Source: https://patents.google.com/patent/JP4536435B2/en
Timestamp: 2019-12-07 16:42:08
Document Index: 42516480

Matched Legal Cases: ['art 1511', 'art 505', 'art 510', 'art 511', 'art 512', 'art 513']

JP4536435B2 - Transmission method and transmission apparatus - Google Patents
Transmission method and transmission apparatus Download PDF
JP4536435B2
JP4536435B2 JP2004190418A JP2004190418A JP4536435B2 JP 4536435 B2 JP4536435 B2 JP 4536435B2 JP 2004190418 A JP2004190418 A JP 2004190418A JP 2004190418 A JP2004190418 A JP 2004190418A JP 4536435 B2 JP4536435 B2 JP 4536435B2
JP2004190418A
JP2005039807A (en
聖峰 小林
雅之 折橋
豊 村上
昭彦 松岡
2003-06-30 Priority to JP2003188898 priority Critical
2004-06-28 Application filed by パナソニック株式会社 filed Critical パナソニック株式会社
2004-06-28 Priority to JP2004190418A priority patent/JP4536435B2/en
2004-06-30 Priority claimed from CN 200480017316 external-priority patent/CN1809980B/en
2005-02-10 Publication of JP2005039807A publication Critical patent/JP2005039807A/en
2010-09-01 Publication of JP4536435B2 publication Critical patent/JP4536435B2/en
Of any one of transmission method X of transmitting modulated signal A and modulated signal B including the same data from a plurality of antennas and transmission method Y of transmitting modulated signal A and modulated signal B having different data from the plurality of antennas, base station apparatus 201 does not change the transmission method during data transmission and changes only the modulation scheme. Base station apparatus 201 transmits modulated signal A and modulated signal B to communication terminal apparatus 251 using the determined transmission method and modulation scheme. In this way, it is possible to improve data transmission efficiency when transmitting data using the plurality of antennas.
The present invention relates to a transmission method, a transmission apparatus, and a communication system that transmit data simultaneously from a plurality of antennas.
Conventionally, the technique disclosed in Non-Patent Document 1 is known as a transmission method using a plurality of antennas. Hereinafter, the content disclosed in Non-Patent Document 1 will be described with reference to the drawings.
FIG. 28 is a diagram showing a conventional frame configuration. In this figure, transmission signal A and transmission signal B are signals transmitted simultaneously from different antennas. The transmission signal A and the transmission signal B are composed of symbol groups including the same data. Here, SyA and SyB in the figure indicate symbols, and the complex conjugate is indicated by “*”. Transmission signal A is composed of frames in the order of data symbols SyA and -SyB *, and transmission signal B is composed of frames in the order of data symbols SyB and SyA *. The transmission signal A and the transmission signal B are transmitted in synchronization. Therefore, the data symbols SyA and SyB are transmitted at the same time, and the data symbols -SyB * and SyA * are transmitted at the same time.
FIG. 29 is a diagram illustrating a conventional communication system. The transmission apparatus 11 includes an antenna 12 and an antenna 13. For example, the transmission apparatus 11 transmits the transmission signal A illustrated in FIG. 28 from the antenna 12 and the transmission signal B from the antenna 13 to the reception apparatus 21. The receiving device 21 receives signals transmitted from the respective antennas of the transmitting device 11 through the antenna 22. Since the signal received by the antenna 22 is composed of the transmission signal A and the transmission signal B, it is demodulated after being separated into the transmission signal A and the transmission signal B.
In such a conventional communication system, the transmission device 11 transmits the transmission signal A from the antenna 12 and the transmission signal B from the antenna 13, and the signals transmitted from the antennas are transmitted through different transmission paths (h1 (t)). And h2 (t)). Utilizing this fact, the frame configuration as shown in FIG. 28 is adopted, and the reception quality can be improved in the reception device 21.
"Space-Time Block Codes from Orthogonal Design" IEEE Transactions on Information Theory, pp.1456-1467, vol.45, no.5, July 1999
However, in the conventional communication system described above, SyA * and -SyB * are demodulated as SyA and SyB in the receiving apparatus, and are substantially the same information as SyA and SyB. For this reason, the same information is transmitted twice, and the data transmission efficiency is poor.
The present invention has been made in view of this point, and an object of the present invention is to provide a communication method and a transmission apparatus that improve data transmission efficiency when data is transmitted using a plurality of antennas.
In order to solve this problem, the transmission method of the present invention includes a first transmission method in which a transmission device including a plurality of antennas transmits a plurality of signals including the same data from the plurality of antennas, respectively. A transmission method determining step for determining any of a second transmission method for transmitting a plurality of signals including different data from a plurality of antennas, respectively, and a modulation method determining step for determining any of the plurality of modulation methods And a control step of controlling the transmission method determination step to perform the determination process at a longer time interval than the modulation scheme determination step performs the determination processing .
According to this method, if the communication time becomes long, the propagation model may change, so by changing the transmission method at a longer time interval than when changing the modulation method, Even when the model changes, it is possible to achieve both improved reception quality and higher transmission speed.
In the transmission method of the present invention, in the above method, the transmission method determination step uses cyclic delay diversity as the first transmission method.
According to this method, by a transmission method using cyclic delay Diversified Ji as the first transmission method, it is possible to improve the data transmission efficiency.
The transmission method of the present invention is a transmission method of a transmission apparatus having a plurality of antennas, and includes the same data using eigenmodes using a singular vector or eigenvector of a channel matrix as a channel signature vector in a MIMO system. One of a first transmission method for transmitting a plurality of received signals from a plurality of antennas, and a second transmission method for transmitting a plurality of signals including different data from each of a plurality of antennas, respectively, A transmission method determination step that switches according to the number of communication partners, a modulation method determination step that determines any of a plurality of modulation schemes, a transmission method determination step that depends on a communication procedure with a communication partner, and / or And a control step for controlling whether or not to perform the determination process in the modulation method determination step .
According to this method, for example, when the number of communication partners is 1, it is possible to reduce interference given to other communication stations by using a transmission method using the eigenmode, and when the number of communication partners is plural, By adopting the second transmission method, it is possible to avoid a decrease in data transmission efficiency.
The transmission method of the present invention is a transmission method of a transmission device including a plurality of antennas, and generates a plurality of vectors used for multiplication / synthesis of a plurality of signals based on information transmitted from a communication partner, A first transmission method of combining the plurality of signals using a plurality of vectors to generate a plurality of transmission signals and transmitting the plurality of transmission signals from the plurality of antennas; and the plurality of transmission signals And a second transmission method for spatially multiplexing the plurality of transmission signals, respectively, according to the number of communication partners, and the determined transmission. Transmitting the plurality of transmission signals from the plurality of antennas using a method .
The transmission method of the present invention further includes a modulation scheme determining step of determining any one of a plurality of modulation schemes as a modulation scheme used in the first transmission method and the second transmission method in the above method. I made it.
The transmission apparatus of the present invention includes a plurality of transmission antennas, a first transmission method for transmitting a plurality of signals including the same data from each of the plurality of antennas, and a plurality of signals including different data from each other. Transmission method determining means for determining any one of the second transmission methods for transmitting from the respective antennas, modulation method determining means for determining any one of the plurality of modulation methods, and the modulation method determining means performing the determination processing Control means for controlling the transmission method determination means to perform determination processing at a time interval longer than that performed, transmission processing means for transmitting a signal to which the determined transmission method and modulation method are applied from the plurality of antennas, The structure which comprises is taken.
According to this configuration, if the communication time becomes long, the propagation model may change, so by changing the transmission method at a longer time interval than when changing the modulation method, Even when the model changes, it is possible to achieve both improved reception quality and higher transmission speed.
The transmission apparatus according to the present invention employs a configuration in which the transmission method determination unit uses cyclic delay diversity as the first transmission method in the above configuration.
According to this configuration, the data transmission efficiency can be improved by adopting the transmission method using cyclic delay diversity as the first transmission method.
The transmission apparatus of the present invention includes a plurality of transmission antennas, a first transmission method for transmitting a plurality of first transmission signals obtained by combining a plurality of signals from the plurality of antennas, and a second plurality of transmission signals. A second transmission method for spatially multiplexing the second plurality of transmission signals, respectively, according to the number of communication partners; and Channel analysis means for generating a plurality of vectors used for multiplication / synthesis of a plurality of signals based on information transmitted from a communication partner, and using the plurality of vectors output from the channel analysis means, the plurality of vectors A multiplexing unit configured to combine the signals to generate the first plurality of transmission signals; and the first output from the multiplexing unit when the transmission method determination unit determines the first transmission method. A plurality of transmission signals are transmitted from the plurality of antennas, respectively, and the second plurality of transmission signals are transmitted from the plurality of antennas when the transmission method determining means determines the second transmission method. And a processing means.
The transmission apparatus according to the present invention uses a plurality of transmission antennas and a plurality of signals including the same data using a plurality of antennas using an eigenmode that uses a singular or eigenvector of a channel matrix in a MIMO system as a channel signature vector. A transmission method for switching between a first transmission method for transmitting from each of the first transmission method and a second transmission method for transmitting a plurality of signals including different data from a plurality of antennas according to the number of communication partners. Whether to perform determination processing in the transmission method determination unit and the modulation method determination unit according to a communication procedure with a determination unit, a modulation method determination unit that determines any of a plurality of modulation methods, and a communication partner Control means for controlling the determined transmission method or a signal to which a modulation method is applied to the plurality of antennas. It adopts a configuration comprising a transmission processing means for transmitting, the.
According to this configuration, for example, when the number of communication partners is 1, it is possible to reduce interference given to other communication stations by using the transmission method using the eigenmode, and when the number of communication partners is plural, By adopting the second transmission method, it is possible to avoid a decrease in data transmission efficiency.
According to the present invention, the transmission apparatus includes a plurality of antennas, and a first transmission method for transmitting a plurality of signals including the same data from the plurality of antennas, and a plurality of signals including different data from each other. Is determined based on a transmission path between transmission and reception, and when determining one of a plurality of modulation schemes, the transmission method is from the start to the end of communication. By determining only the modulation method among the modulation methods, both the data transmission rate and the reception quality can be improved.
Frame Configuration FIG. 1 is a diagram showing a frame configuration in Embodiment 1 of the present invention. 1A shows a frame configuration of modulated signal A and modulated signal B in transmission method X, and FIG. 1B shows a frame configuration of modulated signal A and modulated signal B in transmission method Y. Yes. Propagation model estimation symbol 101 and radio wave propagation environment estimation symbol 103 are symbols used by a communication partner receiving apparatus to estimate channel fluctuation, and are referred to as pilot symbols, preambles, control symbols, known symbols, unique words, and the like. It is.
The transmission method notification symbol 102 is a symbol indicating a transmission method (X or Y) of a modulation signal transmitted by the base station apparatus, a modulation method, and an error correction method.
Data symbol 104 is user information such as voice data, image data, and character data transmitted from the base station apparatus to the communication terminal apparatus.
Transmission Method X and Transmission Method Y The transmission method X is a transmission method disclosed in Non-Patent Document 1 and includes the same data as each other (hereinafter referred to as “space-time coding”). The data symbol is transmitted from two antennas. As a specific example, among the data symbols SyA, SyB, SyA *, and -SyB * ("*" indicates a complex conjugate), the modulation signal A is configured in the order of the data symbols SyA and -SyB *, and the modulation signal B is The data symbols SyB and SyA * are arranged in this order. On the other hand, in the transmission method Y, a frame configuration is performed with data symbols having different information. As a specific example, among data symbols SyA, SyB, SyC, and SyD having different information, the modulation signal A is composed of data symbols SyA and SyC, and the modulation signal B is composed of data symbols SyB and SyD.
Note that both the transmission method X and the transmission method Y shown in FIGS. 1A and 1B transmit the modulated signal A and the modulated signal B in synchronization. For example, in the transmission method X, the data symbols -SyB * and SyA * are transmitted simultaneously, and in the transmission method Y, the data symbols SyC and SyD are transmitted simultaneously. In addition, in the modulation signal A and the modulation signal B, the same kind of symbols are transmitted simultaneously.
FIG. 2 is a schematic diagram showing the communication system according to Embodiment 1 of the present invention. In this figure, a base station apparatus 201 includes an antenna 202 and an antenna 203, and communicates with a communication terminal apparatus 251 via a wireless line. The communication terminal device 251 includes an antenna 252 and an antenna 253. In this figure, a state in which a signal is transmitted from the base station apparatus 201 to the communication terminal apparatus 251 is shown.
Characteristics of Transmission Method X and Transmission Method Y Here, channel fluctuation in the transmission path between the antenna 202 and the antenna 252 is h11 (t), and channel fluctuation in the transmission path between the antenna 202 and the antenna 253 is h12 (t). . Similarly, the channel fluctuation between the antenna 203 and the antenna 252 is h21 (t), and the channel fluctuation between the antenna 203 and the antenna 253 is h22 (t). However, t shows time. The channel fluctuations h11 (t), h12 (t), h21 (t), and h22 (t) are estimated by the communication terminal apparatus 251 using the propagation model estimation symbol 101 and the radio wave propagation environment estimation symbol 103.
At this time, in the transmission method X, if the received signal of the antenna 252 shown in FIG. 2 is R1 (t), the following equation is established.
As can be seen from this equation, in the transmission method X, the data symbols SyA and SyB are repeatedly transmitted at times t = i and t = i + 1. In addition, although the case where a space-time block code is used is described here, for example, a space-time trellis code using the following reference as an example may be used. (Reference: “Space-Time Block Codes for High Data Rate Wireless Communication: Performance Criterion and Code Construction” IEEE Transactions on Information Theory, pp.744-765, vol.44, no.2, March 1998)
On the other hand, in the transmission method Y, when the reception signals of the antennas 252 and 253 shown in FIG. 2 are R1 (t) and R2 (t), the following equations are established.
As can be seen from this equation, in the transmission method Y, the data symbols SyA and SyB are transmitted only at time t = i.
From these facts, when the transmission method X and the transmission method Y are compared, the transmission method X has a lower transmission speed than the transmission method Y, but the reception quality is good. Conversely, the transmission method Y has a higher transmission speed than the transmission method X, but the reception quality tends to deteriorate. In particular, the transmission method Y has a property that reception quality is significantly deteriorated when a direct wave is received. For this reason, it is conceivable that the transmission method X is used when a direct wave is received, and the transmission method Y is used when a direct wave is not received.
As described above, since the error tolerance is strong, the transmission method X having a high reception quality and the transmission method Y having a high transmission rate are determined according to the state of the transmission path, so that both the reception quality and the transmission rate can be improved. it can. That is, by switching between the transmission method X and the transmission method Y and switching the modulation method, it is possible to further improve the reception quality and the transmission speed.
Configuration of transmitting apparatus in base station apparatus 201 FIG. 3 is a block diagram showing the configuration of the transmitting apparatus in base station apparatus 201 according to Embodiment 1 of the present invention. In this figure, the frame generation instruction unit 401 is based on the transmission method request information and the modulation method request information transmitted from the communication terminal apparatus 251, and the transmission method (X or Y) and the modulation method (for example, QPSK, 16QAM, 64QAM). Any one of them is determined, and the determined content is instructed to the data series generation unit 402, the transmission processing unit 403, and the transmission processing unit 404 by the frame generation instruction signal S1.
The data sequence generation unit 402 generates the transmission digital signal S2 of the modulation signal A and the transmission digital signal S3 of the modulation signal B having the frame configuration shown in FIG. 1 from the transmission digital signal according to the instruction of the frame generation instruction unit 401. To do. The generated transmission digital signal S2 of the modulation signal A is output from the data sequence generation unit 402 to the transmission processing unit 403, and the transmission digital signal S3 of the modulation signal B is output from the data sequence generation unit 402 to the transmission processing unit 404.
The transmission processing unit 403 is for the transmission digital signal S2 of the modulation signal A output from the data sequence generation unit 402, and the transmission processing unit 404 is for the transmission digital signal S3 of the modulation signal B output from the data sequence generation unit 402. Transmission processing is performed according to an instruction from each frame generation instruction unit 401. Since the internal configurations of the transmission processing unit 403 and the transmission processing unit 404 are the same, the configuration within the transmission processing unit 403 will be described below.
Modulation section 4031 can modulate with a plurality of modulation schemes, and modulates transmission digital signal S2 of modulated signal A output from data sequence generation section 402 with the modulation scheme instructed from frame generation instruction section 401. Modulated signal S4 is output from modulation section 4031 to spreading section 4032.
The spreading unit 4032 multiplies the signal S4 output from the modulation unit 4031 by a spreading code, and the modulated signal A after spreading is output to the radio unit 4033. The radio unit 4033 performs predetermined processing on the signal S5 after spreading. The wireless processing (D / A conversion, up-conversion, etc.) is performed, and the signal S6 after the wireless processing is output to the amplifier 4034.
The amplifier 4034 amplifies the signal S6 output from the radio unit 4033 and wirelessly transmits the power amplified signal S7 from the antenna 202 to the communication terminal apparatus 251.
Configuration of Receiving Device in Communication Terminal Device 251 FIG. 4 is a block diagram showing a configuration of the receiving device in communication terminal device 251 according to Embodiment 1 of the present invention. In this figure, the antenna 252 receives a combined signal S51 of signals transmitted from the antenna 202 and the antenna 203 of the base station apparatus 201, and the radio unit 501 performs predetermined radio processing (on the signal S51 received by the antenna 252). Down-conversion, A / D conversion, etc.) and the signal S52 after the radio processing is output to the despreading section 502.
The despreading unit 502 multiplies the signal S52 output from the radio unit 501 by a spreading code and performs despreading. The despread signal S53 is output from the despreading section 502 to the frame synchronization section 503, the first transmission path estimation section 504, the second transmission path estimation section 505, the demodulation section 510, and the received electric field strength estimation section 511.
The frame synchronization unit 503 performs frame synchronization of the modulation signal A and the modulation signal B based on the signal S53 output from the despreading unit 502 and the signal S56 output from the despreading unit 507, and forms a timing signal S57. . Timing signal S57 is output from frame synchronization section 503 to first transmission path estimation sections 504 and 508, second transmission path estimation sections 505 and 509, and demodulation section 510.
The first transmission path estimation unit 504 includes the propagation model estimation symbol 101 of the modulated signal A and the radio wave propagation environment in the signal S53 output from the despreading unit 502 in accordance with the timing signal S57 output from the frame synchronization unit 503. The estimation symbol 103 is used to estimate the transmission path of the modulated signal A, that is, estimate the channel fluctuation. The estimated transmission path information of modulated signal A is output from first transmission path estimation section 504 to demodulation section 510 and eigenvalue calculation section 512 as transmission path estimation signal S58. The transmission path estimation signal S58 of the modulation signal A corresponds to h11 (t) in Expression (2).
The second transmission path estimation unit 505 determines the propagation model estimation symbol 101 of the modulated signal B and the radio wave propagation environment in the signal S53 output from the despreading unit 502 in accordance with the timing signal S57 output from the frame synchronization unit 503. By using the estimation symbol 103, the transmission path (channel fluctuation) of the modulated signal B is estimated. The estimated transmission path information of modulated signal B is output from second transmission path estimation section 505 to demodulation section 510 and eigenvalue calculation section 512 as transmission path estimation signal S59. The transmission path estimation signal S59 of the modulation signal B corresponds to h12 (t) in Expression (2).
The signal S54 received by the antenna 253 is processed in the radio unit 506, the despreading unit 507, the first transmission path estimation unit 508, and the second transmission path estimation unit 509 in the same manner as described above. Detailed description thereof is omitted. Incidentally, the transmission path estimation signal S60 output from the first transmission path estimation section 508 to the demodulation section 510 corresponds to h21 (t) in the equation (2), and is output from the second transmission path estimation section 509 to the demodulation section 510. The transmission path estimation signal S61 to be performed corresponds to h22 (t) in Expression (2).
The demodulator 510 performs transmission path estimation signals S58 and S59 output from the first transmission path estimation sections 504 and 508 and the second transmission path estimation sections 505 and 509 in accordance with the timing signal S57 output from the frame synchronization section 503. Using S60 and S61, the signals S53 and S56 output from the despreading unit 502 and the despreading unit 507 are demodulated to obtain the received digital signal of the modulated signal A and the received digital signal of the modulated signal B. At this time, the demodulation unit 510 uses the transmission method notification symbol 102 of the signals S53 and S56 output from the despreading unit 502 and the despreading unit 507 to transmit the signal (X or Y), modulation method, and error correction method. And the data symbol is demodulated according to the acquired content.
The received electric field strength estimation unit 511 estimates the received electric field strength based on the signals S53 and S56 output from the despreading unit 502 and the despreading unit 507, and uses the estimation result as the received electric field strength estimation signal S62 as a modulation method determination unit. 513 and the transmission method determination unit 514. Note that the received electric field strength here means effective carrier power. Further, the transmission path estimation unit and the received electric field strength estimation unit 511 of the first transmission path estimation units 504 and 508 and the second transmission path estimation units 505 and 509 are either the transmission path estimation unit or the received electric field strength estimation unit 511. Alternatively, both function as transmission path estimation means.
When the transmission path information output from the first transmission path estimation sections 504 and 508 and the second transmission path estimation sections 505 and 509 is converted into a channel matrix as shown in Equation (2), the eigenvalue calculation section 512 uses the eigenvalue as a channel matrix. calculate. The calculated eigenvalue is output as an eigenvalue signal S63 from the eigenvalue calculation unit 512 to the modulation scheme determination unit 513 and the transmission method determination unit 514.
The modulation scheme determination unit 513 serving as a modulation scheme request unit is based on the received field strength estimation signal S62 output from the received field strength estimation unit 511 and the eigenvalue signal S63 output from the eigenvalue calculation unit 512. Is determined and output as modulation scheme request information. Note that the modulation scheme may be determined only by the received electric field strength, and in this case, the influence on the transmission rate and transmission quality is small.
The transmission method determination unit 514 serving as a transmission method request unit starts communication based on the eigenvalue signal S63 output from the eigenvalue calculation unit 512 and the estimation signal S62 (reception field strength) output from the reception field strength estimation unit 511. Sometimes the transmission method X or the transmission method Y to be applied by the base station apparatus 201 is determined. The determined information is output from the communication terminal device 251 as transmission method request information. Taking the case of equation (2) as an example and explaining in more detail, the eigenvalue signal S63 output from the eigenvalue calculation unit 512 includes two eigenvalues, and these two eigenvalues are represented by λ1, λ2 (| λ1 (t) |> | Λ2 (t) |), and the difference in magnitude between the eigenvalues is obtained. That is, | λ1 (t) | 2 − | λ2 (t) | 2 is calculated. When this difference is larger than a predetermined value, it is assumed that a direct wave is received and the transmission method X is determined. On the contrary, when this difference is smaller than a predetermined value, it is assumed that only the scattered wave not including the direct wave is received, and the transmission method Y is determined. Incidentally, the calculation result of | λ1 (t) | 2 − | λ2 (t) | 2 reflects the state of the probability density distribution of eigenvalues.
A method for determining whether or not a received signal is a signal arriving with a direct wave A method for determining whether or not a received signal is a signal arriving with a direct wave will be described with reference to FIG. First, tan −1 (Q / I) is calculated from the I component and Q component of the received baseband signal. FIG. 5 is a diagram in which tan −1 (Q / I) is represented on the horizontal axis and the probability density is represented on the vertical axis. FIG. 5A shows a case where a direct wave is received, and the possibility that a peak appears in the phase of the direct wave is high. On the other hand, FIG. 5B shows a case where only a scattered wave that does not include a direct wave is received, and the possibility that a peak appears is reduced. In this way, whether or not a direct wave has been received can be specified by obtaining a probability density of tan −1 (Q / I) and determining which distribution state it will be.
Also, two eigenvalues of the 2 × 2 matrix (hereinafter referred to as “channel matrix”) represented by the channel fluctuation component of the above-described equation (2) are obtained, and eigenvalues are obtained by λ1, λ2 (| λ1 |> | λ2 |). , The presence / absence of direct wave reception is reflected in the relationship between λ1 and λ2. For this reason, it may be determined whether or not a direct wave has been received based on the eigenvalues of the channel matrix. Specifically, the magnitude of the eigenvalue can also be expressed by a probability density distribution, and the reception quality depends on the distribution of the eigenvalue, so whether or not it is the reception quality when the direct wave is received based on the distribution of the eigenvalue. Judgment can be made.
Transmission Method and Modulation Method Applied to Transmission Method Notification Symbol The transmission method notification symbol 102 is information for notifying the transmission method, modulation method, and error correction method of the modulated signal. If this transmission method notification symbol 102 is not demodulated correctly, data is transmitted. Therefore, it is preferable to transmit the transmission method notification symbol 102 by the transmission method X and the modulation method by BPSK. It is even better to incorporate error correction. As a result, the error tolerance of the transmission method notification symbol 102 is increased, and the demodulation accuracy of this symbol can be increased. Therefore, the communication terminal device 251 can accurately acquire the transmission method, modulation method, and error correction method. Therefore, the base station apparatus 201 can accurately transmit the data symbol 104 transmission method, modulation scheme, and error correction scheme information to the communication terminal apparatus 251, and the communication terminal apparatus 251 cannot demodulate the data. The situation can be avoided.
Further, for example, even when the transmission method Y is determined at the start of communication, the transmission method notification symbol is transmitted using the transmission method X, so that the modulation method and the error correction method can be accurately transmitted. Quality will be improved. Since both the transmission method X and the transmission method Y transmit two modulated signals, the transmission method can be changed without changing the number of antennas of the transmission device of the base station device, that is, from the transmission method Y to the transmission method X. Since the transmission method notification symbol is accurately transmitted without changing the hardware of the wireless device, the data reception quality can be easily improved.
Operation of base station apparatus 201 and communication terminal apparatus 251 FIG. 6 is a sequence diagram showing communication procedures of base station apparatus 201 and communication terminal apparatus 251 according to Embodiment 1 of the present invention. In this figure, in step (hereinafter abbreviated as “ST”) 601, communication terminal apparatus 251 requests base station apparatus 201 to start communication, and base station apparatus 201 accepts this request.
In ST602, the base station apparatus 201 sends a request reception notification to the communication terminal apparatus 251 to notify that the communication start request has been received in ST601. At this time, the propagation model estimation symbol 101 shown in FIG. 1 is also transmitted.
In ST603, communication terminal apparatus 251 estimates channel variation using propagation model estimation symbol 101 transmitted in ST602, and base station apparatus 201 transmits based on the eigenvalue of the channel matrix shown in Equation (2). The modulation signal transmission method (X or Y) and modulation method are determined, and the determined transmission method and modulation method are requested to the base station apparatus 201. The base station apparatus 201 accepts this request.
In ST604, base station apparatus 201 determines the transmission method and modulation scheme based on the transmission method and modulation scheme requests transmitted from communication terminal apparatus 251, and transmits the determined transmission method and modulation scheme to transmission method notification symbol 102. And transmitted to the communication terminal device 251.
In ST605, base station apparatus 201 transmits radio wave propagation environment estimation symbol 103 and data symbol 104 to communication terminal apparatus 251 using the transmission method and modulation scheme determined in ST604 according to the frame configuration shown in FIG.
In ST606, during communication with base station apparatus 201, communication terminal apparatus 251 again determines only the modulation scheme based on radio wave propagation environment estimation symbol 103 and requests base station apparatus 201 for the determined modulation scheme. The base station apparatus 201 accepts this request.
In ST607, base station apparatus 201 determines again the modulation scheme based on the modulation scheme request transmitted from communication terminal apparatus 251 and notifies communication terminal apparatus 251 using transmission method notification symbol 102.
In ST608, base station apparatus 201 transmits radio wave propagation environment estimation symbol 103 and data symbol 104 to communication terminal apparatus 251 using the modulation scheme determined in ST607 according to the frame configuration shown in FIG.
In ST609, base station apparatus 201 notifies communication terminal apparatus 251 of the end of communication, and communication terminal apparatus 251 accepts this notification, and communication ends.
How to Change Transmission Method and Modulation Method FIG. 7 shows how the transmission method and modulation method applied by the base station apparatus 201 change with time in the series of communication procedures described above. Here, three modulation schemes, QPSK, 16QAM, and 64QAM are used. In this figure, it is assumed that communication between the base station apparatus 201 and the communication terminal apparatus 251 is started at time t0, and the transmission method X and QPSK are used from time t1 to t2. At time t2, only the modulation scheme is changed from QPSK to 16QAM, and transmission methods X and 16QAM are used at times t2 to t3. Furthermore, only the modulation scheme is changed again at time t3, and is changed from 16QAM to 64QAM. Transmission methods X and 64QAM are used from time t3 to t4, and communication ends at time t5.
Furthermore, when the base station apparatus 201 and the communication terminal apparatus 251 start communication at time t6, it is assumed that the transmission method Y and 64QAM are used at time t7 to t8. At time t8, only the modulation scheme is changed from 64QAM to 16QAM, and from time t8 to t9, the transmission method Y and the modulation scheme 16QAM are used. Furthermore, at time t9, only the modulation scheme is changed again, and is changed from 16QAM to QPSK. Transmission methods Y and QPSK are used from time t9 to t10, and communication ends at time t11.
The change of the modulation method at times t2, t3, t8, and t9 is a result of reflecting the modulation method request in ST606 shown in FIG. 6, and is changed to a modulation method according to the radio wave propagation environment.
Thus, the transmission method is determined at the start of communication, and the transmission method is not changed from the start of communication to the end of communication, and only the modulation method is changed.
How to Change Transmission Method and Modulation Method Other Than those Shown in FIG. 7 In addition to the transmission method and modulation method change shown in FIG. 7, the change method shown in FIG. 8 is also conceivable. Hereinafter, FIG. 8 will be described.
In FIG. 8, communication between the base station apparatus and the communication terminal apparatus is started at time t0, and transmission methods X and QPSK are used at times t1 to t2. At time t2, the transmission method X is changed to the transmission method Y, and the modulation method is changed from QPSK to 16QAM. At time t3, the transmission method Y is changed to the transmission method X, and the modulation method is changed from 16QAM to 64QAM. At time t4, only the transmission method is changed from X to Y, and at time t5, only the modulation scheme is changed from 64QAM to 16QAM. Communication ends at time t7.
In this way, it is conceivable to change both the transmission method and the modulation method during communication in accordance with the radio wave propagation environment. However, in such a change method, there are many combinations of transmission methods and modulation schemes (hereinafter simply referred to as “combinations”) that can be selected at the time of change, resulting in a complicated system. In other words, when one combination is selected from many combinations, it is necessary to estimate the radio wave propagation environment with high accuracy, and a combination that is not suitable for the radio wave propagation environment is selected unless high accuracy estimation is performed. The reception quality may be deteriorated.
Further, if the estimation accuracy of the radio wave propagation environment is improved, a combination suitable for the radio wave propagation environment can be selected. However, if the communication terminal device performs high-precision estimation, the radio wave propagation environment of the communication terminal device Since the stability of the system depends on the estimation accuracy, it is difficult to reduce the size and power consumption of the terminal device.
Therefore, as shown in FIG. 7, the base station apparatus and the communication terminal apparatus do not need to perform complicated communication procedures by changing only the modulation method without changing the transmission method during communication. In addition, the estimation accuracy of the radio wave propagation environment of the communication terminal device may be relaxed, the communication terminal device can be reduced in size and power consumption, and further, the processing load on the entire system can be prevented from increasing. Can do.
Incidentally, even if the transmission method is not changed during communication in this way, the propagation model does not change abruptly. In the transmission method Y, the data transmission speed is high, but the propagation model greatly affects the reception quality.
Modulation method combined with transmission method X or transmission method Y FIG. 9 shows the number of transmission bits per unit time according to a combination of transmission method X and transmission method Y and each modulation method. The transmission method Y can transmit twice the number of transmission bits of the transmission method X in each modulation scheme. Here, considering that the transmission method Y obtains the same transmission amount as the number of bits transmitted per unit time in 64QAM, the transmission method X needs to realize a combination with 4096QAM.
However, the reception quality when the transmission method X is 4096 QAM is worse than the reception quality when the transmission method Y is 64 QAM. For this reason, in order to improve both the reception quality and the transmission speed, it is not preferable to realize 4096 QAM by the transmission method X.
Consider the input / output characteristics of the amplifiers 4034 and 4044 in the base station apparatus 201 shown in FIG. 3 with reference to FIG. FIG. 10 is a diagram showing the input / output characteristics of the amplifier. In this figure, the horizontal axis is the input level, the vertical axis is the output level, the QPSK input range is A1, the 64QAM input range is A2, and the 4096QAM input range is A3. In addition, two different input / output characteristics are indicated by a solid line and a dotted line, respectively. An amplifier having input / output characteristics indicated by a solid line (hereinafter referred to as “amplifier P1”) has an input characteristic within a range of A2, and an amplifier having input / output characteristics indicated by a dotted line (hereinafter referred to as “amplifier P2”) is The input characteristics are in the range A3. If the modulation method does not change, the amplitude fluctuation range of the modulation signal, that is, the input range does not change regardless of the transmission method. In general, the larger the modulation multi-value number, the larger the amplitude fluctuation range of the modulation signal.
If the maximum modulation multi-level number is 64QAM in the transmission method Y, it is sufficient to use the amplifier P1. On the other hand, in order to realize the transmission rate by the combination of the transmission method Y and 64QAM by the transmission method X, it is necessary to use the 4096QAM modulation method, and in this case, the amplifier P2 must be used. Since the output characteristic of the amplifier P2 covers a wider range of output levels than the output characteristic of the amplifier P1, and the receiving apparatus processes a signal having a wide fluctuation range, the receiving apparatus must ensure the linearity of this signal, The circuit configuration becomes complicated.
Further, since the amplifier P2 consumes more power than the amplifier P1, the power efficiency is poor and the scale of the amplifier itself is large.
For these reasons, it is desirable that the maximum modulation multilevel number of the modulation scheme combined with the transmission method X or the transmission method Y is equal. Thereby, the power consumption of the transmission device can be suppressed, and the circuit configuration of the reception device can be simplified.
Maximum number of modulation multi-levels when the number of transmission antennas is four The number of transmission antennas is changed from two to four when the number of transmission antennas is four. When switching to transmitting each modulated signal from, the maximum value of the modulation multilevel number when the number of transmission antennas is four is smaller than the maximum value of the modulation multilevel number when the number of transmission antennas is two As a result, the receiving device does not have to process a signal with a wide fluctuation range, and thus the circuit configuration of the receiving device can be simplified.
The description of the modulation multi-level number described above is not limited to the single carrier scheme, but is the same when a multicarrier scheme including the OFDM scheme is used. Further, the spread spectrum method may or may not be used.
Thus, according to the present embodiment, each of the base station device and the communication terminal device includes a plurality of antennas, and the base station device transmits a plurality of modulated signals A and B including the same data to each other. A transmission method X for transmitting from each antenna, and a transmission method Y for transmitting a modulated signal A and a modulated signal B containing different data from each of a plurality of antennas are determined at the start of communication, By changing only the modulation method without changing the transmission method during communication, it is possible to improve both the data transmission speed and the transmission quality.
In this embodiment, the communication terminal apparatus estimates the propagation model using the propagation model estimation symbol transmitted from the base station apparatus at the start of communication and requests a transmission method. For example, the base station apparatus When communicating with other communication terminal devices, it receives radio wave propagation environment estimation symbols and data symbols transmitted by the base station device, estimates the propagation model using these symbols, and sets the transmission method at the start of communication. You may make it request. As a result, it is not necessary to insert the propagation model estimation symbol into the frame, so that the data transmission rate can be further increased.
In this embodiment, the communication terminal apparatus determines the transmission method and modulation method based on the eigenvalue and the received electric field strength. However, the present invention is not limited to this, and the bit error rate, packet loss rate, and The transmission method and modulation scheme may be determined based on at least one of the frame error rates and the received electric field strength. For example, when the reception field strength is strong but the bit error rate is high, the transmission method X is determined.
Although the first embodiment has been described on the assumption that the transmission method is not changed during communication, the present embodiment describes a case where the transmission method is changed during communication.
Since the configurations of the base station apparatus and the communication terminal apparatus in the present embodiment are the same as those in the first embodiment, FIGS. 3 and 4 are substituted, and detailed descriptions thereof are omitted.
FIG. 11 is a sequence diagram showing a communication procedure between the base station apparatus and the communication terminal apparatus according to Embodiment 2 of the present invention. However, since ST1101 to ST1108 in this figure are the same as ST601 to ST608 in FIG. 6 and ST1111 to ST1114 are the same as ST605 to ST608, detailed description thereof is omitted.
In ST1109, the communication terminal apparatus estimates channel variation using the propagation model estimation symbol transmitted from the base station apparatus, and based on the eigenvalue of the channel matrix shown in Equation (2) of Embodiment 1, A transmission method and a modulation method applied by the apparatus are determined during communication. The communication terminal apparatus requests the determined transmission method and modulation method from the base station apparatus. The base station apparatus accepts this request.
In ST1110, the base station apparatus determines the transmission method and modulation scheme based on the request transmitted from the communication terminal apparatus, and notifies the communication terminal apparatus of the determined combination using the transmission method notification symbol.
In ST1115, the base station apparatus notifies the communication terminal apparatus of the end of communication, and the communication terminal apparatus accepts this notification, and the communication ends.
FIG. 12 shows how the transmission method and modulation scheme applied by the base station apparatus change with time in such a series of communication procedures. Here, three modulation schemes, QPSK, 16QAM, and 64QAM are used. In this figure, it is assumed that communication between the base station apparatus and the communication terminal apparatus is started at time t0, and the transmission method X and QPSK are used from time t1 to t2. At time t2, only the modulation scheme is changed from QPSK to 16QAM, and transmission methods X and 16QAM are used at times t2 to t3. Furthermore, only the modulation scheme is changed again at time t3, and is changed from 16QAM to 64QAM. Transmission methods X and 64QAM are used from time t3 to t4.
At time t4, the communication terminal apparatus makes a request for changing the transmission method and modulation method, and makes a request to transmit method Y for the transmission method and 64QAM for the modulation method.
At time t5, the transmission method is changed during communication, the transmission method X is changed to the transmission method Y, and the modulation method is maintained at 64QAM. Transmission methods Y and 64QAM are used at times t5 to t6.
At time t6, only the modulation scheme is changed from 64QAM to 16QAM, and from time t6 to t7, the transmission method Y and the modulation scheme 16QAM are used. Furthermore, only the modulation scheme is changed again at time t7, and the mode is changed from 16QAM to QPSK. The transmission method Y and QPSK are used from time t7 to t8, and communication ends at time t9.
Thus, by changing the transmission method at predetermined time intervals even during communication, it is possible to cope with the change of the propagation path model. Note that the predetermined time interval is set such that the transmission method is not changed unnecessarily.
As described above, according to the present embodiment, when the communication time becomes long, the propagation model may change. Therefore, by changing the transmission method during communication, the propagation model changed during communication. Even in this case, it is possible to improve both the reception quality and the transmission speed.
In this embodiment, the propagation model is not estimated at the start of communication, but communication is forcibly started using transmission method X, and the propagation model is estimated using the radio wave propagation environment estimation symbol during communication. You may do it. As a result, it is not necessary to insert the propagation model estimation symbol into the frame, so that the data transmission rate can be further increased.
Further, although the spread spectrum communication method has been described in the first and second embodiments, the present invention is not limited to this. For example, the present invention can be similarly applied to a single carrier method or an OFDM method in which a spreading unit is deleted. .
In the first embodiment, the case of the spread spectrum communication method has been described, but in the third embodiment of the present invention, a case where the transmission method and the modulation method at the start of communication in the OFDM method are fixed will be described.
FIG. 13 is a diagram showing a frame configuration in Embodiment 3 of the present invention. However, the parts in FIG. 13 that are the same as those in FIG. 1 are denoted by the same reference numerals as those in FIG. As shown in FIG. 13, the OFDM scheme is a scheme in which symbols are arranged not only in the time direction but also in the frequency direction. Here, the number of carriers is four. Each carrier is arranged in the order of a transmission method notification symbol 102, a radio wave propagation environment estimation symbol 103, and a data symbol 104.
FIG. 13A is a diagram illustrating a frame configuration of the modulation signal A and the modulation signal B in the transmission method X. The carrier 1 is similar to the data symbol arrangement shown in FIG. 1A, and data symbols having such an arrangement are transmitted. For carrier 2 to carrier 4, data symbols to which the same codes as carrier 1 are applied are arranged, and the arranged data symbols are transmitted.
FIG. 13B is a diagram illustrating a frame configuration of the modulation signal A and the modulation signal B in the transmission method Y. The carrier 1 is similar to the data symbol arrangement shown in FIG. 1B, and the carrier 1 transmits data symbols having different information contents. As for carrier 2 to carrier 4, similarly to carrier 1, data symbols having different information contents are arranged, and the arranged data symbols are transmitted.
Although FIG. 13 shows the case of the OFDM system in which the data symbols are encoded in the time domain, the case of the OFDM system in which the data symbols are encoded in the frequency domain as shown in FIG. 14A shows the frame configuration of the transmission method X, and FIG. 14B shows the frame configuration of the transmission method Y. At this time, in the antenna 252 shown in FIG. 2, assuming that the received signal at carrier 1 and time t is R1 (t, 1) and the received signal at carrier 2 and time t is R1 (t, 2), the following equation holds. .
However, the carrier 3 and the carrier 4 may be similarly encoded.
FIG.15 is a block diagram showing a configuration of a base station apparatus according to Embodiment 3 of the present invention. However, the parts in FIG. 15 common to FIG. 3 are denoted by the same reference numerals as those in FIG. In this figure, a data sequence generation unit 1401 transmits a digital transmission signal of a modulation signal A corresponding to the frame configuration shown in FIG. 13 from a transmission digital signal according to an instruction (frame generation instruction signal S71) of a frame generation instruction unit 401. A transmission digital signal S73 of the signal S72 and the modulation signal B is generated. The generated transmission digital signal S72 of the modulation signal A is output from the data sequence generation unit 1401 to the transmission processing unit 1402, and the transmission digital signal S73 of the modulation signal B is output to the transmission processing unit 1405.
The transmission processing unit 1402 is for the transmission digital signal S72 of the modulated signal A output from the data sequence generation unit 1401, and the transmission processing unit 1405 is for the transmission digital signal S73 of the modulation signal B output from the data sequence generation unit 1401. Transmission processing is performed according to an instruction from each frame generation instruction unit 401. Since the internal configurations of the transmission processing unit 1402 and the transmission processing unit 1405 are the same, the configuration within the transmission processing unit 1402 will be described below.
The S / P conversion unit 1403 converts the serial signal S74 output from the modulation unit 4031 into a parallel signal S75, and outputs the converted parallel signal S75 to the IDFT unit 1404.
The IDFT unit 1404 performs an inverse discrete Fourier transform on the parallel signal S75 output from the S / P conversion unit 1403, thereby forming an OFDM signal S76. The radio signal 4033 Output to.
FIG. 16 is a block diagram showing a configuration of a communication terminal apparatus according to Embodiment 3 of the present invention. However, the parts in FIG. 16 that are the same as those in FIG. 4 are given the same reference numerals as those in FIG.
Radio section 501 performs predetermined radio processing (down-conversion, A / D conversion, etc.) on signal S90 received by antenna 252 and outputs radio-processed signal S91 to DFT section 1501 and received field strength estimation section 1509. To do.
The DFT unit 1501 performs discrete Fourier transform on the signal S91 output from the radio unit 501, and the converted signal S92 is converted into a first transmission path estimation unit 1502, a second transmission path estimation unit 1503, and a demodulation unit. 1507 is output.
First transmission path estimation section 1502 performs transmission path estimation of modulated signal A, that is, channel fluctuation estimation, using radio wave propagation environment estimation symbols of modulated signal A in signal S92 output from DFT section 1501. . The estimated transmission path information of modulated signal A is output from first transmission path estimation section 1502 to demodulation section 1507 as transmission path estimation signal S93.
Second transmission path estimation section 1503 estimates the transmission path (channel fluctuation) of modulated signal B using the radio wave propagation environment estimation symbol of modulated signal B out of signal S92 output from DFT section 1501. The estimated transmission path information of modulated signal B is output from second transmission path estimation section 1503 to demodulation section 1507 as transmission path estimation signal S94. The transmission path signals S93 and S94 output from the first transmission path estimator 1502 and the second transmission path estimator 1503 include transmission path information in the carriers 1 to 4.
The signal S95 received by the antenna 253 is processed in the radio unit 506, the DFT unit 1504, the first transmission path estimation unit 1505, and the second transmission path estimation unit 1506. Detailed description is omitted.
The demodulator 1507 uses the transmission path information S93, S94, S98, and S99 output from the first transmission path estimators 1502 and 1505 and the second transmission path estimators 1503 and 1506, from the DFT section 1501 and the DFT section 1504. The output signals S92 and S97 are demodulated. At this time, the demodulation unit 1507 acquires the transmission method (X or Y), modulation method, and error correction method of the signal from the transmission method notification symbols of the signals S92 and S97 output from the DFT unit 1501 and the DFT unit 1504. Then, the data symbol is demodulated according to the acquired contents, and the received digital signal S100 of the modulated signal A and the received digital signal S101 of the modulated signal B are obtained. Note that the demodulation is performed based on the relational expression of Expression (1) and Expression (2). The demodulated signal is output from the demodulator 1507 as received digital signals S100 and S101 and also output to the received quality estimator 1508.
The reception quality estimation unit 1508 calculates a bit error rate, a packet loss rate, a frame error rate, and the like based on the signals S100 and S101 output from the demodulation unit 1507, thereby estimating the reception quality. The estimation result is output as reception quality estimation signal S102 from reception quality estimation section 1508 to transmission method determination section 1510 and modulation scheme determination section 1511.
The received electric field strength estimation unit 1509 estimates the received electric field strength based on the signals S91 and S96 output from the radio unit 501 and the radio unit 506, and uses the estimation result as a received electric field strength estimation signal S103. It outputs to the modulation system determination part 1511.
The transmission method determination unit 1510 requests the base station apparatus based on the reception quality estimation signal S102 output from the reception quality estimation unit 1508 and the reception field strength estimation signal S103 output from the reception field strength estimation unit 1509. The transmission method X or the transmission method Y is determined at a predetermined timing to be described later, and is output as transmission method request information. For example, when the reception field strength is secured but the reception quality is not secured, the transmission method X is determined. When the reception quality is sufficiently secured with respect to the reception field strength, the transmission method Y is determined. To do.
Modulation scheme determination section 1511 requests the base station apparatus based on reception quality estimation signal S102 output from reception quality estimation section 1508 and reception field strength estimation signal S103 output from reception field strength estimation section 1509. The modulation method is determined at a predetermined timing described later. The determined method is output from the communication terminal apparatus as modulation method request information. The modulation scheme request information and the transmission method request information are transmitted to the base station apparatus.
Next, operations of the base station apparatus and communication terminal apparatus having the above-described configurations will be described. FIG. 17 is a sequence diagram showing a communication procedure of the base station apparatus and communication terminal apparatus according to Embodiment 3 of the present invention. In this figure, in ST1601, the communication terminal apparatus requests the base station apparatus to start communication, and the base station apparatus accepts this request.
In ST1602, the base station apparatus accepts the communication start request made in ST1601, and transmits a radio wave propagation environment estimation symbol and a data symbol to the communication terminal apparatus using the transmission method X and the modulation method as BPSK. Thereby, the reception quality of the data symbol immediately after the start of communication can be improved, and high demodulation accuracy can be realized in the communication terminal apparatus.
Hereinafter, ST1603 to ST1609 correspond to ST603 to ST609 in FIG.
FIG. 18 shows how the transmission method and modulation scheme applied by the base station apparatus change with time in such a series of communication procedures. Here, three modulation schemes, QPSK, 16QAM, and 64QAM are used. In this figure, communication between the base station apparatus and the communication terminal apparatus is started at time t0, and transmission methods X and BPSK are forcibly used from time t1 to t3. At time t2, there is a request for changing the transmission method and modulation method from the communication terminal apparatus. At time t3, only the modulation method is changed from BPSK to 16QAM, and from time t3 to t5, transmission methods X and 16QAM are used. Furthermore, at time t4, there is a request for changing only the modulation scheme from the communication terminal apparatus, and at time t5, only the modulation scheme is changed again, changing from 16QAM to 64QAM. Transmission methods X and 64QAM are used from time t5 to t6, and communication ends at time t7.
Furthermore, when the base station apparatus and the communication terminal apparatus start communication at time t8, transmission methods X and BPSK are forcibly used from time t9 to t11. At time t10, there is a request to change the transmission method and modulation method from the communication terminal apparatus, at time t11 the transmission method is changed from X to Y, the modulation method is changed from BPSK to 16QAM, and from time t11 to t13, the transmission method Y and 16QAM is used. Furthermore, at time t12, there is a request for changing only the modulation method from the communication terminal apparatus, and at time t13, only the modulation method is changed again, and 16QAM is changed to QPSK. Transmission methods Y and QPSK are used from time t13 to t14, and communication ends at time t15.
In this way, the base station apparatus simplifies the communication procedure from the start of communication to data transmission by forcibly using the transmission method X and BPSK, which have high error tolerance and high reception quality, at the start of communication. The communication terminal device can reliably demodulate data immediately after the start of communication.
As described above, according to the present embodiment, each of the base station apparatus and the communication terminal apparatus includes a plurality of antennas, and the first modulation signal and the second modulation signal including the same data are transmitted to the plurality of antennas. Any one of the first transmission method for transmitting from the first transmission method and the second transmission method for transmitting the third modulation signal and the fourth modulation signal containing different data from the plurality of antennas, respectively. Among these, by forcibly applying a transmission method and a modulation method with strong error tolerance at the start of communication, the communication procedure from the start of communication to data transmission can be simplified. Data can be reliably demodulated. Also in the OFDM system, it is possible to improve both the data transmission speed and the transmission quality.
In this embodiment, the case where the transmission method and the modulation method are fixed at the start of communication has been described. However, only the transmission method may be fixed and the modulation method may be selectable.
In this embodiment, the transmission method and the modulation method are selected based on the reception quality such as the bit error rate, the packet loss rate, and the frame error rate. However, the channel matrix described in the first embodiment You may perform based on an eigenvalue.
In the third embodiment, the case where the transmission method is changed only once during communication without selecting the transmission method and modulation method at the start of communication has been described. However, in the fourth embodiment of the present invention, a predetermined value is set during communication. A case where the transmission method is changed at a time interval of will be described.
Since the configurations of the base station apparatus and the communication terminal apparatus in the present embodiment are the same as those in Embodiment 3, FIGS. 15 and 16 are used instead, and detailed descriptions thereof are omitted.
FIG. 19 is a sequence diagram showing a communication procedure between the base station apparatus and the communication terminal apparatus according to Embodiment 4 of the present invention. However, only ST1906 and ST1907 in this figure are different from ST1606 and ST1607 in FIG. 17, and other procedures are the same as those in FIG. 17, so only ST1906 and ST1907 will be described.
In ST1906, the communication terminal apparatus determines a transmission method and a modulation scheme applied by the base station apparatus after a predetermined time has elapsed from the start of communication, and requests the determined contents from the base station apparatus. The base station apparatus accepts this request.
In ST1907, the base station apparatus determines the transmission method and modulation scheme based on the request transmitted from the communication terminal apparatus, and notifies the communication terminal apparatus of the determined transmission method and modulation scheme using the transmission method notification symbol.
FIG. 20 shows how the transmission method and modulation scheme applied by the base station apparatus change with time in such a series of communication procedures. Here, three modulation schemes, QPSK, 16QAM, and 64QAM are used. In this figure, communication between the base station apparatus and the communication terminal apparatus is started at time t0, and transmission methods X and BPSK are forcibly used from time t1 to t3. At time t2, the communication terminal apparatus makes a request to change the transmission method from X to Y and the modulation method from BPSK to 16QAM, and at time t3 to t5, transmission methods Y and 16QAM are used. Further, at time t4, the communication terminal apparatus requests to change only the modulation scheme from 16QAM to 64QAM, and transmission methods Y and 64QAM are used from time t5 to t6.
At time t6, the communication terminal apparatus makes a request for changing the transmission method and the modulation method, and requests Y to X for the transmission method and 64QAM for the modulation method.
At time t7, the transmission method is changed during communication, and transmission methods X and 64QAM are used from time t7 to t9.
At time t8, the communication terminal apparatus makes a request to change only the modulation scheme from 64QAM to 16QAM, and from time t9 to t11, transmission methods X and 16QAM are used. Further, at time t10, the communication terminal apparatus again requests to change only the modulation scheme from 16QAM to QPSK, transmission method X and QPSK are used from time t11 to t12, and communication ends at time t13.
In the third and fourth embodiments, the OFDM scheme has been described. However, the present invention is not limited to this, and for example, a spreader may be added and the OFDM scheme using the spread spectrum scheme may be similarly implemented. it can. Further, the same can be applied to a multicarrier system other than the OFDM system.
In Embodiments 1 to 4, a transmission method X uses a space-time block code or a space-time trellis code, and transmission method Y uses a plurality of different data as shown in equation (2). Although the case of using the simultaneous transmission method has been described, in Embodiment 5 of the present invention, cyclic delay diversity (CDD) is used as a transmission method X different from the space-time block code and the space-time trellis code. A transmission method for obtaining a diversity gain such as the above will be described.
Hereinafter, CDD will be described with reference to FIG. FIG. 21 shows a frame configuration when CDD is performed using 12 symbols. In this figure, transmission signal A and transmission signal B are frames transmitted from different antennas. For example, transmission signal A is transmitted from antenna 202 shown in FIG. 2, and transmission signal B is transmitted from antenna 203 shown in FIG. Is done.
The transmission signal A is composed of symbols Sy1, Sy2,..., Sy11, Sy12 used for CDD in order, and each symbol is transmitted at times i + 1, i + 2,.
The transmission signal B is cyclically shifted by 6 symbols in the arrangement of symbols of the transmission signal A, and is composed of Sy7, Sy8,..., Sy5, Sy6 in order, and each symbol is time i + 1, i + 2,. Sent by.
By adopting such a frame configuration, the receiving apparatus can obtain a diversity gain in the equalizer, so that the reception quality of data is improved. Therefore, CDD has a lower transmission speed than transmission method Y, but it can be said that reception quality is good. Therefore, Embodiments 1 to 4 can be implemented using CDD as a transmission method similar to the space-time block code and space-time trellis code.
In the fifth embodiment, a scheme using CDD different from the space-time block code and the space-time trellis code has been described as the transmission method X. However, in the sixth embodiment of the present invention, MIMO (Multiple-Input Multiplex) is further used. -Output) The case where the communication mode called the eigenmode in the system is the transmission method X will be described.
In the MIMO system, when channel state information (channel state information) that is an estimation result of a propagation channel between both stations is known not only at the receiving station but also at the transmitting station, the transmitting station transmits a transmission channel signature vector (channel signature). vector) is transmitted from the transmitting array antenna to the receiving station, and the receiving station uses the received channel signature vector associated with the transmitting channel signature vector from the received signal of the receiving array antenna. Thus, a communication method for detecting and demodulating a transmission signal can be realized.
In this MIMO system, there is an eigenmode (eigenmode) using a singular vector or eigenvector of a channel matrix as a communication mode for multiplex transmission of signals constituting a plurality of channels in a communication space ( For example, the document “Eigenbeam Space Division Multiplexing (E-SDM) System in MIMO Channel” is described in IEICE, IEICE RCS2002-53, May 2002).
This eigenmode is a method of using these singular vectors and eigenvectors as channel signature vectors. Here, the channel matrix is a matrix whose elements are complex channel coefficients of combinations of all or part of the antenna elements of the transmitting array antenna and the antenna elements of the receiving array antenna.
FIG. 22 shows a configuration of a channel multiplexing communication system using a beam space mode typified by an eigenmode in a MIMO system. First, the base station apparatus 2300 will be described. Multiplex frame generation section 2301 generates a plurality of transmission frames in order to map the input transmission data sequence to the multiplexed channel, and outputs the generated plurality of transmission frames to vector multiplexing section 2303.
Based on channel state information between base station apparatus 2300 and communication terminal apparatus 2310, transmission channel analysis section 2302 calculates a plurality of transmission channel signature vectors to form a multiplexed channel. The transmission channel analysis unit 2302 outputs the calculated transmission channel signature vector to the vector multiplexing unit 2303.
The vector multiplexing unit 2303 multiplies each transmission frame output from the multiplex frame generation unit 2301 by the separate channel signature vector output from the transmission channel analysis unit 2302 and combines them. Vector multiplexing section 2303 transmits the combined signal to communication terminal apparatus 2310 via transmission array antenna 2304.
Next, the communication terminal device 2310 will be described. Based on the channel state information between base station apparatus 2300 and communication terminal apparatus 2310, reception channel analysis section 2311 calculates a plurality of reception channel signature vectors in order to separate the multiplexed transmission signals. The reception channel analysis unit 2311 outputs the calculated plurality of reception channel signature vectors to the multiplexed signal separation unit 2313.
The multiple signal demultiplexing unit 2313 generates a plurality of reception frames by multiplying a signal (reception signal) received via the reception array antenna 2312 by each channel signature vector output from the reception channel analysis unit 2311. The multiplexed signal demultiplexing unit 2313 outputs the generated plurality of received frames to the multiframe combining unit 2314.
Multiframe combining section 2314 combines the signals mapped to the multiplexed channels to obtain a received data sequence.
Here, it is assumed that base station apparatus 2300 has a function of switching between transmission method X and transmission method Y, and the configuration of the transmission apparatus included in base station apparatus 2300 is shown in FIG. 23 identical to those in FIG. 3 are assigned the same reference numerals as in FIG. 3, and detailed descriptions thereof are omitted.
In FIG. 23, when the transmission method request information indicates the transmission method X, that is, the eigenmode, the signal processing unit 2401 performs the above-described signal processing using the channel state information from the communication partner (communication terminal device 2310). . On the other hand, when the transmission method request information indicates the transmission method Y, that is, the transmission method as shown in Expression (2), the signal processing unit 2401 outputs the signal S5 as the signal S110 without performing signal processing, S9 is output as a signal S111.
In this way, by using the eigenmode, the reception apparatus can obtain good reception quality in a reception environment where the direct wave is dominant. Therefore, Embodiments 1 to 4 can be implemented even using eigenmode as a transmission method similar to space-time block codes and space-time trellis codes.
In Embodiment 7 of the present invention, a method of switching between the transmission method using the eigenmode described in Embodiment 6 and the transmission method as shown in Equation (2) will be described.
Generally known communication forms include a point-to-multi point type communication form shown in FIG. 24 (a), a point-to-point type communication form shown in FIG. 24 (b), and FIG. There is a point-to-point type communication mode shown in c).
In FIG. 24A, the base station performs communication simultaneously with a plurality of communication terminals, and in FIG. 24B, two communication terminals communicate with each other. Similarly, FIG. 24C shows a state where the base station and one communication terminal are communicating.
By the way, the following can be considered as points to be improved in the eigenmode. First, since it is necessary to acquire channel state information from a communication partner, when communicating with a plurality of communication partners, it is necessary to acquire channel state information from the plurality of communication partners, respectively. The transmission efficiency will decrease. Second, in order to form eigen beams for a plurality of communication partners, it is necessary to perform complicated signal processing.
For these reasons, it is not preferable to use the eigenmode in the point-to-multi point communication mode in which a plurality of communication partners exist. Therefore, the eigenmode is preferably used in a point-to-point type communication mode. That is, by using the eigenmode in the point-to-point communication mode, the transmission method (transmission method Y) as shown in the equation (2) is used without considering the points to be improved in the eigenmode. As a result, the transmission speed can be increased and the reception quality can be improved. However, in order to switch the transmission method according to the number of communication partners, it is necessary to transmit the number of communication partners with which the local station is communicating to the communication partner, so the symbol of “number of communication partners” is added to the transmission frame. Must be inserted.
After the transmission method is set, as described in the first to fourth embodiments, the data transmission rate and the transmission quality can be compatible by changing the modulation method. Note that the transmission method is set using the method described in the first to fourth embodiments.
Here, a further effect when the transmission method is switched according to the number of communication partners as described above will be described with reference to FIG. As shown in FIG. 25, in the cell of the base station communicating with the two communication terminals A and B, the other two communication terminals C and D can communicate in the eigenmode. This is because the transmission method using the eigenmode forms an eigenbeam directed toward the communication partner, and thus does not interfere with the base station and the other communication terminals A and B. However, as shown in FIG. 26, the communication terminals C and D that are performing communication using the eigenmode are connected to the communication station (the base station and the communication terminals A and B in FIG. 26) that are performing the transmission method Y. In the case of giving interference, for example, an interrupt mode for forcibly terminating communication using the eigenmode (eigenbeam communication) may be set in the transmission signal of the base station.
Next, a communication procedure between the base station apparatus and the communication terminal apparatus will be described. FIG. 27 is a sequence diagram illustrating a communication procedure between the base station apparatus and the communication terminal apparatus. In this figure, in ST2801, the communication terminal apparatus requests the base station apparatus to start communication, and requests a transmission method (transmission method using an eigenmode or a transmission method as shown in Equation (2)). The base station apparatus accepts this request. The transmission method requested in the communication terminal apparatus is a transmission method using the eigenmode, particularly when the communication terminal apparatus desires one-to-one (point-to-point, peer-to-peer) communication with the communication partner. The method.
And a base station apparatus switches a transmission method according to the present communication form. That is, the transmission method is switched depending on whether or not one-to-many communication is being performed. Specifically, when point-to-multipoint communication is performed, a transmission method as shown in Expression (2) is determined, and communication with only the communication terminal device that has received the request (point) -To-point type), the transmission method using the eigenmode is determined, and in ST2802, the determined transmission method is notified to the communication terminal apparatus.
In ST2803, the communication terminal apparatus requests a modulation scheme suitable for the determined transmission method, and the base station apparatus accepts this request.
In ST2804, the base station apparatus determines the modulation scheme based on the transmitted modulation scheme request information, and notifies the communication terminal apparatus of the determined modulation scheme.
In ST2805, the base station apparatus transmits data to the communication terminal apparatus using the transmission method notified in ST2802 and the modulation method notified in ST2804.
In ST2806, the communication terminal apparatus transmits data to the base station apparatus using the transmission method and modulation method used for data communication in ST2805.
In ST2807, the base station apparatus notifies the communication terminal apparatus of the end of communication, the communication terminal apparatus accepts this notification, and the communication ends.
As described above, according to the present embodiment, the transmission method using the eigenmode that is the transmission method X in the one-to-one communication, and the transmission method as shown in the expression (2) that is the transmission method Y in the one-to-many communication. By doing so, it is possible to improve both the data transmission speed and the transmission quality as a system.
In each of the above-described embodiments, the communication terminal device has been described as an example of a reception device, and the base station device has been described as an example of a transmission device. However, the present invention is not limited to this, and the communication terminal device is a transmission device. The base station device may function as a receiving device. Further, in each of the above-described embodiments, the receiving device determines the transmission method and the modulation method. However, the present invention is not limited to this, and the transmitting device notifies the eigenvalue and the received electric field strength from the receiving device. The transmission method and the modulation method may be determined.
In each of the above-described embodiments, SyA * which is a complex conjugate of SyA and SyA is transmitted as a data symbol to be transmitted by transmission method X. However, the present invention is not limited to this, and for example, SyA is repeated. You may send it.
Further, in each of the above-described embodiments, the number of transmission antennas and the number of reception antennas are each described as two. However, the present invention is not limited to this, and the number of transmission antennas and the number of reception antennas may be three or more. . At this time, it is needless to say that the number of transmission processing units (for example, a modulation unit, a spreading unit, a radio unit, an amplifier, etc.) in front of the antenna of the transmission device in the base station device is a number corresponding to the number of transmission antennas. The same applies to the receiving device in the communication terminal device. Moreover, you may select arbitrary some antennas from three or more antennas.
For example, the number of transmission antennas may be four, and four systems of modulated signals may be transmitted from the four antennas. At this time, assuming that the transmission method A uses a space-time code and the transmission method B does not use a space-time code, the transmission method X and the transmission method Y when the number of transmission antennas is two, the transmission method A, and the transmission method Any transmission method of B can be selected arbitrarily. Even if the maximum value of the modulation multilevel number of the transmission method X and the transmission method Y is larger than the maximum value of the modulation multilevel number of the transmission method A and the transmission method B, the circuit configuration of the communication terminal apparatus is complicated. Has no effect.
A plurality of antennas may be handled as a set of antennas. That is, the antenna 202 and the antenna 203 may each be a plurality of antennas.
The transmission method and the transmission apparatus according to the present invention have the effect of improving both the data transmission rate and the reception quality, and can be applied to a base station apparatus and a communication terminal apparatus having a plurality of antennas.
The figure which shows the flame | frame structure which the base station apparatus in Embodiment 1 of this invention transmits. Schematic diagram showing a communication system according to Embodiment 1 of the present invention. The block diagram which shows the structure of the transmitter in the base station apparatus which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the receiver in the communication terminal device which concerns on Embodiment 1 of this invention. The figure for demonstrating the method to judge whether a received signal is a signal which arrived by the direct wave. The sequence diagram which shows the communication procedure of the base station apparatus and communication terminal device which concern on Embodiment 1 of this invention The figure which shows the mode of the change with the time transition of the transmission method and the modulation system which the base station apparatus in Embodiment 1 applies The figure for demonstrating how to change the transmission method and a modulation system The figure which shows the transmission bit number per unit time by the combination of the transmission method X and the transmission method Y, and each modulation system Diagram showing input / output characteristics of amplifier The sequence diagram which shows the communication procedure of the base station apparatus and communication terminal device which concern on Embodiment 2 of this invention The figure which shows the mode of the change with the time transition of the transmission method and the modulation system which the base station apparatus in Embodiment 2 applies The figure which shows the flame | frame structure in Embodiment 3 of this invention. The figure which shows the flame | frame structure in Embodiment 3 of this invention. The block diagram which shows the structure of the base station apparatus which concerns on Embodiment 3 of this invention. The block diagram which shows the structure of the communication terminal device which concerns on Embodiment 3 of this invention. The sequence diagram which shows the communication procedure of the base station apparatus and communication terminal apparatus which concern on Embodiment 3 of this invention The figure which shows the mode of the change accompanying the time transition of the transmission method and the modulation system which the base station apparatus in Embodiment 3 applies The sequence diagram which shows the communication procedure of the base station apparatus and communication terminal device which concern on Embodiment 4 of this invention The figure which shows the mode of the change with the time transition of the transmission method and the modulation system which the base station apparatus in Embodiment 4 applies The figure which shows the flame | frame structure when performing CDD using 12 symbols. The figure which shows the structure of the channel multiplexing communication system using the beam space mode represented by the eigenmode in a MIMO system. The figure which shows the structure of the transmitter which the base station apparatus which concerns on Embodiment 6 of this invention has. Diagram showing communication mode Diagram for explaining the effect when switching the transmission method according to the number of communication partners Diagram for explaining the effect when switching the transmission method according to the number of communication partners Sequence diagram showing communication procedure between base station apparatus and communication terminal apparatus Diagram showing conventional frame structure Diagram showing a conventional communication system
DESCRIPTION OF SYMBOLS 101 Propagation model estimation symbol 102 Transmission method notification symbol 103 Radio wave propagation environment estimation symbol 104 Data symbol 201, 2300 Base station apparatus 202, 203, 252, 253 Antenna 251, 2310 Communication terminal apparatus 401 Frame generation instruction section 402, 1401 Data sequence generation Unit 403, 404, 1402, 1405 transmission processing unit 4031, 4041 modulation unit 4032, 4042 spreading unit 4033, 4043, 501, 506 radio unit 4034, 4044 amplifier 502, 507 despreading unit 503 frame synchronization unit 504, 508, 1502, 1505 1st transmission line estimation part 505,509,1503,1506 2nd transmission line estimation part 510,1507 Demodulation part 511,1509 Reception electric field strength estimation part 512 Eigenvalue calculation part 513,151 Modulation method determination unit 514, 1510 Transmission method determination unit 1403, 1406 S / P conversion unit 1404, 1407 IDFT unit 1501, 1504 DFT unit 1508 Reception quality estimation unit 2301 Multiple frame generation unit 2302 Transmission channel analysis unit 2303 Vector multiplexing unit 2304 Transmission array antenna 2311 Reception channel analysis unit 2312 Reception array antenna 2313 Multiplex signal separation unit 2314 Multiframe synthesis unit 2401 Signal processing unit
A transmission apparatus including a plurality of antennas transmits a plurality of signals including the same data from the plurality of antennas, respectively, and a plurality of signals including different data from the plurality of antennas. A transmission method determining step for determining any of the second transmission methods for transmitting each;
A modulation method determining step for determining any of a plurality of modulation methods;
A control step for controlling the transmission method determination step to perform the determination processing at a time interval longer than the modulation scheme determination step performs the determination processing ;
A transmission method comprising:
The transmission method according to claim 1, wherein the transmission method determination step uses cyclic delay diversity as the first transmission method.
A transmission method of a transmission device having a plurality of antennas,
This is different from the first transmission method in which a plurality of signals including the same data are transmitted from a plurality of antennas using an eigenmode that uses a singular or eigenvector of a channel matrix as a channel signature vector in a MIMO system. A second transmission method for transmitting a plurality of signals including data from a plurality of antennas, respectively, and a transmission method determination step for switching according to the number of communication partners,
In accordance with the communication procedure with the communication partner, the control method for controlling whether to perform the determination process in the transmission method determination step and / or the modulation scheme determination step,
A plurality of vectors used for multiplying and combining multiple signals are generated based on information transmitted from a communication partner, and a plurality of transmission signals are generated by combining the plurality of signals using the plurality of vectors. A first transmission method for transmitting the plurality of transmission signals from the plurality of antennas; and a second method for transmitting the plurality of transmission signals from the plurality of antennas to spatially multiplex the plurality of transmission signals. A transmission method determination step of determining any of the transmission methods according to the number of communication partners,
A transmission step of transmitting the plurality of transmission signals from the plurality of antennas using the determined transmission method;
5. The transmission method according to claim 3, further comprising a modulation scheme determination step of determining any one of a plurality of modulation schemes as a modulation scheme used for the first transmission method and the second transmission method. .
Multiple transmit antennas,
A first transmission method for transmitting a plurality of signals including the same data from a plurality of antennas; and a second transmission method for transmitting a plurality of signals including different data from the plurality of antennas. A transmission method determining means for determining one of them;
Modulation scheme determining means for determining any one of a plurality of modulation schemes;
Control means for controlling the transmission method determination means to perform the determination process at a longer time interval than the modulation scheme determination means performs the determination process;
Transmission processing means for transmitting signals to which the determined transmission method and modulation scheme are applied from the plurality of antennas;
The transmission apparatus according to claim 6, wherein the transmission method determination unit uses cyclic delay diversity as the first transmission method.
A first transmission method for transmitting a plurality of first transmission signals obtained by combining a plurality of signals from a plurality of antennas, and a second transmission signal from each of the plurality of antennas. A second transmission method that spatially multiplexes a plurality of two transmission signals, and a transmission method determination unit that determines any one of them according to the number of communication partners;
Channel analysis means for generating a plurality of vectors used for multiplication and synthesis of the plurality of signals based on information transmitted from a communication partner;
Multiplexing means for generating the first plurality of transmission signals by combining the plurality of signals using the plurality of vectors output from the channel analysis means;
When the transmission method determination means determines the first transmission method, the first plurality of transmission signals output from the multiplexing means are transmitted from the plurality of antennas, respectively, and the transmission method determination means Transmission processing means for transmitting the second plurality of transmission signals from the plurality of antennas, respectively, when the second transmission method is determined;
This is different from the first transmission method in which a plurality of signals including the same data are transmitted from a plurality of antennas using an eigenmode that uses a singular or eigenvector of a channel matrix as a channel signature vector in a MIMO system. A second transmission method for transmitting a plurality of signals including data from a plurality of antennas, respectively, and a transmission method determining means for switching according to the number of communication partners,
Control means for controlling whether or not to perform determination processing in the transmission method determination means and the modulation method determination means in accordance with a communication procedure with a communication partner;
Transmission processing means for transmitting the determined transmission method or a signal to which a modulation scheme is applied from the plurality of antennas;
JP2004190418A 2003-06-30 2004-06-28 Transmission method and transmission apparatus Active JP4536435B2 (en)
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US10/562,555 US8000405B2 (en) 2003-06-30 2004-06-30 Transmission method, transmission apparatus and communication system
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