MEVA is an acronym for its Spanish name Mejoras a los Enlaces de Voz ATS. MEVA began as a project of the ICAO North American, Central American and Caribbean Regional Office to improve and modernize the aeronautical fixed services in the Caribbean Basin area. The project resulted in the implementation of a regional telecommunication network based on satellite technology.
The MEVA network is a testament to the positive results that can result from the cooperation of many diverse States to solve a common problem. Implementation of the MEVA network has enhanced air traffic safety in the Caribbean, even as air traffic has increased.
Step 1-A Task Force is Created
ICAO first created a task force to evaluate the network in the Caribbean and determine what might need improvement. The task force made a list of problem areas, which was used to create a modernized aeronautical fixed services network for the central Caribbean.
A consultant was then employed to develop a request for proposal (RFP) from the network requirements and the task force delegated authority to the ICAO regional office to approve the RFP. Twenty-four venders received the RFP and seven sent back proposals within the six week time-frame allotted.
A series of meetings was then scheduled to evaluate the proposals. The States, should they accept the proposals, had to determine whether the financial and technical parts of the MEVA project were justifiable and whether the project as a whole was needed. Also on the discussion table was whether the recommended service provider could meet its obligations. In April 1996, after reviewing the recommendations of the Committee, the States awarded the contract to Satellite Communication Systems, Inc. (http://www.sat-tel.com).
MEVA Basic Network Architecture
The MEVA network uses very small aperture terminal (VSAT) satellite technology in a single channel SCPC configuration with no more than a single satellite hop between users. This eliminates the telephone line link between the air traffic control unit and the nearest switching office of the local phone service provider (thought to be the major source of the previously existing problems in the Caribbean basin area).
The network architecture is entirely digital, based on the international standards recommended by the International Telecommunication Union and the International Organization for Standardization. X.25 protocol is used for the data circuits.
The network uses DAMA, PAMA and voice and data compression techniques which allow the network service provider to control bandwidth cost and charge participating countries individually and directly for use of bandwidth. All air traffic control units except San Juan, Puerto Rico are equipped with at least one PAMA circuit that forms part of the AFTN.
The network architecture includes one network management, operations and control center (NMO&CC) located in Miami, FL. The center allows voice and data circuits to be set up and taken down and provides complete network analysis in real time. Network circuit connectivity and dial numbering plan are maintained at the facility and the center is manned around the clock. The back-up center is located at the corporate headquarters of Satellite Communication Systems, Inc. in Hampton, VA.
Network Maintenance
The vendor guarantees an end-to-end circuit availability of 0.997, which means that any given circuit might have a down time of up to about 26 hours per year. The end-to-end circuit availability is defined by the satellite radio frequency (RF) link, calculated to be 0.99766.
The project provides for equipment spares at each location in the network and network equipment is guaranteed for availability for 10 years.
Each terminal on the network is equipped with a maintenance voice order-wire to coordinate troubleshooting between terminals and the control center.
The project includes installation of an 8 hour UPS and alarm system at each terminal for backup power.
Satellite Coverage
The MEVA network uses the new PanAmSat PAS-5 satellite (located at 58� West Longitude). In the event of a transponder failure within the network on PAS-5, the network will be moved to another transponder within 1 hour.
Network Expansion Capability
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Support for up to 32,768 traffic terminal sand over 8 million parts. | |
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Support for over 25,000 simultaneous active connections. | |
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Sizing of the control channels to support capacity in excess of 30,000 calls per hour. | |
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Support for up to 256 individual service definitions. |
Institutional Aspects
ICAO and the original States involved in the MEVA project created 2 formal documents. The first was a multilateral letter of intention to participate and allowed States to begin final negotiations with the service provider immediately. The second covered the legal and administrative aspects of operating a network shared among several States and an international organization, the Corporacion Centroamericana de Servicios de Navegacion Aerea (COCESNA). The documents were developed by the participating States, with ICAO moderating the discussions, and the agreement was later approved by the respective legal departments of the States involved. All of the participating States and COCESNA signed the first letter of participation.