Abstract:
A method for controlling the power supplied to an RF receiver in a paging receiver is provided. The method includes the step of synchronizing the paging receiver with a paging system which periodically transmits paging data at specified repetitive intervals. The paging data includes preamble data followed by batch data. Power is then periodically supplied to the RF receiver at the specified repetitive intervals. When the RF receiver is being supplied with the power, it is determined whether the RF receiver is receiving the preamble data. If the RF receiver is receiving the preamble data, then self frame data is detected from the batch data Next, it is checked whether information indicating an end of the batch data is being received. If the information is being received, then the power supplied to the RF receiver is cut off.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to paging receivers, and more particularly, to a method for controlling the power supplied to an RF (Radio Frequency) receiver in a paging receiver. 
     2. Description of the Related Art 
     A paging receiver uses a battery as a power source. Thus, in order to minimize power dissipation, the paging receiver supplies power to an RF receiver in the paging receiver on a periodic (non-continuous) basis. 
     In a conventional paging system, paging data is asynchronously transmitted in POCSAG code. Section A of FIG. 1 is a waveform diagram of the paging data, which consists of preamble data PD and batch data BD. The preamble data PD is a reversal code which switches between “1” and “0” during 576 bits, and enables the paging receiver to detect the asynchronously transmitted paging data. The batch data BD consists of a plurality of batches, each having a sync code for synchronizing a codeword and a plurality of frame data. As shown, the paging system transmits the paging data in irregularly alternating intervals (asynchronously). 
     In order to minimize power dissipation and facilitate failure free reception of paging data from the paging system, the paging receiver blocks (cuts off) power to the RF receiver for a specific time interval (ΔT) which is less than the transmission time interval for the preamble data PD. Then, the paging receiver supplies (unblocks) power to the RF receiver for a predetermined time interval during which the RF receiver can receive the transmitted data and check whether the received data is preamble data PD. That is, the paging receiver repeatedly blocks and supplies power to the RF receiver for the time AT and the predetermined time, respectively. 
     Section B OF FIG. 1 is a waveform diagram illustrating the state (i.e., blocked or unblocked) of the power supplied to the RF receiver in the paging receiver. The high state of the waveform of FIG. 1B corresponds to the paging receiver supplying power (unblocked) to the RF receiver, and the low state corresponds to the paging receiver blocking power to the RF receiver. The paging receiver decodes the data received from the RF receiver and then, judges whether or not the received data is preamble data PD. If the decoded data is preamble data PD, the paging receiver drives (sets) the RF receiver in (to) a batch mode in order to enable the RF receiver to receive the batch data following the preamble data PD. However, if the decoded data is not preamble data PD, the paging receiver continues to check whether or not preamble data PD is being received, while repeatedly supplying and blocking power to the RF receiver. 
     It is to be appreciated that since the paging system transmits paging data asynchronously, the paging receiver cannot predict when paging data is going to be transmitted in order to timely supply power to the RF receiver. Therefore, in order to facilitate failure free reception of the paging data transmitted from the paging system, the conventional paging receiver periodically supplies power to the RF receiver for a specific time interval (ΔT) which is shorter than the transmission time interval for the preamble data PD, including during an idle interval where the paging system does not transmit paging data. Accordingly, even when the paging system does not transmits paging data, the paging receiver supplies power to the RF receiver unnecessarily, thereby wasting power. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method for minimizing the power dissipation of an RF receiver in a paging receiver. 
     To achieve the above and other objects, there is provided a method for controlling the power supplied to an RF receiver in a paging receiver. The method includes the step of synchronizing the paging receiver with a paging system which periodically transmits paging data at specified repetitive intervals. The paging data includes preamble data followed by batch data. Power is then periodically supplied to the RF receiver at the specified repetitive intervals. When the RF receiver is being supplied with the power, it is determined whether the RF receiver is receiving the preamble data. If the RF receiver is receiving the preamble data, then self frame data is detected from the batch data Next, it is checked whether information indicating an end of the batch data is being received. If the information is being received, then the power supplied to the RF receiver is cut off. 
     These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings, where the same reference numerals are used to represent the same functional elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows are waveform diagrams illustrating paging data (section A), and the state of the power supplied to an RF receiver in a paging receiver (section B), according to the prior art; 
     FIG. 2 is a block diagram of a paging receiver according to an embodiment of the present invention. 
     FIG. 3 is a flow chart illustrating a method for controlling the power supplied to an RF receiver in a paging receiver according to an embodiment of the present invention; and 
     FIG. 4 shows are waveform diagrams illustrating paging data (section A), and the state of the power supplied to an RF receiver in a paging receiver (section B), according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention will be described in detail hereinbelow with reference to the accompanying drawings. In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known functions or constructions have not been described so as not to obscure the present invention. 
     Initially, it is to be appreciated that in a paging system according to the present invention, paging data is synchronously transmitted. Further, in the illustrative embodiment of the invention, the paging system transmits paging data precisely every minute. This is shown in section A of FIG. 4, which is a waveform diagram illustrating paging data according to the present invention. In section A of FIG. 4, n′ corresponds to the number of elapsed minutes and 00″ corresponds to the number of elapsed seconds, i.e., n′ 00″(n minutes and 0 seconds), (n+1)′ 00″, (n+2)′ 00″, (n+3)′ 00″, and so on. 
     Referring back to FIG. 2, a paging receiver according to the present invention is shown. The paging receiver receives the paging data synchronously transmitted from the paging system, as stated above. An RF receiver  14  amplifies a weak RF signal received through an antenna ANT at a specified channel, frequency-shifts the amplified RF signal to the original frequency band to demodulate it, and then reshapes the demodulated signal. A decoder  12  detects preamble data from the data outputted from RF receiver  14 . The decoder also decodes batch data following the preamble data in order to detect frame data from the batch data based on a CAP code provided from a controller  10 . The detected frame data is then provided to the controller  10 . Further, in case an all-high or all-low pattern is generated at the sync code position of the batch data, decoder  12  provides controller  10  with end information of the batch data to recognize the end of the batch data. Additionally, decoder  12  connects or disconnects a power supplying path to RF receiver  14  according to a power control signal from controller  10 . 
     The controller  10  controls the overall operations of the paging receiver. In particular, controller  10  performs the paging service according to various data provided from decoder  12 , and controls the power supplied to RF receiver  14 . A display  16 , under the control of controller  10 , displays incoming messages and the various statuses generated in the process of the paging service. An alarm  18 , under the control of controller  10 , generates an alarm signal upon receiving an incoming message. 
     FIG. 3 is a flow chart illustrating a method for controlling the power supplied to the RF receiver  14  in the paging receiver according to an embodiment of the present invention. When the paging receiver is powered on, controller  10  provides decoder  12  with the power control signal for supplying power to RF receiver  14  (step  20 ). The decoder  12  connects the power supplying path to RF receiver  14  according to the power control signal. Being supplied with power, RF receiver  14  receives data from the paging system at the specified transmission channel and provides it to decoder  12 . The decoder  12  determines whether or not the received data is preamble data. If the received data is preamble data, then such data is provided to controller  10 . Here, the time interval during which power is supplied to the RF receiver  14  is set equal to the time interval required for the RF receiver  14  to receive data and for the decoder  12  to determine whether or not the received data is preamble data. 
     Referring back to FIG. 3, controller  10  checks whether or not decoder  12  is providing preamble data (step  22 ). If decoder  12  is providing preamble data, then controller  10  proceeds to step  26 . However, if decoder  12  is not providing preamble data, then controller  10  provides decoder  12  with the power control signal for blocking the power supplied to RF receiver  14  (step  24 ). The blocking power control signal is supplied for a time interval (hereinafter “power-off interval”) which is less than the transmission time interval of the preamble data from the paging system. That is, the power-off interval is set in consideration of the transmission time interval of the preamble data from the paging system. Thus, according to the power control signal, the decoder  12  disconnects the power supplying path to RF receiver  14  for the power-off interval. 
     As stated above, the paging receiver is not in sync with the paging system at the initial power-on state of the paging receiver. As a result, controller  10  blocks the power supplied to RF receiver  14  for the power-off interval (which is less than the transmission time interval of the preamble data) and then, supplies the power for the time interval during which the paging receiver can receive data and judge whether or not the received data is preamble data. The controller  10  repeats the steps of blocking and supplying power to RF receiver  14  until preamble data is received. In this way, controller  10  detects the paging data transmitted from the paging system at the initial power-on state. 
     In the meantime, if preamble data is received, then controller  10  corrects a “current time” in order to synchronize the paging receiver with the paging system (step  26 ). Here, as to the correction of the current time, controller  10  corrects an error of a previously set time interval which may be set arbitrarily, e.g., −30sec˜+29sec. For example, if the time when the paging receiver receives preamble data is XX minutes and 1 second, then the current time has an error of 1 second (i.e., the current time is out of sync by 1 second), since the paging system transmits paging data precisely every minute (i.e., XX minutes, 0 seconds). In this case, the time error of 1 second falls within the time interval of −30sec˜+29sec. Accordingly, controller  10  resets the current time to XX minutes and 00 second in order to correct the time error. 
     After correction of the current time, controller  10  provides decoder  12  with the power control signal for driving RF receiver  14  in the batch mode (step  28 ). The decoder  12  controls the power supplied to RF receiver  14  according to the power control signal. Operating in the batch mode, the RF receiver  14  provides its output data to decoder  12 , which detects the self frame data and the batch data end information from the output data of RF receiver  14 . The controller  10  then processes the detected frame data. 
     In the course of processing the frame data, controller  10  checks whether or not decoder  12  has detected the batch data end information (step  30 ). If decoder  12  has detected the batch data end information, then controller  10  proceeds to step  32 . However, if decoder  12  has not detected the batch data end information, then controller  10  continues to process the frame data. 
     At step  32 , controller  10  provides decoder  12  with the power control signal for blocking the power supplied to RF receiver  14 . The decoder  12  cuts off the power supplied to RF receiver  14  according to the power control signal. 
     While the power to RF receiver  14  is blocked, controller  10  checks whether or not the current time corresponds to the next transmission time, i.e., the time at which the paging system is to again transmit preamble data (step  34 ). That is, since the paging system transmits paging data precisely every minute, the next transmission time of preamble data is precisely one minute after the corrected current time. If the current time corresponds the next transmission time of preamble data, then controller  10  proceeds to step  36 . However, if the current time does not correspond to the next transmission time, then the power supplied to RF receiver  14  remains blocked until the next transmission time. 
     At step  36 , controller  10  provides decoder  12  with the power control signal for supplying power to RF receiver  14 . The decoder  12  connects the power supplying path to RF receiver  14  according to the power control signal. Being supplied with power, RF receiver  14  receives the data transmitted from the paging system and provides such data to decoder  12 . The decoder  12  then checks whether or not the received data is preamble data and if so, provides the received data to controller  10 . 
     While RF receiver  14  is being supplied with power, controller  10  checks whether or not decoder  12  is providing preamble data (step  38 ). If decoder  12  is providing preamble data, then controller  10  proceeds to step  28  in order to process the corresponding data. However, if decoder  12  is not providing preamble data, then controller  10  proceeds to step  32  in order to block the power supplied to RF receiver  14  until the current time equals the next transmission time of preamble data. 
     As described above, once the paging receiver is synchronized with the paging system, controller  10  supplies power to RF receiver  14  in sync with the cycle in which the paging system transmits paging data. Then, controller  10  blocks the power supplied to RF receiver  14  in sync with the batch data end information of the paging data. As a result, controller  10  supplies power to RF receiver  14  only while the paging system is transmitting paging data. 
     In sum, upon power-up, the paging receiver according to the present invention checks whether or not paging data is received for a time interval which is shorter than the transmission time interval of preamble data. Once the paging data is initially received, the paging receiver supplies power to the RF receiver in sync with the paging system. That is, power is supplied to the RF receiver for only as long as the paging system transmits paging data. In this manner, the paging reeceiver of the invention minimizes power consumption. 
     As illustrated in section A of FIG. 4, the paging system transmits paging data, consisting of preamble data PD and batch data BD, precisely every minute. The paging receiver supplies power to the RF receiver precisely every minute and then, cuts off the power supplied to the RF receiver at the time point where the end of the batch data is detected. This is shown in section B of FIG. 4, which is a waveform diagram illustrating the state of the power supplied to the RF receiver according to the present invention. The high state of the waveform represents the power supplying interval and the low state represents the power blocking interval. 
     As described above, the paging receiver of the invention supplies power to the RF receiver only when the paging system transmits paging data, thereby minimizing unnecessary power consumption. Further, since the paging receiver corrects the current time in sync with the paging system, it can prevent an out-of-sync condition of the current time. 
     Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention.