Medium access control (MAC) Layer

 Medium access control (MAC) Layer:

Medium access control (MAC) Layer
Medium access control (MAC) Layer

Medium access control (MAC) is the first protocol above the physical layer (PHY) protocol.

The basic task of MAC is to coordinate time among nodes which are accessing a common transmission channel.

Since the spectrum is restricted, the existing bandwidth for communication is also restricted.

Hence, access to this common spectrum should be controlled in such a way that all sensor nodes get an honest share of existing bandwidth and to be utilized efficiently.

In order to address the issues of WSN such as restricted bandwidth, hidden and exposed node problems, error-prone communicating channel, and power consumption a separate set of protocols is needed to control the access to the shared spectrum.

As shown in the image, MAC is a part of Data Link Layer (DLL).

The tasks get divided between MAC and logical link control (LLC). 

The MAC protocol decides the correct timing for a node to send data to access shared spectrum to another node to set of multicast or broadcast nodes.

Error control and flow control supported by L.L.C.

Error control acknowledges the correct transmission of packets and it takes correct action in case packets are lost.

Whereas flow control controls data rate transmission of the sender in order to match the speeds of the sender and receiver.

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