ISO IEC 17417:2011 pdf – Information technology – Telecommunications and information exchange between systems – Short Distance Visible Light Communication (SDVLC).
ISO IEC 17417 specifies a phsical layer (PHY) and medium access control (MAC) for communication of up to 10 cm distance with an f,,, of 120 MHz using visual bght with the wavelength between 380 nm and 780 nm,
In addition it specifies human-detectable bightness control that is independent ol the modulation for the data transfer.
2 Conformance
Contormant implementations:
• have both a Transmitter and a Receiver;
• use 8810B encoding and may use 2B4B encoding;
• use an fm of 120 MHz as specified in 8.3.
3 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO1IEC 18092:2004, Information technology — Telecommunications and information exchange between systems — Near Field Communication — lntedace and Protocol (NFCIP-1)
ISOlIEC 7498-1. Information technology — Open Systems Interconnection — Basic Reference Model: The Basic Model
ISO1IEC 14165-251. Information technology — Fibre Channel — Part 251: Framing and Signaling (FC-FS)
ITU-T Z. 100, Specification and Description Language (SOL)
RFC 791, Internet Protocol — DARPA Internet Program — Protocol Specification
The choice of which frame structure to use may depend on the communication link status. When the communication link between TransniEtter and Receiver Is established with good alignment, the Data Frame structure is used for data communication. The Visible Frame structure is used to control the visible aspect of the communication beam to notify the user of a link failure (such as misalignment between the two devices) when the communication link between Transmitter and Receiver is not established. The decision of which frame structure to use may be made using the InformatIon in the control header, and when the communication link fails or becomes misaligned, the frame structure type may be changed.
The Visible Frame structure may be also used to cause the devices to show a beam whde not transmitting data, thus making visible the communication link.
9.2 Frame Structure Detail
The frame structure for SDVLC shall consist of Start Indicator, Control Header, and either a series of one or
more MAC PDIJs or a Visible Pattern.
9.2.1 Start Indicator Structure
The Start Indicator structure shall consist of Preamble_I and Preamble_2 as specified below.
Preamble_i shall be (1 O)b repeated 800 tImes. Preamble_i may be used by the Recipient to synchronize the receive data clock to the received data.
For 2B4B encoding, Preamble_2 shall be (ill 10000)b repeated five times. For 8BI1OB encoding, Preamble 2 shall be the 88/lOB K28.i symbol repeated four trnies The Recipient shall check Preamble_2 field, and if Preamble_2 is not correct the Recipient shall consider a frame to not be started. Preamble_2 may be used by the Recipient for symbol synchronization to denote the end of the Preamble_i and the start of PHY data.
The Recipient shall send the status of receiving data to the Sender through the Ack/Nack bit assignments.
When the Sender finishes transmitting the last bit of the frame, it shall start a timeout timer. If the Sender does not receive an Ack for a transmitted frame by the time the timeout timer reaches T_ ack, it shall either retransmit the frame or drop the association. If the Sender receives a Nack for a transmitted frame, it shall either retransmit the frame or drop the association.
T_ _ack shall be 10 ms. Management Message
Management messages stan with an 8-bit Management Message Type field. Table 3 below shows the defined management message types in the Management Message Type field. When the Management Message Type is“0″ or RFU, the Management Message Payload shall be discarded.