Tetra DMO Range Extension via DBPSK Modulation
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Solution Overview
Problem
The communication range of TETRA devices operating in direct mode is limited by signal power and quality, leading to reduced connectivity as distance increases, which is a concern in scenarios where infrastructure coverage is unavailable.
Innovation Solution
Implementing π/2 shifted Differential Binary Phase Shift Keying (DBPSK) modulation, which increases the burst length and reduces amplitude modulation, allowing for higher transmitted power without adding an efficient power amplifier, thereby enhancing the communication range without increasing battery drain or heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If devices transmit at higher power to extend communication range, then communication range increases, but battery drain and heat dissipation increase
Solution Approach 1:
The patent changes the modulation scheme from DQPSK to DBPSK, which fundamentally alters the signal characteristics. DBPSK has a constant envelope with lower peak-to-average power ratio, allowing the power amplifier to operate more efficiently and transmit higher average power without increasing peak power requirements, thus extending communication range without proportionally increasing battery drain
Solution Approach 2:
The patent utilizes existing standard TETRA hardware components and modifies only the modulation implementation in software/firmware. This approach avoids expensive hardware upgrades while achieving extended range, effectively using existing resources to solve the problem without requiring additional power amplifier capacity
2Length of stationary object
If devices transmit at higher power to extend communication range, then communication range increases, but heat dissipation increases
Solution Approach 1:
By switching to DBPSK modulation with constant envelope, the patent reduces the peak-to-average power ratio, allowing more efficient power amplifier operation. This efficiency improvement increases the ratio of useful transmitted power to wasted heat, enabling extended communication range without proportionally increasing heat dissipation
3Adaptability or versatility
If DQPSK modulation is used to maintain standard compliance, then compatibility is maintained, but communication range is limited
Solution Approach 1:
The patent modifies the modulation parameter from DQPSK to DBPSK while keeping the system within the TETRA framework. This parameter change improves the power efficiency and extends communication range, demonstrating how changing operational parameters can resolve the contradiction between standard compliance and performance optimization
4Reliability
If burst length is increased to improve signal quality, then signal sensitivity improves, but data transmission time increases
Solution Approach 1:
The patent changes the modulation scheme to DBPSK, which has better power efficiency and signal characteristics. This allows for improved signal sensitivity and longer effective burst lengths without the same penalty in transmission time, as the more efficient modulation allows better signal detection and processing
Data Source
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AI summary
A TETRA device, system, and Direct Mode Operation (DMO) method are presented in which Differential Binary Phase Shift Keying (DBPSK) modulation is used to extend the communication range of direct mode operation TETRA devices. The protocol during various stages of a communication session uses a DBPSK modulation scheme in which one bit is used per symbol and the burst length is twice as long as standard DMO, so that 510 bits are present in consecutive slots. This permits the number of bits per TETRA frame to be the same as standard DMO. The protocol includes specific implementations for ongoing calls, call setup, and master-slave changeover. Although immediate switching between adjacent double slots is not supported using the modulation scheme, the enhanced DMO can use a standard Tetra protocol except for a call setup sequence.