如何在 Gnuradio 中进行通道测量？
测量时空信道的最佳方法是什么 使用 RFX2400 板的编码方案？
据我所知你只能从 USRP 中获取 I 和 Q 流， 我不确定如何获得一组通道系数。
我计划使用测量通道的共轭来 “扭转”传播造成的损害。
What is the best way to measure the channel for use in space-time
coding schemes using an RFX2400 board?
As far as I know you can only get the I and Q streams out of the USRP,
and I'm not sure how you would get a set of channel coefficients.
I am planning on using the conjugate of the measured channel to
'reverse' the damage done by transmission.
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如果您尝试测量通道的脉冲响应，那么
一种技术是传输已知的伪随机比特序列（一个
m 序列）在感兴趣的载波频率上使用 BPSK 调制。 这
序列的码片速率决定了测量系统带宽，而
序列长度决定了测量的“动态范围”。
在接收器处将 LO 设置为与接收端相同的载波频率
发射机。 这里需要对等效低通进行互相关
具有已知 m 序列的接收信号以给出（复数）脉冲
通道的响应。 任何超出您定义的“峰值”
阈值噪声水平将是时域中的通道系数。
这实际上是在 gr-sounder 中实现的。
信道探测发射器正在发送 PRNG 调制的 BPSK
32 Mchips/秒。 你需要以这个速度进行关联； 它不是
可以通过 USB 将这么多数据发送到主机。
软件中的通道探测仪适用于小于 4 的码片速率
微芯片/秒。 但这限制了脉冲响应的分辨率
每个 bin 大约 250 ns，或者在空间域中每个 bin 75 米。
不幸的是，互相关是在非常有限的空间上完成的
FPGA没有频偏补偿，所以产生的脉冲
响应向量在时域中“滚动”。
--
乔纳森·科根 (Johnathan Corgan) 的回答 (c)
If you trying to measure the impulse response of the channel, then
one technique would be to transmit a known pseudo-random bit sequence (an
m-sequence) using BPSK modulation at the carrier frequency of interest. The
chip rate of the sequence determines the measurement system bandwidth, while
the sequence length determines the 'dynamic range' of the measurement.
At the receiver set the LO to the same carrier frequency as that at the
transmitter. Here you need to cross-correlate the equivalent low-pass
received signal with the known m-sequence to give the (complex) impulse
response of the channel. Any 'peaks' that exceed your definition of a
threshold noise level would be your channel coefficients in the time domain.
This is actually implemented in gr-sounder.
The channel sounder transmitter is sending the PRNG modulated BPSK at
32 Mchips/sec. You need to do the correlation at this speed; it's not
possible to send that much data over the USB to the host.
A channel sounder in software would work for chip rates less than 4
Mchip/sec. But that limits the resolution of your impulse response to
about 250 ns per bin, or 75 meters per bin in the spatial domain.
Unfortunately, the cross-correlation done on the very limited space
FPGA has no frequency offset compensation, so the resulting impulse
response vectors "roll" in the time domain.
--
answer (c) by Johnathan Corgan