BS ISO 21460:2015 pdf download – Space data and information transfer systems — Proximity-1 space link protocol — Physical layer.
forward link: That portion of a Proximity space link in which the caller transmits and the responder receives (typically a command link). The term ‘forward’ is used in association with any parameters referring to the forward link. hailing: The persistent activity used to establish a Proximity link by a caller to a responder in either full or half duplex. It does not apply to simplex operations. hailing channel: The forward and return frequency pairs that a caller and responder use to establish physical link communications. physical channel: The RF channel upon which the stream of channel symbols is transferred over a space link in a single direction. PLTU: Proximity Link Transmission Unit, the data unit composed of the Attached Synchronization Marker, the Version-3 Transfer Frame, and the attached Cyclic Redundancy Check (CRC)-32. Proximity link: A full-duplex, half-duplex, or simplex link for the transfer of data between Proximity-1 entities in a session. return link: That portion of a Proximity space link in which the responder transmits and the caller receives (typically a telemetry link). The term ‘return’ is used in association with any parameters referring to the return link. session: A dialog between two or more communicating Proximity link transceivers. NOTE – A session consists of three distinct operational phases: session establishment, data services (which may include resynchronization and/or reconnect subphases), and session termination. Session termination can be coordinated (through the exchange of no-more-data-to-send directives), or, if communication is lost (inability to resynchronize or reconnect), the transceivers will eventually independently conclude the dialog is over. space link: A communications link between transmitting and receiving entities, at least one of which is in space.
2.1 PHYSICAL LAYER OVERVIEW Proximity-1 is a bi-directional Space Link Layer protocol for use by space missions. It consists of a Physical Layer (the subject of this document) and a Data Link Layer (references [2] and [3]). This protocol has been designed to meet the requirements of space missions for efficient transfer of space data over various types and characteristics of Proximity space links. Proximity-1 activities are divided between a send side and a receive side. The send side is concerned with the transmitted physical channel, and also with the acquisition of the received physical channel in order to establish a Proximity-1 link. The operation of the transmitter is state-driven. The receive side is concerned with the reception of data on the received physical channel: the input symbols stream and the protocol data units it contains. Once the receiver is turned on, its operation is modeless. It accepts and processes all valid local and remote directives and received service data units.