SCOPE OF THE DOCUMENT

This document addresses the coexistence aspects of WAIC that arise from the use of the frequency band 4200-4400 MHz. Aspects that are addressed are:

A. that a WAIC system does not cause harmful interference to radio altimeters on board other aircraft,

B. that a WAIC system does not cause harmful interference to WAIC systems on board other aircraft,

C. that a WAIC system performs its intended function in the presence of radio emissions from radio altimeters on board other aircraft,

D. that a WAIC system performs its intended function in the presence of radio emissions from WAIC systems on board other aircraft.

The issue A above stems directly from Resolution 424 (WRC-15) [2] giving radio altimeters priority over WAIC systems. The issues B, C and D stem from WAIC being related to safety and regularity of flight and the resulting need to assure they can operate in the presence of other users of the band, namely radio altimeters and WAIC systems on board other aircraft.

The issues A and B above are addressed in this MASPS by the introduction of limits on the emitted RF power (power spectral flux density and total power flux density) of a WAIC system installed on board an aircraft, as specified by the requirement PR#1. PR#1 is comprised of two requirements, PR#1a and PR#1b, (see section 3.4.1.2). The power limits assure that the interference power received by radio altimeters and WAIC systems on board other aircraft will not cause any degradation of performance for those systems. The issues C and D above are addressed by introducing the requirement PR#2 (see section 3.4.1.2) and the associated interference susceptibility of WAIC systems. Jointly, the requirements PR#1 and PR#2 assure coexistence of a WAIC system installed on board the aircraft that is undergoing certification with radio altimeters and WAIC systems on board other aircraft.

This MASPS does not address the coexistence of WAIC systems with radio altimeters on board the same aircraft. As all systems on board a single aircraft are under the control of the aircraft-level system integrator, coexistence on board the same aircraft can be assured and demonstrated by various appropriate means that need not be constrained by this standard. Therefore, this aspect is out of scope of this document.

For the same reason this MASPS does not address the coexistence of different WAIC communication links on board the same aircraft. Throughout this document, a WAIC system is understood as the entirety of all WAIC components on board the same aircraft. That is, a single aircraft contains only a single WAIC system. Assuring that different components of a single WAIC system can coexist is assumed to be the responsibility of the aircraft-level system integrator and is out of scope of this document.

This MASPS does not address the issue of how to define and quantify the intended function of a WAIC system. It is expected that WAIC will serve various aircraft functions which will place different requirements on the wireless communication links. In broad terms, it is understood that the intended function of a WAIC system is to satisfy the data transfer requirements of all the aircraft functions it serves. It is impossible, however, to define precisely what those requirements will be, as different aircraft functions may be architected to use WAIC data links differently. Also, different WAIC system designers may assure data link availability and quality in different ways. These issues are out of scope of this document.

Finally, this MASPS does not address the issue of WAIC system interoperability. From the aircraft-level system integrator perspective, it may be advantageous to have some form of interoperability between WAIC components on board the same aircraft. In the extreme, however, a WAIC system on board a single aircraft could be a collection of dissimilar point-to-point data links (that are not interoperable), each with its own protocols and access rules. This MASPS does not presuppose which particular WAIC system architecture is chosen and whether data links are interoperable. This issue is out of scope of this document.