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Data over Power Line Operations
Published in Gilbert Held, Understanding Broadband over Power Line, 2016
The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) network protocol represents a layer 2 protocol that controls access to a network. Under CSMA/CA, collision avoidance is used to improve the performance of the network by attempting to reserve its use at a particular point in time to a single device. To do so, it employs a carrier-sensing scheme in which the modulation of data on the network indicates that the network is in use. A device that has data to transmit would first listen to the network. If no carrier is sensed, this would indicate that there is no activity on the network. Then, the device with data to transmit would transmit a jam signal to indicate to other devices that it intends to transmit. After waiting a sufficient period of time for all other devices on the network to receive the jam signal, the device with data to transmit would then begin its transmission. While transmitting, if the device detects the presence of a jam signal issued by another device, it will cease transmission for a random period of time and then repeat the previously described process.
Local Area Networks
Published in Jerry D. Gibson, The Communications Handbook, 2018
Wireless LANs use a common radio channel to provide LAN connectivity without any physical wiring. Protocols for wireless LANs include the IEEE 802.11 standard. One might consider the use of a CSMA/CD protocol in this environment. However, it is not possible to implement the collision detection (CD) part of CSMA/CD in a radio environment. Therefore, a modified protocol known as CSMA/CA is used. CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance. In this variant on CSMA, a station requests permission from a station it wishes to transmit to.
Context-aware Hybrid Adaptive Beaconing for Driver Behavior Dissemination in VANETs
Published in IETE Journal of Research, 2021
Rishu Chhabra, C. Rama Krishna, Seema Verma
With the proliferation in the count of automobiles and improvement in road infrastructure across the globe, to facilitate easy and fast movement of people and goods; a major challenge exists for the transportation systems to improve traffic safety and comfort. Intelligent Transportation Systems (ITS) is one of the major applications of VANET which comprises of Vehicle-to-Vehicle (V2V) communication and Vehicle-to-Infrastructure (V2I) communications. ITS primarily aims at making transportation safe, smart and coordinated. To achieve this, enhancement of IEEE 802.11 standard has been introduced as IEEE 802.11p. In order to support Wireless Access in Vehicular Environments (WAVE), IEEE 802.11p provides enhancements in PHY and MAC layer [1]. It acquires the PHY layer features from 802.11a. However, it reduces the transmission rate and limits the bandwidth from 20 MHz to 10 MHz [2]. In order to support different applications and contention-based differentiated channel access, VANET uses IEEE 802.11e based EDCA mechanism at the MAC layer. It depends on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) with Binary Exponential Backoff for contention-based channel access [3].
A directional multicasting-based architecture for wireless sensor networks
Published in International Journal of Electronics, 2019
At the discovery phase, each node broadcasts its position and identity information by using a contention-based MAC protocol such as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) which IEEE 802.11 (Editors of IEEE, 1997) and 802.15.4 (IEEE Std. 802.15.4-2003, 2003) mainly based on Campolo, Molinaro, Casetti, and Chiasserini (2009) and Zhu, Li, and Liu (2014). Once a node captures the channel as a result of contention, it starts broadcasting by generating the main lobe in Beam 1direction and continues to sweep all the directions counter-clockwise till the starting point. The sweeping method (Korakis et al., 2008) is one of the prominent methods presented in the literature to mitigate the deafness problem. Since the nodes in the directional neighborhood of node1 are unaware of the desired beam direction that the broadcast will take place on, they should be informed by means of traveling every direction in a counter-clockwise manner. In the topology presented in Figure 9, N1 is assumed to capture the channel and starts the broadcasting process on Beam1 and continues with sweeping through all the beams. Nodes further apart than rd (directional coverage range) will not get these broadcast signals such as N6. Nodes N2, N3, N4, and N5, which are waiting in the omnidirectional mode, successfully receive the signals since their distances to N1 is lower than rd.
A flexible and adaptive medium access control protocol for improving quality of service in vehicular ad-hoc networks
Published in International Journal of Computers and Applications, 2022
Yani-Athmane Bennai, Samira Yessad, Louiza Bouallouche-Medjkoune
In 1609.4; the MAC protocol proposed in the IEEE WAVE stack; channel time is divided into periodic segments of 100 ms, and each segment is itself divided into two intervals of 50 ms each (CCH and SCH), a time period named guard is added at the beginning of each interval to solve the desynchronization problem between nodes, its duration varies between 4 ms and 6 ms [9] (see Figure 3). The 1609.4 MAC protocol uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) [10], when a node has data to transmit, it starts by listening to the channel, if it is free, it sends its data, else, the node will have to execute the backoff procedure before trying to transmit again [11,12].