CDMA(Satellite Communication)

50 %
50 %
Information about CDMA(Satellite Communication)
Education

Published on March 13, 2014

Author: actionanand

Source: authorstream.com

PowerPoint Presentation: Anand Raja Presents Seminar On CDMA PowerPoint Presentation: MULTIPLE ACCESS TECHNIQUES F R E Q U E N C Y TIME FDMA TDMA CDMA :  Time Frequency CDMA User 1 User 2 User 3 Code PowerPoint Presentation: SSMA ( S pread S pectrum M ultiple A ccess) Carrier is 1 st modulated by Info wave Its again modulated by unique code waveform The 2 nd modulation is done to spread the spectrum over available BW Therefore CDMA is also called SSMA Let the Info. Signal P(t) & Code Signal c(t) be Polar NRZ code PowerPoint Presentation:  1 x 1 = 1 Multiplication 1 x -1 = -1 -1 x 1 = -1 -1 x -1 = 1 CDMA example: CDMA example Low-Bandwidth Signal: High-Bandwidth Spreading Code: ...repeated... CDMA example: CDMA example Low-Bandwidth Signal: High-Bandwidth Spreading Code: Mix is a simple multiply … and transmit. CDMA example: CDMA example To Decode / Receive, take the signal: CDMA example: CDMA example To Decode / Receive, take the signal: Multiply by the same Spreading Code: … to get ... … which you should recognize as... CDMA example: CDMA example To Decode / Receive, take the signal: Multiply by the same Spreading Code: … to get ... The Code signal: The Code signal Implementation: Implementation D irect- S equence S pread S pectrum( DS/SS ) Frequency Hopped Spread Spectrum Topics explained below CDMA ‘re DS/SS Code signal c(t) Autocorrelation function for c(t) Acquisition & Tracking Spectrum Spreading & Despreading CDMA throughput Direct-Sequence Spread Spectrum(DS/SS) : D irect- S equence S pread S pectrum( DS/SS ) Inputs to the s/m are polar NRZ signals p(t) & c(t) Applied to the multiplier(1 st modulator) O/p is proportional to p(t).c(t) This O/P is applied to 2 nd modulator Direct-Sequence Spread Spectrum(DS/SS): D irect- S equence S pread S pectrum( DS/SS ) @ Rx, an identical c ( t ) generator is synchronized to the c ( t ) of the downlink carrier Done by acquisition & tracking block exactly in synchronism with the transmitted c ( t ), the product c 2 ( t )=1 Thus the output from the multiplier is Code signal c(t): Code signal c(t) chip period T ch -> Chip rate(clock speed) Since the waveform c(t) is periodic, sequence of N period will repeat for each period Thus periodic time T N = NT ch   Code Generation: Code Generation Maximum sequence : N=2 n -1 Pseudo-Noise codes : It has noise-like property, since 1s & 0s ‘re randomly distributed Important Features of code Code Generation: Code Generation dc offset =V/N Autocorrelation function: Autocorrelation function It is a measure of how well a time-shifted version of the waveform compares with the un-shifted version Acquisition and Tracking: Acquisition and Tracking The output from the first multiplier is Spread Spectrum Principle: Spread Spectrum Principle 1 2 3 1 2 3 1&2&3 1 2&3 Spreading De-spreading Spectrum Spreading: Spectrum Spreading Spectrum De-Spreading: Spectrum De-Spreading CDMA throughput: CDMA throughput The parameters needed to find CDMA throughput ‘re No. of channel (K) Processing Gain ( Gp ) No. of channel (K ) Assume for K channels, K- 1 of these will produce noise & that this is evenly spread over the noise bandwidth BN of the receiver : the noise density, in W/Hz, is No. of channel (K) : No. of channel (K) Process Gain(Gp): Process Gain( Gp ) The processing gain Gp is basically the ratio of power density in the un-spread signal to that in the spread signal Throughput Efficiency: Throughput Efficiency Efficiency=CDMA Tran Rate/Single access Tran rate with out spreading

Add a comment

Related presentations

Related pages

CDMA - Satellite Services

CDMA Decades ago, the military organizations of the world adopted the Code Division Multiple Access (CDMA) scheme to meet the need for highly secure and ...
Read more

Fundamentals of Communications Access Technologies: FDMA ...

Fundamentals of Communications Access Technologies ... Early satellite systems shared ... Principles of Electronic Communication ...
Read more

Performance evaluation of MC-CDMA and DS-CDMA schemes in ...

Performance evaluation of MC-CDMA and DS-CDMA schemes in satellite communications based on VSAT networks . 1Mohammed EL JOURMI, 2Hassan EL GHAZI ...
Read more

CDMA in Low Earth Orbit Satellites - DLR

CDMA in Low Earth Orbit Satellites ... Figure 3- an example of CDMA satellite communication in C4I system Figure 4- anti jamming principle of DS/SS.
Read more

Performance analysis of channel coding in satellite ...

Performance analysis of channel coding in satellite communication based on VSAT Network and MC-CDMA scheme . Mohammed El jourmi1, Hassan El ghazi2 ...
Read more

Basic capacity calculation methods and benchmarking for MF ...

Basic capacity calculation methods and benchmarking for MF-TDMA and MF-CDMA communication satellites ... MF-CDMA satellite communication systems in LEO.
Read more

Patent US5875181 - Packetized CDMA/TDM satellite ...

In a satellite communication system a CDMA uplink signal including user data is transmitted in a packetized manner, the packets are switched on board the ...
Read more

Why is CDMA the Solution for Mobile Satellite Communication

Why is CDMA the Solution for Mobile Satellite Communication ? by Klein S. Gilhousen, Irwin M. Jacobs, Roberto Padovani, and Lindsay A. Weaver'
Read more

Patent US20130294224 - Transmit and admission control for ...

A system for performing transmit power and admission control for a satellite based wireless communication systems.
Read more