Wireless AGC Scheduling for Short-Preamble Grid Control Packets
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Solution Overview
Problem
Current wireless communication standards for power grid control, such as WirelessHART and WIA-FA, face challenges in achieving low latency and high reliability due to non-optimized physical communication layers, particularly because of the long preamble sequences used for automatic gain control (AGC), which limit the achievable latency and require discarding initial samples processed by AGC systems.
Innovation Solution
The implementation of a packet receiver with a short preamble and time-based scheduling for automatic gain control, allowing rapid switching between gain values and enabling efficient low-latency wireless communications while maintaining reliability by selecting the appropriate low-pass filter based on packet scheduling, thus avoiding the settling time issues of traditional AGC systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long preamble sequences are used for automatic gain control, then reliable message delivery is ensured, but transmission latency increases
Solution Approach 1:
The patent segments the automatic gain control process into multiple discrete gain stages instead of using a single long preamble. The gain adjustment is divided into steps (e.g., 6 dB stages) that can be applied sequentially, allowing the system to achieve reliable AGC without requiring a uniformly long preamble sequence for each packet.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and storing optimal gain values in a lookup table based on received signal strength indicator (RSSI) measurements. This allows the system to quickly determine the appropriate gain setting without performing complex real-time calculations, reducing the time required for AGC settling.
2Reliability
If traditional AGC systems initialize gain to nominal value and process initial samples, then optimal VGA gain is achieved, but settling time increases latency
Solution Approach 1:
The patent implements dynamic gain adjustment by continuously monitoring RSSI and adapting the gain setting in real-time based on current signal conditions. Instead of initializing to a fixed nominal value and settling, the system dynamically selects from pre-calculated gain values, allowing rapid adaptation without a fixed settling period.
Solution Approach 2:
The patent replaces the traditional mechanical settling process with a digital lookup table approach. Instead of physically settling the gain through sequential sample processing, the system uses pre-computed gain values stored in memory, substituting the mechanical settling time with faster digital retrieval and application of gain settings.
3Reliability
If long preambles are used for AGC, then VGA gain optimization is achieved, but packet transmission efficiency decreases
Solution Approach 1:
The patent changes the parameter of preamble length from fixed and long to variable and short. By using pre-calculated gain values based on RSSI, the system can achieve effective AGC with much shorter preambles, directly improving packet transmission efficiency while maintaining gain optimization.
Data Source
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AI summary
There is provided mechanisms for automatic gain control in a wireless communication network for power grid control. The wireless communication network employs time based scheduling of packets. A method is performed by a packet receiver in the wireless communication network. The method comprises receiving a packet from a packet transmitter. The packet comprises a preamble. The preamble is composed of a single OFDM symbol. The preamble is represented by a sequence of samples. The method comprises applying automatic gain control to the sequence of samples after variable gain amplitude control has been applied to the sequence of samples. The automatic gain control involves applying an LPF to the sequence of automatic gain controlled samples. The LPF is selected from a bank of LPSs. Which LPF to apply depends on, according to the time based scheduling, from which packet transmitter the packet is received.