Cable Modem High Bit Error Rate
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Cable Modem High Speed Internet
452 sending modest-sized email (4 » bats@rr.com bats Anon 2009-Mar-24 7:48 pm what exactly is bit error cable modem dsl rate?and what factors affect it? i'm looking at my cable modem diag page, and it shows downstream snr at 39, signal strength 4.6dbmv, both of which are good, but mer ber cable the bit error rate is hovering at about 4% (this is the highest sustained bit error rate i've seen, usually it's 1% if not 0). my upstream power level is 35.5.is this indicative of anything out of the ordinary? just curious. · actions · 2009-Mar-24 7:48 pm · NSA_CIA@charter.com NSA_CIA Anon 2009-Mar-24 9:01 pm It's indicative of intermittent
Bit Error Ratio
interference that occasionally crosses into the downstream data channel.What frequency is the downstream channel? · actions · 2009-Mar-24 9:01 pm · K PattersonPremium Memberjoin:2006-03-12Columbus, OHkudos:1 K Patterson to bats Premium Member 2009-Mar-24 9:06 pm to batsSomething is not right. The modem estimates the SNR from the bit error rate, and an error rate of 4% would produce an appalingly low SNR. You wouldn't be able to have a connection.can you cut and paste the error rate? · actions · 2009-Mar-24 9:06 pm · bats@rr.com bats Anon 2009-Mar-24 10:15 pm the bit error rate has dropped now. i can't copy and paste because the page keeps refreshing by itself, but right now it says 561mhz, snr 38.7, signal strength 4.5dbmv, bit error rate 0.669%. the error rate is fluctuating, but staying around 0.65-0.67. · actions · 2009-Mar-24 10:15 pm · TurbocpePremium Memberjoin:2001-12-22IA Turbocpe to K Patterson Premium Member 2009-Mar-24 11:57 pm to K PattersonBased on that, then this isn't good, is it?I noticed this one day (last year). · actions · 2009
versus Bit Error Rate Testing Posted by Steve Day Steve Day Steve Day has over 20 years of experience in CATV and telecommunications operations and engineering leadership... User is currently offline on Tuesday, 22 January 2013 in Uncategorized Hits: 42992 0 Comments modulation error ratio Subscribe to updates Print PDF Bookmark | Tweet Bit Error Rate (BER) is what is mer in cable a metric that represents the number of bit errors relating to receive bits of data stream over a communications channel that
Modulation Error Ratio Vs Snr
has been impacted by noise, interference or synchronization errors (Wiki). It can always be impacted by a series of trade offs. Lower bit rate improves BER, but reduces capacity. Increased signal strength of the bit http://www.dslreports.com/forum/r22122577-what-exactly-is-bit-error-rate stream improves BER, but may not be practical. Slower and robust modulation also improves BER. BER = (number of bits) \ (total number of bits) While the basics are simplistic, it is not a trivial measurement. It requires a referenced measurement setup, where a known data stream is sent through a system (transmitter and receiver). This is accomplished over a long period of time. See an example below http://www.cheetahtech.com/component/easyblog/entry/code-error-rate-versus-bit-error-rate-testing from Agilent Technologies that reflects BER testing times at a 95% confidence level. A table of test times at 95% confidence level is given for standard data rates and bit error ratios: (click graphic to enlarge) A typical CATV DOCSIS data stream test can take from 3 to 9 seconds. In the test world, this is significantly long. JDSU states that "BER is an age old technique of characterizing the digital transmission system." For QAM 64 Annex B the symbol rate is 5.0569 Msps and each symbol has 6 bits. A technician who wants to complete a BER 1E-8 (1 error per 100,000,000 bits) would have to wait for the receiver (STB, test set, modem) to receive 100 million bits. At a transmission rate of 30 Mb/s it is a 3.3 second wait. Additionally, testing 256 QAM over IE-9 is a 33 second wait. Just on the argument of time alone, we see that it would be impractical to have a $1,000 field device that tests 100's of channels at the push of a button. Secondly, we have to understand the process involved in FEC (forward error correction) coding. (click graphic to enlarge) With this understanding, we can begin to see how CER replace
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