MWN-07-IntroCell

MWN-07-IntroCell - 03.09.2011 1 Mobil ve Kablosuz A ğ lar...

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Unformatted text preview: 03.09.2011 1 Mobil ve Kablosuz A ğ lar Suat Özdemir Suat Özdemir Gazi Üniversitesi Bilgisayar Mühendisli ğ i Bölümü Hücresel A ğ Hücresel A ğ Konsepti Konsepti 2 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Hücresel a ğ konsepti ¡ İ lk mobil a ğ sistemlerinde amaç tek bir yüksek güçlü anten ile oldukça geni ş bir alan ı kapsamakt ı ¡ max of 12 calls in New York City in 1970 ¡ max of 12 calls in New York City in 1970 ¡ Hücresel a ğ konsepti ¡ replace a high power transmitter with many low power transmitters ¡ each base station gets a portion of all channels 3 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Hücresel a ğ konsepti z Prensip: Talep artt ı kça baz istasyonu say ı s ı n ı art ı r ve iletim gücünü dü ş ür. z Belli say ı daki kanal tekrar tekrar kullan ı larak (channel reuse) göreceli olarak çok say ı daki (channel reuse) göreceli olarak çok say ı daki kullan ı c ı ya hizmet eder. ¡ The design process of selecting and allocating channel groups for all of the cellular base stations within a system is called frequency reuse or frequency planning. 4 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Hücresel yap ı z Space division multiplex pace division multiplex kullan ı l ı r z Bir baz istasyonu belli bir bölgeyi kapsar (cell, hücre) z Mobil istasyonlar sadece baz istasyonu ile z Mobil istasyonlar sadece baz istasyonu ile ileti ş im kurarlar 5 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Hücresel yap ı z Advantages of cell structures: z higher capacity, higher number of users z less transmission power needed more robust decentralized z more robust, decentralized z base station deals with interference, transmission area etc. locally 6 ht p:/ ceng.gazi.edu.tr/~ozdemir/ 03.09.2011 2 Hücresel yap ı z Problems: z A complex infrastructure to connect all base stations z handover (changing from one cell to another) z handover (changing from one cell to another) necessary z interference with other cells z Cell sizes from some 100 m in cities to, e.g., 35 km on the country side (GSM) 7 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Hücrelerin gösterimi ¡ Footprint : the actual radio coverage of a cell circle z gaps and overlapping regions square; equilateral triangle hexagon ¡ square; equilateral triangle; hexagon ¡ hexagon geometry allows the fewest number of cells to cover a geographic area 8 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Kanal tan ı m ı z A channel is characterized by a z frequency band in Frequency Division Multiplexing (FDM) z time slo in Time Division Multiplexing (TDM z time slot in Time Division Multiplexing (TDM) z orthogonal modulating code in Code Division Multiplexing (CDM) z or, a combination of above 9 ht p:/ ceng.gazi.edu.tr/~ozdemir/ Kanal tekrar kullan ı m ı z Channel reuse is possible if a second transmitter using the channel is ``far enough’’ from the main transmitter so that the received energy from the main transmitter dominates energy from the main transmitter dominates the energy from the second transmitter.the energy from the second transmitter....
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This note was uploaded on 01/20/2012 for the course EE 301 taught by Professor Ahmetçakar during the Spring '11 term at Gazi Üniversitesi.

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MWN-07-IntroCell - 03.09.2011 1 Mobil ve Kablosuz A ğ lar...

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