Making TETRA compliant with FCC rules
Jose M. Martin
Executive Vice President & Chief Operating Officer
PowerTrunk Inc.
One Platform, Multiple Technologies: TETRA, P25, WiMAX
The Hilton, New York City
17 June 2010
Background
TETRA is an standard defined by ETSI (European
Telecommunication Standards Institute), a private
association subject to the French law.
TETRA’s Air Interface (including the physical layer) is defined
by ETSI EN 300 392-2 (trunked mode operation) and by ETSI
EN 300 396-2 (direct mode operation).
The RF TETRA signal does not meet several mandatory
requirements described by FCC 47 CFR 90.
Applicable FCC requirements (not met by TETRA)
Mask B (equipment with audio low pass filter). As
defined by FCC 47 CFR § 2.1049 § 90.210.
Occupied bandwidth < 20 KHz1. As defined by FCC
47 CFR § 2.1049 & 90.209.
1Mean powers radiated below the lower and above the upper frequency
limits shall be each equal or less than 0.5 % of the total mean power radiated
by a given emission.
Possible modifications to meet FCC rules
Modulation type: π/4-DQPSK1
Symbol rate: 18 Ksymbol/s1
Modulation filter: root raised cosine (RRC)
filter with roll-off factor α=0.352
1Modifying any of the first two would involve
losing interoperability with standard equipment. 2The roll-off factor can be changed within a
range of values while interoperability is kept.
TETRA square raised cosine spectrum
TfforfG
Tf
Tfor
TffG
TfforfG
2
10)(
2
1
2
1
*2
1**2sin1*5.0)(
2
11)(
Where:
α: roll-off factor (0.35 is the standard value)
T: symbol duration (55.55 microseconds is the standard value)
Occupied bandwidth vs. roll-off value
Roll-off factor (α) RRC Modulation Filter
Occupied Bandwidth (KHz) (as defined FCC 47 CFR § 2.1049) with Square Windowed version RRC filter1
Occupied Bandwidth (KHz) (as defined FCC 47 CFR § 2.1049) with
Hamming Windowed version RRC filter 0.05 18.703 19.969 0.1 19.055 20.250
0.15 19.406 20.602 0.2 19.758 20.953
0.25 20.250 21.445 0.3 20.742 21.867
0.35 (TETRA standard)
21.305 22.359
0.4 21.938 22.922 0.45 22.570 23.484 0.5 23.273 24.680
1Practical implementation of square windowed RRC filter is
contemplated by ETSI EN 300 392-2.
Frequency Band (MHz) Rule / Limit TETRA
Standard TETRA 0.2
410-430
Occupied Bandwidth
FCC Part 90: 20KHz No pass 1 Pass 1
RSS-119: 20KHz No pass 1 Pass 1
Emission Mask
FCC Part 90 with Audio LPF: Mask B No pass 1 Pass 1
FCC Part 90 without Audio LPF: Mask C No pass 1 Pass 1
RSS-119: Mask C No pass 1 Pass 1
450-470
Occupied Bandwidth
FCC Part 90: 20KHz No pass 1 Pass 1
RSS-119: 20KHz No pass 1 Pass 1
Emission Mask
FCC Part 90 with Audio LPF: Mask B No pass 1 Pass 1
FCC Part 90 without Audio LPF: Mask C No pass 1 Pass 1
RSS-119: Mask C No pass 1 Pass 1
806-809 /
851-854
Occupied Bandwidth
FCC Part 90: 20KHz No pass 1 Pass 2
RSS-119: 20KHz No pass 1 Pass 2
Emission Mask
FCC Part 90 with Audio LPF: Mask B No pass 1 Pass 2
FCC Part 90 without Audio LPF: Mask H No pass 1 No pass 1
RSS-119: Mask G No pass 2 Pass 2
809-824 /
854-869
Occupied Bandwidth
FCC Part 90: 20KHz No pass 1 Pass 2
RSS-119: 20KHz No pass 1 Pass 2
Emission Mask
FCC Part 90 with Audio LPF: Mask B No pass 1 Pass 2
FCC Part 90 without Audio LPF: Mask G No pass 2 Pass 2
RSS-119: Mask G No pass 2 Pass 2
Frequency sub-bands vs.
FCC & IC applicable
rules
TETRA 0.2 performance issues (1)
Increment of peak to average ratio (PAR)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8
Peak power/Mean power (PAR) (dB)
CCDF for PI/4 QPSK modulation with RRC filter.
1e-007
1e-005
.001
.1
Pro
ba
bili
ty
ALPHA=0.1
ALPHA=0.2
ALPHA=0.3
ALPHA=0.35
∆PAR ≈ +1.3 dB
Involving the 1 dB
compression point P1dB
for the amplifier is
increased.
State-of-the-art RF
hardware is compliant.
TETRA 0.2 performance issues (2)
Increment of inter-symbol interference (ISI)
Lab tests have shown
that the quality of
the reception stays
within the limits
defined by ETSI EN
300 392-2 and EN
300 396-2 0 40000 80000 111111
Time (ns)
Eye pattern with PI_4 QPSK modulation
-40
-20
0
20
40ALPHA=0.2
RC filter
0 20000 40000 60000 80000 100000
Time (ns)
Eye pattern with PI_4 QPSK modulation
-40
-20
0
20
40ALPHA=0.35
RC filter
Eye Patterns TETRA 0.35 and 0.2
TETRA 0.2 performance issues (3)
Field tests have shown no operational loss of performance1
0.35 0.2 1Source: PowerTrunk (BC Hydro trials in Vancouver area)
TETRA 0.35 and TETRA 0.2 interoperability
TETRA
network
TETRA 0.35 TETRA 0.21
1TETRA 0.2 equipment can pass 100 % of the TETRA Interoperability
Profile (TIP) tests as defined by the TETRA Association, interoperating
with standard equipment from all vendors.
Find TIPs at www.tetra-association.com
0.35 or 0.2
TMO TMO
DMO
Frequently Asked Questions (1)
Is the PowerTrunk-T TETRA implementation really TETRA ?
YES, because it is interoperable with standard TETRA
equipment. The modification of the roll-off factor is not of a
different nature from that of many implementation decisions.
Did PowerTrunk-T receive type acceptance from the FCC and
Industry Canada ? YES
Does the modification involve HW changes ? NO. The
equipment can be re-flashed with the standard software at
any time.
Frequently Asked Questions (2)
Should the FCC grant the waiver requested by the TETRA
Association so that TETRA 0.35 can be accepted in the United
States ? YES, because TETRA has been deployed in more than
100 countries and no interference has been reported so far
(in many cases coexisting with P25 and other technologies).
TETRA 0.2 is available now, but using the same software than
in the rest of the world is a very desirable goal.