Carrier Sense Multiple Access With Collision Avoidance Research Articles

A priority based energy harvesting scheme for charging embedded sensor nodes in wireless body area networks.

This research work proposes a novel priority aware schedule based charging algorithm that uses wireless power transfer (WPT) technique in order to charge embedded sensor nodes (SNs) in a wireless body area network (WBAN). Implanted sensor nodes in WBANs require energy for both information extraction and data transmission to the remote controller unit. Thus, energy shortage of these SNs deteriorates due to the data transmission process of the patient health monitoring system. However, continuous operation by means of electromagnetic induction for energy harvesting, obtained from ambient sources, reduces the overall efficiency of the primary unit. With this paradigm in sight, an algorithm demonstrating the modeling of a priority-based mechanism is proposed in order to ensure proper sensor voltage level and to reduce the transmission losses. Medium access control (MAC) protocols are used for inductive powering from the primary unit to the secondary unit in a collision-free centralized scheduling scheme. Therefore, the proposed wireless charging algorithm for implanted SNs in WBAN is designed as per carrier sense multiple access with collision avoidance (CSMA/CA) technique. Because of this, the overall power consumption of SNs for certain operation periods, successful charging probabilities for multiple SNs, and instantaneous power requirements are considered as key performance measures of analysis. It is assumed that proper energy storage in both transmitters and receivers can handle channel interference and traffic contention. Simulation results verify that a significant reduction in power consumption for the proposed priority aware algorithm will maintain almost similar output. For this reason, saturating class—C as well as class—E driver circuits have been used to justify the performance in two different circuit topologies. Effects of priority with respect to the full charge period have also been observed for the multi-node system. Furthermore, from performance analysis, it has been demonstrated that the scheduling scheme causes both single MOSFET composed saturating class—C and Lchoke modeled class—E associated driver circuits to be considerably more loss efficient than corresponding existing ones.

Cognitive backoff mechanism for IEEE802.11ax high-efficiency WLANs

Carrier sense multiple access with collision avoidance(CSMA/CA) in current IEEE 802.11 wireless local area networks (WLANs) uses a uniformly distributed binary exponential backoff (BEB) mechanism that is mainly based upon exponential increases of the contention window (CW) to avoid repeated collisions. After each consecutive collision, the CW is doubled until it reaches the maximum value. Under dense conditions, however, the blind selection of the CW greatly reduces throughput, whereas under sparse conditions with smaller number of contending stations, the blind exponential increase of the CW for collision avoidance causes unnecessarily long delays. Therefore, it fails to achieve high efficiency in both dense and sparse environments with the current BEB mechanism. In this paper, we propose a cognitive backoff (CB) mechanism that adaptively determines the CW to provide efficient collision avoidance with high throughput and low delay under both dense and sparse conditions. In the proposed CB mechanism, the measured conditional collision probability and the number of backoff stages determine the CW. A performance analysis with an event-driven simulator, NS3, reveals that the proposed CB can achieve higher throughput and lower delay than the BEB, without much implementation complexity while preserving fairness.

Performance Evaluation and Delay-Power Trade-off Analysis of ZigBee Protocol

In this paper, we analyze the superframe structure of the Medium Access Control (MAC) sublayer of IEEE 802.15.4 protocol (ZigBee), designed for Low-Rate Wireless Personal Area Networks (LR-WPANs), and evaluate the effects of the inactive portion of a superframe on average delay, and average power consumption. The four-dimensional Markov chain-based analysis of the slotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithm presented in this work considers backoff freezing and acknowledged packet transmission that are not studied in the existing works. The analytical results prove that the performance of LR-WPANs depends significantly on the length of a superframe's active portion. We introduce a variable-Superframe duration-Beacon interval Ratio (SBR), which is utilized by tuning a few MAC parameters to achieve 35 percent reduced delay, on an average, compared to the existing state of the art. The results show that the proposed model also yields improved performance in terms of power consumption, for short and medium contention windows. In addition to the proposed analysis, this work provides optimized superframe order values that achieve trade-offs between delay and power consumption as demanded by user-provided QoS requirements corresponding to different contexts.

A proposal of novel design on the WAVE MAC algorithm with low-latency for seamless video surveillance in V2X environment

This paper proposed an MAC (Media Access Control) operation method based on the CCH (Control Channel) and SCH (Service Channel) control mode of the WAVE (Wireless Access for Vehicle Environment) network in order to secure service performance sensitive to certain delays with no restriction to services pursued in the present WAVE network. The proposed method configures a new superframe for CCH and SCH frames in the WAVE network defined by IEEE Std. 1609.4 and applies TDM (Time Division Multiplexing) to the CCH frame in order to secure traffic stability and latency minimization in each terminal. CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is applied to the SCH frame in order to secure autonomy in service perspectives. Additionally, delay control is secured despite congestion among multiple terminals in V2V communication without a station RSU (Road Side Unit) since the proposed MAC operation method adopts a new CCH/SCH coordination mode for the WAVE network. The proposed method’s applicability is verified as the simulation analysis results showed satisfactory low latency performance.

A Novel Energy-Efficient Contention-Based MAC Protocol Used for OA-UWSN.

A hybrid optical-acoustic underwater wireless sensor network (OA-UWSN) was proposed to solve the problem of high-speed transmission of real-time video and images in marine information detection. This paper proposes a novel energy-efficient contention-based media access control (MAC) protocol (OA-CMAC) for the OA-UWSN. Based on optical-acoustic fusion technology, our proposed OA-CMAC combines the postponed access mechanism in carrier sense multiple access with collision avoidance (CSMA/CA) and multiplexing-based spatial division multiple access (SDMA) technology to achieve high-speed and real-time data transmission. The protocol first performs an acoustic handshake to obtain the location information of a transceiver node, ensuring that the channel is idle. Otherwise, it performs postponed access and waits for the next time slot to contend for the channel again. Then, an optical handshake is performed to detect whether the channel condition satisfies the optical transmission, and beam alignment is performed at the same time. Finally, the nodes transmit data using optical communication. If the channel conditions do not meet the requirements for optical communication, a small amount of data with high priority is transmitted through acoustic communication. An evaluation of the proposed MAC protocol was performed with OMNeT++ simulations. The results showed that when the optical handshaking success ratio was greater than 50%, compared to the O-A handshake protocol in the literature, our protocol could result in doubled throughput. Due to the low energy consumption of optical communication, the node’s lifetime is 30% longer than that of pure acoustic communication, greatly reducing the network operation cost. Therefore, it is suitable for large-scale underwater sensor networks with high loads.

PCS Threshold Selection for Spatial Reuse in High Density CSMA/CA MIMO Wireless Networks

Multiple-input multiple-out (MIMO) equipment improves the spectral efficiency of wireless local area network (WLAN) systems. However, in a large-scale or dense MIMO WLANs, overlapping radio cells or basic service sets (BSSs) are inherent. This prevents multiple concurrent transmissions and degrades spatial reuse. The inability to separate multiple simultaneous transmissions in space is detrimental to overall system performance. The carrier sense multiple access collision avoidance (CSMA/CA) protocol uses the physical carrier sensing (PCS) threshold to determine channel state at the physical layer (PHY) and decide on the number of concurrent transmissions allowed per time slot. Since the PCS threshold determines the spatial reuse under the CSMA/CA protocol, which consequently determines the interference level and the network aggregate throughput, we address PCS threshold selection for dense uplink (UL) MIMO WLAN systems. A closed-form expression is derived for selecting the PCS threshold based on the fundamental parameters of the network where nodes are randomly placed according to a Poisson point process (PPP). We obtain the PCS threshold value that maximizes the spatial density of throughput (SDT) and study the effectiveness of the proposed framework under moderate to high node density. In addition, we analyze the effect of WLAN density on interference from concurrent transmitters. The key observation is that PCS threshold selection should take into account key network characteristics including node density, target SINR or threshold, path-loss exponent and antenna configuration.

Device-to-Device Communications in Unlicensed Spectrum: Problem Identification and Performance Maximization

Device-to-device (D2D) communication is such a paradigm that anticipated to play a cabalistic role for the next-generation cellular networks especially for the 5G cellular network as it promises to extend the network coverage and offload some traffics from the cellular transceiver’s side to the user devices’ side and it may operate in both licensed and unlicensed spectra simultaneously. D2D communication in the unlicensed spectrum may facilitate the purpose of D2D communication as the licensed spectrum almost possessed. Interference is the main drawback of the unlicensed spectrum. In this paper, we propose the request-to-send/clear-to-send (RTS/CTS) mechanism with the free-to-receive (FTR)-MNAV technique to improve the performance of the D2D communication in the unlicensed spectrum. Deployment of the carrier sense multiple access with collision avoidance (CSMA/CA) protocol can alleviate interference, but collisions occur due to the hidden node problem. The integration of the RTS/CTS mechanism with the CSMA/CA protocol can minimize the hidden node problem, but the blocking and false blocking problems are introduced. The proposed scheme can reduce the blocking and false blocking problems, which improves the performance of the D2D communication in the unlicensed spectrum where neighbor nodes maintain Multiple Network Allocation Vector (MNAV) to resolve the blocking problem and broadcast the FTR control packet to the respective neighbor nodes if the transmission is completed prior to the expiration of the timer or actual communication does not take place due to any reason, thus solving the false blocking problem and improving the performance of the D2D communication in the unlicensed spectrum.

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.

Cooperative control feedback: On backoff misbehavior of CSMA/CA MAC in channel-hopping cognitive radio networks

Due to dynamic channel availability in cognitive radio networks (CRNs), rendezvous problem is known as the most challenging issue in the design of media access control (MAC) protocol, which is a key step for secondary users (SUs) to start communication. With the concept of blind rendezvous, numerous channel-hopping sequence (CHS) based rendezvous schemes have been proposed to solve this problem in these years. Currently, little attention is paid to the design of a carrier sensing multiple access/collision avoidance (CSMA/CA) MAC based on these rendezvous schemes and also the rendezvous de-synchronization problem brought by multiple rendezvous networking paradigm into MAC design. To this end, we propose a cooperative channel-hopping based CSMA/CA MAC (named CoCH-CSMA/CA MAC) which works on the top of existing CHS based rendezvous schemes. Resulting from the rendezvous de-synchronization problem, a new type of collision, named false collision, is identified. As a SU cannot discern the false collision by itself, we design a cooperative control feedback scheme which employs correlation-based signal detection to reduce the coordination overhead of cooperation and helps SUs to avoid backoff misbehavior. Moreover, we analyze the behavior of our MAC protocol and its advantage. Extensive simulations prove that the cooperative control feedback scheme can effectively alleviate the impact of rendezvous de-synchronization problem on backoff misbehavior and improve network performance.

Medium Access Control CSMA/CA Binary Countdown Protocol for SCADA Application

This paper discusses a novel approach toaccess the medium using CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocols for SCADA (Supervisory Control And Data Acquisition) system employed in power systemoperation and control. This method offers superior performance over the existing practices of accessing medium using CSMA/CD protocols. The proposal makes use of binary countdown method with modifications. The requirements of SCADA system such as reliability and real time operation can be achieved by fast data transmission and prompt delivery. In this work, a program is written and the procedure is run to allocate the channel considering the priorities of the RTUs (Remote Terminal Units) and the type of data to be transmitted such as normal data for archival and event triggered data for operation control. The program uses generic statement and is applicable to a system having a MTU (Master Terminal Unit) and any number of RTUs. The results obtained by running the procedure show its novelty. Further, a Moore finite state Moore machine is designed and a VHDL model is developed

The Relation between the Probability of Collision-Free Broadcast Transmission in a Wireless Network and the Stirling Number of the Second Kind

The broadcast performance of the 802.11 wireless protocol depends on several factors. One of the important factor is the number of nodes simultaneously contending for the shared channel. The Medium Access Control (MAC) technique of 802.11 is called the Distributed Coordination Function (DCF). DCF is a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme with binary slotted exponential backoff. A collision is the result of two or more stations transmitting simultaneously. Given the simplicity of the DCF scheme, it was adapted for Dedicated Short Range Communication (DSRC) based vehicular communication. A broadcast mechanism is used to disseminate emergency and safety related messages in a vehicular network. Emergency and safety related messages have a strict end-to-end latency of 100 ms and a Packet Delivery Ratio (PDR) of 90% and above. The PDR can be evaluated through the packet loss probability. The packet loss probability PL is given by, PL = 1 − (1−Pe)(1−PC), where Pe is the probability of channel error and PC is the probability of collision. Pe depends on several environmental and operating factors and thus cannot be improved. The only way to reduce PL is by reducing PC. Currently, expensive radio hardware are used to measure PL. Several adaptive algorithms are available to reduce PC. In this paper, we establish a closed relation between PC and the Stirling number of the second kind. Simulation results are presented and compared with the analytical model for accuracy. Our simulation results show an accuracy of 99.9% compared with the analytical model. Even on a smaller sample size, our simulation results show an accuracy of 95% and above. Based on our analytical model, vehicles can precisely estimate these real-time requirements with the least expensive hardware available. Also, once the distribution of PC and PL are known, one can precisely determine the distribution of Pe.

Framework for Cross Layer Energy Optimization in Wireless Sensor Networks

Cross-layer routing technique interacts among the various layers of the OSI model and exchanges information among them. It enhances the usage of network resources and achieves significant performance improvements in Quality of Service (QoS) parameters. The Low Energy Adaptive Clustering Hierarchy Protocol (LEACH) routing algorithm consumes higher energy due to communication overhead and thus, a hierarchical model-based routing protocol named Cross-Layer Energy Efficient Scalable-Low Energy Adaptive Clustering Hierarchy Protocol (CLEES-LEACH) is proposed. This increases scalability using the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol between the intermediary node and cluster head, with the overhead of latency. A Linear Programming model is used, which further makes use of scheduling to overcome latency. Energy efficiency and latency are addressed with the proposed cross-layer routing algorithm CLEESLEACH. The cross-layer design establishes Physical, Media Access Control (MAC), and Network layer interactions in the proposed algorithm. The present LEACH algorithm also increases the network overhead as there is no mechanism for communication among the network layer and consumes high energy. In the proposed algorithm CLEES-LEACH, latency is reduced to 25% and throughput is maximized to 20% compared to existing Energy-Efficient Distributed Schedule Based protocol (EEDS) and Integer Linear Programming (ILP) protocols. The energy consumption is also reduced to 20 % and the scalability is increased to 10 % compared to the existing LEACH and CL-LEACH protocols. These results are shown by using NS3 simulation.

An Analytical Framework for IEEE 802.15.6-Based Wireless Body Area Networks With Instantaneous Delay Constraints and Shadowing Interruptions

In this paper, a novel queueing analytical framework is proposed to evaluate the performance of IEEE 802.15.6-based carrier-sense multiple access with collision avoidance (CSMA/CA) scheduling in wireless body area networks with joint consideration of instantaneous delay constraints and body shadowing effects. Specifically, we develop an absorbing Markov chain to model the medium access process with error controls that is defined by the IEEE standard and design a random time-limited single vacation to describe the potential body shadowing interruption process. To guarantee the timeliness of received packets and avoid energy waste for transmitting valueless packets, an instantaneous delay constraint is carefully considered, which is then characterized by an overdeadline packet dropping process with a predefined waiting deadline. In our analysis, a Markovian arrival process is also adopted to capture the correlation of arrival traffic, and all other random processes are modeled by phase-type distributions, which make our framework more general and comprehensive. To address the inherent complexity of the original model, based on the transient queueing analysis, we develop a buffer-overflowing queueing principle to approximate the overdeadline packet dropping principle by solving a buffer length optimization problem. After that, we construct a multidimensional discrete-time Markov chain to analyze the stationary distribution through the matrix-geometric method. Performance measures, including the average delay, waiting time distribution, and packet transmission failure probability, are derived. The accuracy of our proposed analytical framework is validated by extensive simulations.

A Network Equivalent-Based Algorithm for Adaptive Parameter Tuning in 802.15.4 WSNs.

Previous studies have shown that in many wireless sensor network applications the IEEE 802.15.4 carrier sense multiple access with collision avoidance (CSMA/CA) mechanism with default parameters cannot guarantee the constraints of reliability, time efficiency, or energy efficiency. Although many adaptive parameter tuning algorithms have been proposed, many of them cannot correctly identify the changes of the network condition and are unable to effectively perform the parameter tuning operation. Considering the randomness that CSMA/CA brings about, for most of the proposed algorithms, it is a challenge to distinguish significant violations that were caused by actual changes of the network from the general fluctuations that were due to CSMA/CA. In this paper, we propose a lightweight algorithm called the network equivalent adaptive parameter tuning (NEAPT) algorithm. It is fully distributed and can work without any predefined information or acknowledgement. NEAPT not only takes reliability as an evaluation of a network condition, but it proposes a synthetic value, called the equivalent node number, and takes it as another reference for a network condition. Simulation results show that by taking both reliability and the equivalent node number into consideration, NEAPT can effectively identify the network changes and provide adequate and steady performances for wireless sensor networks (WSNs) in both stationary and dynamic conditions.

CSMA/CA analysis and enhancement for IEEE 802.11ax WLANs operating in STR mode

An analytical model is described to estimate the performance of the carrier sense multiple access with collision avoidance (CSMA/CA) protocol during the simultaneous transmit/receive (STR) operation of the upcoming IEEE 802.11ax amendment for WLANs. Furthermore, based on that model, an enhancement to the operation of CSMA/CA to increase its performance during the STR mode is proposed.

Hybrid MAC Protocol Design for Mobile Wireless Sensors Networks

With the rapid proliferation of mobile wireless sensors networks (WSNs), which are widely deployed in the Internet of things, the Internet of vehicles, and flying ad hoc networks, more and more researchers are making the effort to improve energy efficiency and throughput of WSNs. In recent years, many protocols have been proposed to solve the energy shortage problem. Some of the protocols are based on cooperative or allocation schemes, some are based on contending schemes, and others are based on the foundation of hybrid schemes. However, it is still difficult to improve the energy efficiency and networks throughput simultaneously. In this article, we present a novel carrier sense multiple accesscollision avoidance and time division multiple access hybrid scheme protocol medium access control (MAC) on the MAC layer to improve the throughput and reduce energy consumption at the same time for mobile WSN with position prediction algorithms in 3-D space. Compared to existing protocols, the proposed protocol can efficiently reduce the energy consumption and significantly improve the throughput, especially for high-speed mobile WSN in the many-to-one communication paradigm. Extensive simulation results prove the performance of the protocol.

Performance Analysis of LTE-LAA Network

3rd generation partnership project (3GPP) has developed 5-GHz unlicensed band long term evolution (LTE), referred to as licensed-assisted access (LAA). LAA adopts listen-before-talk (LBT) operation, resembling Wi-Fi’s carrier sense multiple access with collision avoidance (CSMA/CA), to enable collision avoidance capability. However, the frame structure overhead of each LAA downlink burst varies with the ending time of each preceding LBT operation. Given that, the existing analytic models of Wi-Fi cannot be used to evaluate the performance of LAA due to the fact that, unlike Wi-Fi, LAA frame structure overhead varies with the ending time of the preceding LBT operation. In this letter, we propose a novel Markov chain-based analytic model to cope with the variation of the LAA frame structure overhead. Comparison between analysis and simulation results shows that the difference between them is merely 0.2% on average, demonstrating the accuracy of the proposed model.

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.

Performance Analysis of CSMA/CA and PCA for Time Critical Industrial IoT Applications

Recently proposed IEEE 802.15.4-2015 MAC introduced a new prioritized contention access (PCA) for transfer of time-critical packets with lower channel access latency compared to carrier sense multiple access—collision avoidance (CSMA/CA). In this paper, we first propose a novel Markov-chain-based analytical model for unslotted CSMA/CA and PCA for industrial applications. The unslotted model is further extended to derive the analytical model for slotted CSMA/CA and PCA. Primary emphasis is laid on understanding the performance of PCA compared to CSMA/CA for different traffic classes in industrial applications. The performance analysis shows that the slotted PCA achieves a reduction of 63.3% and 97% in delay and power consumption respectively compared to slotted CSMA/CA, whereas unslotted PCA achieves a delay reduction of 53.3% and reduction of power consumption by 96% compared to unslotted CSMA/CA without any significant loss of reliability. The proposed analytical models for both slotted and unslotted IEEE 802.15.4-2015 MAC offer satisfactory performance with less than 5% error when validated using Monte Carlo simulations. Also, the performance is verified using real-time testbed.

Hybrid Multi-Channel MAC Protocol for WBANs with Inter-WBAN Interference Mitigation.

Herein, we propose a hybrid multi-channel medium access control (HM-MAC) protocol for wireless body area networks (WBANs) that mitigates inter-WBAN interference significantly. In HM-MAC, a superframe consists of a random access phase and a scheduled access phase. That is, a carrier sensing multiple access with collision avoidance (CSMA/CA) phase and a time division multiple access (TDMA) phase are included in a superframe. The random access phase allows higher-priority users to transmit data packets with low latency and high reliability. The retransmission of data packets is also performed in the random access phase. The periodic data are transmitted in the scheduled phase, resulting in no contention and high reliability. A channel selection algorithm is also proposed to avoid collision between neighboring WBANs. The HM-MAC protocol allows multiple transmissions simultaneously on different channels, resulting in high throughput and low collision. The sensor nodes update idle channels by listening to the beacon signal; consequently, the sensor nodes can change the working channel to reduce inter-WBAN interference. According to our simulation results, HM-MAC achieves a higher packet delivery ratio and higher throughput with lower energy consumption than the conventional scheme in multi-WBAN scenarios. HM-MAC also causes lower end-to-end delays for higher-priority users.