CMX998, CMX981 - Tetra White Paper

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