adaptive spectrum radio: a feasibility platform on the path to dynamic spectrum access international...
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Adaptive Spectrum Radio: A Feasibility Platform On The Path To Dynamic Spectrum Access
International Symposium On Advanced Radio Technologies
4-7 March 2003 Boulder, Colorado
5 March 2003
William D. Horne & Peter Weed The MITRE Corporation
703-883-6198; [email protected]; [email protected]
New Paradigms for Spectrum
New paradigms for managing and allocating the electromagnetic spectrum is now possible due to advances in technology and a receptive environment within regulatory agencies
– New technology provides a key component to this possibility as it increases the flexibility for radio transmissions to dynamically adapt and access the spectrum
New paradigms
Traditional Administrative Processes
- Fixed licenses- Block allocations
- etc.
Review of RadioSpectrum Management
Prof. Martin Cave
March 2002
FCC Spectrum
Policy Task Force
Nov 2002
Ad-hoc Networking
Software Defined Radios
Adaptive Spectrum
Access
Emerging Technologies
Dynamic & Adaptive Spectrum Access
The definition of a fully “dynamic” or “adaptive” system is not clearly delineated, but the capabilities of such a system would include:
– Sensing the radio frequency environment;– Controlling its transmissions based on measurements and other a priori
information in an autonomous, opportunistic, and real-time fashion;– Adjusting multiple transmission parameters including, but not limited to,
frequency, power, modulation, signal timing, data rate, coding rate, and antenna; and,
– Operating in cooperative networked systems and/or environments with non-cooperating systems (i.e., opportunistically accessing spectrum).
Scheme Modulation Maximum rate Code rate per slot (kb/s)
MCS-9 8-PSK 59.2 1.0
MCS-8 54.5 0.92
MCS-7 44.8 0.76
MCS-6 29.6 0.49
MCS-5 22.4 0.37
MCS-4 GMSK 17.6 1.0
MCS-3 14.8 0.80
MCS-2 11.2 0.66
MCS-1 8.8 0.53
Increasing “adpativity”
2G/3G (e.g., EDGE)
Unlicensed devices
IEEE 802.11 standards
Future: “Fully” dynamic
and adaptive
DARPA neXt Generation
(XG) program Dynamic Frequency
Selection (DFS)
Adaptive Spectrum Operations ConceptAdaptive Spectrum Operations Concept
Transmit Waveform
Radio Frequency (MHz)
Not all spectrum used 100% of time
See what’s free
Spectrum Picture at T1
Occupied SpectrumOccupied Spectrum
Create waveform to use free spectrum
Multiple Componentsto waveformMonitor channels
& repeat process when environment changes
Waveform compatible with existing spectrum channelization plans and scalable to support wide range of user data rates using non-contiguous spectrum
Waveform compatible with existing spectrum channelization plans and scalable to support wide range of user data rates using non-contiguous spectrum
Dynamic & Adaptive Spectrum Access: Benefits & Challenges
Key benefits for adaptive spectrum access include:– Improved spectrum access and utilization
By adjusting transmissions, adaptive systems can utilize unused frequencies even if they vary over time
– Maintain a quality of service in a changing environment Existing examples include EDGE
– Adjust emissions to reduce or “maintain” levels of interference to other systems Enables interference “temperature” policy concepts
Key challenge: working with regulatory community to determine appropriate “dynamic” and “adaptive” policies and parameters
“Because new, smart technologies can sense the spectrum environment and because they have the agility to dynamically adapt or adjust their operations, increasing access to the spectrum for smart technologies, such as software-defined radios, can improve utilization, through more efficient access, of the radio spectrum without detriment to existing spectrum users.” [FCC Spectrum Policy Task Force]
Demonstrations on the Path to New Spectrum Policy
In order for the policy community to gain confidence in the possibilities of the new paradigms, the technology developers need to demonstrate the capabilities of the systems that enable dynamic spectrum access.
– The MITRE Corporation has developed a feasibility radio platform that demonstrates the principles for dynamically accessing the spectrum
Two principal objectives for demonstrations are: – Feasibility: Inform the policy and regulatory community
of the feasibility for adaptive spectrum access; and,– Policy Considerations: Identify and investigate
considerations for policies using adaptive radio demonstration platforms.
Parallel Development of Policy & Technology
A parallel policy/technology development process can mutually benefit all sides by identifying issues early and by preventing contentious proceedings
– By understanding the capabilities, the policy and regulatory community can better revise and update rules and procedures
– By understanding policy considerations, technologists can incorporate needs early in development
Demonstrations are important component of this parallel process
Emerging Technology & Parallel Policy Example Programs
A good example of a new technology awareness program is the DOD’s Defense Information Systems Agency’s (DISA) Emerging Spectrum Technology program, led by the Defense Spectrum Office (DSO)– This project intends to proactively understand policy
ramifications of new technology having military benefits to ensure that policies do not inhibit their introduction.
– Contact: Rich DeSalvo, 703-325-0435; [email protected]
Other organizations, including the FCC, are also enhancing technology awareness and engagement efforts
Policy Considerations of Demonstration Platforms
Early Adaptive Spectrum Radio platforms, such as MITRE’s, can be used to explore various policy considerations– Band/Channel Blocking
Do policies that prohibit the transmissions in specific bands or channels, even non-contiguous ones, accommodate or limit the introduction of adaptive spectrum access systems? Can different emission levels be set for different channels?
– Technical Parameters. Should policies define acceptable parameter values associated with the
adaptive algorithms (e.g., time required to sense environment, time gap lengths required before “acceptable” to transmit, etc.)?
Are such policies necessary for assuring the performance of other systems? If such parameters specifications are necessary, what are the parameters that need to be defined?
– Databases of Existing Use. Do policies need to be adopted that require the availability of databases to
assist the operation of adaptive spectrum access systems? Do such radios require a priori knowledge of spectrum usage? Does a priori
knowledge improve the performance and interference mitigation capability of these radios?
Future Exploration of Policy Considerations Using the Demonstration Platform
Interference Temperature. The FCC Spectrum Policy Task Force introduced the concept of “interference temperature” as a means for defining the environment in which systems must operate.
– In such a regime, the defined “temperature” and the accuracy of such levels need to be defined--Should policies define permitted limits for transient interference to account for imperfections in the algorithms and protocols for accessing the spectrum?
– What are the achievable sensitivity levels (i.e., margin of error) for sensing the environment? What are the achievable sensitivity levels (i.e., margin of error) when using propagation prediction?
Environments. What environments can adaptive spectrum access systems operate (e.g., dense voice traffic, radar, etc.)?
Refarming. Can the availability of adaptive spectrum access systems improve the efficiency in certain bands by introducing such systems while allowing legacy systems to continue to operate rather than to relocate them?
Secondary/Spot Markets. Can adaptive spectrum access systems enable secondary/spot market “auctions” and trading?
MITRE ASR/SDR Platform
Spectrum Analyzer
Test Signal Source
Optional Single Freq Tx
Spectrum Estimator
Adaptive System
Controller
Transmitter / Modulator
Receive Subsystem
Tx/Rx Chassis Assy
Combined Rx spectrum environment
Implemented Radio FunctionsImplemented Radio Functions
Policy
controller
Rx Subsystem in final implementation
MITRE’s Adaptive Spectrum Radio: Overview
Observe spectrum to detect idle channels Adapt waveform Implement “opportunistic” MAC
Adaptive Spectrum Approach
Sp
ectr
um
@ T
s
Frequency
ASR 1
Sp
ectr
um
@ T
s
ASR 2
Frequency
Negotiate Common Passband
Negotiate Common Passband
Frequency
Dis
join
t P
assb
and
Adaptive Waveform @Ts
ASR Architecture & Design
Periodic estimation of channel’s occupancy state Periodic adaptation of a time-limited waveform in response to
occupancy state estimates Periodic “joint occupancy vector” negotiation w/ subsequent
burst data transfer Measurement of impairments to primary users
ASR Hardware Architecture
r(t)
s(t)
FPGAs
DSPs
FPGAs
ASICs
ASICs
Balancing Performance versus Flexibility
- Highest Performance
- Lowest Flexibility
- Lowest Performance
- Highest Flexibility
A/D
DAC
High-Level Testbed Architecture
Chassis 1
DigitalUpconverterMezzanine
Burst 12 (Coax)
Quad-DSPCarrier Board
Test Signal 2 (Coax)
Test Signal 1 (Coax)Ch1
30.72MHzSignal
Generator
61.44MHzSignal
Generator
DSP_A
DSP_B
DSP_C
DSP_D
Ch2
Chassis 2
DigitalUpconverterMezzanine
Quad-DSPCarrier Board
Ch1
DSP_A
DSP_B
DSP_C
DSP_D
DigitalDownconverter
Mezzanine
Ch2
Ch1
Ch2
Burst 21 (Coax)
Serial
SYNC
10MHz
DigitalDownconverter
Mezzanine
Ch1
Ch2
Ethernet Adapter Board
Host Computer (running Swiftnet S/W, Readyflow BSP, and TI CCS)
COM1 Ethernet
Ethernet Adapter Board
COM1 Ethernet
ASR Tx Functional Partitioning
Test Signal Generator portion of ASR Testbed
Software-defined Radio
Sim
ula
ted
FD
M s
pe
ctr
um
FPGA
DSP
A/D
Pre-processedData - Data formatting
ASIC
- Digital U/C- DAC
- Sequence indexing- Transmit buffering
FPGA
DSP
- Data formatting
ASIC
- Digital D/C- Receive buffering- PSD estimation- OV generation
FPGA
DSP
- Data formatting
ASIC
- Digital U/C- DAC
- Adaptive waveform synthesis- Transmit buffering
Occupancy vector
Pre-processedData
Ad
ap
tiv
e F
DM
Bu
rst
sig
na
l
Channel Occupancy Estimator
Adaptive FDM Burst Modulator
Simulated Test Signal Spectrum
SystemView
-7.5e+6
-7.5e+6
-5e+6
-5e+6
-2.5e+6
-2.5e+6
0
0
2.5e+6
2.5e+6
5e+6
5e+6
7.5e+6
7.5e+6
-40
-50
-60
-70
-80
-90
-100
Mag in
dB
Frequency in Hz (dF = 234.4 Hz)
Simulated Test Signal w/ Coursely Occupied Spectrum
Burst Mod’ Signal Processing
256-element Occupancy Vector(from Channel Occupancy Estimator)
DatadeMUX
Rd =(15kbps)(k)0 < k < 256
C_BB_Data1
HammingPulse-shape
DataSource
HammingPulse-shape
4
C_BB_Data2
C_BB_Data256
4
2
2
Real @ 7.5kbpsImag @ 7.5kbps
42
2
HammingPulse-shape2
HammingPulse-shape2
Real @ 30kspsImag @ 30ksps
2
2
2
512 ptComplex
IFFT
2
2
1
128
129
130
2
2
385
512
384
***
***
***
'0'
2
Real @ 15.36MspsImag @ 15.36Msps
DUC DAC2
122.88Msps