Method for establishing communication in a wireless device and wireless device

Abstract

To reduce communication overhead and power consumption in wireless devices. [Solution] A method for establishing communication between a first wireless device 10 and a second wireless device 20 includes: the first wireless device 10 transmitting a first signal 102 including a synchronization signal using an omnidirectional or quasi-omnidirectional antenna; the second wireless device 20 transmitting a second signal 104 based on having received the first signal 102; the first wireless device 10 estimating the direction of arrival 106 of the second signal 104 based on having received the second signal 104 using an array antenna; the first wireless device 10 transmitting a third signal 108 including system information towards the direction of arrival 106 of the second signal 104 using a directional antenna; and the second wireless device 20 transmitting a fourth signal 110 to establish wireless communication between the first wireless device 10 and the second wireless device 20 based on having received the third signal 108.

Description

Technical Field

[0001] This disclosure relates to communication establishment technology in wireless devices.

Background Art

[0002] Currently, cellular wireless communication systems are used not only for voice calls but also for a variety of services that utilize information communication. Furthermore, cellular wireless communication systems are also used in applications such as remote operation of various sensors or industrial machines in the industrial field. On the other hand, wireless LAN (Local Area Network), which was developed to easily connect personal computers and the like to a network, is also used for a variety of services. Thus, although cellular wireless communication systems and wireless LAN differ in the places and applications where they are used, there is no barrier from the perspective of using services that utilize information communication.

[0003] Regarding cellular wireless communication systems, Non-Patent Document 1 and Non-Patent Document 2 disclose the standard specifications of cellular wireless communication defined by 3GPP (registered trademark). In the standard specifications of the cellular wireless communication, a radio base station uses a directional antenna to transmit a synchronization signal and a signal including information for connecting to the radio base station in various directions where a terminal may exist. A terminal that has received the synchronization signal and the signal including information for connecting to the radio base station transmits a connection request signal. The radio base station that has received the connection request signal is defined to execute a connection procedure with the terminal when it is determined that it is appropriate for the terminal to connect, enabling the transmission and reception of communication data.

Prior Art Documents

Non-Patent Documents

[0004] <000002​​Takeda, et al., "NR Physical Layer Specifications in 5G," NTT DoCoMo Technical Journal, vol.26, no.3, pp.4758, Nov.2018. (https: / / www.docomo.ne.jp / binary / pdf / corporate / technology / rd / technical_journal / bn / vol26_3 / vol26_3_008jp.pdf) [Non-Patent Document 2] Hattori, Fujioka, "5G Textbook: From LTE / IoT to 5G," Impress Publishing, 2018. [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the technologies disclosed in Non-Patent Documents 1 and 2, wireless devices such as base stations and access points can detect the presence of a terminal by receiving a connection request signal, but they cannot detect the direction in which the terminal is located relative to the wireless device. Therefore, wireless devices need to sequentially transmit signals containing information for connecting to the wireless device in various directions in which the terminal may be located, using a directional antenna. As a result, wireless devices end up transmitting signals multiple times using a directional antenna. Accordingly, the communication overhead and power consumption of the wireless device also increase. Therefore, there is a need for technologies to reduce the communication overhead and power consumption of wireless devices.

[0006] This disclosure is made in view of the above-mentioned background, and in one aspect its purpose is to provide a technology for reducing communication overhead and power consumption in wireless devices. [Means for solving the problem]

[0007] According to one embodiment, a method for establishing communication between a first radio device and a second radio device is provided. The method for establishing communication includes: the first radio device transmitting a first signal including a synchronization signal using an omnidirectional or quasi-omnidirectional antenna; the second radio device transmitting a second signal based on having received the first signal; the first radio device estimating the direction of arrival of the second signal based on having received the second signal using an array antenna; the first radio device transmitting a third signal including system information in the direction of arrival of the second signal using a directional antenna; and the second radio device transmitting a fourth signal for establishing wireless communication between the first radio device and the second radio device based on having received the third signal.

[0008] In a given situation, transmitting a second signal by a second radio device based on the reception of a first signal includes receiving the first signal using an array antenna and estimating the direction of arrival of the first signal, and transmitting the second signal in the direction of arrival of the first signal using a directional antenna.

[0009] In a certain scenario, receiving a second signal using an array antenna by a first radio device includes performing a detection process for the reception of the second signal within a predetermined period after the transmission of the first signal.

[0010] In certain situations, the first and second signals are signals generated by modulating a baseband signal based on a pseudo-random sequence.

[0011] According to one embodiment, a wireless device is provided. The wireless device comprises an omnidirectional or quasi-omnidirectional first antenna for transmitting a first signal including a synchronization signal; a second antenna which is an array antenna for receiving a second signal from a wireless terminal; a signal detection unit for estimating the direction of arrival of the second signal; and a third antenna which is a directional antenna for transmitting a third signal including system information in the direction of arrival of the second signal and receiving a fourth signal for establishing wireless communication from a wireless terminal.

[0012] In a certain scenario, receiving a second signal from a wireless terminal includes performing a detection process for the reception of the second signal within a predetermined period after the transmission of the first signal. [Effects of the Invention]

[0013] According to one embodiment, it is possible to reduce the communication overhead and power consumption in wireless devices.

[0014] The above and other purposes, features, aspects and advantages of this disclosure will become apparent from the following detailed description of this disclosure, which will be understood in conjunction with the attached drawings. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows a first example of the procedure for establishing communication between a first wireless device 10 and a second wireless device 20 according to this embodiment. [Figure 2] This figure shows an example of a pseudo-random sequence. [Figure 3] This figure shows an example of the detection process for pseudo-random sequences contained in the first signal 102 in the second wireless device 20. [Figure 4] This figure shows an example of the receiving process for the first signal 102 and the transmitting process for the second signal 104 in the second wireless device 20. [Figure 5] This figure shows an example of the estimation process for the direction of arrival 106 of the second signal 104 in the first wireless device 10. [Figure 6] This figure shows an example of the procedure for establishing communication, including the fourth signal 110. [Figure 7] This figure shows a second example of the procedure for establishing communication between the first wireless device 10 and the second wireless device 20. [Figure 8] This is a diagram showing an example of the configuration of the first wireless device 10. [Figure 9] This figure shows an example of the configuration of the second wireless device 20. [Figure 10] This figure shows an example of the configuration of the array antenna 500 of the first wireless device 10. [Figure 11] FIG. 1100 shows an example of a pseudo-random sequence generator included in the first wireless device 10 and the second wireless device 20. [Figure 12] FIG. 1101 shows an example of the operation flow of the first wireless device 10. [Figure 13] FIG. 1102 shows an example of the operation flow of the second wireless device 20. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the technical idea according to the present disclosure will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. Also, each embodiment, each modification example, each software or program configuration, each hardware configuration, each function, and each process, etc. may be selectively combined as appropriate.

[0017] <D <APPLICATION EXAMPLE> FIG. 1 shows a first example of a communication establishment procedure between the first wireless device 10 and the second wireless device 20 according to the present embodiment. The technology of the present disclosure can reduce the communication overhead in at least one wireless device in the communication establishment between wireless devices. Also, the technology of the present disclosure can reduce the power consumption in at least one wireless device in the communication establishment between wireless devices.

[0018] The technology of the present disclosure is applicable to a cellular wireless communication system, a wireless LAN system, and any other wireless system. In this specification, the "wireless device" includes a base station in a cellular wireless communication system, an access point in a wireless LAN, a router, and any other wireless relay device. Also, the "wireless device" includes any information processing terminal such as a personal computer, a smartphone, a tablet, a wearable computer, and an IoT (Internet of Things) device.

[0019] Referring to Figure 1, the technology of this disclosure will be explained using the procedure for establishing communication between the first wireless device 10 and the second wireless device 20 as an example. The first wireless device 10 is a signal relay device such as a base station or access point. The second wireless device 20 is an information processing terminal such as a smartphone.

[0020] In step S110, the first radio device 10 periodically transmits a first signal 102. More specifically, the first radio device 10 transmits the first signal 102 using an omnidirectional or quasi-omnidirectional antenna. That is, the first radio device 10 transmits the first signal 102 in all directions. As another example, the first radio device 10 may transmit the first signal 102 over a wider range than that covered by a directional antenna, rather than in all directions. The first signal 102 includes a signal called a pseudo-random sequence. The pseudo-random sequence is explained in detail with reference to Figure 2. The first signal 102 can notify other radio devices present around the first radio device 10 of its presence. The first signal 102 is sometimes called a synchronization signal. If other radio devices are present within range of the first signal 102, the first radio device 10 may receive a response signal from the other radio devices.

[0021] In step S120, the second radio device 20 transmits the second signal 104 based on having received the first signal 102. The second signal 104 is a response signal to the first signal 102. More specifically, the second radio device 20 transmits the second signal 104 via an omnidirectional or quasi-omnidirectional antenna. The second signal 104 also contains a pseudo-random sequence. The second signal 104 is sometimes called a discovery signal. Next, the first radio device 10 receives the second signal 104. More specifically, the first radio device 10 receives the second signal 104 via the array antenna 500 (see Figures 5 and 10). The first radio device 10 then analyzes the second signal 104 received by the array antenna 500 and estimates the direction of arrival 106 of the second signal 104. The direction of arrival 106 of the second signal 104 is the direction from which the second radio device 20 is presumed to be located, as viewed from the first radio device 10.

[0022] In step S130, the first radio device 10 transmits the third signal 108 in the direction of arrival 106 of the second signal 104. More specifically, the first radio device 10 transmits the third signal 108 in the direction of arrival 106 of the second signal 104 via a directional antenna. The first radio device 10 is equipped with multiple directional antennas facing in different directions from each other. Each directional antenna covers a range within a certain angle from the center of the signal transmission direction of each directional antenna as the transmission range, reception range, or transmit / receive range of radio waves. The coverage range of each directional antenna is determined based on the hardware design, program design, or both of the directional antenna. Generally, directional antennas radiate stronger radio waves in a specific direction than omnidirectional antennas. By being equipped with multiple directional antennas facing in different directions from each other, the first radio device 10 can cover a wide and long-distance communication range. The third signal 108 may contain information called a System Information Block (SIB). SIB may include base station ID (Identifier) ​​and radio frame information, etc.

[0023] In step S140, the second radio device 20 transmits a fourth signal 110 based on having received the third signal 108. The fourth signal 110 is a signal for initial connection setup. The second radio device 20 may transmit the fourth signal 110 via an omnidirectional antenna. Alternatively, the second radio device 20 may transmit the fourth signal 110 via a directional antenna. Based on having received the fourth signal 110, the first radio device 10 establishes communication with the second radio device 20 by exchanging further signals.

[0024] In conventional cellular wireless communication systems, base stations had to transmit signals containing SIB (corresponding to the third signal 108) multiple times. For example, suppose a base station (corresponding to the first radio device 10) receives a discovery signal (corresponding to the second signal 104) from a terminal (corresponding to the second radio device 20). In this case, the base station could not detect the direction of arrival of the discovery signal or the location of the terminal. Therefore, the base station activated each of its multiple directional antennas in sequence and transmitted signals containing SIB in multiple directions. For example, suppose a base station has 1 to 10 directional antennas. In this case, the base station activates the 1st to 10th directional antennas in sequence and repeatedly transmits signals containing SIB. That is, the base station transmits signals containing SIB many times while changing the transmission direction of the signals containing SIB. Therefore, the communication overhead and power consumption at the base station were large when transmitting signals containing SIB.

[0025] In contrast, in the technology of this disclosure, the first wireless device 10 estimates the direction of arrival of the second signal 104 by analyzing the second signal 104 received by the array antenna 500. Therefore, the first wireless device 10 only needs to transmit the third signal 108, which includes SIB, once in the direction of arrival of the second signal 104. As a result, the communication overhead and power consumption of the first wireless device 10 can be significantly reduced compared to the prior art.

[0026] As described above, the advantages of the technology disclosed herein over existing cellular wireless communication technologies have been explained. The technology disclosed herein is applicable to any wireless communication system other than cellular wireless communication systems. For example, the technology disclosed herein is applicable to any wireless system that can use directional antennas, such as wireless LANs.

[0027] As described above with reference to Figure 1, the present disclosure provides a method for establishing communication between wireless devices. The method for establishing communication includes the first wireless device 10 transmitting a first signal 102, which includes a synchronization signal, using an omnidirectional or quasi-omnidirectional antenna. The method for establishing communication also includes the second wireless device 20 transmitting a second signal 104 based on having received the first signal 102. The method for establishing communication also includes the first wireless device 10 estimating the direction of arrival 106 of the second signal based on having received the second signal 104 using an array antenna. The method for establishing communication also includes the first wireless device 10 transmitting a third signal 108, which includes system information, towards the direction of arrival 106 of the second signal using a directional antenna. Furthermore, the method for establishing communication includes the second wireless device 20 transmitting a fourth signal 110 to establish wireless communication between the first wireless device 10 and the second wireless device 20 based on having received the third signal 108.

[0028] <Processing performed by each wireless device> Figure 2 shows an example of a pseudo-random sequence. A pseudo-random sequence, also called a pseudo-random signal, is a random number that repeats at a fixed period. That is, a "pseudo-random sequence" is a bit sequence consisting of "0s and 1s" with a finite period. As explained with reference to Figure 1, the first signal 102 and the second signal 104 include pseudo-random sequences. The fourth signal 110 may also include a pseudo-random sequence. Pseudo-random sequences are used to improve the processing gain, as explained with reference to Figure 3.

[0029] The pseudo-random sequence is generated by the pseudo-random sequence generator 1100 (see Figure 11). The first radio device 10 and the second radio device 20 are equipped with the pseudo-random sequence generator 1100 as hardware or programmatically. The first radio device 10 can generate the first signal 102 by converting the pseudo-random sequence into a baseband signal and modulating the baseband signal. The second radio device 20 can generate the second signal 104 by a similar procedure. In the example in Figure 2, the first radio device 10 generates the first signal 102 from the pseudo-random sequence 200.

[0030] Pseudorandom sequences can be generated using M sequences, Zadoff-Chu sequences, or other known methods. The pseudorandom sequence generator 1100 shown in Figure 11 is an M sequence generator equipped with 14 shift registers. The first wireless device 10 can obtain a pseudorandom sequence with a repeat length of 16383 bits by shifting each shift register of the pseudorandom sequence generator 1100, by providing an initial value (excluding all zeros) to each shift register. The pseudorandom sequence generator 1100 may be equipped with any number of shift registers other than 14. The pseudorandom sequence generator 1100 may also generate pseudorandom sequences using Zadoff-Chu sequences or other known methods.

[0031] As explained with reference to Figure 2, the first signal 102 and the second signal 104 are signals generated by modulating a baseband signal based on a pseudo-random sequence. The pseudo-random sequences included in the first signal 102 and the second signal 104 may be the same or different.

[0032] Figure 3 shows an example of the detection process for a pseudo-random sequence contained in the first signal 102 in the second wireless device 20. The method for generating the pseudo-random sequence 200 is shared between the first wireless device 10 and the second wireless device 20. Therefore, both the first wireless device 10 and the second wireless device 20 can generate the same pseudo-random sequence.

[0033] The second wireless device 20 compares the first signal 102 received from the first wireless device 10 with the signal 302 generated by the second wireless device 20 and calculates the difference. If the difference is less than or equal to a predetermined threshold, the second wireless device 20 may determine that the first signal 102 is the expected received signal. In other words, the second wireless device 20 may determine that the first signal 102 is the signal from the first wireless device 10. Alternatively, the second wireless device 20 may compare the first signal 102 received from the first wireless device 10 with the signal 302 generated by the second wireless device 20 and calculate the similarity. In this case, if the similarity is greater than or equal to a predetermined threshold, the second wireless device 20 may determine that the first signal 102 is the expected received signal. In other words, the second wireless device 20 may determine that the first signal 102 is the signal from the first wireless device 10. As an example, the second wireless device 20 may perform a sum-of-products operation on the first signal 102 and signal 302. In this case, the second wireless device 20 may multiply the absolute values ​​of the sum-of-products of each bit and compare the multiplication result with a threshold. This comparison process is sometimes called "correlation detection" because it calculates a correlation value. The length 300 of the bit information to be compared is set to a length within a range where the phase shift due to frequency error is negligible. Correlation detection may also be a comparison of modulated signals. Alternatively, correlation detection may be a comparison of pseudo-random sequences contained in each signal. The length 300 of the bit information may include the signal length, the signal sequence length, and the pseudo-random sequence length.

[0034] Here, we will explain "processing gain." Processing gain refers to improving the signal-to-noise ratio (SNR) between the source signal and the received signal. In the example in Figure 3, the processing gain includes improving the SNR between the first signal 102 and the generated signal 302. Wireless signals are subject to noise during transmission. Therefore, the source signal and the received signal do not necessarily match. In particular, signals transmitted by an omnidirectional antenna are susceptible to noise because they lack directional gain. Therefore, the first wireless device 10 transmits a first signal 102 containing multiple bits of information (i.e., a pseudo-random sequence). The second wireless device 20 then compares the multiple bits of information contained in the received first signal 102 with the multiple bits of information contained in the signal 302 it generated and performs correlation detection. In this way, even if a part of the first signal 102 changes during transmission, the second wireless device 20 can determine through correlation detection that the first signal 102 is the expected received signal or the signal from the first wireless device 10.

[0035] Figure 4 shows an example of the reception processing of the first signal 102 and the transmission processing of the second signal 104 in the second wireless device 20. The signal detection unit 908 (see Figure 9) performs the detection processing of the received signal and determines whether or not it has received or detected the first signal 102. Based on the determination that it has received or detected the first signal 102, the signal detection unit 908 outputs a detection notification 400 of the first signal 102 to the wireless protocol control unit 900 (see Figure 9). The signal detection unit 908 can determine whether or not the received signal is the first signal 102 by correlation detection as described with reference to Figure 3.

[0036] Based on the acquisition of the detection notification 400, the wireless protocol control unit 900 outputs a command 410 for generating the second signal 104 to the signal generation unit 910 (see Figure 9). The wireless protocol control unit 900 outputs the command 410 for generating the second signal 104 within a predetermined period 415. The predetermined period 415 may be within a certain period after the reception of the first signal 102. Alternatively, the predetermined period 415 may be set to any period within the interval 418 between the time the second wireless device 20 receives the first signal 102 and the time it receives the first signal 102 again.

[0037] The signal generation unit 910 generates a pseudo-random sequence 420 using a pseudo-random sequence generator 1100. The signal generation unit 910 outputs the pseudo-random sequence 420 to the first baseband signal generation unit 912 (see Figure 9).

[0038] The first baseband signal generation unit 912 converts the pseudo-random sequence 420 into a continuous baseband signal 430 having a predetermined amplitude and phase. The first baseband signal generation unit 912 outputs the generated baseband signal 430 to the radio unit 904.

[0039] The radio unit 904 modulates the acquired baseband signal 430 and includes the baseband signal 430 in the carrier wave 440. The "carrier wave" is a high-frequency signal transmitted and received via the antenna. Hereafter, the carrier wave may also be simply referred to as the signal. In the example in Figure 4, the carrier wave 440 is the second signal 104, which includes the pseudo-random sequence 420. The radio unit 904 transmits the carrier wave 440 as the second signal 104 via the antenna 902. The second signal 104 is a response to the first signal 102. The antenna 902 may be an omnidirectional antenna or a directional antenna.

[0040] The first radio device 10 performs the reception processing for the second signal 104 within a predetermined period 415 after transmitting the first signal 102. That is, the first radio device 10 activates the configuration related to receiving the second signal 104 within a predetermined period 415. Conversely, at any other time, the first radio device 10 may disable some or all of the configuration related to receiving the second signal 104. For example, the first radio device 10 can activate or disable each configuration by controlling the on / off switching of the power supply for each configuration. This allows the first radio device 10 to reduce the power consumption required for the reception processing of the second signal 104. The configuration related to receiving the second signal 104 includes the second radio unit 812 (see Figure 8), the first baseband signal processing unit 814 (see Figure 8), and the signal detection unit 816 (see Figure 8), etc.

[0041] As explained with reference to Figure 4, the second radio device 20 transmits the second signal 104 within a predetermined period 415 after receiving the first signal 102. In other words, the reception of the second signal 104 by the first radio device 10 using an array antenna includes performing a detection process for the reception of the second signal 104 within a predetermined period 415 after the transmission of the first signal 102.

[0042] Figure 5 shows an example of the estimation process for the direction of arrival 106 of the second signal 104 in the first wireless device 10. The first wireless device 10 receives the second signal 104 via the second antenna 810. The second antenna 810 is an array antenna 500. The first wireless device 10 can estimate the direction of arrival 106 of the second signal 104 using algorithms such as the MUSIC (Multiple Signal Classification) method or the ESPRIT (Estimation of Signal Parameter via Rotational Invariance Techniques) method. The direction of arrival 106 of the second signal 104 is represented by a combination of azimuth angle 502 and elevation angle 504. The first wireless device 10 estimates the direction of arrival 106 of the second signal 104 as a combination of azimuth angle 502 and elevation angle 504 such that the signal strength is above a predetermined threshold. Signal strength refers to the radio wave strength of the wireless signal received by the wireless device.

[0043] Graph 510 shows the signal strength of the second signal 104 received by the first radio device 10 for each direction of arrival 106. More specifically, Graph 510 shows the signal strength of the second signal 104 for each combination of azimuth angle 502 and elevation angle 504. According to Graph 510, the signal strength from the direction of azimuth angle 502 and elevation angle 504 (25, 40) (referred to as the "first direction") is higher than the signal strength from other directions. Similarly, the signal strength from the direction of azimuth angle 502 and elevation angle 504 (-20°, 20°) (referred to as the "second direction") is higher than the signal strength from other directions. For example, suppose the predetermined threshold is "-19.6dB". In this case, the signal strength from the first direction and the signal strength from the second direction will exceed the predetermined threshold. Therefore, the first radio device 10 is receiving the second signal 104 from two directions. If multiple second wireless devices 20 are present within the communication range of the first wireless device 10, the first wireless device 10 can receive the second signal 104 from multiple directions.

[0044] Thus, when the first radio device 10 receives the second signal 104, it estimates the direction of arrival 106 of the second signal 104. As a result, the first radio device 10 only needs to transmit the third signal 108 via a directional antenna in the direction of arrival 106 of the second signal 104. Therefore, the communication method of this disclosure can reduce the number of transmissions of the third signal 108 compared to the conventional searchlight method, which sequentially transmits the third signal 108 in all directions. Consequently, the communication method of this disclosure can reduce the communication overhead and power consumption in the transmission of the third signal 108 compared to the searchlight method. Furthermore, the communication method of this disclosure can establish communication between the first radio device 10 and the second radio device 20 in a shorter time compared to the searchlight method.

[0045] Figure 6 shows an example of the procedure for establishing communication, including the fourth signal 110. Based on the receipt of the third signal 108, the second radio device 20 transmits the fourth signal 110 for establishing communication to the first radio device 10. Transmitting the fourth signal 110 to the first radio device 10 may, for example, include the following steps S610 to S650.

[0046] In step S610, the second radio device 20 transmits a random access signal to the first radio device 10. In step S620, the first radio device 10 transmits a response to the random access signal to the second radio device 20. In step S630, the second radio device 20 transmits a message containing the terminal ID to the first radio device 10. In step S640, the first radio device 10 transmits a message to the second radio device 20 acknowledging the terminal ID and assigning a connection ID. In step S650, the first radio device 10 and the second radio device 20 exchange messages containing information regarding higher-layer procedures, authentication, cryptography, etc.

[0047] For example, the fourth signal 110 may be the random access signal in step S610. In this case, the communication processing from step S620 onward is a series of communication processes following the transmission of the fourth signal 110. Alternatively, transmitting the fourth signal 110 may encompass the communication processing in steps S610 to S650.

[0048] Figure 7 shows a second example of the procedure for establishing communication between the first radio device 10 and the second radio device 20. The second example of the communication establishment procedure differs from the first example in that the second radio device 20 estimates the direction of arrival of the first signal 102. In the second example of the communication establishment procedure, the second radio device 20 is equipped with an array antenna and a directional antenna.

[0049] In step S710, the first radio device 10 periodically transmits the first signal 102. Next, the second radio device 20 receives the first signal 102 via an array antenna. The second radio device 20 estimates the direction of arrival 702 of the first signal 102. For example, the second radio device 20 may estimate the direction of arrival 702 using the method described with reference to Figure 5. The direction of arrival 702 of the first signal 102 is the direction in which the first radio device 10 is estimated to be located, as seen from the perspective of the second radio device 20.

[0050] In step S720, the second radio device 20 transmits the second signal 104 via a directional antenna towards the direction of arrival 702. Thus, in the communication establishment procedure shown in Figure 7, the second radio device 20 estimates the direction of arrival 702 of the first signal 102 and transmits the second signal 104 towards the direction of arrival 702. The processes in steps S730 and S740 are identical to the processes in steps S130 and S140, respectively, and therefore their descriptions will not be repeated. The second radio device 20 may correspond to either the first example of the communication establishment procedure or the second example of the communication establishment procedure. Alternatively, the second radio device 20 may correspond to both communication establishment procedures.

[0051] As explained with reference to Figure 7, the second radio device 20 transmits a second signal 104 based on having received the first signal 102. Transmitting the second signal 104 may include receiving the first signal 102 using an array antenna and estimating the direction of arrival 702 of the first signal 102. Transmitting the second signal 104 may also include transmitting the second signal 104 in the direction of arrival 702 of the first signal 102 using a directional antenna.

[0052] In the second example of the communication establishment procedure, the second radio device 20 transmits the second signal 104 using a directional antenna. As a result, the directional gain of the second signal 104 is higher than when transmitted with an omnidirectional antenna, and it can propagate over longer distances. In addition, since the second radio device 20 transmits the second signal 104 only in the direction of arrival 702, the transmission power of the second signal 104 can be reduced compared to when an omnidirectional antenna is used.

[0053] <Configuration of each wireless device> Figure 8 shows an example of the configuration of the first wireless device 10. Each of the configurations shown in Figure 8 may be implemented as hardware. In addition, some of the configurations shown in Figure 8 may be implemented as programs.

[0054] The first wireless device 10 includes a wireless protocol control unit 800. The wireless protocol control unit 800 controls the overall operation of the first wireless device 10 and controls all aspects of communication as shown in Figures 1 and 7.

[0055] The first radio device 10 comprises a signal generation unit 802, a first baseband signal generation unit 804, a first radio unit 806, and a first antenna 808. These components are primarily used for transmitting the first signal 102. More specifically, the signal generation unit 802 generates a pseudo-random sequence to be included in the first signal 102 and outputs the pseudo-random sequence to the first baseband signal generation unit 804. The first baseband signal generation unit 804 converts the acquired pseudo-random sequence into a continuous baseband signal having predetermined amplitude and phase. The first baseband signal generation unit 804 outputs the generated baseband signal to the first radio unit 806. The first radio unit 806 modulates the acquired baseband signal and includes the baseband signal in a carrier wave. The first radio unit 806 transmits the carrier wave as the first signal 102 via the first antenna 808.

[0056] The first wireless device 10 comprises a second antenna 810, a second wireless unit 812, a first baseband signal processing unit 814, and a signal detection unit 816. These components are primarily used for receiving the second signal 104. More specifically, the second wireless unit 812 receives the second signal 104 via the second antenna 810. The second wireless unit 812 demodulates the second signal 104 to generate a baseband signal. The second wireless unit 812 outputs the baseband signal of the second signal 104 to the first baseband signal processing unit 814. The first baseband signal processing unit 814 converts the acquired baseband signal into a pseudo-random sequence. That is, the first baseband signal processing unit 814 converts the acquired baseband signal into bit sequence information. The first baseband signal processing unit 814 outputs the generated pseudo-random sequence to the signal detection unit 816. The signal detection unit 816 determines whether or not the second signal 104 has been received or detected. Based on its determination that it has received or detected the second signal 104, the signal detection unit 816 outputs a detection notification for the second signal 104 to the wireless protocol control unit 800. The signal detection unit 816 may also perform correlation detection by comparing a pseudo-random sequence obtained from the second signal 104 with a pseudo-random sequence generated by the signal detection unit 816. The signal detection unit 816 also estimates the direction of arrival 106 of the second signal 104. The signal detection unit 816 outputs the estimated direction of arrival 106 of the second signal 104 to the wireless protocol control unit 800.

[0057] Based on receiving notification of the detection of the second signal 104, the wireless protocol control unit 800 outputs a command to the transmission data generation unit 818 to transmit the third signal 108. This command includes information on the direction of arrival 106 of the second signal 104. The wireless protocol control unit 800 may estimate the direction of arrival 106 of the second signal 104 instead of the signal detection unit 816. The wireless protocol control unit 800 may enable the second antenna 810, the second radio unit 812, the first baseband signal processing unit 814, and the signal detection unit 816 for a predetermined period 415 after the transmission of the first signal 102. For example, the wireless protocol control unit 800 may turn on the power to these components for a predetermined period 415. The wireless protocol control unit 800 may turn off the power to these components or put them into power-saving mode during other periods.

[0058] Furthermore, the first wireless device 10 includes a transmission data generation unit 818, a second baseband signal generation unit 820, a third wireless unit 822, a third antenna 824, a second baseband signal processing unit 826, and a reception data processing unit 828. These components are mainly used for receiving the third signal 108, transmitting the fourth signal, and subsequent communication.

[0059] More specifically, the transmission data generation unit 818 generates data to be included in the third signal 108. The transmission data generation unit 818 also generates arbitrary data to be transmitted to the second radio device 20 after receiving the fourth signal 110. The transmission data generation unit 818 outputs the generated data to the second baseband signal generation unit 820. The second baseband signal generation unit 820 generates a baseband signal from the acquired data based on predetermined frequencies and amplitudes. The second baseband signal generation unit 820 outputs the generated baseband signal to the third radio unit 822. The third radio unit 822 modulates the acquired baseband signal and includes the baseband signal in the carrier wave. The third radio unit 822 transmits the carrier wave via the third antenna 824. The carrier wave includes the third signal 108 or other arbitrary signals.

[0060] Furthermore, the third radio unit 822 acquires a signal via the third antenna 824. The third radio unit 822 demodulates the acquired signal to generate a baseband signal. The third radio unit 822 outputs the generated baseband signal to the second baseband signal processing unit 826. The second baseband signal processing unit 826 converts the acquired baseband signal into a bit sequence. The second baseband signal processing unit 826 outputs the converted bit sequence to the received data processing unit 828. This bit sequence may include a pseudo-random sequence, user data, control data, etc. If the acquired bit sequence is a pseudo-random sequence, the received data processing unit 828 performs detection processing such as correlation detection on the bit sequence and outputs the result of the detection processing to the radio protocol control unit 800. If the acquired bit sequence is user data or control data, etc., the received data processing unit 828 outputs the bit sequence to the radio protocol control unit 800.

[0061] The first antenna 808 is an omnidirectional or quasi-omnidirectional antenna. The second antenna 810 is an array antenna. The first antenna 808 may also be an array antenna. The first antenna 808 and the second antenna 810 may be configured as a single transmit / receive array antenna. The third antenna 824 is composed of multiple directional antennas or an array antenna capable of forming a desired directivity.

[0062] As described with reference to Figure 8, the first wireless device 10 includes an omnidirectional or quasi-omnidirectional first antenna 808 for transmitting a first signal 102 including a synchronization signal, a second antenna 810 which is an array antenna for receiving a second signal 104 from a wireless terminal, a signal detection unit 816 for estimating the direction of arrival 106 of the second signal 104, and a third antenna 824 which is a directional antenna for transmitting a third signal 108 including system information toward the direction of arrival 106 of the second signal 104 and for receiving a fourth signal 110 for establishing wireless communication from a wireless terminal.

[0063] Furthermore, receiving the second signal 104 from the wireless terminal includes performing a detection process for the reception of the second signal 104 within a predetermined period 415 after the transmission of the first signal 102.

[0064] Figure 9 shows an example of the configuration of the second radio device 20. The second radio device 20 comprises an antenna 902, a radio unit 904, and a radio protocol control unit 900. The antenna 902 transmits and receives signals. The radio unit 904 modulates the baseband signal and incorporates it into the carrier wave. The carrier wave is the signal transmitted via the antenna 902. The radio unit 904 also demodulates the signal received via the antenna 902 to generate a baseband signal. The radio protocol control unit 900 controls the overall operation of the second radio device 20. These configurations are used in all transmission and reception in the second radio device 20.

[0065] The second wireless device 20 also includes a first baseband signal processing unit 906 and a signal detection unit 908. These components are mainly used for receiving the first signal 102. More specifically, the wireless unit 904 receives the first signal 102 via the antenna 902. The wireless unit 904 demodulates the first signal 102 to generate a baseband signal. The wireless unit 904 outputs the baseband signal of the first signal 102 to the first baseband signal processing unit 906. The first baseband signal processing unit 906 converts the acquired baseband signal into a pseudo-random sequence. That is, the first baseband signal processing unit 906 converts the acquired baseband signal into bit sequence information. The first baseband signal processing unit 906 outputs the generated pseudo-random sequence to the signal detection unit 908. The signal detection unit 908 determines whether or not the first signal 102 has been received or detected. Based on its determination that it has received or detected the first signal 102, the signal detection unit 908 outputs a detection notification of the first signal 102 to the wireless protocol control unit 900. The signal detection unit 908 may also perform correlation detection by comparing a pseudo-random sequence obtained from the first signal 102 with a pseudo-random sequence generated by the signal detection unit 908. Alternatively, the signal detection unit 908 may estimate the direction of arrival 702 of the first signal 102. In this case, the signal detection unit 908 outputs the estimated direction of arrival 702 of the first signal 102 to the wireless protocol control unit 900.

[0066] The second radio device 20 also includes a signal generation unit 910 and a first baseband signal generation unit 912. These components are mainly used for transmitting the second signal 104. More specifically, the signal generation unit 910 generates a pseudo-random sequence to be included in the second signal 104 and outputs the pseudo-random sequence to the first baseband signal generation unit 912. The first baseband signal generation unit 912 converts the acquired pseudo-random sequence into a continuous baseband signal having predetermined amplitude and phase. The first baseband signal generation unit 912 outputs the generated baseband signal to the radio unit 904. The radio unit 904 modulates the acquired baseband signal and includes the baseband signal in the carrier wave. The radio unit 904 transmits the carrier wave as the second signal 104 via the antenna 902.

[0067] Furthermore, the second wireless device 20 includes a second baseband signal processing unit 914 and a received data processing unit 916. These configurations are mainly used for receiving the third signal 108 and subsequent signals. More specifically, the wireless unit 904 receives signals via the antenna 902. The wireless unit 904 demodulates the received signal to generate a baseband signal. The wireless unit 904 outputs the baseband signal of the received signal to the second baseband signal processing unit 914. The second baseband signal processing unit 914 converts the acquired baseband signal into a bit sequence. The second baseband signal processing unit 914 outputs the converted bit sequence to the received data processing unit 916. The bit sequence may include a pseudo-random sequence, user data, control data, etc. If the acquired bit sequence is a pseudo-random sequence, the received data processing unit 916 performs detection processing such as correlation detection on the bit sequence and outputs the result of the detection processing to the wireless protocol control unit 900. The received data processing unit 916 outputs the bit sequence to the wireless protocol control unit 900 if the acquired bit sequence is user data or control data, etc.

[0068] The second radio device 20 also includes a transmission data generation unit 918 and a second baseband signal generation unit 920. These configurations are mainly used for transmitting the fourth signal 110 and subsequent signals. More specifically, the transmission data generation unit 918 generates data to be included in the fourth signal. The transmission data generation unit 918 can also generate any data to be transmitted to the first radio device 10. The transmission data generation unit 918 outputs the generated data to the second baseband signal generation unit 920. The second baseband signal generation unit 920 generates a baseband signal from the acquired data based on predetermined frequencies and amplitudes. The second baseband signal generation unit 920 outputs the generated baseband signal to the radio unit 904. The radio unit 904 modulates the acquired baseband signal and includes the baseband signal in a carrier wave. The radio unit 904 transmits the carrier wave via the antenna 902. The carrier wave includes the fourth signal 110 or any other signal.

[0069] Antenna 902 may be an omnidirectional antenna or a quasi-omnidirectional antenna. Antenna 902 may be a plurality of directional antennas. Antenna 902 may also include both omnidirectional and directional antennas. Antenna 902 may also be an array antenna.

[0070] Figure 10 shows an example of the configuration of the array antenna 500 of the first wireless device 10. The array antenna 500 includes multiple antennas, each of which is connected to the wireless unit. The array antenna 500 comprises at least a second antenna 810. The array antenna 500 may also have the functions of both the first antenna 808 and the second antenna 810. A third antenna 824 may also be configured as an array antenna.

[0071] The first radio unit 806, the second radio unit 812, and the third radio unit 822 may be configured as a single radio unit or as separate radio units. Similarly, the first baseband signal generation unit 804 and the second baseband signal generation unit 820 may be configured as a single baseband signal generation unit or as separate baseband signal generation units. The first baseband signal processing unit 814 and the second baseband signal processing unit 826 may be configured as a single baseband signal processing unit or as separate baseband signal processing units.

[0072] Figure 11 shows an example of a pseudo-random sequence generator 1100 provided in the first wireless device 10 and the second wireless device 20. The first wireless device 10 and the second wireless device 20 can use the pseudo-random sequence generator 1100 to obtain a pseudo-random sequence with a repeat length of 16383 bits. The pseudo-random sequence generator 1100 can be configured as hardware or software. The pseudo-random sequence generator 1100 may generate the pseudo-random sequence 200 using a Zadoff-Chu sequence or other known method.

[0073] <Operation of each wireless device> Figure 12 shows an example of the operation flow of the first wireless device 10. The first wireless device 10 can realize the processing shown in Figure 12 by executing a program. The wireless protocol control unit 800 may include a processor, memory, and storage. Alternatively, the wireless protocol control unit 800 may read a program for performing the processing shown in Figure 12 from storage into memory and execute the program using the processor. Part or all of the processing can also be realized as a combination of circuit elements configured to perform the processing.

[0074] In step S1210, the first radio device 10 transmits the first signal 102. If the second radio device 20 receives the first signal, the second radio device 20 transmits the second signal 104. In step S1220, based on having received the second signal 104, the first radio device 10 detects the second signal 104 and estimates the direction of arrival 106 of the second signal 104. The first radio device 10 may detect the second signal 104 using correlation detection techniques. In step S1230, the first radio device 10 determines whether it has succeeded in detecting the second signal 104 and estimating the direction of arrival 106 of the second signal 104. If the first radio device 10 determines that it has succeeded in detecting the second signal 104 and estimating the direction of arrival 106 of the second signal 104 (YES in step S1230), it moves control to step S1240. Otherwise (NO in step S1230), the first wireless device 10 transfers control to step S1210.

[0075] In step S1240, the first radio device 10 transmits the third signal 108 in the direction of arrival 106. When the second radio device 20 receives the third signal 108, the third signal 108 transmits the fourth signal 110. In step S1250, the first radio device 10 detects the fourth signal 110 based on having received it. The first radio device 10 may detect the fourth signal 110 using correlation detection techniques. In step S1260, the first radio device 10 determines whether or not it has detected the fourth signal 110. If the first radio device 10 determines that it has detected the fourth signal 110 (YES in step S1260), it transfers control to step S1270. Otherwise (NO in step S1260), the first radio device 10 transfers control to step S1210. In step S1270, the first radio device 10 performs terminal connection processing. The terminal connection process corresponds to the process shown in Figure 6. Once the terminal connection process is complete, the first wireless device 10 and the second wireless device 20 establish communication with each other.

[0076] Figure 13 shows an example of the operation flow of the second wireless device 20. The second wireless device 20 can implement the processing shown in Figure 13 by executing a program. The wireless protocol control unit 900 may include a processor, memory, and storage. Alternatively, the wireless protocol control unit 900 may read a program for performing the processing shown in Figure 13 from storage into memory and have the processor execute the program. Part or all of the processing can also be implemented as a combination of circuit elements configured to perform the processing. The following steps may be performed in any order.

[0077] In step S1310, the second radio device 20 detects the first signal 102 based on having received it. The second radio device 20 may detect the first signal 102 using correlation detection techniques. Alternatively, the second radio device 20 may estimate the direction of arrival 702 of the first signal 102.

[0078] In step S1320, the second wireless device 20 determines whether or not it has detected the first signal 102. If the second wireless device 20 determines that it has detected the first signal 102 (YES in step S1320), it transfers control to step S1330. Otherwise (NO in step S1320), the second wireless device 20 transfers control to step S1310.

[0079] In step S1330, the second radio device 20 transmits a second signal 104. The second signal 104 may be transmitted via an omnidirectional antenna or a quasi-omnidirectional antenna. Alternatively, the second signal 104 may be transmitted via a directional antenna in the direction of arrival 702 of the first signal. If the first radio device 10 successfully detects the second signal 104 and estimates its direction of arrival 106, it transmits a third signal 108.

[0080] In step S1340, the second wireless device 20 receives the third signal 108. In step S1350, based on having received the third signal 108, the second wireless device 20 transmits the fourth signal 110. In step S1360, the second wireless device 20 performs terminal connection processing. This step is the counterpart to step S1270. In step S1370, the second wireless device 20 determines whether the terminal connection processing was successful. If the second wireless device 20 determines that the terminal connection processing was successful (YES in step S1370), it transfers control to step S1380. Otherwise (NO in step S1370), the second wireless device 20 transfers control to step S1310.

[0081] In step S1380, the second wireless device 20 transmits and receives communication data with the first wireless device 10. This step is performed after communication between the first wireless device 10 and the second wireless device has been established.

[0082] <Summary> As described above, in the technology of this disclosure, the first wireless device 10 estimates the direction of arrival 106 of the second signal 104 by analyzing the second signal 104 received by the array antenna 500. Therefore, the first wireless device 10 only needs to transmit the third signal 108 in the direction of arrival 106 of the second signal 104. As a result, the communication overhead and power consumption in the transmission of the third signal 108 can be significantly reduced compared to the prior art.

[0083] Furthermore, the second radio device 20 may estimate the direction of arrival 702 of the first signal 102. In this case, the second radio device 20 transmits the second signal 104 in the direction of arrival 702 of the first signal 102 via a directional antenna. As a result, the second signal 104 can be transmitted with lower transmission power than when transmitted with an omnidirectional antenna, due to the higher directional gain. Therefore, the second radio device 20 can transmit the second signal 104 without consuming extra transmission power.

[0084] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications are intended to be equivalent to the claims. Furthermore, the disclosures described in the embodiments and each variation are intended to be implemented, as far as possible, individually or in combination. [Explanation of Symbols]

[0085] 10 First radio device, 20 Second radio device, 102 First signal, 104 Second signal, 106, 702 Direction of arrival, 108 Third signal, 110 Fourth signal, 200, 420 Pseudo-random sequence, 300 Length, 302 Signal, 400 Detection notification, 410 Generation command, 415 Predetermined period, 430 Baseband signal, 440 Carrier wave, 500 Array antenna, 502 Azimuth angle, 504 Elevation angle, 510 Graph, 800, 900 Radio protocol control unit, 802, 910 Signal generation unit, 804, 912 First baseband signal generation unit, 806 First radio unit, 808 First antenna, 810 Second antenna, 812 Second radio unit, 814, 906 First baseband signal processing unit, 816, 908 Signal detection unit, 818, 918; Transmission data generation unit, 820, 920; Second baseband signal generation unit, 822; Third radio unit, 824; Third antenna, 826, 914; Second baseband signal processing unit, 828, 916; Receiving data processing unit, 902; Antenna, 904; Radio unit, 1100; Pseudo-random sequence generator.

Claims

1. A method for establishing communication between a first radio device and a second radio device, The first wireless device transmits a first signal including a synchronization signal using an omnidirectional or quasi-omnidirectional antenna. The second wireless device transmits a second signal based on the receipt of the first signal. Based on the fact that the first wireless device has received the second signal using an array antenna, the direction of arrival of the second signal is estimated, The first wireless device transmits a third signal containing system information in the direction from which the second signal is coming, using a directional antenna. A method for establishing communication, comprising: the second wireless device transmitting a fourth signal for establishing wireless communication between the first wireless device and the second wireless device based on the reception of the third signal.

2. The second wireless device transmits the second signal based on the receipt of the first signal. The first signal is received using an array antenna, and the direction of arrival of the first signal is estimated. A method for establishing communication according to claim 1, comprising transmitting the second signal in the direction from which the first signal is coming using a directional antenna.

3. The method for establishing communication according to claim 1 or 2, wherein the first wireless device receives the second signal using an array antenna, and the receiving of the second signal is performed within a predetermined period after the transmission of the first signal.

4. The method for establishing communication according to claim 1 or 2, wherein the first signal and the second signal are signals generated by modulating a baseband signal based on a pseudo-random sequence.

5. An omnidirectional or quasi-omnidirectional first antenna for transmitting a first signal including a synchronization signal, A second antenna, which is an array antenna for receiving a second signal from a wireless terminal, A signal detection unit for estimating the direction of arrival of the second signal, A wireless device comprising a third antenna, which is a directional antenna for transmitting a third signal containing system information in the direction from which the second signal is coming, and for receiving a fourth signal for establishing wireless communication from the wireless terminal.

6. The wireless device according to claim 5, wherein receiving the second signal from the wireless terminal includes performing a detection process for the reception of the second signal within a predetermined period after the transmission of the first signal.

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