WiMAX DLMAP vs ULMAP-Difference between DLMAP and ULMAP
This page describes WiMAX DLMAP and ULMAP messages with all the fields. It mentions basic difference between DLMAP and ULMAP in fixed wimax system as per IEEE 802.16 OFDM MAC specifications.
Figure mentions wimax frame structure as per OFDM specifications. As mentioned wimax frame consists of downlink SF and uplink SF. DLMAP and ULMAP is carried in the downlink SF in the broadcast burst which carries system critical informations. DLMAP carry location information of downlink bursts in the frame and ULMAP carry location information about uplink bursts. It gives this information in units of number of OFDM symbols with respect to start of the frame. The table below mentions all the DLMAP and ULMAP fields with example values. DLMAP consists of DLMAP IE(Information Element) which repeats as per number of downlink bursts i.e. for 4 downlink bursts 4 IEs exist. Similarly ULMAP consists of ULMAP IE which repeats as per number of uplink bursts i.e. for 4 uplink bursts 4 IEs exist.
WiMAX DLMAP
| WiMAX DLMAP Field | Example Value |
|---|---|
| Generic MAC Header(6 bytes) | 0x00, 0x40, 0x16, 0xff, 0xff, 0x00 |
| DLMAP type( 1 byte-8 bits) | 0x02 |
| DCD count (8 bits) | 0x01 |
| BS ID (48 bits) | 0x00, 0x09, 0x02, 0x00, 0x9f, 0x45 |
| CID(2) (16 bits) | 0x00, 0x00 |
| DIUC(2) (4bits) | 0xe (Used for scrambler seed value) (END OF MAP) |
| Preamble(2) (1 bit) | 0 |
| Start time (#Burst2) (11 bits) | Gives Start time of DL Burst#2. In units of symbol duration, relative to the start of the first symbol of the PHY PDU. 3*Ts + (length of Burst#1)*Ts |
| CRC | 0x00, 0x00, 0x00, 0x00 |
DL MAP IE ={ CID, DIUC, preamble present, Start time }
This IEs will repeat as per number of downlink bursts as mentioned.
UL MAP IE ={ CID, start time, sub channel index, UIUC, duration } This IEs will repeat as per number of uplink bursts as mentioned.
WiMAX ULMAP
| WiMAX ULMAP Field | Example Value |
|---|---|
| Generic header(6 bytes) | 0x00, 0x40, 0x1d, 0xff , 0xff, 0x00 |
| UL MAP type(8 bits) | 0x03 |
| Uplink channel ID(8 bits) | 0x00 |
| UCD count(8 bits) | 0x01 |
| Allocation start time-32 bits (in units of PSs) | Starting from3*Ts after how many PSs uplink allocation will start For example, (Long Preamble+FCH+DLB#1+silent period+ TTG=>(5.6ms)=>5600 PSs) { 0x00, 0x00, 0x15, 0xE0} |
| CID(16 bits) | 0xFFFF for broadcast case |
| Start time(11 bits) | 0x000 |
| Sub channel Index(5 bits) | (10000) no subchannelization |
| UIUC (4 bits) | 0x2 |
| Duration(10 bits) | for example 0x008 |
| Midamble rep. interval(8 bits) | 0x00 |
| CRC-4 bytes |
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