Contention Free Period Research Articles

A novel artificial intelligence based wireless local area network channel access control scheme for low latency e‐health applications

AbstractTo effectively support low‐latency e‐health applications, a novel artificial intelligence‐based wireless local area network (WLAN) channel access control scheme named intelligent hybrid channel access (IHCA) is proposed and studied. In the IHCA scheme, each beacon interval comprises multiple cycles, with each cycle containing a contention‐free period (CFP) and a contention period (CP). By adopting an artificial neural network (ANN) and utilizing its calculation outputs to (1) decide whether to poll a hub during the CFP and (2) determine the initial backoff count (IBC) of each hub, polling of empty hubs during CFP can be reduced, and collisions during CP can be relieved. The authors’ simulation results show that the IHCA scheme can effectively reduce latency compared to the Hybrid coordination function Controlled Channel Access (HCCA) and the Request based Polling Access (RPA) reference designs.

Analysis of IEEE 802.15.4-Based Delay and Slot Duration Adjustment Combination Methods on Wireless Sensor Networks

IEEE 802.15.4 is one of the standards of the Wireless Sensor Network (WSN) which is at the Medium Access Control (MAC) layer. IEEE 802.15.4 is also technology and protocol within a computer network that can connect all device quickly, has a large capacity and low power consumption. The challenge of Wireless Sensor Network is how to improve the Wireless Sensor Network network performance matrix (goodput, bandwidth utilization, and energy consumption) both in the Contention Access Period (CAP) and in the Contention Free Period (CFP) based on the IEEE 802.15.4 standard. This research is an analysis combination of adjustment delay and slot duration methods to increase goodput, bandwidth utilization and reduce energy consumption in Wireless Sensor Networks in the allocation guaranteed time slots on fixed data simulated using Castalia Simulator software. The problem of this research is whether the combination method can improve the performance matrix of Wireless Sensor Networks on fixed data compared to other methods (SUDAS, ADES, IEEE 802.15.4 Standard). This reserch it aims to determine the performance matrix of combination methods is when compared to other methods (Superframe Duration Adjustment Scheme (SUDAS), Adjustment Delay Scheme (ADES), IEEE 802.15.4 standard) using quantitative approach research methods. Based on the data obtained, the goodput of the combined method increased by 10%, 416%, and 513% respectively compared to the SUDAS method, ADES method, and IEEE 802.15.4 standards. Bandwidth utilization of the combination methods increased by 0.025, 0.223 and 0.232, respectively compared to the SUDAS method, the ADES method, and the IEEE 802.15.4 standard. And the consumption of the combination methods are respectively reduced by 1.02%, 8.72% and 9.08% compared to the SUDAS, ADES and IEEE 802.15.4 standards. With the combination method of delay adjustment and slot duration it is able to optimize the performance of the Wireless Sensor Network compared to other methods.

Modeling and analysis of priority andrange‐based‐deterministic and synchronous multichannel extension‐guaranteed time slot allocation inIEEE802.15.4emedium access controlprotocol

AbstractInternet of Things (IoT) enabled technology in the current applications such as smart grids, smart cities, and smart health sectors utilize wireless sensor networks (WSN) to establish stable and reliable communication between the nodes. Moreover, the primary requirement of WSN in IoT applications is to provide low‐rate data communication. The IEEE 802.15.4e standard‐based medium access control (MAC) protocol is found suitable for low‐rate data communication in WSN. The IEEE 802.15.4e standard adopts a deterministic and synchronous multichannel extension (DSME) MAC protocol which employs a multisuperframe structure with multichannel data transmission during the contention free period. However, the guaranteed time slot (GTS) allocation process in DSME employed by the standard may not be suitable for an adaptive traffic network scenario that has a direct impact on the throughput and bandwidth utilization. In this article, we develop a priority and range‐based DSME‐GTS allocation algorithm based on the priorities of end nodes and range estimation. Furthermore, the proposed algorithm is developed for the two types of network scenarios encountered in a star topology‐enabled WSN. In scenario‐1, the slots allocation process is carried out based on the priorities of end nodes. Next, in scenario‐2, the slots allocation process is carried out based on the range estimation of end nodes. Detailed mathematical modeling of the proposed methodology is provided for the various performance metrics. The model is validated using the MATLAB 2017a programming tool. Simulation results show that the proposed methodology outperforms the existing DSME‐GTS approaches in terms of performance metrics such as packet delivery ratio, end‐to‐end delay, packet loss ratio, throughput, delay, bandwidth utilization, and the energy consumption.

A Study on the Wireless Body Area Network MAC Protocol Using Dynamic Superframe for e-Health IoT

One of the most remarkable applications of the Internet of Things is health monitoring. Wireless body area networks (WBANs) consist of several body sensors implanted in or place on a human body and a coordinator. One of the essential issues of WBANs is the design of Medium Access Control (MAC) protocol to improve system efficiency. In this paper, we modify the IEEE 802.15.4 standard MAC superframe structure and propose an energy-efficient MAC protocol for WBANs in the e-Health Internet of Things (IoT) systems. In this scheme, the time slots are divided into mini-slots. The lengths of the contention access period and the contention free period are both variable. By using this mechanism, the utility of time slots can be considerably increased.

Energy Efficient Beacon-Enabled IEEE 802.15.4 Guaranteed Time Slot-Based Adaptive Duty Cycle Algorithm for Wireless Sensor Network

In this work, energy-efficient adaptive duty cycle guaranteed time slot algorithm is proposed for beacon-enabled standard medium access control protocol to efficiently handle low, medium and high data traffic loads. The proposed protocol can efficiently handle high traffic load by effective utilization of slots. The protocol can dynamically update the number of slots for contention access period and contention free period in each beacon interval. Therefore, it can capably handle high network load condition. The protocol continuously monitors the utilization capacity of each of the sensor node and allots the contention free period slots to the needy nodes based on their utilization capacity. Simulation analysis is done for three different scenarios. The performance of the proposed protocol is compared with the other existing protocols. Simulation results show the overall superiority of our proposed algorithm in terms of packet delivery and energy consumption.

A new medium access control mechanism for energy optimization in WSN: traffic control and data priority scheme

Over the last few years, energy optimization in wireless sensor networks (WSNs) has drawn the attention of both the research community and actual users. Sensor nodes are powered by attached batteries that are considered as a critical aspect of sensor nodes design. Besides, the constraint of the limited battery capacity is associated with the concern on how to reduce the energy consumption of nodes to extend the network lifetime. In this context, the purpose of this study is to implement an adaptive medium access control (MAC) for energy saving and traffic control enhancement. This program was designed to arrange nodes into two priority groups according to their traffic rate and data transmission packet delay. This fuzzy algorithm depends on their queue length where it is implemented into the carrier sense multiple access with collision avoidance (CSMA/CA) algorithm. However, other types of nodes should send their data during the contention-free period with a GTS reallocation scheme. Those nodes are classified as low priority access to the medium, and their data transmission is scheduled using time division multiple access methods. Moreover, this proposed scheme dynamically adjusts the contention access period length to ensure that nodes can complete their data transmission during the same super-frame. Simulation results are done using the network simulator tool (NS-2), and it has improved efficiency regarding the IEEE-802.15.4 standard.

Traffic-Adaptive CFP Extension for IEEE 802.15.4 DSME MAC in Industrial Wireless Sensor Networks

This paper presents a traffic-adaptive contention-free period (CFP) extension (TaCFPext) protocol for IEEE 802.15.4 deterministic and synchronous multichannel extension (DSME) medium access control (MAC), which aims to satisfy the traffic adaptability requirement of industrial wireless sensor networks (IWSNs). The legacy DSME standard has limitations in accommodating highly varying traffic load in IWSNs due to its fixed multi-superframe structure. TaCFPext enables a node to adaptively use a contention access period (CAP) as an extended CFP (extCFP) on the demands of traffic loads in a distributed manner. The node starts TaCFPext when it determines that the CFP of the current multi-superframe is insufficient to accommodate the traffic load. Then, the node selects a CAP to be used as an extCFP, on which it is allocated an extended guaranteed time slot (extGTS). When the traffic load decreases, the extGTS is deallocated before the GTS in CFP, and the extCFP returns to CAP again. An experimental simulation was performed to verify the superiority of TaCFPext. The results demonstrated that TaCFPext outperforms the legacy DSME for aggregate throughput and average delay under various traffic conditions.

FD-OMAC: A Novel Full-Duplex Optical Media Access Control for IEEE 802.15.7

Optical wireless communication (OWC), the IEEE 802.15.7 standard (revised 2018) is developed in normative reference to low-rate wireless personal area networks IEEE 802.15.4 standard. One significant difference between the two standards is the highly directional transmitters in the OWC networks. This difference opens up the possibility of adding full-duplex communication to wireless networks. Our work proposes adding full-duplex functionality in the contention-free period (CFP) of the OWC media access control (MAC) layer. We justify the significance of our proposal by implementing IEEE 802.15.7 resource allocation scheme for both our proposed full-duplex optical MAC (FD-OMAC) and the IEEE 802.15.7 MAC. Our simulation results demonstrate that the proposed work improves the spectral efficiency in the CFP without compromising delays. We also discuss the minor changes required in the IEEE 802.15.7 MAC for implementing FD-OMAC. We further extend the FD-OMAC to a multiple access point network and evaluate its performance in comparison with IEEE 802.15.7 MAC.

A robust guaranteed time slots allotment scheme for real-time and reliable communication in WBANs

The ever-increasing aging population and expenditure related to healthcare, consequently demand the requirement for a state-of-the-art healthcare system. Wireless body area networks (WBANs) are the potential contender for this requirement. The IEEE 802.15.4 standard is considered a suitable protocol for WBANs and its beacon-enabled mode supports real-time traffic through guaranteed time slots (GTS) feature. Nevertheless, it suffers from reliability and timeliness guarantees. To address this issue, this work advocates a robust guaranteed time slots allotment scheme (RGAS) that consists of two phases, viz.: 1) determination of the severity of sensor data using fuzzy inference system; 2) dynamic allocation of available GTS slots to the contending nodes. Through simulation results, we demonstrate that the proposed RGAS significantly outperforms the existing GTS mechanism specified in the IEEE 802.15.4 in terms of various performance metrics such as packets transmission, packet reception rate, packet loss rate, and effective utilisation of contention free period.

A robust guaranteed time slots allotment scheme for real-time and reliable communication in WBANs

The ever-increasing aging population and expenditure related to healthcare, consequently demand the requirement for a state-of-the-art healthcare system. Wireless body area networks (WBANs) are the potential contender for this requirement. The IEEE 802.15.4 standard is considered a suitable protocol for WBANs and its beacon-enabled mode supports real-time traffic through guaranteed time slots (GTS) feature. Nevertheless, it suffers from reliability and timeliness guarantees. To address this issue, this work advocates a robust guaranteed time slots allotment scheme (RGAS) that consists of two phases, viz.: 1) determination of the severity of sensor data using fuzzy inference system; 2) dynamic allocation of available GTS slots to the contending nodes. Through simulation results, we demonstrate that the proposed RGAS significantly outperforms the existing GTS mechanism specified in the IEEE 802.15.4 in terms of various performance metrics such as packets transmission, packet reception rate, packet loss rate, and effective utilisation of contention free period.

A novel superframe structure and optimal time slot allocation algorithm for IEEE 802.15.4–based Internet of things

IEEE 802.15.4 standard is specifically designed for a low-rate and low-processing Internet of things (IoT) applications and offers guaranteed time slots. A beacon-enabled IEEE 802.15.4 consists of a superframe structure that comprises of the contention access period and contention-free period. During contention-free period, nodes transfer their data using guaranteed time slots without any collision. The coordinator node receives data transmission requests in one cycle and allocates guaranteed time slots to the nodes in the next cycle. This allocation process may cause large delay that may not be acceptable for few applications. In this work, a novel superframe structure is proposed that significantly reduces guaranteed time slots allocation delay for the nodes with data requests. The proposed superframe structure comprises of two contention access periods and one contention-free period, where contention-free period precedes both contention access periods with reduced slot size. In addition, the knapsack algorithm is modified for better guaranteed time slots allocation by allowing more guaranteed time slots requesting nodes to send their data as compared to the IEEE 802.15.4 standard. The simulation and analytical results show that the proposed superframe structure reduces the network delay by up to 80%, increases contention-free period utilization up to 50%, and allocates guaranteed time slots up to 16 nodes in a single superframe duration.

An Analytical Model for CBAP Allocations in IEEE 802.11ad

The IEEE 802.11ad standard extends WiFi operation to the millimeter wave frequencies, and introduces novel features concerning both the physical (PHY) and Medium Access Control (MAC) layers. The hybrid MAC layer provides for two different kinds of resource allocations: Contention Based Access Periods (CBAPs) and contention-free Service Periods (SPs). In this paper, we propose a Markov Chain model to represent CBAPs, taking into account operation interruptions due to scheduled SPs and the deafness and hidden node problems that directional communication exacerbates. We also propose a mathematical analysis to evaluate the interference among stations and derive analytical expressions to assess the impact of various system parameters on some key performance metrics such as throughput, delay, and packet drop rate. This information may be used to efficiently design a transmission scheduler that allocates contention-based and contention-free periods based on the application requirements.

Energy-efficient adaptive GTS allocation algorithm for IEEE 802.15.4 MAC protocol

The standard IEEE 802.15.4 fails to perform optimally for railway monitoring applications due to the deficiency of guaranteed time slots (GTSs). In the present work, an adaptive GTS allocation algorithm (AGAA) is proposed which efficiently deals with a deficiency of GTSs and slot underutilization problem. The proposed AGAA algorithm saves unutilized bandwidth of GTS and the saved bandwidth is utilized by the needy nodes in contention access period (CAP) and contention-free period (CFP). An independent superframe order ( $$SO_{CFP}$$ ) is introduced for adaptive adjustment of slot size in the CFP. The proposed AGAA protocol also deals with the problem of GTS request-failure due to congestion during CAP. A separate contention period is used for GTS request in AGAA protocol. The comparison has been done between the proposed AGAA protocol and the standard IEEE 802.15.4 medium access control (MAC) protocol. Throughput and energy consumption are analyzed and results show that the slot optimization using $$SO_{CFP}$$ saves a fair amount of bandwidth which improves the throughput of the network $$\approx $$ 22%. Moreover, the separate contention period for the GTS request frame reduces the idle state energy consumption of those devices which generate time-constraint data frames. The proposed AGAA protocol consumes $$\approx $$ 18% less energy than the standard IEEE 802.15.4 MAC protocol. The analysis of results also reveals an important fact that the algorithm saves more energy for homogeneous traffic in comparison to heterogeneous traffic which can further be improved in future works.

PAINT: Priority aware interference mitigation techniques for improving coexistence in home area networks of smart grid

SummaryAs smart grid (SG) home area networks (HANs) communicate with various smart devices such as meters, sensors, and actuators on a 2.4‐GHz unlicensed band, the coexistence of different wireless technologies in such networks is a common phenomenon due to the overlapping of channels. In this research, homogeneous and heterogeneous interference are considered to address the coexistence problem in smart utility networks (SUNs). The homogeneous interference is mitigated by utilizing the contention free period (CFP) and the contention access period (CAP) of the MAC layer superframe of IEEE 802.15.4g designed for SUNs. This frame is used to get access for the channel. For this, a slotted CSMA/CA algorithm is used for various priority levels of data with adjustable backoff period (BP) and clear channel assessment (CCA) period in order that nodes (devices) with high priority can achieve high probability of channel access. By modeling the proposed scheme using the Markov chain, the exactness of the proposed scheme is assessed based on throughput, channel access delay, energy consumption per bit, and probability of successful data transmission and collision. A performance evaluation of the proposed scheme is further investigated by comparing it with the existing scheme PA‐MAC. In addition, a channel switching mechanism is explored to mitigate the heterogeneous interference with the help of a Naive Bayes classifier prediction. Finally, the prediction indicates that by choosing the non‐coexisting and the non‐overlapping channel, the proposed channel switching mechanism effectively mitigates the heterogeneous interference.

Bio-Inspired Approach for Inter-WBAN Coexistence

When wireless body area networks (WBANs) using the same channel transmit superframes (SFs) simultaneously, they interfere with each other. To resolve this problem, we propose a co-channel inter-WBAN coexistence method adopting bio-inspired models. The proposed method avoids the inter-WBAN interference by distributing the timing at which each WBAN sends its SF in a distributed manner. We also identify the position of a contention-free period in an SF whereby the time slots in the period do not overlap with any time slots in the SFs of the coexisting WBANs. In addition, we show that the proposed method can limit the number of WBANs interfering with each other during a contention access period. Through simulation studies, we show that the proposed method can adapt to changes in the density and topology of the coexisting WBANs. We also show that in contrast to other conventional methods, our method guarantees that the data frames sent during a contention-free period in an SF are free from collisions regardless of the number of coexisting WBANs. Thus, the proposed method enhances the throughput of a WBAN by increasing the successful data frame transmission rate.

Guaranteed Time Slot Allocation for IEEE 802.15.4-Based Wireless Feedback Control Systems

In this paper, wireless feedback control of multiple machines over a beacon-enabled IEEE 802.15.4 network is considered. In the beacon-enabled IEEE 802.15.4 network, beacons periodically structure superframes on the time axis, and each superframe consists of a contention access period (CAP) and a contention free period (CFP). In the CAP, a carrier sense multiple access/collision avoidance (CSMA/CA) is used; in the CFP, a guaranteed time slot (GTS)-based time division multiple access is used. Because of collision and backoff periods of packet transmission, the probability of communication failure in the CAP is greater than that in the CFP; however, the number of available GTSs is limited to seven by the standard. In order to improve the control performance of wireless feedback control, the controller must effectively allocate GTSs to transmit control input and state feedback of controlled machines. We provide a simple but efficient idea that takes both the feedback control mechanism and packet transmission mechanism of the CAP and CFP into consideration to better allocate GTSs. We propose a superior GTS allocation method that fully conforms to the IEEE 802.15.4 standard and show that the proposed method can further improve control performance.

A Dynamic Adaptation Mechanism for Traffic Conditions in Wireless Sensor Network

As overall network traffic pursue to expand, a lot of low-power medium access control protocols have been proposed to deal with burst traffic in wireless sensor network. Although most of them provide low throughput but do not well optimize the energy consumption. In this paper, we propose a new hybrid carrier sense multiple access with collision avoidance (CSMA/CA) and time division multiple access (TDMA) protocol that arranges nodes into two categories of priority according to their traffic rate and data transmission delay. Nodes that have continuous data should send its data during the contention free period, those one will be classified as low priority and its data will be scheduling using TDMA. Others nodes who have a random data should transmit it immediately during the contention access period (CAP) using a fuzzy logic algorithm, based on their queue length and implemented in the CSMA/CA algorithm. Therefore, the proposed scheme dynamically changes the CAP length to ensure that nodes can complete its transaction during the same super-frame. Simulation results are done using the network simulator tools (NS-2) and have improved good efficiency regarding the IEEE 802.15.4 standard. The mechanism has improved the energy consumption, minimised the packet loss probability, increased the throughput variation in the network and also minimised the average end to end delay.

A novel coexistence scheme for IEEE 802.11 for user fairness and efficient spectrum utilization in the presence of LTE-U

A promising solution satisfying the industry’s demand to have minimum modification in LTE for its operation in unlicensed spectrum is duty cycled LTE-U scheme, which adopts discontinuous transmission to ensure fair coexistence with 802.11 (Wi-Fi) WLANs. Even though the scheme guarantees to maintain Wi-Fi network performance, the fairness among Wi-Fi users still remains arcane. In this work, we present a practical scenario where LTE-U, despite being discontinuous (by following an ON/OFF cycle), results in not only unfair throughput distribution among Wi-Fi users but also causes degradation in Wi-Fi AP’s downlink performance. This is due to the domination of few Wi-Fi users who harness channel in both ON and OFF durations of LTE-U, namely non-victim users over those who get access only in OFF duration, called victim users. In this paper, we studied the performance of victim and non-victim Wi-Fi users, and Wi-Fi AP while varying LTE-U ON fraction (i.e., duty cycle). A propitious scheme is proposed for WLANs, with regard to ease of implementation, employing Point/Hybrid Coordination Function (PCF/HCF) mode of 802.11, promising fairness among Wi-Fi users with improvement in the channel utilization of Wi-Fi network. The key idea is that the victim users, who can only be served during the LTE-U OFF period should be served in Contention Free Period (CFP)—so as to improve their throughputs and make them equally competitive with non-victim users. Also, we present an analytical model to demonstrate guaranteed improvement and to validate our simulation results.

Energy-efficient analysis of an IEEE 802.11 PCF MAC protocol based on WLAN

The point coordination function (PCF) of the IEEE 802.11 standard represents a well-known medium access control (MAC) protocol providing quality-of-service guarantees in wireless local area networks (WLANs). However, few papers theoretically analyze energy efficiency. This paper presents a Parallel Gated Poll (PGP) access mechanism that exploits the PCF defined in the IEEE 802.11. The basic idea is, during the contention free period, idle stations can save energy by turning into sleep and active stations exchange data packet under a gated service polling scheme to improve the energy efficiency. Besides, the mean cycle analysis model is setup to evaluate the energy efficiency of a typically PCF protocol and PGP protocol. By applying the classic 1-limited and parallel gated polling model, the closed expressions of energy efficiency of PCF and PGP are formulated respectively. Simulations show that our analytical results are very accurate with the simulation results. Both analytical and simulation results show the high energy efficiency of PGP.

CDASA-CSMA/CA: Contention Differentiated Adaptive Slot Allocation CSMA-CA for Heterogeneous Data in Wireless Body Area Networks

The implementation of IEEE 802.15.6 in Wireless Body Area Network (WBAN) is contention based. Meanwhile, IEEE 802.15.4 MAC provides limited 16 channels in the Superframe structure, making it unfit for N heterogeneous nature of patient’s data. Also, the Beacon-enabled Carrier-Sense Multiple Access/Collision-Avoidance (CSMA/CA) scheduling access scheme in WBAN, allocates Contention-free Period (CAP) channels to emergency and non-emergency Biomedical Sensors (BMSs) using contention mechanism, increasing repetition in rounds. This reduces performance of the MAC protocol causing higher data collisions and delay, low data reliability, BMSs packet retransmissions and increased energy consumption. Moreover, it has no traffic differentiation method. This paper proposes a Low-delay Traffic-Aware Medium Access Control (LTA-MAC) protocol to provide sufficient channels with a higher bandwidth, and allocates them individually to non-emergency and emergency data. Also, a Contention Differentiated Adaptive Slot Allocation CSMA-CA (CDASA-CSMA/CA) for scheduling access scheme is proposed to reduce repetition in rounds, and assists in channels allocation to BMSs. Furthermore, an On-demand (OD) slot in the LTA-MAC to resolve the patient’s data drops in the CSMA/CA scheme due to exceeding of threshold values in contentions is introduced. Simulation results demonstrate advantages of the proposed schemes over the IEEE 802.15.4 MAC and CSMA/CA scheme in terms of success rate, packet delivery delay, and energy consumption.