WiMAX Ranging Procedure
This page describes fixed wimax ranging procedure and mention various ranging types as per IEEE 802.16 OFDM MAC layer specifications. It covers RNG REQ and RNG RSP MAC messages used for ranging by wimax SS.
As soon as wimax subscriber is switched on it establishes RF communication link by scanning available RF channels. After this, it synchronizes itself with Base Station using received long preamble(2 symbols) and performing time, frequency and channel estimation and equalization. After synchronization it decodes header(coded with BPSK1/2) information which helps to know modulation-code rate information of downlink burst#1 carring broadcast message. This broadcast message transmits DLMAP,DCD,ULMAP and UCD. Based on ULMAP and UCD, SS knows about when it has to transmit ranging messages in the uplink subframe.
The process by which the SS and BS maintain of RF communication link between them is referred as ranging. As mentioned RNG REQ and RNG-RSP MAC management message described below or special CDMA code modulated message is transmitted by the wimax SS for this purpose. There are various wimax ranging procedures as mentioned below.
1. Initial Ranging:
• Acquire correct transmission parameters (Power adjustment, timing
offset estimation, and synchronization) to communicate with the BS
2. Periodic Ranging:
• To maintain uplink communication with the BS
• Adjust transmission parameters
3. Contention Ranging:
• Required by the SS to access the system for the first time
• No dedicated connection resources assigned to the SS
4. Non-Contention Ranging:
• Regulated by the BS to allow the SS to finish system access earlier
when dedicated channel is provided
• Polled initial ranging
WiMAX RNG REQ
| RNG REQ field | Example Value |
|---|---|
| GEN HEADER(6 bytes) | 0x00, 0x40, 0x1a, 0x00, 0x00, 0xbe |
| Ranging req.type( 1 byte) | 0x04 |
| DL Channel ID (1 byte) | 0x00 |
| Requested DL Burst Profile (TLV) | 0x01, 0x01,0x11 |
| SS MAC Address(TLV) | 0x02,0x06,0x00,0x0a,0x1e,0x0a,0x1e,0x01 |
| MAC Version(TLV format) | 0x94,0x01,0x04 |
| CRC(4 bytes) | 0x5d,0x00,0x9c,0xfb |
| padding bytes if any | 0x00,0x00 |
WiMAX RNG RSP
| RNG RSP field | Example Value |
|---|---|
| Genetic MAC Header(6 bytes) | 0x00, 0x40, 0x32, 0x00, 0x00, 0x00 |
| initial ranging msg type | 0x05 |
| Uplink channel id | 0x00 |
| SS mac address | 0x08, 0x06, 0x00, 0x0a, 0x1e, 0x0a, 0x1e, 0x01 |
| basic cid | 0x09, 0x02, 0x00, 0x08 |
| primary cid | 0x0a, 0x02, 0x10, 0x08 |
| ranging status | 0x04, 0x01, 0x01 |
| timing adjust | 0x01, 0x04, 0xff, 0xff, 0xff, 0x9e |
| power level adjust | 0x02, 0x01, 0xec |
| offset frequency adjust | 0x03, 0x04, 0xff, 0xff, 0xfd, 0xdb |
| downlink operational burst profile | 0x07, 0x02, 0x01, 0x01 |
| CRC | 0x00, 0x00, 0x00, 0x00 |
| Padding if required | 0x00, 0x00 |
RNG REQ is transmitted by SS to BS. After performing Synchronization (Time, Freq, Channel) RNG REQ Frame is decoded to bits at BS. Type field just after GMH will describe message type which is '0x04' for RNG REQ, which tells BS what need to be done after receiving the message.
RNG RSP decoded by SS will analyze following:
1. 'Timing Adjust' field (signed 32 bit) and will drive PHY to advance frame Transmission accordingly.
2. 'Power level Adjust' field (signed 8-bit, 0.25dB) and will drive RF attenuators at RF layer accordingly.
3. 'Offset Frequency Adjust' field (signed 32 bit, Hz units) and will drive RF synthesizer/Ref. OCXO accordingly.
4. Ranging Status (if status is 're range') will indicate whether SS need to do retransmit RNG REQ or (if status is 'Success')
start BW REQ transmission for determining slot for SBC REQ.
What is Difference between
difference between FDM and OFDM
Difference between SC-FDMA and OFDM
Difference between SISO and MIMO
Difference between TDD and FDD
Difference between 802.11 standards viz.11-a,11-b,11-g and 11-n
Bluetooth vs zigbee
Bluetooth vs zigbee
wibro vs mobile wimax
Microcontroller vs microprocessor
FDMA vs TDMA vs CDMA
FDM vs TDM
CDMA vs GSM
OFDM vs OFDMA
wimax vs lte
Links to WiMAX MAC Layer resources
REG REQ and REG RSP
SBC REQ and SBC RSP
DSA REQ and DSA RSP
UCD,UIUC,DCD,DIUC
DLMAP and ULMAP
WiMAX Ranging Procedure
WiMAX Bandwidth Request procedure
WiMAX Network Entry Procedure
WiMAX CID vs SFID
WiMAX FCH header format
WiMAX TLV Format basics
WiMAX Timers
WiMAX Network Interface types
WiMAX QoS Classes