WO2010079531A1

WO2010079531A1 - Wireless communication device

Info

Publication number: WO2010079531A1
Application number: PCT/JP2009/000029
Authority: WO
Inventors: 三上純矢
Original assignee: 富士通株式会社
Priority date: 2009-01-07
Filing date: 2009-01-07
Publication date: 2010-07-15

Abstract

A wireless communication device applies phase rotation processing to a signal at the phase rotation amount varying with time depending on patterns different for each device-specific identification information (cell ID) and transmits the signal. With this, because the phase differences of the signals from a plurality of wireless communication devices vary, the state in which the signals from the plurality of wireless communication devices interfere with one another is not maintained to prevent the detection characteristics (cell search characteristics) of the cell IDs of mobile terminals from deteriorating even in the state in which devices (mobile terminals) for receiving the signals remain stationary.

Description

Wireless communication device

The present invention relates to a radio communication apparatus in a mobile radio system, and more particularly to a technique of a radio communication apparatus that transmits a unique identification signal for each apparatus.

LTE (Long, a next generation mobile communication system that evolved from the 3rd generation mobile phone system)
Term Revolution) is currently being standardized by 3GPP (3rd Generation Partnership Project).

LTE standards currently being developed in 3GPP (3GPP
In TS36.211), OFDM (Orthogonal Frequency Division Multiplexing) is adopted as a downlink modulation scheme. OFDM is one of multi-carrier transmission schemes, and transmits data in parallel on a plurality of carrier waves (subcarriers). By utilizing the orthogonality between the subcarriers, each subcarrier can be separated on the receiving side even if a part of the frequency band of the subcarriers is overlapped, so that the frequency can be used efficiently and high-speed transmission is possible.

Also, for synchronization between the base station and the mobile station, the base station multiplexes and transmits PSC (Primary Synchronization Code) and SSC (Secondary Synchronization Code) as synchronization signals in the downlink frame. A cell identification signal (cell ID) is detected (cell search) from the received signal. When the mobile station starts communication with the base station, the operation of detecting the cell ID of the base station in the area where the mobile station exists is called initial cell search, and the mobile station in communication with the base station The operation of detecting the cell ID of the base station is called a neighbor cell search.

The mobile station performs handover for switching the connection when the connection with the base station in communication becomes inappropriate due to movement and there is a more appropriate base station. Therefore, the mobile station needs to detect neighboring base stations in addition to the communicating base station, and performs a neighboring cell search.

FIG. 1 is a diagram showing a downlink radio frame format in the LTE standard. As shown in FIG. 1A, one radio frame of 10 ms is composed of 10 subframes, and PSC and SSC are stored in subframe # 0 and subframe # 5, respectively. FIG. 1B shows a subframe including PSC and SSC. A 1 ms subframe is composed of 14 OFDM symbols, SSC is stored in OFDM symbol # 5, and PSC is stored in OFDM symbol # 6. The In the frequency domain, the OFDM symbol is composed of signals having the number of subcarriers corresponding to the system band, and PSC and SSC use 72 subcarriers in the center of the band regardless of the system bandwidth. Therefore, PSC and SSC are transmitted in a 5 ms period.

PSC is generated from three Zadoff-Chu sequence signals, and SSC is generated using a signal obtained by scrambled a signal obtained by cyclically shifting two types of binary sequence signals.
Is transmitted as a combination of PSC and SSC. The mobile station on the receiving side creates the SSC replica signal corresponding to all the cell IDs that may be received, and correlates with the received SSC to detect the cell ID of the base station to communicate with. .

Japanese Patent Laid-Open No. 2004-228688 despreads a received spread signal using a plurality of unique code group identification codes for identifying a group to which a unique code belongs to each communication station, so that a plurality of communication stations can receive signals from the same path. A wireless communication apparatus capable of detecting each unique code when reception spread signals overlap is disclosed.
Japanese Patent Laid-Open No. 2003-188807

A mobile station that receives signals from a plurality of base stations receives a radio wave composed of a plurality of signals. A signal from another base station becomes an interference wave with respect to the signal to be detected, and a desired signal is attenuated depending on the phase difference.

When the mobile station is moving, the state of the propagation path always changes, so that even if a desired signal may be attenuated by the interference wave, it can be expected to recover over time. However, when the mobile station is stationary, the phase difference between the desired wave and the interference wave may continue to be constant, and when the phase difference stops while the desired wave is attenuated, the desired wave Wave cell ID detection characteristics deteriorate.

FIG. 2 is a diagram illustrating a state in which the mobile station receives signals from a plurality of base stations. When performing a neighbor cell search, the desired wave (signal to be detected) is a signal from a base station (base station 2) different from the base station (base station 1) that is communicating, In many cases, a signal from a high communication base station (base station 1) becomes an interference wave, and in this case, the influence of the interference is large.

Therefore, an object of the present disclosure is to provide a wireless communication apparatus that prevents deterioration of cell ID detection characteristics in cell search.

A first configuration of a wireless communication device for achieving the above object is that a wireless communication device that transmits a signal based on unique identification information at a constant transmission period changes with time in a different pattern for each identification information. A calculation unit that obtains a phase rotation amount for each transmission cycle of the signal, and a phase rotation unit that performs phase rotation processing on the signal according to the phase rotation amount obtained for each transmission cycle by the calculation unit. And

According to a second configuration of the wireless communication apparatus, in the first configuration, the calculation unit obtains a phase rotation amount for each transmission period by selecting one of a plurality of predetermined phase rotation amounts. Is a requirement.

According to a third configuration of the wireless communication device, in the second configuration, the calculation unit generates a pseudo-random number sequence, selects a pseudo-random number having a predetermined length at a different position for each transmission cycle, and It is a requirement to obtain a phase rotation amount corresponding to the selected pseudo-random number among the phase rotation amounts.

According to a fourth configuration of the wireless communication device, in the second configuration, the calculation unit generates a pseudo random number different for each identification information, selects a pseudo random number having a predetermined length at a different position for each transmission cycle, and It is a requirement to obtain a phase rotation amount corresponding to the selected pseudo-random number from a plurality of predetermined phase rotation amounts.

According to a fifth configuration of the wireless communication device, in the fourth configuration, the pseudo-random number sequence that differs for each identification information has a length longer than the predetermined length, and the calculation unit has a position that differs for each transmission period. It is a requirement that a pseudo-random number having a predetermined length is periodically and repeatedly selected.

According to a sixth configuration of the wireless communication apparatus, in the first configuration, the calculation unit includes a CAZAC (Constant Amplitude Zero) having a different sequence number for each identification information.
The requirement is to obtain the amount of phase rotation based on the Auto-Correlation) sequence.

The seventh configuration of the wireless communication device is that, in the first configuration, the calculation unit obtains a phase rotation amount obtained by adding a different value for each identification information for each transmission cycle.

According to this wireless communication device, by transmitting a signal after performing phase rotation processing with a phase rotation amount that changes with time according to a different pattern for each unique identification information (cell ID), Since the phase difference of the signal changes, even when the device (mobile terminal) that receives the signal is stationary, the state in which signals from a plurality of wireless communication devices interfere with each other does not continue. It is possible to prevent the deterioration of the cell ID detection characteristic (cell search characteristic).

It is a figure which shows the downlink radio | wireless frame format in a LTE specification. It is a figure which shows the state in which the mobile station is receiving the signal from several base stations. It is a figure which shows typically the transmission signal containing the synchronizing signal from which phase rotation amount differs for every time and a base station. It is a figure which shows the structural example of the radio | wireless communication apparatus in this Embodiment, and shows the principal part structural example of the transmission function part. 2 is a diagram illustrating a configuration example of a synchronization signal generation unit 10. FIG. 6 is a diagram illustrating a first configuration example of a rotation amount calculation unit 118. FIG. It is a figure which shows the example of allocation for every cell ID of a PN15 signal. It is a figure which shows the example of the rotation amount table 1184. FIG. 6 is a diagram illustrating a second configuration example of a rotation amount calculation unit 118. FIG. FIG. 8 is a diagram illustrating a third configuration example of a rotation amount calculation unit 118. It is a figure which shows the 4th structural example of the rotation amount calculating part.

Explanation of symbols

10: synchronization signal generation unit, 20: pilot signal generation unit, 30: encoder, 40: modulator, 50: OFDM multiple mapping unit, 60: IFFT unit, 70: GI addition unit, 80: wireless transmission unit, 102: PSC number calculation unit, 104: PSC signal table, 106: SSC number calculation unit, 108: binary sequence generation unit, 110: scramble sequence generation unit, 112: scramble unit, 114: multiplexing unit, 116: modulation unit, 118: rotation Quantity calculation unit, 120: PSC phase rotation unit, 122: SSC phase rotation unit, 1181: Pseudorandom number generation unit, 1182: Initial value table, 1183: 40-digit counter, 1184: Rotation amount table, 1185: DSP, 1186: Rotation Amount table, 1187: adder, 1188: rotation amount table

Hereinafter, embodiments of the apparatus of the present disclosure will be described with reference to the drawings. However, such an embodiment does not limit the technical scope of the device of the present disclosure.

The wireless communication apparatus according to the present embodiment applies random phase rotation to the synchronization signals PSC and SSC. The amount of phase rotation changes with time, and the pattern of the change is different for each base station (wireless communication apparatus). Even when the mobile station is stationary, the cell ID detection is performed because the phase difference between the transmission signal (desired wave) from the adjacent base station and the transmission signal (interference wave) from the communicating base station changes. The phase difference state in which the characteristic is deteriorated does not continue, and the deterioration of the cell ID detection characteristic is prevented.

FIG. 3 is a diagram schematically showing a transmission signal including a synchronization signal having a different phase rotation amount for each time and base station. Even when the transmission signals from the base station 1 and the base station 2 are input in phase and continue, the phase at the timing of the synchronization signal can be determined by randomly adding phase rotation to the synchronization signals (PSC and SSC) every 5 ms. The phase difference can be different (the phase difference may coincide by chance, but the case does not continue). In the example of FIG. 3, the phase rotation amount to be applied is selected from four types of 0 degree, 90 degrees, 180 degrees, and 270 degrees, and is randomly selected from the four types for each base station.

FIG. 4 is a diagram illustrating a configuration example of the wireless communication apparatus according to the present embodiment, and illustrates a configuration example of a main part of the transmission function unit. The synchronization signal generation unit 10 generates PSC and SSC, which are synchronization signals, from the cell ID and the frame timing. The pilot signal generation unit 20 generates a pilot signal from the cell ID and the frame timing. The encoder 30 encodes transmission data using a convolutional code or a turbo code. The encoder 30 also performs rate matching and interleaving processing as necessary. The modulator 40 performs processing such as QPSK modulation and QAM modulation on the encoded data. An encoder 30 and a modulator 40 are provided for each physical channel of transmission data. The OFDM multiple mapping unit 50 maps a plurality of physical channels, synchronization signals, and pilot signals to subcarriers. The IFFT unit 60 performs fast inverse Fourier transform on the subcarrier mapped data and converts it into a time domain signal. A GI (guard interval) adding unit 70 adds GI to the output signal from IFFT 60. The radio transmission unit 80 performs radio frequency processing such as up-conversion and filtering, and outputs a transmission signal from the antenna.

FIG. 5 is a diagram illustrating a configuration example of the synchronization signal generation unit 10. The PSC number calculation unit 102 calculates and determines the PSC number from the cell ID. The PSC number table 104 holds the PSC signal calculated in advance as a table, and outputs the PSC signal according to the PSC number. The SSC number calculation 106 calculates and determines the numbers of two binary sequences and scramble sequences of SSC from the cell ID and the frame timing. The two binary sequence generation units 108 generate binary signals of the determined binary sequence. The two scramble sequence generation units 110 generate scramble signals of the determined scramble sequence. The scramble unit 112 scrambles the binary signal by performing an exclusive OR operation on the scramble signal. The multiplexing unit 114 multiplexes the two types of scrambled binary signals. Modulation section 116 performs BPSK modulation on the multiplexed binary signal and outputs it as an SSC signal.

The rotation amount calculation unit 118 calculates a phase rotation amount based on the cell ID and the frame timing. As will be described later, the phase rotation amount calculation processing includes not only processing for actually calculating the phase rotation amount but also processing for selecting a predetermined phase rotation amount from the table.
The PSC phase rotation unit 120 performs phase rotation on the PSC signal based on the calculated phase rotation amount, and outputs it. The SSC phase rotation unit 122 performs phase rotation on the SSC signal based on the calculated phase rotation amount, and outputs it.

FIG. 6 is a diagram illustrating a first configuration example of the rotation amount calculation unit 118. In the initial value table 1181, the pseudo random number generator 1181 generates pseudo random numbers. For example, PN (Pseude Random Number) 15 is used as the pseudorandom number. The PN15 signal is divided by 2 bits, and 20 sets (40 bits in total) are assigned to one cell ID.

FIG. 7 is a diagram showing an example of assignment of each PN15 signal for each cell ID. The first 40 bits of the PN15 signal are assigned to cell ID = 0, the next 40 bits are assigned to cell ID = 1, and similarly, 40 bits are sequentially assigned to the cell ID. The initial value of the 40-bit pseudo random number bit string assigned to each cell ID is the first 15 bits when the pseudo random number is PN15. In FIG. 6, the initial value table 1182 stores an initial value for each cell ID, and outputs an initial value corresponding to the input cell ID to the pseudo-random number generation unit 1181.

The 40-digit counter 1183 is a counter that increments by 2 for each subframe timing and returns to 0 when 39 is exceeded. The pseudo random number generator 1181 receives the initial value corresponding to the cell ID from the initial value table 1812, receives the counter value from the 40-digit counter 1183, and is a counter of the 40-bit pseudo random number bit string determined from the initial value. The corresponding phase rotation amount identification value α is output as the value. When there are four types of phase rotation amounts of 0 degree, 90 degrees, 180 degrees, and 270 degrees, the phase rotation amount identification value α is sufficient with 2 bits and is output as a 2-bit value.
FIG. 8 is a diagram illustrating an example of the rotation amount table 1184. A phase rotation amount corresponding to the 2-bit value α is associated. The rotation amount table 1184 indicates the rotation amount (or the corresponding rotation factor) corresponding to the 2-bit value α from the pseudo random number generation unit 1181 as the PSC phase rotation unit 120 (FIG. 5) and the SSC phase rotation unit 122 (FIG. 5). Output to.

Assuming that a signal of PN15 sequence (M sequence of sequence length = 2 ¹⁵ −1) is R (k), a cell ID is Cid, and a time in units of 5 ms is t, the pseudorandom number generator 1181 has a 2-bit value α (Cid , t) can be obtained by the following equation (1).

Here, the% operation indicates a remainder operation.
The rotation angle (radian) φ (Cid, t) is expressed by the following equation (2) because α indicates rotation in units of 90 degrees (= π / 2 radians).

Since the possible values of the 2-bit value α are four types of values {0, 1, 2, 3}, these are associated with the actual phase rotation amount as shown in FIG.

The PSC phase rotation unit 120 and the SSC phase rotation unit 22 perform phase rotation processing by multiplying the PSC signal and the SSC signal, respectively, by multiplying the PSC signal and the SSC signal by the complex factor represented by the following equation (3). .

Since the PN15 signal has a sequence length of 2 ¹⁵ −1 = 32767, when 40 bits are assigned to each cell, 819 types of cell IDs can be handled. An example of the PN15 signal is shown in the following equation (4).

The initial values R (0) to R (14) are arbitrary values that are not “all 0”.

FIG. 9 is a diagram illustrating a second configuration example of the rotation amount calculation unit 118. The second configuration example is a configuration in which the first configuration example is simplified, and the phase rotation amount identification value α is determined only by the frame timing without using the cell ID.

Specifically, as in the first configuration example, if the signal of the PN15 sequence (M sequence of sequence length = 2 ¹⁵ −1) is R (k), the cell ID is Cid, and the time in units of 5 ms is t. The pseudorandom number generator 1181 obtains the 2-bit value α (Cid, t) by the following arithmetic expression (5).

In equation (5), there is no remainder calculation, and a continuous PN15 sequence is used regardless of the cell ID of the base station. If the cell ID (Cid) does not appear in Equation (5), but the time t in units of 5 ms is independent for each base station (when the time at which t = 0 at each base station is different), the pseudo Random numbers will show different patterns. In the second configuration example, if the time at which t = 0 at each base station coincides, the phase of pseudo-random numbers may coincide by chance at multiple base stations, but phase rotation Since the calculation of the quantity becomes simple, the scale of the arithmetic circuit can be reduced.

The phase rotation amount (rotation angle) φ and the corresponding rotation factor r are expressed by equations (2) and (3), respectively. Further, the rotation amount table 1184 is also shown in FIG.

FIG. 10 is a diagram illustrating a third configuration example of the rotation amount calculation unit 118. In the third configuration example, CAZAC (Constant Amplitude Zero is used to calculate the phase rotation amount.
The Zadoff-Chu sequence, which is one of the Auto-Correlation) sequences, is used. The CAZAC sequence is always zero (Zero) for a time lag with a constant amplitude in both time and frequency domains and a periodic autocorrelation value other than zero.
Auto-Correlation).

Here, the Zadoff-Chu sequence is expressed by the following equation (6).

As is clear from the comparison between Expression (3) and Expression (6), the Zadoff-Chu sequence is an expression representing the twiddle factor r, and the cell ID is Cid from the correspondence between Expression (3) and Expression (6). When the time in units of 5 ms is t, the phase rotation amount (rotation angle φ) in a cycle of 5 ms × 20 = 100 ms is expressed by Expression (7).

Here, the% operation indicates a remainder operation. N indicates the sequence length. For example, N = 31.

In the third configuration example, the DSP 1185 directly calculates the phase rotation amount (rotation angle φ) without using the phase rotation amount identification value α.

The DSP (arithmetic unit) 1185 calculates the phase rotation amount based on the cell ID from the formulas (6) and (7) and writes it to the rotation amount table 1186. The rotation amount table 1186 stores the phase rotation based on the frame timing. Outputs the rotation amount φ.

The phase rotation process is performed by the complex rotation factor r (formula (3)) to be multiplied in the PSC phase rotation unit 120 and the SSC phase rotation unit 122.

FIG. 11 is a diagram illustrating a fourth configuration example of the rotation amount calculation unit 118. In the fourth configuration example, the adder 1187 obtains the rotation amount identification value α by the following equation (8) at each frame timing.

As in the above configuration examples, the cell ID is Cid, and the time in units of 5 ms is t.

The phase rotation amount (rotation angle φ) is expressed by the following equation (9).

N is a value larger than the maximum number of cell IDs, for example, N = 512. The phase rotation amount after 5 ms is obtained by adding a certain angle to the current phase rotation amount, and is different for each cell ID. Therefore, in different cell IDs, the phase difference changes with time.

The adder 1187 adds the cell ID in the equation (8) every frame timing of 5 ms. However, if the value after addition is greater than or equal to N, the remainder is N. By setting N to a power of 2, a simple adder can be used by ignoring overflow.

The phase rotation amount in units of 2π / N is obtained in advance and stored in the rotation amount table 1818, and the phase rotation amount corresponding to the calculation result (rotation amount identification value α) from the adder 1187 is the rotation amount. Output from the table 1188.

The PSC phase rotation unit 120 and the SSC phase rotation unit 122 perform phase rotation processing according to Expression (3) based on the phase rotation amount expressed by Expression (9).

In a mobile radio system, it can be used for a radio communication apparatus that transmits an identification signal unique to the apparatus, and is applied to an identification signal unique to a radio base station included in a downlink signal from the radio base station to the mobile station, for example.

Claims

In a wireless communication device that transmits a signal based on unique identification information at a constant transmission cycle,
A calculation unit for obtaining a phase rotation amount that changes with time in a different pattern for each identification information for each transmission period of the signal;
A wireless communication apparatus comprising: a phase rotation unit that performs phase rotation processing on the signal according to a phase rotation amount obtained for each transmission cycle by the arithmetic unit.
In claim 1,
The said calculating part calculates | requires the amount of phase rotation for every transmission period by selecting one of the predetermined some amount of phase rotation, The radio | wireless communication apparatus characterized by the above-mentioned.
In claim 2,
The arithmetic unit generates a pseudo-random number sequence, selects a pseudo-random number of a predetermined length at a different position for each transmission cycle, and selects a phase corresponding to the selected pseudo-random number from the plurality of predetermined phase rotation amounts A wireless communication apparatus characterized by obtaining a rotation amount.
In claim 2,
The calculation unit generates a pseudo random number different for each identification information, selects a pseudo random number having a predetermined length at a different position for each transmission cycle, and selects the selected phase rotation amount among the predetermined plurality of phase rotation amounts. A wireless communication apparatus characterized in that a phase rotation amount corresponding to a pseudo-random number is obtained.
In claim 4,
The pseudo-random number sequence different for each identification information has a length longer than the predetermined length, and the calculation unit periodically and repeatedly selects pseudo-random numbers having a predetermined length at different positions for each transmission cycle. A wireless communication device.
In claim 1,
The wireless communication device, wherein the arithmetic unit obtains a phase rotation amount based on a CAZAC (Constant Amplitude Zero Auto-Correlation) sequence having a different sequence number for each identification information.
In claim 1,
The said calculating part calculates | requires the phase rotation amount which added the different value for every said identification information for every transmission period, The radio | wireless communication apparatus characterized by the above-mentioned.
In claim 1,
The signal is a mobile communication system LTE (Long
PSC (Primary) for synchronizing with mobile terminal devices according to the Term Revolution standard
Synchronization Code signal and SSC (Secondary)
(Synchronization Code) signal.
In a wireless communication method for transmitting a signal based on unique identification information at a constant transmission cycle,
A calculation step of obtaining a phase rotation amount that changes with time in a different pattern for each identification information for each transmission cycle of the signal;
A phase rotation step for performing phase rotation processing on the signal according to the phase rotation amount obtained for each transmission cycle by the calculation step;
A wireless communication method comprising: a transmission step of transmitting the signal subjected to the phase rotation processing.