KR100976873B1 - Method for transmitting signal - Google Patents

Abstract

In accordance with another aspect of the present invention, a signal transmission method includes setting a plurality of cyclic delay values corresponding to a plurality of transmission antennas, applying the plurality of cyclic delay values to a plurality of broadcast channel symbols, and the plurality of broadcast channels. Transmitting a symbol through the plurality of transmit antennas. Accordingly, by applying a cyclic delay diversity scheme to the broadcast channel information, it is possible to maximize the time diversity gain within the transmission time interval of the broadcast channel information and to efficiently remove interference from adjacent sectors at the sector boundary.

SCH, BCH, sector, cyclic delay diversity, precoding vector, antenna, subframe

Description

Signal transmission method {METHOD FOR TRANSMITTING SIGNAL}

The present invention relates to a signal transmission method.

Currently, 3GPP (3rd Generation Partnership Project) standardization of wireless transmission technology based on orthogonal frequency division multiplexing (OFDM) under the name of 3G Long Term Evolution (LTE).

In a multi-cell system using OFDM, a user should be able to efficiently receive information necessary for initial system access through a broadcast channel. In addition, all users in any sector must satisfy the requirements for reception quality of broadcast channel information, for example, block error rate and delay rate.

However, when a user is at a sector boundary within the same cell, there is a problem that this requirement is not satisfied due to the interference from adjacent sectors.

An object of the present invention is to provide a transmit diversity method for effective demodulation of broadcast channel information. Another object of the present invention is to provide a signal transmission method for improving reception quality of broadcast channel information of a mobile station at a sector boundary of a cell.

In accordance with another aspect of the present invention, a signal transmission method includes setting a plurality of cyclic delay values corresponding to a plurality of transmission antennas, applying the plurality of cyclic delay values to a plurality of broadcast channel symbols, and the plurality of broadcast channels. Transmitting a symbol through the plurality of transmit antennas.

The cyclic delay value may be determined according to the time when the broadcast channel symbol is allocated.

The plurality of cyclic delay values may have the same value for all sectors.

The method may further include applying each of a plurality of precoding phase weighting values corresponding to a time when the plurality of broadcast channel symbols are allocated to the plurality of broadcast channel symbols.

The plurality of precoding phase weighting values may have the same value for all the sectors.

One frame may include a plurality of subframes, and the plurality of broadcast channel symbols may further be allocated to at least two subframes.

The cyclic delay value and the precoding phase weighting value may be determined according to the subframe to which the broadcast channel symbol is assigned.

One frame includes a plurality of subframes, and the broadcast channel symbol may be assigned to only one of the frames.

The cyclic delay value and the precoding phase weighting value may be determined according to a symbol period of the subframe to which the broadcast channel symbol is allocated.

The method may further include applying a phase shift value corresponding to the sector to the plurality of broadcast channel symbols.

The precoding phase weighting value and the phase shifting value may have 0 for one of the plurality of transmitting antennas.

According to the present invention, a cyclic delay diversity scheme is applied to broadcast channel information to maximize the time diversity gain within a transmission time interval (TTI) of broadcast channel information and to prevent interference from adjacent sectors at a sector boundary. It can be removed efficiently.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted for simplicity of explanation, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

In this specification, a mobile station (MS) includes a terminal, a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), and a user equipment. It may also refer to a user equipment (UE), an access terminal (AT), and the like, and may include all or some functions of a terminal, a mobile terminal, a subscriber station, a portable subscriber station, a user device, an access terminal, and the like.

In the present specification, a base station (BS) is an access point (AP), a radio access station (Radio Access Station, RAS), a Node B (Node B), a base transceiver station (Base Transceiver Station, BTS), MMR ( Mobile Multihop Relay) -BS and the like, and may include all or part of functions such as an access point, a radio access station, a Node B, a base transceiver station, and an MMR-BS.

Hereinafter, a communication system according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

1 is a diagram illustrating a communication system according to an embodiment of the present invention, and FIG. 2 is a diagram illustrating a base station according to an embodiment of the present invention.

Referring to FIG. 1, the communication system includes a base station 100 and a mobile station 200. Referring to FIG. 2, the base station 100 includes a first sector transmitter 110, a second sector transmitter 120, and The third sector transmitter 130 is included.

Base station 100 manages cell 10. The cell 10 is composed of a first sector 11, a second sector 12, and a third sector 13. In the embodiment of the present invention, the cell 10 is described as being composed of three sectors. Alternatively, the cell 10 may be composed of two or four sectors. Base station 100 communicates with mobile station 200 within cell 10.

The first sector transmitter 110, the second sector transmitter 120, and the third sector transmitter 130 manage the first sector 11, the second sector 12, and the third sector 13, respectively. . That is, the first sector transmitter 110 communicates with the mobile station in the first sector 11, the second sector transmitter 120 communicates with the mobile station in the second sector 12, and the third sector transmitter 130 Communicate with the mobile station in the third sector 13.

The first sector transmitter 110, the second sector transmitter 120, and the third sector transmitter 130 each have a synchronization channel (eg, a first sector 11, a second sector 12, and a third sector 13). Synchronization channel (SCH) information and broadcast channel (BCH) information are transmitted. SCH information varies from sector to sector, and BCH information is common to all sectors. That is, SCH information is distinguished according to sectors, and BCH information is distinguished according to cells. The BCH information is transmitted on a predefined independent physical channel known to all mobile stations 200. The first sector transmitter 110, the second sector transmitter 120, and the third sector transmitter 130 are synchronized so that the mobile station 200 can demodulate the BCH information through soft-combining.

In an embodiment of the present invention, a sector to which the mobile station 200 belongs to among the plurality of sectors constituting the cell 10 is called a home sector, and the received power of a threshold value or more adjacent to the mobile station among the sectors excluding the home sector. A sector for transmitting a signal is called a target sector.

Hereinafter, a sector transmitter and a signal transmission method according to an embodiment of the present invention will be described with reference to FIGS. 3 to 7.

3 is a block diagram illustrating a sector transmitter according to an embodiment of the present invention.

Referring to FIG. 3, a sector transmitter 400 according to an embodiment of the present invention transmits a signal to an s-th sector, and includes a BCH symbol generator 410, a SCH symbol generator 420, and other channel symbol generators. 430, an OFDM mapping unit 440, a switch 450, a first transmitter 460a, a second transmitter 460b, a first antenna 470a, and a second antenna 470b.

4 is a flowchart illustrating a sector transmission method according to an embodiment of the present invention.

First, the BCH symbol generator 410 generates and outputs a plurality of BCH symbols.

In detail, the channel encoder 411 performs channel coding such as turbo coding or convolutional coding on the BCH data to generate and output channel encoded BCH data (S201).

The interleaver 412 generates and outputs interleaved BCH data by changing the order of channel encoded BCH data output by the channel encoder 411.

The digital modulator 413 performs digital modulation such as binary phase shift key (BPSK) and quadrature amplitude modulation (QAM) on the interleaved BCH data output from the interleaver 412. A plurality of BCH symbols are generated and output (S201).

등이 될 수 있다.On the other hand, the SCH symbol generator 420 generates and outputs a plurality of SCH symbols (S203). The SCH symbol generator 420 generates and outputs an SCH symbol vector by scrambling the SCH symbol using the SCH scrambling code according to the number of SCH symbols included in the subframe in which the SCH symbol exists. The value of the SCH symbol can be changed according to the specification, 1 or

And so on.

On the other hand, the other channel symbol generator 430 generates and outputs a plurality of other channel symbols (S205).

The OFDM symbol mapping unit 440 outputs a plurality of mapped symbols by mapping a plurality of BCH symbols, a plurality of SCH symbols, and a plurality of other channel symbols to a time domain and a frequency domain. That is, the OFDM symbol mapping unit 440 performs time division multiplexing and frequency division multiplexing on the plurality of BCH symbols, the plurality of SCH symbols, and the plurality of other channel symbols (S207).

Hereinafter, a mapping method of the OFDM symbol mapping unit 440 will be described with reference to FIG. 5.

5 illustrates a downlink frame in which SCHs and BCHs are mapped according to various embodiments of the present disclosure.

The sector transmitter 300 may use various bandwidths such as 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz as the system bandwidth.

Referring to FIG. 5, the downlink frame according to the embodiment of the present invention includes 20 subframes. SCH and BCH are mapped to the same frequency of the system bandwidth, for example, 1.25 MHz. Accordingly, the mobile station 200 does not need to perform blind detection on the BCH bandwidth to demodulate the BCH symbol.

When the number of SCHs is two, one is called a primary synchronous channel (P-SCH) and the other is called a secondary chronization channel (S-SCH).

The OFDM symbol mapping unit 440 allocates a plurality of P-SCH symbols and a plurality of S-SCH symbols to two adjacent OFDM symbol intervals by time division multiplexing (TDM). In this case, the S-SCH may be used for channel estimation or, alternatively, the P-SCH may be used for channel estimation.

According to FIG. 5, the OFDM symbol mapping unit 440 multiplexes BCH information into two subframes during one downlink frame period. The BCH information is transmitted to the mobile station 200 in the form of a packet. One BCH information packet may be multiplexed in one frame and transmitted every 10 msec. The BCH information may be multiplexed in two or more frames and 20 msec, 30 msec, or 40 msec. May be sent.

An embodiment of the present invention may use a multiplexing method for transmitting BCH information through a unicast channel, or a multiplexing method for transmitting a BCH information through a multicast channel, a multimedia broadcast and multicast service (MBMS) channel, and the like. Can also be used.

According to FIG. 5, the OFDM symbol mapping unit 440 maps the S-SCH symbol and the P-SCHSCH symbol to the last OFDM symbol interval of each subframe at intervals of 10 subframes. The OFDM symbol mapping unit 440 maps a BCH symbol, a BCH symbol, and a downlink reference signal (DL RS) symbol to OFDM symbol intervals other than the OFDM symbol interval to which the S-SCH symbol and the P-SCHSCH symbol are mapped. do.

The cyclic delay unit 450 applies a cyclic delay value for the corresponding antenna to the plurality of BCH symbols according to the cyclic delay table 451 and outputs the same, while the SCH symbol and other channel symbols are also output to the first / second transmitter 440a. / 440b) (S209).

At this time, the SCH symbol adjacent to the BCH symbol is transmitted to the same first and second transmitters 440a and 440b as the adjacent BCH symbol.

Hereinafter, a cyclic delay diversity scheme according to the present invention will be described with reference to FIGS. 6 and 7.

6 and 7 are cell configuration diagrams illustrating a cyclic delay diversity scheme.

In FIG. 6 and FIG. 7, it is assumed that each sector transmitter has two or four antennas 470a and 470b, and one cell includes three sectors.

The cyclic delay unit 450 applies a cyclic delay value to the BCH symbol, B _{k, i, c} (s) in the subframe s containing the BCH symbol, as shown in Equation 1, and transmits a signal for each transmission antenna a, T produces _{k, i, a, c} (s).

[Equation 1]

Here, k denotes a frequency domain subcarrier index containing BCH information B _{k , i, c} (s) for each sector c. In addition, θ _a (k, s) means a cyclic delay value applied to the subframe s containing the BCH symbols for each antenna a.

As illustrated in FIG. 6, the cyclic delay unit 450 may apply the same cyclic delay value to all sectors included in each cell 10.

Meanwhile, the cyclic delay unit 450 may further apply a phase shift value that further maximizes the time diversity gain and also obtains the spatial diversity gain while applying the cyclic delay value as shown in FIG. 7.

Specifically, the cyclic delay unit 450 generates a transmission signal for each transmission antenna a, T _{k , i, a, c} (s) (a = 0,1) satisfying Equation 2.

[Equation 2]

Here, Ø _{1, a} (i, s) means a precoding phase weighting value applied to the BCH symbol in the OFDM symbol i of the subframe s containing the BCH symbol and at the same time, the phase shift for maximizing the time diversity gain. Ø _{2, a} (c) means a phase shift value for maximizing different spatial diversity gains for each sector for the BCH symbol transmitted through the antenna a.

For example _{, a relationship of} Ø _{1, a} (i, s) = a Ø _1,1 (i, s) and a = 1,2,3 may be satisfied.

This Ø _{1, a} (i, s) can be equally applied to all sectors.

Further, the relationship of Ø _{2, a} (c) = a Ø _2,1 (c) and a = 1, 2, 3 can also be satisfied.

For example, if the number of sectors in cell 10 is 3, Ø _{2, a} (0) = 0, Ø _{2, a} (1) = 2π / 3, Ø _{2, a} (2) = 4π / 3 Ø _{2, a} (c) may be applied as 0, π, π / 2 (-π / 2) depending on the sector. Further, when the number of sectors in the cell 10 is 6, the case where the number of sectors is 3 is extended, so that Ø _{2, a} (s) is 0, 2π / 3, 4π / 3, 0, 2π / 3 for each sector. , 4π / 3 or 0, π, π / 2, 3π / 2, 0, π or π / 2, 3π / 2, 0, π, π / 2, 3π / 2 can be applied.

When different phase shifts are applied to the sectors as described above, even if the precoding phase weighting value and the phase shifting value for temporal diversity are the same, the phase shifting values for the spatial diversity gain are different from sector to sector. When the spatial spatial correlation is relatively large, different beams are formed. Therefore, interference from adjacent sectors can be effectively prevented.

As such, the sector transmitter 400 applies cyclic delay switching to the BCH symbol to lower the block error rate of the BCH information to improve reception quality.

Meanwhile, the cyclic delay unit 450 transmits a plurality of BCH symbols and SCH symbols adjacent in time to the plurality of BCH symbols so as to be transmitted through the same antenna, while transmitting a time-switch transmit diversity (TSTD). Or frequency-switched transmit diversity (FSTD) may be applied to the SCH and the BCH. For example, the cyclic delay unit 460 transmits an SCH symbol and a BCH symbol for some subcarriers to the first transmitter 460a, and transmits an SCH symbol and a BCH symbol for another subcarrier to the second transmitter 460b. To pass on.

The cyclic delay unit 450 may apply the TSTD and the FSTD to the SCH and the BCH simultaneously while performing switching so that a plurality of BCH symbols and SCH symbols adjacent in time to the plurality of BCH symbols can be transmitted through the same antenna. .

The first and second transmitters 460a and 460b receive and process a plurality of channel symbols from the cyclic delay unit 450 and transmit them to the c-th sector through the first and second antennas 470a and 470b. .

In detail, the first and second transmitters 460a and 460b apply a code for obtaining a diversity gain with respect to a BCH symbol.

Such a code may include phase rotation values to obtain delay diversity and / or random diversity, and the phase rotation values must be properly adjusted to obtain high delay diversity gain between sectors.

Meanwhile, different codes may be allocated to adjacent subcarriers in order to obtain a random diversity gain.

The first / second transmitters 460a / 460b scramble the coded BCH symbols with a sector-specific scrambling code or a cell-specific scrambling code to generate and output a plurality of scrambled symbols. Since scrambling the SCH symbol may make initial cell search difficult, the SCH symbol is not scrambling with a sector-specific scrambling code or a cell-specific scrambling code.

The first and second transmitters 460a and 460b generate a time domain signal by performing fast Fourier inverse transform on the scrambled symbols and insert a guard interval such as a cyclic prefix (CP). Next, the first and second transmitters 460a and 460b convert the amplified signals into high frequency signals and amplify them and transmit them to the mobile station 200 through the first and second antennas 470a and 470b.

Meanwhile, as illustrated in FIG. 8, the OFDM symbol mapping unit 440 may multiplex BCH symbols only in one subframe without multiplexing BCH symbols in a plurality of subframes during one frame.

8 shows bandwidth allocation for SCH and BCH according to another embodiment of the present invention.

That is, the OFDM symbol mapping unit 440 may map a BCH symbol only to the first subframe of one frame, for example.

In this case, the cyclic delay unit 450 performs the phase shift described above in units of OFDM symbol intervals in which SCH symbols and BCH symbols are multiplexed.

That is, the cyclic delay unit 450 applies a cyclic delay value for each antenna for the BCH symbol, and applies the cyclic delay value to the frequency domain BCH symbols B _{k, i, c} (s) in the subframe s = 0 including the BCH symbol. As shown in Equation 2 _{, a} transmission signal T _{k, i, a, c} (s) for each transmitting antenna is generated by applying a precoding phase weighting value and a phase shift value for spatial diversity.

In _{Tk, i, a, c} (s) of Equation 2 _, BCH symbols in the subframe s containing BCH information for each antenna, which is the phase shift value of the precoding vector, are applied to the pre-application in FIG. 8. A coding phase weighting value and a phase shift value for maximizing time diversity gain.

In the example of the present invention, it may be differently applied to have orthogonality in units of OFDM symbols for time diversity gain. That is, phase shift values having orthogonality between OFDM symbols are allocated.

As such, when different phase shift values are allocated according to sectors, when the BCH information is different between sectors, that is, sector-specific information, interference from adjacent sectors is effectively reduced. In addition, when the BCH information is the same for sectors in the same cell, that is, the information for common cell use, there is an effect of increasing the soft combining gain.

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram illustrating a communication system according to an embodiment of the present invention.

2 is a diagram illustrating a base station according to an embodiment of the present invention.

3 is a block diagram illustrating a sector transmitter according to an embodiment of the present invention.

4 is a flowchart illustrating a sector transmission method according to an embodiment of the present invention.

5 shows bandwidth allocation for SCH and BCH according to one embodiment of the present invention.

6 and 7 are cell configuration diagrams illustrating a cyclic delay diversity scheme.

8 shows bandwidth allocation for SCH and BCH according to another embodiment of the present invention.

Claims (11)

Setting a plurality of cyclic delay values respectively corresponding to the plurality of transmit antennas, Applying each of the plurality of cyclic delay values to a plurality of broadcast channel symbols; Transmitting the plurality of broadcast channel symbols through the plurality of transmit antennas, and Applying a plurality of precoding phase weighting values corresponding to the time when the plurality of broadcast channel symbols have been allocated to the plurality of broadcast channel symbols, respectively. Signal transmission method comprising a. The method of claim 1, The cyclic delay value is determined by the time the broadcast channel symbol is allocated. Signal transmission method. The method of claim 2, The plurality of cyclic delay values have the same value for all sectors. delete The method of claim 3, And the plurality of precoding phase weight values have the same value for all the sectors. The method of claim 5, One frame includes a plurality of subframes, The plurality of broadcast channel symbols are allocated to at least two subframes Signal transmission method further comprising. The method of claim 6, The cyclic delay value and the precoding phase weighting value are determined according to the subframe to which the broadcast channel symbol is assigned. The method of claim 5, One frame includes a plurality of subframes, The broadcast channel symbol is assigned to only one of the plurality of subframes. Signal transmission method. The method of claim 8, The cyclic delay value and the precoding phase weighting value are determined according to a symbol interval of the subframe to which the broadcast channel symbol is allocated. The method according to any one of claims 7 to 9, Applying a phase shift value corresponding to the sector to the plurality of broadcast channel symbols Further comprising Signal transmission method. The method of claim 10, Wherein the precoding phase weighting value and the phase shifting value have a zero for one of the plurality of transmit antennas.

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