[STDS-802-16] Comment 112

[Radu Selea <Radu@REDLINECOMMUNICATIONS.COM>]

Title: Message

Guys,

 

        I would have a small observation on the comment number #112 . Although I assume that you guys had a technical review of all these comments I should point out some details.

Comment # 112 proposes a method of errored PDU's recovery in case of errored PDU header. In this particular situation as you loose the length information if no specific recovery is done ,  all PDU's contained in a burst can be lost.

The problem is that aside of introducing a new optional mode that is changing the frame (burst) structure ,it does not add value on the technical side for few reasons:

 

1. There are methods for next header recovery that are widely used in ATM for instance, without any OVERHEAD addition and structure change. Some fields in the header have some possible patterns which any correlator can identify .Starting  from there, any simple HW machine can position on the header 'candidate' .When the header candidate is localized the simplest thing is to check the CRC at the end of it. If it matches that means the header is identified. The probability for mistake is almost null.

There are two conditions that have to be met:

    - the pattern

    - CRC on the candidate header sequence  

This algorithm does not require any change ,any overhead and any option.

 

2. The method presented in the contribution is not good  , aside added overhead and special framing. These pointers present in the sequence are exposed to errors as much as any bit in the burst. Then probability of that pointer being errored is the same. That errored pointer does not have any protection and any indication that is errored or not. Based on that you can get in a worse situation ... The only probability on this method to work is to be lucky enough in a noisy environment to receive correct pointers. 

 

3. We talked about this item in the last Orlando meeting and as I remember was rejected on technical ground. I replied to the comment in recirculation but I did not get any feedback .    

 

Cheers,

Radu.       

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