Performance evaluation of channel selection algorithm for multi-channel MAC protocol in ad hoc networks

This thesis aims to provide an approach that is to investigate channel selection algorithm for increasing the performance of ad hoc networks. Although our channel selection algorithms are very simple, multi-channel MAC protocol that employs our channel selection algorithms are effective for increasing the performance of ad hoc networks.学位記番号：工博甲47

Cooperative communication in wireless local area networks

The concept of cooperative communication has been proposed to improve link capacity, transmission reliability and network coverage in multiuser wireless communication networks. Different from conventional point-to-point and point-to-multipoint communications, cooperative communication allows multiple users or stations in a wireless network to coordinate their packet transmissions and share each other’s resources, thus achieving high performance gain and better service coverage. According to the IEEE 802.11 standards, Wireless Local Area Networks (WLANs) can support multiple transmission data rates, depending on the instantaneous channel condition between a source station and an Access Point (AP). In such a multi-rate WLAN, those low data-rate stations will occupy the shared communication channel for a longer period for transmitting a fixed-size packet to the AP, thus reducing the channel efficiency and overall system performance. This thesis addresses this challenging problem in multi-rate WLANs by proposing two cooperative Medium Access Control (MAC) protocols, namely Busy Tone based Cooperative MAC (BTAC) protocol and Cooperative Access with Relay’s Data (CARD) protocol. Under BTAC, a low data-rate sending station tries to identify and use a close-by intermediate station as its relay to forward its data packets at higher data-rate to the AP through a two-hop path. In this way, BTAC can achieve cooperative diversity gain in multi-rate WLANs. Furthermore, the proposed CARD protocol enables a relay station to transmit its own data packets to the AP immediately after forwarding its neighbour’s packets, thus minimising the handshake procedure and overheads for sensing and reserving the common channel. In doing so, CARD can achieve both cooperative diversity gain and cooperative multiplexing gain. Both BTAC and CARD protocols are backward compatible with the existing IEEE 802.11 standards. New cross-layer mathematical models have been developed in this thesis to study the performance of BTAC and CARD under different channel conditions and for saturated and unsaturated traffic loads. Detailed simulation platforms were developed and are discussed in this thesis. Extensive simulation results validate the mathematical models developed and show that BTAC and CARD protocols can significantly improve system throughput, service delay, and energy efficiency for WLANs operating under realistic communication scenarios

MAC/PHY Co-Design of CSMA Wireless Networks Using Software Radios.

In the past decade, CSMA-based protocols have spawned numerous network standards (e.g., the WiFi family), and played a key role in improving the ubiquity of wireless networks. However, the rapid evolution of CSMA brings unprecedented challenges, especially the coexistence of different network architectures and communications devices. Meanwhile, many intrinsic limitations of CSMA have been the main obstacle to the performance of its derivatives, such as ZigBee, WiFi, and mesh networks. Most of these problems are observed to root in the abstract interface of the CSMA MAC and PHY layers --- the MAC simply abstracts the advancement of PHY technologies as a change of data rate. Hence, the benefits of new PHY technologies are either not fully exploited, or they even may harm the performance of existing network protocols due to poor interoperability. In this dissertation, we show that a joint design of the MAC/PHY layers can achieve a substantially higher level of capacity, interoperability and energy efficiency than the weakly coupled MAC/PHY design in the current CSMA wireless networks. In the proposed MAC/PHY co-design, the PHY layer exposes more states and capabilities to the MAC, and the MAC performs intelligent adaptation to and control over the PHY layer. We leverage the reconfigurability of software radios to design smart signal processing algorithms that meet the challenge of making PHY capabilities usable by the MAC layer. With the approach of MAC/PHY co-design, we have revisited the primitive operations of CSMA (collision avoidance, carrier signaling, carrier sensing, spectrum access and transmitter cooperation), and overcome its limitations in relay and broadcast applications, coexistence of heterogeneous networks, energy efficiency, coexistence of different spectrum widths, and scalability for MIMO networks. We have validated the feasibility and performance of our design using extensive analysis, simulation and testbed implementation.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/95944/1/xyzhang_1.pd

Distributed Medium Access Control for QoS Support in Wireless Networks

With the rapid growth of multimedia applications and the advances of wireless communication technologies, quality-of-service (QoS) provisioning for multimedia services in heterogeneous wireless networks has been an important issue and drawn much attention from both academia and industry. Due to the hostile transmission environment and limited radio resources, QoS provisioning in wireless networks is much more complex and difficult than in its wired counterpart. Moreover, due to the lack of central controller in the networks, distributed network control is required, adding complexity to QoS provisioning. In this thesis, medium access control (MAC) with QoS provisioning is investigated for both single- and multi-hop wireless networks including wireless local area networks (WLANs), wireless ad hoc networks, and wireless mesh networks. Originally designed for high-rate data traffic, a WLAN has limited capability to support delay-sensitive voice traffic, and the service for voice traffic may be impacted by data traffic load, resulting in delay violation or large delay variance. Aiming at addressing these limitations, we propose an efficient MAC scheme and a call admission control algorithm to provide guaranteed QoS for voice traffic and, at the same time, increase the voice capacity significantly compared with the current WLAN standard. In addition to supporting voice traffic, providing better services for data traffic in WLANs is another focus of our research. In the current WLANs, all the data traffic receives the same best-effort service, and it is difficult to provide further service differentiation for data traffic based on some specific requirements of customers or network service providers. In order to address this problem, we propose a novel token-based scheduling scheme, which provides great flexibility and facility to the network service provider for service class management. As a WLAN has small coverage and cannot meet the growing demand for wireless service requiring communications ``at anywhere and at anytime", a large scale multi-hop wireless network (e.g., wireless ad hoc networks and wireless mesh networks) becomes a necessity. Due to the location-dependent contentions, a number of problems (e.g., hidden/exposed terminal problem, unfairness, and priority reversal problem) appear in a multi-hop wireless environment, posing more challenges for QoS provisioning. To address these challenges, we propose a novel busy-tone based distributed MAC scheme for wireless ad hoc networks, and a collision-free MAC scheme for wireless mesh networks, respectively, taking the different network characteristics into consideration. The proposed schemes enhance the QoS provisioning capability to real-time traffic and, at the same time, significantly improve the system throughput and fairness performance for data traffic, as compared with the most popular IEEE 802.11 MAC scheme

Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Link Scheduling Algorithms For In-Band Full-Duplex Wireless Networks

In the last two decades, wireless networks and their corresponding data traffic have grown significantly. This is because wireless networks have become an indispens- able and critical communication infrastructure in a modern society. An on-going challenge in communication systems is meeting the continuous increase in traffic de- mands. This is driven by the proliferation of electronic devices such as smartphones with a WiFi interface along with their bandwidth intensive applications. Moreover, in the near future, sensor devices that form the Internet of Things (IoTs) ecosystem will also add to future traffic growth. One promising approach to meet growing traffic demands is to equip nodes with an In-band-Full-Duplex (IBFD) radio. This radio thus allows nodes to transmit and receive data concurrently over the same frequency band. Another approach to in- crease network or link capacity is to exploit the benefits of Multiple-Input-Multiple- Output (MIMO) technologies; namely, (i) spatial diversity gain, which improves Signal-to-Noise Ratio (SNR) and thus has a direct impact on the data rate used by nodes, and (ii) spatial multiplexing gain, whereby nodes are able to form concurrent links to neighbors

Coexistence and interference mitigation for WPANs and WLANs from traditional approaches to deep learning: a review

More and more devices, such as Bluetooth and IEEE 802.15.4 devices forming Wireless Personal Area Networks (WPANs) and IEEE 802.11 devices constituting Wireless Local Area Networks (WLANs), share the 2.4 GHz Industrial, Scientific and Medical (ISM) band in the realm of the Internet of Things (IoT) and Smart Cities. However, the coexistence of these devices could pose a real challenge—co-channel interference that would severely compromise network performances. Although the coexistence issues has been partially discussed elsewhere in some articles, there is no single review that fully summarises and compares recent research outcomes and challenges of IEEE 802.15.4 networks, Bluetooth and WLANs together. In this work, we revisit and provide a comprehensive review on the coexistence and interference mitigation for those three types of networks. We summarize the strengths and weaknesses of the current methodologies, analysis and simulation models in terms of numerous important metrics such as the packet reception ratio, latency, scalability and energy efficiency. We discover that although Bluetooth and IEEE 802.15.4 networks are both WPANs, they show quite different performances in the presence of WLANs. IEEE 802.15.4 networks are adversely impacted by WLANs, whereas WLANs are interfered by Bluetooth. When IEEE 802.15.4 networks and Bluetooth co-locate, they are unlikely to harm each other. Finally, we also discuss the future research trends and challenges especially Deep-Learning and Reinforcement-Learning-based approaches to detecting and mitigating the co-channel interference caused by WPANs and WLANs

MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey

Multi-beam antenna technologies have provided lots of promising solutions to many current challenges faced in wireless mesh networks. The antenna can establish several beamformings simultaneously and initiate concurrent transmissions or receptions using multiple beams, thereby increasing the overall throughput of the network transmission. Multi-beam antenna has the ability to increase the spatial reuse, extend the transmission range, improve the transmission reliability, as well as save the power consumption. Traditional Medium Access Control (MAC) protocols for wireless network largely relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism, however, IEEE 802.11 DCF cannot take the advantages of these unique capabilities provided by multi-beam antennas. This paper surveys the MAC protocols for wireless mesh networks with multi-beam antennas. The paper first discusses some basic information in designing multi-beam antenna system and MAC protocols, and then presents the main challenges for the MAC protocols in wireless mesh networks compared with the traditional MAC protocols. A qualitative comparison of the existing MAC protocols is provided to highlight their novel features, which provides a reference for designing the new MAC protocols. To provide some insights on future research, several open issues of MAC protocols are discussed for wireless mesh networks using multi-beam antennas.Comment: 22 pages, 6 figures, Future of Information and Communication Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_

IEEE 802.11n WLAN에서 프레임 전송 시간 조절을 통한 네트워크 성능 향상 MAC 프로토콜

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 최종호.최근 스마트폰, 태블릿 PC 등의 무선 네트워크를 사용하는 모바일 기기의 사용이 급증함에 따라 무선 랜 (wireless local area network (WLAN))에 대한 수요가 빠르게 증가하고 있다. 하지만, IEEE 802.11 표준에서 기본적으로 사용하는 MAC (medium access control) 프로토콜인 DCF (distributed coordination function) 는 single-cell 네트워크에서 MAC 효율 (MAC efficiency) 성능이 떨어지는 문제점과 ad-hoc 네트워크에서 노드간에 공평성 성능이 크게 저하 되는 문제점을 지니고 있다. 본 논문에서는 이러한 네트워크에서 DCF가 지니고 있는 문제점을 각각 해결할 수 있는 두 가지 다른 방식의 MAC 프로토콜들을 제안하였다. 기존의 MAC 프로토콜에서는 패킷 (packet) 이나 프레임 (frame) 의 크기가 정해지면, 각 노드 (node) 의 데이터 전송 속도에 따라 (data transmission rate) 프레임 전송 시간 (frame transmission duration) 이 정해졌다. 하지만, 본 논문에서는 IEEE 802.11n/ac/ad 표준에서 사용하는 프레임 결합 (frame aggregation) 과 block ACK 기법을 이용하여 프레임 전송 시간을 정확히 조절 할 수 있는 방법을 제안하였다. 만약 이와같이 프레임 전송 시간을 우리가 원하는 데로 정확하게 조절 할 수 있게된다면, 네트워크 상에 각 노드들은 추가적인 오버헤드 (overhead) 없이 자신이 알려주고자 하는 정보를 프레임 전송 시간을 이용하여 자신 주변의 노드들에게 간접적으로 알려줄 수 있게 된다. 즉, 프레임 전송 시간을 정확히 조절하는 것을 통해서 기존의 컨트롤 메시지 (control message) 가 수행했던 역할인 정보 전달의 역할을 수행 할 수 있게 된다. 이 아이디어는 간단하지만, 각 노드들이 네트워크 성능을 향상 시킬 수 있는 정보를 교환하는데 효과적이다. 본 논문에서 제안된 두 개의 MAC 프로토콜들은 이 아이디어를 활용하여 네트워크 성능을 향상시키고자 하였다. 우선, IEEE 802.11 single-cell 네트워크에서의 MAC 효율 성능을 향상시키기 위해 Transmission Order Deducing MAC (TOD-MAC) 프로토콜을 제안하였다. 최근 물리 계층 (physical layer) 에서의 전송 속도가 Gbps 범위까지 비약적으로 발전하고 있다. 하지만, 이러한 물리 계층 전송 속도의 증가가 MAC 계층 (MAC layer) 에서의 처리량 (throughput) 성능 향상에 효과적으로 기여하지 못하고 있는 실정이다. 왜냐하면, 물리 계층에서의 전송 속도가 올라 갈수록 PHY header와 컨텐션 시간 (contention time) 등의 MAC 계층에서 발생하는 오버헤드들이 처리량 성능 향상에 큰 걸림돌이 되기 때문이다. 이러한 문제점을 해결 하기 위해서 TOD-MAC에서 각 노드들은 자신의 전송 순서에 따라 앞서 제안된 방법을 이용하여 프레임 전송 시간을 정확히 조절하여 데이터를 전송한다. 이를 통해 네트워크 상의 각 노드들은 자신 주변 노드들의 전송 순서를 프레임 전송 시간을 통해 추정할 수 있게 되고, 자신에게 알려진 전송 순서 정보를 이용하여 순환 순서 방식 (round robin manner) 으로 데이터를 전송한다. 이를 통해 제안된 MAC 프로토콜은 전송 충돌 (transmission collision) 과 컨텐션 시간을 효율적으로 줄일 수 있게 되고, CSMA/CA (carrier sensing multiple access with collision avoidance) 기반의 single-cell 네트워크에서의 MAC 효율을 극대화 시킬 수 있게 된다. 또한, 실험을 통해 TOD-MAC이 다양한 환경에서 높은 처리량 성능과, 좋은 short/long-term 채널 점유 시간 공평성 (air-time fairness) 성능을 보여주는 것을 확인할 수 있었다. 또한, 본 논문에서는 IEEE 802.11 ad-hoc 네트워크에서의 최대-최소 채널 점유 시간 공평성 (max-min air-time fairness) 을 향상 시킬 수 있는 Max-min Air-time Fairness MAC (MAF-MAC) 프로토콜을 제안하였다. 최근 IEEE 802.11 ad-hoc 네트워크를 기반으로한 서비스에 대한 요구가 빠르게 증하하면서, ad-hoc 네트워크에서 노드들 간에 공평한 서비스를 제공하는 것이 중요한 문제가 되고 있다. 이를 위해 MAF-MAC에서는 각 노드들이 자신의 채널 점유 시간에 대한 정보를 프레임 전송 시간을 통해 주변 노드들에게 알려주고, 각 노드들은 이 정보를 이용하여 자신의 contention window (CW) 값을 적절하게 조절하여 ad-hoc 네트워크에서의 최대-최소 채널 점유 시간 공평성 성능을 향상시키고자 하였다. 이를 통해 제안된 MAC 프로토콜은 네트워크에 있는 노드들에게 보다 공평한 서비스를 제공함과 동시에 채널 점유율과 사용율을 효율적으로 향상 시킬 수 있었다. 또한, 다른 연구에서 제안된 히든 노드 감지 (hidden node detection) 방법과 히든 노드 해결 (hidden node resolving) 방법을 MAF-MAC에 적용함으로써 ad-hoc 네트워크에서 발생 할 수 있는 히든 노드 문제를 효과적으로 해결 할 수 있었다. 시뮬래이션을 통해 히든 노드의 존재 여부와 관계 없이 다양한 환경에서 MAF-MAC에 기반한 방법이 좋은 채널 점유 공평성 성능을 보여줌과 동시에 효율적으로 채널을 사용하고 있다는 것을 확인 할 수 있었다.The demand for wireless local area network (WLAN) has drastically increased due to the prevalence of the mobile devices such as smart phones and tablet PCs. However, the distributed coordination function (DCF), which is the basic MAC protocol used in IEEE 802.11 WLANs, needs to be improved on MAC efficiency in single-cell networks and fairness performance in ad-hoc networks. In this dissertation, we propose two MAC protocols that can enhance MAC efficiency in single-cell network, and max-min air-time fairness in ad-hoc network by adjusting frame transmission duration, respectively. In the traditional MAC protocol, the length of a packet or a frame is usually fixed and the transmission duration is determined by the data rate. However, we show how each node can precisely adjust the transmission duration when the frame aggregation and block ACK features are used in very high-speed IEEE 802.11n/ac/ad WLANs. If the transmission duration can be precisely controlled, it plays the role usually carried out by a control message. Therefore, a node can indirectly announce necessary information to the other nodes, which can sense the transmission of the node, without incurring any overhead. This idea is simple, but very effective to enhance the network performance by exchanging the necessary information without overheads. First, we propose the Transmission Order Deducing MAC (TOD-MAC) protocol to improve MAC layer efficiency in IEEE 802.11 single-cell network. Recently, the physical (PHY) layer transmission rate increases to Gbps range in the IEEE 802.11 WLANs. However, the increase in the PHY layer transmission rates does not necessarily translate into corresponding increase in the MAC layer throughput of IEEE 802.11 WLANs because of MAC overheads such as PHY headers and contention time. TOD-MAC precisely controls the frame length and transmission duration to indirectly provide necessary information to a node to determine the transmission order among all the nodes in a network. Each node transmits frames of different duration, and thus the other nodes can determine the time when they can transmit, which has the same effect as announcing the transmission order, without using a control message. Each node transmits a frame in a round robin manner, which minimizes the idle time between two consecutive transmissions without collisions, and significantly enhances the MAC efficiency in very high speed CSMA/CA wireless networks. The results of extensive simulations indicate that TOD-MAC achieves high throughput performance, short/long-term air-time fairness in multi-rate networks and excellent transient behavior in dynamic environments. Secondly, we propose Max-min Air-time Fairness MAC (MAF-MAC) to improve max-min air-time fairness in IEEE 802.11 ad-hoc networks. As the demand for services based on ad-hoc networks rapidly increases, enhancing fairness among nodes becomes important issue in ad-hoc networks. The concept of max-min fairness is that a node may use more channel resource as long as it does take away the channel resource from the other nodes who uses less channel resource. In MAF-MAC, the transmission duration is adjusted so that it can indirectly perform the function of a control message in announcing the state of a node, called the busy time ratio. On the basis of this information, each node adjusts its $CW$ value to improve max-min air-time fairness. Moreover, we also adopt the hidden node detection and resolving mechanism to MAF-MAC to improve the max-min air-time fairness even when there are hidden nodes in ad-hoc networks. We show through simulation that MAF-MAC incorporating hidden node detection/resolution mechanisms can provide good air-time fairness with high channel occupation and utilization ratio whether or not there are hidden nodes in the network.Docto