System Description

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Chapter 2 SOL230 Overview
SOL230 System Description v1.0 12
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The LTE uses the Incremental Redundancy (IR)-based H-ARQ method and
regards the Chase Combining (CC) method as a special case of the IR method.
The SmallCell uses the asynchronous method for downlink and the synchronous
method for uplink.
Power Control
When transmitting a specific data rate, a too high a power level may result in
unnecessary interferences and a too low a power level may result in an increased
error rate, causing retransmission or delay. Unlike in other schemes such as
CDMA, the power control is relatively less important in LTE. Nevertheless,
adequate power control can improve performance of the LTE system.
Therefore, the UE should use adequate power levels for data transmission in order
not to interfere with nearby cells. Likewise, the power level for each UE could be
controlled for reducing the inter-cell interference level.
In the LTE downlink, the SmallCell can reduce inter-cell interference by
transmitting data at adequate power levels according to the location of UE and the
MCS, which results in improvement of the entire cell throughput.
MIMO
The SmallCell can support the MIMO by using multiple antennas. For this purpose,
the channel card of the SmallCell has the baseband part to process the MIMO, and
individual RF paths can be processed separately. The SmallCell supports various
types of the MIMO to provide the high-performance data service.
The SmallCell uses multiple antennas to support the MIMO. MIMO has the
following schemes.
Direction
Item
Description
Downlink
Space Frequency Block
Coding (SFBC)
This scheme implements the space-time block coding (STBC) on
frequency instead of on time for increased reliability of the link. The
Alamouti codes are used.
Spatial Multiplexing (SM)
Different data are divided to multiple antenna paths for transmission
so as to increase the peak data rate.
(Each path uses the same time/frequency resource.)
 Single User (SU)-MIMO: The SM between one SmallCell and one
UE to increase peak data rate for one UE.
 Open-loop SM: The SM that works without the Precoding Matrix
Indicator (PMI) feedback of UE when the UE's channel is
unknown or changes fast due to fast movement of the UE.
 Closed-loop SM: The SM that works with the Precoding Matrix
Indicator (PMI) feedback of UE when the UE's channel is known
or changes slow due to slow movement of the UE.
Call Processing Function
Cell Information Transmission
In a serving cell, the SmallCell periodically transmits a Master Information Block
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