Re: [STDS-802-16] DCD/UCD message in OFDMA-2048
Dear Jonny,
Your question is very good and very interesting. It seems really a little fault of the standard.
Somebody tells me that the DCD (or UCD) message, if it exists, should follow immediately after the DL-MAP.
The length specified by the FCH should be the total length of DL-MAP and the DCD/UCD message. But I cannot
see all these statements in std. 2005, either.
Best regards,
Aimin Zhang
>Dear all,
>
>According to standard (802.16e-2005), the following rules for DCD/UCD
>message are defined for OFDMA-2048:
>- DCD/UCD are MAC PDU with broadcast (or fragmented broadcast) CID.
>- The position and DIUC code of DCD/UCD message are appointed by DL_MAP.
>- The uplink/downlink burst profile parameters for each UIUC/DIUC code are
>defined and updated by UCD/DCD message (except for the burst profile used by
>DL_MAP, which is defined in the downlink frame prefix).
>- DCD/UCD may not present in every DL subframe. The maximum time interval
>between the transmission of DCD/UCD message will be 10s.
>
>The questions are:
>1. When an MS is entering the network, it can decode the downlink frame
>prefix because the burst profile is well known. And then it can decode the
>DL_MAP because the burst profile is defined in downlink frame prefix. But
>the DIUC code used in the DL_MAP are defiend in previous DCD message. How
>can MS decode the downlink MAC PDU using the burst profile it has no idea
>about? If the MS can not decode the downlink MAC PDU, how can it decode the
>DCD, UCD and UL_MAP. And if the UCD and UL_MAP can not be decoded, how to
>know initial ranging allocation at MS?
>2. Since the DCD/UCD message may not present in every DL subframe, the new
>entering MS may waiting for a few frames before it get the first DCD/UCD
>message. During this period, it can not decode any other message except for
>the DL_MAP/UL_MAP. However, since the DCD/UCD message are treat as generic
>MAC PDU, the MS can not recognize them until decode the PDU. So, is there
>any method to know the presence and position of DCD/UCD in current DL
>subframe?
>
>Thanks.
>
>Best Regards
>Jonny