[op25-dev] LCWs: hamming, rs, serialization

Matt D md123 at nycap.rr.com
Sat Jul 13 17:31:04 UTC 2013


On 07/12/2013 07:45 PM, Steve Glass wrote:
> Hi Matt,
>> 
>> I am trying to get a handle on the data in the Link Control Word.
>> The LCW is 72 bits right? On transmission the 72 bit LCW is
>> serialized into 12 hex bits. And then it is encoded with a
>> (24,12,13) RS code to yield 24 hex bits. The 24 hex bits are then
>> encoded with a (10,6,3) shortened Hamming code to yield 240 bits
>> total.
>> 
>> Is it known how the bits are serialized? Or better yet is there
>> an existing function for unserializing/serializing that will work
>> here?
>> 
> The Common Air Interface specification defines the bit
> interleaving. We typically use a static const array identifying the
> indices of the bits that make up a given logical field.
> 
Hey,
so where the Daniels manual uses the term 'serializing' (for the bits
that make up the LCW) this simply refers to the process of turning the
72 bits into 6 hex bits?  And this is done in the same way for the
data information in the HDU even though it is not explicitly called
serializing in the HDU section of the manual?

Thanks!
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