Lecture 5 - Sept 24 - Chapter4: GSM Handoffregion...

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4.1 Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 Mobile Communications Chapter 4: Wireless Telecommunication Systems  GSM   Handoff region  Frequency reuse  GSM Security
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Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 4.2 Powers of Two Received Signals  as Functions of Distances from Two BSs BS Signal strength due to BS j X 1 Signal strength due to BS BS j X 3 X 4 X 2 X 5 MS P min P (x) P j (x ) Observe: P j (X 1 )    0     P (X )    0 (Modified by LTL)
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Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 4.3 Signal Strength and Cell Parameters [http://en.wikipedia.org/wiki/DBm] dBm   (used in following slides)  = an abbreviation for the power ratio in decibel (dB) of the  measured power referenced to 1 mW (milliwatt) dBm is an  absolute unit  measuring absolute  power Since it is referenced to 1 mW In contrast,  dB  is a  dimensionless  unit, which is used when measuring the  ratio   between two values   (such as signal-to-noise ratio) Examples : 0 dBm = 1 mW 3 dBm   2 mW  Since a 3 dB increase  represents roughly doubling the power 3 dBm   0.5 mW Since a 3 dB decrease  represents roughly cutting in half the power   ©  2007 by Leszek T. Lilien
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Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 4.4 Signal Strength and Cell Parameters – cont. [http://en.wikipedia.org/wiki/DBm] Examples – cont. 60 dBm  = 1,000,000 mW = 1,000 W = 1 kW  Typical RF power inside a  microwave oven  27 dBm  = 500 mW Typical  cellphone transmission  power  (some claim that users’ brains are being fried) 20 dBm = 100 mW Bluetooth Class 1  radio,  100 m range  =  max. output power from unlicensed  FM  transmitter   (4 dBm = 2.5 mW - BT Class 2 radio, 10 m range) 70 dBm  = 100 pW (yes, “ - ”!!!) Average strength of  wireless signal over a network Average for the range:  60 to  80 dBm - 60 dBm=  1 nW = 1,000 pW  - 80 dBm= 10 pW ©  2007 by Leszek T. Lilien
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Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 4.5 Land Propagation The received signal power:  where:  G t  is the transmitter  antenna gain,        G r  is the receiver  antenna gain,         L  is the  propagation loss  in the channel,  i.e.,  L = L P  L S  L F L P G G P t r t r = Fast fading (long-term f.) Slow fading (short-term f.) Path loss
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Prof. Dr.-Ing. Jochen H. Schillerwww.jochenschiller.deMC - 2008 4.6 Path Loss (for Land Propagation) Path loss as a function of distance L p = A d α where: A and α : propagation constants d : distance between transmitter and receiver Value of  α    - 2-4 - normally      - below 2 in some waveguides    - 2 in free space,     
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