Modulation

RFmx Waveform Creator 19.1 Help

Edition Date: October 2019

Part Number: 377064G-01

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Long Term Evolution (LTE) uses Adaptive Modulation and Coding (AMC) to improve data throughput. Based on the channel quality for each user, this technique varies in the downlink modulation coding scheme.

When the link quality is good, the LTE system uses a higher order modulation scheme, which results in more system capacity. On the other hand, when link quality is poor due to problems such as signal fading, the LTE system can change to a lower modulation scheme to maintain reliability and minimize error.

The allowed modulation schemes for DL and UL are shown in the following tables.

Physical channels  Modulation scheme 
PBCH, PCFICH, PDCCH  QPSK 
PDSCH  QPSK, QAM16, QAM64, QAM256, QAM1024 
PHICH  BPSK 
Physical signal  Modulation scheme 
Reference  Orthogonal sequence modulated by binary random sequence 
Primary synchronization  Cycle of three Zadoff-Chu sequence 
Secondary synchronization  Two 31-bit BPSK M-sequence 
Table 1-1 Downlink channels and signals

Physical channels  Modulation scheme 
PUCCH  Based on Zadoff-Chu 
PUSCH  QPSK, QAM16, QAM64, QAM256, QAM1024 
NPUSCH Format 1  BPSK, QPSK 
NPUSCH Format 2  BPSK 
PRACH1  Based on the uth root Zadoff-Chu 
Physical signal  Modulation scheme 
Demodulation reference for PUCCH, PUSCH  Based on Zadoff-Chu 
SRS  Based on Zadoff-Chu 
Table 1-2 Uplink channels and signals

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