KR20090075596A - Method for transmitting preamble in scalable bandwidth system - Google Patents

Abstract

A method for transmitting a preamble in a variable bandwidth system is provided to use the same search routing regardless of a bandwidth of a system in a terminal and cause no scrambling when the terminal synchronizes signal timing at a cell edge. A first sync channel in which a symbol is allocated at interval more than sub carrier waves is transmitted in a start time point of a sync period through a predetermined band among entire system. A second sync channel is transmitted at a predetermined time difference from the first sync channel in the same period through the predetermined band.

Description

Preamble transmission method in variable band system {Method for transmitting preamble in scalable bandwidth system}

The present invention relates to a variable band system, and more particularly, to a preamble transmission method for designing a preamble in consideration of a variable bandwidth to facilitate a preamble search of a terminal and extending a reference signal for position measurement. .

As the application market of wireless communication system is globalized, variety of standards according to communication bands proposed by each country are required. In recent years, standards such as 3GPP LTE, IEEE 802.16, and IEEE 802.22 are designed to operate a standard air interface according to the radio frequency distribution situation in each country. In particular, scalable bandwidth requirements are required for the basic control channel in a system, provided that it must operate over various frequency bandwidths in various frequency bands. In order to find out the system synchronization signal and basic system information that the terminal should search to access the system, the terminal must operate on various assumptions. That is, if there is no consistent signal definition for one wireless communication interface, the terminal should perform reception and decoding attempts for all combinations. This increases the complexity of the terminal. Therefore, in the case of 3GPP LTE, the terminal is initially designed to decode the system information in the minimum band. The 3GPP LTE system is designed to operate in at least 1.25MHz or 1.4MHz band, and the channel search / decoding part that imposes complexity on the terminal, that is, a synchronization channel and a primary broadcast channel (primary BCH), is designed for the minimum system band. . The terminal searches only for the minimum band. Regardless of which 3GPP LTE bands are used, the discovery process only needs to be performed for the minimum system bandwidth, thereby reducing terminal development cost and complexity of the terminal itself.

This requirement is also required in IEEE 802.16m. For current legacy systems, the system bandwidth is fixed at 10 MHz. In the case of 802.16m, which is an improvement of IEEE 802.16 legacy system, the basic system bandwidth is defined as 5MHz to 20MHz or more, and legacy system is a support requirement.

Therefore, the minimum value of the system bandwidth in 802.16m is 5MHz or less, so the system should be designed to be operable for the minimum band. And if you need to support a wider band, you need a structure that can be easily extended to a wider band. Also consider legacy support at 10MHz.

1 illustrates an example of a synchronization channel structure of a 3GPP LTE system.

Synchronization channel (SCH) used in 3GPP LTE is a minimum time band for the first synchronization channel (Primary-SCH; P-SCH) and the second synchronization channel (Secondary-SCH; S-SCH) at regular intervals It is set in a radio frame. In addition, the P-SCH is transmitted in OFDM at two subcarrier intervals, and the S-SCH is configured in an overlapping form of two short codes set at two subcarrier intervals. At this time, one of the two short codes is shifted by one subcarrier. In addition, the structure of the first S-SCH and the second S-SCH is configured differently to distinguish the start position of the radio frame.

2 illustrates an example of a synchronization channel structure of an IEEE 802.16 system.

In the IEEE 802.16e (WiMAX) system, the preamble for the synchronization channel is designed to occupy the entire system band, and the preamble sequence is inserted at three OFDM subcarrier intervals. Here, the preamble for the synchronization channel is referred to as SCH for uniformity.

In FIG. 2, the offset can be given as 0, 1, and 2, so that three distinguishable codes can be transmitted. This is actually associated with the sector. And when the system bandwidth is different, all preamble sequences for the band are defined separately. In 3GPP LTE, a synchronization channel is generated twice in one radio frame, and the synchronization channel is set at 5 ms intervals, whereas the preamble of IEEE 802.16e (WiMAX) is transmitted in a frame unit of 5 m. Therefore, the preamble transmission interval is transmitted at the same rate as 3GPP LTE.

IEEE 802.16m pursues an improved version of IEEE 802.16e and is being developed to meet IMT-Advanced performance requirements. However, the current IEEE 802.16e cannot efficiently support variable bandwidth, and includes a point of being unreasonable for detecting a system signal at a terminal. The preamble sequence of IEEE 802.16e consists of three spaces, but uses different subcarrier offset positions for each sector. If the sector-by-sector signal overlaps, the repetitive feature of the preamble is removed. As a result, the repeating pattern is not known in the time domain at the cell edge.

Accordingly, the terminal needs to perform preamble search corresponding to all system bandwidths according to the current IEEE 802.16e air interface standard, and there is a problem in that the sequence search cannot be efficiently performed at the cell edge.

The technical problem to be achieved by the present invention is to design a preamble in consideration of the variable bandwidth, to enable efficient preamble search in the terminal, to extend the reference signal for position acquisition, and to improve the accuracy of the position measurement The present invention provides a method of transmitting an emblem.

In order to achieve the above technical problem, the preamble transmission method according to an embodiment of the present invention transmits a P-SCH assigned a symbol at two or more subcarrier intervals through a specific band of the entire system band at the start of the synchronization period And transmitting the S-SCH through the specific band with a predetermined time difference from the P-SCH in the synchronization period.

Preferably, the S-SCH may be assigned symbols at two or more subcarrier intervals, and pilot symbols may be arranged between the allocated symbols.

Preferably, the constant time difference may be a time interval corresponding to half of the synchronization period. Alternatively, the P-SCH and the S-SCH may be disposed in adjacent OFDM symbols immediately before or after.

In order to achieve the above technical problem, the method of transmitting a preamble according to another embodiment of the present invention transmits a P-SCH in which symbols are allocated at two or more subcarrier intervals through a specific band of all system bands at the start of a synchronization period. In addition, the S-SCH is transmitted through the remaining bands except the specific band at a predetermined time difference from the P-SCH, and the extended synchronization channel to which the cyclic copy of the S-SCH is applied is transmitted through the specific band. It includes the process of doing.

Preferably, the S-SCH may be transmitted through some or all of the remaining bands excluding the specific band of the entire system band.

Preferably, in the process of transmitting the extended synchronization channel, when larger than the size of the S-SCH, the S-SCH may be repeatedly transmitted through the extended synchronization channel.

Preferably, the S-SCH may be assigned symbols at two or more subcarrier intervals, and pilot symbols may be arranged between the allocated symbols.

Preferably, the constant time difference may be a time interval corresponding to half of the synchronization period.

In order to achieve the above technical problem, the method of transmitting a preamble according to another embodiment of the present invention transmits a P-SCH in which symbols are allocated at two or more subcarrier intervals through a specific band of all system bands at the start of a synchronization period. And transmitting the S-SCH through the remaining bands except for the specific band, and retransmitting the P-SCH and the S-SCH with a predetermined time difference in the synchronization period.

Preferably, the S-SCH may be transmitted through some or all of the remaining bands excluding the specific band of the entire system band.

Preferably, the constant time difference may be a time interval corresponding to half of the synchronization period.

In order to achieve the above technical problem, the preamble transmission method according to another embodiment of the present invention is a preamble OFDM symbol divided into two by adjusting the subcarrier spacing through a specific band of the entire system band at the start of the synchronization period The first S-SCH is transmitted to distinguish the P-SCH and the start position of the frame using the P-SCH. The P-SCH is transmitted through the specific band with a predetermined time difference in the synchronization period. -Transmitting a SCH and a second S-SCH having a structure different from that of the first S-SCH.

Preferably, the P-SCH and the S-SCH may be assigned a symbol at two or more subcarrier intervals.

Preferably, the S-SCH may be a pilot symbol placed between the assigned symbols.

According to the embodiments of the present invention, the same search routine can be used in the terminal regardless of the bandwidth of the system, there is no confusion in synchronizing the signal timing of the terminal at the cell edge, simple searching is possible, and the maximum available band By enabling the transmission of signals, the accuracy of position measurements can be improved.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. However, embodiments of the present invention illustrated below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The preamble can be used for three purposes in IEEE 802.16m. The timing synchronization for detecting the downlink signal synchronization of the basic system, the cell ID information required to distinguish the system signal, and the location measurement for positioning the terminal. The requirements that a signal must have to support each of them can be defined as follows.

The terminal must detect a specific signal pattern, and the number of the signal patterns must be minimum to reduce the search complexity. In addition, when the reception signal itself has a feature that enables the detection operation of the terminal, for example, a signal is repeated, it is easy to detect timing regardless of the state of the channel experienced by the signal. In addition, the structure of the signal pattern should have a form that can be detected at a minimum cost, that is, a minimum chip area and power consumption in the terminal.

When timing detection is completed, the terminal should be ready to detect the ID of the cell. The cell ID is the most basic seed value representing the signal structure of the system. Therefore, all cells in the signal transmission range must use different IDs, and considering the femto cell, a maximum number of cell IDs is required. In transmitting the cell ID, measures to reduce the error probability of the cell ID should also be taken. In particular, it should be possible to prevent degradation due to the channel. In addition, the more cell IDs, the more combinations that the UE needs to detect. Therefore, a cell ID display technique capable of efficiently detecting the cell IDs is required.

Position measurement is a suitable method for use in synchronous systems. In a synchronous system, all cells have the same signal transmission timing, such as through a GPS clock. Therefore, if the terminal can measure the signal transmitted at the same time, it can calculate its position in the form of triangulation. In particular, in order to measure a signal of another cell base station, it is most preferable to use a signal signal specialized in that cell and a known signal pattern, that is, a preamble signal. However, since the accuracy of timing measurement is determined by the sampling rate of the signal, a wideband transmission signal is needed as much as possible.

Hereinafter, the signal structure of the preamble in consideration of the above conditions will be described through some embodiments of the present invention.

3 illustrates a structure of a synchronization channel according to an embodiment of the present invention.

3 shows a form in which preambles are placed only in a partial region of the overall system bandwidth. Here, the preamble is divided into a P-SCH and an S S-SCH. As in IEEE 802.16e, P-SCH and S-SCH may be defined as the same.

In FIG. 3, when the P-SCH and the S-SCH are designed in the same sequence and signal structure, the preamble is placed only in a specific band instead of the entire system band, and the specific band has a constant size regardless of the system band. Has characteristics.

On the other hand, when the P-SCH and the S-SCH are distinguished, the P-SCH becomes a signal structure for timing detection and the S-SCH becomes a signal structure for cell ID detection. P-SCH is preferably formed in a structure having a repeating pattern in the time domain. The more the S-SCH includes the number of cell IDs, the better.

FIG. 4 illustrates a signal structure of a first sync channel in FIG. 3.

In the P-SCH, a sequence or a codeword is preferably applied to two subcarrier intervals or more as shown in FIG. 4. Accordingly, the P-SCH has a repeating pattern.

FIG. 5 illustrates a signal structure of a second synchronization channel in FIG. 3.

Since the channel estimation cannot be applied from the P-SCH when the S-SCH has a large time difference from the P-SCH, the S-SCH is preferably applied at the same interval as the P-SCH, that is, at two subcarrier intervals. A pilot signal for channel estimation may be applied to the remaining subcarrier regions. However, when the S-SCH is close to the P-SCH, i.e., adjacent to the P-SCH, channel estimation can be performed depending on the P-SCH. Therefore, the S-SCH uses all available subcarriers. It is desirable to generate a signal.

6 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

In the case of generating the preamble signal as shown in FIG. 3, since the preamble signal is transmitted only through a predetermined minimum band, it is disadvantageous for position calculation using the preamble. The embodiment of FIG. 6 is a format in which more power can be allocated to each sync channel by dividing the S-SCH and the P-SCH.

In the case of FIG. 6, the band of the P-SCH is present only in a predetermined band Bp, and the S-SCH occupies a part (Bm-Bp) or the entire band (Bs-Bp) of the bands not used by the P-SCH. Indicates. That is, when the system band is Bs Hz, the band used by the P-SCH is Bp Hz, and the minimum band supported by the air interface is Bm Hz, the area where the S-SCH is present is Bm-Bp Hz to Bs-Bp Hz. It is possible until. Here, it is preferable that the signal structures of the P-SCH and the S-SCH have a structure similar to that shown in FIG. The S-SCH may be further classified into S-SCH1 and S-SCH2, and may contain different information. That is, a cell ID can be expressed by a combination of information in two S-SCH1 and S-SCH2. Alternatively, if the cell ID is sufficient to indicate the cell ID through each of the S-SCH1 and the S-SCH2, the S-SCH1 and the S-SCH2 may be in the form of applying a simple repetition of a synchronization channel or one of the two is omitted. When repetition is applied to S-SCH1 and S-SCH2, the frequency diversity of the channel can be improved by transmitting both S-SCH1 and S-SCH2.

FIG. 7 illustrates an example of applying cyclic copy to an extended synchronization channel in FIG. 6.

An extended synchronization channel (E-SCH) can be further defined, which is the same width as that of the P-SCH and can transmit the contents of the S-SCH to the E-SCH.

Repetition or cyclic copy may be applied to the E-SCH. That is, if the size of the E-SCH is sufficiently smaller than the S-SCH, equal cyclic radiation from S-SCH1 and S-SCH2 is applied to the E-SCH, and if the E-SCH is larger than the S-SCH, Cyclic radiation can be applied to the remaining region while repeatedly including the S-SCH in the SCH.

Alternatively, the E-SCH may be in an extended form masked with another sequence, for example, a Walsh, a DFT vector, or the like.

In addition, the P-SCH may be further transmitted through the E-SCH. By sending the P-SCH again, the latency of obtaining the timing of the downlink signal can be reduced. In addition, by further transmitting a signal in the E-SCH region, it is possible to increase the location accuracy. In addition, to obtain higher accuracy, the contents of the S-SCH can be extended and included in the extended region (Ext), where masking versions such as cyclic copy, Walsh expansion of the S-SCH, and DFT vector expansion can be applied. have.

8 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

8 is more compact than the embodiment of FIG. 6. That is, the P-SCH and the S-SCH are transmitted at the same time in the same OFDM symbol. Here, the total amount of power applied to each sync channel can be distinguished.

The structures of the P-SCH and the S-SCH may use structures similar to those of FIGS. 4 and 5. In addition, the contents of S-SCH1 and S-SCH2 may be the same. In the case of using the above structure, the terminal can find out the timing of the downlink signal with the minimum time, and can detect the cell ID directly at the corresponding position. In addition, the P-SCH and the S-SCH can be used simultaneously, and the accuracy of the position measurement can be increased by extending the S-SCH to the system bandwidth or applying an additional sequence.

9 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

Currently, the OFDM structures defined in IEEE 802.16e all have the same symbol length. FIG. 9 illustrates an embodiment in which a preamble OFDM symbol is divided in half when using the same length symbol. In this state, the order of the P-SCH and the S-SCH may come out first, as shown in FIG. 9, and the S-SCH may come out first. This approach does not damage the existing structure while generating a multi-stage preamble structure. Instead, each sync channel may have an extended subcarrier spacing and use a different FFT size. Therefore, the total number of subcarriers is defined to be a power of 2, and the corresponding OFDM symbol length is designed. That is, in a system using an FFT size of 1024, when the OFDM symbols are divided in half, each symbol may use an FFT of 512 or an FFT of 256. In FIG. 9, for the purpose of position measurement, a signal associated with a cell ID may be transmitted using a sequence or a codeword through an area other than a band used as a preamble.

The sequence used for the preamble itself needs a structure suitable for searching and information amount.

The P-SCH sequence is as follows. In order to search for a P-SCH signal in a terminal, a code correlation may be obtained using a sequence or autocorrelation may be obtained using a repetitive pattern present in the P-SCH. In this process, the complexity is defined by how accurately the received signal should be sampled and the number of constellations of the P-SCH sequence itself. If the constellation of the P-SCH sequence is simply binary, such as 1 or -1, the hardware required for the search using the sequence at the receiving end may be simply added and subtracted. Therefore, the P-SCH sequence may be generated from sequences in which the constellation is limited to binary or minimum QPSK among CAZAC or GCL sequences. Alternatively, it is also possible to use Hadamard or m-sequences, which have the disadvantage that the cubic metric is inferior to the CAZAC series. Also, since a large number of sequences are not required for retrieving timing, it is desirable to use only a few sequences that are most suitable for retrieval. That is, when the sequences are conjugated to each other, or when a part of the sequence is in a conjugate relationship, XOR, masking, or the like with a part of another sequence, the receiving end may detect these related sequences at once.

The structure of the S-SCH sequence is as follows. The S-SCH signal is suitable for a structure in which a cell ID can be easily searched or immediately found. The former is a case of directly transmitting a cell ID value. The cell ID is encoded and transmitted through channel encoding. In this case, since the codewords must be decoded for each cell ID, the mapping method of each codeword or the structure of an interleaver used for the codewords can be changed in preparation for the case where the S-SCH signal overlaps with the cell edge. For this purpose, the most basic seed value is a sequence used for the P-SCH. That is, the interleaver used in the codeword of the S-SCH may be changed or the method of mapping to the subcarriers according to the value of the sequence used in the P-SCH. In the case of transmitting the sequence ID without directly transmitting the cell ID, a sequence that can be used for the S-SCH can be identified by a simple transformation, and a mad sequence, an m-sequence, a Golay sequence, and the like can be used. In this case, the terminal may perform a simple transformation for sequence search. On the other hand, when using a CAZAC sequence or the like, the ID of the sequence can be found through a simple differential operation. As such, when a sequence or a codeword is used for the S-SCH, the structure in which the S-SCH1 and the S-SCH2 are transmitted may be in various forms.

10 to 13 illustrate examples of mapping methods when two sequences or two codewords are used in a second synchronization channel.

The sequence or codeword transmitted in one S-SCH region may be simply one sequence or codeword, or may be a combination of one or more sequences or codewords. That is, the cell ID may be expressed by a combination of multiple sequence IDs or a combination of codewords.

10 illustrates a structure in which two sequences or codewords overlap with the pilot subcarriers on the same subcarrier. 11 illustrates a structure in which interacing is applied to two sequences or codewords without a pilot subcarrier. 12 illustrates a structure for concatenating two sequences or codewords together with a pilot subcarrier. 13 is a structure for concatenating two sequences or codewords without a pilot subcarrier.

The structure of the extended sequence is as follows. Since this part can be used for position measurement, the sequence needs to be mapped one-to-one with the cell ID. This is because, in case of one-to-one mapping, a signal delay can be accurately estimated using a combination of a preamble and an extended sequence corresponding to a cell ID.

Therefore, when using a kind of sequence such as P-SCH or S-SCH as an extension sequence, the sequence indicating the cell ID can be reused. In this case, the extended sequence may use the sequence itself representing the original cell ID or use a functional relationship corresponding to the cell ID sequence one-to-one to avoid repetition of the sequence. In this case, a function of simply adding an offset to a cell ID as a function relation, a reverse mapping function that corresponds to a maximum ID number, and the like may be considered.

In addition, when there is not enough extended area, the cell ID sequence may be extended in a cyclic copy format. If the extended area is large enough, the sequence corresponding to the cell ID may be extended by cyclic copy, or the cell ID sequence may be cyclically copied and a one-to-one corresponding sequence may be added to the region where the entire sequence is contained.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. And, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention relates to a preamble transmission method for designing a preamble in consideration of a variable bandwidth to facilitate preamble searching of a terminal and extending a reference signal for position measurement. The present invention relates to 3GPP LTE, IEEE 802.16e, and IEEE. It can be applied to devices such as a base station and a terminal in a system such as 802.16m.

1 illustrates an example of a synchronization channel structure of a 3GPP LTE system.

2 illustrates an example of a synchronization channel structure of an IEEE 802.16 system.

3 illustrates a structure of a synchronization channel according to an embodiment of the present invention.

FIG. 4 illustrates a signal structure of a first sync channel in FIG. 3.

FIG. 5 illustrates a signal structure of a second synchronization channel in FIG. 3.

6 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

FIG. 7 illustrates an example of applying cyclic copy to an extended synchronization channel in FIG. 6.

8 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

9 illustrates a structure of a synchronization channel according to another embodiment of the present invention.

10 to 13 illustrate examples of mapping methods when two sequences or two codewords are used in a second synchronization channel.

Claims (14)

A method of transmitting a preamble to a terminal using a synchronization channel including a first synchronization channel for timing detection and a second synchronization channel for cell ID detection, Transmitting a first sync channel to which a symbol is assigned at two or more subcarrier intervals through a specific band of all system bands at the start of a sync cycle; And Transmitting a second synchronization channel through the specific band with a predetermined time difference from the first synchronization channel in the synchronization period. The preamble transmission method comprising a. The method of claim 1, The second sync channel, A symbol is allocated at two or more subcarrier intervals, and a pilot symbol is disposed between the allocated symbols. The method of claim 1, The constant time difference, And a time interval corresponding to half of the synchronization period. A method of transmitting a preamble to a terminal using a synchronization channel including a first synchronization channel for timing detection and a second synchronization channel for cell ID detection, Transmitting a first sync channel to which a symbol is assigned at two or more subcarrier intervals through a specific band of all system bands at the start of a sync cycle; And Transmitting the extended synchronization channel to which the cyclic copy of the second synchronization channel is applied through the specific band while transmitting the second synchronization channel through the remaining band except the specific band with a predetermined time difference from the first synchronization channel in the synchronization period. Steps to The preamble transmission method comprising a. The method of claim 4, wherein The second sync channel, The preamble transmission method, characterized in that transmitted over a part or all of the remaining bands other than the specific band of the entire system band. The method of claim 4, wherein Transmitting the extended synchronization channel, And transmitting the second synchronization channel repeatedly through the extended synchronization channel when the size of the second synchronization channel is larger than the size of the second synchronization channel. The method of claim 4, wherein The second sync channel, A symbol is allocated at two or more subcarrier intervals, and a pilot symbol is disposed between the allocated symbols. The method of claim 4, wherein The constant time difference, And a time interval corresponding to half of the synchronization period. A method of transmitting a preamble to a terminal using a synchronization channel including a first synchronization channel for timing detection and a second synchronization channel for cell ID detection, Transmitting a first sync channel to which a symbol is allocated at two or more subcarrier intervals over a specific band among all system bands at a start point of a sync cycle, and transmitting a second sync channel through the remaining bands except for the specific band; And Retransmitting the first synchronization channel and the second synchronization channel with a predetermined time difference in the synchronization period. The preamble transmission method comprising a. The method of claim 9, The second sync channel, The preamble transmission method, characterized in that transmitted over a part or all of the remaining bands other than the specific band of the entire system band. The method of claim 9, The constant time difference, And a time interval corresponding to half of the synchronization period. A method of transmitting a preamble to a terminal using a synchronization channel including a first synchronization channel for timing detection and a second synchronization channel for cell ID detection, The first second synchronization channel for distinguishing the first synchronization channel and the start position of the frame using a preamble OFDM symbol divided into two by adjusting the subcarrier spacing through a specific band of the entire system band at the start of the synchronization period Transmitting; And Transmitting a first sync channel and a second second sync channel having a different structure from the first second sync channel by using the divided preamble OFDM symbols over the specific band at a predetermined time difference in the sync period. step The preamble transmission method comprising a. The method of claim 12, The first sync channel and the second sync channel, A method of preamble transmission, characterized in that symbols are allocated at two or more subcarrier intervals. The method of claim 13, The second sync channel, And a pilot symbol is arranged between the allocated symbols.

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