Samsung Mobile WiMAX Outdoor RAS SPI-2331 System Description page 21

CHAPTER 2. Overview of Outdoor SPI-2331
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 outdoor SPI-2331 performs the
subchannelization to mitigate the interference between cells.
The outdoor SPI-2331 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 outdoor SPI-2331 transmits the column of the QAM symbol structure to
the MS via the sub-carriers pertained to each subchannel.
DL/UL MAP Construction
The outdoor SPI-2331 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
outdoor SPI-2331 and includes various control information for the MS.
Power Control
The outdoor SPI-2331 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 outdoor SPI-2331 transmits the power correction command to each MS and then
makes the MS power intensity be the level required in the outdoor SPI-2331 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 outdoor SPI-2331 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 outdoor SPI-2331 provides the MIMO function as follows according to Mobile
WiMAX Wave 2 Profile:
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 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.
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