DMRS Sequences for CoMP Orthogonality
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Solution Overview
Problem
Current wireless communication systems, particularly in LTE-A, face challenges in achieving inter-cell orthogonality for uplink CoMP (Coordinated Multi-point) transmission, which is essential for improving channel estimate quality and reducing interference, but existing DMRS (Demodulation Reference Signal) solutions are limited by scheduling restrictions and poor cross-correlation properties.
Innovation Solution
The implementation of new DMRS sequences with lengths equal to or exceeding the system bandwidth, using Zadoff-Chu sequences and their cyclic shifts, allows for orthogonal sequences to be assigned to CoMP clusters, ensuring orthogonality among UEs within a cluster regardless of their PRB allocations, and providing improved cross-correlation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing DMRS solutions are used for uplink CoMP transmission, then channel estimate quality can be improved, but scheduling flexibility is restricted and cross-correlation properties are poor
Solution Approach 1:
The patent changes the fundamental parameters of the DMRS sequence by using Zadoff-Chu sequences with lengths equal to or exceeding the system bandwidth, and by applying cyclic shifts to these sequences. This parameter change enables orthogonal sequences to be assigned to different CoMP clusters, thereby improving channel estimate quality while simultaneously enabling flexible scheduling without restrictions, as the orthogonal properties maintain good cross-correlation regardless of PRB allocations.
2Measurement precision
If existing DMRS solutions are used for uplink CoMP transmission, then channel estimate quality can be improved, but cross-correlation properties deteriorate
Solution Approach 1:
The patent employs Zadoff-Chu sequences which inherently possess excellent autocorrelation and cross-correlation properties. By using sequences with lengths equal to or exceeding the system bandwidth and applying cyclic shifts, the patent maintains good cross-correlation properties while achieving improved channel estimate quality through orthogonal sequence assignment to CoMP clusters.
3Measurement precision
If orthogonal sequences are assigned to CoMP clusters, then inter-cell orthogonality is achieved, but sequence length requirements increase
Solution Approach 1:
The patent uses Zadoff-Chu sequences with lengths equal to or exceeding the system bandwidth, which provide the necessary orthogonality for inter-cell CoMP transmission. The sequences are designed to span the entire system bandwidth, ensuring that orthogonal sequences can be assigned to different CoMP clusters while maintaining the required sequence length for proper orthogonality across the full frequency range.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
In one exemplary embodiment of the invention, a method includes: receiving, by a mobile device, an indication of a base sequence and an indication of a cyclic shift from a base station; and obtaining, by the mobile device, a mobile device-specific demodulation reference signal sequence by calculating a mobile-device specific sequence and selecting a portion of the calculated mobile- device specific sequence to use as the mobile device-specific demodulation reference signal sequence, where calculating the mobile-device specific sequence includes applying the cyclic shift indicated by the received indication of a cyclic shift to the base sequence indicated by the received indication of a base sequence, where the selected portion of the calculated mobile-device specific sequence corresponds to a mobile-device specific physical resource block allocation.