Medium Access Control Solutions Research Articles

Addressing Multi-User Interference in Vehicular Visible Light Communications: A Brief Survey and an Evaluation of Optical CDMA MAC Utilization in a Multi-Lane Scenario.

Visible Light Communications (VLC) are developing as an omnipresent solution for inter-vehicle communications. Based on intensive research efforts, the performance of vehicular VLC systems has significantly improved in terms of noise resilience, communication range, and latencies. Nevertheless, in order to be ready for deployment in real applications, solutions for Medium Access Control (MAC) are also required. In this context, this article provides an intensive evaluation of several optical CDMA MAC solutions and of their efficiency in mitigating the effect of Multiple User Interference (MUI). Intensive simulation results showed that an adequately designed MAC layer can significantly reduce the effects of MUI, ensuring an adequate Packet Delivery Ratio (PDR). The simulation results showed that based on the use of optical CDMA codes, the PDR can be improved from values as low as 20% up to values between 93.2% and 100%. Consequently, the results provided in this article show the high potential of optical CDMA MAC solutions in vehicular VLC applications, reconfirm the high potential of the VLC technology in inter-vehicle communications, and emphasize the need to further develop MAC solutions designed for such applications.

Survey of Reinforcement-Learning-Based MAC Protocols for Wireless Ad Hoc Networks with a MAC Reference Model.

In this paper, we conduct a survey of the literature about reinforcement learning (RL)-based medium access control (MAC) protocols. As the scale of the wireless ad hoc network (WANET) increases, traditional MAC solutions are becoming obsolete. Dynamic topology, resource allocation, interference management, limited bandwidth and energy constraint are crucial problems needing resolution for designing modern WANET architectures. In order for future MAC protocols to overcome the current limitations in frequently changing WANETs, more intelligence need to be deployed to maintain efficient communications. After introducing some classic RL schemes, we investigate the existing state-of-the-art MAC protocols and related solutions for WANETs according to the MAC reference model and discuss how each proposed protocol works and the challenging issues on the related MAC model components. Finally, this paper discusses future research directions on how RL can be used to enable MAC protocols for high performance.

MAC Protocols for mmWave Communication: A Comparative Survey.

With the increase in the number of connected devices, to facilitate more users with high-speed transfer rate and enormous bandwidth, millimeter-wave (mmWave) technology has become one of the promising research sectors in both industry and academia. Owing to the advancements in 5G communication, traditional physical (PHY) layer-based solutions are becoming obsolete. Resource allocation, interference management, anti-blockage, and deafness are crucial problems needing resolution for designing modern mmWave communication network architectures. Consequently, comparatively new approaches such as medium access control (MAC) protocol-based utilization can help meet the advancement requirements. A MAC layer accesses channels and prepares the data frames for transmission to all connected devices, which is even more significant in very high frequency bands, i.e., in the mmWave spectrum. Moreover, different MAC protocols have their unique limitations and characteristics. In this survey, to deal with the above challenges and address the limitations revolving around the MAC layers of mmWave communication systems, we investigated the existing state-of-the-art MAC protocols, related surveys, and solutions available for mmWave frequency. Moreover, we performed a categorized qualitative comparison of the state-of-the-art protocols and finally examined the probable approaches to alleviate the critical challenges in future research.

Huffman Coding and Multi-Generation Mixing Assisted Network Coding Based MAC for QoS-Centric Secure Data Communication over MANETs

The exponential rise in wireless transmission has gained widespread attention to meet major mobile communication purposes including, Internet of Things (IoT) and Machine-to-Machine (M2M) communications. Mobile Ad-hoc Network (MANET) has emerged as one of the most viable solution to meet aforesaid mobile communication purposes; however, being decentralized and infrastructure-less network it undergoes adversaries including dynamic topology and security breaches due to malicious node attachment during routing. On the contrary, data security and allied Quality-of-Service (QoS) provision are inevitable in NextGen communication systems. Unlike routing-based security measures, Medium Access Control (MAC) based approaches are found more effective for MANETs. However, most of the classical MAC designs either address QoS or security as standalone objective. Unlike existing MAC solutions, in this paper a state-of-art novel Huffman Coding and Multi-Generation Mixing (MGM) assisted random linear network model-based MAC design (HM2-MAC) is proposed for MANET. Realizing the robustness of the network coding algorithms towards reliable, secure and error-free multicast transmission, we designed HM2-MAC in such manner that Huffman coding helps securing the source data packets, while MGM concept enables reduction in redundant packets to make overall communication resource efficient and secure. Unlike redundant packet-per-generation, MGM concept helps in reducing redundant transmission and hence achieves resource efficiency. Since, in HM2-MAC model the coefficient matrix used to encode the data is known only to the sink, no intermediate node can decode it or can pollute it. It makes multicast transmission more secure over MANET. Additionally, the use of iterative buffer flush technique preserves resources or buffer to accommodate more data for transmission and hence higher throughput. Noticeably, error sensitive packetization and MGM control strengthens our proposed model to retain optimal performance. HM2-MAC has been applied as a sub-layer of native IEEE 802.11 MAC and hence retains backward compatibility towards real-world implementation. MATLAB based simulation revealed that our proposed HM2-MAC protocol achieved almost 99.6% throughput even under varying link-loss patterns, which reveals its robustness to ensure QoS delivery with secure data transmission in MANET.

UW-SEEDEX: A Pseudorandom-Based MAC Protocol for Underwater Acoustic Networks

Underwater wireless acoustic networks (UWANs) take advantage of acoustic communication to enable many distinct applications. The peculiar features of underwater acoustic channels, such as long propagation delay, high bit error rates, and severely limited bandwidth, make the use of medium access control (MAC) solutions designed for terrestrial radio networks inefficient in UWANs. This paper proposes UW-SEEDEX, a MAC protocol for UWANs that employs random time slot schedules, created from seeds, to avoid collisions. After exchanging seeds, nodes can know other’s entire schedules, allowing them to then better plan their transmissions. Simulations evaluate how each of UW-SEEDEX’s parameter affects its performance in metrics such as end-to-end delay, energy consumption, transmissions per data reception, and reception rate using different test scenarios. Simulations also show that UW-SEEDEX can perform better than other MAC solutions, delivering more messages than protocols such as UW-Aloha and Slotted FAMA and reduced, on average, up to three times the number of transmissions required for each message reception in networks with grid topologies. UW-SEEDEX presented reception rates close to 100 percent, low energy cost, and fewer transmissions per data reception. Our code is available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://gitlab.com/epmcj/ns-3-dev/-/tree/new-uan-mac-protocols</uri> .

FMAC: A Self-Adaptive MAC Protocol for Flocking of FlyingAd HocNetwork

Considering the high-density and high-dynamic feature of cooperative unmanned aerial vehicles (UAVs) swarm, also referred to as flocking of flying ad hoc networks (FANETs), reliable medium access control (MAC) protocol design for network connectivity maintaining and network information sharing is a challenging issue. In this article, we propose a self-adaptive carrier sense multiple access with collision avoidance (CSMA/CA)-based MAC protocol for flocking of FANET, namely, FMAC, to provide reliable broadcast information service under density-varying flocking scenarios. To represent the varying trend of UAV density during flocking, we define the collective neighboring potential (CNP) in the FMAC protocol. Specifically, at the beginning of each period, each UAV computes the current CNP based on available neighbors' motion states. Then, the value of CNP at the start of the next period regarding the same neighbors is predicted using UAV's kinetic equation. After that, each UAV can update the contention window (CW) size by comparing the current CNP and the predicted CNP, and CW will be decreased (increased) if the current CNP is larger (smaller) than the predicted one for enough period. The simulation results show that the proposed FMAC protocol can ensure high successful transmission probability under density-varying flocking scenarios and outperforms the typical MAC solutions.

Fast Q-Learning for Improved Finite Length Performance of Irregular Repetition Slotted ALOHA

In this paper, we study the problem of designing adaptive Medium Access Control (MAC) solutions for wireless sensor networks (WSNs) under the Irregular Repetition Slotted ALOHA (IRSA) protocol. In particular, we optimize the degree distribution employed by IRSA for finite frame sizes. Motivated by characteristics of WSNs, such as the restricted computational resources and partial observability, we model the design of IRSA as a Decentralized Partially Observable Markov Decision Process (Dec-POMDP). We have theoretically analyzed our solution in terms of optimality of the learned IRSA design and derived guarantees for finding near-optimal policies. These guarantees are generic and can be applied in resource allocation problems that exhibit the waterfall effect , which in our setting manifests itself as a severe degradation in the overall throughput of the network above a particular channel load. Furthermore, we combat the inherent non-stationarity of the learning environment in WSNs by advancing classical Q-learning through the use of virtual experience (VE), a technique that enables the update of multiple state-action pairs per learning iteration and, thus, accelerates convergence. Our simulations confirm the superiority of our learning-based MAC solution compared to traditional IRSA and provide insights into the effect of WSN characteristics on the quality of learned policies.

FM‐MAC: A fast‐mobility adaptive MAC protocol for wireless sensor networks

AbstractAs a subset of the internet of things, wireless sensor networks (WSNs) are increasingly composed of mobile nodes (MNs) to meet the emerging needs. However, nodes mobility presents significant challenges to the design of effective communication protocols, especially at the medium access control (MAC) sublayer. Interestingly, the existing mobility support MAC solutions consider only scenarios requiring slow mobility. Nowadays, some WSN applications require employing high‐speed MNs for some specific tasks. Consequently, the mobility impact is sharp as the existing solutions could no longer guarantee the quality‐of‐service requirements. To deal with high‐speed mobility, we propose in this paper a fast‐mobility adaptive MAC (FM‐MAC) protocol. The FM‐MAC protocol adopts the contention‐based access approach and introduces new mechanisms to enhance both mobility and communication management in WSNs. Our proposal consists of four contributions, ie, (1) an improved algorithm for autonomous mobility‐detection, (2) a new intercluster handover mechanism, (3) a priority‐based contention mechanism prioritizing MNs to access the medium, and finally, (4) a multichannel communication strategy intended to enhance the throughput and communication management aspects. Extensive simulations are conducted to compare FM‐MAC protocol with existing well‐known mobility‐aware MAC protocols. Results and discussion disclose that FM‐MAC performs better in both static and mobile scenarios in terms of reliability, latency, and energy saving. As expected, the advantage of FM‐MAC over its counterparts becomes more evident as the mobility speed increases.

MAC Protocols With Wake-Up Radio for Wireless Sensor Networks: A Review

The use of a low-power wake-up radio in wireless sensor networks is considered in this paper, where relevant medium access control solutions are studied. A variety of asynchronous wake-up MAC protocols have been proposed in the literature, which take advantage of integrating a second radio to the main one for waking it up. However, a complete and a comprehensive survey particularly on these protocols is missing in the literature. This paper aims at filling this gap, proposing a relevant taxonomy, and providing deep analysis and discussions. From both perspectives of energy efficiency and latency reduction, as well as their operation principles, state-of-the-art wake-up MAC protocols are grouped into three main categories: (1) duty cycled wake-up MAC protocols; (2) non-cycled wake-up protocols; and (3) path reservation wake-up protocols. The first category includes two subcategories: (1) static wake-up protocols versus (2) traffic adaptive wake-up protocols. Non-cycled wake-up MAC protocols are again divided into two classes: (1) always-on wake-up protocol and (2) radio-triggered wake-up protocols. The latter is in turn split into two subclasses: (1) passive wake-up MAC protocols versus (2) ultra low power active wake-up MAC protocols. Two schemes could be identified for the last category, (1) broadcast based wake-up versus (2) addressing based wake-up. All these classes are discussed and analyzed in this paper, and canonical protocols are investigated following the proposed taxonomy.

Traffic-Load-Adaptive Medium Access Control for Fully Connected Mobile Ad Hoc Networks

In this paper, we propose an adaptive medium access control (MAC) solution for a fully connected mobile ad hoc network (MANET), supporting homogeneous best-effort data traffic. The MAC scheme achieves consistently high network performance by adapting to the ever-varying network traffic load. Based on the detection of a current network load condition, nodes can make a switching decision between IEEE 802.11 distributed coordination function (DCF) and dynamic time-division multiple access (D-TDMA), when the network traffic load reaches a threshold, referred to as MAC switching point. The adaptive MAC solution determines the MAC switching point to maximize network performance. Approximate and closed-form performance analytical models for both MAC protocols are established, which facilitate the computation of MAC switching point in a tractable way. Extensive analytical and simulation results demonstrate that the adaptive MAC solution provides consistently maximal network performance in the presence of traffic load dynamics.

IEEE 5G Spectrum Sharing Challenge: A Practical Evaluation of Learning and Feedback

We present the results, experiences, and takeaways from comparing a diverse set of dynamic spectrum access methods during the IEEE DySPAN 2015 spectrum challenge. Five solutions for coexistence with a given wireless link were implemented and tested in an unknown environment during the conference in Stockholm. The challenge was framed broadly, enabling participants to use their own hardware, antennas, physical layer, or medium access control solutions to compete in a unified setup. Each solution was run two times and ranked using a single metric. Between the two runs the teams were allowed to improve their solution. The metric considered wanted throughput and unwanted interference. In addition to the metric, all solutions were evaluated by a jury. In this article, we give a detailed overview of the challenge, how we organized it, the participating teams, and finally the winners. We conclude with some takeaways on dynamic spectrum access.

Meta-survey on medium access control surveys in wireless sensor networks

Medium access control layer has been the hotbed of research in the field of wireless sensor networks since huge amount of research in wireless sensor networks has focused on saving energy and lately reducing latency. For the most part, medium access control layer solutions in wireless sensor networks are entrusted to save energy, to reduce latency, and at times to ensure reliability perhaps through cross-layer solutions. In this article, we review the surveys at medium access control layer and point to readers some of their strengths and relevancies to medium access control layer protocols. Furthermore, we classify the surveys subject-wise to show trend and usability. To cross compare, we devise a unified lexicon for the purpose and expose the coverage given to the wireless sensor networks’ medium access control protocols by different studies. We present medium access control solutions’ popularity on a known but hitherto unused metric: average citations/year from over 200 medium access control solutions. Our approach to assess the impact factor of protocols for ranking is validated prima facie from the coverage of these solutions by top ranking surveys. We believe it is the widest of such a study involving more than 30 survey papers and over 200 wireless sensor network medium access control protocols.

&lt;formula formulatype="inline"&gt; &lt;tex Notation="TeX"&gt;$\mu$&lt;/tex&gt; &lt;/formula&gt;-NET: A Network for Molecular Biology Applications in Microfluidic Chips

This paper introduces $\mu$ -NET, a microfluidic LAN that supports the exchange of both digital information and biochemical information carried by droplets moving across molecular processors in a microfluidic chip. The $\mu$ -NET can be used to support molecular biology applications like DNA, RNA, and protein biosynthesis. The $\mu$ -NET is the first realization of a microfluidic networking paradigm that controls movements of droplets in microfluidic chips by exploiting hydrodynamic phenomena only and builds on recent solutions to achieve communications in the microfluidic domain. The $\mu$ -NET integrates techniques to represent addressing information, as well as switching and medium access control solutions. In fact, in $\mu$ -NET, the address of the molecular processor where a droplet should be sent to is encoded into the distance between droplets; switching is executed to steer the droplets inside the microfluidic device; medium access control is applied to avoid collisions between droplets that may result in their fusion and, thus, loss of the biochemical information. In this paper, the design of $\mu$ -NET is presented in detail, and simulation results validating $\mu$ -NET operations are shown.

Goodbye, ALOHA!

The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.

AFDA: Asynchronous Flipped Diversity ALOHA for Emerging Wireless Networks With Long and Heterogeneous Delay

The design of random media access control (MAC) protocol renews great attention for emerging challenged wireless environments, where the propagation delay is long, heterogeneous, and/or varying, such as satellite or underwater acoustic sensor networks. In these environments, the existing MAC solutions based on slotted transmissions, carrier sensing, or channel reservation by control packets are no longer favorable or even feasible. In this paper, we propose the asynchronous flipped diversity ALOHA (AFDA) to tackle the challenges based on a new diversity transmission scheme. Different from the existing diversity transmission schemes, each data packet and its flipped replica are transmitted back to back, and the zigzag decoding technique is adopted to resolve collisions. The performance of AFDA has been evaluated by analysis and simulations. The results show that, without time synchronization or handshaking requirements, the performance of AFDA is unaffected by the duration or variation of the propagation delay, and it substantially improves system performance in terms of throughput, packet loss ratio, and network admission region.

Analysis of priority arbitration in low‐rate CSMA/CA‐based differentiated access with throughput optimization

SummaryA class of applications, such as home energy management and control and utility data acquisition, is emerging in recent times where smart meters, sensors, and appliances are networked together for intelligent management and coordination. Such applications rely on low data rate communication of monitoring and control information at large scale. For the underlying networking infrastructure to facilitate communication of the real‐time and intermittent packet traffic expected, random access‐based protocols are regarded as suitable medium access control solutions. A key challenge in this regard is that the random access protocols are prone to throughput degradation when the number of contending nodes grows, as expected with the infrastructures involved. Besides, provision for certain degree of criticality/priority is needed for some of the packets compared with the rest. With this background, this paper analytically determines the criterion for throughput‐optimal operations in a network based on low‐rate carrier sense multiple access protocol. In addition, ways to provide priority‐wise access differentiation at arbitrary proportions without a negative impact on the achievable throughput is incorporated within a binary exponential backoff‐based collision avoidance scheme. Discrete‐event simulations are performed to validate the accuracy of the approximations made in analysis.

Optimizing Spatial and Temporal Reuse in Wireless Networks by Decentralized Partially Observable Markov Decision Processes

The performance of medium access control (MAC) depends on both spatial locations and traffic patterns of wireless agents. In contrast to conventional MAC policies, we propose a MAC solution that adapts to the prevailing spatial and temporal opportunities. The proposed solution is based on a decentralized partially observable Markov decision process (DEC-POMDP), which is able to handle wireless network dynamics described by a Markov model. A DEC-POMDP takes both sensor noise and partial observations into account, and yields MAC policies that are optimal for the network dynamics model. The DEC-POMDP MAC policies can be optimized for a freely chosen goal, such as maximal throughput or minimal latency, with the same algorithm. We make approximate optimization efficient by exploiting problem structure: the policies are optimized by a factored DEC-POMDP method, yielding highly compact state machine representations for MAC policies. Experiments show that our approach yields higher throughput and lower latency than CSMA/CA based comparison methods adapted to the current wireless network configuration.

A Survey of MAC Protocols Design Strategies and Techniques in Wireless Ad Hoc Networks

Medium access control (MAC) protocols provide a means to nodes to access the wireless medium efficiently and collision free to the best of their ability. In this paper we provide a survey of MAC protocols developed for mobile ad hoc (MANETs) in the past based on certain methods and techniques such as multiple radios, multiple channels and specialized beamforming antennas. We discuss some of the MAC protocols designed for wireless sensor networks (WSNs) and their applicability in a MANET environment. There are some similarities between MANETs and WSN's in general but there is also critical differences between the two that affect the design of MAC protocols for both these networks. Traditionally, MAC protocols have been classified on the basis of two broad categories of contention free and contention based MAC protocols but a number of new algorithms proposed in the recent past merge the two schemes together in a single MAC solution and thus there is a need for a new classification approach. MANETs have their unique constraints and characteristics. In this classification, we will discuss various MAC solutions proposed in the past in the light of these constraints and characteristics. We do not intend to explain each and every protocol since the number of MAC solutions proposed in the past decade or so is very large. The purpose of this article is to give the readers a general idea on the various techniques and methods used in literature to develop MAC protocols for MANETs. The techniques range from algorithmic changes such as cross-layer design to enhancement in hardware such as directional antennas.

Cooperative wireless sensor environments supporting body area networks

Wireless Body Area Network (WBAN) in recent years have received significant attention, due to their potential for increasing efficiency in healthcare monitoring. Typical sensors used for WBAN are low powered single transceiver devices utilizing a single channel for transmission at the Medium Access Control (MAC) layer. However, performance of these devices usually degrades when the density of sensors increases. One approach to counter this performance degradation is to exploit multiple channels at the MAC layer, where optimal usage of the channels is achieved through cooperation between the sensor nodes. In this paper we propose a cooperative WBAN environment that supports multi-hop transmission through cooperation involving both environmental sensors and WBAN nodes. Our solution extends the cooperation at the MAC layer to a cross-layered gradient based routing solution that allows interaction between WBAN and environmental sensors in order to ensure data delivery from WBANs to a distant gateway. Extensive simulations for healthcare scenarios have been performed to validate the cooperation at the MAC layer, as well as the cross-layered gradient based routing. Comparisons to other cooperative multi-channel MAC and routing solutions have shown the overall performance improvement of the proposed approach evaluated in terms of packet loss, power consumption and delay.

ATLAS: A Traffic Load Aware Sensor MAC Design for Collaborative Body Area Sensor Networks

In collaborative body sensor networks, namely wireless body area networks (WBANs), each of the physical sensor applications is used to collaboratively monitor the health status of the human body. The applications of WBANs comprise diverse and dynamic traffic loads such as very low-rate periodic monitoring (i.e., observation) data and high-rate traffic including event-triggered bursts. Therefore, in designing a medium access control (MAC) protocol for WBANs, energy conservation should be the primary concern during low-traffic periods, whereas a balance between satisfying high-throughput demand and efficient energy usage is necessary during high-traffic times. In this paper, we design a traffic load-aware innovative MAC solution for WBANs, called ATLAS. The design exploits the superframe structure of the IEEE 802.15.4 standard, and it adaptively uses the contention access period (CAP), contention free period (CFP) and inactive period (IP) of the superframe based on estimated traffic load, by applying a dynamic “wh” (whenever which is required) approach. Unlike earlier work, the proposed MAC design includes load estimation for network load-status awareness and a multi-hop communication pattern in order to prevent energy loss associated with long range transmission. Finally, ATLAS is evaluated through extensive simulations in ns-2 and the results demonstrate the effectiveness of the protocol.