UMTS Spreading Scrambling modulation
This tutorial on UMTS covers spreading, scrambing and modulation concepts.
Scrambling using scrambling code
Scrambling does not change the bit rate. It only helps in separating signals from different sources. Gold codes are used for this purpose as they have good correlation properties. Long and short type of scrambling codes are available. In the uplink it separates different UEs and in the downlink it s used for separation of cells/sectors.
DPCCH and DPDCH are BPSK modulated.
Synchronization using synchronization code:
These codes will have good auto correlation functionality hence are used for initial cell search and synchronization in the downlink. Primary sync. codes are derived using Golay sequence and secondary words from Hadamard sequence.
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