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