Receiver Gain Control Using Pilot Signals in TDD Fading Channels
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Solution Overview
Problem
In TDD and half duplex FDD communication systems, the interleaved transmission and receive periods make it challenging to continuously monitor and adjust receiver gain accurately, leading to potential signal outages and high packet error rates due to fast channel fading.
Innovation Solution
A pilot signal with known properties is transmitted prior to each receive period to facilitate initial gain setting, allowing for more accurate adjustment of receiver gain by deriving an initial gain setting based on the pilot signal, which has a smaller dynamic range than regular traffic signals, thereby minimizing discontinuity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous RSS monitoring and gain adjustment is implemented, then receiver gain control accuracy is improved, but it becomes impossible in TDD systems where transmit and receive periods are interleaved
Solution Approach 1:
The patent transmits a pilot signal before each receive period to enable preliminary gain estimation. This preliminary action allows the receiver to prepare an initial gain setting based on the pilot signal characteristics before the actual traffic signal arrives, resolving the contradiction by making gain control feasible in TDD systems without requiring continuous monitoring during transmit periods.
Solution Approach 2:
The patent introduces a pilot signal as an intermediary element between the transmit and receive periods. This pilot signal serves as a mediator that carries channel state information, allowing the receiver to estimate gain accurately without needing to continuously monitor during the interleaved transmit periods. The pilot signal bridges the gap created by the TDD interleaving structure.
2Device complexity
If the initial gain setting relies on the outdated RSS value of the last receive period, then the system operates without additional pilot signals, but the received signal may be out of the receiver dynamic range resulting in high packet error rate
Solution Approach 1:
By transmitting a pilot signal before each receive period, the system performs preliminary channel characterization. This allows the receiver to calculate an accurate initial gain setting based on the pilot signal's known properties and measured RSS, rather than relying on outdated information. The preliminary pilot signal transmission ensures the receiver is properly configured before the actual data arrives.
Solution Approach 2:
The patent changes the approach from using outdated RSS values to using real-time pilot signal measurements. By measuring the RSS of the freshly transmitted pilot signal and using its known characteristics, the system dynamically adjusts the initial gain parameter to match current channel conditions, significantly improving reliability without excessive complexity.
3Measurement precision
If a pilot signal is transmitted prior to each receive period, then initial gain setting accuracy is improved, but additional signaling overhead is introduced
Solution Approach 1:
The patent designs the pilot signal to serve multiple functions simultaneously: it enables initial gain estimation, provides channel state information for equalization, and can carry synchronization information. By making the pilot signal multi-functional, the system achieves accurate gain setting without proportionally increasing overhead, as the same signal structure accomplishes multiple tasks.
Solution Approach 2:
The system uses the pilot signal temporarily for gain estimation purposes, then discards it after extracting the necessary information. The pilot signal is not continuously transmitted but only when needed for initial setup, allowing the system to recover the essential gain information without maintaining continuous overhead. This selective use minimizes the quantity overhead while maintaining measurement precision.
Data Source
AI summary
A method and system is disclosed for perform receiver gain control. A pilot signal is transmitted prior to each transmit period to facilitate an initial gain setting for a corresponding receiver period. This pilot signal has known properties and requires a much smaller receiver dynamic range than the rest of the traffic. An initial gain setting is derived based on the pilot signal received at a beginning of a corresponding receive period. A gain setting for traffic signals is then generated following the pilot signal in the receive period based on the initial gain setting.