Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2301

c) storing the MC field of the segment received. The transponder shall not reply to this interrogation. Receipt of another initializing segment shall result in a new setup within the transponder. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-43 22/11/07 3.1.2.7.4.2.2 Transmission acknowledgement. The transponder shall use the TAS subfield to report the segments received so far in an uplink ELM sequence. The information contained in the TAS subfield shall be continually updated by the transponder as segments are received. Note.— Segments lost in uplink transmission are noted by their absence in the TAS report and are retransmitted by the interrogator which will then send further final segments to assess the extent of message completion. 3.1.2.7.4.2.2.1 TAS, transmission acknowledgement subfield in MD. This 16-bit (17-32) downlink subfield in MD reports the segment numbers received so far in an uplink ELM sequence. Starting with bit 17, which denotes segment number 0, each of the following bits shall be set to ONE if the corresponding segment of the sequence has been received. TAS shall appear in MD if KE equals 1 in the same reply. 3.1.2.7.4.2.3 Intermediate segment transfer. The interrogator shall transfer intermediate segments by transmitting Comm-C interrogations with RC equals 1. The transponder shall store the segments and update TAS only if the setup of 3.1.2.7.4.2.1 is in effect and if the received NC is smaller than the value stored at receipt of the initial segment. No reply shall be generated on receipt of an intermediate segment. Note.— Intermediate segments may be transmitted in any order. 3.1.2.7.4.2.4 Final segment transfer. The interrogator shall transfer a final segment by transmitting a Comm-C interrogation with RC equals 2. The transponder shall store the content of the MC field and update TAS if the setup of 3.1.2.7.4.2.1 is in effect and if the received NC is smaller than the value of the initial segment NC. The transponder shall reply under all circumstances as per 3.1.2.7.4.2.5. Note 1.— This final segment transfer interrogation can contain any message segment. Note 2.— RC equals 2 is transmitted any time that the interrogator wants to receive the TAS subfield in the reply. Therefore, more than one “final” segment may be transferred during the delivery of an uplink ELM. 3.1.2.7.4.2.5 Acknowledgement reply. On receipt of a final segment, the transponder shall transmit a Comm-D reply (DF = 24), with KE equals 1 and with the TAS subfield in the MD field. This reply shall be transmitted at 128 microseconds plus or minus 0.25 microsecond following the sync phase reversal of the interrogation delivering the final segment. 3.1.2.7.4.2.6 Completed message. The transponder shall deem the message complete if all segments announced by NC in the initializing segment have been received. If the message is complete, the message content shall be delivered to the outside via the ELM interface of 3.1.2.10.5.2.1.3 and cleared. No later-arriving segments shall be stored. The TAS content shall remain unchanged until either a new setup is called for (3.1.2.7.4.2.1) or until closeout (3.1.2.7.4.2.8). 3.1.2.7.4.2.7 C-timer restart. The C-timer shall be restarted each time that a received segment is stored and the Comm-C II is not 0. Note.— The requirement for the Comm-C II to be non-zero prevents the C-timer from being restarted during a non-selective uplink ELM transaction. 3.1.2.7.4.2.8 Multisite uplink ELM closeout. The interrogator shall close out a multisite uplink ELM by transmitting either a surveillance or a Comm-A interrogation containing: either DI = 1 IIS = assigned interrogator identifier MES = 2, 6 or 7 (uplink ELM closeout) or DI = 0, 1 or 7 IIS = assigned interrogator identifier PC = 5 (uplink ELM closeout) Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-44 The transponder shall compare the IIS of the interrogation to the Comm-C II and if the interrogator identifiers do not match, the state of the ELM uplink process shall not be changed. If the interrogator identifiers match, the transponder shall set the Comm-C II to 0, reset the C-timer, clear the stored TAS and discard any stored segments of an incomplete message. 3.1.2.7.4.2.9 Automatic multisite uplink ELM closeout. If the C-timer period expires before a multisite closeout has been accomplished the closeout actions described in 3.1.2.7.4.2.8 shall be initiated automatically by the transponder. 3.1.2.7.5 NON-SELECTIVE UPLINK ELM Note.— In cases where the multisite protocols are not required (for example, no overlapping coverage or sensor coordination via ground-to-ground communication), the non-selective uplink ELM protocol may be used. Non-selective uplink ELM delivery shall take place as for multisite uplink ELMs described in 3.1.2.7.4.2. The interrogator shall close out an uplink ELM by transmitting PC equals 5 (uplink ELM closeout) in a surveillance or Comm-A interrogation. On receipt of this command, the transponder shall perform closeout, unless the C-timer is running. If the C-timer is running, indicating that a multisite reservation is in effect, the closeout shall be accomplished as per 3.1.2.7.4.2.8. An uncompleted message, present when the closeout is accepted, shall be cancelled. 3.1.2.7.6 ENHANCED UPLINK ELM PROTOCOL Note.— The enhanced uplink ELM protocol provides a higher data link capacity by permitting parallel delivery of uplink ELM messages by up to sixteen interrogators, one for each II code. Operation without the need for multisite uplink ELM reservations is possible in regions of overlapping coverage for interrogators equipped for the enhanced uplink ELM protocol. The protocol is fully conformant to the standard multisite protocol and thus is compatible with interrogators that are not equipped for the enhanced protocol. 3.1.2.7.6.1 General 3.1.2.7.6.1.1 The interrogator shall determine from the data link capability report whether the transponder supports the enhanced protocols. If the enhanced protocols are not supported by both the interrogator and the transponder, the multisite reservation protocols specified in 3.1.2.7.4.1 shall be used. Note.— If the enhanced protocols are supported, uplink ELMs delivered using the multisite protocol may be delivered without a prior reservation. 3.1.2.7.6.1.2 Recommendation.— If the transponder and the interrogator are equipped for the enhanced protocol, the interrogator should use the enhanced uplink protocol. 3.1.2.7.6.1.3 The transponder shall be capable of storing a sixteen segment message for each of the sixteen II codes. 3.1.2.7.6.2 Reservation processing. The transponder shall support reservation processing for each II code as specified in 3.1.2.7.4.1 Note 1.— Reservation processing is required for interrogators that do not support the enhanced protocol. Note 2.— Since the transponder can process simultaneous uplink ELMs for all sixteen II codes, a reservation will always be granted. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-45 22/11/07 3.1.2.7.6.3 Enhanced uplink ELM delivery and closeout. The transponder shall process received segments separately by II code. For each value of II code, uplink ELM delivery and closeout shall be performed as specified in 3.1.2.7.4.2 except that the MD field used to transmit the technical acknowledgment shall also contain the 4-bit (33-36) IIS subfield. Note.— The interrogator may use the II code contained in the technical acknowledgement in order to verify that it has received the correct technical acknowledgement. 3.1.2.7.7 MULTISITE DOWNLINK ELM PROTOCOL 3.1.2.7.7.1 Initialization. The transponder shall announce the presence of a downlink ELM of n segments by making the binary code corresponding to the decimal value 15 + n available for insertion in the DR field of a surveillance or Comm-B reply, DF equals 4, 5, 20, 21. This announcement shall remain active until the ELM is closed out (3.1.2.7.7.3, 3.1.2.7.8.1). 3.1.2.7.7.1.1 Multisite downlink ELM reservation. An interrogator shall request a reservation for extraction of a downlink ELM by transmitting a surveillance or Comm-A interrogation containing: DI = 1 IIS = assigned interrogator identifier MES = 3 or 6 (downlink ELM reservation request) Note.— A multisite downlink ELM reservation request is normally accompanied by a downlink ELM reservation status request (RSS = 3). This causes the interrogator identifier of the reserved interrogator to be inserted in the UM field of the reply. 3.1.2.7.7.1.1.1 Protocol procedure in response to this interrogation shall depend upon the state of the D-timer which indicates if a downlink ELM reservation is active. This timer shall run for TR seconds. Note 1.— The value of TR is given in 3.1.2.10.3.9.

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