Question

You are a help desk support technician at a retail department store and you receive a call from a manager in the administrative offices. He complains that the performance of his 802.11g/n notebook computer decreases several times throughout the day. Upon visiting the customer, you realize several people are performing inventory using 802.11b barcode scanners in the adjacent room. What is most likely the cause of the poor performance for the manager's notebook computer?

Answer 1

Answer: Too many stations trying to transmit at once.

Step-by-step explanation:

Due to the special characteristics of the wireless transmissions, it is not possible for one station to detect collisions.

So, in order to overcome this issue, 802.11 networks try to avoid collisions, using a method called CSMA/CA (instead of the CSMA/CD used by Ethernet 802.3 standard).

This method, in simple words, implies that before sending a packet, the station senses if the channel is clear.

If it detects this condition, waits for a random time, and if the channel is still idle, sends the packet.

If it receives an acknowledgement from the receiving station, repeats the process and continue transmitting.

But if it has no success, doubles the wait time (which is called backoff period) and try again, after sensing if the channel is still idle.

If at a given time, there are many stations repeating this process once and again, the logical consequence will be a general decrease in the actual throughput for all stations, which it is very possible if several people , for instance, try to use 802.11b barcode scanners at the same time.