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**Lavender****Member**- Registered: 2020-Apr-07
- Posts: 20

I ran the wl_example_siso_ofdm_txrx.m sample code and set:

N_OFDM_SYMS=500;

SAMP_FREQ=40MHz;

The final received signal is 1*81445 complex double, so the time corresponding to this signal is (1/40000000*81445) s, is this calculation correct?

Similarly, I set wl_basebandCmd (nodes,'tx_delay', 1000), so the packet sending interval is (1/40000000*1000) s, is this calculation correct?

Thank you.

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**Lavender****Member**- Registered: 2020-Apr-07
- Posts: 20

From the sample code, we can see that the preamble is 1*1280 complex double. According to the calculation method above, the length of the preamble is (1/40000000*1280)s, which is 32μs.

However, the 802.11g protocol specifies a preamble of 16μs, so I wonder where I made a mistake?

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**murphpo****Administrator**- From: Mango Communications
- Registered: 2006-Jul-03
- Posts: 5159

The OFDM example script uses a longer preamble for extra AGC settling time.

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**Lavender****Member**- Registered: 2020-Apr-07
- Posts: 20

I see, thank you.

So is the above method of calculating time correct, ie sampling interval * points？

And I am not sure, the value 1000 of 'tx_delay' represents 1000 sampling points or time, such as ms, μs, ns?

wl_basebandCmd (nodes,'tx_delay', 1000)

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**murphpo****Administrator**- From: Mango Communications
- Registered: 2006-Jul-03
- Posts: 5159

Refer to the user guide

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