Techniques used in Deep Space Communication Network

By- Damodar Y. Tampula

Roll No. 8105

Contents

• Introduction

• History

• Motivation

• Scope

• Techniques used in Deep Space

• Conclusion

• References

Introduction

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

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

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

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

Motivation

• Long distance communication

• Very low signal to noise ratio

• High signal propagation delays and data corruption rates

Scope

• Image source coding techniques

• Channel coding techniques

• Deep space network

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

Wavelet Transform of ICER Compression

Ten sub-bands produced by three stages of wavelet decomposition

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

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

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

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

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

Comparison of Turbo and LDPC code

Deep Space Network

DSN communication protocol stack

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)

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

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

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

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

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

Performance Improvement Factor

Conclusions

• Significant improvements – allowing scientists to expand

their scientific horizons and develop new mission

concepts

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

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

Thank You…

Astronomy compels the Soul to look upwards and leads us from this world to another.

-Plato

ARP-142, Colliding Galaxies

Constellation Fornax- 10,000 Galaxies

Sombrero Galaxy

The Tarantula Nebula

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

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

Antennas