Abstract:
Disclosed is a method and a device for receiving broadcasting service in a digital multimedia broadcasting system which provides the broadcasting service through a first radio path and a second radio path, in which the first radio path allows only digital multimedia broadcasting service to be received therethrough and the second radio path allows the digital multimedia broadcasting service and mobile communication service to be received therethrough, the method including updating information about a received signal input through the radio paths, determining whether the second radio path is switched on, determining a reason when the second radio path is switched off why it is switched off; comparing the information about the received signal with corresponding predetermined threshold values depending on a result of the determination of why the second radio path is switched off; and resetting the second radio path as ‘off’.

Description:
PRIORITY  
       [0001]     This application claims priority under 35 U.S.C. 119(a) to an application entitled “Method And Device For Decreasing Dissipation Of Power In Receiver Of Digital Multimedia Broadcasting System” filed in the Korean Intellectual Property Office on Jun. 14, 2004 and assigned Ser. No. 2004-43759, the contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method and a device for decreasing dissipation of power in a wireless communication system, and more particularly to a method and a device for minimizing dissipation of power in a receiver of a digital multimedia broadcasting system to which antenna diversity is applied.  
         [0004]     2. Description of the Related Art  
         [0005]     Digital multimedia broadcasting (DMB) is based on digital radio broadcasting, i.e., digital audio broadcasting (DAB), which became available in the late 1980&#39;s. DAB is one of the most widely developed types of radio broadcasting. DMB uses digital techniques which have been developed since the early 1980&#39;s. Today DAB development continues at a brisk pace as it has become possible to transmit data regardless of the program format.  
         [0006]     A recently introduced media “DMB”, can transmit images using a digital radio frequency band for the digital radio.  
         [0007]     Meanwhile, DMB can be classified into “terrestrial DMB”, and “satellite DMB”. Terrestrial DMB currently uses the same frequency band as that which is used for conventional television transmission (TV), e.g., a frequency band of 174 to 216 MHz and therefore can utilize existing TV transmission and relay stations. In contrast, satellite DMB uses a high frequency band for transmission (e.g., 2605 to 2655 MHz). A service provider of a terrestrial DMB uses a frequency bandwidth of 1.54 MHz to transmit, while a, service provider of a satellite DMB uses a frequency bandwidth of 25 MHz. Satellite DMB uses a greater frequency bandwidth than that used in the terrestrial DMB. For example, accordingly, terrestrial DMB can simultaneously provide an image channel and approximately three audio/data channels, and satellite DMB can simultaneously provide 10 to 12 image channels and approximately 30 audio/data channels. Satellite DMB focuses on receiving satellite digital multimedia broadcasting service, using a terminal which is similar in size to that of a conventional portable telephone (e.g. cellular telephone). Accordingly, satellite DMB can be classified as a type of mobile broadcasting media.  
         [0008]     Currently, satellite DMB techniques are being developed. Specifically, a satellite DMB terminal using a 2.6 GHz band is under development. Because DMB terminals can simultaneously receive a plurality of data channels, DMB terminals consume a more power than existing terrestrial communication systems, thereby decreasing battery life and degrading reception.  
       SUMMARY OF THE INVENTION  
       [0009]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method and device for decreasing the dissipation of power in a terminal receiver (TR) of a satellite digital multimedia broadcasting system.  
         [0010]     Another object of the present invention is to provide a method and a device for decreasing dissipation of power in a terminal receiver of a satellite digital multimedia broadcasting system including a rake receiver and to which antenna diversity is applied.  
         [0011]     To accomplish these and other objects, in accordance with one aspect of the present invention, there is provided a method for receiving broadcasting service in a digital multimedia broadcasting system which provides the broadcasting service through a first radio path and a second radio path, in which the first radio path allows only digital multimedia broadcasting service to be received therethrough and the second radio path allows the digital multimedia broadcasting service and a mobile communication service to be received therethrough, the method including the steps of updating information about a received signal input through the radio paths determining whether the second radio path of the radio paths is switched on and/or off; determining a reason of an off state of the second radio path when the second radio path is switched off, comparing the information about the received signal with corresponding predetermined threshold values depending on a result of the determination of the reason why the second radio path is switched off, and resetting the second radio path as “off” when all the information about the received signal are greater than the corresponding predetermined threshold values, respectively.  
         [0012]     In accordance with another aspect of the present invention, there is provided a device for receiving broadcasting service in a digital multimedia broadcasting system which provides the broadcasting service through a first radio path and a second radio path, in which the first radio path allows only digital multimedia broadcasting service to be received therethrough and the second radio path allows the digital multimedia broadcasting service and a mobile communication service to be received therethrough, the device including antennas for receiving a digital multimedia broadcasting signal; an analog-to-digital converter (ADC) for receiving the signal received through by antennas through the first radio path or second radio path, receiving an intensity of the received signal, and then outputting a digital signal, a rake receiver for measuring and outputting a signal-to-noise ratio of the signal output from the analog-to-digital converter; a channel codec for measuring a bit error rate of the signal output from the rake receiver, and demodulating, decoding and outputting the signal output from the rake receiver; and a central processing unit for updating information about a received signal by using the received signal intensity, the signal-to-noise ratio and the bit error rate, determining a reason of an off state of the second radio path of the radio paths when the second radio path is switched off, comparing the information about the received signal with corresponding predetermined threshold values depending on a result of the determination of the reason why the second radio path is switched off, and resetting the second radio path as “off” when all the information about the received signal are greater than the corresponding predetermined threshold values, respectively. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0014]      FIG. 1  is a block diagram illustrating a configuration of a terminal receiver employing antenna diversity in a satellite digital multimedia broadcasting (DMB) system according to an embodiment of the present invention; and  
         [0015]      FIG. 2  is a flowchart illustrating an operation of the terminal receiver having decreased power consumption according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Hereinafter, a preferred embodiment according to the present invention will be described with reference to the accompanying drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.  
         [0017]     In the present invention, power consumption of a terminal receiver is minimized to maintain its optimum reception performance of the terminal receiver and a rake receiver is utilized in a Code Division Multiplexing (CDM) scheme to use antenna diversity.  
         [0018]     A block diagram illustrating a configuration of a terminal receiver employing antenna diversity in a satellite digital multimedia broadcasting (DMB) system according to an embodiment of the present invention is shown in  FIG. 1 .  
         [0019]     Signals received through each of antennas  11   a  and  11   b  pass through low-noise amplifiers (LNAs)  12   a  and  12   b  and radio frequency integrated circuits (RFICs)  13   a  and  13   b,  respectively, and are then input to a modem unit  110 . From among the antennas, a first antenna  11   a  can receive only satellite DMB service, and a second antenna  11   b  has a dual mode function and can receive satellite DMB service and conventional mobile communication service capable of using a rake and searcher such as CDMA or WCDMA. In the following description, a path through which a signal received by the first antenna passes is known as a “first path” and a path through which a signal received through the second antenna passes is known as a “second path”.  
         [0020]     The modem unit  110  includes analog-to-digital converters  111   a  and  111   b,  fronts  112   a  and  112   b,  a rake receiver  113 , a searcher  114 , a buffer (desk buffer)  115 , a combiner  116 , a channel codec  117 .  
         [0021]     Radio frequency (RF) signals output from the radio frequency integrated circuits  13   a  and  13   b  are input to the analog-to-digital converters  111   a  and  111   b,  and are converted into digital signals, respectively. The converted digital signals pass through the fronts  112   a  and  112   b  functioning as digital filters, respectively, and then are input to both of the rake receiver  113  and the searcher  114 . Although it is not shown, the radio frequency integrated circuits  13   a  and  13   b  and the analog-to-digital converters  111   a  and  111   b  include automatic gain control (AGC) loops. The AGC loops are used to measure the intensities of signals received through the antennas  11   a  and  11   b.  A signal output from the rake receiver  113  is stored in the buffer  115  and is then input to the combiner  116  so as to be combined. The combined signal is input to the channel codec  117 . The channel codec  117  includes a bit deinterleaver, a Viterbi decoder, a byte deinterleaver and a Reed-Solomon decoder (which are not shown for the sake of clarity). A signal encoded by the channel codec  117  is output to an application processor (AP) (not shown).  
         [0022]     The modem includes a central processing unit (CPU)  120  for controlling the rake receiver  113 . The central processing unit  120  periodically checks receiver parameters including a post automatic gain control (AGC) received signal strength identifier (RSSI), a searcher and rake signal-to-noise ratio (search &amp; rake Ec/Io), a post Viterbi bit error rate (BER), etc., according to a timer signal provided from an operating system (OS) in the CPU, a dump signal of the searcher  114 , a decoder interrupt signal and the like. Herein, the dump signal of the searcher  114  represents an interrupt signal generated by the CPU when a signal search is finished in the modem  110 , and the decoder interrupt signal is generated after (RS) Reed-Solomon decoding is finished. The post AGC RSSI represents the magnitudes of analog signals input to the analog-to-digital converters  111   a  and  111   b,  and the searcher and rake signal-to-noise ratio represents the intensity of a desired signal from among signals input into the searcher  114  and rake receiver  113 .  
         [0023]     The central processing unit  120  outputs on/off control signals to the low-noise amplifiers  12   a  and  12   b,  the radio frequency integrated circuits  13   a  and  13   b,  the fronts  112   a  and  112   b  and the analog-to-digital converters  111   a  and  111   b,  etc.  
         [0024]     Hereinafter, a method for decreasing dissipation of power in the terminal receiver having the above-mentioned configuration will be described. The method for decreasing the dissipation of power includes switching off any one path of the two radio paths when the terminal receiver is in a weak or strong electric field. For example, if it is determined that the second radio path should be shut off, then any element in the second radio path can be shut off e.g., the low-noise amplifier  12   b,  the radio frequency integrated circuit  13   b  and/or elements such as the modem  110  included in the second path, in a weak or strong electric field, the front  112   b,  the analog-to-digital converter  111   b  and at least one half or more of the rake receiver  113  which are included in the second path. If the determination is made to shut off the second path, them selected elements in the second path can be turned off.  
         [0025]      FIG. 2  is a flowchart illustrating an operation of the terminal receiver having a decreased power consumption according to an embodiment of the present invention.  
         [0026]     In order to decrease power consumption of the terminal receiver, the central processing unit  120  updates and stores a signal-to-noise ratio (Ec/Io) using information about a received signal strength indicator (RSSI) from the searcher  114  and rake receiver  113  for each of the received signals whenever a search dump interrupt is generated in the search dump interrupt is generated by the modem unit  110  according to a predetermined operating scheme., When a channel decoder interrupt is generated, the central processing unit  120  updates and stores a bit error rate (BER)When a timer signal “RSSI_Timer” provided by the OS is generated, the central processing unit  120  checks and updates an AGC RSSI, and then checks radio-path-off indicator (rf_off_indicator) information so as to determine whether the second radio path (RF 2 ) is switched on or off. Herein, the “rf_off_indicator” represents an indicator existing in a software code which indicates a “false” when the circuit of the second path (RF 2 ) is switched on and indicates a “true” when the circuit of the second path (RF 2 ) is switched off.  
         [0027]     In step  201 , the central processing unit  120  determines whether an OS timer has expired. When the timer has not expired, proceeds to step  202 . In step  202 , the central processing unit  120  performs a control operation so that the searcher  114  may perform an searching operation. Thereafter, the central processing unit  120  compares a signal-to-noise ratio (Ec/Io) for a received signal from antenna  11   a  with a predetermined threshold value. As a result, when the signal-to-noise ratio is greater than the predetermined threshold value, the central processing unit  120  sets timer A. In contrast, when the signal-to-noise ratio is smaller than the predetermined threshold value, the central processing unit  120  sets timer B.  
         [0028]     Meanwhile, as a result of step  201 , when the OS timer has expired, proceeds to step  211 . In step  211 , the central processing unit  120  checks the “rf_off_indicator” and determines whether the second path (RF 2 ) is switched on or off. As a result of the determination, in step  212 , when the second path is switched off, the central processing unit  120  checks radio-path-off-reason indicator “rf_off_reason_indicator” information and determines why the second path is switched off. Herein, the “rf_off_reason_indicator” represents an indicator existing in a software code, which indicates why the second path is switched off. For example, the second path may be switched off because of a strong electric field, a weak electric field, inter-modulation distortion (IMD) and a middle electric field (electric status in the middle between a weak electric field and a strong electric filed). In the case of a middle electric field, the central processing unit  120  switches off a smaller portion of the circuit than that which is switched off in the cases of a strong electric field and a weak electric field.  
         [0029]     In step  213  when the second path is switched off because of a strong electric field, that is, when the “rf_off_reason_indicator” indicates a strong electric field, the central processing unit  120  checks an AGCI RSSI, an Ec/Io and a BER for a received signal from antenna  11   a  and compares each of the checked values with a corresponding predetermined threshold value in step  213 . As a result of the comparison, when any one of the checked values fails to exceed its corresponding threshold value, the “rf_off_indicator” is set as “false” and the “rf_off_reason_indicator” is set as a “strong electric field” in step  214 . Thereafter, in step  220 , the central processing unit  120  switches on the second path and that portion of the modem, which has been switched off, and then sets timer A. In contrast, as a result of the comparison in step  213 , when all the checked values exceed their corresponding threshold values, the central processing unit  120  continues to step  215  and sets the “rf_off_indicator” to “true” state, and then sets timer A.  
         [0030]     Meanwhile, as a result of step  212 , when the second path is switched off due to a weak electric field or to inter-modulation distortion (IMD), the central processing unit  120  proceeds to step  221 , in which the central processing unit  120  checks the AGC 1  RSSI and compares the checked value with a minimum threshold value (MIN_thresh) for a received signal from antenna  11   a.  When the AGC RSSI is smaller than the minimum threshold value, the central processing unit  120  stops searching during a predetermined time interval, sets the “rf_off_indicator” and “rf_off_reason_indicator” as “true” and “weak electric field”, respectively, in step  222 , and then sets timer B.  
         [0031]     In contrast, as a result of comparison in step  221 , when the AGC RSSI is greater than the minimum threshold value, the central processing unit  120  proceeds to step  223  in which the central processing unit  120  compares a signal-to-noise ratio (Ec/Io) for a received signal from antenna  11   a  with a threshold value. As a result of the comparison, when the signal-to-noise ratio is greater than the threshold value, the central processing unit  120  sets the “rf_off_indicator” as “false” in step  224 , and switches on that portion of the modem which has been previously switched off, in step  230  and then sets timer A. In contrast, as a result of the comparison in step  223 , when the signal-to-noise ratio is smaller than the threshold value (which represents that the second path is at an IMD state), the central processing unit  120  sets the “rf_off_indicator” and “rf_off_reason_indicator” to ‘true’ and ‘IMD’, respectively, in step  225 , and then sets timer A.  
         [0032]     Meanwhile, as a result of the determination in step  211 , when the second path is switched on, the central processing unit  120  proceeds to step  231 , in which the central processing unit  120  compares values of an AGC RSSI, an Ec/Io and a BER with corresponding threshold values for a received signal from antenna  11   a.  As a result of the comparison, when any one of the values is smaller than its corresponding threshold value, the central processing unit  120  compares the three values with corresponding minimum threshold values in step  232 . As a result of the comparison in step  232 , when all of the three values are smaller than the corresponding minimum threshold values, respectively (which represents that the second path is at a “weak electric field” state), the central processing unit  120  proceeds to step  233 . In step  233 , the central processing unit  120  sets the “rf_off_indicator” and “rf_off reason_indicator” as “true” and “weak electric field”, electric field’, respectively, and then sets timer B. In contrast, as a result of the determination step  232 , when all the three values are greater than the corresponding minimum threshold values, the central processing unit  120  sets timer A.  
         [0033]     Meanwhile, as a result of step the comparison in  231 , when all the values of the AGC RSSI, the Ec/Io and the BER are greater than the corresponding threshold values, (which represents that the second path is at a “strong electric field” state), the central processing unit  120  proceeds to step  241 . In step  241 , the central processing unit  120  sets the “rf_off_indicator” and “rf_off_reason_indicator” as “true” and a “strong electric field”, respectively, and then sets timer A.  
         [0034]     According to the embodiment of the present invention, the terminal receiver of a satellite DMB system includes a rake receiver and employs antenna diversity so as to switch off one of radio paths, so that it is possible to decrease power consumption, thereby further improving the terminal receiver&#39;s reception.  
         [0035]     While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the scope of the invention is not to be limited by the above embodiments but by the claims and the equivalents thereof.