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Existing MAC protocols do not address the dynamism and complexity of the environment and applications of today's wireless networks. The running applications and the environment change all the time, and as a consequence the require...
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Existing MAC protocols do not address the dynamism and complexity of the environment and applications of today's wireless networks. The running applications and the environment change all the time, and as a consequence the requirements of the wireless transmissions change. For example, in one moment a client is transmitting video, requiring high throughput; next it will control a robotic arm, requiring bounded delays. In this example, a contention-based MAC protocol would cope with flexible traffic demands, however it does not meet the delay constraints. Reservation based protocols, meanwhile, provide performance guarantees, but at a higher overhead. Hence, wireless networks require adaptive techniques that change how the network reacts over time. To that end, we propose SOMAC (Self-Organizing MAC), a system that uses reinforcement learning techniques to switch the MAC protocol in structured wireless networks according to the ongoing network demand. The novelty of SOMAC lies in its use of reinforcement learning, which solves the following shortcomings in the literature: (i) the lack of models that cope with changes in its environment or lack of representative data during training; (ii) the capacity to self-optimize based on a number of metrics. To showcase its genericity, we evaluated the model using two different optimization metrics (throughput and delay) on a testbed.Results indicate that our solution performs similar to an oracle choosing the most suitable MAC protocol from the list of implemented protocols up to 90% of the time. Further, SOMAC outperforms the state of the art by up to 20% in terms of protocol selection.
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Wireless sensor networks (WSNs) are considered as the appealing research area. WSNs require highly robust medium access control (MAC) protocol to enhance the performance in several application areas, such as intrusion detection, t...
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Wireless sensor networks (WSNs) are considered as the appealing research area. WSNs require highly robust medium access control (MAC) protocol to enhance the performance in several application areas, such as intrusion detection, target detection, industrial automation, environmental monitoring, surveillance system, medical diagnosing system, and tactical system. On the other hand, there are several factors that affect the performance of these applications particularly selection of weak MAC protocol. In this paper, we provide performance impairing drivers for MAC protocols, which affect the efficiency and robustness of MAC protocols in WSN applications. We classify MAC protocols into six categories, as compared with previous MAC surveys that only focused on classifying the MAC protocols into two, three, or four major categories. In addition, we show the link of each category with another based on their existing features. Furthermore, this survey provides a detailed nomenclature in which protocols are categorized based on synchronous and asynchronous communication. This survey also discusses the possible threats and some existing solutions at the MAC layer from 2000 to 2014. Finally, we identify the future research challenges and raise directions for controlling these challenges.
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Flying Ad Hoc Network (FANET) is a novel mobile ad hoc network type where the communicating nodes are Unmanned Aerial Vehicles (UAVs). FANETs promise many new ways for both civilian and military applications. Today, traditional om...
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Flying Ad Hoc Network (FANET) is a novel mobile ad hoc network type where the communicating nodes are Unmanned Aerial Vehicles (UAVs). FANETs promise many new ways for both civilian and military applications. Today, traditional omnidirectional antennas are deployed on UAV nodes which result in reduced spatial reuse and limited network capacity. Alternatively, deployment of directional antennas can significantly increase the capacity, spatial reuse and communication range of FANETs. In addition, being aware of the exact locations of the neighboring nodes in a FANET is vital especially for directional ad hoc multi-UAV scenarios. In this paper, we present a novel MAC protocol, LODMAC (Location Oriented Directional MAC), which incorporates the utilization of directional antennas and location estimation of the neighboring nodes within the MAC layer. By defining a new Busy to Send (BTS) packet along with the Request to Send (RTS) and Clear to Send (CTS) packets, LODMAC effectively addresses the well known directional deafness problem. In terms of throughput, utilization, average network delay and fairness, LODMAC protocol outperforms the well-known DMAC (Directional MAC) protocol which puts LODMAC to be a robust mile-stone for the on-coming FANET MAC protocols. (C) 2015 Elsevier B.V. All rights reserved.
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近年の無線通信の高速化やユビキタス社会実現に向けて，無線アドホックネットワーク(MANET)において多くの通信機会及び高いスループットを実現するMACプロトコルが必要不可欠となる．従来のCSMA/CA with RTS/CTSでは，各端末で共通のキャリアセンス...
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近年の無線通信の高速化やユビキタス社会実現に向けて，無線アドホックネットワーク(MANET)において多くの通信機会及び高いスループットを実現するMACプロトコルが必要不可欠となる．従来のCSMA/CA with RTS/CTSでは，各端末で共通のキャリアセンスレベルを用い，またキャリアセンスには(a)新規通信端末が受ける通信妨害と(b)既存通信端末が受ける通信妨害を回避する役割がある．また，MANETでは，受信SNRが高い通信端末では高いキャリアセンスレベルで低い通信端末では低いキャリアセンスレベルで通信可能となる特徴がある．そして，各端末で共通のキャリアセンスレベルを使用し，受信SNRの低い通信端末が受信SNRの高い通信端末と同時に通信を行うことは通信機会の減少及びスループットの低下を発生させる．本稿では，各端末で予想したCTS受信SNIRから(a)の役割を果たすキャリアセンスを適応的に行うことで，受信SNRの低い通信端末が受信SNRの高い通信端末との同時通信を回避することで，通信機会及びスループットの増加を達成するMACプロトコルを提案する．提案手法の基本性能を計算機シミュレーションにより検討した．
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Wireless Multimedia Sensor Networks (WMSNs) have entered the class of Wireless Sensor Networks (WSNs) to meet the multimedia requirements of new emerging applications, such as surveillance and telepresence. Combining the tradition...
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Wireless Multimedia Sensor Networks (WMSNs) have entered the class of Wireless Sensor Networks (WSNs) to meet the multimedia requirements of new emerging applications, such as surveillance and telepresence. Combining the traditional scalar sensors used in WSN nodes with tiny cameras and microphones, WMSNs commonly carry heterogeneous traffic with different Quality of Service (QpS) requirements. In order to deliver heterogeneous traffic with different requirements in highly resource constrained sensor networks, QoS provisioning and service differentiation become unavoidable. In this paper first we discuss the QoS-provisioning in sensor networks and evaluate the efficiency of existing QpS-aware MAC protocols. As a result of this evaluation, next we design and implement a QoS-aware MAC protocol for WMSNs, Diff-MAC, which integrates different methods to meet the requirements of QpS provisioning to deliver heterogeneous traffic and provides a fair all-in-one QoS-aware MAC protocol. Diff-MAC aims to increase the utilization of the channel with effective service differentiation mechanisms while providing fair and fast delivery of the data. Performance evaluation results of Diff-MAC, obtained through extensive simulations, show significant improvements, in terms of latency, data delivery and energy efficiency, compared to two other existing protocols. Implementation of Diff-MAC on Imote2 platform also reveals that the protocol with moderate complexity can be easily implemented on the resource constrained motps.
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In this paper we introduce a novel MAC protocol that provides Quality of Service (QoS) support for multimedia traffic in UWB-based wireless local area networks. The proposed protocol allocates transmission opportunities to QoS and...
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In this paper we introduce a novel MAC protocol that provides Quality of Service (QoS) support for multimedia traffic in UWB-based wireless local area networks. The proposed protocol allocates transmission opportunities to QoS and best effort traffic using a set of scheduling and resource control algorithms. The algorithms account for the UWB characteristics such as the co-existence of multiple simultaneous transmissions as well as the possibility of dynamically assigning the nodes' transmission rate and power. The simulation results show that the proposed protocol can provide QoS support while optimizing resource utilization.
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The performance of uplink multiuser MIMO (MU-MIMO) transmissions heavily depends on which users to transmit together. In WLANs where each user independently determines when to transmit by random access, the performance degradation...
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The performance of uplink multiuser MIMO (MU-MIMO) transmissions heavily depends on which users to transmit together. In WLANs where each user independently determines when to transmit by random access, the performance degradation occurs when a set of users for concurrent transmissions are not chosen properly. In this paper, we address this problem and propose Delta SNR-MAC protocol to enhance the uplink throughput in MU-MIMO WLANs. In Delta SNR-MAC, a set of users transmitting together are determined one after another through a multi-round contention where the number of rounds equals the number of antennas at the AP. In each round, given winning users that are already transmitting, each user calculates its SNR reduction amount due to the winning users. Delta SNR-MAC gives a higher priority to users with less SNR reduction amounts. To achieve this, each round consists of multiple stages where earlier stages are reserved for users with less SNR reduction amounts. In this way, users with the strong channel orthogonality can transmit together in a fully distributed manner. We theoretically analyze the throughput of Delta SNR-MAC and propose a parameter selection method to maximize the throughput. Our evaluation results confirm that Delta SNR-MAC improves the uplink throughput over existing schemes both in two- and three-antenna AP cases and achieves temporal fairness in mobile environments. (C) 2015 Elsevier B.V. All rights reserved.
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Most current WSN MAC protocol implementations have multiple tasks to perform-deciding on correct timing, sending of packets, sending of acknowledgements, etc. However, as much of this is common to all MAC protocols, there is dupli...
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Most current WSN MAC protocol implementations have multiple tasks to perform-deciding on correct timing, sending of packets, sending of acknowledgements, etc. However, as much of this is common to all MAC protocols, there is duplication of functionality, which leads to larger MAC protocol code size and therefore increasing numbers of bugs. Additionally, extensions to the basic functionality must be separately implemented in each MAC protocol. In this paper, we look at a different way to design a MAC protocol, focusing on the providing of interfaces which can be used to implement the common functionality separately. This leaves the core of the MAC protocol, determining only when to send, which is substantially different for each protocol. We also look at some examples of MAC extensions that this approach enables. We demonstrate a working implementation of these principles as an implementation of B-MAC for TinyOS, and compare it with the standard TinyOS B-MAC implementation. We show a 35% smaller code size, with the same overall functionality but increased extensibility, and while maintaining similar performance. We also present results and experiences from using the same framework to implement T-MAC, LMAC, and Crankshaft. All are
demonstrated with data from real-world experience using our 24 node testbed.
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In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are i...
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In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are involved in the transmission. However, a transmission policy that maximizes the diversity gain or throughput need not maximize the stability region, since queues at the nodes may grow while waiting for a sufficient number of nodes to become available. To address this issue, this paper develops a mechanism for maximizing the throughput while reducing the energy consumption and maintaining queue stability. We develop a sufficient condition that ensures the throughput optimality of a stable transmission policy and then use it to design a distributed, dynamic threshold based Medium Access Control (MAC) protocol for cooperative MIMO transmissions. The MAC protocol requires only limited local information for its operation. Simulation results are provided to evaluate the performance of the proposed protocol and compare it against regular point-to-point and existing cooperative MIMO MAC protocols. The results show that the proposed scheme can provide considerable gains in the throughput and energy savings compared to cooperative MIMO based on fixed number of cooperating nodes.
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