What is precoding matrix of MIMO in LTE?
Precoding is based on transmit beamforming concepts with the pro- vision of allowing multiple beams to be simultaneously transmitted in the MIMO system. The LTE specification defines a set of complex weighting matrices for combining the layers before transmission using up to 4 × 4 antenna configurations [4].
Why precoding is used in LTE?
according to the limited feedback precoding. To reduce this interference, higher accuracy in the channel information feedback is required, which in turn reduces the throughput in the uplink.
What is precoding codebook in LTE?
The codebook based precoding is a promising technology adopted by Long Term Evolution (LTE), which fixes a common codebook comprising a set of vectors and matrices at both the transmitter and the receiver.
What is PMI and RI?
PMI stands for Pre-coding Matrix Indicator, and RI is Rank Indicator. These three values are computed on the fly in LTE systems and used to try to optimize resource allocation among the various user end devices (UEs) that are requesting service.
What is precoding matrix?
Precoding starts with channel sounding that involves sending a coded message (called a sounding packet or a pilot signal) to the receiver. Each of the users send back their individual CSIs to the transmitter. The users’ CSIs are used to set the precoding (spatial mapping) matrix for subsequent data transmission.
What is the difference between beamforming and precoding?
A third answer is that beamforming refers to a single-user transmission with one data stream, such that the transmitted signal consists of one main-lobe and some undesired side-lobes. In contrast, precoding refers to the superposition of multiple beams for spatial multiplexing of several data streams.
What is Ri in LTE?
LTE RI stands for Rank Indicator. RIs are applicable for open loop transmission and closed loop transmission modes. These modes use more than a single layer between layer mapping and precoding modules. • Transmission mode-3 indicates open loop spatial multiplexing.
What is PMI in 5G?
PMI stands for Pre-coding Matrix Indicator. And RI is Rank Indicator. These three values are computed on the fly in LTE/5G NR systems and used to try to optimize resource allocation among the various user end devices (UEs) that are requesting service.
What does The precoding matrix indicator ( PMI ) do?
The Precoding Matrix Indicator (PMI) allows the UE to report its preferred precoding for downlink transmissions on the PDSCH. The PMI is applicable to closed loop and semi-open loop transmission schemes.
What is the precoding matrix indicator in 3GPP evolved?
36.213 3GPP Evolved Universal Terrestrial Radio Access (E-UTRA) Physical layer procedures Release 16 TS For transmission modes 4, 5 and 6, precoding feedback is used for channel dependent codebook based precoding and relies on UEs reporting precoding matrix indicator (PMI).
When to use PMI in LTE precoding process?
The LTE UE use PMI information to signal preferred set of weights to be applied during the precoding process. UE does this in order to maximize the downlink S/N ratio. Table-1 mentions complex weights. Based on following configurations one out of 4 is used by LTE UE. Table-2 mentions complex weights for following configurations.
Which is precoding matrix should be used for downlink transmission?
PMI (Precoding Matrix Indicator), UE indicates to eNB , which precoding matrix should be used for downlink transmission which is determined by RI. RI (Rank Indicator), UE indicates to eNB, the number of layers that should be used for downlink transmission to the UE.