Issues with Current 618/620 Broadcast/Multicast Proposal

1. Issues with Current 618/620 Broadcast/Multicast Proposal • Problem with proposed AN usage/format • The format shown in Sita’s proposal includes an agency code followed by a dash and then a designation for a group of aircraft (example shows a fleet mnemonic) • Aircraft registration numbers are assigned with the country code being the prefix followed by a dash followed by a series of numbers • In the majority of cases, the country code prefix is two characters which could coincide with an agency code • For example: • EK = Emirates = Armenia • C6 = Canjet = Bahamas • OO = Skywest = Belgium • CP = Compass = Bolivia • PR = Philippine Airlines = Brazil……….there are more!!!!! • ADDRESSING A MULTICAST MESSAGE IN THIS WAY WILL ALMOST CERTAINLY GUARANTEE DELIVERING A MESSAGE TO AN INAPPROPRIATE AIRCRAFT

2. Issues with Current 618/620 Broadcast/Multicast Proposal • Problem with using existing user-defined SMI codes/labels – • Using existing user-defined labels is NOT practical as multicast messages should not be acknowledged. If we use user-defined labels some times they would be acknowledged and some times they wouldn’t • Extensive modifications would be needed for both service providers and the avionics in order to use established SMI codes/labels but change the protocol for each of them • A new SMI code and uplink label, or set of SMIs/labels, could be used so that the protocol is the same with each transmission

3. Issues with Current 618/620 Broadcast/Multicast Proposal • We will not be “broadcasting” messages and should strike all references to a broadcast • Broadcast implies that all aircraft at all locations will be sent the message • If user X were to send a broadcast message, user Y and user Z would receive it as well. All users would have an issue with this • Likewise CAA A could send messages to aircraft being controlled by CAA B

4. Proposed 620 Modifications • Add two new TEIs to designate multicast messages • MC • Multicast – designates a set of aircraft to which the message will be sent • Unambiguous; won’t get confused with an actual tail number • GA • Geographic Area – designates the geographic area in which the multicast message will be sent

5. Proposed 620 Modifications • Format for the MC Text Element (Ground/Ground) • Use the three character ICAO agency code to identify the agency followed by four characters (alphanumerics) to identify the subgroup • Format for the GA Text Element (Ground/Ground) • Five alphanumeric characters will be used to identify a geographic area • The user and service provider must agree on the geographic area that these five characters represent • Rules for MC and GA TEI usage • Originators will be authenticated • If the MC TEI is present in an input, the GA TEI must be present as well • Inputs must have either the AN/FI TEIs or the MC/GA TEIs in order for the service provider to accept the message and attempt uplink delivery

6. Proposed 620 Modifications • Multicast SMI codes/uplink labels • SMI codes J60 to J6~ which map to uplink labels 60 to 6~ to be used for multicast • These uplink labels would be defined such that no acknowledgement is expected

7. Proposed 618 Modifications • Format for Air/Ground Address Field for Multicast • <NULL>XX1234 • The first character of the uplink address field will be a null character. This will designate a multicast message to the aircraft. • The next two characters, XX, will be the two character agency code (mapped from the three-character agency code contained in the MC TEI) • The next four characters, 1234, will designate a subgroup of aircraft within the agency • Benefits • Since a null character is used to designate multicast, there is no risk of delivering the message to an inappropriate aircraft • The format fills the address field and provides the necessary agency and subgroup addressing information that is needed to deliver the uplink correctly