Guaranteed Time Slot Allocation Research Articles

A novel scheme to improve lifetime and real-time support for IEEE 802.15.4 based wireless personal area networks

IEEE 802.15.4 defines the working of physical and media access layers of a Low-Rate Wireless Personal Area Network (LR-WPAN). A LR-WPAN is a low cost, low power, and low data-rate network that offers reasonable lifetime and reliable data transfer within a limited range. However, it faces several challenges whilst dealing with applications that are having strict timeliness, energy, and bandwidth requirements. This paper proposes an efficient superframe structure for the MAC layer of IEEE 802.15.4 networks that intends to deal with these challenges by varying the functionalities of Guaranteed Time Slot (GTS) bits. Simulations of different GTS allocation techniques show that our enhanced scheme outperforms the original standard as well as previous techniques in terms of energy consumption, average delay, maximum GTS allocation and reliability.

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.

An efficient medium access control protocol for RF energy harvesting based IoT devices

Energy efficiency is one of the major challenges in IEEE 802.15.4 based Internet of Things (IoT). In the Medium Access Control (MAC) layer of the IEEE 802.15.4 standard, Guaranteed Time Slot (GTS) are allocated to the IoT devices for data transmission. However, GTS allocation does not consider residual energy of IoT devices resulting in reduced life cycle of these devices. In this paper, we propose an efficient MAC protocol for RF harvesting based IoT devices. The proposed protocol uses residual energy based duty cycle adaptation to prioritize transmission of high energy devices, allowing low energy devices to harvest energy in the mean time. Simulation results show that the life cycle and transmitted data of IoT devices is improved up to 94% and 79% respectively by using the proposed protocol, as compared to the IEEE 802.15.4 standard.

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.

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.

Priority based IEEE 802.15.4 MAC by varying GTS to satisfy heterogeneous traffic in healthcare application

This work presents the design of IEEE 802.15.4, the Medium Access Control protocol to ensure that medical data must be delivered in time, along with satisfying QoS requirements of Wireless Body Sensor Network based healthcare applications. Here, we propose the allocation of Guaranteed Time Slots (GTS) as per the varying rate of heterogeneous data traffic sensed by different sensor nodes ensuring energy efficiency, low latency, high throughput etc. Due to the sudden critical condition of the patient, the sensor node with an abrupt increase in data rate is assigned the highest priority and allocated dynamically more GTS. We have simulated different scenarios representing the normal and critical conditions of patients using Castalia 3.3 and OMNeT++. The temporal variation incorporates the movement associated with body which results to capture the fading arises due to the changing environment and movement of the nodes. This gives the practical variation associated with the nodes. We have compared among six different data traffic handling techniques: first where no nodes are allocated any GTS, second where all nodes are allocated fixed number of GTS and third where we propose dynamic GTS allocation as per the varying rate of data traffic. These three conditions are tested with Temporal and noTemporal variation. We have performed the simulation with 8 nodes and 11 nodes. The results show that in proposed technique, there is a significant reduction in energy consumption by $$\approx 20\%$$ by varyGTS vonfiguration. The average of varyGTS, Temporal and varyGTS, noTemporal packets received is $$\approx 76\%$$ in 8 nodes and $$\approx 66\%$$ by varyGTS, noTemporal in 11 nodes within the 240 ms delay permissible in healthcare application.

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.

OGMAD: Optimal GTS-Allocation Mechanism for Adaptive Data Requirements in IEEE 802.15.4 Based Internet of Things

Future Internet of Things (IoT) will utilize IEEE 802.15.4 based low data rate communication for various applications. In the IEEE 802.15.4 standard, nodes send data to their Personal Area Network (PAN) coordinator using the Guaranteed Time Slot (GTS). The standard does not meet the adaptive data requirements of GTS requesting nodes in an efficient manner. If requesting GTSs in an active period are more or less than the available limit, either the requested nodes will not be entertained or GTSs remain underutilized. Consequently, it may cause unnecessary delay or poor GTS utilization. In this paper, an Optimal GTS allocation Mechanism for Adaptive Duty cycle (OGMAD) is proposed that adapts the active period of the superframe in accordance with the requested data. OGMAD also reduces GTS size to improve link utilization as well as accommodate more GTS requesting nodes. Simulation results verify that OGMAD improves link utilization, reduces network delay and offers more nodes to transmit their data as compared to the standard.

A GTS Allocation Scheme to Improve Multiple-Access Performance in Vehicular Sensor Networks

The IEEE 802.15.4 protocol is designed to flexibly support both real-time and contention-based services. When the beacon model is enabled, guaranteed time slot (GTS) scheduling can provide contention-free access to latency-sensitive services based on the time-division multiple-access mechanism. This characteristic makes IEEE 802.15.4 the appropriate candidate for vehicular sensor networks in which mobile nodes need to exchange packets with roadside units (RSUs) within a limited duration. In this paper, using network calculus theory, we analyzed the relationship between time-slot utilization and the corresponding access parameters, such as packet arrival rate, burst size, and vehicles' mobility extent. Then, for a given number of vehicles preparing to access an RSU, we proposed a time-sensitive weighted round-robin (TS-WRR) scheduler to improve the multiple-access performance, which can take the service delay requirement, packet arrival rate, and vehicular mobility level into account. Next, the weight determination and time-slot allocation strategy of the TS-WRR scheduler were issued in detail, which incorporate the special limitations and application requirements in a vehicle-to-infrastructure (V2I) communication environment. To make our model feasible for testing, we also elaborately demonstrated the implementation procedure with pseudocode and simulator design. Numerical results show that our TS-WRR scheduler outperforms some classic schedulers such as First-Come First-Served and WRR, as well as two latest works, i.e., implicit GTS allocation scheme and adaptive real-time GTS allocation mechanism in terms of delay guarantee and GTS utilization maximization in vehicular sensor networks.

A novel channel allocation method for time synchronization in wireless sensor networks

SummaryChannel allocation in the wireless sensor networks is one of the important issues, and these networks must allocate shared channels between sensor nodes in the transmission phase. This paper proposes a novel protocol for channel allocation, so it focuses on energy efficiency and collisions avoidance. The main idea of this protocol is based on the Guaranteed Time Slot approach by using novel high‐rate collaborative codes. The sum rate of the proposed collaborative codes is double than the conventional codes, thus increasing the capacity of codes and allowing more nodes to simultaneously transmit at a given time slot. The proposed protocol has a cluster‐based structure, so the sensor nodes of each cluster can communicate together only inside of the any cluster. The protocol performs clustering (grouping) of the nodes based on the geometric distance from the coordinator node and hence allocating different transmission power to each cluster. Because of the difference in transmission power among the groups, the same codes can be reused in the adjacent groups increasing the overall sum rate of the codes. The performance of a proposed protocol is evaluated through extensive simulation and analysis. It is shown from the results that the proposed scheme outperforms significantly the existing ZigBee Guaranteed Time Slot allocation schemes as well as the conventional collaborative codes. Copyright © 2016 John Wiley & Sons, Ltd.

English

The personal area network (PAN) coordinator can assign a guaranteed time slot (GTS) to allocate a particular duration for requested devices in IEEE 802.15.4 beacon-enabled mode. The main challenge in the GTS mechanism is how to let the PAN coordinator allocate time slot duration for the devices which request a GTS. If the allocated devices use the GTS partially or the traffic pattern is not suitable, wasted bandwidth will increase, which degrades the performance of the network. In order to overcome the abovementioned problem, this paper proposes the Partitioned GTS Allocation Scheme (PEGAS) for IEEE 802.15.4 networks. PEGAS aims to decide the precise moment for the starting time, the end, and the length of the GTS allocation for requested devices taking into account the values of the superframe order, superframe duration, data packet length, and arrival data packet rate. Our simulation results showed that the proposed mechanism outperforms the IEEE 802.15.4 standard in terms of the total number of transmitted packets, throughput, energy efficiency, latency, bandwidth utilization, and contention access period (CAP) length ratio.

GTS size adaptation algorithm for IEEE 802.15.4 wireless networks

IEEE 802.15.4 standard specifies the Medium Access Control (MAC) and Physical (PHY) layer for wireless sensor networks (WSN) applications with limited power and low data rate. This standard supports time critical applications by allowing TDMA based access in beacon enabled networks. In these networks, the PAN coordinator exchanges data with the end devices through guaranteed time slots (GTS). The PAN coordinator can allocate GTS on a first come first serve (FCFS) basis in response to the requests by end devices. In original standard, the coordinator can assign up to the maximum seven GTSs. This fixed number of GTS allocation may result in inefficient utilization of channel bandwidth. In this paper, we propose a new GTS allocation scheme that will set the GTS size adaptively in accordance with the data size of the end device. We call it as GTS Size Adaptation Algorithm (GSAA) and it will optimally use the GTS resources. Simulations have been performed to validate the proposed GSAA.

Traffic differentiation and dynamic duty cycle adaptation in IEEE 802.15.4 beacon enabled WSN for real-time applications

The wireless sensor networks (WSNs) based on the IEEE 802.15.4 beacon enabled mode provide a deterministic resource allocation offered by the guaranteed time slot (GTS) mechanism which is ideal for real-time traffic applications that requires high quality of service (QoS). In the beacon enabled mode the active and optional inactive period is governed by superframe order (SO) and beacon order (BO). Adapting the duty cycle using the SO and BO is desirable to accommodate the changing context of the WSNs traffic for network optimisation. However, existing approaches assumed a fixed SO and BO and segregate the evaluation of the contention access period and the contention free period that forms the active segment. To improve the performance of the IEEE 802.15.4 protocol in respect of the trade-off between power consumption and end-to-end delay, within a required QoS, a combination of dynamic priorities for traffic differentiation and dynamic duty cycle adaptation in the GTS allocation process are introduced. This work demonstrates that the proposed solution provides significantly better performance than the standard allocation method by simultaneously satisfying QoS and service differentiation demands with considerable power savings which is essential for WSNs. The specific novel use of this solution is in an application scenario where the deployed network is situated in an assisted living environment with a rich suite of heterogeneous wireless based communications in place.

Modified GTS Allocation Scheme for IEEE 802.15.4

IEEE 802.15.4 standard is widely used in wireless personal area networks (WPANs). The devices transmit data during two periods: contention access period (CAP) by accessing the channel using CSMA/CA and contention free period (CFP), which consists of guaranteed time slots (GTS) allocated to individual devices by the personal area network (PAN). However, the use of GTS slot size may lead to severe bandwidth wastage if the traffic pattern is not fit or only a small portion of GTS slot is used by allocated device. The proposed scheme devides the GTS slot and then optimizes the GTS slot size by exploiting the value of superframe order (SO) information. The proposed scheme was tested through simulations and the results show that the new GTS allocation scheme perform better than the original IEEE 802.15.4 standard in terms of average transmitted packets, throughput, latency and probability of successful packets.

Adaptive GTS Allocation Scheme with Applications for Real-time Wireless Body Area Sensor Networks

The IEEE 802.15.4 standard not only provides a maximum of seven guaranteed time slots (GTSs) for allocation within a superframe to support time-critical traffic, but also achieves ultralow complexity, cost, and power in low-rate and short-distance wireless personal area networks (WPANs). Real-time wireless body area sensor networks (WBASNs), as a special purpose WPAN, can perfectly use the IEEE 802. 15. 4 standard for its wireless connection. In this paper, we propose an adaptive GTS allocation scheme for real-time WBASN data transmissions with different priorities in consideration of low latency, fairness, and bandwidth utilization. The proposed GTS allocation scheme combines a weight-based priority assignment algorithm with an innovative starvation avoidance scheme. Simulation results show that the proposed method significantly outperforms the existing GTS implementation for the traditional IEEE 802.15.4 in terms of average delay, contention free period bandwidth utilization, and fairness.

An adaptive MAC protocol for real-time and reliable communications in medical cyber-physical systems

With the increasing demands for high-quality health-care services, medical cyber-physical systems over wireless body sensor networks have emerged as a promising solution for vital life signals monitoring. These systems require the communication protocols to be both reliable and real-time in data transmissions. IEEE 802.15.4 can be regarded as the canonical protocols in this area owing to its low-power and low-cost features. However, it falls short of reliability and timeliness guarantees. To address this issue, we propose an adaptive MAC protocol based on IEEE 802.15.4, namely Ada-MAC. The proposed protocol combines schedule-based on time-triggered protocol and contention-based CSMA/CA mechanism. It can not only enable dynamic Guaranteed Time Slots allocation but also provide differentiated services for different nodes according to their data types. The proposed protocol is implemented on the OMNeT++ platform. Extensive simulations are conducted to evaluate the performance of Ada-MAC in comparison with the traditional IEEE 802.15.4 MAC. The results show the superiority of the proposed protocol in terms of reliability and timeliness.

Adaptive GTS allocation in IEEE 802.15.4 for real-time wireless sensor networks

The IEEE 802.15.4 standard is able to achieve low-power transmissions in low-rate and short-distance Wireless Personal Area Networks (WPANs). It supports a Guaranteed Time Slots (GTSs) allocation mechanism for time-critical and delay-sensitive data transmissions. However, the inflexible First-Come-First-Served (FCFS) GTS allocation policy and passive deallocation mechanism significantly impair network efficiency. This paper proposes an Adaptive and Real-Time GTS Allocation Scheme (ART-GAS) to provide differentiated services for devices with different priorities, which guarantees data transmissions for time-sensitive and high-traffic devices. The bandwidth utilization in IEEE 802.15.4-based PAN is thus improved. The proposed scheme is developed based on the IEEE 802.15.4 Medium Access Control (MAC) protocol and is fully compatible with the implementation of IEEE 802.15.4 devices. It is applicable to various real-time systems built upon wireless sensor networks. Simulation results demonstrate that our ART-GAS algorithm significantly outperforms the existing GTS mechanism specified in IEEE 802.15.4 in terms of success probability, average delay, average waiting time, and CFP bandwidth utilization.

Modeling and stability analysis of hybrid multiple access in the IEEE 802.15.4 protocol

To offer flexible quality of service to several classes of applications, the medium access control (MAC) protocol of IEEE 802.15.4 wireless sensor networks (WSNs) combines the advantages of a random access with contention with a time division multiple access (TDMA) without contention. Understanding reliability, delay, and throughput is essential to characterizing the fundamental limitations of the MAC and optimizing its parameters. Nevertheless, there is not yet a clear investigation of the achievable performance of hybrid MAC. In this article, an analytical framework for modeling the behavior of the hybrid MAC protocol of the IEEE 802.15.4 standard is proposed. The main challenge for an accurate analysis is the coexistence of the stochastic behavior of the random access and the deterministic behavior of the TDMA scheme. The analysis is done in three steps. First, the contention access scheme of the IEEE 802.15.4 exponential back-off process is modeled through an extended Markov chain that takes into account channel, retry limits, acknowledgements, unsaturated traffic, and superframe period. Second, the behavior of the TDMA access scheme is modeled by another Markov chain. Finally, the two chains are coupled to obtain a complete model of the hybrid MAC. By using this model, the network performance in terms of reliability, average packet delay, average queuing delay, and throughput is evaluated through both theoretical analysis and experiments. The protocol has been implemented and evaluated on a testbed with off-the-shelf wireless sensor devices to demonstrate the utility of the analysis in a practical setup. It is established that the probability density function of the number of received packets per superframe follows a Poisson distribution. It is determined under which conditions the guaranteed time slot allocation mechanism of IEEE 802.15.4 is stable. It is shown that the mutual effect between throughput of the random access and the TDMA scheme for a fixed superframe length is critical to maximizing the overall throughput of the hybrid MAC. In high traffic load, the throughput of the random access mechanism dominates over TDMA due to the constrained use of TDMA in the standard. Furthermore, it is shown that the effect of imperfect channels and carrier sensing on system performance heavily depends on the traffic load and limited range of the protocol parameters. Finally, it is argued that the traffic generation model established in this article may be used to design an activation timer mechanism in a modified version of the CSMA/CA algorithm that guarantees a stable network performance.

Multi‐hop medium access control protocol for low energy critical infrastructure monitoring networks using wake‐up radio

SUMMARYThe IEEE 802.15.4K Task Group was formed recently to address the low energy critical infrastructure monitoring networks. The aim is to collect scheduled and event data from a large number of non‐mains powered endpoints that are widely dispersed. The application requirements include reliable data transfer, energy efficiency, and long deployment lifetime. To meet the low energy critical infrastructure monitoring network requirements, we propose a multihop medium access control protocol where the scheduled or event data are routed to the coordinator through the cluster heads. The power consumption of the cluster heads is critical as they use more power than the normal endpoints. Our protocol uses the wake‐up radio approach from cluster head to cluster head communication and an efficient guaranteed time slots allocation scheme to minimize the power consumption of the cluster heads. We derive analytical expressions for the average power consumption of cluster heads as well as ordinary endpoints. The results show that our proposed protocol outperforms the IEEE 802.15.4 MAC and SCP MAC in terms of power consumption. High power efficiency is achieved in both the cluster heads and normal endpoints. Copyright © 2012 John Wiley & Sons, Ltd.

A High Capacity Low Latency Guaranteed Time Slot Allocation Scheme for IEEE 802.15.4

A High Capacity Low Latency Guaranteed Time Slot Allocation Scheme for IEEE 802.15.4