Medium Access Control Functions Research Articles

Dy-MAC: Implementation of dynamic MAC stack for IEEE 802.15.4e-TSCH

This paper presents the lessons learnt in the implementation of IEEE 802.15.4e-Time Slotted Channel Hopping (TSCH) Medium Access Control (MAC) protocol on commercially available hardware. Our MAC Application programming Interface (API) called the Dy-MAC is agnostic to the PHY layer and is coded on a ARM cortex M4. MAC functions such as TDMA, FDMA, frame counter, channel access, synchronization and PAN formation are abstracted as part of this API. Dy-MAC is demonstrated for 2.4GHz with O-QPSK modulation and 868MHz with SUN FSK modulation. Furthermore, the API supports star, mesh and tree network to provide flexible topologies in factory environment. Our experiments show that for a 76 byte payload, the TSCH Dy-MAC provides ∼99% packet delivery ratio (PDR) for 26ms timeslot with SUN FSK PHY and ∼97% PDR for 10ms timeslot with O-QPSK PHY. To maintain synchronization over the entire network, we implemented algorithms to successfully communicate between fast and slow nodes. Resilience to interference and range with packet delivery ratio is evaluated. We consolidate our implementation in terms of 10 lessons that were learnt in building the Dy-MAC protocol.

Exclusive-Region-Map-Based Medium Access Control in Mobile Networks With Directional Antennas Through Deep Interference Learning

The medium access control (MAC) design in mobile networks with directional antennas is challenging due to the difficulty of defining the exact RF interference range between two neighboring directional links and the frequent changes of interference range due to node mobility. This research targets directional data reception (Rx) and transmission (Tx) coordination issues based on the computation of directional interference ranges from nearby directional links. An innovative MAC mechanism is designed with three features: (1) ER-map, i.e., the spatial expression of exclusive region (ER) model in the format of a heatmap. The ER-map helps to determine the directional interference range in typical communication scenarios. Different ER-map cases are analyzed based on the spatial layout differences for two nearby directional links. (2) Spatio-temporal ER-map evolution prediction: a Spatio-Temporal Residual Network (ST-ResNet+) model is used to describe the spatial correlations (for the ERs among neighboring links) and temporal correlations (for the ERs across different time instants) as well as the ER map evolution patterns. Such a Deep ST-ResNet+ model is used to predict the next-time ER map’s snapshot. (3) Optimized directional MAC protocol based on ER map predictions: The ST-ResNet+ prediction results are used to determine the MAC operations, such as Tx/Rx schedule arrangement in the one-hop area, sending rate adjustments, etc. Comprehensive simulations are conducted to validate the throughput efficiency for the proposed directional MAC scheme.

Intelligent Terahertz Medium Access Control (MAC) for Highly Dynamic Airborne Networks

The Terahertz (THz) link provides over 100 Gbps of data transmission rate. However, it is extremely vulnerable to obstacles and requires very narrow (highly directional) beams for highly focused energy radiation. The main task of THz medium access control (MAC) protocol is not channel access collision avoidance; instead, it is to coordinate all the one-hop neighbors for scheduled, antenna-aligned line-of-sight communications. This study aims to build an intelligent MAC scheme for highly mobile Terahertz airborne networks (TANs). Our TAN MAC design has three features as follows: (1) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Spatio-temporal TAN state learning:</i> We will build a predictive network state estimation model through deep learning and generative adversarial network (GAN). Based on the predicted node/link status, all the one-hop neighbors can prepare well for the antenna alignment and THz channel scheduling. (2) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Accurate, two-level MAC operation control:</i> we propose to use nested deep reinforcement learning (DRL) with outer/inner policy loops for high-/low-level action determination: The outer loop determines the high-level, coarse actions (such as antenna codebook selection); the inner loop determines the low-level, fine actions (such as individual beam control) under the selected high-level action. (3) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TAN-specific, comprehensive MAC behavior control:</i> Based on the above deep neighbor adaptation (DNA) model, we design a complete TAN MAC protocol that considers the routing context and dynamic network topology. Our simulations demonstrate the smooth, high-rate THz communications in MAC layer with resilient RF links under high node mobility.

A virtual gateway media access placement approach for large-scale Internet of Things

The virtualisation of the Internet of Things (IoT) Gateway (GW) Media Access Control (MAC) component separates the GW MAC functions from the GW device by deploying the GW MAC functions in a selected remote edge Data Centre (eDC). This concept can help support media access for a large number of devices based on concurrent transmissions over Radio Frequency (RF) virtualisation. However, the requests for virtual GW MAC instances are dynamic and the virtual network is characterised by varying resource levels and response times. This can affect the throughput performance of the MAC protocol since the timing deadlines of the MAC functions or frame transmissions may not be met. In this work, the GW MAC functions of the IEEE 802.11ah standard for Large Scale IoT (LS-IoT) networks are virtualised as concurrent virtual Access Groups (vAGs) over a proposed Software Defined Network (SDN) virtual network. A virtual GW MAC placement strategy is proposed to optimally select the host for running the virtual GW MAC instances to minimise the virtualisation delay, improve the robustness of the deployment process and maintain a good MAC throughput performance. The results obtained in this work show that the virtualisation delay is minimised and the MAC throughput versus the number of devices is improved especially for high IoT traffic rates when compared to suboptimal approaches and the dedicated localised GW MAC approach.

Mutual Aid Among Sensors: An Emergency Function for Sensor Networks

A large number of wireless sensor nodes in a certain area results in high contention. Inevitably, the transmissions of any possible critical data packets may fail due to collisions. In this letter, we introduce an aspect of human intelligence in wireless sensor networks, influenced by cooperative networking, which enhances the timely delivery of critical data. Mutual aid among sensors is an emergency out-of-the-box medium access control function for IEEE 802.15.4-2020. Specifically, the network coordinator detects critical data packets and sets an emergency flag to its next beacon to inform the nodes that they may overhear data packets. When a node overhears a critical data packet from a neighboring node, it switches to sleep mode and stays idle until the end of the superframe. Thus, interference is mitigated locally and temporarily. Simulation results, using the CC2650 radio parameters in OMNeT++, show that interference is reduced significantly, in favor of the timely delivery of critical data packets.

IEEE 802.11ba: Low-Power Wake-Up Radio for Green IoT

Low-power devices have manifested their crucial roles in manifold green Internet of Things (IoT) applications, including healthcare, smart home, industrial sensors, and wearable apparatuses. However, to prolong the operation time of these devices, significantly enhancing the battery capacity turns out to be an intractable challenge due to the mandatory constraint of limited form factors. Achieving this goal thus inevitably relies on new designs of physical-layer (PHY)and medium access control (MAC) schemes. This desire has driven IEEE 802.11 Task Group ba (TGba) to launch the normative work of wake-up radios (WURs) since 2017. To comprehend essential knowledge of this new technical feature, in this article, we consequently offer substantial insights of IEEE 802.11ba, including the deployment scenarios, PHY operations (waveform, modulation, data rate selection, and synchronization design), and MAC operations (radio wake-up procedure, WUR duty cycle, WUR mode, channel access scheme, and the format of a MAC packet data unit). The provided insights facilitate further research and implementation of IEEE 802.11ba WUR to empower the next generation green IoT.

Single CCA for IEEE 802.15.4 networks: a cross layer energy model

For data frame transmissions in beacon-enabled mode, an IEEE 802.15.4 node performs two consecutive clear channel assessments (CCAs) to sense the channel after back off. Here, the authors study what would happen if the medium access control (MAC) layer performs only one CCA instead. Although it is apparent that the frame transmission cycle would be shortened with single CCA, it is not straightforward to assess the effect of single CCA on the overall transmission energy. A Markov chain-based MAC operation model is therefore constructed to analyse single-CCA-based MAC layer parameters. A combined physical (PHY) and MAC layer energy model is formulated next. It was found that the single CCA-based MAC outperforms its standard double CCA-based counterpart from the energy efficiency perspective.

An Efficient Cooperative Medium Access Control Protocol for Wireless IoT networks in Smart World System

In recent years, the Internet of Things (IoT) has become the key enabler for Smart World System (SWS). In SWS environment, the IoT is empowering wireless devices/objects with abilities of sensation and communication with each other via Internet and providing simplified, more efficient, and enjoyable lifestyle. However, efficient communication between various wireless devices in IoT network is very important, especially in long distant wireless transmission case. Cooperative Medium Access Control (MAC) protocols for wireless networks supporting the IoT is becoming popular to handle this issue. It considers several metrics, e.g., SNR (Signal to Noise Ratio), delay and residual energy. Nowadays, distance metric has appended a new dimension in the relay selection metric list for Cooperative MAC. Howsoever, protocols that have used distance metric can be optimized further in selecting a relay node by considering reliability. Hence, targeting to optimize relay selection for designing a cooperative MAC protocol, we have proposed a Reliability-based Distance-aware Data-rate-adaptive Cooperative MAC for wireless IoT networks. For the assurance of unfailing and cooperative data transmission, this work strengthens the most suitable relay node selection using a cooperative reliability factor. Distance and residual energy are also used to ascertain that the position of optimal relay possess superior rates. Extensive simulation results demonstrate that proposed reliability-based optimal relay selection as well as MAC operation significantly improves the performance over the existing ones.

Wireless performance and mobile fronthaul bandwidth of uplink joint reception with LLR combining in split-PHY processing

In this paper, we evaluate the wireless uplink performance and the mobile fronthaul (MFH) bandwidth of split-physical layer (PHY) processing (SPP), which is a base station (BS) functional split scheme used to link baseband units (BBUs) and remote radio heads (RRHs) in a centralized/cloud — radio access network (C-RAN). SPP enables MFH bandwidth reduction by splitting the BS functions between channel coding/decoding and modulation/demodulation within the PHY layer functions. SPP also enables high coordinated multipoint (CoMP) transmission and reception performance by employing uplink joint reception (JR) with log likelihood ratio (LLR) combining. Link level simulation results show that SPP with LLR combining achieves a block error rate (BLER) performance of 10% with a signal to noise ratio (SNR) penalty of less than 1 dB compared with that of conventional CRAN, which centralizes PHY layer functions in BBU. In addition, SPP has an SNR gain of more than 3 dB over medium access control (MAC)-PHY split, which splits the BS functions between the MAC and PHY layer functions. System level simulation results show that SPP with LLR combining improves the cell-edge user throughput by more than 33% over MAC-PHY split with selection combining and reduces the MFH bandwidth by 91% when compared with conventional C-RAN. Moreover, link and system level simulation results above are also observed when the channel estimation is non-ideal.

Teaching Communication Technologies and Standards for the Industrial IoT? Use 6TiSCH!

The IETF 6TiSCH stack encompasses IEEE802.15.4 TSCH, IETF 6LoWPAN, RPL, and CoAP. It is one of the key standards-based technologies to enable industrial process monitoring and control, and unleash the Industrial Internet of Things (IIoT). The 6TiSCH stack is also a valuable asset for educational purposes, as it integrates an Internet-enabled IPv6-based upper stack with stateof- the-art low-power wireless mesh communication technologies. Teaching with 6TiSCH empowers students with a valuable set of competencies, including topics related to computer networking (medium access control operation, IPv6 networking), embedded systems (process scheduling, concurrency), and wireless communications (multipath propagation, interference effects), as well as application requirements for the IIoT. This article discusses how the 6TiSCH stack can be incorporated into existing and new curricula to teach the next generation of electrical engineering and computer science professionals about designing and deploying such networks. It also gives a comprehensive overview of the 6TiSCH stack and the tools that exist to support a course based on it.

Cooperative Awareness in VANETs: On ETSI EN 302 637-2 Performance

Cooperative awareness on the road is intended to support the road users by providing knowledge about the surroundings and relies on the information exchange enabled by vehicular communications. To achieve this goal the European telecommunication standard institute (ETSI) delivered the standard EN 302 637-2 for cooperative awareness messages (CAM). The CAM triggering conditions are based on the kinematics of the originating vehicle, which is checked periodically. In this paper, we show that the standardized ETSI protocol may suffer a decrease in communication performance under several realistic mobility patterns. The potential influence of the discovered phenomena on the IEEE 802.11p medium access control operation is studied.

On Quality-of-Service Provisioning in IEEE 802.11ax WLANs

A revolutionary effort to seek fundamental improvement of 802.11, known as IEEE 802.11ax, has been approved to deliver the next-generation wireless local area network (WLAN) technologies. In WLANs, medium access control protocol is the key component that enables efficient sharing the common radio channel while satisfying the quality of service (QoS) requirements for multimedia applications. With the new physical layer design and subsequent new medium access control functions under more demands on QoS and user experience, in this paper, we first survey the QoS support in legacy 802.11. Then, we summarize the IEEE 802.11ax standardization activities in progress and present an overview of current perspectives and expected features on medium access control protocol design to better support QoS and user experience in 802.11ax. We present the motivation behind, explain design principles, and identify new research challenges. To better satisfy customer needs on high bandwidth and low latency, emerging long-term evolution licensed-assisted access and its impacts to QoS provisioning in IEEE 802.11ax are further addressed given the collaboration between cellular and WLANs, and given the trend of 5G cellular over unlicensed bands.

Feasible HCCA Polling Mechanism for Video Transmission in IEEE 802.11e WLANs

IEEE 802.11e standard defines two Medium Access Control functions to support Quality of Service (QoS) for wireless local area networks: Enhanced Distributed Channel Access (EDCA) and HCF Controlled Channel Access (HCCA). EDCA provides fair prioritized QoS support while HCCA guarantees parameterized QoS for the traffics with rigid QoS requirements. The latter shows higher QoS provisioning with Constant Bit Rate traffics. However, it does not efficiently cope with the fluctuation of the Variable Bit Rate (VBR) video streams since its reference scheduler generates a schedule based on the mean characteristics of the traffic. Scheduling based on theses characteristics is not always accurate as these traffics show high irregularity over the time. In this paper, we propose an enhancement on the HCCA polling mechanism to address the problem of scheduling pre-recorded VBR video streams. Our approach enhances the polling mechanism by feed-backing the arrival time of the subsequent video frame of the uplink traffic obtained through cross-layering approach. Simulation experiments have been conducted on several publicly available video traces in order to show the efficiency of our mechanism. The simulation results reveal the efficiency of the proposed mechanism in providing less delay and high throughput with conserving medium channel through minimizing the number of Null-Frames caused by wasted polls.

Reliable geocasting for random-access underwater acoustic sensor networks

Reliable data delivery for underwater acoustic sensor networks is a major concern in applications such as surveillance, data collection, navigation, and ocean monitoring. Geocasting is a crucial communication primitive needed to support these applications, which consists in transmitting one or multiple consecutive data packets – all carrying an atomic message – to nodes located in a certain geographic region. In this article, two versions of a distributed, reliable, and efficient underwater geocasting solution (based on different degrees of neighbor information) are proposed for underwater networks whose acoustic modems use random-access Medium Access Control (MAC) protocols. By jointly considering the position uncertainty of nodes as well as the MAC and routing functionalities, packet transmissions are prioritized and scheduled so to maximize link reliability while limiting the end-to-end geocasting delay. Moreover, a simple yet effective timer-based mechanism is designed to limit the number of transmissions by selecting only a subset of neighbors for packet forwarding. Performance is evaluated and compared via thorough simulations against existing geocasting solutions tuned for the underwater environment that were originally designed for terrestrial wireless networks.

EPON protocol over coax (EPoC): overview and design issues from a MAC layer perspective?

We investigate the challenges in designing the network architecture for running EPON (Ethernet Passive Optical Network) Protocol over Coax, or EPoC in short. EPoC is the transparent extension of EPON over a cable operator's Hybrid Fiber-Coax (HFC) network, and uses a hybrid of optical and coaxial technologies to carry traffic to and from end-users and the Internet backbone. For managing and controlling such a hybrid network, a network operator will prefer to have a unified scheduling, management, and quality-of-service (QoS) environment that includes both the optical and coax portions of the network. This can be achieved by extending the EPON Medium Access Control (MAC) to run over the coax physical layer, to have a centralized end-to-end network control from the cable head-end to the end-users' premises. The use of the coax portion of the network is transparent to EPON protocol operation in the headend, as the same MAC runs over the entire network. In this article, we describe the architecture of EPoC, and outline how the EPON MAC Control, i.e., the EPON Multi-Point Control Protocol (MPCP) can be extended for designing an end-to-end Multi-Point MAC Control for EPoC. We explain the design of several MAC functions and their operation, including framing for coax, Ethernet frame fragmentation, generation of upstream and downstream Media Allocation Plans, and automatic discovery and registration of user equipment. With strong backing from both service operators and equipment vendors, EPoC is set to become a rapidly-evolving standard within the next few years, and the creation of the IEEE 802.3bn Task Force for EPoC is a major step in that direction.

An Efficient Frame Aggregation and Block-ACK Scheme for 60 GHz Short-Range Point-to-Point Transmission

The exploitation of the 60 GHz band is a very promising approach to fulfill the rapidly increasing data rate requirement of wireless indoor communication. One important 60 GHz application is the short-range point-to-point data transmission with Ultra-High-Rate (UHR, up to 10 Gbps) (Krone et al. in International Journal of Microwave and Wireless Technologies, 2011, 189---200). The design of such high data rate systems is very challenging. Except for Analog-Front-End (AFE) and physical layer (PHY) designs, the Medium Access Control (MAC) layer design is also crucial for the achievable system throughput. Among the MAC functionalities, the acknowledgment (ACK) mechanism is a very important component affecting the transmission efficiency and reliability. In this paper, a Hybrid Dynamic Frame Aggregation and Block-Acknowledgment (HD-FABA) scheme is proposed, which enables large-scale frame aggregation and can achieve significant ACK overhead reduction compared to the existing schemes. A theoretical model is developed for throughput analysis, which is verified by packet-level simulation. Both theoretical- and simulation results show that the HD-FABA scheme allows a number of MAC parameters to be optimized according to the PHY conditions (e.g. BER), leading to much higher throughput than with the state-of-the-art scheme.

Enabling Technologies for a Practical Wireless Communication System Operating in TV White Space

This paper proposes the design of enabling technologies for practical wireless communication systems operating in the TV white space (TVWS). The main objective of this paper is to cover a macro perspective on the system design blocks including: (a) targeted use case applications and governing regulations, (b) channelization, physical (PHY) layer and medium access control (MAC) layer designs, and (c) achievable throughput and range. It is the intention of this paper to serve as a general guideline for designing wireless communication systems operating in TVWS. The core system design addresses both PHY and MAC layer issues with realistic system considerations. In the PHY layer, a channelization design that fits into the area-specific TV channels and a transceiver that enables data exchange in the TV bands are designed. In the MAC layer, a cognitive engine that manages access to vacant TV channels and MAC functionalities that facilitate effective medium access are also proposed. As a result, the system is capable of supporting up to a typical throughput of 80 Mbps, and a maximum number of 40 users, assuming all users performing the most bandwidth-hungry application in the use case scenario. The corresponding operating range is found reach up to 400 m.

VPAL: Video Packet Adaptation Layer for reliable video multicast over IEEE 802.11n WLAN

In this paper, we propose a scheme, called Video Packet Adaptation Layer (VPAL), for reliable video multicast over the IEEE 802.11n WLAN. VPAL is composed of (1) Raptor coding for reliable video transmission, (2) header compression and (3) packet aggregation, both for efficient video transmission. Most of the VPAL functionalities reside above the emerging IEEE 802.11n Medium Access Control (MAC) layer while the packet aggregation requires some changes in the MAC functionalities. The reliability of the video multicast under a strict delay requirement, is provided by achieving the target error probability of video packets, which is done by controlling both the Raptor code rate and the physical (PHY) layer transmission rate. This strategy can provide a satisfactory quality of multicast video service irrespective of the channel condition with a minimum bandwidth use. New features of the 802.11n MAC are utilized for the channel status feedback from the users. Redundant header fields in the video packets are compressed, and then these packets are aggregated to further reduce the protocol overheads. We also consider a reduced version of VPAL which does not require any change in the MAC functionalities and simply works with the IEEE 802.11n MAC. The performance of the proposed systems is comparatively evaluated in terms of the perceived video quality, i.e., peak signal-to-noise ratio (PSNR), as well as the amount of required resources via both numerical analysis and simulations.

MAC Essentials for Wireless Sensor Networks

The wireless medium being inherently broadcast in nature and hence prone to interferences requires highly optimized medium access control (MAC) protocols. This holds particularly true for wireless sensor networks (WSNs) consisting of a large amount of miniaturized battery-powered wireless networked sensors required to operate for years with no human intervention. There has hence been a growing interest on understanding and optimizing WSN MAC protocols in recent years, where the limited and constrained resources have driven research towards primarily reducing energy consumption of MAC functionalities. In this paper, we provide a comprehensive state-of-the-art study in which we thoroughly expose the prime focus of WSN MAC protocols, design guidelines that inspired these protocols, as well as drawbacks and shortcomings of the existing solutions and how existing and emerging technology will influence future solutions. In contrast to previous surveys that focused on classifying MAC protocols according to the technique being used, we provide a thematic taxonomy in which protocols are classified according to the problems dealt with. We also show that a key element in selecting a suitable solution for a particular situation is mainly driven by the statistical properties of the generated traffic.

Specification and Verification of the IEEE 802.11 Medium Access Control and an Analysis of its Applicability to Real-Time Systems

The use domain of IEEE 802.11 networks has broadened to several types of application, including those that require quality of service and real-time guarantees. This trend in particular, has motivated the use of formal methods, not only to obtain a more precise knowledge of protocol properties, but also to specify and validate them. In this context, the contribution of this paper is twofold. First, we describe a formal specification of the IEEE 802.11 medium access control functions using UPPAAL, a freeware model checker tool. The described specification allowed us to verify important properties of these functions, taking into account both time and concurrency. Second, we report an experience of model checking a widely used and reasonably complex communication protocol, taking into consideration temporal requirements.