Zebra Media Access Control
Zebra Media Access Control ( Z-MAC , " Zebra Media Access Control ") is a network protocol for sensor networks . As Media Access Control (MAC) it controls the access to the common communication medium of the network.
Network protocols define down to the smallest detail how the computers in a computer network exchange data with one another. Sensor networks consist of tiny, wirelessly communicating sensor nodes that are deployed in large numbers in an area, network independently and monitor their surroundings in group work with sensors until their energy reserves are exhausted. They thus form a special form of the mobile ad hoc network and place completely different requirements on a network protocol than, for example, the Internet.
Z-MAC was introduced in 2005 by Injong Rhee, Ajit Warrier, Mahesh Aia, and Jeongki Min of North Carolina State University . The protocol is in the tradition of the S-MAC , T-MAC , DSMAC , WiseMac , μ-MAC and M-MAC protocols , both in terms of name and content . The origin of the name is unclear; a substantive or metaphorical connection to the zebra does not seem to exist, possibly zebra was only chosen as the pronunciation of the letter Z according to the English spelling table.
Protocol structure
Z-MAC combines the two approaches Carrier Sense Multiple Access (CSMA) and Time Division Multiple Access (TDMA) in such a way that the network behaves as with CSMA when the data load is low and as with TDMA when there is high network traffic.
The protocol begins with a setup phase, in which the following four steps are carried out in succession: setting up the network topology , distributing the time slots , exchanging local time frames and network-wide synchronization . This initialization causes a high network load, which from the developers' point of view is compensated for by a long operating time and efficient data transmission.
Structure of the network topology
Once activated, each sensor node will send a ping every second for 30 seconds . In network technology, pings are short messages that are sent from the sender to the recipient and immediately back again. They are usually used to check connection and line quality. In the case of Z-MAC, the ping contains information about the sending node itself and all information that the node has previously collected about its direct neighbors. By pinging its surroundings, a sensor node learns which nodes it can contact directly (one- hop neighborhood) and which it can contact indirectly with an intermediate station (two-hop neighborhood).
Distribution of the time slots
The neighborhood lists are fed into an algorithm for allocating the time slots in accordance with TDMA. The developers used the DRAND distributed algorithm . This algorithm ensures that no two indirect neighbors get the same time slot.
swell
- ^ I. Rhee, A. Warrier, M. Aia, J. Min: ZMAC: A Hybrid MAC for Wireless Sensor Networks. Technical Report, Department of Computer Science, North Carolina State University, April 2005.