RFTETRA vs TETRA2: Key Differences Explained
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TETRA (Terrestrial Trunked Radio) is an ETSI (European Telecommunications Standards Institute) standard designed to provide secure and reliable wireless communication for mobile stations. It focuses on stable and undisturbed communication, offering various encryption levels for voice and data, ensuring user privacy. This includes authentication, AIE (Air Interface Encryption), and E2EE (End-to-End Encryption).
This article will outline the core differences between the original TETRA standard and its evolution, TETRA2. In a TETRA network, mobile stations (MSs) primarily communicate through TETRA-compliant base stations. However, MSs can also communicate directly without base stations, especially useful when the network is unavailable or base stations are offline. These TETRA-compliant mobile stations can connect with other system mobiles or telephones interfaced with PSTN/PBX, similar to standard mobile phones. Connections can be established in either half-duplex or full-duplex mode.
A significant application of TETRA is its group calling mode. Let’s delve into the basics of TETRA technology.
TETRA Technology Basics
The TETRA standard encompasses air interface specifications, network interface specifications, and other services. Key features are summarized in Table 1 below:
Table 1: TETRA Specifications
| Specifications | TETRA Support |
|---|---|
| Frequency of operation | About 400MHz |
| Space between carriers | 25KHz |
| Access Technique | TDMA (Time Division Multiple Access); 4 timeslots/carrier |
| Spacing between uplink and downlink | 10 MHz |
| Modulation technique employed | pi/4 DQPSK |
| RF carrier data rate | 36kbps |
| Voice coding rate | 7.2 kbps (gross) |
| User data rate per timeslot (voice+data) | 7.2kbps (No Error Protection), 4.8Kbps (Low Error Protection), 2.4Kbps (High Error Protection) |
| Data rate in Packet Data Only mode | 36 Kbps gross rate with 4 timeslots |
| Frame Structure | 1 TETRA multiframe is made of 18 frames; 17 for voice/data, 1 for signalling. Each frame has 4 time slots. |
| Traffic mode of operation | Supports TMO (Traffic Mode Operation) and DMO (Direct Mode Operation). TMO uses base stations, DMO does not. |
| Call Setup Time | 300 ms |
TETRA2: Enhancements and Features
TETRA2 is an upgraded version of the original TETRA (release-1). It is also known as TEDS (TETRA Enhanced Data Service). This iteration focuses on high-speed data enhancements, resulting in increased throughput.
TETRA2 incorporates the following additional features compared to its predecessor:
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New Modulation and Channel Coding: Includes pi/8 D8PSK, 4-level QAM, 16QAM, and 64QAM.
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Various Coding Rates Added
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New Channel Bandwidths: Introduces 50KHz, 100KHz, and 150KHz bandwidths. Within these bandwidths, symbols are distributed on sub-carriers spaced at approximately 2.7KHz intervals.
- 50 KHz band includes 16 transmit carrier frequencies.
- 100 KHz band includes 32 transmit carrier frequencies, and so on.
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Data Rate Enhancements:
- pi/4 DQPSK with 1 slot: ~9 Kbps gross bit rate for 25 KHz bandwidth.
- pi/4 DQPSK with 4 slots: ~36 Kbps gross bit rate for 25 KHz bandwidth.
- pi/8 DQPSK with 4 slots: ~54 Kbps gross bit rate for 25 KHz bandwidth.
- 4-QAM with 4 slots: Supports a gross bit rate of ~38.4kbps (for 25KHz BW), ~76.8kbps (for 50KHz BW), ~153.6Kbps (for 100KHz BW), and ~230.4Kbps (for 150KHz BW).
- 16-QAM with 4 slots: Supports a gross bit rate of ~76.6kbps (for 25KHz BW), ~153.6kbps (for 50KHz BW), ~307.2Kbps (for 100KHz BW), and ~460.8Kbps (for 150KHz BW).
- 64-QAM with 4 slots: Supports a gross bit rate of ~115.2kbps (for 25KHz BW), ~230.4kbps (for 50KHz BW), ~460.8kbps (for 100KHz BW), and ~691.2kbps (for 150KHz BW).
