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Analysis and Classification of Reliable Protocols for Pervasive Wireless Sensor Networks
Published in Syed Ijlal Ali Shah, Mohammad Ilyas, Hussein T. Mouftah, Pervasive Communications Handbook, 2017
Ahmed Badi, Imad Mahgoub, Michael Slavik
The IEEE 802.11® [12] is a wireless communication MAC standard that is widely adopted. In this standard, as a condition to access the medium, the MAC layer checks the value of its network allocation vector (NAV). This is a counter resident at each node and it represents the amount of time for which the communication medium will be busy. Prior to transmitting a frame, a node calculates the amount of time necessary to send the frame based on the frame’s length and the channel’s data rate. The node places a value representing this time in the header’s duration field of the frame. When other nodes receive the frame, they examine this duration field value and use it as the basis for setting their corresponding NAVs. Before a station can attempt to send a frame, its NAV must be zero. This process reserves the medium for the sending station.
Mac Protocols in Cognitive Radio Networks
Published in Mohamed Ibnkahla, Cooperative Cognitive Radio Networks, 2018
Random access protocols in wireless LANs may use channel reservation techniques by exchanging short request-to-send (RTS) and clear-to-send (CTS) control packets before the actual data packets are sent [14]. This allows temporary channel reservation for the data packet transmission. In addition, the neighbors of the receivers (receiving CTS or RTS packets) will defer their transmissions for a duration of network allocation vector (NAV). NAV duration is estimated by each potential transmitter as the time required by the current transmitter to finish its transmission and its related acknowledgments (ACKs).
Wireless Infrared Networking
Published in Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun, Optical Wireless Communications, 2008
Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun
IEEE 802.11e has enhanced the RTS/CTS exchange scheme in IEEE 802.11 by introducing piggybacking — the possibility to attach the ACK of a previously received frame or a poll to a data frame for a specific QSTA. This procedure decreases the overhead by reducing the number of frames to be exchanged. In addition, the network allocation vector (NAV) approach to keep track of the periods that a station does not try to access the wireless medium is also used in IEEE 802.11e.
A directional multicasting-based architecture for wireless sensor networks
Published in International Journal of Electronics, 2019
In the architecture proposed, Directional Virtual Carrier Sensing based collision avoidance protocol is utilized which is inspired from the previous studies proposed in the literature such as Directional Medium Access Control Protocol (DMAC) and Angular MAC (Choudhury, Yang, Ramanathan, & Vaidya, 2002; Sundaresan et al., 2009; Ulukan & Gürbüz, 2004, 2008). As is known, in the ordinary IEEE 802.11 MAC DCF protocol an optional Request-to-Send (RTS)/Clear-to-Send (CTS) is present which is employed to mitigate the hidden and exposed terminal problems. During this handshaking and inherent neighbor notification process, a structure called Network Allocation Vector (NAV) is arranged by the neighboring nodes which identify the availability time of the communication medium. In DNAV of the neighboring nodes of the communicating pair, records are generated for each direction since there are multiple channels arising from multiple directions. A predefined reference direction is arranged usually towards 3 o’clock direction and other directions are determined by rounding counter-clockwise manner with beam-width intervals which are based on the idea of beam-switching. A similar approach is also employed in MRBA. The sender node starts sweeping operation as in the set-up phase after the arrival of the information from the network layer that defines the multi-next-relay hops. Details about the defined relay hop IDs are put in the packet and notified to all nodes in the maximal coverage range rd(beamwidthmin). Figure 10 shows the structure of a Directional RTS (DRTS) packet.