Increasing number of ageing population and people who need continuous health monitoring and rising the costs of health care have triggered the concept of the novel wireless technology-driven human body monitoring. Human body monitoring can be performed using a network of small and intelligent wireless medical sensors which may be attached to the body surface or implanted into the tissues. It enables carers to predict, diagnose, and react to adverse events earlier than ever. The concept of Wireless Body Area Network (WBAN) was introduced to fully exploit the benefits of wireless technologies in telemedicine and m-health. The main focus of this research is the design and performance evaluation of strategies and architectures that would allow seamless and efficient interconnection of patient’s body area network and the stationary (e.g., hospital room or ward) wireless networks. I first introduce the architecture of a healthcare system which bridges WBANs and Wireless Local Area Networks (WLANs). I adopt IEEE 802.15.6 standard for the patient’s body network because it is specifically designed for WBANs. Since IEEE 802.15.6 has strict Quality of Service (QoS) and priorities to transfer the medical data to the medical server a QoS-enabled WLAN for the next hop is needed to preserve the end-to-end QoS. IEEE 802.11e standard is selected for the WLAN in the hospital room or ward because it provides prioritization for the stations in the network. I investigate in detail the requirements posed by different healthcare parameters and to analyze the performance of various alternative interconnection strategies, using the rigorous mathematical apparatus of Queuing Theory and Probabilistic Analysis; these results are independently validated through discrete event simulation models. This thesis has three main parts; performance evaluation and MAC parameters settings of IEEE 802.11e Enhanced Distributed Channel Access (EDCA), performance evaluation and tuning the MAC parameters of IEEE 802.15.6, and designing a seamless and efficient interconnection strategy which bridges IEEE 802.11e EDCA and IEEE 802.15.6 standards for a healthcare system.

In order to efficiently utilize the scarce wireless resource as well as keep up with the ever-increasing demand for Quality-of-Service (QoS) of multimedia applications, wireless networks are undergoing rapid development and dramatic changes in the underlying technologies and protocols. The Medium Access Control (MAC) protocol, which coordinates the channel access and data transmission of wireless stations, plays a pivotal role in wireless networks. Performance modelling and analysis has been and continues to be of great theoretical and practical importance in the design and development of wireless networks. This research is devoted to developing efficient and cost-effective analytical tools for the performance analysis and enhancement of MAC protocols in Wireless Local Area Networks (WLANs) under heterogeneous multimedia traffic. To support the MAC-layer QoS in WLANs, the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol has proposed three QoS differentiation schemes in terms of Arbitrary Inter-Frame Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). This research starts with the development of new analytical models for the TXOP scheme specified in the EDCA protocol under Poisson traffic. A dynamic TXOP scheme is then proposed to adjust the TXOP limits according to the status of the transmission queue. Theoretical analysis and simulation experiments show that the proposed dynamic scheme largely improves the performance of TXOP. To evaluate the TXOP scheme in the presence of ii heterogeneous traffic, a versatile analytical model is developed to capture the traffic heterogeneity and model the features of burst transmission. The performance results highlight the importance of taking into account the heterogeneous traffic for the accurate evaluation of the TXOP scheme in wireless multimedia networks. To obtain a thorough and deep understanding of the performance attributes of the EDCA protocol, a comprehensive analytical model is then proposed to accommodate the integration of the three QoS schemes of EDCA in terms of AIFS, CW, and TXOP under Poisson traffic. The performance results show that the TXOP scheme can not only support service differentiation but also improve the network performance, whereas the AIFS and CW schemes provide QoS differentiation only. Moreover, the results demonstrate that the MAC buffer size has considerable impact on the QoS performance of EDCA under Poisson traffic. To investigate the performance of EDCA in wireless multimedia networks, an analytical model is further developed for EDCA under heterogeneous traffic. The performance results demonstrate the significant effects of heterogeneous traffic on the total delay and frame losses of EDCA with different buffer sizes. Finally, an efficient admission control scheme is presented for the IEEE 802.11e WLANs based on analytical modelling and a game-theoretical approach. The admission control scheme can maintain the system operation at an optimal point where the utility of the Access Point (AP) is maximized with the QoS constraints of various users.

近十年來，由於無線網路的普及與人們對於影像串流服務的需求愈高，導致人們迫切需要更好的服務品質。但在IEEE 802.11無線網路中，本身的設計並非針對影像串流來設計，為讓影像串流能在無線網路更有效率，我們必須重新設計適合影像串流的無線網路。本研究首先探討IEEE 802.11 MAC層DCF (Distributed Coordination Function)與802.11e EDCA (Enhanced Distributed Channel Access)機制的潛在問題。由於DCF與EDCA並未特別對影像串流做設計，會導致具有時延(delay time)限制的影像封包等待過久造成失效，卻仍繼續傳送。本研究提出幾個有效方法，改善原本IEEE 802.11無線網路對影像串流傳輸效能不彰的現象。我們將利用跨層設計使MAC層能取得影像串流封包資訊，並改善DCF與EDCA的重傳(retransmission)機制，使用time limit與retry limit混和設計節省不必要的等待時間，並使用single-video multi-level queue改善傳輸效能。最後本研究將利用網路模擬器NS-2 (Network Simulater ver. 2)與影像串流測試實驗架構myEvalvid-NT作不同效能的驗證比較並評估我們所提出方法的有效性。 / Over the past decade, wireless network access and video streaming services have become more popular than ever. People are eager to have better quality of video streaming services over wireless network. However, IEEE 802.11 DCF and IEEE 802.11e EDCA are not specifically designed for video streaming. This leads to the problem of transmitting overdue video packets and thus degrades both the network performance and video quality. In this paper, we propose a hybrid design framework to improve the quality of video streaming. This framework consists of a MAC-centric cross-layer architecture to allow MAC-layer to retrieve video streaming packet information (slice type and transmission deadline), a retransmission mechanism of hybrid retransmission deadline and retry limit to save unnecessary packet waiting time, and a single-video multi-level queue to prioritize I/P/B slice delivery. Simulations show that the proposed methodology outperforms IEEE 802.11e, IEEE 802.11e Timebase and IEEE 802.11e MultiQ in packet loss rate, invalid packet ratio, lost and invalid packet ratio, delay time, jitter, and PSNR.

This work deals with the wireless Wi-Fi networks, that used unlicenced ISM frequency band 2,4 GHz. These wireless networks are very extended in these days and used mainly for the Internet connection. With the multimedia data transfers expanding it’s necessary to ensure the specific quality of service QoS in wireless networks mainly for applications, which are sensitive to delay or packets lost. The main aim of this work is to describe Wi-Fi networks based on IEEE 802.11b/g/n standards, description of QoS techniques according to IEEE 802.11e standard and description of parameters describing QoS for the VoIP services. The practical part is divided on a two parts. The problems of measuring the radio link quality and the creation of simple program for quality of wireless connection analysis are solved in the first part. The second part incluledes measuring of the lost packets number in Wi-Fi network with the commercial application AirMagnet Laptop Wireless LAN Analyzer and measuring of the signal noise influence with the help of spectrum analyzer and vector signal generator.

In order to efficiently utilize the scarce wireless resource as well as keep up with the ever-increasing demand for Quality-of-Service (QoS) of multimedia applications, wireless networks are undergoing rapid development and dramatic changes in the underlying technologies and protocols. The Medium Access Control (MAC) protocol, which coordinates the channel access and data transmission of wireless stations, plays a pivotal role in wireless networks. Performance modelling and analysis has been and continues to be of great theoretical and practical importance in the design and development of wireless networks. This research is devoted to developing efficient and cost-effective analytical tools for the performance analysis and enhancement of MAC protocols in Wireless Local Area Networks (WLANs) under heterogeneous multimedia traffic. To support the MAC-layer QoS in WLANs, the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol has proposed three QoS differentiation schemes in terms of Arbitrary Inter-Frame Space (AIFS), Contention Window (CW), and Transmission Opportunity (TXOP). This research starts with the development of new analytical models for the TXOP scheme specified in the EDCA protocol under Poisson traffic. A dynamic TXOP scheme is then proposed to adjust the TXOP limits according to the status of the transmission queue. Theoretical analysis and simulation experiments show that the proposed dynamic scheme largely improves the performance of TXOP. To evaluate the TXOP scheme in the presence of ii heterogeneous traffic, a versatile analytical model is developed to capture the traffic heterogeneity and model the features of burst transmission. The performance results highlight the importance of taking into account the heterogeneous traffic for the accurate evaluation of the TXOP scheme in wireless multimedia networks. To obtain a thorough and deep understanding of the performance attributes of the EDCA protocol, a comprehensive analytical model is then proposed to accommodate the integration of the three QoS schemes of EDCA in terms of AIFS, CW, and TXOP under Poisson traffic. The performance results show that the TXOP scheme can not only support service differentiation but also improve the network performance, whereas the AIFS and CW schemes provide QoS differentiation only. Moreover, the results demonstrate that the MAC buffer size has considerable impact on the QoS performance of EDCA under Poisson traffic. To investigate the performance of EDCA in wireless multimedia networks, an analytical model is further developed for EDCA under heterogeneous traffic. The performance results demonstrate the significant effects of heterogeneous traffic on the total delay and frame losses of EDCA with different buffer sizes. Finally, an efficient admission control scheme is presented for the IEEE 802.11e WLANs based on analytical modelling and a game-theoretical approach. The admission control scheme can maintain the system operation at an optimal point where the utility of the Access Point (AP) is maximized with the QoS constraints of various users.