simulation understanding in VISSIM

Altair Forum User

Submitted by sanatanmohanty on Tue, 09/25/2012 - 10:54 

Dear Sir,
I have some doubts to be clarified regarding VisSim/WLAN.

1>Can i do networks and MAC layer simulation for WLAN and UWB using the given blocks in VisSIM? Is it only confined to physical layer simulation?

2>Can i observe the simulation result over varied frequency range?For example ,it is only showing 20MHz in result.

3> I have simulated the exampled IEEE 802.11a OFDM with GI at 12Mbps,at the output only receiving around 2Mbps at the output,when the end time is 1 second;When i am running the same scenaio having end time 10 second, total bits shows 1.2e+8(more than input 1.2e+6)
Why is it so?

4> To simulate IEEE 802.11a at 48Mbps and 54Mbps, what setting to be optimized for better results(in terms of bit errors) in the output?

5> How do i generate a BER plot for that IEEE 802.11a OFDM with GI?

Kindly help me to clear these doubts.

Thanks and regards,
sanatan

Altair Forum User

Submitted by eestinto on Wed, 09/26/2012 - 08:53.

 

Hello,

Here are some quick answers to your questions:

1) VisSim/Comm WLAN only supports the PHY layer. Network layer & MAC layer are not supported.

2) The range of the spectrum plot is based on the simulation rate. The simulation rate can be increased, but many of the examples include delays that are expressed in 'simulation time steps', so some adjustments will need to be made.

3) To simulate the higher 802.11a rates (24, 48, etc..), the example needs to be modified to use 16-QAM or 64-QAM instead of QPSK as the underlying modulation. Changing the above is quite complex, as many other parameters will need to be adjusted. I can try to modify the example for a higher rate and send sometime soon (this will take at least a few days).

4) I am not sure what you mean by 'only 2 Mbps at the output'. The example you mentioned has an input and output bit rate of 12 Mbps, which is further evidenced by the fact that the BER counter shows agreement between the input and output.

5) To produce a BER Plot, the simulation would need to be run several times while changing the simuation Eb/No value. This can be done by turning on the 'Auto Restart' setting in the simulation properties, and using the BER Control or BER Num Errors block and the AWGN block. A good example to look at is the BER_NUM_Errors.vsm example in the Comm Examples/Estimators folder. Given the complexity of the OFDM example, you may want to run the simulation multiple times with different Eb/No values and then plot the results separately.

Regards,

Eugene VisSim/Comm Tech Support