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  • Tuesday, 30 November 2021
Spread Spectrum Technologies

Spread Spectrum Technologies

Spectrum deployment technology is divide into two types: direct sequence spread spectrum spread spectrum (DS-SS) and frequency hopping spread spectrum (FH-SS).

 

Direct spread spectrum is use in the CDMA (Code Division Multiple Access) radio access technology of 3G (IMT-2000) systems, according to some standards, including UMTS (WCDMA) of 3GPP, CDMA2000 of 3GPP2. , TD-SCDMA of CWTS (China) and so on.

 

Spreading is the process by which information at a narrower bandwidth (lower data speed) is spreading over a wider bandwidth (higher data speed) that includes two operations: channelization and scrambling:

 

  • Channelization is the increase in signal bandwidth by converting each data symbol into a number of chips at a chip rate of 3.84 Mcps (in the case of WCDMA) using automated codes. Orthogonal codes) to prevent interference with each other based on OVSF (Orthogonal Variable Spreading Factor) technique. The ratio between the chip rate and the symbol rate is call the spreading factor (SF).

  • The second operation is scrambling, in which scrambling code, a PN code (Pseudo Noise), is applied to a spread signal (spread signal).

  • We know that in a CDMA (Code Division Multiple Access) radio input system, the frequency, which is the only radio channel, is use on all cells, so the entire gap used in each cell. Likewise, the entire gap used in parallel by all UEs at the same time.

  • Channelization codes / OVSF codes used to differentiate between different transmissions to UE (User Equipment / Terminals) in the downlink direction in a cell.

  • Channelization codes / OVSF codes used to differentiate between physical channels / physical data & control channels broadcast from a UE in an uplink direction.

  • Scrambling codes / PN codes used to differentiate between cells in a downlink direction.

  • Scrambling codes / PN codes used to differentiate between different UEs in the uplink direction.

Spread Spectrum Technologies
Spread Spectrum Technologies
Spread Spectrum Technologies
Spread Spectrum Technologies