Fuzzy Based Packet Dropping Scheme in Wireless Cellular Networks

Dynamic rate-based borrowing scheme for QoS provisioning in high speed multimedia wireless cellular networks

This paper presents two novel heuristic algorithms for the design of wireless access multimedia networks. Emphasis was given to the design of CDMA based wireless multimedia networks and fixed wireless multimedia networks. The objectives of these methods are first to place a number of access points/base stations in a number of candidate sites and then to assign a number of fixed wireless terminals to the selected access points/base stations. Both methods are based on graph theory and they are essentially greedy algorithms. Except from capacity constraints, wireless reception characteristics are also considered. The algorithms are capable of designing medium and large-scale networks at polynomial time. Both algorithms were compared with an analogous optimisation problem through a series of tests. The results indicate that as regards design costs the performance of the heuristics is very close to this of the equivalent optimisation problem. The solution times for the heuristics are smaller especially when the number of the candidate access points/base stations becomes large

Disk idle behavior has a significant impact on the energy efficiency of disk storage systems. For example, accurately predicting or extending the idle length experienced by disks can generate more potential opportunities to save energy. This paper employs a trace driven simulation to evaluate the impacts of different disk schedulers and queue length thresholds on the disk idle behavior. Experimental results give three implications: (1) Position based schedulers and long queue length thresholds can significantly reduce the maximal queue length and the average queue length. (2) Position based schedulers and long queue length thresholds can generate more idle periods which are shorter than 1 s, but they do not affect those long idle periods contained in the modern server workloads. (3) Disk idle periods demonstrate both self-similarity and weak long-range dependence, and the disk schedulers and queue length thresholds do impact the Hurst parameter and the correlation behavior of the workloads. The analysis results in this paper provide useful insights for designing and implementing energy efficient policies for the disk drive based storage systems.

Analytic modeling of handoffs in wireless cellular networks

Predictive channel reservation for handoff prioritization in wireless cellular networks

Effective support of real‐time multimedia applications in wireless access networks, viz. cellular networks and wireless LANs, requires a dynamic bandwidth adaptation framework where the bandwidth of an ongoing call is continuously monitored and adjusted. Since bandwidth is a scarce resource in wireless networking, it needs to be carefully allocated amidst competing connections with different Quality of Service (QoS) requirements. In this paper, we propose a new framework called QoS‐adaptive multimedia wireless access (QoS‐AMWA) for supporting heterogeneous traffic with different QoS requirements in wireless cellular networks. The QoS‐AMWA framework combines the following components: (i) a threshold‐based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes between different classes of handoff calls by assigning a threshold to each class, (ii) an efficient threshold‐type connection admission control algorithm, and (iii) a bandwidth adaptation algorithm that dynamically adjusts the bandwidth of an ongoing multimedia call to minimize the number of calls receiving lower bandwidth than the requested. The framework can be modeled as a multi‐dimensional Markov chain, and therefore, a product‐form solution is provided. The QoS metrics—new call blocking probability (NCBP), handoff call dropping probability (HCDB), and degradation probability (DP)—are derived. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the handoff call dropping probability and maintaining the bandwidth utilization efficiently. Copyright © 2006 John Wiley & Sons, Ltd.

Adaptive bandwidth reservation in wireless cellular networks is expected to ensure bounded call level QoS when network conditions such as new call arrival rates or users' mobilities are changing. The feature of the event based adaptive bandwidth reservation is that bandwidth reservation values are distributed by the target base station to the neighboring base stations upon new call arrivals, handoffs and call terminations. This paper considers the problem of maintaining bounded forced call termination probability under adaptive admission algorithm when the user mobility changes. Our analysis shows that in order to control the forced call termination probability, a bandwidth reservation policy must be imposed on the bandwidth reservation values. Several bandwidth reservation policies have been analysed, and the range of call level QoS has been determined under variable user mobility in all the cases. The analytical results have been validated by simulations.

To guarantee the real-time transmission for time-sensitive traffic, we need to take delay-bound quality-of-service (QoS) into account when designing the wireless cellular networks. The traditional powerful QoS guarantee technique, called the homogeneous statistical QoS provisioning, assumes that the QoS provisioning of each link can be individually processed. In order to further significantly increase the global system throughput, the available resources of all links need to be jointly controlled, which is typically suitable for downlink transmissions over wireless cellular networks. Under this setup, we need to consider the diverse delay-bound QoS provisionings for different links at the same time, which represents the new heterogeneous statistical QoS provisioning framework and imposes many new challenges not encountered before in wireless networks. To overcome these problems, in this paper we propose the heterogeneous statistical QoS provisioning framework for high-speed downlink transmissions in wireless cellular networks. In particular, we formulate the optimization problem to maximize the downlink throughput subject to heterogeneous statistical delay-bound QoS requirements. For solving this optimization problem, we develop the heterogeneous-QoS-driven power allocation scheme to derive the closed-form solutions which can maximize the global system throughput while guaranteeing the heterogeneous delay-bound QoS for the entire wireless cellular networks. We show that the heterogeneous-QoS-driven power allocation provides more generic framework for downlink transmissions. The extensive simulation results obtained show that our proposed heterogeneous-QoS-driven power allocation scheme can achieve the global optimization of wireless resource efficiency, thus significantly increasing the global system throughput as compared with the homogeneous statistical delay-bound QoS provisioning schemes.

Network protocols in cellular wireless data networks must update routes as a mobile host moves between cells. These routing updates combined with some associated state changes are called handoffs. Most current handoff schemes in wireless networks result in data loss or large variations in packet delivery times. Unfortunately, many applications, such as real-time multimedia applications and reliable transport protocols, adapt to long term estimates of end-to-end delay and loss. Violations and rapid fluctuations of these estimates caused by handoff processing often result in degraded performance. For example, loss during handoff adversely affects TCP performance [4], and high packet loss and variable delays result in poor real-time multimedia performance. In this paper, we describe a multicast-based protocol that eliminates data loss and incurs negligible delays during a handoff. The basic technique of the algorithm is to anticipate a handoff using wireless network information in the form of received signal strengths and to multicast data destined for the mobile host to nearby base stations in advance. This routing, combined with intelligent buffering techniques at the base stations, enables very rapid routing updates and eliminates data loss without the use of explicit data forwarding. We have implemented this protocol using IP Multicast and Mobile IP-like routing. In our implementation, handoffs typically take between 8 and 15 ms to complete and result in no data loss.

Communication-based train control (CBTC) systems use wireless local area networks (WLANs) for train-ground transmission. Transmission delays and packet drops may cause unnecessary tractions and brakes of trains, degradation of riding comfortability, rising of energy consumption and loss of the line's capacity. In this paper, We model the system to control a group of trains in CBTC as a networked control system (NCS) with transmission delays and packet drops. We study the delays and packet drops in CBTC, analyze their effects on train's control, and propose a method to improve the performance of CBTC. Extensive simulation results are presented. We show that our proposed method has a strong tolerance for transmission delays and packet drops, and outperforms the currently adopted scheme in different channel conditions.

Lyapunov optimized energy-efficient dynamic offloading with queue length constraints

An important quality-of-service (QoS) issue in wireless multimedia networks is how to control handoff drops. We propose admission-control algorithms that adaptively control the admission threshold in each cell in order to keep the handoff-dropping probability below a predefined level. The admission threshold is dynamically adjusted based on handoff-dropping events. We first present a simple admission-control scheme that brings out an important performance evaluation criterion - intercell fairness - and serves as a reference point. We then investigate the intercell unfairness problem and develop two enhanced schemes to overcome this problem. The performance of these protocols is benchmarked and compared with other competitive schemes. The results indicate that our schemes perform very well while, in addition, achieving significantly reduced complexity and signaling load.

In wireless networks carrying multimedia traffic, it becomes necessary to provide a quality of service (QoS) guarantee for multimedia traffic connections. A novel timing-based bandwidth allocation protocol is proposed as a solution to support QoS guarantees in the multimedia wireless networks. Based on the existing network conditions, the proposed scheme makes an adaptive decision for bandwidth reservation and call admission by employing fuzzy inference mechanism, timing based reservation strategy, and round-borrowing strategy in each base station. The amount of reserved bandwidth for each base station is dynamically adjusted, according to the online traffic information of each base station. Simulation results show that our timing-based bandwidth reservation scheme outperforms the previous schemes in terms of connection-blocking probability, connection-dropping probability, and bandwidth utilization.

A key issue in wireless multimedia networking regards the coexistence of different services/traffic types over common wireless resources. Research in Transmitter Power Control (TPC) has proposed various schemes for different traffic types without addressing effectively the problem of coexistence. Each of the TPC schemes of the literature is usually (i) unsuitable/inefficient for supporting diverse traffic types, and (ii) incompatible with each other, leading to conflicts if operated over common wireless channels.In this paper, we tackle the problem of coexistence by presenting novel converged TPC schemes. First, we investigate converged TPC schemes for links carrying the two basic traffic types of media streaming circuit-switched/constant-rate traffic (i.e. voice, CBR video), andpacket-switched elastic traffic (i.e. data).Evaluated against conventional TPC algorithms operating in dedicated wireless resources, the proposed schemes are demonstrated to increase the capacity of the wireless network. Second, we explore new hybrid types of traffic that combine the best-effort grade of service adapting to the network conditions with a guaranteed minimum, and propose appropriate TPC schemes.

Multimedia applications have become an essential part of our daily lives, and their use is flourishing day by day. In Wireless Multimedia Sensor Networks (WMSNs), large volume of multimedia data is transmitted through the network. If the traffic load is greater than the available capacity of the sensor network, congestion occurs and it causes buffer overflow, packet drop, deterioration of network throughput and effect quality of service (QoS). The limited bandwidth should be adjusted for the packets with different priorities precisely. To emphasize the problem, the paper provides A New Approach for Traffic Management in Wireless Multimedia Sensor Network. According to the paper, sensor nodes in one collision area can adjust their sending states adaptively based on packet priority. To improve the received video quality in base stations, proposed technique keeps the I-frames and ignores the other less important frame types of compressed video. Also retransmissions of lost packets are provided with different priorities for enhancing the system performance. The simulations show that the bandwidth adjustment can protect the packets with high priority effectively, and the performance of the retransmission is well positioned to meet the requirement of the multimedia applications. MATLAB is used for simulation purpose.