Extended Range Direct Mode Channel Access in Digital Mobile Radio
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Solution Overview
Problem
In wireless communication networks using portable two-way radios, collisions during simultaneous transmissions by multiple devices lead to impaired communications and inefficient resource use, as the repeater cannot decode corrupted data from colliding signals, causing users to unknowingly miss messages and leading to disparate receptions across the network.
Innovation Solution
Implementing a method where portable communication devices use idle bursts to determine if the repeater has successfully received a transmission, allowing devices to dynamically switch between repeater and direct mode, reducing collisions and ensuring all users receive the same transmission by using an enhanced channel access timer and retry mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If multiple portable communication devices transmit simultaneously using the repeater, then the transmission range is extended, but collisions occur causing corrupted data and impaired communications
Solution Approach 1:
The patent implements a channel access request phase before actual data transmission. Devices must first send a channel access request signal to the repeater, which responds with a channel access grant signal before allowing data transmission. This preliminary coordination prevents simultaneous transmissions and collisions, enabling extended range operation without compromising communication reliability.
Solution Approach 2:
The repeater provides feedback signals to portable communication devices during the transmission process. The channel access grant signal from the repeater confirms successful reception of the access request and authorizes data transmission. This feedback mechanism ensures that only one device transmits at a time through the repeater, eliminating collisions while maintaining extended range capability.
2Reliability
If devices use enhanced channel access to prevent collisions, then communication reliability improves, but device complexity increases due to additional timing and protocol requirements
Solution Approach 1:
The patent employs periodic timing structures where devices transmit channel access requests at predetermined intervals following the reception of idle bursts. The enhanced channel access timer operates in discrete time slots, creating a periodic request-grant-transmission cycle. This periodic approach simplifies the timing control logic compared to continuous arbitration mechanisms, reducing device complexity while maintaining reliable collision-free communication.
3Area of stationary object
If the repeater retransmits signals to extend range, then coverage area increases, but collisions during retransmission cause data corruption and loss
Solution Approach 1:
The patent segments the communication process into distinct phases: channel access request phase, channel access grant phase, and data transmission phase. By separating the channel access negotiation from the actual data transmission, the system ensures that only authorized devices transmit data through the repeater. This segmentation prevents collisions during retransmission while maintaining extended coverage area capability.
Data Source
AI summary
Systems and methods for extended range direct mode enhanced channel access in digital mobile radio systems. One example method for operating a portable communication device includes receiving a transmit request, and, responsive to receiving the transmit request, transmitting a single transmit burst including a source identifier identifying the portable communications device and starting an enhanced channel access timer. The method includes, when the enhanced channel access timer expires without receiving at least one from the group consisting of a receive idle burst and a receive burst, transmitting a signal based on the transmit request. The method includes, when a receive burst including a second source identifier is received while the enhanced channel access timer has not expired, responsive to receiving the receive burst, comparing the source identifier to the second source identifier. The method includes, responsive to determining that the second source identifier matches the source identifier, transmitting the signal.