OFDM Transmitter Variable-Rate Codeblock Modulation
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Solution Overview
Problem
Current OFDM systems face challenges in efficiently managing large system bandwidths, particularly in frequency-selective radio channels, where the coherence bandwidth is often smaller than the system bandwidth, leading to significant channel variations and reduced effectiveness of existing modulation and coding schemes.
Innovation Solution
The proposed method involves transforming information blocks into smaller codeblocks and applying variable-rate Forward Error Correction and modulation schemes tailored to each codeblock's specific channel frequency response, with differential modulation and coding scheme values encoded within physical resources, allowing for independent adjustment of coding rates and modulation orders to match instantaneous channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single overall Modulation and Coding Scheme (MCS) is assigned to the whole transmission, then the system is simple to implement, but the link adaptation to frequency-selective channels deteriorates
Solution Approach 1:
The patent divides the transmission into multiple codeblocks, each of which can be independently encoded and modulated with different MCS values. This segmentation allows the system to apply different modulation and coding rates to different portions of the data based on their specific channel conditions, thereby improving link adaptation while maintaining manageable complexity through structured processing
2Productivity
If the bandwidth reserved for a single user is much greater than the channel coherence bandwidth, then the spectral efficiency is improved, but the channel exhibits significant fluctuations in frequency along the scheduled resources
Solution Approach 1:
The patent applies different MCS values to different codeblocks based on their specific channel frequency responses. Each codeblock receives tailored modulation and coding parameters that match its local channel conditions, allowing the system to maintain high spectral efficiency across large bandwidths while adapting to frequency-selective fading in each local region
3Stability of the object's composition
If the MCS is fitted to the average channel conditions, then the overall transmission is stable, but the detailed frequency response as reported by mobile users is not fully utilized
Solution Approach 1:
The patent dynamically selects different MCS values for different codeblocks based on their specific channel frequency responses. Rather than using a fixed average MCS for the entire transmission, the system adapts the modulation and coding parameters dynamically for each codeblock, maximizing the utilization of detailed frequency response information while maintaining overall transmission stability through structured adaptation
Data Source
AI summary
The method comprising: applying, by a transmitter, a Forward Error Correction to an information block to be sent to a receiver and modulating said information block prior to its transmission, wherein the transmitter has knowledge of a channel frequency response seen by the receiver and the applying and modulating are performed at a variable-rate, at the transmitter side, by: transforming the information block into a number of smaller packets denoted as codeblocks fitting the input sizes accepted by the Forward Error Correction; selecting, a set of modulation and coding schemes to be independently applied to each of the codeblocks; including, information about the selected set of modulation and coding schemes within part of physical resources devoted to user data by reserving specific subcarriers and OFDM symbols; and mapping, said information within physical resources devoted to user data and not reserved for said selected set of modulation and coding schemes, first in order of ascending OFDM symbols and then of ascending subcarriers.