SAE J2369-2000 Standards for ATIS Message Sets Delivered over Reduced Bandwidth Media.pdf
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1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefr
2、om, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. TO PLACE A DOCUMENT ORDER; (724) 776-4970 FAX: (724) 776-0790 SAE WEB ADDRESS http:/w
3、ww.sae.org Copyright 2000 Society of Automotive Engineers, Inc. All rights reserved.Printed in U.S.A. SURFACE VEHICLE 400 Commonwealth Drive, Warrendale, PA 15096-0001 STANDARD Submitted for recognition as an American National Standard J2369 ISSUED MAR2000 Issued2000-03 Standards for ATIS Message Se
4、ts Delivered over Reduced Bandwidth Media ForewordThis document outlines the US standard for sending Advanced Traveler Information Services (ATIS) messages over reduced bandwidth media data streams. It specifies the “over the air” format and method for such data messages at a bit level within the st
5、ructure of the host system. The methodology allows a cooperative sharing of the medias total bandwidth with other non-ATIS data services. It allows for further expansion to other ATIS messages such as transit schedules and weather use. It uses a common directory of messages to divide out those messa
6、ges which are the subject of this specification from others. It can be deployed upon multiple physical modulation types, typically wireless in nature. TABLE OF CONTENTS 1.Scope . 6 2.References. 6 2.Related Documents 6 3.Definitions. 7 4.Overview 12 4.1Message Types Supported 12 4.2The Protocol Stac
7、k. 15 4.3Physical Modulation . 15 4.4The Network Layer. 15 4.5Data Tokens and Stream . 16 4.6The Examples Used in this Document . 17 5.Background Concepts 17 5.1Stream Schemas How the information streams work 17 5.2Tokens and Tables The Theory of Data Compression Used 21 5.3Tiles and Grids Efficient
8、 Representations of Latitude and Longitude Values 26 5.4Traffic Models Shared Models of Link Impedance Modeling. 30 5.5Forward Pointers Indirection to Other Data Sources. 36 5.6Frame Bit Stuffing Unused “Flea Bits” in the Message Frame 37 5.7Frame Headers The Concept of Context. 37 5.8Transit Schedu
9、ling Unified Concepts of Multi Modal Scheduling Tables 37 6.Network/Directory Messages 38 SAE J2369 Issued MAR2000 -2- 6.1Overview of Structure other media do not. The overall success or failure of a given host can be compared to other alternatives by consideration of its MER. 3.30 Message ContextTh
10、at portion of the message frame (often also called the header) which establishes default values for expansion of the frame from which the subsequent data (the message payload) may be parsed. 3.31 Message FrameThe envelope of the message, the frame is the outer layer of the message, typically a multi
11、- byte long structure ATIS message. The actual frame length will vary depending on the host media from as few as 22 bytes to as much as 512 bytes in length. 3.32 MessageIn the most general definition, messages are the groups of coherent thoughts which are packaged together in a set of bytes called a
12、 frame. This term is applied in two different ways in this document. First, a message is taken as being the same as the message frame (containing a context and the payload area). Second, the payload of a frame contains one or more messages (each made up of tokens as specified in the context). 3.33 N
13、ational TableThe table of string entries (names) used by all receivers to save on transmitted text. This table rarely changes and is used (with the other tables, typically the local table) to expand passed strings (street names and free text) back into their original format. It is typically not tran
14、smitted over the media as it would not change as the user moved from one local operational area to another. 3.34 Off-hoursNon-peak hours of operation for the host are typically late at night. These hours are often used to send support files and longer messages which conflict with bandwidth needs dur
15、ing daily operations. This may prove a way to distribute small maps for self contained users. On some hosts, this may also be a time slot when higher speed modulation can be employed based on the pre-established stationary nature of the receiver during this time period. SAE J2369 Issued MAR2000 -10-
16、 3.35 Ordinal Post NameThat part of the name appended to the “number” field of a numerical street designation, the “rd” in 3rd street or the “th” in 123th street. 3.36 Payload, of a frameThe portion of a frame which contains the actual data and is used in conjunction with the context and tables to e
17、xpand into a more complex message for use by the receiving device. 3.37 Post-NameThe portion of the name field at the end of the primary name, such as Street in “North Main Street.” 3.38 Pre-NameThe portion of the name field at the beginning before the primary name, such as North in “North Main Stre
18、et.” 3.39 Primary NameThe portion of the name field containing the primary name, such as Main in “North Main Street.” 3.40 Primary TableA table which is used as the “first entry” for table look-ups. Such tables are typically national or local in scope and do not change very often. They can be used i
19、n conjunction with secondary tables to provide a “one of many” look up function, however, the primary table entry is taken as the preferred value. For example, the primary tables might contain “Main Street” as an entry while the secondary tables provide a value such as “Hwy 39” and thus provide a lo
20、cal alias. 3.41 Raw SymbolsThe smallest data element found in the payload of the message frame. They can vary in length from one to many bits and have no octet alignment properties. Symbols are parsed (using the context and tables) to create values which fit into byte aligned memory attributes in re
21、ceiving devices. 3.42 RDS-TMCRadio Data SystemTraffic Message Channel, the proper term for the delivery of incident text messages over the RDS-RBDS modulation format. This format has been deployed in various ways over the low speed subcarrier in the EC and to a small degree in the US (RDS an 1187-bi
22、t/s raw data rate stream with 200 useable bits per second). The message format used consists of hard coded locations (by index value and therefore requiring a common agreed upon map) combined with textual messages (which can be expanded into the local language of choice). There are no link impedance
23、 concepts in the RDS messages, only short textual descriptions. The text look up tables are not that different from the method used here, however, they are never transmitted over the media and do not change or evolve once issued. 3.43 Retransmission TimeThe stream of data found in some broadcast (on
24、eway) hosts containing messages which are repeated frequently. This is referred to as the retransmission time and can vary due to several considerations including policy decisions, other needs for bandwidth and how often the data itself changes. Messages are also retransmitted to ensure that a user
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