Shengming Jiang

Energy-Efficient Topology Control With Selective Diversity in Cooperative Wireless Ad Hoc Networks: A Game-Theoretic Approach

Due to the scarce bandwidth and limited power supply in mobile terminals, performance and energy consumption in wireless communications must be continually focused upon. Cooperative transmissions improve the capacity performance of wireless ad hoc networks (WANETs). However, when energy efficiency is considered, the advantage of user cooperation over non-cooperation does not always exist since it involves multiple nodes with more energy consumption in transmissions. To exploit the benefits of user cooperation in cooperative WANETs, we propose a distributed energy-efficient selective diversity (EESD) topology control to improve energy efficiency, which jointly considers network capacity and energy consumption in terms of bits per Joule. EESD forms transmission coalitions via cooperative manner (i.e, diversity) selection, by taking into account the cost of channel information exchange. We then formulate EESD as a coalition game and propose an adaptive coalition formation algorithm for EESD with proved convergence property and stable coalition structures. Simulation results show the performance improvement of EESD in energy efficiency and network lifetime compared to the existing topology control schemes.

Subscriber-assisted handoff support in multimedia PCS

Handoff support is one of the key elements in cellular Personal Communication Systems (PCS). Traditional approaches hide handoff support from the subscriber. However, the main difficulty in handoff support stems from terminal mobility which can only be controlled by the subscriber, who may again have different requirements of mobility support under different environments. Therefore, we suggest that the subscriber should participate in handoff support in the following manner: first, the subscriber is encouraged to declare the requirement of mobility support at call setup time; second, when a handoff cannot be supported, the subscriber should be informed in advance so that (s)he can decide whether or not to control movement since a subscriber may sacrifice mobility for maintaining communication in progress. This approach can reduce call dropping rate and improve resource utilization. We will describe this approach and propose a service classification for mobility support in this paper.

Traffic-Aware Link Rate Adaptation for Multi-rate 802.11 Networks

Abstract802.11 networks provide multi-rate capability to offer rate adaptability against the time-varying wireless channel. However, how to switch between the available rates has not been standardized. Existing rate adaptation (RA) solutions assume common transmission power and can only passively tune link rate to match the inferred channel condition via different methods. This simple attitude is neither flexible in traffic-aware link rate selection nor effective in energy conservation and spatial reuse since transmission power may be either too low to sustain the link rate or too high that results in unnecessary energy consumption and worse spatial reuse. Different from existing solutions, we think that link rate switch should be driven by traffic load and power control should be considered with rate adaptation together to conserve energy and increase spatial reuse. To this end, we propose a traffic-aware link rate adaptation scheme (TARA) via power control for multi-rate 802.11 networks. Its basic idea consists of a two-step procedure. Firstly, traffic load is sensed in the MAC layer to decide whether link rate should be increased or decreased for the next transmission. Afterwards, power control is carried out in the PHY layer to guarantee that the new link rate can be sustained while minimizing the transmission power. Extensive simulation results show that TARA outperforms typical existing schemes in terms of energy efficiency and throughput.

A dynamic measurement-based bandwidth allocation scheme with QoS guarantee for mobile wireless networks

This paper presents a new dynamic and adaptive bandwidth allocation scheme to prevent handoff failure due to lack of resources in mobile cellular networks, known as the measurement-based preassignment (MPr) technique. This technique is particularly useful in micro/pico cellular networks which offer quality of service (QoS) guarantees against call dropping. The proposed MPr scheme distinguishes itself from the well-known guarded channel based schemes in that it allows the handoff calls to utilize a pre-reserved channel pool before competing for the shared channels with new call arrivals. The key advantage of the proposed MPr scheme is that it can easily derive the number of channels that needs to be reserved for handoff based on a pre-determined call dropping probability, without the need for solving the often complex Markov chain required in guarded channel schemes, thus making the proposed MPr scheme simple and efficient for implementation. In addition, the MPr scheme is dynamical in that it can adjust the number of reserved channels for the handoff according to the traffic changes in the system.

A deadline-aware and distance-aware packet scheduling algorithm for wireless multimedia sensor networks

We propose a wireless differentiated queuing service (WDQS) algorithm to meet the diverse delay requirements in wireless multimedia sensor networks (WMSNs). WDQS adopts novel latest departure time (LDT) scheduling criteria to differentiate forwarding emergency by considering the packets’ lifetime, the known delay it has already experienced, and the remaining delay it will experience. We also propose an effective approach to estimate the unknown delay for the remaining journey without any message overhead by exploiting the query mechanism of the sink. We further discuss analytically the packets lifetime setting to meet the end-to-end (e2e) delivery requirement. The simulation results verify our analytical discussion and show performance improvements in terms of e2e delay and packet drop rate.

Energy-Efficient Topology Management With Interference Cancellation in Cooperative Wireless Ad Hoc Networks

With recent advances in parallel cooperative transmissions between multiple source-destination pairs, interference cancellation (IC) can be achieved to improve the capacity performance of wireless networks. However, from energy efficiency perspective, user cooperation may not be always appealing, since the increased data rate of one user comes at the price of the energy consumed by another user. In this paper, we study the potential benefits/drawbacks of cooperative communications on network-level issues, such as the capacity and the energy efficiency. We show that, in terms of network energy efficiency, cooperative communications do not always outperform non-cooperative communications, and cooperative communications should be dynamically applied in topology control to optimize the overall network energy efficiency. Specifically, we propose an energy-efficient topology control scheme by jointly considering the capacity and energy consumption of non-cooperative and cooperative communications. Simulation results are presented to show the effectiveness of the proposed scheme.

Frequency scheduling for cascaded wireless relay networks with half duplex

This paper investigates the scheduling problem for K-hop frequency-division-duplex cascaded wireless relay networks, where the source, the relays, and the destination form a chain. Two scenarios are considered: 1) directed transmission, in which each relay node only transmits its radio wave to its neighboring downstream node; 2) undirected transmission, in which the radio wave can be received by the two neighboring upstream and downstream nodes, which causes hidden-terminal (HT) problem. The problem of frequency band allocation is formulated, which can be solved to maximize the network rate with decode-and-forward relay strategy. Optimal solution is derived based on a naive scheme, whose achievable rate shows a similar expression as that of time-division-duplex. We further show that the effect of half duplex and HT can be alleviated by increasing the spectrum efficiency of all relay hops when K > 3.

Energy-efficient topology control with selective diversity in cooperative wireless ad hoc networks

When energy efficiency is considered, cooperative communications may not be appealing since it involves multiple nodes in transmissions. To exploit the benefits of distributed user cooperation in cooperative wireless ad hoc networks (WANETs), we propose a distributed energy-efficient selective diversity (EESD) topology control to improve energy efficiency in the network, which jointly considers network capacity and energy consumption in terms of bits per Joule. EESD forms transmission coalitions via cooperative manner (i.e, diversity) selections, by taking into account the cost of channel information exchange. We then formulate EESD as a coalition game and propose an adaptive coalition formation algorithm for EESD with proved convergence property and stable coalition structures. Simulation results show the performance improvement of EESD in energy efficiency compared to the existing topology control schemes.

An AAL3/4-based architecture for interconnection between ATM and cellular networks

With the increased popularity of ATM technology and the high demand for multimedia applications in wireless systems, the interconnection between wireless systems and wired ATM networks becomes important to support multimedia applications. This paper presents an AAL3/4-based architecture for the interconnection between wireless and ATM networks. The main advantage of this architecture is that modification or additional functions are not necessary to the ATM layer to support mobility, and the ATM part of the connection is totally transparent to the mobiles so that the existing wireless protocols can be used without any change.

User-Network Cooperation-Based Sleep Scheduling for Communication Networks

The redundant design and dynamic nature of traffic raise an energy inefficiency issue in communication networks. We exploit the selfishness of both users and the network to schedule cooperatively the idle links and nodes into sleep to save energy. We first formulate the sleep scheduling problem from a perspective of routing, and then propose a greedy algorithm to solve the problem. To reduce the complexity of centralized computation, we further propose a user-network cooperation-based mechanism, where the network publishes a proportionally weighted cost-sharing rule related to energy consumption, while the users selfishly choose their routes with the least cost accordingly. The proposed cooperation mechanism attracts users to aggregate their traffic on fewer links and nodes. The network then simply puts the idle links and nodes into sleep. Selfish routing behaviors are modeled by an α-approximate routing game, where the α factor is adopted to consider the energy consumption, packet losses, and delay during re-routing. We prove the equilibrium existence, convergence, and convergence speed of the best responses, and evaluate the lower bound performance in terms of price of anarchy with further improvement by an advertisement method. Distributed algorithms based on the best responses are also developed to implement the cooperative mechanism. Simulation results over network instants from SNDlib show that our game-based algorithms outperform the greedy and heuristic centralized algorithms in saving energy.