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WCDMA3G_TFCIDecoder


Description: TFCI decoder
Library: 3GPPFDD 10-99, Channel Coding
Class: SDFWCDMA3G_TFCIDecoder

Parameters

Name

Description

Default

Type

Range

LinkDir

link direction: Downlink, Uplink

Downlink

enum

 

TFCIBitsNum

number of TFCI bits

6

int

[1, 10]

DPCHType

dedicated physical channel type: DPCH_15_kbps, DPCH_30_kbps, DPCH_60_kbps, DPCH_120_kbps, DPCH_240_kbps, DPCH_480_kbps, DPCH_960_kbps, DPCH_1920_kbps

DPCH_15_kbps

enum

 

Pin Inputs

Pin

Name

Description

Signal Type

1

TFCI

input TFCI information

real

Pin Outputs

Pin

Name

Description

Signal Type

2

TFCIOut

decoded TFCI information

int

Notes/Equations
  1. This model is used to implement transport format combination indicator (TFCI) decoding. The TFCI decoder decodes a (30,10) punctured sub-code of the second-order Reed-Muller code into a TFCI information value.
    Each firing, one TFCIOut token is produced when 30 or 120 TFCI tokens are consumed depending on DCHType. The default value for TFCIBitsNum is 6 and default value for DCHType is DPCH_15_kbps.
  2. Model functions
    Input TFCI information is read from the input buffer.
    A determination is made for repeating input TFCI information. In downlink, when the SF is lower than 128 the encoded and punctured TFCI code words are repeated four times yielding 120 output bits. The two kinds of output code words are:
    • TFCIOut information without repetition:
    • TFCIOut information with repetition:
    If the repetition is used, the 30 average values bi are taken from the input 120 TFCI bits as follows:

    bi = (bi1+bi2+bi3+bi4)/4 i = 0, 1, ... , 29

    If TFCIBitsNum ≤ 6, calculating the coherent value between the 32 input bits with the possible code words C32,0, C32,1, ..., C32,31, refer to WCDMA3G_TFCIEncoder. Assume the n th coherent value has the greatest absolute value, then if the n th coherent value is positive, the decimal value of TFCI is 2n, otherwise is (2n+1).
    If TFCIBitsNum > 6, up to four masks are used. The decoding scheme, illustrated in the following figure, is described:
    • Multiply the input 32 bits by the possible masks (0 to 15) and calculate the coherent value.
    • Store the maximum absolute coherent value and TFCI value for this mask.
    • After storing all possible masks, find the maximum coherent value under all masks. Assume the n th coherent value has the greatest absolute value; the n th TFCI value is the decoded value.

    Decoder structure while masks are used
    The decoded TFCI bits are output to the output buffer.

References
  1. 3GPP Technical Specification TS25.212 V3.0.0,"Multiplexing and Channel Coding (FDD)," October 1999
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