1 overview of telecommunications means for the gts li xiang telecommunication division, nmc, china...
TRANSCRIPT
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Overview of telecommunications means for the GTS
LI XiangTelecommunication Division, NMC, China
E-mail: [email protected]
1. Leased circuits
DTE
Data Terminal Equipment: - acting as sources or sinks for data communication link - Terminal/Computer
DCE DCE DTE
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
Data Communications Equipment:Converting the digital signals to the signals more suitable for transmission
A digital connection, consisting of- a Transmit Data line- a Receive Data line - many hardware handshaking control lines.
1.1 Analogue Circuits
PC +Communication
Software
ModemPhone
Line Modem
DTE
At the source - digital to analogue conversion- modulateAt the destination - Demodulate - analogue to digital conversion
- a analogue connection- analogue signals
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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
- a digital connection- digital baseband signals
1.2 Digital circuits
PC +
Communication
Software
Computer +Communication
Software
Modem ModemDigital
circuit
• source encoding/decoding• channel coding/decoding• synchronization
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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
Features of digital circuits
1.3 Examples of use of Leased Circuits (1)
Beijing – Moscow GTS link
Physical link - analogue circuitPhysical Layer- V.34Data Link Layer - Link Access Procedure Balanced (LAPB) Network Layer - X.25 Packet Layer Protocol (PLP)
Physical link- digital circuitPhysical Layer - V.35 Data Link Layer - Link Access Procedure Balanced (LAPB) Network Layer - X.25 Packet Layer Protocol (PLP)
Beijing – Offenbach GTS link
1.3 Examples of use of Leased Circuits (2)
1.3 Examples of use of Leased Circuits (3)
Using TCP/IP protocol to exchange data over a leased circuit
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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
Concept of Frame Relay communicate
A router
Frame Relay
Network
Frame Relay
Network
B router
HT
FR data packet
H
T
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
-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.
PVC
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
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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.
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PVC
Permanent Virtual Circuits A PVC is a dedicated connection through the shared Frame-Relay network r
eplacing 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.
Examples of use of Frame Relay service
CNCFrame Relay
KDDI Frame Relay
CIR 32K
Router
Router
Sun
Port 256K Port 192K
CMA
Sun
KT Frame Relay
JMA
Router
Port 128KSun
KMA
CIR 32K
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3. Introduction to VSAT,and satellite based DVB, DAB
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3. 1 Introduction to VSAT
Very Small Aperture Terminal Self-contained hub station Unbalanced traffic in outroute and inrout
e The utilization rate of VSAT network imp
roved with the increase of remote terminals
Support of broadcast
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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
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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
satellite
RF/IF DEMOD PROCESSING
STATION / TERMINALINTERFACE
TERMINAL
DEMOD IF/RFPROCESSING MOD
STATION / TERMINALINTERFACE
TERMINAL
SATELLITE NETWORK
earth stati onearth stati on
USERUSER
Model of a transmission channel from one terminal to another (VSAT)
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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 an
d Ulan Bato)r Data broadcasting system Covered regional, provincial ,city and county level weather centers
VSAT Control Center
VSAT Control Center
PBX
Server
TCP/IPCHINAPAC
Regional Centers
Provincialcenters
City bureau
National network center
CMA’s Intranet
National operationalcenters
SWANtwo-way systemOne outbound
channel: 512kbpsEight inbound
channels: 8*128kbps
Remotes to Hub: ftp
Hub to Remotes: multicast
SWAN
MultiplexPC Card
LNB
PCVSAT databroadcasting network
CMA’s PCVSAT data broadcasting network
PCVSAT broadcasting systemOne way systemBroadcasting rates: 2MbpsSupporting 256 logical channels, the typical logical
channel rate is 64kbpsAuthorization and management centralized at hub
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3.2 Introduction to DVB
DVB: international standard for digital video broadcasting
Based on ISO 13818 MPEG-2 coding and multiplexing specifications
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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.
Concept of DVB Signal Generation
analog-digital
converter
MPEG 2digital
compressioncoder
Analog audioand video
signals
mu
ltiple
xe
r
mo
du
lato
r
amplifier
broadcasting
Digital signals Digital compressionsignals
DVBdigital signals
video signal
Data Server
digital broadcastingor
digitization TV program
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What a end user needs?
Satellite dish
PC DVB card
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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
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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, aut
hor 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
DATACASTING : DATA BROADCASTING VIA DAB
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Procedures on data sending and receiving
At the sending end, User’s data files being sent to the local uplink site of the DAB ser
vices provider, such as WorldSpace, via FTP or other means. The services provider‘s scheduler at the uplink site auto
matically 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 t
ransforms 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.
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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
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Thank you