InterPlanetary Internet Deep Space Network

2. InterPlanetary InternetDeep Space Network

3. InterPlaNetary Internet Architecture • InterPlaNetary Backbone Network • InterPlaNetary External Network • PlaNetary Network

4. PlaNetary Network Architecture • PlaNetary Satellite Network • PlaNetary Surface Network

5. CHALLENGES • Extremely long and variable propagation delays • Asymmetrical forward and reverse link capacities • Extremely high link error rates • Intermittent link connectivity, e.g., Blackouts • Lack of fixed communication infrastructure • Effects of planetary distances on the signal strength and the protocol design • Power, mass, size, and cost constraints for communication hardware and protocol design • Backward compatibility requirement due to high cost involved in deployment and launching processes

6. Planned InterPlaNetary Internet Missions

7. Proposed Consultative Committee for Space Data Systems (CCSDS) Protocol Stack for Mars Exploration Mission Communications

8. Proposed Delay Tolerant Networking (DTN) Protocol Stack

9. Transport Layer Issues • Extremely High Propagation Delays • High Link Error Rates • Asymmetrical Bandwidth • Blackouts

10. Extremely Long Propagation Delays

11. Performance of Existing TCP Protocols • Window-Based TCP’s are not suitable!!! ForRTT = 40 min  20B/sthroughput on1Mb/s link !! O. B. Akan, J. Fang, I. F. Akyildiz, “Performance of TCP Protocols in Deep Space Communication Networks”, IEEE Communications Letters, Vol. 6, No. 11, pp. 478-480, November 2002.

12. Space Communications Protocol Standards – Transport Protocol (SCPS-TP) • Addresses link errors, asymmetry, and outages • SCPS-TP: Combination of existing TCP protocols: • Window-based • Slow Start • Retransmission timeout • TCP-Vegas congestion control scheme – variation of the RTT value as an indication of congestion • SCPS-TP Rate-Based: • Does not perform congestion control • Uses fixed transmission rate New Transport Protocols are needed !!! * Space Communications Protocol Specification-Transport Protocol (SCPS-TP)", Recommendation for Space Data Systems Standards, CCSDS 714.0-B-1, May 1999.

13. Hold Blackout Decrease Increase TP-Planet*O. B. Akan, J. Fang and I.F. Akyildiz, “TP-Planet: A Reliable Transport Protocol for InterPlaNetary Internet”, to appear in IEEE Journal of Selected Areas in Communications (JSAC), early 2004. Steady State • Objective:To address challenges of InterPlaNetary Internet • A New Initial State Algorithm • A New Congestion Detection Algorithm in Steady State • A NewRate-Based scheme instead of Window-Based t=2*RTT Initial State t=RTT Immediate Start FollowUP Follow Up

14. Multimedia Transport in InterPlaNetary Internet Additional Challenges * Bounded Jitter * Minimum Bandwidth * Smoothness * Error Control

15. OPERATIONAL State t=RTT Increase BEGIN State Blackout Decrease RCP-Planet: OverviewJ. Fang and I.F. Akyildiz, “RCP Planet: A Rate Control Scheme for Multimedia Traffic in InterPlaNetary Internet”, July 2003. • Objective:To Address the Challenges • Framework: * A New Packet Level FEC * A New Rate-Based Approach * A New BEGIN State Algorithm * A New Rate Control Algorithm in OPERATIONAL State

16. Transport LayerOpen Research Issues • End-to-End Transport: • Feasibility of the end-to-end transport should be investigated and new end-to-end transport protocols should be devised accordingly. • Extreme PlaNetary Distances: • Deep Space links with extreme delays such as Jupiter, Pluto have intermittent connectivity even within an RTT. • Cross-layer Optimization: • The interactions between the transport layer and lower/higher layers should be maximized to increase network efficiency for scarce space link resources.

17. Network Layer Issues • Naming and Addressing in the InterPlaNetary Internet • Routing in the InterPlaNetary Backbone Network • Routing in PlaNetary Networks

18. Naming and Addressing • Purpose: To provide inter-operability between different elements in the architecture • Influencing Factors: • What objects are named? (Typically nodes or data objects) • Whether a name can be directly used by a data router in order to determine the delivery path? • The method by which name/object binding is managed?

19. Domain Name System (DNS) Approach in Internet If an application on a remote planet needs to resolve an Earth based name to an address: • Problems: • If query an Earth-resident name server: A significant delay of a round-trip time in the commencement of communication • If maintain a secondary name server locally: State updates would dominate communication channel utilization • If maintain a static list of host names and addresses: Not scale well with system’s growth

20. Tiered Naming and Addressing • Name Tuple = {region ID, entity ID} • Region ID identifies the entity’s region and is known by all regions in the InterPlaNetary Internet • Entity ID is a name local to its entity’s local region and treated as opaque data outside this region  The opacity of entity names outside their local region enforces Late Binding: the entity ID of a tuple is not interpreted outside its local region which avoids a universal name-to-address binding space and preserves a significant amount of autonomy within each region.

21. The “Backbone” Earth’s Internet Mars’ Internet SRC DST GW1 GW2 IPN region: earth.sol IPN region: mars.sol IPN region: ipn.sol An InterPlaNetary Internet: Example and Host Name Tuples

22. ChallengesNetwork Layer • Long and Variable Delays • Without timely distribution of topology information, routing computations fail to converge to a common solution, resulting in route inconsistency or oscillation • The node movement adds to the variability of delays • Intermittent Connectivity • Determine the predicted time and duration of intermittent links and the degree of uncertainity • Obtain knowledge of the state of pending messages • Schedule transmission of the pending messages when links become available SCPS-NP  possible solution???

23. Open Research IssuesNetwork Layer • Distribution of Topology Information • Combination of link state and distance vector information exchange • Distribution of trajectory and velocity information • Path Calculation • Hop-by-hop routing is expected using incomplete topology information and probabilistic estimation • Adaptive algorithms are needed for rerouting and caching decisions • Interaction with Transport Layer Protocols

24. ChallengesNetwork Layer (Planet) • Extreme Power Constraints • Space elements mainly depend on rechargeable battery using solar energy • Frequent Network Partitioning • The network can be partitioned due to harsh environmental factors • Adaptive Routing through Heterogeneous Networks • Fixed elements (e.g., landers) • Satellites with scheduled movement • Mobile elements with slow movement (e.g., rovers) • Mobile elements with fast movement (e.g., spacecraft) • Low-power sensor nodes in clusters

25. Medium Access Control InterPlaNetary Backbone Network • Challenges: • Very Long Propagation Delays • Physical Design Change Constraints • Topological Changes • Power Constraints

26. Medium Access Control InterPlaNetary Backbone Network • Vastly unexplored research field • The suitability and performance evaluation of fundamental MAC schemes, i.e., TDMA, CDMA, and FDMA, should be investigated • Thus far, Packet Telecommand, and Packet Telemetry standards developed by CCSDS are used to address deep space link layer issues (Virtual Channelization method!!!)

27. Error ControlInterPlaNetary Backbone Network • Deep space channel is generally modelled as Additive White Gaussian Noise (AWGN) channel • Scientific space missions require bit-error rate of 10-5 or better after physical link layer coding  Error control at link layer is necessary

28. Error ControlInterPlaNetary Backbone Network • CCSDS Telemetry Standard: (Telemetry Channel Coding): • For Gaussian Channels  ½ Rate Convolutional Code • For Bandwidth-Constrained Channels  Punctured Convolutional Codes • For Further Constrained Channels  Concatenated Codes (i.e.,Convolutional code as the inner code and the RS code as the outer code) Own Experience  TORNADO CODES!!!

29. Error ControlInterPlaNetary Backbone Network • Advance Orbiting Systems Rec. by CCSDS  Space Link (ARQ) Protocol (SLAP) • Packet Telecommand Standard of CCSDS  Command Operation Procedure (COP) (GoBack N)

30. Open Research IssuesLink Layer • MAC for InterPlaNetary Backbone Network • MAC for PlaNetary Networks • Error Coding Schemes • Cross-layer Optimization • Optimum Packet Sizes

31. Physical Layer Issues InterPlaNetary Backbone Network • Possible approach is to increase radiated RF signal energy: • Use of high power amplifiers such as travelling wave tubes (TWT) or klystrons which can produce output powers up to several thousand watts • This comes with an expense of increased antenna size, cost and also power problems at remote nodes • Current NASA DSN has several 70m antennas for deep space missions • DSN operates in S-Band and X-Band (2GHz and 8GHz, respectively) for spacecraft telemetry, tracking and command • Not adequate to reach high data rates aimed for InterPlaNetary Internet • New 34m antennas are being developed to operate in Ka-Band (32 GHz) which will significantly improve data rates

32. Open Research IssuesPHYSICAL LAYER • Signal Power Loss: • Powerful and size-, mass-, and cost-efficient antennas and power amplifiers need to be developed • Channel Coding: • Efficient and powerful channel coding schemes should be investigated to achieve reliable and very high rate bit delivery over the long delay InterPlaNetary Backbone links • Optical Communications: • Optical communication technologies should be investigated for possible deployment in InterPlaNetary Backbone links • Hardware Design: • Low-power low-cost transceiver and antennas should be developed • Modulation Schemes: • Simple and low-power modulation schemes should be developed for PlaNetary Surface Network nodes. Ultra-wide Band (UWB) could be explored for this purpose

33. Challenges in Deep Space Time Synchronization • Variable and long transmission delays • The long and variable delays may cause a fluctuating offset to the clock • Variable transmission speed • It may produce a fluctuating offset problem • Variable temperature • It may cause the clock to drift in different rate • Variable electromagnetic interference • This may cause the clock to drift or even permanent damage to the crystal if the equipment is not properly shielded

34. Challenges in Deep Space Time Synchronization (cont’d) • Intermittent connectivity • The situation may cause the clock offset to fluctuate and jump • Impractical transmissions • A time synchronization protocol can not depend on message retransmissions to synchronize the clocks, because the distance between deep space equipments are simply too large • Distributed time servers • Deep space equipments may require to synchronize to their local time servers, and the time servers have to synchronize among themselves

35. Related Work • Network Time Protocol • Can not handle mobile servers and clients (variable range and range rate with intermittent connectivity) • Has time offset wiggles of few milliseconds of amplitude • DSN Frequency and Time Subsystems • Uses several atomic frequency standards to synchronize the devices and provide references for the three DSN sites, i.e., Goldstone, USA; Madrid, Spain; Canberra, Australia • Recommendation for proximity-1 space link protocol • Finds the correlation between the clocks of proximity nodes. The correlation data and UTC time are used to correct the past and project the future UTC values

36. Conclusions • InterPlaNetary Internet will be the Internet of next generation deep space networks. • There exist many significant challenges for the realization of InterPlaNetary Internet. • Many researchers are currently engaged in developing the required technologies for this objective.

37. FiNAL WORDS NASA’s VISION: to improve life here, to extend life to there, to find life beyond... NASA’s MISSION: to understand and protect our home planet, to explore the Universe and search for life, to inspire the next generation of explorers… OUR AIM: to point out the research problems and inspire the researchers worldwide to realize these objectives!!!!!!!!!