Rake Receiver Parallel DFE for CCK Signal ISI and ICI
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Solution Overview
Problem
Wireless local area networks (WLANs) using the IEEE 802.11.B/G standard face significant challenges with energy loss and interference due to multi-path fading, leading to transmission errors and system performance degradation, as conventional rake receivers struggle to effectively eliminate inter-symbol interference (ISI) and inter-chip interference (ICI) in CCK signals.
Innovation Solution
A rake receiver is designed with a decision feedback equalizer (DFE) structure connected in parallel per chip to detect and eliminate inter-chip interference (ICI) components, in addition to the existing DFE structure per symbol to address ISI, utilizing a channel matched filter, correlators, and detectors to process and compensate for distortion in CCK signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional rake receiver is used to compensate for energy loss in multi-path fading channels, then energy loss compensation is achieved, but inter-symbol interference (ISI) and inter-chip interference (ICI) cannot be effectively eliminated
Solution Approach 1:
The interference cancellation is divided into two separate stages: ISI cancellation for symbols and ICI cancellation for chips. The receiver processes symbols first to cancel ISI, then extracts chips to cancel ICI. This segmentation allows each stage to focus on a specific type of interference without being overwhelmed by both simultaneously, thereby improving overall reliability while maintaining energy loss compensation.
Solution Approach 2:
The receiver performs preliminary ISI cancellation before chip-level processing. By first removing inter-symbol interference from the received signal and then extracting chip sequences, the system prepares the signal in advance for more effective ICI cancellation. This preliminary action reduces the complexity of subsequent processing and improves the accuracy of interference elimination.
2Object-affected harmful factors
If a DFE structure per symbol is used to eliminate ISI, then inter-symbol interference is reduced, but inter-chip interference (ICI) remains unaddressed
Solution Approach 1:
The chip extraction unit acts as an intermediary between the symbol-level ISI cancellation stage and the chip-level ICI cancellation stage. It takes the ISI-cancelled symbol signal, extracts individual chip sequences, and prepares them for dedicated ICI cancellation processing. This intermediary step bridges the two interference types, allowing systematic elimination of both ISI and ICI without direct conflict between the two cancellation processes.
3Productivity
If signal processing is performed in a multi-path fading channel environment, then communication is enabled, but multi-path fading causes signal distortion and interference
Solution Approach 1:
The receiver employs decision feedback equalization at both symbol and chip levels. The detected symbols and chips are fed back to generate estimates of ISI and ICI components, which are then subtracted from the received signal. This feedback mechanism continuously corrects signal distortion caused by multi-path fading, maintaining signal integrity while enabling reliable communication in challenging channel conditions.
Data Source
AI summary
Provided is a method of compensating for energy loss and eliminating inter-symbol interference (ISI) and inter-chip interference (ISI) in wireless signals, and a rake receiver for wireless LANs adopting the same. The rake receiver compensates for energy loss of a CCK signal transmitted in a multi-path wireless channel environment and eliminates ISI and ICI from the received CCK signal because a DFE structure per chip used for calculating ICI components, is connected in parallel with a DFE structure per symbol, thus eliminating ISI and ICI components.