Mixed Modulation Scheduling for ITS Message Congestion
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Solution Overview
Problem
Intelligent transportation systems (ITS) face medium congestion issues due to high message rates from vehicles broadcasting common awareness messages (CAMs), leading to increased error rates and channel access delays, which can compromise road safety by reducing the accuracy of environmental information for vehicles.
Innovation Solution
The implementation of a wireless communications device that adjusts the modulation scheme for CAM transmission based on a pattern, allowing nearby vehicles to receive all messages while more remote vehicles receive only those transmitted with sufficiently long-range schemes, thereby reducing medium load without compromising safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vehicles broadcast CAM messages at a high rate of 10 Hz to maintain real-time information accuracy, then the reliability of environmental information is improved, but the wireless medium becomes congested leading to increased error rates and channel access delays
Solution Approach 1:
The patent segments the uniform message transmission approach by introducing multiple modulation schemes (e.g., BPSK, QPSK, 16-QAM, 64-QAM) with different transmission ranges. Messages are divided into different transmission categories based on the modulation scheme used, allowing nearby vehicles to receive all messages while remote vehicles receive only those transmitted with long-range schemes. This segmentation reduces overall medium load while maintaining reliability for nearby vehicles.
Solution Approach 2:
The patent applies local quality by making transmission characteristics location-dependent. Different modulation schemes are used based on the intended reception distance: shorter modulation schemes (BPSK, QPSK) for nearby vehicles and longer modulation schemes (16-QAM, 64-QAM) for remote vehicles. This ensures that each vehicle receives sufficient information quality appropriate to its distance from the transmitter, reducing unnecessary transmissions to remote areas while maintaining high reliability for nearby vehicles.
2Object-affected harmful factors
If vehicles reduce the CAM message broadcast rate below 10 Hz to free up the wireless medium, then the medium congestion is reduced, but the accuracy of real-time environmental information deteriorates
Solution Approach 1:
The patent introduces dynamic transmission behavior by varying the modulation scheme used for each CAM message based on current medium conditions and vehicle density. The system dynamically selects from multiple modulation schemes (BPSK, QPSK, 16-QAM, 64-QAM) with different ranges and data rates, allowing the transmission strategy to adapt to changing conditions. This dynamic approach maintains information accuracy by using appropriate modulation schemes while reducing overall medium load compared to uniform high-rate transmission.
3Object-affected harmful factors
If vehicles reduce transmission power to free up the wireless medium, then the medium load is reduced, but the transmission range and coverage area decrease
Solution Approach 1:
The patent changes the modulation scheme parameter instead of simply reducing transmission power. By selecting from multiple modulation schemes (BPSK, QPSK, 16-QAM, 64-QAM) with inherently different transmission ranges and power requirements, the system achieves medium load reduction while maintaining appropriate coverage. Shorter-range modulation schemes naturally require less power and create less medium load, while still providing sufficient coverage for nearby vehicles that need the most frequent updates.
Data Source
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AI summary
Various exemplary embodiments relate to a wireless communications device and related method and machine-readable storage medium including: at least one antenna; a transmission circuit to transmit data via the at least one antenna and a wireless communications medium according to any of a plurality of modulation schemes; a reception circuit to receive data via the at least one antenna; an application controller to generate a series of messages having a message type and associated with an application; and a message scheduler to provide modulation settings to the transmission circuit for respective messages of the series to be transmitted according to different modulation schemes of the plurality of modulation schemes, wherein modulation schemes are chosen for transmission based on a modulation scheme pattern, whereby a first message is transmitted according to a first modulation scheme and a second message is transmitted according to a second modulation scheme.