User's Manual

Mobile WiMAX RAS SPI-2213 System Description/Ed.02

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-2213 performs the subchannelization to

mitigate the interference between cells.

The SPI-2213 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-2213

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-2213 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-2213 and

includes various control information for the MS.

Power Control

The SPI-2213 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-2213 transmits the power correction command to each MS and then makes the MS

power intensity be the level required in the SPI-2213 when the MS transmits the modulated

uplink signal in a specific QAM modulation method.

Hybrid-ARQ (H-ARQ) Operation

H-ARQ is the physical layer retransmission method using the stop-and-wait protocol.

The SPI-2213 carries out the H-ARQ function and raises data throughput by re-transmitting

or combining the frame from the physical layer to minimize the effect attending to the

change of wireless channel environment or the change in the interference signal level.

MIMO

The SPI-2213 provides the MIMO function as follows according to Mobile WiMAX Wave

2 Profile:

y Downlink

− Matrix A (STC)

Transmission ratio of the Matrix A or STC is 1 and equal to that of Single Input

Single Output (SISO). However The Matrix A or the STC reduces the error of the

signal received from the MS by raising the stability of the signal received from the

MS by means of the Tx diversity. This technology is, also, effective in low Signal

to Noise Ratio (SNR) and provides excellent performance even when the MS

moves in high speed.

− Matrix B (SM, vertical encoding)

Matrix B or SM method raises the effectiveness of the frequency by raising the

transmission ratio in proportion to the number of antenna in comparison with SISO.

This technology is effective when the reception SNR is high.