User's Manual

Mobile WiMAX RAS SPI-2L10 System Description/Ed.00

2-3

2.2 Main Functions

2.2.1 Physical Layer Processing Function

OFDMA Ranging

The ranging supported by the OFDMA system is roughly divided by the uplink timing

synchronization method and the contention based bandwidth request method.

y Uplink Timing Synchronization

In the uplink timing synchronization method, the SPI-2L10 detects the timing error of

the uplink signal by using the ranging code transmitted from MS and transmits the

timing correction command to each MS to correct the transmission timing of the uplink.

The uplink timing synchronization method has initial ranging, periodic ranging,

handover ranging, etc.

y Contention Based Bandwidth Request

In the contention based bandwidth request method, the SPI-2L10 receives the

bandwidth request ranging code from each MS and allocates uplink resources to the

corresponding MS to enable to transmit the bandwidth request header. The contention

based bandwidth request method has bandwidth request ranging or something.

OFDMA Sub-carrier Allocation

The subchannelization is the process to tie the sub-carriers of OFDMA as a transmission

unit after grouping them by a certain rule. The SPI-2L10 performs the subchannelization to

mitigate the interference between cells.

The SPI-2L10 maps the column of the modulated downlink QAM symbol structure with

each sub-carrier and carries out the subchannelization when the column of the QAM

symbol structure is transmitted to the MS over the wireless line. In such way, the SPI-2L10

transmits the column of the QAM symbol structure to the MS via the sub-carriers pertained

to each subchannel.

DL/UL MAP Construction

The SPI-2L10 informs the air resources for the uplink and the downlink to the MS by using

DL/UL MAP. The DL/UL MAP consists of the scheduling information of the SPI-2L10 and

includes various control information for the MS.

Power Control

The SPI-2L10 carries out the power control function for the uplink signal received from

multiple MSs and then set the power intensity of the uplink signal to a specific level.

The SPI-2L10 transmits the power correction command to each MS and then makes the

MS power intensity be the level required in the SPI-2L10 when the MS transmits the

modulated uplink signal in a specific QAM modulation method.