JP2015142291A - Radio communication method and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve communication characteristics by having a terminal station device appropriately select an antenna element to be used from a plurality of antenna elements in a radio communication system in accordance with IEEE802.11 standard.SOLUTION: A radio communication method includes: a signal transmission step of using a base station device to transmit an antenna selection signal following a beacon signal; a reception level measuring step using a terminal station device to measure a reception level when receiving the antenna selection signal for a virtual antenna obtained by combining any of a plurality of second antenna elements and/or per effective antenna of a plurality of candidates made up of individual second antenna elements after detecting reception of the beacon signal; an antenna control step using the terminal station device to determine reception using an effective antenna corresponding to the maximum reception level among reception levels per effective antenna; and a radio communication step of using the terminal station device to perform radio communication with the base station device using the effective antenna selected in the antenna control step.

Description

  The present invention relates to a wireless communication method and a wireless communication system.

  With the spread of the Internet in recent years, lines using optical fibers are already available in 90% of all households. In this way, the trend toward broadband has been steadily progressing, but in reality there are areas (unprofitable areas) where profitability is not expected due to the laying of optical lines, so how to eliminate the broadband zero area? There is a current situation where it is difficult to find a way to solve this problem.

  As a countermeasure in such an unprofitable area (conditionally disadvantaged area), it is advantageous to use a wireless line. For example, “Regional WiMAX” that secures a 10 MHz frequency channel for a service using a wireless standard called WiMAX (registered trademark, the same shall apply hereinafter), and applies a WiMAX service using this frequency channel mainly in conditionally disadvantaged areas. The so-called measures are being implemented. In WiMAX used for this measure, for example, a base station performs signal transmission with a large transmission power of about 10 W, and as a result, an area with a radius of about 3 km can be covered by one station.

In general, in an environment with a clear line of sight, the loss of a signal accompanying propagation between a transmitting station and a receiving station is inversely proportional to the square of the distance. In the case of non-line-of-sight, the degree of attenuation becomes inversely proportional to the 3rd to 4th power of the distance, and a more severe restriction is imposed on the circuit design. Even if a line of sight is assumed, in order to extend the transmission distance by a factor of 2, it is necessary to increase the transmission power to 2 ² = 4 times, and a transmission amplifier with higher linearity is required. However, such a transmission amplifier is expensive and the power efficiency is significantly reduced, so that the required power consumption increases rapidly.

  In recent years, environmental issues have attracted particular attention, and there has been a demand for lower power consumption of infrastructure including wireless communication. Communication using such an inefficient high-power transmission amplifier is not preferable. As a method for solving such a problem, for example, a plurality of antenna elements and an RF circuit for each antenna element are provided on the receiving side, and a signal for each antenna element is synthesized so that the gain is maximized. The reception diversity technique and the transmission diversity technique are effective.

  FIG. 15 is a block diagram illustrating a configuration example of a receiving apparatus to which a conventional receiving diversity technique is applied. As shown in the figure, the receiving apparatus includes antenna elements 101-1 to 101-M, low noise amplifiers (LNA) 102-1 to 102-M, mixers 103-1 to 103-M, and a filter 104-. 1 to 104-M, A / D converters 105-1 to 105-M, a local oscillator 106, and a reception signal processing circuit 107. Here, M is a natural number, which is the number of RF reception systems provided in the receiving apparatus.

  In the receiving apparatus, weak signals received by the antenna elements 101-1 to 101-M are amplified by the low noise amplifiers 102-1 to 102-M. The low noise amplifiers 102-1 to 102-M output the received signals obtained by amplification to the mixers 103-1 to 103-M.

  The mixers 103-1 to 103-M receive the received signals from the low noise amplifiers 102-1 to 102-M and the local oscillation signal having a predetermined frequency output from the local oscillator 106. Mixers 103-1 to 103-M synthesize the received signal and the local oscillation signal, and output the signals frequency-converted to baseband by synthesis to filters 104-1 to 104-M.

  Filters 104-1 to 104-M remove signals outside the assumed frequency band from signals included in the signals input from mixers 103-1 to 103-M, and perform A / D converter 105-1. To 105-M. The A / D converters 105-1 to 105-M sample the baseband analog signals input from the filters 104-1 to 104-M and convert them to digital baseband signals.

  The reception signal processing circuit 107 receives the digital baseband signal output from the A / D converters 105-1 to 105-M, performs a series of signal detection processing on the digital baseband signal, and transmits the transmission base station. The signal transmitted by the side is played back and output. Although not shown in FIG. 15, signal processing of the MAC layer and higher layers is performed in the subsequent stage of the reception signal processing circuit 107. By this signal processing, a signal in a format used by a user is reproduced and output to the outside (for example, a network, a PC, a communication device, etc.).

  For example, when the receiving apparatus receives a signal using an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, the received signal processing circuit 107 is a digital base that is input from the A / D converters 105-1 to 105-M. Timing detection is performed based on the band signal. The received signal processing circuit 107 cuts out the digital baseband signal at the detected symbol timing, performs the FFT processing after removing the guard interval, and converts the signal on the time axis into the signal on the frequency axis.

  A signal for channel estimation is usually added to the head of the signal cut out by the reception signal processing circuit 107. The reception signal processing circuit 107 calculates the coefficient of the reception weight of each of the antenna elements 101-1 to 101 -M based on the channel estimation result performed using the channel estimation signal. The reception signal processing circuit 107 multiplies the digital baseband signal by the calculated reception weight coefficient, and adds and synthesizes the multiplication results. Since the signal obtained by the addition synthesis becomes one system signal, the reception signal processing circuit 107 performs a series of channel estimation, reception signal detection, error correction (including deinterleaving, etc.), etc. for this one system signal. Apply the process. These processes are similarly performed even in a system other than the OFDM modulation system such as an SC-FDE (Single Carrier Frequency Domain Equalizer) system that performs equalization processing on the frequency axis.

  FIG. 16 is a block diagram illustrating a configuration example of a transmission apparatus to which a conventional transmission diversity technique is applied. As shown in the figure, the transmitting apparatus includes antenna elements 111-1 to 111-N, a high power amplifier (HPA), filters 113-1 to 113-N, mixers 114-1 to 114-N, D / A converters 115-1 to 115 -N, a local oscillator 116, and a transmission signal processing circuit 117 are provided. Here, N is a natural number and is the number of RF transmission systems provided in the transmission apparatus.

  The transmission signal processing circuit 117 receives data that has been subjected to signal processing in the MAC layer and higher layers. The transmission signal processing circuit 117 performs a series of signal processing on the input data, and outputs signals obtained by the signal processing to the D / A converters 115-1 to 115 -N. The D / A converters 115-1 to 115 -N convert the digital baseband signal input from the transmission signal processing circuit 117 into an analog baseband signal.

  The mixers 114-1 to 114 -N multiply the analog baseband signals input from the D / A converters 115-1 to 115 -N by local oscillation signals and convert the signals to radio frequency signals. The local oscillation signal is a signal having a predetermined frequency output from the local oscillator 116. Filters 113-1 to 113 -N receive signals converted to radio frequencies by mixers 114-1 to 114 -N, remove out-of-band frequency components included in the signals, and perform high-power amplifiers 112-1 to 112-1. To 112-N. The high power amplifiers 112-1 to 112 -N amplify the signals input from the filters 113-1 to 113 -N and send them from the antenna elements 111-1 to 111 -N.

  The transmission signal processing circuit 117 performs general transmission signal processing on input data. For example, the transmission signal processing circuit 117 performs error correction coding processing (including interleaving), transmission signal mapping processing, and the like. When the transmission apparatus transmits a signal using the OFDM modulation scheme, the transmission signal processing circuit 117 performs an IFFT process on the transmission signal, assigns a guard interval to the signal obtained by the IFFT process, Perform related processing such as waveform shaping.

  Among them, the transmission signal processing circuit 117 attaches a preamble signal for timing detection or channel estimation to the head of the signal as necessary. These processes are similarly performed even in a system other than the OFDMA modulation system such as the SC-FDE system. The signal generated in this manner is multiplied by a predetermined transmission weight coefficient for each series connected to the antenna elements 111-1 to 111-N as necessary, and the D / A converters 115-1 to 115-115. -N is output.

  In the above description, each of reception diversity and transmission diversity has been described as multiplying a predetermined reception weight and transmission weight (hereinafter referred to as transmission / reception weight). In this way, it is possible to maximize the characteristics by maximizing the use of signals from all antenna elements. For example, if it is a reception weight, a maximum ratio combining weight may be used.

  However, there is a trade-off relationship between the characteristics and the circuit configuration, and it is not necessarily aimed at maximizing the characteristics, and a simple circuit configuration may be selected although it is slightly inferior to the maximum characteristics. For example, it is possible to select only one good antenna element from a plurality of antenna elements without using a complicated transmission / reception weight and perform communication using only the antenna element. In this case, as a realization method, it is also possible to operate each circuit only with the antenna element selected simply. In addition, the transmission / reception weight multiplied by the reception signal processing circuit 107 or the transmission signal processing circuit 117 can be realized by setting the selected one system to 1 and the other to 0 (zero). In the case of such selection diversity, it is not always necessary to provide a plurality of RF systems as described above, and a simpler configuration can be provided.

  FIG. 17 is a block diagram showing another configuration example of a receiving apparatus to which the conventional receiving diversity technique is applied. As shown in the figure, the receiving apparatus includes antenna elements 101-1 to 101 -M, an antenna selector switch 108, a low noise amplifier 102-1, a mixer 103-1, a filter 104-1, and an A / D converter 105-1. A local oscillator 106 and a received signal processing circuit 107. In addition, the same code | symbol is attached | subjected to the structure same as the structure with which the receiver shown in FIG. 15 is provided.

  The differences between the receiving apparatus shown in FIG. 17 and the receiving apparatus shown in FIG. 15 are low noise amplifiers 102-1 to 102-M, mixers 103-1 to 103-M, filters 104-1 to 104-M, A / The point that the M systems configured by the D converters 105-1 to 105-M are integrated into one system, and the antenna elements 101-1 to 101-M connected to the configuration of one system are switched by the antenna changeover switch 108. It is the point made into composition. The basic operation of the receiving apparatus shown in FIG. 17 is the same as that of the receiving apparatus shown in FIG. 15, and the communication state is maintained well by switching the antenna selector switch 108 as necessary.

  FIG. 18 is a block diagram illustrating another configuration example of a transmission apparatus to which a conventional transmission diversity technique is applied. As shown in the figure, the transmission apparatus includes antenna elements 111-1 to 111-N, an antenna selector switch 118, a high power amplifier 112-1, a filter 113-1, a mixer 114-1, and a D / A converter 115-. 1, a local oscillator 116, and a transmission signal processing circuit 117. In addition, the same code | symbol is attached | subjected with respect to the same structure as the structure with which the transmitter shown in FIG. 16 is provided.

  The differences between the transmission apparatus shown in FIG. 18 and the transmission apparatus shown in FIG. 16 are high power amplifiers 112-1 to 112 -N, filters 113-1 to 113 -N, mixers 114-1 to 114 -N, D / A converters 115-1 to 115-N are integrated into one system, and the antenna selector switch 118 is configured to switch the antenna elements 111-1 to 111-N. is there. The basic operation of the transmission device shown in FIG. 18 is the same as that of the transmission device shown in FIG. 16, and the antenna changeover switch 118 is switched as necessary to maintain a good communication state.

  The switching of antenna elements by the antenna changeover switch 108 and the antenna changeover switch 118 in the receiving apparatus shown in FIG. 17 and the transmitting apparatus shown in FIG. 18 is performed when, for example, transmission / reception of a desired signal fails or the reception level decreases. This is performed when any state change is detected. As an example, the following describes antenna selection management processing in the prior art.

  FIG. 19 is a flowchart showing antenna selection management processing in the prior art. When communication is started by turning on the power of the transmission device and the reception device (step S901), a control circuit (not shown) includes a plurality of antenna elements (antenna elements 101-1 to 101-M, antenna element 111-). 1-111-N) is selected from the initial antenna elements (step S902), and communication is continued.

  During this communication, the control circuit periodically confirms that the reception level is normal reception such as the reception level is equal to or higher than the threshold (step S903). If the reception state is normal (YES in step S903), the control circuit is selected. Continue communication using antenna elements. When the control circuit detects that the normal reception state such as the reception level is less than the threshold value is not maintained (NO in step S903), the control circuit selects an antenna element different from the selected antenna element (step S904), The process ends (step S905).

  In addition, since the selection of the antenna element by the control circuit is continued during the communication, the process actually moves to step S903 after step S904, and the above-described process is repeated. Although an example has been shown here, for example, the normal reception confirmation process in step S903 can be realized by another method.

  As a specific example, in the case of communication with a TDMA frame period, it is determined whether or not signal reception from a base station is performed without a code error periodically (error detection should be received at a TDMA frame period). If the signal cannot be received, it may be determined as abnormal), and after transmitting, a successful transmission confirmation by ACK cannot be obtained with a high frequency (that is, frequent transmission failures are detected) and normal It may be determined that it is not an operation (corresponding to NO in step S903).

  In general wireless communication devices, the transmission system and the reception system often share the same antenna element. In particular, when TDD (Time Division Duplex) is used, transmission and reception are performed using a TDD switch. Often switched. In that case, if a TDD switch is arranged between the low noise amplifier 102-1 and the antenna changeover switch 108 and between the high power amplifier 112-1 and the antenna changeover switch 118, the antenna element can be shared. . When the antenna element is shared, the optimum antenna element is shared for both transmission and reception. Therefore, it is only necessary to perform switching by detecting that the state has deteriorated in either transmission or reception. The configuration of the above transmission diversity and reception diversity (hereinafter referred to as transmission / reception diversity) is described in Patent Document 1, for example.

JP-A-6-006275

  Currently, a wireless communication system that is widely used is a wireless communication system that conforms to the IEEE 802.11 standard called WiFi (registered trademark, hereinafter the same). This wireless communication system is a wireless communication system that employs a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) system as a wireless communication system. In this wireless communication system, communication is performed in an autonomous and distributed manner while avoiding signal collision (interference) with other wireless communication systems. In this wireless communication system, unlike a wireless wireless communication system, station design is not performed, and a user arbitrarily installs an access point (base station). Therefore, in order to avoid the occurrence of interference, it is common to operate with the transmission power suppressed to some extent. This makes it difficult for a terminal station away from the access point to receive a signal at a desired reception level, resulting in a limited service area.

  In addition, when a public wireless access service using WiFi is implemented, if the user to be used is indoors, the terminal station is located indoors. Furthermore, the radius of the service area tends to decrease. Increasing the transmission power of the access point increases the radius of the service area, but since the area where the interference wave reaches increases, it goes against the original policy of effectively using frequency resources while sharing them. In such a case, if the gain between specific radio stations can be increased by using a technique such as transmission / reception diversity, for example, the service area can be expanded without increasing the area where the interference wave reaches.

  Therefore, a technique for obtaining an efficient transmission / reception diversity gain is very important, particularly in a wireless communication system to which WiFi is applied. However, on the other hand, if a non-standard function is added to a wireless communication device that conforms to the standard, mutual compatibility with other WiFi devices will be lost. It is necessary to deal with it. Furthermore, in the situation where many devices that comply with WiFi are produced and the cost is very low, a major change in the wireless communication device will increase the price of the new wireless communication device. It is preferable that the number of modifications is limited.

On the other hand, when transmitting and receiving diversity is performed, the characteristics basically tend to improve as the number of antenna elements used increases. In particular, when all antenna elements are utilized and all received signals are utilized to the maximum using appropriate reception weights, for example, when signals of the same level are received by each antenna element, N antenna elements Can be combined to increase the amplitude N times and the received power N ² times. Here, the noise also increases by N times, so the actual improvement in SNR (Signal to Noise Ratio) remains N times (equivalent to 10 Log (N) [dB]), but avoids the effects of level fluctuations due to fading and the like. In practice, the communication characteristics can be greatly improved.

  In order to improve the characteristics, it is preferable to increase the number of antenna elements as much as possible. However, when the number of antenna elements is increased, the circuit scale and signal processing load increase as the number of antenna elements increases. It becomes. Since the configuration described in Patent Document 1 includes a configuration in which individual reception signal processing circuits are provided for each of a plurality of antenna elements, the reception signal level corresponding to each antenna element is simultaneously grasped at the time of signal reception. Is possible. Further, the received signal levels obtained at the same time are compared, and the antenna element having the higher received level can be selected instantaneously to perform the received signal processing.

  In the configuration described in Patent Document 1 having the configuration shown in FIGS. 15 and 16, the signal processing of the portion corresponding to the reception signal processing circuit 107 is received even though signals from a plurality of antenna elements are received. In order to simplify the processing, the antenna element is selected, and the signal processing is effectively equivalent to one antenna element. In this way, when the number of antenna elements actually used is one, the configuration shown in FIGS. 17 and 18 can be used to complete one RF system circuit. The configuration simplified so far is preferable.

  However, in the case of this configuration, signal processing can be performed simultaneously on a signal of one antenna element, and an optimum antenna element cannot be selected from a plurality of antenna elements. Therefore, in a normal operation, only very simple and limited control of detecting that the communication state has deteriorated and switching the antenna element can be realized. In this case, since it is not possible to select an optimal antenna element, it does not make much sense to provide a large number of antenna elements. Therefore, only two or at most three antenna elements are selected. It never happened. However, as described above, if the optimum antenna element can be selected, the characteristics can be improved as the number of candidate antenna elements increases.

  On the other hand, in the case of the configuration described with reference to FIGS. 15 and 16, it is possible to maximize the characteristics by applying transmission / reception weights. However, the transmission / reception weights are not based on accurate channel information at the time of communication. It is not possible to obtain sufficient characteristics. In particular, in order to earn transmission diversity gain at the time of transmission, it is necessary to accurately grasp channel information in the transmission direction. In general, the channel information between the transmitting-side antenna element and the receiving-side antenna element is recognized to be symmetrical between the uplink and the downlink.

  However, since the channel information actually acquired at the time of reception includes the amplitude and phase fluctuation amount in the high power amplifier of the wireless station of the communication partner and the amplitude and phase fluctuation amount in the low noise amplifier of the own station, Uplink and downlink channel information actually acquired on the receiving side due to a circuit in the transmitting / receiving device that is not included in the channel information between the transmitting side antenna element and the receiving side antenna element Has no symmetry. At the time of reception, the signal received by each antenna element is amplified by a separate low-noise amplifier and includes individual amplitude and phase fluctuation amounts. Since the circuit performs channel estimation processing, nonuniformity in individual amplitude / phase fluctuation amounts for each antenna system does not matter.

  On the other hand, in the case of transmission, each signal amplified by a separate high-power amplifier includes individual amplitude and phase fluctuation amounts. Therefore, if information on the amplitude and phase fluctuation amounts cannot be grasped, channel information at the time of reception is obtained. Even if it is known, channel information at the time of transmission (obtained at the receiving side at the communication partner station) cannot be predicted. Therefore, in general, it is necessary to transmit a predetermined training signal, have the channel information for each antenna element fed back from the receiving side, calculate the transmission weight based on the channel information, and perform transmission diversity control There is.

  That is, the reception diversity at the time of reception can accurately estimate the channel information at the moment of reception, and a high gain can be expected by high-precision control. On the other hand, in the case of transmission, in principle, there is no way to accurately acquire channel information at the moment of transmission. Therefore, even if the past channel information is used, an overhead for transmitting / receiving control information is required for feedback of the channel information. If the feedback period is lengthened in order to compress this overhead, the channel information at the time of transmission must be used considerably for the channel information at the time of transmission. There is a high possibility that a sufficient gain cannot be obtained. As described above, periodic information feedback is required in order to increase transmission diversity gain, and it may become unstable depending on the accuracy of channel information even though very high level control is required.

  The present invention has been made in view of such a situation, and is a wireless communication system compliant with the IEEE 802.11 standard, in which a terminal station apparatus appropriately selects an antenna element to be used from a plurality of antenna elements for communication. It is an object of the present invention to provide a radio communication system capable of improving the characteristics of the radio communication method and a radio communication method in the radio communication system.

  One embodiment of the present invention includes a base station apparatus having one first antenna element and a terminal station apparatus having a plurality of second antenna elements, and the base station apparatus and the terminal station apparatus are connected to IEEE 802. 11. A wireless communication method in a wireless communication system compliant with the 11 standard, wherein the base station apparatus transmits a signal for antenna selection following a beacon signal, and the terminal station apparatus receives the beacon signal. The antenna selection signal for each of a plurality of candidate effective antennas configured by virtual antennas obtained by combining any of the plurality of second antenna elements after detection and / or individual second antenna elements. A reception level measuring step for measuring a reception level when receiving the signal, and the terminal station apparatus receives the maximum reception level among the reception levels for each effective antenna. An effective antenna control step for determining to perform reception using an effective antenna corresponding to a level, and wireless communication for performing wireless communication with the base station device using the effective antenna selected by the terminal station device in the effective antenna control step A wireless communication method comprising: steps.

  In addition, according to one aspect of the present invention, in the wireless communication method described above, the terminal station device has an operation state of an initial operation mode and a normal operation mode, and the terminal station device is in an initial state. The initial operation mode is selected, and the initial operation mode is a beacon signal detection step in which reception is repeated until a beacon signal transmitted by the base station apparatus is detected by sequentially switching different effective antennas at a predetermined cycle. And a first state transition step for transitioning an operation state to the normal operation mode when the beacon signal is detected, wherein the normal operation mode includes the reception level measurement step, the effective antenna control step, and the wireless communication. And when the beacon signal cannot be received continuously for a predetermined time or longer, the operation state is changed to the initial operation mode. Characterized in that it comprises a second state transition step of.

  Further, according to one aspect of the present invention, in the wireless communication method described above, in the signal transmission step, a signal of another device is transmitted during a period in which the base station device transmits the beacon signal and the antenna selection signal. Information for prohibiting transmission is included in the beacon signal.

  One embodiment of the present invention includes a base station apparatus having one first antenna element and a terminal station apparatus having a plurality of second antenna elements, and the base station apparatus and the terminal station apparatus are In the wireless communication system compliant with the IEEE 802.11 standard, the base station apparatus includes a signal transmission unit that transmits a signal for antenna selection following a beacon signal that is periodically transmitted, and the terminal station apparatus includes: And receiving with one effective antenna selected from a virtual antenna obtained by combining any of the plurality of second antenna elements and / or a plurality of candidate effective antennas configured by the individual second antenna elements. Antenna switching means for outputting the signal, wireless communication means for receiving the signal via the antenna switching means, and the wireless communication means for receiving the beacon signal A reception level measuring means for measuring the reception level of the antenna selection signal for each effective antenna, and a maximum reception level searching means for searching for a maximum reception level among the reception levels measured by the reception level measurement means; The antenna switching means continuously receives an effective antenna corresponding to the maximum reception level detected by the maximum reception level search means until the wireless communication means finishes receiving the beacon signal again. It is a radio | wireless communications system characterized by using for this.

According to the present invention, the terminal station apparatus has an optimal effective antenna among a plurality of effective antennas configured using a plurality of second antenna elements based on a reception level of an antenna selection signal following a beacon signal. By selecting an antenna, it becomes possible to communicate with the base station apparatus in a situation where the transmission / reception gain is maximized, and by appropriately selecting an antenna element to be used from a plurality of second antenna elements, communication characteristics can be selected. Can be improved.
In the present invention, even if the system for processing the signal received by the effective antenna is made one system, the effective level is selected for each effective antenna that can be selected and the effective antenna is selected. Even with a simple circuit configuration for processing the above, a high diversity gain can be obtained.

It is a 1st figure which shows the basic processing flow of the operation principle of the radio | wireless communication apparatus in a base technology. It is a 2nd figure which shows the basic processing flow of the operation principle of the radio | wireless communication apparatus in a premise technique. It is a block diagram which shows the structural example of the radio | wireless communication apparatus in a premise technique. It is a block diagram which shows another structural example of the radio | wireless communication apparatus in a base technology. It is a block diagram which shows the example of a different structure of the radio | wireless communication apparatus in a base technology. It is a figure which shows an example of the antenna connection pattern in the antenna changeover switch 10 in the structural example 3 of a base technology. It is a figure which shows an example of a structure of the radio | wireless communications system in 1st Embodiment which concerns on this invention. It is a figure which shows an example of the data communication of general WiFi. It is a figure which shows an example of the data communication in the radio | wireless communications system in 1st Embodiment. It is a figure which contrasts the process by the base station apparatus 200 in 1st Embodiment, and the process in a prior art. It is a flowchart which shows the optimal antenna selection process in the terminal station apparatus 300 of 1st Embodiment. It is a state transition diagram of the operation mode of the terminal station apparatus 300 in 2nd Embodiment. It is a flowchart which shows a process when the operation mode of the terminal station apparatus 300 of 2nd Embodiment is an initial operation mode. It is a flowchart which shows the optimal antenna selection process in the terminal station apparatus 300 of 2nd Embodiment. It is a block diagram which shows the structural example of the receiver with which the conventional receiving diversity technique was applied. It is a block diagram which shows the structural example of the transmitter with which the conventional transmission diversity technique was applied. It is a block diagram which shows another structural example of the receiver with which the conventional receiving diversity technique was applied. It is a block diagram which shows another structural example of the transmitter with which the conventional transmission diversity technique was applied. It is a flowchart which shows the process of the antenna selection management in a prior art.

  The wireless communication method and the wireless communication system according to the present invention can reduce the transmission power on the reception side while suppressing the transmission power on the transmission side in an environment where strict restrictions on circuit design are imposed by increasing the transmission distance in wireless transmission. The present invention relates to a wireless communication technique for improving received power or signal-to-noise ratio (SNR) and performing efficient transmission with low power consumption. Prior to describing the wireless communication method and the wireless communication system according to the embodiment of the present invention, a technique for realizing transmission / reception diversity assumed in the wireless communication method and the wireless communication system will be described.

[Operation Principle of Technology Presumed in the Embodiment]
The feature of the technology (hereinafter referred to as “premise technology”) premised on the embodiment of the present invention is that the signal of the communication partner station is grasped and received by the antenna element or the antenna element at a predetermined period during reception of the signal. It is to perform reception level measurement for a virtual antenna when signals are analog-synthesized, and to perform communication using an antenna element or a virtual antenna corresponding to the maximum reception level obtained by the measurement.

  1 and 2 are diagrams showing a basic processing flow of the operation principle of the wireless communication apparatus in the base technology. When the optimum antenna selection process is started in the wireless communication apparatus (step S1), a signal from the communication partner station with the own apparatus is searched using the previously selected antenna condition (step S2). As the search here, for example, based on the identifier of the transmitting station accommodated in the received wireless packet, information for identifying the transmitting station, etc., the condition of the wireless station selected as the communication partner station is met. Search for the radio station you want. In communication between a base station and a plurality of terminal stations, since the terminal station knows the identifier of the base station or information for identification, it searches for a signal from the communication partner station based on the identifier or information. Here, the antenna condition is, for example, information indicating an antenna element or a combination of antenna elements used for signal reception.

  If the wireless communication apparatus detects a signal from the communication partner station and cannot obtain a signal that can be used to search for the optimum antenna (NO in step S3), the process returns to step S2 to further communicate with the communication partner station. Is continuously searched (step S 2 → step S 3 → step S 2 →... Are repeated).

  When a signal that can be used for detecting a signal from the communication partner station and searching for an optimum antenna is obtained (YES in step S3), the wireless communication device has a plurality of antenna elements provided in the device itself. The value of the counter k for identifying is reset to “1” (step S4). The wireless communication device performs reception level measurement for a signal from the communication partner station for a predetermined time using the k-th antenna condition indicated by the counter k (step S5). When the measurement using the k-th antenna condition ends, the wireless communication apparatus determines whether or not the counter k matches the total number K of antenna conditions (step S6).

If the counter k does not match the total number K of antenna conditions (NO in step S6), the wireless communication apparatus adds “1” to the value of the counter k to update the value (step S7), and the process goes to step S5. The process of steps S5, S6, and S7 is repeated in order.
When the counter k matches the total number K of antenna conditions (YES in step S6), the wireless communication apparatus searches for the antenna condition corresponding to the maximum reception level among the reception levels of the antenna conditions of the K pattern measured so far. (Step S8).

The wireless communication apparatus selects an antenna condition corresponding to the detected maximum reception level as an antenna to be used for communication (step S9), and ends the optimum antenna selection process (step S10). The wireless communication device uses the effective antenna selected in step S9 in the subsequent communication.
The above is the flow of processing for searching for the optimum antenna (antenna condition that maximizes the reception level).

  FIG. 2 shows a flow in communication including optimal antenna selection processing. When communication using the selected antenna condition is started (step S11), the wireless communication device resets the timer (step S12) and sequentially monitors timeout (step S13). Before reaching the timeout (NO in step S13), it is determined whether the timeout has been reached repeatedly and monitoring the timeout. If it is detected that the timeout has been reached (YES in step S13), the timeout monitoring is terminated.

When the time-out monitoring is terminated, the wireless communication apparatus executes the optimum antenna selection process shown in FIG. 1 (step S14). When the optimum antenna selection process is completed, the wireless communication apparatus determines whether or not the communication with the communication partner station has been completed (step S15). If not completed (NO in step S15), the process proceeds to step S12. It returns and repeats the process of step S12, S13, and S14 in order.
If the communication has ended (YES in step S15), the wireless communication apparatus ends the communication process (step S16).

  The antenna condition selected in step S9 of the optimum antenna selection process is not changed until the next antenna condition is selected, that is, between step S10 → step S15 → step S12 to S13 → step S1 to S4. However, if the signal of the communication partner station cannot be detected with the default antenna conditions immediately after the wireless communication device is turned on, this is not the case, and the antenna conditions may be changed as necessary. It doesn't matter.

  In the process of measuring the reception level in step S5, for example, if the function of measuring the reception level is implemented in the RF circuit, the measurement result of the reception level performed on the analog signal (usually RSSI (Received (Signal Strength Indicator: received signal strength) value) may be used. Or, for a sampling value sampled at the time of A / D conversion, either a square value of an absolute value of each sampling value or an approximate value of a square value of the absolute value of each sampling value is set over a predetermined number of samples. It is possible to add and synthesize (accumulate) and use the value obtained by addition and synthesis as the reception level.

  The reception level in step S5 does not necessarily have to be expressed using an absolute reception level, for example, [dBm] or [mW] as a unit. The evaluation value used as the reception level has a monotonically increasing or monotonic decreasing relationship with the intensity of the receiving level represented by [dBm] or [mW], and the strength of the receiving level is determined by the magnitude relationship of the evaluation values. If possible, any evaluation value may be used as the reception level.

In addition, regarding the sum total over a predetermined number of samples of the square value of the absolute value of the sampling value, the accuracy of the predetermined number of samples should be the number of samples corresponding to the effective symbol time length when using the OFDM modulation method. Is preferred. However, it is not always necessary to use the number of samples corresponding to the effective symbol time length in order to keep the time required for the optimum antenna selection process short. For example, in WiFi, one OFDM symbol length is 4 μs, and the time length excluding the guard interval is 3.2 μs. The time length of 3.2 μs is 64 samples corresponding to the number of FFT points. However, even if this half value of about 32 samples (or a smaller value) is used, it is possible to select an antenna condition that maximizes the reception level with a certain degree of accuracy although the estimation accuracy is reduced. Further, other sample numbers can be used in consideration of the estimation accuracy.
Hereinafter, a detailed configuration example of the wireless communication device in the base technology will be described in detail.

[Configuration example 1 in the base technology]
FIG. 3 is a block diagram illustrating a configuration example of a wireless communication device in the base technology. Of the components shown in the figure, the same components as those in the receiving apparatus shown in FIG. As shown in FIG. 3, the wireless communication device includes antenna elements 1-1 to 1-M, an antenna changeover switch 2, a switch changeover management circuit 3, a communication control circuit 4, a communication partner station signal detection circuit 5, and a reception level measurement circuit. 6, reception level storage circuit 7, maximum reception level search circuit 8, low noise amplifier 102-1, mixer 103-1, filter 104-1, A / D converter 105-1, local oscillator 106, and reception signal processing circuit 107.

  Each of the signals received by the antenna elements 1-1 to 1-M is input to the antenna selector switch 2. The antenna changeover switch 2 is a signal received by any one of the antenna elements 1-1 to 1-M or a predetermined antenna among the antenna elements 1-1 to 1-M according to the control of the switch changeover management circuit 3. A signal when the elements are received in combination is selectively output to the low noise amplifier 102-1. The combination here means coupling in the form of, for example, connecting signal lines from a plurality of antenna elements in an analog manner, and further incorporating a circuit for suppressing impedance matching and reflection. As a result, signals input from the respective antenna elements are combined on the analog circuit and output from the antenna changeover switch 2.

  The low noise amplifier 102-1 amplifies a weak signal input from the antenna changeover switch 2 and outputs the amplified signal to the mixer 103-1. The signal amplified by the low noise amplifier 102-1 and the local oscillation signal having a predetermined frequency output from the local oscillator 106 are input to the mixer 103-1. Mixer 103-1 synthesizes the local oscillation signal with the amplified signal and outputs the signal frequency-converted to baseband to filter 104-1.

  The filter 104-1 removes a signal that is included in the signal input from the mixer 103-1, and is outside the assumed frequency band, and outputs the signal to the A / D converter 105-1. The A / D converter 105-1 samples the baseband analog signal input from the filter 104-1, and converts it into a digital baseband signal. The A / D converter 105-1 outputs the digital baseband signal to the reception signal processing circuit 107 and the reception level measurement circuit 6.

  The received signal processing circuit 107 performs a series of signal detection processing on the digital baseband signal input from the A / D converter 105-1, and reproduces the signal transmitted by the communication partner station (transmitting station). Output data. Although not specified here, in the subsequent stage of the reception signal processing circuit 107 as in the reception apparatus shown in FIG. 15, signal processing of the MAC layer and higher layers is performed, and a signal in a format used by the user is reproduced. Is output externally. Here, the output destination is, for example, a network, a PC, or a communication device. The reception signal processing circuit 107 outputs a part of the reproduced signal to the communication control circuit 4.

  The communication control circuit 4 acquires control information necessary for communication control from the signal input from the reception signal processing circuit 107. The communication partner station signal detection circuit 5 receives the control information acquired by the communication control circuit 4 and the signal reproduced by the reception signal processing circuit 107. The communication partner station signal detection circuit 5 analyzes the reproduced signal based on the control information, and determines whether the signal or the subsequent signal is a signal from the communication partner station. The communication partner station signal detection circuit 5 uses, for example, information such as a TDMA frame structure, signal periodicity, an identifier of a transmission station attached to the signal, a wireless packet indicated by separately transmitted control information, and the like. It is determined whether or not the signal reproduced by the reception signal processing circuit 107 is a signal transmitted from the communication partner station.

  When the communication partner station signal detection circuit 5 detects the reception of the test signal for searching for the optimum antenna from the signal transmitted from the communication partner station, the communication partner station signal detection circuit 5 outputs information indicating that the test signal has been detected to the communication control circuit 4. At the same time, the reception level measurement circuit 6 is instructed to measure the reception level. When receiving the instruction from the communication partner station signal detection circuit 5, the reception level measurement circuit 6 calculates the square of the absolute value of the sampling data input from the A / D converter 105-1 or its approximate value at a predetermined timing. Start with The reception level measurement circuit 6 adds and synthesizes sampling data of a predetermined number of samples, and stores the value obtained by the addition synthesis in the reception level storage circuit 7 as a reception level. Here, the reception level is the sum of the squares of the absolute values of the sampling values. The reception level storage circuit 7 stores the reception level calculated by the reception level measurement circuit 6 in association with the antenna condition when the reception level is calculated.

  When the reception level measurement circuit 6 measures the reception level, the communication control circuit 4 controls the switch switching management circuit 3 to switch the antenna. The switch change management circuit 3 outputs a signal for changing the antenna to the antenna change switch 2 under the control of the communication control circuit 4. Note that the control of the communication control circuit 4 does not necessarily need to be performed every time switching is performed, and may be control instructing the start of a series of switching. In this case, when receiving the start instruction, the switch change management circuit 3 autonomously outputs a signal for changing the antenna at predetermined time intervals to the antenna change switch 2 thereafter.

  The communication control circuit 4 manages the timing for ending the measurement of the reception level for a series of predetermined candidate antenna conditions. When the communication control circuit 4 ends the measurement of the reception level, the communication control circuit 4 outputs an instruction for causing the maximum reception level search circuit 8 to select the optimum antenna. When receiving an instruction from the communication control circuit 4, the maximum reception level search circuit 8 selects an optimum antenna based on the reception level stored in the reception level storage circuit 7. The maximum reception level search circuit 8 searches the maximum reception level among the reception levels stored in the reception level storage circuit 7 and selects the antenna condition corresponding to the maximum reception level. The maximum reception level search circuit 8 outputs the selected antenna condition to the communication control circuit 4 as information indicating the optimum antenna.

  The communication control circuit 4 continuously controls the antenna changeover switch 2 via the switch changeover management circuit 3 so as to select the optimum antenna indicated by the information input from the maximum reception level search circuit 8 in the subsequent communication. . Thereafter, the antenna changeover switch 2 continues communication using the optimum antenna again until there is an instruction from the switch changeover management circuit 3 again.

  In the configuration example 1, the optimum antenna is any one of the antenna elements 1-1 to 1-M. The antenna condition is information indicating which antenna element is selected and used from the antenna elements 1-1 to 1-M.

  Here, the communication control circuit 4 and the communication partner station signal detection circuit 5 are described as functional blocks that are physically different for the purpose of explicitly indicating a function of appropriately selecting a signal whose reception level is to be measured. In general, the communication control circuit 4 can be regarded as a configuration including the communication partner station signal detection circuit 5. In this case, the signal reproduced by the reception signal processing circuit 107 is input to the communication control circuit 4, and based on this signal, it is determined whether or not the signal is a signal transmitted from the communication partner station. When it is determined that the signal is transmitted from the other station, the reception level measurement circuit 6 is instructed to measure the reception level.

  Here, the communication partner station signal detection circuit 5 or the communication control circuit 4 does not always measure the level while switching the antenna selector switch 2 even when the received signal is recognized as a signal from the communication partner station. It is not always determined that the target signal is to be performed. This is because the received signal becomes discontinuous by switching the antenna, which causes inconvenience in the received signal processing in the received signal processing circuit 107. Thus, for example, TDMA frame structure, signal periodicity, control information attached to the signal (including an identifier indicating the control information type of the radio packet if a signal to be used for antenna selection is defined) As a result, it is understood that the signal is from the communication partner station, and a signal that does not hinder the operation of the received signal processing circuit 107 even when the antenna changeover switch 2 is switched (or appropriate for use in the optimum antenna selection process). The optimum antenna may be selected while switching the antenna selector switch 2 for a signal that does not hinder the operation of the received signal processing circuit 107. Whether or not the operation of the received signal processing circuit 107 is hindered is determined by the communication partner station signal detection circuit 5 or the communication control circuit 4.

  In general wireless communication systems, when an error occurs in signal transmission / reception, the same signal is generally retransmitted to perform code error compensation. In this case, the operation of selecting the optimum antenna is performed while switching the antenna changeover switch 2 during reception of a certain wireless packet. Even if the operation of the reception signal processing circuit 107 is hindered by this effect, A generated code error (radio packet loss) can be relieved by retransmission. In this case, if the communication partner station signal detection circuit 5 or the communication control circuit 4 can grasp the signal from the communication partner station, the optimum antenna is selected while switching the antenna selector switch 2 for the signal. The operation may be performed.

  According to the wireless communication device of Configuration Example 1, the reception levels of the antenna elements 1-1 to 1-M are measured by the RF circuit integrated in one system, and the antenna elements 1-1 to 1-1 are measured based on the measurement results. The antenna element to be used is selected from 1-M. As a result, the wireless communication apparatus can improve the communication characteristics by maximizing the reception level of the signal from the communication partner station while taking a simple configuration in which the RF configuration is one system.

[Configuration Example 2 in Premise Technology]
FIG. 4 is a block diagram illustrating another configuration example of the wireless communication device in the base technology. In the configuration shown in the figure, the same components as those in the wireless communication device shown in FIG. 3, the reception device shown in FIG. 15, and the transmission device shown in FIG. As shown in FIG. 4, the wireless communication device in Configuration Example 2 includes antenna elements 1-1 to 1-M, an antenna changeover switch 2, a switch changeover management circuit 3, a communication control circuit 4, a communication partner station signal detection circuit 5, Reception level measurement circuit 6, reception level storage circuit 7, maximum reception level search circuit 8, TDD switch (TDD-SW) 9, low noise amplifier 102-1, mixer 103-1, filter 104-1, A / D converter 105 -1, a received signal processing circuit 107, a high power amplifier 112-1, a filter 113-1, a mixer 114-1, a D / A converter 115-1, and a transmission signal processing circuit 117.

  The difference between the wireless communication apparatus shown in FIG. 4 and the wireless communication apparatus shown in FIG. 3 is that the TDD switch 9 is provided to share the same antenna elements 1-1 to 1-M for transmission and reception. And having a configuration for transmission and a configuration for reception.

  Since the communication control circuit 4 manages the transmission timing and the reception timing, it instructs the TDD switch 9 to switch according to the timing for switching between transmission and reception. Further, since the local oscillator 106 shown in FIGS. 3 and 15 and the local oscillator 116 shown in FIG. 16 can be shared, the local oscillation signal output from the local oscillator 106 in the wireless communication apparatus in the configuration example 2 is possible. Are used in the mixer 103-1 and the mixer 114-1.

  The process of selecting the optimal antenna in the wireless communication apparatus of Configuration Example 2 is the same process as the process of selecting the optimal antenna performed by the wireless communication apparatus in the wireless communication apparatus of Configuration Example 1. That is, the reception level of each of the antenna elements 1-1 to 1-M is measured by an RF circuit integrated in one system, and the optimum antenna is selected based on the measured reception level. The selected optimum antenna can be used at the time of transmission to obtain a transmission diversity gain.

[Configuration example 3 in the base technology]
FIG. 5 is a block diagram illustrating a different configuration example of the wireless communication device in the base technology. In the configuration shown in the figure, the same components as those in the wireless communication device shown in FIGS. 3 and 4, the reception device shown in FIG. 15, and the transmission device shown in FIG. Yes. As shown in FIG. 5, the wireless communication device in Configuration Example 3 includes antenna elements 1-1 to 1-M, an antenna changeover switch 10, a switch changeover management circuit 3, a communication control circuit 4, a communication partner station signal detection circuit 5, Reception level measurement circuit 6, reception level storage circuit 7, maximum reception level search circuit 8, TDD switch 9, low noise amplifier 102-1, mixer 103-1, filter 104-1, A / D converter 105-1, reception signal A processing circuit 107, a high power amplifier 112-1, a filter 113-1, a mixer 114-1, a D / A converter 115-1, and a transmission signal processing circuit 117 are provided.

  The difference between the wireless communication apparatus shown in FIG. 5 and the wireless communication apparatus shown in FIG. 4 is that the antenna changeover switch 2 is replaced with the antenna changeover switch 10. In the wireless communication apparatus (FIG. 4) in the configuration example 2, the antenna selector switch 2 selects one of the antenna elements 1-1 to 1-M and connects the selected antenna element to the TDD switch 9. It was the composition to do. However, a configuration in which a plurality of antenna elements among the antenna elements 1-1 to 1-M are appropriately combined and connected in an analog manner may be used. That is, the signal obtained by synthesizing signals received by a plurality of antenna elements among the antenna elements 1-1 to 1-M may be output to the TDD switch 9.

  In the wireless communication device in the configuration example 3, the antenna changeover switch 10 synthesizes signals received by the plurality of antenna elements instructed from the switch changeover management circuit 3 on the analog circuit (for example, a plurality of signals using a distributor / combiner) The system is synthesized in an analog manner), and a signal obtained by the synthesis is output to the TDD switch 9. Here, a combination of a plurality of antenna elements instructed by the switch switching management circuit 3 is determined in advance as an antenna condition, and is handled as a reception level measurement target in step S5 of the flow shown in FIG.

  FIG. 6 is a diagram illustrating an example of an antenna connection pattern (antenna condition) in the antenna changeover switch 10 in the configuration example 3 of the base technology. The antenna connection pattern shown in FIG. 6 is an internal connection pattern of the antenna changeover switch 10, and shows eight patterns (a) to (h). For convenience, here, a case where the wireless communication apparatus includes four antenna elements is illustrated. The antenna ports corresponding to the four antenna elements are indicated by # 1 to # 4, and the port to which the TDD switch 9 is connected is indicated by # 0. Since the antenna selector switch 2 shown in FIGS. 3 and 4 is configured to select one antenna element, the selectable antenna conditions are the four patterns (a) to (d) shown in FIG.

  On the other hand, if a plurality of antenna elements are synthesized in an analog manner using a distribution synthesizer or the like, the number of connection patterns can be further increased. In the wireless communication apparatus of Configuration Example 3, in addition to the case where one antenna element is selected from the four antenna elements (four patterns (a) to (d)), two antennas are formed from the four antenna elements. A case of selecting an element (four patterns (e) to (h)) is provided. In general, the connection pattern in the antenna changeover switch 10 may be any combination, and more combinations such as selecting three or more antenna elements may be defined as antenna conditions.

  When a plurality of antenna elements are combined in an analog manner using a distribution synthesizer or the like, it physically appears as a plurality of antenna elements. However, an effective antenna (hereinafter referred to as an effective antenna) can be regarded as a single virtual antenna having a beam pattern corresponding to the synthesis. Therefore, as the antenna connection patterns (antenna conditions), the antenna connection patterns (a) to (d) and the antenna connection patterns (e) to (h) can be treated as equivalent without any particular distinction. is there. By using the antenna changeover switch 10 having such a plurality of antenna connection pattern options, it is possible to use more effective antennas than the number of antenna elements 1-1 to 1-M included in the wireless communication device. . Note that a single antenna element that does not involve synthesis can also be regarded as a part of the effective antenna in a broad sense. That is, each of the virtual one antenna obtained by analogly combining a plurality of antenna elements among the antenna elements 1-1 to 1-M is an effective antenna in the wireless communication apparatus, and the antenna element 1- Each of the antenna elements 1 to 1-M may be regarded as an effective antenna in the wireless communication apparatus.

  The wireless communication device in the configuration example 3 is a candidate (or, alternatively, a plurality of virtual antennas corresponding to antenna connection patterns obtained by combining the antenna elements 1-1 to 1-M and the antenna elements 1-1 to 1-M). The reception level in the case of using each of these candidates) may be measured, and the antenna element and / or one virtual antenna may be determined based on the measured reception level. Either can be selected. The switch change management circuit 3 outputs an instruction to use the selected antenna element or one virtual antenna as an effective antenna to the antenna change switch 10, so that the wireless communication apparatus can perform good communication using the optimum effective antenna. Can be performed.

[First Embodiment]
Hereinafter, a radio communication system according to an embodiment of the present invention to which the above-described base technology is applied will be described. FIG. 7 is a diagram illustrating an example of a configuration of the wireless communication system according to the first embodiment of the present invention. As shown in the figure, the wireless communication system in the first embodiment includes a base station apparatus (access point: AP) 200 having one antenna element, and a plurality of terminal station apparatuses 300 having a plurality of antenna elements ( 300-1 to 300-3). Moreover, although the radio | wireless communications system shown in the figure is provided with the three terminal station apparatuses 300, the structure provided with the 2 or 4 or more terminal station apparatus 300 may be sufficient.

  In the following description, the name “access point (AP)” is used when the description is based on WiFi of the prior art, which is an apparatus equivalent to the “base station apparatus 200” of the present invention. There is no particular distinction between an access point and a base station apparatus.

  The terminal station devices 300-1 to 300-3 in the first embodiment have the same configuration as any of the wireless communication devices (FIGS. 3, 4, and 5) described in the base technology. That is, each of the terminal station devices 300-1 to 300-3 receives an effective antenna (any one of the antenna elements or the antenna) that has the maximum reception level when receiving the signal transmitted by the base station device 200 that is the communication counterpart station. An antenna configured by combining elements) is selected. The terminal station apparatuses 300-1 to 300-3 perform signal transmission / reception with the base station apparatus 200 using the selected effective antenna.

  Here, an outline of general WiFi data communication is shown. FIG. 8 is a diagram illustrating an example of general WiFi data communication. FIG. 8 shows an example in which one access point (AP) and three terminal stations # 1 to # 3 perform data communication. In FIG. 8, reference numerals 21, 25 and 28 denote beacon signals. Reference numerals 22, 24, and 27 denote data wireless packets transmitted by the access point. Reference numerals 23 and 26 denote ACK signals transmitted by the access point. Reference numeral 29 denotes an ACK signal transmitted from the terminal station # 1. Reference numeral 30 denotes a data wireless packet transmitted by the terminal station # 1. Reference numeral 31 denotes a data wireless packet transmitted by the terminal station # 2. Reference numeral 32 denotes an ACK signal transmitted by the terminal station # 2. Reference numeral 33 denotes an ACK signal transmitted by the terminal station # 3. In FIG. 8, the horizontal axis represents the time axis, and time flows from left to right in FIG. Signals transmitted by the access point and each of the terminal stations # 1 to # 3 are shown on each time axis. Further, the dotted dotted arrow in the vertical direction indicates who the signal is addressed to. However, since the access points are signals addressed to the terminal stations # 1 to # 3, the beacon signals 21, 25, and 28 are not indicated by dotted arrows.

  The access point broadcasts beacon signals 21, 25, and 28 containing various control information in addition to service operator identification information and its own station identifier to terminal stations # 1 to # 3 located in the service area. Send as. The beacon signals 21, 25 and 28 are transmitted to the access point at a predetermined cycle. The access point transmits a signal as a result of performing carrier sense at the timing of transmitting the beacon signals 21, 25, and 28. The basic cycle for transmitting the beacon signal is, for example, 100 milliseconds or 500 milliseconds, and can be set at the access point.

  The access point communicates with each of the terminal stations # 1 to # 3 during the period during which the beacon signals 21, 25, and 28 are periodically transmitted. In the example shown in FIG. 8, the access point transmits the data radio packet 22 to the terminal station # 1. When the terminal station # 1 normally receives the data wireless packet 22, the terminal station # 1 transmits an ACK signal 29 to the access point. The access point normally receives the ACK signal 29 from the terminal station # 1, thereby determining that the terminal station # 1 has received the data wireless packet 22 normally, and grasps that the transmission of the data wireless packet 22 has been completed. To do.

  Further, in the example shown in FIG. 8, the access point performs similar operations “transmission of data radio packet 24 and reception of ACK signal 33”, “reception of data radio packet 30 and transmission of ACK signal 26”, and “data radio packet 27. Transmission and reception of the ACK signal 32 "in order. It should be noted that the beacon signals 21, 25, 28, the data wireless packets 22, 24, 27, 30, 31, and the ACK signals 23, 26, 29, 32, etc. are given the identifier of the source station and the identifier of the destination station. By referring to it, for example, each of the terminal stations # 1 to # 3 recognizes that the received signal is a signal from an access point which is a communication partner station, and also recognizes that it is a signal addressed to itself. . Similarly, it is possible to recognize whether or not the beacon signal is 21, 25, or 28 from various control information described in the received signal.

  FIG. 9 is a diagram illustrating an example of data communication in the wireless communication system according to the first embodiment. 9, the same signals as those shown in FIG. 8 are denoted by the same reference numerals. In FIG. 9, reference numerals 34, 35, and 36 indicate antenna selection test signals. Although it is the same as the data communication shown in FIG. 8, the base station apparatus 200 transmits the beacon signals 21, 25, and 28 at a predetermined beacon frame period. As shown in FIG. 9, the base station apparatus 200 transmits antenna selection test signals 34, 35, 36 following the beacon signals 21, 25, 28. In the terminal station devices 300-1 to 300-3 in the first embodiment, the antenna selection test signals 34, 35, 36 are transmitted from the base station device 200 immediately after the beacon signals 21, 25, 28. Is known. Here, “immediately after” may be that the signal is physically continuous, or may be followed by a predetermined time interval from the end of the beacon signals 21, 25, and 28.

  When the terminal station apparatus 300-1 to 300-3 detects reception of the beacon signal 21, for example, the terminal station apparatus 300-1 to 300-3 waits for reception of the antenna selection test signal 34, and is determined in advance during the reception period of the antenna selection test signal 34. Among the antenna conditions (effective antennas), the antenna conditions that maximize the reception level are searched. Here, the terminal station apparatus 300 grasps the reception start of the antenna selection test signals 34, 35, and 36. For example, the terminal station apparatus 300 grasps the start of reception using detection of a preamble at the head of the test signal 34 for antenna selection subsequent to the beacon signal 21 or detection of a reception level. Or the terminal station apparatus 300 may grasp the start of reception of the test signal 34 for antenna selection using the fact that a predetermined time has passed since the end of reception of the beacon signal 21. Alternatively, when the beacon signal 21 and the antenna selection test signal 34 are continuous, the reception end time of the beacon signal 21 may be grasped as the reception start timing of the antenna selection test signal 34. In the example shown in FIG. 9, as a result of receiving the antenna selection test signal 34 and selecting the antenna condition, the terminal station apparatus 300-1 selects the antenna # 1, and the terminal station apparatus 300-2 selects the antenna # 5. The terminal station device 300-3 selects antenna # 7. As described above, the terminal station apparatuses 300-1 to 300-3 perform communication by selecting an optimum antenna condition based on the reception level when the antenna selection test signal is received.

  The terminal station devices 300-1 to 300-3 fix the effective antenna selected continuously until the reception of the antenna selection test signal 35 transmitted immediately after the next beacon signal 25 is used for communication. Here, in the detection of the reception start of the antenna selection test signal 35 in the terminal station apparatuses 300-1 to 300-3, similarly, detection of the preamble at the head of the antenna selection test signal or detection of the reception level is performed. The elapse of a predetermined time from the reception end time of the beacon signal 25 is used. In the example shown in FIG. 9, as a result of receiving the antenna selection test signal 35 and selecting the antenna condition, the terminal station device 300-1 selects the antenna # 2, and the terminal station device 300-2 selects the antenna # 3. Select and change the effective antenna used for communication. On the other hand, the terminal station device 300-3 continuously selects the antenna # 7.

  Here, a process for preventing signals from being transmitted from other radio stations during a period in which the base station apparatus 200 transmits the antenna selection test signals 34, 35, and 36 will be described. FIG. 10 is a diagram comparing the processing by the base station apparatus 200 in the first embodiment with the processing in the prior art. FIG. 10A shows a setting state of a conventional NAV (Network Allocation Vector). FIG. 10B shows the setting status of the NAV in the first embodiment. In addition, in the signal shown in FIG. 10, the same code | symbol is attached | subjected to the signal same as the signal shown in FIG. In FIG. 10, it is not clearly shown which device the transmitting station is in particular, and all signals are shown side by side on the same time axis.

  As shown in FIG. 10A, in the prior art, when an access point transmits a beacon signal 21, it is for prohibiting signal transmission of other radio stations in accordance with the transmission period length of the beacon signal 21. NAV information indicating the NAV period is set in a predetermined control information storage area in the beacon signal 21. The wireless station that has received this beacon detects that transmission is prohibited during the period set in the NAV period, and does not perform signal transmission in that period. Similarly, when the access point transmits the data wireless packet 22 addressed to the terminal station # 1, and the terminal station # 1 returns an ACK signal 29 to the access point, the access point transmits the data wireless packet 22 to be transmitted. NAV information is set in a predetermined control information storage area. At this time, the NAV information set by the access point indicates a period during which signal transmission of other radio stations is prohibited in accordance with the period length from the top of the data radio packet 22 to the end of the ACK signal 29.

  On the other hand, in the wireless communication system according to the first embodiment, when the base station apparatus 200 transmits the beacon signal 21, it matches the period length from the beginning of the beacon signal 21 to the end of the antenna selection test signal 34. Thus, NAV information for prohibiting signal transmission of other radio stations is set in a predetermined control information storage area in the beacon signal 21. Thus, even if the terminal station that has received the beacon signal 21 in which the NAV information is set does not have the configuration described as the base technology, it is possible to detect the prohibition of signal transmission in the NAV period. For this reason, the operation is performed so that signal transmission is not performed during the period in which the test signal 34 for antenna selection is transmitted. Note that the data wireless packet 22 transmitted from the base station apparatus 200 to the terminal station apparatus 300, the ACK signal 29 transmitted from the terminal station apparatus 300 to the base station apparatus 200, and the like are the same as those in the prior art.

  If the beacon signal 21 and the antenna selection test signal 34 are within a predetermined time called SIFS, for example, other wireless stations can access the access point even if NAV information is not set. Since it is not performed, the setting of NAV information is not necessarily required. However, if a predetermined WiFi-compliant preamble signal is not given to the antenna selection test signal 34, the radio station may be mistaken for a signal of another wireless communication system that is not WiFi-compliant depending on the reception situation. Therefore, if the preamble signal or the like is omitted in consideration of setting the symbol length of the test signal 34 for antenna selection to be short, the NAV period having a period length up to the end of the test signal 34 for antenna selection is set. preferable.

  FIG. 11 is a flowchart illustrating the optimum antenna selection process in the terminal station apparatus 300 according to the first embodiment. The operation is basically the same as the optimum antenna selection process shown in FIG. 1, but the operation is shown in a form corresponding to WiFi. In the terminal station device 300, when the optimum antenna selection process is started (step S21), the normal communication state is continued (step S22). The communication control circuit 4 and the communication partner station signal detection circuit 5 determine whether or not the received signal is a beacon signal transmitted from the base station device 200 of the communication partner station (step S23).

When the received signal is not a beacon signal transmitted from the base station apparatus 200 of the communication partner station (NO in step S23), the communication control circuit 4 and the communication partner station signal detection circuit 5 return the processing to step S22 and perform normal communication. Let the state continue.
When the received signal is a beacon signal transmitted from the base station apparatus 200 of the communication counterpart station (YES in step S23), the communication control circuit 4 performs an ordinary beacon signal reception process and an antenna following the beacon signal. It waits until reception of the test signal for selection starts (step S24).

  When reception of the test signal for antenna selection is started, the communication control circuit 4 resets the value of the counter k for identifying the antenna condition to “1” (step S4). The communication control circuit 4 controls the antenna changeover switch 2 via the switch changeover management circuit 3, and causes the reception level measurement circuit 6 to measure the reception level under the kth antenna condition for a predetermined time (step S5). When the terminal station device 300 has the configuration shown in configuration example 3 (FIG. 5) in the base technology, the communication control circuit 4 controls the antenna switch 10 instead of the antenna switch 2.

When the reception level measurement by the reception level measurement circuit 6 is completed, the communication control circuit 4 determines whether or not the counter k matches the total number K of antenna conditions in the own device (step S6). If so (NO in step S6), "1" is added to the value of the counter k to update the value (step S7), the process returns to step S5, and the processes of steps S5, S6, and S7 are repeated in order.
When the counter k is equal to the total number K of antenna conditions (YES in step S6), the maximum reception level search circuit 8 follows the instruction from the communication control circuit 4 and stores the reception level in each of the K pattern antenna conditions. The maximum reception level is searched from the reception levels stored in the circuit 7, and the antenna condition corresponding to the maximum reception level is output to the communication control circuit 4 (step S8).

  The communication control circuit 4 selects an effective antenna indicated by the antenna condition input from the maximum reception level search circuit 8 as an antenna to be used for communication, and controls the antenna change switch 2 via the switch change management circuit 3 to perform communication. The effective antenna to be used is switched to the selected effective antenna (step S9). After the optimum effective antenna is selected in step S9, the communication control circuit 4 returns the process to step S22 to perform transmission / reception while continuously using the selected effective antenna, and repeats each process after step S22. Do it. The optimum antenna selection process (FIG. 1) described in the base technology is executed each time a timeout is detected in the communication flow shown in FIG. However, since the beacon signal is periodically received in the wireless communication system according to the first embodiment, it is not necessary to manage the timing at which each process is repeated with a timer or the like.

[Second Embodiment]
The basic operation has been described in the first embodiment. However, when the terminal station device 300 is actually operated, the optimum effective antenna is not selected when the power is turned on. There is a possibility that a desired beacon signal cannot be received by the antenna. Thus, a description will be given from the state in which the optimum effective antenna is not selected at the time of power-on (initial operation mode) to the state in which the optimum antenna selection process shown in FIG. 11 is performed (normal operation mode). That is, the radio communication system in the second embodiment is a radio in which a function for switching from the initial operation mode to the normal operation mode such as when the power is turned on is added to the terminal station apparatus 300 of the radio communication system in the first embodiment. It is a communication system.

  FIG. 12 is a state transition diagram of the operation mode of the terminal station device 300 according to the second embodiment. As shown in FIG. 12, the terminal station device 300 has three operation modes (states): a power-off 41, an initial operation mode 42, and a normal operation mode 43. The power off 41 is a state in which no power is supplied to the terminal station device 300.

  When the terminal station device 300 in the power-off state is turned on by a user operation, the operation mode transitions from the power-off 41 to the initial operation mode 42. In the initial operation mode 42, the terminal station apparatus 300 performs signal reception by switching the effective antennas in order at predetermined time length cycles, and receives a beacon signal from the base station apparatus 200 that is a communication partner station without a code error. It is determined whether it has been completed.

  At this time, if an effective antenna that cannot obtain a sufficient gain is selected, the terminal station apparatus 300 cannot receive the beacon signal itself, or performs reception in a state where there is a code error even though it can be received. Become. In addition, the terminal station device 300 selects an effective antenna capable of receiving a beacon signal while sequentially switching effective antennas. The effective antenna that can receive the beacon signal at this time does not need to be an effective antenna that maximizes the reception level of the beacon signal. By receiving the beacon signal, the terminal station device 300 detects the reception timing of the test signal for antenna selection subsequent to the beacon signal.

  As described above, when the terminal station apparatus 300 detects the reception timing of the subsequent antenna selection test signal by normally receiving the beacon signal, the terminal station apparatus 300 shifts the operation mode from the initial operation mode 42 to the normal operation mode 43. When the operation mode becomes the normal operation mode 43, the terminal station apparatus 300 interrupts step S24 of the process illustrated in FIG. 11 and continues the subsequent processes. However, when the beacon signal cannot be received from the base station apparatus 200 for a predetermined time or more in the process of step S22 in the optimum antenna selection process shown in FIG. 11, it is assumed that an abnormality has been detected, and the operation mode is changed from the normal operation mode 43. Transition to the initial operation mode 42. By this operation mode transition, the terminal station device 300 detects the beacon signal by switching the effective antenna in order until the beacon signal can be received from the base station device 200 which is the communication counterpart station in the initial operation mode again. I do.

  FIG. 13 is a flowchart illustrating processing when the operation mode of the terminal station apparatus 300 according to the second embodiment is the initial operation mode. In the terminal station device 300 in which the operation mode is in the power off state, when the user switches the power on, the operation mode transitions to the initial operation mode (step S32). The communication control circuit 4 selects a predetermined initial antenna condition (step S33), and sets the antenna change switch 2 via the switch change management circuit 3 so that the antenna element of the effective antenna indicated by the initial antenna condition is selected. Control.

The communication control circuit 4 assigns “0” to the effective antenna selection timer t ′ in the initial operation mode and resets it (step S34). The communication control circuit 4 and the communication partner station signal detection circuit 5 determine whether or not a beacon signal from the base station apparatus 200 that is the communication partner station has been detected (step S35).
When a beacon signal is detected from the base station apparatus 200 that is the communication counterpart station (YES in step S35), the communication control circuit 4 ends the process in the initial operation mode (step S38), and sets the operation mode to the normal operation mode. The process is switched to the step S24 of the optimum antenna selection process (FIG. 11).

When a beacon signal is not detected (NO in step S35), the communication control circuit 4 determines whether or not the value of the timer t ′ is equal to or greater than a predetermined threshold value t ′ _max (step S36), and the value of the timer t ′. Is less than the threshold t ′ _max and is not timed out (NO in step S36), the process returns to step S35 to continue the process. Here, the threshold value t ′ _max is a value determined in advance according to the time allocated to the presence or absence of detection of a beacon signal for each antenna condition.

When the value of the timer t ′ is equal to or greater than the threshold value t ′ _max and is timed out (YES in step S36), the communication control circuit 4 selects another antenna condition. The communication control circuit 4 controls the antenna changeover switch 2 via the switch changeover management circuit 3 so that the antenna element of the effective antenna indicated by the selected antenna condition is selected (step S37), and returns the process to step S34. Continue processing.

  FIG. 14 is a flowchart illustrating an optimal antenna selection process in the terminal station apparatus 300 according to the second embodiment. The optimum antenna selection process shown in FIG. 14 is different from the optimum antenna process (FIG. 11) of the first embodiment in that it corresponds to the state transition shown in FIG. When the optimum antenna selection process is started in the terminal station device 300 (step S21), the communication control circuit 4 sets the value of the timer t ″ for determining whether or not the transition to the initial operation mode is possible to “0”. Reset (step S41) and continue the normal communication state (step S22).

The communication control circuit 4 and the communication partner station signal detection circuit 5 determine the presence / absence of signal reception and whether or not the received signal is a beacon signal transmitted from the base station device 200 of the communication partner station (step S23).
When the received signal is not a beacon signal transmitted from the base station apparatus 200 of the communication partner station or when no signal is received (NO in step S23), the communication control circuit 4 sets the value of the timer t ″ to a predetermined threshold value t. _'' determines whether a _max or more (step S42), the timer t 'if the value of' is less than the threshold t _{'' max} (NO at step S42), the normal operation mode returns the process to step S22 Continue.

When the value of the timer t ″ is equal to or greater than the threshold value t ″ _max (YES in step S42), the communication control circuit 4 ends the optimum antenna selection process, transitions the operation mode to the initial operation mode, and initializes the process. The operation mode is shifted to step S32 (step S43). Here, the threshold value t ″ _max is a value that determines in what period a transition to the initial operation mode is made when the beacon signal cannot be detected (received), and is a predetermined value.

  In step S23, when the signal is received and the received signal is a beacon signal transmitted from base station apparatus 200 of the communication counterpart station (YES in step S23), communication control circuit 4 performs normal beacon signal reception processing. And waits until reception of a test signal for antenna selection following the beacon signal is started (step S24). In addition, since the process after step S24 is the same as the optimal antenna selection process shown in FIG. 11, description is abbreviate | omitted. In the optimum antenna selection process in the second embodiment, after step S9, the communication control circuit 4 returns the process to step S41 in order to perform transmission / reception while continuously using the selected effective antenna.

  As described above, the terminal station apparatus 300 according to the second embodiment can stably obtain the gain of transmission / reception diversity while managing the state transition shown in FIG.

  Note that the antenna selection test signal transmitted after the beacon signal in each embodiment may be any signal. For example, a signal such as RTS / CTS (Request To Send / Clear To Send) used to avoid a hidden terminal station in WiFi is defined. Among these, a CTS signal is a dummy for setting a NAV period. May be sent automatically. If this CTS signal is prepared by setting the symbol length of the payload portion to a length corresponding to the time length required for selecting the optimum effective antenna, it can be used as a test signal for antenna selection. Or the amplitude of the signal in one symbol varies, but when a predetermined number of samplings are performed, if the variation in amplitude is biased for each sampling interval, the correct reception level cannot be evaluated. The area following the minimum information for identifying a WiFi-compliant signal such as a preamble without performing processing for interval and waveform shaping shall be a continuous training signal without a guard interval. Is also possible. Furthermore, when the NAV is set during the transmission period of the antenna selection test signal, even a signal not accompanied by a WiFi-compliant preamble signal can be detected from the positional relationship with the beacon signal. That is, any test signal for antenna selection may be used.

  In each of the embodiments, the antenna selection test signal is transmitted after the beacon signal. However, this information purposely adds information for indicating the presence of the antenna selection test signal. It is one configuration for saving. If a control signal for indicating the presence of a test signal for antenna selection is newly defined, the newly defined control signal is used to indicate the presence of the test signal for antenna selection, and an optimum signal is determined based on the control signal. It is also possible to perform processing for selecting an effective antenna. However, at the present time, neither a field for accommodating such a control signal nor control information is defined in WiFi, and when operating using such undefined control information, the terminal shown in each embodiment Although the station apparatus 300 can be operated, compatibility with other radio stations may not be maintained. However, since the radio communication system shown in each embodiment is configured so that the antenna selection test signal is transmitted immediately after the beacon signal, the antenna selection test signal that is undefined in WiFi is used. The base station apparatus 200 and the terminal station apparatus 300 are completely compatible with any terminal station that is fully compliant with WiFi, and can be operated stably.

  Furthermore, although the test signal for antenna selection is transmitted immediately after the beacon signal, in addition to the case where the test signal is physically continuous, a predetermined time interval (for example, the SIFS time interval or shorter in the general WiFi standard) It does not matter as long as it is transmitted with a time interval. If the conditions are unified in advance, the terminal station apparatus 300 side can reliably select the optimum effective antenna using the test signal for antenna selection.

  In addition, the change point of the base station apparatus 200 in each embodiment is that the test signal for antenna selection is transmitted following the transmission of the beacon signal, and the test signal for antenna selection as NAV information set in the beacon signal. This is the point of notifying the neighboring wireless stations of the signal transmission prohibition by other wireless stations during the period until the transmission is completed. The latter change is not essential.

  In the radio communication system in each embodiment, that is, the radio communication system to which the IEEE 802.11 standard is applied, the base station apparatus 200 transmits a test signal for antenna selection used for reception level estimation after transmitting a beacon signal, and a terminal station The apparatus 300 selects an effective antenna that maximizes the reception level using a test signal for antenna selection. With this processing, the wireless communication system simply selects only one antenna element from a plurality of antenna elements while making the configuration of the RF system of the terminal station device 300 one simple configuration in conformity with the IEEE 802.11 standard. Compared with the conventional diversity method, the characteristics can be greatly improved.

  Further, the base station apparatus 200 in the wireless communication system of each embodiment transmits a beacon signal and an antenna selection test signal, that is, from the beginning of the beacon signal to the end of the antenna selection test signal. NAV information for prohibiting signal transmission of other radio stations is included in the beacon signal. Accordingly, the wireless communication system of each embodiment can be applied even in an environment where an existing wireless station compliant with the IEEE 802.11 standard is used.

  Each time the terminal station device 300 in the wireless communication system of each embodiment receives the beacon signal transmitted from the base station device 200 as the communication partner station, the terminal station device 300 uses the antenna selection test signal subsequent to the beacon signal. Based on this, the optimum effective antenna is selected. That is, the terminal station apparatus 300 continuously uses the effective antenna corresponding to the maximum reception level for communication until the beacon signal is received again. Thereby, since the terminal station apparatus 300 repeats selection of an optimal effective antenna according to the period of a beacon signal, it becomes possible to maintain favorable communication. In the example of data communication illustrated in FIG. 9, the terminal station device 300 has been described as selecting the effective antenna every time reception of the beacon signal is completed, but without selecting the effective antenna every time. The effective antenna may be selected every other time, every second time, or every predetermined number of times. Alternatively, the effective antenna may be selected when a predetermined time has elapsed after receiving the beacon signal.

  Further, in a wireless communication system that includes a base station apparatus having one antenna element and a terminal station apparatus that has a plurality of antenna elements and communicates with the base station apparatus, the wireless communication system is compliant with the WiFi standard (or IEEE 802.11 standard). Based on the beacon signal transmitted from the base station device and the test signal for antenna selection, by using the terminal station device of each embodiment to which the configuration of any one of the configuration examples 1 to 3 in the base technology is applied The optimum antenna condition is selected from a large number of effective antenna candidates configured by a large number of antenna elements 1-1 to 1-M or virtual antennas, and reception is performed using the effective antenna indicated by the selected antenna condition. Communication with the base station apparatus can be performed in a situation where the gain or the transmission / reception gain is maximized. According to a separately performed simulation, when the optimum effective antenna is selected for the number of effective antenna candidates that can be selected (including an antenna with a single antenna element and a virtual antenna that is a combination of multiple antenna elements) N It is evaluated that the gain improvement effect is about 10 Log (N) [dB]. For example, when N, which is the number of options, is 32, a gain of about 15 [dB] can be expected.

  In addition, the circuit scale required when the terminal station apparatus in each embodiment is mounted includes signal processing for one system in all of the RF system and baseband signal processing excluding the antenna elements 1-1 to 1-M. Therefore, it is possible to suppress an increase in circuit scale. In the prior art, when RF systems and baseband signal processing systems corresponding to the number of antenna elements are provided, the potential can be maximized by applying transmission / reception weights, but the circuit scale increases accordingly. . That is, the terminal station apparatus in each embodiment can obtain a high diversity gain while having a simple configuration including a signal processing function for one system in the basic part such as RF system and baseband signal processing. .

  In addition, the terminal station apparatus to which the configuration example 3 of the base technology is applied uses the signals received by the plurality of antenna elements 1-1 to 1-M by analog synthesis. As a result, the terminal station apparatus actually transmits and receives using a plurality of antenna elements, but it can be considered that the terminal station apparatus is actually transmitting and receiving with a single virtual antenna synthesized in an analog manner. it can. The signal line route used in analog synthesis for signals received by multiple antenna elements is shared by the uplink and downlink (ie, for reception and transmission), so the amplitude and phase within the circuit The amount of variation in rotation is symmetrical between the uplink and the downlink. In transmission diversity technology using transmission weights in the prior art, different high power amplifiers are used for each antenna element system, so the amount of amplitude and phase rotation variation for each high power amplifier must be considered for each antenna element system. was there. On the other hand, in the terminal station apparatus, it is guaranteed that the antenna (antenna element or virtual antenna) that is optimal at the time of reception is the optimal antenna at the time of transmission because of the symmetry between the uplink and the downlink. The Therefore, the terminal station apparatus can surely obtain the gain of transmission diversity based on the state at the time of reception while performing simple control.

  As described above, the terminal station apparatus to which the configuration example 3 of the base technology is applied has a configuration in which the transmission system and the reception system are switched by the TDD switch 9, so that the reception diversity gain can be improved while having a simple circuit configuration. In addition, a high transmission diversity gain can be obtained.

  In the description of the base technology, the configuration in which the output of the A / D converter 105-1 is input to the reception level measurement circuit 6 is shown. However, for example, when RSSI information is used in the reception level measurement circuit 6, it is provided in the low noise amplifier 102-1 (or a circuit associated therewith, which is not explicitly shown in FIGS. 3 to 5). The RSSI value used in the AGC processing function may be input to the reception level measuring circuit 6.

  In addition, since the communication control circuit 4 is responsible for all types of communication control, the input / output with respect to the signals clarified in the description in the base technology is represented as signal lines between the circuits in FIGS. In practice, however, necessary information is input / output to / from other circuits using signal lines not shown in FIGS. For example, sampling information from the A / D converter 105-1 or RSSI value from the low noise amplifier 102-1 is input to the reception level measurement circuit 6, which part should be cut out when measuring the reception level. The communication control circuit 4 instructs the reception level measurement circuit 6 for timing information such as. Further, since fine processing such as MAC control is not directly related to the configuration in each embodiment centering on the physical layer, these signal lines and the like are also omitted. As described above, the description with reference to the drawings in the present specification explicitly indicates the part related to the essence of the present invention, and indicates that information not described herein is not necessary for the circuit configuration. It is assumed that the necessary functions as well as the general apparatus configuration are similarly implemented in the terminal station apparatus of each embodiment.

  Although the embodiments of the wireless communication system according to the present invention have been described above, the present invention can be implemented in various other forms without departing from the technical idea or the main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  You may make it implement | achieve the base station apparatus 200 and the terminal station apparatus 300 in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, a “computer-readable recording medium” dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case may be included and a program that holds a program for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

1-1, 1-2, 1-M antenna element 2, 10 antenna switching switch 3 switch switching management circuit 4 communication control circuit 5 communication partner signal detection circuit 6 reception level measurement circuit 7 reception level Memory circuit 8... Maximum reception level search circuit 9... TDD switch 101-1, 101-2, 101 -M ... Antenna element 102-1, 102-2, 102 -M ... Low noise amplifier 103-1, 103-2, 103 -M ... Mixers 104-1, 104-2, 104-M ... Filters 105-1, 105-2, 105-M ... A / D converter 106 ... Local oscillator 107 ... Received signal processing circuit 108 ... Antenna changeover switch 111 -1, 111-2, 111-M ... antenna elements 112-1, 112-2, 112-N ... high power amplifiers 113-1, 113-2, 1 13-N: Filters 114-1, 114-2, 114-N ... Mixers 115-1, 115-2, 115-N ... D / A converters 116 ... Local oscillator 117 ... Transmission signal processing circuit 118 ... Antenna selector switch 200 ... base station apparatus 300, 300-1, 300-2, 300-3 ... terminal station apparatus

Claims (4)

A base station apparatus having one first antenna element and a terminal station apparatus having a plurality of second antenna elements, wherein the base station apparatus and the terminal station apparatus are wirelessly compliant with the IEEE 802.11 standard. A wireless communication method in a system, comprising:
A signal transmission step in which the base station apparatus transmits a signal for antenna selection following the beacon signal; and
A plurality of candidates configured by a virtual antenna obtained by combining any of the plurality of second antenna elements after the terminal station apparatus detects reception of the beacon signal and / or individual second antenna elements A reception level measuring step for measuring a reception level when the antenna selection signal is received for each effective antenna;
An effective antenna control step for determining that the terminal station apparatus performs reception using an effective antenna corresponding to a maximum reception level among reception levels for each effective antenna;
A wireless communication method comprising: a wireless communication step in which the terminal station device performs wireless communication with the base station device using the effective antenna selected in the effective antenna control step. The wireless communication method according to claim 1,
The terminal station device has an operation state of an initial operation mode and a normal operation mode,
The terminal station apparatus, the initial operation mode is selected as an initial state,
The initial operation mode is:
Beacon signal detection step of repeatedly performing reception until the beacon signal transmitted by the base station device is detected by sequentially switching different effective antennas in a predetermined cycle;
And a first state transition step for transitioning the operation state to the normal operation mode when detecting the beacon signal,
The normal operation mode is:
The reception level measuring step;
The effective antenna control step;
The wireless communication step;
And a second state transition step of transitioning an operation state to the initial operation mode when the beacon signal cannot be received continuously for a predetermined time or longer. In the radio | wireless communication method in any one of Claim 1 or Claim 2,
In the signal transmission step,
The wireless communication method, wherein the beacon signal includes information for prohibiting signal transmission of another device during a period in which the base station device transmits the beacon signal and the antenna selection signal. A base station apparatus having one first antenna element and a terminal station apparatus having a plurality of second antenna elements, wherein the base station apparatus and the terminal station apparatus are wirelessly compliant with the IEEE 802.11 standard. A system,
The base station device
A signal transmission means for transmitting a signal for antenna selection following a beacon signal periodically transmitted;
The terminal station device
Received by one effective antenna selected from a virtual antenna obtained by combining any of the plurality of second antenna elements and / or a plurality of candidate effective antennas configured by the individual second antenna elements Antenna switching means for outputting a signal;
Wireless communication means for receiving signals via the antenna switching means;
After the wireless communication means receives the beacon signal, reception level measuring means for measuring the reception level of the antenna selection signal for each effective antenna;
Maximum reception level search means for searching for the maximum reception level among the reception levels measured by the reception level measurement means;
Have
The antenna switching means is
An effective antenna corresponding to the maximum reception level detected by the maximum reception level search means is continuously used for reception until the wireless communication means finishes receiving the beacon signal again.

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