Description of Project
Global demand for mobile phone-based communications has exploded over the past 20 years. Proponents of International Mobile Telecommunications (IMT) have responded by pressing for ever-increasing allocation of frequency spectrum for IMT applications through the International Telecommunications Union – Radiocommunication Sector (ITU-R) and through national spectrum management organizations. This has put pressure on frequency bands currently allocated for aeronautical applications to maintain these existing allocations in order to maintain existing functionality and preserve frequency spectrum for future functionality, especially for Aeronautical Mobile (Route) Services (“AM(R)S”) due to the implications to the safety and regularity of flight of existing aircraft.Recent and current actions through the ITU-R and the United States Congress by the proponents of IMT have targeted opening the 3700 – 4200 MHz frequency band for licensed commercial use. This frequency band is currently allocated for VSAT communications, and is adjacent to the aeronautical ARNS band for radio altimeters (“RA band”). In the last cycle of ITU-R (culminating at the World Radiocommunication Conference in November 2015), attempts to obtain an allocation in several potential bands were denied by the efforts of the users of incumbent services in the affected bands. Due to the aforementioned demand, this result can only be viewed as temporary. Indeed, IMT proponents have initiated a bill before the U. S. Congress1 and action before the U.S. Federal Communication Commission (FCC).2
Members of the aerospace industry have suggested that it is imperative to obtain data that characterizes the potential effects of IMT operation on radio altimeters (RAs) operating in the adjacent frequency band (4200 – 4400 MHz). The potential loss of accuracy of RAs due to IMT interference is a safety issue, especially near airports where airplanes are in the landing phase of flight. Empirical data that quantifies the scope of the issue must be provided to the appropriate rule making bodies to ensure they can preserve continued safe operation of aircraft.
The results of the project will provide the participants with data necessary to assess the potential impact of an allocation of adjacent frequency bands for IMT services. This is a necessary first step for ensuring the continued safety of the current aeronautical mobile route services currently allocated in the 4200 – 4400 MHz frequency band.
The objectives of the testing described in this AFE and the accompanying plan are the following:
- Characterize the interference power level at which altitude reported by a set of representative RAs is noticeably affected, goes outside DO-155 or ARINC 707- 7b specified accuracy, and/or is not able to compute an altitude (NCD).
- Characterizetheinterferencesignalbandwidth(equivalenttomultipleemitterson adjacent channels) at which altitude reported by a set of representative RAs is noticeably affected.
- Characterize the effect of interference signal frequency separation from the 4200 – 4400 MHz the band edge.
Note that these out-of-band interference (OOBI) tests will be conducted on a standardized laboratory bench for static platform conditions and at benign environmental conditions.