DFT-Spread PUCCH Interlace Multiplexing Under PSD Limits
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently multiplexing multiple users in frequency spectra due to power spectral density (PSD) requirements, which limit the number of users that can be frequency-multiplexed, and existing methods for user multiplexing can lead to interference and complex receiver processing.
Innovation Solution
The use of discrete Fourier transform (DFT) precoded frequency interlaces with orthogonal cover codes (OCCs) for user multiplexing, where different users are assigned different block-spreading codes, allowing them to transmit on the same frequency interlace without interference, and applying DFT spreading to reduce peak-to-average power ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If frequency occupancy is spread over a wider bandwidth to meet PSD requirements, then transmit power can be increased, but the number of users that can be frequency-multiplexed decreases
Solution Approach 1:
The frequency spectrum is divided into multiple frequency interlaces, where each interlace consists of non-contiguous resource blocks. Users are assigned to specific interlaces, allowing the system to maintain wide frequency occupancy for power efficiency while enabling multiple users to share the overall spectrum through interlace-based segmentation.
Solution Approach 2:
The patent introduces a new dimension for user multiplexing by applying Discrete Fourier Transform (DFT) precoding across frequency interlaces. This transforms the traditional frequency-domain resource allocation into a DFT-spread domain, where users are separated by their unique DFT precoding matrices rather than just by frequency resources, thereby increasing multiplexing capacity without sacrificing power efficiency.
2Quantity of substance
If traditional frequency-multiplexing methods are used to increase user capacity, then more users can be supported, but interference between users increases and receiver processing becomes complex
Solution Approach 1:
DFT precoding is applied at the transmitter before resource allocation. This preliminary transformation ensures that users' signals are orthogonalized in the DFT domain, eliminating the need for complex interference cancellation or sophisticated receiver processing. The orthogonality is built-in beforehand, simplifying the receiver structure while supporting multiple users.
3Ease of manufacture
If contiguous frequency resources are allocated to users, then simple resource allocation is achieved, but peak-to-average power ratio increases and power efficiency decreases
Solution Approach 1:
Frequency resources are segmented into non-contiguous resource blocks within each interlace. This segmentation allows users to transmit over distributed frequency resources rather than contiguous blocks, reducing peak-to-average power ratio and improving power efficiency while maintaining relatively simple resource allocation through interlace-based assignment.
Data Source
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AI summary
Wireless communications systems and methods related user multiplexing with discrete Fourier transform (DFT) precoded frequency interlaces are provided. A first wireless communication device identifies a first block-spreading code from a set of block-spreading codes associated with user multiplexing. The first wireless communication device communicates, with a second wireless communication device using a frequency interlace in a frequency spectrum, a first communication signal including a first block of information symbols spread across a set of resource blocks (RBs) within the frequency interlace based on the first block-spreading code. The first communication signal is generated by block-spreading the first block of information symbols based on the first block-spreading code to produce a first block of spread information symbols, performing a DFT on the first block of spread information symbols, and mapping the first block of spread information symbols to the set of RBs.