Re: [rohc] RFC4815 no TS bits

Jer-ming Lin <cs202050@csie.ncu.edu.tw> Thu, 04 February 2010 10:35 UTC

Message-ID: <20100204183404.x04djumysgw4oggg@webmail.csie.ncu.edu.tw>
Date: Thu, 04 Feb 2010 18:34:04 +0800
From: Jer-ming Lin <cs202050@csie.ncu.edu.tw>
To: Carl Knutsson <carl.knutsson@effnet.com>
References: <20100203210741.gfnig61ao84wsgo0@webmail.csie.ncu.edu.tw> <4B6A8BE7.8060701@effnet.com>
In-Reply-To: <4B6A8BE7.8060701@effnet.com>
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Cc: rohc@ietf.org
Subject: Re: [rohc] RFC4815 no TS bits
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Dear Sir,

Quoting Carl Knutsson <carl.knutsson@effnet.com>om>:
>> ..
>> TS_STRIDE and the relationship of delta_TS. Is that right?
>
> No, the compressor must first establish the TS_STRIDE by sending it
> as-is together with unscaled TS. From those two values, TS_SCALED and
> TS_OFFSET can be derived and used for later for compression.
>

    After establishing the TS_STRIDE and TS_OFFSET, the compressor  
sends scaled TS bits or no TS bits if scaled TS has the relationship  
of "delta_TS=delta_SN*default-slope(TS)."

    For performance issue, if the scaled TS(derived from unscaled  
TS/TS_STRIDE) also have the relationship of delta_TS in consecutive  
IR/IR-DYN/UOR-ext3 packets. Can the compressor send no-TS bits  
directly after the establishing packets? The RFC did not mention this.  
I think this can reduce the compressed header size since no-TS bits  
are sent.


For example,

SN,     TS, TS_STRIDE, scaled TS,  Type,  transmit TS bits,
  1,  26189,       280,        93,    IR,                32
  2,  26469,       280,        94,    IR,                32
  3,  26749,       280,        95,    IR,                32
  4,  27029,       280,        96,  UO-0,                 0

The first, sencond, third construct the TS_STRIDE and the relationship  
of delta_TS. The forth cand send no-TS bits.

Sincerely yours,
Jer-ming


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[rohc] RFC4815 no TS bits Jer-ming Lin
Re: [rohc] RFC4815 no TS bits Carl Knutsson
Re: [rohc] RFC4815 no TS bits Jer-ming Lin