neonet 2006
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NEONet 2006. Investigating 802.16 for Aeronautical Use Steven Bretmersky Cleveland State University March 1, 2006. Background. - PowerPoint PPT PresentationTRANSCRIPT
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Glenn Research Center at Lewis Field
NEONet 2006
Investigating 802.16 for
Aeronautical Use
Steven BretmerskyCleveland State University
March 1, 2006
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Glenn Research Center at Lewis Field
Background
The airport surface is a highly dynamic environment that encompasses many diverse users with different needs. Future operations will make more use of data communications and will require a wireless link.
In the technology pre-screening phase of the Future Communication Study (a joint Eurocontrol / FAA study) 802.16 was identified as one possible enabling technology for the airport surface for ATC. This technology could benefit other surface users as well.
This work investigates the possible uses of 802.16 for the airport surface.
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Glenn Research Center at Lewis Field
Uses of a surface wireless network
• As a data link to aircraft for Air Traffic Control (ATC) and Aeronautical Operational Communications (AOC) messages
• As a data link for surface vehicles (fuel trucks, baggage carts, maintenance vehicles)
• As a backup link for existing ATC fixed surface systems (radar sites, voice radio sites, navaid sites)
• As a primary link for new surface systems located in remote or hard-to-reach areas (ASDE-X multilateration sensors, wake vortex sensors)
• As a network connection for airport staff (technicians in the field)
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Glenn Research Center at Lewis Field
Wireless Surface Scenario
Weather Radar
ILS
Aircraft
Emergency Vehicles
FAA
Airlines
PortAuthority
Technicians
Fuel TruckBaggageHandlers
RTR
Radar
Snow Removal Equipment
ALS
Wake Vortex SensorRWSL
ASDE-XSensor
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Glenn Research Center at Lewis Field
Current Communications Systems
• To Aircraft – VHF voice and character-based messaging system (ACARS)
• To surface vehicles – VHF voice to ATC, mobile radios
• To existing surface systems – copper, leased telco lines, microwave wireless links, and/or fiber. All existing surface systems use point-to-point analog interfaces (modems)
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Future System Requirements
• High reliability• Pre-emption / prioritization (QoS)• Privacy / Security
– Encryption– Authentication
• Mobility• Operate in a protected band (safety of flight)
– C-band identified as good candidate – MLS extension band (5.091 – 5.150 GHz) is unutilized and
currently protected as aeronautical radionavigation
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Glenn Research Center at Lewis Field
802.16 Flavors
✔ ✔Mesh✔ ✔ ✔Mobility✔ ✔ ✔ ✔Spaced Time Coding (STC)✔ ✔ ✔ ✔Adaptive Antenna System (AAS)✔ ✔ ✔ ✔Automatic Repeat Request (ARQ)
10 – 66 GHz
2 - 11 GHz
2 - 11GHz
2 - 11GHz
2 - 11GHz
Frequency
TDDFDD
TDDFDD
TDDFDD
TDDFDD
TDDDuplexing
WirelessMAN-SC
WirelessMAN-SCa
WirelessMAN-OFDM
WirelessMAN-OFDMA
WirelessHUMAN
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Glenn Research Center at Lewis Field
802.16 OFDM Waveform
• 8 Pilot Subcarriers– Used as reference for phase and amplitude
• 192 Data Subcarriers• Combination of all subcarriers creates an OFDM
symbol
Pilot SubcarriersData Subcarriers
Guard Band Guard Band
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Glenn Research Center at Lewis Field
TDD Frame Structure
Downlink Subframe
UL BurstDL Burst iDL Burst 1 UL Burst
DL PHY PDU UL PHY PDU UL PHY PDU
Uplink Subframe
Frame
Preamble
Frame Control Header
DL-MAP, UL-MAP, DCD, UCD
Burst 1 MAC PDU 1
Burst 1 MAC PDU k
Burst i MAC PDU 1
Burst i MAC PDU l
Transmit/Receive Turnaround Gap
Initial Ranging Contention Slot
BW Request Contention Slot
SS 1 PHY PDU Preamble
SS 1 MAC PDU 1
SS 1 MAC PDU m
SS x PHY PDU Preamble
SS x MAC PDU 1
SS x MAC PDU n
Receive/Transmit Turnaround Gap
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802.16 on High Reliability
• 802.16 uses multiple modulations and FEC rates to offer best performance for link conditions. – Modulation / FEC selection is a tradeoff between robustness and data
rate.
– WirelessMAN-OFDM modulations:• BPSK• QPSK• 16-QAM• 64-QAM
– WirelessMAN-OFDM FEC algorithms• Reed-Solomon-Convolutional Code (RS-CC) at rates of 1/2, 2/3, and 3/4• Block Turbo Coding (BTC) at rates of 1/2, 3/5, 2/3, 3/4, 4/5, and 5/6
(optional)• Convolutional Turbo Codes (CTC) at rates of 1/2, 2/3, and 3/4 (optional)
• 802.16 offers ARQ that can be enabled on a per-service-flow basis
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Glenn Research Center at Lewis Field
802.16 on QoS
• 802.16 offers four types of services– Unsolicited Grant Service
• Real-time fixed-rate flows
– Real Time Polled Service• Real-time variable rate flows
– Non-Real Time Polled Service– Best Effort Service
• QoS for real-time services– Priority (8 levels)– Tolerated jitter– Maximum tolerated latency– Minimum tolerated traffic rate
• 802.16 scheduler is not standardized
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Glenn Research Center at Lewis Field
802.16 on Privacy / Security
• Key management– X.509 digital certificates– RSA public key encryption/authentication– Optional EAP authentication in 802.16e– HMAC with SHA-1 authentication
• Data encryption– DES with 56-bit keys– AES with 64 and 128 bit keys
• Data authentication– AES with 128-bit keys in 802.16e
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Glenn Research Center at Lewis Field
802.16 on Mobility
• 802.16e adds the mobility component to the base standard– Designed to accommodate vehicular speeds (< 120 km/h)– Cannot support takeoff/landing speeds (~250 km/h),
although this is not a big issue since the aircraft will likely be using the terminal area data link during these periods
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Glenn Research Center at Lewis Field
Study Approach
• Identify surface applications and scenarios• Create 802.16 OFDM model to use in OPNET
simulations• Identify and implement appropriate scheduling
algorithm• Evaluate scenario options and verify with simulations
– Single vs. multiple systems – Channel size
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Glenn Research Center at Lewis Field
802.16 Model
• Implementation of 802.16 P2MP protocols in progress– MAC Common Part Sublayer
– Convergence Sublayer
– Overhead from Privacy Sublayer
– Overhead from OFDM PHY
• 802.16e extensions to be added in the future
• Creation of physical layer model to begin soon– Waiting for inputs from Ohio
University Sounding Study
Scope of Standard
Service-SpecificConvergence Sublayer (CS)
MAC Common Part Sublayer(MAC CPS)
Privacy Sublayer
Physical Layer (PHY)
Transmission Convergence (TC)
CS SAP
MAC SAP
PHY SAP
PHY
MAC
Scope of Model
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Glenn Research Center at Lewis Field
Scheduling Algorithm
• Must determine when to grant bandwidth to services to meet QoS requirements– minimum rate– maximum latency– maximum jitter– priority
• Must poll subscribers at appropriate time• Must take into account the current modulation and
FEC rate being used by the subscriber
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Glenn Research Center at Lewis Field
Bandwidth Options
• Channel bandwidth is configurable (between 1.25 and 25 MHz, 802.16e up to 5 MHz)
• Example (OFDM, G = 1/32)– 1.25 MHz channel (minimum)
• BPSK with RS-CC ½ (most robust)– 524 kbps raw data rate
• 64-QAM with RX-CC ¾ (least robust)– 4.7 Mbps raw data rate
– 25 MHz channel• BPSK with RS-CC ½ (most robust)
– 10.5 Mbps raw data rate
• 64-QAM with RX-CC ¾ (least robust)– 94.2 Mbps raw data rate
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Glenn Research Center at Lewis Field
Scenario Options
• Single system scenario– All nodes use same wireless channel(s)
• Multiple system scenarios– Separate wireless channels for fixed nodes and for mobiles– Separate point-to-multipoint and mesh channels
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Glenn Research Center at Lewis Field
Comments?