Get Here about CDMA technology and How CDMA Works, CDMA Solution and CDMA RF Optimization.
A pilot channel: Assist mobile station to be connected with CDMA network Handles multi-path searching Provide the phase reference for coherent demodulation and help the mobile station estimate the transmission power The mobile station measures and compares the pilot channel powers from the base stations during the handoff Forward pilot channel is spread over W0 … Read more
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 mobile communication channel is a multi-path fading channel and any transmitted signal reaches a receive … Read more
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 possible drop call. T_ADD affects the percentage of MS in handoff. It should be low … Read more
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 control means that based on the detected signals from a base station, a mobile station … Read more
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 mobile stations In a reverse direction, different long codes are used for the information … Read more
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 enter the interleaver at the receive end row by row and are read out column … Read more
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 is divided into sub bands as shown above.The Total Band of 25MHz is divided into … Read more
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 is possible because the CDMA mobile is synchronized to the serving base station. The mobile’s … Read more
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 multipath conditions. Several start-up companies developed advanced proprietary solutions that provided significant performance gains over … Read more
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 station receives the signals from multiple base stations (two in most cases) at the same … Read more