Your SlideShare is downloading. ×
0
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Introduction To Telecom
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Introduction To Telecom

4,027

Published on

Just want to share my knowledge with others

Just want to share my knowledge with others

2 Comments
1 Like
Statistics
Notes
No Downloads
Views
Total Views
4,027
On Slideshare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
89
Comments
2
Likes
1
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide
  • Establishing a basic voice call between two telephony agents is the main call processing task. A basic voice telephone call has the following characteristics: Each of the two telephony agents involved in the call can be either a line or a trunk. No custom calling features are active during the call. The functional steps required to process this call can be expressed in general terms as follows : Detecting the incoming call, that is, detecting a line origination or the seizure of an incoming trunk Receiving the digits, that is, determining what type of signaling the originating agent is using, and collecting the digits Translating the digits, that is, analyzing them to determine the call destination Selecting a terminating agent, that is, finding the best available route for the call Establishing the telephony connection, that is, setting up a speech path between the originating and terminating agents Signaling the terminating agent: if the terminator is a line, apply ringing and give audible ring-back tone to the originator if the terminator is a trunk, out-pulse the digits Detecting an answer by detecting an answer signal from the terminating agent recording the answer time in the billing information for the call, if a billing record is required Detecting disconnect by detecting a disconnect signal from either the originator or the terminator recording the disconnect time in the billing information for the call, if a billing record is required taking down the telephony connection idling the originating and terminating agents
  • In the U.S., the telephone company will be providing its BRI customers with a U interface . The U interface is a two-wire (single pair) interface from the phone switch. It supports full-duplex data transfer over a single pair of wires, therefore only a single device can be connected to a U interface. This device is called an Network Termination 1 (NT-1). The situation is different elsewhere in the world, where the phone company is allowed to supply the NT-1, and thereby the customer is given an S/T interface. The NT-1 is a relatively simple device that converts the 2-wire U interface into the 4-wire S/T interface. The S/T interface supports multiple devices (up to 7 devices can be placed on the S/T bus) because, while it is still a full-duplex interface, there is now a pair of wires for receive data, and another for transmit data. Today, many devices have NT-1s built into their design. This has the advantage of making the devices less expensive and easier to install, but often reduces flexibility by preventing additional devices from being connected. Technically, ISDN devices must go through an Network Termination 2 (NT-2) device, which converts the T interface into the S interface (Note: the S and T interfaces are electrically equivalent). Virtually all ISDN devices include an NT-2 in their design. The NT-2 communicates with terminal equipment, and handles the Layer 2 and 3 ISDN protocols. Devices most commonly expect either a U interface connection (these have a built-in NT-1), or an S/T interface connection. Devices that connect to the S/T (or S) interface include ISDN capable telephones and FAX machines, video teleconferencing equipment, bridge/routers, and terminal adapters. All devices that are designed for ISDN are designated Terminal Equipment 1 (TE1). All other communication devices that are not ISDN capable, but have a POTS telephone interface (also called the R interface), including ordinary analog telephones, FAX machines, and modems, are designated Terminal Equipment 2 (TE2). A Terminal Adapters ( TA ) connects a TE2 to an ISDN S/T bus. Going one step in the opposite direction takes us inside the telephone switch. Remember that the U interface connects the switch to the customer premises equipment. This local loop connection is called Line Termination (LT function). The connection to other switches within the phone network is called Exchange Termination (ET function). The LT function and the ET function communicate via the V interface .
  • The ISDN Physical Layer is specified by the ITU I-series and G-series documents. The U interface provided by the Telco for BRI is a 2-wire, 160 kbps digital connection. Echo cancellation is used to reduce noise, and data encoding schemes (2B1Q in North America, 4B3T in Europe) permit this relatively high data rate over ordinary single-pair local loops. 2B1Q (2 Binary 1 Quaternary) is the most common signaling method on U interfaces. This protocol is defined in detail in 1988 ANSI spec T1.601. In summary, 2B1Q provides: two bits per baud, 80 k-baud per second, transfer rate of 160 kbps The input voltage level can be one of 4 distinct levels ( 00 –3 –2.5v, 01 –1 -0.833v, 10 1 0.833v, 11 3 2.5v).(note: 0 Volts is not a valid voltage under this scheme).These levels are called Quaternaries. Each quaternary represents 2 data bits, since there are 4 possible ways to represent 2 bits, as in the table above. Each U interface frame is 240 bits long. At the prescribed data rate of 160 kbps, each frame is therefore 1.5 ms long. Each frame consists of : Frame overhead - 16 kbps, D channel - 16 kbps, 2 B channels at 64 kbps - 128 kbps The Sync field consists of 9 Quaternaries (2 bits each) in the pattern +3 +3 -3 -3 -3 +3 -3 +3 -3. (B1 + B2 + D) is 18 bits of data consisting of 8 bits from the first B channel, 8 bits from the second B channel, and 2 bits of D channel data. The Maintenance field contains CRC information, block error detection flags, and "embedded operator commands" used for loop-back testing without disrupting user data. Data is transmitted in a super-frame consisting of 8 240-bit frames for a total of 1920 bits (240 octets). The sync field of the first frame in the super-frame is inverted (i.e. -3 -3 +3 +3 +3 -3 +3 -3 +3).
  • Flag (1 octet) - This is always 7E16 (0111 11102) C/R (Command/Response) bit indicates if the frame is a command or a response EA0 / EA1 (Address Extension) bit indicates whether this is the final octet of the address or not TEI (Terminal Endpoint Identifier) 7-bit device identifier (see below) Control (2 octets) - The frame level control field indicates the frame type (Information, Supervisory, or Unnumbered) and sequence numbers (N(r) and N(s)) as required. Information - Layer 3 protocol information and User data CRC (2 octets) - Cyclic Redundancy Check is a low-level test for bit errors on the user data. SAPI : Service Access Point Identifier (SAPI) is a 6-bit field that identifies the point where Layer 2 provides a service to Layer 3. ( TEI ) : Terminal Endpoint Identifiers are unique IDs given to each device (TE) on an ISDN S/T bus. This value may be assigned statically when the TE is installed, or dynamically when activated.
  • Establishing the Link Layer The Layer 2 establishment process is very similar to the X.25 LAP-B setup, if you are familiar with it. The TE (Terminal Endpoint) and the Network initially exchange Receive Ready (RR) frames, listening for someone to initiate a connection The TE sends an Unnumbered Information (UI) frame with a SAPI of 63 (management procedure, query network) and TEI of 127 (broadcast) The Network assigns an available TEI (in the range 64-126) The TE sends a Set Asynchronous Balanced Mode (SABME) frame with a SAPI of 0 (call control, used to initiate a SETUP) and a TEI of the value assigned by the network The network responds with an Unnumbered Acknowledgement (UA), SAPI=0, TEI=assigned. At this point, the connection is ready for a Layer 3 setup.
  • The ISDN Network Layer is also specified by the ITU Q-series documents Q.930 through Q.939. Layer 3 is used for the establishment, maintenance, and termination of logical network connections between two devices. Service Profile IDs (SPIDs) They are used to identify what services and features the Telco switch provides to the attached ISDN device. SPIDs are optional; when they are used, they are only accessed at device initialization time, before the call is set up. The format of the SPID is defined in a recommendation document, but it is only rarely followed. It is usually the 10-digit phone number of the ISDN line, plus a prefix and a suffix that are sometimes used to identify features on the line, but in reality it can be whatever the Telco decides it should be. If an ISDN line requires a SPID, but it is not correctly supplied, then Layer 2 initialization will take place, but Layer 3 will not, and the device will not be able to place or accept calls. See ITU spec Q.932 for details. Information Field Structure The Information Field is a variable length field that contains the Q.931 protocol data. Protocol Discriminator (1 octet) - identifies the Layer 3 protocol. If this is a Q.931 header, this value is always 0816. Length (1 octet) - indicates the length of the next field, the CRV. Call Reference Value (CRV) (1 or 2 octets) - used to uniquely identify each call on the user-network interface. This value is assigned at the beginning of a call, and this value becomes available for another call when the call is cleared. Message Type (1 octet) - identifies the message type (i.e., SETUP, CONNECT, etc.). This determines what additional information is required and allowed. Mandatory and Optional Information Elements (variable length) - are options that are set depending on the Message Type.
  • Layer 3 – Initialization These are the steps that occurs when an ISDN call is established. In the following example, there are three points where messages are sent and received; 1) the Caller, 2) the ISDN Switch, and 3) the Receiver. 1. Caller sends a SETUP to the Switch. 2. If the SETUP is OK, the switch sends a CALL Proceeding to the Caller, and then a SETUP to the Receiver. 3. The Receiver gets the SETUP. If it is OK, then it rings the phone and sends an ALERTING message to the Switch. 4. The Switch forwards the ALERTING message to the Caller. 5. When the receiver answers the call, is sends a CONNECT message to the Switch 6. The Switch forwards the CONNECT message to the Caller. 7. The Caller sends a CONNECT Acknowledge message to the Switch 8. The Switch forwards the CONNECT ACK message to the Receiver. 9. Done. The connection is now up.
  • Separation of the whole spectrum into smaller frequency bands A channel gets a certain band of the spectrum for the whole time Advantages: no dynamic coordination necessary works also for analog signals Disadvantages: waste of bandwidth if the traffic is distributed unevenly Inflexible guard spaces
  • A channel gets the whole spectrum for a certain amount of time Advantages: only one carrier in the medium at any time throughput high even for many users Disadvantages: precise synchronization necessary
  • A channel gets a certain frequency band for a certain amount of time Advantages: Better protection against tapping Protection against frequency selective interference Higher data rates compared to code multiplex But: precise coordination required
  • The audio signal of each channel is encoded using a unique pair of psuedo random bit sequences (PRBS). The output is then used to modulate the given carrier and sent over the radio interface. All channels use the same spectrum at the same time Advantages: Bandwidth efficient No coordination and synchronization necessary Good protection against interference and tapping Disadvantages Lower user data rate More complex signal regeneration Implemented using spread spectrum technology, also called Spread Spectrum Multiple Access ( SSMA )
  • The Network Switching System (NSS) The switching system (SS) is responsible for performing call processing and subscriber-related functions. The switching system includes the following functional units. home location register (HLR)—The HLR is a database used for storage and management of subscriptions. The HLR is considered the most important database, as it stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. When an individual buys a subscription from one of the PCS operators, he or she is registered in the HLR of that operator. mobile services switching center (MSC)—The MSC performs the telephony switching functions of the system. It controls calls to and from other telephone and data systems. It also performs such functions as toll ticketing, network interfacing, common channel signaling, and others. visitor location register (VLR)—The VLR is a database that contains temporary information about subscribers that is needed by the MSC in order to service visiting subscribers. The VLR is always integrated with the MSC. When a mobile station roams into a new MSC area, the VLR connected to that MSC will request data about the mobile station from the HLR. Later, if the mobile station makes a call, the VLR will have the information needed for call setup without having to interrogate the HLR each time. authentication center (AUC)—A unit called the AUC provides authentication and encryption parameters that verify the user's identity and ensure the confidentiality of each call. The AUC protects network operators from different types of fraud found in today's cellular world. equipment identity register (EIR)—The EIR is a database that contains information about the identity of mobile equipment that prevents calls from stolen, unauthorized, or defective mobile stations. The AUC and EIR are implemented as stand-alone nodes or as a combined AUC/EIR node. Base Station Sub-System (BSS) All radio-related functions are performed in the BSS, which consists of base station controllers (BSCs) and the base transceiver stations (BTSs). BSC—The BSC provides all the control functions and physical links between the MSC and BTS. It is a high-capacity switch that provides functions such as handover, cell configuration data, and control of radio frequency (RF) power levels in base transceiver stations. A number of BSCs are served by an MSC. BTS—The BTS handles the radio interface to the mobile station. The BTS is the radio equipment (transceivers and antennas) needed to service each cell in the network. A group of BTSs are controlled by a BSC. Additional Functional Elements Other functional elements shown in Figure 2 are as follows: message center (MXE)—The MXE is a node that provides integrated voice, fax, and data messaging. Specifically, the MXE handles short message service, cell broadcast, voice mail, fax mail, e-mail, and notification. mobile service node (MSN)—The MSN is the node that handles the mobile intelligent network (IN) services. (GMSC)—A gateway is a node used to interconnect two networks. The gateway is often implemented in an MSC. The MSC is then referred to as the GMSC. GSM interworking unit (GIWU)—The GIWU consists of both hardware and software that provides an interface to various networks for data communications. Through the GIWU, users can alternate between speech and data during the same call. The GIWU hardware equipment is physically located at the MSC/VLR.
  • Transcript

    • 1. Introduction To Telecom [email_address]
    • 2. Agenda – 1st Session
      • Components of a telecom network
      • Classification of switches
      • Time & space switching
      • H/w overview of a DSS
      • S/w overview of a DSS
      • Events in Basic Voice Call
      • Types of Line access
      • Types of trunk interfaces
      • Signaling protocols on voice trunks
    • 3. Agenda – 2nd Session
      • Intelligent Network (IN) at a glance
      • Multiple Access Technologies
      • GSM Network Overview
      • Next Generation Networks – Birds eye View
      • Transmission Standards in use
      • Customer demands at a Glance
      • Future Trends in Telecom
    • 4. Components of a Telecom Network
      • Customer premises equipment (CPE)
      • Customer loop
      • Switch or Node
      • Links/Trunks interconnecting switches
      • Signaling Systems
      • Transmission Backbone
      • Network Management Centre (NMC)
    • 5. Customer premises equipment
      • Telephone, Telex, ISDN terminal, & Fax
      • Computer, Modems, LAN
      • VSAT
      • PBX
      • Satellite receiver
      • Mobile hand set and Pagers
      • Video-conferencing terminals
    • 6. Customer loop
      • Wireless In Local Loop (WILL)
      • Fiber to the Kerb / Home / Neighborhood
      • ISDN access
      • Wide band on copper ( DSL )
      There is a problem with any copper wire transmission system -- Cross-talk . This is caused by the electrical signal in one wire being induced onto an adjacent wire, a problem that is especially prevalent in central offices, where large bundles of wires enter the building. The solution was relatively simple. Experiments showed that balancing out the undesired induced currents by "turning over" or transposing the relative positions of the disturbing and disturbed circuits could solve the inductance problem. Physically, this can be accomplished very easily on wire pairs (two wires) by giving them a twist every few inches. The careful manufacture of twisted-pair wires effectively eliminated this problem. Twisted pair wires are the 22- or 24-gauge subscriber line wires in your house that connect your telephone or computer modem to the telephone central office.
      • Pair of copper wire ( twisted pair ?)
    • 7. The Switch
      • Why is a switch required ?
      The increase in the cost cabling will be directly proportional to the increase in size of the network. Number of links required for connecting “n” subscribers is given as n!/(2*(n-2)!) The increase in the number of devices at CPE will be directly proportional to the increase in the size of the network. The cost of maintaining such a setup will spiral up as the size of the network increases. 1 2 3 4 5
    • 8. What is the Solution ? to/from other locations Local Exchange (switch) A switched Network
    • 9. The Structure of a typical Telephone Network EO EO EO Access tandem TAX TAX Access tandem EO EO EO AT AT AT AT
    • 10. Classification of Switches
      • Circuit Switches
      • Packet Switches
      • Packet switches take a user's data stream, break it down into smaller segments , called packets.
      • They add network control information, and then transmit the packets through the network in bursts .
      • The size of the packet can vary based on nature/needs of the application.
      • Unlike circuit switches, packet switches don't use dedicated paths .
      • All packet-switched traffic comes in bursts with a variable bit rate (VBR)
      • In a packet switch, incoming traffic is passed through the switch on a first-come, first-served basis, and packet traffic is routed according to the address in the packet header.
      • Since a customer's data can arrive at the switch at any time, packet switching is called asynchronous switching.
      • Circuit switch provides a physical, dedicated path -- called a time slot -- for a call through the switching matrix.
      • No other callers can use that switch path until the call is ended.
      • The call has an end-to-end dedicated circuit for the duration of the call, hence the switch is called a circuit switch.
      • Circuit switching is used for voice switching and to support data services that have a constant bit rate (CBR).
      • Circuit switching is called synchronous because the user's information is transmitted in a specific time slot, and only in that time slot.
      • This concept of a dedicated path guarantees high-quality, almost error-free transmission for the call.
      • Since the average voice conversation is about three to four minutes long, network switch resources used to set up the path can be reused over and over during the course of the day.
    • 11.  
    • 12. Basic TDM switch LP filter OUTPUTS Switch Address Memory Counter 1 2 3 4 5 6 7 1 2 3 4 5 6 7 inputs outputs
    • 13. Digital Multiplexing M U L T I P L E X E R F I L T E R S A M P L E R Q U A N T I S E R E N C O D I N G 125 us 125 us 125 us 125 us
    • 14. Time Switch Read address 3 17 17 3 SAM Counter Write address Y X 17 3 X Y 17 3 3 17 VM - 1 VM - 2 3 17 read write write read
    • 15. T-S-T switch T T S T T n 17 2 1 1 2 5 n 1 2 5 n X X X n 5 2 1 n 7 2 Y n 7 2 Y n 17 2 Y 1 1 Y X n 5 2 1
    • 16. Time Switch
      • Information interchange occurring at different instances
      • Implemented using memory
      • Sequential writing & Random reading
      • Random writing & Sequential reading
      • Faster memory for bigger size switches
      • Engineering Problems at higher mux rate
      • No blocking
    • 17. Merits of Digital Switching
      • Faster call set up
      • Smaller in size
      • Noise immunity & reduced cross talk
      • Less maintenance
      • More reliable
      • More services to the customer
      • Flexible for enhancement of features
      • Integration of Voice & Data
      • Modular growth to large sizes
      • Redundancy and Load sharing modes
    • 18. Basic DSS Hardware Architecture Signaling Trunk Interface (Analog/Digital) Line Interface (Analog/Digital) Control Processor + Switch control` Ringer ckts Line Trunk Voice (TDM) Voice (TDM) Voice I/O System Tone/Annc. Switch ( TDM)
    • 19. DSS Software Architecture SYSTEM SOFTWARE APPLICATION SOFTWARE Call Processing Feature processing Maintenance Administrative HARDWARE Signalling
      • System Software
      • Switch Operating Systems
      • Scheduling, process management
      • Memory and resource management
      • Database management
      • Man-machine Interface
      • Signaling
      • Line
      • Trunk
      • Protocols
      • Messaging
      • Call Processing
      • Event Handlers
      • Digit Collection and Analysis
      • Translation
      • Routing
      • Termination
      • Supervision
      • Billing Records
      • Feature Processing
      • Call Services
        • Call Forward
        • Call Wait
        • DoNot Disturb
        • Conf Call
        • 3WC
      • Feature Activation
      • Feature Charging
      • Administrative Software
      • Subscriber Configuration and User Privileges
      • Provisioning
      • Configuration of Hardware
      • Maintenance Software
      • Auditing of resources
      • Fault Detection and Correction
    • 20. Basic Call Process
      • Detecting the incoming call,
      • Receiving the digits,
      • Translating the digits,
      • Selecting a terminating agent,
      • Speech Path,
      • Signaling => terminating agent
      • Detecting an answer
      • Detecting disconnect
    • 21. Line Interface
      • Subscriber loop
        • Wired and Wireless (Copper , Cellular, WILL)
        • Analog and Digital
          • Analog
            • Digital conversion at the switch
            • Analog loop functions - BORSCHT
          • Digital
            • Digital conversion at the CPE. E.g. ISDN terminal
            • Basic Rate Interface ( BRI )
              • 2B + D = 144 KBPS
            • Primary Rate Interface ( PRI used for EPABX’s )
              • E1 is 30B + D = 2.048 MBPS
              • T1 is 23B + D = 1.544 MBPS
    • 22. POTS Access P O T S • • • • Line cards subscriber loop Max : 150 miles RSC RLU RCC T1 / DS1 Line unit RSC Matrix Central Control
    • 23. Business Access Joe's Small Business Department of Injustice Kathy's home Business Betty's Bigger Business subscriber line subscriber lines lines or trunks IBN (Centrex) lines KTS PBX Centrex Call Processing POTS Call Processing Digital Class 5 Local Office
    • 24. ISDN - What Is It?
      • Is Someone Dreaming Nonsense
      • I Studied Data Networks
      • I Still Don't kNow
      • Integrated Services Digital Network
    • 25. ISDN Access - What is ISDN?
      • "Digital end-to-end connectivity through a limited set of network interfaces providing a wide range of service features evolving from the telephone IDN to meet market needs into the 21st century.” - From ITU definition of "ISDN".
      ISDN Access Interfaces Terminals PBXs LANs ISDN Voice Networks Data Networks Broadband Networks ISDN Network Interface
    • 26. ISDN Access Types
    • 27. ISDN Subscriber – System Configuration NT - 1 Terminal Adapter TE1 NT2 TE2 S T U ISDN Exchange ISDN Modem NT - 2 R S Customer Premises S R V LT ET
    • 28. ISDN User – Network Interface Protocols Layer 3 Layer 2 Layer 1 Layer 3 Layer 2 Layer 1 Q.931 Layer 3 protocol Q.921 Layer 2 protocol Layer 1 protocol (Physical)
    • 29. Layer – I ( Physical Layer for BRI)
      • U interface Frame – 240 bits in length – 1.5 ms duration
      • U Interface – 2 wire, 160 kbps connection
        • Frame overhead – 16 kbps
        • 2 voice channels – 128 kbps
        • 1 Data channel - 16 kbps
      • Echo cancellation for noise reduction
      • Data encoding schemes (2B1Q in North America, 4B3T in Europe)
      • Synchronization bits - +3 +3 -3 -3 -3 +3 -3 +3 -3
      • Super-frame consists of 8 - 240-bit frames for a total of 1920 bits (240 octets).
      • The sync field of the first frame in the super-frame is inverted (i.e. -3 -3 +3 +3 +3 -3 +3 -3 +3).
      Sync Bits ( 16 ) 12 * ( B1 + B2 + D channel ) ( 216 ) Maintenance Bits ( 8 )
    • 30. Layer – II ( Data Link Layer)
      • Link Access Protocol – D Channel (LAPD)
      Flag (8) Address ( 8/16 ) Control (16) Information ( Layer –3) CRC (16) Flag (8) SAPI ( 6 ) 1 2 3 4 5 6 7 8 Address Field C/R EA0 TEI ( 7 ) EA1
    • 31. Layer – II - Initialization Receive Ready (RR) frames Unnumbered Information (UI) frame with a SAPI of 63 and TEI of 127 TEI (in the range 64-126) Set Asynchronous Balanced Mode (SABME) frame with a SAPI of 0 and TEI TE Unnumbered Acknowledgement (UA), SAPI=0, TEI=assigned ISDN Network
    • 32. Layer – III Message Type 1 2 3 4 5 6 7 8 Information Field Length of CRV Protocol Discriminator 0 0 0 0 Call Reference Value (1 or 2 octets) 0 Mandatory & Optional Information Elements (variable)
    • 33. Layer – III - Initialization Caller ISDN Switch Called Setup Message Call Proceeding Message Setup Message Alerting Message Alerting Message Connect Message Connect Message Connect ACK Message Connect ACK Message B Channel Communication Disconn Message Disconn Message Rel Message Rel Message Relcom Message Relcom Message
    • 34. Layer – III ( Messages exchanged during the conversation phase)
      • SUSP Requests suspension of call.
      • SUSP ACK Indicates suspension acknowledge.
      • SUSP REJ Indicates suspend rejected.
      • RES Request that suspended call has resumed.
      • RES REJ Indicates suspended call cannot be resumed.
      • USER INFO Use to user signal.
    • 35. Layer – III ( Messages exchanged during the Call Clearing phase)
      • DISC Call disconnection request.
      • REL Indicates channel disconnection completed.
      • REL COM Indicates channel & call reference release completed.
      • REST Requests initialization completed.
      • REST ACK Indicates initialization completed.
    • 36. Layer – III ( Miscellaneous messages )
      • FAC Requests & ACK supplementary service initialization.
      • INFO Information on additional call control.
      • NOTIFY Indicates info. Related to the call.
      • STATUS ENQ Inquires about station status.
      • STATUS Indicates user/network status.
      • CON CON Congestion control of user to user signaling.
    • 37. Digital Subscriber Lines
      • DSL
      • ADSL
      • HDSL
      • RADSL
      • VADSL
      • VDSL
      • Universal ADSL
      Digital subscriber line, which operates at a maximum of 144 Kb/s for ISDN subscriber, lines. ISDN is used for voice and data communications. Asymmetric digital subscriber line, which operates at 32Kb/s to 8.19 Mb/s downstream to the customer and 16 to 640 Kb/s upstream to the network over existing twisted-pair copper wire. ADSL is envisioned for use for Internet access, video on demand (VOD), simplex video, remote LAN access, and interactive multimedia. High-bit rate digital subscriber line delivers data symmetrically at rates up to at 1.544 Mb/s full-duplex for equivalent T1/E1 service, or at 2.48 Mb/s duplex (requires two pairs of wire) for subscriber lines. It delivers at 2.49 Mb/s duplex (requires three pairs of wire) for feeder plant, WAN services, LAN access, or server access. Rate adaptive ADSL is a version of ADSL where the ADSL modems test the line at start up and adapts the data rate to within 32 Kb/s of the maximum throughput the line is capable of supporting. Very high-bit-rate asymmetric digital subscriber line, which operates at a subset of speeds of VDSL when it supports symmetric operation. It describes a form of ADSL that does not require a splitter at the customer location to separate voice signals from digital signals in the data stream. This approach leads to a "plug-and-play" ADSL where the user can simply connect the line to a PC and be in service. Universal ADSL will operate at lower bit rates than "existing" ADSL systems, but it is up to 25 times faster than today's 56Kb/s modems and just as easy to install. Very high-bit rate digital subscriber line is under development for twisted-pair access service at 12.9Mb/s to 52.8Mb/s downstream and 1.5 to 2.3Mb/s upstream. However, the maximum reach will be reduced from 4,500 to 1,000 feet and it will need fiber-optics cable. Applications are the same as ADSL, plus high-definition TV.
    • 38. Trunk Interfaces
      • Analog trunks
        • Two Wire
        • 4 Wire
      • Digital Trunks
        • Code conversion (HDB3 to Binary)
        • Frame alignment
        • Signaling Information injection/extraction
        • Transmission system interface
        • E1(30 channel)/T1 (24 channel)
    • 39.  
    • 40. Subscriber signaling
      • Analog
        • Pulse signaling
        • DTMF signaling
      • Digital
        • ISDN (Digital subscriber signaling system 1)
    • 41. Pulse Signaling
      • Pulse signaling uses the concept of loop make & break
      • E.g. Suppose you want to dial 31
      Make period Break period Inter-digit timer
    • 42. DTMF Signaling
      • A dial pad key is represented by a combination of two frequencies
      1 2 3 4 5 6 7 8 9 * 0 # 1209 1336 1477 697 770 852 941 Hz
    • 43. Trunk signaling Request for Trunk (seizure) Acknowledgement of the seizure (Seize Ack ) Answer Conversation End of the call (release) Acknowledgement of the release Dial digits
    • 44.
      • Regional Signaling systems (R1 for N.A. R2 for Europe and rest of the world). Also referred to as Channel Associated signaling systems
      • CCITT recommended signaling systems (SS1 to SS7). SS6 & 7 also referred to as common channel signaling systems.
      Signaling systems
    • 45. T1 - Overview
      • 24 channels each with a 64kbps capacity.
      • 8000 frames per second (125 us per frame)
      • Each frame consists of 193 bits
      • One bit per frame for frame alignment
      • 12 frames make a super frame.
      • LSB in 6th and 12th frame is used for signaling ( bit stealing or robbed bit signaling)
      • Total bandwidth 1.544kbps
    • 46. T1 - Frame Structure Frame 1 Frame 12 Frame 6 Frame X Frame alignment bit TS N TS 0 TS 23 Signaling bit (Frame 6 and 12) TS 23 TS N TS 0 TS 0 TS N TS 23 TS 0 TS N TS 23
    • 47. E1 - Overview
      • 32 channels each with 64kbps capacity
      • 8000 frames per second (125 us per frame)
      • 256 bits per frame
      • 30 channels are used for transmitting voice
      • TS0 of each frame is used for frame alignment
      • TS16 of each frame is used for line signaling
      • 16 frames make a Multi frame
      • Total bandwidth 2.048 Mbps
    • 48. E1 - Frame Structure Frame alignment byte TS 0 TS 16 TS 31 TS 31 TS 0 TS 31 Signaling byte (Frames 1-15) synch byte Frame 0 TS16 ABCD TS1 ABCD TS17 ABCD TS15 ABCD TS31 Frame 1 Frame 0 Frame 15 TS 16 TS 0 TS 16
    • 49. Line signaling v/s Register signaling
      • Line Signaling
        • Used for line (trunk) supervision
        • Represents the events that occur on a trunk I.e SZD, SZA, ANS, CLF, RLG
      • Register Signaling
        • Used for address signaling I.e. called party number etc.
        • Normally done using MF tones but pulse signaling is also possible
    • 50. R1 Line Signals
      • Analog system
        • A continuous tone of 2600 Hz represents onhook
        • Offhook is represented by absence of supervision tone
      • Digital system (T1)
        • Only the bit in the 6th frame is actually used for signaling
        • Offhook is 1, Onhook is 0
    • 51. R1 line signals
      • Forward signals
        • Seize (Onhook -> Offhook)
        • Clear forward (Offhook -> Onhook)
      • Backward signals
        • Wink (Offhook pulse)
        • Answer (Onhook -> offhook)
        • clear backward (offhook -> onhook)
    • 52. R1 register signals
      • Six frequencies are used (700, 900, 1100, 1300, 1500, 1700) Hz
      • A combination of two frequencies represent a digit
      • R1 register signals are sent only in forward direction
    • 53. A typical R1 call Send connect Delayed dial Audible ringing Conversation Send hang up Send hang up Dial digits Proceed to send Answer
    • 54. R2 Signaling system
      • Used in Europe and most parts of the world
      • Analog system uses SF tone of 3825 Hz (out of band) for line signaling.
      • Digital System (E1) uses a dedicated time slot for signaling (No bit stealing here!). Only AB bits are used
    • 55. R2 line signals
      • Line signal protocols vary from country to country
      • Typical Forward line signals (Digital system)
        • Seize (1,0 --> 0,0)
        • Clear forward (0,0 --> 1,0)
      • Backward line signals
        • Seize Ack (1,0 --> 1,1)
        • Answer (1,1 --> 0,1)
        • Clear back (0,1 -->1,1)
        • Release Guard (x,1 -->1,0)
    • 56. R2 register signaling
      • Multi Frequency Compelled signaling is used for register signaling
      • Frequencies used in forward direction
        • 1380, 1500, 1620, 1740, 1860, 1980 Hz
      • Frequencies used in backward direction
        • 1140, 1020, 900, 780, 660 and 540 Hz
    • 57. R2 signaling groups
      • R2 register signals are divided in following group
        • Forward Signal Group I
          • Used for transmitting calling and called party digits
        • Forward Signal Group II
          • Used for transferring calling and called party categories
    • 58.
      • Backward signaling is done to acknowledge forward signals
        • Backward signal Group A
          • Used to acknowledge Group I signals
        • Backward signal Group B
          • Used to acknowledge Group II signals
      R2 signaling groups (contd ..)
    • 59. A typical R2 call Seize Seize Ack Answer Conversation Clear forward Release Gaurd Register signaling
    • 60. Inter-register signaling Seize Seize Ack Answer Forward group I signal (called party digit) Forward Group II signal (regular) Forward Group III signal (end of digits) Forward Group III signal (calling party digit) Forward group II signal (regular) Backward group A-1 signal (next digit) Backward Group A-6 signal (req_dn_cat) Backward Group C-1 signal (next ANI digit) Backward group C-1 signal (next ANI digit) Backward group A-3 signal (req_bill_cat) Backward Group B signal (connect_call_chg) Forward group I signal (called party digit)
    • 61. Overall Architecture of CCS7 Message Transfer Part ( MTP ) ISUP TUP SCCP TCAP DUP 1 - 3 1-3 4-7 4 - 6 7 User Parts OSI Layer Mapping OSI Layer Mapping
    • 62. CCS7 Network Components Signal Transfer Point (STP) is node in the Network that routes messages between nodes. It does not originate any CCS7 messages other then NM messages Service Control Point(SCP)provides network access to transaction services ( Database queries ) Service Switching Point (SSP) is a node in the network that originates & terminates CCS7 messages ( both connection oriented and connectionless ) SSP A SCP SSP B STP - II STP - I Voice Signaling Point(SP) is a node in the network that provides CCS7 trunk signaling only Quasi Associated Associated Mode SP Trunks
    • 63. CCS7 Signaling Link-Sets STP STP STP STP SCP SSP SP SSP a a a a e f b b b b c c a a f Access links connect SP, SSP & SCP to STPs Bridge links connect mated STP pairs to other mated STP pairs Cross links connect two STP nodes creating a mated pair Fully Associated links connect SP, SSP & SCP nodes using associated signaling Extended links connect an SP, SSP & SCP to an STP of a different region. Diagonal links connect STP quads in different regions ( for instance primary to secondary STP )
    • 64. Basic CCS7 ISUP Call Switch X - Originator Switch Y - Terminator IAM SAM ACM ANM REL RLC Talking Line Line
    • 65. IN Components It is not a physical network but a set of software features packages It enhances switch call processing capabilities to use centralized operating company-provided service logic programs placed at SCP Queries & responses between DMS & SCP use CCS7 protocol . IP Service Creation Environment SMS STP SCP SS7 Network Upload Service Query Response Exchange
    • 66. IN Services examples
      • 1-800 numbers (1-600 service in Bangalore)
      • MCCS (Mechanized Calling Card Services)
      • Billed Number Screening
      • Centralized translations & routing
    • 67. Time of Day Call Routing What is the time now? 9:00 a.m. to 5:00 p.m. Office Residence A
    • 68. Neighborhood Dealer Routing The nearest distribution point to this caller is the West-side location Advertised DN Pizza Hut 999-9999 West-side Location Eastside Location Pizza Hut Pizza Hut
    • 69. IN Advantages
      • Service Independence
      • Multi-vendor Support
      • Decrease in the time-to-market for new services
      • Telephone operating company control of service “building blocks”
      • Seamless multi-vendor environment
    • 70. Frequency Division Multiple Access k 2 k 3 k 4 k 5 k 6 k 1 f t c
    • 71. Time Division Multiple Access f t c k 2 k 3 k 4 k 5 k 6 k 1
    • 72. Frequency & Time Division Multiple Access f t c k 2 k 3 k 4 k 5 k 6 k 1
    • 73. Code Division Multiple Access k 2 k 3 k 4 k 5 k 6 k 1 f t c
    • 74.
      • Combination of TDMA and FDMA
      • 890 – 915 MHz for Uplink
      • 935 – 960 MHz for Downlink
      • 124 Radio carriers, inter carrier spacing of 200 KHz
      • 8 channels per carrier
      • Air interface at 13 kb/sec
      • Uses RPE - linear predictive speech encoding - information from previous samples to predict the current sample
      GSM Network Architecture
    • 75. GSM Network Elements
    • 76. GSM Network Areas
    • 77. GSM Signaling Protocols
    • 78. RADIO RESOURCE MANAGEMENT (RR)
      • ESTABLISHES CONNECTION BETWEEN MS & MSC FOR THE DURATION OF CALL AND MAINTAIN THEM TAKING INTO ACCOUNT USER MOVEMENTS.
      • MUST COPE WITH LIMITED RADIO RESOURCES AND SHARE IT DYNAMICALLY BETWEEN ALL NEEDS
      • RESPONSIBILTY OF THE HANDOVER PROCESS LIES ENTIRELY WITHIN THE RR LAYER FUNCTION
      • FUNCTIONS OF RR LAYER ARE MAINLY PERFORMED BETWEEN MS & BSC
    • 79. MOBILITY MANAGEMENT (MM)
      • RESPONSIBLE FOR THE MOBILITY MANAGEMENT & SECURITY MANAGEMENT.
      • AUTHENTICATION, IMSI DETACH/ATTACH
      • LOCATION REGISTRATION
      • MACHINES CONCERNED WITH MOBILITY MANAGEMENT ARE MAINLY THE
      • MS (MORE PRECISELY THE SIM INSIDE THE MS)
      • HLR (MORE PARTICULARLY THE AuC INSIDE THE HLR) , MSC/VLR
    • 80. COMMUNICATION MANAGEMENT (CM)
      • RESPONSIBLE FOR CALL SETUP , CALL RELEASE AND MAINTAINING CALL FOR GSM USERS
      • MSC/VLR , GMSC, HLR, IWF ARE RESPONSIBLE FOR THE BASIC CALL MANAGEMENT FUNCTIONS
      • ANOTHER IMPORTANT ASPECT OF CM FUNCTION IS ROUTING THROUGH DIFFERENT GSM ENTITIES.
      • CM LAYER ALSO MANAGES THE SUPPLEMENTARY SERVICES.
      • CM LAYER IS RESPONSIBLE FOR POINT-TO-POINT SHORT MESSAGE SERVICES IN CONTACT THROUGH SHORT MESSAGE SERVICE CENTRE
    • 81. PSTN GMSC GSM/PLMN
      • PSTN SUBSCRIBER DIALS MOBILE NUMBER
      • LINK IS SET UP FROM LOCAL EXCHANGE TO THE GMSC
      MOBILE TERMINATED CALL
    • 82. PSTN GMSC GSM/PLMN HLR VLR MSC
      • HLR TRANSLATES THE DIALLED MOBILE NUMBER
      • INTO A GSM/PLMN IDENTITY ( IMSI)
      • MSISDN TO IMSI
      • HLR POINTS OUT THE SERVICE AREA OF THE CALLED NUMBER AND
      • SENDS THE IMSI TO THE VLR WITH A REQUEST FOR MSRN
    • 83. PSTN GMSC GSM/PLMN HLR VLR MSC
      • VLR WILL TEMPORARILY ALLOCATE A ROAMING NUMBER (MSRN)
      • TO THE CALLED SUBSCRIBER AND SENDS IT BACK TO THE HLR .
      • HLR WILL SEND IT THE GATEWAY MSC (GMSC)
    • 84. PSTN GMSC GSM/PLMN HLR VLR MSC
      • LINK IS SET UP FROM GMSC TO MSC/VLR
      • GMSC IN POSSESSION OF THE CORRECT MSRN WILL BE
      • SET UP THE INCOMING CALL TO THE MSC/VLR WHERE
      • CALLED SUBSCRIBER IS CURRENTLY LOCATED
    • 85. PSTN GMSC GSM/PLMN HLR VLR MSC BTS BSC
      • PAGING MESSAGE IS SENT TO THE BSS
      • VLR POINTS TO THE LOCATION AREA IDENTITY (LAI) FOR THE CALLED
      • SUBSCRIBER (IMSI --- LAI)
      • MSC/VLR SENDS THE PAGING MESSAGE TO ALL THE BASE STATIONS
      • (BTS) WITHIN THE LOCATION AREA
    • 86. PSTN GMSC GSM/PLMN HLR VLR MSC BTS BSC
      • BTS ON RECEIVING THE PAGING MESSAGE WILL SEND IT OVER THE
      • RADIO PATH ON THE PAGING CHANNEL
      • MS WILL RECEIVE PAGING MESSAGE ON ONE OF THE CELLS BELONGING
      • TO THE LOCATION AREA, RECOGNISES THE IMSI AND THEN SENDS A
      • RESPONSE TO THE PAGING MESSAGE```
    • 87. PSTN GMSC GSM/PLMN HLR VLR MSC BTS BSC
      • LINK IS SET-UP FROM THE MSC/VLR TO THE MS
      • CONNECTION IS ESTABLISHED BETWEEN THE PSTN & MOBILE
      • SUBSCRIBER
    • 88. Need for convergence of Voice and Data Networks
      • Attractive because of low cost , flat rate pricing of public internet
      • Optimization of bandwidth utilized in data network when compared to fixed bandwidth in telecom network
      • Growth in technology faster in data networks than in telecom networks
      • Demand for new types of integrated voice/data applications
    • 89. Convergence of Telecom and Data Networks CALL SERVER T1/E1/ J1/T3 ISDN, R1/R2, CAS SS7 Signal & Trunk Access Gateway Fast Ethernet SS7 ATM IP T1/E1/ J1/T3 ISDN, R1/R2, CAS SS7 SS7 Fast Ethernet EO EO PBX PBX Network Management System Signal & Trunk Access Gateway
    • 90. 2000 1850 10 10 12 10 6 Mono-mode fibre 1,7,16 Gbs/s 3600ch M/W 60ch coax First telephone Ist telephone ch multi mode fibre 140 Mbs/s 10800ch over coaxial voice ch ~ 600bps voice ch ~1200 voice ch~4800bps PCM voice ch~56bps Strowger Crossbar Electronic switches Satcom High capacity Radios Bits/s The Telecom story
    • 91. Customer Demands
      • More and more facilities and features.
      • Image communication, video services to home
      • Digital film on demand for normal quality 1-2Mbps and HDTV (15-20Mbps)will be reality in 2005. Any movie can be selected
      • Personalized assistance in business, shopping, & home activities
    • 92. Customer demands (contd)
      • Video conferencing popular among business users- Videophone, video education
      • Multimedia services: basic components of broadband service: voice, image, video and data
      • Demand for mobility, any where any time personal communication ...
    • 93. The Crystal view -Technology Trends
      • Information highways and use of CCS no7 signaling
      • Intelligent Networks and AIN
      • B- ISDN (Integrated services digital network)
      • PCs and phone merge- computer telephony
      • Merger of transmission and switching
      • Interactive video on demand
      • SDH hierarchy in transmission technology
    • 94. Technology Trends (contd.)
      • Communication satellites at lower orbits
      • ATM as prime multimedia standard
      • Same infrastructure for telecom and Entertainment
      • Wide band on copper
      • Passive optical networks
    • 95. Technology Trends (contd.)
      • Wireless in the local loop
      • Cellular mobile radios
      • Fixed radio access
      • Personal communication services
      • Satellite networks like TDM/TDMA
    • 96. These and many more futuristic technological challenges make it exciting to work in the area of Telecom in general and Telecom software in particular.
    • 97. Thank you for your attention!

    ×