Communication device, communication method, and program for efficiently sharing frequency band among plurality of generations of wireless communication systems

Abstract

This communication device: receives a synchronization signal transmitted by broadcasting from a network of a first wireless communication system that is compliant with a cellular communication standard of a first prescribed generation; and receives, on the basis of the synchronization signal, a prescribed signal associated with the synchronization signal and transmitted by broadcasting from a network of a second wireless communication system that is compliant with a cellular communication standard of a second prescribed generation and that uses a frequency band shared with the first wireless communication system.

Description

Communication device, communication method, and program for efficiently sharing frequency bands by multiple generations of wireless communication systems

[0001] The present invention relates to a technology for sharing frequency bands by multiple generations of wireless communication systems.

[0002] Currently, the fifth-generation (5G) cellular communication system is widely deployed and used. In the future, with the development of mobile communication technology, the introduction of systems such as the sixth generation (6G) is expected. During the transitional period of system replacement across generations, it is assumed that multiple generations of wireless communication systems will use the same frequency band.

[0003] The present invention provides a technology for improving communication efficiency when switching between multiple generations of wireless communication systems.

[0004] A communication device according to an aspect of the present invention receives a synchronization signal broadcast transmitted from a network of a first wireless communication system compliant with a first predetermined generation of cellular communication standards, and based on the synchronization signal, a predetermined signal broadcast transmitted from a network of a second wireless communication system compliant with a second predetermined generation of cellular communication standards and using a frequency band common to the first wireless communication system, which is associated with the synchronization signal. It has receiving means for receiving.

[0005] According to the present invention, it is possible to improve communication efficiency when switching between multiple generations of wireless communication systems.

[0006] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar configurations are given the same reference numerals.

[0007] The attached drawings are included in the specification and constitute a part thereof, illustrating embodiments of the present invention and are used to explain the principles of the present invention together with the description thereof. Figure 1 is a diagram showing an example of the configuration of a wireless communication system. Figure 2 is a diagram showing an example of an SS / PBCH transmission method according to this embodiment. Figure 3 is a diagram showing an example of an SS / PBCH transmission method according to this embodiment. Figure 4 is a diagram showing an example of an SS / PBCH transmission method according to this embodiment. Figure 5 is a diagram showing an example of the hardware configuration of a terminal device. Figure 6 is a diagram showing an example of the functional configuration of a terminal device. Figure 7 is a diagram showing an example of the processing flow executed in a terminal device.

[0008] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0009] (System Configuration) Figure 1 shows an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system is a cellular communication system that performs communication compliant with, for example, fifth-generation (5G) and sixth-generation (6G) cellular communication standards. The communication equipment of this wireless communication system includes, for example, a 5G base station device 101, a 6G base station device 102, and a terminal device 103 capable of performing at least 6G communication. Here, only one 5G and one 6G base station device and one terminal device are shown, but of course, there can be many of these communication devices. The terminal device 103 may be configured to perform 5G communication. The base station devices 101 and 102 may be located in the same position or in different positions. In the example in Figure 1, the base station devices 101 and 102 are assumed to be located in the same position. Furthermore, the base station devices 101 and 102 are configured to form beam groups 111 and 112, respectively, and to communicate with the terminal device 103 using one or more beams included in the beam groups. In Figure 1, as an example, beam group 111 and beam group 112 are formed oriented in the same direction, and each beam in beam group 111 corresponds to one of the beams in beam group 112, but this is not limited to this. For example, the geographical area covered by one beam in beam group 111 (the area where a signal transmitted from the base station device 101 reaches at a predetermined level or higher by that beam) may be covered by multiple beams in beam group 112. That is, the beams in beam group 112 may be set to have a narrower beam width than the beams in beam group 111. Also, the beams in beam group 112 may be configured to cover, for example, the boundary region of the area covered by two beams in beam group 111. Furthermore, one beam in beam group 112 may be configured to cover the area covered by multiple beams in beam group 111. In other words, the areas covered by the multiple beams in beam group 111 and the multiple beams in beam group 112 may be configured arbitrarily, as long as they are configured to cover a common geographical area.

[0010] Furthermore, the 5G wireless communication system and the 6G wireless communication system shall communicate using a common frequency band (shared). Sharing a common frequency band here means that at least a portion of the frequency band used by the 5G wireless communication system and the frequency band used by the 6G wireless communication system overlap. That is, one frequency band may encompass the entirety of the other, or the frequency bands may be configured such that a portion of one frequency band overlaps with a portion of the other, while the remaining portions do not overlap. Also, the frequency bands used by the two wireless communication systems may be the same. Furthermore, 5G and 6G are examples of different generations of wireless communication systems, and are not limited to these. For example, the following discussion can be applied in an environment where a first wireless communication system of a predetermined first generation and a second wireless communication system of a predetermined second generation, such as 6G and seventh generation (7G), share a frequency band. In this embodiment, a cellular communication system is used as an example, but the following discussion may also be applied to non-cellular communication systems with a similar configuration.

[0011] Traditionally, in environments where the frequency band is shared between fourth-generation (4G) and 5G wireless communication systems, a frequency sharing technology called Dynamic Spectrum Sharing (DSS) has been used. DSS is a technology that separates the time / frequency resources used by 4G and 5G to prevent mutual interference. Therefore, in DSS, known signals, such as synchronization signals, are placed on different time / frequency resources that do not interfere with each other, based on known symbol sequences. In cellular communication systems, the time / frequency resources on which known signals are placed cannot be used for user data communication. Therefore, in environments where multiple wireless communication systems coexist, the placement of known signals for each wireless communication system increases the amount of time / frequency resources that cannot be used for user data communication, which can reduce the overall resource utilization efficiency of the system.

[0012] In this embodiment, in view of these circumstances, a technology is provided to reduce overhead due to known signals and improve frequency utilization efficiency in an environment where multiple wireless communication systems share a common frequency band.

[0013] Figure 2 shows an example configuration of the synchronization signal (SS) and physical broadcast channel (PBCH) for 5G and 6G according to this embodiment. In this embodiment, the terms synchronization signal (SS) and physical broadcast channel (PBCH) are used, but if other terms are used in standards for 6G and later, they should be interpreted as terms representing signals with similar functions as used in those standards. That is, SS may be interpreted as any signal for establishing time synchronization, generated using at least a known symbol sequence, and PBCH may be interpreted as a predetermined signal that carries information including system information, which is received when synchronization is established.

[0014] In this embodiment, the 5G SS is reused to establish synchronization of the 6G downlink. That is, the terminal device 103 establishes downlink time synchronization using, for example, the 5G PSS (Primary SS) / SSS (Secondary SS), and receives the 6G PBCH based on that time synchronization. In other words, the 5G terminal device establishes time synchronization with PSS 201 and SSS 202 broadcast from the 5G base station device 101, and receives the 5G PBCH 203 broadcast from the same 5G base station device 101 to acquire system information transmitted by the PBCH 203. In contrast, the 6G terminal device 103 establishes time synchronization with PSS 201 and SSS 202 broadcast from the 5G base station device 101, and then receives the 6G PBCH 221 (broadcast) transmitted from the 6G base station device 102 to acquire 6G system information. Furthermore, a 6G PBCH 221 (which can be obtained by establishing time synchronization using the PSS 201 / SSS 202) may be transmitted from the 6G base station equipment 102 after a predetermined period has elapsed since the 5G base station equipment 101 transmitted the PSS 201 and SSS 202. This predetermined period may be uniquely specified in the standard, for example. That is, the PBCH for a particular 6G beam may be configured to be transmitted after a predetermined period specified in the standard has elapsed since the PSS / SSS that serve as the reference for time synchronization in that beam was transmitted. In this case, similar to the relationship between PSS 201 / SSS 202 and PBCH 221, PBCH 231 may be transmitted after a predetermined period has elapsed since the transmission of PSS 211 / SSS 212, and the terminal equipment 103 can receive PBCH 231 based on PSS 211 / SSS 212 and obtain system information regarding the beam to which PBCH 231 is transmitted. Furthermore, when a 5G terminal device establishes time synchronization based on PSS211 / SSS212, it receives the 5G PBCH213.

[0015] In the example in Figure 2, a 5G PSS / SSS and a 6G PBCH are described as being transmitted using different time resources and the same frequency resources. However, different resources may be used in the frequency direction. That is, within the system bandwidth, a 6G PBCH may be transmitted using different frequency resources than those used to transmit the 5G PSS / SSS. In this case, the 6G PBCH may be transmitted using the same time resources as the 5G PSS / SSS but with different frequency resources. The amount of shift in the frequency domain (the frequency difference between the frequency resource location where the 5G PSS / SSS (or SS / PBCH block) is transmitted and the frequency resource location where the 6G PBCH is transmitted) may be predetermined in the standard. Furthermore, when one 5G PSS / SSS corresponds to multiple 6G PBCHs, the locations of those multiple PBCHs may be predetermined in the standard. For example, a provision may be provided that allows the location of the 6G PBCH time / frequency resource to be specified, such as the first PBCH being transmitted at a time / frequency resource that is on the same frequency as the 5G PSS / SSS and after a predetermined period, and the second PBCH being transmitted at a time / frequency resource that is shifted in the frequency direction by a predetermined amount from the frequency position of the 5G PSS / SSS and after a predetermined period. In addition, one or more resources on which the 6G PBCH is transmitted may be sandwiched between the resources of two 5G SS / PBCH blocks (SSBs). For example, PBCH221 may be transmitted at a timing between an SSB containing PSS201 / SSS202 and an SSB containing PSS211 / SSS212.

[0016] Furthermore, information for a predetermined period may be transmitted, for example, in a 5G PBCH. For example, terminal device 103 may receive PBCH 203 based on PSS 201 / SSS 202 and identify the resources to which a 6G PBCH 221 contained within it is transmitted. Similarly, terminal device 103 may receive PBCH 213 based on PSS 211 / SSS 212 and identify the resources to which a 6G PBCH 231 contained within it is transmitted. Note that, for example, if multiple 6G PBCHs are received under time synchronization based on a common PSS / SSS, the 5G PBCH may be transmitted with information that identifies the location of the time / frequency resources of those multiple 6G PBCHs. In this way, it becomes unnecessary to transmit 6G SS corresponding to 6G PBCHs, thereby improving the resource utilization efficiency of the entire system.

[0017] Furthermore, the 6G base station equipment 102 may transmit only PBCH assuming the reuse of the 5G PSS / SSS, but it may also transmit a 6G synchronization signal for a 6G beam directed in a direction where a 5G beam is not formed. For example, as shown in Figure 1, the 6G base station equipment 102 may form a beam group 113 directed in a different direction from the 5G beam group 111. In one example, the 6G base station equipment 102 may form a beam directed upwards. Conventionally, beams directed upwards are not formed, so the 5G base station equipment 101 does not form such a beam. For this reason, the 6G base station equipment 102 may transmit 6G SS and PBCH for such a beam group 113. In addition, the 6G base station equipment 102 may also transmit 6G SS and PBCH in a geographical area covered by a beam provided by any of the 5G base station equipment. For example, the 6G base station equipment 102 may transmit not only PBCH but also SS for beams that attempt to cover a geographical range covered by 5G base station equipment located at different geographical locations. Furthermore, even for beams corresponding to a geographical range covered by 5G base station equipment 101 located at (approximately) the same geographical location, the 6G base station equipment 102 may transmit SS in those beams, for example, when high-resolution synchronization is required for 6G.

[0018] In such cases, as shown in Figure 3, for example, the 6G base station device 102 transmits the 6G PSS / SSS and its corresponding PBCH (PSS301 / SSS302 and its corresponding PBCH321, and PSS311 / SSS312 and its corresponding PBCH331). Also, as in the case of Figure 2, if the 6G base station device 102 reuses the 5G PSS / SSS, it may transmit only the PBCH (PBCH221, PBCH231) corresponding to that PSS / SSS. When the terminal device 103 receives the 5G PSS / SSS, it receives the 6G PBCH associated with that PSS / SSS, and at the same time, it also receives the 6G PSS / SSS and the 6G PBCH associated with that 6G PSS / SSS. Even in this case, since it becomes unnecessary to transmit dedicated SSs corresponding to some PBCHs in 6G, the overall resource utilization efficiency of the system can be improved. Note that the relationship between the resource locations of 6G SSs and PBCHs in Figure 3 is just one example; 6G SSs and PBCHs may be transmitted together in a single resource, similar to 5G SS / PBCH.

[0019] Furthermore, it is not necessary to reuse only the 5G PSS and not the SSS. For example, the 6G base station device 102 may transmit the SSS and PBCH corresponding to the PSS, and the terminal device 103 may receive the 6G SSS and PBCH corresponding to the 5G PSS when it receives it. This eliminates the need to transmit the PSS in 6G, thereby reducing the consumption of time / frequency resources. Moreover, by transmitting the SSS, it becomes possible to utilize 6G-specific SSS, such as transmitting information through the SSS transmission pattern (sequence and arrangement of time / frequency resources).

[0020] Furthermore, the 6G PBCH may transmit the difference between it and the 5G PBCH. That is, some of the system information transmitted by the 5G PBCH may be reused, and the system information other than the reused portion may be transmitted by the 6G PBCH. For example, as shown in Figure 4, the 5G PBCH may be made a shared PBCH (5G / 6G-shared PBCH 401 / 411) that is shared with 6G, and the 6G system information not included in the shared PBCH may be made into a differential PBCH for 6G (6G differential PBCH 421, 431). The 6G base station equipment 102 receives the system information transmitted by the shared PBCH from the 5G base station equipment 101 (via an Xn interface, etc.) and generates the system information to be included in the differential PBCH. Note that the shared PBCH may be the same as the conventional 5G PBCH. That is, it does not have to contain any information for 6G. Furthermore, the shared PBCH may include information not included in conventional 5G PBCHs, such as information indicating the corresponding 6G PBCH (e.g., information on the time / frequency resources on which the differential PBCH is transmitted). The terminal device 103 can receive the shared PBCH and the corresponding differential PBCH to reconstruct 6G system information. The terminal device 103 may prioritize the information contained in the differential PBCH for information elements contained in both the shared PBCH and the differential PBCH. That is, some of the system information acquired by the shared PBCH may be overwritten by the system information acquired by the differential PBCH. In the example in Figure 4, the terminal device 103 combines, for example, the information contained in the shared PBCH 401 and the differential PBCH 421 corresponding to the shared PBCH 401 to acquire 6G system information regarding the beam on which the differential PBCH 421 is transmitted. Furthermore, the terminal device 103 combines, for example, the information contained in the shared PBCH 411 and the differential PBCH 431 corresponding to the shared PBCH 411 to acquire 6G system information regarding the beam transmitted by the differential PBCH 431.

[0021] In this way, by making the system information transmitted via 6G PBCH the difference from the system information transmitted via 5G PBCH, the amount of information transmitted via 6G PBCH can be reduced. Therefore, the amount of resources required to transmit PBCH can be reduced, and the overall resource utilization efficiency of the system can be improved.

[0022] The terminal device 103 can determine which PBCH to receive depending on the received strength of the SS (e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), etc.). For example, in the example in Figure 2, the terminal device 103 receives and demodulates the PBCH 231 corresponding to the PSS 211 / SSS 212 if the measured wireless quality of the PSS 211 / SSS 212 exceeds a predetermined level. On the other hand, if the measured wireless quality of the PSS 201 / SSS 202 falls below a predetermined level, the terminal device 103 may choose not to demodulate the PBCH 221 corresponding to the PSS 201 / SSS 202.

[0023] (Device Configuration) Next, an example of the configuration of the terminal device 103 according to this embodiment will be described. In one example, the terminal device 103 is configured to include a processor 501, ROM 502, RAM 503, storage device 504, and communication circuit 505. The processor 501 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or ASIC (Application-Specific Integrated Circuit), and executes the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 502 and storage device 504. The ROM 502 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the terminal device 103. The RAM 503 functions as a workspace when the processor 501 executes programs and is a random access memory that stores temporary information. The storage device 504 is configured to include, for example, a removable external storage device. The communication circuit 505 is configured to include, for example, a circuit for LTE or 5G wireless communication. Although Figure 5 shows one communication circuit 505, the terminal device 103 may have multiple communication circuits. For example, the terminal device 103 may have a wireless communication circuit that supports 5G or earlier generations of communication standards (legacy standards), a wireless communication circuit for 6G, and an antenna common to these wireless communication circuits. The terminal device 103 may also have separate antennas for legacy standards and 6G. Furthermore, the terminal device 103 may have communication circuits for other wireless communication systems such as wireless LANs. The terminal device 103 may have separate communication circuits 505 for each of the multiple usable frequency bands, or it may have a common communication circuit 505 for at least a portion of those frequency bands. The base station devices 101 and 102 may also have a hardware configuration similar to that of the terminal device 103. The base station devices 101 and 102 may include a communication circuit 505 for wired communication (and possibly wireless communication) with other devices, such as other base station devices or each node in the core network.

[0024] Figure 6 shows an example of the functional configuration of the terminal device 103. The terminal device 103 has, for example, an SS receiving unit 601, a resource identification unit 602, a PBCH receiving unit 603, and a communication processing unit 604. Note that Figure 6 shows only the functions particularly relevant to this embodiment, and various other functions that the terminal device 103 may have are omitted from the illustration. For example, the terminal device 103 naturally has other functions that terminal devices performing 5G and 6G communication generally have. Also, the functional blocks in Figure 6 are shown schematically, and each functional block may be implemented as an integrated unit or further subdivided. Furthermore, each function in Figure 6 may be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or storage device 504, or by a processor located inside the communication circuit 505 executing predetermined software. A storage medium containing a program for implementing this function may also be provided. Furthermore, the details of the processes performed by each functional unit will not be explained here, but only their general functions will be outlined.

[0025] The SS receiving unit 601 receives synchronization signals (SS). For example, the SS receiving unit 601 receives 5G PSS / SSS. The SS receiving unit 601 also receives SS if the 6G base station equipment 102 is transmitting an SS. The SS receiving unit 601 measures the radio quality of the received SS and determines whether the measurement result meets a predetermined standard. For example, the SS receiving unit 601 determines whether the measurement result of the radio quality exceeds a predetermined threshold, or whether the measurement result is at least a predetermined level higher than the radio quality of the cell currently in the area. Then, the SS receiving unit 601 establishes time synchronization based on the SS whose measurement result meets the standard. The resource identification unit 602 identifies the location of the time / frequency resource of the 6G PBCH associated with the SS that the SS receiving unit 601 has targeted for time synchronization establishment. The resource identification unit 602 can identify the resource from which the PBCH is transmitted by adding, for example, an offset value (in the time or frequency domain) defined in the standard to a value indicating the location of the time / frequency resource from which the SS was transmitted. Alternatively, the resource identification unit 602 may identify the location of the resource from which the 6G PBCH is transmitted based, for example, information contained in the 5G PBCH.

[0026] The PBCH receiving unit 603 receives PBCH at the resource identified by the resource identification unit 602 and acquires 6G system information. If the PBCH transmitted at the resource identified by the resource identification unit 602 is a differential PBCH, the PBCH receiving unit 603 may also receive the 5G PBCH (shared PBCH) associated with the SS targeted for time synchronization establishment by the SS receiving unit 601. In this case, the PBCH receiving unit 603 combines the shared PBCH and the differential PBCH to acquire 6G system information. The communication processing unit 604 establishes a connection with the 6G base station device 102 and communicates based on the system information acquired by the PBCH receiving unit 603. For example, the communication processing unit 604 executes random access procedures, such as transmitting a random access preamble at the resource identified by the system information, to establish a connection with the 6G base station device 102.

[0027] The 5G base station equipment 101 has the same functional configuration as conventional 5G base station equipment. That is, the base station equipment 101 has the function of transmitting SS and PBCH, and the function of establishing a connection with 5G terminal equipment and performing communication. However, in cases such as transmitting the shared PBCH mentioned above, the functions may be modified, such as the function of including information that identifies the resource location of the 6G PBCH in the PBCH and transmitting it, or the function of notifying the 6G base station equipment 102 of system information transmitted by the shared PBCH. The 6G base station equipment 102 also has the functional configuration that is expected of a typical 6G base station equipment. The base station equipment 102 also has the function of transmitting SS and PBCH, and the function of establishing a connection with 6G terminal equipment and performing communication. Furthermore, the base station device 102 is configured such that, for example, in beams that reuse 5G SS, it does not transmit 6G SS but transmits PBCH using the resources corresponding to the 5G SS, and in beams that do not reuse 5G SS, it transmits both 6G SS and PBCH. In addition, when transmitting the differential PBCH described above, the base station device 102 may have a function to acquire system information transmitted via shared PBCH from the 5G base station device 101.

[0028] (Processing Flow) Next, the processing flow executed by the terminal device 103 will be outlined using Figure 7. First, the terminal device 103 receives 5G PSS / SSS transmitted from the 5G base station device 101 (S701). If PSS / SSS is also transmitted from the 6G base station device 102, the terminal device 103 will also receive that PSS / SSS. Then, the terminal device 103 measures the reception quality of each SS, identifies the SS whose reception quality meets a predetermined standard, and identifies the time / frequency resource on which the 6G PBCH corresponding to that SS is transmitted (S702). The terminal device 103 receives the 6G PBCH at the identified resource and acquires system information (S703). Then, based on the acquired system information, the terminal device 103 establishes a connection with the 6G base station device 102 and performs wireless communication (S704).

[0029] The above example describes an example where 5G synchronization signals are reused, but it is not limited to this. That is, the above method can be applied to a configuration in which a 6G terminal device receives an arbitrary known signal of 5G generated based on a known sequence, and receives a predetermined signal related to 6G based on that known signal. Furthermore, 5G and 6G are just examples, and the above method can be used in multiple generations of cellular communication systems, such as 5G and 7G, or 6G and 7G.

[0030] Thus, in this embodiment, a terminal device is provided that receives a known signal (synchronization signal) based on a known sequence transmitted from a first wireless communication system network (base station equipment) such as 5G, and receives a predetermined signal transmitted from a second wireless communication system network such as 6G based on that known signal. This makes it possible to reduce the time / frequency resources used to transmit the known signal in the second wireless communication system, and to improve the overall resource utilization efficiency of the system. Therefore, it becomes possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0031] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.

[0032] This application claims priority based on Japanese Patent Application No. 2024-199189, filed on November 14, 2024, and all of its contents are incorporated herein by reference.

Claims

1. A communication device having receiving means for receiving a synchronization signal broadcast from a network of a first wireless communication system conforming to a first predetermined generation cellular communication standard, and for receiving a predetermined signal broadcast from a network of a second wireless communication system that conforms to a second predetermined generation cellular communication standard and uses a frequency band common to the first wireless communication system, based on the synchronization signal.

2. The communication device according to claim 1, wherein the receiving means receives the predetermined signal associated with the second synchronization signal when it receives the second synchronization signal broadcast from the network of the second wireless communication system.

3. The communication device according to claim 1, further comprising communication means for performing communication in the second wireless communication system based on the predetermined signal.

4. The communication device according to claim 1, wherein the predetermined signal includes system information of the second wireless communication system.

5. The communication device according to claim 4, wherein the receiving means further receives a second predetermined signal broadcast from the network of the first wireless communication system, the predetermined signal includes information of the difference between the system information in the first wireless communication system and the second wireless communication system, and the communication device further has an acquisition means for acquiring system information in the second wireless communication system from the system information of the first wireless communication system and the difference information.

6. The communication device according to claim 5, further comprising communication means for performing communication in the second wireless communication system based on the predetermined signal and the second predetermined signal.

7. The communication device according to any one of claims 1 to 6, wherein the first wireless communication system is a fifth-generation (5G) cellular communication system, and the second wireless communication system is a sixth-generation (6G) cellular communication system.

8. A communication method performed by a communication device, comprising receiving a synchronization signal broadcast from a network of a first wireless communication system conforming to a first predetermined generation cellular communication standard, and, based on the synchronization signal, receiving a predetermined signal broadcast from a network of a second wireless communication system conforming to a second predetermined generation cellular communication standard and using a frequency band common to the first wireless communication system, which is associated with the synchronization signal.

9. A program for causing a computer provided in a communication device to execute the communication method described in claim 8.

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