Multidrop Network Distance Measurement Using Fractional Round Trips
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Solution Overview
Problem
The existing Open Alliance (OA) TC14 specification for network topology discovery in multidrop networks does not account for fractional round-trip times, leading to inaccuracies in distance measurements due to the potential loss of the last round trip if the measurement duration is not evenly divisible by the round-trip time.
Innovation Solution
A method is introduced to determine distance by measuring the duration of a predetermined number of round trips instead of relying on a fixed time duration, utilizing fractional round-trip times and adjusting for measurement window errors, thereby improving measurement accuracy by reducing inaccuracy to a fraction of a clock cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed time duration is used for measurement, then the measurement process is simple, but measurement precision deteriorates due to potential loss of the last round trip when measurement duration is not evenly divisible by round-trip time
Solution Approach 1:
The patent transforms the fixed time duration approach into a dynamic measurement method where the measurement window automatically adapts to the actual round-trip time. The system measures for a predetermined number of round trips rather than a fixed duration, allowing the measurement to dynamically adjust based on the actual propagation characteristics of the network medium, thereby eliminating the rounding errors associated with fixed time windows.
Solution Approach 2:
The patent changes the measurement parameter from fixed time duration to a count-based approach (predetermined number of round trips). By measuring the time required to complete a specific number of round trips and then calculating the average round-trip time, the system transforms the measurement into a parameter that is inherently divisible and eliminates the remainder error that occurs with fixed time duration measurements.
2Measurement precision
If measurement duration is made variable to account for fractional round-trip times, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent employs preliminary action by having the reference node transmit a sequence of pulses at regular intervals before the actual measurement begins. The measured node then counts how many of these pre-transmitted pulses are received during the measurement window. This preliminary pulse transmission sequence allows the system to pre-establish a timing reference that simplifies the actual measurement process, avoiding the need for complex real-time adjustment mechanisms.
Solution Approach 2:
The measurement system performs self-service by using the reference node's own pulse transmission schedule to facilitate the measurement. The reference node's regular pulse transmissions serve as both the measurement stimulus and the timing reference, eliminating the need for external synchronization signals or complex control mechanisms. The system uses itself to enable accurate measurement of fractional round-trip times.
Data Source
AI summary
A method may include: generating round-trip pulses at one or more nodes of a multidrop network, respective ones of the round-trip pulses selectively traversing one or more of: internal circuitry of the one or more nodes, or a physical medium between a first node and a second node of the one or more nodes; determining a total delay and an internal delay of the one or more nodes at least partially based on a measurement window error and measured round trips of the round-trip pulses within a predetermined measurement window; and determining a distance between the first node and second node at least partially based on the measured round trips of the round-trip pulses and the internal delay of at least one of the first node or the second node.