Adaptive unequal protection for wireless video transmission over IEEE 802.11e networks

Packet loss of video streams cannot be avoided at wireless links for limited wireless bandwidth and frequently changed environments. To provide differentiated Quality of Service (QoS) guarantees between multimedia and data services, IEEE 802.11e was proposed. However, its performance and flexibility need to be further improved. In this paper, after a survey on various modifications of IEEE 802.11e, we formulate the problem of video transmission over IEEE 802.11e networks to help scheme design and performance analysis. Then accompanied with in-depth analysis, an adaptive unequal protection schema is proposed, which is composed of three mechanisms: (1) Insert each video packet into the access category (AC) with the minimum relative queuing delay; (2) Assign each packet dynamically to a proper AC based on several parameters to guarantee the transmission of high priority frames; (3) Apply fuzzy logic controllers to adjust parameters so as to reply quickly to the variation of video data rate, coding structure and network load. Finally, regarding MPEG-4 codec as the example, we perform extensive evaluations and validate the effectiveness and flexibility of proposed scheme. Simulations are divided into WLAN and multihop parts, involving different video sequences and various traffic modes of data streams. Beside performance comparison between proposed scheme and other ones, influence of parameter setting and combination with routing algorithms are also evaluated.     

Distributed scheduling algorithms for channel access in TDMA wireless mesh networks

In this paper, we have considered the distributed scheduling problem for channel access in TDMA wireless mesh networks. The problem is to assign time-slot(s) for nodes to access the channels, and it is guaranteed that nodes can communicate with all their one-hop neighbors in the assigned time-slot(s). And the objective is to minimize the cycle length, i.e., the total number of different time-slots in one scheduling cycle. In single-channel ad hoc networks, the best known result for this problem is proved to be K ² in arbitrary graphs (IEEE Trans Comput C-36(6):729–737, 1987) and 25K in unit disk graphs (IEEE/ACM Trans Netw pp 166–177, 1993) with K as the maximum node degree. There are multiple channels in wireless mesh networks, and different nodes can use different control channels to reduce congestion on the control channels. In this paper, we have considered two scheduling models for wireless mesh networks. The first model is that each node has two radios, and the scheduling is simultaneously done on the two radios. We have proved that the upper bound of the cycle length in arbitrary graphs can be 2K. The second model is that the time-slots are scheduled for the nodes regardless of the number of radios on them. In this case, we have proved that the upper bound can be (4K?2). We also have proposed greedy algorithms with different criterion. The basic idea of these algorithms is to organize the conflicting nodes by special criterion, such as node identification, node degree, the number of conflicting neighbors, etc. And a node cannot be assigned to a time-slot(s) until all neighbor nodes, which have higher criterion and might conflict with the current node, are assigned time-slot(s) already. All these algorithms are fully distributed and easy to realize. Simulations are also done to verify the performance of these algorithms.     

A Fast Formation Flocking Scheme for a Group of Interactive Distributed Mobile Nodes in Autonomous Networks

Ubi-Com promises to provide a diversity of services at anytime and anyplace. The mobile nodes are envisioned to cooperate freely and move on a plane with the help of the efficient control and distributed coordination strategies. To achieve this goal, mobile nodes group communications in Ubi-Com is becoming increasing important and challenging. In this paper, we focus on the formation flocking in a group of autonomous mobile nodes. In the scenario, there are two kinds of nodes: the leader node and the follower nodes. The follower nodes are required to follow the leader node wherever it goes (following), while keeping a particular formation they are given in input (flocking). A novel scheme is proposed on the basis of the relative motion theory. Extensive theoretical analysis and simulation results have demonstrated that this scheme provides the follower nodes an efficient and timely method to follow the leader with the shortest path and the shortest time. In addition, the reported scheme is scalable in the sense that the processing load in each node is not increasing with more nodes in a group.     

A Resilient and Scalable Flocking Scheme in Autonomous Vehicular Networks

Vehicular Ad hoc NETworks (VANET) is emerging as a highly promising technology, which aims to provide road safety, environment protection and personal-oriented services. The vehicle ad hoc wireless communications form an indispensable part of truly ubiquitous communications networking. VANET is formed by spontaneously moving autonomous vehicles with the self-organization and self-management capability. In this paper, we focus on the decentralized coordination of multiple unmanned vehicles such that they can freely move and adaptively cooperate in a complex environment. During this procedure, flocking is one of the key operations and requirements. Here, flocking refers to the formation and maintenance of a desired pattern by a group of mobile vehicles without collision during movement. We propose a resilient and scalable flocking scheme for a group of vehicles, which follows the leader–followers moving pattern. In the absence of obstacles, a collision avoidance algorithm is presented to maintain a desired distance among vehicles. This will ensure information completeness and is significant in certain mission critical situations without collision between a unmanned vehicle and its neighboring vehicles. In the presence of obstacles in an environment, this algorithm is able to avoid collision between a vehicle and its neighbor (either a neighboring vehicle or a neighboring obstacle). Theoretical proof has been presented to demonstrate the effectiveness and correctness of the algorithm to guarantee collision-free. In addition, with increasing number of vehicles, the performance of the proposed flocking scheme performs without increasing the processing overhead, which demonstrates the desirable scalability.     

A Distributed Privacy Preservation Approach for Big Data in Public Health Emergencies Using Smart Contract and SGX

Security and privacy issues have become a rapidly growing problem with the fast development of big data in public health. However, big data faces many ongoing serious challenges in the process of collection, storage, and use. Among them, data security and privacy problems have attracted extensive interest. In an effort to overcome this challenge, this article aims to present a distributed privacy preservation approach based on smart contracts and Intel Software Guard Extensions (SGX). First of all, we define SGX as a trusted edge computing node, design data access module, data protection module, and data integrity check module, to achieve hardware-enhanced data privacy protection. Then, we design a smart contract framework to realize distributed data access control management in a big data environment. The crucial role of the smart contract was revealed by designing multiple access control contracts, register contracts, and history contracts. Access control contracts provide access control methods for different users and enable static access verification and dynamic access verification by checking the user’s properties and history behavior. Register contract contains user property information, edge computing node information, the access control and history smart contract information, and provides functions such as registration, update, and deletion. History contract records the historical behavior information of malicious users, receives the report information of malicious requestors from the access control contract, implements a misbehavior check method to determines whether the requestor has misbehavior, and returns the corresponding result. Finally, we design decentralized system architecture, prove the security properties, and analysis to verify the feasibility of the system. Results demonstrate that our method can effectively improve the timeliness of data, reduce network latency, and ensure the security, reliability, and traceability of data.     

An effective simulation method for search strategy in unstructured P2P network

Modeling and Simulation Techniques focus on simulation modeling and analysis challenges to develop principles or gain in existing networking technologies, including simulation methodology or application in unstructured P2P network. In this paper, we focus on the simulation in the random unstructured P2P network.The correlation between topology and search algorithm is less paid attention to in unstructured P2P network, current techniques used in existing unstructured P2P system are often very inefficient because of the existence of large number of redundant messages. In this paper, we analyze the reason of engendering redundant data packet and focus on designing better search algorithm to adapt to the current network rather than to design the universal algorithm to adapt to a variety of network. Analyzing the characteristics that the flooding algorithm showing in different search stages in different network, we put forward the segment search algorithm. Furthermore, we present an effective simulation method in the random unstructured P2P network. Through simulation analysis, we find that our algorithm is better than the original flooding algorithm. In addition, we design our algorithm to be simple as a module, which can be easily applied to existing unstructured P2P systems for immediate impact.     

A self-adaptive K selection mechanism for re-authentication load balancing in large-scale systems

Since the 802.16e standard has been released, there are few authentication pattern schemes and Extensible Authentication Protocol (EAP) selection proposals for manufacturers to choose from in large-scale network systems. This paper focuses on the re-authentication method??s design, improvement, and optimization for the PMP mode of the IEEE 802.16e standard in large-scale network systems to ensure the security of the keys. We first present an optimized scheme, called EAP_AKAY, based on the EAP-AKA authentication method (Arkko and Haverinen in Extensible Authentication Protocol Method for UMTS Authentication and Key Agreement (EAP-AKA), 2004), and then a self-adaptive K selection mechanism is proposed for re-authentication load balancing based on EAP_AKAY in large-scale network systems. This presented mechanism considers the cost of authentication, not only at the server end, but also at the client end. Thus, this scheme would minimize the total cost and resolve the limitation in current schemes. Furthermore, the K value would be re-selected, not only when MS is roaming to another BS region, but also in residing time to adapt to network environment changes. The simulation results and relevant analysis demonstrate that our scheme is effective in terms of the total cost of authentication, master key renewal, and good security.     

A cache-based search algorithm in unstructured P2P networks

Peer-to-Peer (P2P) network is an important component to implement next generation Internet, how to quickly and efficiently search the resources in P2P networks has become one of the most critical issues, at the same time, this is one of greatest concern to users. This paper describes the basic Flooding Peer-to-Peer network search method, followed by analysis of several new search methods pros and cons, and then further analysis of these algorithms is proposed based on a cache-based search algorithm: When a node of the remaining load capacity is high, it will become the center node, and form a joint topology area with the nearby nodes together, then the center node and ordinary nodes also need to store the index cache, at the local region the overheating resources will be copied to the local (that is, the contents cache). The simulation shows that the algorithm can effectively improve the hit rates of resources searching, reduce the query delay.