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Wireless Communication

Wireless Communication. Introduction to Mobile Communication and Cellular System bitwali Lecture 1-2. Mobile Communications-Layered Model. Service Location, New/Adaptive Applications Multimedia, Congestion/Flow Control, Quality of Service Addressing, Routing, Device Location, Hand-over

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Wireless Communication

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  1. Wireless Communication Introduction to Mobile Communication and Cellular Systembitwali Lecture 1-2 bitwali.com

  2. Mobile Communications-Layered Model Service Location, New/Adaptive Applications Multimedia, Congestion/Flow Control, Quality of Service Addressing, Routing, Device Location, Hand-over Authentication, Media Access/Control, Multiplexing, Encryption Modulation, Interference, Attenuation, Frequency Application layer Transport layer Network layer Data link layer Physical layer bitwali.com

  3. Communication • Transmitting voice and data using electromagnetic waves in open space • Electromagnetic waves • Travel at speed of light (c = 3x108 m/s) • Has a frequency (f) and wavelength (l) c = f x l 1/f l bitwali.com

  4. Frequency Carriers/Channels • The information from sender to receiver is carrier over a well defined frequency band (range of frequencies). • This is called a channel • Each channel has a fixed frequency bandwidth (in KHz) and Capacity (bit-rate) • Different frequency bands (channels) can be used to transmit information in parallel and independently. bitwali.com

  5. Example • Assume a spectrum of 90KHz is allocated over a base frequency b for communication between stations A and B • Assume each channel occupies 30KHz. • There are 3 channels • Each channel is simplex (Transmission occurs in one way) • For full duplex communication: • Use two different channels (front and reverse channels) • Use time division in a channel Station A Channel 1 Station B Channel 2 Channel 3 bitwali.com

  6. Simplex Communication • Normally, on a channel, a station can transmit only in one way. • This is called simplex transmission • To enable two-way communication (called full-duplex communication) • We can use Frequency Division Multiplexing • We can use Time Division Multiplexing bitwali.com

  7. Duplex Communication - FDD • FDD: Frequency Division Duplex Base Station B Mobile Terminal M Forward Channel Reverse Channel Forward Channel and Reverse Channel use different frequency bands bitwali.com

  8. Duplex Communication - TDD • TDD: Time Division Duplex Base Station B Mobile Terminal M M B M B M B A single frequency channel is used. The channel is divided into time slots. Mobile station and base station transmits on the time slots alternately. bitwali.com

  9. What is Mobility • Initially Internet and Telephone Networks is designed assuming the user terminals are static • No change of location during a call/connection • A user terminals accesses the network always from a fixed location • Mobility and portability • Portability describes a radio terminal that can be used by someone at walking speed (e.g. walkie talkie or cordless telephone at home) Mobility describes a radio terminal that is attached to a high speed platform (e.g. a cellular telephone in a fast moving vehicle) bitwali.com

  10. Degrees of Mobility • Walking Users • Low speed • Small roaming area • Usually uses high-bandwidth • Vehicles • High speeds • Large roaming area • Usually uses low-bandwidth • Uses sophisticated terminal equipment (cell phones) bitwali.com

  11. How to realize Ubiquitous Computing • Small and different sizes computing and communication devices • Tabs, pads • Laptops, Cell-phones • A communication network to support this • Anywhere, anytime access • Seamless, wireless and mobile access • Need for Personal Communication Services (PCS) bitwali.com

  12. What is PCS • Personal Communication Services • A wide variety of network services that includes wireless access and personal mobility services. • Provided through a small terminal. • Enables communication at any time, at any place, and in any form. • The market for such services is tremendously(بہت زیادہ ) big • Eg. cell-phone market bitwali.com

  13. Several PCS systems • High-tier(درجہ) Systems • GSM: Global System for Mobile Communications • The mobile telephony system that we are using • IS-136 • USA digital cellular mobile telephony system • TDMA (Time division multiple access ) based multiple access • Personal Digital Cellular • IS-95 cdmaOne System • CDMA (Code division multiple access ) based multiple access bitwali.com

  14. Several PCS systems • Wideband wireless systems • For Internet access and multimedia transfer • Cdma2000 • W-CDMA (Wideband Code Division Multiple Access) , proposed by Europe • SCDMA (Synchronous Code Division Multiple Access), proposed by China/Europe bitwali.com

  15. Several PCS systems • Other PCS Systems • Special data systems • CDPD: Cellular Digital Packet Data • ARDIS :Advanced Radio Data Information System • Paging Systems • Mobile Satellite Systems • LEO( Low-Earth Orbit ), MEO( Medium -Earth Orbit ) satellites for data/voice • ISM (industrial, scientific, and medical radio )band systems: Bluetooth, 802.11, etc. bitwali.com

  16. Teledensity Pakistan bitwali.com

  17. Cellular Mobile Subscribers bitwali.com

  18. Paging Systems • Sending brief messages (numeric, voice messages) • Message sent to paging subscriber via paging system access number with telephone keypad or modem • Wide area paging systems consisting of number of telephone lines, many base station transmitters and large radio towers bitwali.com

  19. Wide Area Paging system bitwali.com

  20. Cordless Telephone Systems • Full duplex communication systems using radio to connect a portable hand set to a dedicated fixed base station • The base station then connected to a dedicated telephone line with a specific telephone number on the PSTN • Limited range and mobility • Early cordless telephones operate solely ( سراسر٬ محض )as extension telephones to a transceiver connected to a subscriber line on the PSTN bitwali.com

  21. Cordless Telephone Systems

  22. Cellular Telephone Systems • Why cellular networks? • To address requirement for greater capacity • For efficient use of frequency • To address the poor quality of non cellular mobile networks and increases coverage • Replaces a large transmitter with smaller ones in cells • Smaller transmitting power • Each cell serves a small geographical service area • Each cell is assigned a portion of the total frequency • Why Hexagonal Cell Structure? • No proper coverage of the area with theoretical circles • Polygon near to the circle • Hexagon is selected for further technical simplicity

  23. R Description of a Cell • Approximated to be a hexagonal coverage • Best approximation of a circular area • Served by a base station • Low powered transceiver Antenna system • May be divided into 6 equilateral triangles • Different groups of channels assigned to base station • Area of a cell is: bitwali.com

  24. Cellular System Definitions • Mobile Station • A station in the cellular radio service intended for use while in motion at unspecified locations. They can be either hand-held personal units (portables) or installed on vehicles (mobiles) • Base station • A fixed station in a mobile radio system used for radio communication with the mobile stations. Base stations are located at the center or edge of a coverage region. They consists of radio channels and transmitter and receiver antennas mounted on top of a tower. bitwali.com

  25. Cellular System Definitions • Mobile Switching Center • Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connections the cellular base stations and the mobiles to the PSTN (Public Switched Telephone Network). It is also called Mobile Telephone Switching Office (MTSO) • Subscriber • A user who pays subscription(چندہ) charges for using a mobile communication system • Transceiver • A device capable of simultaneously transmitting and receiving radio signals bitwali.com

  26. Cellular System Definitions • Control Channel • Radio channel used for transmission of call setup, call request, call initiation and other beacon(چھوٹاساگھر -روشن مینار) and control purposes. • Forward Channel • Radio channel used for transmission of information from the base station to the mobile • Reverse Channel • Radio channel used for transmission of information from mobile to base station bitwali.com

  27. Communication System Definitions

  28. Cellular System bitwali.com

  29. bitwali.com

  30. Types of Mobile Communication Cells The size of a cell is dictated by capacity demand • Macro Cell • Large, covering a wide area • Range of several hundred kilometers (km) to 10 km • Mostly deployed in rural and populated areas • Micro Cell • Medium cell, coverage area smaller than in macro cells • Range of several hundred meters to a couple of meters • Deployed mostly in crowded areas, stadiums, shopping malls • Umbrella Cell Approach • Micro cells inside A macro cell. • Macro cell is defined by high power and lengthy tower • Micro cells are defined inside the macro cell with less power and less height towers • High speed MS are handled by macro cell and low speed subscribers are handled by micro cell bitwali.com

  31. Types of Mobile Communication Cells • Pico Cell • Small, covering a very small area • Range of several tens of meters • Low power antennas • Can be mounted on walls or ceilings • Used in densely populated areas, offices, lifts, tunnels etc • Mega Cell • These cells are formed by LEO and MEO bitwali.com

  32. Cellular Generations bitwali.com

  33. Cellular Generations… • 1G: Analog Voice (FDMA) • AMPS: Advanced Mobile Phone System • TACS: Total Access Communication System • 2G: Digital Voice (TDMA) • CdmaOne: Qualcomm International Standard (IS-95) • D-AMPS: (Digital AMPS) • GSM: Global System for Mobile Communication • 2.5G: Voice + Data • 1xEV-DO: Evolution Data Optimized • 1xEV-DV: Evolution Data and Voice • General Packet Radio Service (GPRS) • Enhanced Data Rate for GSM Evolution (EDGE) bitwali.com

  34. Cellular Generations… • 3G: Voice + High-speed data. All CDMA • CDMA2000: Qualcomm. International Standard IS-2000 • W-CDMA: Wideband CDMA • TD-SCDMA: Time Division Synchronous Code Division Multiple Access (Chinese 3G) • 3.5: Voice + Higher-speed data • EDGE Evolution • High-Speed Packet Access (HSPA) • Evolved HSPA (HSPA+) • Ultra Mobile Broadband (UMB) • 3.9G: High-Speed Data. VOIP. OFDMA • WiMAX 16e (Worldwide Interoperability for Microwave Access) • Long Term Evolution (LTE) • 4G: Very High-Speed Data • WiMAX 16m • LTE-Advanced bitwali.com

  35. Section 1 – GSM Architecture Overview GSM:A brief background • At the beginning of the 1980s a problem was that the European countries were using many different, incompatible mobile phone systems. These systems are referred to as 1G (first generation) systems. • In Europe, the most common 1G system was NMT (Nordic Mobile Telephone) and TACS (Total Access Communications System). In the United States, as well as in other American countries, AMPS (Advanced Mobile Phone System) wasthe most common system. bitwali.com

  36. Section 1 – GSM Architecture Overview GSM:A brief background • With the passage of time, the need for telecom services was remarkably increased. Due to this, CEPT (ConférenceEuropéenne des Postes et Télécommunications) founded a group to specify a common mobile system for Western Europe. • This group was named “GroupeSpéciale Mobile” and the system name GSM arose. This abbreviation has since been interpreted in other ways, but the most common expression nowadays is Global System for Mobile communications. • GSM is a 2G (second generation) system. bitwali.com

  37. Section 1 – GSM Architecture Overview Expectations From GSM System • The GSM system must be an open system. • The system should be able to support several network operators in each country. • GSM networks must be built without causing any major changes to the already existing Public Switched Telephone Networks (PSTN). • The system must maintain a good speech quality. • The system must use radio frequencies as efficiently as possible. • The system must have high / adequate capacity. • The system must be compatible with ISDN and other data communication specifications. • The system must maintain good security both for subscriber and transmitted information. bitwali.com

  38. Section 1 – GSM Architecture Overview Advantages Of GSM • GSM uses radio frequencies efficiently, and due to the digital radio path, the system tolerates more inter - cell disturbances. • The average speech quality is better than in analogue systems. • Data transmission is supported throughout the GSM system. • Speech is encrypted and subscriber information security is guaranteed. • With ISDN compatibility, new services are offered. • International roaming is technically possible within all countries using the GSM system. • The large market increases competition and lowers the prices both for investments and usage. bitwali.com

  39. Section 1 – GSM Architecture Overview Requirement Of Telecom Network • A connection between two people “a caller and the called person” is the basic service of all telephone networks. • To provide this service, the network must be able to set up and maintain a call, which involves a number of tasks: • Identifying the called person. • Determining the location. • Routing the call. • Ensuring that the connection is sustained as long as the conversation lasts. • After the transaction, the connection is terminated and (normally) the calling user is charged for the service he has used. bitwali.com

  40. Section 1 – GSM Architecture Overview Requirement Of Mobile Telecom Network • In a mobile network, however, the establishment of a call is a far more complex task, as the wireless (radio) connection enables the users to move at their own free will, providing they stay within the network's service area. • In practice, the network has to find solutions to three problems before it can even set up a call. bitwali.com

  41. Section 1 – GSM Architecture Overview Requirement Of Mobile Telecom Network • In other words, the subscriber has to be LOCATED and IDENTIFIED to provide him/her with the requested services. • In order to understand how we are able to serve the subscribers, it is necessary to identify the main interfaces, the subsystems and network elements in the GSM network, as well as their functions. bitwali.com

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