ADSL(VDSL).pptVIP

Case Study ADSL Modems Geert Leus Fac. EEMCS, TUDelft leus@cas.et.tudelft.nl ADSL Modems Overview ADSL (VDSL) modems Modem technology : voice-band vs. xDSL Communication impairments (...call for DSP solutions) Equalization Echo Cancellation ADSL (VDSL) Modems References: J.A.C. Bingham, `The theory and practice of modem design’, Wiley, 1980 J.A.C. Bingham, `Multicarrier modulation for data transmission, an idea whose time has come’, IEEE Communications Magazine, May 1990, pp.5-14 W.Y. Chen, `DSL simulation techniques and standards development for digital subscriber line systems’, Macmillan, 1998 ... ADSL (VDSL) Modems Modem Technology : …-1970 : development of efficient modulation techniques for transmission over band limited channels, spurred by military applications (- … 9.6 kbits/sec) 1970-1980 : Semiconductor technology (size power reduction) 1980-1990 : Introduction of coding techniques (- … 19.2 kbits/sec) 1990-2000 : reaching Shannon limit (- 33kbits/sec, asymmetric 56kbits/sec modems) 1995-… : ADSL (8Mbits/sec downstream, 60 kbits/sec upstream) 2000-… : VDSL (52Mbits/sec downstream, 6Mbits/sec upstream), ... ADSL (VDSL) Modems Performance improvement results from: improved telephone channel quality (digital switches, etc.) improved modulation/coding/DSP techniques (QAM, trellis coded modulation (TCM), echo cancellation (EC), adaptive equalization,…) semiconductor technology ADSL (VDSL) Modems PS: duplexing techniques Frequency division duplexing (FDD) `downstream’ = central office - remote user `upstream’ = remote user - central office Time division duplexing (TDD) : `ping-pong’ Full duplex with echo-cancellation (EC) ADSL (VDSL) Modems ADSL : `Asymmetric Digital Subscriber Line’ …-1993: ADSL spurred by interest in video-on-demand (VOD) 1995 : ADSL/VOD interest decline 1996 : ADSL technology trials prove viability. 1997-... : ADSL deployment, reoriented to