Comparing 1000BASE-T and 100BASE-TX, given the same cabling and distance, in an environment with substantial electronic noise, theoretically, which of the two will be more resistant to noise?
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The IEEE engineering of the UTP variants of ethernet aims to have each with the same noise immunity when run on a certified cabling plant (passes the category test suite).– Ron Maupin ♦Dec 30, 2021 at 16:41
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@RonMaupin, what about STP?– madhat1Jan 2, 2022 at 17:22
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See my comment under Zac's answer. Category cables, except for Category-8, are all UTP. ANSI/TIA defines cable categories, and currently only categories 3, 5e, 6, 6A, and 8 are recognized, and they are UTP (except 8).– Ron Maupin ♦Jan 2, 2022 at 17:26
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1 Answer
100BASE-TX uses 4b/5b encoding with MLT-3 over dedicated send and receive pairs with a spectral bandwidth of just 31.25 MHz. 1000BASE-T uses PAM-5, twice the bandwidth and bidirectional send/receive over all pairs - but its four-dimensional trellis coded modulation should make it no more sensitive to external noise than 100BASE-TX.
In a high-noise environment you might want to consider using fiber which is practically immune to induced noise.
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Shielded cat6 is also a thing, perhaps worth considering? Especially if you can ground the shielding in a useful way at one end of the run. If you have existing equipment, that might be cheaper and/or easier. (Or not, I'm not an expert on how effective shielding is against what kinds of noise, or in hubs / NICs with connections for the shield.) Dec 30, 2021 at 22:21
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1Shielding can be very helpful but only if it's properly grounded at both ends. Most of the time it isn't really done correctly. Fiber is the carefree choice and not really expensive unless you let a premium vendor rip you off.– Zac67 ♦Dec 30, 2021 at 22:25
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2@PeterCordes, shielding is most often used to have inferior cable pass the category test suite because it would not pass without it, and not having a continuous end-to-end shield with proper grounding actually exacerbates noise problems with the cabling. You can say a shielded cable passes the Category-6 test, but the cable categories are made by ANSI/TIA, and they are all unshielded, except for Category-8, so there really is no such thing as shielded Category-6. The ISO/IEC has cable classes (not categories), some of which are shielded and correspond to categories.– Ron Maupin ♦Dec 31, 2021 at 2:08
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Yes, I was referring to 1000BASE-T, it's a copy mistake, fixed in the question. So in your opinion, when nearing each standard's limit (100 Mbit for 100BASE-TX and 1Gbit in 1000BASE-T), is the noise immunity still the same?– madhat1Jan 2, 2022 at 17:13
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Very much so. The exact differences would depend on the predominant frequencies of noise and the cable parameters. No way to tell from afar, you'll like have to test. Still, fiber is the carefree way.– Zac67 ♦Jan 2, 2022 at 17:22