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CDMA cellular radio network
The document outlines the design principles for CDMA cellular radio networks, focusing on the relationship between carrier-to-interference (C/I) ratios and frame error rates (FER). It discusses the impact of uniform and nonuniform cell scenarios on transmitter power and interference. Key considerations include the unique challenges of CDMA compared to TDMA systems and the need to optimize network performance to tolerate interference.
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CDMA cellular radio network
- 1. CDMA Cellular RadioNetwork PRESENTED BY Md Khanjahan Ali
- 2. Outline • System DesignPhilosophy • Key Element in Designing a CDMA System -Relationship Between C/I and FER • Uniform Cell Scenario -For the Forward Link -For the Reverse Link • Nonuniform Cell Scenario -Transmit Power on the Forward Link Channel -Transmit Power on the Reverse Link Channel - Designing a CDMA System
- 3. System Design Philosophy •In TDMA system, capacity increase as elimination of Interference from desire signal. • In CDMA system, the capacity increase depend on how much interference the desire signal can tolerate. • In CDMA , All user share the same radio channel.If one user take more power than it need, then other will be suffer and capacity will be decreased. • This presentation adresses how to tune The CDMA cellular radio network in order to tolarate interference.
- 4. Key Element inDesigning a CDMA System • In analog and TDMA system ,the most importent key element is C/I. -Measured C/I : indicate the voice quality of system. -Specified C/I : specified value for the system. • Therefore field strength meters use to design TDMA. • In CDMA all voice channels served by a single radio channel. -m-voice channel cell, -1 is trafic channel and m-1 interference channel. - C/I is hard to obtain by using a signal strength meter. • The key element in designing a CDMA system are different from Designin TDMA system.
- 5. Relationship Between C/Iand FER • In CDMA ,The key element Eb/Io which is related to FER (Frame Error Rate). • We can design CDMA On the basis of following equation. where, Eb= Energy/Bit, Io=Power/Herz. Rb = Bit/sec, B = Bandwidth. • Eb/Io always varies in order to meet a specified FER • From Equation We can find a required (C/I) from Specified Eb/Io • Have two different Requirement for C/I: -(C/I)F for the forward link channel -(C/I)R for the Reverse link channel B R I E I C b o b
- 6. Uniform Cell Scenario Forthe Forward link Channel
- 7. • The C/Ireceived at a mobile station A to the transmitted powers of all cell sites: home cell 2 adjacent cells 3 interim cells 6 distant cells (I1) (I2,I3) (I4,I5,I6) (I7,I8,I9,I10,I11,I12) • The relationship between of the three maximum transmitted powers of the three cells is 1 4 1 4 1 3322 1 )633.2()2( )1( 1 / mm m IC 3 3 2 2 1 1 m p m p m p
- 8. For the Reverselink
- 9. • The receivedC/I at the desired voice channel can be expressed as: • The worst-case scenario is when: CmrCmrCm C IC 321 .)1( / 1312 321 13121 1 mrmrm 1 / 1 321 1312 IC mrmrm
- 10. Nonuniform Cell Scenario TransmittedPower on the Forward link Channels
- 11. • All thecell size are not the same in a nonuniform CDMA system • Consider only the three cells most affected by location of three vehicles • The (C/I)F Received at vehicle 1,2,3 Respectively: 1 4 333 4 222 4 111 4 11 11 )1( )/( IRmRmRm R IC F 2 4 333 4 111 4 222 4 22 22 )1( )/( IRmRmRm R IC F 3 4 222 4 111 4 333 4 33 33 )1( )/( IRmRmRm R IC F
- 12. Transmitted Power onthe Forward link Channels
- 13. • Interference atcell site 1,2,3 respectively • Under the physical condition ,the following relation have to be held. '' ' 1 4 13313 4 1212 4 111 4 11 11 2')1( )/( IRmrRmrRm R IC R 4 23323 4 21121 4 222 4 22 22 '' ' ')1( )/( RmrRmrRm R IC R 4 32232 4 31131 4 333 4 33 33 '' ' ')1( )/( RmrRmrRm R IC R 1 )/( 1 ,, 321 RIC mmm
- 14. Designing a CDMAsystem • First have to check whether all requirement express above equation are met with our condition • Then find the transmit Power .
- 15.