1

Common Coding and Synchronization Layer: Next Steps

NASA Optical Communications Working Group17 April 2015

3/9/2015

2

Common Coding & Synch Proposal

3/9/2015

3

Common Coding & Synch Proposal: Next Steps

• NASA has proposed a High Data Throughput Coding & Synch White Book, including:– Physical layer framing (1024-bit header)– Forward Error Correction (DVB-S2)– Channel interleaving

• This White Book proposal is also NASA’s proposal for a common Coding & Sync layer– NASA is requesting participating agencies to evaluate this proposal for

their high data throughput needs– Alterations or alternative proposals will be considered by Optical Comm

Working Group• Optical Comm Working Group should come to a consensus on the

common proposal before collaboration begins with Coding & Synch Working Group

3/9/2015

4

Backup

3/9/2015

Physical Layer Framing

• 1024-bit header is appended to each (interleaved) codeword at physical layer

• Header contents may be encoded separately from payload data with a code that may be decoded at space relay

• Includes information necessary for switching, multiplexing and demultiplexing performed at physical layer– Unique ID– Content specifier (data vs. fill frame)– Channel state – Frame sequence number– Physical layer controlUnique Word

(384b) Interleaved Codeword (64800b)Channel State, FSN, etc. (640b)

1024-bit Header

Forward Error Correction

• Links primarily utilize ½-rate DVB-S2 code– Industry standard, based on ETSI EN 302 307– BCH outer code + LDPC inner code

• Other DVB-S2 code rates may be used with coordination between user and ground relay

BCH LDPC

64,800 code bits

32,400code bits

32,208 source bits

Channel Interleaving

• Channel interleaver is used for all links going through the Earth atmosphere

• Convolutional bit interleaver with data-rate dependent parameters