signal-processing - GNU radio DQPSK 误码率

Question

大约一个月前，我开始从事数字通信项目其中涉及到GNUradio。我正在努力克服一些错误或不匹配在 GNURadio 中遇到。我迫切需要一些专家的帮助。我仅使用 GNURADIO 伴侣制作了 DQPSK 调制器和解调器。(提供屏幕截图)

给出具有位 0,1,0,1 的向量源并在输入上重复PSK 调制器。我还使用错误率 block 来计算误码率。(矢量源位于错误率模块的引用上，DQPSK 解调器输出位于输入上)。我已将 wx gui 范围连接到错误率模块，并将星座接收器连接到 PSK 调制器。现在几乎所有出现在瞄准镜上的东西都完全是错了。

如果我没有添加任何噪声(即max 考虑到我们将正确恢复 50% 位机会)。连接到 PSK 调制器输出的示波器显示四个星座点即使我只传输一个符号，即 (0,1)。

我做错了什么？有人能好心地看一下屏幕截图并告诉我吗我的错误。

Answer 1

正如 Timothée Cocault 所说 in his answer to your mail on the gnuradio-discuss@gnu.org mailing list :

Hi Haaris,

The documentation of the PSK Mod says : "The input is a byte stream (unsigned char), treated as a series of packed symbols. Symbols are grouped from MSB to LSB." You should add an "Unpacked to Packed block" with 2 bits per chunk and MSB endianness before. Likewise, you should add a "Pack K bits" block with K=2 after the PSK Demod.

Also, your assumption that you should have one point in the constellation sink is wrong. You're using DQPSK so the (0, 1) symbol will add 90 degrees to the phase, and you will cycle through the 4 points of your constellation.

And last, keep in mind that each block has a delay, and you can't compare the input and output bits directly. Try to use a "Scope plot" with 2 inputs, and add a delay block before the input bits to synchronise the two.

Timothée.