Waveform Generator Precoding for Multi-User Interference Reduction
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Solution Overview
Problem
Current wireless access technologies, including OFDMA, face limitations in achieving high data throughputs with low block-error rates due to frequency selective fading, multipath propagation, and multi-user interference, which restricts spectral efficiency in high-speed data transmissions to multiple receivers.
Innovation Solution
The implementation of a waveform generator using a pre-coding scheme that combines orthogonal Walsh sequences and pseudorandom noise sequences, allowing for adaptive modulation and frequency diversity, which optimally utilizes the channel and reduces multi-user interference by allocating unique spreading codes and complex pseudorandom noise sequences to each receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDMA is used for high-speed data transmission to multiple receivers, then data throughput is improved, but block-error rate increases due to frequency selective fading and multi-user interference
Solution Approach 1:
The patent segments the transmitted signal into multiple orthogonal frequency subcarriers, with each subcarrier carrying a portion of the data for multiple receivers. This segmentation allows the system to transmit high-speed data while managing frequency selective fading by distributing data across multiple frequency components, thereby improving throughput while controlling error rates through selective mapping and equalization.
Solution Approach 2:
The patent introduces precoding as an intermediary processing step between data generation and transmission. The precoder applies orthogonal Walsh sequences and pseudorandom noise sequences to the data symbols before mapping to subcarriers, which reduces multi-user interference and improves spectral efficiency. This intermediary processing layer enables high throughput transmission while maintaining low block-error rates by pre-conditioning the signal to be more robust against channel impairments.
2Productivity
If frequency subcarriers are assigned to multiple users in OFDMA, then spectral efficiency is improved, but multi-user interference increases
Solution Approach 1:
The patent applies preliminary precoding operations to data symbols before they are mapped to frequency subcarriers. The precoder uses orthogonal Walsh sequences and pseudorandom noise sequences to pre-process the data in a way that reduces interference before transmission. This preliminary action ensures that when multiple users share the same frequency subcarriers, the interference is already mitigated, allowing high spectral efficiency without excessive multi-user interference.
3Productivity
If adaptive modulation is implemented to optimize channel utilization, then data throughput is improved, but system complexity increases
Solution Approach 1:
The patent implements adaptive modulation through dynamic mapping of precoded data symbols to frequency subcarriers based on channel conditions. The system can adaptively adjust modulation schemes and resource allocation to optimize throughput for different receivers. This dynamic adaptation is achieved through the flexible precoding structure that allows different processing for different users and subcarriers, enabling high throughput while managing complexity through structured adaptive algorithms.
Data Source
AI summary
Methods and a system are described for generating a waveform for transmitting data over a channel divided into a plurality of adjacent frequency subcarriers. One method includes receiving a plurality of data bits, each destined for a different receiver of a plurality of receivers. For each received data bit, the method further includes coding the data bit using a unique spreading code of a first set of spreading codes to generate a corresponding group of multiple copies of a data symbol. Additionally, the groups of data symbols, corresponding to the plurality of data bits, are interleaved to generate a sequence of interleaved data symbols, and the sequence of interleaved data symbols is mapped to the plurality of adjacent frequency subcarriers to generate a waveform symbol.