JP2006311286A - Transmitter, receiver, transmitting method, receiving method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter and a receiver for embedding MLI (modulation level information) information and transmission data in a pilot signal and transmitting the pilot signal. <P>SOLUTION: The transmitter calculates coherence bandwidth from root mean square of delay threads of a pilot symbol transmitted from the receiver, divides a sub-carrier into blocks by the coherence bandwidth, determines a modulation level for each block on the basis of feedback information transmitted from the receiver, adaptively modulates each sub-carrier and differentially modulates the modulation level information to be allocated to sub-carriers being a portion of the pilot signal. A portion of the transmission data is differentially modulated and embedded in the remaining sub-carriers of the pilot signal. The receiver compares the received sub-carrier signal with a replica obtained by modulating a signal obtained by demodulation once more at the allocated modulation level, evaluates a channel response and transmits the sub-carrier signal as feedback information together with the pilot symbol. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission apparatus, a reception apparatus, a transmission method, a reception method, which perform transmission by embedding MLI information and transmission data in a pilot signal in communication in which differential modulation / demodulation is performed using a pilot signal and adaptive modulation / demodulation is performed for each subcarrier. The present invention relates to a program that realizes these on software radio.

  In recent years, the importance of mobile radio communication has been increasing, and it is desired to achieve a high-speed radio access protocol that supports a data rate of 100 Mbps. In such a radio communication environment, signals are faded. In general, its quality is affected by

  For example, if the signal amplification rate changes significantly due to fading, or if inter-symbol interference (ISI) occurs, the bit error rate (BER) increases, and in some cases communication is impossible. It becomes.

  On the other hand, in OFDM communication, the influence of such a multipath channel can be efficiently reduced by inserting a guard interval.

  In general, which modulation scheme is selected is determined by a trade-off between spectral efficiency and BER, and in order to obtain a required BER, it is necessary to select a modulation scheme that can achieve the highest spectral efficiency. As described above, there is an expectation for an adaptive modulation scheme (AMS) that appropriately selects an efficient modulation scheme during communication.

  In OFDM communication using AMS, each subcarrier is controlled by a parameter called a modulation level, which selects an appropriate modulation scheme.

Also, the MLI is sent from the transmission side to the reception side together with the modulated transmission data, and the reception side selects an appropriate demodulation scheme for each subcarrier using the MLI and demodulates the signal. In general, the MLI is transmitted as part of a data symbol. The related art of the present invention is described in the following documents.
T.Nakanishi, S.Sampei and N.Morinaga, Variable coding rate OFDM transmission on one-cell reuse TDMA systems, IEICE Technical Report, March 2004 C. Ahn and I. Sasase, The effects of modulation combination, target BER, Doppler frequency, and adaptive interval on the performance of adaptive OFDM in broadband mobile channel, IEEE Trans.Computer, vol.48, no.1, pp.167 -174, February 2002

  [Non-Patent Document 1] describes a technique for reducing the amount of MLI transmission by grouping adjacent subcarriers into the same modulation level in order to prevent a decrease in throughput when MLI is transmitted as part of a data symbol. Is disclosed.

  [Non-Patent Document 2] reports how the performance of a combination of various modulation schemes in OFDM communication changes depending on BER, Doppler frequency, switching interval of adaptive modulation, and the like.

  Therefore, when an adaptive modulation technique is used, a technique for improving throughput while appropriately using MLI and FBI is strongly demanded.

  The present invention has been made to solve the above-described problems. In communication in which differential modulation / demodulation is performed using a pilot signal and adaptive modulation / demodulation is performed for each subcarrier, MLI information and transmission data are embedded in the pilot signal. It is an object of the present invention to provide a transmission device, a reception device, a transmission method, a reception method, and a program that realizes these using software radio.

  In order to achieve the above object, the following invention is disclosed in accordance with the principle of the present invention.

  A transmission apparatus according to a first aspect of the present invention includes an uplink reception unit, a root mean square calculation unit, a coherence bandwidth calculation unit, a modulation level determination unit, a transmission side serial / parallel conversion unit, an adaptive modulation unit, a differential modulation unit, A multiplex part, a transmission side parallel / serial conversion part, and a downlink transmission part are provided and configured as follows.

  Here, the uplink receiving unit receives an uplink signal transmitted from the receiving device.

  On the other hand, the mean square calculation unit calculates the mean square of the delay spread based on the pilot symbols included in the received uplink signal.

  The coherence bandwidth calculator calculates a coherence bandwidth that is inversely proportional to the calculated mean square of the delay spread.

  Further, the modulation level determination unit divides a plurality of subcarriers into a plurality of blocks for each calculated coherence bandwidth, and determines a modulation level for each block based on feedback information included in the received uplink radio signal. To do.

  On the other hand, the transmission side serial-parallel conversion unit serial-parallel converts a part of the transmission data and acquires a signal for each of the plurality of subcarriers.

  Further, the adaptive modulation unit adaptively modulates the signal acquired for each of the plurality of subcarriers by the transmission side serial-parallel conversion unit with the modulation level assigned to the block to which the subcarrier for the signal belongs.

  Then, the differential modulation section differentially modulates the remainder of the transmission data and the modulation level determined for each block into the pilot signals of the plurality of subcarriers.

  On the other hand, the multiplex unit multiplexes the adaptively modulated signal and the differentially modulated signal for each of the plurality of subcarriers.

  Further, the transmission side parallel / serial conversion unit performs parallel / serial conversion on the multiplexed signals to obtain a downlink signal.

  Then, the downlink transmission unit transmits the acquired downlink signal.

  A receiving apparatus according to another aspect of the present invention includes a downlink receiving unit, a receiving side serial / parallel converting unit, a demultiplexing unit, a differential demodulating unit, an adaptive demodulating unit, a receiving side parallel / serial converting unit, an output unit, and feedback information. A generation unit and an uplink transmission unit are provided and configured as follows.

  Here, the downlink reception unit receives the downlink signal transmitted from the transmission device.

  On the other hand, the receiving side serial / parallel conversion unit performs serial / parallel conversion on the received downlink signal to obtain a signal for each of the plurality of subcarriers.

  Further, the demultiplexing unit demultiplexes each of the plurality of signals subjected to serial / parallel conversion, and divides it into a pilot signal portion and a data signal portion.

  Then, the differential demodulator differentially demodulates the demultiplexed pilot signal portion to obtain the remaining transmission data and the modulation level determined for each block.

  On the other hand, the adaptive demodulation unit adaptively demodulates the data signal portion demultiplexed for each of the plurality of subcarriers with the modulation level acquired for the block to which the subcarrier for the data signal portion belongs.

  Further, the receiving side parallel-serial conversion unit performs parallel-serial conversion on the plurality of adaptively demodulated signals to obtain a part of the transmission data.

  The output unit combines the part of the transmission data acquired by the parallel-serial conversion unit with the remainder of the transmission data acquired by the differential demodulation unit, and outputs the transmission data.

  On the other hand, the feedback information generation unit compares the data signal portion demultiplexed with respect to each of the plurality of subcarriers with the adaptively demodulated signal, performs channel evaluation, and generates feedback information.

  Further, the uplink transmission unit transmits an uplink signal including pilot symbols and generated feedback information to the transmission apparatus.

  A transmission method according to another aspect of the present invention includes an uplink reception step, a root mean square calculation step, a coherence bandwidth calculation step, a modulation level determination step, a transmission side serial / parallel conversion step, an adaptive modulation step, a differential modulation step, a multi A plex process, a transmission side parallel / serial conversion process, and a downlink transmission process are provided and configured as follows.

  Here, in the uplink reception step, an uplink signal transmitted from the receiving device is received.

  On the other hand, in the mean square calculation step, the mean square of delay spread is calculated based on the pilot symbols included in the received uplink signal.

  In the coherence bandwidth calculation step, a coherence bandwidth that is inversely proportional to the calculated mean square of the delay spread is calculated.

  Further, in the modulation level determination step, a plurality of subcarriers are divided into a plurality of blocks for each calculated coherence bandwidth, and a modulation level is determined for each block based on feedback information included in the received uplink radio signal. To do.

  On the other hand, in the transmission side serial / parallel conversion step, a part of transmission data is serial / parallel converted to obtain signals for each of the plurality of subcarriers.

  Further, in the adaptive modulation step, the signal acquired for each of the plurality of subcarriers in the transmission side parallel-serial conversion step is adaptively modulated at the modulation level assigned to the block to which the subcarrier for the signal belongs.

  Then, in the differential modulation step, the remainder of the transmission data and the modulation level determined for each block are differentially modulated to the pilot signals of the plurality of subcarriers.

  On the other hand, in the multiplexing step, the adaptively modulated signal and the differentially modulated signal are multiplexed for each of the plurality of subcarriers.

  Further, in the transmission side parallel-serial conversion step, the downlink signals are obtained by parallel-serial conversion of the multiplexed signals.

  In the downlink transmission step, the acquired downlink signal is transmitted.

  A reception method according to another aspect of the present invention includes a downlink reception step, a reception side serial / parallel conversion step, a demultiplexing step, a differential demodulation step, an adaptive demodulation step, a reception side parallel / serial conversion step, an output step, and feedback information. A generation process and an uplink transmission process are provided and configured as follows.

  Here, in the downlink reception step, the downlink signal transmitted from the transmission device is received.

  On the other hand, in the receiving side serial / parallel conversion step, the received downlink signal is serial / parallel converted to obtain a signal for each of the plurality of subcarriers.

  Further, in the demultiplexing step, each of the plurality of signals subjected to serial / parallel conversion is demultiplexed and divided into a pilot signal portion and a data signal portion.

  In the differential demodulation step, the demultiplexed pilot signal portion is differentially demodulated to obtain the remaining transmission data and the modulation level determined for each block.

  On the other hand, in the adaptive demodulation step, the data signal portion demultiplexed for each of the plurality of subcarriers is adaptively demodulated at the modulation level acquired for the block to which the subcarrier for the data signal portion belongs.

  Further, in the receiving side parallel / serial conversion step, the plurality of adaptively demodulated signals are parallel / serial converted to obtain a part of the transmission data.

  In the output step, the transmission data is output by combining a part of the transmission data acquired in the parallel-serial conversion step and the remainder of the transmission data acquired in the differential demodulation step.

  On the other hand, in the feedback information generating step, channel evaluation is performed by comparing the data signal portion demultiplexed with respect to each of the plurality of subcarriers and the adaptively demodulated signal to generate feedback information.

  Further, in the uplink transmission step, an uplink signal including pilot symbols and generated feedback information is transmitted to the transmission apparatus.

  A program according to another aspect of the present invention includes a software radio (including an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), and various computers) as described above. It is configured to function as a receiving device or to cause the software radio to execute the above transmission method or reception method.

  The program of the present invention can be recorded on a software radio-readable information storage medium such as a compact disk, a flexible disk, a hard disk, a magneto-optical disk, a digital video disk, a magnetic tape, and a semiconductor memory.

  The above program can be distributed and sold via a computer communication network independently of the software radio on which the program is executed. The information storage medium can be distributed and sold independently from the software radio.

  According to the present invention, in communication in which differential modulation / demodulation is performed using a pilot signal and adaptive modulation / demodulation is performed for each subcarrier, a transmission apparatus, a reception apparatus, a transmission method, and reception that perform transmission by embedding MLI information and transmission data in the pilot signal It is possible to provide a method and a program that realizes these by software radio.

  Embodiments of the present invention will be described below. The embodiments described below are for explanation, and do not limit the scope of the present invention. Therefore, those skilled in the art can employ embodiments in which each or all of these elements are replaced with equivalent ones, and these embodiments are also included in the scope of the present invention.

  In the following, first, the principle of the present invention will be described, and then the specific configuration of the apparatus will be described. That is, after describing the coherence bandwidth, MLI for downlink subcarrier block modulation, and channel evaluation, the configurations of the transmission device and the reception device will be described.

(Coherence bandwidth)
In OFDM (Orthogonal Frequency Division Multiplexing), the channel response at a certain subcarrier frequency is not completely independent of the adjacent subcarrier frequency. Accordingly, the channel responses at adjacent subcarrier frequencies have a certain correlation, and this correlation varies depending on the coherence band width (coherent band width) Bc of the channel.

  On the other hand, in an FDD (Frequency Division Multiplexing) system, the separation width between the uplink frequency and the downlink frequency is about 5 percent of the average frequency.

  Thus, the instantaneous phase and amplitude variance caused by fading in the uplink is not correlated with that in the downlink. That is, the principle of interdependence cannot be used immediately.

  However, in a small frequency segment, the uplink channel and the downlink channel have various common properties. For example, the number of routes, the delay of the route, and the direction of arrival (DOA) are such properties.

  These will have the same properties in both uplink and downlink and are not frequency independent.

  Therefore, in the FDD system, the channel frequency response evaluated on each uplink subcarrier is not used as a channel parameter used in downlink adaptive modulation transmission in the base station, and the number of routes, the delay of the route, etc. Will be used.

  In order to obtain channel information such as the number of paths and path delay at the base station, IFFT (Inverse Fast Fourier Transformation) is used for the channel impulse response in the frequency domain evaluated from the pilot signal. It ’s fine.

Since the pilot signal transmitted from the mobile station is already known, in the following, the value p _{i, t} of the t-th pilot signal in the i-th subcarrier is expressed.
p _{i, t} = 1
Assume that

  Since the channel response evaluation result includes a fading term, the amplitude and phase of the received signal can be compensated.

Here, Np is the number of pilot symbols (the transmission time of pilot symbols divided by the time length of each pilot symbol), and the pilot signal received for the t-th pilot symbol in the i-th subcarrier is r _{i. , t} , the i-th uplink channel impulse response H _i can be calculated as follows:
H _i = Σ _{t = 1} ^Np r _{i, t} / Np

In order to obtain an accurate channel impulse response, it is necessary to average the pilot symbols to suppress the influence of noise. Here, two pilot symbols are considered as an averaging interval for channel tracking. The above equation for H _i shows the channel impulse response in the frequency domain.

By using the above equation relating IFFT operations and H _i, channel information such as delay of the number of routes and paths are obtained. In particular, the path delay can be obtained by calculation if the channel impulse response is used.

  FIG. 1 is an explanatory diagram showing the power density in the uplink, and FIG. 2 is an explanatory diagram showing the power density in the downlink. Hereinafter, a description will be given with reference to FIG.

Here, as shown in this figure, there are N propagation paths, the uplink power density is discrete, the power density in the nth path is h _n , and the delay time of the _nth path is τ _n , Maximum delay spread τ _max = τ _N −τ ₁ , root-mean-square (rms) τ _rms of delay spread of transmission channel is
τ _rms = (E (τ ² )-τ _av ² ) ^1/2 ;
E (τ ² ) = Σ _{n = 1} ^N | h _n | ²・ τ _n ² / Σ _{n = 1} ^N | h _n | ² ;
τ _av = Σ _{n = 1} ^N | h _n | ²・ τ _n / Σ _{n = 1} ^N | h _n | ²
You can get like that.

Now, the coherence bandwidth Bc is almost inversely proportional to the RMS delay spread τ _rms , but the frequency correlation function in the multipath environment changes over time, and an accurate relationship between the two cannot be obtained.

However, by experiment, if a strong constraint on the frequency correlation function is imposed, the coherence bandwidth Bc is approximately
Bc = 1 / (5 ・ τ _rms )
I know that

Here, considering an OFDM system having a transmission bandwidth of 100 MHz, an average frequency of 5 GHz, and 1024 subcarriers, the subcarrier bandwidth Δf is
Δf = 1 × 10 ⁶ Hz / 1024 = 97Hz
It becomes.

If the RMS delay spread τ _rms in a mobile communication system is about 500 ns, the approximate value of the coherence bandwidth Bc is
Bc = 1 / (5 ・ τ _rms ) = 0.4MHz ≒ 4.12Δf
It becomes.

  As a result, four adjacent subcarriers are faded coherently.

  Thus, in the present invention, the downlink coherence bandwidth is calculated from the delay spread of the uplink channel.

(MLI for downlink subcarrier block modulation)
As described above, based on the coherence bandwidth Bc, think of “a block in which adjacent subcarriers are grouped, and the subcarriers are assumed to be coherently (and similarly) affected by fading”. Can do.

  In the above example, this subcarrier block is composed of four consecutive subcarriers, and it can be assumed that the fading received by these four subcarriers is the same.

  When considering such a subcarrier block, it is not necessary to provide MLI (Modulation Level Information) for each subcarrier, and only one is required for each block.

  FIG. 3 is an explanatory diagram showing a conventional packet structure, and FIG. 4 is an explanatory diagram showing a packet structure used in the present invention. Hereinafter, a description will be given with reference to FIG.

  As shown in the figure, conventionally, the MLI is differentially modulated and transmitted for each subcarrier. However, according to the present invention, the size of the subcarrier block (“4” in the above example) Since it is sufficient to send information obtained by differentially modulating the MLI for each block, a portion remaining in the packet appears.

  Therefore, adaptively modulated data is also inserted in that portion.

  As a result, the communication system of the present invention can improve the transmission rate as compared with the conventional OFDM using differentially modulated pilot symbol assistance (DMPSA).

  In the following, the MLI on the pilot signal and the data transmission procedure will be described. Here, a Rayleigh frequency selective fading channel is assumed. Under this assumption, the received signal is lost due to other noise and fading.

In the following, using the complex baseband notation at time t, the i-th subcarrier pilot symbols p _i, and _t, the noise n _i, i affected by _t-th subcarrier signals x _{i, t-} If it is received by the receiving antenna, the received pilot signal is
x _{i, t} = h _{i, t} p _{i, t} + n _{i, t}
It becomes. Here, n _{i, t} is noise according to a complex Gaussian distribution with an average of 0 and unit dispersion.

The transmitted pilot signal is normalized to be unit power in the time direction,
E (| p _{1, t} | ² ) = 1
And

If the data rate per channel is R bits, the required number of symbols L is
L = 2 ^R
It is.

Due to the general technique of PSK (Phase Shift Keying), the symbol used in this case is the Lth root of 1;
v [k] = exp (j2πk / L), (k = 0,1,…, L-1)
It becomes.

From the above analysis, when the OFDM transmission bandwidth is Bw and the subcarrier bandwidth is Δf, the number of subcarrier blocks Nsb and the number of subcarriers Ncoh included in one subcarrier block are:
Ncoh = floor (Bc / Δf);
Nsb = floor (Bw / Bc) + 1
It becomes. Here, floor (·) is an operation that rounds off the decimal part.

In the present invention, the pilot signal in the i-th subcarrier is an integer sequence.
z _{i, 1} , z _{i, 2} , ..., z _{i, Np}
Suppose you want to transmit. However,
z _{i, t} ∈ {0, 1, ..., L-1}, (t = 1, 2, ..., Np)
It is. This integer string represents information on subcarrier blocks such as the block size Ncoh and the number of blocks Nsb, MLI, and data to be transmitted.

At this time, the symbol stream
p _{i, 0} , p _{i, 1} , p _{i, 2} , ..., p _{i, Np}
Shall be sent. Each element of this stream is
p _{i, 0} = 1;
p _{i, t} = v [z _{i, t} ] p _{i, t-1} , (t = 1, 2, ..., Np-1)
And Since the first pilot signal does not send any information, p _{i, 0} = 1. This corresponds to a reference signal.

  Also, how to allocate MLI and data to subcarriers will be described.

  Transmission of the number Nsb of blocks and the block size Ncoh is allocated to the first Nbl subcarriers. The value of Nbl is typically “1”, and this information is transmitted on the first subcarrier.

  The MLI for the nsb-th subcarrier block is allocated to, for example, the nsb · Nsb + Nbl-th subcarrier (where nsb = 1, 2,..., Nsb). Typically, the length of the pilot symbol sequence and the amount of information of the MLI are adjusted so that the MLI for one block can be expressed by the pilot symbol sequence assigned to one subcarrier.

  Therefore, first, by examining the first Nbl subcarriers and obtaining the values of Nsb and Ncoh, it becomes easy to know what subcarrier the MLI is put in.

  The remaining subcarriers transmit data to be transmitted.

Assuming that the fading coefficient changes slowly, an ML (Modulation Level) decoder can be defined as follows. However, y _{i, t} is the result of ML decoding the part corresponding to z _{i, t} .
y _{i, t} = argmin _k | x _{i, t} -v [k] x _{i, t-1} | ²

The argument of argmin _k in this expression is
^{_{| x i, t | 2 +}} | x i, t-1 | 2 - 2 | x i, t || x i, t-1 cos (arg (x i, t / x i, t-1) - 2πk / L)
Therefore, we can find k that minimizes the cos argument. Therefore,
y _{i, t} = round (arg (x _{i, t} / x _{i, t-1} ) L / (2π))
Is obtained. Here, round (•) is a function that rounds off the decimal point.

  As described above, the values embedded in the pilot signal can be obtained for the Nsb subcarrier, the MLI subcarrier, and the transmission data subcarrier by differential demodulation.

  Next, a method for improving the transmission rate in the present invention will be described.

When the present invention is applied to an OFDM system with an effective transmission rate ηe, assuming that the number of data symbols Nd, the number of pilot symbols Np, the number of subcarriers Nc, and the number of subcarriers Nbl into which subcarrier block size information is stored, Nbl As a result of applying the invention, the effective transmission rate ζe is
ζe = ηe + (ηe / Nd) ・ (Nc-Nsb-Nbl) / (Nc) ・ Np-1
To improve. Here, (ηe / Nd) is an effective transmission rate per unit data symbol.

  When the number of pilot symbols is small, the influence of transmitting MLI information on an empty pilot signal is small.

  On the other hand, when the number of pilot symbols is large, more data can be transmitted as pilot symbols.

  Furthermore, the throughput depends on the delay spread. When the delay spread is large, the coherence bandwidth becomes narrow, and the throughput deteriorates.

(Channel evaluation)
The role of pilot symbols is to calculate channel response vectors to compensate for faded received packets. However, in the system of the present invention, as described above, since data and MLI are further transmitted on the pilot symbols, the channel evaluation procedure is slightly different from the conventional method.

Hereinafter, a channel evaluation procedure will be described. First, it is assumed that the first pilot symbol p _{i, 0} of the i-th subcarrier is known and its value is p _{i, 0} = 1. This corresponds to a reference signal.

Assuming that x _{i, 0} is received corresponding to the first pilot symbol of the i-th subcarrier, this includes a channel response term and a noise term for each subcarrier. That is,
x _{i, 0} = h _{i, 0} + n _{i, 0}
It is.

  In an environment where Eb / No is low, the power of noise is large, so it is difficult to accurately compensate the received data packet even if the first pilot symbol is used.

  Since the noise symbol is a random signal with an average of 0, if the pilot symbol can be averaged, the noise term can be reduced. However, since pilot symbols include unknown MLI and data, pilot symbols cannot be averaged.

  Therefore, in order to obtain an accurate channel response, replica pilot symbols are created.

Using y _{i, t} obtained by the above method, the pilot symbol replica q _{i, t} is
q _{i, 0} = 1;
q _{i, t} = v [y _{i, t} ] q _{i, t-1} , (t = 1, 2, ..., Np)
Can be obtained as follows.

Using this, the channel response G _i of the i-th subcarrier is
G _i = Σ _{t = 1} ^Np (x _{t, i} / q _{i, i} ) / Np
It is required as follows.

The noise power No _i of the i-th subcarrier is the received pilot symbol Σ _{t = 1} ^Np x _{t, i}
And the square of the difference between the channel response evaluated for that subcarrier and the product of the replica pilot symbol,
No _i = (Σ _{t = 1} ^Np (x _{t, i} -G _i q _{t, i} ) / Np) ²
Can be calculated as follows.

Finally, to calculate Es _i / No _i for the i-th subcarrier,
Es _i / No _i = G _i ² / No _i
What should I do?

  From these results, received data packets are compensated, and feedback information designating them is returned to the transmitting side and used for the next adaptive modulation.

Note that Σ _{t = 1} ^Np may be calculated as Σ _{t = 0} ^Np , taking into account the reference signal as appropriate.

  In the following, details of the transmitting device and the receiving device will be described. However, in order to facilitate understanding of the principle of the present invention, the description will be omitted as appropriate when a known technique is applicable.

(Transmitter)
FIG. 5 is a schematic diagram showing a schematic configuration of a transmission apparatus 501 according to one embodiment of the present invention. Hereinafter, a description will be given with reference to FIG.

  The transmission apparatus 501 includes an uplink reception unit 502, a root mean square calculation unit 503, a coherence bandwidth calculation unit 504, a modulation level determination unit 505, a transmission side parallel / parallel conversion unit 506, an adaptive modulation unit 507, a differential modulation unit 521, A plexer 508, a transmission side parallel / serial converter 509, and a downlink transmitter 510 are provided.

  First, the uplink receiving unit 502 receives an uplink signal transmitted from the receiving device. The uplink signal includes pilot symbols and feedback information.

On the other hand, the root mean square calculation unit 503 calculates the mean square of the delay spread based on the pilot symbols included in the received uplink signal. Τ _rms is calculated by the above method.

  The coherence bandwidth calculation unit 504 calculates a coherence bandwidth that is inversely proportional to the calculated mean square of the delay spread. Bc is calculated by the above method.

  Further, the modulation level determination unit 505 divides a plurality of subcarriers into a plurality of blocks for each calculated coherence bandwidth, and determines a modulation level for each block based on feedback information included in the received uplink radio signal. decide. As described above, once Bc is determined, it is determined how many subcarriers are put in one block, and adaptive modulation with the same modulation level is performed on subcarriers belonging to the same block. In determining the modulation level, feedback information transmitted from the receiving apparatus is applied by a known technique.

  On the other hand, the transmission side serial / parallel conversion unit 506 performs parallel / serial conversion on a part of the transmission data to obtain a signal for each of the subcarriers. The “part of transmission data” here is for entering the data signal portion instead of the pilot signal portion in FIG.

  Here, an arbitrary data stream can be adopted as the “transmission data”. For example, an FEC encoder is used in the transmission device 501 to obtain “transmission data”, and the reception device uses “transmission data”. On the other hand, an FEC decoder may be used.

  Further, adaptive modulation section 507 adaptively modulates the signal acquired for each of the plurality of subcarriers by transmission side serial-parallel conversion section 506 at the modulation level assigned to the block to which the subcarrier for the signal belongs. . That is, the above-mentioned “part of transmission data” is adaptively modulated for each subcarrier at a modulation level assigned to each block.

  Then, the differential modulation unit 521 differentially modulates the remaining transmission data and the modulation level determined for each block into the pilot signals of the plurality of subcarriers. The “remaining transmission data” here is for entering the pilot signal portion instead of the data signal portion in FIG. The method of differential modulation is as described above. Which subcarrier is assigned a block size and a coherence bandwidth, which subcarrier is assigned an MLI, and which subcarrier is assigned a “remaining transmission data” It can be changed as appropriate.

In the case of differential modulation, an initial value p _{i, 0} ≠ 0 is required, which corresponds to the reference signal shown in FIG.

  In addition, which part of the data string is “partial” and which part is “residual” is appropriately changed according to Bc, but if Bc is determined, information on the data part to be put in one packet Since both the amount and the amount of information put in the pilot part are determined, it may be appropriately separated according to the value.

  On the other hand, multiplexing section 508 multiplexes the adaptively modulated signal and the differentially modulated signal for each of the plurality of subcarriers. That is, as shown in FIG. 4, the pilot signal portion and the data portion are connected in the time direction.

  Further, the transmission-side parallel-serial converter 509 performs parallel-serial conversion on the multiplexed signals to obtain a downlink signal. At this time, it is desirable to provide a guard interval.

  And the downlink transmission part 510 transmits the acquired downlink signal from an antenna.

(Receiver)
FIG. 6 is a schematic diagram showing a schematic configuration of a receiving apparatus according to one embodiment of the present invention. Hereinafter, a description will be given with reference to FIG.

  The receiving apparatus 601 of this embodiment includes a downlink receiving unit 602, a receiving side serial / parallel converting unit 603, a demultiplexing unit 604, a differential demodulating unit 605, an adaptive demodulating unit 606, a receiving side parallel / serial converting unit 607, and an output unit. 608, a feedback information generation unit 609, and an uplink transmission unit 610.

  Here, the downlink reception unit 602 receives the downlink signal transmitted from the transmission device 501 via the antenna.

  On the other hand, the receiving side serial / parallel conversion unit 603 performs serial / parallel conversion on the received downlink signal to acquire a signal for each of the plurality of subcarriers. At this time, the guard interval is removed.

  Further, the demultiplexing unit 604 demultiplexes each of the plurality of signals subjected to parallel-serial conversion, and divides the signal into a pilot signal portion and a data signal portion. That is, the packet shown in FIG. 4 is divided into two in the time direction.

  Then, the differential demodulator 605 differentially demodulates the demultiplexed pilot signal part to obtain the remaining transmission data and the modulation level determined for each block. As described above, the coherence bandwidth Bc, the number of blocks Nsb, the number of subcarriers Ncoh belonging to each block, etc. are first obtained, thereby obtaining the MLI, and the “remaining transmission data” from the subcarrier portion other than the MLI. To get.

  On the other hand, adaptive demodulation section 606 adaptively demodulates the data signal portion demultiplexed for each of the plurality of subcarriers at the modulation level acquired for the block to which the subcarrier for the data signal portion belongs. As described above, the MLI acquired for each block is used for adaptive demodulation of subcarriers belonging to the block.

  Further, the receiving side parallel / serial conversion unit 607 performs parallel / serial conversion on the plurality of adaptively demodulated signals to obtain a part of the transmission data, and the output unit 608 outputs the transmission data acquired by the parallel / serial conversion unit. A part and the remainder of the transmission data acquired by the differential demodulator 605 are combined to output the transmission data. The processing reverse to that of the transmission device 501 is performed.

  On the other hand, feedback information generation section 609 compares the data signal portion demultiplexed with respect to each of the plurality of subcarriers and the adaptively demodulated signal to perform channel evaluation, and generates feedback information. . In the channel evaluation, the above-described replica generation and comparison techniques are used.

  Further, uplink transmission section 610 transmits an uplink signal including pilot symbols and generated feedback information to transmitting apparatus 501. As a result, the transmission apparatus 501 can determine the coherence bandwidth and MLI.

  As described above, according to the present invention, in communication in which differential modulation / demodulation is performed using a pilot signal and adaptive modulation / demodulation is performed for each subcarrier, a transmission apparatus that performs transmission by embedding MLI information and transmission data in a pilot signal, and reception It is possible to provide a device, a transmission method, a reception method, and a program that realizes these by software radio.

It is explanatory drawing which shows the power density in an uplink. It is explanatory drawing which shows the power density in a downlink. It is explanatory drawing which shows the conventional packet structure. It is explanatory drawing which shows the packet structure of this invention. It is explanatory drawing which shows schematic structure of the transmitter which concerns on one of embodiment of this invention. It is explanatory drawing which shows schematic structure of the receiver which concerns on one of embodiment of this invention.

Explanation of symbols

501 Transmitting apparatus 502 Uplink receiving unit 503 Mean square calculating unit 504 Coherence bandwidth calculating unit 505 Modulation level determining unit 506 Transmission side serial / parallel conversion unit 507 Adaptive modulation unit 508 Multiplex unit 509 Transmission side parallel / serial conversion unit 510 Downlink transmission Unit 521 differential modulation unit 601 reception device 602 downlink reception unit 603 reception side serial / parallel conversion unit 604 demultiplexing unit 605 differential demodulation unit 606 adaptive demodulation unit 607 reception side parallel / serial conversion unit 608 output unit 609 feedback information generation unit 610 uplink transmitter

Claims (6)

An uplink receiver for receiving an uplink signal transmitted from the receiving device;
A mean square calculation unit for calculating a mean square delay delay according to a pilot symbol included in the received uplink signal,
A coherence bandwidth calculator that calculates a coherence bandwidth inversely proportional to the calculated mean delay spread
A modulation level determination unit that divides a plurality of subcarriers into a plurality of blocks for each calculated coherence bandwidth, and determines a modulation level for each block according to feedback information included in the received uplink radio signal;
A transmission-side serial-parallel converter that acquires a signal for each of the plurality of subcarriers by serial-parallel converting a part of the transmission data;
An adaptive modulation unit that adaptively modulates a signal acquired for each of the plurality of subcarriers by the transmission side serial-parallel conversion unit at a modulation level assigned to a block to which the subcarrier for the signal belongs,
A differential modulation unit that differentially modulates the remainder of the transmission data and the modulation level determined for each block to the pilot signals of the plurality of subcarriers,
A multiplexing unit that multiplexes the adaptively modulated signal and the differentially modulated signal for each of the plurality of subcarriers;
A transmission-side parallel-serial converter that obtains a downlink signal by parallel-serial converting the plurality of multiplexed signals;
A transmission apparatus comprising: a downlink transmission unit that transmits the acquired downlink signal. A downlink receiver for receiving a downlink signal transmitted from the transmitter;
A receiving side serial / parallel conversion unit for serially parallel converting the received downlink signal to obtain a signal for each of a plurality of subcarriers;
A demultiplexing unit that demultiplexes each of the plurality of signals subjected to the serial-parallel conversion and divides the signal into a pilot signal part and a data signal part,
A differential demodulator that differentially demodulates the demultiplexed pilot signal portion to obtain the remainder of the transmission data and the modulation level determined for each block;
An adaptive demodulator that adaptively demodulates the demultiplexed data signal portion for each of the plurality of subcarriers at a modulation level acquired for a block to which the subcarrier for the data signal portion belongs;
Receiving-side parallel-serial converter that obtains a part of transmission data by parallel-serial converting the plurality of adaptively demodulated signals;
An output unit that outputs transmission data by combining a part of the transmission data acquired by the parallel-serial conversion unit and the remainder of the transmission data acquired by the differential demodulation unit,
A feedback information generator for performing channel evaluation by comparing the demultiplexed data signal portion with the adaptive demodulated signal for each of the plurality of subcarriers, and generating feedback information;
A receiving apparatus comprising: an uplink transmitting unit that transmits an uplink signal including a pilot symbol and the generated feedback information to the transmitting apparatus. An uplink reception step of receiving an uplink signal transmitted from the receiving device;
A mean square calculation step of calculating a delay spread root mean square according to pilot symbols included in the received uplink signal;
A coherence bandwidth calculation step of calculating a coherence bandwidth inversely proportional to the calculated mean delay spread
A modulation level determining step of dividing a plurality of subcarriers into a plurality of blocks for each calculated coherence bandwidth and determining a modulation level for each block according to feedback information included in the received uplink radio signal;
A transmission-side serial-parallel conversion step of acquiring a signal for each of the plurality of subcarriers by serial-parallel conversion of a part of transmission data;
An adaptive modulation step of adaptively modulating the signal acquired for each of the plurality of subcarriers in the transmission-side serial-parallel conversion step at a modulation level assigned to a block to which the subcarrier for the signal belongs;
A differential modulation step of differentially modulating the remainder of the transmission data and the modulation level determined for each block to each pilot signal of the plurality of subcarriers;
A multiplexing step for multiplexing the adaptively modulated signal and the differentially modulated signal for each of the plurality of subcarriers;
A transmitting-side parallel-serial conversion step of acquiring a downlink signal by parallel-serial converting the plurality of multiplexed signals;
A transmission method comprising: a downlink transmission step of transmitting the acquired downlink signal. A downlink reception step of receiving a downlink signal transmitted from the transmission device;
A receiving side serial / parallel conversion step of performing serial / parallel conversion on the received downlink signal to obtain a signal for each of a plurality of subcarriers,
A demultiplexing step of demultiplexing each of the plurality of signals subjected to the serial-parallel conversion to divide into a pilot signal portion and a data signal portion;
A differential demodulation step of differentially demodulating the demultiplexed pilot signal portion to obtain the remainder of the transmission data and the modulation level determined for each block;
An adaptive demodulation step of adaptively demodulating the demultiplexed data signal portion for each of the plurality of subcarriers at a modulation level acquired for a block to which the subcarrier for the data signal portion belongs;
Receiving-side parallel-serial conversion step of obtaining a part of transmission data by parallel-serial converting the plurality of adaptively demodulated signals;
An output step of outputting transmission data by combining a part of the transmission data acquired by the parallel-serial converter and the remainder of the transmission data acquired in the differential demodulation step,
A feedback information generating step of performing channel evaluation by comparing the demultiplexed data signal portion with respect to each of the plurality of subcarriers and the adaptive demodulated signal to generate feedback information;
An uplink transmission step of transmitting an uplink signal including a pilot symbol and the generated feedback information to the transmission device.   A program for causing a software radio to function as each unit of the transmission device according to claim 1.   A program for causing a software radio to function as each unit of the receiving device according to claim 2.

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