Ka band Broadband Mobile Earth Station for WINDS Satellite · Ka-band Broadband Mobile Earth Station for . WINDS. Satellite. Akira AKAISHI. 1, Takashi TAKAHASHI. 2, Kazuyoshi KAWASAKI.

Ka-band Broadband Mobile Earth Station

for WINDS Satellite

Akira AKAISHI1, Takashi TAKAHASHI2, Kazuyoshi KAWASAKI3,

Norihiko KATAYAMA4, Byeongpyo JEONG5 and Toshio ASAI6

†National Institute of Information and Communications Technology,

893-1 Hirai, Kashima, Ibaraki, 314-8501 Japan

The National Institute of Information and Communications Technology (NICT) has developed a Ka-band

mobile earth station which achieves 24 Mbps in land mobile regions using the wideband internet engineering

test and demonstration satellite. The mobile earth station is installed with a dual reflector antenna of 650 mm

diameter, a block up converter with an output of 20 W, and a mono-pulse tracking system with 3-axis gimbals

mechanisms for satellite tracking and communications.

Using this terminal, the transmission data rate of 18 Mbps were confirmed. High definition television

(HDTV) transmission was also conducted using an onboard HDTV camera in suburban and expressway

areas. In this test, successful HDTV transmission was confirmed under the moving conditions.

Nomenclature

NICT = National Institute of Information and Communications Technology

WINDS = Wideband Internet Engineering Test and Demonstration Satellite

HDTV = High Definition Television

MBA = Multiple Beam Antenna

USAT = Ultra Small Aperture Terminal

ABS = ATM-based Baseband Switch

BUC = Block Up Converter

iperf = A network testing tool to measure the throughput

UDP = User Datagram Protocol

SSPA = Solid State Power Amplifier

LNA = Low Noise Amplifier

ODU = Outdoor Unit

AIU = Antenna Interface Unit

IDU = Indoor Unit

TDMA = Time Division Multiple Access

I. Introduction

uring natural disasters, such as the Tohoku Region Pacific Coast Earthquake in 2011, all telecommunications

system were interrupted by damage to the terrestrial communication infrastructures. Telecommunication

satellites are considered the most effective means of maintaining communications in the worst-struck disaster zones.

Mobile earth stations that quickly and easily establish a telecommunications link are expected to become particularly

useful for this purpose.

Moreover, terrestrial communications systems have become increasingly linked with broadband internet systems

through optical-fiber networks. This has led to the need for modern satellite communications to have broadband

capability.

1Technical Staff, NICT, 893-1, Hirai, Kashima, Ibaraki, 314-8501, Japan/[email protected] 2 Research Manager, NICT, 893-1, Hirai, Kashima, Ibaraki, 314-8501, Japan/[email protected] 3 Senior Researcher, NICT, 893-1, Hirai, Kashima, Ibaraki, 314-8501, Japan/[email protected] 4 Researcher, NICT, 4-2-1, Nukuikitamachi, Koganei, Tokyo, 184-8795, Japan/[email protected] 5 Senior Researcher, NICT, 2-1-3, Katahira, Aobaku, Sendai, Miyagi, 980-0812, Japan/[email protected] 6 Technical Staff, NICT, 893-1, Hirai, Kashima, Ibaraki, 314-8501, Japan/[email protected]

D

ICSSC 7-10 September 2015, Gold Coast, QLD, Australia 33rd AIAA International Communications Satellite Systems Conference AIAA 2015-4314

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However, the populated C-band and Ku-band satellite systems are insufficient for broadband communications

because of their narrow frequency bandwidth and shortage of usable orbital locations. In contrast, Ka-band satellites

are less frequently used because their availability, which is limited by heavy rain attenuation. However, the Ka-band

offers a promising alternative to broadband communications because of its wide frequency bandwidth.

A wideband internet engineering test and demonstration satellite (WINDS) was successfully launched on

February 23, 2008. The aim was to establish an advanced broadband satellite communications network using the

Ka-band. Following the Tohoku Region Pacific Coast Earthquake, the National Institute of Information and

Communications Technology (NICT) has developed a broadband mobile earth station for disaster

telecommunications. This study presents the mobile ultra-small aperture terminal (USAT) developed by NICT. The

USAT has a 0.65 m diameter antenna with a 20 W block up converter (BUC) mounted on the roof of a van. The

USAT was subjected to satellite aquisition and tracking tests were and data transmission was eveluated by an iperf

user datagram protocol (UDP) test. A high-definition televisin (HDTV) transmission test was also successfully

conducted using an onboard camera in suburban and expressway areas under moving conditions.

II. WINDS Mobile Communications Test System

A. Satellite Links

This section gives an overview of the WINDS repeater1. WINDS supports both the regenerative and bent-pipe

repeater modes, which are based on a TDMA system. WINDS communications payload consists of two multiple

beam antennas (MBAs) with 2.4 m diameter dishes, two active-phased array antennas comprising 128 elements for

transmission and reception, an ATM-based baseband switch (ABS) for the regenerative repeater and IF switch

matrices for the bent-pipe repeater. The MBA dishes are used to establish communications over Japan and Southeast

Asia with 19 fixed-spot beams. Table 1 summarizes the satellite payload parameters of MBA.

The multi-rate demodulator supports four up-link transmission rates; namely, 1.5, 6, 24 and 51 Mbps. Through

this system, user can select the transmission rate suits the desired communications services. The modulator for the

down-link signal uses a fixed data rate of 155 Mbps. Table 2. lists the earth station parameters of the mobile station

road and all-weather conditions. For this purpose, the USAT antenna is equipped with a high-speed automatic

satellite tracking system and a radome to ensure protection from rain and dust.

B. Mobile Communications Test Network

The mobile communications test network was developed as an experimental system for applications such as

maintaining terrestrial communications during disasters. The configuration of the mobile satellite test networks

shown in Fig.1. The mobile earth station is an USAT with parameters listed in Table 2. The opposite earth station is

equipped with a 1.2 m diameter antenna with a 40 W SSPA. This test was conducted in regenerative repeater mode.

The test network was connected to the test PC, a teleconference system and an encoder/decoder. The test PC checks

the connection and data transmission test. The teleconference system establishes contact with both stations, and the

encoder/decoder is used in HDTV transmission. This system operates an internet protocol, which connects any

equipment via the LAN port and operates under the maximum transmission data rate.

Items MBA Remarks

Antenna Two 2.4 m Offset-feedCassegrain Antennas

Frequency RX : 27.5 GHz - 28.06 GHzTX : 17.7 GHz - 18.25 GHz Regenerative Mode

EIRP < 67.9 dBW 66.1 dBW for NICT Kashima

G/T >16.9 dB/K 20.0 dB/k for NICT Kashima

Service Area Japan beam : 9Asian beam : 10

Items Earth Station Remarks

Antenna 0.65 mRingfocus Antenna

Frequency TX : 27.5 GHz - 28.06 GHzRX : 17.7 GHz - 18.25 GHz Regenerative Mode

BUC Output Power 20 W

EIRP 55.5 dBW Nominal

G/T 16.0 dB/K Nominal

Off-axis e.i.r.p.density ITU-R S.524-9

Table 1. Satellite Payload Parameters Table 2. Mobile USAT Parameters



C. Link Budget

Tables 3. shows the link budget between the USAT and the WINDS in regenerative mode under clear sky

conditions. The parameters are set to their measured or nominal values for a realistic estimation. According to the

link budget, the up-link and down-link realizes 24 Mbps transmission and 155 Mbps reception, respectively, with

link margins of 5.2 and 7.6 dB respectively.

Items Up-Link Remarks Down-Link Remarks

USAT⇒WINDS WINDS⇒USAT

Frequency 27.537 GHz 17.7925 GHz

Data Rate 24 Mbps 155 Mbps

EIRP 55.5 dBW Nominal 66.1 dBW WINDS MBA forNICT Kashima

Free Space Loss 212.7 dB NICT Kashima 208.9 dB NICT Kashima

Polarization Loss 0.2 dB 0.2 dB

Atmospheric Loss 0.3 dB 0.2 dB

G/T 20.0 dB/K WINDS MBA forNICT Kashima 16.0 dB/K Nominal

C/N0 90.94 dB-Hz 101.5 dB-Hz

Required C/N0 85.7 dB-Hz 93.9 dB-Hz

Margin 5.2 dB 7.6 dB

Figure 1. Mobile Communications Test Network

Table 3. Link Budget



D. Mobile Earth Station

The mobile earth station was designed to track WINDS while mounted on a moving van. Figure 2. is a block

diagram of the communications system, which comprises an outdoor unit (ODU), an antenna interface unit (AIU)

and an indoor unit (IDU).

The ODU composed of an antenna with a mono-pulse feeder, low-noise amplifiers (LNAs), down-converters and

BUC installed 20 W SSPA. The designed antenna subsystem satisfies two main requirements. First, the RF and

antenna performance must support the required maximum up-link data rate (up to 24 Mbps), and the down-link data

rate (155 Mbps) under clear sky conditions. Second, the antenna must track the satellite within a certain permissible

pointing error. Because no pointing error had been decided for the Ka-band mobile systems, the Ku-band onboard

vessel antenna requirement of (±0.2° peak) was adopted for this system. The system is also installed with an

interlock functions that indicates when the pointing error exceeds the requirement and detect satellite beacon fade.

To satisfy the electromagnetic performance, tracking requirements, and acceptable dimensional constraints, a ring-

focus antenna of 0.65 m diameter was selected. The AIU provides DC power and the standard frequency of 10MHz

to the ODU, GPS data to modem and antenna control GUI data to the external computer. The antenna subsystem (comprising the ODU and the AIU) has three operating modes, namely searching, tracking and

gyro-holding, which are automatically selected by the internal computer. The searching mode, which is basically an open

loop tracking mode, is used for initial acquisition, and for re-acquisition when the satellite has not been tracked. The

tracking mode is a closed-loop tracking. The beacon is used to estimate the pointing error, which is then used to

continuously steer the antenna back to the satellite. A TE21 mode mono-pulse tracking was selected for this closed-

loop tracking because it provides quick and precise error determination properties. The gyro-holding mode points the

antenna toward a consistent location in the sky during periods when the beacon is suddenly lost. Once the beacon is

reacquired, the antenna subsystem switches back to the tracking mode. The requirements of the antenna subsystem are

listed in Table 4.

The IDU operates as a TDMA regenerative modem. The Up-link data rates are 1.5, 6, 24 and 51 Mbps and the

down-link rate is 155 Mbps. This modem has capabilities to track the TDMA timing using GPS positioning data

from AIU and to operate moving speed up to 100 km/h.

Figure 3. and 4. illustrate the outward appearance of the antenna subsystem without the radome and the mobile

earth station installed on the van respectively.

Figure 2. Block Diagram of the Mobile Earth Station



III. Satellite Tracking Test

A. Satellite Acquisition

The satellite acquisition is performed automatically to turn on the power switch only. As experimental results,

the average acquisition time was approximately 4 minutes for the specified value of 12 minutes. After the

acquisition, the antenna will lock and track to the satellite automatically. When the satellite tracking is lost and the

lost time is less than 60 seconds, reacquisition will occurs immediately. This reacquisition is held by the gyro-

holding functions. When the tracking lost time exceeds 60 seconds, the antenna begins to search the satellite. The

acquisition of this case will need for several minutes.

B. Tracking Test

To verify the correct tracking operation of the antenna system, the moving tests were performed for various

situations. Figure 5. shows the moving test track at the expressway entrance. This traveling speed was approximately

30 km/h and the satellite was continuously tracked even on curved section of road and when obscured by obstacle:

namely, the over pass and the expressway gate. Figure 6. Shows the moving track along the expressway, where the

traveling speed was approximately 100 km/h. Again, the satellite was continuously tracked in the presence of

several obstacles such as the over pass and trees. Along these tracks, the red and black dots show the high and low

beacon C/N0 of about 50 dB-Hz and 30 dB-Hz respectively. Therefore, this antenna tracking functions were

operated correctly in the suburban and the expressway routes.

Table 4. Antenna Subsystem Requirements

F

Figure 3. Antenna Subsystem

F

Figure 4. Mobile Earth Station

Items Requirements Remarks

Antenna 650 mm φ Ring-focus Antenna

Frequency TX: 27.5 GHz - 28.05 GHzRX: 17.7 GHz - 18.25 GHz Regenerative Mode

BUC Output Power 20 W (Linear) 40 W (Saturated)

EIRP >55.0 dBW 55.5 dBW Nominal

G/T >13.5 dB/K 16.0 dB/K Nominal

Off-axis e.i.r.p. Density ITU-R S.524-9

Polarization Linear TX, RX parallel

Azimuth Tracking 360° Continuous

Elevation 20° - 90°

Cross Elevation ±15°

Tracking Accuracy <±0.2°

Satellite Acquisition <12 minute Cold Start<1s, for 60 s, lost

Tracking Performance 100 km/h for Seal Road20 km/h for Off-Road

Inter-Lock Beacon Fade or Lost Tracking

IF Interface TX: 1.9 GHz - 2.5 GHzRX: 1.38 GHz - 1.98 GHz Regenerative Mode

Operating Temperature -20 ℃ to +40 ℃

Installed Generator AC 100 V, 2.8 kVA

Power Consumption <1.5 kVA Include Cooling Unit

Mass <120 kg Include Cooling Unit

Dimensions 985 mm φ x 801 mm H x

1386 mm L Include Cooling Unit



C. Beacon Level

The beacon signal levels were also measured simultaneously as beacon C/N0. Figure 7. shows the measured

C/N0 of the moving track presented in Fig. 5. The two C/N0 falls coincide with obstruction by the overpass and the

expressway entrance gate. Figure 8. shows the measured C/N0 of the moving track in Fig. 6. These C/N0 falls

coincide with obstruction by 7 overpasses, an antenna tower of the mobile phone and forest trees

D. Tracking Error

The tracking error was also simultaneously measured during the tracking operation. Figure 9. And 10. show the

measured tracking errors while moving along the tracks of Figs. 5 and 6, respectively. Along the expressway

entrance and expressway, the tracking errors remains bellow 0.09° and 0.11° respectively. According to these results,

the antenna tracking errors satisfy the requirements of < ±0.2°, and the whole error increase with proportion to the

vehicle speed.

F

Figure 5. Moved Track along Expressway

F

Figure 8. Beacon C/N0 along Expressway

F

Figure 7. Beacon C/N0 along Expressway Entrance

F

Figure 6. Moved Track along Expressway

F

Figure 9. Tracking Error along Expressway Entrance

F

Figure 10. Tracking Error along Expressway



IV. Data Transmission Test

A. Link Performances

NICT developed two identical mobile earth stations installed on the van. Two mobile earth stations were

distinguished to USAT#1 and USAT#2. The up-link margins were measured using iperf UDP test varying the output

power for 24 Mbps and 51 Mbps modes. The down-link margin was measured from the C/N0 of the IDU modem.

The actual tested data rates of the up-link were reduced to 18 Mbps and 36 Mbps because of the TDMA slot

assignment constraints and the overhead of the transmission protocol. The results of the link margin measured at

NICT Kashima in Table 5. confirm good agreement between the expected and measured results.

B. Data Transmission Test

The HDTV transmission test was conducted on a city road2, and in suburban and expressway areas. For this

purpose, an onboard camera was installed on the vehicle exterior. Figure 11. And 12. are photographs captured by

the HDTV camera on the moving van in suburban and expressway areas respectively. In this test, the transmission

data rate was 8 Mbps.

Evaluating of the acquired images, we confirmed that the HDTV data were successfully transmitted in most

cases, but were interrupted by obstacles buildings, pedestrian overpasses and utility poles. Once the vehicle had

passed the obstacles, data transmission was frozen at one time but the data transmission was successfully resumed.

This mobile earth station is designed not only for land mobile use, but also ocean use. It has recently been

installed in a reseach ship and used in a tele-operation experiment3.

Table 5. Link Margins

F

Figure 11. Expressway Entrance Gate

F

Figure 12. Expressway Traveing about 100 km/h

Earth Station

Expected Measured Expected Measured Expected Measured

USAT#1 5.2 dB 6.0 dB 2.2 dB -0.1 dB 7.6 dB 6.6 dB

USAT#2 5.2 dB 5.4 dB 2.2 dB 0.3 dB 7.6 dB 7.4 dB

Up-link

24 Mbps Mode

Up-link

51 Mbps Mode

Down-link

155 Mbps Mode



V. Conclusion

NICT has developed a Ka-band mobile earth station with a 650 mm aperture antenna and a 20 W BUC. The

developed mobile earth station can transmit the peak data rate of 24 Mbps using WINDS domestic beams. The

satellite acquisition and tracking performances satisfied the requirements. The earth station tested on a van in

suburban and expressway areas. We confirmed that the antenna operates at the moving speed of 100 km/h. We

further confirmed a transmission data rate of 18 Mbps using the regenerative repeater mode of WINDS. HDTV data

were successfully transmitted as the vehicle traveled along the expressway.

Acknowledgments

The authors thank JEPICO Corporation for the integration of the van, and also thank EM Solutions for the

development of the mobile antenna subsystem as a key subsystem.

References 1“Special Issue on Wideband Internet Engineering Test and Demonstration Satellite (WINDS)”, Journal of the

National Institute of Information and Communications Technology, vol. 54, no. 4, December 2007. 2Akira, A., Takashi, T., Kazuyoshi, K., Norihiko, K., Byeongpyo, J., and Toshio, A., “Ka-band Mobile Earth

Station for WINDS”, 29th International Symposium on Space Technology and Science. 3Takahashi, T., Naoko, Y., Akira, A., Norihiko, K., Morio, T., Naoto, K., Shojiro, I., Tatsuya, F., and Hiroshi, Y.,

“The Tele-operation Experiment of the Hybrid Remotely Operated Vehicle Using Satellite Link” Proceeding of the

34th International Conference on Ocean, Offshore and Arctic Engineering OMAE2015 May 31-June 5, 2015, St,

John’s, NL, Canada.



Ka band Broadband Mobile Earth Station for WINDS Satellite · Ka-band Broadband Mobile Earth Station for . WINDS. Satellite. Akira AKAISHI. 1, Takashi TAKAHASHI. 2, Kazuyoshi KAWASAKI.

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