In wireless network (IEEE 802.11) while i increaseing data transfer speed, throughput decreasing and increasing random manner in simulation tool. what are the parameter depends on the speed in the wireless network for fixed number of node?
Hi,
Number of nodes, algorithms (mechanisms) that you are using for channel access, SNR in channel (based on that different MCS-Modulation and coding scheme is selected which is directly impacting speed of link). I do not know which simulation tool are you using, but those above are major parameters. In real world you have other things that can influence on SNR, like interference from other technologies, multi path fading...
The more the speed of the receiver or the transmitter or both the more the doppler spread. This means that your baseline carrier frequency changes considerably at high speeds. Also due to high speed variations in mulipaths the receiver would not be able to deocode the data correctly. Third thing is the channel estimation at very high speeds.
Aamir is right also from pure PHY layer prospective. So it depends which simulator are you using...
If you are considering a Mobile network and if your nodes a moving at high velocity then certainly Doppler shift, multipath play a role. Moreover, one needs to also consider the protocol which Is being used for data transfer and the load on the network. The overall bandwidth available for all the nodes plays a role and when a node is transmitting what is the overall traffic load in the network. I mean if the network is already having heavy traffic because of other nodes communicating... there will be effect on the contention delay for the node to get the channel.. so in that case it has to be ascertained whether the network is getting in a congested state. One also needs to check the buffer (queue) allocated so in that case even you increase the speed the throughput may not increase proportionally. One needs to also see the Packet Error rate... if the error rate is high and you are using TCP based protocols in the transport layer the throughput may come down due to the presence of wireless losses and TCPs reaction to it. In fact when you consider TCP which is basically used there may be many causes for this phenomenon.
Hope it helps. All the best for the Research.
Channel contention is the key parameter than all which effects the speed
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