forming a temporary network without the aid of any established infrastructure or centralized administration. In order to support the basal networking functions like routing and packet forwarding, the nodes in wireless ad hoc network should be cooperate with each other due to the limited range of wireless transmission. However, nodes are unwilling to relay packets for others considering the poor energy and bandwidth especially in the open community environment. Some approaches to stimulate nodes cooperation have been introduced recently. In this paper, we provide a novel method based on cross-layer design to solve the cooperation problem both in MAC and network layer. The method with the help of reputation mechanism and utility function based on game theoretical approach can promote nodes to cooperate and make the whole network to reach Nash equilibrium

Improving throughput through dynamically tuning contention window size in dense wireless network

Abstract With the boom of wireless devices, the number of wireless users under wireless local area networks (WLANs) has increased dramatically. However, the standard backoff mechanism in IEEE 802.11 adopts fixed initial contention window (CW) size without considering changes of network load, which leads to a high collision probability and low channel utilization in bursty arrivals. In this paper, a novel CW dynamic adjustment scheme is proposed to achieve high throughput performance in dense user environment. In the proposed scheme, the initial CW size is dynamically adjusted to optimum according to the measured packet collision probability. Simulation results show that the proposed scheme can significantly improve the throughput performance.