Sub-PRB Subcarrier Selection and DMRS Mapping for Distributed Interference
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Solution Overview
Problem
The challenge in wireless communication networks is the need for a mechanism to select and map subcarriers effectively for sub-Physical Resource Block (PRB) transmissions, particularly for three subcarriers with SC-FDMA Pi/2 BPSK modulation, to enhance spectral efficiency and manage interference in sub-PRB transmissions over PUSCH.
Innovation Solution
The solution involves selecting two adjacent subcarriers out of three allocated subcarriers based on cell classification as even or odd, using a cell identifier, random selection, or a random number generator, and mapping Demodulation Reference Signals (DMRS) in predefined or pseudorandom patterns to optimize interference distribution and channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If three subcarriers are allocated for sub-PRB transmission, then spectral efficiency is improved, but interference management becomes more difficult
Solution Approach 1:
The patent segments the three allocated subcarriers into two adjacent subcarriers for actual transmission. This segmentation allows the system to utilize only the necessary number of subcarriers (two instead of three) while maintaining sub-PRB transmission structure, thereby improving spectral efficiency by avoiding wasted resources and simplifying interference management by reducing the number of active subcarriers that could cause or experience interference
Solution Approach 2:
The patent applies partial action by allocating three subcarriers but using only two of them for transmission. This approach allows the system to maintain the flexibility of having three allocated subcarriers while actually utilizing only the necessary two, thus achieving spectral efficiency improvement without the full interference complexity that would arise from using all three subcarriers
2Productivity
If two adjacent subcarriers are selected from three allocated subcarriers, then resource utilization is optimized, but subcarrier selection complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-determining the selection of two adjacent subcarriers from the three allocated subcarriers before transmission. This pre-selection process, which can be based on fixed patterns, cell ID, or random selection, eliminates the need for complex real-time selection algorithms during transmission, thereby optimizing resource utilization while keeping the selection complexity manageable through advance preparation
Solution Approach 2:
The patent changes the parameter of subcarrier selection from a dynamic, complex real-time process to a predetermined or semi-static selection based on parameters such as cell ID, coverage enhancement mode, or random selection patterns. This parameter change approach optimizes resource utilization by ensuring consistent and efficient subcarrier usage while reducing selection complexity by replacing complex algorithms with simpler parameter-based decisions
3Productivity
If SC-FDMA Pi/2 BPSK modulation is used with two subcarriers, then spectral efficiency is enhanced, but modulation complexity increases
Solution Approach 1:
The patent applies local quality by using SC-FDMA Pi/2 BPSK modulation specifically for the two selected adjacent subcarriers in sub-PRB transmissions, rather than applying complex modulation schemes universally. This localized application of enhanced modulation where it is most needed (in the two active subcarriers) improves spectral efficiency for coverage-enhanced devices while avoiding the need to implement complex modulation schemes across all subcarriers and all device types, thus managing overall system complexity
Data Source
AI summary
Systems and methods for selecting subcarriers to be used for sub-Physical Resource Block (PRB) transmission and, in some embodiments, for mapping Demodulation Reference Signals (DMRS) to resources on the selected subcarriers are disclosed. In some embodiments, a method of operation of a radio node for providing sub-PRB transmission comprises selecting two adjacent subcarriers from a set of three allocated subcarriers that are allocated for a sub-PRB transmission that uses Single Carrier Frequency Division Multiple Access (SC-FDMA) Pi/2 Binary Phase Shift Keying (BPSK) modulation using only two adjacent subcarriers out of the set of three allocated subcarriers with Discrete Fourier Transform (DFT) spread length of 2. In some embodiments, the selection is such that the selected adjacent subcarriers varies, e.g., from one cell to another. In doing so, interference is distributed.