Full Duplex TDMA Radio Using Adjacent Time Slots
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Solution Overview
Problem
Existing direct mode TDMA communication systems face challenges in implementing full duplex voice and/or data communications without requiring radios to switch synthesizers between transmit and receive frequencies within the limited time between adjacent slots, leading to increased costs due to the need for additional synthesizers.
Innovation Solution
A method and system that enable full duplex direct mode calls by detecting a request for a full duplex call, transmitting a call request or header on a single frequency, and interleaving outbound and inbound voice/data transmissions within adjacent time slots, eliminating the need for synthesizer switching between transmit and receive frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a second synthesizer is incorporated to enable full duplex communications on separate frequencies, then full duplex voice and data communications can be achieved, but manufacturing costs substantially increase
Solution Approach 1:
The patent merges transmit and receive operations into a single frequency by combining outbound transmissions in first time slots with inbound receptions in second time slots that are immediately adjacent. This eliminates the need for separate synthesizers for different frequencies, resolving the contradiction between full duplex capability and manufacturing cost.
Solution Approach 2:
The patent transitions from frequency-based separation (requiring multiple synthesizers) to time-based separation using adjacent time slots. By moving the differentiation dimension from frequency to time, the system achieves full duplex functionality without additional synthesizer hardware, thus reducing manufacturing costs.
2Adaptability or versatility
If synthesizer switching between transmit and receive frequencies is implemented, then full duplex communications can be achieved, but the system requires additional hardware complexity
Solution Approach 1:
The patent merges transmit and receive operations into a single frequency by combining outbound transmissions in first time slots with inbound receptions in second time slots that are immediately adjacent. This eliminates the need for separate synthesizers for different frequencies, resolving the contradiction between full duplex capability and manufacturing cost.
Solution Approach 2:
The patent extracts the frequency switching function entirely from the system by operating both transmit and receive paths on the same frequency through time-division multiplexing. This removes the synthesizer switching mechanism and associated hardware complexity while maintaining full duplex functionality.
3Productivity
If radios transmit asynchronously in 12.5 KHz operation, then spectral efficiency is improved, but guard intervals between time slots are reduced to approximately 2.5 ms
Solution Approach 1:
The patent assigns specific time slot patterns in advance where outbound transmissions occur in first time slots and inbound receptions occur in immediately adjacent second time slots. This preliminary assignment ensures that radios know when to transmit and when to receive, eliminating the need for extensive guard intervals while maintaining asynchronous operation and spectral efficiency.
Data Source
AI summary
A method for enabling full duplex direct mode calls between radios in an N:1 slotting ratio TDMA radio system includes detecting a request for a full duplex direct mode call at a first radio, transmitting in a particular slot of a first recurring time slot of N recurring time slots on a first single frequency one of a call request and a call header identifying the call as a full duplex call. Subsequently transmitting, by the first radio, during a plurality of subsequent first recurring time slots, outbound voice and/or data transmissions. And receiving, during a plurality of second recurring time slots of the N recurring time slots, each second recurring timeslot positioned immediately adjacent a respective first recurring time slot in an interleaved manner, inbound voice and/or data transmissions from the second radio and playing back the inbound voice and/or data transmission at the first radio.