WO2010146985A1 - 無線通信システム、送信機および無線通信方法 - Google Patents
無線通信システム、送信機および無線通信方法 Download PDFInfo
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- WO2010146985A1 WO2010146985A1 PCT/JP2010/059226 JP2010059226W WO2010146985A1 WO 2010146985 A1 WO2010146985 A1 WO 2010146985A1 JP 2010059226 W JP2010059226 W JP 2010059226W WO 2010146985 A1 WO2010146985 A1 WO 2010146985A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
- H04L5/0051—Allocation of pilot signals, i.e. of signals known to the receiver of dedicated pilots, i.e. pilots destined for a single user or terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
- H04L27/262—Reduction thereof by selection of pilot symbols
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
Definitions
- the present invention relates to a technique for performing communication by spreading data in the frequency domain using any one of a plurality of types of frame formats with different insertion positions of propagation path estimation symbols.
- DFT-S-OFDMA also called Discrete-Fourier-Transform-Spread-Orthogonal-Frequency-Division-Multiple Access, SC-FDMA: Single-Carrier-Frequency-Division-Multiple Access, or DFT-Precoded OFDM
- SC-FDMA Single-Carrier-Frequency-Division-Multiple Access
- DFT-Precoded OFDM DFT-Precoded OFDM
- this is a system with very good PAPR (Peak to Average Power Ratio) characteristics.
- a communication system called Clustered DFT-S-OFDM has been proposed for the purpose of improving frequency utilization efficiency. This method divides a frequency signal generated by DFT-S-OFDM into a group composed of a plurality of subcarriers called Cluster, and uses the frequency in a discrete manner, and allows deterioration of PAPR characteristics. This is a method for enhancing the frequency selective diversity effect and the frequency utilization efficiency.
- FIG. 8 is a block diagram showing a schematic configuration of a transmitter that transmits a DFT-S-OFDM signal.
- the scramble unit 100 performs randomization such as concealment on transmission data.
- the modulation unit 101 performs error correction and digital modulation.
- the DFT Pre-coding unit 102 performs Pre-coding by DFT.
- the propagation path estimation signal generation unit 103 generates a propagation path estimation signal for demodulation.
- the selection unit 104 switches between transmission data and a propagation path estimation signal.
- the resource map unit 105 allocates data to be transmitted to subcarriers to be transmitted. Then, when generating a DFT-S-OFDM signal, mapping is performed for continuous subcarriers, and when generating a Clustered DFT-S-OFDM signal, data is mapped to discrete subcarriers.
- a unit in which a mobile station accesses a base station is referred to as a resource block (hereinafter referred to as RB), and RB is composed of one or a plurality of subcarriers.
- the OFDM signal generator 106 generates an OFDM signal including a guard interval.
- the RF unit 107 includes an analog circuit from a D / A conversion (digital / analog conversion) unit to an antenna.
- FIG. 9 is a diagram illustrating an example of a frame format for transmitting a signal.
- the vertical direction indicates frequency and the horizontal direction indicates time.
- FIG. 9 shows the case where 24 subcarriers are used, and 1 RB is composed of 12 subcarriers. Further, one frame shows a case of 14 OFDM symbols, and propagation path estimation signals are used for the fourth and eleventh symbols.
- FIG. 9 shows an example in which all subcarriers are used as propagation path estimation signals in an OFDM symbol into which propagation path estimation signals are inserted.
- the frame format shown here is shown in Non-Patent Document 1.
- the communication method using the frame format shown in Non-Patent Document 1 is DFT-S-OFDM, and it is not assumed that Clustered DFT-S-OFDM is used.
- the receiver needs to estimate the propagation path in other OFDM symbols from the two propagation path estimation symbols.
- the interval at which the propagation path estimation symbol is transmitted is 6 OFDM, and in mobile communication, the propagation path estimation accuracy deteriorates as the moving speed of the terminal increases.
- the present invention has been made in view of such circumstances, and in a system for switching the insertion pattern of a plurality of propagation path estimation signals, even when the terminal moves at high speed, the propagation path estimation system is degraded.
- An object is to provide a wireless communication system, a transmitter, and a wireless communication method that can be suppressed.
- the radio communication system of the present invention uses any one of a plurality of types of frame formats with different insertion positions of propagation path estimation symbols, and spreads data in the frequency domain to perform communication.
- the type of frame format includes at least a first frame format having a propagation path estimation symbol that uses all subcarriers as propagation path estimation signals, a propagation path estimation signal and data multiplexed in the frequency domain. And a second frame format having a path estimation symbol.
- each type of frame format at least the first frame format having a propagation path estimation symbol having all subcarriers as propagation path estimation signals, the propagation path estimation signal, and data are multiplexed. Therefore, it is possible to suppress degradation of the channel estimation accuracy even when the moving speed of the terminal is high.
- each type of frame format includes the same number of data transmission subcarriers for each frame.
- each type of frame format includes the same number of data transmission subcarriers for each frame, the density in the time direction and the density in the frequency direction of the channel estimation signal depend on the type of the frame format. And can be changed. As a result, propagation path estimation accuracy in the time domain can be increased by increasing the density in the time direction. Furthermore, the information transmission amount for each frame is not changed.
- the PAPR (Peak to Average to Power Ratio) characteristic of the data transmission subcarrier of the second frame format is a subcarrier transmitting a symbol to which only data is allocated. It is characterized by being the same as the PAPR characteristic.
- This configuration makes it possible to suppress deterioration of the PAPR (Peak to Average Power Ratio) characteristics of the data transmission subcarrier in the second frame format.
- PAPR Peak to Average Power Ratio
- the second frame format is characterized in that propagation path estimation signals and data are arranged at regular intervals in the frequency axis direction.
- the propagation path estimation signal and the data are arranged at regular intervals in the frequency axis direction, it is possible to suppress the deterioration of the PAPR characteristic.
- the wireless communication system of the present invention is characterized in that the frame format to be used is switched according to a parameter relating to the moving speed of the transmitting terminal.
- the frame format to be used is switched according to the parameter relating to the moving speed of the transmitting terminal, it is possible to suppress deterioration in propagation path estimation accuracy due to the moving speed of the transmitting terminal.
- the wireless communication system of the present invention is characterized in that a plurality of types of communication methods can be used, and one of the plurality of types of frame formats is determined based on the communication method used. .
- the communication method includes at least DFT-S-OFDM (Discrete-Fourier-Transform-Spread-Orthogonal-Frequency-Division-Multiplexing) and Clustered DFT-S-OFDM.
- DFT-S-OFDM Discrete-Fourier-Transform-Spread-Orthogonal-Frequency-Division-Multiplexing
- Clustered DFT-S-OFDM Discrete-Fourier-Transform-Spread-Orthogonal-Frequency-Division-Multiplexing
- S-OFDM Discrete-Fourier-Transform-Spread-Orthogonal-Frequency-Division-Multiplexing
- a second frame format having a propagation path estimation symbol in which a propagation path estimation signal and data are multiplexed is used.
- the first frame format having a propagation path estimation symbol having all subcarriers as propagation path estimation signals is used, while Clustered DFT-S-OFDM is used.
- the frame format including the propagation path estimation symbol corresponding to each PAPR characteristic is selected. It is possible to cope with high-speed movement of the transmission terminal.
- the wireless communication system of the present invention is characterized in that one of the plurality of types of frame formats is determined based on a parameter relating to transmission power.
- one of the plurality of types of frame formats is determined based on the parameter relating to transmission power, communication can be performed without considering signal distortion due to a difference in PAPR characteristics.
- the parameter related to the transmission power is a transmission power reserve (Power Headroom).
- the parameter related to transmission power is transmission power reserve (Power Headroom)
- communication can be performed without considering signal distortion due to the difference in PAPR characteristics.
- the wireless communication system of the present invention is characterized in that one of the plurality of types of frame formats is determined based on a modulation scheme to be used.
- any one of a plurality of types of frame formats is determined based on the modulation scheme to be used, it is possible to obtain propagation path estimation accuracy corresponding to the modulation scheme.
- the radio communication system of the present invention is characterized in that it includes symbols having different multiplexing ratios of the propagation path estimation signal and the data.
- both the density in the time direction and the density in the frequency direction of the propagation path estimation signal are set according to the type of frame format. Can be changed. As a result, propagation path estimation accuracy in the time domain can be increased by increasing the density in the time direction.
- the transmitter of the present invention is a transmitter that uses any one of a plurality of types of frame formats having different insertion positions of propagation path estimation symbols, and spreads data in the frequency domain for transmission.
- a multiplexing unit for selecting one; and a transmission unit for transmitting the propagation path estimation signal and data; and a PAPR (Peak to Average to Power Ratio) characteristic of a subcarrier for data transmission of the second frame format is The PAPR characteristics of subcarriers that transmit symbols to which only data is allocated are the same Yes.
- each type of frame format at least the first frame format having a propagation path estimation symbol having all subcarriers as propagation path estimation signals, the propagation path estimation signal, and data are multiplexed. Therefore, it is possible to suppress degradation of the propagation path estimation accuracy even when the moving speed and communication speed of the terminal are high.
- the wireless communication method of the present invention is a wireless communication method that uses any one of a plurality of types of frame formats having different insertion positions of propagation path estimation symbols and spreads data in the frequency domain for communication.
- a first frame format having a propagation path estimation symbol having all subcarriers as propagation path estimation signals or a second frame format having a propagation path estimation symbol in which the propagation path estimation signal and data are multiplexed And at least a step of transmitting the propagation path estimation signal and data, and a PAPR (Peak-to-Average-Power-Ratio) characteristic of a data transmission subcarrier of the second frame format Is the same as the PAPR characteristic of the subcarrier that transmits a symbol to which only data is allocated. It is characterized by being.
- each type of frame format at least the first frame format having a channel estimation symbol that uses all subcarriers as a channel estimation signal, the channel estimation signal, and data are multiplexed. Therefore, it is possible to suppress degradation in propagation path estimation accuracy even when the moving speed and communication speed of the terminal are high.
- the present invention it is possible to suppress deterioration in propagation path estimation accuracy performed in the receiver even in an environment where the transmitting terminal moves at high speed, and an efficient communication system can be constructed.
- a signal known by a transmitter / receiver transmitted to estimate a propagation path is referred to as a propagation path estimation signal, and the propagation path estimation signal can be assigned in units of subcarriers.
- a symbol including a propagation path estimation signal is referred to as a propagation path estimation symbol, and if all subcarriers are not propagation path estimation signals, data can be multiplexed.
- DFT-S-OFDM or Clustered DFT-S-OFDM is used as a communication method. These communication methods can be understood as an OFDM signal obtained by spreading data in the frequency domain by DFT.
- FIG. 1A is a diagram showing a basic frame format in the present embodiment.
- FIG. 1A has the same configuration as FIG.
- this frame format is referred to as a “basic frame format”.
- the vertical direction indicates frequency and the horizontal direction indicates time.
- This figure shows a case where 24 subcarriers are used, and 1 RB is assumed to be composed of 12 subcarriers.
- one frame shows a case where it is composed of 14 OFDM symbols, and is a case where propagation path estimation symbols are used for the fourth and eleventh symbols.
- all subcarriers are used as propagation path estimation signals in an OFDM symbol into which propagation path estimation symbols are inserted.
- FIG. 1B is a diagram showing an example of an extended frame format in the present invention.
- this frame format is referred to as “extended frame format b”.
- propagation path estimation symbols are inserted into 2, 4, 6, 9, 11, and 13 OFDM symbols.
- all subcarriers are not propagation path estimation signals, but are used as propagation path estimation signals for every three subcarriers. That is, the number of subcarriers used for data transmission is shown by inserting a channel estimation signal at a density three times that in the time direction and inserting a channel estimation signal at a density of 1/3 in the frequency direction.
- 1A and FIG. 1B are kept constant.
- the propagation path is estimated with respect to the frequency domain, and then the propagation path in all OFDM symbols is estimated by interpolation in the time domain.
- the number of signals for channel estimation required in the frequency domain depends on the frequency selectivity of the channel (channel variations in the frequency domain), and the channel estimation signal is reduced with the channel estimation symbol. In some cases, this does not cause degradation.
- a mobile station In a wireless communication system using these two frame formats, for example, a mobile station notifies a base station of parameters relating to a moving speed, selects a format used by the base station, notifies a terminal, and performs data communication. Therefore, it is possible to construct a communication system that suppresses degradation of propagation path estimation accuracy even in an environment where the movement speed is high, without changing the communication speed depending on the movement speed of the terminal.
- Another advantage of not having to change the data communication speed is that the frame format change does not need to depend on data retransmission. This is because the same amount of data as that of the initial transmission may be assumed at the time of retransmission.
- the density of the propagation path estimation signal in the time direction is high, but the data is multiplexed at the same time as the density in the frequency direction is low.
- PAPR characteristics deteriorate. This is due to the fact that subcarriers for transmitting data are not continuous, and further degradation of the PAPR characteristic is increased by multiplexing the channel estimation signal.
- FIG. 1C is a diagram showing an example of another extended frame format, which is an extended frame format in view of the above problems.
- this frame format is referred to as an extended frame format c.
- the propagation path estimation symbols are inserted in 3, 6, 10, 13 OFDM symbols.
- FIG. 1B in the propagation path estimation symbol, not all subcarriers are used as propagation path estimation signals as shown in FIG. 1A, but are propagation path estimation signals every two subcarriers.
- the PAPR characteristic is the best when the frequency is used continuously and when it is used at regular intervals.
- this frame format shown in FIG. 1C since the subcarriers used for the propagation path estimation signal are arranged for each subcarrier, data is transmitted.
- the PAPR characteristics focused only on subcarriers are comparable to symbols other than the propagation path estimation symbols. That is, it has the characteristics of a single carrier. Therefore, the PAPR characteristic in the propagation path estimation symbol is better than that shown in FIG. 1B even when the propagation path estimation signal and data are multiplexed.
- the frame format shown in FIG. 1C has an advantage that the deterioration of the PAPR characteristic can be suppressed as much as possible in addition to the characteristics of the frame format shown in FIG. 1B.
- the PAPR characteristic in the uplink is an important factor, and it can be said that the frame format of FIG. 1C is a very useful frame format in the uplink.
- FIG. 2 is a block diagram showing a schematic configuration of the transmitter according to the embodiment of the present invention.
- the scramble unit 10 performs randomization such as concealment on transmission data.
- the modulation unit 11 performs error correction and digital modulation.
- the DFT Pre-coding unit 12 performs Pre-coding by DFT.
- the propagation path estimation signal generator 13 generates a demodulation propagation path estimation signal, and the multiplex section 14 switches the transmission data and the propagation path estimation signal by the controller 18. Further, the multiplex unit 14 multiplexes the transmission data and the propagation path estimation signal by the control unit 18.
- the resource map unit 15 allocates data to be transmitted to subcarriers to be transmitted. Further, when generating a DFT-S-OFDM signal, mapping is performed for continuous subcarriers, and when generating a Clustered DFT-S-OFDM signal, data is mapped to discrete subcarriers.
- the OFDM signal generation unit 16 generates an OFDM signal including a guard interval.
- the RF unit 17 includes an analog circuit from a D / A conversion (digital / analog conversion) unit to an antenna.
- the control unit 18 controls the operation of the multiplex unit 14.
- the multiplex unit 14 functions as a switching unit at the timing of transmitting the propagation path estimation symbol,
- the frame format shown in FIG. 1B or 1C it functions as a multiplexing unit.
- each type of frame format includes a frame format having at least a propagation path estimation symbol that uses all subcarriers as propagation path estimation signals (see FIG. 1A). And a frame format (FIG. 1B or FIG. 1C) having a propagation path estimation symbol in which a propagation path estimation signal and data are multiplexed are included, so that propagation path estimation can be performed even when the moving speed or communication speed of the terminal is high. It becomes possible to suppress deterioration of accuracy.
- the communication method to be used (sometimes referred to as an access method) is notified from the base station to the mobile station through the downlink control channel.
- the communication method to be used (sometimes referred to as an access method) is notified from the base station to the mobile station through the downlink control channel.
- two notification bits are required for normal notification. Since it is preferable that the amount of information notified by the downlink is as small as possible, it is possible to reduce the amount of information by uniquely defining the frame format according to the access method, and in the case of the previous example, it can be handled with 1 bit. .
- the access method is characterized by RBs to be used, such as DFT-S-OFDM and Clustered DFT-S-OFDM as in the example shown here, that is, when the frequency is used continuously, DFT- When S-OFDM is used in a discontinuous manner, the amount of information can be further reduced if it is determined as Clustered DFT-S-OFDM, and information bits other than specifying the RB to be used are not necessary.
- the high-speed mobile terminal always selects Clustered DFT-S-OFDM as the communication method, it is possible to make it less susceptible to the degradation of the propagation path estimation accuracy.
- it is difficult for a high-speed mobile terminal to properly switch between Clustered DFT-S-OFDM and DFT-S-OFDM depending on transmission power even if Clustered DFT-S-OFDM continues to be used, The effect shown, that is, an increase in throughput due to switching between Clustered DFT-S-OFDM and DFT-S-OFDM by transmission power is not reduced as a whole cell.
- FIG. 3 is a block diagram showing a schematic configuration of the transmitter according to the present embodiment. Blocks having the same functions as those in FIG.
- the communication method is switched between DFT-S-OFDM and Clustered DFT-S-OFDM.
- the difference between FIG. 2 and FIG. 3 is only the control unit 19.
- the control unit 19 controls the resource map unit 15 to select continuous RBs, and the multiplexing unit 14 includes the DFT-Precoding unit 12 And control to switch between propagation path estimation signals.
- the resource map unit 15 is controlled to select discontinuous RBs, and the multiplexing unit 14 is controlled by the DFT-Precoding unit 12. And the output from the propagation path estimation signal generation unit 13 are controlled to be multiplexed.
- a frame format having a channel estimation symbol that uses all subcarriers as a channel estimation signal (see FIG. 1A).
- a frame format (FIG. 1B or FIG. 1C) having a channel estimation symbol in which a channel estimation signal and data are multiplexed is used. It is possible to cope with high-speed movement of the transmission terminal while considering the PAPR characteristic.
- a clustered DFT-S-OFDM is used as a communication scheme for a high-speed mobile terminal as a communication scheme.
- Clustered DFT-S-OFDM has a PAPR characteristic compared to DFT-S-OFDM. Since it is bad, the problem that power efficiency is bad remains.
- the high-speed mobile terminal uses DFT-S-OFDM as a communication method and switches the frame format depending on transmission power.
- FIG. 1D shows a frame format for a high-speed mobile terminal according to the third embodiment.
- FIG. 1D shows subcarriers that are not used by the data portion as compared to FIG. 1C.
- the number of subcarriers used for data communication is different, but the PAPR characteristics in the channel estimation signal are excellent, and the power of subcarriers not used is allocated to the channel estimation signal.
- the subcarriers that can be used are frame formats that have a merit that a propagation path estimation signal can be transmitted from another antenna.
- this frame format is referred to as an extended frame format d.
- a method of switching the frame format depending on the transmission power is shown.
- the change of the transmission power and the frame format may not be instantaneously supported.
- the present embodiment an example is shown in which the mobile station selects a frame format based on transmission power and performs communication by estimating which format the base station has transmitted, but the present invention is applicable only to the present embodiment. Of course, this is naturally applicable to a system in which the base station selects a frame format.
- FIG. 4 is a block diagram showing a schematic configuration of a transmitter according to the third embodiment. Blocks having the same functions as those in FIG. 3 are given the same numbers.
- the communication method is switched between DFT-S-OFDM and Clustered DFT-S-OFDM.
- the difference between FIG. 3 and FIG. 4 is only the control unit 40.
- the control unit 40 controls the gain of the transmission power control amplifier included in the RF unit 17, and when the transmission power is lower than a predetermined threshold in the multiplexing unit 14, the frame format is as shown in FIG. When it is higher than the threshold value, control is performed as shown in FIG. 1D. By controlling in this way, the probability that the signal is distorted can be lowered, and the transmission data amount can be maintained as much as possible.
- FIG. 5 is a block diagram illustrating a schematic configuration of a receiver according to the third embodiment.
- this receiver is a receiver of a base station, a plurality of users access it at the same time, but in order to simplify the explanation, a case where a signal of one user is demodulated will be described.
- the RF unit 27 converts the signal so that the received signal can be digitally processed.
- the OFDM demodulator 26 demodulates the OFDM signal.
- the data extraction unit 25 extracts user data to be demodulated.
- the propagation path estimation / transmission format determination unit 24 estimates the propagation path between the user's mobile station to be demodulated and the base station, and determines the transmission format.
- the propagation path compensation unit 23 performs propagation path compensation on the received data.
- the DFT-Decoding unit 22 performs De-coding of data pre-coded by the transmission device.
- the demodulation unit 21 performs demodulation such as QPSK and error correction.
- the descrambling unit 20 unscrambles the scramble performed by the transmitter. In FIG. 5, except for the propagation path estimation / transmission format determination unit 24, the configuration of the receiver in the conventional base station.
- the propagation path estimation / transmission format determination unit 24 compares the average powers of even and odd carriers in the propagation path estimation symbol. If the average power is the same level, propagation path estimation is performed assuming that frame format c is transmitted. If the difference is large, propagation path estimation is performed assuming that frame format d is transmitted.
- frame determination methods there are a method in which a correlation between a received signal and a propagation path estimation signal is obtained, and a method in which demodulation is performed in both formats.
- the present invention can be applied to a parameter related to transmission power, and one of them is transmission power reserve (Power Headroom: PH).
- PH is a value related to the difference between the maximum transmission power unique to the terminal and the transmission power, and generally means that the signal is distorted when it becomes a negative value.
- communication characteristics can be improved by changing the frame format depending on the modulation method.
- the description will be made on the assumption of QPSK, 16QAM, and 64QAM.
- the present invention is not limited to this, and the modulation scheme includes a coding rate for error correction.
- the amount of information that can be transmitted by QPSK is 1, it is possible to transmit an information amount of 2 for 16 QAM and 3 for 64 QAM.
- FIG. 6A to 6C are diagrams showing examples of the frame format according to the present embodiment.
- FIG. 6A shows a frame format used when 64QAM
- FIG. 6B shows 16QAM
- FIG. 6C shows a frame format used when QPSK is transmitted.
- the higher the modulation multi-level number the higher the accuracy required for propagation path estimation.
- a frame format is used in which the number of propagation path estimation symbols in the time domain is changed to obtain propagation path estimation accuracy corresponding to each multi-value number.
- the method of changing the number of propagation path estimation symbols in the time domain is shown, but the method of changing the number of propagation path estimation signals in the frequency domain, the number of propagation path estimation signals in the frequency domain, the propagation path estimation symbols in the time domain A method of changing both numbers simultaneously is also applicable.
- the third embodiment since one of a plurality of types of frame formats is determined based on the modulation scheme to be used, it is possible to obtain propagation path estimation accuracy according to the modulation scheme. It becomes.
- FIG. 7 is a diagram illustrating an example of a frame format according to the fourth embodiment.
- symbols having different multiplexing ratios of the propagation path estimation signal and the data are included.
- subcarriers for transmitting data and subcarriers for transmitting propagation path estimation signals are arranged every other frame.
- subcarriers that transmit propagation path estimation signals are arranged between every three subcarriers that transmit data.
- both the density in the time direction and the density in the frequency direction of the propagation path estimation signal are set according to the type of the frame format. Can be changed. As a result, propagation path estimation accuracy in the time domain can be increased by increasing the density in the time direction.
- the present invention has been described on the assumption that the transmitting terminal moves at a high speed.
- the present invention is not limited to this, and can be used for communication with a transmitting terminal having a fast fluctuation with respect to the time of the propagation path received by the receiving apparatus. Is clear.
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Abstract
Description
本実施形態では、最初に、基本的なフレームフォーマットに対し、高速移動通信のために拡張されるフレームフォーマットのデータ伝送用に使用されるサブキャリア数が同一となる拡張フレームフォーマットを示す。ただし、それぞれのフレームフォーマットでは伝搬路推定シンボルの挿入間隔が異なる。更に、アップリンクではPAPR特性が重要であることを考慮し、PAPR特性の劣化を極力抑えることが可能なフレームフォーマットについても示す。
第2の実施形態では、使用するアクセス方式に従ってフレームフォーマットを変更する形態について説明する。次世代のアップリンクの通信方式では、DFT-S-OFDMとClustered DFT-S-OFDMを切り替える方法が提案されている(例えば、非特許文献2:R01-090020)。これは、端末の位置がセルエッジ等の送信電力が制限されるような環境下では、PAPR特性に優れたDFT-S-OFDMを使用し、セル中央等の送信電力に余裕がある環境下では、周波数使用効率に優れたClustered DFT-S-OFDMを使用することで、セルのスループット特性の改善を目的とした方法である。
第2の実施形態では通信方式として、高速移動端末にClustered DFT-S-OFDMを通信方式として使用する場合を示したが、Clustered DFT-S-OFDMはPAPR特性がDFT-S-OFDMに比べて悪いため、電力効率が悪いという問題が残ってしまう。本実施形態では、高速移動端末は通信方式としてはDFT-S-OFDMを使用することを前提とし、送信電力によってフレームフォーマットを切り替える例を示す。
図7は、第4の実施形態に係るフレームフォーマットの例を示す図である。本実施形態では、伝搬路推定用信号とデータとの多重割合が異なるシンボルを含む。図7に示すように、1フレーム前半の第3、第6シンボルには、データを送信するサブキャリアと伝搬路推定信号を送信するサブキャリアとが1つ置きに配置されているが、1フレームの後半の第8、第10、第12、第14シンボルには、データを送信するサブキャリアの間に、3つおきに伝搬路推定信号を送信するサブキャリアが配置されている。このように、伝搬路推定用信号とデータとの多重割合が異なるシンボルを含むので、フレームフォーマットの種類に応じて、伝搬路推定用信号の時間方向の密度と、周波数方向の密度との双方を変えることができる。その結果、時間方向の密度を増やすことによって、時間領域における伝搬路推定精度を高めることが可能となる。
11 変調部
12 DFT Pre-coding部
13 伝搬路推定用信号生成部
14 マルチプレクス部
15 リソースマップ部
16 OFDM信号生成部
17 RF部
18、19、40 制御部
Claims (14)
- 伝搬路推定用信号の挿入位置が異なる複数種類のフレームフォーマットのいずれかを使用し、データを周波数領域に拡散して通信を行なう無線通信システムにおいて、
前記各種類のフレームフォーマットには、少なくとも、すべてのサブキャリアを伝搬路推定用信号とする伝搬路推定シンボルを有する第1のフレームフォーマットと、伝搬路推定用信号とデータとが周波数領域で多重される伝搬路推定シンボルを有する第2のフレームフォーマットとが含まれ、
前記各種類のフレームフォーマットは、1フレーム毎に同数のデータ送信用サブキャリアを含むことを特徴とする無線通信システム。 - 前記伝搬路推定用信号とデータが多重されるフレームフォーマットとして、伝搬路推定信号が含まれるシンボルではデータを送信しないフレームフォーマットを含むことを特徴とする請求項1記載の無線通信システム。
- 前記第2のフレームフォーマットのデータ送信用サブキャリアのPAPR(Peak to Average Power Ratio)特性は、データのみが割り当てられたシンボルを送信するサブキャリアのPAPR特性と同一であることを特徴とする請求項1記載の無線通信システム。
- 前記第2のフレームフォーマットでは、伝搬路推定用信号とデータとがそれぞれ周波数軸方向に一定間隔に配置されることを特徴とする請求項1記載の無線通信システム。
- 送信端末の移動速度に関するパラメータによって、使用するフレームフォーマットを切り替えることを特徴とする請求項1記載の無線通信システム。
- 複数種類の通信方式を使用可能であって、
使用する通信方式に基づいて、前記複数種類のフレームフォーマットのいずれかを決定することを特徴とする請求項1記載の無線通信システム。 - 前記通信方式には、少なくとも、DFT-S-OFDM(Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing)およびClustered DFT-S-OFDMが含まれ、
前記DFT-S-OFDMを使用する場合は、すべてのサブキャリアを伝搬路推定用信号とする伝搬路推定シンボルを有する第1のフレームフォーマットを使用する一方、
前記Clustered DFT-S-OFDMを使用する場合は、伝搬路推定用信号とデータとが多重される伝搬路推定シンボルを有する第2のフレームフォーマットを使用することを特徴とする請求項6記載の無線通信システム。 - 送信電力に関するパラメータに基づいて、前記複数種類のフレームフォーマットのいずれかを決定することを特徴とする請求項1記載の無線通信システム。
- 前記送信電力に関するパラメータは、送信電力余力(Power Headroom)であることを特徴とする請求項8記載の無線通信システム。
- 使用する変調方式に基づいて、前記複数種類のフレームフォーマットのいずれかを決定することを特徴とする請求項1記載の無線通信システム。
- 伝搬路推定用信号とデータとの多重割合が異なるシンボルを含むことを特徴とする請求項1記載の無線通信システム。
- 伝搬路推定用信号の挿入位置が異なる複数種類のフレームフォーマットのいずれかを使用し、データを周波数領域に拡散して送信する送信機であって、
すべてのサブキャリアを伝搬路推定用信号とする伝搬路推定シンボルを有する第1のフレームフォーマットまたは伝搬路推定用信号とデータとが多重される伝搬路推定シンボルを有する第2のフレームフォーマットのいずれか一方を選択するマルチプレクス部と、
前記伝搬路推定用信号およびデータを送信する送信部と、を備え、
前記第2のフレームフォーマットのデータ送信用サブキャリアのPAPR(Peak to Average Power Ratio)特性は、データのみが割り当てられたシンボルを送信するサブキャリアのPAPR特性と同一であることを特徴とする送信機。 - 伝搬路推定用信号の挿入位置が異なる複数種類のフレームフォーマットのいずれかを使用し、データを周波数領域に拡散して通信を行なう無線通信方法であって、
すべてのサブキャリアを伝搬路推定用信号とする伝搬路推定シンボルを有する第1のフレームフォーマットまたは伝搬路推定用信号とデータとが多重される伝搬路推定シンボルを有する第2のフレームフォーマットのいずれか一方を選択するステップと、
前記伝搬路推定用信号およびデータを送信するステップと、を少なくとも含み、
前記第2のフレームフォーマットのデータ送信用サブキャリアのPAPR(Peak to Average Power Ratio)特性は、データのみが割り当てられたシンボルを送信するサブキャリアのPAPR特性と同一であることを特徴とする無線通信方法。 - 伝搬路推定用信号の挿入位置が異なる複数種類のフレームフォーマットのいずれかを使用し、データを周波数領域に拡散して通信を行なう無線通信システムにおいて、
前記各種類のフレームフォーマットには、少なくとも、すべてのサブキャリアを伝搬路推定用信号とする伝搬路推定シンボルを有する第1のフレームフォーマットと、伝搬路推定用信号とデータとが周波数領域で多重される伝搬路推定シンボルを有する第2のフレームフォーマットとが含まれることを特徴とする無線通信システム。
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