Question

Briefly describe channel probing in MAC protocols (PAMAS MAC protocol). List disadvantages.

Answer 1

Channel Probing:

The PAMAS(Power Aware Medium access protocol and Signaling )  in which the nodes that are not actively transmitting or receiving power off by themselves. The approach requires the nodes to use two separate channels for control and data.

The control channel is utilized for handshaking whereas the  data channel is used for regular traffic. Using two channels minimizes the potential and rate of collisions. A node senses the data channel medium and correspondingly responds to requests only if its adjacent nodes are not trans-receiving

Senders that cannot establish a connection turn  to sleep mode . The duration of a node stay in the sleep mode is determined based on the exchange of special probe messages on the control channel among nodes in closest.  

This technique has cost saving of upto 70% because nodes which are powered off by themselves don't participate in other processes

Disadvantages :

1)This  protocol requires the nodes to have two separate channels a)Control and B) For Data , which requires two mediums at each node thus increasing overall  cost and size.

2) Protocol requires the nodes to sense the medium to transmit and does not eliminate or avoid collisions completely.