A Survey of Adaptive and Real-Time Protocols Based on IEEE 802.15.4
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paper_title: A Smart Gateway for Health Care System Using Wireless Sensor Network

paper_content:

Using Wireless Sensor Networks (WSNs) in health care system has yielded a tremendous effort in recent years. However, in most of these researches, tasks like sensor data processing, health state decisions making and emergency messages sending are completed by a remote server. Transmitting and handing with a large scale of data from body sensors and home sensors consume a lot of communication resource, bring a burden to the remote server and delay the decision time and notification time. In this paper, we present a prototype of a smart gateway that we have implemented. This gateway is an interconnection and services management platform especially for WSN health care systems at home environment. By building a bridge between a WSN and public communication networks, and being compatible with an on-board data decision system and a lightweight database, our smart gateway system is enabled to make patients' health state decisions in low-power and low-cost embedded system and get faster response time o the emergencies. We have also designed the communication protocols between WSN, gateway and remote servers. Additionally Ethernet, Wi-Fi and GSM/GPRS communication module are integrated into the smart gateway in order to report and notify information to care-givers. We have conducted experiments on the proposed smart gateway by performing it together with a wireless home e-health care sensor network. The results show that the smart gateway design is feasible and has low latency.
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paper_title: Improving the IEEE 802.15.4 Slotted CSMA/CA MAC for Time-Critical Events in Wireless Sensor Networks

paper_content:

In beacon-enabled mode, IEEE 802.15.4 is ruled by the slotted CSMA/CA Medium Access Control (MAC) protocol. The standard slotted CSMA/CA mechanism does not provide any means of differentiated services to improve the quality of service for timecritical events (such as alarms, time slot reservation, PAN management messages etc.). In this paper, we present and discuss practical service differentiation mechanisms to improve the performance of slotted CSMA/CA for time-critical events, with only minor add-ons to the protocol. The contribution of our proposal is more practical than theoretical since our initial requirement is to leave the original algorithm of the slotted CSMA/CA unchanged, but rather tuning its parameters adequately according to the criticality of the messages. We present a simulation study based on an accurate model of the IEEE 802.15.4 MAC protocol, to evaluate the differentiated service strategies. Four scenarios with different settings of the slotted CSMA/CA parameters are defined. Each scenario is evaluated for FIFO and Priority Queuing. The impact of the hiddennode problem is also analyzed, and a solution to mitigate it is proposed.
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paper_title: Performance Evaluation of IEEE 802.15.4 MAC with Different Backoff Ranges in Wireless Sensor Networks

paper_content:

The IEEE 802.15.4 MAC (Medium Access Control) is a protocol used in many applications including the wireless sensor network. Yet the IEEE 802.15.4 MAC layer cannot support different throughput performance for individual nodes with the current specifications. However, if certain nodes are sending data more frequently compared to others, with the standard MAC, it is hard to achieve network efficiency. Therefore, we modified the IEEE 802.15.4 MAC and additionally proposed a new State Transition Scheme. By adjusting the minBE value of some nodes to a smaller value and by dynamically changing the value depending on the transmission conditions, we shortened the backoff delay of nodes with frequent transmission. It was observed through our simulations that the throughput of the node with a lower minBE value increased significantly, compared to nodes with the original BE range of 3 to 5. Also by the use of the State Transition Scheme the total network efficiency increased leading to increase in throughput performance.
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paper_title: Adaptation of MAC Layer for QoS in WSN

paper_content:

In this paper, we propose QoS aware MAC protocol for Wireless Sensor Networks. In WSNs, there can be two types of traffic one is event driven traffic which requires immediate attention and another is periodic reporting. Event driven traffic is classified as Class I(delay sensitive) traffic and periodic reporting is classified as Class II(Best Effort) Traffic. MAC layer adaptation can take place in terms of (i) Dynamic contention window adjustment per class, (ii) Reducing the delay suffered by difference in Sleep schedules(DSS) of communicating nodes by dynamically adjusting Duty Cycle based on Utilization and DSS delay of class I traffic, (iii) Different DIFS (DCF Inter Frame Spacing) per class, (iv) Adjusting all the three schemes proposed above simultaneously.
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paper_title: Analysis of the contention access period of IEEE 802.15.4 MAC

paper_content:

The recent ratification of IEEE 802.15.4 PHY-MAC specifications for low-rate wireless personal area networks represents a significant milestone in promoting deployment of wireless sensor networks (WSNs) for a variety of commercial uses. The 15.4 specifications specifically target wireless networking among low-rate, low-power and low-cost devices that is expected to be a key market segment for a large number of WSN applications. In this article, we first analyze the performance of the contention access period specified in the IEEE 802.15.4 standard in terms of throughput and energy consumption. This analysis is facilitated by a modeling of the contention access period as nonpersistent CSMA with backoff. We show that, in certain applications in which having an inactive period in the superframe may not be desirable due to delay constraints, shutting down the radio between transmissions provides significant savings in power without significantly compromising the throughput. We also propose and analyze the performance of a modification to the specification which could be used for applications in which MAC-level acknowledgements are not used. Extensive ns-2 simulations are used to verify the analysis.
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paper_title: Resource-aware scheduled control of distributed process systems over wireless sensor networks

paper_content:

This paper presents an integrated model-based networked control and sensor scheduling framework for spatially-distributed processes modeled by parabolic PDEs controlled over a resource-constrained wireless sensor network (WSN). The framework aims to enforce closed-loop stability with minimal information transfer over the WSN. Based on an approximate finite-dimensional system that captures the dominant dynamics of the PDE, a feedback controller is initially designed together with a state observer a copy of which is embedded within each sensor. Information transfer over the WSN is reduced by embedding within the controller and the sensors a finite-dimensional model. Communication is suspended periodically for extended time periods during which the model is used by the controller to generate the necessary control action and by the observers to generate state estimates. Communication is then re-established at discrete times according to a certain scheduling strategy in which only one sensor is allowed to transmit its state estimate at a time to update the states of the models, while the rest are kept dormant. A hybrid system formulation is used to explicitly characterize the interplays between the communication rate, the sensor transmission schedule, the model uncertainty and the spatial placement of the sensors. Finally, the proposed methodology is illustrated through an application to a diffusion-reaction process example.
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paper_title: An Efficient Analysis for Reliable Data Transmission in Wireless Sensor Network

paper_content:

Ubiquitous technology through sensor networks is being applied to numerous industrial fields specially to increase the quality of human life (QoL). Therefore, Wireless Sensor Networks (WSNs) lossless data is one of the communications challenges to provide accurate data. Although, end-to-end data retransmission has evolved as a reliable transportation in Internet, this method is not applicable to WSNs due to the lack of reliability of wireless link and resource constraints in sensor nodes. In our previous paper, we proposed a reliable data transfer using path-reliability and implicit ACK called RTOD on WSN. However, path reliability calculation components such as RSSI, channel error rate, number of transmission in RTOD method have not been studied thoroughly. In this paper, we analysis path reliability components and simulate by using NS-2. Moreover, we propose limited number of transmission method (LTM) for WSNs. Proposed scheme shows average 4.1% fault tolerance.
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paper_title: Distributed Activity Recognition with Fuzzy-Enabled Wireless Sensor Networks

paper_content:

Wireless sensor nodes can act as distributed detectors for recognizing activities online, with the final goal of assisting the users in their working environment. We propose an activity recognition architecture based on fuzzy logic, through which multiple nodes collaborate to produce a reliable recognition result from unreliable sensor data. As an extension to the normal fuzzy inference, we incorporate temporal order knowledge of the sequences of operations involved in the activities. The performance evaluation is based on experimental data from a car assembly trial. The average recognition accuracy is 93.53\%. We also present early experiences with implementing the recognition system on sensor nodes. The results show that the algorithms can run online, with execution times less than 40ms for the whole recognition chain and memory overhead in the order of 1.5kB RAM.
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paper_title: Building Automation Systems Using Wireless Sensor Networks: Radio Characteristics and Energy Efficient Communication Protocols

paper_content:

Building automation systems (BAS) are typically used to monitor and control heating, ventila- tion, and air conditioning (HVAC) systems, manage building facilities (e.g., lighting, safety, and security), and automate meter reading. In recent years, the technology of wireless sensor network (WSN) has been at- tracting extensive research and development efforts to replace the traditional wired solutions for BAS. Key challenges of integrating WSN to a BAS include characterizing the radio features of BAS environments, and fulfilling the requirements of the extremely low energy consumption. In this survey paper, we first describe the radio characteristics of indoor environments, and then introduce the important medium access control (MAC) protocols developed for WSN which can be potentially used in BAS systems.
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paper_title: An Analytical Model for Evaluating IEEE 802.15.4 CSMA/CA Protocol in Low-Rate Wireless Application

paper_content:

The IEEE 802.15.4/ZigBee is developed to meet the needs in wireless personal area networks by adopting CSMA/CA algorithm as the retransfer mechanism after the collision occurred. But existed evaluation for 802.15.4 mainly bases on simulation and the only few existed mathematical models are either developed immaturely or based on inaccurate assumption, thus failing to meet the rapid evolution and increasing complexity for low-rate wireless applications such as wireless sensor networks (WSN). Therefore, to evaluate the performance of 802.15.4 protocol and better utilize its strength for low-data-rate wireless application, this paper presents an accurate two- dimensional discrete Markov chain model for evaluating the 802.15.4 CSMA/CA mechanism, focusing on the analysis of relationship between throughput and related parameters. By building a Markov chain for the backoff counter, computing the stable distribution probability and success transmission probability in channel collision, this paper finally gives the throughput and energy consumption formula. In the experimental part, we use ns2 simulator to evaluate the performance of 802.15.4 at the 2.4 GHz scale under different circumstances and the final performance well validates our theoretical conclusion. Considering the former work mainly bases on simulation and existing models lack accuracy, our theory and simulation combined analytical model is both novel and valuable.
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paper_title: Wireless sensor networks for structure health monitoring: recent advances and future research directions

paper_content:

Purpose – The purpose of this paper is to provide a contemporary look at the current state‐of‐the‐art in wireless sensor networks (WSNs) for structure health monitoring (SHM) applications and discuss the still‐open research issues in this field and, hence, to make the decision‐making process more effective and direct.Design/methodology/approach – This paper presents a comprehensive review of WSNs for SHM. It also introduces research challenges, opportunities, existing and potential applications. Network architecture and the state‐of‐the‐art wireless sensor communication technologies and standards are explained. Hardware and software of the existing systems are also clarified.Findings – Existing applications and systems are presented along with their advantages and disadvantages. A comparison landscape and open research issues are also presented.Originality/value – The paper presents a comprehensive and recent review of WSN systems for SHM applications along with open research issues.
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paper_title: A Novel MAC Protocol for Event-Based Wireless Sensor Networks: Improving the Collective QoS

paper_content:

WSNs usually combine periodic readings with messages generated by unexpected events. When an event is detected by a group of sensors, several notification messages are sent simultaneously to the sink, resulting in sporadic increases of the network load. Additionally, these messages sometimes require a lower latency and higher reliability as they can be associated to emergency situations. Current MAC protocols for WSNs are not able to react rapidly to these sporadic changes on the traffic load, mainly due to the duty cycle operation, adopted to save energy in the sensor nodes, resulting in message losses or high delays that compromise the event detection at sink. In this work, two main contributions are provided: first, the collective QoS definitions are applied to measure event detection capabilities and second, a novel traffic-aware Low Power Listening MAC to improve the network response to sporadic changes in the traffic load is presented. Results show that the collective QoS in terms of collective throughput, latency and reliability are improved maintaining a low energy consumption at each individual sensor node.
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paper_title: Analysis of the contention access period of IEEE 802.15.4 MAC

paper_content:

The recent ratification of IEEE 802.15.4 PHY-MAC specifications for low-rate wireless personal area networks represents a significant milestone in promoting deployment of wireless sensor networks (WSNs) for a variety of commercial uses. The 15.4 specifications specifically target wireless networking among low-rate, low-power and low-cost devices that is expected to be a key market segment for a large number of WSN applications. In this article, we first analyze the performance of the contention access period specified in the IEEE 802.15.4 standard in terms of throughput and energy consumption. This analysis is facilitated by a modeling of the contention access period as nonpersistent CSMA with backoff. We show that, in certain applications in which having an inactive period in the superframe may not be desirable due to delay constraints, shutting down the radio between transmissions provides significant savings in power without significantly compromising the throughput. We also propose and analyze the performance of a modification to the specification which could be used for applications in which MAC-level acknowledgements are not used. Extensive ns-2 simulations are used to verify the analysis.
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paper_title: Performance modeling and analysis of IEEE 802.15.4 slotted CSMA/CA protocol with ACK mode

paper_content:

Abstract In this paper, we propose an analytic model to analyze a wireless sensor network (WSN) operating the IEEE 802.15.4 slotted CSMA/CA protocol with ACK mode. Based on the renewal approximation for the data frame transmission process, we first develop an analytic model for a homogeneous WSN where all nodes in the network have the same traffic characteristic. Using our analytical model, we obtain performance metrics such as network throughput, average service time for successful transmissions, the transmission success probability, the frame dropping probability due to transmission failures, and the frame dropping probability due to CCA failures. Through numerical studies and simulations, we validate our analytic model.
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paper_title: Modeling and analysis of IEEE 802.15.4 CSMA/CA with sleep mode enabled

paper_content:

According to the widely used IEEE 802.15.4, one of the most effective ways to reduce the power consumption of sensor nodes is to enable the optional sleep mode by radio shutdown. In this paper, we propose an extended Markov-based analytical model for IEEE 802.15.4 slotted carrier sense multiple access/collision avoidance (CSMA/CA) algorithm considering the newly enabled sleep mode. For taking account of the active/sleep transitions in our model, we particularly analyze the impact of duty cycle on throughput and power consumption. Moreover, some discussion based on the numerical results of the model is carried out for further understanding. It is showed that the results given by our model have an accurate match with the simulations, and the impacts of the sleep mode on IEEE 802.15.4 can be studied by the model well.
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paper_title: An Analytical Model for Evaluating IEEE 802.15.4 CSMA/CA Protocol in Low-Rate Wireless Application

paper_content:

The IEEE 802.15.4/ZigBee is developed to meet the needs in wireless personal area networks by adopting CSMA/CA algorithm as the retransfer mechanism after the collision occurred. But existed evaluation for 802.15.4 mainly bases on simulation and the only few existed mathematical models are either developed immaturely or based on inaccurate assumption, thus failing to meet the rapid evolution and increasing complexity for low-rate wireless applications such as wireless sensor networks (WSN). Therefore, to evaluate the performance of 802.15.4 protocol and better utilize its strength for low-data-rate wireless application, this paper presents an accurate two- dimensional discrete Markov chain model for evaluating the 802.15.4 CSMA/CA mechanism, focusing on the analysis of relationship between throughput and related parameters. By building a Markov chain for the backoff counter, computing the stable distribution probability and success transmission probability in channel collision, this paper finally gives the throughput and energy consumption formula. In the experimental part, we use ns2 simulator to evaluate the performance of 802.15.4 at the 2.4 GHz scale under different circumstances and the final performance well validates our theoretical conclusion. Considering the former work mainly bases on simulation and existing models lack accuracy, our theory and simulation combined analytical model is both novel and valuable.
---
paper_title: Improving the IEEE 802.15.4 Slotted CSMA/CA MAC for Time-Critical Events in Wireless Sensor Networks

paper_content:

In beacon-enabled mode, IEEE 802.15.4 is ruled by the slotted CSMA/CA Medium Access Control (MAC) protocol. The standard slotted CSMA/CA mechanism does not provide any means of differentiated services to improve the quality of service for timecritical events (such as alarms, time slot reservation, PAN management messages etc.). In this paper, we present and discuss practical service differentiation mechanisms to improve the performance of slotted CSMA/CA for time-critical events, with only minor add-ons to the protocol. The contribution of our proposal is more practical than theoretical since our initial requirement is to leave the original algorithm of the slotted CSMA/CA unchanged, but rather tuning its parameters adequately according to the criticality of the messages. We present a simulation study based on an accurate model of the IEEE 802.15.4 MAC protocol, to evaluate the differentiated service strategies. Four scenarios with different settings of the slotted CSMA/CA parameters are defined. Each scenario is evaluated for FIFO and Priority Queuing. The impact of the hiddennode problem is also analyzed, and a solution to mitigate it is proposed.
---
paper_title: Performance Evaluation of IEEE 802.15.4 MAC with Different Backoff Ranges in Wireless Sensor Networks

paper_content:

The IEEE 802.15.4 MAC (Medium Access Control) is a protocol used in many applications including the wireless sensor network. Yet the IEEE 802.15.4 MAC layer cannot support different throughput performance for individual nodes with the current specifications. However, if certain nodes are sending data more frequently compared to others, with the standard MAC, it is hard to achieve network efficiency. Therefore, we modified the IEEE 802.15.4 MAC and additionally proposed a new State Transition Scheme. By adjusting the minBE value of some nodes to a smaller value and by dynamically changing the value depending on the transmission conditions, we shortened the backoff delay of nodes with frequent transmission. It was observed through our simulations that the throughput of the node with a lower minBE value increased significantly, compared to nodes with the original BE range of 3 to 5. Also by the use of the State Transition Scheme the total network efficiency increased leading to increase in throughput performance.
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paper_title: Adaptive backoff exponent algorithm for zigbee (IEEE 802.15.4)

paper_content:

The IEEE 802.15.4 is a new wireless personal area network standard designed for wireless monitoring and control applications. In this paper a study of the backoff exponent (BE) management in CSMA-CA for 802.15.4 is conducted. The BEs determine the number of backoff periods the device shall wait before accessing the channel. The power consumption requirements make CSMA-CA use fewer Bes which increase the probability of devices choosing identical Bes and as a result wait for the same number of backoff periods in some cases. This inefficiency degrades system performance at congestion scenarios, by bringing in more collisions. This paper addresses the problem by proposing an efficient management of Bes based on a decision criterion. As a result of the implementation potential packet collisions with other devices are restricted. The results of NS-2 simulations indicate an overall improvement in effective data bandwidth, validating our claim.
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paper_title: Priority-Based Service-Differentiation Scheme for IEEE 802.15.4 Sensor Networks in Nonsaturation Environments

paper_content:

In this paper, we propose two mechanisms, i.e., 1) backoff exponent differentiation (BED) and 2) contention window differentiation (CWD), to provide multilevel differentiated services for IEEE 802.15.4 sensor networks. The beacon-enabled mode with the slotted carrier-sense multiple-access mechanism with collision avoidance (CSMA/CA) algorithm is considered for nonsaturation. A mathematical model based on a discrete-time Markov chain is presented and analyzed to measure the performance of the proposed mechanisms. Numerical results show the effects of varying parameters. It shows that BED is better for service differentiation and channel utilization, regardless of the number of devices and the packet-arrival rate. It also shows that the throughput depends on the backoff exponent (BE), contention window (CW), and packet size and that the relative delay for successfully transmitted packets for BED is longer than that for CWD, which enables a higher relative gain for CWD. In addition, we obtain the number of unit backoff periods required to process all of the head packets of devices. Based on the numerical results, we obtain a criterion that provides guidelines for choosing a mechanism that is suitable for the objective function and determining the optimal length of the superframe to process the packets in the system.
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paper_title: Priority-based delay mitigation for event-monitoring IEEE 802.15.4 LR-WPANs

paper_content:

IEEE 802.15.4 slotted carrier-sense multiple access with collision avoidance (CSMA-CA) adopts periodic sleeping for energy efficiency support. However, such a periodic sleeping mechanism, especially with contention-based medium access, tends to cause additional sleep delay due to heavy contention. In this letter, we propose a priority-based scheme, comprising frame tailoring and priority toning, in order to relax such a problematic delay and guarantee time-bounded delivery of high priority packets in event-monitoring networks.
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paper_title: An implicit GTS allocation mechanism in IEEE 802.15.4 for time-sensitive wireless sensor networks: theory and practice

paper_content:

Timeliness guarantee is an important feature of the recently standardized IEEE 802.15.4 protocol, turning it quite appealing for Wireless Sensor Network (WSN) applications under timing constraints. When operating in beacon-enabled mode, this protocol allows nodes with real-time requirements to allocate Guaranteed Time Slots (GTS) in the contention-free period. The protocol natively supports explicit GTS allocation, i.e. a node allocates a number of time slots in each superframe for exclusive use. The limitation of this explicit GTS allocation is that GTS resources may quickly disappear, since a maximum of seven GTSs can be allocated in each superframe, preventing other nodes to benefit from guaranteed service. Moreover, the GTS may be underutilized, resulting in wasted bandwidth. To overcome these limitations, this paper proposes i-GAME, an implicit GTS Allocation Mechanism in beacon-enabled IEEE 802.15.4 networks. The allocation is based on implicit GTS allocation requests, taking into account the traffic specifications and the delay requirements of the flows. The i-GAME approach enables the use of one GTS by multiple nodes, still guaranteeing that all their (delay, bandwidth) requirements are satisfied. For that purpose, we propose an admission control algorithm that enables to decide whether to accept a new GTS allocation request or not, based not only on the remaining time slots, but also on the traffic specifications of the flows, their delay requirements and the available bandwidth resources. We show that our approach improves the bandwidth utilization as compared to the native explicit allocation mechanism defined in the IEEE 802.15.4 standard. We also present some practical considerations for the implementation of i-GAME, ensuring backward compatibility with the IEEE 801.5.4 standard with only minor add-ons. Finally, an experimental evaluation on a real system that validates our theoretical analysis and demonstrates the implementation of i-GAME is also presented.
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paper_title: An Adaptive GTS Allocation Scheme for IEEE 802.15.4

paper_content:

IEEE 802.15.4 is a new standard uniquely designed for low-rate wireless personal area networks. It targets ultralow complexity, cost, and power for low-rate wireless connectivity among inexpensive, portable, and moving devices. IEEE 802.15.4 provides a guaranteed time slot (GTS) mechanism to allocate a specific duration within a superframe for time-critical transmissions. This paper proposes an adaptive GTS allocation (AGA) scheme for IEEE 802.15.4, which considers low latency and fairness. The scheme is designed based on the existing IEEE 802.15.4 medium access control protocol, and IEEE 802.15.4 devices can receive this AGA service without any modification. A simulation model and an analytical model are developed to investigate the performance of our AGA scheme. The numerical results show that the proposed scheme significantly outperforms the existing IEEE 802.15.4 implementation.
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paper_title: Adaptive polling algorithm for PCF mode of IEEE 802.11 wireless LANs

paper_content:

An adaptive PCF polling algorithm based on recent polling feedback is proposed to improve the medium utilisation rate of IEEE 802.11 wireless LANs. It is compatible with the IEEE 802.11 standard and requires a simple extension. Simulation studies show that the PCF performance can be improved in terms of the successful poll rate and the aggregate throughput.
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paper_title: An implicit GTS allocation mechanism in IEEE 802.15.4 for time-sensitive wireless sensor networks: theory and practice

paper_content:

Timeliness guarantee is an important feature of the recently standardized IEEE 802.15.4 protocol, turning it quite appealing for Wireless Sensor Network (WSN) applications under timing constraints. When operating in beacon-enabled mode, this protocol allows nodes with real-time requirements to allocate Guaranteed Time Slots (GTS) in the contention-free period. The protocol natively supports explicit GTS allocation, i.e. a node allocates a number of time slots in each superframe for exclusive use. The limitation of this explicit GTS allocation is that GTS resources may quickly disappear, since a maximum of seven GTSs can be allocated in each superframe, preventing other nodes to benefit from guaranteed service. Moreover, the GTS may be underutilized, resulting in wasted bandwidth. To overcome these limitations, this paper proposes i-GAME, an implicit GTS Allocation Mechanism in beacon-enabled IEEE 802.15.4 networks. The allocation is based on implicit GTS allocation requests, taking into account the traffic specifications and the delay requirements of the flows. The i-GAME approach enables the use of one GTS by multiple nodes, still guaranteeing that all their (delay, bandwidth) requirements are satisfied. For that purpose, we propose an admission control algorithm that enables to decide whether to accept a new GTS allocation request or not, based not only on the remaining time slots, but also on the traffic specifications of the flows, their delay requirements and the available bandwidth resources. We show that our approach improves the bandwidth utilization as compared to the native explicit allocation mechanism defined in the IEEE 802.15.4 standard. We also present some practical considerations for the implementation of i-GAME, ensuring backward compatibility with the IEEE 801.5.4 standard with only minor add-ons. Finally, an experimental evaluation on a real system that validates our theoretical analysis and demonstrates the implementation of i-GAME is also presented.
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paper_title: Guaranteeing Real-Time Services for Industrial Wireless Sensor Networks With IEEE 802.15.4

paper_content:

Industrial applications of wireless sensor networks require timeliness in exchanging messages among nodes. Although IEEE 802.15.4 provides a superframe structure for real-time communication, a real-time message-scheduling algorithm is still required to schedule a large number of real-time messages to meet their timing constraints. We propose a distance-constrained real-time offline message-scheduling algorithm which generates the standard specific parameters such as beacon order, superframe order, and guaranteed-time-slot information and allocates each periodic real-time message to superframe slots for a given message set. The proposed scheduling algorithm is evaluated and analyzed extensively through simulations. In addition, a guaranteed time service is implemented in a typical industrial sensor node platform with a well-known IEEE 802.15.4-compliant transceiver CC2420 and ATmega128L to verify the feasibility of the guaranteed time service with the schedule generated by the proposed scheduling algorithm. Through experiments, we prove that the real system runs accurately according to the schedule calculated by the proposed algorithm.
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paper_title: An Optimization-Based GTS Allocation Scheme for IEEE 802.15.4 MAC with Application to Wireless Body-Area Sensor Networks

paper_content:

IEEE 802.15.4 standard is widely used in wireless personal area networks (WPANs). This standard supports a limited number of guaranteed time slots (GTSs) for time-critical or delay-sensitive data transmission.We propose a GTS allocation scheme to improve reliability and bandwidth utilization in IEEE 802.15.4-based wireless body area sensor networks (WiBaSe-Nets). A knapsack problem is formulated to obtain optimal GTS allocation such that a minimum bandwidth requirement is satisfied for the sensor devices. Simulation results show that the proposed scheme can achieve better GTS utilization and higher packet delivery ratio than the standard IEEE 802.15.4 scheme does.
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paper_title: Body Area Sensor Networks: Challenges and Opportunities

paper_content:

Body area sensors can enable novel applications in and beyond healthcare, but research must address obstacles such as size, cost, compatibility, and perceived value before networks that use such sensors can become widespread.
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paper_title: An optimal GTS scheduling algorithm for time-sensitive transactions in IEEE 802.15.4 networks

paper_content:

IEEE 802.15.4 is a new enabling standard for low-rate wireless personal area networks and has been widely accepted as a de facto standard for wireless sensor networking. While primary motivations behind 802.15.4 are low power and low cost wireless communications, the standard also supports time and rate sensitive applications because of its ability to operate in TDMA access modes. The TDMA mode of operation is supported via the Guaranteed Time Slot (GTS) feature of the standard. In a beacon-enabled network topology, the Personal Area Network (PAN) coordinator reserves and assigns the GTS to applications on a first-come-first-served (FCFS) basis in response to requests from wireless sensor nodes. This fixed FCFS scheduling service offered by the standard may not satisfy the time constraints of time-sensitive transactions with delay deadlines. Such operating scenarios often arise in wireless video surveillance and target detection applications running on sensor networks. In this paper, we design an optimal work-conserving scheduling algorithm for meeting the delay constraints of time-sensitive transactions and show that the proposed algorithm outperforms the existing scheduling model specified in IEEE 802.15.4.
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paper_title: A comprehensive simulation study of slotted CSMA/CA for IEEE 802.15.4 wireless sensor networks

paper_content:

In this paper, we analyze the performance limits of the slotted CSMA/CA mechanism of IEEE 802.15.4 in the beacon-enabled mode for broadcast transmissions in WSNs. The motivation for evaluating the beacon-enabled mode is due to its flexibility for WSN applications as compared to the non-beacon enabled mode. Our analysis is based on an accurate simulation model of the slotted CSMA/CA mechanism on top of a realistic physical layer, with respect to the IEEE 802.15.4 standard specification. The performance of the slotted CSMA/CA is evaluated and analyzed for different network settings to understand the impact of the protocol attributes (superframe order, beacon order and backoff exponent) on the network performance, namely in terms of throughput (S), average delay (D) and probability of success (Ps). We introduce the concept of utility (U) as a combination of two or more metrics, to determine the best offered load range for an optimal behavior of the network. We show that the optimal network performance using slotted CSMA/CA occurs in the range of 35% to 60% with respect to an utility function proportional to the network throughput (S) divided by the average delay (D).
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paper_title: Evaluating IEEE 802.15.4 for Cyber-Physical Systems

paper_content:

With rapid advancements in sensing, networking, and computing technologies, recent years have witnessed the emergence of cyber-physical systems (CPS) in a broad range of application domains. CPS is a new class of engineered systems that features the integration of computation, communications, and control. In contrast to general-purpose computing systems, many cyber-physical applications are safety critical. These applications impose considerable requirements on quality of service (QoS) of the employed networking infrastruture. Since IEEE 802.15.4 has been widely considered as a suitable protocol for CPS over wireless sensor and actuator networks, it is of vital importance to evaluate its performance extensively. Serving for this purpose, this paper will analyze the performance of IEEE 802.15.4 standard operating in different modes respectively. Extensive simulations have been conducted to examine how network QoS will be impacted by some critical parameters. The results are presented and analyzed, which provide some useful insights for network parameter configuration and optimization for CPS design.
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paper_title: PECAP: Priority-Based Delay Alleviation Algorithm for IEEE 802.15.4 Beacon-Enabled Networks

paper_content:

A new priority-based algorithm for IEEE 802.15.4 beacon-enabled networks is proposed in order to alleviate an end-to-end delay while maintaining energy efficiency. In this paper, the active period is temporally increased to reduce the sleep delay that makes up a large portion of the end-to-end delay. Nodes having high-priority packets request the coordinator to execute an extended contention access period by sending a priority toning signal. The simulation results show that the proposed algorithm alleviates the end-to-end delay of high priority packets.
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Title: A Survey of Adaptive and Real-Time Protocols Based on IEEE 802.15.4

Section 1: Introduction
Description 1: Introduce the deployment of Wireless Sensor Networks (WSNs) using IEEE 802.15.4, its limitations, and the requirements for adaptive and real-time protocols.

Section 2: Overview of IEEE 802.15.4 Medium Access Control
Description 2: Provide an overview of the IEEE 802.15.4 standard, including channel access methods, superframe structure, CSMA/CA algorithm, and GTS mechanism.

Section 3: Approaches for Contention Access Period
Description 3: Discuss approaches to improve network efficiency during the contention access period, highlighting mechanisms such as adaptive backoff exponent, adaptive contention window, and other CSMA/CA-based solutions.

Section 4: Approaches for Contention-Free Period
Description 4: Examine strategies for enhancing the performance of the GTS mechanism during the contention-free period, including adaptive GTS allocation, implicit allocation mechanism, knapsack algorithm, and GTS scheduling algorithm.

Section 5: Cross-Period Approaches
Description 5: Explore approaches that dynamically adjust the length of CAP or CFP based on operating conditions, including the setting of BO and SO parameters and strategies for handling different traffic loads.

Section 6: Conclusions
Description 6: Summarize the limitations of the original IEEE 802.15.4 MAC protocols and review the various adaptive and real-time protocols discussed, highlighting the existing challenges and future research directions.