Randomly Addressed Polling

1. The first step is the Base Station signals readiness to all mobile terminals if not busy. 

2. The terminals ready to send can now transmit a random number without collision with the help of CDMA or FDMA. The random number can be seen as a dynamic address. 

3. The Base Station now chooses one address for polling from the list of all random numbers. But collision occurs if two terminals choose the same address.

4.  The Base Station acknowledges correct packets and continues polling the next terminal.

5. The cycle from step 1 to step 4 starts again after polling all terminals of the list.

Advantages

• Unlike in TDMA or CSMA, no slot is ever wasted.
• It provides maximum efficiency and bandwidth utilization.

Disadvantages

• Time is wasted during polling as we have to wait for the medium to be free to start transmission.
• Link sharing is not fair since each station has an equal probability of winning in each round.
• Few stations might starve for sending the data.

Polling is strictly centralized. If one terminal in wireless communication can be heard by all others, this central terminal also known as Base Terminal(BS) can poll all other terminals according to some schemes like the round-robin scheme, random address scheme, and as per reservation scheme.