Terminology » WiMAX » WiMAX Channel Descriptors: UCD, UIUC, DCD, and DIUC Explained

WiMAX Channel Descriptors: UCD, UIUC, DCD, and DIUC Explained

wimax channel descriptor ucd dcd ieee 802.16

This document explains the WiMAX channel descriptors: Uplink Channel Descriptor (UCD), Uplink Interval Usage Code (UIUC), Downlink Channel Descriptor (DCD), and Downlink Interval Usage Code (DIUC). It details various fields used within these descriptors as per the IEEE 802.16 fixed WiMAX standard’s MAC layer specifications.

These channel descriptors convey modulation and coding rate information for data bursts. Specifically:

  • UCD/UIUC: Describe the modulation and coding rate information for uplink burst profiles.
  • DCD/DIUC: Describe the modulation and coding rate information for downlink burst profiles.

UCD and DCD Fields Comparison

Here’s a comparison of key fields found in the UCD and DCD:

WiMAX UCD FieldsWiMAX DCD Fields
Generic MAC Header (6 bytes)Generic MAC Header (6 bytes)
UCD Type (8 bits)DCD Type (8 bits)
CCC (8 bits)DL channel ID (8 bits)
Ranging Back off start (8 bits)CCC (8 bits)
Ranging Back off End (8 bits)Base station EIRP
Request Back Off Start (8 bits)Request Back Off End (8 bits)
downlink center frequencyBS ID
Contention based reservation time outContention ranging request opportunity size
Frame duration codeMAC version
Contention ranging request burst sizeframe number
Uplink center frequency
CRCCRC (4 bytes)

The following table lists common UIUC values and their corresponding usage or function:

UIUC ValueUsage/Function
0Reserved
1Initial ranging
2REQ Region Full
3REQ region focused
4Focused contention IE
5-12UCD Burst profiles
13Subchannelization network entry
14End of Map
15Extended UIUC table

The following table lists common DIUC values and their corresponding usage or function:

DIUC ValueUsage/Function
0STC Zone
1-11DCD Burst profiles
12Reserved
13Gap
14End of Map
15Extended DIUC table

UCD and DCD Burst Profile Encoding (OFDM)

  • UCD burst profile encoding for OFDM: { FEC code rate(TLV format), DIUC mandatory exit threshold, DIUC min. entry threshold, TCS_enable}

  • DCD burst profile encoding for OFDM: {FEC code rate, DIUC mandatory exit threshold, DIUC min. entry threshold, TCS_enable}

Where:

  • FEC code type = {150,1,FEC_value}

  • FEC_value = 0 for BPSK 1/2, 1 for QPSK 1/2, 2 for QPSK 3/4, 3 for 16QAM 1/2, 4 for 16QAM 3/4, 5 for 64QAM 2/3, 6 for 64QAM 3/4, and so on.