JP5397427B2 - Wireless communication method, wireless communication system, and user terminal - Google Patents

Description

  The present invention relates to a wireless communication method, a wireless communication system, and a user terminal, and in particular, each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station. The present invention relates to a radio communication method, a radio communication system, and a user terminal that multiplex pilot signals with data signals and transmit them to the base station.

In a wireless communication system such as a cellular system, it is common to perform timing synchronization and propagation path estimation (channel estimation) using a known pilot signal on the receiving side, and to perform data demodulation based on the timing synchronization and propagation path estimation (channel estimation). Also, in adaptive modulation schemes that improve throughput by adaptively changing the modulation scheme and coding rate according to the channel quality, channel quality is used to determine the optimum modulation scheme and coding rate. For example, a pilot signal is also used when estimating a signal-to-interference power ratio (SIR).
An OFDM (Orthogonal Frequency Division Multiplexing) scheme is a radio access scheme that is resistant to frequency selective fading due to multipath in broadband wireless communication. However, OFDM has a problem that the PAPR (Peak to Average Ratio) of a transmission signal is large, and is not suitable as an uplink transmission method from the viewpoint of power efficiency of a terminal. Therefore, in 3GPP LTE, which is a next-generation cellular system, single carrier transmission is performed as an uplink transmission method, and frequency equalization is performed on the receiving side (Non-Patent Document 1). Single carrier transmission means that transmission data and pilot signals are multiplexed only on the time axis, and PAPR can be significantly reduced as compared with OFDM that multiplexes data and pilot signals on the frequency axis.

Single Carrier Transmission FIG. 23 is a frame format example of single carrier transmission, and FIG. 24 is an explanatory diagram of frequency equalization. Each frame is constituted by time-division multiplexing data Data and pilot pilots each consisting of N samples. In FIG. 23, two pilot blocks are inserted in one frame. At the time of frequency equalization, the data / pilot separation unit 1 separates the data Data and the pilot pilot, and the first FFT unit 2 performs FFT processing on the N sample data to generate N frequency components to generate the channel compensation unit 3. To enter. The second FFT unit 4 performs FFT processing on the N sample pilots to generate N frequency components, and the channel estimation unit 5 uses the N frequency components and the N frequency components of known pilots for each frequency. The channel characteristics are estimated and the channel compensation signal is input to the channel compensation unit 3. The channel compensation unit 3 multiplies the N frequency components output from the first FFT unit 2 by the channel compensation signal for each frequency to perform channel compensation, and the IFFT unit 6 performs IFFT processing on the N frequency components subjected to channel compensation. Is converted into a time signal and output.

CAZAC sequence When frequency equalization is performed on the receiving side in single carrier transmission, in order to perform channel estimation with high accuracy in the frequency domain, the pilot signal has a constant amplitude in the frequency domain, in other words, any periodic time. It is desirable that the autocorrelation of the shift is zero. On the other hand, it is desirable that the amplitude is constant in the time domain from the viewpoint of PAPR. There is a CAZAC (Constant Amplitude Zero Auto Correlation) sequence as a pilot sequence that realizes these characteristics, and 3GPP LTE has decided to apply this CAZAC sequence as an uplink pilot. Since CAZAC sequences have ideal autocorrelation characteristics, cyclic shifts from the same sequence are orthogonal to each other. In 3GPP LTE, a method of multiplexing pilot signals of different users or pilot signals of different antennas by the same user using CAZAC sequences having different cyclic shift amounts is called CDM (Code Division Multiplex).

ここで、kとLは互いに素で、それぞれ系列番号、系列長を表す。nはシンボル番号で、qは任意の整数、L%2はLを2で割ったときの余りであり、Lmod(2)と表記される場合もある。Lの素因数分解を

とすると(giは素数)、Lと互いに素であるLよりも小さい自然数の個数φ（L）すなわちCAZAC系列の系列数は、次式

で与えられる。具体的に、L=12であれば、L=12=2²×3¹であるため、g1=2、e1=2,g2＝3、e2=1であり、(3)式より, CAZAC系列の系列数kは4となる。このため、Ｌが大きく、かつ、素因数が少ないほど系列数が多くなる。換言すれば、Lが素数であればCAZAC系列の系列数kは（L−1）となる。 A Zadoff-Chu sequence that is a typical CAZAC sequence is expressed by equation (1) (Non-patent Document 2).

Here, k and L are relatively prime and represent a sequence number and a sequence length, respectively. n is a symbol number, q is an arbitrary integer, L% 2 is the remainder when L is divided by 2, and may be expressed as Lmod (2). L prime factorization

(Gi is a prime number), the number of natural numbers φ (L) smaller than L, which is relatively prime to L, that is, the number of CAZAC sequences is

Given in. Specifically, if L = 12, because L = 12 = 2 ² × 3 ¹ , g1 = 2, e1 = 2, g2 = 3, and e2 = 1. From the equation (3), the CAZAC sequence The number of series k is 4. For this reason, the number of series increases as L increases and the prime factor decreases. In other words, if L is a prime number, the number k of CAZAC sequences is (L−1).

で表される。以下の(5)式

に示すとおり、ZC_k(n)とZC_k(n-c)との相関R(τ)はτ=c以外の点において0となるので、系列番号が同じ母系列ZC_k(n)に異なる巡回シフト量を加えて出来た系列同士は互いに直交する。 ZC _k (n−c) _obtained by cyclically shifting the CAZAC sequence ZC _k (n) by c is given by

It is represented by Equation (5) below

Since the correlation R (τ) between ZC _k (n) and ZC _k (nc) is 0 at points other than τ = c, different cyclic shifts to the same series ZC _k (n) Sequences created by adding quantities are orthogonal to each other.

により決めることができる（非特許文献３）。 When a plurality of pilots multiplexed by CDM by cyclic shift are received at the radio base station, the pilots can be separated from the place where the peak appears by taking the correlation with the base sequence. The narrower the cyclic shift interval, the weaker the tolerance to multipath and reception timing shifts, so there is an upper limit to the number of possible multiplexes. Assuming that the multiplexing number by the cyclic shift is P, the cyclic shift amount c _p assigned to the p-th pilot is, for example,

(Non-patent Document 3).

As described above, in the uplink of 3GPP LTE, pilot and data are time-multiplexed and transmitted using the SC-FDMA scheme. FIG. 25 is a block diagram of the SC-FDMA transmission unit, where 7 ′ is a DFT (Discrete Fourier Transformer) of size N _TX , 8 ′ is a subcarrier mapping unit, 9 ′ is an IDFT unit of size N _FFT , and 10 is CP (Cyclic Prefix) insertion part. In 3GPP LTE, in order to reduce the processing amount, N _FFT is an integer that is a power of 2, and IDFT after subcarrier mapping can be replaced with IFFT.
The process of adding the cyclic shift c to the parent sequence ZC _k (n) can be performed either before DFT or after IFFT. If it is performed after IFFT, it may be cyclically shifted by c × N _FFT / N _Tx samples. Since the processing is essentially the same, hereinafter, a case where cyclic shift processing is performed before DFT will be described as an example.

Problems of the prior art In order to reduce inter-cell interference, it is necessary to repeatedly use CAZAC sequences with different sequence numbers as pilots between cells. This is because the greater the number of repetitions, the greater the distance between cells using the same sequence, and thus the less likely that serious interference will occur. To that end, it is necessary to secure a large number of CAZAC sequences, and due to the nature of CAZAC sequences, it is required to make the sequence length L a large prime number. FIG. 26 is an explanatory diagram of interference between cells. When the number of CAZAC sequences that can be used is 2 as shown in (A), since the CAZAC sequence having the same sequence number is used between adjacent cells, Interference occurs. As shown in (B), when the number of CAZAC sequences is 3, the CAZAC sequence with the same sequence number is not used between adjacent cells, but the CAAZAC sequence with the same sequence number is used because the number of repetitions is as small as 3. The distance between cells is short and the possibility of interference is large. As shown in (C), when the number of CAZAC sequences is 7, the number of repetitions is as large as 7, so that the inter-cell distance using the CAZAC sequence of the same sequence number increases and the possibility of interference gradually decreases.
By the way, in 3GPP LTE, as shown in FIG. 27 (A), the number of occupied subcarriers of data is set to a multiple of 12, and the pilot subcarrier interval is set to twice the data subcarrier interval in order to increase transmission efficiency. . In this case, assuming that the CAZAC sequence length L is 6, the number of sequences k is 2, and the CAZAC sequence having the same sequence number is used in adjacent cells, and pilot interference occurs. Further, if the sequence length L is 5, k becomes 4, but is still small. Furthermore, as shown in FIG. 27B, subcarriers of data not covered by the pilot are generated, and the channel estimation accuracy is deteriorated.

Therefore, it is considered to secure a sufficient sequence length by transmitting the pilot signal with a wider transmission band than the data transmission band (3GPP R1-060925, R1-063183). FIG. 28 shows an example where the number of multiplexed pilot signals is two. When the sequence length L is set to 12, only four CAZAC sequences can be taken, and the inter-cell interference increases (k = 4). Therefore, the sequence length L is set to a prime number 11. When L = 11, 10 CAZAC sequences can be obtained (k = 10), and inter-cell interference can be reduced. Note that the sequence length L cannot be 13 or more. The reason is that interference with adjacent frequency bands occurs when the number is 13 or more.
Pilot signals of different users are multiplexed by CDM by cyclic shift. That is, a CAZAC sequence ZC _k (n) of L = 11 subjected to cyclic shift c1 is used as the pilot of user 1, and a CAZAC sequence ZC _k (n) subjected to cyclic shift c2 is used as the pilot of user 2. Use as

However, when the CAZAC sequence ZC _k (n) of L = 11 is cyclically shifted and used for the users 1 and 2, as is clear from FIG. The relative relationship between the transmission frequency bands is different, and the channel estimation accuracy is different. That is, the subcarriers 23 and 24 out of the transmission frequency band of the user 2 data are out of the pilot transmission frequency band, and the channel estimation accuracy in the subcarrier deteriorates.
In FIG. 28, the pilot subcarrier interval is set to double the data subcarrier interval based on the current 3GPP LTE specifications, but the above problem occurs even if the ratio of the subcarrier intervals changes.

3GPP TR25814-700 Figure9.1.1-1 B.M. Popovic, "Generalized Chirp-Like Polyphase Sequences with Optimum Correlation Properties", IEEE Trans. Info. Theory, Vol. 38, pp.1406-1409, July 1992. 3GPP R1-060374, "Text Proposal On Uplink Reference Signal Structure", TI Instruments

From the above, an object of the present invention is to enable accurate channel estimation of data subcarriers that deviate from the pilot transmission frequency band.
Another object of the present invention is to use subcarriers allocated to each user even when a predetermined sequence (for example, CAZAC sequence ZCk (n)) subjected to a different amount of cyclic shift is used as a pilot for multiplexed users. It is to be able to perform channel estimation with high accuracy.
Another object of the present invention is to perform channel estimation by separating pilots of each user by a simple method, even if a predetermined amount of cyclic shift is applied to a predetermined CAZAC sequence as pilots of multiplexed users. It is to make it.
Another object of the present invention is to improve the channel estimation accuracy of a data subcarrier of a user even if the user has a poor propagation path condition.

The present invention provides wireless communication in which a data signal is transmitted to the base station using frequencies of different data transmission bands assigned by the base station, and a pilot signal is multiplexed with the data signal and transmitted to the base station. A reception unit that receives uplink resource information from a base station, a pilot generation unit that generates a pilot according to an instruction of the uplink resource information, and a transmission unit that transmits the pilot signal to the base station A pilot generation unit configured to generate a Zadoff-Chu sequence as a pilot signal based on the resource information, cyclically shift the Zadoff-Chu sequence by a predetermined amount, and copy a part of the shifted sequence A subcarrier mapping unit for mapping the sequence generated by adding to the shifted sequence. To have.
The radio communication method of the present invention receives uplink resource information from a base station, generates a Zadoff-Chu sequence as a pilot signal based on the uplink resource information, and cyclically shifts the Zadoff-Chu sequence by a predetermined amount. , Mapping a sequence generated by copying a part of the sequence after the shift and adding it to the sequence after the shift, and transmitting the mapped pilot signal
In the wireless communication system of the present invention, the base station includes a first transmission unit that transmits uplink resource information to each user terminal, and each of the user terminals receives the uplink resource information. A pilot generation unit that generates a pilot according to an instruction of the uplink resource information, and a transmission unit that transmits the pilot signal to the base station. The pilot generation unit uses a Zadoff as a pilot signal based on the resource information. A CAZAC sequence generation unit that generates a Chu sequence, a sub-map that maps a sequence generated by cyclically shifting the Zadoff-Chu sequence by a predetermined amount, copying a portion of the shifted sequence, and adding it to the shifted sequence A carrier mapping unit is provided.

ADVANTAGE OF THE INVENTION According to this invention, the channel estimation of the data transmission subcarrier which remove | deviates from a pilot transmission frequency band can be performed with a sufficient precision.
Further, according to the present invention, even if a pilot sequence of users to be multiplexed is _obtained by applying a predetermined amount of cyclic shift to a predetermined sequence (for example, CAZAC sequence ZC _k (n)), Carrier channel estimation can be performed with high accuracy.
Further, according to the present invention, even when a pilot of a user to be multiplexed is obtained by applying a different amount of cyclic shift to a predetermined sequence, the pilot of each user is separated and channel estimation is performed by a simple method. Can do.
In addition, according to the present invention, by preferentially assigning an intermediate portion of the pilot transmission band to a user with a poor channel condition, channel estimation of the data transmission subcarrier of the user can be performed even for a user with a poor channel condition. Accuracy can be increased.
Further, according to the present invention, by hopping the data transmission band to be allocated to the user at the intermediate part and the end part of the pilot transmission band, even if the user has a poor channel condition, the channel of the transmission data subcarrier of the user The estimation accuracy can be increased.

It is a 1st principle explanatory drawing of this invention. It is a 2nd principle explanatory drawing of this invention. It is a 3rd principle explanatory drawing of this invention. FIG. 6 is an explanatory diagram of pilot generation processing on the transmission side that realizes a frequency offset for subcarriers and a cyclic shift of (c ₂ −s (k, d, L)). It is offset explanatory drawing of a subcarrier mapping part. It is a channel estimation process explanatory drawing of the receiving side. It is 2nd pilot production | generation process explanatory drawing. It is a copy method explanatory drawing in the transmission side. It is a 2nd channel estimation process explanatory drawing by the side of reception. It is a frame block diagram. It is explanatory drawing of a pilot separation method. It is a 3rd channel estimation process explanatory drawing by the side of reception. It is a block diagram of a mobile station. It is a block diagram of a pilot production | generation part. It is a block diagram of a base station. It is a block diagram of a channel estimation part. It is a block diagram of the pilot production | generation part and channel estimation part which perform a 2nd pilot production | generation process and a channel estimation process. It is a block diagram of the pilot production | generation part and channel estimation part which perform a 3rd pilot production | generation process and a channel estimation process. It is frequency allocation explanatory drawing in case a multiplexing number is four. It is explanatory drawing which performs hopping control so that the transmission band allocated to each user for every frame may be switched, and is explanatory drawing of allocation in an odd-numbered frame. It is explanatory drawing which performs hopping control so that the transmission band allocated to each user for every frame may be switched, and is explanatory drawing of allocation in the even-numbered frame. It is a block diagram of the pilot production | generation part in the case of performing hopping control. It is an example of a frame format of single carrier transmission. It is explanatory drawing of frequency equalization. It is a block diagram of an SC-FDMA transmission unit. It is interference explanatory drawing between cells. It is the 1st explanatory view of the conventional data transmission band and pilot transmission band. It is the 2nd explanatory view of the conventional data transmission band and pilot transmission band.

で表現される。この(7)式と(4)式とを用いて変形すると次式

が成り立つ。なお、d(modL)はdをLで割った余りである。
(8)式から分かるように、時間領域においてCAZAC系列に巡回シフトcを加えることは、周波数領域においてdサブキャリア分巡回シフトとの位相回転を加えることと同等である。ここで、kとLは互いに素であるので、c(<L)はkとdによって一意的に決まる。cがk,d,Lによって決まることを分かり易く示すため改めてc=s(k,d,L)とおく。表１はＬ＝１１の場合の種々のs(k,d,L)とkの組み合わせに応じたcの値を示すものである。例えば、ｋ＝１、ｄ＝１、Ｌ＝１１であればｃ＝１、ｋ＝２，ｄ＝１、Ｌ＝１１であればｃ＝６である。

(A) Principle of the present invention As shown in FIG. 1A, a CAZAC sequence ZC _k (n) subjected to cyclic shift c1 is used as a pilot for user 1, and a CAZAC sequence ZC _k (n) is cyclic When the one subjected to the shift c2 is used as the pilot of the user 2, as described in FIG. 28, the subcarriers 23 and 24 out of the transmission frequency band of the data of the user 2 are out of the transmission frequency band of the pilot. The channel estimation accuracy in subcarriers is degraded. In FIG. 1, DFT {ZC _k (n−c1)} and DFT {ZC _k (n−c2)} respectively apply cyclic shifts c1 and c2 to the CAZAC sequence ZC _k (n) of L = 11. Thereafter, pilots in the frequency domain obtained by subjecting ZC _k (n−c1) and ZC _k (n−c2) to DFT processing.
Therefore, as shown in FIG. 1B, if the pilot is multiplexed with a frequency offset according to the data transmission band for each user, the pilot transmission band always covers the data transmission band. . In the example of FIG. 1B, the pilot DFT {ZC _k (n−c2)} of user 2 may be offset by one subcarrier.
However, if the pilot DFT {ZC _k (n−c2)} is offset, the correlation between the received pilot and the known pilot replica ZC _k (n) does not peak at τ = c2 on the receiving side, and the peak position shifts. As a result, the pilot cannot be correctly restored, and as a result, channel estimation cannot be performed. Hereinafter, the reason why the correlation peak position is shifted will be described.
-Relationship between frequency offset and time-domain cyclic shift First, the relationship between frequency offset and time-domain cyclic shift will be described. If F (m) is the result of applying DFT transformation to CAZAC sequence ZC _k (n), then F (m) is

It is expressed by When this equation (7) and equation (4) are used,

Holds. D (modL) is a remainder obtained by dividing d by L.
As can be seen from the equation (8), adding a cyclic shift c to the CAZAC sequence in the time domain is equivalent to adding a phase rotation with a cyclic shift for d subcarriers in the frequency domain. Here, since k and L are relatively prime, c (<L) is uniquely determined by k and d. In order to clearly show that c is determined by k, d, and L, c = s (k, d, L) is set again. Table 1 shows the value of c corresponding to various combinations of s (k, d, L) and k when L = 11. For example, if k = 1, d = 1, and L = 11, c = 1, and if k = 2, d = 1, and L = 11, c = 6.

From the above, adding a frequency offset for one subcarrier for pilot 2 as shown in FIG. 2 (A) added a cyclic shift for one subcarrier in the frequency domain as shown in FIG. 2 (B). This corresponds to moving the component p11 in the subcarrier 1 to the subcarrier 12 later. As a result, from equation (8), the correlation peak position of pilot 2 (see equation (5)) is shifted by s (k, d, L) (τ = c2 + s (k, d, L)). Since the correlation peak position of pilot 1 (τ = c1) does not deviate, the correlation peak position of pilot 2 and pilot 1 changes relatively by s (k, d = 1, L = 11), and the pilot is correctly restored on the receiving side. As a result, channel estimation cannot be performed.
In order to make the correlation peak position as before, the cyclic shift amount may be changed from c ₂ to (c ₂ −s (k, d, L)). That is, as shown in FIG. 3A, pilot 2 is given both a frequency offset of d subcarriers (d = 1 in the figure) and a cyclic shift of (c ₂ −s (k, d, L)). In addition, the relationship between pilots 1 and 2 is as shown in FIG. By doing so, the correlation peak positions of the pilots 1 and 2 are not shifted, and the pilot can be correctly restored on the receiving side, so that the channel estimation accuracy can be improved. That is, pilot 1 and pilot 2 can be separated by the position of the correlation peak value (τ = c1, τ = c2) as before the frequency offset in FIG.

(A) First pilot generation process and channel estimation process FIG. 4 shows a transmission side that realizes the frequency offset of d subcarriers and the cyclic shift of (c ₂ −s (k, d, L)) described in FIG. It is a pilot generation process explanatory drawing.
The CAZAC sequence generation unit 11 generates, for example, a CAZAC sequence ZC _k (n) of L = 11 as a pilot, and the cyclic shift unit 12 cycles the CAZAC sequence ZC _k (n) by c ₂ −s (k, d, L). Shift to generate ZC _k (n−c2 + s (k, d, L)) and input it to the DFT unit 13. The DFT unit 13 of N _TX size (N _TX = L = 11) performs DFT arithmetic processing on ZC _k (n−c 2 + s (k, d, L)) and performs pilot DFT {ZC _k (n−c 2 + s (k, d) , L))}. The subcarrier mapping unit 14 offsets the 11 pilot components p1 to p11 in the frequency domain by d subcarriers (d = 1 in the figure) and inputs them to the IFFT unit 15.
FIG. 5 is an explanatory diagram of the offset of the subcarrier mapping unit 14, (A) shows the case where there is no offset (d = 0), and the subcarrier mapping unit 14 converts 11 pilot components p 1 to p 11 into the IFFT unit 15. Input to the terminals of the frequencies f _i , f _{i + 1} , f _{i + 2} ,,, f _{i + 10} , and input 0 to the other terminals. (B) shows a case where there is an offset (d = 1), and the subcarrier mapping unit 14 converts the 11 pilot components p1 to p11 into the frequencies f _{i + 1} , f _{i + 2} , f _{i + 3 of the} IFFT unit 15. ,,, f _{i + 11} and 0 are input to the other terminals. The _NFT size (for example, N _FFT = 128) IFFT unit 15 performs IDFT arithmetic processing on the input subcarrier component to convert it into a time domain signal, and the CP (Cyclic Prefix) insertion unit 16 is a cyclic for preventing interference. Output with prefix. (C) is another example of realization with offset (d = 1). In this case, the cyclic shift unit 12 cyclically shifts the CAZAC sequence ZC _k (n) by c ₂ to generate ZC _k (n−c 2) and inputs it to the DFT unit 13. DFT unit 13 generates a pilot _{DFT {ZC k (n-c2} )} is subjected to DFT processing to ZC _k (n-c2). The subcarrier mapping unit 14 inputs the pilot components p2 to p11 to the terminals of the IFFT units f _{i + 1} , f _{i + 2} ,, f _{i + 10} , and inputs the pilot component p1 to the terminals of the IFFT unit f _{i + 11} To do.

FIG. 6 is an explanatory diagram of channel estimation processing on the receiving side.
In the channel estimation unit, pilot 1 and pilot 2 (see FIG. 3B) transmitted from user 1 and user 2, respectively, are multiplexed in the air and subcarrier frequencies f _i , f _{i + 1} , f _{i + 2} , f _{i + 3,} ,, f _{i + 11} are input as subcarrier components (p1 to p12). The subcarrier addition unit 52 adds the subcarrier components p12 and p1 that do not overlap each other, and newly sets the addition result as the subcarrier component p1 of the subcarrier frequency f1.
The replica signal multiplication unit 53 multiplies the pilot replica signal (a known CAZAC sequence ZC _k (n) having a zero cyclic shift amount subjected to DFT operation processing) qi and the received pilot signal pi for each subcarrier, The unit 54 performs an IDFT operation process on the replica multiplication result and outputs a time domain delay profile. Since the time-domain delay profile is L samples in length and has a correlation peak at t = c1, t = c2, the profile extraction unit 55 separates the correlation peak at t = (c1 + c2) / 2, and the users 1, 2 Generate profiles PRF1 and PRF2 with length L / 2 samples. The L-size DFT unit 56a inserts L / 4 zeros on both sides of the profile PRF1 having the length of L / 2 to make the length L, and performs the DFT calculation. Thus, the sub-carrier frequency from the DFT unit _{56a f i, f i + 1} , f i + 2, f i + 3 ,,, f i + 10 channel estimates h1~h11 users 1 in is obtained. Similarly, the L-size DFT unit 56b inserts L / 4 zeros on both sides of the L / 2 sample length profile PRF2 to make the length L, and performs DFT calculation. Thus, channel estimation values h2 to h12 of user 2 at subcarrier frequencies f _{i + 1} , f _{i + 2} , f _{i + 3} ,, f _{i + 11} are obtained from the DFT unit 56b. However, since as the subcarrier component of subcarrier frequency f _i and the subcarrier addition unit 52 adds p1 and p12, sub-carrier frequency channel estimation value of the subcarrier frequency f _i to be output from the DFT unit 56b f _{i +} Let ₁₁ channel estimation h12.
From the above, if the distortion due to the propagation state is small for each of pilot 1 and pilot 2, the components that do not overlap each other are added on the receiving side as shown in FIG. Separation is possible in a completely orthogonal form. When distortion due to propagation conditions is large, subcarrier addition may be omitted and separation may be performed on the time domain delay profile after direct replica multiplication.

(B) In the second pilot generation process and channel estimation process in the first channel estimation process, it adds the subcarrier components p12 and p1 that do not overlap each other, regards the addition result as a component of the subcarrier frequency f _i It was. However, if reached the value carrier component of subcarrier frequency f _i has already added the p12 and p1 of the received signal, there is no need to add subcarriers on the receiving side.
FIG. 7 is an explanatory diagram of second pilot generation processing, where (A) shows data subcarriers of user 1 and user 2.
As shown in FIG. 7B, the transmission side (user 1) copies the subcarrier component p1 of the subcarrier frequency f _i of pilot 1 so as to be the subcarrier component of subcarrier frequency f _{i + 11} , and , user 2 as shown in FIG. 7 (C) copies and transmits subcarrier component p12 of subcarrier frequency f _{i + 11} of pilot 2 so that the subcarrier component of subcarrier frequency f _i. As a result, as shown in FIG. 7D, these pilots are multiplexed and received by the receiving side, and the carrier component of the subcarrier frequency f1 of the received signal is a value obtained by adding p1 and p12, and the subcarrier frequency The carrier component is also a value obtained by adding p1 and p12, and subcarrier addition on the receiving side is not necessary.

FIG. 8 is an explanatory diagram of a copy method on the transmission side. FIG. 8A is a copy method of pilot 1 for user 1. Subcarrier mapping unit 14 uses subcarrier frequency f _i of carrier component p1 of pilot 1 as a subcarrier. It is also input to the terminal of frequency f _{i + 11} of the IFFT unit 15 as is also the subcarrier component of the frequency f _{i + 11.} (B) is a copy method of pilot 2 in user 2, and subcarrier mapping section 14 ensures that carrier component p12 of subcarrier frequency f _{i + 11} of pilot 12 is also a subcarrier component of subcarrier frequency f _i. The signal is also input to the terminal of the frequency f _i of the IFFT unit 15. (C) is another implementation example of the copy method of pilot 2 in user 2, and corresponds to FIG.

FIG. 9 is an explanatory diagram of channel estimation processing on the receiving side. In the channel estimation unit, pilot 1 and pilot 2 (see FIGS. 7B and 7C) transmitted from user 1 and user 2, respectively, are multiplexed in the air and subcarrier frequencies f _i , f _{i + 1} , The subcarrier components (p1 to p12) of f _{i + 2} , f _{i + 3,} ..., f _{i + 11} are input (FIG. 7D).
The replica signal multiplier 53 for the user 1 multiplies the pilot replica signal qi (q1 to q11) and the received pilot signal pi (p1 to p11) for each subcarrier, and thereafter, the IDFT unit 54, the correlation separator 55, The DFT unit 56 performs the same processing as in FIG. 6 and generates the channel estimation values h1 to h11 of the user 1.
On the other hand, replica signal multiplier 53 'for user 2 multiplies pilot replica signal qi (q1 to q11) and received pilot signal pi (p2 to p12) for each subcarrier, and thereafter IDFT unit 54' The separation unit 55 ′ and the DFT unit 56 ′ perform the same processing as the user 1 and generate the channel estimation values h2 to h12 of the user 2.

(C) Third Pilot Generation Process and Channel Estimation Process In the first channel estimation process, the correlation separating unit 55 separates the pilot component of the user 1 and the pilot component of the user 2 as shown in FIG. Thus, for example, when two pilot blocks are included in one frame, they can be separated as follows. FIG. 11 is an explanatory diagram of the pilot separation method, and (A) shows data subcarriers of user 1 and user 2.
Each subcarrier of the first pilot 1 (= DFT {ZC _k (n−c1)}) and pilot 2 (= DFT {ZC _k (n−c2 + s (k, d, L))}) of user 1 and user 2 As shown in (B) and (C), the components are transmitted by being multiplied by +1, and the subcarrier components of the next pilot 1 and pilot 2 are respectively +1, as shown in (D) and (E), respectively. Multiply by -1.
As a result, the receiving side first starts with the following pilot multiplexed signal:
DFT {ZC _k (n−c1)} × (+1) + DFT {ZC _k (n−c2 + s (k, d, L)) × (+1)
And then the following pilot multiplexed signal
DFT {ZC _k (n−c1)} × (+1) + DFT {ZC _k (n−c2 + s (k, d, L)) × (−1)
Receive.
Therefore, in order to generate the pilot of user 1 on the receiving side, the next pilot multiplexed signal may be added to the first pilot multiplexed signal. That is, since the polarity of pilot 2 is different, pilot 2 is canceled by addition and pilot 1 remains. In order to generate the pilot of user 2 on the receiving side, the next pilot multiplexed signal may be subtracted from the first pilot multiplexed signal. That is, since the polarity of pilot 1 is the same, pilot 1 is canceled by subtraction, and pilot 2 remains.

FIG. 12 is an explanatory diagram of channel estimation processing on the receiving side. In the channel estimation unit, pilot 1 and pilot 2 (see FIGS. 11 (B), (C); (D), (E)) respectively transmitted from user 1 and user 2 are multiplexed in the air and are subcarriers. frequency _{f i, f i + 1,} f i + 2, f i + 3 ,,, f i + 11 become sub-carrier component (P1 to P12) of the inputs.
The inter-block subcarrier calculating unit 61 receives and stores the first received pilot signal. Next, when generating the pilot of the user 1, the inter-block subcarrier calculating unit 61 adds the first and second received pilot signals for each subcarrier when receiving the second received pilot signal. Carrier components p1 to p11 of carriers f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,, f _{i + 10} are generated. The replica signal multiplier 53 for the user 1 multiplies the pilot replica signal qi (q1 to q11) and the received pilot signal pi (p1 to p11) for each subcarrier, and thereafter, the IDFT unit 54, the correlation separator 55, The DFT unit 56 performs the same processing as in FIG. 6 and generates the channel estimation values h1 to h11 of the user 1. Although the accuracy is reduced, the replica signal multiplication results can be set as channel estimation values h1 to h11.
On the other hand, when generating the pilot of the user 2, the inter-block subcarrier calculating unit 61 subtracts the first and second received pilot signals for each subcarrier to obtain the subcarriers f _{i + 1} and f _{i + 2 of the} pilot _2. , f _{i + 3,} ..., f _{i + 11} carrier components p2 to P12 are generated. The replica signal multiplier 53 'for the user 2 multiplies the pilot replica signal qi (q1 to q11) and the received pilot signal pi (p2 to p12) for each subcarrier, and thereafter, the IDFT unit 54' and the correlation separator 55 'and the DFT unit 56' perform the same processing as that of the user 1 and generate the channel estimation values h2 to h12 of the user 2.
The above is a case where the number of pilot blocks is 2, but the third pilot generation process and the channel estimation process can be applied even when the number of pilot blocks is an even number. In such a case, the base station instructs one user terminal to multiply the pilot signal of all blocks by +1, another user terminal multiplies half the pilot signal by +1, and −1 to the other half pilot signal. Instruct to multiply. Then, when the base station multiplex-receives the pilot signal transmitted from each user terminal, arithmetic processing of addition / subtraction is performed on the pilot signals of all blocks so that only the pilot signal from the predetermined user terminal (user terminal 1 or 2) remains. And multiplying the operation result by a replica of the pilot signal, converting the replica multiplication result into a time domain signal, and then separating the signal portion of the user terminal from the time domain signal to perform channel estimation.

(B) Mobile station FIG. 13 is a block diagram of a mobile station.
When uplink transmission data occurs, the mobile station (user terminal) makes a resource allocation request to the base station, and the base station performs resource allocation based on the propagation path state of the mobile station in response to the request, and the resource allocation information is transmitted to the mobile station. Notify The mobile station transmits the notified data and pilot. That is, the radio unit 21 converts the radio signal received from the base station into a baseband signal and inputs it to the received signal baseband processing unit 22. The baseband processing unit 22 separates data and other control information from the received signal, and also separates resource allocation information and inputs it to the transmission resource management unit 23. Resource allocation information includes data transmission frequency band, timing, modulation method, pilot transmission frequency band, CAZAC sequence number and sequence length L used as pilot, cyclic shift amount, frequency offset amount d, etc. Is included.
The transmission resource management unit 23 inputs information necessary for data and control information transmission processing to the data processing unit 24, and inputs information necessary for pilot generation / transmission processing to the pilot generation unit 25. The data processing unit 24 performs data modulation and single carrier transmission processing on the data and control information based on the information input from the transmission resource management unit 23 and outputs the data and control information. The pilot generation unit 25 outputs an instruction from the transmission resource management unit 23. Accordingly, processing such as CAZAC sequence generation, cyclic shift, and frequency offset is performed to generate a pilot, and the frame generator 26 time-division multiplexes 6 data blocks and 2 pilot blocks as shown in FIG. Created and transmitted from the wireless unit 21 to the base station.

FIG. 14 is a configuration diagram of the pilot generation unit 25, and is a configuration diagram in the case where pilots are generated according to the first pilot generation processing described in FIG. 3, and FIG. 14A is a case in which cyclic shift is performed before DFT. Configuration diagram, (B) is a configuration diagram when cyclic shift is performed after IFFT.
In FIG. 14 (A), the transmission resource management unit 23 includes parameters necessary for generating and transmitting pilots (CAZAC sequence number, sequence length, both cyclic shift, and frequency offset) included in the resource allocation information received from the base station. input.
CAZAC sequence generator 11 generates CAZAC sequence ZC _k (n) having the specified sequence length L and sequence number as a pilot, and cyclic shift unit 12 cyclically shifts CAZAC sequence ZC _k (n) by the specified c samples. Then, the obtained ZC _k (n−c) is input to the DFT unit 13. For example, if the pilot 1 in FIG. 3 (B), the cyclic shift unit 12 generates a ZC _k (n-c1) shifted by c1 the ZC _k (n), if pilot 2, c ₂ - A cyclic shift is performed by s (k, d, L) to generate ZC _k (n−c 2 + s (k, d, L)), which is input to the DFT unit 13. The DFT unit 13 of N _TX size (N _TX = L) performs DFT arithmetic processing on the input pilot ZC _k (n−c) to generate a frequency domain pilot DFT {ZC _k (n−c)}. The subcarrier mapping unit 14 controls the pilot mapping position to perform frequency offset based on the instructed frequency offset amount d, and the _NFT size (N _FFT = 128) IFFT unit 15 converts the input subcarrier component into the input subcarrier component. An IFFT operation process is performed to convert the signal into a time domain signal and input to the frame generation unit 26.
FIG. 14B is a configuration diagram of the pilot generation unit 25 when the cyclic shift is performed after IFFT, and the cyclic shift unit 12 performs the cyclic shift by c × N _FFT / N _Tx samples to perform FIG. ) Is exactly the same as

(C) Base Station FIG. 15 is a block diagram of the base station.
When uplink transmission data is generated, the mobile station (user) executes a procedure for establishing a communication link with the base station, and transmits a propagation path condition to the base station in the course of this procedure. That is, the mobile station receives the common pilot transmitted from the base station, performs radio measurement (SIR or SNR measurement), and reports the radio measurement result to the base station as a propagation path condition. For example, the base station divides the transmission band into a plurality of transmission frequency bands, transmits a common pilot for each transmission frequency band, the mobile station performs radio measurement for each transmission frequency band, and sends the measurement result to the base station. When the base station acquires the propagation path condition from the mobile station and receives the resource allocation request, the base station allocates resources based on the propagation path condition of the mobile station and sends the resource allocation information to the mobile station.
The radio unit 31 converts the radio signal received from the mobile station into a baseband signal, the demultiplexing unit 32 demultiplexes the data / control information and the pilot, inputs the data / control information to the data processing unit 33, and the pilot is channel estimated. Input to the unit 34. The data processing unit 33 and the channel estimation unit 34 have the frequency equalization configuration shown in FIG.
The data processing unit 33 demodulates the propagation path condition data transmitted from the mobile station when the communication link is established, and inputs the demodulated channel state data to the uplink resource management unit 35. The uplink resource management unit 35 performs resource allocation based on the propagation path situation, creates resource allocation information, and inputs the resource allocation information to the downlink signal baseband processing unit 36. In the resource allocation information, in addition to the data transmission frequency band, timing, modulation method, etc., the pilot transmission frequency band, the CAZAC sequence number and sequence length L used as the pilot, the cyclic shift amount, the frequency offset amount d, etc. included. The downlink signal baseband processing unit 36 time-division multiplexes downlink data, control information, and resource allocation information and transmits them from the radio unit 31.
When the mobile station receives the resource allocation information, the mobile station performs the processing described with reference to FIGS. 13 and 14, and transmits a frame composed of data and pilot.
The channel estimation unit 34 performs the first channel estimation process described with reference to FIG. 6 using the pilot separated and input by the separation unit 32 and inputs the channel estimation value to the data processing unit 33. The data processing unit 33 performs channel compensation based on the channel estimation value, and demodulates data based on the channel compensation result. The uplink resource management unit 35 includes a cyclic shift amount calculation unit 35a and a link assignment information instruction unit 35b.

FIG. 16 is a block diagram of the channel estimator 34, and the same parts as those in FIG.
The DFT unit 51 performs DFT calculation processing on the pilot signal input from the separation unit 32 and converts the pilot signal into frequency domain pilot signals (subcarrier components p1 to p12). The subcarrier addition unit 52 adds the subcarrier components p12 and p1 that do not overlap each other, and newly sets the addition result as the subcarrier component p1 of the subcarrier frequency f1.
The replica signal multiplication unit 53 multiplies the pilot replica signal qi and the reception pilot signal pi for each subcarrier, and the IDFT unit 54 performs IDFT calculation processing on the replica multiplication result and outputs a time-domain pilot signal. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and if it is a received signal from the user 1, selects the profile PRF1 (see FIG. 6), and the DFT unit 56 performs a DFT operation on the profile PRF1. To output channel estimation values h1 to h11. On the other hand, if the received signal is from the user 2, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs a DFT operation on the profile PRF2 and outputs channel estimation values h2 to h12.

(D) Second Pilot Generation Unit and Channel Estimation Unit FIG. 17A is a configuration diagram of a pilot generation unit that performs the second pilot generation process described with reference to FIG. 7, and the pilot generation unit of FIG. The same parts as those in FIG. The difference is that the subcarrier mapping unit 14 performs two operations of subcarrier mapping based on the frequency offset amount d and copying of a pilot component of a predetermined subcarrier, and the other operations are the same.
CAZAC sequence generator 11 generates CAZAC sequence ZC _k (n) having the specified sequence length L and sequence number as a pilot, and cyclic shift unit 12 cyclically shifts CAZAC sequence ZC _k (n) by the specified c samples. Then, the obtained ZC _k (n−c) is input to the DFT unit 13. For example, in the case of pilot 1 for user 1 in FIG. 7B, cyclic shift unit 12 shifts ZC _k (n) by c1 to generate ZC _k (n−c1), and pilot for user 2 If it is 2, ZC _k (n−c2 + s (k, d, L)) is generated by cyclic shift by c ₂ −s (k, d, L) and input to the DFT unit 13. The DFT unit 13 of N _TX size (N _TX = L) performs DFT arithmetic processing on the input pilot ZC _k (n−c) to generate a frequency domain pilot DFT {ZC _k (n−c)}.
The subcarrier mapping unit 14 performs subcarrier mapping based on copy information and frequency offset information instructed from the transmission resource management unit 23. For example, the subcarrier mapping process shown in FIG. 8A is performed on the pilot 1 of the user 1 in FIG. 7B, and the pilot 2 of the user 2 in FIG. The subcarrier mapping process shown in B) is performed. The IFFT unit 15 having an N _FFT size (for example, N _FFT = 128) performs IFFT arithmetic processing on the input subcarrier component to convert it into a pilot signal in the time domain and inputs it to the frame generation unit 26.

FIG. 17B is a configuration diagram of the channel estimation unit 34 that performs the second channel estimation process described in FIG. 9, and the same reference numerals are given to the same parts as those of the channel estimation unit in FIG. The difference is that the subcarrier adding unit 52 is deleted and the multiplication processing of the replica signal multiplying unit 53 is different.
The DFT unit 51 performs DFT calculation processing on the pilot signal input from the separation unit 32 and converts the pilot signal into frequency domain pilot signals (subcarrier components p1 to p12). If the replica signal multiplier 53 receives the pilot 1 from the user 1, the subcarriers f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,. , f _{i + 10} components p1 to p11 and replica signals q1 to q11 are multiplied, and if pilot 2 from user 2 is received, subcarriers f _{i + 1} and f of the received pilot output from DFT section 51 _{i + 2,} multiplies the f _{i + 3} ,,, component p2~p12 and replica signal f _{i + 11.}
Thereafter, the IDFT unit 54 performs an IDFT calculation process on the replica multiplication result and outputs a time domain delay profile. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and if it is a pilot signal from the user 2, selects the profile PRF1 (see FIG. 6), and the DFT unit 56 performs a DFT operation on the profile PRF1. To output channel estimation values h1 to h11. On the other hand, if the received signal is from the user 1, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs DFT computation on the profile PRF2 and outputs channel estimation values h2 to h12.

(E) Third Pilot Generation Unit and Channel Estimation Unit FIG. 18A is a configuration diagram of a pilot generation unit that performs the third pilot generation processing described with reference to FIG. 11, and the pilot generation unit of FIG. The same parts as those in FIG. A different point is that a polarity imparting unit 61 is added, and other operations are the same.
CAZAC sequence generator 11 generates CAZAC sequence ZC _k (n) having the specified sequence length L and sequence number as a pilot, and cyclic shift unit 12 cyclically shifts CAZAC sequence ZC _k (n) by the specified c samples. Then, the obtained ZC _k (n−c) is input to the DFT unit 13. For example, in the case of pilot 1 for user 1 in FIGS. 11B and 11D, cyclic shift unit 12 shifts ZC _k (n) by c1 to generate ZC _k (n−c1), and the user In the case of pilot 2 for 2, cyclic shift is performed by c ₂ −s (k, d, L) to generate ZC _k (n−c 2 + s (k, d, L)), which is input to the DFT unit 13. The DFT unit 13 of N _TX size (N _TX = L) performs DFT arithmetic processing on the input pilot ZC _k (n−c) to generate a frequency domain pilot DFT {ZC _k (n−c)}.
The subcarrier mapping unit 14 performs subcarrier mapping based on the frequency offset information instructed from the transmission resource management unit 23. The polarity assignment unit 61 attaches the polarity instructed from the transmission resource management unit 23 to the output of the subcarrier mapping unit 14 and inputs it to the IFFT unit 15. For example, in the case of pilot 1 for user 1, the polarity of +1 is indicated in the first and second pilot blocks (see FIGS. 11B and 11D), so the polarity adding unit 61 performs subcarrier mapping. All carrier components output from the unit 14 are multiplied by +1 and input to the IFFT unit 15. In the case of pilot 2 for user 2, the +1 polarity is instructed in the first pilot block, and the -1 polarity is instructed in the second pilot block (FIGS. 11C and 11E). The polarity assigning unit 61 multiplies all carrier components output from the subcarrier mapping unit 14 by +1 in the first pilot block and inputs them to the IFFT unit 15, and multiplies by -1 in the second pilot block. Input to the IFFT unit 15.
The IFFT unit 15 of N _FFT size (N _FFT = 128) performs IFFT operation processing on the input subcarrier component to convert it into a time domain pilot signal and inputs it to the frame generation unit 26.

FIG. 18B is a block diagram of the channel estimation unit 34 that performs the third channel estimation process described in FIG. 12, and the same reference numerals are given to the same parts as those of the channel estimation unit in FIG. The difference is that an inter-block subcarrier addition unit 62 is provided instead of the subcarrier addition unit 52.
The DFT unit 51 applies DFT calculation processing to the pilot signal of the first pilot block input from the demultiplexing unit 32 to convert it into frequency domain pilot signals (subcarrier components p1 to p12). The pilot signals (subcarrier components p1 to p12) are stored in a built-in memory. Thereafter, the DFT unit 51 performs DFT calculation processing on the pilot signal of the second pilot block input from the separation unit 32 to convert it into a frequency domain pilot signal (subcarrier components p1 to p12), and adds the subcarriers between the blocks. Input to the unit 62.
When receiving the pilot 1 from the user 1, the inter-block subcarrier adding unit 62 stores the saved pilot signal of the first pilot block (subcarrier components p1 to p12) and the pilot signal of the second pilot block ( The subcarrier components p1 to p12) are added for each subcarrier. Thereby, pilot signal components from other users (for example, user 2) multiplexed are removed. Further, if the inter-block subcarrier adding unit 62 receives the pilot 2 from the user 2, the pilot signal of the second pilot block from the stored pilot signal (subcarrier components p1 to p12) of the first pilot block is received. The signal (subcarrier components p1 to p12) is subtracted for each subcarrier. Thereby, pilot signal components from other users (for example, user 1) multiplexed are removed.
If the replica signal multiplier 53 receives the pilot 1 of the user 1, the subcarriers f _i , f _{i + 1} , f _{i + 2} , f _{i + of} the received pilot output by the inter-block subcarrier adder 62 are received. ₃ ,,, f _{i + 10} multiplies the components p1~p11 the replica signal q1~q11 of, if receiving a pilot 2 of the user 2, sub-carrier of the received pilot that is output from the inter-block subcarrier addition unit 62 The components p2 to p12 of f _{i + 1} , f _{i + 2} , f _{i + 3} ,, f _{i + 11} and the replica signals q1 to q11 are multiplied.
Thereafter, the IDFT unit 54 performs an IDFT calculation process on the replica multiplication result and outputs a time domain pilot signal. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and if it is a pilot signal from the user 1, selects the profile PRF1 (see FIG. 6), and the DFT unit 56 performs DFT calculation on the profile PRF1. To output channel estimation values h1 to h11. On the other hand, if the received signal is from the user 2, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs a DFT operation on the profile PRF2 and outputs channel estimation values h2 to h12.

(F) Adaptive Control As described above, the uplink resource management unit 35 (FIG. 15) from the base station determines the pilot transmission frequency band, CAZAC sequence number and sequence length L, cyclicity based on the propagation path condition of the mobile station. The shift amount, frequency offset d, etc. are determined and notified to the mobile station. Further, the uplink resource management unit 35 of the base station also determines the multiplexing number in the transmission frequency band based on the propagation path condition of each mobile station.
FIG. 19 is an explanatory diagram of frequency allocation when the number of multiplexing is 4, in which the first 12 subcarriers are allocated to user 1, the second 12 subcarriers are allocated to user 2, and the third 12 subcarriers are allocated to user 3. This is a case where the last 12 subcarriers are assigned to the user 4 and the CAZAC sequence ZC _k (n) having a sequence length L = 19 is used as a pilot for each user while changing the cyclic shift amount.

に従って計算する。ここで、i，pはそれぞれデータ送信帯域番号とユーザ番号を表す。また、s(k,d,L)は系列番号k、系列長L、周波数オフセットによって生じる巡回シフト量を表し、次式

の関係が成り立つ。p番目のユーザのc_pは例えば次式

により計算することができる。Pは巡回シフトによって多重されるパイロット数(ユーザ数)を表す。図１９の場合、ユーザ１〜ユーザ４の巡回シフト量c₁〜c₄は
c₁＝0
c₂＝[L/４]
c₃＝[2・L/４]−s(k,d,L)
c₄＝[3・L/４]−s(k,d,L)
となる。 The pilot frequency offset is set so as to cover the data transmission bandwidth of each user as much as possible. The cyclic shift calculation unit 35a (FIG. 15) calculates the cyclic shift amount of each user by the following equation.

Calculate according to Here, i and p represent a data transmission band number and a user number, respectively. Further, s (k, d, L) represents a cyclic shift amount caused by a sequence number k, a sequence length L, and a frequency offset.

The relationship holds. The p-th user's c _p is, for example:

Can be calculated. P represents the number of pilots (number of users) multiplexed by the cyclic shift. In the case of FIG. 19, the cyclic shift amounts c _{1 to} c ₄ of the users ₁ to ₄ are
c ₁ = 0
c ₂ = [L / 4]
c ₃ = [2 · L / 4] −s (k, d, L)
c ₄ = [3 · L / 4] −s (k, d, L)
It becomes.

By the way, depending on the pilot signal reception method, channel estimation characteristics at both ends of the pilot transmission band may be poor, and channel estimation characteristics at the intermediate portion may be good. That is, the channel estimation accuracy is poor in the transmission bands of subcarriers 1 to 12 and 37 to 48 in FIG. 19, and the channel estimation accuracy is good in the transmission bands of subcarriers 13 to 24 and 25 to 36.
Therefore, the transmission bands of the intermediate subcarriers 13 to 24 and 25 to 36 are preferentially assigned to users with poor propagation path conditions, and the transmission bands of subcarriers 1 to 12 and 37 to 48 on both sides are assigned to users with good propagation path conditions. Assign. In this way, there is no user whose channel estimation accuracy is extremely deteriorated. FIG. 19 shows an example in which user 2 and user 3 are assigned to an intermediate transmission band.
Further, as shown in FIGS. 20 and 21, control (hopping control) can be performed so as to switch the transmission band assigned to each user for each frame. FIG. 20 is an explanatory diagram of allocation in odd-numbered frames, and FIG. 21 is an explanatory diagram of allocation in even-numbered frames.
In the odd-numbered frame, as shown in FIG. 20, user 1 and user 4 are assigned subcarriers 1 to 12 and 37 to 48 on both sides, and user 2 and user 3 are assigned intermediate subcarriers 13 to 24 and 25 to 36. . In the even-numbered frame, as shown in FIG. 21, intermediate subcarriers 13 to 24 and 25 to 36 are assigned to user 4 and user 1, and subcarriers 1 to 12, 37 to 48 on both sides are assigned to user 3 and user 2. Assign. In the odd-numbered frame, the frequency offset is applied to the pilots of the user 3 and the user 4, and in the even-numbered frame, the frequency offset is applied to the pilots of the user 1 and the user 2. In this way, there is no user whose channel estimation accuracy is extremely deteriorated.

FIG. 22 is a configuration diagram of a pilot generation unit in the case of performing hopping control, and the same reference numerals are given to the same parts as the pilot generation unit of FIG. A different point is that a frequency offset switching control unit 71 is added, and other operations are the same.
CAZAC sequence generator 11 generates CAZAC sequence ZC _k (n) having the specified sequence length L and sequence number as a pilot, and cyclic shift unit 12 cyclically shifts CAZAC sequence ZC _k (n) by the specified c samples. Then, the obtained ZC _k (n−c) is input to the DFT unit 13. The DFT unit 13 of N _TX size (N _TX = L) performs DFT arithmetic processing on the input pilot ZC _k (n−c) to generate a frequency domain pilot DFT {ZC _k (n−c)}. The frequency offset switching control unit 71 determines whether or not to perform frequency offset based on the frequency offset amount d and the hopping pattern instructed from the transmission resource management unit 23. The subcarrier mapping unit 14 performs subcarrier mapping according to whether or not frequency offset is performed. The _NFT size (N _FFT = 128) IFFT unit 15 performs IDFT calculation processing on the input subcarrier component to convert it into a time domain pilot signal and inputs it to the frame generation unit 26.

(Appendix)
(Appendix 1)
Each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station, and time-multiplexes the pilot signal with the data signal and transmits the data signal to the base station. In a wireless communication method in a wireless communication system,
Determining a pilot transmission band of the user terminal by performing a frequency offset for each user terminal so that the pilot transmission band of the user terminal covers the data transmission band of the user terminal;
Instructing the user terminal to transmit a pilot signal using the frequency of the determined pilot transmission band for each user terminal;
A wireless communication method comprising:
(Appendix 2)
Using a CAZAC sequence as the pilot signal pattern,
The wireless communication method according to supplementary note 1, wherein:
(Appendix 3)
The instruction step includes
Calculating a cyclic shift amount corresponding to the offset amount of the frequency offset and the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the user terminal to frequency offset the pilot signal by the frequency offset amount;
The wireless communication method according to supplementary note 2, characterized by comprising:
(Appendix 4)
When the base station multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals, a step of adding frequency components of pilot signals that do not overlap each other,
Multiplying the summation result by a replica of the pilot signal;
Converting a replica multiplication result into a time domain signal, and then separating a signal portion of a predetermined user terminal from the time domain signal to estimate a channel;
The wireless communication method according to appendix 1 or 3, characterized by comprising:
(Appendix 5)
The instruction step includes
Calculating a cyclic shift amount corresponding to the offset amount of the frequency offset and the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the pilot signal to be frequency offset by the frequency offset amount, and pilot transmission of the entire frequency band and the user terminal Instructing the user terminal to copy the frequency component of the opposite side band of the pilot signal to a band that does not overlap with the band;
The wireless communication method according to supplementary note 2, characterized by comprising:
(Appendix 6)
When the base station multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals, a step of multiplying a frequency component corresponding to the pilot transmission band of the predetermined user terminal by a pilot signal replica;
Converting the replica multiplication result into a time domain signal, and then separating the signal portion of the user terminal from the time domain signal and performing channel estimation;
The wireless communication method according to appendix 5, characterized by comprising:
(Appendix 7)
When there are an even number of pilot blocks in one frame, one user terminal is instructed to multiply the pilot signals of all blocks by +1, another user terminal is multiplied by +1 by half the pilot signal, and the remaining Instructing the half pilot signal to be multiplied by -1;
When the base station multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals, a step of performing addition / subtraction arithmetic processing on the pilot signals of all blocks so that a pilot signal of a predetermined user remains,
Multiplying the operation result by a replica of the pilot signal;
Converting the replica multiplication result into a time domain signal, and then separating the signal portion of the user terminal from the time domain signal and performing channel estimation;
The wireless communication method according to appendix 1, further comprising:
(Appendix 8)
Obtaining mobile station propagation path conditions;
A step of preferentially allocating an intermediate band of all the frequency bands as a data transmission band of a user terminal having a poor propagation path state and notifying the user terminal;
The wireless communication method according to claim 1, further comprising:
(Appendix 9)
Performing a hopping control for periodically assigning an intermediate band and an end band of all the frequency bands as a data transmission band of each user terminal;
The wireless communication method according to claim 1, further comprising:
(Appendix 10)
Each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station, and transmits a pilot signal to the base station in a time-multiplexed manner with respect to the data signal. In the base station of the communication system,
The pilot transmission band of the user terminal is determined by frequency offset for each user terminal so that the pilot transmission band of the user terminal covers the data transmission band of the user terminal, and the frequency of the determined pilot transmission band is used. A resource management unit that instructs the user terminal to transmit a pilot signal;
A base station characterized by comprising:
(Appendix 11)
Using a CAZAC sequence as the pilot signal pattern,
The base station as set forth in appendix 10, wherein:
(Appendix 12)
The resource management unit
A cyclic shift amount calculation unit that calculates a cyclic shift amount according to the offset amount of the frequency offset and the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the user terminal to frequency offset the pilot signal by the frequency offset amount,
The base station according to appendix 10, characterized by comprising:
(Appendix 13)
The resource management unit
A cyclic shift amount calculation unit for calculating a cyclic shift amount according to the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the user terminal to move a subcarrier frequency component corresponding to the frequency offset of the pilot signal to an opposite side band of the pilot signal An instruction section for instructing,
The base station according to appendix 10, characterized by comprising:
(Appendix 14)
The base station includes a channel estimation unit that estimates a channel for each user terminal,
The channel estimation unit
A receiver that multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals;
An adder for adding a frequency component of a pilot signal portion in which the plurality of pilot signals do not overlap each other;
A replica multiplier for multiplying the addition result by a replica of the pilot signal;
A conversion unit for converting a replica multiplication result into a time domain signal;
A separation unit for separating a signal portion of a predetermined user terminal from the time domain signal;
An estimation unit for converting the separated time signal into a frequency domain signal to estimate a channel;
The base station according to appendix 10 or 12, characterized by comprising:
(Appendix 15)
The resource management unit
A cyclic shift amount calculation unit that calculates a cyclic shift amount according to the offset amount of the frequency offset and the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount, and instructing the pilot signal to be frequency offset by the frequency offset amount, and pilot transmission of the entire frequency band and the user terminal An instruction unit that instructs the user terminal to copy the frequency component of the opposite side band of the pilot signal to a band that does not overlap with the band;
The base station as set forth in appendix 14, characterized by comprising:
(Appendix 16)
The resource management unit
A cyclic shift amount calculation unit for calculating a cyclic shift amount according to the number of multiplexed user terminals for each user terminal;
Instructing the user terminal to circulate the pilot signal of the CAZAC sequence by the cyclic shift amount and copying the subcarrier frequency component corresponding to the frequency offset of the pilot signal to the opposite band of the pilot signal An instruction unit for instructing,
The base station according to appendix 10, characterized by comprising:
(Appendix 17)
The base station includes a channel estimation unit that estimates a channel for each user terminal,
The channel estimation unit
A receiver that multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals;
A replica multiplier for multiplying a replica of a pilot signal by a frequency component corresponding to a pilot transmission band of a predetermined user terminal;
A conversion unit for converting a replica multiplication result into a time domain signal;
A separation unit for separating a signal portion of a predetermined user terminal from the time domain signal;
An estimation unit for converting the separated time signal into a frequency domain signal to estimate a channel;
The base station according to appendix 15, characterized by comprising:
(Appendix 18)
The base station includes a channel estimation unit that estimates a channel for each user terminal,
The channel estimation unit
A receiver that multiplex-receives a plurality of pilot signals transmitted from a plurality of user terminals;
The resource management unit instructs one user terminal to multiply the pilot signal of all pilot blocks by +1, and another user terminal multiplies the pilot signal of half pilot block by +1, and the other half pilot An addition / subtraction unit that performs addition / subtraction processing on pilot signals of all pilot blocks so that a pilot signal of a predetermined user remains when the pilot signal of the block is instructed to be multiplied by -1.
A replica multiplier for multiplying the operation result by a replica of the pilot signal;
A conversion unit for converting a replica multiplication result into a time domain signal;
A separation unit for separating a signal portion of a predetermined user terminal from the time domain signal;
An estimation unit for converting the separated time signal into a frequency domain signal to estimate a channel;
The base station according to appendix 10, characterized by comprising:
(Appendix 19)
The resource management unit acquires a propagation path situation of a mobile station, preferentially assigns a middle band of all the frequency bands as a data transmission band of a user terminal having a poor propagation path situation, and notifies the user terminal,
The base station as set forth in appendix 10, wherein:
(Appendix 20)
The resource management unit performs hopping control for periodically allocating an intermediate band and an end band of all the frequency bands as a data transmission band of each user terminal.
The base station as set forth in appendix 10, wherein:
(Appendix 21)
Each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station, and transmits a pilot signal to the base station in a time-multiplexed manner with respect to the data signal. In a user terminal of a communication system,
A receiving unit for receiving uplink resource information from the base station;
A pilot generation unit that generates a pilot according to an instruction of the uplink resource information, the pilot generation unit,
CAZAC sequence generator for generating a CAZAC sequence having a predetermined sequence length and sequence number as a pilot signal based on the resource information,
A first converter that converts a CAZAC sequence, which is a time domain pilot signal, into a frequency domain pilot signal;
A subcarrier mapping unit that maps a subcarrier component of a pilot signal based on frequency offset information included in the resource information;
A second converter for converting the subcarrier mapped pilot signal into a time domain signal;
A cyclic shift unit that cyclically shifts a CAZAC sequence based on a shift amount included in the resource information before the first conversion or after the second conversion;
A user terminal comprising:
(Appendix 22)
A data signal addressed to the first and second users is transmitted using the first and second subcarrier groups, respectively, and a pilot signal addressed to the first and second users is transmitted with respect to the data signal addressed to the user. In a wireless communication system that multiplexes and transmits automatically,
The frequency at which a pilot signal addressed to a first user among the plurality of users is arranged is different from the frequency at which a pilot signal addressed to a second user among the plurality of users is arranged,
A wireless communication method.

21 Radio unit 22 Received signal baseband processing unit 23 Transmission resource management unit 24 Data processing unit 25 Pilot generation unit 26 Frame generation unit

Claims (3)

Wireless communication in which each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station and multiplexes a pilot signal with the data signal and transmits the data signal to the base station In the user terminal of the system,
A receiving unit for receiving uplink resource information from the base station;
A pilot generating unit that generates a pilot according to an instruction of the uplink resource information;
A transmitter for transmitting the pilot signal to the base station;
The pilot generation unit includes:
CAZAC sequence generating unit that generates a Zadoff-Chu sequence as a pilot signal based on the resource information,
And a subcarrier mapping unit that maps a sequence generated by cyclically shifting the Zadoff-Chu sequence by a predetermined amount and copying a part of the shifted sequence and adding it to the shifted sequence. User terminal. Wireless communication in which each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station and multiplexes a pilot signal with the data signal and transmits the data signal to the base station In the system wireless communication method,
Receive uplink resource information from the base station,
A Zadoff-Chu sequence is generated as a pilot signal based on the uplink resource information,
The Zadoff-Chu sequence is cyclically shifted by a predetermined amount, and a sequence generated by copying a part of the shifted sequence and adding it to the shifted sequence is mapped,
Send the mapped pilot signal,
A wireless communication method. Wireless communication in which each user terminal transmits a data signal to the base station using frequencies of different data transmission bands assigned by the base station and multiplexes a pilot signal with the data signal and transmits the data signal to the base station In the system,
The base station
A first transmitter that transmits uplink resource information to each user terminal;
Each of the user terminals is
A receiving unit for receiving the uplink resource information;
A pilot generating unit that generates a pilot according to an instruction of the uplink resource information;
A transmitter for transmitting the pilot signal to the base station;
The pilot generation unit includes:
CAZAC sequence generating unit that generates a Zadoff-Chu sequence as a pilot signal based on the resource information,
And a subcarrier mapping unit that maps a sequence generated by cyclically shifting the Zadoff-Chu sequence by a predetermined amount and copying a part of the shifted sequence and adding it to the shifted sequence. Wireless communication system.

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