Subscriber line technology Subscriber line is the last mile to the - PowerPoint PPT Presentation

Lic.Tech. Marko Luoma (1/68) Lic.Tech. Marko Luoma (2/68) Subscriber line technology ÿ Subscriber line is the last mile to the customer þ Conventionally only PSTN subscriber lines ÿ Twisted pair copper S-38.192 Verkkopalvelujen tuotanto þ One or several pairs to each house S-38.192 Network Service Provisioning þ In urban areas CATV subscriber lines provide same service ÿ Hybrid fiber coax network þ Power lines are the last to arrive to the scene Lecture 3: Subscriber line technologies ÿ Power lines are used to transmit also data traffic þ Conventionally only control messages to fusebox ÿ Subscriber lines are the most expensive part of the network þ A lot of physical construction work for each customer Lic.Tech. Marko Luoma (3/68) Lic.Tech. Marko Luoma (4/68) Subscriber line technology xDSL ÿ ÿ Technology options for broadband data connections are XDSL is based on the digitalized subscriber line technologies þ XDSL over PSTN subscriber lines þ IDSL (ISDN Digital Subscriber Line) was the initial invention þ DOCSIS over CATV lines ÿ Also local loop can be digitized with high reliability and low bit error rate þ Power line communication (PLC) þ Both ends of the subscriber line is equipped with modems þ Wireless local loops ÿ Information is modulated to frequency range that best serves the ÿ 802.11 WLAN / HiperLAN communication ÿ 802.16 WiMax þ PSTN copper pairs are in general old and contain a lot non- linearities ý Joints made with variable mechanisms ý irregular twisting of pairs ý Highly variable di-electric properties of insulations ý Optimized for frequency range below 4kHz

Lic.Tech. Marko Luoma (5/68) Lic.Tech. Marko Luoma (6/68) xDSL HDSL ÿ ÿ Non-linearities cause a lot of problems in high data rate communications HDSL (High Bit-Rate Digital Subscriber Line) þ Attenuation þ First real xDSL-technique þ Crosstalk þ Baseband operation (2B1Q) þ Distortion ÿ Subscriber line cannot be used same time for POTS services ÿ þ Symmetric operation Magnitude depends on frequency and other usage of copper infrastructure ÿ Suitable for corporate LAN interconnection þ Copper pairs do not run individually on the ground ;-) ÿ PBX subscriber lines þ Part of the time-slots can be left out of usage þ Uses multiple copper pairs ÿ Two pairs – 1.5Mbps (T1) ÿ Three pairs – 2Mbps (E1) þ Maximum distance 3-4 km Lic.Tech. Marko Luoma (7/68) Lic.Tech. Marko Luoma (8/68) 2B1Q SDSL ÿ Four level baseband transmission ÿ SDSL (Single-Line Digital Subscriber Line) þ 2 bits per symbol þ Single copper pair version of HDSL ÿ Used in ÿ Uses same modulation (2B1Q) þ ISDN subscriber line (IDSL) ÿ Transmission rates are same as in HDSL þ HDSL þ More popular than HDSL ÿ Copper pairs are expensive to rent in urban area BAUDI þ Maximum distance 3 km +3 +1 -1 -3

Lic.Tech. Marko Luoma (9/68) Lic.Tech. Marko Luoma (10/68) ADSL G.SHDSL ÿ ADSL (Asymmetric Digital Subscriber Line) ÿ G.SHDSL (Symmetric High Bit-Rate Digital Subscriber Line) þ Most popular xDSL technique þ ITU-T Recommendation G.991.2 þ Asymmetric uplink and downlink ÿ T1E1 - HDSL2 þ Three bands ÿ ETSI - SDSL ÿ 0-3400Hz POTS þ Transmission rates 192 kbps - 2.312 Mbps ÿ 20-160kHz Bidirectional data band þ Coding 16-Level TC-PAM (Trellis Coded Pulse Amplitude ÿ 240-1100kHz downlink data band Modulation) þ Bands are divided into 256 carriers þ Single copper pair technology ÿ Carriers can be activated and passivated þ Information is framed based on various technologies: þ Downlink maximum rate 1.5-8Mbps ÿ ATM þ Uplink maximum rate 1.5 Mbps ÿ TDM þ Maximum distance 3-4 km ÿ IP Lic.Tech. Marko Luoma (11/68) Lic.Tech. Marko Luoma (12/68) CAP/QAM DMT ÿ ÿ Carrierless AM/PM - Quadrature Amplitude Modulation Discrete Multitone þ Two dimensional code space þ N x CAP/QAM ÿ Orthogonal components ÿ Linecode in divided into N subcomponents þ Amplitude þ ADSL -> N = 256 þ Phase ÿ Subcomponents are produced with Fourier transformation (DFT) ÿ þ Used in Used in þ ADSL ÿ ADSL þ VDSL ÿ VDSL þ DOCSIS 3.4 30 1104 138

Lic.Tech. Marko Luoma (13/68) Lic.Tech. Marko Luoma (14/68) ADSL ATU-R ÿ ÿ DMT based ADSL system measures the quality of copper pair and ADSL Transceiver Unit Remote adapts symbol rate in each carrier to compensate possible defects þ Subscriber network termination þ Crosstalk ÿ Either þ Bit error rate þ Separate active device (bridge, router) þ Attenuation þ NIC in PC ÿ Can be equipped with low pass filter to extract voice signal (analog)from data. 3.4 30 138 1104 3.4 30 138 1104 Lic.Tech. Marko Luoma (15/68) Lic.Tech. Marko Luoma (16/68) ATU-C XDSL Framing ÿ ÿ ADSL Transceiver Unit Central Office XDSL systems are typically build for data transmission þ Core network termination ÿ Data is transmitted between ÿ Counterpart for user side mode þ Residential subscriber and ISP (Internet) þ Usually build into larger unit (DSLAM) þ Residential subscriber and corporate network (Intranet) ÿ Several modems þ Corporate offices (LAN interconnection) ÿ Multiplexing unit which concentrates the traffic into high speed ÿ In all cases subscriber can be operated as backbone link þ Routed þ ATM 155 – ATM 622 ÿ Subscriber has its own subnet þ Bridged ÿ Several subscribers share one subnet

Lic.Tech. Marko Luoma (17/68) Lic.Tech. Marko Luoma (18/68) XDSL Framing RFC 2684 ÿ ÿ RFC2684: Multiprotocol Encapsulation over ATM Adaptation Layer 5 RFC 2684 : Multiprotocol Encapsulation over ATM Adaptation Layer 5 þ Previous version RFC 1483 (Classical IP) ÿ RFC2364: Point to Point Protocol over ATM ÿ RFC 2516: A Method for Transmitting PPP Over Ethernet (PPPoE) ATU-C PC ATU-R DSLAM BRAS ÿ Point to Point Protocol over Ethernet over ATM ATU-C PC ATU-R DSLAM BRAS RFC2684 RFC2684 Framing Framing ATM ATM ATM ATM ATM ATM ATM ATM LLC/SNAP Framing VCMUX PPP Lic.Tech. Marko Luoma (19/68) Lic.Tech. Marko Luoma (20/68) RFC2684 RFC 2684 ÿ ÿ Two modes VC-multiplexing is based on raw ATM AAL5:n CPCS-interface þ VC-multiplexing þ Routed protocols are interleaved directly in to CPCS-PDU ÿ No framing -> individual ATM PVC can be used only for þ Bridged protocols require destination MAC-address for delivery transmitting one type information ÿ Both ends of the connection must share common view of the PAD =00-00 structure of information MAC Destination CPCS-PDU ÿ Efficient MAC frame þ LLC-encapsulation PAD (0-47 octet) LAN FCS (depends VC:) ÿ IEEE 802.2 encapsulation is added to information -> contains CPCS-UU (1 octet) PAD (0-47 octet) pointer to data type CPI (1 octet) = 0x00 CPCS-UU (1 octet) Length (2 octet) CPI (1 octet) =0x00 CRC (4 octet) Length (2 octet) CRC (4 octet)

Lic.Tech. Marko Luoma (21/68) Lic.Tech. Marko Luoma (22/68) Routed protocols RFC 2684 ÿ LLC-encapsulation þ LLC header expresses frame type (protocol) þ IP uses LLC/SNAP encapsulation Subnet A Subnet B AA-AA-03 -> SNAP Destination SAP =AA Source SAP =AA Frame Type =03 OUI =00-00-00 00-00-00 -> Ethertype 08-00 -> IPv4 Ethertype =08-00 IP IP IP IPv4 packet Ethernet Ethernet AAL5 AAL5 PAD (0-47 octet) ATM ATM ATM ATM CPCS-UU (1 octet) CPI (1 octet) =0x00 Length (2 octet) CRC (4 octet) Lic.Tech. Marko Luoma (23/68) Lic.Tech. Marko Luoma (24/68) Bridged protocols RFC 2684 ÿ Ethernet bridging uses same LLC/SNAP encapsulation as IP Destination SAP =AA does Subnet A Source SAP =AA AA-AA-03 -> SNAP Frame Type =03 00-80-C2 -> Bridging OUI =00-80-C2 00-01 -> FCS preserved PID =00-01 / 00-07 00-07 -> FCS not preserved MAC Destination IP IP MAC frame Ethernet Ethernet Ethernet LAN FCS (PID=00-01) PAD (0-47 octet) AAL5 AAL5 CPCS-UU (1 octet) ATM ATM ATM ATM CPI (1 octet) =0x00 Length (2 octet) CRC (4 octet)

Lic.Tech. Marko Luoma (25/68) Lic.Tech. Marko Luoma (26/68) CATV Network with data Classical CATV Network connections ÿ ÿ Designed for transmission of Root amplifier of tap network is TV/Radio signals changed þ 6 - 446 Mhz þ Connection to data network (Internet) Active Passive ÿ Access network Active Passive þ Modulates the data CATV Core Network þ Amplifier lines CATV Core Network -Channel distribution to high frequency -Channel distribution þ Passive tap network at area last mile CATV Access Network ÿ 470 – 860 MHz CATV Access Network -Amplification ÿ Up to 500 subscribers -Amplification Lic.Tech. Marko Luoma (27/68) Lic.Tech. Marko Luoma (28/68) (Euro) DOCSIS CATV Network (Euro) DOCSIS ÿ ÿ ÿ Amplifiers in coax segment are US Europe changed to bidirectional þ Frequency ranges þ Frequency ranges þ Uplink ÿ Uplink 5 – 42 MHz ÿ Uplink 5 – 65 MHz ÿ Data Active Passive ÿ Dowlink 50 – 750 MHz ÿ Downlink 50 – 860 MHz þ 5 – 42 Mhz CATV Core Network þ 6 MHz video channels þ 8 Mhz video channels -Channel distribution þ Downlink 0.2/1/2 MHz upstream channels ÿ Video and data QPSK CATV Access Network -Amplification 1/2 MHz downstream channels þ 50 – 860 MHz QPSK 8 MHz DVB-C channels QAM 5 65 70 130 300 862