Home' RTCA Documents for Review : DO-262D Contents 16
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Performance in a Shared Environment
All requirements for data integrity and timing shall consider the effect of other active
aircraft data links performing transfer operations in both directions at their nominal
It is strongly recommended that the AES receiver design take into account the
existence and/or probable deployment of other mobile communications systems
operating in the airspace, on-board the aircraft, or in the proximate airport
environment. Because the power flux densities (both composite and per carrier) of
such systems may be very much higher than the power flux density of the desired
NGSS downlink carriers, particular attention needs to be paid to the dynamic range of
the AES receiver, to avoid saturation and consequent intermodulation products. At
the same time, the receiver design should provide as much selectivity as possible as
near to the input port as possible in the receiver down-conversion process. Despite
these precautions, it may prove infeasible to independently and simultaneously
operate two NGSSs or a NGSS and a Chapter 4 SARPs-compliant satellite
communications equipment on the same aircraft.
EQUIPMENT PERFORMANCE REQUIREMENTS, STANDARD CONDITIONS
Figure 2-1 provides a graphical guide to the organization of the equipment
performance requirements discussed in the following subsections.
In the event of a conflict between a requirement stated in Section 2 of this document
and a requirement stated in a system-specific 2 appendix, the requirement in the
system-specific appendix shall take precedence.
Precedence is given to the system-specific appendices because, by their
very nature, these appendices represent later, more up-to-date
information than the main body of this document.
Avionics Subsystem Definitions and Overall Requirements
Single-channel AES equipment shall support voice-only or packet-data-only or non-
simultaneous voice-or-data operations. Enhancements to single channel AES
equipment may include optional data rates or simultaneous voice and data operations.
Multi-channel AES equipment shall support either voice-only or packet-data only, or a
combination of simultaneous voice and packet mode data, and may support circuit
mode data services. The manufacturer shall declare any limitations on the
combination of voice and data services supported by the equipment.
NOTE 1: For the purposes of this requirement, a distinction is made between
packet mode data and circuit mode data services. Packet mode data
utilizes services that operate by transferring independent packets of
information over the subnetwork interface. Circuit mode data, such as
facsimile is transferred via a point-to-point connection between the local
(airborne) and remote users. This document places no restriction on the
method used to implement either packet mode or circuit mode data.
Because AMS(R)S circuit mode data requirements have not yet been
established, the minimum requirement is for packet mode.
Digitized voice shall utilize the protocol, including any forward-error-correction coding
and interleaving, determined for the vocoder implementation specified in the
NOTE 2: Digitized voice operation is expected, but not required, to utilize a circuit
2 In this document, the terms system-specific, technique-specific, and satellite-specific all refer to requirements
contained in the normative appendices (Appendix D and later) of this document.
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