FA-NOMA Base Station Pre-Processing for Frequency Offset Interference
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Solution Overview
Problem
In frequency-asynchronous non-orthogonal multiple access (FA-NOMA) systems, the intentional frequency offset causes interference that affects channel estimation performance, leading to reduced accuracy in signal transmission and reception.
Innovation Solution
A method is introduced where a base station determines a frequency offset for signals transmitted to user equipment (UEs), calculates interference information, and applies pre-processing factors to prevent interference, allowing UEs to stably receive pilot symbols and enhance channel estimation by compensating for frequency offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intentional frequency offset is applied in FA-NOMA systems to enable frequency-asynchronous operation, then system capacity and spectral efficiency are improved, but interference is generated that degrades channel estimation performance
Solution Approach 1:
The base station performs pre-processing on pilot symbols before transmission, calculating and applying pre-processing factors that compensate for the expected interference caused by frequency offset. This preliminary action ensures that when UEs receive the pilots, the interference has already been mitigated, enabling accurate channel estimation despite the intentional frequency offset used for frequency-asynchronous operation
Solution Approach 2:
Pre-processing factors act as an intermediary mechanism between the frequency offset application and channel estimation. These factors are calculated based on the frequency offset and used to modify pilot symbols before transmission, serving as a mediator that allows the system to maintain both frequency-asynchronous operation and accurate channel estimation
2Productivity
If frequency offset is used to differentiate signals for multiple UEs, then signal separation and system throughput are enhanced, but interference affects signal reception accuracy
Solution Approach 1:
The base station calculates pre-processing factors based on the frequency offset before transmitting pilot symbols to UEs. This preliminary processing ensures that the interference caused by frequency offset is compensated in advance, allowing UEs to accurately receive and process signals even when frequency offset is intentionally applied for signal differentiation and increased system throughput
Solution Approach 2:
The system uses feedback mechanisms where UEs report channel estimation results and the base station adjusts pre-processing factors accordingly. This feedback loop ensures that the pre-processing factors remain effective in compensating for interference, maintaining signal reception accuracy while preserving the throughput benefits of frequency offset
Data Source
AI summary
The disclosure relates to post-4th generation (4G) communication systems, such as 5th generation (5G) or 6th generation (6G), which support a higher data rate than the long term evolution (LTE) or 4G communication systems. A method and an apparatus for transmitting and receiving signals in a frequency-asynchronous non-orthogonal multiple access (FA-NOMA) communication system are provided. The method for transmitting a signal by a base station in an FA-NOMA system includes determining a frequency offset to be applied to a first signal transmitted to a first user equipment (UE) based on a second signal transmitted to a second UE, determining information for interference caused by the frequency offset, determining at least one pre-processing factor for the first UE based on the information for the interference, and transmitting a third signal including at least one first pilot to the first UE using the at least one pre-processing factor. The second signal includes at least one second pilot.