Advanced PHY Performance Internal

Transcript Advanced PHY Performance Internal

Advanced PHY Performance

ADVANCED PHY PERFORMANCE

RON HRANAC Note: This presentation is intended for Cisco internal audiences and customers under NDA only. This presentation contains confidential intellectual property information that is proprietary to Broadcom Corporation and Texas Instruments.

DOCSIS

Background

Data Over Cable Service Interface Specification

•

DOCSIS 1.0 gave us standards-based interoperability, which means “certified” cable modems from multiple vendors work with “qualified” cable modem termination systems (CMTSs) from multiple vendors.

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DOCSIS 1.1 added a number of features, including quality of service (QoS), more robust scheduling, packet classification and other enhancements that facilitate voice services.

DOCSIS Background

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DOCSIS 1.0 and 1.1

—collectively known as DOCSIS 1.x

— support two downstream modulation formats: 64-QAM (quadrature amplitude modulation) and 256-QAM.

Modulation format 64-QAM (DOCSIS) 256-QAM (DOCSIS) 64-QAM (Euro-DOCSIS) 256-QAM (Euro-DOCSIS) 6 6 8 8 Channel bandwidth, MHz Symbol rate, Msym/sec 5.056941

5.360537

6.952

Raw data rate, Mbps 30.34

Nominal data rate, Mbps ~27 42.88

41.71

55.62

~38 ~37 ~50

DOCSIS Background

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DOCSIS 1.x supports several upstream data rates, ranging from a low of 320 kbps to a high of 10.24 Mbps. It also supports two modulation formats — quadrature phase shift keying (QPSK) and 16 QAM —as well as five upstream RF channel bandwidths.

Channel bandwidth, MHz 0.200

0.400

0.800

1.60

3.20

Advanced PHY Performance

Symbol rate, ksym/sec 160 320 640 1,280 2,560 QPSK raw data rate, Mbps 0.32

0.64

1.28

2.56

5.12

QPSK nominal data rate, Mbps 16-QAM raw data rate, Mbps ~0.3

0.64

~0.6

~1.2

1.28

2.56

~2.3

~4.6

5.12

10.24

16-QAM nominal data rate, Mbps ~0.6

~1.2

~2.4

~4.8

~9.0

DOCSIS Background

• • • • •

DOCSIS 1.1 added some enhancement to upstream transmission robustness, using 8-tap adaptive equalization.

DOCSIS 2.0: Higher upstream data throughput per RF channel, up to 30.72 Mbps DOCSIS 2.0 supports 64-QAM in the upstream —plus 8-QAM and 32-QAM channels.

—and optionally supports 128-QAM trellis coded modulation (TCM) encoded modulations for S-CDMA Higher orders of modulation require more robust data transmission To facilitate more robust upstream data transmission, DOCSIS 2.0 introduced advanced PHY

What is Advanced PHY?

PHY: Physical Layer

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Advanced PHY – 2 nd Generation Burst Mode RX Direct sampled RF front end Ingress cancellation Frequency stacking Spectrum management Improved adaptive equalizer from 2.0 Spec Improved burst mode RX preamble

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Improves 1.x as well as 2.0 cable modems

What is Advanced PHY?

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Symbol (T)-spaced adaptive equalizer with 24 taps compared to 8 taps in DOCSIS 1.x

Allows operation in the presence of more severe multipath and microreflections, and should accommodate signals near the band edge where group delay is more prevalent

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Improved burst acquisition Carrier and timing lock, power estimates, equalizer training and constellation phase lock are all done simultaneously. This allows shorter preambles, and reduces implementation loss.

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Better forward error correction (FEC) DOCSIS 1.x provides for the correction of up to 10 errored bytes per Reed Solomon block (T=10) with no interleaving, while DOCSIS 2.0 allows correction of up to 16 bytes per Reed Solomon block (T=16) with programmable interleaving.

What is Advanced PHY?

•

Advanced PHY silicon incorporates ingress cancellation technology in the upstream receiver chip, which further enhances upstream data transmission robustness. Think of ingress cancellation as a way to digitally remove in-channel impairments such as ingress and common path distortion.

Performance Concepts

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Implementation Margin Closeness to ‘theoretical’ in an additive white Gaussian noise (AWGN) environment Example – If the theoretical bit error rate (BER) at 21 dB carrier-to noise ratio (CNR) is 1x10 -6 but a CMTS actually needs 23 dB CNR to achieve a 1x10 -6 BER, the implementation margin is 2 dB.

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Processing Gain Processing to improve performance (e.g., FEC or ingress cancellation) Example – When ingress cancellation is turned off and a carrier-to interference ratio (C/I) of 10 dB yields 1x10 -6 BER, then turning on ingress cancellation allows C/I = 0 dB for 1x10 -6 BER, processing gain is 10 dB.

MC16C/S, MC28C/E Burst Mode Receivers - 1

Generation

Broadcom’s BCM3137 is within 2 dB of theory @16-QAM AND Burst Error Rate vs. Frequency Offset 2.56 Msym/sec, 16-QAM 10-Byte Preamble, RS(236,220)

1.00E+00 14 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 16 18 20 22 0 kHz RS(236,220) Theory

CNR (dB) Implementation margin of analog receiver (VCO, SAW…) adds another 2-3 dB Broadcom Confidential

MC28U/X – 2

Generation Direct Sampled Burst Mode Digital Receiver

Gmax = 32 dB F-connector A/D To PHY LPF PGA Amplifier LPF G = 1 To FFT Subsystem (AWACs) From AGC

All frequency conversion and selectivity in PHY ASIC Total implementation margin < 0.5 dB of theory

Cisco’s Advanced PHY

MC28U/X MC16U/X – Annex A/B Upstream Broadcom BCM3138 (same as BCM3140 2.0 chip, but without S-CDMA) 5-65 MHz dual A-TDMA, adaptive ingress cancellation, integrated FFT Downstream – Broadcom BCM3034 Annex A/B Modulator No SAW filter required with downstream chip MC5x20U – Annex A/B Upstream Texas Instruments TI4522 series 5-65 MHz A-TDMA, advanced PHY including ingress cancellation Downstream – Broadcom BCM3034 Annex A/B modulator No SAW filter required with downstream chip

Cisco’s Advanced PHY

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Advanced RF front end and Cisco MAC hardware, allow Cisco’s MC5x20U and MC28U Broadband Processing Engines (BPE) to offer improved capacity, performance and reliability.

Operates within 0.5 dB of theory Advanced PHY with ingress cancellation Greater than 17 Mbps single modem upstream throughput

Advanced PHY Performance

Line rate DOCSIS 1.1 and 2.0 processing using the advanced Cisco DOCSIS MAC technology

Cisco’s Line Card RF Front End

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High density —2 downstreams, 8 upstreams (MC28U) or 5 downstreams, 20 upstreams (MC5x20U) per line card

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Enhanced RF robustness

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Embedded upstream ingress cancellation

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Direct sampling

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Integrated upconverters

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ATDMA-capable

RF Performance: BER vs. AWGN

MC28U Packet Error Rate Versus AWGN

QPSK

1.00E+00 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 8 8.5

Advanced PHY Performance 9 3.51E-02 1.53E-02 6.44E-04 1.71E-04 9.5

CNR (dB)

10.5

11 2.00E-06 4.04E-07 11.5

12 Frequency: 30 MHz Mod: QPSK Symbol Rate: 1,280 ksym/sec Power: 0 dBmv Packet Size: 64 Bytes Packet Rate: 100 Packets: 1000000 RS_N=84 RS_T=3 MC28U Theoretical © 2003 Cisco Systems, Inc. All rights reserved.

MC28U Packet Error Rate Versus AWGN

16-QAM

1.00E+00 1.00E-01 1.00E-02 2.25E-01 9.08E-02 3.94E-02 1.61E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 15 15.5

16 4.48E-04 1.04E-04 16.5

CNR (dB)

Frequency: 30 MHz Mod: 16QAM Symbol Rate: 1,280 ksym/sec Power: 0 dBmv Packet Size: 64 Bytes Packet Rate: 100 Packets: 1000000 RS_N=88 RS_T=5 1.00E-06 8.55E-08 17.5

18 MC28U Theoretical

MC28U Packet Error Rate Versus AWGN

64-QAM

1.00E+00 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 19 19.5

20.5

2.64E-02 9.63E-03 21

CNR (dB)

21.5

1.84E-04 2.46E-05 2.00E-06 4.31E-07 Frequency: 30 MHz Mod: 64QAM Symbol Rate: 5,120 ksym/sec Power: 0 dBmv Packet Size: 64 Bytes Packet Rate: 100 Packets: 1000000 RS_N=96 RS_T=9 MC28U Theoretical 22 22.5

MC28U/MC28C Comparison

Cisco MC28C/U AWGN Impairment Performance: QPSK

1.00E+00 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 8.5

7.81E-02 9.5

9.5

1.53E-02 10.5

10.5

1.71E-04 11.5

5.50E-02 5.79E-03 11.5

4.04E-07 12.5

CNR (dB)

Frequency: 30 MHz Mod: QPSK Symbol Rate: 1,280 ksym/sec Power: 0 dBmv Packet Size: 64 Bytes Packet Rate: 100 Packets: 1000000 RS_N=84 RS_T=3 2.35E-04 13.5

2.80E-05 14.5

4.00E-06 MC28C MC28U Theoretical 15.5

MC28U/MC28C Comparison

Advanced PHY Performance

Cisco MC28C/U AWGN Impairment Performance: 16-QAM

1.00E+00 1.00E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 14.5

2.25E-01 9.08E-02 3.94E-02 1.61E-02 1.86E-02 8.56E-03 2.03E-03 4.48E-04 1.04E-04 4.59E-04 9.40E-05 1.80E-05 4.00E-06 Frequency: 30 MHz Mod: 16-QAM Symbol Rate: 1,280 ksym/sec Power: 0 dBmv Packet Size: 64 Bytes Packet Rate: 100 Packets: 1000000 RS_N=88 RS_T=5 1.00E-06 MC28C MC28U Theoretical 16.5

8.55E-08 18.5

CNR (dB)

20.5

22.5

MC520S/U BER Versus AWGN

Within Measurement Uncertainty of Theory QPSK

MC520S/U BER Versus AWGN

Within Measurement Uncertainty of Theory 16-QAM

MC520S/U BER Versus AWGN

Within Measurement Uncertainty of Theory 64-QAM

Lower Implementation Margin Advantages

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Can operate at lower CNR for a given BER than earlier generation CMTSs

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Provides improved operating headroom

RF Performance: Ingress Cancellation

Ingress Cancellation

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Opens previously unusable spectrum

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Enables reliable operation in the presence of ingress

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Narrowband and wideband

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Works with all DOCSIS 1.0, 1.1, & 2.0 cable modems

16-QAM 10 -8 BER Texas Instruments Confidential

MC28/16 U/X w/ Broadcom BCM3138 Adaptive Ingress Cancellation

RX AFE Demod Ingress Cancel & Equalizer

Broadcom Confidential

Broadcom BCM3138 Ingress Performance

Static CW Ingress (64-QAM, SIR = 0 dB)

Cluster SNR = 28.83 dB

Broadcom Confidential

Broadcom BCM3138 Ingress Performance

Wideband Ingressors 20 kHz and 100 kHz (16-QAM, SIR = 9 dB)

Cluster SNR = 20.96 dB

Broadcom Confidential

Broadcom BCM3138 Ingress Performance

Four CW Ingressors (64 QAM, SIR = 6 dB)

Cluster SNR = 26.94 dB

Broadcom Confidential

Broadcom BCM3138 Ingress Performance

Four CW Ingressors (16-QAM, SIR = 0 dB)

Cluster SNR = 22.79 dB

Broadcom Confidential

CableLabs PHY22B Ingress Cancellation

CableLabs optional PHY test Packet error rate in presence of single CW interferer & AWGN PER <0.5%, 64-byte packets Note: Negative C/I indicates interferer is larger than desired signal C/I Single CW Ingress MC28/16U/X

QPSK 1.28MBaud

AWGN = -20 dB

-20.2 dB

16QAM 2.56MBaud

AWGN = -25dB

-18.2 dB

64QAM 5.12Mbaud

AWGN = -30dB

-10.7 dB

RF Performance: Receive Equalizer

DOCSIS 2.0 ADTMA Equalizer

•DOCSIS 1.1 specifies an 8-tap T-Spaced Pre-Equalizer which can mitigate micro reflections of –10dB (at .5 micro-sec delay) with 27 dB MSE DOCSIS 1.1 Pre-Equalizer enables reliable operation at 16-QAM in channels that could only support QPSK in DOCSIS 1.0

•DOCSIS 2.0 specifies a 24-tap T-Spaced Pre-Equalizer which can mitigate micro reflections of –10dB (at .5 micro-sec delay) with 33 dB MSE DOCSIS 2.0 Pre-Equalizer can enable reliable operation at 64-QAM even in channels that can only support QPSK in DOCSIS 1.0

24-tap adaptive equalizer can operate in DOCSIS 1.0 Mode to compensate linear plant errors (slope, group delay, microreflections) increasing DOCSIS 1.0 modem channel capacity Advanced PHY Performance © 2003 Cisco Systems, Inc. All rights reserved.

Cisco Systems Confidential

24-Tap Adaptive Equalizer Operate 1.0 cable modems at band edge 16-QAM 2.56 Msym/sec over –3.4dB slope and 125 nsec group delay Impaired 39 – 42 MHz Band BER < 1x10 -8 : Reed Solomon T=0 (Off) DOCSIS 1.0 8-tap equalizer could only support QPSK or 1.28 Msym/sec

RF Performance: Downstream MER

RF Downstream Path

MC16C/S BCM3033 Modulator High Speed D/A SAW UPX DSx BCM3034 Modulator MC28U/16U No SAW Filter !!

High Speed D/A UPX DSx

Downstream Constellation

256-QAM @ 857 MHz Total EVM = 1.18% !

Does Advanced PHY Work?

SCTE Cable-Tec Expo Advanced PHY Demo

AM carriers from comb generator No packet loss!

SCTE Cable-Tec Expo Advanced PHY Demo

CPD from downstream feed and diode circuit No packet loss!

SCTE Cable-Tec Expo Advanced PHY Demo

Noise from HP signal generator No packet loss!

SCTE Cable-Tec Expo Advanced PHY Demo

CBT screen shot showing all three impairments

24-Tap Adaptive Equalization Lab Test

6.4 MHz bandwidth 64-QAM signal

Before adaptive equalization:

Correctable FEC errors were incrementing about 7000 codewords per second (232 bytes per codeword). The CMTS’s upstream SNR (MER) estimate was 23 dB

After adaptive equalization:

No correctable FEC errors and the CMTS’s upstream SNR estimate increased to 36+ dB

Customer Field Test

16-QAM signal riding on top of S-CDMA signal, with CW carrier in-channel No packet loss!

Customer Field Test

Spectrum analyzer screen shot showing 16-QAM signal at ~12 MHz center frequency

No packet loss!

Advanced PHY: The Bottom Line

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Improves upstream data transmission robustness

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Allows use of spectrum that was previously unusable

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Facilitates higher orders of modulation

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Provides additional operating headroom

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Many advanced PHY features work with DOCSIS 1.x cable modems

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Cost-effective way to kick-start the deployment of new services

Q and A

Advanced PHY Performance Internal

Transcript Advanced PHY Performance Internal