Network Cabling http://www.innovaglobal.com 877-448-4968

927 views

Published on

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
927
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
2
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Network Cabling http://www.innovaglobal.com 877-448-4968

  1. 1. The Future of Network Cabling By Paul Kish, NORDX/CDT June 2000
  2. 2. Table of ContentsINTRODUCTION ……………………………………………………………………… 2Gigabit Networking Technology ……………………………………………………. 2Evolution of Cabling Standards …………………………………………………….. 3Advances in Cabling Technology ………………………………………………….. 3Shaping the Future ……………………………………………………………….….. 4Channel Performance ………………………………………………………………. 5Signal-to-Noise Ratio due to NEXT and FEXT …………………………………… 6Bandwidth and Information Capacity ……………………………………………..... 9Test Results Summary ……………………………………………………………… 11CONCLUSIONS..…………………………………………………………………….. 14 1
  3. 3. IntroductionA lot has been written recently about better cabling to support gigabit networking.TIA published a new cabling standard for gigabit networking over copper inJanuary 2000. It is available through Global Engineering Documents asAddendum No. 5 (TIA/EIA 568-A-5) to the TIA/EIA 568-A standard. It buildsupon the installed base of Category 5 cabling and is called Category 5e, or“enhanced Category 5”.The TIA/EIA Category 5e cabling standard was developed by TIA in harmonywith the IEEE 802.3 committee responsible for the 1000BASE-T Ethernetstandard. It incorporates several new transmission parameters that are requiredto support full duplex, parallel transmission systems, namely: Power Sum NearEnd Crosstalk (PSNEXT), Power Sum Equal Level Far End Crosstalk(PSELFEXT) and Return Loss. These are additional transmission parametersand are intended to complement and not to supercede the transmissionparameters already specified for Category 5 cabling.I will not spend much time in this paper to explain or define these newtransmission parameters for Category 5e. Rather, the focus of this paper will beon what’s ahead for the next generation copper cabling standard. What types ofcables and connecting hardware will be required to support the multi-gigabitapplications that are coming in the future? What transmission parameters areparticularly important to system designers of these future networks?Gigabit Networking TechnologyGigabit networking over copper will employ parallel, full-duplex transmission. Forexample, 1000BASE-T will simultaneously transmit and receive 250 Mb/s ofinformation on each pair of a 4-pair Category 5 channel to achieve an aggregatedata rate of 1000 Mb/s. It will employ a five-level Pulse Amplitude Modulation(PAM-5) line code for transmission over each cable pair. PAM-5 encodes 2 bitsof information into one symbol. Thus, the actual line rate is 125 Mbaud or 125Mega-symbols per second, the same as 100BASE-T. This facilitates theimplementation of common circuitry for both 100BASE-TX and 1000BASE-T. Infact, it is envisaged that a 1000BASE-T network card will support both 100BASE-TX and 1000BASE-T data connections using an auto-sensing feature. The firstnetworks based on the new gigabit Ethernet technology over copper becamecommercially available in 1999(see http://www.gigabit-ethernet.org/news/releases/090399.html).* TIA/EIA Category 6 working draft 6 (May 2000) 2
  4. 4. Evolution of Cabling StandardsCategory 5 cabling has evolved over the last 10 years to become the workhorsein the industry. Category 5e completes the picture for Category 5 by filling in themissing pieces that are essential to support advanced networking protocols suchas gigabit Ethernet. Looking back at the evolution of Category 5, Category 5e iswhat Category 5 should have been all along once all the pieces had been puttogether.Before the ink is even dry on the Category 5e cabling standard, both TIA andISO are already hard at work developing the next generation standard forCategory 6 (UTP/ScTP) and Category 7 (STP) cabling. These new cablingcategories will have an extended bandwidth of at least 200 MHz. It is expectedthat the standards for Category 6 and 7 cabling will be approved sometime in theyear 2001. There are many technical issues that are still open. For example,the issue of interoperability between different vendor’s products and the issue ofbackward compatibility with Category 5 and 5e connecting hardware need to beresolved before a standard can be published. The next generation cablingstandard will also need to set a useful performance benchmark for designers offuture networking applications.Advances in Cabling TechnologyCabling technology is advancing at a very rapid pace. The cabling industry isundergoing an exciting phase in the development of a standard for Category 6*.The door is open to many innovative new product ideas for cables andconnecting hardware. These have resulted in various proposals that are underconsideration by TIA TR 42.7, the Copper Cabling Systems sub-committee. Onesuch proposal is from NORDX/CDT for an alternate low attenuation Category 6*cable with improved crosstalk performance.At NORDX/CDT, we have completed an extensive series of tests in our IBDNsystems laboratory on a variety of channel configurations using a low attenuationCategory 6* cable that incorporates 23 AWG copper conductors a cross-webseparator. Our test results demonstrate that a channel comprised of IBDN4800LX cable and newly developed PS6LX cords and GigaFlex PS6+connectivity hardware can provide an available bandwidth of 300 MHz for aworst case 4-connector topology. This is 50% higher than the objective for aminimally compliant Category 6* channel (see http://www.beyondcat6.com). Thetest results for the new IBDN System 4800LX are presented later in this paper.One of the transmission parameters of paramount importance for Category 6* isthe channel attenuation. A more correct term would be the channel insertionloss since insertion loss, by definition, includes the effects of impedancemismatch between components and cabling terminations. Most people in the* TIA/EIA Category 6 working draft 6 (May 2000) 3
  5. 5. industry incorrectly use the term attenuation to be synonymous with insertionloss. The TIA TR 42.7 sub-committee members recognize this inconsistencyand intend to clarify the usage of these terms in future editions of the standard.The IEEE 802.3 committee responsible for the gigabit Ethernet standard is onrecord stating that a 1 dB improvement in cabling attenuation is more valuable todesigners of future systems than a 1 dB improvement in crosstalk performance.This is because of advances in digital signal processing (DSP) techniques thatcan be used to cancel out certain types of correlated noise such as NEXT andechoes. Therefore, the overriding constraint becomes channel attenuation orinsertion loss as well as insertion loss deviation that is a new parameter understudy for Category 6*. NORDX/CDT understands and openly supports the IEEEposition. It is the basis of our Category 6* cable proposal to the TIA committee.It is also the cornerstone of our IBDN System 4800LX offering.Shaping the FutureThe IBDN 4800LX Cable from NORDX/CDT sets a new performance benchmarkcompared to Category 5 & 5e cables. More detailed information on the cableconstruction and performance is presented in a companion article [1 ]. The newcable provides 4 dB lower attenuation at 100 MHz and at least 6 dB lowerattenuation at 200 MHz. What does this mean to the network system designer?First, system designers are constrained by the maximum transmit signal that canbe applied at the active equipment interface. This is because of EMC guidelinesfor computer equipment and peripherals that limit the radiated emissions above30 MHz. Typically, the output signal amplitude is constrained to about 1 voltpeak-to-peak (ATM 155) or 2 volts peak-to-peak (100BASE-TX or 1000BASE-T).Second, system designers are constrained by the minimum level of the receivesignal because of environmental noise and receiver sensitivity. Environmentalnoise is principally caused by power line disturbances, RFI, and alien crosstalkfrom adjacent cabling. Other sources of noise that must be considered includethermal noise and stray couplings within the equipment.The above constraints place an upper bound on the level of the transmit signaland a lower bound on the level of the receive signal. The difference betweentransmit signal output and the receive signal input is the insertion loss of achannel. Let’s assume that the maximum insertion loss of a channel is limited to35 dB because of these constraints. This limitation would restrict the applicabilityof finer gauge cables at high frequencies and is independent of any othertransmission constraints such as PSACR (Power Sum Attenuation-to-CrosstalkRatio).* TIA/EIA Category 6 working draft 6 (May 2000)The insertion loss of a channel is particularly important for future applicationsthat will employ crosstalk cancellation techniques. For such applications, 4
  6. 6. insertion loss, insertion loss deviation and environmental noise are the governingfactors that limit the available bandwidth of a system and not the PSACR.Channel PerformanceThe transmission parameters for the IBDN System 4800LX are summarized intable 1 below. There are major improvements in all the transmission parametersfor the IBDN System 4800LX compared to the Category 5e standard andCategory 6* proposal. The significance of this can be appreciated by looking atthe signal-to-noise ratio (SNR) at the receiver. The signal-to-noise ratiodetermines the ultimate information capacity of the channel and the system errorrate performance. Channel Parameter Category 5e Category 6* IBDN System Comment 4800LXInsertion Loss @ 100 MHz 24.0 21.3 18.4 The (dB/100m) @ 200 MHz 35.3 31.5 27.0 lower @ 300 MHz 39.7 34.1 the better PSNEXT @ 100 MHz 27.1 37.1 42.0 The (dB) @ 200 MHz 31.9 37.0 higher @ 300 MHz 34.2 the better PSACR @ 100 MHz 3.1 15.8 23.6 The (dB) @ 200 MHz 0.4 10.0 higher @ 300 MHz 0.1 the better PSELFEXT @ 100 MHz 14.4 20.3 24.4 The (dB) @ 200 MHz 14.2 18.4 higher @ 300 MHz 14.9 the better Return Loss @ 100 MHz 10.0 12.0 12.8 The (dB) @ 200 MHz 9.0 9.8 higher @ 300 MHz 8.0 the betterTable 1 - Worst case channel performance (4-connector topology)* TIA/EIA Category 6 working draft 6 (May 2000) 5
  7. 7. Signal-to-Noise Ratio due to NEXT and FEXTTo illustrate the point, I will derive the SNR due to NEXT and FEXT. It mayseem laborious to go through this exercise, however, I have found in discussionswith my colleagues that these concepts are not well understood, particularly as itrelates to PSFEXT and PSELFEXT. Therefore, I feel that going through amathematical derivation will help to clarify these concepts.First, let’s designate the two ends of the channel as end A and end Brespectively. The four pairs will be designated as pair 1,2,3 and 4 respectively.All values derived in the following expressions are given in decibels (dB). Tx(4A) Tx(4B) Hybrid Hybrid Tx(3A) Tx(3B) Hybrid Tx(2A) Hybrid Hybrid Hybrid Tx(2B) ΣNx(1A) ΣFx(1B) Hybrid Hybrid Tx(1B) Rx(1A) IL(1) Figure 1 - Parallel, full duplex transmission using a hybrid couplerNote: The following derivations do not include the added loss of the hybridcircuit. The added loss of the hybrids do not affect the SNR due to NEXT andFEXT since the signal and the noise are attenuated by the same amount.As illustrated in Figure 1, let us designate the receive signal on pair 1A asRx(1A) and the transmit signal at the opposite end of pair 1A as Tx(1B).By definition, the receive signal is Rx(1A) = Tx(1B) - IL(1) …………………………….…………………………(1)* TIA/EIA Category 6 working draft 6 (May 2000)where, 6
  8. 8. IL(1) is the insertion loss for pair 1, often referred to as attenuationThe Near End Crosstalk noise on pair 1A due to a near-end transmit signal onpair 2A is Nx(2A,1A) = Tx(2A) - NEXT(2A,1A) ………….…..…………………………(2)where, NEXT(2A,1A) is the NEXT coupling loss between pair 2A and pair 1AThe total Near End Crosstalk noise on pair 1A calculated as a power sum is ΣNx(1A) = 10*log(10Nx(2A,1A)/10 + 10Nx(3A,1A)/10 +10Nx(4A,1A)/10) ……………(3)For the purpose of simplifying the equations, let’s assume that all the transmitsignals on all pairs are at the same level at both ends of the channel, i.e. Tx = Tx(1A)=Tx(2A)=Tx(3A)=Tx(4A)=Tx(1B)=Tx(2B)=Tx(3B)=Tx(4B)Using this simplification in equation (3), it follows that the total NEXT noise onpair 1A is ΣNx(1A) = Tx + 10*log(10-NEXT(2A,1A)/10 + 10-NEXT(3A,1A)/10 +10-NEXT(4A,1A)/10) ΣNx(1A) = Tx - PSNEXT(1A) ……….………………..………………………..(4)The signal-to-noise ratio due to NEXT is SNRNx = Rx(1A) - ΣNx(1A) SNRNx = Rx(1A) -Tx + PSNEXT(1A) SNRNx = PSNEXT(1A) - IL(1) ………………….……….……………………(5) SNRNx = PSACRThe Far End Crosstalk noise on pair 1A due to a far-end transmit signal on pair2B is* TIA/EIA Category 6 working draft 6 (May 2000) Fx(2B,1A) = Tx(2B) - FEXT(2B,1A) …………….…..………………………..(6)The total Far End Crosstalk noise on pair 1A calculated as a power sum is 7
  9. 9. ΣFx(1A) = 10*log(10Fx(2B,1A)/10 + 10Fx(3B,1A)/10 +10Fx(4B,1A)/10) …..………(7)If all the transmit signals are at the same level, then the total FEXT noise poweron pair 1A is ΣFx(1A) = Tx + 10*log(10-FEXT(2B,1A)/10 + 10-FEXT(3B,1A)/10 +10-FEXT(4B,1A)/10) ΣFx(1A) = Tx - PSFEXT(1A) …………..………………..…………………..(8)The signal-to-noise ratio due to FEXT is SNRFx = Rx(1A) - ΣFx(1A) SNRFx = PSFEXT(1A) - (Tx - Rx(1A)) SNRFx = PSFEXT(1A) - IL(1)……..…..….……………………………(9) SNRFx = PSELFEXTBoth equation (5) and equation (9) can be used to determine the availablebandwidth of a channel. PSNEXT is usually the dominant noise source at higherfrequencies and determines the available bandwidth. If NEXT and echocancellation are used in the active electronics, then PSFEXT and otherenvironmental noise sources become the governing factors that determine thebandwidth and the ultimate data rate capability.From Table 1 above, the signal-to-noise ratio due to PSNEXT (PSACR) for theIBDN System 4800LX remains positive right up to 300 MHz and establishes theNEXT limited bandwidth for a worst-case channel configuration. At 200 MHzthere is an additional headroom of 10 dB compared with the current Category 6*proposal.PSELFEXT can be considered as the signal-to-noise ratio due to PSFEXT and isimportant for networks that employ advanced DSP technology for NEXTcancellation and echo cancellation. The IBDN System 4800LX provides aboutthe same PSELFEXT at 300 MHz as the Category 6* proposal at 200 MHz andCategory 5e at 100 MHz. The improved PSELFEXT performance ensures more* TIA/EIA Category 6 working draft 6 (May 2000)reliable transmission for today’s applications and additional information capacityfor multi-gigabit applications in the future. 8
  10. 10. Bandwidth and Information CapacityThere is a fundamental relationship between the bandwidth of a channelexpressed in MHz and the information capacity expressed in Mb/s. Thisrelationship was discovered a long time ago by Claude Shannon in his famouswork published in 1948. The maximum information capacity of a noisy channel(C) according to Shannon is given by: SNR w. log2 1 10 C 10 …………………..…………..…………….(10) where, w is the bandwidth S SNR 10 . log N f0 w S Signal f) d f ( f0 f0 w N Noise( f) d f f0Shannon’s equation was used to calculate the maximum information capacity forCategory 5, 5e, 6* and for an IBDN System 4800LX Channel. The data ratecapability relative to Category 5 is shown in Figure 2 and Figure 3. Figure 2represents the data rate capability for a channel that is limited by power sumNEXT noise, i.e. SNRNX as given by equation (5). Figure 3 represents the datarate capability for a channel that is limited by PSFEXT noise, i.e. SNRFX as givenby equation (9) or by the Insertion Loss which is assumed to be 35.3 dBmaximum due to EMC considerations and receiver sensitivity.Figure 2 below, is applicable for simple electronics. Figure 3 below, is applicablefor sophisticated electronics which uses digital signal processing techniques forNEXT cancellation.TIA/EIA Category 6 working draft 6 (May 2000)From Figure 2, an IBDN System 4800LX Channel provides the capability ofsupporting almost 2 ½ times the data rate of basic Category 5 for a bandwidth of100 MHz and up to 4 times the data rate for a bandwidth of 300 MHz. Figure 3illustrates that it is possible to increase the data rate of a Category 5 channel byalmost 2 times by using sophisticated electronics and an extended bandwidth of 9
  11. 11. 200 MHz. The comparable increase with the IBDN System 4800LX is 6 ½ timesfor an extended bandwidth of 300 MHz. Maximum Information Capacity (PSNEXT limited bandwidth) 450% 400% 350% 300% P Cat 5 e 250% Cat 5e r c 200% Cat 6 e 4800LX n 150% t 100% 50% 0% 100 200 300 Bandwidth (MHz) Figure 2 - Maximum information capacity for a channel limited by PSNEXT* TIA/EIA Category 6 working draft 6 (May 2000) 10
  12. 12. Maximum Information Capacity (PSFEXT and Insertion Loss limited bandwidth) 700% IL = 35.3 dB @ 320 MHz 600% 500% P IL = 35.3 dB @ 240 MHz e 400% Cat 5 r Cat 5e c Cat 6 e 300% 4800LX n IL = 35.3 dB @ 200 MHz t 200% 100% 0% 100 200 240 300 320 Bandwidth (MHz) Figure 3 - Max. info. capacity for a channel limited by PSFEXT & Ins. lossTest Results SummaryThe test results for the IBDN System 4800LX Channel are presented in Figures5 through 7 for the test configuration shown in Figure 4.Figure 5 is a plot of the PSNEXT and Insertion loss as a function of frequency.The two curves intersect at a frequency of about 300 MHz which is the PSNEXTlimited bandwidth for the channel under test. At high frequencies it is observedthat the connector NEXT is the major contributor to the PSNEXT of a channel.For example, we have noticed a very sharp drop in performance above 200 MHzfor certain designs of proposed Category 6 connecting hardware on the market.The results obtained for the IBDN System 4800LX Channel are contingent uponhaving well behaved connecting hardware with extended performance up to 300MHz. Another important point is the insertion loss. The relatively smoothinsertion loss traces at frequencies above 100 MHz are contingent upon havingwell matched components with good return loss performance.* TIA/EIA Category 6 working draft 6 (May 2000)The PSELFEXT results shown in Figure 6 and the Return Loss results shown inFigure 7 significantly exceed the proposed Category 6* requirements. 11
  13. 13. GigaFlex GigaFlex GigaFlex PS6+ PS6+ PS6+ Optional CP PS6LX Eq. Cbl. Patch Cord 4800LX IBDN cable WA cord 3m ½, 1, 2 & 3m 90m 3m TC TO Figure 4 - IBDN System 4800LX Channel Test Configuration Channel Insertion Loss vs. PSNEXT (measured from TC) 100 90 PSNEXT Pr 1 PSNEXT Pr 2 80 PSNEXT Pr 3 70 PSNEXT Pr 4 60 Ins. Loss Pr 1 dB Ins. Loss Pr 2 50 Ins. Loss Pr 3 40 Ins. Loss Pr 4 30 Ins. Loss C6a PSNEXT C6a 20 Ins. Loss C5e 10 300 MHz PSNEXT C5e 0 1 10 100 1000 PS-6 9-Oct-98 Frequency (MHz) Figure 5 - IBDN System 4800LX [Power Sum NEXT and Insertion Loss Results]* TIA/EIA Category 6 working draft 6 (May 2000) 12
  14. 14. Channel PSELFEXT 0 -10 -20 -30 PSELFEXT Pr 1 PSELFEXT Pr 2 dB -40 PSELFEXT Pr 3 PSELFEXT Pr 4 -50 PSELFEXT Cat 6 -60 -70 -80 1 10 100 1000 PS-6 Frequency (MHz) 9-Oct-98 Figure 6 - IBDN System 4800LX [Power Sum ELFEXT Results] Channel Return Loss (measured from TC) 0 -10 -20 RL Pair 1 RL Pair 2 dB -30 RL Pair 3 RL Pair 4 RL Cat 6 -40 -50 -60 1 10 100 1000 PS-6 Frequency (MHz) 9-Oct-98 Figure 7 - System 4800LX [Return Loss Results]* TIA/EIA Category 6 working draft 6 (May 2000) 13
  15. 15. ConclusionsCabling technology is progressing at a rapid pace. The development work on anew cabling standard for Category 6* is nearing completion. NORDX/CDT is atthe forefront of this technology by announcing two new products. The first is aninnovative UTP cable design with a cross-web filler that provides the highestsignal strength and the highest signal-to-noise performance in the industry. Thesecond is a new series of GigaFlex PS6+ connecting hardware and PS6LX patchcords. The new connectivity hardware is small in size and big on performance.The mated plug-jack connection is fully backward compatible with Category 5 asspecified in TIA/EIA 568-A, A2, A4 & A5.The new 4800LX cable, GigaFlex PS6+ connectivity hardware and PS6LX cordsmake up the IBDN System 4800LX which delivers an unsurpassed bandwidth of300 MHz and an information capacity up to 4 times that of Category 5.NORDX/CDT has taken a strong position in the marketplace and in thestandards forums to recognize and promote better cabling. We support the IEEErecommendation that the next generation of cables should have a lowerattenuation performance. Our IBDN System 4800LX meets this objective whileproviding more headroom. The channel attenuation (insertion loss) is 4.5 dBlower and the PSACR is 10 dB higher than the current Category 6* proposal at200 MHz. The additional headroom in channel attenuation and PSACR is asafeguard against adverse environmental conditions such as elevatedtemperatures, installation variables and alien crosstalk that can degrade systemperformance and data throughput. It is especially important to take into accountthe maximum cable operating temperature, which can significantly 20 degrees Cthat is currently specified in the draft Category 6* standard.We believe that a Category 6* channel that meets 200 MHz of bandwidth underall worst case conditions, will become the embedded base cabling for systemdesigners developing new applications. Whatever the future brings, whether it’s2.4 Gb/s, 4 Gb/s or 4.8 Gb/s, the next generation cabling system will need tohave the reserve capacity built-in for what’s coming next.References[1] Article “The Next Generation of Cable Technology” A technology primer fromNORDX/CDT, November 1998AcknowledgementsThe author is grateful to the all the members of the PLM, Marketing andTechnology team who contributed to the success of this project.* TIA/EIA Category 6 working draft 6 (May 2000) 14

×