LTE Signaling
R&S
®
CMW-KM5xx/-KS5xx
35
User Manual 1173.9628.02 ─ 16
channel) and receiver side (output of radio channel). As a special MIMO technique,
beamforming improves the transmission to users at the cell edges via directional down-
link transmission.
Different gains can be achieved via MIMO depending on the used transmission
scheme. The "LTE signaling" application supports the following transmission schemes:
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Spatial multiplexing
Spatial multiplexing uses at least two transmit antennas and two receive antennas.
Different data streams are transmitted simultaneously on the same resource
blocks. The data streams can belong to one single user (SU-MIMO) or to different
users (MU-MIMO). While SU-MIMO increases the data rate of one user, MU-MIMO
increases the overall capacity.
Spatial multiplexing requires precoding at the transmitter side. Two types of spatial
multiplexing are defined, using different mechanisms for selection of the precoding
matrix. For Closed Loop (CL) spatial multiplexing, the UE estimates the radio chan-
nel, determines the optimum matrix and proposes this precoding matrix by report-
ing a PMI value to the eNodeB. This is not required for Open Loop (OL) spatial
multiplexing, where the eNodeB selects a matrix without UE feedback.
The "LTE signaling" application supports open-loop and closed-loop spatial multi-
plexing for a single user.
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Transmit diversity
Transmit diversity uses several antennas transmitting essentially the same stream
of data. This increases the signal to noise ratio at the receiver side and thus the
robustness of data transmission, especially in fading scenarios.
●
Receive diversity (SIMO)
Receive diversity uses several antennas at the receiver side to receive the same
data stream. Like transmit diversity, this increases the signal to noise ratio.
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Beamforming
Beamforming uses multiple antennas. It controls the direction of the wavefront by
weighting the magnitude and phase of the individual antenna signals. This makes it
possible, to provide better coverage to specific areas along the cell edges.
The UE-specific reference signals and the data transmission use the same
antenna weightings. The signals are transmitted via antenna port 5 for transmis-
sion mode 7, and port 8 for transmission mode 8 with single-layer beamforming.
For dual-layer beamforming, they are transmitted via port 7 and port 8.
For the cell-specific reference signals there is no beamforming. For transmission
mode 7, they are transmitted via port 0. For transmission mode 8, they are trans-
mitted via port 0 and port 1.
For transmission schemes without beamforming, the number of used antennas is
denoted as AxB, indicating A transmit antennas and B receive antennas. The "LTE sig-
naling" application supports the following antenna configurations for the LTE downlink:
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SISO 1x1
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SIMO 1x2 (requires R&S CMW-KS520)
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MIMO 2x2 (requires R&S CMW-KS520)
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MIMO 4x2 (requires R&S CMW-KS520 plus R&S CMW-KS521)
General Description
深圳德标仪器
135-1095-0799
