VHTMIMOPac​ketErrorRa​teExample - Why is LDPC on IEEE 802.11ac worst than BCC ??

Hi All, I ran the WLAN System Toolbox example VHTMIMOPacketErrorRateExample, which basically provide a PER simulation of IEEE 802.11ac on a 8x8 MIMO configuration based on BCC as channel coding.

Now, I tried to use LDPC instead of BCC, and I was expecting it to perform a bit better (it does on IEEE 802.11n). But the output is totally worse...

Would anybody know where this poor performance could come from? I used the based TGacChannel and did not change anything from the example beside the channel coding.

Thanks in advance,

BR,

Jérôme

Answer 1

[BABA CHOUDHURY]

Hi Jerome, I know its very late now to respond to your query.

Still, I was also running similar simulations and found LDPC to outperfrom BCC in every scenario. Maybe some other parameters is affecting the calculations.

Answer 2

[Darcy Poulin]

I had exactly the same issue, and spoke with Mathworks support.

It turns out that you should configure the LDPC decoding method to use 'norm-min-sum' rather than the default 'bp' algorithm. When I made this change, I saw the predicted improvement in link performance.

For 11ac, you configure it like this:

rxPSDU=wlanVHTDataRecover(vhtdata,chanEst,nVarVHT,cfgVHT, 'LDPCDecodingMethod','norm-min-sum')

The same thing occurs in 11ax. Here you configure it like this:

rxPSDU = wlanHEDataBitRecover(eqDataSym,nVarEst,csi,cfgHE,'LDPCDecodingMethod','norm-min-sum');