Code Division Multiple Access Project
INTRODUCTION
CDMA stands for CODE Division Multiple Access. Code division multiple access ( CDMA ) is a channel access method used by various radio communication technologies.
CDMA is an example of multiple access , which is where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). To permit this to be achieved without undue interference between theusers CDMA employs spread- spectrum technology and a special coding scheme (where each transmitter is assigned a code).
CDMA is used as the access method in many mobile phone standards such as cdmaOne, CDMA2000 (the 3G evolution of cdmaOne), and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA.It is a spread spectrum multiple access technique.a spread spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power.A spreading code is a pseudo random code that has a narrow ambiguity function,unlike other narrow pulse codes.In CDMA a locally generated code runs at a much higher rate than the data to be transmitted.Data for transmission is combined via bitwise XOR(exclusive OR)with the faster code.
Each user in a CDMA system uses a different code to modulate their signal.Choosing the codes used to modulate the signal is very important in the performance of CDMA systems.The best performance will occur when there is good separation between the signal of a desired user and the signals of the other users.The separation of the signals is made by correlating the received signal with the locally generated code of the desired user.IF the signal matches the desired user’s code then the correlating function will be high and the system can extract that signal.If the desired user’s code has nothing in common with the signal the correlation should be as close to zero as possible(thus eliminating the signal);this is
CDMA stands for CODE Division Multiple Access. Code division multiple access ( CDMA ) is a channel access method used by various radio communication technologies.
CDMA is an example of multiple access , which is where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies (see bandwidth). To permit this to be achieved without undue interference between theusers CDMA employs spread- spectrum technology and a special coding scheme (where each transmitter is assigned a code).
CDMA is used as the access method in many mobile phone standards such as cdmaOne, CDMA2000 (the 3G evolution of cdmaOne), and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA.It is a spread spectrum multiple access technique.a spread spectrum technique spreads the bandwidth of the data uniformly for the same transmitted power.A spreading code is a pseudo random code that has a narrow ambiguity function,unlike other narrow pulse codes.In CDMA a locally generated code runs at a much higher rate than the data to be transmitted.Data for transmission is combined via bitwise XOR(exclusive OR)with the faster code.
Each user in a CDMA system uses a different code to modulate their signal.Choosing the codes used to modulate the signal is very important in the performance of CDMA systems.The best performance will occur when there is good separation between the signal of a desired user and the signals of the other users.The separation of the signals is made by correlating the received signal with the locally generated code of the desired user.IF the signal matches the desired user’s code then the correlating function will be high and the system can extract that signal.If the desired user’s code has nothing in common with the signal the correlation should be as close to zero as possible(thus eliminating the signal);this is