Full Duplex Calls via Single Frequency Repeaters
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Solution Overview
Problem
Existing N:1 TDMA communication systems face challenges in providing full duplex voice and data communications without requiring subscriber units (SUs) to switch synthesizers between transmit and receive frequencies within the limited time between adjacent slots, which increases costs and complexity.
Innovation Solution
Implementing a method and system that assigns a single frequency for both inbound and outbound transmissions using single frequency repeaters (SFRs), allowing SUs to operate on immediately adjacent time slots without the need for additional synthesizers or repeaters, thereby enabling full duplex calls within the N:1 TDMA protocol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate frequencies are assigned for inbound and outbound transmissions in conventional repeater systems, then full duplex calls can be supported, but additional synthesizers and repeaters are required, increasing system cost and complexity
Solution Approach 1:
The patent combines inbound and outbound transmissions onto a single frequency by using TDMA time slots. Instead of requiring separate frequencies and additional repeaters, the system merges both directions of communication into one frequency resource, accessed through time-division multiplexing. This eliminates the need for additional synthesizers and repeaters while maintaining full duplex capability.
Solution Approach 2:
The patent transitions from frequency-domain separation to time-domain separation. Instead of using different frequencies for inbound and outbound transmissions, the system introduces a time dimension by assigning different time slots within the same frequency for different transmission directions. This dimensional shift resolves the contradiction by maintaining full duplex functionality without increasing hardware complexity.
2Productivity
If subscriber units switch synthesizers between transmit and receive frequencies within limited time between adjacent slots, then N:1 TDMA protocol can be implemented, but system cost and complexity increase due to additional synthesizer requirements
Solution Approach 1:
The patent merges transmit and receive operations onto the same frequency by using TDMA time slot assignment. Instead of requiring synthesizer switching between different frequencies, the system combines both functions into a single frequency resource, accessed at different times. This eliminates the need for complex synthesizer switching mechanisms while maintaining efficient time slot utilization.
Solution Approach 2:
The patent extracts the frequency switching requirement from the system by keeping the operating frequency constant. Instead of changing frequencies between transmit and receive modes, the system removes the frequency switching element entirely and relies solely on time-division multiplexing. This extraction simplifies the synthesizer requirements while preserving N:1 TDMA protocol efficiency.
3Device complexity
If a single frequency is used for both inbound and outbound transmissions, then costs and complexity are reduced, but full duplex communications must be enabled through time slot assignment
Solution Approach 1:
The patent introduces a controller as an intermediary that manages time slot assignments for inbound and outbound transmissions. This controller coordinates the use of the single frequency by assigning specific time slots to different transmission directions, eliminating the need for complex synthesizer switching while maintaining full duplex operation. The controller acts as a mediator that simplifies the overall system architecture.
Data Source
AI summary
A method for enabling full duplex individual calls in repeater mode between two subscriber units (SUs) in a N:1 slotting ratio time division multiple access (TDMA) radio system includes receiving a request for a full duplex individual call from a first SU identifying a second SU as a target of the call. Determining to grant the request and subsequently assigning a first time slot of the N time slots on a first single frequency for one of inbound and outbound transmissions for the call between an assigned second repeater and the first SU and a second time slot on the first single frequency for the other of inbound and outbound transmissions for the call between the assigned second repeater and the first SU. Further, a grant message is transmitted to the first SU indicating the assigned first single frequency and assigned first and second time slots.