What is precoding matrix indicator in LTE?
The precoding matrix determines how the individual data streams (called layers in LTE) are mapped to the antennas. 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.
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].
What is precoding matrix indicator in 5G?
This is a E-UTRA parameter related to MIMO feedback for some of the E-UTRA transmission modes. The precoding feedback is used for channel dependent codebook based precoding and relies on UEs reporting the desired PMI (Precoding Matrix Indicator).
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.
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.
Why is precoding used?
As described below, precoding uses channel state information at the transmitter to improve performance and increase spectral efficiency. It is used to implement the superposition of multiple beams, including several different data streams of information for spatial multiplexing.
What is the difference between beamforming and precoding?
The word precoding refers more to a software implementation of communication theory, and beamforming refers more to the hardware implementation and the antennas in the system. And precoding generally refers to the transmitter side, while beamforming can be applied to both transmitters and receivers.
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.
How is CQI calculated in LTE?
CQI (Channel Quality Indication) – Instead of expressing the CQI as a received signal quality, the CQI expressed as a data rate that terminal (UE) can support under the actual radio conditions. SINR is used for calculating CQI. In LTE, CQI has only 15 codes. MCS parameter is assigned based on the CQI value.
What is precoding technique?
Precoding is a technique that exploits transmit diversity by weighting the information stream, i.e. the transmitter sends the coded information to the receiver to achieve pre-knowledge of the channel. The receiver is a simple detector, such as a matched filter, and does not have to know the channel state information.
What is precoding and beamforming?
Precoding involves preprocessing of the transmit signal in an RF system. The word precoding refers more to a software implementation of communication theory, and beamforming refers more to the hardware implementation and the antennas in the system.
Is precoding and beamforming same?
One answer is that beamforming and precoding are two words for exactly the same thing, namely to use an antenna array to transmit one or multiple spatially directive signals. In the latter category, different signals are designed for each antenna in the digital domain.
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.
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.
What’s the problem with precoding in LTE?
One thing very tricky about Precoding in LTE is that there are so many variations and is very hard to figure out which one to be applied to which case. Just taking a look at the list of sub titles listed below whenever you have chance.
Can a precoding be mapped to a transmission mode?
Each of those variants of the precoding can be mapped to each of Transmission Mode and the number of Antenna also influence on which type of procoding will be used in a specific situation of Transmission Mode. Also, go through the following table whenever you have chance.
https://www.youtube.com/watch?v=lD_vEClWagQ