White Paper A Knowledge Base document from CML Microcircuits TETRA Enhanced Data Services on TETRA 1 Hardware 1 © 2010 CML Microsystems Plc WP/TEDS/1 February 2010 Introduction to TETRA Enhanced Data Services (TEDS) From TETRA to TEDS Today, many business organisations across Europe have come to rely on dedicated TETRA networks for mission critical communications. TETRA was developed by the European Telecommunications Standards Institute (ETSI) to carry data as well as voice in order to address the unique needs of public safety agencies. The success of TETRA is reflected in the fact that more than 80 countries worldwide have now adopted it. The use of TETRA encompasses public safety and commercial industries, underlying its capability to support critical communications requirements. In its initial release, TETRA was designed as a voice priority service, with capacity to support status messaging, text messaging and packet data. These data services are sufficient to support mission critical services such as database queries, Automatic Vehicle Location and resource management. With the introduction of MSPD (Multislot Packet Data) in 2005, which increased the throughput for packet data by nearly a factor of 4, applications like image transfer have started to become more widely used. As users became interested in developing richer applications, the TETRA Association responded by working with ETSI to develop the TEDS standard, a wideband data solution, which enhances TETRA with a much higher capacity and throughput for data. About TEDS In addition to those provided by TETRA, TEDS uses a range of adaptive modulation schemes and a number of different carrier sizes from 25kHz to 150kHz. Initial implementations of TEDS will be in the existing TETRA radio spectrum, and will likely employ 50kHz channel bandwidths as this enables an equivalent coverage footprint for voice and TEDS services. Advances in DSP technology have led to the introduction of multi-carrier transmission standards employing QAM modulation. WiMAX, Wi-Fi and TEDS standards are part of this family. TEDS performance is optimised for wideband data rates, wide area coverage and spectrum efficiency. Evaluation The purpose of this whitepaper is to examine the capability of existing CML devices, already used for TETRA 1 designs, to be re-used as a platform for TETRA Enhanced Data Services (TEDS) within the 3, 4 TETRA 2 release standard, . 2 © 2010 CML Microsystems Plc WP/TEDS/1 February 2010 ADC EV9980 Basics The EV9980 includes a CMX998 IC along with all signal path-matching components and an RF5110G power amplifier at 450MHz. Feedback coupling allows the loop to be linearised. The CML DAC ASIC uses a very similar Digital to Analogue converter to the CMX981, so it is expected that this device could be used per existing TETRA 1 platforms. Results The test configuration, (taken with the CMX998 Cartesian Loop IC plus the RFMD RF5110G PA) is shown diagrammatically in Figure 1. The input conditioning amplifiers were configured to accepted signals biased at 1.6V with a unity voltage gain. The loop filter was configured with a gain of 34dB, a first pole at 32kHz, a second pole at 48kHz and a zero at 200kHz. The RF5110G PA can produce +33dBm to +34dBm PEP so, with an expected peak to mean of just a little under 8dB, it was anticipated that +25dBm to +26dBm mean output power would be produced. The plot in Figure 2 shows that this is achieved with an ACP of 60dBc, comfortably meeting the TETRA Release 2 requirements of –55dBc. M ar k e r 1 [T1] 2.78 dBm 4 48 . 0 0315631 MHz Ref Lvl 3 0. 8 dBm RBW VBW SWT 500 Hz 5 kHz 3 s RF Att 3 0 dB Unit dB m 30 .8 30 . 8 dB O f fs e t 1 [T1] 2 . 78 448.00315 6 31 CH PWR 25 . 96 ACP Up -60 . 30 ACP Low -60 . 57 20 10 dBm A MHz dBm dB dB 1 0 1R M - 10 - 20 - 30 - 40 - 50 C0 C0 cl1 cl 1 - 60 cu1 cu1 - 69 .2 C e n te r 448 M H z 15 kHz/ Span 1 50 k H z Figure 2 The plot in Figure 3 shows a comparison between the open loop (red trace/upper) and the closed loop (green trace/lower) performance. This demonstrates that the loop is achieving approximately 25dB to 30dB of linearisation. The other key RF parameter is the wideband noise; typical results for the test system are shown in Table 1. It will be observed that the TETRA requirements are comfortable achieved. 4 © 2010 CML Microsystems Plc WP/TEDS/1 February 2010 M ar k e r 1 [T2] 5.11 dBm 4 48 . 0 0006613 MHz Ref Lvl 3 0. 8 dBm RBW VBW SWT 500 Hz 5 kHz 3 s RF Att 3 0 dB Unit dB m 30 .8 30 . 8 dB O f fs e t 1 [T2] 5 . 11 448.00006 6 13 CH PWR 26 . 07 ACP Up -33 . 73 ACP Low -34 . 04 20 10 dBm A MHz dBm dB dB 1 0 1 VI EW 2 VI EW 1R M 2R M - 10 - 20 - 30 - 40 - 50 cu1 cu1 C0 C0 - 60 cl1 cl 1 - 69 .2 C e n te r 448 M H z 15 kHz/ Span 1 50 k H z Figure 3 Offset (kHz) Noise (dBc) +112.5 -112.5 +262.5 -262.5 +500 -500 +/-5000 -80 -78 -86 -85 -87 -85 -101 TETRA 2 Requirements (<3W) dBc -68 -68 -72 -72 -78 -78 -95 TETRA 2 Requirements (≥ 5,6 W) dBc -70 -70 -75 -75 -80 -80 -95 Table 1 - 50kHz QAM WBN Measurements Conclusion The tests show that the CML hardware solutions combined with the Etherstack2 modulator software comfortably meets the key RF performance requirements of the TETRA Release 2 standard. References 1. Rhode & Schwartz. TETRA/TETRA 2. Technology overview. 2. http://www.etherstack.com/ 3. ETSI EN 300 392-2 V3.2.1 (2007-09) 4. ETSI TS 100 392-2 V3.3.1 (2008-10) 5 © 2010 CML Microsystems Plc WP/TEDS/1 February 2010 6 © 2010 CML Microsystems Plc WP/TEDS/1 February 2010