By Dr. Ernest Simo
2.0 Multi-Carrier versus Direct Spread
When the spreading rate N>1, CDMA2000 supports wideband CDMA in two seperate formats:
- The first allows operation on three distinct, 1.25 MHz carriers, (Multi-Carrier Operation) each of which is spread by the 1.2288 Mps code and compatible with the operation of IS-95A.
- The second option allows a single wideband carrier (Nx1,25 MHz), to be used (Direct Spread) for third generation operation. Here, the message is directly spread with a chip rate of N x 1.2288Mcps.
- The CDMA2000 system supports 3x1.25 MHz channel operation within a 5 MHz channel. Guard bands and interference considerations permit operation in a 5 MHz PCS block.
- Data rates can reach 2 MB/s on CDMA2000. This compares with 9600 bps on IS-95A and 115,200 bps on IS-95B. CDMA2000 provides support for bandwidths up to 15 MHz as multiples of the original IS-95A/B bandwidth of 1.25 MHz.
CDMA Online Tech Talk
By Dr. Ernest Simo
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