Home' RTCA Documents for Review : DO-262D Contents 39
© RTCA, 2018
Signaling and system management actions for circuit-mode calls in either the air-
originated or ground-originated direction shall be queued and processed within the
AES in an order corresponding to each call’s Circuit-mode Priority per Table 2-8, with
the higher Circuit-mode Priority numbers having the higher precedence. The lowest
priority in-progress shall be interrupted immediately if necessary to make AES
resources (e.g., transmitter power, channel unit, vocoder) available for a higher-priority
call of either air or ground origination. If a new ground-originated call has the same or
lower priority as the lowest-priority call in progress, and if sufficient AES resources are
not available to support the new circuit, then the AES shall indicate “busy” to the
If an AES does not support Priority Level 1 (low) non-safety communications, a request
for Priority Level 1 service shall be refused.
When circuit-mode preemption is necessary, the AES channel resources shall be
available within 4 seconds of the user request.
Satellite Subnetwork Data Protocol (Satellite Layer 2)
The AES shall support the satellite subnetwork data protocols specified for the
individual satellite network, as detailed in the appropriate normative appendix.
Implementation of the Satellite Layer 2 Protocols shall include any actions and
protocols necessary to acquire the satellite, maintain a connection over an extended
period of time, transfer digital data and digitized voice information, and participate in
the overall system management functions of the satellite subnetwork.
The AES shall register itself with the satellite system so that it is enabled to receive or
transmit data or voice, as appropriate, on the subnetwork. This registration may occur
either automatically or by manual command.
1. Satellite Layer 2 is a generic term for the internal protocol(s) used
by the NGSS. For information on the context see the MASPS or
RTCA DO-215A, Change 1. This document uses the term Satellite
Layer 2 to avoid confusion with the Satellite Subnetwork
Dependent Protocols discussed in Section 184.108.40.206.3.
2. This registration action is referred to as "system log on", and an
AES which has completed this action is referred to as being in a
Vocoded voice information shall be transmitted and processed in accordance with the
system-specific protocols identified in the appropriate normative portion of the system-
specific appendix. Any voice services supported by the avionics shall be certified by
the satellite network operator as compliant with the voice protocol specified in the
technique-specific appendix or underlying technique-specific documents.
As evidenced by this requirement, this MOPS assumes digital
transmission of voice, as explained in Section 1.5.6.
Vocoder Interoperability with Satellite Subnetwork
The vocoder algorithm implemented in the AES shall exhibit 100% interoperability with
the standard vocoder algorithm used by the underlying satellite telecommunications
architecture. In the event the vocoder algorithm is not identical to the algorithm used
in the satellite subnetwork, the manufacturer shall be responsible for demonstrating
the required 100% interoperability to the satisfaction of the satellite network operator,
and shall be certified as achieving this compliance by the satellite network operator.
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