Lecture 18

Lecture 18 - Cellular usc-den-ee555-spring-2009 - Access...

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Cellular usc-den-ee555-spring-2009 - Access Network Technologies 46 Cellular Wireless Networks • key technology for mobiles wireless nets et key technology for mobiles, wireless nets etc • developed to increase mobile phone capacity • based on multiple low power transmitters based on multiple low power transmitters • area divided into cells – in a tiling pattern to provide full coverage – each with own antenna – each with own range of frequencies ser ed b base station – served by base station – adjacent cells use different frequencies to avoid crosstalk usc-den-ee555-spring-2009 - Access Network Technologies 47
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Cellular Geometries usc-den-ee555-spring-2009 - Access Network Technologies 48 Frequency Reuse • must manage reuse of frequencies • power of base transceiver controlled – allow communications within cell on given frequency – limit escaping power to adjacent cells – allow re-use of frequencies in nearby cells – typically 10 – 50 frequencies per cell – example for Advanced Mobile Phone Service (AMPS) N cells all using same number of frequencies N K total number of frequencies used in systems • each cell has K/N frequencies K =395, N =7 giving 57 frequencies per cell on average usc-den-ee555-spring-2009 - Access Network Technologies 49
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Frequency Reuse Patterns usc-den-ee555-spring-2009 - Access Network Technologies 50 Increasing Capacity • add new channels add new channels – not all channels used to start with frequency borrowing • frequency borrowing – taken from adjacent cells by congested cells – or assign frequencies dynamically • cell splitting – non-uniform topography and traffic distribution – use smaller cells in high use areas usc-den-ee555-spring-2009 - Access Network Technologies 51
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Cell Splitting usc-den-ee555-spring-2009 - Access Network Technologies 52 Increasing Capacity • cell sectoring cell sectoring – cell divided into wedge shaped sectors (3–6 per cell) – each with own channel set – directional antennas • microcells – move antennas from tops of hills and large buildings to tops of small buildings and sides of large buildings – use reduced power to cover a much smaller area – good for city streets, roads, inside large buildings usc-den-ee555-spring-2009 - Access Network Technologies 53
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Options for Radio Interfaces usc-den-ee555-spring-2009 - Access Network Technologies 54 Driving Forces • trend toward universal personal telecommunications • universal communications access • GSM cellular telephony with subscriber identity module, is step towards goals • personal communications services (PCSs) and personal communication networks (PCNs) also form objectives for communication networks (PCNs) also form objectives for third-generation wireless • technology is digital using time division multiple access or code-division multiple access • PCS handsets low power, small and light usc-den-ee555-spring-2009 - Access Network Technologies 55
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First Generation - Analog First Generation Analog • original cellular telephone networks
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Lecture 18 - Cellular usc-den-ee555-spring-2009 - Access...

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