Quasi-Co-located Reference Signal Reception in LTE Networks
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Solution Overview
Problem
In wireless communication networks, especially in LTE and CoMP scenarios, the introduction of user-specific DMRS complicates channel estimation due to reduced density and variability of reference signals, leading to inadequate channel estimation quality and performance degradation, particularly when dealing with quasi-co-located antenna ports with different statistical properties.
Innovation Solution
The network provides assistance information indicating the timing or frequency offset of a second reference signal relative to a first reference signal, allowing the wireless device to configure its receiver timing or frequency offset for improved reception of the second signal from a quasi-co-located antenna port, reducing the search space and enhancing channel estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If user-specific DMRS are used for channel estimation in CoMP scenarios, then channel estimation can be performed for individual transmission points, but the density of reference signals is reduced leading to inadequate channel estimation quality
Solution Approach 1:
The patent combines channel estimation from multiple reference signal sources (CRS from first antenna port and DMRS from second antenna port) to achieve improved channel estimation quality. The UE receives both CRS and DMRS and uses them together for channel estimation, merging the benefits of dense CRS with the transmission-point-specific DMRS.
Solution Approach 2:
The patent makes the first reference signal (CRS) serve multiple functions: it provides channel estimation for the first antenna port and also serves as a reference for estimating timing and frequency offsets for the second antenna port's DMRS. This multi-functionality allows the sparse DMRS to benefit from the dense CRS without requiring additional reference signals.
2Loss of time
If assistance information is provided to indicate timing or frequency offset of quasi-co-located antenna ports, then the search space for reception is reduced, but additional signaling overhead is introduced
Solution Approach 1:
The patent provides partial assistance information - specifically timing and frequency offset relationships - rather than complete channel state information. This partial information is sufficient to reduce the search space for DMRS reception without requiring excessive signaling overhead, achieving a balance between search space reduction and signaling cost.
Data Source
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AI summary
In one aspect, the teachings herein disclose methods and apparatuses for reference signal reception in a wireless device configured for operation in a wireless communication network. In one embodiment, the network provides assistance information that indicates a received timing or frequency offset of a second reference signal relative to a first reference signal that is transmitted from a first antenna port. The second reference signal is transmitted by the wireless communication network from a second antenna port that is quasi co- located with the first antenna port with respect to timing, frequency and/or delay spread, and the wireless device is configured to use the assistance information to configure its receiver timing and/or frequency offset for reception of the second reference signal.