Wireless Sensor Alarm Handling via Wake-Up Overhear Relay
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Solution Overview
Problem
IEEE 802.11-based wireless security and fire alarm systems face challenges in network lifetime and communication reliability due to power saving modes and poor channel quality, which hinder timely and reliable alarm message transmission.
Innovation Solution
The wake-up-overhear-relay method, where sensors in sleep mode periodically wake up to overhear neighboring transmissions and relay alarm messages to the access point, ensuring reliable communication even with poor channel quality, without requiring dedicated relay stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If sensors stay in power saving mode to extend network lifetime, then energy consumption is reduced and network lifetime is extended, but the sensors cannot receive or transmit alarm packets timely
Solution Approach 1:
The patent implements periodic wake-up cycles where sensors alternately sleep and wake to check for alarm packets. During each wake period, sensors monitor the channel and can transmit/receive packets. This periodic operation allows sensors to extend battery life through sleep mode while ensuring alarm packets are not missed during wake periods, resolving the contradiction between energy saving and reliable communication.
2Speed
If sensors transmit alarm packets directly to the access point, then transmission speed is fast, but the channel quality is too poor for reliable delivery
Solution Approach 1:
The patent introduces intermediate relay nodes (other sensors in the network) that can forward alarm packets from the source sensor to the access point. When a sensor transmits an alarm packet and does not receive acknowledgment from the access point, other waking sensors can overhear and relay the packet through better channels, improving delivery reliability while maintaining relatively fast transmission through multi-hop routing.
3Reliability
If sensors wake up frequently to monitor channels for alarm packets, then packet reception reliability is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic wake-up cycles where sensors alternately sleep and wake to check for alarm packets. During each wake period, sensors monitor the channel and can transmit/receive packets. This periodic operation allows sensors to extend battery life through sleep mode while ensuring alarm packets are not missed during wake periods, resolving the contradiction between energy saving and reliable communication.
Data Source
AI summary
A method of wirelessly transmitting alarm signals includes wirelessly transmitting an alarm signal from a transmitting station. It is determined whether an acknowledgement signal wirelessly transmitted from an access point in response to the access point receiving the alarm signal has been received by the transmitting station. A relaying station is woken up and kept awake during a plurality of periodic time intervals for overhearing transmissions from the transmitting station. If it is determined that an acknowledgement signal from the access point has not been received by the transmitting station, then the alarm signal is wirelessly re-transmitting from the transmitting station during at least one of the time intervals in which the relaying station is awake. The alarm signal is received at the relaying station. The alarm signal is transmitted from the relaying station to the access point.