Rate Adaptation in Wireless Systems Using RSSI and Retry Count
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Solution Overview
Problem
Current wireless devices in the IEEE 802.11 family of specifications often waste bandwidth and experience packet failures due to inefficient data rate selection strategies, leading to TCP timeouts and decreased link throughput, as they initiate transmission at the highest possible data rate and only lower it step-wise upon failure.
Innovation Solution
A transceiver with a rate selector module that adjusts data rates based on received signal quality and packet loss indicators, using a table of available data rates and confidence values to select the optimal rate, and includes a state machine to monitor packet loss and adjust signal quality measures, while also adapting transmit power to optimize data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wireless device initiates transmission at the highest possible data rate, then the potential throughput is maximized, but packet failures increase and bandwidth is wasted
Solution Approach 1:
The patent applies preliminary action by measuring signal quality (RSSI, SNR, SINR) and packet loss indicators before transmission to predict the optimal data rate. The rate selector uses these pre-measured parameters to choose an appropriate data rate from a table, avoiding the need to start at the highest rate and step down upon failure. This predictive approach selects the optimal rate in advance based on current channel conditions.
Solution Approach 2:
The patent implements feedback by continuously monitoring packet loss indicators (retry counters, CRC errors) and signal quality metrics during transmission. The rate selector uses this feedback to dynamically adjust the data rate selection, comparing actual transmission outcomes against expected performance and adapting the rate choice accordingly to maintain both high throughput and reliability.
2Reliability
If the data rate is lowered step-wise upon packet failure, then packet transmission reliability is improved, but bandwidth is wasted and TCP timeouts occur
Solution Approach 1:
Instead of reacting to packet failures by stepping down rates, the patent performs preliminary rate selection based on pre-measured signal quality and packet loss indicators. The rate selector determines the optimal data rate before transmission attempts, selecting from a table of available rates based on confidence values calculated from RSSI, SNR, SINR, and retry counter data. This prevents unnecessary transmissions at inappropriate rates.
Solution Approach 2:
The system continuously monitors transmission outcomes and adjusts rate selection based on feedback from packet loss indicators and signal quality measurements. The state machine tracks transmission success/failure patterns and modifies the rate selection strategy accordingly, allowing the system to adapt to changing channel conditions without wasting bandwidth on repeated failures.
3Device complexity
If the wireless device uses a simple highest-rate-first strategy, then the device complexity is minimized, but bandwidth efficiency decreases and TCP timeouts increase
Solution Approach 1:
The patent introduces a rate selector that performs preliminary calculations using pre-defined tables and confidence value computations based on RSSI, SNR, SINR, and packet loss indicators. Rather than complex real-time optimization, the system uses pre-computed tables mapping signal quality metrics to optimal data rates, reducing computational complexity while improving bandwidth efficiency through informed rate selection.
Solution Approach 2:
The patent changes the selection criterion from a fixed highest-rate-first approach to a dynamic parameter-based selection using confidence values derived from signal quality metrics (RSSI, SNR, SINR) and packet loss indicators. The rate selector computes confidence values for different data rates and selects based on these parameters, transforming the rate selection from a simple but inefficient strategy to a parameter-driven optimized approach.
Data Source
AI summary
A transceiver in an ad hoc network may use a rate adaptation module to select an optimal data rate for a given wireless environment. The rate adaptation module may use a measured RSSI (Received Signal Strength Indicator) from a receive section and a retry count from a transmit section to determine the optimal data rate.