KR100724981B1 - Method and apparatus for scanning channel in broadcasting system - Google Patents

Abstract

The present invention relates to a method for searching for a channel in a DMB system and a broadcast receiver according to the present invention. The method of the present invention includes a first process of receiving a signal of a service channel being broadcast, and a second process of confirming reception capability of the broadcast service channel. And searching for a frequency band of another channel when the reception performance is less than or equal to a predetermined reference value. The broadcast receiver of the present invention includes a RF tuner for receiving a broadcast signal, a reception performance measurer for measuring a reception performance of a currently received broadcast signal, and a channel search for searching a frequency band of another channel when the reception performance is less than a predetermined reference value. And a display unit for indicating a reception state of the searched other channels.

DMB, MFN, SFN, RSSI

Description

Channel search method and apparatus in broadcasting system {METHOD AND APPARATUS FOR SCANNING CHANNEL IN BROADCASTING SYSTEM}

1 is a block diagram showing a general receiver used in a terrestrial DMB system

2 is a block diagram showing a broadcast receiver according to a preferred embodiment of the present invention.

3 is a flowchart illustrating a broadcast signal search method according to a preferred embodiment of the present invention.

4 is a flowchart illustrating a channel search process according to an embodiment of the present invention.

5 is a timing diagram showing an example when searching for a broadcast channel according to a preferred embodiment of the present invention.

The present invention relates to a method for searching a channel in a broadcasting system and a broadcast receiver according to the present invention, and more particularly to a method for searching for a channel in a digital multimedia broadcasting (DMB) system and a broadcast receiver according to the present invention.

In general, DMB system is divided into satellite DMB and terrestrial DMB. The satellite DMB system sends a program to a satellite in the satellite DMB broadcasting center and broadcasts it to DMB terminals nationwide through radio waves. Terrestrial DMB transmits programs on the ground using frequencies. Therefore, the broadcast signal is transmitted to the DMB terminal by using an empty broadcast channel.

As described above, since the satellite DMB system uses a satellite, a single frequency band (SFN) is used, and the terrestrial DMB system uses an existing broadcasting channel. Will be used.

Then, the terminal used in the terrestrial DMB system will be described with reference to FIG. 1. 1 is a block diagram showing a general receiver 100 used in a terrestrial DMB system.

Referring to FIG. 1, an RF tuner 103 receives a broadcast signal through an antenna 101. Here, the RF tuner 103 down-converts the received broadcast signal by controlling a phase locked loop (PLL) 113 based on information according to an external channel condition to the controller 115. -Converting) That is, the controller 115 controls the PLL 113 according to the channel information input from the user interface (UI) 117 to convert the broadcast signal into baseband. Therefore, when a channel conversion is desired, the user must determine which frequency to demodulate directly through the UI 117.

The baseband signal thus obtained is converted into an analog signal into a digital signal through an analog to digital converter (ADC) 105. The broadcast signal converted into the digital signal is converted into a signal capable of demodulation through a low pass filter (LPF) 107. The changed broadcast signal is finally decoded through the demodulator 109 and the codec 111.

In a broadcast receiving system, a shadow area always exists. Therefore, the broadcast receiver 100 inevitably cannot operate normally in such a shaded area while the broadcast receiver 100 is moving. In this case, in general, the broadcast receiver 100 displays a message on the display unit that the viewer cannot view because of the current shadow area through the UI 117 in order to reduce inconvenience of the user. However, when terrestrial broadcasting such as terrestrial DMB system, all frequency channels may be astigmatism at the same time, but in most cases, some channels cannot be viewed but others can be viewed. In this case, in the conventional broadcast receiver 100, in order to watch another frequency channel, the broadcast receiver that is currently receiving must be stopped and newly scanned for a desired frequency. That is, when the broadcast receiver 100 moves out of a single frequency band, broadcast reception is interrupted. For example, when the broadcast receiver 100 moves to a different regional broadcasting area while receiving a broadcast of a broadcast channel of a specific region, the broadcast receiver 100 enters a weak electric field while the user does not take any action, and the broadcast signal is transmitted. You will be cut off.

Therefore, in order to prevent such a case in the conventional broadcast receiver 100, all the possible frequency channels must be searched in order to find a desired frequency channel, and thus, a considerable time is required and a problem cannot be received in the meantime.

Accordingly, an object of the present invention for solving the above problems is to provide a method for searching for a broadcast service of another channel without interruption of a broadcast service when moving in a multi-frequency broadcasting (MFN) system and a broadcast receiver accordingly. have.

Another object of the present invention is to provide a method for seamlessly switching a broadcast service of another channel in a multi-frequency broadcasting (MFN) system in a multi-frequency broadcasting (MFN) system, and a broadcast receiver accordingly. .

Another object of the present invention is to provide a method for seamless handover to another channel when a mobile terminal moves in a regional broadcasting system, and a broadcast receiver accordingly.

According to an aspect of the present invention, there is provided a method of receiving a broadcast service by a broadcast receiver in a broadcast system using a multi-frequency frequency band (MFN). And a second step of checking a reception performance of the broadcast service channel; a third step of searching for a frequency band of another channel when the reception performance is less than or equal to a predetermined reference value; It further comprises a fourth process.

The third process includes the steps of measuring the received signal strength of the channel for a predetermined time by transitioning to a frequency of a predetermined channel among the other channels, and returning to the current broadcast service channel after measuring the received signal strength of the channel. And checking whether the signal strengths of all the other channels are measured, and measuring the signal strengths of all the other channels, and re-measurement of all the other channels after the delay checking time.

The indicator of the reception performance is characterized in that one of a bit error rate (BER), a frame error rate (FER), a signal power to noise power ratio (SNR).

The present invention for achieving the above object is a broadcast receiver of a broadcasting system using a multi-frequency band (MFN), receiving a broadcast signal to receive the RF tuner and the reception performance of the currently received broadcast signal; And a reception unit for measuring the reception performance, a channel search unit for searching a frequency band of another channel when the reception performance is less than or equal to a predetermined reference value, and a display unit for indicating a reception state of the searched other channels.

The channel searching unit transitions to a frequency of a predetermined channel among the other channels, measures the received signal strength of the channel for a predetermined time, returns to the current broadcast service channel, and delays when the measurement of the signal strength of all the channels is completed. After the confirmation time is characterized in that the process of measuring all the measured channels again.

DETAILED DESCRIPTION Hereinafter, detailed descriptions of preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible. Specific details are set forth in the following description, which is provided to aid a more general understanding of the invention. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention provides a method for searching a channel without disconnection when a mobile station moves out of a single frequency band (SFN) in a broadcasting system using a multi-frequency frequency band (MFN) and a broadcast receiver accordingly. Will be explained. To this end, in the following description, a broadcast receiver according to the present invention will be described and a broadcast service reception method according to the present invention will be described.

2 is a block diagram illustrating a broadcast receiver 200 according to a preferred embodiment of the present invention. In FIG. 1, the same apparatus as in FIG. 1 uses the same term.

Referring to FIG. 2, the broadcast receiver 200 includes a reception performance measuring unit 215 and a channel search unit 221 that can search for channels in a different single frequency band when the mobile terminal moves.

The apparatus of the broadcast receiver 200 will be described in detail. The automatic gain control (AGC) 213 measures the power of a received sample of the analog to digital converter (ADC) 205. By controlling the gain of the amplifier in the RF tuner 203 to maintain a constant reference power. In addition, in the present invention, the AGC 213 moves to the boundary of a single frequency band when the mobile station moves to inform the received signal strength indication (RSSI) required for channel search of another channel. The control signal at the time of controlling the gain of the amplifying element is an amount that is inversely proportional to the actual received power, so that the RSSI can be known from the amount of the control signal.

The reception performance measurer 215 measures the reception performance indicators received from the demodulator 209 and the codec 211 to control the enable signal informing whether the channel search unit 221 is operating. The reason why the reception performance measurer 215 controls the operation of the channel search unit is that the broadcast receiver 200 searches for a broadcast signal of another channel only when the performance of the reception channel is degraded. Accordingly, the reception performance measuring unit 215 determines a predetermined reference value in advance, and turns on the enable signal on the channel search unit when the reception performance index is less than or equal to the reference value. The reception performance index may be a bit error rate (BER), a frame error rate (FER), a signal power to noise power ratio (SNR), or the like.

The channel search unit 221 performs a channel scanning task according to the present invention when the reception performance is less than or equal to a predetermined reference value. The channel search operation searches for other broadcasting channel frequencies or frequencies of other SFNs using the period in which the RF tuner 203 does not receive a broadcast signal currently being received. After the channel search process, the channel search unit 221 informs the control unit 217 of a reception state of another broadcast channel or another SFN. Since the channel searching method according to the present invention will be described later, it will be omitted here.

The phase control unit (PLL) 219 is a frequency negative feedback circuit configured to adjust the phase of the RF tuner 203 to maintain a constant frequency of the output signal at all times. 221 is controlled.

The controller 217 receives a reception state of another channel transmitted from the channel searcher 221 and controls a corresponding operation. In this case, the corresponding operation may be controlled so that the broadcast receiver 200 may automatically perform handover to the same broadcast when moving, and may be displayed on a display unit (not shown) so that the user may know.

Next, a channel search method according to the present invention will be described with reference to FIGS. 3 and 4.

3 will be described with reference to the broadcast signal search method of the present invention using the broadcast receiver 200.

Referring to FIG. 3, first, in step 301, the broadcast receiver 200 demodulates a received signal currently being broadcast. Then, in step 303, the reception performance measurement unit 215 of the broadcast receiver 200 determines whether the reception performance state of the received reception signal is greater than or equal to a predetermined reference value. As described above, the step 303 is for the broadcast receiver 200 to search for other broadcast channel frequencies or frequencies of different SFNs when the performance of the current received signal is degraded when it is moving. Therefore, when the reception performance of the current reception signal is equal to or greater than the reference value, the process proceeds to step 301 to continue receiving the current broadcast.

However, if the reception performance of the current reception signal is less than or equal to the reference value, in step 305 to search for other broadcasting channel frequencies or frequencies of another SFN, the received signal strength (RSSI) is measured for all channels. The process of searching for the received signal strength (RSSI) is shown in FIGS. 4 and 5 below.

 4 is a diagram illustrating a channel search process according to the present invention.

Referring to FIG. 4, the channel search unit 221 of the broadcast receiver 200 transitions to another channel frequency other than the channel currently being broadcast using the phase controller 219 in step 401. For example, assuming that the broadcast receiver 200 is at the boundary of a single frequency band (SFN) and has four frequency channels in the other single frequency band (SFN) when the mobile receiver 200 moves, the broadcast receiver 200 One of the frequency channels 1 to 4 of the other single frequency band (SFN). The frequency channel selection can be made sequentially or arbitrarily.

When the frequency of the selected channel is shifted, the broadcast receiver 200 calculates a received signal strength (RSSI) for the channel in step 403. When the received signal of the selected channel is measured in step 403, the current reception channel is returned in step 405, and a predetermined time is waited as in step 407. The reason for waiting for the predetermined time is to be not affected by receiving a channel currently being broadcast. Herein, a time measured for calculating the received signal strength (RSSI) of the selected channel is represented as a delay time, and the predetermined time means a time for measuring the received signal strength (RSSI) of the next channel. In the description, the delay time will be referred to as a delay.

After the delay time, the broadcast receiver 200 checks whether the frequency search of all other broadcast channels is completed in step 407. If all channel frequencies are not searched for in step 409, the broadcast receiver 200 selects the next channel in step 411 and repeats steps 401 to 407. Therefore, the search is repeated until all the search is completed from the frequency channel 1 to the frequency channel 4.

When all the frequency search is completed, the process proceeds to step 307 of FIG.

In this case, various methods may be used to check whether all the frequencies have been searched. In the above example, if the frequency (F) of the channel currently searched in step 409 is determined as the last frequency channel 4, the channel search may be completed.

5 is a timing diagram illustrating an example of a broadcast channel search according to the present invention. The horizontal axis t represents time and the vertical axis represents received signal strength (RSSI).

Referring to FIG. 5, f1 to f4 represent channels of different single frequency bands (SFN), and widths of each of f1 to f4 represent measurement times 503. Delay 501 represents a time interval between each f1 to f4. Looking at the timing diagram, it can be seen that the measurement time 503 occupies an extremely short period compared to the delay time 501. In general, since the measurement time 503 of the RF tuner 201 is several hundred us or less, it is a very short period compared to the unit of the entire channel coding or interleaver. Therefore, it can be seen that the channel search method of the present invention can measure the quality of other frequency channels with little degradation in reception performance such as disconnection. It hardly gives performance degradation such as disconnection to broadcast receiver.

As shown in FIG. 4, when all frequency searches for other broadcast channels are completed, as shown in step 307 of FIG. 3, the received signal strength (RSSI) of all channels is measured again after the confirmation timer. Because measuring the received signal strength (RSSI) once is not reliable as it is, and the received signal strength (RSSI) shows a large vibration due to channel fading in wireless communication. This is to prevent. The reconfirmation method may include various methods such as using a delay of a timer as the most basic method.

After the reconfirmation method is performed in step 307, the broadcast receiver 200 performs the corresponding operation in step 311 when the received signal strength RSSI reconfirmed in step 309 is a frequency higher than a predetermined threshold. That is, in step 311, a frequency higher than the threshold value means that a service of a corresponding channel can be received. In this case, the handless operation may be performed directly to another channel, or the reception state of the channel may be displayed on the display unit. .

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention can provide the terminal users using the broadcast service with convenience of providing the availability of other channels in the shadow area, thereby greatly improving the competitiveness of the terminal. Unlike this, it is possible to make seamless handover operation with only a simple timer and confirmation detector without the need for a separate complicated searcher.

Claims (8)

In a method for receiving a broadcast service by a broadcast receiver in a broadcast system using a multi frequency network (MFN), Receiving a signal of a service channel being broadcast; Checking a reception quality of the broadcast service channel; When the reception quality is equal to or less than a predetermined reference value, transitioning to a frequency of a predetermined channel among broadcast service channels and measuring the received signal strength of the determined channel for a predetermined time; Returning to the current broadcast service channel after measuring the received signal strength of the transitioned channel; Checking whether signal strengths of all broadcasting service channels are measured; And measuring signal strength of all broadcast service channels after a confirmation timer after measuring a signal strength of all broadcast service channels. The method of claim 1, And displaying a service reception state of the measured channel on a liquid crystal display (LCD). delete The method of claim 1, wherein the reception quality is, A method of receiving broadcast service, characterized in that one of bit error rate (BER), frame error rate (FER), signal power to noise power ratio (SNR). In a broadcast receiver of a broadcasting system using a multi frequency network (MFN), An RF tuner for receiving a broadcast signal, A reception performance measurement unit for determining reception performance by measuring a reception channel quality of a broadcast signal currently received; When the reception performance is less than or equal to a predetermined reference value, the signal transitions to a frequency of a predetermined channel among the broadcast service channels, measures the received signal strength of the determined channel for a predetermined time, and then returns to the current broadcast service channel. A channel searching unit searching for a channel by re-measuring the signal strengths of all the broadcast service channels after a confirmation timer when the measurement of the signal strength is completed; And an automatic gain control unit for measuring the strength of a received signal when searching for the channel. The method of claim 5, And a display unit for indicating a service reception state of the searched other channel. delete The method of claim 5, wherein the reception quality is, And a bit error rate (BER), a frame error rate (FER), and a signal power to noise power ratio (SNR).

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