Talk:Line code
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We should have pictures showing everything, including:
- raised cosine pulses, nyquist pulses (same thing?), triangle pulses? instead of just rectangular
- unipolar and bipolar (pseudo-trinary or alternate mark inversion) instead of just polar
- and whatever else there is - Omegatron 02:43, May 2, 2005 (UTC)
[edit] Modulation
I think It should be explained the relation with modulation.
I added a brief mention of modulation -- anything else I need to add? --68.0.120.35 20:27, 9 December 2006 (UTC)
[edit] clock sync
Maybe I'm just missing it, but it doesn't seem like any of the immediately related pages mention *why* clock sync is important. Explaining for example why constant synchronization is required, rather than just syncing at the start and sending data for the rest (ie. cheap clocks are not nearly accurate enough). Where does this sort of thing belong? Line code is a pretty weak page in general, and I'm not sure this applies only to line codes. It's pretty relevant for any sort of digital communication regardless of scope. On small scales it's usually out-of-band, but perhaps this is worth mentioning as well?
Thoughts?
Some communication systems (such as the Local Interconnect Network) *do* transmit a "sync header" at the start to synchronize clocks, then just data for the rest of the packet/sector. Is there a good reason some systems sync at the beginning, while other systems use a self-clocking signal ?
Yes, I would like a paragraph explaining why clock sync is important. It certainly does apply to all line codes, so perhaps we could stick it in the "line code" article for now, until we find a better (more general) place to put the explaination. Perhaps telecommunication or synchronization or modulation or digital communication or self-clocking signal or intersymbol interference ? The Run Length Limited article has a one-sentence explanation ... --68.0.120.35 19:15, 9 December 2006 (UTC)
The kind of "clock sync" that all line codes deal with is finding the beginning and ending of each symbol. This kind of sync is sometimes called Phase synchronization. With accumulate-and-dump systems such as PRML, slight errors in starting and stopping accumulation lead to increased ISI which leads to increased errors.
Line codes that transmit 8 data bits at a time (such as 8B10B) can also help find the beginning and ending of each byte of 8 data bits (a different kind of clock sync), reducing framing error.
--68.0.120.35 07:23, 13 December 2006 (UTC)
The clock recovery article might be a good place to discuss this. --75.37.227.177 16:24, 7 August 2007 (UTC)
[edit] "code" vs. "symbol"
The text seems use the word "code" both for "symbol" and for "code" (a set of symbols). That makes some text quite confusing, e.g., "design each transmitted code such that every code that ..."
The text should use "symbol," or at least disambiguate the references (e.g., by using multiword phrases for one or both meanings of "code").
12.109.151.100 (talk) 20:15, 27 November 2007 (UTC)
- Please help me make this page easier to understand.
- I agree that this article ought to use a different word for a specific single pattern -- such as the pattern "1010", used to represent the data sequence "101" in 3b/4b encoding -- and the full list of replacement patterns -- such as the entire "3b/4b encoding".
- Alas, I must protest using "symbol" for either of these meanings.
- To me, symbol (data) is closely tied to the analog bandwidth.
- Using "3b/4b encoding", transmitting 3 data bits requires sending 4 symbols.
- Using 2B1Q encoding, transmitting 4 data bits requires sending 2 symbols.
- (As you can see, some encodings use more than 1 symbol per data bit; others use less than 1 symbol per data bit).
- Would using "code word" for the replacement pattern, and "code" for a particular full set of code words, be better?
- --75.19.73.101 05:39, 3 December 2007 (UTC)
