Packet-switched Wireless Networks Research Articles

ALGORITHM FOR CALCULATING THE RECOMMENDED AUDIO COMMUNICATION SESSION DURATION IN A MOBILE AD HOC NETWORK

In the process of carrying out search and rescue operations and emergency response measures, organization of manpower and equipment management based on ensuring effective information exchange is of great importance. Moreover, tasks are often carried out in conditions of inoperative or absent telecommunication infrastructure and possible destructive external influences. In such situations, for the transfer of information, it is preferable to deploy a mobile ad hoc network, which has an arbitrary decentralized topology and is able to operate without base stations. In order to ensure the transmission of streaming data with the required quality in wireless packet-switched networks, various algorithms for the dynamic distribution and reservation of channel resources have been developed. However, insufficient attention has been paid to substantiating the duration of the transmission of streams of audio information in a mobile ad hoc network. The article presents the results of the development and research of an algorithm for obtaining the recommended duration of sessions for transmitting voice information streams to support decision-making to ensure the effectiveness of audio communications in a mobile ad hoc network. The recommended duration of the communication session depends on the limit number of packets in the audio stream, the calculation of which is based on the use of mathematical models to estimate the average volume of a multimedia message, the transmission of which can be carried out with the required quality for the given characteristics of the network. Implementation of the proposed algorithm will allow users of a mobile ad hoc network to receive messages about the recommended duration of audio communication sessions.

A Markovian Design of Bi-Directional Robust Header Compression for Efficient Packet Delivery in Wireless Networks

As a major tool for improving transport efficiency by reducing header redundancy, robust header compression (ROHC) plays an important role in modern packet-switched wireless networks. However, widespread ROHC deployment is in sharp contrast to extremely limited number of research works on ROHC analysis and design optimization. In this paper, we investigate a novel trans-layer approach in designing a bi-directional ROHC under unreliable wireless channel conditions. We propose a novel ROHC compressor design based on a new formulation in terms of a partially observable Markov decision process (POMDP). This new formulation robustly explores the lower protocol layer signaling to optimize the compressor actions dynamically on the header level and feedback polling. Our design approach improves the transmission efficiency and curtails the required ROHC feedback overhead. Furthermore, to reduce the complexity of our optimized POMDP design, we propose a low-complexity suboptimal ROHC compressor. Our novel trans-layer designs achieve more flexible trade-offs between transmission efficiency and feedback overhead than existing ROHC compressors. They also demonstrate a substantial performance improvement under poor channel conditions and long feedback delay.

Traffic Differentiation-Based Network Selection Scheme in Wireless Heterogeneous Networks

The emergence of wireless packet-switched networks such as Universal Mobile Telecommunications System (UMTS), and wireless local area networks (WLANs) can provide voice, data, and video services for users. In this paper, we propose a network selection scheme in the wireless heterogeneous networks based on the traffic differentiation, conversational class, interactive class, streaming class, and background class. Simulation results demonstrate that the proposed network scheme can decide the optimal network to handoff according to the traffic class.

TCP-Aware Call Admission Control in High Altitude Platforms Using Cross-Layer Design

In this paper, a new cross-layer design is proposed employing the predictability of rain faded channels to guarantee QoS requirements in High Altitude Platform (HAP) networks. Both a centralized and a distributed scheme are proposed for call admission control of packet-switched HAP wireless networks using a cross-layer approach aiming at keeping the call dropping probability below a predefined threshold. In both schemes, a new call is accepted if there are sufficient resources for the ongoing calls and for the new one to guarantee their QoS requirements for their whole connection. The performance of the proposed schemes is investigated using markov chain analysis and bounds of the call blocking probability are determined analytically.

Call admission control scheme for real-time services in packet-switched OFDM wireless networks

A call admission control scheme is proposed for real-time services in packet-switched orthogonal frequency division multiplexing (OFDM) wireless cellular networks. The main idea of the proposed scheme is to use maximum acceptance ratio to maintain maximum channel utilization for real-time services according to the desired packet-level and call-level quality-of-service (QoS) requirements. The acceptance ratio is periodically adjusted by using a time discrete Markov chain and Wiener prediction theory according to the varying traffic load. Extensive simulation results show that this algorithm maintains high channel utilization, even as it guarantees packet-level and call-level QoS requirements for real-time services.

A Dynamic TCP-Aware Call Admission Control Scheme for Generic Next Generation Packet-Switched Wireless Networks

Traditional call admission control (CAC) schemes only consider call-level performance and are mainly designed for circuit-switched wireless network. Since future wireless communications will become packet-switched systems, the packet-level features could be explored to improve the system performance. This is especially true when the TCP-type of elastic applications are running over such packet-switched wireless networks, as the elasticity of TCP applications has more tolerance toward the throughput/delay variation than non-elastic traffic does. In order to efficiently utilize the system resource from an admission control perspective, we propose a TCP-aware CAC scheme to regulate the packet-level dynamics of TCP flows. We analyze the system performance under realistic scenarios in which (i) the call holding time for non-elastic traffic like voice is independent of system states and (ii) the call holding time for TCP type of traffic depends on the system state, i.e., on the TCP flow's transmission rate. Extensive simulations are presented under different scenarios to show that the proposed scheme can effectively improve the system performance in terms of call blocking probability, call-level throughput (call/min) and link utilization, in accordance with our theoretical results.

Supporting Real-Time Service in Packet-Switched Wireless Networks

The requirement of providing real-time data service by wireless networks is a critical issue in the design of current wireless networks. Distributed Queueing Request Update Multiple Access (DQRUMA) has been proposed as a demand assignment medium access control (MAC) protocol to efficiently control the medium sharing by multiple mobile users. With the help of a packet transmission policy, DQRUMA has a potential to provide QoS service for the time-constrained burst data traffic. In this article, we study the problem of providing real-time service to fixed-size packets with or without time constraints in wireless networks. In particular, we propose a novel scheduling scheme for the DQRUMA protocol to control the packet transmission in packet-switched wireless networks. We have conducted extensive simulation experiments to evaluate the performance of the proposed algorithm and to compare its real-time performance with those of other packet transmission policies. This study proves that the new algorithm is an efficient transmission policy for the DQRUMA to support real-time service in wireless networks.

An efficient wireless resource management scheme to support handoff data recovery in packet-switched cellular multicast networks

To support data transfer reliability similar to that of a fixed multicast network, migrating terminals in a packet-switched cellular wireless multicast network supporting reliable multicast data transfer need to recover lost data during handoffs before they can merge into the respective multicast groups in the new cells. The multicast groups in packet-switched wireless networks typically share resources on a statistical multiplexed basis. To minimize impact on other terminals, this paper proposes to allow part of a multicast group's assigned bandwidth to be shared by the handoff terminals for transient data recovery using the proposed Weighted Fair Share (WFS) method with optimal weight selection. Handoff terminals are admitted into the new cell using the proposed Multicast Connection Admission Control (MCAC) scheme. These methods together constitute the Fair and Efficient Wireless Multicast resource management Scheme (FEWMS) presented in this paper. Under FEWMS, a migrating terminal can quickly recover lost data and merge into the existing multicast group during a handoff. Simulations using self-similar traffic sources show that the proposed method reduces the handoff failure probability of migrating terminals and the average packet delay of the multicast group, and increases the overall system throughput, compared with an existing proposal. Evaluations of different performance measures show that the system throughput does not give a complete picture of the system performance, as different resource management schemes may have substantial impact on other performance measures such as average delay and handoff failure probability.

Soft QoS provisioning using the token bank fair queuing scheduling algorithm

Future-generation wireless packet networks will support multimedia applications with diverse QoS requirements. Much of the research on scheduling algorithms has been focused on hard QoS provisioning of integrated services. Although these algorithms give hard delay bounds, their stringent requirements sacrifice the potential statistical multiplexing performance and flexibility of the packet-switched network. Furthermore, the complexities of the algorithms often make them impractical for wireless networks. There is a need to develop a packet scheduling scheme for wireless packet-switched networks that provides soft QoS guarantees for heterogeneous traffic, and is also simple to implement and manage. This article proposes token bank fair queuing (TBFQ), a soft scheduling algorithm that possesses these qualities. This algorithm is work-conserving and has a complexity of O(1). We focus on packet scheduling on a reservation-based TDMA/TDD wireless channel to service integrated real-time traffic. The TBFQ scheduling mechanism integrates the policing and servicing functions, and keeps track of the usage of each connection. We address the impact of TBFQ on mean packet delay, violation probability, and bandwidth utilization. We also demonstrate that due to its soft provisioning capabilities, the TBFQ performs rather well even when traffic conditions deviate from the established contracts.

Adaptive Quality of Service Support for Packet-Switched Wireless Cellular Networks

In this paper, we propose an adaptive quality of service (QoS) design approach via resource reservation and rate adaptation to support multimedia over wireless cellular networks. Three contributions of this work are: (a) an adaptive QoS model that seeks to provide QoS assurances within bounds for each packet flow and to make advance resource reservation in order to support seamless mobility, (b) a revenue-based resource adaptation design that seeks to maximize network revenue while satisfying the QoS requirements, and (c) a resource reservation protocol that supports both application-initiated resource reservation and network-initiated resource adaptation. Our initial implementation and measurements confirm the effectiveness of the proposed design.

Optimising delay and throughput in packet-switched CDMA network with collision resolution using stack algorithm

The authors address the effect of code division multiple access (CDMA) on the performance of wireless packet-switched networks. Although CDMA can enhance throughput, the delay at small traffic loads suffers from bandspreading. For imperfect signal separation at the receiver, performance benefits from CDMA may be lost. The capacity of the particular stack algorithm addressed for collision resolution can be enhanced from 0.32 to approximately 0.40 if a 10 dB spreading gain with perfect signal separation is employed. >