Download Broad-Band Satellite Networks

Broad-Band Satellite Networks The Global IT Bridge
By Abbas Jamalipour
In Proc. of the IEEE, Vol. 89, No.1
Presented by
Tsoline Mikaelian
November 26, 2002
Overview
• Evolution of Satellite Systems
• Broad-band Satellite Networks
- Wireless ATM (WATM)
- Mobile IP (MIP)
- QoS Requirements
- Traffic Requirements
- Applications
Fixed Satellite Systems
• Fixed => Geostationary satellite (GEO)
• INTELSAT (1965), INMARSAT(1982)
• Used for long distance telecommunication and
broadcasting
• Do not offer Personal Communication Services
(PCS)
- Long propagation delay
- Long propagation loss
- No coverage of high-latitude regions
Mobile Satellite Systems
• Use satellites on lower orbits (LEO, MEO)
- Reduce transmission delay and transmitter power,
can cover high-latitude regions => offer PCS
- Complicated mobility management issues
• Developed in parallel with 2nd generation terrestrial
cellular systems
- Only voice, fax, low bit rate data apps
=> Called Narrow-band satellite networks
- Ex. Iridium, Globalstar
• Provide mobility in a broader range
- Coverage area, geographical coverage vs population
coverage
Broad-band Satellite Networks: Motivation
• Service requirements changed:
- High-data rate Internet-based apps
- Multimedia services
=> Called Broad-band satellite networks
• Complement existing wireless nets
• Provide global access
• Consider Integration of ATM and IP technologies
into a satellite link
Wireless ATM Networks (WATM)
• Provides mobility-supported high-efficiency
multimedia services
• WATM has traditional wired ATM network as its
backbone
WATM Protocol Architecture
• ATM Protocol needs
modification to
support mobility
• Mobility management:
- Location
management
- Handover
management
Wireless IP Networks: Mobile IP (MIP)
• MIP: Provides macromobility in wireless IP networks,
wireless access to Internet users
• - Physical, data link layers: provided by cellular networks
- Network, transport layers: modified to route packets
correctly to mobile users
• IP address: network prefix used to route datagrams
But MIP has no logical network prefix
• - Mobile node (MN) is given a virtual home network
- Constant IP address assigned
- Location information database maintained on home net
MIP Packet Flow
•
•
•
•
•
Detect change of MN location
MN acquires new IP address (CoA)
Registration with HA: notify HA of new location
Data packets routed to default MN’s home
Tunneling: HA redelivers based on CoAs registered
MIP Tunneling: IP-within-IP Encapsulation
MIP and Broad-band Satellites
• MIP is a starting point for implementing IP
services over broad-band satellite link
• Inefficiencies:
- Registration with HA at every handover
and waste of resources
- Packet losses during handover
- High data latency due to tunneling
ATM-based Satellite Networks
• Operate at Ka-band usually (30/20 Ghz uplink/downlink)
• ~ 2 Mbps or higher data rates
• Satellites may be considered as ATM nodes with onboard
processing capabilities => Apply ATM-based algorithms
• Satellites may have mutual connections via Inter-Satellite
Links (ISL)
• Communication between mobile and fixed terminals
Global Connectivity in ATM Networks
Directly
connectable
terminal:
Contains a
satellite
Adaptation
Unit (also
includes all
physical
layer
functionality)
Global Connectivity in ATM Networks
Satellite
Processing:
Mux/demux,
coding/
decoding,
ATM
switching
Global Connectivity in ATM Networks
Gateway
Station:
Connectivity
between
satellite and
ground
segments.
Contains
Interworking
Unit (IWU)
Global Connectivity in ATM Networks
Ground
Networks:
Include
PSTN,
NB/BB ISDN,
frame relay,
Internet,
public/private
ATM, fixed
user
terminals can
be connected
to those
Global Connectivity in ATM Networks
Network
Control Center
(NCC):
Overall control
of satellite
resources and
operations:
call routing,
management,
location
update,
handover,
registration,
authentication
QoS Requirements
• Main Parameters: Timeliness, bandwidth, reliability,
perceived QoS based on application type, cost, security
• QoS management techniques:
- Static functions (definition of QoS, admission control,
resource reservation)
- Dynamic functions (measuring QoS, maintenance,
adaptation)
• Mobility => change of QoS => adapt
• More sophisticated QoS management in mobile
environment
- Short loss of communication during handover
- New point of attachment => resources + renegotiation
- Blind spots unavoidable
Traffic Requirements
• Unavoidable delay and delay variation in mobile
satellite networks
=> UBR, ABR for implementation of TCP/IP over
ATM satellites
• Integrate IP traffic into ATM mobile satellites =>
aggregate multiple IP flows onto a single VC (by
QoS manager)
• Wireless satellite link => high BER
=> develop new congestion control and traffic
management mechanisms in TCP layer
Applications
Conclusion
Integration of mobile satellite, ATM
and IP technologies can connect all
terrestrial high-speed networks and can
provide global mobility to multimedia
terminals