OFDM Receiver Sleep-Mode ADC Switching for Fast Wake-Up
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Solution Overview
Problem
In Orthogonal Frequency Division Multiplexing (OFDM) systems, receivers face delays in establishing or re-establishing control parameters, especially when in sleep mode, due to the time required for determining time offset, carrier frequency offset, and channel profile estimates, and are not notified in advance of wake-up times, leading to inefficiencies in power consumption and wake-up times.
Innovation Solution
Implementing an auxiliary reduced power ADC and processing chain during sleep periods to maintain up-to-date control parameters, allowing the main ADC and processing chain to be turned off, and switching to them only when necessary for data reception, using a multiplexer and controller to manage the transition between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the receiver enters sleep mode to save power, then power consumption is reduced, but the receiver must re-acquire control parameters after every sleep cycle which increases wake-up time and delays data reception
Solution Approach 1:
The receiver performs preliminary acquisition of control parameters (time offset, carrier frequency offset, channel profile) before entering sleep mode. This preliminary action allows the receiver to maintain these parameters in memory during sleep, eliminating the need to re-acquire them upon waking, thus reducing wake-up time while maintaining power savings
Solution Approach 2:
The invention extracts the control parameter acquisition process from the main data reception flow. By separating the parameter acquisition function and performing it independently before sleep mode, the receiver can enter low-power state without compromising the ability to quickly resume data reception, effectively decoupling power consumption from wake-up time penalties
2Loss of time
If the receiver acquires all control parameters before sleep mode, then wake-up time is reduced, but the complexity of managing parameter updates and synchronization increases
Solution Approach 1:
The receiver applies local quality by acquiring and maintaining only the specific control parameters necessary for quick wake-up (time offset, carrier frequency offset, channel profile) rather than all possible parameters. This selective approach reduces the burden of parameter management while still achieving fast wake-up capability
Solution Approach 2:
Control parameters are preliminarily acquired and stored in memory before sleep mode activation. This preliminary action creates a ready-state parameter set that can be immediately used upon wake-up, simplifying the wake-up process while maintaining the ability to update parameters as needed without increasing overall system complexity
3Adaptability or versatility
If the receiver uses MAC scheduling algorithms without advance notification, then scheduling flexibility is maintained, but the receiver cannot prepare control parameters in advance leading to longer wake-up delays
Solution Approach 1:
The receiver performs preliminary acquisition of control parameters before the scheduled wake-up time indicated by MAC scheduling. This allows the receiver to be fully prepared for data reception at the scheduled time without requiring advance notification, thus maintaining scheduling flexibility while eliminating parameter acquisition delays
Solution Approach 2:
The receiver serves itself by autonomously acquiring and maintaining control parameters in readiness for scheduled wake-up times. This self-service capability eliminates the need for external advance notification while maintaining compatibility with MAC scheduling algorithms, allowing the receiver to independently prepare for data reception
Data Source
AI summary
An auxiliary reduced power analog-to-digital converter (ADC) is provided for use during sleep periods of a receiver. The auxiliary ADC has a reduced dynamic range but sufficient accuracy to allow demodulation of signaling information contained in an input signal and to update control parameters used for synchronization and channel estimation. As such, a main higher power, higher dynamic range ADC can be turned off during sleep periods, reducing receiver power consumption. The main ADC is turned on at the end of a sleep period, and the receiver can be ready for receiving data immediately using the main ADC because the control parameters are maintained up to date during the sleep period using the auxiliary ADC.