KR20070097281A - Method for transmitting in mobile communication system - Google Patents

Abstract

A communication method in a mobile communication system is provided to grasp the transmission timing of a channel in a communication system rapidly so that the data transmitted through the channel can be swiftly demodulated. A mobile terminal receives signals through a multichannel containing an SCH(Synchronization CHannel), a pilot channel, and a BCH(Broadcast CHannel)(S400). The mobile terminal searches the SCH and acquires the initial time synchronization(S410). Then the mobile terminal checks an SCH signal and confirms whether the BCH is transmitted after the transmission of the SCH(S420). In case the BCH is transmitted, the mobile terminal confirms the transmission timing of the BCH(S430). In other words, the mobile terminal catches the transmission timing of the BCH through the SCH. Then the mobile terminal demodulates the BCH and acquires necessary information for the system(S440).

Description

Method for transmitting in mobile communication system

1 is a block diagram illustrating an OFDM scheme.

2 is a view for explaining a preferred embodiment of the present invention.

3 is a view for explaining another preferred embodiment of the present invention.

4 is a flowchart according to a preferred embodiment of the present invention.

5 is a view for explaining another preferred embodiment of the present invention.

6 is a flow chart according to another preferred embodiment of the present invention.

The present invention relates to a system for communicating using a plurality of channels, and more particularly, to a method for more quickly demodulating information transmitted through the channel.

1 is a block diagram illustrating an OFDM scheme. Hereinafter, an orthogonal frequency division multiplexing (OFDM) scheme, which is an example of a communication system using a plurality of subcarriers, will be described with reference to FIG. 1.

The OFDM method divides a data string having a high data rate into a large number of data strings having a low data rate, and transmits a data through a carrier for each of the data strings. Each of the plurality of carriers is called a subcarrier. Since orthogonality exists between a plurality of carriers used in the OFDM scheme, even if the frequency components of the carriers overlap each other, they can be detected by the receiving end. The high data rate data stream is converted into a plurality of low data rate data streams through the serial / parallel converter 110 for transmission in the OFDM scheme. After each subcarrier is multiplied by a plurality of data streams converted into parallel streams, the data streams are summed and transmitted to the receiving end (120). A plurality of parallel data streams generated by the serial / parallel transform unit 110 may be transmitted to a plurality of subcarriers by an inverse discrete fourier transform (IDFT) module 130, and the IDFT 130 may be inversely fast. It can be efficiently implemented using the Inverse Fast Fourier Transform (IFFT). Since the symbol duration of the low carrier subcarrier is increased, relative signal dispersion in time caused by multipath delay spread is reduced. Inter-symbol interference (ISI) can be reduced by inserting a guard interval longer than the delay spread of the channel between OFDM symbols. In addition, if a part of the OFDM signal is copied to the guard period and placed at the beginning of the symbol, the OFDM symbol may be cyclically extended to protect the symbol (150).

Hereinafter, an orthogonal frequency division multiple access (OFDMA) scheme as an example of a multiple access method will be described. The OFDMA scheme refers to a multiple access method for realizing multiple access by providing each user with a part of subcarriers available in a modulation system using a plurality of orthogonal subcarriers. The OFDMA scheme provides a frequency resource called a subcarrier to each user, and each frequency resource is provided to a plurality of users independently of each other so that they do not overlap each other.

 In the mobile communication method using the CDMA method, since each channel is divided into codes, multiple channels can be transmitted at the same time. Thus, a broadcast channel (BCH) can always be allocated so that timing of signal transmission through the broadcast channel can be understood as a relationship with the frame transmission time of other channels. However, in the mobile communication method using the OFDMA scheme, since a broadcast channel must be transmitted at a different frequency band or at a different time with respect to other channels, a method for knowing when a broadcast channel can be transmitted is required.

The present invention has been made to solve the problems of the prior art as described above, to provide a method for transmitting and receiving data more efficiently, so that it is possible to quickly know the reception time of the channel to which data information is transmitted. It is for.

The present invention relates to a method for providing information on a transmission time of a channel in which predetermined information is transmitted in a system for communicating using a plurality of channels. In one embodiment, a method of presetting a transmission time interval between transmission channels is proposed. In another embodiment, a method for providing a transmission time of a frame through the differentiated channel is provided in a frame including the channels. For example, in the present invention, when transmitting a sync channel and a broadcast channel, the transmission time of the broadcast channel can be predicted by searching for the sync channel by setting the two channel transmission time intervals to a fixed value. It provides a way to be more efficient.

The objects, structures and other features of the present invention described above will become apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the case of exchanging data between a base station and a user terminal in a mobile communication system, the transmission of data from the base station to the terminal side is called downlink transmission, and the transmission of data from the terminal to the base station side is called uplink transmission. . Scheduling for a data transmission method is used for the data exchange. Hereinafter, the scheduling will be described.

In a mobile communication system, a base station transmits and receives data through a wireless channel environment with a plurality of terminals in a cell. In a multi-carrier and similar system, the base station receives packet data (traffic) from the network and transmits the received traffic to each terminal using a predetermined communication scheme. At this time, it is downlink scheduling that the base station decides which timing region to use to transmit data to which terminal and through which format. In addition, the base station receives and demodulates the packet data transmitted from the terminal and transmits the packet data to a network (for example, the Internet network). It is uplink scheduling that determines, at what timing, which baseband the base station transmits to each terminal, how much uplink data is to be transmitted, and in what format.

Hereinafter, an embodiment of a method for initially connecting a terminal to a base station will be described. In order for a terminal to perform communication such as receiving data from a base station, time / frequency synchronization must be synchronized. An example of the time synchronization method will be described. In a wireless mobile communication system, when a terminal attempts an initial access to a base station, an initial time synchronization may be obtained by searching for a predefined synchronization channel (SCH) transmitted by base stations of each cell. Through the synchronization channel (SCH), a synchronization channel code is transmitted for the base station and the terminal to synchronize the time / frequency synchronization for data transmission and reception between each other. That is, the terminal searches for the synchronization channel when establishing initial synchronization. When searching, it searches for what frequency offset a known sync channel code is currently being received at. Then, the received synchronization channel is detected, and the timing of receiving the synchronization channel is determined as a reference point for time synchronization. The sync channel uses a different code for each cell, and the terminal searches for possible codes during initial synchronization, and detects the code actually transmitted therefrom using a correlator to identify the cell to which the terminal attempts to access. Acquire.

If it is determined that the synchronization channel is being received at a specific frequency offset at a specific time, it is possible to check whether the synchronization channel is being detected or is receiving an interference signal or noise while adjusting the time / frequency more precisely. In other words, if the synchronization channel is detected, it may be said that the time / frequency synchronization is performed to some extent.

When the first time synchronization is obtained through the method, the terminal receives data related to system information transmitted by the corresponding base station. The channel through which the data is transmitted is called a broadcast channel (BCH). By reading the broadcast channel signal, it is possible to obtain basic information necessary for data transmission and reception mainly through the corresponding cell. For example, what scrambling code will be used to access the terminal at the time of access for initial access on the uplink, which multi-antenna transmission technique is used for which channel on the downlink, Various information such as which channel of the downlink uses which code is transmitted.

In a system for communicating using a plurality of subcarriers, a method of knowing a transmission point of a broadcast channel will be described. In order to provide the information, a synchronization channel (SCH) may be used. A method of providing information using the synchronization channel (SCH) will be described.

2 is a view for explaining a preferred embodiment of the present invention. Hereinafter, a method of presetting a fixed transmission time interval between the synchronization channel (SCH) and the broadcast channel (BCH) so that the transmission time of the broadcast channel (BCH) is known will be described with reference to FIG. 2.

The transmission time interval for transmitting the synchronization channel (SCH) 220 and the broadcast channel (BCH) 230 signals is determined to have a predetermined value 210. That is, the time for transmitting the sync channel 220 and the time for transmitting the broadcast channel 230 are set to have a predetermined time interval. Accordingly, the terminal can know the transmission time of the broadcast channel 230 using only time information on which the synchronization channel signal is transmitted, and can read the signal transmitted through the broadcast channel 230.

For example, if the sync channel 220 signal is transmitted at time t, the broadcast channel 230 signal is set to be transmitted at time t + T. That is, in this case, the time interval for transmitting the synchronization channel 220 and the broadcast channel is T 210. If the system defines that the broadcast channel signal is transmitted after the time of T 210 at the time of transmission of the synchronization channel signal, the terminal does not have to process frame synchronization after acquiring time synchronization through the search for the synchronization channel 220. A transmission time t + T of the broadcast channel signal 230 may be predicted. Accordingly, the signal transmitted through the broadcast channel 230 may be demodulated more quickly.

In addition, the present invention can be applied not only to a case where a broadcast channel is transmitted after the sync channel signal is transmitted, but also to a case where the broadcast channel is transmitted before. That is, it may be set that the broadcast channel is transmitted before a certain time interval before the transmission time of the sync channel. Even in this case, the terminal can quickly find out information at the time of transmission of the broadcast channel using only time information on which the synchronization channel is transmitted. If the transmission time of the broadcast channel signal is known, the broadcast channel signal is demodulated to obtain information included in the signal.

If the sync channel and the broadcast channel are transmitted periodically instead of only once, the above / after distinction of the sync channel described above may mean the same. For example, a sync channel and a broadcast channel are transmitted once in 10 slots, the broadcast channel is transmitted in 2 sync slots after the sync channel is transmitted, and the broadcast channel is transmitted 8 slots before the sync channel is transmitted. It can mean the same thing.

Although the broadcast channel BCH is set to be transmitted at a predetermined time interval T after or before the synchronization channel SCH is transmitted as described in the above embodiment, the above-described setting is performed according to the communication status and situation. It may not be possible to transmit as it is. In a special case, it may be necessary to transmit a broadcast channel at a time interval T2 different from a predetermined time interval T that is transmitted and set a synchronization channel.

Even in this case, it is advantageous to demodulate if the transmission time of the broadcast channel signal is known quickly. As a method for determining the transmission time, the transmission information is transmitted through a synchronization channel (SCH) including information related to the transmission time of the broadcast channel signal. For example, whether the broadcast channel signal is transmitted after or before the transmission of the synchronization channel signal on the synchronization channel (SCH), or after the synchronization channel signal is transmitted. It may include at least one of information on whether it is transmitted at a time T and another time T2 and whether it is transmitted after or before another possible time. An embodiment of the method for transmitting the information may include a method for differently configuring and transmitting at least one of a code transmitted through the synchronization channel, a method of configuring the code, and a position on a time / frequency of the code. have.

3 is a view for explaining another preferred embodiment of the present invention. Hereinafter, an embodiment of a case where a synchronization channel is transmitted more frequently than a broadcast channel will be described with reference to FIG. 3. In order for the terminal to acquire time synchronization quickly, the synchronization channel signal may be transmitted more frequently than the broadcast channel signal. If the sync channel is transmitted more frequently than the broadcast channel as described above, there may be a case where the broadcast channel is not transmitted before or after the sync channel transmission. That is, depending on the synchronization channel, in some cases, the broadcast channel 330 signal is transmitted before or after the synchronization channel 320 signal transmission, but in some cases, the broadcast channel 330 signal is not transmitted before or after the transmission. In this case, the broadcast channel 330 may be transmitted before or after the sync channel 320 is transmitted. When the signal is transmitted through at least two sync channels, when the broadcast channel 330 signal is transmitted after or before the sync channel 320 among the sync channel signals, the broadcast channel 330 signal. Transmit including the information that is transmitted.

For example, as shown in FIG. 3, a signal is periodically transmitted through a broadcast channel (BCH) 330, and a sync channel signal is transmitted before and after the broadcast channel 330. That is, when information related to the transmission time of the broadcast channel (BCH) 330 is transmitted through the synchronization channel (SCH) 320 transmitted before the signal is transmitted through the broadcast channel, the broadcast channel shown in the figure The information may be transmitted through a synchronization channel (SCH) 320 that is previously transmitted among two synchronization channels (SCH) before and after transmission of the (BCH). The information is not transmitted to the synchronization channel (SCH) 340 which is transmitted after the signal is transmitted through the broadcast channel (BCH). On the contrary, when the information is transmitted through a channel transmitted after the signal is transmitted through the broadcast channel (BCH), the information may be transmitted through the channel 340 transmitted later. An example of a method of transmitting the information may include a code of a sync channel and a sync channel having a transmission time and whether or not the broadcast channel is related to the broadcast channel, a method of configuring the code, and a time / code of the sync channel. There is a method of changing at least one of the positions on the frequency.

4 is a flowchart according to a preferred embodiment of the present invention. Hereinafter, the procedure of an embodiment will be described in more detail with reference to FIG. 4.

The terminal receives a signal transmitted through a multi-channel (S400). The channel includes a synchronization channel, a pilot channel and a broadcast channel. The initial time synchronization is obtained by searching the synchronization channel (S410). When the synchronization is obtained, the synchronization channel signal (code) is searched to determine whether a broadcast channel is transmitted after the synchronization channel is transmitted (S420). As a result of the check, when the broadcast channel is transmitted, the time point at which the broadcast channel is transmitted is checked (S430). The sync channel may be searched to know when the broadcast channel is transmitted. This is because the base station transmits the synchronization channel to be transmitted at a predetermined time interval (for example, T 210 of FIG. 2) in relation to the transmission time of the broadcast channel. That is, by searching only the synchronization channel, the transmission time of the broadcast channel can be known quickly. Thereafter, the broadcast channel is demodulated to obtain information necessary for a system (S440).

In another embodiment, in a frame including the channels so that a transmission time of a broadcast channel (BCH) can be known, information on a transmission time of the frame can be provided, whereby a transmission channel can be determined. Suggest. In a mobile communication system, a relative relationship between a transmission point of a frame and a transmission point of a broadcast channel is predetermined. By the way, it is common for the terminal to know the frame timing through the synchronization channel at the time of initial cell access. That is, the transmission time of the broadcast channel can be known through the relationship between the synchronization channel-> frame timing-> broadcast channel timing.

In a mobile communication system that configures and transmits one radio frame, two or more sync channels (SCH) may be transmitted in the radio frame. When two or more sync channels are transmitted per frame, if each signal is transmitted without distinction through the sync channels, it is difficult to distinguish the boundary of each frame. That is, it is difficult to ascertain where each frame starts and ends. Since it is difficult to know when each frame starts, the transmission time of a broadcast channel (BCH) preset to be transmitted in the frame also becomes difficult to know. Thus, there is a difficulty in demodulating the broadcast channel signal. However, in a preferred embodiment of the present invention, by configuring a frame to transmit a synchronization channel including one information per frame, including information distinguished from information transmitted through other synchronization channels, the period of the frame We propose a known transmission method. Accordingly, an embodiment of the present invention provides a method for transmitting by including information distinguished from other channels in one channel among the synchronization channels included in the radio frame and transmitted.

5 is a view for explaining another preferred embodiment of the present invention. Hereinafter, referring to FIG. 5, a method of confirming a transmission time of a channel through information on a transmission time of a frame and information on each frame interval by transmitting information classified into a specific channel will be described.

Among the two or more sync channels 510 and 530 transmitted in one frame 500, one sync channel 530 includes information that can distinguish the sync channel from other sync channels 510. Thus, the terminal may interpret the synchronization channel signal including the distinguished information based on the distinguished information to predict when the transmitted radio frame starts. Therefore, it is possible to know when the frame starts. If the starting point of the frame is known, when the frame is transmitted in a predetermined format, the broadcast channel (BCH) 520 belonging to the frame may be known. Accordingly, if the transmission time of the broadcast channel 520 set in the radio frame is known, the broadcast channel signal can be more easily interpreted.

 By demodulating knowing when the broadcast channel is transmitted, it is possible to demodulate more easily and accurately.

Information distinguished from other sync channels may be transmitted in a first or last sync channel among two or more sync channels transmitted in each frame. In case of transmitting information distinguished from other sync channels in the first sync channel, if the information included in the sync channel is searched, it can be seen that the first frame includes the first sync channel. When information distinguishing from other sync channels is transmitted to the last sync channel, when a sync channel including the distinguished information is transmitted, the next sync channel transmission point is a time point at which one frame including the sync channels starts. You can predict it.

A code transmitted through a predetermined channel, a method of constructing the code, and a position on a time / frequency of the code as a method for informing information (differentiated information) in which the broadcast channel is transmitted and the timing of the transmission in the above description. It will be described in detail how to change at least one of them. The predetermined channel may be a synchronization channel and a pilot channel. Among the information that may be included in the synchronization channel, a code on a time / frequency axis constituting the sync channel and a method of configuring the code and information transmitted by varying a position on the time / frequency axis of the code may be distinguished. .

First, different time / frequency codes constituting the synchronization channel change the bit configuration of the code of each synchronization channel similarly to the method of differently determining each synchronization channel code for each cell. A case where a 4-channel sync channel code is defined on the time axis will be described in more detail, for example. There are many codes that can be sync channel codes. For example, the first sync channel code is defined as (+1, +1, +1, +1), and the second sync channel code is defined as (+1, +1, -1, -1). And, it is assumed that four sync channels are transmitted in one frame. In this case, the defined second sync channel code is transmitted through the third sync channel 530, and the defined first sync channel code is transmitted through the remaining sync channels 510. That is, a code distinguished from other sync channels 510 is transmitted through the third sync channel 530. When each sync channel signal using the first, first, second, and first sync channel codes is transmitted in order within one frame 500, the terminal detects when the second sync channel code is transmitted and periodically It is possible to know the boundary of a frame to be transmitted.

Second, an example of how to configure the code differently will be described. In the sync channel for transmitting the information of the sync channel code in (+1, +1, +1, +1) and transmitting the divided information, another code may be added to the code by a CDM (code division multiplexing) method.

Third, an example of a method of changing the position on the time / frequency axis of the code will be described. Different frequency bands for transmitting codes can be transmitted. That is, the sync channel code may be transmitted through a frequency band of f1, and the sync channel code for transmitting distinguished information may be transmitted through a frequency band of f2.

6 is a flow chart according to another preferred embodiment of the present invention. Hereinafter, the procedure will be described in more detail with reference to FIG. 6.

The terminal receives a signal transmitted in the frame unit from the base station through a multi-channel (S600). The signal transmitted through the synchronization channel is searched among the signals for time synchronization. The frame synchronization may be performed by searching the synchronization channel (S620). This is because the base station transmits a signal distinguished from another sync channel signal through one of two or more sync channels belonging to the frame. When frame synchronization is matched, a time point at which a broadcast channel is transmitted through a preset channel structure in the frame can be known (S630). The transmission time is checked to demodulate the channel signal (S640).

The synchronization channel SCH described above may be composed of two layers instead of one. That is, the first synchronization channel (Primary SCH) and the second synchronization channel (Secondary SCH) can be made hierarchically. In this case, a combination of information transmitted through a synchronization channel of two layers may be transmitted, or information included in the present invention may be included in one of the synchronization channels of the two layers.

In a system for communicating using a plurality of subcarriers, information on a transmission time of a broadcast channel may be provided through a pilot channel or a reference channel.

After searching for a synchronization channel (SCH) transmitted by the terminal to the base station, the pilot signal (pliot signal) transmitted by the base station is detected, and only after reading the broadcast channel. Therefore, the pilot signal is searched before the broadcast channel (BCH), like the search for the synchronization channel (SCH) before the search for the broadcast channel (BCH). That is, the above-mentioned information may be transmitted using the pilot channel, which previously transmitted information indicating the time point at which the broadcast channel BCH is transmitted using the synchronization channel SCH. Accordingly, the terminal can find out the transmission time of the broadcast channel using only time information on which the pilot channel signal is transmitted and can read the signal transmitted through the broadcast channel.

The pilot may carry information indicating whether a broadcast channel signal is transmitted later. That is, the downlink transmission can be transmitted by changing the time / frequency code (or scrambling), the code configuration method, and the position of the code on the time / frequency axis according to whether or not the associated broadcast channel (BCH) is transmitted and the transmission time point. have. The scrambling prevents loss of timing information among consecutive input data and suppresses a single frequency component generated by repeating a periodic data pattern to prevent modulation or the like in a transmission path section. Convert to a random code sequence. By detecting the pilot signal, the terminal can know whether the signal transmitted through the broadcast channel can be demodulated and when the signal is transmitted through the broadcast channel, thereby making it easier to demodulate the broadcast channel signal. .

What has been described above are embodiments of the present invention. That is, to those skilled in the art to which the present invention pertains can be converted and changed within the scope without departing from the technical spirit of the present invention, the scope of rights is not limited by the embodiments and the accompanying drawings. .

The present invention has the effect that it is possible to quickly determine the transmission time of the channel in the mobile communication system. That is, it is possible to know the transmission time, which is advantageous when demodulating data transmitted through the channel.

Claims (15)

In a system for performing communication using the OFDM scheme, Transmitting a signal through a first channel; And Transmitting a second channel at a predetermined time interval with a transmission time of the first channel, transmitting the first channel signal and transmitting a signal through the second channel after the set predetermined time; Communication method comprising a. The method of claim 1, If the second channel signal can not be transmitted after the predetermined time, And at least one of information indicating that the information cannot be transmitted after the predetermined time and information that is transmitted after a predetermined time different from the predetermined time. The method of claim 2, The information may be transmitted by differently configuring at least one of a transmission code of the first channel, a method of configuring the transmission code, and a time / frequency resource. The method of claim 3, wherein If the first channel is composed of two or more layers, The information may be transmitted through any one of a method of combining and transmitting information between the first channels and a method of transmitting by using a first channel of any one of the two or more layers. . The method of claim 2, The information may be transmitted by differently configuring at least one of a transmission code of a reference signal, a method of configuring the transmission code, and a time / frequency resource. The method according to any one of claims 1 to 4, And the first channel is a synchronization channel for searching for the first channel and transmitting a signal for time synchronization. The method according to any one of claims 1 to 4, The second channel is a communication channel for transmitting basic system information for data communication. In a communication system using the OFDM scheme, Transmitting two or more sync channels; And A transmission time of a broadcast channel for transmitting information for demodulating data is set at a predetermined time interval with a transmission time of any one of the two or more synchronization channels to transmit the synchronization channel signal, and after the predetermined time. Transmitting a broadcast channel for transmitting a signal through the broadcast channel Communication method comprising a. The method of claim 8, Information for distinguishing between the first sync channel and the second sync channel when the two or more sync channels include a first sync channel which is a reference point of a broadcast channel transmission time and a second sync channel independent of the broadcast channel transmission time Communication method characterized in that the transmission. The method of claim 9, The information may be configured to transmit at least one of a transmission code of the first synchronization channel, a method of configuring the transmission code, and a time / frequency resource differently from the second synchronization channel. The method of claim 9, The information may be transmitted by differently configuring at least one of a transmission code of a reference signal (pilot), a method of configuring the transmission code, and a time / frequency resource. In a communication system using the OFDM scheme, Receiving a signal through a first channel for transmitting information distinguished from another first channel included in one frame and at least one second channel included in the one frame; Searching for a first channel for transmitting distinguished information in the transmitted frame and checking a transmission start time of a frame including the first channel; And Confirming the second channel transmission time point transmitted at a specific time point in the frame through the identified frame transmission start time point; Communication method comprising a The method of claim 12, And the first channel is one of a synchronization channel and a pilot channel through which a signal for time synchronization is transmitted. The method of claim 12, The second channel is a communication channel for transmitting information for demodulating data. The method according to any one of claims 12 to 14, The distinguished information may be configured to transmit at least one of a transmission code of a first channel for transmitting the distinguished information, a method of configuring the transmission code, and time / frequency resources differently from other first channels. Communication method.

Images