Non-Contiguous Reference Signal Transmission for Flexible Scheduling
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Solution Overview
Problem
Existing wireless communication systems face limitations in transmitting reference signals on contiguous subcarriers, which restrict resource allocation and scheduling, and result in higher peak-to-average-power ratio, limiting output power and efficiency.
Innovation Solution
The system allows User Equipments (UEs) to transmit demodulation reference signals on multiple non-contiguous clusters of resources using code division multiplexing (CDM) or frequency division multiplexing (FDM), with options to generate a single reference signal sequence matching the total cluster length or separate sequences for each cluster, enabling simultaneous transmission by multiple UEs and improved channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reference signals are transmitted on contiguous subcarriers, then channel estimation can be performed, but resource allocation flexibility is limited and peak-to-average-power ratio increases
Solution Approach 1:
The patent divides the continuous frequency spectrum into multiple non-contiguous clusters of subcarriers. Each cluster can be independently allocated to different UEs, enabling flexible resource allocation while maintaining reference signal functionality. This segmentation resolves the contradiction by allowing adaptive resource allocation without requiring contiguous subcarrier blocks.
Solution Approach 2:
The patent introduces a new dimension of resource allocation by allowing reference signals to be transmitted on non-contiguous clusters across multiple frequency domains. This dimensional expansion enables flexible scheduling while distributing the peak-to-average-power ratio across multiple separated frequency locations, resolving both aspects of the technical contradiction.
2Productivity
If multiple UEs transmit reference signals simultaneously on the same clusters, then scheduling flexibility improves, but inter-cell pilot interference increases
Solution Approach 1:
The patent assigns different reference signal sequences to different UEs based on their specific cluster allocations. Each UE uses a unique sequence (e.g., Zadoff-Chu sequences with different roots or cyclic shifts) tailored to its allocated clusters, enabling simultaneous transmission without mutual interference. This local differentiation resolves the contradiction by allowing flexible scheduling while maintaining signal distinguishability.
Solution Approach 2:
The patent employs copy-based differentiation where multiple UEs use variations of reference signal sequences (different cyclic shifts, different root indices) that are locally unique to each UE's cluster allocation. This copying approach enables simultaneous transmissions to be distinguished at the receiver, resolving the interference issue while maintaining scheduling flexibility.
3Measurement precision
If reference signals are transmitted in multiple symbol periods, then channel estimation accuracy improves in high Doppler scenarios, but transmission time increases
Solution Approach 1:
The patent transmits reference signals across multiple symbol periods continuously, ensuring that channel estimation can track time-varying channel conditions in high Doppler scenarios. By maintaining continuous reference signal presence across multiple time slots, the system achieves accurate channel estimation without gaps, resolving the contradiction between precision and time loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces inter-cell pilot interference, enhances scheduling flexibility, and improves channel estimation and data demodulation performance, particularly in high Doppler scenarios, by allowing UEs to transmit reference signals in multiple symbol periods and using precoding with multiple antennas.
Implementation Method 1
The UE may generate the reference signal with code division multiplexing (CDM) or frequency division multiplexing (FDM)
Implementation Method 2
The UE may generate the reference signal with code division multiplexing (CDM) or frequency division multiplexing (FDM)
Implementation Method 3
A base station may receive the reference signal from the UE and may process the received reference signal to derive a channel estimate for the UE
Implementation Method 4
The UE may generate the reference signal with precoding and may transmit the reference signal from multiple antennas
Data Source
AI summary
A reference signal is transmitted on multiple non-contiguous clusters of resources. A user equipment (UE) may be scheduled for data transmission on the multiple non-contiguous clusters, and each cluster may cover a set of contiguous subcarriers. The UE may generate the reference signal based on at least one reference signal (RS) sequence using code division multiplexing (CDM) or frequency division multiplexing (FDM). In a design, the UE generates the reference signal with CDM based on a single RS sequence having a length matching the total length of the multiple non-contiguous clusters. In another design, the UE generates the reference signal with CDM based on one RS sequence for each cluster. In yet another design, the UE generates the reference signal with FDM and transmits the reference signal on a subset of all subcarriers for the multiple non-contiguous clusters.