SOURCEFORGE » RALF » 2015 Erasure codes for Cubesat missions

h1. IV - Extra

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h2. 1. CubeSat performances.

h3. 1.1 Measurement of encoding/decoding time.

h4. 1.1.1 In simulation.

POSIX requires that CLOCKS_PER_SEC equals 1000000 independent of the actual resolution.

p=. !Clock1.png!

*1000 ticks per milliseconds*

p=. !Clock2.png!

*Time measurement of data encoding*

p=. !Clock3.png!

*Printing clock data*

p=. !Time_RS_resized.PNG!

*Chart of Reed Solomon time measurement*

h4. 1.1.2 With Floating-Point OPeration (FLOP)

p=. !FLOPs2.png!

Hence, encoding stands for *O(nbytes x NPAR)* with _nbytes_ is the codeword length, _NPAR_ the number of parity bits.

Since it is a systematic code _nbytes = information_word_length + NPAR_ encoding stands for *O(information_word_length)* with NPAR constant.

Note that a more accurate way would be to consider processor speed and Salvo function OSGetTiks :

p=. !OSGetTiks.PNG!

h3. 1.2 Busy memory on CubeSat.

p=. !Memory.png!

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h2. 2. Current topics.

For the purpose of reliability for Land Mobile Satellite (LMS) channel, a solution is discussed about error correcting code on the Transport layer [1]. Regarding new trends of erasure codes related to satellites [2], an efficient way to perform encoding over LMS channel is to consider _Non-Binary codes_ such as Reed-Solomon code (studied in [[III - Advanced Project]] chapter) or Non-Binary LDPC code (which is highly complex to implement). The Non-Binary characteristic would be to consider a whole packet or a sliced packet as a symbol in order to decrease the error probability of packets. 

A possible continuity to this project could be to integrate the OpenFEC code available on "OpenFEC - Downloads":http://openfec.org/downloads.html in the CubeSat Kit. This would be easily done by following chapter [[II - Tutorial - Simple project on CubeSat Kit|II - Tutorial]] and [[III - Advanced Project|III - Advanced Project]] that could be a integration pattern for any CubeSat project.

Research papers proposed on IEEE Website :

[1] "Transport layer coding for the land mobile satellite channel":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1391458&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D1391458

[2] "Erasure Codes for Space Communications: Recent Findings and New Challenges":http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6333092&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6333092

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