doc.: IEEE 802.18-07-0096r0
Spectrum Alternatives for
Aircraft Onboard Wireless Systems
Date: 2007-11-13
Authors
Affiliations
Frank Whetten
The Boeing Company Seattle, WA 206-852-8914
Submission
Address Phone
email
Frank.L.Whetten@Boeing.com
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
What Kind of Spectrum Do We Want?
•
•
•
Lower frequencies propagate better
– Less shadowing and better material penetration, signals will propagate
throughout aircraft with low power
– Require larger antennas
Higher frequencies are more attenuated
– More line of sight (LOS) propagation, shadowing and absorption become
major factors
– Very small antennas can be used, but more power required
Desirable to have aviation spectrum near unlicensed bands
– Can adapt COTS equipment to avionics use via firmware load
– Leverage significant wireless industry investment into technology upgrades and
improvements
Submission
Frank Whetten, Filename.ppt
Boeing | 2
doc.: IEEE 802.18-07-0096r0
Where Will the Spectrum Come From?
•
•
Essentially all usable spectrum is already allocated to primary and secondary users
around the world
So how might we find spectrum? Two basic options:
1. Obtain new spectrum by taking it away from an incumbent user
• Resistance to getting more spectrum allocations will be high
• Maximum opportunity for new spectrum is above 30GHz
2. Reuse existing spectrum already allocated to aviation
• Aviation has a large number of dedicated frequency bands allocated in
around the world
• Opportunities exist for more efficient use of existing aviation spectrum
– MLS is not deployed, DSB-AM still in use
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Obtaining New Spectrum
•
•
•
•
Best opportunity for new spectrum is above 30GHz:
– Line of Sight (LOS) propagation
– High absorption due to rain, snow, etc. in atmosphere
Resulting intra-airplane usage might be appropriate for:
– Very short distance, high-bandwidth applications
– Very small devices, but with sufficient power availability
Examples of suitable applications might include
– LRU-LRU communications within an equipment rack, within the flight deck,
or multiple sensors with a nearby data concentrator
Examples of ill-suited applications could include
– Extremely low-power devices attempting to communicate long distances or in a
highly shadowed environment, such as along the length of the fuselage
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Reusing Existing Spectrum
•
•
•
Existing aviation spectrum is largely below 10GHz
– Consequently, the advantages of low frequencies apply
Is it be possible to reuse existing spectrum? Many factors apply:
– Particular classification of existing spectrum (in ITU terms)
– Incumbent system characteristics
– Bandwidth potentially available for reuse
How can we reuse existing spectrum? Two basic possibilities:
– Cognitive – the new systems can detect which parts of the frequency band the
incumbent is using, and move elsewhere
– Underlayment – the new systems operate at power levels below what the
incumbent systems can detect (the UWB model)
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Existing Aeronautical Allocations
Avionics Receivers
Freq Range
(MHz)
Allocation
(Service)
ADF
0.190-1.750
ARNS
HF Voice
HF Datalink
Marker Beacon
2-30
75
Limiting Footnotes
No limiting footnotes. Service Definition:
Aeronautical Radionavigation - A radionavigation service intended for the benefit and for the safe operation
of aircraft
AM(R)S
AM(OR)S
No limiting footnotes. Service Definitions:
Aeronautical Mobile (Route) Service – reserved for communications relating to safety and regularity of
flight (Air Traffic Control)
Aeronautical Mobile (Off-Route) Service - intended for communications, including those relating to flight
coordination (Aeronautical Operational Control)
ARNS
5.180 The frequency 75 MHz is assigned to marker beacons. Administrations shall refrain from assigning
frequencies close to the limits of the guardband to stations of other services which, because of their power
or geographical position, might cause harmful interference or otherwise place a constraint on marker
beacons.
No AR limiting footnotes. AM(R) – (VHF Radio) allocation by footnote:
5.197A The band 108-117.975 MHz may also be used by the aeronautical mobile (R) service on a primary
basis, limited to systems that transmit navigational information in support of air navigation and
surveillance functions in accordance with recognized international aviation standards.
ILS Localizer
VHF Data Broadcast
VHF Omnirange (VOR)
108-118
ARNS
VHF Voice & Data Link
118-137
AM(R)S
ILS Glide Slope
329-335
ARNS
5.258 The use of the band 328.6-335.4 MHz by the aeronautical radionavigation service is limited to
Instrument Landing Systems (glide path).
962-1213
982
1030
1030
1090
1164-1215
ARNS
5.328 The use of the band 960-1 215 MHz by the aeronautical radionavigation service is reserved on a
worldwide basis for the operation and development of airborne electronic aids to air navigation and any
directly associated ground-based facilities. (WRC-2000)
DME
UAT
Mode AC Transponder
Mode S Transponder
TCAS Interrogator
GNSS L5/E5
Submission
No limiting footnotes.
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Existing Aeronautical Allocations
Avionics Receivers
Freq Range
(MHz)
Allocation
(Service)
Limiting Footnotes
5.357A In the bands 1 545-1 555 MHz and 1 646.5-1 656.5 MHz, priority shall be given to
accommodating the spectrum requirements of the aeronautical mobile-satellite (R) service
providing transmission of messages with priority 1 to 6 in Article 44. Aeronautical mobilesatellite (R) service communications with priority 1 to 6 in Article 44 shall have priority access
and immediate availability, by pre-emption if necessary, over all other mobile-satellite
communications operating within a network.
AMS(R)S SATCOM
1530-1559
No Allocation
Footnote Only
GNSS/ GPS
1559-1610
ARNS
No Limiting Footnotes
ARNS
5.438 Use of the band 4 200-4 400 MHz by the aeronautical radionavigation service is reserved
exclusively for radio altimeters installed on board aircraft and for the associated transponders
on the ground. However, passive sensing in the Earth exploration-satellite and space research
services may be authorized in this band on a secondary basis (no protection is provided by the
radio altimeters).
Radio Altimeter
4200-4400
MLS
MLS Extension Band
5030-5090
5090-5150
ARNS
5.444 The band 5 030-5 150 MHz is to be used for the operation of the international standard
system (microwave landing system) for precision approach and landing. The requirements of
this system shall take precedence over other uses of this band.
5.367 Additional allocation: The bands 1 610-1 626.5 MHz and 5 000-5 150 MHz are also
allocated to the aeronautical mobile-satellite (R) service on a primary basis, subject to
agreement obtained under No. 9.21
Weather Radar
5350-5470
ARNS
5.449 The use of the band 5 350-5 470 MHz by the aeronautical radionavigation service is
limited to airborne radars and associated airborne beacons.
Weather Radar
Submission
9300-9500
No Allocation Footnote Only
5.475 The use of the band 9 300-9 500 MHz by the aeronautical radionavigation service is
limited to airborne weather radars and ground-based radars. In addition, ground-based radar
beacons in the aeronautical radionavigation service are permitted in the band 9 300-9 320 MHz
on condition that harmful interference is not caused to the maritime radionavigation service. In
the band 9 300-9 500 MHz, ground-based radars used for meteorological purposes have
priority over other radiolocation devices.
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Cognitive Approaches
•
•
•
What is Cognitive Radio, and what does it have to do with reality?
– Cognitive radio is the concept of a coexisting system detecting another system,
and moving out of the way
– Regulatory authorities world-wide are looking at cognitive as an answer to
the shortage of good spectrum
– IEEE 802.11a/n operation in 5GHz band using DFS is an early
implementation of cognitive capability
Thus, to reuse existing avionics spectrum the new systems would:
– Need to know where the incumbent system is operating, and
– Operate around it or under it
How?
– Announcements (via a systems bus, beacon, etc.)
– Detection of emissions (proven, but difficult)
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Underlayment Approaches
•
•
•
What is underlayment, and what does it have to do with reality?
– Underlaying an existing spectrum allocation relies upon operating a new system
in such a way that the existing system is not interfered with in a harmful way
(FAA/FCC nomenclature)
– Again, a major push by regulators looking for ways to gain more utility from
over-desired spectrum
Thus, to reuse existing avionics spectrum, the new systems would:
– Operate at power levels which would not interfere with the input receivers of
incumbent systems
How? Two factors:
– Output power, directionality, and gain of new system
– Interference path loss (IPL) between new system and the incumbent receiving
antenna
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
How Much Bandwidth is Available?
•
Shannon’s Law
– The theoretical maximum bit-rate through any noise-limited channel is
C  B  log 2 (1   )
•
– where C=channel capacity in bits, B=channel bandwidth in Hz, and  is
numeric signal-to-noise ratio
Shannon’s law can be modified by MIMO technology to
  2

C   B  log 2 1   i ( H )
 N

i 1toN
– Where (H) is a bunch of channel and path correlation factors, and N is the
number of MIMO channels
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
How Close to Shannon Are We?
180
45%
Shannon Limit (Mbps)
Ratio of Shannon to Actual (%)
140
Bit Rate (Mbps)
40%
802.11a Data Rate (Mbps)
35%
120
30%
100
25%
80
20%
60
15%
40
10%
20
5%
0
Percentage of Theoretical (%)
160
0%
8
10
12
14
16
18
20
22
24
Signal-Noise Ratio (dB)
Submission
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Underlaying Existing Systems
Avionics Receiver
ADF
HF Voice
HF Datalink
Marker Beacon
ILS Localizer (Cat I DH)
ILS Localizer (Coverage Limits)
VHF Data Broadcast
VHF Omnirange (VOR)
VHF Voice Comm.
VDL Mode 2
VDL Mode 3
VDL Mode 4
ILS Glide Slope (Cat I DH)
ILS Glide Slope (Coverage Limits)
Distance Measuring Equipment (DME)
Universal Access Transceiver (UAT)
Mode A/C Transponder Receiver
Mode S Transponder Receiver
TCAS Interrogator Receiver
GNSS L5/E5
AMS(R)S SATCOM
GNSS L1
Radio Altimeter
Microwave Landing System (MLS)
MLS Extension Band
Weather Radar
Weather Radar
Submission
DO-294B Limits (dBm/Hz)
DO-294B
802.11a
Gap
Difference
Receiver
Hypothetical
style
802.11a style
Operational
between
between
Aggregate
Shannon
technology technology
Frequency BW (MHz) Susceptibility TNF and
DO-160 &
Limit within
could
could deliver
Range (MHz)
DO-yyy
DO-294
Threshold
Gap (bps)
deliver
in BW (Mbps)
(dB)
values
PSD
(bps)
(dBm/Hz)
1.56
n/a
0.190-1.750
n/a
0
0
0.000
0.000
28
n/a
2-30
n/a
0
0
0.000
0.000
28
n/a
n/a
0
0
0.000
0.000
2-30
0
13
75
-113
61
6
1.927
0.000
4
34
108-112
-154
20
4
1.168
4.674
4
26
108-112
-146
28
5
1.562
6.248
4
45
108-112
-165
9
3
0.451
1.805
10
45
108-118
-165
9
3
0.451
4.513
19
35
118-137
-155
19
4
0.953
18.100
19
42
118-137
-162
12
4
0.571
10.857
19
42
118-137
-162
12
4
0.571
10.857
19
42
118-137
-162
12
4
0.571
10.857
6
38
329-335
-145
29
5
1.579
9.471
6
33
329-335
-140
34
5
1.653
9.919
251
63
962-1213
-167
7
3
0.000
0.000
0
63
982
-167
7
3
0.000
0.000
0
42
1030
-162
12
4
0.571
0.000
0
42
1030
-162
12
4
0.571
0.000
0
47
1090
-167
7
3
0.000
0.000
51
78.5
1164-1215
-180
0
0
0.000
0.000
29
70
1530-1559
-187
0
0
0.000
0.000
51
64
1559-1610
-181
0
0
0.000
0.000
200
67
4200-4400
-160
14
4
0.781
156.144
60
66
5030-5090
-174
0
0
0.000
0.000
60
n/a
5090-5150
n/a
0
0
0.000
0.000
120
68
5350-5470
-160
14
4
0.781
93.686
200
n/a
9300-9500
n/a
0
0
0.000
0.000
Frank Whetten, Boeing
doc.: IEEE 802.18-07-0096r0
Conclusions
• Two approaches to obtain dedicated and protected spectrum for intra-airplane use
– Pursue a new aviation allocation through international treaties organizations
– Develop methodology to re-use existing spectrum in a safe and efficient
manner
• A new allocation
– Would likely be challenging to obtain spectrum below 10GHz, due to strong
competition for spectrum resources
– Would likely take several cycles of the World Radio Conference to approve
• Reusing existing allocations
– Significant engineering challenges in ensuring that multiple communications
systems can use the same spectrum without harmful interference
– Regulatory challenges pertaining to avoiding being limited by the current
regulatory language and footnotes on existing bands
Submission
Frank Whetten, Boeing