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Cell Phone Technologies

Cell Phone Technologies. Overview of Cellular Phone Technologies Technology Generations Cellular Networks Messaging Services By: Matt Smith. Cell Phone Technologies. The “Gs” Cellular networks are broken up into three generations of technologies

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Cell Phone Technologies

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  1. Cell Phone Technologies Overview of Cellular Phone Technologies • Technology Generations • Cellular Networks • Messaging Services By: Matt Smith UK Aerial Robotics Team University of Kentucky

  2. Cell Phone Technologies The “Gs” • Cellular networks are broken up into three generations of technologies • 1G: Analogue cell phone standards introduced in the 1980’s • Analogue signal was modulated to higher frequencies (150MHz and up) • Required more bandwidth and poor noise rejection • 2G: The call is encoded into digital signal • Can be compressed and multiplexed more effectively for better use of bandwidth • More susceptible to drop outs and loss of tonality in someone's voice • 3G: The second generation digital technology • Increased bandwidth to allow for the transfer of voice and non-voice data simultaneously UK Aerial Robotics Team University of Kentucky

  3. Cell Phone Technologies The popular 2G cellular networks: • GSM: Developed by an international association (Cingular) • Advantages: Better international coverage, and battery life • CDMA: Proprietary network developed by Qualcomm (Sprint/Verizon) • Advantages: Better U.S coverage and higher data transfer rates UK Aerial Robotics Team University of Kentucky

  4. GSM Network • Basic diagram of a GSM network: UK Aerial Robotics Team University of Kentucky

  5. Accessing the GSM network Subscriber Identity Module (SIM) card: Programmed with the users phone identity and personal information Base Transceiver Station: The mobile phone mast that mobile phones attempt to establish a connection Home Resource Locator: SIM record is stored in database by the home phone company Visitor Resource Locator: Contact the HRL to retrieve information about services available to the user UK Aerial Robotics Team University of Kentucky

  6. After Establishing a Connection Once a connection to the network has been established a number of services are open to the end user including: • Voice calls: Encodes audio signals in a digital form and routes the audio data to the Public Switched Telephone Network via a message switching center • Direct Data Services: Several services implemented to deal with digital data directly without inefficient conversions to and from audio UK Aerial Robotics Team University of Kentucky

  7. Direct Data Services Established connection data services: • Circuit Switched Data (CSD) • General Packet Radio Service (GPRS) • Enhanced Data Rates for GSM Evolution (EDGE) UK Aerial Robotics Team University of Kentucky

  8. Communication Paradigms • Circuit switching: When the connection is established the full bandwidth is reserved for the duration of the connection. • Generally charged for by the minute because bandwidth is be used even if nothing is being transferred • Packet switching: Users share the same channel and bandwidth is only used during transfers • Generally charged by data transferred because bandwidth is not reserved during the connection UK Aerial Robotics Team University of Kentucky

  9. Data Transfer Service • Circuit Switched Data: GSM first data transmission • CSD reserved one time slot for data rates up to 9.4 kbps • High Speed Circuit Switched Data: Based off of CSD, it provide faster data rates through better coding and by reserving up to four time slots UK Aerial Robotics Team University of Kentucky

  10. Data Transfer Services (cont.) General Packet Radio Service: Packet switching service that take advantage of unused time slots. Data transfer rates of about 40 kbps. EDGE: Defines a new hardware layer for GSM network and triples the gross data rate offered by the network UK Aerial Robotics Team University of Kentucky

  11. Connecting to GPRS • Mobile device must attach to the GPRS network then activate a PDP context • Packet Data Protocol: Data structure allocated that contains subscriber’s session information Once the context has been activated the device can transmit packets of its supported packet data protocol type • Generally IP is the only supported data protocol UK Aerial Robotics Team University of Kentucky

  12. Short Message Service • SMS uses a store and forward approach to send messages • Messages are sent to a short message service center (SMSC) • The SMSC will attempt to send the message to the recipient, if the recipient cannot be reached the message is stored and the SMSC will retry delivery when the destination is reachable • Message delivery is best effort. There are no guarantees the message will be delivered. Delays and complete message loss is not uncommon • Payload is limited to 140 bytes • Long SMS is segmented over multiple messages. In this case a user data header (UDH) is defined lowering the effective payload to 134 bytes UK Aerial Robotics Team University of Kentucky

  13. Final Notes • GPRS compatibility classes • Three classes exist • Most devices are class B • The device can be connected to GPRS service or GSM service. If the device needs to use a GSM service (voice, SMS) the GPRS service is suspended and automatically resumed when the GSM service completes • Most mobile devices have a defined AT command set that allows an external device to use the mobile device • Command State: the mobile device receives AT commands • Data State: Once PDP context has been activated the mobile device enters a data state to send and receive data packets. The device stays in this state until the layer 2 termination procedure has been completed successfully. UK Aerial Robotics Team University of Kentucky

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