Modified Cyclic Prefix for Virtual TDM in SC-FDMA
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Solution Overview
Problem
In wireless communication systems, particularly in OFDMA and SC-FDMA, multiplexing reference signals (RS) and data within a single symbol while maintaining low Peak-to-Average Power Ratio (PAPR is challenging, especially for uplink transmissions in mobile devices, where high PAPR can lead to energy inefficiency.
Innovation Solution
The solution involves using a modified cyclic prefix (CP) that is copied from the reference signal (RS) rather than the data, enabling virtual Time Division Multiplexing (TDM) before discrete Fourier transform (DFT) spreading, which allows for RS and data multiplexing within a single SC-FDMA symbol, thereby reducing PAPR and preventing inter-symbol interference (ISI).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency division multiplexing is used to multiplex reference signals and data in a single symbol, then multiplexing is achieved, but peak-to-average power ratio becomes high
Solution Approach 1:
The patent segments the time domain by inserting a cyclic prefix that separates the reference signal portion from the data portion, enabling virtual time division multiplexing before DFT spreading. This segmentation allows independent power control for each portion while maintaining single-symbol transmission, resolving the contradiction between multiplexing capability and PAPR control.
Solution Approach 2:
The patent applies preliminary action by performing virtual TDM multiplexing of reference signals and data before the DFT spreading operation. The cyclic prefix is inserted and configured in advance to enable this pre-multiplexing, which prevents high PAPR from occurring during the subsequent DFT processing while maintaining efficient single-symbol transmission.
2Reliability
If conventional cyclic prefix is used copied from data, then inter-symbol interference is prevented, but reference signal multiplexing with data in single symbol is not achieved
Solution Approach 1:
The patent inverts the conventional approach by copying the cyclic prefix from the reference signal portion rather than from the data portion. This inversion enables the cyclic prefix to serve the reference signal's timing requirements while allowing virtual TDM multiplexing of both reference signals and data within a single symbol, achieving both ISI prevention and enhanced multiplexing efficiency.
Solution Approach 2:
The patent makes the cyclic prefix multi-functional by configuring it based on the reference signal properties to simultaneously protect both the reference signal and data portions from inter-symbol interference. This universal cyclic prefix configuration enables single-symbol transmission with virtual TDM multiplexing, improving productivity while maintaining reliability.
3Ease of operation
If reference signals and data are transmitted separately, then transmission simplicity is maintained, but symbol duration increases and spectral efficiency decreases
Solution Approach 1:
The patent merges reference signal transmission and data transmission into a single symbol by using virtual time division multiplexing before DFT spreading. The cyclic prefix insertion and configuration enable both signals to share the same time-frequency resource simultaneously, reducing symbol duration and improving spectral efficiency while maintaining transmission simplicity through a unified processing approach.
Data Source
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AI summary
Aspects of the disclosure relate to methods and apparatus of time-domain multiplexing (TDM) for reference signals (RS) and data using a modified cyclic prefix. A reference signal (RS) and data are multiplexed either in a single symbol or in two time consecutive symbols that respectively including the RS and data. The cyclic prefix (CP) is added to the single symbol using a portion of the RS or to a first symbol of the two time consecutive symbols using a portion of the RS. The CP may be copied from the RS or the end of the symbol, but not the data, in a manner that affords a virtual Time Division Multiplexing (TDM) of the RS and data before discrete Fourier transform (DFT) spreading is performed in a transceiver to provide lower peak to average power ratios and no Inter-symbol interference.