Medium Access Control Scheduling Research Articles

An Overview of MAC Scheduling techniques in 5G-NR

The advent of 5G technology has brought about a paradigm shift in wireless communication, enabling unprecedented data rates, ultra-low latency, and massive connectivity. At the heart of this technological revolution lies the 5G New Radio (5G-NR) standard, a key component that facilitates the seamless interaction between devices and networks. Within the 5G-NR architecture, the Medium Access Control (MAC) layer plays a pivotal role in optimizing the utilization of radio resources and ensuring efficient data transmission. This comprehensive overview delves into the intricate realm of MAC scheduling techniques within the context of 5G-NR. Scheduling, a fundamental aspect of wireless communication, is the process through which resources are allocated to different user devices to enable simultaneous and efficient data transmission. NR is essentially a scheduled system where the scheduler in the gNB controls downlink and uplink transmissions. This paper describes the details around dynamic scheduling, including associated functionality such as buffer-status report and power-headroom reports.

Adaptive Scheduling MAC Protocol in Underwater Acoustic Broadcast Communications for AUV Formation

With the rapid development of autonomous underwater vehicles (AUVs) and the continuous improvement of marine exploration requirements, AUV formation has emerged as a promising technique for performing underwater tasks with greater flexibility, adaptability, and scalability. To achieve AUV formation control, underwater acoustic communication networks (UACNs) are widely used to support information exchange among AUVs. Considering broadcast communications in fully connected mobile UACNs, existing medium access control (MAC) protocols face severe packet collision risk or low reuse efficiency. To improve the timeliness and reliability of the information exchange among AUVs, we develop an efficient scheduling-based adaptive broadcasting MAC (AB-MAC) protocol. The AB-MAC protocol is incompletely centralized, which can be reflected in two aspects. First, to ensure the consistency of the transmission schedule in the network, the AB-MAC protocol selects a control node for each frame to schedule the transmission of all nodes according to the updated network topology. The slot lengths and transmission sequences are changeable in each frame to avoid packet collisions and minimize frame lengths. Second, to further improve the efficiency and robustness of the protocol, all nodes adaptively adjust their transmission time by integrating the information contained in their previously received control packets and ordinary packets. The transmission scheduling problem is formulated as a combinatorial optimization problem, which can be solved by our proposed improved Genetic Algorithm. Numerical results demonstrate that the AB-MAC protocol not only performs well in terms of network throughput and average update interval but also has a high level of robustness even in low-quality underwater acoustic channels.

A Hybrid Network User Satisfaction-Based Downlink Scheduling in LTE-A Network

To provide high-quality wireless network multimedia services, the 4G/5G network media access control (MAC) layer has adopted the concept of the quality of service (QoS) with different traffic classification service requirements. To efficiently allocate the limited radio resources for achieving a good balance in QoS, throughput and fairness are necessary for the wireless network MAC scheduling issues. While many conventional scheduling schemes only considered one factor: rate or delay, network users might actually have different rate and delay requirements in concert. Herein, a hybrid network user satisfaction-based downlink scheduling approach, namely, max rate delay urgency first (MRDUF), is developed. The MRDUF approach simultaneously considers rate and delay requirements and adopts a hybrid strategy comprising time- and frequency-domain schedulers using two schemes, namely, the first come first serve (FCFS) and max throughput (MT), for the LTE-A downlink environment. Simulation study results have shown that our proposed approach outperforms the conventional scheduling schemes, including MT, proportional fair (PF), blind equal throughput (BET), and earliest deadline first (EDF). The benefit of MRDUF in terms of fairness of satisfaction of rate and delay is demonstrated by the simulation study.

Power Saving MAC Protocols for Wireless Body Area Networks (WBANs)

Two important criteria of wireless body area networks (WBANs) are low power consumption and delay. These criteria can be met by designing efficient medium access control (MAC) protocols. In this paper, two TDMA-based MAC protocols are proposed. The first protocol, TM–MAC makes use of only a main radio. The second proposed protocol, TWM–MAC makes use of a WUR alongside the main radio. The two proposed protocols are compared with different categories of standard MAC protocols and it is shown that they outperform the standard ones by improving the power consumption and delay. The TWM–MAC consumes 55% less power consumption than the Scheduled Channel Polling MAC (SCP–MAC) protocol for a high traffic scenario on the high-rate platform while the TM-MAC consumes 85% less power consumption than the SCP–MAC. For a low traffic scenario, the TWM–MAC performs 53.5% better than the SCP–MAC protocol and 77.5% better than the very low power MAC (VLPM) protocol on the high and low-rate platforms respectively. An improvement in delay was observed with the TWM–MAC protocol for high traffic situations. The TWM–MAC protocol surpasses the VLPM protocol by 81.1% in terms of latency for a high traffic scenario and 3.2% for a low traffic scenario.

A Multilevel Scheduling MAC Protocol for Underwater Acoustic Sensor Networks(UASN)

Underwater acoustic sensor networks (UASNs) have attracted great attention in recent years and utilizes as a part of oceanic applications. This network has to deal with propagation delay, energy constraints and limited bandwidth which are strenuous for designing a Medium Access Control (MAC) protocol for underwater communication. There also exists an idle channel listening and overhearing problem which sets down the energy into starvation in the contention-based MAC protocols. Alternatively, lengthy time slots and time synchronization equated by schedule-based MAC protocols, outcomes the variable transmission delay and degrades the network performances. To iron out these problems, we propose a cluster-based MAC protocol, tagged as Multilevel Scheduling MAC (MLS-MAC) protocol for UASN in the paper. The cluster head is a decision maker for packet transmission and aids to inflate the lifetime of sensor nodes. To reinforce the channel efficiency, the multilevel scheduling in data phase is initiated with two queues depending on the applications fixed by the cluster head. The simulation result shows that the MLS-MAC has increased the network throughput and has decreased energy consumption.

A Flexible Enhanced Throughput and Reduced Overhead (FETRO) MAC Protocol for ETSI SmartBAN

Smart body area networks (SmartBAN) is an emerging wireless body area networks (WBAN) standard proposed by the European Telecommunications Standards Institute (ETSI). This paper first examines the potential of SmartBAN medium access control (MAC) layer with scheduled access to support a myriad of WBAN applications, having diverse data rate requirements. Extra scheduled access slots can be allocated to high date rate sensor nodes for managing their data rate requirements. High data rate sensor nodes can also be re-assigned to use the available time slots of low data rate sensor nodes in Inter-Beacon Interval (IBI) by the central hub. But these two schemes incorporate different physical (PHY) and MAC layer overheads related to frame transmission, frame acknowledgement and slot re-assignment. This redundant overhead transmission results in high overhead energy consumption and reduced effective throughput. Therefore, an innovative and flexible enhanced throughput and reduced overhead (FETRO) MAC protocol for scheduled access is proposed in this article. In the proposed scheme, the sensor node data rate requirements are considered while assigning the scheduled access slot duration by allowing minimal changes in the base-line standard implementation. This infers the provision of scheduled access slots with variable slot durations within an IBI. We also evaluate the existing techniques of extra slot allocation and slot re-assignment in SmartBAN as well as the proposed FETRO MAC protocol with variable slot length. The proposed FETRO MAC scheme results in optimizing both the overall throughput and normalized overhead energy consumption per kilo bits per second (Kbps). Additionally, the impact of various WBAN channel models over these throughput management approaches is also investigated. The proposed FETRO MAC protocol with variable slot duration gives an average reduction of 65.5 and 59.16 percent, respectively, in the hub and nodes normalized overhead energy consumption per Kbps outcomes, as compared to the de-facto SmartBAN MAC scheduling strategies.

A full-duplex MAC technique to improve spectrum-efficiency on 5G mobile wireless networks

Full-duplex (FD) communications shall play an important role on the next generation (5G) mobile wireless networks as they are expected to enhance spectrum usage and throughput. Unleashing the benefits of FD communications, however, requires a fitted design of medium access control (MAC) schemes. In spite of that, existing full-duplex MAC schemes are build upon the IEEE 802.11 which is designed to operate on half-duplex radios. The main contribution of this work is to propose a full-duplex communication mechanism devised to improve spectrum usage and throughput in the context of FD communications. The proposed scheme, named Full-Duplex Dynamic Scheduling MAC (FDDS-MAC), uses a novel strategy to select a communicating pair that maximizes the probability of establishing a full-duplex communication between sending and receiving nodes. A mathematical analysis of the proposed strategy is presented to show the potential improvement that can be achieved using FDDS-MAC. Moreover, in order to compare FDDS-MAC throughput with state-of-art full-duplex communications mechanisms, an analytical model addressing the details of a FD communication is proposed. Analytical evaluation shows that the proposed scheme provides throughput gain up to 50% as compared to the state-of-art full-duplex communications mechanisms. Furthermore, an enhanced version of FDDS-MAC (termed FDDS-MAC*) is proposed to further reduce the time spent selecting the receiver node that maximizes the probability of establishing a full-duplex communication. Numerical results reveals that FDDS-MAC* achieved an improvement over existing full-duplex MAC schemes up to 59% in terms of throughput, thus showing the positive impact of FDDS-MAC* deployment.

A novel selective cross layer based routing scheme using ACO method for vehicular networks

Internet of Vehicles (IoVs) as one of the developing paradigm in the current scenario intends to present a plenty of inventive applications and services. These developing applications force to attain a specific quality of service (QoS) requirements for Vehicle Ad-Hoc Networks (VANETs). Because of high node density and substantial mobility the complexity of VANET increases tremendously, which results the process of routing, security and QoS challenging. This yields an emerging need to design a more productive and intellectual routing protocol in VANET. In this paper we propose a novel selective cross layer design based Ant Colony Optimized Ad-Hoc On Demand Distance Vector (ACO-AODV) routing protocol. The cross-layer design proposed in this work selectively optimizes the information acquired from Application (APP) layer, Transport layer; physical layer and the Media Access Control (MAC) layer in the networks. We used the advantage of ACO to resolve the route selection issue and Particle Swarm Optimization (PSO)based MAC scheduling mechanism for slot assignment during data transmission. Simulation results & Comparisons are presented to show the significance of the proposed routing protocol with improved QoS.

Systematic Medium Access Control in Hierarchical Airborne Networks With Multibeam and Single-Beam Antennas

A heterogeneous medium access control (MAC) scheme (with both scheduled and random communications) is proposed for airborne networks. These networks have a hierarchical topology with a small number of powerful aircraft nodes with multibeam antennas and long-distance links at the higher level, and high-density unmanned aerial vehicle (UAV) nodes with single-beam directional antennas at the lower level. Our proposed MAC scheme has the following three parts: First, multibeam, long-distance MAC for aircraft to aircraft links : a dynamic, scheduled MAC is proposed to take advantage of the multibeam features to achieve high-throughput transmissions, and the beam locking/synchronization issues are solved; second, uplink MAC for UAV to aircraft communication : conventional IEEE 802.11n MAC is enhanced with fame aggregation and compressive-sensing-based request polling; and third, MAC for UAV to UAV links : IEEE 802.11e DCF MAC is enhanced through parameter adjustment for channel access. Our simulation results show the significant performance improvement over conventional MAC protocols.

Throughput and Channel Aware MAC Scheduling for SmartBAN Standard

In this paper, a throughput- and channel-aware (TCA) medium access control (MAC) scheduling scheme is presented and evaluated for smart body area network (SmartBAN) standard, developed by the European Telecommunication Standard Institute (ETSI). The presented algorithm utilizes the radio link signal-to-noise ratio (SNR) to select the candidate nodes for a given time slot in the first phase, while, in the second phase, the slot is assigned to one of the chosen nodes based on their priority level and data packet availability. The algorithm uses an m-periodic scheduling technique, in which the nodes are considered for slot assignment according to their data packet generation rates during the second phase. Subsequently, a comprehensive explanation of the TCA algorithm execution through the slot reassignment method in SmartBAN is provided. For performance comparison, we use four key performance indicators (KPIs), which include packet reception rate (PRR), latency, energy consumption per successful transmission, and throughput. The simulation results indicate a significant performance gain of the SmartBAN-complaint TCA algorithm in terms of PRR and energy efficiency over the reference SmartBAN MAC scheduling with and without repetition. The average improvement in the PRR results is approximately 40%, whereas a maximum enhancement of 66% is observed in terms of energy efficiency while satisfying the throughput and latency requirements of the use case considered during simulations. Furthermore, we introduce some enhancements in the primary TCA to decrease the frequency of TCA execution via slot re-assignment frames transmission for reducing energy consumption, which results in a slight improvement of energy efficiency.

A novel QoS aware medium access control scheduler for LTE-advanced network

LTE-A specification mandates Medium Access Control (MAC) scheduler entity to ensure strict guaranteed quality of service (QoS) both in downlink and uplink direction. To the best of our knowledge the LTE-A MAC schedulers proposed so far constitute of an objective function dependent on single constraints like number of radio resources, user throughput, user channel conditions, user data buffer or user's downlink power requirement. In real world scenario if all the above constraints are not simultaneously taken into consideration, then it would be difficult to meet LTE-A QoS requirements. In this regard, to the best found knowledge, for first time in this paper, we propose a Multi Objective QoS aware LTE-A Downlink-MAC Scheduler (MOQDS) algorithm which adhere to two level QoS and fairness requirements of LTE-A specification. MOQDS algorithm does scheduling at two levels with each level has its objective function with its multiple operational constraints. Every transmission time interval, MOQDS uses multi-objective optimization to selects right user(s) and its corresponding application(s) to meet LTE-A QoS requirements. Simulation results are being compared with well referred LTE-A schedulers like modified largest weighted delay first, exponential rule proportional fairness and log rule under various ITU channel models. MOQDS achieves an average of 50% reduction in packet drop rate and minimum three times increased cell throughput as compared to above mentioned schedulers’ types and also with respect to all the other MAC schedulers mentioned in the references.

Centralised against distributed medium access control scheduling for environmental monitoring sensors

The field of wireless sensor networks (WSNs), although started long back ago, has now reached its maximum usage in research and several kinds of monitoring and surveillance applications. Since the very small size and very low power working nature of the nodes, several challenges are faced by the entire network as a whole. Several scheduling and routing protocols were designed for the WSN. All of them are basically centralised or distributed in nature. For some of the well-known scheduling protocols, their behaviour under centralised and distributed manner is detailed here. It also specifies which type of schedule is suitable for which type of application and using either centralised or distributed approach. The scheduling algorithm which is best suitable for radiation monitoring application is described and also been proved that it is more energy efficient comparing to the existing protocols.

Decentralized Traffic Aware Scheduling in 6TiSCH Networks: Design and Experimental Evaluation

This paper capitalizes on two emerging trends, i.e., the growing use of wireless at the edge of industrial control networks and the growing interest to integrate IP into said networks. This is facilitated by recent design contributions from the IEEE and the IETF, where the former developed a highly efficient deterministic time–frequency scheduled medium access control protocol in the form of IEEE 802.15.4e timeslotted channel hopping (TSCH) and the latter IPv6 networking paradigms in the form of 6LoWPAN/ROLL, and scheduling approaches in the form of 6TiSCH. The focus of the present work is on advancing the state-of-the-art of deterministic 6TiSCH schedules toward more flexible but equally reliable distributed approaches. In addition, this paper aims to introduce the first implementation of 6TiSCH networks for factory automation environments: it outlines the challenges faced to overcome the scalability issues inherent to multihop dense low-power networks; the experimental results confirm that the naturally unreliable radio medium can support time-critical and reliable applications. These developments pave the way for wireless industry-grade monitoring approaches.

Improving QoS Routing in Hybrid Wireless Mesh Networks, Using Cross-Layer Interaction and MAC Scheduling

Abstract Delivering Quality of Services (QoS) for cooperative Wireless Mesh Networks (WMN) is an important issue when enabling heterogeneous wireless technologies on the client side. A standard approach for satisfying the QoS requirements of different wireless clients appears to be a complex task due to the capacity variations. In addition to the routing layer, the information at the lower layers, such as Physical and Medium Access Control (MAC) layers must be considered for providing the QoS guarantee. The strength of a signal received from heterogeneous clients at the physical layer and the coupled network capacity at the MAC layer plays an important role in the efficient path assignment and time scheduling management for routing. Therefore, this paper proposes an Adaptive Multipath-Dynamic Source Routing (AM-DSR) protocol. It supports Cross-Layer Interaction (CLI) for path assignment and MAC scheduling mechanism for slot assignment to improve the mesh backbone performance for providing multimedia services to various wireless clients in a hybrid WMN. The proposed strategy measures the cross-layer parameter, such as the network capacity, using the Signal to Noise Ratio (SINR) and assigns a route that maximizes the efficiency of the multimedia services. Finally, the performance evaluation shows that the proposed cross-layer based AM-DSR protocol provides efficient QoS support for the mesh backbone enabling connections to multiple clients.

Traffic-based queue-aware scheduling for 3GPP LTE system

Although the medium access control (MAC) signaling has been well-defined in the 3rd generation partnership project (3GPP) long term evolution (LTE) specifications, the scheduling algorithm crucial to guarantee QoS performance, still remains as open issues. In this article, a traffic-based queue-aware scheduling (TQS) algorithm is proposed for evolved nodeB's (eNB's) MAC scheduler in 3GPP LTE broadband wireless networks. The proposed TQS is divided into three sub-algorithms: firstly, the authors propose a traffic model construction (TMC) algorithm which can construct a discrete-time Markov-modulated Poisson process (dMMPP) to represent each flow. Secondly, a newly traffic state estimation (TSE) algorithm is designed to obtain the queue's analytical statistics. Thirdly, based on the derived results of TSE and the channel states, a scheduling action decision (SAD) algorithm is presented that can adaptively allocate bandwidth to flows by considering both queue states and spectrum efficiency. Simulation shows that the TMC and TSE algorithm can capture the fluctuation of traffic and queue accurately. Moreover, compared with a widely accepted traffic-based scheduling algorithm, the proposed TQS has better average queue length and overflow probability performance.

Topological Persistence for Medium Access Control

The primary function of the medium access control (MAC) protocol is managing access to the shared communication channel. From the viewpoint of the transmitters, the MAC protocol determines each transmitter's channel occupancy, the fraction of time that it spends transmitting over the channel. In this paper, we define a set of topological persistences that conform to both network topology and traffic load. We employ these persistences as target occupancies for the MAC layer protocol. A centralized algorithm is developed for calculating topological persistences and its correctness is established. A distributed algorithm and implementation are developed that can operate within scheduled and contention-based MAC protocols. In the distributed algorithm, network resources are allocated through auctions at each receiver in which transmitters participate as bidders to converge on the topological allocation. Very low overhead is achieved by piggybacking auction and bidder communication on existing data packets. The practicality of the distributed algorithm is demonstrated in a wireless network via simulation using the ns-2 network simulator. Simulation results show fast convergence to the topological solution and, once operating with topological persistences, improved performance compared to IEEE 802.11 in delay, throughput, and drop rate.

A Cooperative MAC Scheduling Scheme for Underwater Sensor Networks

The long propagation delay in underwater acoustic sensor networks renders existing media access control (MAC) protocols for terrestrial wireless networks undesirable. In this paper, we propose a new cooperative MAC protocol for underwater sensor networks that is used to detect objects and monitoring the environment. Our proposed MAC protocol tries to prevent data collisions through short term scheduling among neighbor nodes with exchange of short data message. By adapting the all sensor nodes to the transmitting schedules in which time is optimized we can minimize the collision rate between nodes. Through simulations, we show our proposed protocol can minimize data collisions and not only offers a higher throughput, but also indicates a better end-to-end delay.

Performance analysis of distributed resource reservation in IEEE 802.11e-based wireless networks

Guaranteeing quality of service (QoS) is one of the most critical challenges in IEEE 802.11-based wireless networks. This study proposes an analytical framework to evaluate hybrid medium access control (MAC) scheduling mechanisms with distributed resource reservation (RR), that was proposed for the IEEE 802.11e-enhanced distributed channel access protocol for guaranteeing QoS. The hybrid MAC scheduling mechanisms split the airtime into service intervals with contention-free period for QoS guaranteed real-time sessions (RTSNs), and contention access period for other traffic sessions. The distributed RR ensures that the resources are allocated to RTSNs without the support of a centralised controller–this makes it suitable for ad hoc networking applications. The proposed analytical framework models the QoS (i.e. delay and throughput) performance of RTSNs with dedicated resources in a distributed environment, and also estimates the overall capacity of the network. Moreover, the derived models can be used to investigate the impact of changes to individual system parameters, such as service interval or size of transmission opportunity. The simulation results show that the proposed analytical framework precisely models the QoS performance of RTSNs and predicts the optimum resource allocation for improved network capacity.

A Cross-Layer Design for the Performance Improvement of Real-Time Video Transmission of Secondary Users Over Cognitive Radio Networks

Cognitive radio (CR) has been proposed as a promising solution to improve connectivity, self-adaptability, and efficiency of spectrum usage. When used in video applications, user-perceived video quality experienced by secondary users is a very important performance metric to evaluate the effectiveness of CR technologies. However, most of the current research only considers spectrum utilization and effectiveness at medium access control (MAC) and physical layers, ignoring the system performance of the upper layers. Therefore, in this paper, we aim to improve the user experience of secondary users for wireless video services over CR networks. We propose a quality-driven cross-layer optimized system to maximize the expected user-perceived video quality at the receiver end under the constraint of packet delay bound. By formulating network functions such as encoder behavior, cognitive MAC scheduling, transmission, as well as modulation and coding into a distortion-delay optimization framework, important system parameters residing in different network layers are jointly optimized in a systematic way to achieve the best user-perceived video quality for secondary users in CR networks. Furthermore, the proposed problem is formulated into a MIN-MAX problem, and solved by using dynamic programming. The performance enhancement of the proposed system is evaluated through extensive experiments based on H.264/AVC.

NW-MAC: multiple wake-up provisioning in asynchronously scheduled duty cycle MAC protocol for wireless sensor networks

To reduce the energy cost of wireless sensor networks (WSNs), the duty cycle (i.e., periodic wake-up and sleep) concept has been used in several medium access control (MAC) protocols. Although these protocols are energy efficient, they are primarily designed for low-traffic environments and therefore sacrifice delay in order to maximize energy conservation. However, many applications having both low and high traffic demand a duty cycle MAC that is able to achieve better energy utilization with minimum energy loss ensuring delay optimization for timely and effective actions. In this paper, nW-MAC is proposed; this is an asynchronously scheduled and multiple wake-up provisioned duty cycle MAC protocol for WSNs. The nW-MAC employs an asynchronous rendezvous schedule selection technique to provision a maximum of n wake-ups in the operational cycle of a receiver. The proposed MAC is suitable to perform in both low- and high-traffic applications using a reception window-based medium access with a specific RxOp. Furthermore, per cycle multiple wake-up concept ensures optimum energy consumption and delay maintaining a higher throughput, as compare to existing mechanisms. Through analysis and simulations, we have quantified the energy-delay performance and obtained results that expose the effectiveness of nW-MAC.