This application claims the priority benefit of Taiwan application serial no. 100131325, filed on Aug. 31, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
1. Field of the Invention
The present invention relates to a device and method for improving ensemble auto searching efficiency, and more particularly, to a device and method for improving ensemble auto searching efficiency which is adapted for digital audio broadcasting (DAB).
2. Description of Related Art
The ensemble auto searching mechanism used by current digital audio broadcasting (DAB) is subject to limitation of synchronization mechanism or signal receiving condition (e.g. noise interference), which can lead to the misjudgement of an ensemble. As a result, the DAB often wastes time in searching ensemble information that even does not exist, which slows down the ensemble auto searching and thus wastes time and power of the corresponding electronic device. What is desired, therefore, is to reduce the time waste due to misjudgement during ensemble auto searching, thus effectively reducing the time for ensemble auto searching.
Accordingly, the present invention is directed to a device and method for improving ensemble auto searching efficiency which can reduce waste of time due to misjudgment during ensemble auto searching.
The prevent invention provides a method for improving ensemble auto searching efficiency, adapted for ensemble auto searching of a digital audio broadcasting (DAB) system. In this method, a first digital audio broadcasting transmitted signal is received, and a time interval between null symbols of adjacent ones of multiple continuous transmitted frames in the first digital audio broadcasting transmitted signal is calculated. If the time interval fits a preset transmitted frame time duration, it is then determined that a first channel corresponding to the first digital audio broadcasting transmitted signal is a preliminarily identified digital audio broadcasting channel. A first phase reference symbol (PRS) of the first digital audio broadcasting transmitted signal is then detected, and a first correlation value between the first phase reference symbol and a preset phase reference symbol is calculated. If the first correlation value is greater than or equal to a threshold, it is then determined that the first channel is a valid digital audio broadcasting channel.
In one embodiment, the method for improving ensemble auto searching efficiency further comprises, if the time interval does not fit the preset transmitted frame time duration, determining the first channel corresponding to the first digital audio broadcasting transmitted signal to be an invalid digital audio broadcasting channel; and proceeding to a next channel for execution of the ensemble auto searching.
In one embodiment, if the correlation value between the first phase reference symbol and the preset phase reference symbol calculated with respect to each carrier frequency offset is different, the highest correlation value is selected as the first correlation value.
In one embodiment, the method for improving ensemble auto searching efficiency further comprises using the first correlation value for frequency synchronization and phase synchronization of the ensemble auto searching.
In one embodiment, the method for improving ensemble auto searching efficiency further comprises, if the first correlation value is less than the threshold, determining the first channel corresponding to the first digital audio broadcasting transmitted signal to be an invalid digital audio broadcasting channel; and proceeding to a next channel for execution of the ensemble auto searching.
In one embodiment, the method for improving ensemble auto searching efficiency further comprises collecting digital content service information in the first channel after determining the first channel corresponding to the first digital audio broadcasting transmitted signal to be a valid digital audio broadcasting channel.
In one embodiment, when the collected amount of digital content service information in the first channel has reached a desired amount, the digital content service information is stored.
In one embodiment, when the collected amount of digital content service information in the first channel does not reach a desired amount within a predetermined time limit, the method controls the digital audio broadcasting system to proceed to a next channel for execution of the ensemble auto searching.
In one embodiment, the method for improving ensemble auto searching efficiency further comprises obtaining a mapping value by mapping the first correlation value to signal quality criteria and determining the current signal quality of the first channel based on the mapping value.
The present invention is also directed to a device for improving ensemble auto searching efficiency, adapted for ensemble auto searching of a digital audio broadcasting system. The device includes a transceiver module, a storage unit and a control module. The transceiver module receives a first digital audio broadcasting transmitted signal. The storage unit provides a storage space for storing a preset phase reference symbol. The control module is coupled to the transceiver module and the storage unit for calculating a time interval between null symbols of adjacent ones of multiple continuous transmitted frames in the first digital audio broadcasting transmitted signal. If the time interval fits a preset transmitted frame time duration, the control module determines a first channel corresponding to the first digital audio broadcasting transmitted signal to be a preliminarily identified digital audio broadcasting channel. The control module then detects a first phase reference symbol of the first digital audio broadcasting transmitted signal, and calculates a first correlation value between the first phase reference symbol and the preset phase reference symbol. If the first correlation value is greater than or equal to a threshold, the control module determines the first channel to be a valid digital audio broadcasting channel.
In view of the foregoing, the prevent invention provides a method and device for improving ensemble auto searching efficiency. In order to improve the ensemble searching efficiency, the method and device takes advantage of characteristics of the phase reference symbol in the digital audio broadcasting transmitted signal to effectively avoid waste of time due to misjudgement during ensemble auto searching, thus reducing the time for ensemble auto searching.
Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.
The phase reference symbol is an orthogonal frequency division multiplex (OFDM) symbol which is defined as follows:
In the above equations, z1,k represents the complex differential quadrature reference phase shift keying symbol (Complex D-QPSK Symbol) of the phase reference symbol corresponding to the kth carrier, where K is the number of the transmission carriers, and the values of hi,k-k′, i, k′, n depend upon the frequency and phase, the relationship of which is defined in Table 39-43 of DAB specification EN300-401 established by ETSI.
The DAB systems in the same area adopt the fixed and same transmission mode. Therefore, the control module 330 determines whether a first channel corresponding to the current first DAB transmitted signal is a possible DAB channel by determining whether the time interval between adjacent null symbols fits the preset transmitted frame time duration. In other words, if the determining result of step S420 is yes, it is then preliminarily determined that the first channel corresponding to the first DAB transmitted signal is a preliminarily identified DAB channel (step S425). Otherwise, i.e. if the time interval does not fit the preset transmitted frame time duration, the control module 330 determines that the first channel corresponding to the first DAB transmitted signal is an invalid DAB channel and then proceeds to a next channel for execution of ensemble auto searching (step S430).
However, it may be insufficient if only the preliminary identification is performed. If whether it is a valid DAB channel is determined only by such a mechanism of determining whether the time interval between the null symbols fits the preset transmitted frame time duration, then the setting mechanism will affect the accuracy of determination when setting the preset transmitted frame time duration. For example, when the DAB systems in this area use the transmission mode IV in which TF specified in the specification is 48 ms, if the upper and lower limits of the preset transmitted frame time duration are too loosely set, for example, are set as 48 ms±10 ms, this may easily result in many actually invalid DAB channels being searched. On the contrary, if the time duration is set too strictly, for example, it is set such that only a channel that has a time interval of 48 ms as specified in the transmission mode IV in the specification can be considered as a valid DAB channel, the searching may miss some valid DAB channels due to poor signal. Therefore, a further screening mechanism is needed to avoid the problems existing in setting the preset transmitted frame time duration.
This further screening mechanism may be implemented by taking advantage of the phase reference symbol. Subsequent to step S425 where it is preliminarily determined that the first channel corresponding to the first DAB transmitted signal is a preliminary identified DAB channel, the control module 330 detects a first phase reference symbol of the first DAB transmitted signal (step S435) and then calculates a first correlation value between the first phase reference symbol and a preset phase reference symbol (step S440). The preset phase reference symbol may be stored in the storage unit 320. The phase reference symbols of the DAB systems in the same area are the same. The control module 330 also uses the first correlation value for frequency and phase synchronization mechanism of the ensemble auto searching.
The control module 330 then determines whether the calculated first correlation value is greater than or equal to a threshold (step S450). The threshold may be stored in the storage unit 320, which may be defined by a user or a default value.
After execution of step S410 to step S470, step S475 is executed to inspect whether the searching over the entire band of the DAB system is finished. If not, the control module 330 then proceeds to a next channel for execution of the ensemble auto searching (step S430). If yes, the entire flowchart of the ensemble auto searching ends.
In another embodiment of the present invention, the first correlation value between the first phase reference symbol and the preset phase reference symbol that is calculated by the control module 330 can further be used to determine the received signal quality. The control module 330 obtains a mapping value by mapping the first correlation value to signal quality criteria and determines the current signal quality of the first channel based on the mapping value. The signal quality criteria are stored in the storage unit 320 for the control module 330 to use.
In summary, the prevent invention provides a method and device for improving ensemble auto searching efficiency by taking advantage of characteristics of the phase reference symbol. In embodiments of the present invention, the correlation value between the phase reference symbol of the received DAB transmitted signal and a preset phase reference symbol is calculated for further screening out valid DAB channels. This reduces the possibility of misjudgment of validity of a DAB channel which would happen when only the mechanism of determining whether the time interval of the null symbols fits a preset transmitted frame is used. As can be seen from the sharp contrast between the correlation values of
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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100131325 | Aug 2011 | TW | national |