MU PPDU Edge Subcarrier Nulling for Aliasing Noise Reduction
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Solution Overview
Problem
In wireless communication systems, particularly those adhering to the IEEE 802.11be standard, the challenge lies in preventing degradation of communication efficiency due to aliasing noise when terminals receive signals with channel widths larger than their operating channel width, leading to increased frame error rates and reduced Carrier Noise Ratio (CNR) caused by insufficient filtering and down-sampling.
Innovation Solution
The system employs a communication method where, when transmitting a downlink Multi-User Physical Layer Protocol Data Unit (MU PPDU), the subcarrier at the end of the frequency domain is not modulated with demodulation target data, and instead, a different subcarrier is modulated, allowing for efficient data transmission by avoiding the use of subcarriers at the ends of the operating channel, thereby reducing aliasing noise and improving data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a terminal receives a signal with a channel width larger than its operating channel width and performs filtering processing to extract the operating channel signal, then the circuit scale and power consumption are reduced, but aliasing noise occurs when signals outside the operating channel are closer than 2 MHz interval, degrading the Carrier Noise Ratio (CNR)
Solution Approach 1:
The transmitting terminal performs preliminary action by not modulating data on subcarriers at the frequency edges before transmission. This prevents strong signals from being transmitted in regions that would cause aliasing noise during the receiving terminal's filtering and down-sampling process, thereby maintaining good CNR while allowing the receiving terminal to operate with lower power consumption
Solution Approach 2:
The transmitting terminal applies preliminary anti-action by deliberately leaving subcarrier regions at the frequency edges unused for data transmission. This creates a protective measure against the harmful aliasing noise that would otherwise occur during receiving terminal's filtering process, preventing the degradation of CNR before the receiving terminal even performs filtering
2Productivity
If the interval between signals assigned to different terminals in OFDMA-based downlink multi-user transmission is smaller than 2 MHz, then frequency usage efficiency is improved, but aliasing noise occurs during filtering processing, increasing frame error rate
Solution Approach 1:
The transmitting terminal performs preliminary action by avoiding data modulation on edge subcarriers before transmission. This allows the system to achieve high frequency usage efficiency with small intervals between allocated signals, while the receiving terminal can still perform filtering and down-sampling without suffering from aliasing noise that would increase frame error rate
Solution Approach 2:
The transmitting terminal applies local quality by treating edge subcarrier regions differently from central subcarrier regions. Edge subcarriers are deliberately left unused to prevent aliasing noise, while central subcarriers carry data at high density, achieving both high frequency usage efficiency and low frame error rate
Data Source
AI summary
A communication system including a first communication apparatus and a second communication apparatus, wherein the first communication apparatus receive from the second communication apparatus, information indicating a bandwidth to be used by the second communication apparatus to communicate with the first communication apparatus, transmitting, in transmitting a downlink Multi-User Physical Layer Protocol Data Unit (MU PPDU) to a plurality of communication apparatuses including the second communication apparatus with a predetermined bandwidth in a case where the bandwidth to be used by the second communication apparatus indicated by the received information is smaller than the predetermined bandwidth, an MU PPDU in which a subcarrier at the end of a frequency domain is not modulated with demodulation target data but a subcarrier different from the subcarrier at the end is modulated with demodulation target data, from among subcarriers that are to store data to be transmitted to the second communication apparatus.