The evolution of the intemet protocol (IP) to offer quality of service (QoS) makes it a suitable core network protocol for next generation networks (NGN). The QoS features incorporated to IP will enable future lP-based wireless networks to meet QoS requirements of various multimedia traffic. The Differentiated Service (Diffserv) Architecture is a promising QoS technology due to its scalability which arises from traffic flow aggregates. For this reason, in this dissertation a network infrastructure based on DiffServ is assumed. This architecture provides assured service (AS) and premium service (PrS) classes in addition to best-effort service (BE). The medium access control (MAC) protocol is one of the important design issues in wireless networks. In a wireless network carrying multimedia traffic, the MAC protocol is required to provide simultaneous support for a wide variety of traffic types, support traffic with delay and jitter bounds, and assign bandwidth in an efficient and fair manner among traffic classes. Several MAC protocols capable of supporting multimedia services have been proposed in the literature, the majority of which were designed for wireless A1M (Asynchronous Transfer Mode). The focus of this dissertation is on time division multiple access and code division multiple access (TDMAlCDMA) based MAC protocols that support QoS in lP-based wireless networks. This dissertation begins by giving a survey of wireless MAC protocols. The survey considers MAC protocols for centralised wireless networks and classifies them according to their multiple access technology and as well as their method of resource sharing. A novel TDMAlCDMA based MAC protocol incorporating techniques from existing protocols is then proposed. To provide the above-mentioned services, the bandwidth is partitioned amongst AS and PrS classes. The BE class utilizes the remaining bandwidth from the two classes because it does not have QoS requirements. The protocol employs a demand assignment (DA) scheme to support traffic from PrS and AS classes. BE traffic is supported by a random reservation access scheme with dual multiple access interference (MAl) admission thresholds. The performance of the protocol, i.e. the AS or PrS call blocking probability, and BE throughput are evaluated through Markov analytical models and Monte-Carlo simulations. Furthermore, the protocol is modified and incorporated into IEEE 802.16 broadband wireless access (BWA) network. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

Thesis (M.Eng. (Electrical, Electronic and Computer Engineering)) -- University of Pretoria, 2007. / Includes bibliographical references (leaves 95-98)

Thesis (M.Eng (Electrical, Electronic and Computer Engineering)) -- University of Pretoria, 2008. / Includes bibliographical references (leaves [128]-135)

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: SRMA currently used on the SUNSAT field station is an effective MAC layer protocol but lacks several features. Sufficient support for flexible communication, acknowledgement of individual data packets, simultaneous communication of multiple instances from a higher layer over a single underlying layer, and a robust FTP procedure to transfer large amounts of data are some of the features that the SUNSA T field station should cater for. ORBCOMM, GSM and WAP implementations are discussed. Some features from these implementations that are useful in the LEO communication environment are designed into an additional layer of software. This additional layer, called middleware, is proposed and uses SRMA services to deliver store-and-forward services. It supports high volumes of short transactions and session suspend and resume facilities between the SUNSA T satellite and field station. Keywords: SUNSAT, Communication, Field station, WAP, GSM, ORBCOMM / AFRIKAANSE OPSOMMING: Die SRMA pakketkommunikasie-protokol op SUNSA T se prototipe grondterminaal is voldoende om die oordrag van boodskappe oor die kommunikasieverbinding te reguleer. Dit is onvoldoende om fasiliteite soos kommunikasie van 'n aantal instansies in 'n hoër kommunikasie laag oor 'n enkele laer laag en om 'n robuuste data oordrag protokol vir groot hoeveelhede data van 'n grondterminaal te ondersteun. ORBCOMM, GSM en WAP stelsel toepassings word bespreek. Resultate wat spruit uit die drie toepassings word gebruik om kommunikasie in 'n lae wentelbaan kommunikasie omgewing te bevorder. 'n Bykomende sagteware laag, bekend as middle-ware, word aanbeveel om voorafgenoemde funksionaliteit mee te implimenteer. Die middle-ware gebruik die beskikbare dienste van die SRMA pakketkommunikasie-protokol om toegang te verkry na die kommunikasie kanaal. Sodoende kan hoë volumes kort transaksies, en sessie-stop en hervat fasiliteite 'n werklikheid gemaak word. Sleutelwoord: SUNS AT, Kommunikasie, grondterminaal, WAP, GSM, ORBCOMM

Wireless Application Development has become a major area of research in recent times. With the increasing availability of wireless technologies such as cellular, Bluetooth, Infrared etc. it has become essential to develop applications that suit the various types of hardware that support such wireless technologies. The goal of this thesis is to explore the motivations behind application development methodologies and the tools associated with it, for small mobile devices that employ cellular technologies. Due to extremely high demand of cell phones among people who have over the years become extra mobile, there has been a trend of decreasing costs for users for the last several years. As more people start using these devices every day the demand for support of various applications and services are on the rise. This thesis will explore the leading application development tools and technologies for small mobile devices WAP (Wireless Application Protocol), J2ME (Java 2 Platform, Micro Edition) and some others. This thesis will also take a brief look into cellular network technology termed 3G, in terms of its usefulness for applications developed using the aforementioned technologies. The thesis includes the development of a J2ME application using a wireless device emulator.

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes.

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes.

Multi-hop wireless networks or ad-hoc networks face several limiting characteristics that make it difficult to support a multitude of applications. It is in this context that we find smart antennas to find significant applications in these networks, owing to their ability to alleviate most of these limitations. The focus of my research is thus to investigate the use of smart antennas in ad-hoc networks and hence efficiently design network protocols that best leverage their capabilities in communication. There are two parts to the proposed objective of designing efficient network protocols that pertain to the nature of the smart antenna network considered, namely, homogeneous and heterogeneous smart antenna networks. Unlike heterogeneous smart antenna networks, where different devices in the network employ different antenna technologies, homogeneous smart antenna networks consist of devices employing the same antenna technology. Further, in homogeneous smart antenna networks, different antenna technologies operating in different strategies tend to perform the best in different network architectures, conditions and application requirements. This motivates the need for developing a {em unified} framework for designing efficient communication (medium access control and routing) protocols for homogeneous smart antenna networks in general. With the objective of designing such a unified framework, we start by designing efficient MAC and routing protocols for the most sophisticated of the smart antenna technologies, namely multiple-input multiple-output (MIMO) links. The capabilities of MIMO links form a super-set of those possible with other antenna technologies. Hence, the insights gained from the design of communication protocols for MIMO links are then used to develop unified MAC and routing frameworks for smart antennas in general. For heterogeneous smart antenna networks, we develop theoretical performance bounds by studying the impact of increasing degree of heterogeneity on network throughput performance. Given that the antenna technologies are already unified in the network, unified solutions are not required. However, we do develop efficient MAC and routing protocols to best leverage the available heterogeneous capabilities present in the network. We also design efficient cooperation strategies that will further help the communication protocols in exploiting the available heterogeneous capabilities in the network to the best possible extent.

Mobile communications are becoming integrated into society at an explosive rate. While 2nd generation (2G) systems limit the user to basic services such as voice and low-bit rate data, 3G networks are characterized by their ability to accommodate wideband multi-media traffic with Quality of Service (QoS) guarantees. In the design of a system the Medium Access Control (MAC) layer is responsible for multiplexing heterogeneous traffic onto a common transmission link and its design is critical to the overall performance of a system. A number of MAC protocols for wireless networks have been proposed in the literature - the majority having time division multiple access (TDMA) at the MAC layer. However in 3G systems there is a trend towards the use of code division multiple access (CDMA) due to its proven advantages in a wireless environment. Although several papers on CDMA based MAC protocols have been published, virtually none of them tackle the analysis aspect of the protocols. Those papers that do perform analyses of CDMA protocols don't often consider heterogeneous traffic, and even fewer support QoS. The thesis addresses these shortcomings by proposing a MAC protocol that supports QoS in the form of Bit Error Rate (BER) and packet delay guarantees. The thesis begins by giving an overview of proposed wireless ATM and 3G CDMA protocols and then details how power control may be used to support BER guarantees. Various Markov based analyses are presented along with Monte-Carlo Simulations. An Equilibrium Point Analysis is then performed and the work discusses how such analyses are generally infeasible for systems supporting heterogeneous traffic. After an overview of conventional scheduling algorithms the thesis proceeds to outline a novel approach by which delay guarantees may be offered using packet dropping rates as the QoS metric. Using a stochastic source model as opposed to the conventional leaky bucket traffic regulator the thesis diverges significantly from conventional literature. The thesis also details how to calculate the probability of QoS violation and concludes with suggestions on further research avenues. As a whole the work is unique in its approach to analyse heterogeneous traffic and the methods it uses to construct session admission zones for QoS guarantees. / Thesis (Ph.D.)-University of Natal,Durban, 2002.

The emergence of portable terminals in work and living environments is accelerating the progression of wireless networks. A wireless ad hoc network is a new network concept where users establish peer-to-peer communication among themselves independently, in their small area. Since the wireless medium is a shared resource, it becomes an important design issue to efficiently allocate bandwidth among users. MAC (Medium Access Control) layer arbitrates the channel access to the wireless medium and is also responsible for bandwidth allocation to different users, therefore a large amount of research has been conducted on various MAC protocols for ad hoc wireless networks. This dissertation begins with a survey of existing wireless MAC protocols. The survey includes protocols designed for different network generations and topologies, classifying them based on architecture and mode of operation. Next, we concentrate on the MAC protocols proposed for distributed wireless networks. We propose a new MAC protocol based on a token-passing strategy; which not only incorporates the advantages of the guaranteed access scheme into the distributed type of wireless networks, but also the data rate and delay level QoS guarantees. Data rate QoS provides fairness into sharing of the channel, while delay level QoS introduces a flexible prioritized access to channels by adjusting transmission permission to the current network traffic activities. A simulation model for the protocol is developed and delay and throughput performance results are presented. To examine the efficiency and performance of the proposed MAC scheme in an ad hoc wireless environment, it is incorporated into the Bluetooth structured network. The model is then simulated in the Bluetooth environment and performance results are presented. Furthermore, an analytical model is proposed and an approximate delay analysis conducted for the proposed MAC scheme. Analytical results are derived and compared with results obtained from computer simulations. The dissertation concludes with suggestions for improvements and future work. / Thesis (M.Sc.-Engineering)-University of Natal, 2003.