MSAS Signal Structure

MSAS
Title	MSAS Signal Structure
Author(s)	GMV.
Level	Basic
Year of Publication	2011

The Multi-functional Satellite Augmentation System (MSAS) is the Japanese SBAS System: a GPS Augmentation system with the goal of improving its accuracy, integrity, and availability, and that uses the Multifunctional Transport Satellites (MTSAT) owned and operated by the Japanese Ministry of Land, Infrastructure and Transport and the Japan Meteorological Agency (JMA). MSAS for aviation use was declared operational on September 27, 2007.

GPS signals are received at the MSAS Ground Monitor Stations (GMS) and MSAS Monitor & Ranging Stations. These stations check operational status of GPS, and transmit GPS data to Master Control Stations that analyze GPS error and ionospheric delay. Then, these Master stations compute Augmentation information and broadcast it to GEO MTSAT (Multi-functional Transport Satellite) satellites. Those satellites, MTSAT, rebroadcast the correction messages back to Earth, where MSAS-enabled GPS receivers use the MSAS corrections to compute a reliable and accurate position.

MSAS Signal Structure

• Signal characteristics are compliant with ICAO SARPs:

– Frequency ; L1 = 1575.42MHz.

– Bandwidth ; L1 ±2.2 MHz band.

– Data Rate; 500 symbols per Second, 1/2 convolutional encoded with a Forward Error Correction (FEC) code (250 effective bits per second).

– Signal strength on the earth surface >-161dBw at 5 degrees elevation.

• The future lines of improvement of MSAS signals are:

– Band width expansion for L1.

– L5 signal (preparation for Dual-Frequency operations).

– Compatibility & Interoperability achivement between the different SBAS and GNSS constellations.