Patent Application
20140292577
In recent years, use of radio devices using wideband millimeter waves (30 GHz to 300 GHz) has become increasingly widespread. The millimeter-wave radio technology has been expected to be used especially for high-rate radio data communication in the order of gigabit such as radio transmission of high-resolution images (for example, see Non-patent literatures 1, 2 and 3).
However, millimeter waves having high frequencies have a high rectilinear propagation property, and therefore they cause a problem in cases where radio transmission is to be implemented indoors. In addition to the high rectilinear propagation property, millimeter waves are significantly attenuated by a human body or a similar object. Therefore, if a person stands between the transmitter and the receiver in a room or a similar circumstance, no unobstructed view can be obtained, thus making the transmission very difficult (shadowing problem). This problem results from the fact that the propagation environment has been changed because of the increase in the rectilinear propagation property of the radio waves, which results from the increase in the frequency. Therefore, this problem is not limited to the millimeter waveband (30 GHz and above). Although it is impossible to clearly specify the transition frequency at which the propagation environment of the radio waves changes, it has been believed to be around 10 GHz. Note that according to recommendations of the International Telecommunications Union (“Propagation data and prediction methods for the planning of indoor radio communication systems and radio local area networks in the frequency range 900 MHz to 100 GHz,” ITU-R, P. 1238-3, April, 2003), a power loss coefficient, which indicates the attenuation amount of a radio wave with respect to the propagation distance, is 22 for 60 GHz in an office, while it is 28 to 32 for 0.9 to 5.2 GHz. Considering that it is 20 in the case of free-space loss, the effects of scattering, diffraction, and the like are considered to be small in higher frequencies such as 60 GHz.
To solve the problem described above, Patent literature 2, for example, discloses a system in which a plurality of transmission paths are provided by installing a plurality of receiving units in the receiver, so that when one of the transmission paths between the transmitter and the receiving units is shielded, the transmission is carried out by another transmission path(s).
Further, as another method for solving the problem, Patent literature 3 discloses a contrivance to secure a plurality of transmission paths by installing reflectors on the walls and ceilings.
The method disclosed in Patent literature 2 cannot carry out transmission when shielding occurs in the vicinity of the transmitter or when all of the installed receiving units are shielded. Meanwhile, the method disclosed in Patent literature 3 requires users to give particular consideration to the configuration. For example, the reflectors need to be installed with consideration given to the positions of the transmitter and the receiver.
However, recent studies on propagation properties of millimeter waves have found out that reflected waves could be utilized without intentionally installing reflectors.
Therefore, when the direct wave is blocked, it is necessary to ensure a sufficient received-signal level by pointing a narrow beam having a high directive gain to a DOA of a reflected wave as shown in
To implement beam forming, it is necessary to use an antenna having function of controlling its directivity. Typical antennas for such use include a phased array antenna. For millimeter waves having a short wavelength (e.g., 5 mm in the case of a frequency of 60 GHz), the phased array antenna can be implemented in a small area, and phase shifter arrays and oscillator arrays for use in those antenna arrays have been developed (for example, see Non-patent literatures 3 and 4). In addition to the phased array antenna, a sector-selectable antenna and a mechanically-direction-adjustable antenna may be also used to implement the antenna directivity control.
Further, as a technique for a different purpose from the beam forming using an antenna array, direction-of-arrival (DOA) estimation techniques have been known. The DoA estimation techniques are used in, for example, radars, sonar, and propagation environment measurements, and used for estimating the DoAs and the power of radio waves to be received at antenna arrays with high accuracy. When a DoA estimation technique is used in propagation environment measurement with an installed radio wave source, an omni (nondirectional) antenna is often used as the radio wave source. For example, Non-patent literature 6 shows an example of such a technique.
In indoor millimeter wave systems, when the direct wave is blocked and the radio transmission is to be continued by using reflected waves, the following problem arises.
When the wave (direct wave, reflected wave) that is actually used is switched, it is desirable to minimize the period during which the transmission is disconnected. Such minimization of the transmission disconnected period becomes especially an important requirement, for example, in the transmission of non-compressed images that requires a real-time capability. Meanwhile, when a reflected wave is used, it is necessary to increase the directive gain of the antenna and thereby to increase the reception strength by narrowing the antenna beam width.
However, the number of directions (steps) in which the search needs to be performed increases as the beam width becomes narrower. Therefore, the time necessary to search the beam directions and thereby set an optimal beam direction becomes longer, and therefore transmission-disconnected time also becomes longer. Accordingly, it has been desired to develop a beam direction setting method that can shorten the transmission-disconnected time even in such situations. It should be noted that the use of a device capable of temporally storing data is impractical because a huge buffer memory is required when the transmission-disconnected time becomes longer.
Characteristics of propagation paths between two communication devices are expressed by a channel response matrix. It has been known that if this channel response matrix is determined, the optimal combination of the antenna settings (hereinafter called “antenna-setting pair”) of the transceivers can be obtained by using SVD (Singular-Value Decomposition). However on the other hand, since SVD is complex and requires a long processing time, it is very difficult to implement SVD, for example, in a non-compressed image transmission apparatus that requires a high-rate processing capability.
Accordingly, Patent literature 4, for example, discloses a method for obtaining an optimal AWV (Array weight vector) with which the signal strength is maximized by adding a unitary matrix (e.g., Hadamard matrix) as phases of the antenna array and repeating the training of the antenna array of the transmitter and the training of the antenna array of the receiver. Although this method can reduce the processing time in comparison to SVD, it still requires a certain time to obtain the optimal AWV combination because the switching between the transmission and the reception needs to be repeatedly carried out.
Meanwhile, Non-patent literature 5 discloses a technique to optimize a transmitting/receiving beam direction (antenna setting) by gradually increasing the beam resolution. However, this technique also requires measuring communication quality for a number of combinations of the transmitting/receiving beam directions (antenna settings) while repeatedly carrying out the switching between the transmission and the reception, and thereby requiring a huge amount of time to obtain an optimal beam combination.
Further, this literature also brings up an idea called “quasi-omni (quasi-nondirectional) pattern” as a beam having the lowest resolution. This quasi-omni pattern means a pattern having a constant antenna gain over a very wide angle in the space around the transceiver, though it is not a complete omni (nondirectional) pattern. Since it is often very difficult to obtain a complete omni pattern in antenna arrays, this quasi-omni pattern is often used as a substitute in such cases. Further, in the millimeter waveband, there are cases where it is very difficult to obtain a good quasi-omni pattern. Note that the “good quasi-omni pattern” means a radiation pattern having a sufficiently small antenna gain variation over a wide or desired angular range.
In general, when a link is to be established at the initial stage, it would be acceptable if the acquisition of an optimal antenna setting requires a long time. However, in a case where a link needs to be re-established due to disconnection of the transmission on the previously-established link, a fast search for another optimal antenna-setting pair is required. Further, in the case of multipoint communication, a faster search for an optimal antenna-setting pair is also required because it requires re-establishment of a plurality of links.
The present invention has been made in view of the above-described problems, and an object thereof is to provide a radio control method capable of, when radio communication is performed by using beam forming, reducing the time necessary for finding and setting a beam direction (antenna setting) and thereby reducing the transmission-disconnected time.
A method according to a first aspect of the present invention is a control method of a radio communication system including first and second communication devices. The first communication device is configured to be able to control a transmission beam direction of a first transmitting antenna by changing transmitting-antenna setting and to control a reception beam direction of a first receiving antenna by changing receiving-antenna setting. Further, the second communication device is configured to be able to control a transmission beam direction of a second transmitting antenna by changing transmitting-antenna setting and to control a reception beam direction of a second receiving antenna by changing receiving-antenna setting. The method according to this aspect includes the following steps (a) to (k):
(a) transmitting a training signal from the first transmitting antenna while changing antenna setting of the first transmitting antenna;
(b) receiving the training signal by the second receiving antenna in a state where a fixed beam pattern is set in the second receiving antenna;
(c) obtaining a data string describing a relation between antenna setting of the first transmitting antenna and a reception signal characteristic of the second receiving antenna based on a reception result of a training signal obtained in the step (b);
(d) determining at least one first transmitting-antenna-setting candidate, which serves as a candidate to be used for communication, of the first transmitting antenna by using the data string;
(e) determining at least one second transmitting-antenna-setting candidate, which serves as a candidate to be used for communication, of the second transmitting antenna, by performing the steps (a) to (d), which were performed by using the first transmitting antenna and the second receiving antenna, for a combination of the second transmitting antenna and the first receiving antenna;
(f) transmitting a training signal from the first transmitting antenna in a state where a fixed beam pattern is set in the first transmitting antenna;
(g) receiving the training signal by the second receiving antenna while changing antenna setting of the second receiving antenna;
(h) obtaining a data string describing a relation between antenna setting and a reception signal characteristic of the second receiving antenna based on a reception result of a training signal obtained in the step (g);
(i) determining at least one second receiving-antenna-setting candidate, which serves as a candidate to be used for communication, of the second receiving antenna by using the data string;
(j) determining at least one first receiving-antenna-setting candidate, which serves as a candidate to be used for communication, of the first receiving antenna, by performing the steps (f) to (i), which were performed by using the first transmitting antenna and the second receiving antenna, for a combination of the second transmitting antenna and the first receiving antenna; and
(k) using the combination of the first transmitting-antenna-setting candidate and the second receiving antenna candidate, and the combination of the first receiving-antenna-setting candidate and the second transmitting antenna candidate for communication between the first and second communication devices.
A second aspect of the present invention relates to a radio communication system including first and second communication devices. The first communication device is configured to transmit a radio signal from a first transmitting antenna and to receive a radio signal by a first receiving antenna. The second communication device is configured to transmit a radio signal from a second transmitting antenna and to receive a radio signal by a second receiving antenna. Further, the first and second communication devices are configured to perform a process of determining a transmitting-antenna-setting candidate and a receiving-antenna-setting candidate used for radio communication in a cooperative manner. The determination process includes the following processes (a) to (k):
(a) transmitting a training signal from the first transmitting antenna while changing antenna setting of the first transmitting antenna and thereby changing a transmission beam direction;
(b) receiving the training signal by the second receiving antenna in a state where a fixed beam pattern is set in the second receiving antenna;
(c) obtaining a data string describing a relation between antenna setting of the first transmitting antenna and a reception signal characteristic of the second receiving antenna based on a reception result of a training signal obtained in the process (b);
(d) determining at least one first transmitting-antenna-setting candidate, which serves as a candidate to be used for communication, of the first transmitting antenna by using the data string;
(e) determining at least one transmitting-antenna-setting candidate, which serves as a candidate to be used for communication, of the second transmitting antenna, by performing similar processes to the processes (a) to (d) for determining the at least one first transmitting-antenna-setting candidate, for a combination of the second transmitting antenna and the first receiving antenna;
(f) transmitting a training signal from the first transmitting antenna in a state where a fixed beam pattern is set in the first transmitting antenna;
(g) receiving the training signal by the second receiving antenna while changing antenna setting of the second receiving antenna and thereby changing a reception beam direction;
(h) obtaining a data string describing a relation between antenna setting and a reception signal characteristic of the second receiving antenna based on a reception result of a training signal obtained in the process (g);
(i) determining at least one second receiving-antenna-setting candidate, which serves as a candidate to be used for communication, of the second receiving antenna by using the data string obtained in the process (h);
(j) determining at least one first receiving-antenna-setting candidate, which serves as a candidate to be used for communication, of the first receiving antenna, by performing similar processes to the processes (f) to (i) for determining the at least one second receiving-antenna-setting candidate, for a combination of the second transmitting antenna and the first receiving antenna; and
(k) using the combination of the first transmitting-antenna-setting candidate and the second receiving antenna candidate, and the combination of the first receiving-antenna-setting candidate and the second transmitting antenna candidate for communication between the first and second communication devices.
A third aspect of the present invention relates to a radio communication apparatus that performs radio communication with a corresponding device. The radio communication apparatus includes a transmitting-antenna setting control unit, a receiving-antenna setting control unit, and a processing unit. The transmitting-antenna setting control unit controls a transmission beam direction of a first transmitting antenna by changing transmitting-antenna setting. The receiving-antenna setting control unit controls a reception beam direction of a first receiving antenna by changing receiving-antenna setting. The processing unit performs a process of determining a transmitting and receiving-antenna-setting candidate in a cooperative manner with the corresponding device, the transmitting and receiving-antenna-setting candidate being used for radio communication with the corresponding device. The determination process includes the following processes (a) to (c):
(a) determining at least one first transmitting-antenna-setting candidate to be used at a time of transmission performed by the radio communication apparatus and at least one first receiving-antenna-setting candidate to be used at a time of reception performed by the radio communication apparatus by performing at least one of (i) a first training in which the radio communication apparatus transmits a first training signal while changing transmitting-antenna setting and thereby changing a transmission beam direction and the corresponding device receives the first training signal while maintaining a reception beam pattern in a fixed state, and (ii) a second training in which the corresponding device transmits a second training signal while maintaining a transmission beam pattern in a fixed state and the radio communication apparatus receives the second training signal while changing receiving-antenna setting and thereby changing a reception beam direction;
(b) determining at least one second transmitting-antenna-setting candidate to be used at a time of transmission performed by the corresponding device and at least one second receiving-antenna-setting candidate to be used at a time of reception performed by the corresponding device by performing at least one of (i) a third training in which the corresponding device transmits a third training signal while changing transmitting-antenna setting and thereby changing a transmission beam direction and the radio communication apparatus receives the third training signal while maintaining a reception beam pattern in a fixed state, and (ii) a fourth training in which the radio communication apparatus transmits a fourth training signal while maintaining a transmission beam pattern in a fixed state and the corresponding device receives the fourth training signal while changing receiving-antenna setting and thereby changing a reception beam direction; and
(c) applying a combination of the first transmitting-antenna-setting candidate and the second receiving-antenna-setting candidate, and a combination of the first receiving-antenna-setting candidate and the second transmitting-antenna-setting candidate for communication between the radio communication apparatus and the corresponding device.
A fourth aspect of the present invention relates to a control method of a radio communication system in which first and second communication devices perform radio communication with each other. The method includes the following steps (i) to (iii):
(i) selecting a transmission beam candidate of the first communication device by making the first communication device scan a beam direction and thereby transmit a first training signal and making the second communication device receive the first training signal with a fixed beam pattern;
(i) selecting a reception beam candidate of the second communication device by making the first communication device transmit a second training signal with a fixed beam pattern and making the second communication device scan a beam direction and thereby receive the second training signal; and
(iii) performing a training for combining the transmission beam candidate with the reception beam candidate.
A fifth aspect of the present invention relates to a radio communication system in which first and second communication devices perform radio communication with each other. The first and second communication devices are configured to perform a control method including the following steps (i) to (iii) in a cooperative manner:
(i) making the first communication device scan a beam direction and thereby transmit a first training signal and making the second communication device receive the first training signal with a fixed beam pattern;
(ii) making the first communication device transmit a second training signal with a fixed beam pattern and making the second communication device scan a beam direction and thereby receive the second training signal; and
(iii) combining a transmission beam candidate selected based on transmission/reception of the first training signal with a reception beam candidate selected based on transmission/reception of the second training signal.
According to each of the above-described exemplary embodiments of the present invention, when radio communication is performed using beam forming, it is possible to find and set a beam direction having good communication quality in a short time.
Specific exemplary embodiments to which the present invention is applied are explained hereinafter in detail with reference to the drawings. The same signs are assigned to the same components throughout the drawings, and duplicate explanation is omitted as appropriate for clarifying the explanation.
A radio communication system according to this exemplary embodiment includes transceivers 400 and 500 having a directivity-controllable antenna for beam forming. There is no particular restriction on the directivity control mechanism of the directivity-controllable antenna of the transceivers 400 and 500. For example, the directivity-controllable antenna of the transceivers 400 and 500 may be a phased array antenna, a sector-selectable antenna, or a mechanically-movable antenna.
A process/arithmetic circuit 406 provides instructions about the setting of the antenna setting circuit 404 through a control circuit 407. By changing both or either of the amplitude and the phase of each signal, it is possible to control the direction, the width, or the like of the beam radiated from the transmitter.
Meanwhile, a receiver 402 has a reversed configuration to the transmitter 401. Signals received by a receiving antenna array composed of radiating elements 411-1 to 411-N are adjusted in both or either of the amplitude and the phase in AWV control circuits 410-1 to 419-N and combined. Then, a receiver circuit 409 receives the combined signal, and outputs data externally. As in the case of the transmitter 401, a process/arithmetic circuit 406 controls both or either of the amplitude and phase of each of the AWV control circuits 410-1 to 419-N.
In
An overall radio control procedure in a radio communication system according to this exemplary embodiment is explained with reference to a transition diagram shown in
Note that as described above, the antenna-setting pair means a combination of an antenna setting for a transmitting antenna and an antenna setting for a receiving antenna. The antenna setting may be any setting information that defines a directivity pattern (e.g. beam direction or beam pattern) of a transmitting antenna or a receiving antenna. For example, when a phased array antenna is used as the directivity-controllable antenna as shown in
In a state S14, one of the antenna-setting pair candidates obtained in the state S13 is selected, and communication is performed in a state S15. The method of selecting the antenna-setting pair performed in the state S14 is also explained later. During the communication, the transceivers 400 and 500 monitor the communication state. For example, when the transceiver 500 is operated for reception, the communication quality may be measured in the receiver circuit 509 or the process/arithmetic circuit 506. For example, communication quality such as a received-signal level, a signal to noise ratio (SNR), a bit error rate (BER), a packet error rate (PER), and a frame error rate (FER) may be measured. Meanwhile, the monitoring of the communication state in the transceiver 400, which is operated as a transmitter at this time, may be implemented by measuring a reception status of a communication quality deterioration alert from the transceiver 500 or a reception status of a reception confirmation response (ACK). It should be noted that since publicly-known common techniques may be used as the communication state monitoring technique, detailed explanation of the monitoring technique in this exemplary embodiment is omitted.
When deterioration in communication quality such as disconnected communication is detected during the communication, the transceivers 400 and 500 select another antenna-setting pair from the data string stored in both or either of the storage circuits 408 and 508 (S16).
In a state S17, it is determined whether the quality of the communication using the newly-selected antenna-setting pair is satisfactory or not. When the transceiver 500 is operated for reception, for example, the receiver circuit 509 or the process/arithmetic circuit 506 determines whether the communication quality is satisfactory or not by measuring a received-signal level, an SNR, or the like. When the communication quality is determined to be satisfactory in the state S17, the transceivers 400 and 500 return to the communication state (S15). On the other hand, when the communication quality is determined to be unsatisfactory in the state S17, the transceivers 400 and 500 change to a state S16 and select an antenna-setting pair again.
As an alternative form of operation, when the transceivers 400 and 500 change from the state S15 to the state S16, the transceivers 400 and 500 may check the communication quality of all or some of the antenna-setting pairs obtained in the state S13 and resume the communication by using an antenna-setting pair having good communication quality based on the check result.
When any antenna-setting pair having a satisfactory communication state is not found from the antenna-setting pairs stored in the storage circuits 408 and 508, the procedure returns to the training (S12) and repeats the processes from there.
Next, the training procedure performed in the state S12 in
As an example, assume a propagation environment shown in
Steps S102-1 and S102-2 shown in
In this state, the communication device 2 (transceivers 500) performs a receiving operation in the step S102-2. The storage circuit 508, the process/arithmetic circuit 506, the control circuit 513, and the antenna setting circuit 510 work together and thereby generate a quasi-omni pattern in the receiving antenna (e.g., antenna array 511-1 to 511-L). Further, the receiver circuit 509 also works together in this state. In this way, the communication device 2 receives the training signal transmitted from the communication device 1 with a fixed beam pattern, more specifically, with a quasi-omni pattern.
Next, the communication device 1 and 2 interchange their roles, and perform similar processes. Steps S103-1 and S103-2 are a training for determining transmitting-antenna-setting candidates of the communication device 2 (transceivers 500). That is, in the step S103-2, the communication device 2 performs a transmitting operation, and transmits a training signal while changing its antenna setting and thereby scanning the beam direction. In this state, in the step S103-1, the communication device 1 receives the training signal transmitted from the communication device 2 in a state where a quasi-omni pattern is generated.
Next, in steps S104-1 and S104-2, a training for determining receiving-antenna-setting candidates of the communication device 2 is performed. In the step S104-1, the communication device 1 performs a transmitting operation, and transmits a training signal in a state where a quasi-omni pattern is generated in the transmitting antenna. In this state, in the step S104-2, the communication device 2 performs a receiving operation, and receives the training signal while changing its antenna setting and thereby scanning the beam direction.
Next, the communication device 1 and 2 interchange their roles, and perform similar processes. That is, steps S105-1 and S105-2 are a training for determining receiving-antenna-setting candidates of the communication device 1. In the step S105-2, the communication device 2 performs a transmitting operation, and transmits a training signal in a state where a quasi-omni pattern is generated in the transmitting antenna. In this state, in the step S105-2, the communication device 1 performs a receiving operation, and receives the training signal while changing its antenna setting and thereby scanning the beam direction.
Through the above-described steps S102 to S105, reception results of four training signal are obtained. A procedure for determining four pluralities of antenna-setting candidates of four antennas (transmitting antenna and receiving antenna of communication device 1 and 2) from these reception results is explained hereinafter.
Firstly, a procedure for determining transmitting-antenna-setting candidates of the communication device 1 in a step S106-2 by using the training signal reception result obtained in the step S102-2 is explained hereinafter.
A data string describing a relation between antenna settings (i.e., transmission beam directions) of the transmitting antenna of the communication device 1 and received-signal powers in the receiving antenna of the communication device 2 is obtained from the training signal reception result in the step S102-2. The antenna setting of the transmitting antenna of the communication device 1 is sent from the communication device 1 to the communication device 2 in advance by, for example, adding the antenna settings to the information element of the training signal when the training signal is transmitted. Note that although a data string describing a relation between antenna settings and received-signal powers is obtained in this example, reception signal characteristics other than the received power may be also used. Examples of the received signal characteristics other than the received power include a signal to noise ratio (SNR).
However, when the angular resolution of the beam scanning performed in the step S102-1 is high, there is a possibility that the above-described method cannot detect antenna settings that properly correspond to the signal paths. That is, there is a possibility that antenna settings in or around a beam direction corresponding to a relatively high received power occupy higher ranks of the relative received powers and are detected as antenna settings corresponding to the signal paths. In such cases, it is desirable to perform peak detection by using information on the scanned beam direction (radiation angle or angle of departure) of the transmitting antenna of the communication device 1. To that end, it is necessary to send the information on the beam direction of the transmitting antenna of the communication device 1 in advance from the communication device 1 to the communication device 2. This information may be sent by adding it to the information element of the training signal transmitted in the step S102-1, or may be sent by transmitting separate data dedicated for the delivery of angle information. In such cases, the data string may be, for example, one shown in
Note that in this specification, a planar (two-dimensional) propagation environment as shown in
A procedure for determining transmitting-antenna-setting candidates of the communication device 2 in a step S106-1 by using the training signal reception result obtained in the step S103-1 is similar to that performed in the above-described step S106-2, and therefore its explanation is omitted. That is, the procedure in the step S106-1 may be executed by performing the above-described procedure in the step S106-2 in a state where the roles of the communication device 1 and the communication device 2 are interchanged.
Next, a procedure for determining receiving-antenna-setting candidates of the communication device 2 in a step S106-2 by using the training signal reception result obtained in the step S104-2 is explained hereinafter. A data string describing a relation between antenna settings (i.e., reception beam directions) of the receiving antenna and received powers of the communication device 2 is obtained from training signal reception result obtained in the step S104-2. The process described below is similar to the above-described procedure for determining transmitting-antenna-setting candidates of the communication device 1 performed in the step S106-2. However, in this process, training signal reception results that are obtained by scanning the reception beam direction of the receiving antenna (S104-2) are used. Therefore, in contrast to the case where a training signal is transmitted from an antenna performing beam scanning, there is no need to send the information on antenna settings and beam directions. Further, the information on the beam direction that is used to perform beam detection is angles of arrival.
A procedure for determining receiving-antenna-setting candidates of the communication device 1 in a step S106-1 by using the training signal reception result obtained in the step S105-1 is similar to that performed in the above-described step S106-2, and therefore its explanation is omitted. That is, the procedure in the step S106-1 may be performed by performing the above-described procedure in the step S106-2 in a state where the roles of the communication device 1 and the communication device 2 are interchanged.
Through the above-described processes, four pluralities of antenna-setting candidates of four antennas (transmitting antenna and receiving antenna of each of communication device 1 and 2) are determined. Next, the communication devices 1 and 2 transmit and receive information necessary for performing round-robin trainings between the determined antenna-setting candidates (S109 to S110). That is, in a step S107, transmitting-antenna-setting candidates of the communication device 2 and the total number of receiving-antenna-setting candidates of the communication device 1 are sent from the communication device 1 to the communication device 2. Similarly, in a step S108, transmitting-antenna-setting candidates of the communication device 1 and the total number of receiving-antenna-setting candidates of the communication device 2 are sent from the communication device 2 to the communication device 1. However, when the total number of antenna-setting candidates with which the round-robin trainings are performed is determined in advance, there is no need to transfer the total number of antenna-setting candidates. Further, for example, identification numbers of antenna settings may be used as the information on transmitting-antenna-setting candidates as shown in
In a step S109, round-robin trainings are performed between the transmitting-antenna-setting candidates of the communication device 1 and the receiving-antenna-setting candidates of the communication device 2. Similarly, in a step S110, round-robin trainings are performed between the transmitting-antenna-setting candidates of the communication device 2 and the receiving-antenna-setting candidates of the communication device 1. Details of the procedure of these round-robin trainings are explained later. By performing these trainings, appropriate combinations between antenna-setting candidates (i.e. antenna-setting pairs) are found, and they are arranged in descending order of their communication quality (e.g., descending order of received power). The obtained data string of the antenna-setting pairs arranged according to the communication quality is called “antenna-setting-pair list”. Note that other cases where the list is arranged according to parameters other than the communication quality are also included the scope of the present invention.
In a step S111, an antenna-setting-pair list for the receiving antenna of the communication device 1 and the transmitting antenna of the communication device 2 obtained in the step S110 is transmitted from the communication device 1 to the communication device 2. Similarly, in a step S112, an antenna-setting-pair list for the transmitting antenna of the communication device 1 and the receiving antenna of the communication device 2 obtained in the step S109 is transmitted from the communication device 2 to the communication device 1. However, the information sent in the step S111 needs to include only the information on the transmitting-antenna setting of the communication device 2. Therefore, among the information items shown in
The communication device 1 and 2 each selects an antenna setting in the same rank from the antenna-setting pairs that are stored in the storage circuits 408 or 508 by the above-described method, and resume the communication (S14 and S15 in
When the communication using the antenna-setting pair in the selected rank deteriorates and the deterioration is detected in the steps S116 and S117, the communication device 1 and 2 select another antenna-setting pair in the same rank from the antenna settings stored in the storage circuits 408 and 508 (S16 in
Next, the operation that is explained above with reference to the simplified sequence diagram shown in
Steps S602 to S605 show an example of the procedure performed in the step S102 shown in
Steps S606 to S609 show an example of the procedure performed in the step S103 shown in
Steps S610 to S613 show an example of the procedure performed in the step S104 shown in
Steps S614 to S617 show an example of the procedure performed in the step S105 shown in
Steps S622 to S626 show an example of the procedure performed in the step S109 shown in
Firstly, the communication device 1 sets the first antenna setting (e.g., antenna setting identification number 14 in
Steps S627 to S632 show an example of the procedure performed in the step S110 shown in
The purpose of carrying out the round-robin trainings (i.e. communication quality tests) for the combinations of all the antenna-setting candidates of the transmitting and receiving antennas in the steps S622-S626 and S627 to S632 is explained hereinafter.
Assume a case where the process of determining antenna-setting candidates of the four antennas (transmitting antenna and receiving antenna of each of communication device 1 and communication device 2) can be carried out with high accuracy in the steps S602 to S621. Assume a propagation environment shown in
However, when the accuracy of the quasi-omni pattern is poor, i.e., when there are variations in the antenna gain depending on the radiation direction or when other measurement errors occur, there is a possibility that errors occur in the combinations of antenna-setting candidates. Note that the error means that antenna-setting candidates corresponding to different propagation paths are combined. The probability that such errors occur depends on the propagation environment as well as on the antenna characteristic described above. For example, the probability of errors could increase when propagation losses of two or more propagation paths are close to each other. Further, even when the combinations of antenna-setting candidates are properly made, there is a possibility that the antenna-setting pairs are not properly arranged according to the received power.
The problem like this can be avoided by performing round-robin trainings (communication quality tests) for the combinations of all the antenna-setting candidates of the transmitting and receiving antennas. Further, in general, the number of detected and determined antenna-setting candidates is reduced to a sufficiently small number in advance in comparison to the number of antenna settings for the beam direction scanning performed in the steps S602 to S621. Therefore, even when round-robin trainings are performed, they do not cause any significant increase in the total training time.
However, in order to further reduce the processing time, the above-described procedure to measure communication quality for the combinations of all the antenna-setting candidates may be modified as shown below. Firstly, antenna-setting pairs are determined according to the received power (or other communication quality) measured when the antenna-setting candidates are determined. For example, an antenna-setting pair is determined by combining a transmitting-antenna-setting candidate of the communication device 1 for which the received power is highest with a receiving-antenna-setting candidate of the communication device 2 for which the received power is highest. A communication quality test is carried out for a plurality of antenna-setting pairs that are formed in this manner, and only an antenna-setting pair(s) that does not satisfy a predetermined communication quality criterion is cancelled. Then, for the antenna-setting candidates that are cancelled because their communication quality is lower than the communication quality criterion, a search for new antenna-setting pairs is performed by carrying out communication quality tests for all the combinations. After that, the priority order of antenna-setting pairs may be determined again based on the above-described two set of communication quality tests. By employing the method like this, among the antenna-setting pairs that are determined based on the measurement results obtained at the time of determination of the antenna-setting candidates, the available antenna-setting pairs can be excluded from the antenna-setting pairs for which the round-robin-based communication quality measurements are to be performed in order to find new combinations, and thus making it possible to reduce the processing time. The procedure like this is effective when, for example, the number of antenna-setting candidates is large.
Next, an operation performed when deterioration in communication quality such as disconnected communication occurs is explained with reference to
When a problem such as disconnected communication occurs, the transceiver 500, which is performing the receiving operation, detects the deterioration in communication quality (S702-2), and notifies the transceiver 400 of the deterioration (S703-2). The transceiver 400 receives the notification of the communication quality deterioration from the transceiver 500. Alternatively, the transceiver 400 recognizes the disconnected communication (or deteriorated communication state) based on the fact that the ACK signal, which would be transmitted from the transceiver 500 upon the successful data reception under normal communication circumstances, has not been received. At this point, the transceivers 400 and 500 obtain their respective next antenna-setting candidates from their own databases (i.e. antenna-setting-pair lists) (S704-1 and S704-2).
In a step S705-1, the transceiver 400 sets the antenna setting circuit 404 with the next antenna setting candidate. Similarly, in a step S705-2, the transceiver 500 sets antenna setting circuit 510 with the next antenna setting candidate. After that, the transceivers 400 and 500 resume the communication (S706-1 and S706-2). After the communication is resumed, the transceiver 500 checks the communication quality (S707-2). When the communication quality is satisfactory, the communication is continued, whereas when it is unsatisfactory, the transceiver 500 transmits a notice of antenna setting change (S708-2). The transceiver 400 continues the communication without making any change unless it receives the notice of antenna setting change or cannot receive an ACK signal from the transceiver 500 (S709-1). If not so, the transceivers 400 and 500 attempt the communication using the next antenna-setting pair candidate as long as there is another antenna setting candidate (S710-1 and S710-2). If the communication quality cannot be improved with any of the antenna-setting pair candidates stored in the storage devices 408 and 508 and there is no remaining candidate, the transceivers 400 and 500 returns to the training.
The procedure described above in this exemplary embodiment is merely an example. For example, there is flexibility in the order of those steps, the communication devices that perform various processing and calculation, the content of transmitted and received information, and so on. Therefore, various cases where any of these matters is different from those shown in the above exemplary embodiment are also included the scope of the present invention. Further, in the explanation, a group of two or more processes is sometimes handled as one step as in the case of the step S104-1 shown in
According to this exemplary embodiment, it is possible to resume the communication without delay by selecting another antenna-setting pair candidate that is generated in advance when deterioration in communication quality such as disconnected communication occurs. In other words, it is unnecessary to carry out a training whenever deterioration in communication quality occurs in this exemplary embodiment, and thus making it possible to determine a new antenna setting in a short time. The training time in this exemplary embodiment could become longer depending on the number of antenna settings for the beam direction scanning performed in the steps S602 to S621. However, in general, the training is performed before the start of communication. Therefore, it is acceptable to take a longer time for the training in comparison to the time acceptable when the communication is restored after disconnection of the communication. Therefore, it does not cause any significant problem.
Further, in this exemplary embodiment, as a procedure for determining antenna-setting pairs, a specific example in which round-robin communication quality measurements are performed for all the combination of antenna-setting candidates and the antenna-setting pairs are determined based on the measurement results is shown. As described above, when the accuracy of the quasi-omni pattern is poor, i.e., when there are variations in the antenna gain depending on the radiation direction, or when other measurement errors exist, there is a possibility that errors occur in the combinations of antenna-setting candidates. To cope with this problem, round-robin trainings among the antenna-setting candidates are performed, so that it is possible to obtain antenna-setting pairs that are properly combined and properly arranged even when the accuracy of the quasi-omni pattern is poor or when other measurement errors exist in the process for detecting and determining antenna-setting candidates.
The following is supplementary explanation for the reason why this method is effective for millimeter waves or microwaves that are higher than or equal to around 10 GHz and have a high rectilinear propagation property when the method is used indoors. The propagation paths that can be used for radio communication are limited. That is, only the direct wave and reflected waves from certain objects such as walls, windows, and furniture can be used. Therefore, angles at which waves (signals) should be emitted for respective propagation paths or angles at which waves (signals) should be received are widely different from one wave (signal) to another. Meanwhile, when propagation paths having a low rectilinear propagation property such as a 2.4 GHz microwave band are used, it is necessary to give consideration to effects caused by multiple scattering and diffraction. Therefore, in general, directional antennas are not used. Therefore, situations are different between communication using microwaves and millimeter waves that have higher than or equal to around 10 GHz and communication using microwaves in the order of 2.4 GHz. It should be noted that there are some examples of development of adaptive antennas having directivity for the purpose of eliminating interferences even in the field of communication using 2.4 GHz microwaves. However, even when an adaptive-type directional antenna is used, it is relatively easy to ensure satisfactory communication quality at the angle of the direct wave or angles close to the direct wave in the 2.4 GHz band because diffraction effects can be expected in the 2.4 GHz band.
In indoor communication using beam forming in millimeter-wave bands, it is necessary to take the following properties into consideration. As described above, the number of reflected waves other than the direct wave is limited. Further, even if a certain direct wave or a reflected wave is blocked by an obstacle (e.g., human body), there is no correlation between the blocked certain wave and other waves. Therefore, as described with this exemplary embodiment, in millimeter wave communication systems, it is possible to secure reserve beam directions while performing communication in a beam direction having the best communication condition. Meanwhile, when the frequency is lower than around 10 GHz, contribution of multiple reflections and diffractions on the communication quality is large. Therefore, even if a directional antenna is used, the propagation state of the reserve beam directions varies depending on the presence/absence of an obstacle. That is, there is a high possibility that a received signal state of a reserve beam direction, which has satisfactory quality when no obstacle exists, is changed due to the presence of an obstacle. Therefore, it is difficult to obtain an advantageous effect of the present invention in 2.4 GHz microwave communication and the like.
Further, in millimeter wave communication, a local reflection may sometimes create a propagation path.
In the above explanation, an omni pattern or a quasi-omni pattern is used as the radiation pattern of the antenna of the communication device in some of the steps. However, when it is difficult to generate an omni or quasi-omni pattern, other fixed beam patterns may be also used as a substitute. However, it is preferable to use a radiation pattern having an antenna gain over a sufficiently wide angular range. If the radiation pattern of the antenna is known in advance, a process of eliminating the effects caused by the directional dependence of the antenna gain of the fixed beam pattern from the received data obtained in the steps S102 to S105 shown in
In the above explanation, beam forming between two communication devices is explained. Such operations are often performed between two communication devices in a system including three or more communication devices. In general, there is a communication device having special authority called “Piconet coordinator” or “access point” in the system. The decision on which two communication devices perform a beam forming operation therebetween among the three or more communication devices is typically made by instructions from this communication device called “Piconet coordinator” or “access point”. The Piconet coordinator or the access point may receive requests from other general communication devices and issue these instructions.
Further, in this exemplary embodiment, the roles of two communication devices are interchanged and then similar processes are performed therebetween. The decision on which of the two communication devices performs which of the roles before the other communication device may be also made by instructions from the communication device called “Piconet coordinator” or “access point”.
Further, although expressions such as “to operate a communication device for reception” and “to generate an omni (nondirectional) or quasi-omni (quasi-nondirectional) pattern” are used in the above explanation, these processes may be, in general, performed in accordance with a program that are incorporated in advance into the process/arithmetic circuits 406 and 506 or the like of the transceivers 400 and 500.
A second exemplary embodiment according to the present invention is explained with reference to a transition diagram shown in
In a state S18 in
In the state S18, the process/arithmetic circuit 406 and 506 calculate antenna-setting pair candidates again. The process/arithmetic circuits 406 and 506 update the antenna-setting-pair list stored in the storage circuits 408 and 508 with the antenna-setting pairs obtained by the recalculation (S19).
In this exemplary embodiment, conditions of reserve beam directions (antenna settings) are periodically or appropriately examined by the additional training and the antenna-setting-pair list is thereby updated. In this way, the radio communication system in accordance with this exemplary embodiment can keep the antenna-setting-pair list that is constantly updated to the newest state. Note that the additional training (S18) may be divided and performed during intervals of the communication. In this way, it can eliminate the need to suspend the communication for a long time. Further, when the communication is disconnected or the communication quality is deteriorated, it is desirable to recover the communication in an extremely short time. However, since this additional training does not need to be performed immediately, no strong restriction is imposed on the training time.
Furthermore, since this additional training often requires less immediacy in comparison to the initial training, the beam direction scanning, which is performed by changing the antenna setting, may be performed with a higher angular resolution. In this way, it is possible to find antenna-setting pairs that make it possible to achieve better communication quality.
Further, the beam direction scanning in the additional training may be performed with such a condition that the scan range is limited to ranges in and around the beam direction corresponding to each of the antenna-setting pairs obtained in the initial training. In this way, the search for antenna-setting pairs that make it possible to achieve better communication quality can be performed in a shorter time.
Note that in the additional training explained above, the procedure from the determination of antenna-setting candidates to the creation of antenna-setting-pair list, i.e., the whole training procedure (part corresponding to S12 and S13) is performed. However, it is possible to adopt another form of operation in which communication quality tests are performed for all or some of the antenna-setting pairs obtained in the state S13 and the update of the antenna-setting-pair list (e.g. rearrangement of antenna-setting pairs included in the antenna-setting-pair list, or removal of some of the antenna-setting pairs) is carried out based on their results. Alternatively, it is also possible to adopt another form of operation in which round-robin communication quality tests between communication devices are performed for all or some of the antenna-setting candidates determined in the state S12 (corresponding to S109 and S110 in
Further, an update result of the antenna-setting-pair list that is obtained by performing an additional training may be immediately reflected on the antenna-setting pair that is currently used for the communication, or may be reflected when the state changes from the state S15 to the state S16 due to deterioration of the communication quality.
A third exemplary embodiment according to the present invention is explained with reference to a transition diagram shown in
In this exemplary embodiment, when deterioration in communication quality such as disconnected communication occurs, the next antenna-setting pair candidate listed on the antenna-setting-pair list is selected (S16) and a fine adjustment is made in that state (S20). The fine adjustment means a method for searching for an optimal beam (antenna setting) without spending too much time. Specifically, the fine adjustment may be performed by slightly changing the antenna setting and thereby changing the beam direction so that better communication quality is obtained. Further, simplified beam searching procedure such as “Beam Tracking” disclosed in Patent literature 4 may be applied. Furthermore, processes similar to those of the initial training may be performed with an angular resolution higher than that in the initial training in and around the beam direction corresponding to the newly-selected antenna-setting pair.
For example, in a case where the antenna-setting pair is shifted from one antenna-setting pair to another in descending order of their corresponding received power as described in detail with the first exemplary embodiment, there is a possibility the received power becomes gradually smaller and the accuracy deteriorates gradually. Accordingly, this exemplary embodiment provides an advantageous effect that an antenna-setting pair with which stable transmission can be performed with high accuracy can be found, for example, by performing a gain adjustment for the receiving operation and performing a fine adjustment in the optimal state in a state where shielding occurs and the received power is thereby weakened.
A fourth exemplary embodiment according to the present invention is explained with reference to a transition diagram shown in
In this exemplary embodiment, after an antenna-setting-pair list is obtained in the state S13, fine adjustments are made for all or some of the antenna-setting pairs included in the list before the start of communication (S21). The fine adjustment means, for example, an adjustment to antenna setting that is made in and around the beam direction corresponding to an antenna-setting pair included in the list with an angular resolution higher than that in the training performed in the state S12. After that, an antenna-setting pair is selected from the antenna-setting-pair list for which the fine adjustment has been made (S14), and the communication is started (S15).
According to this exemplary embodiment, communication quality between the transceivers 400 and 500 can be improved when the communication is performed by using one of the antenna-setting pairs included in the antenna-setting-pair list. Further, since fine adjustments are made before the start of communication, the communication disconnection time can be shortened in comparison to the case where the fine adjustment is made when the antenna-setting pair is changed due to the occurrence of communication disconnection.
A fifth exemplary embodiment according to the present invention is explained with reference to a transition diagram shown in
Two or more of the procedures that are added to the first exemplary embodiment in second to fourth exemplary embodiments explained above may be applied at the same time. This exemplary embodiment is an example in which all the procedures (S18 and S19, S20, and S22) are incorporated at the same time.
A sixth exemplary embodiment according to the present invention is explained with reference to a transition diagram shown in
In the first to fifth exemplary embodiments, when communication disconnection or communication quality deterioration occurs during the communication (S15), another antenna-setting pair is selected from the antenna-setting-pair list (S16); if necessary, a fine adjustment is made (S20); and after the communication quality is checked (S17), the communication is resumed (S15). However, as described in this exemplary embodiment, the procedure may be modified in such a manner that one antenna-setting pair is selected from the antenna-setting-pair list (S14), and when communication disconnection or communication quality deterioration occurs during the communication (S15), a training is performed again (S12). In the state S14, when one antenna-setting pair is selected from the antenna-setting-pair list (S14), it is desirable to select an antenna-setting pair for which the received power (or other communication quality index) measured in the training in the states S12 and S13 is highest.
In this exemplary embodiment, it is impossible to obtain the advantageous effect that the communication can be quickly resumed by changing the antenna-setting pair when communication disconnection or communication quality deterioration occurs, which is achieved by storing reserve antenna-setting pairs in advance. However, as stated in the first exemplary embodiment, the present invention can provide another advantageous effect that it is possible to obtain antenna-setting pairs that are properly combined and properly arranged even when the accuracy of the quasi-omni pattern is poor or when other measurement errors exist in the process for detecting and determining antenna-setting candidates. Therefore, even when the stored reserve antenna-setting pairs are not used as in the case of this exemplary embodiment, the present invention is effective.
A seventh exemplary embodiment according to the present invention is explained with reference to a sequence diagram shown in
In the first exemplary embodiment, a quasi-omni pattern is used in the process for determining antenna-setting candidates for each antenna (S102 to S105 in
The sequence diagram shown in
The above-mentioned “desired angular range” means, for example, an angular range (direction range) including all the propagation paths used for the communication. Non-patent literature 5 discloses a method for covering a necessary angular range with a plurality of quasi-omni patterns in a manner like this.
An eighth exemplary embodiment according to the present invention is explained with reference to a sequence diagram shown in
As stated in the end of the first exemplary embodiment, there are various flexibilities in the order of those steps, the communication devices that perform various processing and calculation, the content of transmitted and received information, and so on when the present invention is put into practice. This exemplary embodiment shows an example of such modifications. An operation is explained hereinafter along the sequence diagram shown in
Firstly, the communication device 2 sets the receiving-antenna setting with values for a training, i.e., values for generating a quasi-omni pattern in this example (S602-2). The communication device 1 repeatedly transmits training signal (S604-1) while changing the transmitting-antenna setting (S603-1) until signal transmissions in all of the predetermined antenna settings have been completed (S605-1). The communication device 2 receives the training signal (S604-2).
Next, the communication device 2 feeds measurement data received in the step S604-2 back to the communication device 1 (S647-2). The communication device 1 receives this measurement data (S647-1) and determines its own transmitting-antenna-setting candidates by using this measurement data.
In steps S606 to S650, the procedure of the above-described steps (S602 to S648) is performed in a state where the roles of the communication device 1 and 2 are interchanged.
The steps S610 to S613 are exactly the same as those in the first exemplary embodiment (
In steps S614 to S619, the procedure of the above-described steps (S610 to S651) is performed in a state where the roles of the communication device 1 and 2 are interchanged.
In this exemplary embodiment, the content of information to be transmitted and received in the steps S652 and S653 is also different from that in the first exemplary embodiment. In this exemplary embodiment, the determination of antenna-setting candidates is performed by the communication devices themselves in which the respective antennas are mounted. Therefore, the transmission and reception of antenna-setting candidates like the one performed in
A ninth exemplary embodiment according to the present invention is explained with reference to a sequence diagram shown in
In the first exemplary embodiment, the round-robin communication quality tests between transmitting-antenna-setting candidates of the communication device 1 and receiving-antenna-setting candidates of the communication device 2 (S622 to S627 in
A tenth exemplary embodiment according to the present invention is explained with reference to a sequence diagram shown in
In the steps S622 and S623 in the first exemplary embodiment shown in
Through a similar procedure to that in the first exemplary embodiment, antenna-setting candidates of each antenna are determined before and in the step S619 (S618 and S619). Since the round-robin communication quality tests are not performed in this exemplary embodiment, there is no need to transfer the number of antenna-setting candidates. Therefore, in a step S665, only the transmitting-antenna-setting candidates of the communication device 2 are sent from the communication device 1 to the communication device 2. Similarly, in a step S666, only the transmitting-antenna-setting candidates of the communication device 1 are sent from the communication device 2 to the communication device 1. After that, the communication device 1 notifies the communication device 2 of an antenna-setting pair number (S636), and the communication devices 1 and 2 perform antenna setting (S637) and start the communication (S638). The delivery of an antenna-setting pair number in the step S636 may be performed from the communication device 2 to the communication device 1. Alternatively, when the order of antenna-setting pair numbers to be used for the communication is determined in advance, this delivery may be omitted.
Note that when the round-robin communication quality tests between antenna-setting candidates are omitted as in the case of this exemplary embodiment, it is impossible to completely eliminate the possibility that an error occurs in the combination or order of antenna settings. However, even if an error occurs in the combination or order of antenna settings, it never causes any fatal effect such as prolonged communication disconnection and complete communication stop. This is because since, for example, the communication quality is checked in the state S17 in
The above explanation has been made on the assumption that communication is performed between communication devices each equipped with an antenna having a directivity control function. However, the present invention can be also applied to communication between a communication device equipped with an antenna that forms a fixed beam and a communication device equipped with an antenna having a directivity control function.
In this exemplary embodiment, antenna-setting candidates may be determined only for the transmission and receiving antennas of the communication device 1 (S603 to S619). That is, there is no need to perform the procedure of determining antenna-setting candidates for the communication device 2 forming a fixed beam. Further, since there is no need to determine antenna-setting pairs, no round-robin quality tests between setting candidates are performed.
Note that in this exemplary embodiment, the communication device 2 determines transmitting-antenna-setting candidates of the communication device 1 by using measurement data obtained in the step S604-2 (S618-2), and feeds them back to the communication device 1 (S667). However, the measurement data obtained in the step S604-2 may be fed back to the communication device 1 and the communication device 1 may determine the transmitting-antenna-setting candidates on its own.
Further,
A twelfth exemplary embodiment is characterized in that the training and the acquiring/setting of antenna-setting pairs are performed at a low rate (with a narrow band) and actual communication is performed at a relatively high rate (with a wide band). Alternatively, it is characterized in that parts the training and the acquiring/setting of antenna-setting pairs are performed at a low rate (with a narrow band) and the remaining part of the training and the acquiring/setting of antenna-setting pairs as well as actual communication is performed at a relatively high rate (with a wide band). The other operations may be performed by using the method according to one of the first to eleventh exemplary embodiments.
In millimeter wave communication, since free space propagation losses are large, the received power is expected to be small. Therefore, if an antenna is set so as to generate an omni or quasi-omni pattern in the training, there is a possibility that a sufficient CNR (Carrier to Noise Ratio) is not achieved. Accordingly, it is expected that the use of the low rate (narrow band) having better reception sensitivity provides advantageous effects such as making the training possible and improving the accuracy. It should be noted that the “use of low rate (narrow band)” means to narrow the frequency band used to transmit a training signal in order to narrow the noise bandwidth or to adopt a modulation technique having a small necessary CNR. Note that “to adopt a modulation technique having a small necessary CNR” means, in other words, to adopt a modulation technique in which the distance between signal points on the constellation is large (typically a smaller transmission rate). It should be noted that it is assumed that a narrow beam width is used in this exemplary embodiment. Therefore, there is no significant difference in optimal beam combinations (antenna-setting pairs) regardless of whether the transmission is preformed at a low rate (narrow band) or at a high rate (wide band) because the correlative bandwidth is wide.
In the first to twelfth exemplary embodiments, examples in which each of the transceivers 400 and 500 includes both the transmitting antenna (405-1 to 405-M, or 505-1 to 505-K) and the receiving antenna (411-1 to 411-N, or 511-1 to 511-L) are shown. Further, no particular assumption is made for the relation between the length of the propagation path and the distance between the transmitting antennas 405-1 to 405-M and the receiving antennas 411-1 to 411-N of the transceivers 400. Similarly, no particular assumption is made for the relation between the length of the propagation path and the distance between the transmitting antennas 505-1 to 505-K and the receiving antennas 511-1 to 511-L of the transceivers 500. Further, cases where configurations of the transmitting antenna and the receiving antenna of each transceiver are usually different are shown. That is, examples where (i) a training for determining antenna setting candidates of the transmitting antennas 405-1 to 405-M of the transceiver 400 (S102), (ii) a training for determining antenna setting candidates of the receiving antennas 411-1 to 411-N of the transceiver 400 (S105), (iii) a training for determining antenna setting candidates of the transmitting antennas 505-1 to 505-K of the transceiver 500 (S103), and (iv) a training for determining antenna setting candidates of the receiving antennas 511-1 to 511-L of the transceiver 500 (S104), are separately performed are shown.
However, when each of the transceivers 400 and 500 has only one antenna array and the one antenna array is used for both the transmission and the reception by switching or by using a similar scheme, the workload of the procedure described in the first to twelfth exemplary embodiments is reduced to about the half. Because it can be considered that the transmitting-antenna-setting candidates (transmission beam direction) of the transceivers 400 are the same as its own receiving antenna-setting candidates (reception beam direction). This also holds true for the transmitting-antenna-setting candidates of the transceivers 500 (transmission beam direction) and its own receiving antenna-setting candidates (reception beam direction). For example, among the four steps S102 to S105 for determining antenna-setting candidates in
Further, even when each of the transceivers 400 and 500 has both the transmitting antenna and the receiving antenna, the workload of the procedure described in the first to twelfth exemplary embodiments can be reduced to about the half in a similar manner to the above-described manner when the distance between the transmitting antenna and the receiving antenna of each communication device is sufficiently small in comparison to the length of the propagation path and the configurations of the transmitting antenna and the receiving antenna of each communication device are identical to each other.
Incidentally, the term “communication quality” has been used in the above-described first to twelfth exemplary embodiments. The communication quality may be any value representing communication quality such as a received-signal level, a signal to noise ratio (SNR), a bit error rate (BER), a packet error rate (PER), and a frame error rate (FER), and one or more than one of them may be used. Further, a certain data string in a preamble contained in a transmission data string of the transmitter 401 or transmitter 501 may be used for the communication quality evaluation.
Further, controls and arithmetic operations for the generating and switching of antenna-setting candidates that are performed in the transceivers 400 and 500 in the above-described first to twelfth exemplary embodiments can be implemented using a computer, such as a microprocessor(s), to execute a program(s) for transceiver. For example, in the case of the first exemplary embodiment, these processes may be implemented by causing a computer running a transmission/reception control program to execute the steps of calculations and transmission/reception controls shown in the sequence diagram in
Further, in addition to the process/arithmetic circuits 406 and 506, part of the transmitter circuits 403 and 503 (modulation process and the like), part of the receiver circuits 409 and 509 (demodulation process and the like), and components relating to digital signal processing or device control of the control circuits 407 and 507 and the like may be implemented by a computer(s) such as a microcomputer(s) or a DSP(s) (Digital Signal Processor). Further, the so-called “software-antenna technology” may be applied to the transceivers 400 and 500. Specifically, the antenna setting circuits 404, 410, 504 and 510 may be constructed by digital filters, or a computer(s) such as a DSP(s).
In the above explanation, situations where communication is performed between two transceivers are explained as examples. However, the present invention is applicable to other situations where three or more transceivers perform communication.
Further, the present invention is not limited to the above-described exemplary embodiments, and needless to say, various modifications can be made without departing from the spirit and scope of the present invention described above.
This application is based upon and claims the benefit of priority from Japanese patent application No. 2009-253118, filed on Nov. 4, 2009, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-253118 | Nov 2009 | JP | national |
This application is a Continuation Application of U.S. application Ser. No. 13/505,692 filed May 2, 2012, which is a National Stage of PCT/JP2010/006470 filed Nov. 2, 2010, which claims the benefit of priority of Japanese patent application No. 2009-253118, filed Nov. 4, 2009, the disclosures of which are incorporated by reference in their entirety. The present invention relates to a system that performs radio communication by adaptively controlling radio beams, and its control method.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13505692 | May 2012 | US |
| Child | 14301381 | US |
