Title: CPDLC - Start Collision in CPDLC

PDR Reference: 				97060006
Originator Reference: 			PRDSRT
SARPs Document Reference: 		CPDLC SARPs, Section 2.3.7.5
Status: 					ADOPTED
PDR Revision Date: 			22/09/97 (SUBMITTED -> ACCEPTED)
						06/10/97 (ACCEPTED -> PROPOSED)
						29/10/97 (RESOLVED)
PDR Submission Date:			27/06/97
Submitting State/Organization: 		ATNP WG3/SG2
Submitting Author Name: 		Hamelink, J
						Esser, R
Submitting Author E-mail Address: 	Jhamelin@adsystech.com
						esser@nlr.nl
Submitting Author Supplemental 
Contact Information:
SARPs Date: 				IV1.1, March 97
SARPs Language: 				English

Summary of Defect: 

CPDLC/CPDLC collision:
When both the aircraft and ground initiate a CPDLC-start such that the CPDLC-start indication is received prior to the receipt of a CPDLC-start confirmation (i.e., "crossing starts") both sides are locked out from doing anything other than an abort. 

DSC/CPDLC collision:
When both the aircraft initiates a DSC-start and the ground initiates a CPDLC-start such that the CPDLC-start indication is received by the aircraft prior to the receipt of a DSC-start confirmation from the ground and a DSC-start indication is received by the ground prior to the receipt of a CPDLC-start confirmation from the air (i.e.,"crossing starts") both sides are locked out from doing anything other than an abort.  

This is operationally unacceptable and very inefficient.

Assigned SME: 				Sub-Volume II SME

Proposed SARPs amendment: 

Restrict any action taken on a given dialogue, not between a given pair as is currently stated.  If two dialogues end up created between a given air/ground pair the SARPs already have the rules of what to do:
  - A DSC and a CDA between a pair, the air would end (not abort) the DSC
  - A DSC and a NDA between a pair is valid an no action is required
  - Two CDA links between a pair, the first would be aborted
  - Two NDA links between a pair, the first would be aborted    


Modify CPDLC SARPs as follows:

1.  Change 2.3.7.4.1.1.3 from:
If a CPDLC-air-user has invoked a CPDLC-start request, the CPDLC-air-user shall be prohibited from invoking any CPDLC-service primitive pertaining to the ground system addressed in the CPDLC-start service, except the 
CPDLC-user-abort request, until after it has received a CPDLC-start confirmation.

To:
If a CPDLC-air-user has invoked a CPDLC-start request, the CPDLC-air-user shall be prohibited from invoking any CPDLC-service primitive on the CPDLC dialogue initiated by the CPDLC-start request, except the CPDLC-user-abort request, until after it has received a CPDLC-start confirmation.

2. Change 2.3.7.4.2.1.3 from:
If a CPDLC-air-user has invoked a DSC-start request, the CPDLC-air-user shall be prohibited from invoking any CPDLC-service primitive pertaining to the ground system addressed in the DSC-start service, except the CPDLC-user-abort request, until after it has received a CPDLC-start confirmation.

To:
If a CPDLC-air-user has invoked a DSC-start request, the CPDLC-air-user shall be prohibited from invoking any CPDLC-service primitive on the CPDLC dialogue initiated by the DSC-start request, except the CPDLC-user-abort request, until after it has received a DSC-start confirmation.

3. Change 2.3.7.5.1.1.2 from: 
If a CPDLC-ground-user has invoked a CPDLC-start request, the CPDLC-ground-user shall be prohibited from invoking any CPDLC-service primitive, except the CPDLC-user-abort request with that aircraft, until after it has received a CPDLC-start confirmation.

To:
If a CPDLC-ground-user has invoked a CPDLC-start request, the CPDLC-ground-user shall be prohibited from invoking any CPDLC-service primitive on the CPDLC dialogue initiated by the CPDLC-start request, except the CPDLC-user-abort request, until after it has received a CPDLC-start confirmation.

SME Recommendation to CCB: 		-

CCB Decision:				CCB-2(Langen): SUBMITTED
					atnp_ccb_chair: ACCEPTED (22/09/97)
					CCB-3: RESOLVED