Information transmission system, information transmission method, terminal program, and base station program

Abstract

To suppress a packet collision with a PLIM system.SOLUTION: A logic index determination part determines a logic frequency channel index expressing a logic frequency channel, and a logic time slot index expressing a logic time slot. A physical index calculation part calculates a physical peripheral channel index expressing an available physical frequency channel, and a physical time slot index expressing an available physical time slot. A transmission part transmits a packet between the physical time slot by using the physical frequency channel. A physical index detection part detects the physical peripheral channel index, and the physical time slot index. The physical index calculation part calculates the logic frequency channel index and the logic time slot index. An information binding part restores a transmission data by binding the packet, the logic frequency channel index, and the logic time slot index.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an information transmission system, an information transmission method, a terminal program, and a base station program, and more particularly to an information transmission system using a terminal and a base station that perform wireless communication, an information transmission method used by the information transmission system, a terminal program used by the terminal, and a base station program used by the base station. [Background technology]

[0002] There is a demand for a large number of IoT (Internet of Things) terminals to transmit relatively small amounts of data from each terminal to a single base station. For example, by aggregating sensor data detected by sensors on each terminal at a base station or gateway, meaningful statistical data can be obtained at the aggregating base station, even if the amount of data from each sensor is relatively small.

[0003] Such IoT devices need to be low power consuming and capable of long-distance transmission. To address this, standards such as LoRaWAN (Long Range Wide Area Network) have been developed as LPWAN (Low Power Wide Area Network) wireless communication standards. LoRaWAN uses a simple MAC (Medium Access Control) layer access protocol and is known for its low power consumption and long-distance transmission capabilities.

[0004] However, as the total number of terminals sharing a limited number of frequency bands in the same wireless communication system increases, the possibility of packet collisions may increase. Also, if a part of the frequency band used by the wireless communication system to which these terminals belong is occupied by another wireless communication system, packet collisions may occur across the wireless communication system in the occupied frequency band.

[0005] In relation to the above, Non-Patent Document 1 (LoRa Alliance, Inc., "LoRaWAN™ 1.0.3 Specification", 2018, Internet<URL:https: / / lora-alliance.org / sites / default / files / 2018-07 / lorawan1.0.3.pdf> ) discloses the LoRaWAN specification version 1.0.3. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] LoRa Alliance, Inc., "LoRaWAN(TM) 1.0.3 Specification," 2018, Internet<URL:https: / / lora-alliance.org / sites / default / files / 2018-07 / lorawan1.0.3.pdf> Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, one object of the present disclosure is to provide an information transmission system, an information transmission method, a terminal program, and a base station program that suppress packet collisions. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] The following describes the means for solving the problems using the numbers used in the (Mode for Carrying Out the Invention). These numbers are added to clarify the correspondence between the statements in the (Claims) and the (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in the (Claims).

[0009] According to one embodiment, an information transmission system (1) includes a terminal (2) that transmits transmission data as packets (P) using a PLIM (Packet-Level Index Modulation) method, and a base station (3) that receives the packets. The terminal (2) includes a logical index determination unit (216), a physical index calculation unit (217), and a transmission unit (218). The logical index determination unit (216) extracts a portion of the transmission data and determines a logical frequency channel index (k') that represents a logical frequency channel using a first number of bits and a logical time slot index (q') that represents a logical time slot using a second number of bits. The physical index calculation unit (217) calculates a physical frequency channel index (k) representing an available physical frequency channel with a third number of bits equal to or greater than the first number of bits and a physical time slot index (q) representing an available physical time slot with a fourth number of bits equal to or greater than the second number of bits, based on the logical frequency channel index (k'), the logical time slot index (q'), and packet header information included in the packet (P). The transmission unit (218) transmits the packet (P) during the physical time slot using the physical frequency channel. The base station (3) includes a physical index detection unit (312), a logical index calculation unit (313), and an information combination unit (314). The physical index detection unit (312) detects a physical frequency channel index (k) representing a physical frequency channel including the reception frequency and a physical time slot index (q) representing a reception time slot including the reception time, based on the reception frequency and reception time at which the packet (P) was received. The logical index calculation unit (313) calculates a logical frequency channel index (k') and a logical time slot index (q') based on the physical frequency channel index, the physical time slot index, and packet header information of the packet (P). The information combination unit (314) combines the packet (P), the logical frequency channel index (k'), and the logical time slot index (q') to restore the transmission data.

[0010] According to one embodiment, the information transmission method includes a terminal (2) transmitting transmission data as a packet (P) using the PLIM scheme, and a base station (3) receiving the packet (P). The transmitting step includes extracting a portion of the transmission data and determining (S104) a logical frequency channel index (k') representing a logical frequency channel using a first number of bits and a logical time slot index (q') representing a logical time slot using a second number of bits. The transmitting step further includes calculating (S105) a physical frequency channel index (k) representing an available physical frequency channel using a third number of bits equal to or greater than the first number of bits and a physical time slot index (q) representing an available physical time slot using a fourth number of bits equal to or greater than the second number of bits, based on the logical frequency channel index (k'), the logical time slot index (q'), and packet header information included in the packet (P). The transmitting step further includes transmitting (S106) the packet (P) during the physical time slot using the physical frequency channel. The receiving includes detecting (S108) a physical frequency channel index (k) representing a physical frequency channel including the reception frequency and a physical time slot index (q) representing a physical time slot including the reception time based on the reception frequency and reception time at which the packet (P) was received. The receiving further includes calculating (S109) a logical frequency channel index (k') and a logical time slot index (q') based on the physical frequency channel index (k), the physical time slot index (q), and packet header information of the packet (P). The receiving further includes restoring transmission data by combining the packet (P), the logical frequency channel index (k'), and the logical time slot index (q') (S110).

[0011] According to one embodiment, the terminal program is executed to realize a process in which a terminal (2) transmits transmission data as a packet in the PLIM scheme. This process includes extracting a portion of the transmission data and determining a logical frequency channel index (k') representing a logical frequency channel using a first number of bits and a logical time slot index (q') representing a logical time slot using a second number of bits (S104). This process further includes calculating a physical frequency channel index (k) representing an available physical frequency channel and a physical time slot index (q) representing an available physical time slot based on the logical frequency channel index (k'), the logical time slot index (q'), and packet header information included in the packet (S105). This process further includes transmitting a packet (P) during the physical time slot using the physical frequency channel (S106).

[0012] According to one embodiment, the base station program is executed to realize a process in which a base station (3) receives a packet (P) transmitted from a terminal (2) using the PLIM method. This process includes detecting (S108) a physical frequency channel index (k) representing a physical frequency channel including the reception frequency and a physical time slot index (q) representing a physical time slot including the reception time, based on the reception frequency and reception time of the packet (P). This process further includes calculating (S109) a logical frequency channel index (k') and a logical time slot index (q') determined by the terminal (2) based on transmission data transmitted as the packet (P) from the terminal (2), based on the physical frequency channel index (k), the physical time slot index (q), and packet header information of the packet (P). This process further includes combining the packet (P), the logical frequency channel index (k'), and the logical time slot index (q') to restore the transmission data (S110). [Effects of the Invention]

[0013] According to one embodiment, packet collisions can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram for explaining the PLIM method. [Figure 2] FIG. 2 is a diagram for explaining the difference between a logical index and a physical index. [Figure 3] FIG. 3 is a diagram for explaining conversion from a logical index to a usable physical index. [Figure 4] FIG. 4 is a diagram for explaining conversion from a logical index to a physical index whose use is not prohibited. [Figure 5] FIG. 5 is a diagram illustrating an example of a configuration of an information transmission system according to an embodiment. [Figure 6] FIG. 6 is a block circuit diagram showing an example of the configuration of a terminal according to an embodiment. [Figure 7] FIG. 7 is a block circuit diagram showing an example of the configuration of a base station according to an embodiment. [Figure 8] FIG. 8 is a flowchart showing an example of a configuration of an information transmission method according to an embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of a configuration of a part of an information transmission method according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a logical index according to one embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a physical index according to one embodiment. [Figure 12] FIG. 12 is a flowchart showing an example of a configuration of a part of an information transmission method according to an embodiment. [Figure 13] FIG. 13 is a table showing an example of simulation parameters for an information transmission method according to an embodiment. [Figure 14]FIG. 14 is a graph showing an example of a simulation result relating to the influence of the number of prohibited frequency channels on the throughput in the information transmission method according to one embodiment. [Figure 15] FIG. 15 is a graph showing an example of a simulation result relating to the influence of the number of frequency channels on the data overhead generated for storing a resource map in an information transmission method according to an embodiment and a related technique. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the accompanying drawings, embodiments for implementing an information transmission system, an information transmission method, a terminal program, and a base station program according to the present disclosure will be described below.

[0016] (Related Technology) To better understand the problem of one embodiment, a related art will be described first, in which information is transmitted using a packet-level index modulation (PLIM) method.

[0017] Fig. 1 is a diagram for explaining the PLIM method. In Fig. 1, the horizontal axis represents time t and the vertical axis represents frequency f. Time t is divided into a plurality of time frames, each having a predetermined frame length. One time frame is divided into a plurality of time slots, each having a predetermined slot length. Frequency f is divided into a plurality of frequency channels, each having a predetermined frequency width.

[0018] In the PLIM scheme, one transmitter transmits up to one packet P during one time frame. The packet P is transmitted during one of multiple time slots included in the time frame using one of multiple available frequency channels. More specifically, the transmitter divides data to be transmitted into a frequency channel index representing the frequency channel, a time slot index representing the time slot, and packet data included in the packet P. The transmitter transmits the packet P using the time slot and frequency channel corresponding to the time slot index and frequency channel index obtained in this manner. In addition, in the PLIM scheme, the receiver detects the time slot index corresponding to the time slot in which the packet P was received and the frequency channel index corresponding to the frequency channel in which the packet P was received. The receiver restores the original data based on the time slot index, the frequency channel index, and the packet data included in the packet P. This enables the PLIM scheme to increase transmission capacity without modifying existing communication standards. A transmitter and a receiver using the PLIM method share conversion and inverse conversion formulas that represent the correspondence between frequency channels and frequency channel indexes, and the correspondence between time slots and time slot indexes.

[0019] A different time slot index is assigned to each of the multiple time slots included in one time frame. The time slot index is, on the one hand, an identification number that identifies the time slot represented by that time slot index within the time frame in which that time slot is included, and, on the other hand, partial data obtained by extracting a predetermined number of bits from the data to be transmitted. This predetermined number of bits is called the time slot bit number. Since this partial data can take on all values ​​that can be expressed by the time slot bit number, it is preferable that the possible values ​​of this identification number also cover a range of values ​​equal to 2 to the power of the number of time slot bits. In the example of Figure 1, the total number of time slots included in one time frame is greater than or equal to 2 to the fourth power and less than 2 to the fifth power. Therefore, the total number of logically possible values ​​of the time slot index, "Q," is 16, and the number of time slot bits is 4. However, it should be noted that the total number of physically available time slots included in one time frame, "Q ￣" (more precisely, the bar symbol "￣" is above "Q"), may be greater than Q.

[0020] Similarly, each frequency channel is assigned a different frequency channel index. The frequency channel index is, on the one hand, an identification number for identifying the frequency channel represented by that frequency channel index, and, on the other hand, partial data obtained by extracting a predetermined number of bits from the data to be transmitted. This predetermined number of bits is called the frequency channel bit number. Since this partial data can take on all values ​​expressible by the frequency channel bit number, it is preferable that the possible values ​​of this identification number also cover a range of values ​​equal to 2 to the power of the number of frequency channel bits. In the example of FIG. 1, the total number of frequency channels included in the available frequency band is equal to or greater than 2 to the power of 1 and less than 2 to the power of 2. Therefore, the total number of values ​​"K" that the frequency channel can logically take on is 2, and the number of frequency channel bits is 1. However, it should be noted that the total number of physically available frequency channels included in the available frequency band, "K￣" (to be precise, the bar symbol "￣" is above "K"), may be greater than K.

[0021] Hereinafter, the total number of values ​​that the time slot index can logically take, "Q," will be referred to as the "number of logical time slots Q." Furthermore, the total number of physically available time slots will be referred to as the "number of physical time slots Q" (more precisely, the bar symbol "" is above the "Q"). Similarly, the total number of values ​​that the frequency channel index can logically take, "K," will be referred to as the "number of logical frequency channels K." Furthermore, the total number of physically available frequency channels will be referred to as the "number of physical frequency channels K" (more precisely, the bar symbol "" is above the "K"). For simplicity's sake, we will continue the explanation using an example in which the number of logical time slots Q is 4, the number of physical time slots Q is 5, the number of logical frequency channels K is 2, and the number of physical frequency channels K is 3, as shown in Figure 2.

[0022] In the PLIM scheme, the number of logically possible combinations of time slots and frequency channels may be fewer than the number of physically available combinations. Hereinafter, the logically available combinations of time slots and frequency channels are referred to as logical indexes. Similarly, the physically available combinations of time slots and frequency channels are referred to as physical indexes. In the example of Figure 2, combinations that are included in the physical indexes but not included in the logical indexes—i.e., combinations that are physically available but cannot be logically selected—are indicated by diagonal hatching. In the example of Figure 2, the total number of physical indexes is 15, calculated by multiplying the number of physical time slots Q by the number of physical frequency channels K, and the total number of logical indexes is 8, calculated by multiplying the number of logical time slots Q by the number of logical frequency channels K. As a result, nearly half of the available combinations cannot be effectively used for packet transmission. Packet collisions occur when multiple transmitters transmit packets on the same frequency channel in the same time slot. Therefore, if even a portion of the combinations that are included in the physical indexes but not included in the logical indexes can be used for packet transmission, packet collisions can be reduced. Here, the set of physical indexes is referred to as the resource map.

[0023] Therefore, in this disclosure, packet collisions are suppressed by converting a logical index into one of the physical indexes. Furthermore, by performing an inverse conversion from a physical index to a logical index, the receiver can calculate a logical time slot index from a physical time slot index of a physical time slot in which a packet is received, and calculate a logical frequency channel index from a physical frequency channel index of a physical frequency channel in which a packet is received. The transmitter and receiver share these conversion and inverse conversion formulas.

[0024] As a result of such conversion, packets that are transmitted using logical indexes in the example of Fig. 2, such as packets P1 and P3 shown in Fig. 3, may be transmitted using physical indexes other than the logical indexes. Also, packet P2, which is transmitted using a logical index, may be transmitted using a different logical index, such as packet P2 shown in Fig. 3.

[0025] Furthermore, when performing such conversion, frequency channels in the available frequency band that are prohibited for use for some reason may be avoided. Hereinafter, a physical index including a frequency channel whose use is prohibited is referred to as a prohibited index. In such a case, the logical index may be converted to a physical index other than the prohibited index. As a result of such conversion, a packet transmitted using a logical index in the example of FIG. 2, such as packet P1 shown in FIG. 4, may be transmitted using a combination that is physically available, not prohibited for use, and cannot be logically selected. Furthermore, packets transmitted using a logical index, such as packets P2 and P3 shown in FIG. 4, may be transmitted using a different logical index.

[0026] (First embodiment) 5, an information transmission system 1 according to one embodiment includes a plurality of terminals 2A, 2B, 2C, and 2D, and a base station 3. When there is no need to distinguish between the terminals 2A, 2B, 2C, and 2D, they are collectively referred to as terminals 2. The total number of terminals 2 is arbitrary and does not limit one embodiment.

[0027] Each terminal 2 may transmit information independently of the other terminals 2. In other words, each terminal 2 may operate asynchronously with the other terminals 2 when transmitting information. The base station 3 receives the information transmitted from the terminals 2.

[0028] 6, a terminal 2 according to one embodiment includes a bus 20, a computing device 21, a storage device 22, a communication device 23, and a sensor device 24. The computing device 21, the storage device 22, the communication device 23, and the sensor device 24 are communicatively connected via the bus 20.

[0029] The arithmetic unit 21 includes a receiver 211, a resource map updater 212, a data generator 213, an information divider 214, a packet generator 215, a logical index determiner 216, a physical index calculator 217, and a transmitter 218. By executing a terminal program, the arithmetic unit 21 realizes the functions of the receiver 211, the resource map updater 212, the data generator 213, the information divider 214, the packet generator 215, the logical index determiner 216, the physical index calculator 217, and the transmitter 218. In other words, the receiver 211, the resource map updater 212, the data generator 213, the information divider 214, the packet generator 215, the logical index determiner 216, the physical index calculator 217, and the transmitter 218 are virtual functional units that realize predetermined functions through cooperation between the arithmetic unit 21 and the terminal program. The functions realized by these functional units will be described later.

[0030] The storage device 22 includes a terminal program storage unit 221 and a resource map storage unit 222. The terminal program storage unit 221 stores a terminal program. The resource map storage unit 222 stores a resource map. Details of the resource map will be described later. The terminal program and the resource map may be read from an external recording medium 220, or may be received via the communication device 23. The recording medium 220 may be a non-transitory and tangible medium.

[0031] The communication device 23 performs wireless communication with the base station 3. The communication device 23 transmits packet information to be received by the base station 3 under the control of a transmitter 218, and receives information transmitted from the base station 3 under the control of a receiver 211.

[0032] The sensor device 24 measures a desired parameter representing an ambient condition and outputs measurement data representing the result of this measurement. As an example, the sensor device 24 may be an air temperature sensor that measures the ambient air temperature, a humidity sensor that measures the ambient humidity, a carbon dioxide concentration sensor that measures the ambient carbon dioxide concentration, etc.

[0033] 7, a base station 3 according to one embodiment includes a bus 30, a calculation device 31, a storage device 32, and a communication device 33. The calculation device 31, the storage device 32, and the communication device 33 are connected via the bus 30 so as to be able to communicate with each other.

[0034] The arithmetic device 31 includes a receiver 311, a physical index detector 312, a logical index calculator 313, an information combiner 314, a resource map updater 315, and a transmitter 316. By executing a base station program, the arithmetic device 31 realizes the functions of the receiver 311, the physical index detector 312, the logical index calculator 313, the information combiner 314, the resource map updater 315, and the transmitter 316. In other words, the receiver 311, the physical index detector 312, the logical index calculator 313, the information combiner 314, the resource map updater 315, and the transmitter 316 are virtual functional units that realize predetermined functions through cooperation between the arithmetic device 31 and the base station program. The functions realized by these functional units will be described later.

[0035] The storage device 32 includes a base station program storage unit 321 and a resource map storage unit 322. The base station program storage unit 321 stores a base station program. The resource map storage unit 322 stores a resource map. Details of the resource map will be described later. The base station program and the resource map may be read from an external recording medium 320, or may be received via the communication device 33. The recording medium 320 may be a non-transitory and tangible medium.

[0036] The communication device 33 performs wireless communication with the terminal 2. The communication device 33 receives packet information transmitted from the terminal 2 under the control of a receiving unit 311, and transmits information to be transmitted to the terminal 2 under the control of a transmitting unit 316.

[0037] An example of the configuration of an information transmission method according to an embodiment will be described with reference to the flowchart of Fig. 8. The flowchart of Fig. 8 includes steps S101 to S110. Steps S101 to S106 are included in a terminal program executed by the arithmetic device 21 of the terminal 2. Steps S107 to S110 are included in a base station program executed by the arithmetic device 31 of the base station 3.

[0038] Before the flowchart of FIG. 8 starts, a resource map may be shared between the terminal 2 and the base station 3. In this case, first, the calculation device 31 of the base station 3 executes a base station program, thereby realizing the function of the resource map update unit 315. The resource map update unit 315 generates or updates a resource map and stores it in the resource map storage unit 322. Then, the calculation device 31 of the base station 3 executes the base station program, thereby realizing the function of the transmitter 316. The transmitter 316 reads the resource map from the resource map storage unit 322 and controls the communication device 33 to transmit the resource map to the receiver 211 of the terminal 2. Meanwhile, the calculation device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the receiver 211. The receiver 211 controls the communication device 23 to receive the resource map and stores the received resource map in the resource map storage unit 222. Then, the calculation device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the resource map update unit 212. The resource map update unit 212 updates the resource map. More specifically, the most recently received resource map is registered as the valid resource map among those stored in resource map storage unit 222. If other resource maps are stored in resource map storage unit 222, resource maps other than the valid resource map may be deleted.

[0039] 8 starts, step S101 begins. In step S101, the arithmetic device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the data generation unit 213. The data generation unit 213 generates transmission data to be transmitted to the base station 3. The data generation unit 213 controls the sensor device 24 to acquire measurement data, and converts the measurement data to generate transmission data as digital data.

[0040] After step S101, step S102 is executed. In step S102, the calculation device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the information division unit 214. The information division unit 214 divides the information of the transmission data to generate first data of a first number of bits, second data of a second number of bits, and third data of the remaining number of bits. As an example, the first data is used as a logical time slot index, the second data is used as a logical frequency channel index, and the third data is used as packet data.

[0041] After step S102, step S103 is executed. In step S103, the processing device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the packet generation unit 215. The packet generation unit 215 generates a packet to be transmitted by the terminal 2 to the base station 3. Of the packets generated by the packet generation unit 215, the packet data includes third data. Furthermore, of the packets generated by the packet generation unit 215, the packet header includes device address information indicating a device address, which is a number for identifying the terminal 2, and packet counter information indicating a packet counter, which is a number for identifying the currently generated packet.

[0042] After step S103, step S104 is executed. In step S104, the arithmetic device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the logical index determination unit 216. The logical index determination unit 216 determines a logical index based on the first data and the second data. More specifically, it determines a logical time slot index based on the first data, and determines a logical frequency channel index based on the second data. Here, the logical time slot index may be the first data itself. Similarly, the logical frequency channel index may be the second data itself.

[0043] After step S104, step S105 is executed. In step S105, the calculation device 21 of the terminal 2 executes the terminal program, thereby realizing the function of the physical index calculation unit 217. The physical index calculation unit 217 calculates the physical index based on the logical index, the packet header, maximum packet counter information indicating the maximum value of the packet counter, the number of available resources, and the resource map. Here, the number of available resources is the total number of combinations of physical frequency channels and physical time slots whose use is not prohibited, and is calculated as the product of the total number of physical frequency channels other than prohibited frequency channels and the number of physical time slots Q, as shown in the following equation (1).

[0044]

number

[0045] The physical indexes calculated by physical index calculation unit 217 have a one-to-one correspondence with the logical indexes. This allows logical index calculation unit 313 of base station 3 to later calculate the logical indexes corresponding to the physical indexes. In other words, the process by which physical index calculation unit 217 of terminal 2 uniquely calculates the physical indexes corresponding to the logical indexes is a type of modulation process or encryption process, and the method by which logical index calculation unit 313 of base station 3 uniquely calculates the logical indexes corresponding to the physical indexes is a type of demodulation or decoding process.

[0046] A specific example of the process in which the physical index calculation unit 217 of the terminal 2 calculates the physical index according to an embodiment will be described later.

[0047] After step S105, step S106 is executed. In step S106, the processing device 21 of the terminal 2 executes a terminal program, thereby realizing the function of the transmitter 218. The transmitter 218 transmits a packet using the physical frequency channel indicated by the physical frequency channel index during the physical time slot indicated by the physical time slot index.

[0048] 8 returns to step S101 in the terminal 2, and proceeds to step S107 in the base station 3. In step S107, the calculation device 31 of the base station 3 executes the base station program, thereby realizing the function of the receiving unit 311. The receiving unit 311 receives a packet transmitted from the terminal 2. The receiving unit 311 stores the received packet in the storage device 32.

[0049] After step S107, step S108 is executed. In step S108, the calculation device 31 of the base station 3 executes a base station program, thereby realizing the function of the physical index detection unit 312. The physical index detection unit 312 detects a physical index, which is a combination of a physical time slot index and a frequency channel index, based on the physical time slot and physical frequency channel on which the packet was received, the packet header, the maximum packet counter information, the number of available indexes, and the resource map.

[0050] After step S108, step S109 is executed. In step S109, the arithmetic device 31 of the base station 3 executes a base station program, thereby realizing the function of the logical index calculation unit 313. The logical index calculation unit 313 calculates a logical index based on the physical index, device address information, and packet counter information. At this time, the logical index calculation unit 313 refers to a packet stored in the storage device 32, and reads out the device address information and packet counter information included in the packet header of this packet.

[0051] As described in relation to step S105 above, the logical index calculation unit 313 of the base station 3 uniquely calculates a logical index corresponding to a physical index. A specific example of a process in which the logical index calculation unit 313 of the base station 3 according to an embodiment calculates a logical index will be described later.

[0052] After step S109, step S110 is executed. In step S110, the calculation device 31 of the base station 3 executes a base station program, thereby realizing the function of the information combination unit 314. The information combination unit 314 combines the information obtained in steps S107 to S108 to restore the transmission data. More specifically, the information combination unit 314 combines first data obtained as a logical time slot index, second data obtained as a logical frequency channel index, and third data obtained as packet data included in the received packet to restore the transmission data. The information combination unit 314 then stores the transmission data in the storage device 32.

[0053] Furthermore, after that, the transmission unit 316 may output the transmission data to the outside. As an example, an external server or the like may analyze the multiple pieces of transmission data that the base station 3 has acquired from the multiple terminals 2, respectively.

[0054] After step S110, the processing of the flowchart in Fig. 8 ends. However, the processing of the base station 3 may return to step S107 to receive the next packet.

[0055] (Physical index calculation) The process performed by the physical index calculation unit 217 of the terminal 2 in step S105 of the flowchart in FIG. 8 will be described in detail with reference to the flowchart in FIG.

[0056] 9 starts and step S201 is executed when step S103 of the flowchart in Fig. 8 is executed. In step S201, the physical index calculation unit 217 prepares arguments. As an example, the arguments include a logical time slot index included in the logical index, a logical frequency channel index included in the logical index, device address information included in the packet header, packet counter information included in the packet header, maximum packet counter information, the number of available resources, and a resource map including a list of prohibited frequency channels.

[0057] After step S201, step S202 is executed. In step S202, the physical index calculation unit 217 calculates a logical number X' corresponding to the logical index of interest. The logical number X' is a number that uniquely represents the logical index, which is a combination of a logical time slot index and a logical frequency channel index. The logical number X' is defined, for example, as in the following equation "Number 2".

[0058]

number

[0059] After step S202, step S203 is executed. In step S203, the physical index calculation unit 217 calculates the pseudo-random number X p Calculate the pseudorandom number X p In order to prevent packet collisions, the logical number X' is calculated using the device address so that even if different terminals 2 transmit the same transmission data in the same time frame, the logical number X' is different from each other. pis calculated using a packet counter so that logical number X' changes in successive time frames so that packet collisions do not occur again when the same terminal 2 transmits the same transmission data in the next time frame after a packet collision has occurred. p is defined as the following equation (3), for example.

[0060]

number

[0061] After step S203, step S204 is executed. In step S204, the physical index calculation unit 217 calculates a physical number X. The physical number X is a number that uniquely represents a physical index, which is a combination of a physical time slot index and a physical frequency channel index. The physical number X is defined, for example, as in the following equation (4).

[0062]

number

[0063] After step S204, step S205 is executed. In step S205, physical index calculation unit 217 calculates a physical index. More specifically, physical index calculation unit 217 calculates a physical time slot index and a physical frequency channel index included in the physical index. Here, the third number of bits required to represent the physical time slot index may be equal to or greater than the first number of bits required to represent the logical time slot index q'. Furthermore, the fourth number of bits required to represent the physical frequency channel index may be equal to or greater than the second number of bits required to represent the logical frequency channel index k'. The physical time slot index q and the physical frequency channel index k can be calculated, for example, using the following equations "Equation 5" and "Equation 6."

[0064]

number

number

[0065] After step S205, the flowchart in FIG. 9 ends, and the process returns to step S105 in the flowchart in FIG. 8, and then proceeds to step S106.

[0066] As described above, according to one embodiment, by calculating physical indexes that correspond one-to-one to logical indexes, the logical index calculation unit 313 of the base station 3 can uniquely calculate logical indexes based on physical indexes. Also, packet collisions can be suppressed by effectively utilizing physical time slots that are not included in logical time slots and physical frequency channels that are not included in logical frequency channels. Furthermore, the pseudo-random number X p By introducing the following, packet collisions can be further suppressed.

[0067] As an example, physical indexes B1 to B7 shown in Fig. 11 are calculated based on logical indexes A1 to A7 shown in Fig. 10. In the example of Fig. 10, among combinations of time slots and frequency channels, combinations that cannot be selected as logical indexes are indicated by diagonal hatching. Also, in the example of Fig. 11, among combinations of time slots and frequency channels, physical indexes that include prohibited frequency channels are indicated by diagonal hatching. A resource map indicating whether physical indexes are usable may include information defining whether or not each physical index is usable, as shown in Fig. 11. Alternatively, the resource map may include only information defining whether or not each physical frequency channel is usable.

[0068] (Calculating logical index) The process performed by the logical index calculation unit 313 of the base station 3 in step S109 of the flowchart in FIG. 8 will be described with reference to the flowchart shown in FIG.

[0069] 8, the flowchart of FIG. 12 starts and step S301 is executed. In step S301, the logical index calculation unit 313 prepares arguments. As an example, the arguments include a physical time slot index q included in the physical index, a physical frequency channel index k included in the physical index, device address information included in the packet header, packet counter information included in the packet header, maximum packet counter information, the number of available resources, and a resource map including a list of prohibited frequency channels.

[0070] After step S301, step S302 is executed. In step S302, the logical index calculation unit 313 calculates a physical number X corresponding to the physical index at which the packet was received. The physical number X is a number that uniquely represents a physical index that is a combination of a physical time slot index q including the time at which the packet was received and a physical frequency channel index k including the frequency band at which the packet was received. The physical number X can be calculated, for example, using the following equation (7):

[0071]

number

[0072] After step S302, step S303 is executed. In step S303, the logical index calculation unit 313 calculates the pseudo-random number X p The process in step S303 is the same as step S203 in the flowchart of FIG.

[0073] After step S303, step S304 is executed. In step S304, the logical index calculation unit 313 calculates a logical number X'. The logical number X' is a number that uniquely represents a logical index that is a combination of a logical time slot index and a logical frequency channel index. The logical number X' is defined, for example, as in the following equation "Number 8".

[0074]

number

[0075] "mod" is defined by the following formula (9).

[0076]

number

[0077] In step S305, the logical index calculation unit 313 calculates a logical index. More specifically, the logical index calculation unit 313 calculates a logical time slot index q' and a logical frequency channel index k' included in the logical index. The logical time slot index q' and the logical frequency channel index k' can be calculated, for example, by the following equations (10) and (11).

[0078]

number

number

[0079] After step S305, the flowchart in FIG. 12 ends, and the process returns to step S109 in the flowchart in FIG. 8, and then proceeds to step S110.

[0080] As described above, according to one embodiment, the logical index calculation unit 313 of the base station 3 can uniquely calculate logical indexes that correspond one-to-one to physical indexes.

[0081] The information transmission system 1 according to the embodiment can suppress packet collisions by implementing the information transmission method described above.

[0082] (Simulation results, part 1) 13 and 14, a simulation result for evaluating the characteristics of the information transmission method according to one embodiment will be described.

[0083] Fig. 13 is a table showing an example of simulation parameters for an information transmission method according to an embodiment. In the example of Fig. 13, the number of terminals N, which represents the number of terminals 2, is selected as any integer in the range of 1 to 10,000. The number of logical frequency channels K is 16. The number of logical time slots Q is 16. The packet size D, which represents the amount of information in a packet, is 10 bytes. The transmission period T of terminal 2, which is the length of the time frame, is 120 seconds. The number of prohibited frequency channels K p selects an integer between 0 and 15.

[0084] In addition, the simulation was performed under the following conditions: All terminals 2 transmit packets at the same transmission period. Terminals 2 transmit packets asynchronously with each other. A logical index is determined randomly each time a packet is transmitted. The theoretical value of throughput S is defined as in the following equation (Number 12).

[0085]

number

[0086] FIG. 14 shows the relationship between the number of prohibited frequency channels K and the throughput S in the information transmission method according to one embodiment. p 14 is a graph showing an example of a simulation result relating to the influence of the number of prohibited frequency channels K. In the graph of FIG. p The vertical axis represents the throughput S in bits per second. Of the two graphs included in Fig. 14, the first graph G11 represents the simulation results of the information transmission method according to the related art, and the second graph G12 represents the simulation results of the information transmission method according to one embodiment. In the example of Fig. 14, the number of terminals N is 100.

[0087] In the information transmission method according to the related art, the logical indexes are used as physical indexes without being converted into physical indexes. As a result, as shown in Figure 14, the throughput S in the information transmission method according to the embodiment is improved compared to the throughput in the related art. However, if the number of prohibited frequency channels K pis 0, 8, 12, 14 or 15, in other words, when the total number of available physical frequency channels is 1, 2, 4, 8 or 16, the throughput S in the information transmission method according to one embodiment is equal to the throughput of the related art. This is because when the total number of available physical frequency channels (=K -K p ) is a power of 2 and the number of physical time slots Q is a power of 2, the total number of logical indexes is equal to the total number of physical indexes. In other words, there is no combination of redundant time slots and frequency channels that are included in the physical indexes and not included in the logical indexes. Conversely, if the number of physical time slots Q is not a power of 2, the number of prohibited frequency channels K p Regardless of the throughput S, the information transmission method according to the embodiment always improves over the throughput of the related art.

[0088] (Simulation results, part 2) The results of a simulation evaluating the characteristics of an information transmission method according to one embodiment and the related technology will be described with reference to Fig. 15. The related technology differs from the one embodiment in that it uses logical frequency channels as physical frequency channels and logical time slots as physical time slots.

[0089] 15 is a graph showing an example of a simulation result relating to the influence of the number of frequency channels on the data overhead generated for storing a resource map in an information transmission method according to one embodiment and a related technology. In the graph of FIG. 15, the horizontal axis represents the number of frequency channels, and the vertical axis represents the data overhead in bits. Note that the number of frequency channels on the horizontal axis represents the number of logical frequency channels K in the related technology, and represents the number of physical frequency channels K in one embodiment.

[0090] 15, the first graph G21 represents the memory usage for terminal 2 to store all resource maps in storage device 22 when the number of logical time slots Q is 64. Similarly, the second graph G22 represents the memory usage for terminal 2 to store all resource maps in storage device 22 when the number of logical time slots Q is 16. Furthermore, the third graph G23 represents the memory usage for terminal 2 to store all resource maps in storage device 22 when the number of logical time slots Q is 4.

[0091] A fourth graph G24 represents the memory usage for terminal 2 to store one resource map in storage device 22 when the number of logical time slots Q is 64. Similarly, a fifth graph G25 represents the memory usage for terminal 2 to store one resource map in storage device 22 when the number of logical time slots Q is 16. Furthermore, a sixth graph G26 represents the memory usage for terminal 2 to store one resource map in storage device 22 when the number of logical time slots Q is 4.

[0092] A seventh graph G27 represents the memory usage required by the terminal 2 to store in the storage device 22 information indicating whether or not each physical frequency channel in the resource map is a prohibited frequency channel.

[0093] In relation to the first graph G21 to the sixth graph G26, the memory usage D per logical index including the prohibited frequency channel rec (K p ) can be calculated using the following equation (Number 13).

[0094]

number

[0095] In relation to the fourth graph G24 to the sixth graph G26, the memory usage per resource map D map (K p ) can be calculated using the following equation (Number 14).

[0096]

number

[0097] Regarding the first graph G21 to the third graph G23, the memory usage D when all resource maps are stored total can be calculated using the following equation (Number 15).

[0098]

number

[0099] In relation to the seventh graph G27, the memory usage D for the terminal 2 to store in the storage device 22 information indicating whether each physical frequency channel in the resource map is a prohibited frequency channel or not is prop is calculated as shown in the following equation (16).

[0100]

number

[0101] 15, when the number of physical time slots Q is the same, the memory usage of the first graph G21 to the third graph G23 is equal to or greater than the memory usage of the fourth graph G24 to the sixth graph G26. Furthermore, the memory usage of the seventh graph G27 is less than any of the first graph G21 to the sixth graph G26. Therefore, in order to save memory usage in the storage device 22 of the terminal 2, it is preferable that information in the resource map that indicates only whether or not use of each frequency channel is prohibited is shared between the terminal 2 and the base station 3.

[0102] The invention made by the inventor has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the embodiments and can be modified in various ways without departing from the spirit of the invention. Furthermore, the features described in the embodiments can be freely combined within the scope of technical compatibility.

[0103] In the above embodiment, before starting the flowchart of Fig. 8, a case has been described in which the resource map is updated and shared by base station 3 transmitting the updated resource map and terminal 2 receiving it. As a variation, base station 3 may update the resource map at any timing in response to changes in the wireless environment, including the operation of other communication systems, or may transmit the resource map at any timing. Furthermore, terminal 2 may receive the resource map when it is transmitted, or may store the resource map in storage device 22 when it is received. However, terminal 2 and base station 3 register the updated resource map as a valid resource map when the time frame changes.

[0104] In the above embodiment, a case has been described in which step S104 and step S105 are executed after step S103 in the flowchart of Fig. 8 is executed. As a modification, step S103 may be executed between step S104 and step S105, or may be executed after step S104 and step S105 are executed, or may be executed in parallel with step S104 and / or step S105. In any case, step S103 is executed after step S102 and before step S106.

[0105] In the above embodiment, a case has been described in which the logical time slot index q' is the first data itself and the logical frequency channel index k' is the second data itself in step S104 of the flowchart in FIG. 8. As a variation of step S104, the logical time slot index q' may be a value obtained by converting the first data according to a predetermined conversion rule. Similarly, the logical frequency channel index k' may be a value obtained by converting the second data according to a predetermined conversion rule. However, in this case, in step S109, the logical index calculation unit 313 of the base station 3 calculates a logical index using an inverse conversion rule corresponding to the conversion rule of step S104.

[0106] In the above embodiment, in the flowchart of FIG. 9, in order to calculate the physical indexes that correspond one-to-one to the logical indexes, a pseudo-random number X defined as in the formula "3" is used. p As a modification, the pseudorandom number X p may be defined as the following equation (17).

[0107]

number

[0108] In this case, in step S303 of the flowchart in FIG. 12, the pseudorandom number X is calculated using the above formula (17). p At this time, the integer N is shared between the terminal 2 and the base station 3. [Explanation of symbols]

[0109] 1. Information Transmission System 2, 2A, 2B, 2C, 2D terminals 20 Bus 21 Arithmetic unit 211 Receiving unit 212 Resource Map Updates 213 Data Generation Unit 214 Information division section 215 Packet Generation Unit 216 Logical Index Determination Unit 217 Physical Index Calculation Unit 218 Transmitter 22 Storage device 220 Recording Media 221 Terminal program storage unit 222 Resource Map Storage 23 Communication equipment 24 Sensor Device 3 base station 30 Bus 31 Arithmetic unit 311 Receiving unit 312 Physical Index Detector 313 Logical Index Calculation Unit 314 Information connection part 315 Resource Map Updates 316 Transmitter 32 Storage device 320 Recording Media 321 Base Station Program Storage Unit 322 Resource Map Storage 33 Communication equipment A1, A2, A3, A4, A5, A6, A7 logical index B1, B2, B3, B4, B5, B6, B7 Physical index D Packet Size f frequency G11, G12 graphs G21, G22, G23, G24, G25, G26, G27 graphs k physical frequency channel index k' logical frequency channel index K number of logical frequency channels K - Number of physical frequency channels K p Number of prohibited frequency channels N number of terminals P, P1, P2, P3 packets q Physical time slot index q' logical time slot index Q Number of logical time slots Q ￣ Number of physical time slots t time T Transmission cycle

Claims

1. a terminal that transmits transmission data as packets using a PLIM (Packet-Level Index Modulation) method; a base station that receives the packet; Equipped with The terminal a logical index determination unit that extracts a portion of the transmission data and determines a logical frequency channel index that represents a logical frequency channel with a first number of bits and a logical time slot index that represents a logical time slot with a second number of bits; a physical index calculation unit that calculates a physical frequency channel index representing an available physical frequency channel by a third number of bits equal to or greater than the first number of bits and a physical time slot index representing an available physical time slot by a fourth number of bits equal to or greater than the second number of bits, based on the logical frequency channel index, the logical time slot index, and packet header information included in the packet; a transmitter that transmits the packet using the physical frequency channel during the physical time slot; Equipped with The base station a physical index detection unit that detects, based on a reception frequency and a reception time at which the packet is received, the physical frequency channel index that indicates the physical frequency channel that includes the reception frequency and the physical time slot index that indicates the physical time slot that includes the reception time; a logical index calculation unit that calculates the logical frequency channel index and the logical time slot index based on the physical frequency channel index, the physical time slot index, and the packet header information of the packet; an information combining unit that combines the packet, the logical frequency channel index, and the logical time slot index to restore the transmission data; Equipped with Information transmission system.

2. 2. The information transmission system according to claim 1, Another terminal that operates asynchronously with the terminal Further equipped Information transmission system.

3. 3. The information transmission system according to claim 2, the packet header information includes a device address for identifying the terminal and a packet counter for identifying the packet; Information transmission system.

4. 4. The information transmission system according to claim 3, the physical index calculation unit calculates the physical frequency channel index and the physical time slot index further based on a maximum value of the packet counter; The logical index calculation unit calculates the logical frequency channel index and the logical time slot index further based on the maximum value of the packet counter. Information transmission system.

5. In the information transmission system according to any one of claims 1 to 4, the physical index calculation unit calculates the physical frequency channel index and the physical time slot index further based on a resource map including information on prohibited frequency channels whose use is prohibited; The logical index calculation unit calculates the logical frequency channel index and the logical time slot index further based on the resource map shared with the terminal. Information transmission system.

6. The terminal transmits the transmission data as packets using a PLIM (Packet-Level Index Modulation) method; a base station receiving the packet; Including, The transmitting step includes: extracting a portion of each of the transmission data to determine a logical frequency channel index representing a logical frequency channel using a first number of bits and a logical time slot index representing a logical time slot using a second number of bits; calculating a physical frequency channel index representing an available physical frequency channel by a third number of bits equal to or greater than the first number of bits and a physical time slot index representing an available physical time slot by a fourth number of bits equal to or greater than the second number of bits, based on the logical frequency channel index, the logical time slot index, and packet header information included in the packet; transmitting said packet using said physical frequency channel during said physical time slot; Including, The receiving includes: Detecting the physical frequency channel index representing the physical frequency channel including the reception frequency and the physical time slot index representing the physical time slot including the reception time based on the reception frequency and the reception time at which the packet was received; calculating the logical frequency channel index and the logical time slot index based on the physical frequency channel index, the physical time slot index, and the packet header information of the packet; combining the packet, the logical frequency channel index, and the logical time slot index to recover the transmitted data; Contains Information transmission method.

7. A terminal program for realizing a process in which a terminal transmits transmission data as packets using a PLIM (Packet-Level Index Modulation) method, the program comprising: The process comprises: extracting a portion of each of the transmission data to determine a logical frequency channel index representing a logical frequency channel using a first number of bits and a logical time slot index representing a logical time slot using a second number of bits; calculating a physical frequency channel index representing an available physical frequency channel and a physical time slot index representing an available physical time slot based on the logical frequency channel index, the logical time slot index, and packet header information included in the packet; transmitting said packet using said physical frequency channel during said physical time slot; Contains Terminal program.

8. A base station program for implementing a process in which a base station receives a packet transmitted from a terminal using a PLIM (Packet-Level Index Modulation) method, the process comprising: The process comprises: Detecting a physical frequency channel index representing a physical frequency channel including the reception frequency and a physical time slot index representing a physical time slot including the reception time based on a reception frequency and a reception time at which the packet was received; Calculating a logical frequency channel index and a logical time slot index determined by the terminal based on transmission data transmitted as the packet by the terminal based on the physical frequency channel index, the physical time slot index, and packet header information of the packet; combining the packet, the logical frequency channel index, and the logical time slot index to recover the transmitted data; Contains Base station program.

Images