NOMA Techniques for Narrowband IoT Signal Interference
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Solution Overview
Problem
Current multiple access techniques for wireless communication systems, such as LTE and NR, are limited in supporting a large number of users simultaneously on a set of system resources, particularly in narrowband Internet of Things (NB-IoT) and machine type communication (MTC) scenarios, due to mutual interference and limited scheduling flexibility.
Innovation Solution
The implementation of non-orthogonal multiple access (NOMA) techniques, specifically resource spread multiple access (RSMA), which involves spreading and scrambling data streams using a spreading factor and a non-linear scrambling sequence, allowing for repeated transmissions of signals with cyclically shifted pilot signals to enhance communication efficiency and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional multiple access techniques (TDMA, FDMA, OFDMA) are used, then system resources are shared efficiently, but the number of users that can simultaneously communicate on a set of system resources is limited
Solution Approach 1:
The patent merges multiple access techniques by combining resource spread multiple access (RSMA) with non-orthogonal multiple access (NOMA). RSMA allows multiple users to share the same time-frequency resources by spreading codes, while NOMA enables simultaneous transmission without orthogonal separation. This combination increases the number of users that can communicate simultaneously on a set of system resources while managing mutual interference through code division and power domain multiplexing.
Solution Approach 2:
The patent changes the access parameters from orthogonal to non-orthogonal. Traditional techniques use orthogonal codes and time slots to avoid interference, while this patent employs non-orthogonal spreading codes and power levels. By changing from orthogonal to non-orthogonal parameters, the system can support more users simultaneously on the same resources, with interference managed through advanced decoding techniques and power domain separation.
2Adaptability or versatility
If orthogonal multiple access techniques are used, then scheduling is straightforward, but scheduling flexibility and adaptability to varying traffic patterns is limited
Solution Approach 1:
The patent introduces dynamic scheduling capabilities through the RSMA framework. The system can dynamically allocate spreading codes and power levels to different users based on real-time traffic conditions and channel state information. This dynamic allocation enables flexible adaptation to varying traffic patterns while maintaining manageable scheduling complexity through automated code selection and power control mechanisms.
Solution Approach 2:
The patent employs preliminary code allocation and configuration before actual data transmission. Spreading codes are pre-assigned to users, and the scheduling decisions are made in advance based on predicted traffic patterns. This preliminary action reduces the complexity of real-time scheduling while maintaining high adaptability to changing conditions.
3Reliability
If signal repetition is applied to enhance reliability, then transmission robustness improves, but the transmission time and spectral efficiency are reduced
Solution Approach 1:
The patent maintains continuity of useful action by overlapping signal repetitions with other users' transmissions. Through RSMA, multiple users can simultaneously transmit repeated signals on different spreading codes within the same time resources. This allows the system to achieve transmission robustness through repetition while maintaining high spectral efficiency, as the repetition process does not create idle time but rather concurrent productive transmission.
Solution Approach 2:
The patent resolves the time-efficiency contradiction by moving to another dimension - the code domain. Instead of repeating signals sequentially in time, the system uses different spreading codes to multiplex repeated signals from multiple users simultaneously. This dimensional transition from time to code space allows parallel repetition processing, maintaining robustness while improving spectral efficiency.
Data Source
AI summary
Repeated signals for narrowband internet of things (NB-IoT) and machine type communication (MTC) may be transmitted using various non-orthogonal multiple access (NOMA) techniques. A user equipment (UE) may generate a set of modulated symbols associated with the data stream, spread the set of symbols using a spreading factor, and may subsequently apply a scrambling sequence to the set of symbols. The spread and scrambled symbols may be transmitted as a time domain waveform that includes one or more repetitions of a transmission time interval (TTI) or a resource unit (RU). Additionally, or alternatively, the UE may perform rate matching and apply the scrambling sequence to achieve the repetitions of the TTIs or RUs. In some cases, the UE may transmit a set of orthogonal pilot signals with the repetitions of the TTIs or RUs, where the pilot signals include different cyclically shifted versions of a base pilot signal.