Low Rate PHY Structure for Long Range Sensor Connectivity
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Solution Overview
Problem
The existing IEEE 802.11ac PHY structure does not meet the requirements for long-range, low-data-rate wireless communications, particularly for battery-powered sensors, as it lacks a sufficiently long preamble for proper device detection and channel estimation, leading to increased overhead and power consumption.
Innovation Solution
A low-rate PHY structure is developed, which includes a modified preamble comprising a low-rate short training field (LR-STF) and low-rate long training field (LR-LTF), eliminating unnecessary overhead fields like L-SIG, and using OFDM signals to enable hardware reuse, with repetition techniques for BPSK and QPSK modulation schemes to extend range and reduce power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the IEEE 802.11ac PHY structure is used for long-range, low-data-rate communications, then the system can provide wireless connectivity for common devices, but the preamble is insufficiently long for proper device detection and channel estimation, leading to increased overhead and power consumption
Solution Approach 1:
The PHY structure is segmented into distinct functional components: a shortened legacy preamble for basic detection, followed by a new training field (TF) for channel estimation, and then data. This segmentation allows each part to be optimized for its specific function, with the legacy preamble kept short and the new TF providing the necessary channel estimation capability without extending the overall structure excessively.
Solution Approach 2:
The invention extracts and separates the channel estimation function from the legacy 802.11ac preamble structure. A new dedicated training field is introduced that can be selectively used based on channel conditions, allowing the system to remove unnecessary legacy fields (like L-SIG in some configurations) and reduce overall overhead while maintaining detection and estimation capabilities.
2Reliability
If the IEEE 802.11ac PHY structure is used with standard preamble fields, then device detection can be performed, but overhead is increased and power consumption rises for battery-powered sensors
Solution Approach 1:
The legacy short training field (L-STF) and legacy long training field (L-LTF) are positioned at the very beginning of the PHY structure to perform preliminary device detection and basic channel characterization. This preliminary action allows receiving devices to quickly identify transmissions and prepare for data reception without requiring the full legacy preamble, enabling the truncation of subsequent fields like L-SIG to reduce overhead.
Solution Approach 2:
A new training field (TF) is introduced as an intermediary element between the legacy preamble and the data portion. This TF serves as a mediator that provides enhanced channel estimation capability when needed, while allowing the system to operate with reduced legacy preamble fields. The TF can be configured with different repetitions and lengths based on channel conditions, acting as a flexible intermediate structure that balances detection reliability with overhead reduction.
3Length of moving object
If repetition techniques are used for BPSK and QPSK modulation schemes, then range can be extended and power requirements reduced, but the PHY structure requires modification from IEEE 802.11ac
Solution Approach 1:
The training field employs periodic repetition of signal sequences to extend detection range. The L-STF and L-LTF can be repeated multiple times within the TF structure, with each repetition providing additional opportunities for correlation-based detection. This periodic repetition allows battery-powered sensors to detect signals at lower power levels and from greater distances, while the repetition count can be adjusted based on channel conditions and range requirements.
Data Source
AI summary
Certain embodiments of the invention may include systems, methods, and apparatus for a low rate PHY structure. According to an example embodiment of the invention, a method is provided for generating a low rate PHY structure with low overhead. The method may include generating a preamble comprising one or more training fields; generating a data field; grouping the preamble and the data field into a low rate PHY structure; and converting the low rate PHY structure for wireless transmission over a hardware transmission medium.