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Improving Satellite Capacity and RobustnessUCLA & UCSD - Team Internship Program
Christina Yin, Yujia Wang, Alexander Chan
Project Supervisor: Jordan Corey Technical Advisor: Sanford Leong
8PSK and 16APSK encoding allows for 3 bits and 4 bits per symbol to be transmitted, respectively. Compared to legacy encoding which used BPSK and QPSK, (one and two bits per symbol,) we can achieve much higher throughput and thus more efficient and powerful use of bandwidth. QPSK 8PSK 16APSK
WHY 8PSK AND 16APSK?
We achieved higher throughput on both the forward and return links:oHigher quality of service, specifically for video and audio transmissiono Increased transmission robustness for handling partial signal loss
Future Work:o Improve SNR detection for 16APSKo Implement adaptive return link transmission for smaller payload sizeso Research and introduce a more accurate channel model
CONCLUSION AND FUTURE WORK
1. Find new modulation codes for higher transmission, specifically using 8-PSK and 16-APSK constellations
2. Update ROM on transmitting FPGA
3. Edit and implement new encoding / decoding schemes for new modulation codes
FORWARD LINK OBJECTIVE
RETURN LINK ENCODING AND INTERLEAVING
Channel Model:
Objectives1. Design and implement Reed-Solomon encoder2. Design message and header processing for shortened
code, burst interleaving and transmission3. Modify existing RL code to recognize new burst and
header structure and properly recover message.4. Insert modifications into kernel layer of transceiver .
RETURN LINK OVERVIEW
16APSK Image QPSK Image
MODULATION COMPARISON
8PSK AND 16APSK PERFORMANCEPlot demonstrating that 8PSK and 16APSK transmission is properly decoded by the transceiver at the tradeoff of higher power needed per transmission.
To augment existing forward and return link transmission schemes to achieve higher throughput and robustness for BFT-2.
PROJECT OVERVIEW
o Reed-Solomon Code based on Galois Field size 256: Operates on bytes to avoid additional processing and bit waste in the payload.
o Interleaving between bursts: Increase probability of correct message decoding when transmissions are partially lost. Partial loss of transmission in the legacy system requires full re-transmission of the message. Interleaving thus dramatically reduces overhead.
o Shortened code: Reduce overhead by removing zero padding before transmission without any loss of message integrity.
RETURN LINK DESIGN FEATURES
Forward Link
ReturnLink
SGS
FPGA Layer
Satellite
Transceiver
Kernel Layer
Software Layer
Transmissions are first de-interleaved, then decoded following a reverse procedure as detailed in the encoding and interleaving processes above.An additional step is taken to correct errors and erasures in the transmission by using the Forney algorithm.
RETURN LINK DECODING AND DE-INTERLEAVING
Messages are split into transmitted segments called bursts. Each burst requires pre-processing and the attachment of parity bits. Pre-processing messages to be split into integer number of segments. Parity bits generated by an RS encoder are used by the decoder to correct transmission errors.
Images taken from “Big Buck Bunny.”
(Each number corresponds to a particular code rate)
8PSK/16APSKOld Encoding