SOURCEFORGE » RALF » 2015 Simplified communications schemes of Voyager I probe

h1. Our coding solution

*Cascade coding simulation* 

In this section, we will simulate cascade coding: convolution coding plus RS coding, the communication chain is shown as following:

!Communication_chain_cascade.jpg!

Block diagram of cascade encode and decode

The cascade coding above insert a interleave module in order to improve the coding gain for burst errors. The convolution encoding rate is 2/3, and punched from CC(2,1,7;133,171). The convolution decoding uses soft decoding, so the total code rate is 0.614.

We just use the same simulate block diagram but change the encoding and decoding module as the figure above shows. Then we get the BER data:

BER results of BPSK simulation with cascade coding

!BPSK_simulation_cascade_Results.jpg!

!BER_all_coding_schemes.jpg!

BER simulation of 3 types of coding

We can see above that the cascade coding rate is 0.614, it is higher than Golay code(0.5), but it has almost 5.4dB coding gain.

So if the Down link of voyage 1 uses this cascade coding, there will be at least 5.2 dB coding gain. And we will not use Manchester coding because it increases the channel data rate, and decreases the channel Eb/N0, and then leads to decrease the performance of link. So this is our solution for Voyager 1 Down link.