NOMA DMRS Sequence Design for Concurrent Channel Estimation
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Solution Overview
Problem
Current non-orthogonal multiple access (NOMA) wireless communication systems face challenges in efficiently managing reference signal transmissions, leading to bottlenecks in system access due to the use of orthogonal reference signal resources, which limits the number of transmitters that can concurrently transmit during a time period.
Innovation Solution
The proposed solution involves using different sequences for concurrent reference signal transmissions by NOMA transmitters, allowing receivers to decode and perform channel estimation for each transmitter, with sequences formed by concatenating short sequences in the time domain and applying them to frequency resources, and selecting sequences based on available resources to ensure low cross-correlation and error correction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If orthogonal reference signal resources are used for NOMA transmitters, then channel estimation can be performed for each transmitter, but the number of transmitters that can concurrently transmit is limited
Solution Approach 1:
The reference signal sequence is segmented into multiple short sequences in the time domain, where each short sequence can be independently selected from a codebook. This segmentation allows multiple NOMA transmitters to use different short sequences with low cross-correlation, enabling concurrent transmissions while maintaining channel estimation accuracy for each transmitter.
Solution Approach 2:
The patent changes the parameters of reference signal sequences by selecting different root indices and cyclic shifts for different NOMA transmitters. This parameter variation ensures low cross-correlation between sequences from different transmitters, allowing the system to support more concurrent transmitters while maintaining measurement precision through proper sequence design.
2Productivity
If different sequences are used for concurrent reference signal transmissions, then more transmitters can access resources concurrently, but sequence selection and management becomes more complex
Solution Approach 1:
A universal codebook of short sequences is defined that can be used by all NOMA transmitters in the system. Each transmitter selects sequences from this common codebook based on simple criteria (root index and cyclic shift), which simplifies sequence management while enabling multiple concurrent transmissions. The same codebook structure serves all transmitters uniformly.
Solution Approach 2:
The codebook of short sequences is pre-defined and configured in advance, with sequences designed to have low cross-correlation properties. This preliminary preparation eliminates the need for complex real-time sequence generation and selection, reducing system complexity while supporting concurrent transmissions.
3Adaptability or versatility
If short sequences are concatenated to form reference signal sequences, then asynchronous transmissions with bounded timing offset are supported, but sequence generation complexity increases
Solution Approach 1:
The reference signal sequence is divided into multiple short sequences that are concatenated in the time domain. Each short sequence is independently selected from a codebook with low cross-correlation properties, which naturally handles timing offsets between asynchronous transmitters. This segmentation approach supports asynchronous transmissions while keeping individual short sequences simple.
Solution Approach 2:
Different root indices and cyclic shifts are assigned to different short sequences to accommodate asynchronous transmissions. These parameter variations ensure that even with timing offsets, the cross-correlation between sequences from different transmitters remains low, maintaining channel estimation accuracy without complex generation procedures.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that provide for concurrent reference signal transmissions using common resources, such as demodulation reference signal (DMRS) transmissions, from a number of non-orthogonal multiple access (NOMA) transmitters. Different transmitters may use different sequences for reference signal transmissions, which may allow a receiver, such as a wireless base station, to decode the reference signal transmissions for each NOMA transmitter and perform channel estimation for each NOMA transmitter. The reference signal transmissions may be asynchronous with a bounded timing offset or quasi-synchronous, and the reference signal sequence selection may provide for relatively reliable channel estimation and coherent demodulation.