IV - Extra¶

• Table of contents
• IV - Extra
  • 1. CubeSat performances.
    • 1.1 Measurement of encoding/decoding time.
      • 1.1.1 In simulation.
      • 1.1.2 With Floating-Point OPeration (FLOP)
    • 1.2 Busy memory on CubeSat.
  • 2. Current topics.

1. CubeSat performances.¶

1.1 Measurement of encoding/decoding time.¶

1.1.1 In simulation.¶

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

1000 ticks per milliseconds

Time measurement of data encoding

Printing clock data

Chart of Reed Solomon time measurement

1.1.2 With Floating-Point OPeration (FLOP)¶

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 :

1.2 Busy memory on CubeSat.¶

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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 in the CubeSat Kit. This would be easily done by following chapter II - Tutorial and III - Advanced Project

Research papers proposed on IEEE Website :
[1] Transport layer coding for the land mobile satellite channel
[2] Erasure Codes for Space Communications: Recent Findings and New Challenges

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