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Overview of telecommunications means for the GTS

Overview of telecommunications means for the GTS. LI Xiang Telecommunication Division, NMC, China E-mail: lixiang@cma.gov.cn. 1. Leased circuits. D ata C ommunications E quipment: Converting the digital signals to the signals more suitable for transmission. DTE. DTE. DCE. DCE.

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Overview of telecommunications means for the GTS

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  1. Overview of telecommunications means for the GTS LI Xiang Telecommunication Division, NMC, China E-mail: lixiang@cma.gov.cn

  2. 1. Leased circuits Data Communications Equipment: Converting the digital signals to the signals more suitable for transmission DTE DTE DCE DCE Data Terminal Equipment: - acting as sources or sinks for data communication link - Terminal/Computer • Leased circuit: • point-to-point dedicated data transmission circuit between two points • leased by an organization from a telecommunication service provider • permanently open connection • medium: copper wire, optical fiber,... • signals: analog, digital

  3. 1.1 Analogue Circuits • At the source • digital to analogue conversion • modulate • At the destination • - Demodulate • - analogue to digital conversion DTE Phone Line Modem Modem PC + Communication Software • A digital connection, consisting of • - a Transmit Data line • a Receive Data line • many hardware handshaking control lines. - a analogue connection - analogue signals

  4. Features of analogue circuits • Dedicated voice-grade circuit • Using existing telephone cable network to provide a fixed and transparent connection between two points in the voice frequency band 300 - 3400 Hz • Supporting low-speed data communication • Typical date rates over analogue circuits are: 300, 1200, 2400, 9600, 14.4k, 19.2k, 28.8kbps • Low costs

  5. 1.2 Digital circuits • source encoding/decoding • channel coding/decoding • synchronization Digital circuit Modem Modem PC + Communication Software Computer + Communication Software - a digital connection - digital baseband signals

  6. Features of digital circuits • High quality communication links • providing a fixed and transparent connection between two points • terminated by a digital interface • supporting high-speed data communication: 64Kbps – 155Mbps

  7. 1.3 Examples of use of Leased Circuits (1) Physical link - analogue circuit Physical Layer - V.34 Data Link Layer - Link Access Procedure Balanced (LAPB) Network Layer - X.25 Packet Layer Protocol (PLP) Beijing – Moscow GTS link

  8. 1.3 Examples of use of Leased Circuits (2) Physical link - digital circuit Physical Layer - V.35 Data Link Layer - Link Access Procedure Balanced (LAPB) Network Layer - X.25 Packet Layer Protocol (PLP) Beijing – Offenbach GTS link

  9. 1.3 Examples of use of Leased Circuits (3) Using TCP/IP protocol to exchange data over a leased circuit

  10. 2. Frame Relay • A protocol standard for sending information, which is divided into frames or packets, over a wide area network. • A fast and efficient packet-switching technology • A Frame-Relay network doesn't perform error detection • The intelligent network devices connected to a Frame-Relay network are responsible for the error correction and frame formatting • Frame Relay typically operates at 56 Kbps to 1.544 Mbps. • Frame Relay is protocol independent, it can process traffic from different networking protocols like IP, IPX, and SNA. • Multiple logical connections can be established over a single physical connection

  11. Concept of Frame Relay communicate Frame Relay Network router A T H T FR data packet PVC • Translating existing data communications protocols for transmission over a Frame-Relay network • Routing the data across the network to another frame router or other Frame-Relay compatible device • Handling many types of protocols, including LAN protocols • Each router supports one of many physical data interfaces and can provide several user ports. FR data packet • Frame Relay sends information in packets called frames through a shared Frame-Relay network. • A frame contains all the information necessary to route it to the correct destination H router B

  12. DLCI: Data-Link Connection identifier, represents the address of the frame and corresponds to a PVC. C/R: Command/Response Field Bit, designates whether the frame is a command or response. EA: Extension Bit, can be used for expanding the number of possible addresses. DE: Discard Eligibility Indicator, provides the network a signal to determine which frame to discard. When there is a congestion on the line, in order to free the line, the network will discard frames with a DE value of 1 before discarding other frames. FECN: Forward Explicit Congestion Notification. If FECN is changed to 1 as a frame is sent downstream toward the destination location when congestion occurs during data transmission. BECN: Backward Explicit Congestion Notification. If BECN is changed to 1 as a frame traveling back toward the source of data transmission on a path where congestion is occurring. FCS: Frame Check Sequence

  13. CIR • Committed Information Rate • Instead of being allocated a fixed amount of bandwidth, Frame-Relay services offer a CIR at which data is transmitted. • If traffic and the service agreement allow, data can burst above the committed rate.

  14. PVC • Permanent Virtual Circuits • A PVC is a dedicated connection through the shared Frame-Relay network replacing a dedicated end to-end line. • A PVC is needed for each site in the network. But in a Frame Relay network, the bandwidth is shared among multiple users. So any single site can communicate with any other single site without the need for multiple dedicated lines. • PVCs function via a Local Management Interface (LMI), which provides control procedures. The control procedures function in three ways: • link integrity verification initiated by the user device • network status report giving details of all PVCs • network notification of whether a PVC's status changes from active to inactive • Data-Link Connections (DLCs) are PVCs pre-configured by both sides of the connection. The DLC identifier (DLCI) is used as the logical address for frame-layer multiplexing.

  15. Examples of use of Frame Relay service Router KDDI Frame Relay Port 256K Port 192K CIR 32K JMA Router CNC Frame Relay CMA CIR 32K Router KT Frame Relay Port 128K KMA

  16. 3. Introduction to VSAT,and satellite based DVB, DAB

  17. 3. 1 Introduction to VSAT • Very Small Aperture Terminal • Self-contained hub station • Unbalanced traffic in outroute and inroute • The utilization rate of VSAT network improved with the increase of remote terminals • Support of broadcast

  18. Types of VSAT network • Star network: mostly adopted by data communications network. • Full mesh network: mostly adopted by telephony communications network. • Hybrid architecture: applied to integrated services network

  19. Generally, VSAT systems operate in the Ku-band and C-band frequencies. • Ku-band system • Smaller sizes of VSAT antennas at remotes • 0.6 ~ 2.4 m antenna • Abundant in frequency resource • Existing the propagation problems caused by rain • C-band system • Larger sizes of VSAT antennas at remotes • 1.8 ~ 2.4 m antenna • Most C-band frequency resource already used • Existing the interference problem between adjacent channels because of the congestion of channels

  20. Model of a transmission channel from one terminal to another (VSAT)

  21. CMA’s VSAT system • Communication Satellite • Satellite: AsiaSat II • Frequency Band: Ku-band • Coverage: China and some other Asia countries adjacent to China • Consisting of three parts • Satellite telephony network • One hub, about 350 remotes • Full mesh network • Covered regional, provincial and city level weather centers • Satellite Wide Area network • One hub, about 350 remotes • Star network • Covered regional, provincial and city level weather centers • PCVSAT broadcasting system • One hub, over 2000 remotes (including the remotes installed in Pyongyang and Ulan Bato)r • Data broadcasting system • Covered regional, provincial ,city and county level weather centers

  22. SWAN SWAN • two-way system • One outbound channel: 512kbps • Eight inbound channels: 8*128kbps • Remotes to Hub: ftp • Hub to Remotes: multicast

  23. CMA’s PCVSAT data broadcasting network • PCVSAT broadcasting system • One way system • Broadcasting rates: 2Mbps • Supporting 256 logical channels, the typical logical channel rate is 64kbps • Authorization and management centralized at hub

  24. 3.2 Introduction to DVB • DVB: international standard for digital video broadcasting • Based on ISO 13818 MPEG-2 coding and multiplexing specifications

  25. Types of DVB standards • DVB-S • DVB-S satellite transmission standard, based on QPSK, is now the de-facto world satellite transmission standard for digital TV applications • DVB-C • cable delivery mechanism, is closely related to DVB-S, and is based around 64-QAM, although higher order modulation schemes are also supported. • DVB-T • Based on COFDM (Coded Orthogonal Frequency Divisional Multiplexing) and QPSK, 16 QAM and 64 QAM modulation, it is the most sophisticated and flexible digital terrestrial transmission system available today.

  26. Concept of DVB Signal Generation

  27. What a end user needs? PC DVB card

  28. Why DVB? • Smaller VSAT antenna • Secure transmission with entitlement control • Higher data rates, 256Kpbs – 58Mbps • Support for Multi-protocol Encapsulation (MPE) of IP data • Multiplexing of up to 8192 streams • Integration of data with video and audio • Co-existence between multiple DVB steams • Multicast enabled • Ease of implementation & upgrade • Open architecture

  29. 3.3 Introduction to DAB • DAB: Digital audio broadcasting • Based on two techniques • Musicam • is a digital compression system based on MPEG technology • makes the signal down to 10 times lighter • provides an CD-like quality of sounds • enables the association of data to the audio programmes (title, CD cover, author of the song) • Digicast • eliminates traditional reception problems (distortion, interferences, etc.) by spreading signals in time on several frequencies. The information that are broadcast separately remain linked by encoding. • eliminates interferences ; propagation echoes become an advantage by enforcing the reception quality including in more complex areas. • is able to send independently audio Streams (ex : Musicam) and Packet Datas (ex : NPAD) • Operating via multiplexes. Each multiplex is composed of programmes and associated services. A sole transmitter can broadcast several programmes. The output can be up to 1.5 Mbps. • Supporting Datacasting

  30. DATACASTING : DATA BROADCASTING VIA DAB

  31. Procedures on data sending and receiving • At the sending end, • User’s data files being sent to the local uplink site of the DAB services provider, such as WorldSpace, via FTP or other means. • The services provider‘s scheduler at the uplink site automatically picks up the data and places it into the defined bin at which point it is sent up to the satellite. • At the receiving end, • A PC-adaptor, connected to a satellite digital receiver and a PC transforms the receiver into a one-way satellite modem that can receive data at the rate up to 128 kbps. • The delivered files are stored in the end user's designated directory on the hard drive.

  32. Why DAB? • Wide coverage • DAB services: almost all over the world • Datacasting: Africa and Asia • Lower transmission costs for broadcasters : US$10 per MB • Smaller antenna • Wide choice of equipments at receiving ends • Higher data rates • Broadcasting rate: up to 1.5Mpbs • Receiving rate: up to 128kbps

  33. Thank you

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