Method and apparatus for defining resource elements for the provision of channel state information reference signals

Abstract

Methods, apparatus and computer program products define additional resource elements of a physical resource block (PRB) to be allocated for the provision of channel state information reference signals in a manner that does not create issues relating to backwards compatibility for legacy mobile terminals. A method may include receiving a definition of a plurality of resource elements of a PRB to be allocated for provision of channel state information reference signals. At least some of the plurality of resource elements of the PRB that are allocated for the provision of channel state information reference signals correspond in position to resource elements of the PRB that are interpreted by a different type of mobile terminal to be muted. The method also causes, channel state information reference signals to be received via the plurality of resource elements of the PRB that are allocated for the provision of channel state information reference signals.

Description

TECHNOLOGICAL FIELD[0001]Embodiments of the present invention relate generally to communications technology and, more particularly, to methods and apparatus for defining a plurality of resource elements for the provision of channel state information reference signalsBACKGROUND[0002]Some wireless communications systems utilize multiple-input and multiple-output (MIMO) technology. MIMO technology involves the use of multiple antennas for both the transmitter and a receiver so as to improve communication performance, such as by offering significant increases in data throughput and link range without additional bandwidth or transmit power as a result of its higher spectral efficiency as measured, for example, in bits per second per hertz of bandwidth, and link reliability or diversity. For example, systems that operate in accordance with Releases 8, 9 and 10 of the Long Term Evolution (LTE) specification support MIMO, that is, MIMO transmissions from a transmit point (which can be also ...

AI Technical Summary

Benefits of technology

Enhances channel state information and interference estimation accuracy without disrupting legacy mobile terminal operations, supporting more precise CQI and rank feedback for improved transmission schemes and reduced throughput loss.

Problems solved by technology

In this regard, the density of one resource element for CSI-RS per PRB per port may be insufficient for interference covariance estimation or, at least, may lead to an undesirably large error in the estimation of the interference covariance which, in turn, may cause erroneous CQI and erroneous rank feedback which may lead to a poor selection of transmission scheme, both modulation and coding scheme (MCS) and rank, by the base station.

These poor selections may, in turn, lead to throughput loss at the system level.

This scenario may cause less accurate CQI and rank estimation in typical fractional load scenarios than is desired.

However, the current CSI-RS density is too low to provide the desired channel state information / interference accuracy.

Furthermore, there is an ongoing effort to support heterogeneous networks which exhibit difficult interference characteristics.

Thus, there is a tendency in 3rd Generation Partnership Project (3GPP) networks to reduce CRS usage, as CRS may be problematic from the inter-cell interference perspective.

As such, it cannot be assumed that the mobile terminal will always have sufficient CRS to perform interference estimation in the future.

Notwithstanding the potential for increased utilization of the CSI-RS, efforts to simply increase the density of the reference signals, such as the CSI-RS, within a PRB in order to support the additional feedback that is desired creates backwards compatibility issues with legacy mobile terminals, such as those mobile terminals that operate in accordance with prior releases of a respective specification.

In this regard, since these legacy mobile terminals would not be aware of the additional reference signal transmissions, such as the additional CSI-RS, the additional reference signal transmissions may disadvantageously interfere with data transmissions of the legacy mobile terminals.

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