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

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

E2MaC: an energy efficient MAC protocol for multimedia traffic

Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present a novel MAC protocol that achieves a good energy efficiency of wireless interface of the mobile and provides support for diverse traffic types and QoS. The scheduler of the base station is responsible to provide the required QoS to connections on the wireless link and to minimise the amount of energy spend by the mobile. The main principles of the E2MaC protocol are to avoid unsuccessful actions, minimise the number of transitions, and synchronise the mobile and the base-station. We will show that considerable amounts of energy can be saved using these principles. In the protocol the actions of the mobile are minimised. The base-station with plenty of energy performs actions in courtesy of the mobile. We have paid much attention in reducing the cost of a mobile for just being connected. The protocol is able to provide near-optimal energy efficiency (i.e. energy is only spent for the actual transfer) for a mobile within the constraints of the QoS of all connections in a cell, and only requires a small overhead

Buffer management and cell switching management in wireless packet communications

The buffer management and the cell switching (e.g., packet handoff) management using buffer management scheme are studied in Wireless Packet Communications. First, a throughput improvement method for multi-class services is proposed in Wireless Packet System. Efficient traffic management schemes should be developed to provide seamless access to the wireless network. Specially, it is proposed to regulate the buffer by the Selective- Delay Push-In (SDPI) scheme, which is applicable to scheduling delay-tolerant non-real time traffic and delay-sensitive real time traffic. Simulation results show that the performance observed by real time traffics are improved as compared to existing buffer priority scheme in term of packet loss probability. Second, the performance of the proposed SDPI scheme is analyzed in a single CBR server. The arrival process is derived from the superposition of two types of traffics, each in turn results from the superposition of homogeneous ON-OFF sources that can be approximated by means of a two-state Markov Modulated Poisson Process (MMPP). The buffer mechanism enables the ATM layer to adapt the quality of the cell transfer to the QoS requirements and to improve the utilization of network resources. This is achieved by selective-delaying and pushing-in cells according to the class they belong to. Analytical expressions for various performance parameters and numerical results are obtained. Simulation results in term of cell loss probability conform with our numerical analysis. Finally, a novel cell-switching scheme based on TDMA protocol is proposed to support QoS guarantee for the downlink. The new packets and handoff packets for each type of traffic are defined and a new cutoff prioritization scheme is devised at the buffer of the base station. A procedure to find the optimal thresholds satisfying the QoS requirements is presented. Using the ON-OFF approximation for aggregate traffic, the packet loss probability and the average packet delay are computed. The performance of the proposed scheme is evaluated by simulation and numerical analysis in terms of packet loss probability and average packet delay

Flat Cellular (UMTS) Networks

Traditionally, cellular systems have been built in a hierarchical manner: many specialized cellular access network elements that collectively form a hierarchical cellular system. When 2G and later 3G systems were designed there was a good reason to make system hierarchical: from a cost-perspective it was better to concentrate traffic and to share the cost of processing equipment over a large set of users while keeping the base stations relatively cheap. However, we believe the economic reasons for designing cellular systems in a hierarchical manner have disappeared: in fact, hierarchical architectures hinder future efficient deployments. In this paper, we argue for completely flat cellular wireless systems, which need just one type of specialized network element to provide radio access network (RAN) functionality, supplemented by standard IP-based network elements to form a cellular network. While the reason for building a cellular system in a hierarchical fashion has disappeared, there are other good reasons to make the system architecture flat: (1) as wireless transmission techniques evolve into hybrid ARQ systems, there is less need for a hierarchical cellular system to support spatial diversity; (2) we foresee that future cellular networks are part of the Internet, while hierarchical systems typically use interfaces between network elements that are specific to cellular standards or proprietary. At best such systems use IP as a transport medium, not as a core component; (3) a flat cellular system can be self scaling while a hierarchical system has inherent scaling issues; (4) moving all access technologies to the edge of the network enables ease of converging access technologies into a common packet core; and (5) using an IP common core makes the cellular network part of the Internet

Comparative Analysis of Location Management Schemes in Wireless ATM Networks

Mobility is the cornerstone of wireless networks. Supporting mobility requires some form of tracking to locate mobile terminals within the network. In the wireline ATM network, the terminal is fixed and the terminal is located by identifying the terminal and following the routing information provided at each switch along the path. As terminals become mobile, the path to the mobile becomes dynamic; the terminal and the path are no longer synonymous. Signalling traffic incurred in tracking mobile users and delivering enhanced services causes an additional load in the Wireless ATM (WArM) network. Efficient database and location management schemes are needed to meet the challenges from high density and mobility of users, and various service scenarios. In this thesis the three "natural" Location Management Strategies, i.e., Timer-Based, Location Area Based and Movement Based are studied and analysed for a W ATM network. The model used for depicting user motion and call arrival is Brownian motion with drift process and Poisson arrival process, respectively. The Timer-Based location management strategy is one in which the user updates its location periodically after an "optimum" interval of time. This optimum interval of time is based upon the user's mobility and call arrival characteristics and is therefore best suited for that particular mobile. In the Adaptive Location Area Based strategy, the user updates its location on each LA boundary crossing. The size of the LA changes according to the user' s mobility characteristics. The objective is to minimise the combined average signalling cost of both paging and registration for each individual mobile user such that the overall system-wide signalling cost for location tracking can be minimised

Performance Comparison of Handover Rerouting Schemes in Wireless ATM Networks

The major issue of the integration of wireless and wired ATM is the support of user mobility. In effect, many technical challenges have been posed due to mobility support. One of the most important challenges is the rerouting of active connections of mobile user during handover. The rerouting of connections must exhibit low handover latency, limit the handover delay or disruption time, maintain efficient routes and minimise the impact on existing infrastructure. To date, two dominant approaches have been proposed to support mobility into fixed ATM network. The first is the mobility enhanced switches approach and the second is the separate network-elements specific to mobility approach. The first approach implies updating the existing ATM switches with mobile specific features. The mobility functions in the second approach are entrusted to a control station attached to the ATM switch as is implemented by the Magic WAND projects. In this thesis, we investigate how mobility can be supported using both approaches. To demonstrate the effectiveness of the above approaches, we compare the performance by analytically derived formulate for their hand over latency, hand over delay, buffer size, and bandwidth requirements. The formulate were derived for both backward and forward hand overs using a number of potential rerouting schemes proposed for wireless ATM network. The results show that the mobility enhanced switches approach has slightly better performance than the separate network elements approach. The results also show that backward handover has better performance than forward handover in terms of the handover delay and buffer requirement. Finally, the results show that the Anchor Switch rerouting scheme is the best among other rerouting schemes proposed for wireless ATM