Satellite Networking Cheryl-Annette Kincaid

Why satellites? Global coverageGlobal coverage Remote locationsRemote locations High-velocity mobile usersHigh-velocity mobile users

Frequency Bands C band: 4-8 GHzC band: 4-8 GHz Ku band: GHzKu band: GHz Ka band: GHzKa band: GHz

Space Segment Orbits GSO – Geostationary OrbitGSO – Geostationary Orbit Revolution: synchronized with Earth’s rotation.Revolution: synchronized with Earth’s rotation. Altitude: 35,786 km above equatorAltitude: 35,786 km above equator Coverage: approx. 1/3 of Earth’s surfaceCoverage: approx. 1/3 of Earth’s surface Propagation Delay: msPropagation Delay: ms Real estate: limitedReal estate: limited

Space Segment Orbits NGSO – Nongeostationary OrbitNGSO – Nongeostationary Orbit MEO – Medium Earth OrbitMEO – Medium Earth Orbit Altitude: 3000 km – GEO altitudeAltitude: 3000 km – GEO altitude Propagation Delay: Typically msPropagation Delay: Typically ms LEO – Low Earth OrbitLEO – Low Earth Orbit Altitude: 200 – 3000 kmAltitude: 200 – 3000 km Propagation Delay: Typically msPropagation Delay: Typically ms

Ground Segment GS - Gateway stationsGS - Gateway stations NCC - Network control centerNCC - Network control center OCC - Operation control centerOCC - Operation control center

Architectural options Bent-pipe architecture

Architectural options OBP and ISL architecture

Architectural options DBS – Direct broadcast satellite

Challenge – Traffic Management Many user terminals are located within a single satellite’s footprint. These terminals must contend with each other for the uplink channel.

Challenge – Traffic Management Objectives: FairnessFairness Efficient Resource UtilizationEfficient Resource Utilization Bounded Queuing DelayBounded Queuing Delay StabilityStability Fast Transient ResponseFast Transient Response ScalabilityScalability

Challenge – Traffic Management Medium Access Control schemes: Fixed AssignmentFixed Assignment FDMAFDMA TDMATDMA CDMACDMA Random AccessRandom Access ALOHA and variantsALOHA and variants Demand AssignmentDemand Assignment DAMADAMA

Challenge – Traffic Management Medium Access Control schemes: Fixed AssignmentFixed Assignment FDMA & TDMAFDMA & TDMA Contention free channelsContention free channels Some QoS guaranteesSome QoS guarantees Inefficient resource utilizationInefficient resource utilization Best suited for small-scale networks with stable traffic patternsBest suited for small-scale networks with stable traffic patterns CDMACDMA Efficient resource utilizationEfficient resource utilization Flexible for system expansionFlexible for system expansion

Challenge – Traffic Management Medium Access Control schemes: Random AccessRandom Access ALOHA and variants Accommodates bursty trafficAccommodates bursty traffic Low throughput when congestedLow throughput when congested

Challenge – Traffic Management Medium Access Control schemes: Demand AssignmentDemand Assignment DAMA – Demand Assignment Multiple AccessDAMA – Demand Assignment Multiple Access Dynamically allocates bandwidth in response to user requestsDynamically allocates bandwidth in response to user requests Explicit or implicit requestsExplicit or implicit requests

Challenge – Traffic Management Medium Access Control schemes: Demand AssignmentDemand Assignment DAMA Variants: Reservation ALOHAReservation ALOHA PODA – Priority-Oriented Demand AssignmentPODA – Priority-Oriented Demand Assignment FODA – FIFO Ordered Demand AssignmentFODA – FIFO Ordered Demand Assignment CFDAMA – Combind Free/Demand Assignment Multiple AccessCFDAMA – Combind Free/Demand Assignment Multiple Access CRRMA – Combined Random Access and TDMA-reservation Multiple AccessCRRMA – Combined Random Access and TDMA-reservation Multiple Access RRR – Round-Robin ReservationRRR – Round-Robin Reservation

Challenge – Routing Dynamic Topology LEO satellites have a very short visible period to motionless users. Efficient methods of handling intersatillite handover are needed. Frequent interbeam handover also occurs within a satellite’s visible period.

Challenge – Routing Dynamic Topology DT-DVTR – Discrete-time Dynamic Virtual Topology Routing Takes advantage of periodic nature of orbitsTakes advantage of periodic nature of orbits Works completely offlineWorks completely offline Divides system period into intervalsDivides system period into intervals Changes in topology only occur at the beginning of an intervalChanges in topology only occur at the beginning of an interval Stores each interval as a static routing tableStores each interval as a static routing table

Challenge – Routing Dynamic Topology VN – Virtual Node Hides topology changes from routing protocolsHides topology changes from routing protocols Sets up a virtual topology that does not change with satellite movementSets up a virtual topology that does not change with satellite movement Stores routing tables and user information as state information in the virtual nodesStores routing tables and user information as state information in the virtual nodes Transfers the assignment of VNs to new satellites as neededTransfers the assignment of VNs to new satellites as needed

Challenge – Routing External Routing Issues Details of heterogeneous internal routing schemes should remain hidden from the terrestrial Internet.Details of heterogeneous internal routing schemes should remain hidden from the terrestrial Internet. Isolation is achieved by means of autonomous systems.Isolation is achieved by means of autonomous systems.

Challenge – Routing External Routing Issues

Challenge – Routing Unidirectional Routing With unidirectional routing, such as is used in DBS, direct reverse links do not exist. Three solutions to this problem are: Routing Protocol ModificationRouting Protocol Modification TunnelingTunneling Static routingStatic routing

Challenge – Routing Unidirectional Routing Routing Protocol Modification FeederFeeder ReceiverReceiver As the receiver obtains routing updates, it identifies potential feeders and stores useful information about the topology. Periodically, the receiver sends a routing update via the terrestrial reverse channel.As the receiver obtains routing updates, it identifies potential feeders and stores useful information about the topology. Periodically, the receiver sends a routing update via the terrestrial reverse channel.

Challenge – Routing Unidirectional Routing Tunneling Link layer approach to hide network asymmetry from routing processLink layer approach to hide network asymmetry from routing process Packets from the user are encapsulated and sent along a virtual link by means of the reverse channelPackets from the user are encapsulated and sent along a virtual link by means of the reverse channel Packets are decapsulated at the satellite and forwarded to the routing protocolPackets are decapsulated at the satellite and forwarded to the routing protocol Path appears to be bidirectional to protocolPath appears to be bidirectional to protocol

Challenge – Quality of Service Issues LatencyLatency ScintillationScintillation FadeFade Geomagnetic StormsGeomagnetic Storms ThroughputThroughput SecuritySecurity

Challenge – Quality of Service Layered view

Other Challenges TCP PerformanceTCP Performance Cross Layer Protocol DesignCross Layer Protocol Design InterworkingInterworking StandardsStandards

Future - HAP High Altitude Platforms

Future – Global heterogeneous

Conclusion Satellite networking provides global coverage and enables remote regions to connect with the rest of the global network.Satellite networking provides global coverage and enables remote regions to connect with the rest of the global network. Satellite technologies are beginning to offer more real-time, high bandwidth services to more users.Satellite technologies are beginning to offer more real-time, high bandwidth services to more users. Satellites have several unique attributes that lead to many challenges. These must be overcome before satellite networking can become a reliable backbone in the next generation of global communication.Satellites have several unique attributes that lead to many challenges. These must be overcome before satellite networking can become a reliable backbone in the next generation of global communication.

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