The Benefit of Low Bit Rate Voice Compression Technologies as Part of a Converged Network Deployment Strategy

Transcription

1 The Benefit of Low Bit Rate Voice Compression Technologies as Part of a Converged Network Deployment Strategy DSLcon Spring 2000 San Jose, CA 4 April 2000 Session: T-210 Dennis R Gatens Product Management Director Telogy Networks-A Texas Instruments Company Century Blvd Germantown, MD T: F: dgatens@telogy.com 1

2 Abstract The Benefit of Low Bit Rate Voice Compression Technologies as Part of a Converged Network Deployment Strategy This presentation will discuss voice compression technologies and the benefit to access providers through their use in the delivery of Voice over DSL (VoDSL) services. Access providers can realize significant benefit through the implementation of voice compression technologies in central office gateway and customer premise Integrated Access Devices (IAD). Improvement of bandwidth resource utilization can be realized in the WAN resulting in reduced or deferred capital expenditures or lower operating costs. Lower bandwidth requirements in the local loop can result in lower cost services to the residential and business customer while providing the same quality as PCM/ADPCM based services. The flow of the presentation will include a review of compression technologies and their implementation, a comparison to non-compressed techniques, and an analysis of their deployment concluding with a case study-like review of access provider network requirements. 2

3 Agenda! Market Overview! Basics of Voice Processing! Overview of VoDSL Transport Models! Compression Techniques! Summary! Q&A 3

4 Market Overview and Trends! VoDSL considered a killer DSL application " VoDSL services expected to be widely deployed " ATM centric DSL infrastructure supports QoS requirements for voice transport! PCM/ADPCM are widely deployed technologies " Require 64/32 kbps of bandwidth " PCM/ADPCM Physical Layer Voice Transport (PLVT) gaining mindshare! Mass deployment will bring about widespread network convergence " Compression technologies will enable better network resource utilization # Local loop and WAN 4

5 VOIP Forecast VOIP Minutes for Business Users Billions of Minutes Source: IDC YEAR 5

6 VoDSL Market Forecast US VoDSL Service Revenues Forecast ($M) $10,000 $9,000 $8,000 $7,000 $6,000 $5,000 $4,000 $3,000 $2,000 $1,000 $ Source: Cahner In-Stat 6

7 Network Convergence Corporate Office IP Phone IP Phone Remote Office IP Phone Corporate Gateway IP Phone Integrated Access Device DSLAM WAN Corporate Router SOHO IP Phone Voice Gateway PSTN Remote DSLAM Integrated Access Device 7

8 Value Proposition-End User!Services " Telecommuter and Small/Remote Office # Virtual PBX # Bundled voice and data services " Consumer # Multiple managed lines # Lines on demand 8

9 Value Proposition-Service Provider!CLECs " Bundled services # Expanded range of services " Lower cost to provision additional lines # No additional line lease costs " Expand the reach of their switch infrastructure!ilecs # Backhaul traffic over GR-303 to existing switches " Bundled services # Expanded range of services " Lower cost to provision additional lines 9

10 Basics-Analog Voice to PCM An analog voice signal is received The Signal is converted to a Pulse Code Modulation (PCM) digital stream

11 Basics-PCM Processing! The PCM stream is analyzed " Echo is removed " Voice Activity Detector (VAD) removes silence " Tone Detection is performed! Remaining PCM samples are forwarded to the CODEC 11

12 Basics-PCM to Frames The PCM stream is fed into the CODEC And Voice frames are created Each Frame is 10 ms long (G.729a) and contains 10 bytes of speech

13 Key Network Parameters! Latency! Delay Variation or Jitter! Lost Packets! Out of Order Packets! Echo Cancellation 13

14 Gateway Architecture-TDM Network Gateway Product phone fax modem PBX Key Systems Central Office Physical Interfaces Analog ulaw alaw linear pulse dialing 2W/4W loop start ground start gain control Digital T1/E1 T3 OC1/OC3 Tone Interfaces Tone Generation DTMF Call Progress Tone Tone Detection DTMF V.21 Call Progress MF (R1, R2) Modem Tone DTMF Tone Relay Signaling Interfaces CAS FXS FXO E & M Transparent CCS Q.931 QSIG Transparent Voice/Fax Processing Echo Cancellation VAD Voice Coding Voice Playout Fax Modem V.21 V.27ter V.29 V.17 V.33 N e t w o r k I n t e r f a c e Packet Network 14

15 Gateway Architecture-Packet Network Gateway Product H.323 Gateway T e l e p h o n y I n t e r f a c e Network Management Interface Functions Address Translation and Parsing Signaling Translation CAS H.323/FRF.11/ATM CCS H.323/FRF.11/ATM Fax Relay/ Advanced Local Processing H.323 Network Protocol Interface FRF.11 Network Protocol Interface ATM Standard In Work Proprietary Today P ro t o c o l S ta c k s IP Networks Frame Relay Networks ATM Networks Frame Relay Gateway ATM Gateway PC w/ H.323 Node 15

16 DSL Overview! DSL Types " SDSL # Upstream and downstream bandwidth as high as 1.5 Mbps " ADSL Typically 768 kbps # Upstream bandwidth as high as 640 kbps # Downstream bandwidth as high as 8 Mbps! Bandwidth available on the local loop dependent on the following: " Loop length " Wire gauge " Presence of bridge taps " Coupled interference 16

17 VoDSL Transport Methods!ATM (AAL2)/DSL!IP/ATM (AAL5)/DSL!Physical Layer Voice Transport (PLVT) " Voice mapped directly over ADSL physical layer channel 17

18 VoDSL Transport Methods VoIP IP IP VoIP PPP PPP AAL2 AAL5 AAL5 AAL2 VoATM ATM ATM ADSL INTERLEAVED PATH ISP or Core PLVT ADSL FAST PATH PLVT Lifeline POTS DSL Client Access Network Lifeline POTS 18

19 Voice Connection ATM Profiles-ITU I Identifier Description of Profile Packet Length 0 Not used 1 PCM-64/SID 40/1 2 PCM-64/ADPCM-40/32/24/16/SID 40/25/20/15/10/1 3 PCM-64/G /12.8/9.6/16/12.8/9.6/SID 40/20/16/12/10/8/6/1 4 PCM-64/G /12.8/9.6/SID 40/10/8/6/1 5 PCM-64/G /G.729-8/SID 40/25/20/10/2 6 PCM-64/G.729-8/SID 40/10/2 7 PCM-64/G /G.729-8/SID 40/20/10/2 8 PCM-64/G /G.729-8/SID 40/25/10/2 19

20 Voice Connection ATM Profiles-ATM Forum Identifier Description of Profile Packet Length 0 Not used 1 LPC-10 (High Efficiency) 42 2 LPC-10 (Low Delay) 14 3 CVSD CVSD CVSD G (6.4/5.3/SID) 24/20/4 7 G.711/G.726 (PCM/ADPCM/SID) 44/44/1 20

21 70 ITU-T Speech Coding Standards Bandwidth Requirements 64 kbps Bandwidth kbps G.711 G.726 G.728 G.729AB G kbps 10 8 kbps 5.3 kbps 0 1 Voice CODEC 21

22 Voice CODEC Quality Comparison 5 Mean Opinion Score (MOS) G.711 PCM G.726 ADPCM G.728 LD-CELP G.729 G.729AB GSM G.723.1A Source: IEEE Communications Magazine, 9/97 Kbps 22

23 VoDSL Channel Density Comparison Downstream/Upstream Bandwidth Required (kbps) Voice Channels Typical SDSL service Maximum upstream bandwidth for ADSL 256 kbps service G.711 G.726 G

24 VoDSL Service Definition Example 256 kbps Symmetrical Service! Assume: " Minimum service is 256 kbps " Data + 4 channels of voice are required! PCM " 4 voice channels: 256 kbps+overhead " Data: 0 kbps! ADPCM " 4 voice channels: 128 kbps+overhead " Data: < 128 kbps! G.729 " 4 voice channels: 32 kbps+overhead " Data: < 224 kbps 24

25 VoDSL Service Definition Example 768 kbps Symmetrical Service! Assume: " 768 kbps symmetrical service " Data + 8 channels of voice are required! PCM " 8 voice channels: 512 kbps+overhead " Data: < 256 kbps! ADPCM " 8 voice channels: 256 kbps+overhead " Data: < 512 kbps! G.729 " 8 voice channels: 64 kbps+overhead " Data: < 704 kbps 25

26 Benefit of Compression!Gain of 4:1 can be realized over ADPCM " Impact of loop quality on available bandwidth is mitigated!expansion of remote access service offerings over DSL-enabled local loop " Longer reach with VoDSL services " Higher voice channel density over the local loop " Higher bandwidth available for data services over the local loop " Lower speed services can offer equivalent voice channel density!itu P.800 MOS score of 4.0 can be achieved " 4.0 considered toll quality 26

27 Summary! VoDSL considered a killer DSL application " VoDSL services expected to be widely deployed " ATM centric DSL infrastructure supports QoS requirements for voice transport! Mass deployment will bring about widespread network convergence " Compression technologies will enable better network resource utilization! Compression technologies can reduce the bandwidth requirements over the local loop and in the WAN and provide for an expansion of service offerings 27

28 Further Reading! ATM Forum af_vtoa_0113! ATM Forum af_vtoa_les-01.05draft! DSL Forum WT-043! ITU I

29 Biography Dennis R Gatens is a Product Management Director with Telogy Networks, a Texas Instruments company. He has over 15 years experience in the communications industry. At TI he is responsible for the application of TI s Telogy Software solutions in the Remote Access Server, VoDSL, Gateway and CPE Gateway market spaces, and 3 rd party programs. Prior to joining TI, Dennis was the Product Manager for Broadband Access Products with Pulsecom where he was responsible for the WavePacer Broadband DSL Solution. Prior to joining Pulsecom, Dennis was employed with FiberCom (Now Litton-Network Access Systems). In his 11 years at FiberCom he had a range of responsibilities from Hardware Design Engineer to Manager of Commercial Product Development. He holds a Bachelor of Science Degree in Electrical Engineering from Virginia Tech and a Master in Business Administration from Radford University. He has been published in Telephony magazine and regularly speaks at DSLcon and IEC ComForum seminars. Dennis is also a participating member of the DSL Forum. 29