FIELD OF THE INVENTION

Tliis invention relates to a method of tuning digital radios and other end-user digital receivers. It solves the complexity of manually selecting a desired service.

DESCRIPTION OF THE PRIOR ART

As digital media broadcast techniques continue to proliferate, both in audio and video application and with further upcoming data services, the design of end-user receiver equipment faces new challenges in terms of usability.

Set-Top-Boxes (STBs), as digital television receivers, are now commonplace. The number of services available is numerous. STBs have solved the problem of service selection by providing the user with menus of services to choose from. These menus are typically populated by the user activating a "search" process, often automatically triggered as the equipment is first installed. This process, whereby the equipment systematically tunes through a range of different frequencies, will typically take several minutes to compile the menu (or service database).

The time consuming nature of this process makes it unsuitable to applications where the availability of services is dynamic.

In light of developments in digital radio, including Digital Radio Mondiale (DRM) and Digital Audio Broadcasting (DAB), the conventional, manual user selection of services is becoming impractical. This is because services are commonly available on different frequencies, different broadcast standards (and therefore modulation and encoding techniques), at different times of the day, in different languages and different locations.

For example, DRM occupies a spectrum capable of carrying over 2,500 services (over 25MHz of spectrum (150kHz to 27MHz) at 10kHz per channel). The spectrum used is such that propagation may vary in distance from a few tens to many thousands of kilometres. Ionospheric conditions affect propagation which varies between day and night time.

When we consider that broadcasters are likely to transmit media content over multiple channels (such as DRM, DAB and traditional FM), then the choice of selecting a service becomes more complex: "which service do I want", "when is it available", "where is it available" "which source is the best quality", "when should I change to another source" etc.

Even the concept of "tuning" through the services becomes impractical as the coding and modulation techniques used for broadcast evolve. For instance, tuning across the DRM spectrum requires the receiver to pause for a significant fraction of a second to decode sufficient signal to establish the availability and quality of a service at each frequency slot. For 2500 possible channels at 1 second per channel the scan time for a single pass is over 40 minutes. Add to this the AM and FM bands, DAB on band III and L-Band, satellite radio etc. the process of scanning the spectrum, automatically or otherwise, potentially numerous times per day, is inefficient and costly to accomplish in the receiver equipment and detrimental to the normal use of the equipment.

SUMMARY OF THE PRESENT INVENTION

The invention is a method of tuning digital end-user receivers, comprising the steps of:

a. Systematically receiving and logging service information that defines what services are available on what frequencies by means of distributed monitoring receivers;

b. Compiling a database of service information, using information from the distributed monitoring receivers;

c. Making available the compiled database to the end-user receivers to enable the receivers to automatically tune to a service.

Hence, in order to enable consumers to populate the service database of their receiver equipment with only the most appropriate and most up to date service list, a network of monitoring receivers is deployed "in the field" to listen to broadcasts and report back what services are available on what frequency, potentially over the internet, to a centralized database. At the centralised database, Service Information (SI) and service linking information (such as scheduled changes of frequency) is automatically compiled and categorized. Such SI is available in DRM through the Fast Access Channel and Service Description Channels. In other transmissions SI is also available, for instance the Fast Information Channel in DAB, RDS in FM and the forthcoming AMSS in AM.

This information is then made available to end-users, typically by means of a web site or broadcast, to automatically populate the service databases locally stored on end-user receiver equipment. An end— user can then rapidly select a particular station by locating it in the local SD of his receiver; the receiver then automatically tunes to that station.

By the consumer connecting their receiver equipment to an Internet connected PC and selecting the appropriate web site, it is possible to download the latest service database.

Typically, user specific criteria will define the location, type of receiver and other listening preferences, to ensure their receiver's service database is populated only with pertinent services.

The monitoring stations could either be professionally owned and operated, or could be privately owned consumer receivers running a specific load of software.

Note that the use of a monitoring method alleviates the need for the broadcaster to continually update a centralised database of information. Indeed, for services which are transmitted in the HF (or Short Wave) band the propagation is quite variable and may propagate to areas beyond the normally recognised footprint under certain conditions dictated by the time-of-day. In these cases it is valuable to be able to recognise such channels and have recorded entries for them.

It is also envisaged that the resulting dynamically updated database may be used by Broadcasters to modify their broadcast configuration from time to time to achieve optimum service delivery. For instance, a digital radio service may be configured to use a higher protection level in situations of poor propagation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to Figure 1, which shows a schematic view of an implementation of the invention.

IMPLEMENTATION

The implementation of the system is shown in Figure 1. Referring to Figute 1 we see a range of broadcast transmission types DRM (1), AM (2), DAB (3) and FM (4). Each type has multiple transmitters and those transmitters may be located anywhere in the world. The objective is to ensure that up to date databases of services exist for a number of global areas. These global areas may be quite large or may be relatively focused. For example we may have a database for Europe but may also have one for Germany or the UK. Similarly in Asia where there may be databases for greater China and South-East Asia but we could also have a database specifically for Taiwan or Malaysia.

Placed in the field are a number of Multi-Standard Monitoring Receivers (6) which receive the broadcasts (5) as available at that site. The monitoring receivers (6) will generally be in a continuous scan mode where they will cycle through each broadcast standard and all the available channels and frequencies for that standard. As the available frequencies depend on location, i.e. different countries have different frequency bands for some services, e.g. the extended L-Band spectrum for DAB in Canada, the scanning of the frequency bands can be made location dependent. This can be done by simply selecting the location at installation time (e.g. entering the Latitude and Longitude) or could be done automatically via a GPS receiver.

There are a number of ways to detect the services which may be broadcast. For digital services the channel may be sampled and an energy detection undertaken to determine whether there is a signal of sufficient power present. If the detector finds a signal, i.e. the energy detected is greater than a specific threshold (which may be dynamic) then the Monitoring Receiver will decode the signal. Alternatively a trial signal decode could be undertake where the Monitoring Receiver (MR) assumes the presence of a signal. If the receiver does not find the appropriate signals it concludes that there is no signal present. Generally, the latter method is preferred as it uses more a-priori knowledge of the signal and hence the Probability of Detection and False Alarm are generally superior to a simple energy detection method. Given a positive detection the MR will then extract the SI from the signal. The SI is then recorded in a local database on the MR.

For analogue broadcasts like AM and FM there are again two possibilities. First, the simple energy detection strategy may be employed to determine whether a signal is present. This energy detection may also use some of the characteristics of the signal, i.e. determination of

Modulation Index or analysis of the spectral characteristics to determine the nature of the signal. In many countries FM has an associated data channel, called RDS in Europe, which contains SI. Once the Signal has been detected the SI can be extracted and recorded in the local database. Similarly with AM, although the implementation of the AM data channel, called AMSS, is, at the time of writing, still being standardised.

Typically the SI will be organised dependent on the broadcast type. For example DRM broadcasts may contain multiple channels but they all emanate from die same broadcaster. Similarly with AM and FM. For DAB, there are multiple sub-channels associated with each channel and hence the sub-channels need to be recorded also. Indeed for DAB the sub- channel bit rate may change over time. Also, as the bit rate may change there is the possibility of time dependent sub-channels, i.e. a sub-channel may only be broadcast at certain times of the day. Hence the local Service Database (SD) may also have a time dependent component. This is also the case with DRM as, due to the nature of ionospheric propagation, some channels will only be available at certain times of die day. Also, at the time of writing, some broadcasters only transmit a signal at certain times of the day. Consequently the scanning of the broadcast bands needs to occur on a regular, timely basis.

Hence an embodiment of the SD would be partitioned across both the frequencies in the band of interest, e.g. LW, MW and SW for DRM, as well as by time of day. In a preferred embodiment this time interval would be hourly. We note that all channels in all bands cannot be detected simultaneously, however as broadcasters tend to change their configuration, or even decision to transmit, on hourly boundaries this is a useful subdivision within the SD. The common (or master) service database hence includes information regarding the availability and reception quality of a service on a time of day basis. The time of day basis can be synchronised to a broadcaster's service switching schedule.

Once the SD has been constructed it needs to be downloaded (7) to a database system at a Central Site for processing (8). The network of monitoring receivers, distributed in location, can be interconnected such that monitoring processes, logging processes and database processes are administered remotely. The SDs in a region are then jointly processed to generate a 'Master Service Database' (MSD) for that region. It is the MSDs which are then used by the end-user or Consumer Receivers (12) by being downloaded or otherwise received in order to populate the service database (SD) on each Consumer Receiver (12).

The amount of traffic for a download from the MR to the Central Site may be approximated in the maximum as 3000 channels (allowing 2500 channels for DRM/AM channels and a total of FM and DAB channels of 500 including DAB sub-channels). Given 100 bytes of info per channel we have 300kbytes of data to be transferred. Typical such transfers would occur on a daily basis but they could be more or less regular. Given a 3 to 1 ratio to account for error protection and correction, some data compression and overheads we have approx 1 Mbyte per day, which even over a dial up telephone connection of 40kbits/sec requires only about 200 seconds to transmit.

There are a number of methods by which the SDs can be combined into the MSD. Here we define some of those options, but not exhaustively. First we will generally wish to start with a knowledge base. As shown in Figure 1 manual updates (10) can be made to the databases (9) under the control of the database system (8). These manual updates can be full or partial and may be the initial data or updates after automatic updates have occurred. A simple way to update a MSD for a region is to include all detected signals. Initially this may be simple, however issues arise when there are more than one service detected on a specified channel or frequency. This can arise due to 'skip' at SW frequencies or due to high density of transmissions as is sometimes the case for AM. In this case the MSD must choose, for a time slot e.g. the hour between 14:00 and 14:59:59, which service to record in the MSD. One option would be to record the service with the maximum signal during that period, however a preferred embodiment is to be consistent over the period of a day. When two or more services are detected at a single frequency at different times of the day the service which has the most time coverage during a 24 hour period could be selected as the 'resident' service at that frequency in that region. Note however that the consumer/user can be given the choice of a day based or hour based SD. Clearly the choice will be dependent on the availability of non-volatile memory in the Consumer Radio.

Typically, Consumer Receivers would be distributed from manufactures with a default SD, generally one which is representative of the region where they will be sold and reside. As new services will emerge and other existing services change from time to time the SD on the Consumer Receiver will require to be updated periodically. This update can be done via Service Scans by the Consumer Receiver or by downloading the latest SD from a central site as described above. The Consumer Receiver can hence be adapted such that the locally stored service database may be updated or modified via an internet connection or digital radio

broadcast means. Other receivers, typically other than those performing the primary monitoring function, when connected for the purpose of synchronizing or downloading a service database, may exchange service logging information.

Once the MSDs have been established for the regions of interest, the Consumer Receivers (12) may upload the required SD as a copy of the MSD at the central site. Typically this would be done via the Internet and is simply a matter of logging into a website, selecting the region/location of choice and updating the SD on local Consumer Receiver. Typically, a single

SD would be resident in a Consumer Receiver, however for world travellers a number of SDs may be preferred. It is a simple matter to allow for multiple SDs in a Consumer Receiver as long as the Consumer Receiver has sufficient non- volatile memory. The compiled database can incorporate electronic programme guide (EPG) data.

An alternative distribution method would be to broadcast the database to a region regularly. For example, for DRM the entire SD could be transmitted over a period of, say, 10 hours. Given the same size as before for compression, protection and encapsulation of 1 Mbyte, a data rate of 223bits/sec would be sufficient. This represents approximately 10% of a typical DRM service and hence the broadcaster may wish to be a bit more selective in the data that is transmitted. Indeed if the data rate was limited to 20bits/sec then over a 24 hour period 216kbytes could be transmitted. This would generally be more than sufficient as it should be enough to contain at least 720 channels (at lOObytes per channel and 3x overhead).