Performance Evaluation of Quasi – Zenith
Satellite System L5S Signal in the Asia-Oceania Region
Nian-Jhen Wu and Shau-Shiun Jan
Takeyasu Sakai

National Cheng Kung University, Taiwan
Electronic Navigation Research Institute, Japan

Motivation and Objective
The overall objective of this project is to develop an equipment to assess the realaugmentation performance of QZSS L5S signal in the Asia-Oceania Region.

Convolution encoder

Signal quality analysis#QZS-2 IGSO : June 1, 2017
The research objectives for the third year (from summer 2019 to spring 2020) are asfollows.
• Analysis of the QZSS L5S signal characteristic• Signal quality analysis of QZSS L5S signal
We have developed a software defined radio (SDR) receiver for all the necessary
L5S signal processing techniques in the first and second year. The flow chart of thethird year project is depicted below, that is, we first analyze the QZSS L5S signal
frequency and modulation type. After the L5S signal is acquired and tracked
successfully, we perform the analyses of the carrier frequency stability, code/carrier
frequency coherence and code phase deviation.
Third year (2019~2020)

Reception of the QZSS L5S signal• Analyze the QZSS L5S signal frequency and modulation type• Analyze the carrier frequency stability• Analyze the code/carrier frequency coherence• Calculate the maximum code phase deviation

Signal Quality Analysis

GNSS signals are continuously broadcast by satellites. Due to the free-space pathloss and interference in the transmitting path, the user receives discontinuous andvarying-strength signals from satellites. When the received signal power is below
specified levels, the ranging error increases since the autocorrelation function causeserrors in the code tracking loop. The carrier-to-noise density ratio (C/N0) is used toshow the signal strength and quality.

 ( NA / 2)2 C
 10log10 2
N0 2Ta IQ the cycle slip number for the carrier phase measurement for each satellite was used
to analyze the signal continuity.

samples without cycle slips
signal continuity 100%
total samples

Experimental Setup
The hardware of the developed SDR receiver consists of a NovAtel GPS-703-GGG
triple-frequency antenna and the Universal Software Radio Peripheral (USRP)platform, which converts radio waves picked up by the antenna into digital copies.
The software implementation of our SDR receiver includes the complete receiver’s
chain, namely, digital signal processing, signal acquisition and tracking of theavailable satellite signals and decoding navigation message.

• Compare the carrier-to-noise ratio of QZSS IGSO/GEO withGPS MEO• Analyze the occurrence of carrier-to-noise ratio drop
• Analyze the L5S signal continuity and signal strength

QZSS L5S Signal
QZSS L5S Modulation

QZSS L5S prototype receiver
The antenna was mounted on the roof of the Department of Aeronautics andAstronautics (DAA) building at National Cheng Kung University (NCKU). The
experiment location is shown in below.

The L5S message is modulated with PRN code by exclusive OR (modulo 2 addition)with the I5 PRN code on the in-phase channel. The 20-bit NH code uses modulo-2
addition to modulate on the quadrature channel.

The experiment location on the roof of DAA building at NCKU, Taiwan

Experimental Results
The comparison of signal strength
The following results were received at 03:45 (local time) on July 24th, 2019. Thevisible satellites for the test are shown in below.

QZSS L5S signal modulation
Different from the L1 signal, the Forward Error Correction (FEC) is applied in themodernized CNAV message which contains higher precision representations andnominally more accurate data than the legacy L1 navigation message. The FEC isalso applied in the L5S message. The L5S message bit streams are rate 1/2
convolution encoded with a FEC code. The convolution coding is constraint length
7, with a convolution encoder logic arrangement. The 250 bps L5S messages areextended to 500 sps.

The visible satellites at 03:45 on July 24th, 2019

Performance Evaluation of Quasi – Zenith
Satellite System L5S Signal in the Asia-Oceania Region
Nian-Jhen Wu and Shau-Shiun JanTakeyasu Sakai

National Cheng Kung University, Taiwan
Electronic Navigation Research Institute, JapanThe GPS is stronger than the other signals. The strength of PRN 194 isapproximately 2.9 dB stronger than PRN 196. In the figure, the analysis shows thatdropped when the interference signal was received, which occurred about every 12seconds. The histogram of the signal samples distribution shows most of samples
are located between 40 dB and 45 dB.

The signal strength of QZSS L5S PRN 200 on March 6th, 2020

The comparison and histogram distribution of C/N0After receiving the 2-minute data every hour from March 1st to March 9th, 2020, The
received data without the interference signal at 20:00 on March 6th, 2020 and there
is no C/N0 drops. The following figure show the time interval of occurrence of thereceived interference signal. The signal was received at 12:00 (UTC+8) from March
1st to March 8th, 2020, and the elevation angle was 50 degrees. The time interval ofreceiving the interference signal was about 12 seconds.

Time
06:00
07:00
08:00
09:00
10:00
11:00
12:00
13:00
15:00
16:00
17:00
Averaged

PRN 196
PRN 197
PRN 200
Mean (dB) Std (dB) Mean (dB) Std (dB) Mean (dB) Std (dB)
43.2635
1.769938.7898
1.784936.3738
1.764143.9971
1.773636.4032
1.822343.8290
1.691038.57421.677836.4883
1.810043.4787
1.678737.0803
1.787442.23141.705138.4246
1.702538.3240
1.785640.13101.685538.47121.748041.2670
1.765740.2269
1.640838.4784
1.711242.8695
1.656441.6374
1.716138.3698
1.740742.9247
1.772742.24631.751038.41211.782742.6927
1.792942.9071
1.721738.3735
1.770841.4039
1.736943.6225
1.705138.4247
1.719337.70321.700042.5064
1.712638.4798
1.737539.4119
1.7631The signal strength of QZSS L5S on March 6th, 2020
The figure illustrate the signal data of PRN 200 received from March 1st to March
9th, 2020. The signal is received at 12:00 (UTC+8) every day to evaluate the signal
strength and stability and the elevation angle is 50 degrees. The averaged mean ofC/N0 is 40.6320 dB and the averaged standard deviation was 1.6112 dB.
Date
2020/03/01
2020/03/02
2020/03/03
2020/03/06
2020/03/07
2020/03/08
2020/03/09
Averaged

Mean of C/N0
39.9608
39.5932
40.4670
41.351140.6961
40.600341.8558
40.6320

Std of C/N0
1.69651.74671.5435
1.69351.73291.53701.32801.6112The signal strength of QZSS L5S PRN 200 for one week

Signal continuity

The received data without C/N0 and time interval of the interference signal

We calculate the cycle slip number for the carrier-phase measurement in the filtered
PLL discriminator to analyze the signal continuity. The period for each signal
collection was set at two minutes in the following results. The average continuity ofPRN 196, 197 and 200 are 100 %, 100 % and 100 %.

The signal strength of continuous data
The received data of QZSS PRN 196, 197 and 200 are shown in the below plots
were from March 1st to March 9th, 2020. The orbit of QZSS PRN 196 (J02), PRN
197 (J07) and 200 (J03) from 0:00 to 23:00 on March 6th, 2020.

The orbit of QZSS satellites from 0:00 to 23:00 on March 6th, 2020.
The signal strength of PRN 196, 197 and 200 received on March 6th is shown inbelow. The averaged C/N0 are 42.51 dB, 38.48 dB and 39.41dB, respectively.

Signal continuity of QZSS L5S on March 6th, 2020

Conclusions and Future Work

The signal strength of QZSS L5S PRN 196 and 197 on March 6th, 2020

In the third year project, we analyzed the reception of QZSS L5S signal and applied
the signal quality analysis. We developed the prototype equipment that can acquire,
track and decode the new QZSS L5S signal. According to the QZSS L5S frequencyand modulation type, the signal was required, tracked and decoded successfully. The
one-week continuous data was received and the signal quality analysis was applied.