WO2006001351A1 - 送信方法および装置 - Google Patents
送信方法および装置 Download PDFInfo
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- WO2006001351A1 WO2006001351A1 PCT/JP2005/011563 JP2005011563W WO2006001351A1 WO 2006001351 A1 WO2006001351 A1 WO 2006001351A1 JP 2005011563 W JP2005011563 W JP 2005011563W WO 2006001351 A1 WO2006001351 A1 WO 2006001351A1
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- WIPO (PCT)
- Prior art keywords
- signal
- known signal
- packet format
- unit
- signals
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Classifications
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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
- H04L5/14—Two-way operation using the same type of signal, i.e. duplex
- H04L5/1438—Negotiation of transmission parameters prior to communication
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0006—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission format
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
- H04B7/0689—Hybrid systems, i.e. switching and simultaneous transmission using different transmission schemes, at least one of them being a diversity transmission scheme
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
- H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0078—Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location
- H04L1/0079—Formats for control data
Definitions
- the present invention relates to a transmission technique, and more particularly to a transmission method and apparatus for transmitting a packet format signal.
- Adaptive array antenna technology controls the amplitude and phase of signals transmitted and received by multiple antennas to form antenna directivity patterns.
- a device equipped with an adaptive array antenna changes the amplitude and phase of signals received by a plurality of antennas, adds the changed reception signals, and changes the amplitude and phase.
- Receive a signal equivalent to the signal received by the antenna with the directivity pattern according to hereinafter referred to as “weight”.
- signals are transmitted using antenna directivity patterns according to weights.
- an example of processing for calculating weights is a method based on a minimum mean square error (MMSE) method.
- MMSE minimum mean square error
- the Wiener solution is known as a condition that gives the optimum value of the weight, and a gradual equation with a smaller amount of calculation than directly solving the Wiener solution is also known.
- an adaptive algorithm such as an RLS (Recursive Least Squares) algorithm or an LMS (Least Mean Squares) algorithm is used.
- RLS Recursive Least Squares
- LMS Least Mean Squares
- data may be subjected to multi-carrier modulation and a multi-carrier signal may be transmitted (for example, refer to Patent Document 1). Kaihei 10-210099
- MIMO multiple input multiple output
- the transmitter and receiver each have multiple antennas, and one channel is set for each antenna.
- channels up to the maximum number of antennas are set to improve the data transmission speed.
- the data transmission speed can be further increased by combining such a MIMO system with technology for transmitting multicarrier signals.
- the transmitted signal since the signal transmitted by the transmitting apparatus is accurately received by the receiving apparatus, the transmitted signal generally includes a preamble that is a known signal.
- the preamble signal is defined by a fixed pattern. However, if the preamble signal pattern is changed in consideration of the characteristics of the wireless transmission path and the packet utilization efficiency, a flexible wireless communication system can be realized with respect to the characteristics of the wireless transmission path.
- the present invention has been made in view of these circumstances, and an object thereof is to provide a transmission method and apparatus for changing the format of a preamble signal.
- a transmitting apparatus includes a first known signal defined by the first wireless communication system and a first known signal different from the first wireless communication system.
- a storage unit for storing the second known signal defined in the wireless communication system 2, a packet format in which the second known signal is arranged at the head portion, and the first known signal before the second known signal A selection unit that selects one of the packet formats in which the signal is further arranged; and a transmission unit that transmits the signal in the packet format selected by the selection unit.
- Another aspect of the present invention is also a transmission device.
- This device uses the same number of carriers as the first known signal defined by the first wireless communication system to transmit signals using a plurality of carriers and the number of carriers for transmitting signals by the first wireless communication system.
- a storage unit for storing the second known signal, a packet format in which the second known signal is arranged at the head portion, and a packet in which the first known signal is further arranged in front of the second known signal.
- a selection unit that selects whether the format is different; and a transmission unit that transmits a signal in a packet format selected by the selection unit.
- the second known signal stored in the storage unit may be defined in a plurality of types according to the number of antennas to which signals should be transmitted in the second wireless communication system. Since the pattern of the second known signal is changed according to the number of antennas, the communication quality can be improved.
- the selection unit selects the second type that is defined by a plurality of types if the number of antennas to which the signal is transmitted becomes one.
- One of the known signals may be arranged. Even if the number of antennas is changed from a plurality to one, since the second known signal corresponding to one of the plurality of antennas is used, switching to the first wireless communication system becomes unnecessary.
- the selection unit selects the first known signal and the second known signal between the first known signal and the second known signal.
- Information indicating that two known signals are arranged may be arranged.
- the second known signal is placed after the first known signal, and information indicating that the second known signal is inserted is inserted, so the communication device of the first wireless communication system is informed of the content of the subsequent signal. be able to.
- a monitoring unit that monitors the presence of a communication device that is compatible with the first wireless communication system without being compatible with the second wireless communication system, and the selection unit is based on the monitoring result of the monitoring unit. Therefore, the packet format may be selected. Since the switching of the presence / absence of the first known signal is executed based on the presence / absence of the terminal device of the first wireless communication system, even if the switching is performed, the other communication devices are not affected.
- Another aspect of the present invention is also a transmission device.
- This apparatus includes a transmission unit that transmits signals defined in a predetermined packet format in parallel from a plurality of antennas, a storage unit that stores a known signal to be placed at the beginning of the packet format, and a known signal. Packet When placing at the beginning of the format, the arrangement is such that the known signal is transmitted from multiple antennas at the same timing, and the arrangement is such that the known signal is transmitted at multiple timings with different antenna powers! / And a selection unit for selecting whether to shift.
- the deriving unit that derives the characteristics of the wireless transmission path to which the signal is to be transmitted and the selection unit may select the arrangement of the known signals based on the derived characteristics of the wireless transmission path. Since the configuration of the known signal to be transmitted is changed based on the quality of the wireless transmission path, the configuration of the known signal suitable for the quality of the wireless transmission path can be selected.
- Yet another aspect of the present invention is a transmission method.
- This method is the same as the first known signal defined in the first wireless communication system that should transmit signals using a plurality of carriers and the number of carriers for transmitting signals in the first wireless communication system.
- the second known signal specified by the second wireless communication system that should transmit signals from multiple antennas in parallel while using the same number of carriers is specified, and the second known signal is placed at the beginning.
- the selected packet format and the packet format in which the first known signal is further arranged before the second known signal are selected to transmit the signal.
- Yet another aspect of the present invention is also a transmission method.
- This method stores a first known signal defined by a first wireless communication system and a second known signal defined by a second wireless communication system different from the first wireless communication system. Selecting a difference between a step, a packet format in which the second known signal is arranged at the head portion, and a packet format in which the first known signal is further arranged in the preceding stage of the second known signal. Transmitting a signal in the packet format selected in the step.
- Yet another aspect of the present invention is also a transmission method.
- This method is the same as the first known signal defined in the first wireless communication system that should transmit signals using a plurality of carriers and the number of carriers for transmitting signals in the first wireless communication system.
- the second known signal stored in the storing step may be defined in a plurality of types according to the number of antennas that should transmit signals in the second wireless communication system.
- a plurality of types of second known signals defined One of them may be arranged.
- the selecting step includes selecting the second known signal between the first known signal and the second known signal when selecting a packet format in which the first known signal is further arranged in front of the second known signal. Information indicating that is placed may be placed.
- the method further includes a step of monitoring the presence of a communication device compatible with the first wireless communication system without being compatible with the second wireless communication system, and the step of selecting is based on a monitoring result in the monitoring step.
- the packet format may be selected.
- the second known signal stored in the storing step includes a plurality of portions having different signal patterns, and the selecting step transmits at least one of the plurality of portions from the plurality of antennas at the same timing, respectively. You may choose the second known signal placement and the second known signal placement to transmit at least one of the multiple parts at different timings with multiple antenna powers! / ⁇ .
- the second known signal arrangement may be selected based on the derived characteristics of the wireless transmission path.
- Yet another aspect of the present invention is also a transmission method.
- a known signal is transmitted from a plurality of antennas at the same timing with respect to a known signal to be disposed at the beginning of the packet format of a signal to be transmitted in parallel from a plurality of antennas. Select one of the arrangements so that the known signal is transmitted at different timings with multiple antenna forces.
- Yet another aspect of the present invention is also a transmission method.
- This method includes a step of transmitting a signal defined in a predetermined packet format in parallel with a plurality of antenna forces, a step of storing a known signal to be placed at the head portion of the packet format, and a bucket of the known signal.
- the known signal is transmitted from multiple antennas at the same timing, and the known signal is transmitted at different timings from multiple antennas. ! / Step of selecting between the two.
- the arrangement of the known signals may be selected based on the derived characteristics of the wireless transmission path.
- FIG. 1 is a diagram showing a spectrum of a multicarrier signal according to an embodiment of the present invention.
- FIG. 2 is a diagram showing a packet format configuration according to an embodiment of the present invention.
- FIG. 3 is a diagram showing a concept of a communication system according to an embodiment of the present invention.
- FIG. 4 is a diagram showing a configuration of the transmission device in FIG. 3.
- FIG. 5 is a diagram showing a configuration of a control unit in FIG.
- FIGS. 6 (a)-(b) are diagrams showing packet formats selected by the selection unit in FIG.
- FIGS. 7A to 7B are diagrams showing the format of the LTS selected by the selection unit in FIG.
- FIG. 8 is a diagram showing the relationship between the number of transmitting antennas and the transmitting antenna force used for selection by the selection unit in FIG. 5, and the relationship between STS patterns to be transmitted.
- FIG. 9 is a diagram showing a configuration of the receiving device in FIG. 3.
- FIG. 10 is a diagram showing a configuration of a first radio unit in FIG. 9.
- FIG. 11 is a diagram showing a configuration of a correlation unit in FIG.
- FIG. 12 is a diagram showing a configuration of a first processing unit in FIG. 9.
- FIG. 13 is a flowchart showing a procedure of transmission processing in the transmission device of FIG. 3.
- FIG. 14 is another flowchart showing a procedure of transmission processing in the transmission device of FIG. 3.
- Embodiments of the present invention relate to an Ml MO system including a transmission device including a plurality of antennas and a reception device including a plurality of antennas.
- the MIMO system transmits a signal by a multicarrier, specifically, an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and the transmitted signal is defined in a packet format.
- a preamble signal is arranged at the beginning of the packet format, and the receiving device that receives the signal executes AGC (Automatic Gain Control) setting, timing synchronization, carrier reproduction, and the like based on the preamble signal.
- AGC Automatic Gain Control
- a MIMO system a plurality of antenna power independent signals of a transmitting device are transmitted, and a receiving device separates the received signals by adaptive array signal processing and demodulates a desired signal.
- the conventional system transmits signals using the OFDM modulation method in the same way as the MIMO system.
- the signal is transmitted by setting one channel between the transmitter and receiver.
- the power to reduce the signal redundancy in the packet format in the MIMO system by adding a preamble signal that is compatible only with the MIMO system.
- the conventional system cannot recognize such a preamble signal. May not be recognized. This is equivalent to the fact that if the conventional system uses CSMA, carrier sense will not be performed correctly, and it will determine that no signal is being transmitted and will transmit the signal itself.
- the transmitter adds a preamble signal compatible with the conventional system to the beginning of the packet format, If there is no receiving device compatible with the conventional system in the vicinity, a preamble signal compatible with the conventional system is not added to the head of the packet format.
- FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention.
- This corresponds to a multicarrier signal transmitted in the conventional system and a multicarrier signal in which one antenna force of the MIMO system is also transmitted.
- the conventional system is a wireless LAN (Local Area Network) conforming to the IEEE802.11a standard (hereinafter, a wireless LAN conforming to the IEE E802.11a standard is also referred to as “conventional system”).
- one subcarrier is designated by a “subcarrier number”.
- the IEEE802.11a standard defines 53 subcarriers from subcarrier numbers “26” to “26”.
- the subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal.
- Each subcarrier is modulated by BPSK (Binary Phase Shift Keying), QSPK (Quadrature Phase Shift Keying), 16 QAM (Quadrature Amplitude Modulation), and 64QAM.
- FIG. 2 shows a packet format configuration according to the embodiment of the present invention. This corresponds to the call channel of the conventional system.
- the OFDM modulation method generally, the total of the Fourier transform size and the number of symbols in the guard interval is used as one unit. This single unit is an OFDM symbol in this embodiment.
- the size power of Fourier transform is 1 ⁇ 24 (hereinafter, one FFT (Fast Fourier Transform) point is referred to as “FFT point”), and the number of FFT points in the guard interval is 16. The symbol is equivalent to 80 FFT points.
- the preamble of “40 FDM symbol”, “signal” of “10 FDM symbol”, and “data” of an arbitrary length are arranged from the head.
- the preamble is a known signal transmitted for AGC setting, timing synchronization, carrier recovery, etc. in the receiving apparatus.
- a signal is a control signal, and data is information to be transmitted from a transmitting device to a receiving device.
- the “preamble” of the “40FDM symbol” is separated into “STS (Short Training Sequence)” of “20FD M symbol” and “LTS (Long Training Sequence)” of “20FDM symbol”.
- the STS is composed of ten signal units “tl” to “tlO”, and one unit “tl” or the like has 16 FFT points. In this way, the STS uses 12 subcarriers among the 53 subcarriers shown in FIG. 1 in the force frequency domain where the unit of the time domain is 16 FFT points. STS is used especially for AGC setting and timing synchronization.
- the LTS is composed of two signal units “T1” and “T2” and a guard interval “GI2” that is twice as long. One unit “T1”, etc., is 64 FFT points. “GI2” is 32FFT points. LTS is used especially for carrier reproduction.
- a signal in the frequency domain as shown in FIG. 1 is indicated by S, and the subscript is a subcarrier number.
- the STS of the conventional system is expressed as follows.
- FIG. 3 shows a concept of the communication system 100 according to the embodiment of the present invention.
- the communication system 100 includes a transmission device 10 and a reception device 12.
- the transmitting device 10 includes a first transmitting antenna 14a and a second transmitting antenna 14b, which are generically referred to as a transmitting antenna 14, and the receiving device 12 is a first receiving antenna 16a, which is generically referred to as a receiving antenna 16. And a second receiving antenna 16b.
- the transmitting device 10 transmits a predetermined signal, but transmits different signals from the first transmitting antenna 14a and the second transmitting antenna 14b.
- the receiving device 12 receives signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b by the first receiving antenna 16a and the second receiving antenna 16b.
- the receiving device 12 separates the received signals by adaptive array signal processing, and independently demodulates the signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b.
- the transmission path characteristic between the first transmission antenna 14a and the first reception antenna 16a is hll
- the transmission path characteristic between the first transmission antenna 14a and the second reception antenna 16b is hl2
- if the transmission path characteristic between the second transmission antenna 14b and the first reception antenna 16a is h21
- the transmission path characteristic between the second transmission antenna 14b and the second reception antenna 16b is h22
- the receiving device 12 operates by adaptive array signal processing so that only the signals h1 and h22 are effectively transmitted and the signals transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b can be demodulated independently.
- a problem when a preamble signal of a conventional system, for example, an STS is transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b in Fig. 3 will be described. If the signal transmitted from the first transmitting antenna 14a is SI (t), the signal transmitted from the second transmitting antenna 14b is S2 (t), and the noise is nl (t) and n2 (t), then A signal received by the first receiving antenna 16a is indicated as XI (t), and a signal received by the second receiving antenna 16b is indicated as X2 (t) as follows.
- a preamble signal such as STS suitable for the MIMO system as described above is added to the head portion of the packet format.
- the reception device 12 can receive the packet signal.
- a conventional system receiving apparatus (not shown) also receives a packet signal to which a preamble signal suitable for a MIMO system is added.
- the correlation value is predetermined. It will not be larger than the value. As a result, the receiving device cannot detect the packet signal.
- the receiving device and the transmitting device are integrated to form a communication device.
- the above-described operation corresponds to the fact that the packet signal is not detected by the communication device, so the communication device transmits the signal. This corresponds to the fact that carrier sense is accurately executed in the communication device !, which is likely to cause signal collision.
- FIG. 4 shows a configuration of the transmission device 10.
- the transmitting apparatus 10 includes a first radio unit 24a, a second radio unit 24a, a first modulation unit 22a, a second modulation unit 22b, an Nth modulation unit 22n, and a radio unit 24. It includes a radio unit 24b, an Nth radio unit 24n, a control unit 26, and an Nth transmitting antenna 14 ⁇ .
- the first modulation unit 22a includes an error correction unit 28, an interleaving unit 30, a preamble addition unit 32, an IFFT unit 34, a GI unit 36, and an orthogonal modulation unit 38.
- the first radio unit 24a includes a frequency conversion unit 40. And an amplifying unit 42.
- the data separator 20 separates data to be transmitted according to the number of antennas.
- the error correction unit 28 performs a code for error correction on the data.
- the interleave unit 30 interleaves the data subjected to the convolutional code.
- the preamble adding unit 32 adds a preamble signal to the head of the knot signal.
- a plurality of types of preamble signals to be added by the preamble adding unit 32 are defined, and one of them is selected based on an instruction from the control unit 26. Details thereof will be described later.
- IFFT unit 34 performs IFFT (Inverse Fast Fourier Transform) in units of FFT points, and converts a frequency domain signal using a plurality of subcarrier carriers into a time domain signal.
- the GI unit 36 adds a guard interval to the time domain data. As shown in Fig. 2, the guard interval added to the preamble signal and the data signal is different.
- the quadrature modulation unit 38 performs quadrature modulation.
- the frequency converter 40 converts the orthogonally modulated signal into a radio frequency signal.
- the amplifying unit 42 is a power amplifier that amplifies a radio frequency signal. Finally, signals are transmitted in parallel from a plurality of transmitting antennas 14.
- the control unit 26 controls the timing of the transmission device 10 and selects a preamble signal to be added by the preamble adding unit 32.
- this configuration can be used with any computer CPU, memory, or other LS. It can be realized with I, and in terms of software, it is realized by a program with a reservation management function loaded with memory, but here, functional blocks realized by those linkages are shown. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.
- FIG. 5 shows a configuration of the control unit 26.
- the control unit 26 includes a selection unit 110, a monitoring unit 112, a transmission path characteristic acquisition unit 114, and a storage unit 116.
- the storage unit 116 stores a preamble signal specified in the conventional system and a preamble signal specified in the MIMO system.
- the conventional system transmits signals using a plurality of subcarriers, and the MIMO system uses the same number of subcarriers as that of the conventional system while using a plurality of transmitting antennas 14 in parallel. Transmit the signal.
- a plurality of types of preamble signals defined by the MIMO system are defined according to the number of transmitting antennas 14 to which signals should be transmitted. A plurality of types of specified preamble signals will be described later.
- the preamble signal of the MIMO system is also specified to include STS and LTS.
- STS and LTS have different signal patterns.
- the monitoring unit 112 monitors the presence of a communication device that does not support the MIMO system but supports the conventional system.
- the transmission apparatus 10 and a reception apparatus integrally constitute a communication apparatus, for example, a base station apparatus compatible with a MIMO system.
- the receiving device searches for the signal received from the communication device of the conventional system among the received signals. In other words, it is determined whether the packet format of the received packet signal corresponds to the packet format of the conventional system shown in FIG.
- the monitoring unit 112 determines that there is no communication device corresponding to the conventional system when the receiving device does not detect the packet signal defined by the conventional system over a predetermined period. On the other hand, when the receiving device detects a packet signal defined by the conventional system within a predetermined period, it is determined that there is a communication device compatible with the conventional system.
- the transmission path characteristic acquisition unit 114 derives the characteristics of the wireless transmission path with the receiving device 12.
- the characteristics of the wireless transmission path are measured by a predetermined method.
- One method is the receiver shown in Fig. 3. 12 is the measurement, and another method is that the communication device including the transmission device 10 measures.
- the former corresponds to the characteristic of the wireless transmission path from the transmitting apparatus 10 to the receiving apparatus 12, and the latter corresponds to the characteristic of the directivity wireless transmission path from the receiving apparatus 12 to the transmitting apparatus 10.
- the communication device including the reception device 12 notifies the communication device including the transmission device 10 of the measurement result.
- the characteristics of the wireless transmission path include received power, delay profile, delay spread, error rate, and the like.
- Selection section 110 selects a packet format based on the monitoring result of monitoring section 112.
- two types of packet formats are defined.
- 6A to 6B show packet formats selected by the selection unit 110.
- FIG. Figure 6 (a) shows a packet format in which a preamble signal corresponding to a MIMO system is placed at the beginning (hereinafter referred to as “exclusive format”).
- exclusive format a packet format in which a preamble signal corresponding to a MIMO system is placed at the beginning
- signals are transmitted from the first transmitting antenna 14a and the second transmitting antenna 14b among the transmitting antennas 14, and the packet format of the signal transmitted from the first transmitting antenna 14a is shown in the upper section. 2
- the packet format of the signal transmitted from the transmitting antenna 14b is shown below.
- “STS1” and “LTS1” are transmitted as preamble signals, and from the second transmitting antenna 14b, “3-c3 &” and “1/13 &” are transmitted as preamble signals.
- “STS1” and “ST Sa”, and “LTS1” and “LTSa” are signals having different patterns. Details of these signals will be described later.
- Fig. 6 (b) shows a packet format in which a preamble signal corresponding to the conventional system is further arranged before the preamble signal corresponding to the MIMO system (hereinafter referred to as "mixed format").
- the STS and LTS of the preamble signals corresponding to the conventional system are indicated as “conventional STS” and “conventional LTS”, respectively.
- the conventional STS pattern is as described in Fig. 2.
- the part corresponding to the preamble signal of the MIMO system is the same as in Fig. 6 (a).
- a “signal” is arranged between the preamble signal compatible with the conventional system and the preamble signal compatible with the MIMO system.
- “Signal” includes information indicating that a preamble signal corresponding to the MIMO system is arranged. Therefore, even if the communication device of the conventional system receives the packet signal, the content power of “signal” may discard the packet signal. Also, the information indicating that the preamble signal is arranged may be the length of the packet signal, that is, if it can be determined that some signal continues for a certain period of time.
- the dedicated format has few redundant signal components, the use efficiency of packets can be improved.
- the mixed format is detected by a communication device compatible with the conventional system because a packet signal compatible with the conventional system is added. If the monitoring unit 112 has not detected a communication device compatible with the conventional system, the selection unit 110 selects a dedicated format, and if the monitoring unit 112 has detected a communication device compatible with the conventional system, the selection unit 110 Select a mixed format.
- selection section 110 selects an LTS arrangement based on the characteristics of the wireless transmission path derived by transmission path characteristic acquisition section 114.
- 7 (a) — (b) shows the LTS format selected by the selection unit 110.
- FIG. Figures 7 (a)-(b) show the preamble signal part of the MIMO system in the case of the mixed force format described in the dedicated format.
- Fig. 7 (a) shows a case where LTSs are transmitted from a plurality of transmitting antennas 14 at the same timing (hereinafter, such a format is referred to as a "continuous format"), from the first transmitting antenna 14a. “LTS1” is transmitted, and “LTSa” is transmitted from the second transmitting antenna 14b.
- FIG 7 (b) shows the case where LTSs are transmitted from multiple transmitting antennas 14 at different timings (hereinafter, this format is called “separation format”). As shown in the figure, “LTS1” And “LTSa” are not transmitted at the same time.
- the continuous format has few redundant signal components, it is possible to improve packet utilization efficiency.
- “LTS1” and “LTSa” are transmitted at different timings, and interference between signals is reduced. Therefore, estimation of transmission path characteristics, response vectors, Vector estimation is accurate and communication quality is improved. If the wireless channel characteristics acquired by the channel characteristics acquisition unit 114, for example, the error rate is not worse than the threshold value, the selection unit 110 selects the continuous format, and the error rate becomes worse than the threshold value. The selection unit 110 selects a separation format.
- FIG. 8 shows the relationship used when selecting by selection section 110, showing the relationship between the number of transmitting antennas and the pattern of STS transmitted from the transmitting antenna.
- LTS LTS
- the number of transmitting antennas 14 is shown in the vertical direction in the figure, and the transmitting antenna 14 to be used and the corresponding STS are shown in the horizontal direction in the figure according to the number of transmitting antennas 14.
- RU that is, when the power S of the transmitting antenna 14 is S “l”, the conventional STS is transmitted from the first transmitting antenna 14a.
- the selection unit 110 may transmit “ST Sl” defined by the MIMO system if the number of transmitting antennas 14 to which signals are to be transmitted becomes one. As a result, switching to a preamble signal corresponding to the conventional system can be omitted.
- STSa transmitted from the second transmitting antenna 14b when the number of transmitting antennas 14 is “2” and third transmitting antenna when the number of transmitting antennas 14 is "3" It has a function of notifying the receiving device 12 of the number of transmitting antennas 14 that are transmitting signals, depending on the pattern difference between rSTSbj transmitted from the antenna 14c. Therefore, these STSs are different to the extent that “STSa” and “STSb” can be identified from the signal received by the receiving device 12. That is, the cross-correlation value between “STSa” and “STSb” is defined to be small.
- the number of transmitting antennas 14 is determined by the control unit 26.
- the control unit 26 determines the number of transmission antennas 14 according to the characteristics of the wireless transmission path acquired by the transmission path characteristic acquisition unit 114. That is, if the characteristics of the wireless transmission path are good, the number of transmitting antennas 14 is increased. Further, the control unit 26 may determine the number of transmitting antennas 14 based on the capacity of information to be transmitted. For example, if the capacity of information to be transmitted is large, the number of transmitting antennas 14 is increased.
- FIG. 9 shows a configuration of the receiving device 12.
- the receiving device 12 includes an Nth receiving antenna 16n, The first radio unit 50a, the second radio unit 50b, the N-th radio unit 50n, and the first processing unit 52a, the second processing unit 52b, the N-th processing unit 52n, which are collectively referred to as the line unit 50, A first demodulator 54a, a second demodulator 54b, an Nth demodulator 54n, a data combiner 56, and a controller 58, which are collectively referred to as a demodulator 54, are included.
- a first radio reception signal 200a, a second radio reception signal 200b, a second radio reception signal 200b, an Nth radio reception signal 200n, and a first baseband reception signal 202a are used as signals.
- Radio section 50 performs frequency conversion processing, amplification processing, AD conversion processing, and the like between radio frequency radio reception signal 200 and baseband baseband reception signal 202.
- the radio frequency of radio reception signal 200 corresponds to the 5 GHz band.
- correlation processing is performed for timing detection.
- the processing unit 52 performs adaptive array signal processing on the baseband received signal 202 and outputs a composite signal 204 corresponding to the transmitted plurality of signals.
- the demodulator 54 demodulates the composite signal 204. It also performs guard interval removal, FFT, Dinterleave, and decoding.
- the data combiner 56 combines the signals respectively output from the demodulator 54 corresponding to the data separator 20 in FIG.
- the control unit 58 controls the timing of the receiving device 12 and the like.
- FIG. 10 shows a configuration of the first radio unit 50a.
- the first radio unit 50a includes an LNA unit 60, a frequency conversion unit 62, an orthogonal detection unit 64, an AGC 66, an AD conversion unit 68, and a correlation unit 70.
- the LNA unit 60 amplifies the first radio reception signal 200a.
- the frequency conversion unit 62 performs frequency conversion between a radio frequency 5 GHz band and an intermediate frequency on a signal to be processed.
- the AGC 66 automatically controls the gain so that the amplitude of the signal is within the dynamic range of the AD converter 68. In the initial setting of AGC66, the STS of the received signal is used, and control is performed so that the STS strength approaches a predefined value.
- the AD conversion unit 68 converts an analog signal into a digital signal.
- the quadrature detection unit 64 performs quadrature detection on the intermediate frequency signal, generates a baseband digital signal, and outputs it as the first baseband received signal 202a.
- baseband signals include two components, an in-phase component and a quadrature component! /, So they should be indicated by two signal lines.
- the baseband signal is shown by a single signal line. The same applies to the following.
- correlator 70 In order to detect STS from first baseband received signal 202a, correlator 70 performs correlation processing on first baseband received signal 202a and previously stored STS, and outputs a correlation value.
- the correlation unit 70 since the STS is set for each unit of the transmitting antenna 14, the correlation unit 70 performs correlation processing on each of the plurality of STSs and outputs a plurality of correlation values.
- the correlation value is input to the control unit 58 in FIG. 9 through a signal line (not shown).
- the control unit 58 determines the reception start of the packet signal based on the plurality of correlation values input from the plurality of correlation units 70, and notifies the processing unit 52, the demodulation unit 54, and the like to that effect.
- allocation of the processing unit 52 and the demodulation unit 54 to each signal is determined and notified to the processing unit 52, the demodulation unit 54, and the like.
- FIG. 11 shows the configuration of the correlation unit 70.
- the correlation unit 70 includes a conventional STS correlation unit 330, an STSa correlation unit 332, an STSb correlation unit 334, and a selection unit 336.
- STSa correlation section 332 stores in advance a signal sequence obtained by converting STSa into the time domain, and calculates a correlation value between the stored signal sequence and the received signal sequence (hereinafter referred to as “correlation for two antennas"). Value ”).
- STSb correlation section 334 stores in advance a signal sequence obtained by converting STSb into the time domain, and calculates a correlation value between the stored signal sequence and the received signal sequence (hereinafter referred to as “correlation value for three antennas”). ).
- Conventional STS correlation section 330 stores in advance a signal sequence obtained by converting the above-described conventional STS into the time domain, or a signal sequence obtained by converting some of the subcarrier signals of the conventional STS into the time domain. . Further, conventional STS correlation section 330 calculates a correlation value between the stored signal sequence and the received signal (hereinafter referred to as “correlation value for one antenna”). Note that the signal sequence stored in the conventional STS correlator 330 may correspond to an STS corresponding to the MIMO system, for example, STS 1 in FIG.
- Selection section 336 compares the magnitudes of the 2-antenna correlation value, the 3-antenna correlation value, and the 1-antenna correlation value, and selects the maximum correlation value.
- An estimation unit determines the number of transmission antennas 14 that are transmitting data based on the selected correlation value. That is, if the correlation value for two antennas is large, the number of transmitting antennas 14 is determined to be “2”, and three antennas If the correlation value for transmission is large, the number of transmission antennas 14 is determined to be “3”, and if the correlation value for one antenna is large, the number of transmission antennas 14 is determined to be “1”.
- FIG. 12 shows a configuration of the first processing unit 52a.
- the first processing unit 52a includes a synthesis unit 80, a reception response vector calculation unit 82, and a reference signal storage unit 84.
- Combining unit 80 includes a first multiplying unit 86a, a second multiplying unit 86b, an Nth multiplying unit 86n, and an adding unit 88, which are collectively referred to as multiplying unit 86.
- the signals include a first reception weight signal 206a, a second reception weight signal 206b, an Nth reception weight signal 206n, and a reference signal 208, which are collectively referred to as a reception weight signal 206.
- the reference signal storage unit 84 stores LTS1 and the like. It is also assumed that the LTS is selected according to the STS selected by the conventional STS correlator 330.
- Reception response vector calculation unit 82 calculates reception weight signal 206 from baseband reception signal 202 and reference signal 208 as reception response characteristics of the reception signal with respect to the transmission signal.
- the calculation method of the reception weight signal 206 may be arbitrary, but is executed based on correlation processing as shown below as an example. Note that the reception weight signal 206 and the reference signal 208 are input not only from the first processing unit 52a but also from the second processing unit 52b and the like through a signal line (not shown).
- the first baseband received signal 202a is denoted by xl (t)
- the second baseband received signal 202b is denoted by x2 (t)
- the reference signal 208 corresponding to the first transmitting antenna 14a is SI (t)
- the second transmitted If the reference signal 208 corresponding to the trusted antenna 14b is represented as S2 (t), xl (t) and x2 (t) are represented by the following equations.
- the first correlation matrix R1 is given by the following equation, where E is the ensemble average.
- the second correlation matrix R2 between the reference signals 208 is also calculated as follows: [0070] [Equation 7]
- Reception weight signal 206 may be derived by an adaptive algorithm such as an LMS algorithm.
- Multiplier 86 weights baseband received signal 202 with reception weight signal 206, and adder 88 adds the outputs of multiplier 86 and outputs synthesized signal 204.
- FIG. 13 is a flowchart showing a procedure of transmission processing in the transmission apparatus 10.
- the monitoring unit 112 monitors whether there is a communication device compatible with the conventional system. If there is a communication device compatible with the conventional system (Y in S10), the selection unit 110 selects a mixed format (S12). On the other hand, if there is no communication device compatible with the conventional system (N in S10), the selection unit 110 selects a dedicated format (S14). Further, the selection unit 110 selects STSs and LTSs corresponding to the number of transmission antennas 14 from the storage unit 116 (S16), and arranges them in the selected format.
- the transmission device 10 transmits a packet signal (S18).
- FIG. 14 is another flowchart showing a procedure of transmission processing in the transmission apparatus 10.
- the transmission path characteristic acquisition unit 114 acquires the characteristics of the wireless transmission path, for example, the error rate. If the characteristics of the wireless transmission path are good (Y in S50), that is, if the error rate is lower than the threshold value, the selection unit 110 selects the continuous format (S52). On the other hand, if the characteristics of the wireless transmission path are not good (N in S50), the selection unit 110 selects a separation format (S54). Further, selection section 110 selects STS and LTS corresponding to the number of transmitting antennas 14 from storage section 116 (S56), and arranges them in the selected format. The transmission device 10 transmits a packet signal (S58).
- S58 packet signal
- the preamble signal in the conventional system is added to the leading portion of the packet signal, so that the communication apparatus in the conventional system can receive the packet signal.
- compatibility with conventional systems can be maintained.
- the communication device of the conventional system can be notified of the existence of the packet signal.
- the probability of signal collision can be improved.
- the presence / absence of the preamble signal in the conventional system is switched, compatibility with the conventional system and improvement in packet utilization efficiency can be selected. Further, since the switching of the presence / absence of the preamble signal of the conventional system is executed based on the presence / absence of the terminal device of the conventional system, other communication devices are not affected.
- the preamble signal pattern is changed according to the number of antennas, the communication quality can be improved.
- a preamble signal corresponding to one of the plurality of antennas is used, so switching to a conventional system is not necessary.
- the signal is inserted after the preamble signal of the conventional system, it is possible to inform the communication device of the conventional system of the contents of the subsequent signal.
- the configuration of the preamble signal to be transmitted with multiple antenna forces is changed, the transmission quality of the signal and the packet utilization efficiency can be selected. Since the configuration of preamble signals to be transmitted from multiple antennas is changed based on the quality of the radio transmission path, a preamble configuration suitable for the quality of the radio transmission path can be selected.
- a wireless LAN compliant with the IEEE802.11a standard is exemplified as the conventional system.
- the present invention is not limited to this.
- another communication system may be used.
- the communication system 100 may be the other communication system described as a MIMO system.
- the present invention can be applied to various communication systems 100.
- the conventional system and the communication system 100 need only have some compatibility such as the same radio frequency.
- the transmission method and apparatus which change the format of a preamble signal can be provided.
Abstract
Description
Claims
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CN2005800218250A CN1977484B (zh) | 2004-06-28 | 2005-06-23 | 发送方法与装置 |
EP05753340.8A EP1768294B1 (en) | 2004-06-28 | 2005-06-23 | Apparatus for transmitting signals |
BRPI0512704A BRPI0512704B1 (pt) | 2004-06-28 | 2005-06-23 | aparelho para transmissão de sinais |
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US8265055B2 (en) | 2012-09-11 |
TW200618520A (en) | 2006-06-01 |
US20100246379A1 (en) | 2010-09-30 |
EP1768294A1 (en) | 2007-03-28 |
RU2383998C2 (ru) | 2010-03-10 |
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US8254361B2 (en) | 2012-08-28 |
US8817767B2 (en) | 2014-08-26 |
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CN1977484B (zh) | 2012-12-05 |
BRPI0512704A (pt) | 2008-04-01 |
CN1977484A (zh) | 2007-06-06 |
TWI279999B (en) | 2007-04-21 |
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US20050286484A1 (en) | 2005-12-29 |
US20130022159A1 (en) | 2013-01-24 |
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