Transcript PPT
Homework Final Exam Wednesday, 3 May, 5:30-7:20 pm Readings: [26] “Cable It’s not just for TV” [27] “Battling for Local Phone Customers” [28] “IP/ATM Integrated Services over Broadband Access Copper Technologies” Video... Uncompressed NTSC video requires about 90 Mbps Broadcast Quality compressed video requires 45 Mbps ‘VHS Quality’ compressed video requires 1.5 Mbps The OSU Teleconferencing system is running at 384 Kbps MPEG 1 Compression of motion video & audio at about 1.5 Mbps Targeted at digital playback & storage Has Random Access capabilities Employs Motion Estimation Algorithms, Discrete Cosine Transforms, & Huffman Coding Codes frames as Intrapictures, Predicted Pictures, and Bidirectional Pictures Standard since 1992 MPEG 2 Targets higher quality compression, typically at 3-6 Mbps bit rates Being used for Direct Broadcast TV Large chunks of MPEG2 used in U.S. HDTV standard Standard since 1994 MPEG 4 Aimed at Multimedia Coding Bit rates from 8 Kbps - 35 Mbps Codes objects as opposed to 8x8 blocks Ability to interact & manipulate objects Standard in 1999 MPEG 7 Ability to describe and search for multimedia objects (under development) Audio clips video images MP3 Web audio clips Uses audio compression from MPEG 1 12-1 typical compression ratio H.261 (a.k.a. Px64) Subset of MPEG Targets real time videoconferencing Bit rates from 64 Kbps to 2.048 Mbps 64 Kbps - 128 Kbps: Face shot (video phone) 384 Kbps: considered to be minimum speed for decent full screen videoconferencing H.263 is a modified H.261 Offers better quality Requires more processing power Channel Capacity (C) C = W*Log2(1 + SNR) bps W = channel bandwidth (Hz) SNR = channel signal-to-noise ratio Maximum bit rate that can be reliably shoved down a connection EX) Analog Modem (30 dB SNR) C = 3500 *Log2(1 + 1000) = 34,885 bps EX) 6 MHz TV RF Channel (42 dB SNR) C = 6,000,000 *Log2(1 + 15,849) = 83.71 Mbps Local Loop Capacity about 34.8 Kbps due to filter at input of CO A/D converter Copper Copper Fiber Local Local Optic Loop Loop Trunk CO CO Phone Phone 4 Wire 2 Wire Analog ‘4 Wire’ Digital TDM 64 Kbps 2 Wire 4 Wire Analog 56 Kbps Modem requires Digital Source Copper Local Loop Copper Local Loop Fiber Optic Trunk CO CO Phone Server 4 or 2 Wire ‘4 Wire’ Digital (ISDN, xDSL, etc.) 2 Wire 4 Wire Analog Delivery: Over the Air 300 m Analog FDM Digital by 2006 (FCC edict) 50-60 miles Video Delivery Systems Satellite Older systems analog 1 channel per 6 MHZ of RF bandwidth Newer Systems digital MPEG2 & TDM allow 4-6 channels per 6 MHz of RF bandwidth Cable TV Distribution systems originally all coax Fiber deployed from Head End side moving out Who will be your one-stop telecom provider? Cable TV Companies? Physical Tree with Large Bandwidth Simplex & No Switching Fair/Poor quality cable plant Solution: Cable Modems Re-engineer system for 2-way traffic Shared Access Install data switches at Head End Install voice switches at Head End PC to ISP Connectivity: Cable Voice network Voice Switch Voice Video Mux Data ISP Router To Internet Headend PC Ethernet NIC Data Cable Modem Voice Cable Modem will use shared bandwidth to get to Cable TV Headend. Home Who will be your one-stop telecom provider? Local Telephone Companies? Physical Star with Narrow Bandwidth Full Duplex & Switched Good quality cable plant Solution: Digital Subscriber Lines Switched Access Install data switches at CO Install video switches at CO Home PC to ISP Connectivity Voice network Voice Switch Local Loop Modem PC CO Home ISP Modem Bank To Internet This configuration causes call blocking problems at some CO switches due to longer than designed-for call holding times. PC to ISP Connectivity: DSL Voice network PC Voice Switch CO ADSL Modem Voice DSLAM Data ISP Router To Internet Data Splitter Voice Home ADSL will off load data traffic from CO voice switches, & provide more CO-Home bandwidth. Who will be your one-stop telecom provider? The Typical Telco can get xDSL running on existing twisted pair cable plant with less reengineering than the typical Cable Company requires to get Cable Modems running on existing coax/fiber networks. But Cable network has more bandwidth Whoever gets to market first, with a costeffective solution, will be in the driver’s seat. Advantage ???