Energy-efficient adaptive wireless network design

Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present an energy-efficient highly adaptive architecture of a network interface and novel data link layer protocol for wireless networks that provides quality of service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations are necessary to achieve energy efficiency and an acceptable quality of service. The paper provides a review of ideas and techniques relevant to the design of an energy efficient adaptive wireless networ

Energy-efficient wireless communication

In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

MAC-layer approaches for security and performance enhancement in IEEE 802.11

Over the past few years, wireless networks are becoming increasingly popular. The dominant question facing the wireless network today is: how can the network meet the needs of various users and applications? Two basic and primary needs for users are efficiency and security. To deal with these two concerns, this dissertation investigates the two areas and proposes four MAC-level approaches for security and performance enhancement in IEEE 802.11.;In the first part, we propose three MAC-level approaches to improve the throughput performance in wireless LANs, i.e., the Freeze Counter scheme (FC), the Dynamically Adaptive Retransmission (DAR), and the Quick Acknowledgement (QA) scheme. The Freeze Counter scheme is an adaptive error recovery mechanism in 802.11, which can perform different actions according to the reasons for frame losses. Dynamically Adaptive Retransmission scheme is an enhanced feedback scheme in 802.11. We propose a Quick Acknowledgement (QA) scheme as a replacement for positive acknowledgement in IEEE 802.11. By using similar concepts as selective ACK and negative ACK, the proposed protocol solves the inefficiency problem of positive ACK in 802.11.;In the second part, we propose a lightweight statistical authentication protocol for wireless networks. With more and more applications on wireless networks, new concerns are raised when it comes to security issues. Authentication service particularly becomes one of the basic but necessary security measures for wireless applications. However, traditional authentication protocols for wired networks do not work well in a wireless environment due to unique characteristics. To meet this target, we propose a lightweight statistical authentication protocol for wireless networks, namely Shepherd. To solve the inherent out-of-sync problem with Shepherd protocol, we develop three synchronization schemes with their statistical methods. In Shepherd, the legitimacy of a mobile node is determined by continuously checking a series of random authentication bits where each bit in this stream is piggybacked by a packet. Such an authentication bit stream is generated by both mobile node and access point using the same random number generator under the same shared seed as a key. The complete evaluation and analysis of all proposed approaches have been discussed

Traffic Management and Congestion Control in the ATM Network Model.

Asynchronous Transfer Mode (ATM) networking technology has been chosen by the International Telegraph and Telephony Consultative Committee (CCITT) for use on future local as well as wide area networks to handle traffic types of a wide range. It is a cell based network architecture that resembles circuit switched networks, providing Quality of Service (QoS) guarantees not normally found on data networks. Although the specifications for the architecture have been continuously evolving, traffic congestion management techniques for ATM networks have not been very well defined yet. This thesis studies the traffic management problem in detail, provides some theoretical understanding and presents a collection of techniques to handle the problem under various operating conditions. A detailed simulation of various ATM traffic types is carried out and the collected data is analyzed to gain an insight into congestion formation patterns. Problems that may arise during migration planning from legacy LANs to ATM technology are also considered. We present an algorithm to identify certain portions of the network that should be upgraded to ATM first. The concept of adaptive burn-in is introduced to help ease the computational costs involved in virtual circuit setup and tear down operations

Adaptive fair channel allocation for QoS enhancement in IEEE 802.11 wireless LANs

The emerging widespread use of real-time multimedia applications over wireless networks makes the support of quality of service (QoS) a key problem. In this paper, we focus on QoS support mechanisms for IEEE 802.11 wireless ad-hoc networks. First, we review limitations of the upcoming IEEE 802.11e enhanced DCF (EDCF) and other enhanced MAC schemes that have been proposed to support QoS for 802.11 ad-hoc networks. Then, we describe a new scheme called adaptive fair EDCF that extends EDCF, by increasing the contention window during deferring periods when the channel is busy, and by using an adaptive fast backoff mechanism when the channel is idle. Our scheme computes an adaptive backoff threshold for each priority level by taking into account the channel load. The new scheme significantly improves the quality of multimedia applications. Moreover, it increases the overall throughput obtained both in medium and high load cases. Simulution results show that our new scheme outperforms EDCF and other enhanced schemes. Finally, we show that the adaptive fair EDCF scheme achieves a high degree of fairness among applications of the same priority level

Applications of satellite technology to broadband ISDN networks

Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about $190M whereas the second architecture would be about$250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization