Transcript
Alien Crosstalk Measurements and Performance with Screened Cat 5e Cable Larry Cohen Carlos Aldana SolarFlare Communications
cohen_5_21_2003_screened.pdf
IEEE802.3 Interim May 2003 10GBASE-T
[email protected] [email protected]
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Overview • Purpose: – Determine if screened Cat 5e cable provides a viable means of alien crosstalk mitigation to support 10GBase-T operation
• • • •
Measurement method and test setup Measurement results Channel capacity results Summary IEEE802.3 Interim May 2003 10GBASE-T
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Why Screened Cable (FTP)? • Relatively inexpensive – Cost is <1.5X of same class UTP – Significantly less expensive than Cat 7/Class F.
• Compatible with UTP RJ45 connectors • Not necessary to use screened RJ45 connectors • Screened patch cords are readily available
IEEE802.3 Interim May 2003 10GBASE-T
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Alien NEXT Measurement Setup Tight bundle cross-section
Network Analyzer S
R
50Ω
Six disturber cables A
50Ω
Victim cable
50Ω
Attenuator matched to line interface matching pads Matching pad
50Ω Attenuator 50:100Ω Interface
Cable ties
50:100Ω Interface
Matching pad 6 dB Splitter
10 cm
Disturber
Victim
Isolated interconnect span (2 meters UTP patch cord)
Screened Cat 5e test cable bundle (horizontal cable)
100 Ohm Terminations
40 meters
1 meter UTP patch cords
10 cm
Cat 5e Keystone jack panels
IEEE802.3 Interim May 2003 10GBASE-T
100 Ohm Terminations
1 meter UTP patch cords
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Alien Crosstalk Cable Test Bed
Bundled cable
Unbundled cable
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Procedure • Measure pair-to-pair coupling between all wire pairs of victim and six surrounding disturber cables (96 total measurements) • Calculate channel capacity of victim cable using power sum coupling into each victim pair from the six surrounding disturber cables • Test with screened Cat 5e cable and standard Cat 5e UTP Keystone jack panel; shield is left floating
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Measurement Results Measured Power Sum Alien NEXT Coupling - Worst Pair -20
Insertion gain (dB)
-30
•FTP provides effective mitigation even with unscreened connectors (foil shield is floating)
-40
-50
-60
-70
-80
Preliminary Cat 5e alien NEXT model FTP Cat 5e w/ unscreened Keystone jacks 0
50
100
150
200
250
300
350
400
450
500
Frequency (MHz) IEEE802.3 Interim May 2003 10GBASE-T
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Measurement Summary • Screened cable provides substantial reduction of alien crosstalk • Cable foil screen may be left floating – Eliminates potential ground loop problems – Simplifies installation; compatible with installed base of UTP patch panels, connectors, and Keystone jacks
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Capacity Calculations • 10GBase-T Cabling Ad Hoc Channel Models: – Established models for Category 5e Insertion Loss, Return Loss, self NEXT and self FEXT (April 17, 2003).
• Alien crosstalk model for Cat 5e based on coupling measurements on tightly bundled screened Cat 5e cable • Background Noise – Upper bound noise level of -150 dBm/Hz appears consistent with actual data center noise.2,3
• Launch power of 10 dBm. IEEE802.3 Interim May 2003 10GBASE-T
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Capacity Calculations • Self-Impairment Cancellation: – 55 dB Return Loss Cancellation (15 dB Hybrid, 40 dB PHY) – 40 dB NEXT Cancellation – 25 dB FEXT Cancellation
• No Established Level for Alien NEXT Mitigation. Mitigation of 0 dB to 25 dB Realized through Combination of One or More Alternatives: – PHY (0 dB to 10 dB)4 – Improved Installation Practices (0 dB to 10 dB)1 – Enhanced Cable Design/Specification (0 dB to 25 dB)5 IEEE802.3 Interim May 2003 10GBASE-T
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Channel Capacity Results 18
16
Capacity for FTP CAT5E with uns creened Keys tone jacks
16.0
16.6
16.9
17.0
17.1
17.1
5
10
15
20
25
Capacity (Gb/s )
14
12
10
8
6
4
0
Alien Mitigation (dB)
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Summary • Capacity greater than 10 Gbps can be achieved with: – Ad hoc Cat 5e models and alien crosstalk measurement models from screened cable – Reasonable levels of impairment cancellation – No alien crosstalk PHY mitigation
• Established the existence of low alien crosstalk cable that is low cost and compatible with the installed base UTP connectors IEEE802.3 Interim May 2003 10GBASE-T
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References 1Cohen,
L., “Alien Crosstalk Measurements,” IEEE802.3 Contribution, Jan. 2003. 2Pagnanelli, C., “Data Center Background Noise Measurements,” IEEE802.3 10GBASE-T Contribution, May 2003. 3Cobb, T., “Background Noise,” IEEE802.3 10GBASE-T Contribution, May 2003. 4Solarflare Communications, “10GBASE-T Tutorial,” IEEE802.3 Contribution, Nov. 2002. 5Cobb, T., “Experimental Cat6 Cable Developed with Improved Alien NEXT,” IEEE802.3 Contribution, March 2003. IEEE802.3 Interim May 2003 10GBASE-T
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