Re: question on parity

Hello Si Chuanyu,


I haven't looked at OpenGPSSim for a long time. I'll try to 
answer your question from what I still remember...

I assume what you did was something like that:

    ./bin/ogsencdec nav-01-template-01-06.txt

and then

    ./bin/ogsxmit -n nav-01-template-01-06

However, the 'transmitter' program 'ogsxmit' inputs
the _encoded_ navigation data stored in the file 
'nav-01-template-01-06'. So the last two bits of sf[1][2] 
could be anything. As Cliff already said it's the _decoded_ 
HOW word that should end with 00 (or 11).


Regards

Georg

At 16:34 21.07.2004, you wrote:
>It looks like you are using Georg Beyerle's data and code which may be
>somewhat different from OpenSource GPS.
>
>Georg, can you take this question?
>
>Thanks,
>
>Cliff
>----- Original Message ----- 
>From: "si chuanyu" <[email protected]>
>To: <[email protected]>
>Sent: Tuesday, July 20, 2004 12:53 AM
>Subject: Re: [OpenSource_GPS] question on parity
>
>
>> thanks Kelley.
>>
>> yes, you said it.
>> but in my side, when i use nav-01-template-01-06.txt as input, after
>> encoding and parity adding, sf[1][2]'s last two bit was "ff 01" in the
>> memory. so it is 01 or 10(polarity is unkown)
>> I've tried several time and get the same result. I used Visual Studio 6.0
>> for development.
>>
>> I added a break point in ogsxmit.cpp 's main function after read the nav
>> bit from nav-01-template-01-06 into buffer NavBit[], and watched the
>memory
>> contents in the debug window, and get NavBit[58]=ff NavBit[59]=01;
>> so I am wondering why this ocurr? could you please give me some
>information
>> on that?
>>
>> Thank you very much!
>>
>>
>> >From: "Clifford Kelley" <[email protected]>
>> >Reply-To: "Clifford Kelley" <[email protected]>
>> >To: "si chuanyu"
>> <[email protected]>,<[email protected]>
>> >Subject: Re: [OpenSource_GPS] question on parity
>> >Date: Tue, 8 Jun 2004 21:48:17 -0700
>> >
>> >I'm not sure which reference you are referring to but the last two bits
>of
>> >HOW when decoded should be 00.  If the polarity is unknown it could be
>11.
>> >The reference to check with is ICD-GPS-200.
>> >
>> >Cliff
>> >----- Original Message -----
>> >From: "si chuanyu" <[email protected]>
>> >To: <[email protected]>
>> >Sent: Monday, June 07, 2004 2:37 AM
>> >Subject: [OpenSource_GPS] question on parity
>> >
>> >
>> > > hi
>> > >    I found in the reference that the sum of the last two bits of HOW
>in
>> > > each subframe should be +2 or -2. but in the reference code, after
>> >encoding
>> > > the subframe and adding parity, the last two bits of subframe[][2] was
>> 1
>> >or
>> > > -1. thus in the receiver, we can't pass parity check. what's the
>> problem
>> > > with that? do I missed something else? thanks a lot!
>> > >
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