Techniques used in Deep Space Network are introduced. Source coding and Channel coding techniques are explained in brief. Deep Space Network is also explained in detail with the protocols used.
5. Introduction
• Deep space usually refers to the outer space more than 2
million kilometers away from the earth
• Exploration and utilization of the deep space are the
dreams of human beings
• Soviet Union began to explore the moon by using moon-1
in January 1959
6. History
• Mariner 4 launched in 1965, communicated using S band
(2.3GHz)
• No error correcting code nor data compression
• Data rate is only 8.33bps
7. History
• Mars Global Surveyor (MGS) launched in 1997, used X
band (8.4GHz)
• The channel code adopts the constraint length 7, rate 1/2
convolutional code concatenated with the (255, 223)
Reed-Solomon code
• Source code is Rice compression code
• Data rate is 128kbps
8. History
• In the Mars Reconnaissance (MRO) explorer launched in
2006 at operating Frequency of 35Ghz by America
• Turbo and LDPC code is used as channel code
• Fast and Efficient Lossless Image Compression System
(FELICS) is used as source code
• The data rate is 12Mbps
9. Motivation
• Long distance communication
• Very low signal to noise ratio
• High signal propagation delays and data corruption rates
10. Scope
• Image source coding techniques
• Channel coding techniques
• Deep space network
11. Image Source Coding
• Storage and transmission of image data (such as images
of landform and physiognomy of remote planet) occupy
large part of the resource and bandwidth
• Limited storage and transmission capability of the
explorer
• Thus, requirement for bandwidth and storage capacity,
high efficient image compressing coding method
12. Wavelet Transform of ICER
Compression
Ten sub-bands produced by three stages of wavelet
decomposition
13. Channel Coding
• Large distance between the transmitting space craft and
the receiving earth station
• Thus, limited transmitting power result in a very poor
signal-to-noise ratio at the receiver side
• Leads to large amount of transmission errors
14. Channel coding
• Improves the small scale link performance by adding
redundant data bits in the transmitted message
• Block codes, Convolutional Codes and turbo codes
• Turbo coding scheme result in a 3 dB performance
improvement over the Block and Convolutional codes
15. Channel coding
• In contrast to TCCs, TPCs use extended hamming codes
and parity code to build 2D and 3D block structures
• Far less complex to decode than the TCCs and is scalable
to easily support the full range of data rate requirements
up to gigabits per second
• Less expensive decoders for cost sensitive applications
16. Channel coding
• An LDPC code is based on an H matrix containing a low
count of ones
• The BCH outer code has the effect of lowering the error
floor, which is subjected to the LDPC code
17. Comparison of Turbo and LDPC code
• LDPC codes have more gain than turbo codes by 2 dB
• TPC 16K block size codes perform close to the LDPC
codes at code rates approaching 0.9
– The modulation used is BPSK and the channel is AWGN
• But turbo code has predominance in the case of short
length code (eg. <1000bits) and the encoding process of
Turbo code is more simple than that of LDPC code
21. DSN communication protocol stack
• The network protocol stacks in MER communication
System include:
– Space wireless frequency and modulation (layer 1)
– Space channel coding and space link (layer 2)
– Space networking (layer 3)
– Space end-to-end security (layer 4)
– Space end-to-end reliability (layer 5)
– and space file transfer (layer 6) (including CCSDS File
Delivery Protocol) and SCPS (Space Communication
Protocol Standards)
22. DSN communication protocol stack
• Internet or Internet related protocols are used to form local
networks with low-delay relatively low-noise environments
such as around Earth, within a free-flying spacecraft, on and
around another planet
• SCPSTP mechanisms are combination of existing TCP
protocols with some modifications and extensions to
address link errors, bandwidth asymmetry, and link
outages
23. DSN communication protocol stack
• The CCSDS File Delivery Protocol (CFDP) has also been
developed for reliable file transport over space links
• Space end-to-end security consist of rate-based Additive-
Increase Multiplicative Decrease (AIMD) congestion
control, whose AIMD parameters are adjusted to
compensate for throughput degradation
24. DSN communication protocol stack
• In order to reduce the effects of blackout conditions on
throughput performance, TP-Planet incorporates a
Blackout State procedure into protocol operation
• In reliable transport protocol, Two novel algorithms, are
used:
– Initial State
– Steady State
25. DSN communication protocol stack
• Initial State replaces the inefficient slow start algorithm in
order to capture link resources in a very fast controlled
manner
• In Steady State a new congestion detection and control
mechanism is deployed to minimize erroneous congestion
decisions due to high link errors
26. DSN communication protocol stack
• Delay tolerant network Research Group (DTNRG)
proposed space/earth protocol stack
• It is mainly dependent of middle layer-Bundling Protocol
layer, which lies between application layer and lower
layers
• Bundling Protocol layer uses store and forward
mechanism
29. References
[1] Xiao Song, Li Yunsong, Bai Baoming, ZhouYouxi, ‘‘The Key
Technologies of Deep Space Communications’’ China
Communications Dec 2006
[2] A. Imbriale, “Large Antennas of the Deep Space Network”
Issued by the Deep-Space Communications and Navigation
Systems Center of Excellence Jet Propulsion Laboratory
publications, California Institute of Technology, Feb 2002
[3] Barry Geldzahler, “Future Plans for the Deep Space Network
(DSN)” Jet Propulsion Laboratory (JPL)California Institute
of Technology September 1, 2009
[4] A. Mileant, S. Hinedi, “Overview of arraying techniques in
deep space network”, TDA progress Report, Jan 1991
30. References
[5] A. Kiely and M. Klimesh, “The ICER Progressive
Wavelet Image Compressor” IPN Progress Report, Page
no. 42-155 November 15, 2003
[6] Joseph I. Statman, Charles D. Edwards, “Coding,
Modulation, and Relays for Deep Space Communication
Mars Rovers Case Study” The 23rd IEEE Convention of
Electrical and Electronics Engineers in Israel, September
2004
36. Deep Space Network
• Three major tracking sites around the globe, with 16 large
antennas, provide continuous communication and
navigation support for the world’s deep space missions
• Currently services- 35 spacecraft both for NASA and
foreign agencies
– Includes missions devoted to planetary, heliophysics,
and astrophysical sciences as well as to technology
demonstration
37. Deep Space Network
• Each complexes consist of:
– One 70m antenna sensitive antenna(track spcaecraft
upto 16 billion km range)
– 34m high efficiency antenna
– 26m antenna for tracking earth orbiting satellites upto
1000 kms
