Wired and Wireless Phone Networks An overview of telephony network technology Dean Churchill, Ph.D. Enterprise Architectur...
Outline of Talk <ul><ul><li>1. History of phone networks – analog, and digital </li></ul></ul><ul><ul><li>2. Circuit switc...
History <ul><li>First networks (1800s) were “point-to-point”. Required  N*(N-1)/2  phone lines between  N  phones. </li></...
Circuit Switched Architecture
Circuit Switched Networks <ul><li>Dedicated connections: local loop, switch, and trunk resources are dedicated to the two ...
Packet Switched Land-line Networks
Packet Switched Attributes <ul><li>Voice, video, images, pure data, get broken into small segments </li></ul><ul><li>calle...
Connection-less packet services <ul><li>Connection-less packet-switched services send packets that  </li></ul><ul><li>are ...
Connection-oriented packet services <ul><li>All packets sent from same source access the same path </li></ul><ul><li>acros...
Voice Wireless Architecture
Provisioning Data Architecture
GSM attributes <ul><li>Voice and high-speed data (27-115 kbps) - carried over Internet Protocol (IP) </li></ul><ul><li>Pac...
General Packet Radio Service (GPRS) <ul><li>Wireless extension of the Internet all the way to mobile device </li></ul><ul>...
GPRS Description continued <ul><li>Provides packet-data transport at rates from 40 to 271 kilobits per seconds (as one to ...
GPRS Spectrum Utilization
GPRS Characteristics <ul><ul><li>A single mobile device can transmit on one to eight  channels of the same frame.  </li></...
GPRS Characteristics (continued) <ul><ul><li>Multiple users can share one channel </li></ul></ul><ul><ul><li>Upload and do...
GPRS Network
Gateway GRPS Support Node (GGSN) <ul><li>GGSN is the interface between GPRS Network and external packet data networks (e.g...
Authentication Center (AuC) <ul><li>Stores security-related data, such as encryption keys. </li></ul><ul><li>Indexed by th...
Authentication and Encryption
Summary <ul><li>Phone networks are evolving from analog-only, land-line circuit switched networks to include wireless digi...
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Cellular Networks Presentation

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  • Recall development of IP by DOD in 1960s, intended to survive a nuclear attack: as individual nodes fail, other nodes carry the load. Wireless network stayed up and running in New York City, despite losing towers
  • 900 MHZ Example: Uses two radio frequency bands: 890 - 915 MHz from mobile device (uplink); 935 - 960 MHz to mobile device (downlink). Each band is divided into 124 frequency channels, called Time Division Multiple Access (TDMA) frames , each lasting 4.613 milliseconds Each frame is divided by time into 8 conversation channels that last 576.9 microseconds.
  • Cellular Networks Presentation

    1. 1. Wired and Wireless Phone Networks An overview of telephony network technology Dean Churchill, Ph.D. Enterprise Architecture, AT&T Wireless, Bothell [email_address]
    2. 2. Outline of Talk <ul><ul><li>1. History of phone networks – analog, and digital </li></ul></ul><ul><ul><li>2. Circuit switched vs. packet switched networks </li></ul></ul><ul><ul><li>3. Architecture of cellular networks </li></ul></ul><ul><ul><li>4. Multiplexing – TDMA and GSM networks </li></ul></ul><ul><ul><li>5. GPRS: Internet on a cell phone </li></ul></ul><ul><ul><li>6. GPRS Network Architecture </li></ul></ul>
    3. 3. History <ul><li>First networks (1800s) were “point-to-point”. Required N*(N-1)/2 phone lines between N phones. </li></ul><ul><li>First telephone offices used patch panels with human operators. Required N phone lines, but required a manual connection for each call placed. </li></ul><ul><li>First mechanical switches developed in late 1800s. </li></ul><ul><li>Digital “land-line” connections began in 1960s. </li></ul><ul><li>Analog wireless phones took off in 70s. </li></ul>
    4. 4. Circuit Switched Architecture
    5. 5. Circuit Switched Networks <ul><li>Dedicated connections: local loop, switch, and trunk resources are dedicated to the two end-points. </li></ul><ul><li>Must be heavily over-designed to handle peak call volumes </li></ul><ul><li>Expensive, inefficient </li></ul><ul><li>Good for voice quality; bad for Internet connections </li></ul><ul><li>Billing is based on duration of call. </li></ul>
    6. 6. Packet Switched Land-line Networks
    7. 7. Packet Switched Attributes <ul><li>Voice, video, images, pure data, get broken into small segments </li></ul><ul><li>called packets. </li></ul><ul><li>Each packet is encapsulated in a frame </li></ul><ul><li>Packet streams from multiple users are combined into a single stream </li></ul><ul><li>More economical, as multiple users share a common resource. </li></ul>
    8. 8. Connection-less packet services <ul><li>Connection-less packet-switched services send packets that </li></ul><ul><li>are routed independently of each other. </li></ul><ul><li>Can be routed through the network however the network </li></ul><ul><li>prefers. </li></ul><ul><li>Packets may arrive out of order, and higher-level protocol </li></ul><ul><li>may be needed to reorder packets. </li></ul><ul><li>Internet Protocol is an example (with TCP used to reorder) </li></ul><ul><li>Very stable networks are produced, that work around failures. </li></ul><ul><li>Has high overhead – lots of redundant routing information </li></ul>
    9. 9. Connection-oriented packet services <ul><li>All packets sent from same source access the same path </li></ul><ul><li>across the network, ensuring sequential delivery. </li></ul><ul><li>Has low overhead – little redundant routing information </li></ul><ul><li>Requires a very reliable infrastructure ( like fiber optics) </li></ul><ul><li>Example protocols: X.25, Frame Relay, and ATM </li></ul>
    10. 10. Voice Wireless Architecture
    11. 11. Provisioning Data Architecture
    12. 12. GSM attributes <ul><li>Voice and high-speed data (27-115 kbps) - carried over Internet Protocol (IP) </li></ul><ul><li>Packet switched rather than circuit switched </li></ul><ul><li>Short Message Service (over 1 billion messages per month are passed over GSM systems worldwide) </li></ul><ul><li>Unified messaging: integrates e-mail with voice mail. Access both from one mailbox using any phone or Internet-connected computer. Users can listen to their e-mail. </li></ul><ul><li>mobile commerce applications </li></ul><ul><li>E911 location service </li></ul>
    13. 13. General Packet Radio Service (GPRS) <ul><li>Wireless extension of the Internet all the way to mobile device </li></ul><ul><li>Optimized for “bursty” packet-data traffic (e.g. web site downloads). </li></ul><ul><li>Billing may be based on the amount of data transferred, rather than duration of call. </li></ul><ul><li>Allows a customer to view web pages “on line” without incurring additional cost. </li></ul><ul><li>Has higher transfer rates, shorter access times, improved utilization of radio spectrum </li></ul>
    14. 14. GPRS Description continued <ul><li>Provides packet-data transport at rates from 40 to 271 kilobits per seconds (as one to eight channels are used) </li></ul><ul><li>Voice and data operations can occur concurrently. </li></ul>
    15. 15. GPRS Spectrum Utilization
    16. 16. GPRS Characteristics <ul><ul><li>A single mobile device can transmit on one to eight channels of the same frame. </li></ul></ul><ul><ul><li>Channels are allocated only when data packets are sent or received, and they are released after the transmission. </li></ul></ul><ul><ul><li>Users experience being “on-line”, though the data channels of the radio connection may have been reallocated. </li></ul></ul><ul><ul><li>Channels can be mapped dynamically into packet switched (GPRS) service or circuit switched (conventional) service on demand. </li></ul></ul>
    17. 17. GPRS Characteristics (continued) <ul><ul><li>Multiple users can share one channel </li></ul></ul><ul><ul><li>Upload and download can occur simultaneously </li></ul></ul><ul><ul><li>High speed downloads available on demand </li></ul></ul><ul><ul><li>Command and control channels allow mobile device to acquire data channels dynamically. </li></ul></ul>
    18. 18. GPRS Network
    19. 19. Gateway GRPS Support Node (GGSN) <ul><li>GGSN is the interface between GPRS Network and external packet data networks (e.g. Internet). </li></ul><ul><li>Converts GPRS packets from SGSN into IP packets </li></ul><ul><li>Receives IP packets and converts them into GPRS packets </li></ul><ul><li>Sends packets to the SGSN </li></ul><ul><li>Performs authentication and charging functions </li></ul>
    20. 20. Authentication Center (AuC) <ul><li>Stores security-related data, such as encryption keys. </li></ul><ul><li>Indexed by the IMSI </li></ul><ul><li>Stores a secret key ( Ki ) </li></ul><ul><li>Key, Kc , is used for data encryption of the radio channel using the value of Ki </li></ul><ul><li>Kc is requested by the VLR during the setup of a connection. </li></ul><ul><li>The Ki and Kc pair are used for authentication and identification. </li></ul>
    21. 21. Authentication and Encryption
    22. 22. Summary <ul><li>Phone networks are evolving from analog-only, land-line circuit switched networks to include wireless digital packet-switched networks </li></ul><ul><li>Next phase of the industry is to provide high-speed Internet service on top of voice phone service. </li></ul><ul><li>Heavy reliance on TCP/IP networking for the digital, packet-based components. </li></ul><ul><li>Global roaming on GSM phones is a likely result in the long run. </li></ul>

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