KR20070077023A - Method for transmitting/receiving common control channel in cellular communication systems supporting scalable bandwidth - Google Patents

Abstract

A method for transmitting and receiving common control channels in a cellular wireless communication system which supports scalable bandwidths is provided to speedily execute cell searching and handover by enabling a UE(User Equipment), which has a smaller Rx bandwidth than a system bandwidth, to always receive an SCH(Synchronous CHannel) from a neighbor cell while maintaining a low SCH overhead. A UE confirms a system bandwidth(1600). If the system bandwidth is 20 MHz, the UE judges whether a shift to a band of 10 MHz on the right or left side of the system bandwidth is required(1602). In case the UE camps at the center of the system band or the system bandwidth is smaller than 20 MHz, the UE applies a band limiting filter for a band of 1.25 MHz, the center of the system band(1604). Then the UE executes cell searching from an SCH signal outputted from the of the band limiting filter(1606).

Description

METHODS FOR TRANSMITTING / RECEIVING COMMON CONTROL CHANNEL IN CELLULAR COMMUNICATION SYSTEMS SUPPORTING SCALABLE BANDWIDTH}

1 illustrates the structure of an OFDM transmission signal in the frequency and time domain.

2 illustrates an example of frequency resource mapping of a synchronization channel in a system supporting scalable bandwidth.

3 illustrates another example of frequency resource mapping of a synchronization channel in a system supporting scalable bandwidth.

4 shows an example in which terminals of various reception bandwidths are allocated in the entire system band in the system.

5 is a diagram illustrating frequency domain mapping of a synchronization channel according to a first embodiment of the present invention.

6 is a diagram illustrating an example in which a plurality of terminals are allocated within a system bandwidth under a synchronization channel structure according to the first embodiment of the present invention.

7 is a diagram illustrating frequency domain mapping of a synchronization channel according to a second embodiment of the present invention.

8 illustrates an example in which a plurality of terminals are allocated within a system bandwidth under a synchronization channel structure according to a second embodiment of the present invention.

9 illustrates frequency domain mapping of a synchronization channel and a broadcast channel according to a third embodiment of the present invention.

10 illustrates frequency domain mapping of a paging channel according to a fourth embodiment of the present invention.

11 is a diagram illustrating frequency domain mapping of a synchronization channel and a broadcast channel according to a fourth embodiment of the present invention.

12 illustrates frequency domain mapping of a synchronization channel according to a fifth embodiment of the present invention.

13 illustrates a structure of a transmitter according to an embodiment of the present invention.

14 illustrates a structure of a receiver according to an embodiment of the present invention.

15 is a diagram illustrating an operation procedure of a transmitter according to an embodiment of the present invention.

16 is a diagram illustrating an operation procedure of a receiver according to an embodiment of the present invention.

The present invention relates to a cellular wireless communication system, and more particularly, to a method for transmitting and receiving a downlink common control channel in a communication system using Orthogonal Frequency Division Multiplexing (OFDM) technology.

Recently, orthogonal frequency division multiplexing (OFDM) technology has been widely applied as a technology for broadcasting and mobile communication systems. OFDM technology has the advantage of eliminating interference between multipath signal components existing in a wireless communication channel and ensuring orthogonality among multiple access users and enabling efficient use of frequency resources. As a result, it is useful for high-speed data transmission and broadband systems as compared to direct sequence code division multiple access (DS-CDMA) technology such as Wideband Code Division Multiple Access (WCDMA) or cdma2000.

1 shows the structure of an OFDM signal in the time and frequency domain.

Referring to FIG. 1, one OFDM symbol 100 is composed of N subcarriers 102 in the frequency domain. Each of the subcarriers 102 is loaded with a modulation symbol 104 corresponding to transmission information and transmitted simultaneously in parallel. As described above, the OFDM technology is a multi-carrier transmission technology, and may transmit data and control channel information to multiple subcarriers in parallel and transmit them in parallel.

In a cellular wireless communication system, in order to demodulate received data and control information, synchronization and cell search must first be performed between a transmitter and a receiver. In the OFDM-based cellular wireless communication system, a cell search method similar to that used in the WCDMA system may be applied. The cell search procedure in an OFDM-based system may be performed in three steps similarly to a WCDMA system.

In the first step, symbol timing synchronization is performed to find the starting points 106 and 108 of the OFDM symbol. The second step is to find the group index of the scrambling sequence used for transmission of the downlink channel with frame timing synchronization. In the third step, the cell-specific scrambling code belonging to the scrambling sequence group is finally found. In this way, the terminal can demodulate the received data and the control channels by acquiring frame timing synchronization and scrambling code information of the cell to which the terminal belongs.

One of the important features in an OFDM based cellular wireless communication system is the support of scalable bandwidth. A system based on scalable bandwidth may have a bandwidth of, for example, 20/15/10/5 / 2.5 / 1.25 MHz. Service providers may provide a service using a selected one of the bandwidths, and there may be various types of terminals, such as those capable of providing services up to 20 MHz bandwidth to supporting only 1.25 MHz bandwidth.

An important challenge in the scalable bandwidth-based system is how to allow a terminal initially accessing the system to succeed in cell discovery in the absence of information about the bandwidth of the system.

2 shows an example of frequency resource mapping of a synchronization channel (SCH) according to system bandwidth in a system supporting scalable bandwidth.

Referring to FIG. 2, the horizontal axis 200 represents a frequency, and the synchronization channel 204 is transmitted in the middle of a system band with a bandwidth of 1.25 MHz regardless of the system bandwidth. Therefore, in this case, the terminal searches for an RF carrier 202 in the system band regardless of the system bandwidth and performs cell search for a band of 1.25 MHz with respect to the RF carrier 202. Acquire.

Meanwhile, FIG. 3 illustrates a case where the transmission bandwidth of the synchronization channel is different according to the system bandwidth. That is, when the system bandwidth is 2.5 MHz (300) or less, the synchronization channel is transmitted with a bandwidth of 1.25 MHz (302). When the system bandwidth is 5 MHz (306) or more, the synchronization channel is transmitted with a bandwidth of 5 MHz (304). do. The main reason for transmitting as described above is to improve cell search performance by transmitting a synchronization channel using a wide band in a system having a large system bandwidth.

Another important challenge in systems supporting scalable bandwidth is the support of seamless handover. If the terminal is located at the cell boundary and the received power from the cell to which it currently belongs is not sufficient, handover to another neighboring cell that enables larger receive power is needed. For this purpose, it is important to design a synchronization channel so that a terminal having a lower bandwidth than the system can perform a cell search for a synchronization channel of an adjacent cell even when receiving a service in some bands of the system. For similar reasons, in the case of other common control channels such as broadcast channels, it is necessary to design the terminal so that it can be accessed smoothly.

The present invention provides a method for transmitting / receiving a synchronization channel capable of smoothly performing a cell search for an adjacent cell so that a terminal located at a cell boundary can be quickly handed over in a system supporting scalability of the system and terminal bandwidth. do.

The present invention provides a method for transmitting / receiving a synchronization channel that can perform adjacent cell search in a handover situation without degrading initial cell search performance.

The present invention provides a method for allowing all terminals in a system to receive a common bandwidth of a constant bandwidth regardless of the bandwidth of the system while maintaining an appropriate level of overhead of a common control channel such as a synchronization channel or a broadcasting channel and a paging channel. To provide.

A preferred embodiment of the present invention is a method for transmitting a common control channel in a cellular communication system supporting a scalable system bandwidth and using a multiple access technology.

If the system bandwidth is less than twice the minimum available bandwidth of the terminals, the process of transmitting the common control channel sequence in the center of the system band using a bandwidth at least greater than or equal to the minimum bandwidth required for reading the common control channel. and,

When the system bandwidth is twice the minimum reception bandwidth, transmitting the common control channel sequence at the center of the system band using at least twice the minimum bandwidth required for the terminal to read the common control channel sequence and,

If the system bandwidth is greater than twice the minimum reception bandwidth, transmitting at least three sync channel sequences over a system band at predetermined intervals,

Herein, the at least three sync channel sequences may allow a terminal using the allocated minimum reception bandwidth on the system band to receive a sequence equal to the same bandwidth regardless of the system bandwidth among the at least three sync channel sequences. And arranged on the system band.

Hereinafter, embodiments of the present invention will be described in detail with the accompanying drawings. In addition, in describing the present invention, when 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. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The main subject of the present invention described below is a synchronous channel (SCH) or a broadcast channel (BCH) and a paging channel (PCH) in a cellular communication system using multiple access technology and supporting scalable bandwidth. It is to efficiently arrange the band where the common control channel such as) is located.

In the following description of embodiments of the present invention, an Orthogonal Frequency Division Multiplex (OFDM) transmission technology based system and its channels will be mainly targeted. The main subject matter is applicable to other communication systems having a similar technical background and channel form with a slight modification without departing from the scope of the present invention, which is judged by those skilled in the art. It will be possible.

One of the main characteristics of the system that supports the scalable bandwidth is different from the existing system is that there are various user equipments (UEs) having different bandwidth support capabilities in the system. As an example, FIG. 4 shows that the terminals UE # 1, UE # 2, UE # 3, UE # 4 (404, 406, 408, 410) of 5/10/20 MHz bandwidth from a system of 20 MHz bandwidth 400 are shown. It shows the situation of receiving service. Reference numeral 402 denotes a synchronization channel sequence.

Referring to FIG. 4, the synchronization channel 402 is transmitted with a bandwidth of 5 MHz based on the center frequency in all cells in the system. The terminals 404, 406, 408, and 410 complete the cell search for the synchronization channel 402 and receive data service in each allocated band of the current cell where each terminal is located. The terminals 404, 406, 408, and 410 being present in different bands within the entire system band 400 indicate that the bands used by the terminals 404, 406, 408, and 410 are in the system band 400. By spreading evenly within), it is to prevent the concentration of frequency resource requirements in a specific band.

In the situation of FIG. 4, the UE # 2 406, the UE # 3 408, the UE # 4 410, etc. may receive the full or partial band of the synchronization channel 402 from the neighbor cell, but the UE # 1 404 is located in a frequency band in which the sync channel 402 is not transmitted and thus cannot receive the sync channel 402. Therefore, in order for the UE # 1 404 to receive the synchronization channel 402 from the neighbor cell, a cell search time for the neighbor cell must be agreed between the system and the UE # 1 404. That is, UE # 1 404 stops the reception from the current cell during the discovery time and changes the received RF frequency to the frequency band in which the synchronization channel 402 is transmitted to the synchronization channel 402 from the adjacent cell. The cell search may be performed for the cell. In a conventional system such as WCDMA or CDMA2000, when a terminal performs cell search for another cell in the same system, it is possible to freely search a cell without agreement of a neighbor cell search time with a base station.

In the following embodiments, in the system supporting the scalable bandwidth, a synchronization channel mapping that allows the terminal to freely search for adjacent cells and does not affect cell search when the terminal initially accesses the system is provided. The proposed technique proposes a band and bandwidth for transmitting each sync channel when the bands used by the terminals are scattered within the entire system band when the minimum bandwidth of the terminal that can access the system is determined.

Specifically, embodiments of the present invention transmit a sync channel sequence in the center of the system band when the system bandwidth is less than or equal to twice the minimum available bandwidth of the terminals. On the other hand, if the system bandwidth is greater than twice the minimum available bandwidth of the terminals, then at least three sync channel sequences are transmitted, where one sync channel sequence is transmitted at the center of the system band and the other sync channel sequences are The transmission is spaced apart from the center of the band by a predetermined interval. In this case, the at least three sync channel sequences are necessary for a terminal using the allocated minimum reception bandwidth on the system band to read the same bandwidth (at least a sync channel, regardless of the system bandwidth, among the at least three sync channel sequences). Is arranged on the system band so that a sequence as many as a minimum bandwidth can be received.

<< first embodiment >>

This first embodiment is a case where the minimum reception bandwidth of the terminal allowed in the system band is 10 MHz as shown in FIG. Thus, for example, when the system bandwidth is 20 MHz, a terminal having a reception bandwidth of 10/15/20 MHz may exist. If the system bandwidth is less than 10 MHz, the entire system band is allocated as the reception band of the terminal. In addition, each terminal basically needs to receive a synchronization channel sequence of a bandwidth of 1.25 MHz. That is, the minimum bandwidth of the synchronization channel required for the terminal to read the synchronization channel is 1.25 MHz.

The synchronization channel mapping of FIG. 5 differs from the conventional synchronization channel mapping shown in FIGS. 2 and 3 in that the same bandwidth of 1.25 MHz is used for the synchronization channel 500 in the system band of 15 MHz or less. In the system band of MHz 504, a bandwidth of 2.5 MHz is allocated to the synchronization channel 502. The basic reason for allocating a synchronization channel as described above is that the bandwidth of the synchronization channel actually received by each terminal when the terminals entering the active mode after the initial synchronization acquisition have received the synchronization channel from the neighbor cell for handover is obtained. In order to make the same, to ensure the same neighbor cell search performance.

Reference numerals 508, 510, 512, and 514 denote basic sequences in the frequency domain used for the synchronization channel, wherein at least two of the four basic sequences 508 to 514 are combined to form one synchronization channel sequence 500 Or 502). As can be seen from the structure in the frequency domain of the OFDM symbol shown in Fig. 1, each symbol constituting each basic sequence is carried on a subcarrier in a corresponding 0.625 MHz subband. As shown in FIG. 5, two basic sequences 508 and 510 are used in all system bandwidths and are transmitted in the central 1.25 MHz band of the entire system band, while the other two basic sequences 512 and 514 are 20 MHz systems. Used additionally in bandwidth.

With reference to FIG. 6, the above-described matters will be described in more detail. In FIG. 6, UEs # 1 612, UE # 2 614, and UEs having a reception bandwidth of at least 10 MHz within each system bandwidth of 20 MHz (600), 10 MHz (602), and 2.5 MHz (604). The situation in which # 3 616 and UE # 4 618 exist is shown. In the case of UE # 5 620, since the system bandwidth is 2.5 MHz, the entire system band is used as the reception band.

In the situation of FIG. 4, the UE # 1 404 could not receive the synchronization channel of the neighbor cell, that is, the synchronization channel sequence at all, whereas in the situation of FIG. 6, all terminals 612 to 618 have at least 1.25 MHz bandwidth. It is possible to receive as many sync channels. Specifically, UE # 1 616 having a reception bandwidth of 10 MHz receives two basic sequences 626 and 622 on a synchronization channel 606 from an adjacent cell to perform cell discovery, and UE # 2 614. Receives two basic sequences 624 and 628 from an adjacent cell to perform a cell search. Meanwhile, the UE # 3 616 having a reception bandwidth of 20 MHz may receive the entire sequence 622 to 628 of the synchronization channel 606 from an adjacent cell, so that the UE # 1 616 and the UE # 2 614 may receive the UE # 3 616. Better synchronization performance can be obtained compared to). In addition, since UE # 4 618 and UE # 5 620 have a reception bandwidth over the entire system band, the UE # 4 618 and the UE # 5 620 always receive the synchronization channels 608 and 610 of the 1.25 MHz band from an adjacent cell and perform cell searching. .

As shown in the example of FIG. 6, when the terminal in the active mode performs a cell search for a neighbor cell, a problem occurs when the bandwidth of the system is larger than the reception bandwidth of the terminal. When the terminal in the active mode is present in a system having a system bandwidth larger than its own reception bandwidth as in the case of FIG. 4, the terminal does not receive a synchronization channel from a neighbor cell or receives a synchronization channel of a smaller bandwidth. Is important for smooth neighbor cell search and is an important consideration when designing a synchronization channel.

To avoid this problem, as can be seen in Figure 6, the synchronization of at least part of the reception band used by the terminal, in case the terminal of the smallest allowable reception bandwidth is evenly arranged in the entire system band 600. Send the channel. Specifically, by receiving two basic sequences 626 and 622 each having a bandwidth of 0.625 MHz at the right end of the band allocated to UE # 1 612, UE # 1 612 receives a total of 1.25 MHz sync channels. Receive from neighbor cells. In addition, by receiving two basic sequences 624 and 628 having a bandwidth of 0.625 MHz at the left end of a band allocated to UE # 2 614, UE # 2 614 also receives a total of 1.25 MHz sync channels from an adjacent cell. can do.

5 and 6, when performing initial cell search, the terminal searches for sync channel sequences 508 and 510 transmitted in a band of 1.25 MHz with respect to an RF carrier. Accordingly, even if the terminal does not know the system bandwidth of the cell to which the terminal is currently accessing, it is possible to perform cell search successfully. Accordingly, the synchronization channel structure shown in FIGS. 5 and 6 allows smooth neighbor cell search in a handover situation without causing problems in initial cell search.

<< 2nd Example >>

The second embodiment shows an example of a synchronization channel structure for the case where the minimum allowable bandwidth of the terminal is 5 MHz. As in the first embodiment, in cases where the system bandwidth is 10/15/20 MHz, the synchronization channel is mapped onto the frequency resource so that the active mode terminal can receive the synchronization channel of at least a certain band from the adjacent cell. In this case, each terminal basically needs to receive a synchronization channel with a bandwidth of 1.25 MHz.

7 shows an example of mapping a synchronization channel to a frequency resource according to the second embodiment of the present invention. Similarly, if the system bandwidth is less than 5 MHz (720, 722, 724), the terminal uses the entire system band as the reception band. In the system bandwidth 720, 722, 724 of 5 MHz or less, which is the minimum bandwidth of the terminal, the basic sequences 708,710 of the synchronization channel 700 are transmitted using the 1.25 MHz band in the center of the system band. Can receive a synchronization channel of.

FIG. 8 illustrates a case where terminals having a reception bandwidth of at least 5 MHz exist in each system bandwidth in the situation of FIG. 7. 7 and 8, each cell additionally transmits two basic sequences 810 and 812 when the system bandwidth is 10 MHz (726), so that the synchronization channel 718 has a total bandwidth of 2.5 MHz. use. Then, as shown in FIG. 8, when the terminals UE # 8, UE # 9 (800, 802) having 5 MHz bandwidth are present in the system bandwidth of 10 MHz, synchronization as much as 1.25 MHz bandwidth from an adjacent cell in the active mode. It is possible to receive a channel, i.

When the system bandwidth is 15 MHz 706, the terminals 810, 812, and 814 having a reception bandwidth of 5 MHz are optimally allocated as shown in FIG. 8 within the 15 MHz system bandwidth 706. Each cell transmits sync channels 716 and 808 as shown in FIGS. 7 and 8 within a 15 MHz system bandwidth 706. Specifically, a cell using the 15 MHz system bandwidth 706 transmits three sync channel sequences so that they are not adjacent to each other, and the interval between the sync channel sequences is 1.25 * 6 MHz. As a result, the 5 MHz terminals 810, 812, and 814 can perform cell search for the adjacent cell using the synchronization channels 716 and 808 of the 1.25 MHz band, which are always transmitted in the middle portion of the allocated band. have. In FIG. 8, the patterns of the sync channel sequences 826 and 828 transmitted for the UE # 5 810 and the UE # 7 814 are just examples, and other sequence patterns may be used. Sequence patterns used in the band to which the terminals 810 and 814 are allocated are promised between the system and the terminal.

When the system bandwidth is 20 MHz (704, 826), the frequency domain mapping of the synchronization channel is similar to that in the first embodiment. 1.25 MHz in the right region of the band to which UE # 1 816 and UE # 2 818 are allocated when 5 MHz bandwidth terminals 816, 818, 820, 822 are allocated under 20 MHz system bandwidth 826 The synchronization channel sequences 830 and 826 are additionally transmitted to receive the synchronization channel of. In addition, sync channel sequences 828 and 832 are additionally transmitted such that UE # 3 820 and UE # 4 822 can receive a 1.25 MHz sync channel in the left region of the allocated band. Here, the patterns of the sync channel sequence transmitted for the UE # 1 816 and the UE # 4822 are only examples and other sequence patterns may be used. Patterns of sequences used in the band to which the terminals 816 and 822 are allocated are committed between the system and the terminal.

<< third embodiment >>

In the third embodiment, transmission of a synchronization channel and another common control channel (eg, a broadcast channel (BCH)) are considered together. The minimum reception bandwidth of the terminal is 10 MHz, and the terminal basically needs to receive a synchronization channel with a bandwidth of 1.25 MHz regardless of the system bandwidth. The broadcast channel is a channel for transmitting information about a system and a cell to which a terminal is connected, and is a channel which is demodulated first when the terminal finishes searching for a cell. By reading the broadcast channel, the terminal obtains information necessary to receive data channels and other control channels such as cell ID, system bandwidth, channel setting, and the like.

FIG. 9 illustrates mapping of a synchronization channel to another common control channel, for example, a broadcast channel, into a frequency domain according to the third embodiment. Cells using system bandwidths from 1.25 MHz (902) to 15 MHz (900) transmit broadcast channel 906 in the same band as sync channel 904. However, if the system bandwidth is 20 MHz 912, two broadcast channel sequences 910 and 914 are transmitted. This means that both the UEs UE # 1 612 and UE # 2 614 having a reception bandwidth of 10 MHz can receive at least the basic sequence of a broadcast channel, that is, a broadcast channel, from an adjacent cell, as shown in FIG. 6. To make it work.

Thus, like the terminals 612 and 614, it receives a broadcast service data such as a multimedia broadcast and multicast service (MBMS) in an idle mode (IDLE) that does not establish a connection with any cell, or in an active mode. For a terminal located in the left or right 10 MHz band of the system band, the terminal may perform a cell search for neighboring cells and obtain system information by transmitting a common control channel different from the synchronization channel as described above. To help.

<< fourth embodiment >>

In the fourth embodiment, transmission of a paging channel (PCH) is considered as another example of a common control channel. PCH is used when the system calls a terminal in idle mode to establish a connection. If there is information to call itself in the PCH, the terminal starts the procedure of connecting with the system.

In the case where the minimum reception bandwidth of the terminal is 10 MHz, an example of transmission of the PCH is illustrated in FIG. 10. In the case of SCH and BCH transmission in FIG. 9, the PCH is not limited to the central 1.25 MHz band, and the PCH sequence consisting of the PCH subcarrier symbols 1000 is spread over the entire system band. In other words, the transmission bandwidth of PCH depends on the system bandwidth.

In FIG. 10, when the system bandwidths are 1.25 MHz (1006) and 2.5 MHz (1004), PCH subcarrier symbols are transmitted in the 1.25 MHz band. However, when the system bandwidth is 5 MHz (1002) and 10 MHz, PCH subcarrier symbols are spread and transmitted in the 5 MHz band. By spreading and transmitting the PCH subcarrier symbols in a wider frequency range, the reception efficiency can be improved by increasing the frequency diversity gain. Since the PCH is a channel received after cell discovery and system information acquisition through SCH and BCH, the terminal transmits the PCH according to the system bandwidth of the system transmitting the PCH when the method of transmitting the PCH is predetermined as shown in FIG. 10. PCH can be received.

In the mapping of the PCH illustrated in FIG. 10, the case where the system bandwidth is 202 (1002) and the case where 15 MHz (1010) is designed in consideration of the scalability bandwidth. If the system bandwidth is 20 MHz (1002), the terminal of the 10 MHz reception bandwidth may be located in the left or right 10 MHz band (1012 or 1014) to receive MBMS data in idle mode, and does not receive MBMS data. The terminal in idle mode is located in the center of the system band. Therefore, the PCH should be mapped so that it can be received by the two different idle mode terminals. Therefore, when the system bandwidth is 20 MHz (1002), the PCH subcarrier symbols are repeatedly transmitted over two non-overlapping 5 MHz bands 1016 and 1018 in the middle of the entire system band. In this case, since the terminal located in the center of the system band can receive both PCHs transmitted in both 5 MHz bands, the detection performance of the PCH can be improved.

On the other hand, when the system bandwidth is 15 MHz (1010), the terminal in the idle mode for receiving MBMS data may be located in the 10 MHz band biased to the left or right, so that the idle mode is located in the center of the terminal and the system band Considering all the terminals, the PCH is transmitted over the 5 MHz band 1020 in the center of the system band.

In the fourth embodiment, the above descriptions are similarly applied not only to the PCH but also to other common control channels that the terminal in the idle mode needs to receive. For example, as illustrated in FIG. 11, a structure similar to the PCH described above may be applied to the SCH and the BCH.

Referring to FIG. 11, when the system bandwidth is 15 MHz (1120) or less, the SCH 1108 and the BCH 1110 are transmitted in the 1.25 MHz band in the center of the system band, and when the system bandwidth is 20 MHz (1122), the left side is used. SCHs 1100 and 1104 and BCHs 1102 and 1106 are transmitted in the 5 MHz band 1116 and the right 5 MHz band 1118, respectively. By transmitting SCH and BCH as described above, when the terminal of 10 MHz reception bandwidth is located in the center 10 MHz band 1120 of the system band, it is possible to receive both SCH and BCH transmitted in both 5 MHz bands. Cell search performance and BCH decoding performance can be obtained. When the terminal performs initial cell search, the terminal acquires synchronization for at least one of the two SCHs 1100 and 1104, and the terminal is located in either 10 MHz band 1112 and 1114 for communication. The cell search may be performed using the SCHs 1100 and 1104 within the corresponding band. The same sequence is transmitted to the SCHs 1100, 1104, and 1108 regardless of the system bandwidth, so that the UE may perform cell search even if the terminal does not know the system bandwidth.

<< Fifth Embodiment >>

The fifth embodiment is an embodiment of a SCH transmission method for allowing a terminal to perform cell search for a neighboring cell with low complexity assuming that a minimum reception bandwidth of a terminal allowed in a system band is 10 MHz. . 12 shows mapping of the SCH when the system bandwidth is 20 MHz. If the system bandwidth is 1510 MHz or less, the structure according to the first embodiment of the present invention as shown in FIG. 115 may be applied as it is.

The transmission method considered in this embodiment is to enable the cell search for the adjacent cells with low complexity when the 10 MHz terminal is located in the left 10 MHz band 1212 or the right 10 MHz band 1214. In FIG. 12, the SCH 1206 is a channel used by the terminal for initial cell search, and the SCH 1208 and the SCH 1210 are located in the left 10 MHz band 1212 or the right 10 MHz band 1214. When used for cell search for neighboring cells. The SCH 1206 may also be used when a terminal having a reception bandwidth of 20 MHz performs a cell search for an adjacent cell. The SCHs 1206, 1208, and 1210 may apply the same sequence, different sequences, and different bandwidths.

In FIG. 12, it is important that the frequencies of the received RF carriers 1202 and 1204 of the terminal located in the corresponding 10 MHz band coincide with the center of the band occupied by the SCH 1208 and the SCH 1210, respectively. The receive RF carriers 1202 and 1204 of the terminal are generally located in the center of the effective receive bands 1216 and 1218 of the terminal. Accordingly, as shown in FIG. 12, when the receiving SCH is located at the center of the effective reception band of the terminal, the baseband filter having the same bandwidth as that of the SCH is used when the terminal performs cell search for the adjacent cell. The cell search can be performed by receiving only the SCH from the neighbor cell. On the other hand, as in the case of UE # 1 612, UE # 2 614 of FIG. 6, or UE # 1-4 (816, 818, 820, 822) of FIG. In order to perform the cell search by receiving the SCHs from an adjacent cell, the cell search complexity is relatively increased because pass-band filtering or down-conversion of the received signal is required so that the SCH is located in the baseband. .

In FIG. 12, the terminal reception RF carriers 1202 and 1204 may not coincide with the centers 1224 and 1226 of the left or right 10 MHz band. This is because guard bands 1228 and 1230 may overlap each other between reception bands 1232 and 1234 of terminals located in the left or right 10 MHz band 1212 or 1214.

In general, in a cellular communication system, a frequency raster is defined so that an RF carrier 1200 of a transmission downlink signal transmitted from a base station is necessarily present on the frequency raster so that the terminal can perform cell searching smoothly. do. In the case of the WCDMA system, since the frequency raster has a 200 kHz spacing, the terminal performs cell search by changing the frequency of the received RF carrier in units of 200 kHz when the power is initially turned on, and the frequency of the received RF carrier is the transmit carrier of the base station. The cell search can be successfully performed when the frequency of the signal coincides with. In FIG. 11, the SCHs 1100 and 1104 have their center frequencies present on the frequency raster for the purpose of initial cell search.

On the other hand, in FIG. 12, the SCH 1206 may be used for initial cell search in which its center band coincides with the RF carrier 1200 of the base station transmitter. However, in the case of the SCH 1208 and 1210, the center frequency is on the frequency raster. It may be difficult to be used for initial cell search since it is not guaranteed to be present at. Therefore, in the structure of FIG. 12, the initial cell search uses the SCH 1206, and the terminal is located in the left or right 10 MHz bands 1212 and 1214 after the initial cell search. It is based on the procedure of applying the baseband filtering to search neighbor cells with low complexity. If the SCHs 1208 and 1210 exist on the frequency raster, the SCHs 1208 and 1210 are not found during the initial cell search by assigning a sequence different from the SCH 1206 to the SCHs 1208 and 1210. You can do this.

13 illustrates a structure of a base station transmitter according to an embodiment of the present invention.

Referring to FIG. 13, the SCH subcarrier symbol generator 1300 generates SCH subcarrier symbols corresponding to the system bandwidth under the control of the SCH generation and mapping controller 1306. For example, when the SCH structure according to the first embodiment shown in FIG. 5 is applied, when the system bandwidth is 15 MHz or less, a subcarrier symbol for SCH transmitted in the central 1.25 MHz band is generated in the entire system band, and the system bandwidth is In the case of 20 MHz, subcarrier symbols for the SCH transmitted in the 2.5 MHz band are generated. In addition, if the SCH structure according to the fifth embodiment shown in FIG. 12 is applied, symbols for three SCHs located in the center 1.25 MHz band of the total 20 MHz system bandwidth and the center 1.25 MHz band of both 10 MHz system bandwidths Is generated. The generated SCH subcarrier symbols are applied to the corresponding input of the IFFT unit 1304 through the subcarrier symbol mapper 1302 and then transmitted together with the subcarrier symbols of other channels in the same OFDM symbol (1308).

14 shows the structure of a terminal receiver according to an embodiment of the present invention.

Referring to FIG. 14, the RF controller 1402 controls a received RF frequency according to a system band in which a terminal is to be camped, and the RF unit 1400 signals according to the frequency controlled by the RF controller 1402. Receive The frequency received by the RF unit 1400 is down-converted from the frequency converter 1410 to an IF or baseband signal. The down-converted signal is removed by the band limiting filter 1404 to remove signals out of band to which the SCH to perform cell search. The band and bandwidth of the band limiting filter 1404 may vary according to the system bandwidth and the band to which the terminal belongs by the control of the reception filter controller 1406. For example, according to the SCH structure according to the first embodiment shown in FIG. 6, when the system bandwidth is 20 MHz and the terminal is camping with the UE # 1 612, the band limiting filter 1404 is UE # 1. By receiving the 1.25 MHz band at the right end of the 10 MHz reception band of 612, only SCHs belonging to the band are received, and signals existing in other bands are removed. On the other hand, when applying the SCH structure according to the fifth embodiment shown in Figure 12, the baseband of the bandwidth of 1.25 MHz regardless of whether the terminal camps in either the center of the 20 MHz system band or either 10 MHz Only apply filters. Then, only the SCHs 1206, 1208, and 1210 belonging to the corresponding band can be received, and the signals belonging to the other bands can be removed. The SCH signal passing through the band limiting filter 1404 is input to the cell searcher 1408 to perform a cell search.

15 illustrates an operation procedure of a base station transmitter according to an embodiment of the present invention.

Referring to FIG. 15, in step 1500, the transmitter maps the SCH to the center 1.25 MHz band of the system band regardless of the system bandwidth. In step 1502, the system bandwidth is checked. If the system bandwidth is 20 MHz, the SCH is additionally mapped to both 10 MHz bands in step 1504. For example, in the SCH structure according to the first embodiment of the present invention shown in FIG. 5, SCHs are additionally mapped to both 0.675 MHz of the central 1.25 MHz band, and the SCH according to the fifth embodiment of the present invention shown in FIG. 12 is illustrated. In the structure, the SCH is additionally mapped to the center 1.25 MHz band of the terminal to be camped in each 10 MHz band. When the mapping of the SCH is completed as described above, in step 1506 it is transmitted with the signals of the other channels in the same OFDM symbol. If the system bandwidth is not 20MHz, the process proceeds to step 1506 without additional mapping of step 1504.

16 illustrates a receiving operation procedure of a terminal according to an embodiment of the present invention.

Referring to FIG. 16, the terminal checks the system bandwidth in step 1600. If the system bandwidth is 20 MHz, the terminal checks whether it is necessary to move to the left / right 10 MHz band in step 1602. If the terminal is camping in the center of the system band in step 1602 or if the system bandwidth is less than 20 MHz in the step 1600, the terminal performs the band limit filter for the center 1.25 MHz band of the system band in step 1604. After application, a cell search is performed from the filter output SCH signal in step 1606. On the other hand, if the system bandwidth is 20 MHz and the terminal camps in the left or right 10 MHz band, the terminal changes the received RF frequency to the center of the corresponding 10 MHz band in step 1608. In step 1610, the SCH transmitted in the band is received, and the band limit filter is applied to remove signals in the other band. In operation 1616, the cell search is performed from the filter output SCH signal.

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 defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, in a cellular wireless communication system supporting scalable bandwidth, a terminal having a reception bandwidth smaller than the system bandwidth can always receive the synchronization channel from an adjacent cell while maintaining low synchronization channel overhead. Cell search and handover can be made quickly. In addition, since a consensus process for the neighbor cell measurement time is not required between the terminal and the base station to which the terminal belongs, the operation of the system and the terminal can be simplified.

Claims (4)

A method of transmitting a common control channel in a cellular communication system supporting a scalable system bandwidth and using a multiple access technology, If the system bandwidth is less than twice the minimum available bandwidth of the terminals, the process of transmitting the common control channel sequence in the center of the system band using a bandwidth at least greater than or equal to the minimum bandwidth required for reading the common control channel. and, If the system bandwidth is twice the minimum reception bandwidth, transmitting the common control channel sequence at the center of the system band using at least twice the minimum bandwidth required for the terminals to read the common control channel sequence Method of transmitting a common control channel, characterized in that it comprises a. The method of claim 1, further comprising transmitting at least three sync channel sequences at predetermined intervals through the system band when the system bandwidth is greater than twice the minimum reception bandwidth. Here, the at least three sync channel sequences may be received by a terminal using the minimum received bandwidth allocated on the system band by the same bandwidth regardless of the system bandwidth among the at least three sync channel sequences. And transmitting the common control channel on the system band. The common control channel of claim 1, wherein when the system bandwidth is twice the minimum reception bandwidth, a basic sequence constituting the common control channel sequence is repeatedly transmitted at least twice in the center of the system band. Way of transmission. The method of claim 1, wherein the common control channel, A method of transmitting a common control channel, characterized in that one of a synchronization channel (SCH), a broadcast channel (BCH), a paging channel (PCH).

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