SC-FDMA Transmitter PAPR Reduction via Cyclic Shift Segmentation
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Solution Overview
Problem
In SC-FDMA systems, particularly in the uplink, there is a challenge to reduce the peak-to-average power ratio (PAPR) to enhance power amplifier efficiency and battery lifespan of mobile terminals, while also applying space-time or space-frequency codes without increasing PAPR or complexity of the frequency-domain equalizer.
Innovation Solution
The implementation of a space-time/space-frequency diversity transmitter structure that includes an M-point DFT module, space-time or space-frequency encoding, and sub-carrier mapping, using Alamouti codes to encode symbols from adjacent symbol sets and map them to antennas, maintaining the same sequence and sub-carrier interval, thereby reducing PAPR and enabling effective frequency-domain equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space-time or space-frequency codes are applied in SC-FDMA systems, then spatial diversity gain is achieved, but PAPR increases and the complexity of the frequency-domain equalizer increases
Solution Approach 1:
The patent segments the transmitted signal into multiple layers (first layer and second layer) with different cyclic shifts. The first layer uses a first cyclic shift value while the second layer uses a second cyclic shift value that is an integer multiple of the first. This segmentation allows the receiver to process different layers separately through frequency-domain equalization, reducing overall complexity while achieving spatial diversity.
Solution Approach 2:
The patent introduces a new dimension of differentiation through cyclic shift values. Instead of using complex space-time coding matrices that increase equalizer complexity, the invention uses cyclic shifts in the time domain (which translate to phase rotations in frequency domain) to create distinguishable signal layers. This dimensional approach simplifies the equalization process while maintaining spatial diversity benefits.
2Reliability
If space-time or space-frequency codes are applied in SC-FDMA systems, then spatial diversity gain is achieved, but PAPR increases
Solution Approach 1:
The patent divides the transmitted signal into multiple layers with different cyclic shift values. By segmenting the signal in this manner, the peak power contributions from different layers can be distributed more evenly in time, reducing the overall PAPR compared to conventional space-time coding schemes that concentrate power peaks.
Solution Approach 2:
The patent changes the cyclic shift parameter for different signal layers. The first layer uses cyclic shift value α1 and the second layer uses cyclic shift value α2 (where α2 is an integer multiple of α1). This parameter variation in the time domain translates to controlled phase relationships in the frequency domain, achieving spatial diversity while controlling PAPR through proper parameter selection.
Data Source
AI summary
A method and device for the baseband process of space-time/space-frequency/spatial diversity transmitter in the SC-FDMA system, the device is characterized in that: 1) an encoding means is connected to the output end of the M-point DFT module; 2) a space-time encoding means, for encoding the corresponding symbol of at least two adjacent symbol sets, and outputting at least two data sets; each sub-carrier mapping means maps respectively each data set to the corresponding antenna, so that the mapped data satisfy the requirements: The symbols mapped on each antenna keep the same sequence as the M symbols outputted by the M-point DFT module; the mapped symbols keep the same sub-carrier interval; the M data of each mapped SC-FDMA symbol are the M outputted data of the DFT module, or the inverse of the M outputted data, or the complex conjugate of the M outputted data, or the inverse complex conjugate of the M outputted data. The present invention implements effective space diversity, reduces PAPR, and makes frequency domain equalization feasible.