CDMA

Get Here about CDMA technology and How CDMA Works, CDMA Solution and CDMA RF Optimization.

Transmit Diversity of CDMA

Diversity technology means that after receiving two or more input signals with mutually uncorrelated fading at the same time, the system demodulates these signals and adds them up. Thus, the system can receive more useful signals and overcome fading. A…

What is T_ADD,T_DROP and T_TDROP in CDMA?

Pilot Detection Threshold (T_ADD) Any Pilot that is strong but is not in the Handoff Direction Message is a source of interference. This Pilot should be immediately moved into the active set for handoff to avoid voice/data degradation or a…

Types of Power Control in CDMA

Reverse power control Open loop power control Closed loop power control Inner loop power control:  800 Hz Outer loop power control Forward power control Message transmission mode: threshold transmission periodic transmission Closed loop power control    Reverse open loop power…

Long Code & Short Code In CDMA

The long code is a PN sequence with period of 242-1chips The functions of a long code: Scramble the forward CDMA channel Control the insertion of power control bit Spread the information on the reverse CDMA channel to identify the…

Interleaving in CDMA

It can be seen from the figure that the data are read row by row into an interleaver at the transmit end,read column by column out (this process is called interleaving) and propagated after other modulation process. Then, the data…

CDMA Channel Frequencies & Calculation

The 850MHz CDMA band is most popularly used all over the world.This band as mentioned in the previous slide works between       824-849MHz Used for the Reverse link communication       869-894MHz Used for the Forward link communication The CDMA band…

Why Power Control Essential in CDMA ?

Power control is essential for the smooth operation of a cdma system. Because all users share the same rf band through the use of pn codes Each user looks like random noise to other users. The power of each individual user…

What is RAKE RECEIVER and its Purpose in CDMA

Rake Receiver Instead of trying to overpower or correct multipath problems, CDMA takes advantage of the multipath to improve reception quality in fading conditions. CDMA does this by using multiple correlating receivers and assigning them to the strongest signals.  This…

Second-Generation Broadband Systems

Second-generation broadband wireless systems were able to overcome the LOS issue and to provide more capacity. This was done through the use of a cellular architecture and  implementation of advanced-signal processing techniques to improve the link and system performance under…

Soft/Softer Handoff in CDMA

Multi-path combination in the BSC during soft handoffMulti-path combination in the BTS during softer handoffs       Soft handoff means that during the handoff of a mobile station at the coverage edge areas of two or multiple base stations, the mobile…

Forward Power Control in CDMA

Message Transmission Mode MS measures the frame quality and informs the base station to the result i.e. whether it is in the threshold or periodical  mode. Base station determines whether  to change the forward transmitting power or not.In IS-95 system,…

Scrambling (M) sequence in CDMA

  Two points are important here:  Maximum number of shift register (N)  Mask The period of out put sequence is 2N-1 bits Only sequence offset is change when the mask is changed PN stands for Pseudorandom Noise sequence In CDMA…