Thread Links |
Date Links |
||||
---|---|---|---|---|---|

Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |

*To*: STDS-802-3-10GBT@listserv.ieee.org*Subject*: [10GBT] Questions regarding error rates for LDPC & PAM modulation*From*: Hugh Barrass <hbarrass@CISCO.COM>*Date*: Mon, 4 Oct 2004 10:14:53 -0700*In-Reply-To*: <9418406DEC3B8A4BBDB1B87291D851AF116B66@wcosmb05.cos.agilent.com>*Organization*: Cisco Systems*References*: <9418406DEC3B8A4BBDB1B87291D851AF116B66@wcosmb05.cos.agilent.com>*Reply-To*: Hugh Barrass <hbarrass@CISCO.COM>*Sender*: stds-802-3-10gbt@IEEE.ORG*User-Agent*: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax)

All, If you are not deeply involved in PAM modulation or LDPC codes, you should probably switch off now. Many of the following will appear meaningless to 99.9% of the world's population. If you are still reading at this point you have my sympathy :-) In order to make a realistic analysis of the mean time to false packet acceptance, we need to understand how PAM modulation and LDPC coding generates errors. I have a list of questions to kick off the discussion, as we progress on the subject I will gladly sponsor ad-hoc calls or meetings to discuss the false packet acceptance rate. 1. PAM modulation At a given SNR, we have a corresponding BER (or probability of error). However, with more than 1 bit per symbol, there should be separate probabilities for P(single bit error), P(double bit error) - where this is not simply P(single bit error) squared. Also, I would expect some correlation between errors on one pair and errors on the other pairs. For the PAM-12 proposal there are 2 coded bits on each symbol, so I expect that there will be a set of probabilities for 1 bit error; multiple bit errors on multiple pairs; and multiple bits on one pair (also with errors on other pairs). Finally, the uncoded bits on the same symbols should have a higher (effective) SNR but I expect that there will be a BER for those bits. Bit errors on uncoded bits should correlate (strongly) with errors on the coded bits. Could someone post a detailed analysis of these factors when examining the error rates of PAM modulated (especially the adopted PAM) systems? 2. LDPC coding I am more familiar with RS coding than LDPC, but I understand that the proposed LDPC codes are based on RS (rather than irregular codes). Is there an indication of "detected, uncorrected" errors in an LDPC code block? If so, what are the corresponding rates for undetected errors for LDPC? Do the BER simulations presented represent "undetected, uncorrected" errors? Also, is the error correction and detection mechanism favorable to bytes (as opposed to bits)? In other words should we be looking at the error rate in terms of byte errors (or other unit size)? Finally, I assume that any block code will have a strong likelihood of multiple errors. For a given P(error) in a codeblock, what is the P(second error)? Is there any spatial relationship between errors within the block? Could someone post a detailed analysis of the nature of errors after LDPC coding? This effort will tae some serious though, many thanks for your input on this, Hugh.

**References**:**[10GBT] Question about previous analysis of codes and undetected errors.***From:*Pat Thaler <pat_thaler@AGILENT.COM>

- Prev by Date:
**[10GBT] FW: [802ALL:] The Hyatt & Wyndham are almost Sold-Out for the November 14-19, 2004 Plenary Session** - Next by Date:
**[10GBT] Apology** - Prev by thread:
**[10GBT] Question about previous analysis of codes and undetected errors.** - Next by thread:
**Re: [10GBT] Question about previous analysis of codes and undetected errors.** - Index(es):