Communication device, control method, and computer-readable storage medium

Abstract

The communication device involved in the present invention is a communication device that communicates with other communication devices. The communication device detects signals from the other communication devices, determines the amount of resources used when communicating a certain amount of data from the other communication devices to the communication device, and sends a prescribed signal corresponding to the determined amount of resources from a plurality of prescribed signals to the other communication device, wherein the plurality of prescribed signals are a plurality of prescribed signals known in the communication device and the other communication devices, and the plurality of prescribed signals respectively correspond to different amounts of resources including at least any one of the frequency and time used when communicating a certain amount of data.

Description

[0001] This application is a divisional application of Chinese patent application 201680026887.9, entitled “Communication device, control method and computer-readable storage medium”, filed on May 10, 2016. Technical Field

[0002] The present invention relates to a communication device, a control method and a computer-readable storage medium, and in particular to a coverage extension technology in wireless communications. Background Art

[0003] In recent years, research has been conducted on technologies for supporting low-cost, low-power terminals used for small amounts of data communication within cellular networks (Non-Patent Document 1). Such terminals could be used, for example, to acquire observational data related to natural phenomena and monitor the status of certain devices. Furthermore, such terminals are not necessarily located within normal human access, making them sometimes beyond the reach of typical cellular networks.

[0004] Non-Patent Document 1 studies technologies for extending coverage to prevent such situations. For example, coverage can be extended by having a transmitter repeatedly transmit the same signal. In this case, even if a receiver fails to receive the signal because it was only transmitted once (i.e., even if it cannot decode the signal's content through demodulation, etc.), the gain generated by the repeated transmissions can still enable successful reception. This enables terminals within the base station to communicate with the base station even though they would otherwise be unable to communicate.

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-Patent Document 1: 3GPP TR36.888 V12.0.0, June 2013 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] When expanding coverage, certain resources are used redundantly. For example, when repeatedly transmitting a signal, for example, a single data transmission uses more resources, either frequency or time, than a single transmission, corresponding to the number of repetitions. If a communication device repeatedly transmits data too many times to ensure reliable communication with other devices, resources are wasted. On the other hand, if the number of repetitions is insufficient, communication ultimately becomes impossible. Therefore, in such coverage expansion technologies, it is important to determine the amount of resources that allows communication without unnecessary waste.

[0010] Methods used to solve problems

[0011] A communication device involved in one embodiment of the present invention is a communication device that communicates with other communication devices, and comprises: a determination unit that detects a signal from the above-mentioned other communication device and determines the amount of resources used when communicating a certain amount of data from the above-mentioned other communication device to the above-mentioned communication device; and a sending unit that sends a prescribed signal corresponding to the amount of resources determined in the above-mentioned determination unit from a plurality of prescribed signals to the above-mentioned other communication device, wherein the above-mentioned plurality of prescribed signals are a plurality of prescribed signals known in the above-mentioned communication device and the above-mentioned other communication devices, and the above-mentioned plurality of prescribed signals respectively correspond to different amounts of resources including at least any one of the frequency and time used when communicating a certain amount of data.

[0012] In addition, another embodiment of the present invention relates to a communication device that communicates with other communication devices, and comprises: a sending unit that sends information specifying multiple prescribed signals to the above-mentioned other communication devices, wherein the above-mentioned multiple prescribed signals are multiple prescribed signals known in the above-mentioned communication device and the above-mentioned other communication devices, and the above-mentioned multiple prescribed signals respectively correspond to different amounts of resources including at least any one of the frequency and time used when communicating a certain amount of data; a receiving unit that receives any one of the above-mentioned multiple prescribed signals from the above-mentioned other communication devices; and a determination unit that determines the amount of resources required to use when communicating data from the above-mentioned communication device to the above-mentioned other communication devices based on the signal received by the above-mentioned receiving unit.

[0013] Effects of the Invention

[0014] According to the present invention, in the coverage expansion technology, it is possible to determine the amount of resources that enables communication without wasting resources unnecessarily.

[0015] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention, and together with the description, serve to explain the principles of the present invention.

[0017] Figure 1 This is a diagram showing a configuration example of a wireless communication system.

[0018] Figure 2 This is a diagram showing an example of the hardware configuration of a wireless control station and a terminal.

[0019] Figure 3This is a diagram showing an example of the functional structure of a terminal.

[0020] Figure 4 This is a diagram showing an example of the functional configuration of a wireless control station.

[0021] Figure 5A This is a schematic diagram showing the correspondence between the number of iterative transmissions and the preamble ID used when gain is obtained by iterative transmission.

[0022] Figure 5B This is a schematic diagram showing the correspondence between the number of iterative transmissions and the preamble ID used when gain is obtained by iterative transmission.

[0023] Figure 5C This is a schematic diagram showing the correspondence between the number of iterative transmissions and the preamble ID used when gain is obtained by iterative transmission.

[0024] Figure 6A This is a schematic diagram showing the correspondence between the number of repeated transmissions and the number of retransmissions and the preamble ID used when the transmission power is changed during retransmission of repeated transmissions.

[0025] Figure 6B This is a schematic diagram showing the correspondence between the number of repeated transmissions and the number of retransmissions and the preamble ID used when the transmission power is changed during retransmission of repeated transmissions.

[0026] Figure 6C This is a schematic diagram showing the correspondence between the number of repeated transmissions and the number of retransmissions and the preamble ID used when the transmission power is changed during retransmission of repeated transmissions.

[0027] Figure 7 This is a diagram showing an example of the flow of resource amount determination processing in uplink communication.

[0028] Figure 8 This is a diagram showing an example of the flow of resource amount determination processing in downlink communication.

[0029] Figure 9 This is a diagram showing an example of the flow of resource amount determination processing in uplink communication and downlink communication.

[0030] Figure 10A This is a diagram showing an example of preamble IDs that can be used in resource amount determination processing in uplink communication and downlink communication.

[0031] Figure 10B This is a diagram showing an example of preamble IDs that can be used in resource amount determination processing in uplink communication and downlink communication. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] (Structure of Wireless Communication System)

[0034] Figure 1 , an example of the structure of a wireless communication system according to the present embodiment is shown. This wireless communication system includes, for example, a terminal 101 and a wireless control station 102, each of which operates as a wireless communication device. In addition, although a system including one terminal 101 and one wireless control station 102 is shown as an example, there may be multiple such communication devices. The wireless control station 102 is, for example, a base station device. In addition, this wireless communication system is, for example, a cellular communication system such as Long Term Evolution (LTE), but may also be a wireless communication system such as a next-generation cellular communication system or a wireless LAN. That is, the following technology can be applied to a case where a technology for extending the communicable range between two communication devices is used, and its application is not limited to a specific system such as a cellular communication system.

[0035] In this wireless communication system, wireless control station 102 or terminal 101 repeatedly transmits the same data multiple times. The receiving device utilizes the gain gained from repeatedly transmitting the same data, enabling it to receive the data. Furthermore, "sending the same data multiple times" does not necessarily mean "sending the same signal multiple times." That is, the same data can be transmitted multiple times using the same signal. For example, the same data can be transmitted multiple times using multiple different signals generated by applying different encoding methods to the same data. Specifically, "the same data" refers to the data being transmitted, and the signal itself used to transmit the same data, as well as the content conveyed by the signal (e.g., the encoded / undecoded bit string), can vary between transmissions. As mentioned above, if the transmitting device transmits the same data more times than necessary, at least one of frequency and time resources (e.g., resource blocks) is wasted. Furthermore, if a terminal transmits the signal too many times, for example, power consumption increases, failing to meet low power requirements. On the other hand, if the number of data transmission repetitions is too small, communication becomes impossible. Furthermore, in this case, resources used to attempt communication are also wasted.

[0036] Therefore, this wireless communication system introduces a method for determining an appropriate amount of resources to be used in communications between wireless control station 102 and terminal 101. Furthermore, this information is available to wireless control station 102, which performs communication control. The "appropriate amount of resources" referred to here refers to an amount of resources "related to the communication of a certain amount of data," an amount that allows communication without excessive resource waste. In other words, while the amount of resources generally increases when the amount of data being transmitted is large, this amount of resources is determined to be independent of the amount of data being transmitted. For example, this "certain amount" can be the amount of data transmitted in regular communications between terminal 101 and wireless control station 102, equivalent to one resource block in LTE.

[0037] For example, the resource amount can be defined as the minimum number of repetitions required for wireless control station 102 to successfully receive the preamble of a random access channel transmitted by terminal 101 (i.e., to successfully determine which preamble was transmitted). Alternatively, the resource amount can be defined as a combination of the minimum number of repetitions and transmit power required for wireless control station 102 to successfully receive the preamble of a random access channel transmitted by terminal 101. Furthermore, the resource amount can be defined by factors other than the number of repetitions. For example, the resource amount can be defined by the spreading ratio used when spreading the transmission of a single piece of data. In this case, the transmitting device can, for example, spread the data before transmission and transmit the spread data using multiple resource blocks. At the receiving device, a higher spreading ratio yields greater gain, enabling better reception of signals transmitted from further away.

[0038] In this embodiment, the receiving device detects the preamble of the random access channel transmitted by terminal 101 or the report signal transmitted by wireless control station 102 to determine the amount of resources required for data communication. These signals are examples, and signals other than the preamble of the random access channel and the report signal may be used to determine the amount of resources. For example, certain channels defined by 3GPP (Third Generation Partnership Project) may be used. Furthermore, terminal 101 detects the report signal transmitted by wireless control station 102 to determine the amount of resources required for downlink use and notifies wireless control station 102 of the result. Terminal 101 may use the preamble of the random access channel for this notification.

[0039] Below, use Figure 2 The following drawings describe examples of the configurations of the terminal 101 and the wireless control station 102 and the flow of processing executed therein.

[0040] (Hardware structure of wireless control station and terminal)

[0041] Figure 2 1 is a diagram showing an example of the hardware configuration of the wireless control station 102 and the terminal 101. In one example, the wireless control station 102 and the terminal 101 have Figure 2 The hardware configuration shown includes, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication device 205. In the wireless control station 102 and the terminal 101, for example, the CPU 201 executes a program stored in any of the ROM 202, RAM 203, and external storage device 204 for implementing the functions of the wireless control station 102 and the terminal 101. Furthermore, the wireless control station 102 and the terminal 101 communicate with each other or with the terminal 101 by, for example, controlling the communication device 205 through the CPU 201.

[0042] In addition, although Figure 2 In the example, the wireless control station 102 and the terminal 101 are each provided with a single communication device 205. However, for example, the wireless control station 102 may also include a communication device for communication between wireless control stations and a communication device for communication with the terminal 101. Furthermore, the terminal 101 may include, for example, multiple communication devices corresponding to multiple frequency bands. Furthermore, for direct communication between terminals, the terminal 101 may include, for example, both a communication device for receiving uplink signals and a communication device for transmitting downlink signals.

[0043] Furthermore, the wireless control station 102 and the terminal 101 may have dedicated hardware to perform their respective functions, and the hardware may perform some functions while a computer executing a program may perform other functions. Alternatively, the wireless control station 102 and the terminal 101 may all perform their functions using a computer and a program.

[0044] (Functional Structure of Terminal)

[0045] Figure 3 1 is a diagram showing an example of a functional configuration of the terminal 101. The terminal 101 includes, for example, a transmitter 301, a receiver 302, a used resource amount determiner 303, and a preamble ID acquirer 304 as its functional configuration.

[0046] The transmitter 301 is a functional unit for transmitting signals to the wireless control station 102 by repeatedly transmitting the same data signal one or more times, for example. Furthermore, when the terminal 101 is within the coverage area of ​​the wireless control station 102, the transmitter 301 generally transmits the data signal once. When the terminal 101 is not within the coverage area of ​​the wireless control station 102 and coverage needs to be extended, the transmitter 301 transmits the data signal multiple times. Furthermore, the transmitter 301 transmits a preamble of a predetermined random access channel corresponding to the amount of resources required for uplink or downlink communications, as determined or specified by the used resource amount determination unit 303, described later, to the wireless control station 102. A specific method for this will be described later.

[0047] The receiving unit 302 is a functional unit that receives data signals transmitted one or more times from the wireless control station 102 and acquires the contents of the data. When the terminal 101 is within the coverage area of ​​the wireless control station 102, the receiving unit 302 typically receives the data signal only once to acquire the data contained in the signal. On the other hand, when the terminal 101 is not within the coverage area of ​​the wireless control station 102 and coverage needs to be extended, the receiving unit 302 receives the data signal multiple times to acquire the data.

[0048] The resource usage amount determination unit 303 determines the resource amount used when the terminal 101 transmits a signal, and determines the resource amount required to acquire data from a signal transmitted by the wireless control station 102 .

[0049] The resource usage determination unit 303 independently determines the resource usage for the terminal 101 to use when transmitting a signal. For example, if the resource usage is the number of signal repetitions, the resource usage determination unit 303 initially determines to transmit each data signal only once. Later, if the wireless control station 102 fails to receive the data signal, for example, because no ACK is received from the wireless control station 102 after the signal transmission, the resource usage determination unit 303 increases the number of repetitions. This increases the probability of successful data signal reception at the wireless control station 102. In other words, the resource usage determination unit 303 attempts to expand the coverage of the wireless control station 102 by increasing the number of data signal transmissions. Generally speaking, gradually increasing the resource usage can gradually increase the probability that the wireless control station 102 will be able to receive the data signal. Furthermore, if a minimum number of signal transmissions has been previously determined through external input, the resource usage determination unit 303 may repetitively transmit data signals according to the number of signal transmissions, regardless of whether an ACK is received from the wireless control station 102. That is, the initial number of times the signal is repeatedly sent does not need to be set to once, and the signal can be repeatedly sent multiple times from the beginning (and can be set to always depending on the situation).

[0050] Furthermore, the number of repeated signal transmissions may correspond to the gain (dB) achieved through the repeated transmissions. The gain to be achieved may be discrete, for example, every 5dB. In this case, the resource usage determination unit 303 may initially attempt to transmit data once with a gain of 0dB. If this fails, it may attempt to transmit data a number of times that achieves a gain of 5dB, and thereafter, attempt to transmit data a number of times that achieves a gain of 10dB.

[0051] Furthermore, although the description here uses repeated transmission as a method for obtaining gain, even when a method other than repeated transmission is used, the obtained gain can be associated with the transmission method. The fact that the method for obtaining gain can be a method other than repeated transmission also applies to the subsequent descriptions.

[0052] Furthermore, regarding signals repeatedly transmitted by the wireless control station 102, the used resource amount determination unit 303 can determine the number of receptions during which the signal was successfully received (i.e., the data associated with the signal was successfully acquired). For example, the wireless control station 102 repeatedly transmits a report signal containing a system information block (SIB), and the terminal 101 can acquire the contents of the report signal by receiving the report signal more than once. Furthermore, in this case, the used resource amount determination unit 303 determines the number of receptions during which the contents of the report signal were successfully acquired.

[0053] The preamble ID acquisition unit 304 acquires, for example, information (preamble ID) for identifying a plurality of preamble types (preamble patterns) of random access channels corresponding to respective amounts of used resources from the radio control station 102 . Figure 5C An example of the information obtained here is shown in Figure 5C In the case of , different IDs are assigned according to the number of repeated transmissions as follows: the preamble ID is A when no repeated transmission is performed, the preamble ID is B when the number of repeated transmissions is three, the preamble ID is C when the number of repeated transmissions is five, and so on. Figure 5C This is just an example, and the preamble ID does not necessarily need to be allocated for odd numbers of times such as once, three times, or five times. The preamble ID may be allocated for various numbers of repetitions.

[0054] The preamble ID acquisition unit 304 can acquire information on the correspondence between the amount of used resources and the preamble ID by receiving a report signal transmitted by the wireless control station 102, or can acquire information on the correspondence between the amount of used resources and the preamble ID using other signals. Furthermore, if the correspondence between the amount of used resources and the preamble ID does not change over time, the wireless control station 102 can notify the terminal 101 only once. Furthermore, if the correspondence between the amount of used resources and the preamble ID may change over time, the terminal 101 can monitor the signal transmitted by the wireless control station 102 and update the pre-stored correspondence if the signal changes.

[0055] In addition, the preamble ID can be specified by a single preamble ID or a group ID that specifies a group of multiple preambles. Figure 5CIn the case of , A, B, and C, which are the preamble IDs for the cases of one, three, and five repetitions, can be notified, respectively. Furthermore, if a group containing A, B, and C as the preamble IDs corresponding to the cases of one, three, and five repetitions is predefined, the group ID can be notified. Furthermore, when notifying the relationship between the number of repetitions (gain) and the preamble ID, for example, if the number of repetitions is determined based on a field within the notification, there is no need to explicitly notify the number of repetitions. For example, if the first W bits of the notification correspond to the preamble ID for a case of one repetition, the preamble ID acquisition unit 304 can obtain the preamble ID for a case of one repetition by simply reading the first W bits of the received notification. Furthermore, if the W+1th to 2Wth bits of the notification correspond to a case of three repetitions, the preamble ID acquisition unit 304 can obtain the preamble ID for a case of three repetitions by reading the W+1th to 2Wth bits of the notification. This eliminates the need to transmit information related to the number of repetitions, thereby reducing the amount of information required for notification. Furthermore, even if the number of repetitions is used as another value related to the gain, a similar notification can be generated.

[0056] The transmitting unit 301 determines and transmits one of the preambles corresponding to the plurality of preamble IDs acquired by the preamble ID acquiring unit 304 based on the resource amount determined or determined by the used resource amount determining unit 303. Figure 5C In the case of a corresponding relationship, when the resource amount determination unit 303 determines the number of repeated transmissions when transmitting to the wireless control station 102 to be three times, the transmission unit 301 transmits the preamble corresponding to the preamble ID: B in units of three times. In addition, when the resource amount determination unit 303 determines the number of repeated transmissions when transmitting to the wireless control station 102 to be five times, the transmission unit 301 transmits the preamble corresponding to the preamble ID: C in units of five times. Here, retransmission is usually performed while increasing the transmission power until the receiving side device receives the preamble of the random access channel. However, the situation in which repeated transmission is required is originally a situation in which the signal arrives at a level that cannot be demodulated if it arrives at the receiving side device only once. Therefore, if Figure 5A and Figure 5BIn this way, the transmitter 301 can perform multiple retransmissions at the same power, using the number of repetitions of the same preamble determined by the resource usage determination unit 303 as a unit. Specifically, if the resource usage determination unit 303 determines the number of repetitions to be three, the transmitter 301 will also retransmit the preamble corresponding to preamble ID: B three times. In this case, the transmitter 301 transmits the same signal a total of six times by performing the initial transmission and the first retransmission.

[0057] In addition, the transmitting unit 301 can increase the transmission power while performing the above retransmission. In this case, the transmitting unit 301 can also change the preamble code sent according to the number of retransmissions. For example, Figure 6A and Figure 6C As shown in FIG, when the number of repeated transmissions is three, as the first transmission, the transmission unit 301 transmits a preamble with a preamble ID of BA. Then, when the number of repeated transmissions is three, the transmission unit 301 transmits a preamble with a preamble ID of BB. Similarly, when the number of repeated transmissions is five, as shown in FIG. Figure 6B and Figure 6C As shown, during the first transmission, the transmitter 301 transmits a preamble with a preamble ID of CA. Furthermore, during the first, second, and third retransmissions, the transmitter 301 repeatedly transmits preambles with preamble IDs of CB, CC, and CD five times, respectively. In this case, the preamble ID acquisition unit 304 acquires information on the number of repeated transmissions and the correspondence between the number of retransmissions and the preamble ID, corresponding to the preamble ID that varies depending on the number of retransmissions.

[0058] also, Figure 5C and Figure 6C The preamble ID for the case where the number of repeated transmissions is one is determined in [1]. However, the preamble for the first transmission may be the same preamble as the preamble for the conventional random access channel. Furthermore, the transmitter 301 may increase the transmission power during retransmissions only when the number of repeated transmissions is one. Furthermore, when the number of repeated transmissions is multiple, the preamble may be transmitted at the maximum transmission power for both the first transmission and the retransmissions.

[0059] Alternatively, the preamble ID may be determined based on the respective gains obtained, rather than the number of repeated transmissions: for a gain of 0 dB, the preamble ID may be determined to be D, for a gain of 5 dB, the preamble ID may be determined to be E, for a gain of 10 dB, and so on. In this case, the transmitter 301 transmits the preamble using the signal transmission method corresponding to each gain. For example, to obtain a gain of 5 dB, the transmitter 301 determines a predetermined number of signal transmissions corresponding to the 5 dB gain, and repeatedly transmits the preamble with the preamble ID E for the predetermined number of transmissions. Furthermore, to obtain a gain of 5 dB, the transmitter 301 may determine a spreading ratio corresponding to the 5 dB gain, and spread and transmit the preamble with the preamble ID E at the spreading ratio.

[0060] If the wireless control station 102 successfully receives the preamble, it can determine the amount of resources (number of repetitions) required for the terminal 101 to transmit a signal to the wireless control station 102 based on the preamble ID at that time. In this case, the wireless control station 102 can notify the terminal 101 of the determined amount of resources, for example, using a control signal. Furthermore, the notification of the resource amount can be based on the preamble ID, that is, it can be notification of a preamble ID that has already been determined. Furthermore, if the wireless control station 102 successfully receives preambles with multiple preamble IDs, it can select the minimum amount of resources corresponding to those preamble IDs. Thus, when the terminal 101 transmits a signal to the wireless control station 102, it can use the amount of resources necessary for successful reception, but not an unnecessary amount.

[0061] When notifying the wireless control station 102 of the number of repetitive transmissions (gain) required for signal transmission from the wireless control station 102 to the terminal 101, the transmitter 301 can also determine and transmit a preamble in the same manner as described above. Specifically, the resource usage determination unit 303 determines the number of signal receptions required to demodulate (obtain the data contained in) the signal transmitted from the wireless control station 102. Based on this number, the transmitter 301 can determine and transmit a preamble. For example, if the number of receptions required for signal demodulation is one, the transmitter 301 can transmit a preamble with a preamble ID of X. If the number of receptions required for signal demodulation is two, the transmitter 301 can transmit a preamble with a preamble ID of Y. This allows the wireless control station 102 to determine the required coverage expansion gain when transmitting to the terminal 101, based on which preamble it receives. Therefore, the wireless control station 102 repeatedly transmits the signal only the minimum number of times required for the terminal 101 to successfully receive the signal, thereby making it possible to use resources sufficient for communication and prevent waste of resources.

[0062] (Structure of wireless control station)

[0063] Figure 4 1 is a diagram showing an example of a functional configuration of the wireless control station 102. The wireless control station 102 includes, for example, a transmitter 401, a receiver 402, a used resource amount determiner 403, a used resource amount notification unit 404, and a preamble ID notification unit 405 as its functional configuration.

[0064] The transmitter 401 is a functional unit for transmitting a signal to the terminal 101 by repeatedly transmitting the same data signal one or more times, for example. Furthermore, when the terminal 101 is within the coverage area of ​​the wireless control station 102, the transmitter 401 generally transmits the data signal once. However, when the terminal 101 is not within the coverage area of ​​the wireless control station 102 and coverage needs to be extended, the transmitter 401 transmits the data signal multiple times.

[0065] The receiving unit 402 is a functional unit that receives data signals or preambles transmitted one or more times from the terminal 101 and acquires the content of the data or the preamble ID. Furthermore, when the terminal 101 is within the coverage area of ​​the wireless control station 102, the receiving unit 402 can generally acquire the data contained in the data signal by receiving the data signal only once. On the other hand, when the terminal 101 is not within the coverage area of ​​the wireless control station 102 and coverage needs to be extended, the receiving unit 402 can acquire the data by receiving the data signal multiple times.

[0066] The resource usage determination unit 403 determines the resource usage (number of repetitions) based on which preamble ID the terminal 101 sends the preamble in the above manner. Figures 5A to 5CIn the example, if the wireless control station 102 successfully receives a signal with preamble ID B, the used resource amount determination unit 403 determines that three repetitions are required for signal transmission from the terminal 101 to the wireless control station 102. Furthermore, in this case, the wireless control station 102 can also determine the required number of repetitions by determining the number of preamble detections required until the preamble from the terminal is successfully received. On the other hand, if a preamble determined based on the number of repetitions is used, the wireless control station 102 can determine the minimum required number of repetitions even if it cannot detect one or more of the repetitions. For example, if the terminal 101 repetitively transmits a preamble three times, and the wireless control station 102 detects the preamble twice, it is considered that the preamble has been determined. In this case, if the preamble and the number of repetitions do not correspond, the wireless control station 102 determines the number of repetitions to be two. However, if the number of repetitions is notified based on the preamble ID, the number of repetitions can be determined to be three. Furthermore, the used resource amount determination unit 403 determines a gain to be obtained based on, for example, the preamble ID, and inputs the gain to the used resource amount notification unit 404 .

[0067] Furthermore, the used resource amount determination unit 403 can determine the amount of resources required for the wireless control station 102 to transmit a signal to the terminal 101, based on which preamble ID the preamble transmitted by the terminal 101 in the above manner corresponds to. Furthermore, the used resource amount determination unit 403 can, for example, determine the required gain based on the preamble ID and instruct the transmission unit 401 to use a communication method that can achieve the aforementioned gain.

[0068] The used resource amount notification unit 404 notifies the terminal 101, via the transmitter 401, of the amount of resources required by the terminal 101 to transmit a signal to the wireless control station 102, as determined by the used resource amount determination unit 403. For example, this notification can be made using the amount of resources required by the wireless control station 102 to transmit a signal to the terminal 101, as determined by the used resource amount determination unit 403. The preamble ID notification unit 405 notifies the terminal 101, via the transmitter 401, of the preamble ID for each used resource amount. This notification has already been described in the description of the preamble ID acquisition unit 304 of the terminal 101, and therefore its detailed description is omitted.

[0069] (Processing Flow)

[0070] Next, several examples of the flow of the resource amount determination process performed between the terminal 101 and the wireless control station 102 as described above will be described.

[0071] <Processing Example 1>

[0072] In this processing example, the amount of resources required for uplink (a link for transmitting signals from the terminal 101 to the wireless control station 102) is determined. Figure 7 This process will be described. In this example, wireless control station 102 first notifies terminal 101 of initial access parameters (S701). The initial access parameters may include, for example, information indicating the correspondence between the aforementioned number of repetitions (or the amount of resources used or the required gain) and the preamble ID. Furthermore, the initial access parameters may include at least one of a parameter related to the initial transmission power of the preamble and the number of retransmission attempts.

[0073] Next, terminal 101 independently determines the number of times to repeatedly transmit a signal (S702), identifies a preamble with a preamble ID corresponding to the number of times (S703), and repeatedly transmits the identified preamble the number of times determined in S702 (S704). For example, terminal 101 may initially avoid repeatedly transmitting a signal and instead attempt to transmit a preamble on a random access channel as usual. Upon receiving this preamble, wireless control station 102 notifies terminal 101 that repeated transmission is unnecessary (S708). In this case, terminal 101 does not perform repeated transmission in subsequent communications.

[0074] On the other hand, if the wireless control station 102 cannot successfully receive the preamble without repeated transmission, the terminal 101 increases the number of repeated transmissions (S705) to attempt to expand the coverage area. Furthermore, in response to the change in the number of repeated transmissions, the terminal 101 determines the preamble to be used (S706) and repeatedly transmits the determined preamble the number of times determined in S705 (S707).

[0075] Furthermore, if the notification of S708 is not received even though the number of preamble retransmission attempts has reached the value notified by the initial parameter in S704, the terminal 101 may determine that the wireless control station 102 cannot successfully receive the preamble unless retransmission is repeated. Figure 5A and Figure 5B The preamble can be retransmitted at a constant power as shown in Figure 6A and Figure 6B The preamble is retransmitted while gradually increasing the power as shown in FIG. Figure 6C As shown in FIG, different preamble codes may be sent according to the number of retransmissions per repeated transmission unit, or as shown in FIG. Figure 5C As shown in FIG, the same preamble is sent regardless of the number of retransmissions. Figure 5A and Figure 5B While retransmitting at constant power as shown, Figure 6C As shown in FIG. , a different preamble is transmitted according to the number of retransmissions per retransmission unit. Furthermore, when a different preamble is transmitted according to the number of retransmissions, the preamble to be transmitted is determined for each retransmission. When the wireless control station 102 successfully receives a preamble, it determines the number of retransmissions (required gain) based on the preamble ID of the preamble and notifies the terminal 101 ( S708 ).

[0076] Furthermore, the required gain level (coverage extension level) may be divided into a predetermined number of stages, for example. In this case, in order to determine to which of the predetermined number of stages the terminal 101 and the wireless control station 102 belong, a method may be performed. Figure 7 For example, if there are four levels of required gain: 0 dB, 0-5 dB, 5-10 dB, and 10-20 dB, terminal 101 uses a signal transmission method that can achieve gains of 0 dB, 5 dB, 10 dB, and 20 dB at each level. Furthermore, any signal transmission method can be used as long as it can achieve gain by, for example, adjusting the number of repeated transmissions or the spreading factor as described above. In this case, wireless control station 102 notifies terminal 101 of the preamble ID corresponding to each of the four levels. Terminal 101 then transmits preambles corresponding to these levels to wireless control station 102, for example, in order from the lowest gain level to the highest gain level. This allows wireless control station 102 to determine the required degree of coverage expansion.

[0077] <Processing Example 2>

[0078] In this processing example, the amount of resources required for the downlink (the link for transmitting signals from the wireless control station 102 to the terminal 101) is determined. Figure 8 This process will be explained. In this example, wireless control station 102 first periodically transmits a report signal (S801). Terminal 101 then determines how many times it will receive the report signal, or how many times it will detect the report signal until demodulation is successful. This report signal is just an example; any signal can be used as long as it is transmitted multiple times.

[0079] Next, the terminal 101 determines the preamble code to be used based on the number of receptions required until demodulation of the report signal is successful (S802). In addition, the wireless control station 102 may notify the terminal 101 of information for determining the preamble code to be used at this time through the report signal in S801. Then, the terminal 101 transmits the preamble code determined in S802 to the wireless control station 102 (S803). At this time, the terminal 101 may transmit the preamble code determined in S802 to the wireless control station 102, for example, through Figure 7 The preamble may be transmitted according to the number of uplink repetitions determined by the processing, or it may be repeatedly transmitted until an acknowledgment response is received from the wireless control station 102. Furthermore, the preamble transmitted at this time may be associated with the required number of receptions itself, or it may be associated with the gain obtained based on the determined number of receptions. For example, the required gain level (coverage extension level) may be pre-classified into a predetermined number of stages. In this case, the terminal 101 may determine which of these predetermined stages the number of receptions falls within. For example, if there are four required gain levels: 0 dB, 0-5 dB, 5-10 dB, and 10-20 dB, the terminal 101 may determine which of these stages the required number of receptions falls within and transmit the preamble corresponding to the determination result. This allows the number of preamble types to be limited to four, thereby reducing the number of preambles required to be prepared.

[0080] <Processing Example 3>

[0081] In this processing example, the amount of resources required for both uplink and downlink is determined. Figure 9 This process will be described. In this processing example, similar to Processing Example 2, the wireless control station 102 first periodically transmits a report signal (S901). At this point, the terminal 101 also determines, similar to Processing Example 2, the number of times the report signal is received and the number of times the report signal is detected. The terminal 101 then independently determines, for example, the number of times to repeatedly transmit the preamble to the wireless control station 102 (S902). The initial value of this number may be notified by the wireless control station 102, or may be determined based on the required number of receptions determined in S901. The terminal 101 then determines the preamble to be transmitted based on the required number of receptions determined in S901 and the number of preamble transmissions determined in S902 (S903), and repeatedly transmits the preamble for the determined number of transmissions (S904). The preamble determined here corresponds to the number of times the report signal is detected and the number of times the preamble is repeatedly transmitted.

[0082] Figure 10A An example of the correspondence between the preamble ID used at this time and the above-mentioned number of transmissions and receptions is shown in FIG. Figure 10AAs shown, for example, when the number of receptions required until the signal transmitted by the wireless control station 102 is successfully received is one and the preamble is not repeatedly transmitted (when the number of transmissions is one), the terminal 101 transmits a preamble with the preamble ID AX. Similarly, when the number of receptions required until the signal transmitted by the wireless control station 102 is successfully received is three and the preamble is repeatedly transmitted five times, the terminal 101 transmits a preamble with the preamble ID CZ. Figures 6A to 6C As shown in FIG, each time the preamble is retransmitted as a unit, a different preamble ID may be used. In this case, Figure 10B As shown, for example, a preamble ID may be determined corresponding to the number of repeated transmissions, the number of repeated receptions, and the number of retransmissions. For example, if the number of receptions required for the terminal 101 to successfully receive a signal is two and the number of repeated transmissions is five, a preamble with a preamble ID of CAY is transmitted during the first transmission, and a preamble with a preamble ID of CBY is transmitted during the first retransmission.

[0083] For example, if the preamble is transmitted in S904 but the wireless control station 102 does not notify the terminal 101 of the number of repetitions required for communication, the terminal 101 may determine that the wireless control station 102 has not successfully received the preamble. In this case, the terminal 101 changes the number of repetitions for the preamble and attempts to transmit the preamble again. Specifically, the terminal 101 first re-determines the number of repetitions (S905). In this case, the re-determined number of repetitions may be greater than the number of repetitions determined in S902. Subsequently, as a result of increasing the number of repetitions, the preamble ID required for transmission changes. Therefore, the terminal 101 determines the preamble ID with the changed number of repetitions (S906) and transmits the preamble with the determined preamble ID (S907). The terminal 101 then receives notification of the number of repetitions from the wireless control station 102 (S908). Furthermore, the preamble in S907 notifies the wireless control station 102 of the number of repetitive transmissions required for the downlink (the number of repetitive receptions for the terminal 101). Therefore, the wireless control station 102 can repeatedly transmit the notification in S908 at the notified number of transmissions. Furthermore, the terminal 101 can determine the appropriate number of repetitive transmissions in the uplink based on the notification in S908.

[0084] In addition, when using Figure 10BIn such a correspondence, terminal 101 changes the preamble ID each time it retransmits. Specifically, for example, if there is no response (notification of the number of retransmissions) from wireless control station 102 after the initial transmission of a preamble with the number of retransmissions determined in S902, terminal 101 increases the transmission power and retransmits the preamble. In this case, terminal 101 retransmits a preamble with a different ID than the initial transmission. Furthermore, if there is no notification from wireless control station 102 even after the number of retransmissions has reached, for example, the number of retransmissions notified as an initial access parameter, terminal 101 increases the number of retransmissions and attempts to transmit the preamble at the initial transmission power. In this case, the number of retransmissions also changes, and therefore the preamble to be transmitted also changes. Terminal 101 then repeats the same process until it receives a response from wireless control station 102.

[0085] As described above, the wireless control station 102 can determine the appropriate number of repetitions for both the uplink and downlink at once by determining the preamble transmitted from the terminal 101. Furthermore, as described in Processing Examples 1 and 2, the target for determination in this case need not be the number of repetitions; for example, the coverage extension level can be determined. Specifically, the wireless control station 102 can determine the degree of coverage extension (or the degree of gain required) required for communication with the terminal 101. Furthermore, for example, a preamble ID can be assigned to each of the coverage extension levels divided into a predetermined number of stages. In this case, for example, the terminal 101 can determine the coverage extension level rather than the number of preamble transmissions, determine the preamble corresponding to that level, and then repetitively transmit the preamble the number of times required to achieve that coverage extension level. Furthermore, methods other than repetition (e.g., expansion) can be used to achieve a certain coverage extension level.

[0086] Furthermore, the above method has been described as notifying the coverage expansion level (number of repetitions) by transmitting a predetermined preamble from the terminal to the wireless control station, but this is not limiting. For example, the preamble can be a predetermined signal known between the terminal and the wireless control station and need not be a preamble of a random access channel. Furthermore, for example, when the wireless control station notifies the terminal of the correspondence between the coverage expansion level and the preamble ID, it may notify at least a portion of the preamble, rather than all at once. As can be seen, the above embodiments are provided for illustrative purposes only, and the invention disclosed herein is not limited thereto.

[0087] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are attached to make the scope of the present invention known to the public.

[0088] This application claims the benefit of priority from Japanese Patent Application No. 2015-099499, filed on May 14, 2015, the entire contents of which are incorporated herein by reference.

Claims

1. A communication device is a communication device that communicates with other communication devices, The communication device is characterized in that The communication device comprises: a determining unit configured to detect a signal from the other communication device and determine a resource to be used when communicating a certain amount of data from the other communication device to the communication device; and a sending unit configured to send a prescribed signal corresponding to the resource determined in the determining unit to the other communication device from among a plurality of prescribed signals, wherein: The plurality of prescribed signals are a plurality of prescribed signals known to the communication device and the other communication device, and each of the plurality of prescribed signals corresponds to a resource including at least one of a frequency and a time used when communicating a certain amount of data. The transmitting unit selects the one prescribed signal from the plurality of prescribed signals based on the coverage expansion level, and transmits the selected one prescribed signal to the other communication device. The plurality of predetermined signals respectively correspond to a combination of a resource used when communicating a certain amount of data from the communication device to the other communication device and a resource used when communicating a certain amount of data from the other communication device to the communication device.

2. The communication device according to claim 1, wherein The plurality of predetermined signals known to the communication device and the other communication devices correspond to resources including both frequencies and times used when communicating a certain amount of data.

3. The communication device according to claim 1 or 2, characterized in that The prescribed signal is a random access preamble.

4. A control method for a communication device that communicates with another communication device, The control method is characterized in that: The control method includes: a determining step of detecting a signal from the other communication device and determining a resource to be used when communicating a certain amount of data from the other communication device to the communication device; and a sending step of sending, to the other communication device, one of a plurality of prescribed signals corresponding to the resource determined in the determining step, wherein the plurality of prescribed signals are a plurality of prescribed signals known to the communication device and the other communication device, and each of the plurality of prescribed signals corresponds to a resource including at least one of a frequency and a time used when communicating a certain amount of data; In the transmitting step, the one prescribed signal is selected from the plurality of prescribed signals based on the coverage expansion level, and the selected one prescribed signal is transmitted to the other communication device. The plurality of predetermined signals respectively correspond to a combination of a resource used when communicating a certain amount of data from the communication device to the other communication device and a resource used when communicating a certain amount of data from the other communication device to the communication device.

5. A communication system comprising a communication device communicating with other communication devices, The communication system is characterized in that The communication device comprises: a determining unit configured to detect a signal from the other communication device and determine a resource to be used when communicating a certain amount of data from the other communication device to the communication device; and a sending unit configured to send a prescribed signal corresponding to the resource determined in the determining unit to the other communication device from among a plurality of prescribed signals, wherein: The plurality of prescribed signals are a plurality of prescribed signals known to the communication device and the other communication device, and each of the plurality of prescribed signals corresponds to a resource including at least one of a frequency and a time used when communicating a certain amount of data. The transmitting unit selects the one prescribed signal from the plurality of prescribed signals based on the coverage expansion level, and transmits the selected one prescribed signal to the other communication device. The plurality of predetermined signals respectively correspond to a combination of a resource used when communicating a certain amount of data from the communication device to the other communication device and a resource used when communicating a certain amount of data from the other communication device to the communication device.

6. A computer-readable storage medium storing a program for causing a computer included in a communication device that communicates with another communication device to execute a determining step and a sending step, In the determining step, a signal is detected from the other communication device, and resources used when a certain amount of data is communicated from the other communication device to the communication device are determined. In the sending step, one predetermined signal corresponding to the resource determined in the determining step is sent to the other communication device from among a plurality of predetermined signals, wherein: The plurality of prescribed signals are a plurality of prescribed signals known to the communication device and the other communication device, and each of the plurality of prescribed signals corresponds to a resource including at least one of a frequency and a time used when communicating a certain amount of data. In the transmitting step, the one prescribed signal is selected from the plurality of prescribed signals based on the coverage expansion level, and the selected one prescribed signal is transmitted to the other communication device. The plurality of predetermined signals respectively correspond to a combination of a resource used when communicating a certain amount of data from the communication device to the other communication device and a resource used when communicating a certain amount of data from the other communication device to the communication device.

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