Re: [Discuss-gnuradio] Digital Communication using GNU Radio.

[Sachi]

Hi, Eric

 

Thanks very much for your information. It really helps me a lot. But I still have a couple of questions:

1. Does this synchronization algorithm have any specific name?

2. I notice that at the TX side, a payload file need to be sent. So what kind of file should I use here? Any file? Does it have any special format? On the other hand, at the RX side, what should be observed to convince me that the file has been received correctly? Receiving a same file? If possible, could you please give me more information about the how to run the experiments (the command, arguments)

3. I directly use 29.xMHz for transmission and reception (without freq. tuner) with two USRP boards at two PCs, because I think the DAC and ADC can work well for this frequency. I just use two amplifiers at both ends to increase the SNR. So do you think this scenario could work well?

 

Thanks very much for your time

 

Regards

 

Sachi

Eric Blossom <address@hidden> wrote:

> On Thu, Jun 02, 2005 at 09:21:59AM -0700, Sachi wrote:
> > Hi, all
> > I am still studying the codes of the FSK_R(T)X.py.
> > It's a little bit confusing because the comments are
> > rather limited. 
> > Which algorithm or book chapter does the author refer
> > to when he wrote the codes, especially for the time
> > synchronization part? I think that information can
> > help me understand the code line by line much better.
> > 
> > Thanks in advance
> > 
> > Sachi 
>
> Hi Sachi,
>
> The time synchronization method is a standard open loop technique that
> works fine for many uses. It results in establishing both bit timing
> and frame alignment. Fundamentally we start with a signal that is
> oversampled 8 times, and then look for a particular synchronization
> pattern at every possible offset. When we find the best one,
>  we
> declare that we are synchronized, and use that alignment for the
> duration of the current frame. It's similar to the oversampling
> techinque used in UARTs to find the middle of the start bit.
>
> Synchronization is generally not well covered in intro comms texts.
>
> Frerking, "Digital Signal Processing in Communication Systems" is full
> of practical digital comms techniques, including some having to do
> with synchronization.
>
> Meyr, Moeneclaey and Fechtel, "Digital Communications Receivers:
> Synchronization, Channel Estimation, and Signal Processing" is pretty
> much all about synchronization, but is pretty heavy going.
>
> Eric

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