Evaluation of Slotted CSMA/CA of IEEE 802.15.4

2006

The IEEE 802.15.4 has been adopted as a communication protocol standard for Low-Rate Wireless Private Area Networks (LRWPANs). While it appears as a promising candidate solution for Wireless Sensor Networks (WSNs), its adequacy must be carefully evaluated. In this paper, we analyze the performance limits of the slotted CSMA/CA medium access control (MAC) mechanism in the beacon-enabled mode for broadcast transmissions in WSNs. The motivation for evaluating the beacon-enabled mode is due to its flexibility and potential 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), the number of nodes and the data frame size on the network performance, namely in terms of throughput (S), average delay (D) and probability of success (Ps). We also analytically evaluate the impact of the slotted CSMA/CA overheads on the saturation throughput. 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).

Lecture Notes in Computer Science, 2016

Low rate wireless applications are under attraction since last decade. For such applications, IEEE designed a standard known as IEEE 802.15.4. The standard operates at 868, 915 and 2400MHz with or without using super frame structure. Most of the low rate Wireless PAN applications follow superframe structure. A superframe structure comprises of contention based and contention free periods by offering slotted CSMA/CA and TDMA like operation respectively. This paper analyzes the performance of slotted CSMA/CA algorithm. CSMA/CA algorithm highly depends upon backoff period that is why its impact is analyzed in this work. The performance analysis is based on probability determined by using discrete markov chain model. The performance analysis comprises of nodes waiting time before transmission, channel busy probability and ultimately throughput and reliability is calculated. Results show that network reliability along with throughput of a wireless network increases gradually with the increase in backoff period at the cost of increase in average wait time of nodes.

AEU - International Journal of Electronics and Communications, 2011

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, 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.

2012 International Symposium on Telecommunication Technologies, 2012

Different Medium Access Control (MAC) Protocols for Wireless Sensor Networks (WSNs) have been proposed over the last few years. IEEE 802.15.4 MAC protocol standard is designed for low-power, low-cost, and low-rate Wireless Personal Area Networks (LR-WPANs). The contention period of IEEE 802.15.4

Here, we present the collision probability of the IEEE 802.15.4 slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) mechanism over a real-time wireless sensor network (RT-WSN), also called a synchronous network system. The “backoff,” the random delay of CSMA/CA, can be used to create a probability model and to determine the average packet delay over RT-WSN. The proposed theoretical analysis model was nearly consistent with the simulation and with experimental results. This suggests that the slotted CSMA/CA mechanism cannot be applied effectively to RT-WSN because it cannot avoid a high collision rate with RT-WSN application requirements and, therefore, may waste a great deal of system bandwidth. We found that the packet collision rate increased up to 731% compared to an ideal model with more than 10 users within an RT-WSN. Without improvements in methodology, the high collision rate makes this slotted CSMA/CA mechanism unsuitable for RT-WSN applications.

2006

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.

2006

Abstract—IEEE 802.15.4-2003 [1] was introduced to address the market need for connecting low-rate devices in a wireless personal area network (WPAN). A slotted CSMA/CA medium access control (MAC) protocol is defined in the standard to coordinate the channel access of a ...

IEEE Communications Letters, 2000

Two mechanisms are proposed to enhance throughput and energy efficiency of IEEE 802.15.4 CSMA-CA. The first one is an enhanced collision resolution (ECR) mechanism that adjusts the backoff exponent (BE) based on both consecutive clear channel assessment (CCA) busy results and a packet transmission. The second one is an enhanced backoff (EB) mechanism that shifts the range of backoff counters by utilizing the CCA outcome. The simulation results demonstrate that the proposed mechanisms significantly enhance both throughput and energy efficiency of IEEE 802.15.4. Index Terms-IEEE 802.15.4, LR-WPAN, CSMA-CA.