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WCDMA3G_DnLkDeSpreading


Description: Downlink de-spreading and de-scrambling
Library: 3GPPFDD 10-99, User Equipment
Class: SDFWCDMA3G_DnLkDeSpreading

Parameters
Name Description Default Sym Type Range
SF spreading factor: SF_4 , SF_8 , SF_16, SF_32, SF_64, SF_128, SF_256, SF_512 SF_256 N SF enum  
UseExtSpreadingCode use external spreading code: Yes, No No   enum  
SpreadingCodeIndex spreading code index 0   int [0, N SF -1]
ScramblingCodeIndex scrambling code index 0   int [0, 8191]]
DL_DPCHType downlink dedicated physical channel: DPCH_15kbps_TF0_T2_P4, DPCH_15kbps_TF2_T2_P4, DPCH_30kbps_TF0_T2_P2, DPCH_30kbps_TF2_T2_P2, DPCH_30kbps_TF0_T2_P4, DPCH_30kbps_TF2_T2_P4, DPCH_30kbps_TF0_T2_P8, DPCH_30kbps_TF2_T2_P8, DPCH_60kbps_TF0_T2_P4, DPCH_60kbps_TF2_T2_P4, DPCH_60kbps_TF0_T2_P8, DPCH_60kbps_TF2_T2_P8, DPCH_120kbps_TF8_T4_P8, DPCH_120kbps_TF0_T4_P8, DPCH_240kbps_TF8_T4_P8, DPCH_240kbps_TF0_T4_P8, DPCH_480kbps_TF8_T8_P16, DPCH_480kbps_TF0_T8_P16, DPCH_960kbps_TF8_T8_P16, DPCH_960kbps_TF0_T8_P16, DPCH_1920kbps_TF8_T8_P16, DPCH_1920kbps_TF0_T8_P16 DPCH_30kbps_TF2_T2_P8   enum †
DL_TXDiversity transmitting diversity in downlink: No_Diversity, DL_STTD No_Diversity   enum  
SampleRate number of samples per chip 8   int [1, 32]]
PathNum number of paths 1   int [1, 16]]
MaxDelay maximum path delay in terms of chips 20   int [0, 1280]]
SearchDir path search direction based on current timing: Forward, Backward, Bidirection Backward   enum  
EstMethod channel estimation method: Averaging, Interpolation, WMSA, NoEst Interpolation   enum  
† where
TF n = number of transmit format indicator bits
T n = number of transmit power control bits
P n = number of pilot bits
F n = number of feedback indicator bits

Pin Inputs

Pin

Name

Description

Signal Type

1

In

input data

complex

2

SpreadingCodeExt

external spreading code

int

Pin Outputs

Pin

Name

Description

Signal Type

3

Out

output data

complex

Notes/Equations
  1. This subnetwork is used to perform de-spreading and de-scrambling in a downlink.
    When UseExtSpreadingCode = Yes, spreading code is input though pin SpreadingCodeExt; otherwise, WCDMA3G_OVSF generates the spreading code.
    Refer to the following table for the values of NSF.
    Relation between SF and NSF

    SF

    NSF

    SF_4

    4

    SF_8

    8

    SF_16

    16

    SF_32

    32

    SF_64

    64

    SF_128

    128

    SF_256

    256

    SF_512

    512
    The schematic for this subnetwork is shown in the following figure. Input data (spreading code generated by WCDMA3G_OVSF or input by pin SpreadingCodeExt) and scrambling code generated by WCDMA3G_Scrambler are input to WCDMA3G_1CHRakeReceiver, which de-spreads and de-scrambles the input data. WCDMA3G_1CHRakeReceiver implements coherent Rake receiver with maximal ratio combining (MRC) on one code channel.

    WCDMA3G_DnLkDeSpreading Schematic

References
  1. 3GPP Technical Specification TS 25.213 V3.0.0 "Spreading and Modulation (FDD)," October 1999.
  2. 3GPP Technical Specification TS25.211 V3.0.0, "Physical channels and mapping of transport channels onto physical channels (FDD)," October 1999.
  3. Andrew J.Viterbi, "CDMA: Principles of Spread Spectrum Communication," Wesley Publishing Company, 1995.
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