Coordinated Multipoint Transmission Resource Element Selection
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Solution Overview
Problem
Coordinated multipoint (CoMP) transmission in LTE Advanced faces challenges due to conflicting techniques with LTE Rel. 8, leading to increased overhead and performance degradation, particularly in channel estimation and interference management, especially with different frequency shifts and reference signals.
Innovation Solution
The solution involves controlling resource elements for CoMP transmission by detecting the presence of specific elements like reference signals or control channel symbols, selecting resource elements without these elements for coordinated transmission, and using orthogonal precoded dedicated reference signals for channel estimation and interference cancellation, allowing for coherent precoding while maintaining backward compatibility with LTE Rel. 8.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coherent precoding is applied in CoMP transmission, then performance gains and interference cancellation are improved, but overhead regarding channel estimation, feedback and backhaul traffic increases
Solution Approach 1:
The patent applies universality by using a single common reference signal for channel estimation across multiple terminals and cooperating eNBs, rather than allocating separate reference signals to each terminal-eNB pair. This multi-functional approach allows the same reference signal resource to serve multiple purposes and multiple users, thereby reducing the overall overhead while maintaining the capability for coherent precoding and interference cancellation.
Solution Approach 2:
The patent merges the reference signal resources by having all cooperating eNBs transmit the same common reference signal on the same resource elements. This combining approach consolidates what would otherwise be duplicate or separate reference signal transmissions into a single unified signal that serves all terminals in the cooperation area, directly reducing the overhead associated with channel estimation.
2Productivity
If CoMP techniques are implemented, then spectral efficiency is increased, but backward compatibility with LTE Rel. 8 is compromised
Solution Approach 1:
The patent uses a common reference signal that serves dual purposes: it enables advanced CoMP operations for LTE Advanced terminals while simultaneously maintaining compatibility with LTE Rel. 8 terminals that expect standard reference signal behavior. This universal reference signal approach allows the system to deliver spectral efficiency gains through CoMP without breaking backward compatibility, as the reference signal structure remains consistent with previous releases.
3Measurement precision
If multiple reference signals are transmitted for different terminals, then channel estimation accuracy is improved, but overhead increases and compromises CoMP improvements
Solution Approach 1:
The patent implements a single common reference signal that is universally used by all terminals for channel estimation. This reference signal is transmitted by all cooperating eNBs simultaneously and can be used by multiple terminals to estimate their respective channels to multiple eNBs. This approach maintains measurement precision because each terminal can still estimate the channel from each eNB using the same reference signal, while dramatically reducing overhead compared to allocating separate reference signals to each terminal-eNB pair.
4Productivity
If CoMP transmission is performed on all resource elements, then transmission efficiency is maximized, but resource elements containing reference signals or control channels cause interference and performance degradation
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different resource elements. Specifically, resource elements designated for common reference signals and control channels are excluded from CoMP transmission in certain cooperating eNBs to avoid interference, while other resource elements continue to participate in CoMP transmission. This localized adjustment ensures that critical signaling resources maintain their integrity while maximizing CoMP benefits on data-bearing resources.
Solution Approach 2:
The patent segments the resource elements into different categories: those containing common reference signals, those containing control channel elements, and those available for data transmission. This segmentation allows the system to apply CoMP transmission selectively to appropriate resource elements while excluding those that would cause or suffer from interference, thereby optimizing both transmission efficiency and interference management.
Data Source
AI summary
A method is described, which includes controlling a coordinated transmission between network control elements and terminals on resource elements, detecting whether a resource element includes a specific element, and selecting a resource element for the coordinated transmission, when it is detected that the resource element does not include a specific element. The application also describes some further aspects to improve a coordinated transmission such as a coordinated multipoint transmission is improved.