About wireless throughput
Last Post: August 9, 2005:
If I am not misunderstanding, the reasons that cut the wireless throughput into half are due to the CSMA/CA and header overhead right?
In the case of wireless client to wireless client, why is the throughput becomes half again?
Take a 802.11g network for example, wireless node A to wired B we get 24Mbps and wireless node B to wireless node C we get 12Mbps instead.
Can someone gives me a detail explanation please?
Hi Raul of Taiwan:
When a station is transmitting RF symbols, the number of bits carried in those symbols per second is a nominal transmission rate for that PHY, for example 11 Mbps. Data payload throughput cannot exceed this limit. And there are several reasons data payload throughput is typically no more than half of the nominal data rate.
When a station is transmitting it must transmit more than the data payload carried in frame bodies. This includes control frames, management frames, and headers and trailers on data frames. These cause the data payload throughput to be diminished.
Even in perfect conditions of no contention with other stations, no interference from other RF sources, and no retransmissions, no one station transmits continuously. There are quiet times between frames, designed to help avoid collisions with other station transmissions, that cause the data payload throughput to be diminished.
When a station waits for other stations to finish or RF interference to end, data payload throughput for that station is diminished.
When a station retransmits data after a failed acknowledgment, data payload throughput is diminished.
When an ERP station (802.11g) takes extraordinary steps to avoid colliding with slower 2.4 GHz stations, data payload throughput is diminished.
If a frame body is destined for another WLAN station in the same infrastructure service set, it must be transmitted twice in the same channel, first by the source then again by the access point. Assuming the two nominal data rates used are the same, data payload throughput is cut in half.
I hope this helps. Thanks. /criss
Oh great answer!
Thks a lot for the info Criss!!
Criss, thanks for your help.
You have a great knowledge in wireless network.