European Mode S Station Surveillance Co-ordination Interface Control Document

Transcription

1 EUROPEAN ORGANISATION FOR THE SAFETY OF AIR NAVIGATION EUROCONTROL European Mode S Station Surveillance Co-ordination Interface Control Document Edition : 2.06 Edition Date : 9 May 2005 Status : Released Issue Class : General Public EUROPEAN AIR TRAFFIC MANAGEMENT PROGRAMME

2 DOCUMENT IDENTIFICATION SHEET DOCUMENT DESCRIPTION Document Title European Mode S Station Surveillance Co-ordination EATMP INFOCENTRE REFERENCE: 05/05/29-01 PROGRAMME REFERENCE INDEX: EDITION: 2.06 EDITION DATE: 9 May 2005 Abstract Keywords Mode S SSR Monopulse Radar Surveillance Datalink Station PILOT Cluster ATN GDLP SCN IP CONTACT PERSON: Nicolas EERTMANS TEL: 3363 UNIT: DAS/CSM DOCUMENT STATUS AND TYPE STATUS CATEGORY CLASSIFICATION Working Draft Executive Task General Public Draft Specialist Task EATMP Proposed Issue Lower Layer Task Restricted Released Issue INTERNAL REFERENCE NAME: ELECTRONIC BACKUP HOST SYSTEM MEDIA SOFTWARE Microsoft Windows NT4 Type: Microsoft Word 97 Media Identification:

3 European Mode S Station Surveillance Coordination DOCUMENT APPROVAL The following table identifies all management authorities who have successively approved the present issue of this document. AUTHORITY NAME AND SIGNATURE DATE Author Laurent HONET Mode S System TF Chairman Eric POTIER Mode S Programme Manager John LAW Edition : 2.06 Released Issue Page iii

4 European Mode S Station Surveillance Coordination DOCUMENT CHANGE RECORD The following table records the complete history of the successive editions of the present document. EDITION DATE REASON FOR CHANGE Jun 1998 POEMS SCN ICD, Contract Amendment baseline Jan 2001 First version of the European Mode S SCF ICD. SECTIONS PAGES AFFECTED Mar 2001 Missing NNCOP Clarification SUR/POEMS.TSC.RII/NE008 added April 2001 Released Issue. References updated. Chapter Jan 2005 Simplification of TASP initialisation table Table 6-3, , Feb 2005 Inclusion of Internet Protocols Chapter April 2005 Proposed issue following review by MSTF# May 2005 Released Issue - Page iv Released Issue Edition : 2.06

5 European Mode S Station Surveillance Coordination TABLE OF CONTENTS DOCUMENT IDENTIFICATION SHEET...ii DOCUMENT APPROVAL...iii DOCUMENT CHANGE RECORD...iv EXECUTIVE SUMMARY...1 Chapter 1 INTRODUCTION...2 Chapter 2 SCOPE...3 Chapter 3 RELATED DOCUMENTS...4 Chapter 4 OVERVIEW OF INTER-SITE CO-ORDINATION...5 Chapter 5 CLUSTER OPERATION Introduction Standalone operation Autonomous State Central Mode Distributed Mode...11 Chapter 6 CLUSTER CO-ORDINATION PROTOCOLS Introduction Network Monitoring Protocol (NMP) Target Acquisition and Support Protocol (TASP) New Node & Change-over Protocol (NNCOP)...24 Chapter 7 Solution lists Introduction Coverage Maps...27 Chapter 8 SCN Connection Management Introduction Set-up of SCN connections by OLM...31 Edition : 2.06 Released Issue Page v

6 European Mode S Station Surveillance Coordination Chapter 9 Network Overload management Preventive Measures for Network Overload Corrective Measures for Network Overload...33 Annex A Cluster Controller protocols...34 Annex B Definitions...36 Page vi Released Issue Edition : 2.06

7 European Mode S Station Surveillance Coordination EXECUTIVE SUMMARY The present document describes the European Mode S Station Surveillance Co-ordination. Edition : 2.06 Released Issue Page 1

8 European Mode S Station Surveillance Coordination CHAPTER 1 INTRODUCTION Eurocontrol is embarking on an implementation of SSR Mode S ground stations. These will form the next generation of SSR systems and enable the introduction of significant benefits to the ATC environment. Mode S ground stations with overlapping coverage must be co-ordinated to ensure they work correctly from both a surveillance and a data-link point of view. This co-ordination is achieved by a combination of techniques which include using II and SI code allocation, coverage map design (see [Ref.4.]) and providing ground stations with network connections for inter-station coordination. In order to reduce FRUIT and cater for the limited number of II codes available within Mode S, common use of a single II or SI Code within a cluster of ground stations is to be adopted in the European implementation of Mode S. These clustered stations will co-ordinate the handover of aircraft passing between adjacent ground station coverage such that the acquisition performance of the ground stations can be maintained. This will be achieved by means of a Surveillance Co-ordination Network (SCN). The network will enable lockout to be achieved following initial acquisition of an aircraft, thus significantly reducing FRUIT levels and associated garble in the SSR environment. A Surveillance Co-ordination Function (SCF) provides the information interchange over the SCN to allow interrogators to operate in such a cluster. When operating as part of a cluster the station s operation is termed Network Aided. This document describes the protocols necessary to support this operation in any Cluster Mode or State. These Modes include: Central Mode where the cluster operation is maintained by a Cluster Controller (CC); Distributed Mode where the cluster operation is maintained by processes operating at each of the ground stations. In addition to network aided operation within a cluster, the SCF can also support Standalone operation when the connection between ground station and the surveillance co-ordination network is disabled. A separate specification ([Ref.1.]) exists for the European Mode S ground station and the Cluster Controller (CC). This Interface and Control Document defines the interfacing required between the co-ordination network nodes. [Ref.2.] describes the proposed SCF messages coded in ASTERIX format which is the standard to be used for the European Mode S equipment. Page 2 Released Issue Edition : 2.06

9 European Mode S Station Surveillance Coordination CHAPTER 2 SCOPE This specification defines the interface requirements and the message protocols necessary to ensure compatibility between all nodes connected as part of a European Mode S cluster. Edition : 2.06 Released Issue Page 3

10 European Mode S Station Surveillance Coordination CHAPTER 3 RELATED DOCUMENTS The following documents should be read in conjunction with this specification: [Ref.1.] Eurocontrol Mode S Station Functional Specifications; SUR/MODES/EMS- SPE-01 (form. SUR.ET2.ST SPC-01-00), 3.11, 9 May [Ref.2.] EUROCONTROL Standard Document For Surveillance Data Exchange Part 5 Category 017 Mode S Surveillance Coordination Function Messages, SUR.ET2.ST SPC-02-00, Edition: 1.0, October Annex A: Coordinate transformation algorithms for the hand-over of targets between POEMS interrogators. [Ref.3.] European Mode S Station Coverage Map, SUR/MODES/EMS-ICD-03 (form. SUR.ET2.ST SPC-01-00), 1.16, 9 May [Ref.4.] Coverage map definitions for POEMS interrogators, DA255D006/1.3, 5 August Page 4 Released Issue Edition : 2.06

11 European Mode S Station Surveillance Coordination CHAPTER 4 OVERVIEW OF INTER-SITE CO-ORDINATION In order to co-ordinate surveillance activity Mode S radars are connected via a ground network. The overall network topology consists of a large number of interconnected nodes. Some of these nodes which operate with the same II or SI code are grouped into clusters. The nodes within a cluster co-ordinate their Mode S surveillance activities via the network and using a Surveillance Coordination Function (SCF). Each cluster will consist of a number of nodes - radar nodes and the Cluster Controller (CC) node. In Central Mode, surveillance co-ordination in the cluster will be controlled by the CC. However, if the CC fails or is not present the radars will act as a distributed system. In the Distributed Mode the radars will be responsible for the co-ordination between the nodes. This section describes the Surveillance Co-ordination Function (SCF) at the individual cluster nodes which provide the inter-site coordination. The SCF can be considered to consist of two parts, the Communication Process and the Co-ordination Process. Figure 4-1 shows a simplified schematic of this two-part SCF. Edition : 2.06 Released Issue Page 5

12 European Mode S Station Surveillance Coordination RF Head and Interrogator RF Head and Interrogator GS Co-ordination Process CC Co-ordination Process GS Co-ordination Process Co-ordination Environment Communications Environment GS Comms Process CC-GS Connection CC Comms Process CC-GS Connection GS Comms Process GS-GS Connection Key: CC - Cluster Controller, GS - Ground Station Figure 4-1 SCF System Schematic The Communications Process continually synthesises the network topology i.e. the Communications Process knows which nodes can be accessed through the network. The Network Monitoring Protocol (NMP) is used to obtain information on which nodes can currently be seen. The messages within the Network Monitoring Protocol are known as Network Information Messages (NIMs). The Communications Process uses the NMP to continuously examine the network topology, determine the cluster stability and define the Mode and State in which the node should be operating. Depending on the Mode and State, the Communication Process at each cluster node selects the appropriate operating parameters, which consist of: a selected coverage map indicating the surveillance, lockout and datalink coverage to be maintained; the II or SI code to be used by the station; Page 6 Released Issue Edition : 2.06

13 European Mode S Station Surveillance Coordination (c) and where the lockout override shall be applied. When the SCF connection to the SCN is enabled, the station s surveillance operation is Network Aided in that the station uses the network derived information to initiate and support the tracking of targets. When the network connection is disabled the station is now said to be operating surveillance Standalone and the station must acquire and track targets solely through the use of all-calls, and its own internal roll call. When operating standalone or network aided and no stable cluster configuration can be selected, the Communication Process selects the Autonomous State. In this State the station coverage map and II or SI code are selected to ensure that it does not interfere with any other station having overlapping coverage. The Co-ordination Process uses the parameters described in 4.4 to perform track acquisition and support using the Target Acquisition and Support Protocol (TASP). This protocol provides target handover between sites and track information to sites which have had a track miss, see section 6.3. The Cluster Controller will operate one other Protocol, sending instructions to the radar nodes. This protocol is the Central Mode System Control Protocol, described in Appendix A. Figure 4-2 provides an overview of the Surveillance Co-ordination Function (SCF). The Communication Process provides the coverage map and II or SI code to the Co-ordination Process. Edition : 2.06 Released Issue Page 7

14 European Mode S Station Surveillance Coordination Surveillance Operation Network Aided Standalone Operating Modes Surveillance Co-ordination Protocols (Messages passed over the SCN) Network Monitoring Protocol Surveillance Co-ordination Network (SCN) Central Target Acquisition and Support Solution List State State State n -... CtoD DtoC Distributed Target Acquisition and Support Coverage map, II or SI code selection Dependent on Mode and Cluster Stability, select a solution. Cluster Mode & State Determination Central Mode if CC part of cluster; otherwise Distributed Mode. If Cluster is unstable for greater than 3 x T 2 then choose Autonomous State else choose State according to the network topology. Cluster Stability Determination At T2 expiry, establish if the cluster is stable else declare cluster to be unstable. Solution List State State State n -... Network Topology Determination Send NIMs (containing nodes seen and local station status) to all networked nodes. Use received NIMs to synthesise Network Topology. Network Information Messages (NIMs) Note that Standalone operation can be forced by disabling the connection to the SCN thereby forcing the NMP to select the Autonomous state. It shall then be possible to re-load the coverage map and II or SI code parameters associated with all states. To enter network aided operation the connection to the SCN shall be enabled. The NMP shall then select the appropriate Mode and State. CtoD: DtoC: Key to Mode Transitions These Mode transitions shall be made between the Distributed Mode and Central Mode, maintaining the same State. Figure 4-2 Overview of the Surveillance Co-ordination Function Page 8 Released Issue Edition : 2.06

15 European Mode S Station Surveillance Coordination CHAPTER 5 CLUSTER OPERATION 5.1 Introduction The following definitions of Operation, State and Mode have been adopted: (c) Operation - Two types have been defined: (i) (ii) Network aided, where the SCF s connection to the SCN is enabled; Standalone where, the SCF s connection to the SCN is disabled. State - This describes the unique II or SI code and coverage maps (surveillance, datalink, lock-out, intermittent lock-out and lock-out override) with their associated parameters (including power, probability of reply and interlace patterns). Mode - When a node is in Network Aided operation it can operate in (i) (ii) Central Mode i.e. the Cluster Controller Communication Process selects each station State or Distributed Mode i.e. the Communication Process at the radar node determines and selects the State The possible Mode and State transitions are shown in figure Standalone operation The ground station is in standalone operation when its connection to the SCN is disabled and it is functioning in an autonomous State. This operational State may be used for commissioning, maintenance, emergency operations etc Following successful power up tests manual and automatic enabling of the connection between the ground station and the SCN shall be possible to put the station into Network Aided operation. The Communication Process then selects the appropriate Mode Before effectively entering Network Aided operation, the ground station shall be in standalone operation during at least 10 scans. Note: This is to minimise the network load, when a new radar enters the cluster. Edition : 2.06 Released Issue Page 9

16 European Mode S Station Surveillance Coordination 5.3 Autonomous State When the station is operating in an autonomous State, the coverage map and II or SI code are chosen to ensure the station does not interfere with any other station having overlapping coverage Interrogators in the Autonomous State derive all their surveillance acquisitions by All-Call. TASP is not run with any other node on the network The Autonomous State is selected on power up, when the station is operating standalone, or when the available network connections are not able to support a stable cluster The SCF will attempt to promote the node from the autonomous State to another State at the earliest opportunity. 5.4 Central Mode The CC is responsible for selecting interrogators to acquire targets, to monitor the targets positions and to manage track support functions On entering the Central Mode the CC examines the network topology to select the State of each station. The CC informs the connecting cluster stations with a Move Node to New Cluster State message. The CC will compile a global roll-call which is used to control track acquisition and track support. The global roll-call will be created and updated using ASTERIX Cat 48 messages from the ATCC output of all radar nodes in the network When operating in Central Mode, the CC uses the following protocols: Network Monitoring Protocol (NMP) Central Mode System Control Protocol (see appendix A for details) The CC shall send Track Data messages to the radar nodes, when the CC detects a track miss in the category 48 output of that radar. The SCFs are responsible for operating the following protocols: (c) Network Monitoring Protocol (NMP); Central Mode System Control Protocol (see appendix A for details); The acceptance of Track Data messages from the CC The following transitions are possible from Central Mode: Central Mode: the CC announces the new Central State. Distributed Mode: the SCF determines a new Distributed State from the solution list. Page 10 Released Issue Edition : 2.06

17 European Mode S Station Surveillance Coordination 5.5 Distributed Mode Nodes enter Distributed Mode when either the CC fails or is not present (i.e. the CC plays no active part in the operation of the cluster) In Distributed Mode, the individual interrogator SCFs are responsible for: determining the network topology, the cluster stability and selection of the state i.e. the function of the Communication Process (refer to section 4.1). the operation of the surveillance protocols i.e. the function of the Coordination Process (refer to section 4.1) During Distributed Mode operation, the SCFs use the following protocols: (c) Network Monitoring Protocol (NMP) Track Acquisition and Support Protocol (TASP) New Node / Change-over Protocol (NNCOP) The following transitions are possible from Distributed Mode: Distributed Mode: the SCF determines a new Distributed State from the solution list. Central Mode: NMP announces the presence of a CC which will provide the Central State. Edition : 2.06 Released Issue Page 11

18 European Mode S Station Surveillance Coordination CHAPTER 6 CLUSTER CO-ORDINATION PROTOCOLS 6.1 Introduction This section details the protocols required to support Surveillance Coordination Functions operating within the cluster configuration on the Surveillance Co-ordination Network The following definitions are used for co-ordination protocols: (c) A Surveillance Co-ordination Network (SCN) is a predefined group of nodes as listed in the SCF. The network topology is a list of nodes in the SCN, which are operating as network aided, In distributed mode, nodes in a SCN determining the same network topology will form a stable cluster. The cluster will become unstable when all nodes in the cluster do not determine the same network topology. Cluster stability is not relevant in central mode. Note: When a node is operating as Standalone, it is still a member of the group of nodes in a SCN. This is to allow the node to join the desired cluster when it starts to operate as Network Aided. The following timers are used for co-ordination protocols and shall be operational parameters: T1 for the sending of Network Information Messages (range: seconds, with 0.1 second increments), T2 for the determination of the network topology and the cluster stability (range: seconds, with 0.1 second increments), (c) T3, T4 and T5 to detect messages lost in the network (T3 range: 3-15 seconds, T4 range: 1-5 seconds, T5 range: 1-10 seconds, all with 0.1 second increments). Note: It is recommended that T2 is set to be greater than T1, and preferably greater than twice the longest T1 setting of any node in the cluster. In distributed mode a node will only change state following connection/disconnection of another node after the first T2 expiry following T2 expiry on all other nodes. Therefore, changes in distributed mode state may take a period of up to twice the longest T2 period setting of any node in the cluster. Page 12 Released Issue Edition : 2.06

19 European Mode S Station Surveillance Coordination The SCF manages the network and the clusters, i.e. : (c) (d) Determines the network topology, Determines the cluster stability; Determines the Cluster Mode and State; Runs co-ordination protocols to ensure cluster surveillance operation. The message types referred to in the following sections are described in [Ref.2.]. PAF - Track Initialisation (section ) - Track Update (section ) - Track Miss (update with no measured position, section ) - Track Drop (section ). Network Information (section 6.2) SCF SCN. Track Data Request (section ). Track Data (section ). Cancellation of Track Data (section ). Track Data Stop (section ). Track Data Stop Acknowledgement (section ) - New Node / Change-over (section 6.4) - New Node / Change-over reply (section 6.4) Figure 6-1 Distributed Mode Information Flow between SCF/SCF and PAF/SCF PAF SCF In Distributed Mode, the SCF processes the information, indicated in Figure 6-1, received from the PAF (see [Ref.1.], section ) and received over the SCN. The SCF also sends messages over the SCN. In Central Mode, the SCF processes the information indicated in Figure 6-2, received over the SCN from the CC. The SCF also sends messages over the SCF. Network Information (section 6.2) SCN. Track Data (appendix B). Move Node to new Cluster State (section 6.2). Move Node to new Cluster State Ack (section 6.2) CC Figure 6-2 Central Mode information Flow between the SCF and the SCN SCN to the CC. Edition : 2.06 Released Issue Page 13

20 European Mode S Station Surveillance Coordination Note: In Central Mode and Distributed Mode, track data is passed to the PAF from the SCN, for the initiation and maintenance of tracks. 6.2 Network Monitoring Protocol (NMP) This section defines how the Network Topology is maintained and how the states, modes and operations at a node are determined and selected. The syntax of the state tables is as follows: (c) (d) States, Modes And Operations are defined in CAPITALS. The events and corresponding conditions are specified in the first column. Events are in Italic, conditions for the events are in normal font. A reaction to an event and its corresponding condition can be the change to another state as shown by the other columns. In addition an action could be initiated or a message could be sent to create a compatible reaction at the other node. In a particular cell, a state change is specified first and actions or messages are specified below the separating line. Non-specified events will be ignored Monitoring the network topology Table 6-1 shows the operation in which network monitoring shall be performed. The figure also shows under which events and conditions the network monitoring shall be changed. Table 6-1 Monitoring Network Topology EVENTS & CONDITIONS SCF /SCN CONNECTION ENABLED SCF / SCN CONNECTION DISABLED T1 EXPIRY NODE WITH LOWER ADDRESS RECEIVE NIM NIM RECEIVED FROM NODE WITH HIGHER ADDRESS RECEIVE NIM NIM RECEIVED FROM NODE WITH LOWER ADDRESS STAND ALONE OPERATION NETWORK AIDED OPERATION NETWORK AIDED OPERATION STAND ALONE OPERATION NETWORK AIDED OPERATION SEND NIM TO THE NODE WITH THE LOWER ADDRESS NETWORK AIDED OPERATION REPLY WITH NIM ADD NODE TO NETWORK TOPOLOGY NETWORK AIDED OPERATION ADD NODE TO NETWORK TOPOLOGY Page 14 Released Issue Edition : 2.06

21 European Mode S Station Surveillance Coordination The protocol consists of the following stages: At T 1 expiry, the node sends to other nodes of lower address, and which are members of the same SCN, a Network Information Message (NIM). When a node receives a NIM, the node will add the originating node to the network topology. The receiving node will then send a NIM to the originating node if the originating node is a node of a higher address. The 16 bit address of a node is composed of Source Area Code (MSB) and Source Identity Code (LSB) as defined in [Ref.2.]. The NIMs indicate the network topology as seen by transmitting node at (not after) the last T2 expiry, or the currently seen topology if there has been no T2 expiry ever Monitoring the Cluster Mode, Stability and State Table 6-2 specifies on which events and under which conditions state and mode changes shall occur. Table 6-2 Monitor and Select States EVENTS & CONDITIONS DISTRIBUTED MODE CENTRAL MODE AUTONOMOUS STATE DISTR. STATES CENTRAL STATES T2 EXPIRY CC PRESENT RECEIVE MOVE NODE TO NEW CLUSTER STATE T2 EXPIRY CC NOT PRESENT STABLE CLUSTER CENTRAL MODE CLEAR NETWORK TOPOLOGY CENTRAL MODE CLEAR NETWORK TOPOLOGY CENTRAL MODE CLEAR NETWORK TOPOLOGY N/A TO DISTRIBUTED MODE N/A TO DISTRIBUTED MODE CENTRAL MODE DISTR. MODE CLEAR NETWORK TOPOLOGY DETERMINE AND SELECT NEW STATE DISTR. MODE CLEAR NETWORK TOPOLOGY DETERMINE AND SELECT STATE DETERMINE AND SELECT NEW STATE SEND MOVE NODE TO NEW CLUSTER STATE ACK. DISTR. MODE CLEAR NETWORK TOPOLOGY DETERMINE AND SELECT STATE T2 EXPIRY CC NOT PRESENT UNSTABLE CLUSTER UNSTABLE FOR LESS THAN 3 X T 2 T2 EXPIRY CC NOT PRESENT UNSTABLE CLUSTER UNSTABLE FOR MORE THAN 3 X T 2 DISTR. MODE CLEAR NETWORK TOPOLOGY DISTR. MODE CLEAR NETWORK TOPOLOGY DISTR. MODE CLEAR NETWORK TOPOLOGY DISTR. MODE CLEAR NETWORK TOPOLOGY DETERMINE AND SELECT AUTONOMOUS STATE DISTR. MODE CLEAR NETWORK TOPOLOGY DISTR. MODE CLEAR NETWORK TOPOLOGY DETERMINE AND SELECT AUTONOMOUS STATE Note: The state (entry in the solution list) will be selected dependent on the Network Topology. In general the state will remain the same. Only when nodes are added, removed or in case of hardware failures in the cluster or network, will the state change. Edition : 2.06 Released Issue Page 15

22 European Mode S Station Surveillance Coordination At T 2 expiry, if a CC is present in the network topology (detected by its address), the Communication Process selects the Central Mode, otherwise the Distributed Mode is selected. In both modes the cluster stability is assessed. This assessment is achieved by analysing the content of the most recent NIM received from each node within the last T 2 period. If all nodes of the cluster see the same network topology, then the cluster is stable. PAF PAF Node A Node B SCF SCN SCF Figure 6-3 Information and Message Flow between Nodes A and B In Distributed Mode, the Communication Process determines and selects, from the solution list, the State according to the Network Topology if the cluster is stable. In Distributed Mode, if the cluster is unstable, the state is not changed unless the cluster has been unstable for greater than T 2 x 3 seconds. In this case the Communication Process selects the autonomous State. After all processing associated with T 2 expiry, the network topology is cleared in preparation for the next T 2 period. In Central Mode, the State is determined by the CC and included in the Move Node To New Cluster State message. The SCF Communication Process will select the State contained in this message. It shall then send back to the CC the Move Node to New Cluster State Acknowledgement message. 6.3 Target Acquisition and Support Protocol (TASP) This protocol enables the acquisition of targets and the support of target misses through co-ordination over the SCN. To facilitate the acquisition of targets, the protocol ensures that all interrogators are aware of any new tracks entering their coverage. To facilitate the support of target misses, the protocol ensures that a radar node, having one or more track misses in regions covered by other radars of the cluster, can maintain the track using track information from all these radars until successful surveillance is resumed. Page 16 Released Issue Edition : 2.06

23 European Mode S Station Surveillance Coordination The TASP operates upon reception of information from the PAF or upon reception of messages from the SCN (excluding NIMs). At any node, TASP shall operate for all other nodes in the cluster. The following sections and the state tables define the operation of TASP. In these sections only the operation between two nodes (node A and node B) is described : Node A will be receiving information from the PAF and will be providing resulting messages to node B. Node B will be processing these messages from node A and will be sending appropriate reply messages to node A. The configuration is as shown in figure 6.5. It should be noted that for every track of node A, state tables must be maintained for all other nodes in the same cluster as Node A. The syntax of the state tables is as follows: (c) (d) States are defined in CAPITALS. For a particular node, states are maintained for the relationship between that node (node A) and all other nodes (e.g. node B) per track. The following states are recognised: (i) (ii) (iii) (iv) (v) ; the track of node A is not in the overlapping coverage of node A and node B, according to the coverage maps in both nodes. SENDING, node A sends Track Data messages to node B to assist node B in the (re-)acquisition of the target. The track data message sent will be from the latest track update, be it measured or extrapolated. RECEIVING, node A is receiving Track Data messages from node B or is waiting to receive Track Data messages as a result of a Track Data Request message. EXCHANGING, the node A and node B are both sending and receiving Track Data messages. This state could be caused by e.g. misses in both radar on the track during the same period. The track data message sent will be from the latest track update, be it measured or extrapolated. ACQUIRED, the track is in the overlapping coverage of both radar and both radar have acquired the target. The events and corresponding conditions are specified in the first column of the table. Events are in Italic, conditions for the events are in normal font. A more detailed description from each event is given in sections and A reaction to an event and its corresponding condition can be the change to another state as shown in the other columns. In addition to the state change an action could be initiated or a message could sent to create a compatible reaction in the other node. If an action is initiated or messages are generated, it will be shown in the cell under the separating line. Non-specified events shall be ignored. Edition : 2.06 Released Issue Page 17

24 European Mode S Station Surveillance Coordination Table 6-3 TASP Initialisation EVENT & CONDITIONS TRACK INITIATED NOT RECEIVED FROM B IN THE LAST SCAN PERIOD TRACK NOT IN THE COVERAGE OF NODE B TRACK INITIATED RECEIVED FROM B IN THE LAST SCAN PERIOD TRACK NOT IN THE COVERAGE OF NODE B TRACK INITIATED TRACK IN THE COVERAGE OF NODE B INITIAL STATE & ACTIONS SEND CANCELLATION OF TO B SENDING SEND TO B Page 18 Released Issue Edition : 2.06

25 European Mode S Station Surveillance Coordination Table 6-4 TASP State Table STATES SENDING ACQUIRED RECEIVING EXCHANGING EVENT & CONDITIONS TRACK UPDATE TRACK UPDATE WITH MEASURED POSITION TRACK IN THE COVERAGE OF NODE B TRACK UPDATE TRACK UPDATE WITH MEASURED POSITION TRACK NOT IN THE COVERAGE OF NODE B TRACK UPDATE TRACK UPDATE WITH MEASURED POSITION BAD ALTITUDE (CREDIBILITY CHECK FAILED) TRACK UPDATE TRACK UPDATE WITH NO MEASURED POSITION TRACK IN THE COVERAGE OF NODE B TRACK UPDATE TRACK UPDATE WITH NO MEASURED POSITION TRACK NOT IN THE COVERAGE OF NODE B TRACK DROP (NOTE : NO STATE MEANS THAT THE TRACK IS KILLED AND DO NOT EXIST ANYMORE FOR THE NODE. T4 IS ONLY ASSOCIATED TO THE EVENT OF RECEIVING THE STOP ACKNOWLEDGEMENT AND IS NOT ASSOCIATED TO ANY TRACK) SENDING SEND TRACK DATA EXCHANGING SEND TRACK DATA SEND TRACK DATA REQUEST RESET AND START T3 NO STATE SENDING TRACK DATA SEND SEND STOP RESET AND START T4 SEND STOP RESET AND START T4 EXCHANGING SEND SEND REQUEST RESET AND START T3 SEND STOP RESET AND START T4 NO STATE SEND STOP RESET AND START T4 ACQUIRED RECEIVING SEND REQUEST RESET AND START T3 ACQUIRED SEND CANCELLATION OF STOP AND RESET TIMER T3 SEND CANCELLATION OF STOP AND RESET T3 SEND CANCELLATION OF STOP AND RESET T3 RECEIVING SENDING TRACK DATA SEND CANCELLATION OF STOP AND RESET TIMER T3 SEND SEND CANCELLATION OF STOP AND RESET T3 SEND STOP RESET AND START T4 SEND CANCELLATION OF STOP AND RESET T3 SEND STOP RESET AND START T4 EXCHANGING SEND NO STATE SEND STOP RESET AND START T4 NO STATE SEND STOP RESET AND START T4 SEND STOP RESET AND START T4 NO STATE SEND STOP RESET AND START T4 Edition : 2.06 Released Issue Page 19

26 European Mode S Station Surveillance Coordination STATES SENDING ACQUIRED RECEIVING EXCHANGING EVENT & CONDITIONS RECEIVE REQUEST TRACK INITIATED AND MAINTAINED TRACK IN THE COVERAGE OF NODE B RECEIVE REQUEST TRACK INITIATED AND MAINTAINED TRACK NOT IN THE COVERAGE OF NODE B RECEIVE REQUEST TRACK NOT INITIATED AND NOT MAINTAINED RECEIVE TRACK UPDATE WITH MEASURED POSITION RECEIVED CORRELATES WITH THE TRACK UPDATE RECEIVE TRACK UPDATE WITH NO MEASURED POSITION RECEIVE CANCELLATION OF SEND TRACK DATA STOP RESET AND START T4 SEND TRACK DATA STOP RESET AND START T4 SENDING TRACK DATA SEND STOP RESET AND START T4 SENDING TRACK DATA SEND SEND STOP RESET AND START T4 STATE : NO APPLICABLE STATE EXCHANGING SEND SEND STOP RESET AND START T4 EXCHANGING SEND STOP RESET AND START T4 (THE TRACK DOES NOT EXIST AT THE PAF LEVEL NOR AT THE SCF LEVEL) FOR THIS EVENT WITH THE MENTIONED CONDITION SEND STOP RESET AND START T4 (SEE ALSO NOTE FOR THE «TRACK DROP» EVENT) SEND CANCELLATION OF STOP AND RESET TIMER T3 SENDING TRACK DATA SEND CANCELLATION OF STOP AND RESET TIMER T3 SENDING TRACK DATA ACQUIRED SEND CANCELLATION OF STOP AND RESET TIMER T3 ACQUIRED ACQUIRED SEND CANCELLATION OF STOP AND RESET TIMER T3 RECEIVING RESET AND START TIMER T3 ACQUIRED ACQUIRED RECEIVING SENDING TRACK DATA SEND CANCELLATION OF STOP AND RESET TIMER T3 EXCHANGING RESET AND START TIMER T3 RECEIVING TRACK DATA RECEIVE STOP TRACK INITIATED AND MAINTAINED SEND TRACK DATA STOP ACK. SENDING TRACK DATA SEND STOP ACK. SENDING TRACK DATA SEND STOP ACK. SENDING TRACK DATA STOP AND RESET TIMER T3 SENDING TRACK DATA STOP AND RESET TIMER T3 RECEIVE STOP TRACK NOT INITIATED AND NOT MAINTAINED RECEIVE STOP ACKNOWLEDGEMENT TRACK NOT INITIATED OR NOT MAINTAINED RECEIVE STOP ACKNOWLEDGEMENT TRACK INITIATED AND MAINTAINED STOP AND RESET TIMER T4 STATE : NO APPLICABLE STATE SEND STOP ACK. SEND STOP ACK. (THE TRACK DOES NOT EXIST AT THE PAF LEVEL NOR AT THE SCF LEVEL) FOR THIS EVENT SEND STOP ACKNOWLEDGEMENT STATE : NO APPLICABLE STATE (THE TRACK DOES NOT EXIST AT THE PAF LEVEL NOR AT THE SCF LEVEL) FOR THIS EVENT SENDING TRACK DATA STOP AND RESET TIMER T4 STOP AND RESET TIMER T4 ACQUIRED STOP AND RESET TIMER T4 RECEIVING STOP AND RESET TIMER T4 EXCHANGING STOP AND RESET TIMER T4 Page 20 Released Issue Edition : 2.06

27 European Mode S Station Surveillance Coordination STATES SENDING ACQUIRED RECEIVING EXCHANGING EVENT & CONDITIONS T3 EXPIRY LAST TRACK UPDATE WITH NO MEASURED POSITION T4 EXPIRY TRACK NOT INITIATED AND NOT MAINTAINED STOP AND RESET T3 EXCHANGING SEND REQUEST RESET AND START T3 RECEIVING SEND REQUEST RESET AND START T3 STATE : NO APPLICABLE STATE RECEIVING SEND REQUEST RESET AND START T3 EXCHANGING SEND REQUEST RESET AND START T3 (THE TRACK DOES NOT EXIST AT THE PAF LEVEL NOR AT THE SCF LEVEL) FOR THIS EVENT WITH THE MENTIONED CONDITION T4 EXPIRY TRACK INITIATED AND MAINTAINED SEND TRACK DATA STOP RESET AND START T4 SENDING TRACK DATA SEND STOP RESET AND START T4 SEND STOP RESET AND START T4 ACQUIRED SEND STOP RESET AND START T4 RECEIVING SEND STOP RESET AND START T4 EXCHANGING SEND STOP RESET AND START T4 The sections that follow (6.3.2 and 6.3.3) provide general guidance information about TASP and should be used to aid the understanding of the state tables, which forms the basis of the requirement Information from the PAF This section explains that part of the state table describing the operation of the SCF at node A when receiving information from the PAF. This section only applies to an SCF operating in Distributed Mode Track Initialisation If the track is in the overlapping coverage with node B provided that the network overload prevention measure is not active, then the SCF initialises the state for node B to SENDING. This allows the other sensors in the cluster to be informed about the existence of the track. In all other cases the state is selected Track Update When during the track update, node A detects that the track has (re-)entered the overlapping coverage of node B and when the network overload prevention measure is not active, then node A sets the state to SENDING or EXCHANGING. This allows the other sensors in the cluster to be informed about the existence of the aircraft, when it enters their coverage. In case the state is RECEIVING or EXCHANGING and the track is updated with a measured position, a Cancellation of Track Data Edition : 2.06 Released Issue Page 21

28 European Mode S Station Surveillance Coordination message is sent and the state is set to ACQUIRED or SENDING TRACK DATA respectively. Node A returns to the state, when the track is no longer in the surveillance coverage of node B. A Track Data Stop message is sent in case node A has been sending Track Data messages Track Miss (Track update with no measured position) When radar node A detects a miss and when the network overload prevention measure is not active, it sends a Track Data Request message to all radar with overlapping coverage (for example node B) and selects the RECEIVING or EXCHANGING state Track Drop For an explanation of the conditions to drop a track see [Ref.1.]: section When a track is dropped at node A, node A sends Track Data Stop messages to the other nodes in the cluster. The track and state tables for the track cease to exist Messages to/from the SCN This section explains that part of the state table describing the operation of the SCF at node A and node B when receiving or sending messages through the SCN. All sections of apply to an SCF operating in Distributed Mode Reception of Track Data Request Receipt at node A of a Track Data Request Message from node B indicates that node B requires track support following a miss for its track. If the track is initiated and maintained at node A and in the coverage of node B according to the maps at node A, node A selects the SENDING or EXCHANGING state and it sends Track Data to node B. On entry of those states node A sends the Track Data message immediately using the most recent track update. Afterwards it sends Track Data to node B each time the track is updated at node A. In all other cases node A sends to node B a Track Data Stop message Reception of Track Data Reception of Track Data occurs at node A; in the RECEIVING or EXCHANGING states, when node A has had requested support for this track from node B, or; Page 22 Released Issue Edition : 2.06

29 European Mode S Station Surveillance Coordination in any state (mostly ) or before a state has been defined, when node B has detected that a track has entered the surveillance coverage of node A. The received track data may be used by the PAF at node A to initialise a new track or maintain an existing one. On receipt of a track data message from node B, the SCF at node A shall: if the last track update at node A was achieved using a measured position, node A selects the ACQUIRED or SENDING state or it remains in the state. Node A also sends a Cancellation of Track Data message to node B; if the last track update at node A was not achieved using measured position, node A remains in the same state. On receipt of a Track Data message from node B, node A shall stop the timer T 3. Timer T 3 is only active in the RECEIVING and EXCHANGING states, it will be activated on transition to those states and reset and started again on each track-data message. On exit of those states the timer will be reset and stopped Reception of Cancellation of Track Data On receipt of a Cancellation of Track Data Message from node B, node A stops the sending of track data by selecting the ACQUIRED state (after the SENDING state) or RECEIVING state (after the EXCHANGING state) Reception of Track Data Stop On receipt of a Track Data Stop message from node B, node A sends a Track Data Stop Acknowledgement and stops the timer T 3, if it is active (See section ). Before sending the Track Data Stop, node B will have selected the state or will have dropped the track. Node A will select the SENDING state for node B if it is maintaining a track for the aircraft (the existing state is not ). Node B will receive track data from node A until; Node A also detects that the track has left the coverage of node B. Node B re-acquires the target, because the aircraft has returned to the coverage of node B. When an aircraft enters or exits the coverage of a sensor, Track Data messages will be exchanged until both nodes agree on the in coverage or out of coverage situation. This use of Track Data messages and Track Data Stop message will compensate for map inaccuracies. Edition : 2.06 Released Issue Page 23

30 European Mode S Station Surveillance Coordination Reception of Track Data Stop Acknowledge On receipt of a Track Data Stop Acknowledge message from node B, node A shall stop the timer T 4. The sending of Track Data Stop shall be guarded by acknowledgement, which should be received before timer T 4 expires. If this acknowledgement is not received before the expiry of T 4, the Track Data Stop will be repeated and the T 4 timer reset and re-started. Note: In case the network connection has been broken, the loop of sending Track Data Stop, time out T 4 and resending Track Data Stop will be interrupted by NMP Duplicate Address; The protocol allows target acquisition and target support for duplicate Mode S address tracks. (c) (d) (e) (f) (g) (h) Whenever a message is received with a Mode S Address for which two or more tracks are present in the receiving node, TASP should be run for every track with that address. When an SCF receives two or more Track Data messages with different positions but the same address, it is up to the PAF to maintain the tracks correctly, even if there are e.g. duplicates or triplicates (see [Ref.1.], section [E2]). If a node has tracks with duplicate Mode-S addresses, it shall assign a Duplicate Address Reference Number to each track (DRN). All track data messages sent for a track which has a known duplicate address shall include the DRN assigned to that track ([Ref.2.]). If track data is received from node A with a DRN and this track data correlates with an existing track, the DRN will be inserted in subsequent Cancellation of Track Data messages sent for this track for node A. If a Track Data message is received from node A without a DRN and this track data correlates with an existing track, subsequent Cancellation of Track Data message sent for this track to node A will not include DRN. When a node receives a Cancellation of Track Data message with a DRN included, it will only process this message for the track, which has the same DRN assigned to it. The SCF shall ignore a Cancel Track Data message, which does not contain a DRN, if a DRN is expected. 6.4 New Node & Change-over Protocol (NNCOP) This NNCOP protocol is used by a node when entering a cluster or when executing channel change-over. This protocol is only used in Distributed Page 24 Released Issue Edition : 2.06

31 European Mode S Station Surveillance Coordination Mode. The protocol shall be executed for all other nodes in the cluster. The purpose of the protocol is; to inform the other nodes (e.g. node B) in the cluster in case of a change-over (e.g. node A); to reduce the network load when a new node enters the cluster or in case of a change-over. Figure 6.8 describes the NNCOP for Node A sending and receiving messages from Node B. Table 6-5 NNCOP State Table EVENTS TASP NOT RUNNING TASP RUNNING A IS SWITCHING TO A NEW STATE, WHICH IS A STATE OF THE DISTRIBUTED MODE OR A HAS EXPERIENCED A SWITCH-OVER RECEPTION OF NEW NODE / CHANGE-OVER MESSAGE FROM B TIMER T 5 EXPIRED RECEPTION OF NEW NODE / CHANGE-OVER REPLY MESSAGE FROM NODE B A DETECTS NEW NODE B CREATE TASP STATE TABLES FOR B (SET STATES TO ) SEND NEW NODE / CHANGE- OVER MESSAGE TO B START TIMER T 5 TASP RUNNING CREATE TASP STATE TABLES FOR B (SET STATES TO ) SET INITIAL STATES FOR TASP STATE TABLES FOR B SEND NEW NODE / CHANGE- OVER REPLY MESSAGE TO NODE B SEND NEW NODE / CHANGE- OVER NODE MESSAGE TO B RESTART TIMER T 5 TASP RUNNING SET INITIAL STATES FOR TASP STATE TABLES FOR B STOP T 5 CREATE TASP STATE TABLE (SET STATES TO ) SET INITIAL STATES FOR TASP STATE TABLES FOR B SEND NEW NODE / CHANGE- OVER REPLY MESSAGE TO NODE B The sections that follow (6.4.1 and 6.4.2) provide general guidance information about NNCOP and should be used to aid the understanding of the state tables, which forms the basis of the requirement State Definition Constraints TASP RUNNING, in this state TASP is active at node A for node B. TASP NOT RUNNING, in this state TASP is inactive at node A for node B. The New Node / Change-over message and the New Node / Changeover Reply message include the unique Mode-S addresses of aircraft tracked by the sending node which are located in the overlapping coverage with the receiving node. Edition : 2.06 Released Issue Page 25

32 European Mode S Station Surveillance Coordination The Set Initial States for the TASP State Table process initialises the state for the track node pair to ACQUIRED, if the mode S Address has been received in the message from that node, else the state shall be set to. Note that this process modifies all states in the TASP State Table for node B and no TASP actions are permitted for node B while the process is running. (c) For the New Node / Change-over message and the New Node / Change-over Reply message, the following processing is required: (i) (ii) In the sending node no duplicate Mode S Addresses shall be sent. In the receiving node, received Mode-S addresses corresponding to two or more tracks shall be ignored. The TASP state shall be set to for these tracks. Page 26 Released Issue Edition : 2.06

33 European Mode S Station Surveillance Coordination CHAPTER 7 SOLUTION LISTS 7.1 Introduction Each node SCF on the cluster determines the network topology and cluster stability and hence from this selects the State to be used. Each State has an associated solution list entry which specifies the coverage map, the II and/or SI code configuration to be used, and the site specific set-up, including Mode Interlace Pattern, Radiated Power (for range and azimuth) settings, etc. 7.2 Coverage Maps For further information refer to [Ref.1.], [Ref.3.]and [Ref.4.]. These documents contain all requirements related to coverage maps Each cluster node will store and access coverage maps. There will be one Coverage Map for each possible State A map at a ground station is built up from a number of cells with the exception of the lockout override map which is defined on a per sector basis. Each cell represents a volume of airspace approximately 5NM x 5NM (refer to Reference 5 for further details) and with a vertical extent defined as the minimum and maximum altitude at which the station can provide cover. Each radar node that has any vertical overlap with the cell of another node is listed for that cell A coverage map shall consist of: (c) (d) (e) Surveillance map; Intermittent lock-out map; Lock-out map; Datalink map; Lock-out override map Surveillance map A bit is assigned to each radar that could carry out surveillance in the cell volume. The bits are set to 1 for radars that are expected to carry out surveillance in the cell volume and set to 0 for radars not providing surveillance coverage for that cell. Edition : 2.06 Released Issue Page 27

34 European Mode S Station Surveillance Coordination Intermittent lock-out map Lock-out map Datalink map This map defines where the ground station shall apply intermittent lock out. This map defines where the ground station shall have Lock-out responsibility and apply lock out. The datalink bit is used to indicate whether the station informs the GDLP and Local User on the full acquisition of targets which enter the cell. Full acquisition is defined as confirmation of a non-zero value for the Mode S subnetwork version field of BDS 1, Lock-out override map This map defines the sectors to be used for lock-out override In addition the Solution Lists will include Mode Interlace Pattern, Power settings associated with the site Range and Azimuth requirements and other parameter settings that are determined as necessary for the operation of each and every State. Page 28 Released Issue Edition : 2.06

35 European Mode S Station Surveillance Coordination CHAPTER 8 SCN CONNECTION MANAGEMENT 8.1 Introduction The Connection Management Service facilitates connection of the SCF to the SCN to enable the operation of the Cluster Co-ordination Protocols defined in section 6. The Connection Management Service is part of the Output Link Management (OLM) defined in [Ref.1.]. Connection management only operates when the SCF is operating networkaided, either in central or in distributed mode. Cluster Co-ordination Protocols Connection Management (OLM) Network (e.g. X.25, TCP/IP) The table specifies the environment of Connection Management. The Cluster Co-ordination Protocols use the SCF Connection Management Service by passing to it the data to be transmitted and the destination ground station address. The connections to be managed are full duplex logical links between ground station SCFs via the SCN. For the purposes of this document, it is assumed that the SCN will provide interfaces complying to: ITU-T Recommendation X.25 (1988) or, TCP/IP internet standards as defined by RFC793 and RFC791. For X.25, a full duplex logical link refers to an established Switched Virtual Circuit (SVC). For TCP/IP, a full duplex logical link refers to an established TCP connection. Edition : 2.06 Released Issue Page 29

36 European Mode S Station Surveillance Coordination Figure 8-1 represents an example of an X.25 configuration with 3 stations and Node 1: EMS C C H H A A N N N N E E L L 1 2 OLM Node 2: EMS C C H H A A N N N N E E L L 1 2 DTE DTE OLM DTE DTE DCE DCE X.25 Wide Area Network DCE DCE DCE DCE DCE DCE DTE DTE DTE OLM DTE Node 3: CC C C H H A A N N N N E E L L 1 2 Node 4: EMS Figure 8-1 Example SCN Cluster using X.25 a Cluster Controller and Figure 8-2 represents an example of an IP configuration with 3 stations and a Cluster Controller Page 30 Released Issue Edition : 2.06