Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2271

c) for a reply probability equal to 0.25 or less: the smaller of 10 interrogations per 3 dB beam dwell or 125 interrogations per second. Note.— These limits have been defined in order to minimize the RF pollution generated by such a method while keeping a minimum of replies to allow acquisition of aircraft within a beam dwell. 3.1.2.5.2.1.4.2 Field content for a selectively addressed interrogation used by an interrogator without an assigned interrogator code. An interrogator that has not been assigned with a unique discrete interrogator code and is authorized to transmit shall use the II code 0 to perform the selective interrogations. In this case, selectively addressed interrogations used in connection with acquisition using lockout override shall have interrogation field contents restricted as follows: UF = 4, 5, 20 or 21 PC = 0 RR ≠ 16 if RRS = 0 DI = 7 IIS = 0 LOS = 0 except as specified in 3.1.2.5.2.1.5 TMS = 0 Note.— These restrictions permit surveillance and GICB transactions, but prevent the interrogation from making any changes to transponder multisite lockout or communications protocol states. 3.1.2.5.2.1.5 Supplementary acquisition using II equals 0 Note 1.— The acquisition technique defined in 3.1.2.5.2.1.4 provides rapid acquisition for most aircraft. Due to the probabilistic nature of the process, it may take many interrogations to acquire the last aircraft of a large set of aircraft in the same beam dwell and near the same range (termed a local garble zone). Acquisition performance is greatly improved for the acquisition of these aircraft through the use of limited selective lockout using II equals 0. Note 2.— Supplementary acquisition consists of locking out acquired aircraft to II=0 followed by acquisition by means of the Mode S-only all-call interrogation with II=0. Only the aircraft not yet acquired and not yet locked-out will reply resulting in an easier acquisition. 3.1.2.5.2.1.5.1 Lockout within a beam dwell 3.1.2.5.2.1.5.1.1 Recommendation.— When II equals 0 lockout is used to supplement acquisition, all aircraft within the beam dwell of the aircraft being acquired should be commanded to lock out to II equals 0, not just those in the garble zone. Note.— Lockout of all aircraft in the beam dwell will reduce the amount of all-call fruit replies generated to the II equals 0 all-call interrogations. 3.1.2.5.2.1.5.2 Duration of lockout 3.1.2.5.2.1.5.2.1 Interrogators performing supplementary acquisition using II equals 0 shall perform acquisition by transmitting a lockout command for no more than two consecutive scans to each of the aircraft already acquired in the beam dwell containing the garble zone and shall not repeat it before 48 seconds have elapsed. Chapter 3 Annex 10 — Aeronautical Telecommunications 3-21 22/11/07 Note.— Minimizing the lockout time reduces the probability of conflict with the acquisition activities of a neighbouring interrogator that is also using II equals 0 for supplementary acquisition. 3.1.2.5.2.1.5.2.2 Recommendation.— Mode S only all-call interrogations with II=0 for the purpose of supplementary acquisition should take place within a garble zone over no more than two consecutive scans or a maximum of 18 seconds. 3.1.2.5.2.2 All-call reply, downlink format 11 DF CA AA PI The reply to the Mode S-only all-call or the Mode A/C/S all-call interrogation shall be the Mode S all-call reply, downlink format 11. The format of this reply shall consist of these fields: Field Reference DF downlink format 3.1.2.3.2.1.2 CA capability 3.1.2.5.2.2.1 AA address announced 3.1.2.5.2.2.2 PI parity/interrogator identifier 3.1.2.3.2.1.4 3.1.2.5.2.2.1 CA: Capability. This 3-bit (6-8) downlink field shall convey information on the transponder level, the additional information below, and shall be used in formats DF = 11 and DF = 17. Coding signifies Level 1 transponder (surveillance only), and no ability to set CA code 7 and either airborne or on the ground reserved reserved reserved signifies Level 2 or above transponder and ability to set CA code 7 and on the ground signifies Level 2 or above transponder and ability to set CA code 7 and airborne signifies Level 2 or above transponder and ability to set CA code 7 and either airborne or on the ground signifies the DR field is not equal to 0 or the FS field equals 2, 3, 4 or 5, and either airborne or on the ground When the conditions for CA code 7 are not satisfied, Level 2 or above transponders in installations that do not have automatic means to set the on-the-ground condition shall use CA code 6. Aircraft with automatic on-the-ground determination shall use CA code 4 when on the ground and 5 when airborne. Data link capability reports (3.1.2.6.10.2.2) shall be available from aircraft installations that set CA code 4, 5, 6 or 7. Note.— CA codes 1 to 3 are reserved to maintain backward compatibility. 3.1.2.5.2.2.2 AA: Address announced. This 24-bit (9-32) downlink field shall contain the aircraft address which provides unambiguous identification of the aircraft. 3.1.2.5.3 Lockout protocol. The all-call lockout protocol defined in 3.1.2.6.9 shall be used by the interrogator with respect to an aircraft once the address of that specific aircraft has been acquired by an interrogator provided that: Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-22 — the interrogator is using an IC code different from zero; and — the aircraft is located in an area where the interrogator is authorized to use lockout. Note 1.— Following acquisition, a transponder is interrogated by discretely addressed interrogations as prescribed in 3.1.2.6, 3.1.2.7 and 3.1.2.8 and the all-call lockout protocol is used to inhibit replies to further all-call interrogations. Note 2.— Regional IC allocation bodies may define rules limiting the use of selective interrogation and lockout protocol (e.g. no lockout in defined limited area, use of intermittent lockout in defined areas, and no lockout of aircraft not yet equipped with SI code capability). 3.1.2.5.4 Stochastic all-call protocol. The transponder shall execute a random process upon acceptance of a Mode S-only all-call with a PR code equal to 1 to 4 or 9 to 12. A decision to reply shall be made in accordance with the probability specified in the interrogation. A transponder shall not reply if a PR code equal to 5, 6, 7, 13, 14 or 15 is received (3.1.2.5.2.1.1). Note.— The random occurrence of replies makes it possible for the interrogator to acquire closely spaced aircraft, replies from which would otherwise synchronously garble each other. 3.1.2.6 ADDRESSED SURVEILLANCE AND STANDARD LENGTH COMMUNICATION TRANSACTIONS Note 1.— The interrogations described in this section are addressed to specific aircraft. There are two basic interrogation and reply types, short and long. The short interrogations and replies are UF 4 and 5 and DF 4 and 5, while the long interrogations and replies are UF 20 and 21 and DF 20 and 21. Note 2.— The communications protocols are given in 3.1.2.6.11. These protocols describe the control of the data exchange. 3.1.2.6.1 SURVEILLANCE, ALTITUDE REQUEST, UPLINK FORMAT 4 UF PC RR DI SD AP The format of this interrogation shall consist of these fields: Field Reference UF uplink format 3.1.2.3.2.1.1 PC protocol 3.1.2.6.1.1 RR reply request 3.1.2.6.1.2 DI designator identification 3.1.2.6.1.3 SD special designator 3.1.2.6.1.4 AP address/parity 3.1.2.3.2.1.3 3.1.2.6.1.1 PC: Protocol. This 3-bit, (6-8) uplink field shall contain operating commands to the transponder. The PC field shall be ignored for the processing of surveillance or Comm-A interrogations containing DI = 3 (3.1.2.6.1.4.1). Chapter 3 Annex 10 — Aeronautical Telecommunications 3-23 22/11/07 Coding signifies no action signifies non-selective all-call lockout (3.1.2.6.9.2) not assigned not assigned signifies close out Comm-B (3.1.2.6.11.3.2.3) signifies close out uplink ELM (3.1.2.7.4.2.8) signifies close out downlink ELM (3.1.2.7.7.3) not assigned. 3.1.2.6.1.2 RR: Reply request. This 5-bit, (9-13) uplink field shall command the length and content of a requested reply. The last four bits of the 5-bit RR code, transformed into their decimal equivalent, shall designate the BDS1 code (3.1.2.6.11.2 or 3.1.2.6.11.3) of the requested Comm-B message if the most significant bit (MSB) of the RR code is 1 (RR is equal to or greater than 16). Coding RR = 0-15 shall be used to request a reply with surveillance format (DF = 4 or 5); RR = 16-31 shall be used to request a reply with Comm-B format (DF = 20 or 21); RR = 16 shall be used to request transmission of an air-initiated Comm-B according to 3.1.2.6.11.3; RR = 17 shall be used to request a data link capability report according to 3.1.2.6.10.2.2; RR = 18 shall be used to request aircraft identification according to 3.1.2.9; 19-31 are not assigned in section 3.1. Note.— Codes 19-31 are reserved for applications such as data link communications, airborne collision avoidance systems (ACAS), etc. 3.1.2.6.1.3 DI: Designator identification. This 3-bit (14-16) uplink field shall identify the structure of the SD field (3.1.2.6.1.4). Coding signifies SD not assigned except for IIS signifies SD contains multisite and communications control information signifies SD contains control data for extended squitter signifies SD contains SI multisite lockout, broadcast and GICB control information 4-6 signifies SD not assigned signifies SD contains extended data readout request, multisite and communications control information. 3.1.2.6.1.4 SD: Special designator. This 16-bit (17-32) uplink field shall contain control codes which depend on the coding in the DI field. Note.— The special designator (SD) field is provided to accomplish the transfer of multisite, lockout and communications control information from the ground station to the transponder. DI CODE SD FIELD STRUCTURE IIS Annex 10 — Aeronautical Telecommunications Volume IV 22/11/07 3-24 IIS MBS MES LOS RSS TMS TCS RCS SAS SIS LSS RRS IIS RRS LOS TMS 3.1.2.6.1.4.1 Subfields in SD. The SD field shall contain information as follows:

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