OCC Reference Signal Mapping for LTE Channel Estimation
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Solution Overview
Problem
In LTE-Advanced wireless communication systems, existing demodulation reference signal (DM RS) patterns fail to ensure adequate channel estimation accuracy and reliability, especially when multiple antennas are used, due to limitations in orthogonality and peak power randomization across multiple resource blocks.
Innovation Solution
The method involves allocating multiple physical resource blocks (PRBs) to mobile devices and mapping orthogonal cover code (OCC) reference signal patterns to these blocks according to specific OCC mapping rules, ensuring 2-D orthogonality and peak power randomization, which are transmitted to associated antenna ports, allowing for effective channel estimation and improved throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing DM RS patterns are used for channel estimation, then the system can operate with multiple antennas, but channel estimation accuracy and reliability deteriorate due to limitations in orthogonality and peak power randomization
Solution Approach 1:
The patent extends the OCC mapping from single resource block to multiple resource blocks by introducing a second dimension (resource block index). The OCC pattern is mapped across multiple PRBs using the formula l = 2m + (n mod 2), where m is the time domain index and n is the resource block index. This dimensional extension enables 2-D orthogonality across both time and frequency domains, improving channel estimation reliability while maintaining manageable pattern complexity.
Solution Approach 2:
The patent segments the reference signal pattern allocation by dividing the frequency domain into multiple physical resource blocks and applying different OCC mapping rules to different PRB segments. Each PRB can have its own OCC pattern assignment, allowing independent optimization of orthogonality and peak power randomization in each segment. This segmentation resolves the contradiction by enabling reliable channel estimation through localized pattern control.
2Productivity
If multiple antennas are used to improve throughput, then data transmission capacity increases, but orthogonality and peak power randomization across resource blocks deteriorate
Solution Approach 1:
The patent introduces 2-D orthogonality by extending OCC mapping across both time domain (OFDM symbols) and frequency domain (resource blocks). The mapping rule l = 2m + (n mod 2) creates orthogonal patterns in two dimensions simultaneously, enabling multiple antennas to transmit data with maintained orthogonality. This resolves the contradiction by providing sufficient orthogonal resources for multiple antennas while preserving channel estimation accuracy through structured 2-D pattern allocation.
Solution Approach 2:
The patent changes the OCC mapping parameters by introducing resource block index-dependent mapping rules. Different PRBs use different OCC pattern assignments based on the formula involving (n mod 2), which creates peak power randomization across resource blocks. This parameter change enables multiple antennas to operate simultaneously with improved throughput while maintaining channel estimation accuracy through controlled parameter variation across the frequency domain.
3Reliability
If OCC patterns are mapped to multiple PRBs, then 2-D orthogonality and peak power randomization are achieved, but the complexity of signal mapping increases
Solution Approach 1:
The patent applies local quality by assigning different OCC mapping characteristics to different resource block segments. Each PRB can have locally optimized OCC pattern assignment based on the formula l = 2m + (n mod 2), where the mapping behavior adapts to the specific PRB index. This local optimization achieves 2-D orthogonality and peak power randomization without requiring globally complex mapping rules, as each local segment follows a simple, repeatable pattern based on its position.
Data Source
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AI summary
A method for reference signal pattern allocation for a eNodeB in a wireless communication system is disclosed. The method comprises allocating a plurality of physical resource blocks, hereinafter called PRBs, to at least one mobile device; and mapping a plurality of reference signal patterns to the PRBs according to a mapping rule.