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WO1992008303A1 - Multichannel operation of rds - Google Patents

Multichannel operation of rds Download PDF

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Publication number
WO1992008303A1
WO1992008303A1 PCT/GB1991/001871 GB9101871W WO9208303A1 WO 1992008303 A1 WO1992008303 A1 WO 1992008303A1 GB 9101871 W GB9101871 W GB 9101871W WO 9208303 A1 WO9208303 A1 WO 9208303A1
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WO
WIPO (PCT)
Prior art keywords
data
channels
channel
tmc
rds
Prior art date
Application number
PCT/GB1991/001871
Other languages
French (fr)
Inventor
John Lawrence Riley
Andrew Kevin Mcparland
Simon John Parnall
Original Assignee
British Broadcasting Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Broadcasting Corporation filed Critical British Broadcasting Corporation
Priority to JP3517126A priority Critical patent/JPH06504413A/en
Priority to AU87493/91A priority patent/AU649740B2/en
Publication of WO1992008303A1 publication Critical patent/WO1992008303A1/en
Priority to FI931853A priority patent/FI931853L/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/18—Arrangements for synchronising broadcast or distribution via plural systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J4/00—Combined time-division and frequency-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/28—Arrangements for simultaneous broadcast of plural pieces of information
    • H04H20/33—Arrangements for simultaneous broadcast of plural pieces of information by plural channels
    • H04H20/34—Arrangements for simultaneous broadcast of plural pieces of information by plural channels using an out-of-band subcarrier signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H2201/00—Aspects of broadcast communication
    • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
    • H04H2201/13—Aspects of broadcast communication characterised by the type of broadcast system radio data system/radio broadcast data system [RDS/RBDS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H2201/00—Aspects of broadcast communication
    • H04H2201/40—Aspects of broadcast communication characterised in that additional data relating to the broadcast data are available via a different channel than the broadcast channel

Definitions

  • the present invention relates to the Radio Data System (RDS) and, in particular, its use as a Traffic Message Channel ('TMC').
  • RDS Radio Data System
  • 'TMC' Traffic Message Channel
  • TMC Traffic Message Channel
  • TMC data cannot occupy all the available capacity of an RDS channel: other background data must also be present.
  • Other types of RDS data occupy more than three quarters of the data capacity available and, consequently, the capacity available for TMC is likely to be limited to 10-20% of the total, that is, one or two groups per second out of the eleven provided on the RDS system.
  • the minimum data rates stipulated for the main RDS features prevent the TMC data capacity in any one channel being greater than this.
  • a method of transmitting data over a radio data system in which the data is transmitted over a plurality of radio data channels, data being transmitted at intervals over each channel such that data is transmitted over the respective channels at different times and such that the channels carry the data transmission in turn, whereby the rate at which data is transmitted over the plurality of channels taken in combination is greater than the rate at which it is transmitted over any one channel.
  • the TMC groups would need to be "bunched-up" or compressed on each channel so that there is an opportunity, in between processing them, to re-tune to another channel for more data.
  • the multiplexing would be at a low cycle rate in the order of a second or so. Although this restricts when the TMC data can be inserted on any one channel, it should be possible for an intelligent RDS encoder to arrange the overall transmission of RDS groups so as to maintain the minimum requirements for the repetition of the standard group types.
  • This method requires synchronisation of the TMC data on different channels but this can be accomplished by reference to the Clock Time (CT) Groups.
  • CT Clock Time
  • the necessary phasing information could be signalled as part of the TMC data, in a system message.
  • the RDS data transmission rate is defined to be 1187.5 bit/sec ⁇ .0.125 bit/sec. This implies a Group transmission rate of between 685.0240386 and 685.168269 Groups/minute.
  • TMC message cycles are restrained to start and finish at minute-edge boundaries governed, when present, by a CT Group 4A.
  • the end of this Group is defined to occur within 100 ms of the minute/second edge and it occupies one of the 685+ Group slots each minute. Some minute periods will contain 684 other RDS Group slots between successive CT Groups and others will contain 685.
  • CT Groups would not interfere with these reserved slots. If other RDS data needed to occupy the reserved TMC slots, the TMC data would not be sent at that time.
  • Type 14B Groups which signal the start of a traffic message broadcast via EON, might be considered of higher priority than TMC and the next TMC data would be 'pushed on' until the next vacant normal slot in the RDS data system.
  • the switching cycle envisaged would be between about 1 ⁇ 4 second and several seconds.
  • each channel is allocated a time-slot to which TMC data is confined, although not every group period is necessarily occupied by TMC data. Indeed, the basic requirements of the minimum repetition frequencies of the main features must be met first.
  • the precise phases of the time slots allocated to each channel would be signalled in separate system messages carried within the TMC data. In a multichannel system, the time-slots of the other channels and their RF frequencies would also be signalled both within the TMC data and using the EON feature.
  • the TMC data (Type 8A) Groups can be arranged at the RDS encoder to occupy declared time-slots which are defined by a particular phase relationship with the minute or second edge observed after a Clock Time (CT) Group. This phase relationship can be signalled in a system message. If the TMC data, carried on different channels, occupies different time-slots and with a sufficient time-margin between them, a receiver can increase its TMC data throughput.
  • Clock Time Clock Time
  • the allocated time-slots represent those times outside which TMC data is not allowed for that channel. It is not intended that all slots allocated to 'N', for example, would be occupied by TMC Groups; that would infringe the minimum
  • the margin of several RDS Groups between TMC-Group slots is required both for re-tuning/RDS decoding and to allow for any time-slot which results from the non-synchronisation of Group boundaries between one channel and another.
  • the two possible phases for TMC data can be identified by a single address bit.
  • Other examples could be defined in a similar manner and these could spread to multiplex cycles longer than about one second as used in the examples given. Further channels could be multiplexed at these longer multiplex cycle times but this would further restrict the broadcaster in the timing of the bunches of TMC data.
  • a listener accesses TMC data by a single function
  • the receiver is sufficiently frequency-agile and intelligent to perform all the necessary processing to render its operation transparent to the listener.
  • the receiver recognises a TMC channel by one of two methods: by simply detecting Type 8A RDS groups or by indirect reference from a variant of a Type 1A group. Once a TMC channel is found its data- can immediately be decoded and used to build up a stored repertoire of current messages in the receiver. This is a straightforward case of single channel TMC operation.
  • some of the TMC data contains system messages which gives information about the format of messages in the tuned channel and the PI codes of other relates TMC channels.
  • this information includes phasing data which defines the time-slots allocated to the channel .
  • the receiver then knows when it can expect TMC data and when it is free to do other things.
  • the PI codes "of related channels allows the receiver to acquire their TMC data as well.
  • the frequency of the other channels and their time-slots can be signalled by the EON feature.
  • This receiver incorporates a remotely-tunable front-end, RDS demodulator and decoding facilities.
  • it was programmed in HP BASIC to operate a cycle of alternate tuning to two off-air signals and displaying the decoded PI code in each case. The speed at which it could do this process could be adjusted until the RDS decoding became corrupted. This was found to occur when about a 11 ⁇ 2 second was allowed for each re-tuning, settling and RDS decoding process.
  • the front-end receiver used in the Reference receiver is not intended for fast switching; it is basically a monitoring receiver. For this application, the time constants in the AGC feedback loop have been reduced to allow a faster re-tuning response. This cannot, however, be expected to approach the switching speed of a synthesiser controlled directly as part of an integrated receiver design. This 3 second cycling to access two channels could be considered a "worst case".
  • the ESVP receiver is capable of re-tuning faster than the Reference receiver.
  • the demodulated FM multiplex signal was fed into an RDS decoder and the data/clock connected to a parallel interface associated with a PC.
  • the PC acted as an interface with the SUN and converted the data bit-stream into a byte-serial form.
  • the PC was connected via a serial interface to a SUN workstation which was programmed in C to decode the RDS data in real-time.
  • the same re-tuning cycle, described above, was implemented with this system and it was found that a re-tuning, settling and RDS decoding process could be achieved in between one-quarter and one-third of a second.
  • the number 684 happens to have factors of 9, 12, and 18 so that reserved TMC slots could be allocated in such a way as to allow differently phased slots to be used on different channels and with sufficient free groups in between to allow for

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Circuits Of Receivers In General (AREA)
  • Medicines Containing Material From Animals Or Micro-Organisms (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

Data, for example, data over a traffic message channel, is transmitted over a radio data system by multiplexing across several available channels. Data is transmitted at intervals over each channel so that data is transmitted at different times on different channels. As a result, the rate at which data is transmitted over the plurality of channels taken in combination is greater than the transmission rate over any one channel.

Description

MULTICHANNEL OPERATION OF RDS
The present invention relates to the Radio Data System (RDS) and, in particular, its use as a Traffic Message Channel ('TMC'). Such a system is discussed in J.L. Riley, March 1989 "Some ideas on a Traffic Message Channel (TMC) for the Radio Data System (RDS)" BBC Research Department Technical Memorandum
EL-1758, March 1989
TMC data cannot occupy all the available capacity of an RDS channel: other background data must also be present. Other types of RDS data occupy more than three quarters of the data capacity available and, consequently, the capacity available for TMC is likely to be limited to 10-20% of the total, that is, one or two groups per second out of the eleven provided on the RDS system. The minimum data rates stipulated for the main RDS features prevent the TMC data capacity in any one channel being greater than this. During the gaps between TMC data there is an opportunity to gather TMC data from other channels and
effectively increase the amount of TMC data which can be gathered in a given time.
In accordance with the invention, there is provided a method of transmitting data over a radio data system in which the data is transmitted over a plurality of radio data channels, data being transmitted at intervals over each channel such that data is transmitted over the respective channels at different times and such that the channels carry the data transmission in turn, whereby the rate at which data is transmitted over the plurality of channels taken in combination is greater than the rate at which it is transmitted over any one channel.
We have appreciated that an improvement could be obtained if the data were time-multiplexed on different channels so that a receiver could continually re-tune in between receiving TMC groups of data on one channel to acquire similar data on other channels. If a broadcaster has control of several channels, there is an opportunity to spread the TMC data across these channels and to arrange them in such a way that they are time-multiplexed, each occupying different time-slots with reference to the absolute clock time (CT) which each channel can broadcast via the CT features. An intelligent receiver can, therefore, frequency 'hop' from channel to channel to acquire all the TMC data available in an effectively continuous stream.
The TMC groups would need to be "bunched-up" or compressed on each channel so that there is an opportunity, in between processing them, to re-tune to another channel for more data.
The multiplexing would be at a low cycle rate in the order of a second or so. Although this restricts when the TMC data can be inserted on any one channel, it should be possible for an intelligent RDS encoder to arrange the overall transmission of RDS groups so as to maintain the minimum requirements for the repetition of the standard group types.
This method requires synchronisation of the TMC data on different channels but this can be accomplished by reference to the Clock Time (CT) Groups. The necessary phasing information could be signalled as part of the TMC data, in a system message.
A system in accordance with the invention will now be described in greater detail, by way of example only.
The RDS data transmission rate is defined to be 1187.5 bit/sec ±.0.125 bit/sec. This implies a Group transmission rate of between 685.0240386 and 685.168269 Groups/minute.
TMC message cycles are restrained to start and finish at minute-edge boundaries governed, when present, by a CT Group 4A. The end of this Group is defined to occur within 100 ms of the minute/second edge and it occupies one of the 685+ Group slots each minute. Some minute periods will contain 684 other RDS Group slots between successive CT Groups and others will contain 685. Considering the allocation of RDS Group types to these slots, it would be possible to reserve particular slots for TMC groups without affecting the repetition rates of other RDS data. CT Groups would not interfere with these reserved slots. If other RDS data needed to occupy the reserved TMC slots, the TMC data would not be sent at that time. For example, Type 14B Groups which signal the start of a traffic message broadcast via EON, might be considered of higher priority than TMC and the next TMC data would be 'pushed on' until the next vacant normal slot in the RDS data system.
The switching cycle envisaged would be between about ¼ second and several seconds. Within this cycle, each channel is allocated a time-slot to which TMC data is confined, although not every group period is necessarily occupied by TMC data. Indeed, the basic requirements of the minimum repetition frequencies of the main features must be met first. The precise phases of the time slots allocated to each channel would be signalled in separate system messages carried within the TMC data. In a multichannel system, the time-slots of the other channels and their RF frequencies would also be signalled both within the TMC data and using the EON feature.
As an option, and on any radio channel, the TMC data (Type 8A) Groups can be arranged at the RDS encoder to occupy declared time-slots which are defined by a particular phase relationship with the minute or second edge observed after a Clock Time (CT) Group. This phase relationship can be signalled in a system message. If the TMC data, carried on different channels, occupies different time-slots and with a sufficient time-margin between them, a receiver can increase its TMC data throughput.
The allocated time-slots represent those times outside which TMC data is not allowed for that channel. It is not intended that all slots allocated to 'N', for example, would be occupied by TMC Groups; that would infringe the minimum
repetition rates for other background RDS data. Where three adjacent slots are indicated, for example, only one or maybe two of these would actually be used for TMC.
The margin of several RDS Groups between TMC-Group slots is required both for re-tuning/RDS decoding and to allow for any time-slot which results from the non-synchronisation of Group boundaries between one channel and another.
Two alternative possibilities A and B are illustrated in the Table appended to this description. In each of these cases, there are two channels, represented by 'N' for National and 'L' for local. In alternative A with a multiplex cycle of 12 the data
transmission rates might be:-
Figure imgf000006_0002
In alternative B with a multiplex cycle of 18 the data
transmission rates might be:-
Figure imgf000006_0001
The two possible phases for TMC data can be identified by a single address bit. Other examples could be defined in a similar manner and these could spread to multiplex cycles longer than about one second as used in the examples given. Further channels could be multiplexed at these longer multiplex cycle times but this would further restrict the broadcaster in the timing of the bunches of TMC data.
It should be possible to re-tune and gather RDS data from different FM channels at a sub-second rate. In order to allow time for synchronisation margins between different transmitters it would probably be unwise to consider more than about two excursions per second but more channels over a cycle of a few seconds might be possible.
A listener accesses TMC data by a single function
selection. The receiver is sufficiently frequency-agile and intelligent to perform all the necessary processing to render its operation transparent to the listener.
The receiver recognises a TMC channel by one of two methods: by simply detecting Type 8A RDS groups or by indirect reference from a variant of a Type 1A group. Once a TMC channel is found its data- can immediately be decoded and used to build up a stored repertoire of current messages in the receiver. This is a straightforward case of single channel TMC operation.
In a multichannel TMC scenario, some of the TMC data contains system messages which gives information about the format of messages in the tuned channel and the PI codes of other relates TMC channels. In the tuned channel, this information includes phasing data which defines the time-slots allocated to the channel . The receiver then knows when it can expect TMC data and when it is free to do other things. The PI codes "of related channels allows the receiver to acquire their TMC data as well. The frequency of the other channels and their time-slots can be signalled by the EON feature. Once the receiver has acquired the system information about all the related TMC channels, it can. 'hop' between them at will and operate at the full TMC data capacity intended by the broadcaster.
Two experimental receiver systems were used to determine whether adequate response times could be achieved.
RDS Reference Receiver
This receiver incorporates a remotely-tunable front-end, RDS demodulator and decoding facilities. For the test, it was programmed in HP BASIC to operate a cycle of alternate tuning to two off-air signals and displaying the decoded PI code in each case. The speed at which it could do this process could be adjusted until the RDS decoding became corrupted. This was found to occur when about a 1½ second was allowed for each re-tuning, settling and RDS decoding process. The front-end receiver used in the Reference receiver is not intended for fast switching; it is basically a monitoring receiver. For this application, the time constants in the AGC feedback loop have been reduced to allow a faster re-tuning response. This cannot, however, be expected to approach the switching speed of a synthesiser controlled directly as part of an integrated receiver design. This 3 second cycling to access two channels could be considered a "worst case".
ESVP and SUN
The ESVP receiver is capable of re-tuning faster than the Reference receiver. The demodulated FM multiplex signal was fed into an RDS decoder and the data/clock connected to a parallel interface associated with a PC. The PC acted as an interface with the SUN and converted the data bit-stream into a byte-serial form. The PC was connected via a serial interface to a SUN workstation which was programmed in C to decode the RDS data in real-time. The same re-tuning cycle, described above, was implemented with this system and it was found that a re-tuning, settling and RDS decoding process could be achieved in between one-quarter and one-third of a second.
The number 684 happens to have factors of 9, 12, and 18 so that reserved TMC slots could be allocated in such a way as to allow differently phased slots to be used on different channels and with sufficient free groups in between to allow for
re-tuning. Two examples are given below, both are for two channels; a national channel denoted by N and a local channel denoted by L. It should be stressed that not all the allocated time-slots can be filled by TMC Groups, because of the need to maintain normal RDS data repetition rates.
Figure imgf000009_0001

Claims

1. A method of transmitting data over a radio data system in which the data is transmitted over a plurality of radio data channels, data being transmitted at intervals over each channel such that data is transmitted over the respective channels at different times and such that the channels carry the data transmission in turn, whereby the rate at which data is transmitted over the plurality of channels taken in combination is greater than the rate at which it is transmitted over any one channel.
2. A method according to claim 1 in which each data
transmission on each channel occurs at a substantially fixed interval or intervals from a clock signal transmitted over the channel at regular intervals.
3. Apparatus for receiving data transmitted over a radio data system by a method according to any of claims 1 or 2, the apparatus comprising tuning means operable to tune automatically to each of a plurality of channels in turn so as to receive data transmitted at intervals on those channels.
PCT/GB1991/001871 1990-10-25 1991-10-25 Multichannel operation of rds WO1992008303A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP3517126A JPH06504413A (en) 1990-10-25 1991-10-25 RDS multichannel operation
AU87493/91A AU649740B2 (en) 1990-10-25 1991-10-25 Multichannel operation of RDS
FI931853A FI931853L (en) 1990-10-25 1993-04-23 FLERKANALIG OPERATION AV ETT RADIODATASYSTEM

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB909023307A GB9023307D0 (en) 1990-10-25 1990-10-25 Multichannel operation of rds
GB9023307.3 1990-10-25

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AU (1) AU649740B2 (en)
FI (1) FI931853L (en)
GB (2) GB9023307D0 (en)
WO (1) WO1992008303A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997047101A1 (en) * 1996-05-30 1997-12-11 Robert Bosch Gmbh Method for processing of data with a radio receiver

Families Citing this family (6)

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Publication number Priority date Publication date Assignee Title
US5649297A (en) * 1994-10-21 1997-07-15 Seiko Communications Holding N.V. Transmitting digital data using multiple subcarriers
EP0762680A3 (en) * 1995-08-23 2001-04-25 Fraunhofer-Gesellschaft Zur Förderung Der Angewandten Forschung E.V. Method for transmission and installation and/or actualisation of software and/or data
JP4447053B2 (en) 1995-10-24 2010-04-07 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Radio broadcast system, transmitter and receiver used in such a system, radio broadcast method, and radio broadcast signal
DE19650429A1 (en) * 1996-12-05 1998-06-10 Bosch Gmbh Robert Method and device for sending messages with fluctuating volumes as radio data signals
DE50110149D1 (en) * 2001-03-15 2006-07-27 Siemens Ag Method for determining an RDS code with a radio receiver
DE50110332D1 (en) * 2001-03-15 2006-08-10 Siemens Ag RDS-TMC radio receiver and method for calibrating an internal timer in a radio receiver

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US2705795A (en) * 1949-07-06 1955-04-05 Fisk Bert Data transmission system
EP0196723A2 (en) * 1985-03-29 1986-10-08 Philips Patentverwaltung GmbH Method and circuit for the synchronization of receiving devices in a digital multiplex communication system
WO1988000417A2 (en) * 1986-07-02 1988-01-14 ETAT FRANÇAIS représenté par LE SECRETARIAT D'ETAT Method and installation for digital communication, particularly between and toward moving vehicles
WO1989012881A1 (en) * 1988-06-18 1989-12-28 Robert Bosch Gmbh A method of evaluating digitally encoded traffic information received in a data telegram and radio receivers
US4922483A (en) * 1987-10-02 1990-05-01 Kabushiki Kaisha Kenwood Multi-channel PCM music broadcasting system

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GB2208984B (en) * 1987-08-24 1991-05-29 British Broadcasting Corp Improved radio data system

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2705795A (en) * 1949-07-06 1955-04-05 Fisk Bert Data transmission system
EP0196723A2 (en) * 1985-03-29 1986-10-08 Philips Patentverwaltung GmbH Method and circuit for the synchronization of receiving devices in a digital multiplex communication system
WO1988000417A2 (en) * 1986-07-02 1988-01-14 ETAT FRANÇAIS représenté par LE SECRETARIAT D'ETAT Method and installation for digital communication, particularly between and toward moving vehicles
US4922483A (en) * 1987-10-02 1990-05-01 Kabushiki Kaisha Kenwood Multi-channel PCM music broadcasting system
WO1989012881A1 (en) * 1988-06-18 1989-12-28 Robert Bosch Gmbh A method of evaluating digitally encoded traffic information received in a data telegram and radio receivers

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Title
EBU REVIEW- TECHNICAL. no. 233, February 1989, BRUSSELS BE pages 9 - 16; D. KOPITZ: 'Radio Data System - from specification to practical reality' see page 15, paragraph 5.3 *
VEHICLE NAVIGATION & INFORMATION SYSTEMS CONFERENCE RECORD - Pages A44-A48 11-13 September 1989 TORONTO, CA P. Davies: "The Radio System-Traffic Channel" see the whole document *

Cited By (1)

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Publication number Priority date Publication date Assignee Title
WO1997047101A1 (en) * 1996-05-30 1997-12-11 Robert Bosch Gmbh Method for processing of data with a radio receiver

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AU8749391A (en) 1992-05-26
GB9122683D0 (en) 1991-12-11
AU649740B2 (en) 1994-06-02
JPH06504413A (en) 1994-05-19
EP0555304A1 (en) 1993-08-18
FI931853A0 (en) 1993-04-23
GB9023307D0 (en) 1990-12-05
FI931853L (en) 1993-04-23
GB2251767A (en) 1992-07-15

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