JP7202637B2 - wireless communication system - Google Patents

Description

The present invention relates to wireless communication systems that collect data signals from multiple terminals using non-orthogonal multiple access.

Currently, research and development toward the realization of the 5th generation mobile communication system (5G) is underway in countries around the world. 5G is required not only to increase the capacity of the 4th generation mobile communication system (4G), but also to efficiently handle small-sized data transmitted from devices such as IoT (Internet of Things). In IoT communication, it is expected that services that require low delay, such as automatic driving, will appear, and in this case, low-delay communication will be required in addition to an increase in the number of simultaneous connections. As an attempt to improve the number of simultaneous connections of such terminals and the delay at the time of connection, for example, the communication system of Patent Document 1 has been proposed.

In the contention-based communication system in Patent Document 1, a preamble part in which a signal for estimating channel characteristics is included and a phase shift is performed for a predetermined sequence signal assigned to each wireless terminal, terminal identification information and payload A frame-structured signal having a data portion containing and is used. The preamble part phase-shifts the Zadov-Chu sequence signal by the amount assigned to each wireless terminal, adds a cyclic prefix (CP), and transmits the signal. Then, it is multiplied by the complex conjugate signal of the series signal, subjected to inverse Fourier transform, and converted to the time axis to obtain an impulse response signal. Each of these is assigned to slots for each wireless terminal by a time filter, and each of the obtained response signals is used to estimate transmission path characteristics, and the data part is separated and demodulated.

JP 2018-121204 A

However, in the communication system of Patent Document 1, while it is possible to improve the delay at the time of connection, no consideration is given to reducing the delay for transmitting and receiving data signals within a specified time. For this reason, it is expected to realize both a large number of connections and a low delay.

SUMMARY OF THE INVENTION Accordingly, the present invention has been devised in view of the above-described problems, and an object of the present invention is to provide a wireless communication system that achieves both multiple connections and low delay.

To solve the above problems, the inventors have invented a wireless communication system that uses non-orthogonal multiple access to collect data signals from multiple terminals. A wireless communication system comprises transmitting and receiving means. The transmitting/receiving means transmits data signals generated by some of the plurality of terminals to the base station from some of the plurality of terminals based on delay tolerance values set in advance for each of the plurality of terminals.

A radio communication system according to a first invention is a radio communication system that collects data signals from a plurality of terminals using non-orthogonal multiple access, and based on a delay tolerance set in advance for each of the plurality of terminals, transmitting/receiving means for superimposing and transmitting the data signal generated from some of the terminals out of the plurality of terminals to a base station from the part of the terminals , wherein the transmitting/receiving means is the number of the plurality of terminals; , and calculating means for calculating the number of superimposed data signals based on the allowable delay value set for each terminal .

A wireless communication system according to a second aspect of the present invention is the first aspect, wherein the transmission/reception means includes notification means for transmitting notification information including a delay specified value from the base station to a plurality of the terminals; A reference signal is transmitted to the base station from a comparison means for comparing the specified delay value and the allowable delay value, and a first terminal set with the allowable delay value higher than the specified delay value, and the delay is transmitting means for transmitting the reference signal and the data signal to the base station from the second terminal in which the delay tolerance value equal to or less than a specified value is set.

A radio communication system according to a third aspect of the invention is characterized in that, in the second aspect of the invention, the transmitting means is performed during random access communication.

A wireless communication system according to a fourth aspect of the invention is the wireless communication system according to any one of the first to third aspects of the invention, wherein the transmitting/receiving means sets the transmission power range for transmitting the data signal from the terminal to the base station by a plurality of classifying means for classifying into multiple slots; allocating means for allocating each of said multiple slots to one multiple slot terminal from a plurality of said terminals; and multi-slot transmission means for transmitting to the base station using the transmission power which is equal to or greater than the transmission power.

A wireless communication system according to a fifth aspect of the present invention is the wireless communication system according to the fourth aspect, wherein the classifying means includes transmission power that the terminal can transmit, the type of the terminal, the distance between the terminal and the base station, and the distance between the terminal and the base station. classifying means for classifying the plurality of terminals into a plurality of classes based on at least one of provided topography, wherein the assigning means selects one of the plurality of terminals classified for each class; Also, the terminal with the lower delay tolerance value is preferentially assigned as the multi-slot terminal.

According to the first invention, the transmitting/receiving means superimposes and transmits data signals from some terminals to the base station based on the delay tolerance. Therefore, it is possible to preferentially transmit data signals from terminals that cannot tolerate delays, and to suppress delays occurring in all of a plurality of terminals. This makes it possible to achieve both multiple connections and low delay.
Further, according to the first invention, the calculation means calculates the number of superimposed data signals based on the number of terminals and the allowable delay value. Therefore, it is possible to further suppress the delay occurring in all of the plurality of terminals. This makes it possible to easily realize both multiple connections and low delay.

In particular, according to the second invention, the notification means transmits notification information from the base station to the plurality of terminals. Also, the transmission means transmits the reference signal and the data signal from the second terminal, for which the delay tolerance value equal to or less than the specified delay value is set, to the base station. Therefore, the number of data signals to be preferentially transmitted can be adjusted by the specified delay value according to the situation. This makes it possible to increase the probability that the base station can receive the data signal.

In particular, according to the third invention, the notifying means, the comparing means, and the transmitting means are performed during random access communication. Therefore, data signals can be collected at the initial stage of communication between the terminal and the base station. This makes it possible to further reduce the delay.

In particular, according to the fourth invention, the multislot transmission means transmits data signals possessed by each multislot terminal to the base station using transmission power corresponding to the multislot. Therefore, data signals are transmitted using different transmission power for each multi-slot terminal, and it is possible to minimize reception power adjustment necessary for receiving data signals at the base station. This makes it possible to suppress an increase in the packet error rate that accompanies a drop in transmission power.

In particular, according to the fifth aspect, the assigning means preferentially assigns a terminal having a low set delay tolerance among a plurality of terminals classified by class as a multi-slot terminal. Therefore, it is possible to easily set the priority of the terminals that perform data transmission. As a result, it is possible to further suppress the delay occurring in the entire plurality of terminals.

FIG. 1 is a schematic diagram showing an example of an overview of a wireless communication system according to an embodiment. FIG. 2(a) is a schematic diagram showing an example of the configuration of a radio frame, and FIG. 2(b) is a schematic diagram showing a state in which a plurality of terminal signals are superimposed. FIG. 3 is a schematic diagram showing an example of configurations included in a base station and a terminal. FIG. 4(a) is a flowchart showing an example of the operation of the radio communication system according to the embodiment, and FIG. 4(b) is a timing chart showing an example of the operation in the base station and terminal. FIG. 5(a) is a flow chart showing an example of information confirmation means, and FIG. 5(b) is a schematic diagram showing an example of information confirmation means. FIG. 6(a) is a flowchart showing an example of normal signal transmission means, and FIGS. 6(b) and 6(c) are schematic diagrams showing an example of terminal numbers and delay tolerance values stored in a storage unit. is. FIGS. 7A and 7B are schematic diagrams showing a first modification of terminal numbers and delay tolerances stored in the storage unit. FIG. 8 is a flowchart showing another example of normal signal transmission means. FIG. 9 is a schematic diagram showing another example of the normal signal transmission means. FIG. 10(a) is a schematic diagram showing an example of received power classified for each class, and FIG. 10(b) is a schematic diagram showing an example of a multi-slot terminal classified for each multi-slot, FIG. 10(c) is a schematic diagram showing an example of the superimposed signal. FIG. 11(a) is a schematic diagram showing another example of multi-slot terminals classified for each multi-slot, and FIG. 11(b) is a schematic diagram showing another example of superimposed signals. FIG. 12(a) is a flow chart showing still another example of the normal signal transmission means, and FIGS. It is a schematic diagram which shows a modification. FIGS. 13(a) and 13(b) are schematic diagrams showing a third modification of the terminal numbers and delay tolerances stored in the storage unit.

(Embodiment: Wireless Communication System 100)
The wireless communication system 100 as an embodiment of the present invention will be described in detail below. FIG. 1 is a schematic diagram showing an example of an outline of a wireless communication system 100 according to this embodiment.

A wireless communication system 100 includes a base station 1 . In the wireless communication system 100, a base station 1 mainly uses non-orthogonal multiple access (NOMA: Non-Orthogonal Multiple Access) to connect a plurality of terminals 2 (2-1, 2-2, 2-3, 2-3 in FIG. 1, 2-4, 2-5) transmitted from terminal signals D (D-1, D-2, D-3, D-4, D-5 in FIG. 1) are collected.

The base station 1 establishes a connection with the terminal 2 by, for example, transmitting a signal for enabling communication to the terminal 2 in advance. The base station 1 can allocate one radio resource to a plurality of (for example, five) terminals 2 and share the radio resource of the terminal signal D transmitted from each terminal 2 .

As the terminal 2, for example, a device having a wireless communication function called an IoT (Internet of Things) device is used. For example, a wearable terminal, a connected car, a sensor terminal, a drone, or the like is used. is used. When transmitting the terminal signal D from the terminal 2 to the base station 1, for example, random access communication for obtaining a grant is used, for example, semi-persistent communication for periodically transmitting an uplink signal, and GF (Grant Free) Communication or the like is used.

A delay tolerance value is set in advance for each terminal 2 . The allowable delay value indicates a delay time allowable when transmitting the data signal DS included in the terminal signal D to the base station 1 by a numerical value. For example, when the delay tolerance is small, it is necessary to transmit the data signal DS in a short period of time, and as the delay tolerance increases, the period during which the data signal DS is transmitted can be lengthened. The allowable delay value can be set according to, for example, the terminal type and environment of each terminal 2 . By setting the delay tolerance value, the priority of transmitting the data signal DS in each terminal 2 can be easily controlled. In the wireless communication system 100, transmission of the data signal DS in the entire terminal 2 is performed within the delay tolerance value set for each terminal 2, thereby achieving low delay.

The wireless communication system 100 transmits data signals DS generated from some terminals 2 among a plurality of terminals 2 to a base station 1 from some terminals 2 based on a delay tolerance set in advance for each terminal 2. It can be superimposed and transmitted. Therefore, it is possible to preferentially transmit the data signal DS from the terminal 2 that cannot tolerate delay, and suppress the delay that occurs in all of the plurality of terminals 2 . This makes it possible to achieve both multiple connections and low delay.

In the radio communication system 100, for example, as shown in FIG. 2(a), a time division duplex (TDD) can be used as a duplex method. In FIG. 2( a ), the configuration of the radio frame is 10 sub-frames (Sub-Frame) for 1 frame (Frame) of 10 ms, and the ratio of downlink (DL) and uplink (UL) A case of 2:8 is shown. Each component and value can be set arbitrarily. Moreover, in the wireless communication system 100, frequency division duplex (FDD) may be used in addition to the above-described time division duplex.

An uplink subframe is composed of, for example, a reference signal RS (reference signal) and a data signal DS (data signal). That is, the terminal signal D transmitted from each terminal 2 can contain the reference signal RS and the data signal DS.

The reference signal RS contains an identification signal and is used for identification of the terminal 2 and channel estimation. For the reference signal RS, for example, a sequence obtained by extending Zadoff-chu is used, and is different for each terminal 2 on the frequency axis so that a plurality of terminal signals D multiplexed by non-orthogonal multiple access can be separated. A phase rotation (cyclic shift on the time axis) is given.

The data signal DS includes a data body (payload) and indicates various information acquired by the terminal 2, for example. The data signal DS includes, for example, the speed of a traveling vehicle, the temperature monitored by a sensor, etc., and is arbitrarily set according to the application and the type of the terminal 2 .

Note that the reference signal RS and data signal DS may include, for example, cyclic prefix CP and guard time GT. Also, the order, data length, and number (frequency) in which the reference signal RS and the data signal DS are arranged on the time axis are arbitrary.

The base station 1 acquires a plurality of terminal signals D. The base station 1 receives a signal (superimposed signal DC) in which a plurality of terminal signals D sharing the same time and the same frequency are superimposed, as shown in FIG. 2(b), for example. The number of terminal signals D to be superimposed can be arbitrarily set. The base station 1 separates a plurality of terminal signals D included in the superimposed signal DC and acquires a plurality of data signals DS (decoding processing). This allows large amounts of data to be transmitted at the same time and at the same frequency.

The base station 1 acquires the channel estimation value from the reference signal RS included in the superimposed signal DC, for example. The base station 1 separates the data signal DS included in the superimposed signal DC using the acquired channel estimation value. Algorithms for separation include known techniques such as Parallel Interference Cancellation (PIC) and Successive Interference Cancellation (SIC).

Note that in the radio communication system 100, the number of terminals 2 that are simultaneously connected may be increased by using frequency division multiplexing and space division multiplexing, for example.

Next, configurations of the base station 1 and the terminal 2 will be described. FIG. 3 is a schematic diagram showing an example of configurations included in the base station 1 and the terminal 2. As shown in FIG.

<Base station 1>
The base station 1 has a control unit 11, a transmission/reception unit 12, a storage unit 13, and may have a calculation unit 14, for example. Each configuration is connected by an internal bus.

The control unit 11 controls operations related to transmission and reception of information (signals) in the base station 1 . The control unit 11 separates the superimposed signals DC and obtains a plurality of data signals DS. A processor such as a CPU (Central Processing Unit) is used as the control unit 11 .

The transmitting/receiving unit 12 communicates with a plurality of terminals 2 via wireless communication. The transmitting/receiving unit 12 uses, for example, an antenna to transmit/receive various types of information to/from a plurality of terminals 2 (arrows in FIG. 3).

The storage unit 13 stores terminal signals D and the like received from the plurality of terminals 2 . As the storage unit 13, for example, a known data storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive) is used. The storage unit 13 includes, for example, RAM (Random Access Memory) and ROM (Read Only Memory), and stores programs and the like executed by the base station 1 . Each function executed by the base station 1 can be realized by the control unit 11 executing a program stored in the storage unit 13 using the RAM as a work area.

The calculator 14 calculates, for example, the number of terminal signals D to be superimposed. The calculation unit 14 calculates the timing for transmitting the terminal signal D suitable for each terminal 2 based on, for example, the delay tolerance value set for each terminal 2 . The calculator 14 calculates, for example, a specified delay value G for transmission to a plurality of terminals 2 . The delay specification G can be compared with the delay tolerance and is used to prioritize terminals 2 transmitting data signals DS.

<Terminal 2>
The terminal 2 has a control unit 21, a transmission/reception unit 22, a storage unit 23, and may have a calculation unit 24, for example. Each configuration is connected by an internal bus.

The control unit 21 controls operations related to transmission and reception of information in the terminal 2 . A processor such as a CPU is used as the control unit 21, for example.

The transmitter/receiver 22 communicates with the base station 1 via wireless communication. The transmitting/receiving unit 22 transmits/receives various information to/from the base station 1 using, for example, an antenna.

The storage unit 23 stores the delay tolerance set for each terminal 2, various information received from the base station 1, and the like. As the storage unit 23, for example, in addition to the HDD, a known data storage device such as an SSD is used. The storage unit 23 includes, for example, RAM and ROM, and stores programs and the like executed by the terminal 2 . Each function executed by the terminal 2 can be realized by the control unit 21 executing a program stored in the storage unit 23 using the RAM as a work area.

The calculator 24 compares, for example, the specified delay value G received from the base station 1 and the allowable delay value, and selects the content of the signal to be transmitted to the base station 1 .

(Embodiment: Operation of wireless communication system 100)
Next, the operation of the wireless communication system 100 according to this embodiment will be described. FIG. 4(a) is a flowchart showing an example of the operation of the radio communication system 100 according to this embodiment, and FIG. 4(b) is a schematic diagram showing an example of the operation of the radio communication system 100 according to this embodiment. .

The radio communication system 100 comprises, for example, transmitting/receiving means S110, as shown in FIG. 4, and may comprise post means S140, for example.

<transmitting/receiving means S110>
The transmitting/receiving means S110 receives data signals DS generated from some terminals 2 out of the plurality of terminals 2 based on a delay tolerance set in advance for each of the plurality of terminals 2, as shown in FIG. 4(a), for example. are superimposed and transmitted from some terminals 2 to the base station 1 . Therefore, it is possible to preferentially transmit the data signal DS from the terminal 2 that cannot tolerate delay, and suppress the delay that occurs in all of the plurality of terminals 2 . As a result, the number of terminals 2 that retransmit the data signal DS can be reduced, for example, in post-processing S140, which will be described later.

The transmitting/receiving means S110 includes, for example, as shown in FIG. 4(b), information existence confirmation means S120 and normal signal transmitting means S130.

<Existing information confirmation means S120>
The available information confirmation means S120 transmits broadcast information (Broadcast Information) including system information, coding method, etc. from the base station 1 to each terminal 2. FIG. Each terminal 2 can grasp the basic parameters of the system by receiving the broadcast information. The existence information confirmation means S120 uses, for example, a random access method, and this period is defined as the time of random access communication.

Further, the information existence confirmation means S120 transmits an information existence confirmation signal (Payload Confirmation) from the base station 1 to each terminal 2. FIG. The information existence confirmation signal is a signal for confirming whether or not each terminal 2 has a data signal DS to be transmitted. It is a signal to give instructions not to

Of the terminals 2 that have received the information confirmation signal, the terminal 2 that has the data signal DS to be transmitted transmits a information confirmation response (Payload Confirmation Response) signal from the terminal 2 to the base station to notify that it has the data signal DS. Send to station 1. The information-bearing acknowledgment signal includes the reference signal RS and is transmitted by a random access method. This allows the base station 1 to recognize the terminal 2 having the data signal DS to be transmitted.

For example, as shown in FIG. 5(a), the existence information confirmation means S120 may include notification means S121, comparison means S122, and transmission means S123.

<<notifying means S121>>
The notification means S121 transmits notification information including the specified delay value G from the base station 1 to each terminal 2. FIG. In addition to calculating the specified delay value G based on the communication environment and the like, the calculation unit 14 may acquire the specified delay value G stored in advance in the storage unit 13, for example. The base station 1 transmits notification information to each terminal 2 via the transmission/reception unit 12 . Each terminal 2 receives the notification information via the transmitter/receiver 22 .

<<comparing means S122>>
Next, the comparing means S122 compares the specified delay value G and the allowable delay value for each of the plurality of terminals 2. FIG. The calculation unit 24 acquires the specified delay value G included in the notification information, and acquires the allowable delay value stored in the storage unit 23, for example. For example, as shown in FIG. 5B, the calculator 24 compares the delay specified value G and the delay allowable value. Comparison results include a case where the allowable delay value is higher than the specified delay value G (first result) and a case where the allowable delay value is equal to or less than the specified delay value G (second result). Note that, for example, the first result may have a delay tolerance value equal to or greater than the specified delay value G, and in this case, the second result may have a delay tolerance value smaller than the specified delay value G.

<<transmitting means S123>>
Next, the transmitting means S123 transmits to the base station 1 an information acknowledgment signal including the reference signal RS from the terminal 2 (first terminal) from which the first result is obtained. Further, the transmitting means S123 transmits to the base station 1 an information confirmation signal including the reference signal RS and the data signal DS from the terminal 2 (second terminal) from which the second result is obtained. That is, the first terminal transmits an information confirmation signal that does not contain the data signal DS. Therefore, the number of data signals DS to be preferentially transmitted can be adjusted by the specified delay value G according to the situation.

The transmitting means S123 transmits the information confirmation response signal during random access communication. Therefore, the data signal DS can be collected at the initial stage of communication between the terminal 2 and the base station 1 . In addition, since the number of terminals 2 that can transmit the data signal DS can be limited, it is possible to increase the probability that the data signal DS can be separated.

<Normal Signal Transmission Means S130>
The normal signal transmission means S130, for example, as shown in FIG. Send to The instruction signal is a signal for allocating radio resources to the terminal 2 . For example, the calculation unit 14 of the base station 1 generates an instruction signal based on the reference signal RS included in the information confirmation response signal, and transmits the instruction signal to the terminal 2 via the transmission/reception unit 12 . At this time, for example, a different instruction signal is generated for each reference signal RS.

Next, the terminal 2 that has received the instruction signal transmits a normal payload (terminal signal D) while sharing radio resources with a plurality of other terminals 2 (NOMA transmission). Thereby, the base station 1 receives a superimposed signal DC in which a plurality of terminal signals D are superimposed. For example, the control unit 21 of the terminal 2 controls various conditions such as transmission power for transmitting the terminal signal D based on the instruction signal, and transmits the terminal signal D via the transmitting/receiving unit 22 .

After that, the terminal 2 may not require the random access scheme, but may change the radio resource based on the instruction signal transmitted from the base station 1 .

The normal signal transmission means S130 may have a calculation means S131 and an instruction signal transmission means S132, for example, as shown in FIG. 6(a).

<<calculation means S131>>
The calculation means S131 calculates the number of superimposed terminal signals D including the data signal DS based on the number of terminals 2 and the delay tolerance set for each of the terminals 2 . In the storage unit 13 of the base station 1, for example, as shown in FIG. 6(b), the number of terminals 2 and the allowable delay value set for each of the terminals 2 are stored in advance. The base station 1 may acquire at least one of the number of terminals 2 and the allowable delay value based on the information confirmation response signal acquired by the information confirmation means S120, for example. In this case, the information confirmation response signal is transmitted from the terminal 2 to the base station 1 in a state in which the delay tolerance value set in the terminal 2 is included.

The calculation unit 14 of the base station 1 calculates the number of superimposed terminal signals D (the number of superimpositions Fa), for example, using a preset arbitrary specified value T. FIG. The calculation unit 14 calculates the superposition number Fa according to the result of comparing the allowable delay values of all the terminals 2 and the specified value T. FIG.

For the specified value T, for example, the time required for retransmission control in post-processing S140, which will be described later, is set. At this time, if the delay tolerance is T or more, even if the transmission fails and retransmission is executed, the delay tolerance can be kept within the range. That is, since there is a margin in the delay tolerance value, the calculation unit 14 calculates so as to increase the superposition number Fa. On the other hand, when the delay tolerance is less than T, if the transmission fails and retransmission is executed, the delay tolerance is out of range, and packet loss or the like may occur. That is, since there is no margin in the delay tolerance, the calculation unit 14 calculates so as to reduce the number of overlaps Fa so as to improve the block error rate (BLER).

For example, when the delay tolerance values of all terminals 2 are equal to or greater than the specified value T (third result), the calculation unit 14 calculates the maximum multiplex number F in non-orthogonal multiple access of the radio communication system 100 as the superimposition number Fa. In the third result, since there is a margin in the allowable delay value, it is possible to control so as to maximize the superposition number Fa and increase the throughput. This makes it possible to positively utilize retransmission control and realize a state in which efficient transmission is possible. Also, by maintaining a high throughput, it is possible to prepare surplus resources that can be used when, for example, high reliability and low delay communication conditions are required.

On the other hand, for example, when there is a terminal 2 for which a delay tolerance value less than the specified value T is set (fourth result), the calculation unit 14 calculates the number of overlaps Fa based on [Formula 1]. Here, D _num (t) indicates the number of terminals 2 whose delay tolerance is t. However, when the delay tolerance value t is 0, in order to avoid the occurrence of terminal 2 that suffers packet loss without transmitting as much as possible, under the condition of D _num (0)>Fa, it is calculated based on [Equation 2] .

For example, when the calculation unit 14 calculates the number of overlaps Fa based on the allowable delay value for each terminal 2 shown in FIG. Calculated. At this time, if the terminals 2 are arranged according to the delay tolerance as shown in FIG.

<<Instruction Signal Transmission Means S132>>
The instruction signal transmitting means S132 transmits an instruction signal from the base station 1 to the target terminal 2 based on the calculated number of superimposed terminal signals D of the terminal 2 (superimposition number Fa). The control unit 11 selects terminals 2 corresponding to the number of superimposed numbers Fa calculated by the calculation unit 14 in descending order of the delay tolerance value, and transmits an instruction signal to the selected terminals 2 . For example, in FIG. 6(c), when the superposition number Fa=3, in addition to the terminals 2-2 and 2-4 whose delay tolerance is 0, the terminal 2-9 whose delay tolerance is 1 is selected. Instruction signals are transmitted to the terminals 2-2, 2-4 and 2-9. Note that the terminal 2-1 may be selected instead of the terminal 2-9, but in either case, the terminals 2 are selected in descending order of delay tolerance.

After the instruction signal is transmitted, for example, as shown in FIG. 7, the allowable delay value is decreased by one compared to before the transmission of the instruction signal, and selection of the terminal 2 and transmission of the instruction signal are performed again in the same manner as described above. Transmission may be performed. At this time, for example, after adding new candidates for transmitting instruction signals (terminals 2-19 and 2-20 in FIG. 7), the calculation unit 14 calculates (updates) the superposition number Fa. The instruction signal may be transmitted to the target terminal 2 without changing the number Fa.

By performing the above-described calculation unit S131, it is possible to further suppress the delay occurring in all of the plurality of terminals 2. FIG. For example, when non-orthogonal multiple access is used, there may be a concern about the trade-off relationship between the number of overlaps Fa and the error rate. Even in such a case, by performing the calculation unit S131, it is possible to calculate the optimal superposition number Fa according to the situation. That is, the calculation unit S131 can update the superimposition number Fa for each frame according to the number of terminals 2 and the allowable delay value change with time. This makes it possible to easily realize both multiple connections and low delay.

The normal signal transmitting means S130 may comprise, for example, as shown in FIG. 8, a classifying means S133, an allocating means S134, and a multi-slot transmitting means S135. Classification means S133 has class classification means S133a, for example.

<<class classification means S133a>>
When various signals are transmitted from the terminal 2 to the base station 1, the class classification means S133a classifies the terminal 2 into the class CL according to the reachable transmission power. For example, as shown in FIG. 9, the control unit 11 classifies each terminal 2 into the 0th class CL0 to the 5th class CL5 based on the information confirmation response signal. The control unit 11 classifies each terminal 2 into a class CL based on, for example, the reception power of the information confirmation response signal. Note that the number of classes CL to be classified is arbitrary. The control unit 11 controls, for example, the transmission power that can be transmitted by the terminal 2, the type of the terminal 2, the distance between the terminal 2 and the base station 1, the terrain where the terminal 2 is provided, short-term fluctuations (shadowing), and instantaneous Each terminal 2 may be classified into class CL based on at least one of value fluctuations (Rayleigh fading, etc.).

In the classifying means S133a, for example, as shown in FIG. 10(a), the control unit 11 may classify into six levels of classes CL according to the received power at the base station 1. FIG. For example, if the received power is less than a specified value, there is a possibility that the signal to noise power ratio (SNR) is not satisfied, so the target terminal 2 is classified into the 0th class CL0, and various signals are transmitted. may be disallowed.

<<classifying means S133>>
The classifying means S133 classifies the range of transmission power for transmitting the terminal signal D from the terminal 2 to the base station 1 into a plurality of multiplex slots. The control unit 11 sets, for example, transmission power corresponding to each classified class CL. In this case, multiplexed slots with different transmission power ranges are classified for each class CL. For example, FIG. 10(b) shows a case where the superposition number Fa is 5, and five multiplexed slots are classified.

<<allocation unit S134>>
The allocating means S134 allocates from a plurality of terminals 2 to one corresponding terminal 2 (multi-slot terminal 2s) for every plurality of multi-slots. For example, the control unit 11 allocates one multi-slot terminal 2 s corresponding to each linked multi-slot from the terminals 2 classified for each class CL. In FIG. 10(b), multi-slot terminals 2s-1 to 2s-5 are assigned to five multi-slots, respectively, and terminal 2 with a low delay tolerance value is preferentially assigned as multi-slot terminal 2s. The control unit 11 transmits the instruction signal to the target terminal 2 via the transmitting/receiving unit 12, including the information of the allocation result as the multi-slot terminal 2s in the instruction signal.

For example, when there are a plurality of terminals 2 (terminals 2-2, 2-3) for which a low delay tolerance value is set in one class CL (for example, the fifth class CL5), the control unit 11 selects the low class CL (fourth Any one of a plurality of terminals 2 may be assigned as a multi-slot terminal 2s (terminal 2-3) to a multi-slot corresponding to class CL4).

<<multi-slot transmitting means S135>>
The multi-slot transmitting means S135 transmits the terminal signal D for each of the plurality of multi-slot terminals 2s to the base station 1 using the transmission power corresponding to the multi-slot. For example, as shown in FIG. 10(c), when the base station 1 acquires the superimposed signal DC, the superimposed signal DC is acquired in a state classified into a plurality of reception powers corresponding to each class CL (multiple slots). be able to.

Since the base station 1 acquires the above-described superimposed signal DC, SIC can be easily performed when separating the superimposed signal DC, and the error rate of NOMA transmission can be reduced. In addition, since each terminal 2 can transmit the terminal signal D in a state where the transmission power is kept as low as possible, it is possible to suppress the reduction in SNR caused by keeping the transmission power high.

For example, as shown in FIG. 11, the classification means S133 may classify into multiplex slots of a number smaller than the number of classes CL. In this case, the terminal signal D of the terminal 2 (multi-slot terminal 2s) having a low delay tolerance value can be preferentially transmitted to the base station 1. FIG.

Further, for example, as shown in FIGS. 12 and 13, the above calculation means S131 and class classification means S133a may be combined. This makes it possible to easily realize both multiple connections and low delay, and to easily implement SIC when separating the superimposed signal DC.

<Post-facto means S140>
In post-means S140, for example, the controller 11 of the base station 1 separates (decodes) the received superimposed signal DC. The control unit 11 generates response information (ACK/NACK) based on the decoded signal, and transmits it to the target terminal 2 via the transmission/reception unit 12 . Also, when there is an error in the received signal and retransmission is necessary, a retransmission control indicator signal is transmitted to the target terminal 2 .

The terminal 2 that has received the retransmission control instruction signal transmits retransmission control information (terminal signal D) to the base station 1 . At this time, NOMA transmission is used similarly to the normal signal transmitting means S130, and a superimposed signal DC in which a plurality of terminal signals D are superimposed is transmitted. The controller 11 of the base station 1 decodes the received superimposed signal DC. The control unit 11 generates response information (ACK/NACK) based on the decoded signal, and transmits it to the target terminal 2 via the transmission/reception unit 12 . After that, the retransmission control instruction may be transmitted again to the target terminal 2 as necessary.

By performing the operations described above, the operation of the wireless communication system 100 in the present embodiment ends. In addition, the order of each means mentioned above is an example, and you may implement so that one means may be repeated multiple times, for example.

According to this embodiment, the transmitting/receiving means S110 superimposes and transmits the data signal DS from some terminals 2 to the base station 1 based on the allowable delay value. Therefore, it is possible to preferentially transmit the data signal DS from the terminal 2 that cannot tolerate delay, and suppress the delay that occurs in all of the plurality of terminals 2 . This makes it possible to achieve both multiple connections and low delay.

Further, according to this embodiment, the notification means S121 transmits notification information from the base station 1 to the plurality of terminals 2. FIG. Further, the transmission unit S123 transmits the reference signal RS and the data signal DS to the base station 1 from the terminal 2 (second terminal) for which the delay tolerance value equal to or less than the specified delay value G is set. Therefore, the number of data signals DS to be preferentially transmitted can be adjusted by the specified delay value G according to the situation. This makes it possible to increase the probability that the base station 1 can receive the data signal DS.

Further, according to this embodiment, the transmitting means S123 is performed at the time of random access. Therefore, the data signal DS can be collected at the initial stage of communication between the terminal 2 and the base station 1 . This makes it possible to further reduce the delay.

Further, according to this embodiment, the multislot transmitting means S135 transmits the data signal DS of each of the plurality of multislot terminals 2s to the base station 1 using the transmission power corresponding to the multislot. Therefore, the data signal DS is transmitted using different transmission power for each multi-slot terminal 2s, and the reception power adjustment necessary for receiving the data signal DS at the base station 1 can be minimized. This makes it possible to suppress an increase in the packet error rate BLER due to a decrease in transmission power. In particular, SIC can be easily implemented when separating the superimposed signal DC, and the error rate of NOMA transmission can be reduced.

Further, according to the present embodiment, the assigning unit S134 preferentially assigns a terminal 2 having a low set delay tolerance among a plurality of terminals 2 classified by class CL as a multi-slot terminal 2s. Therefore, it is possible to easily set the priority of the terminal 2 that performs data transmission. As a result, it is possible to further suppress the delay occurring in the entirety of the plurality of terminals 2 .

Further, according to the present embodiment, the calculating means S131 calculates the number of superimposed data signals DS based on the number of terminals 2 and the allowable delay value. Therefore, it is possible to further suppress the delay that occurs in all of the plurality of terminals 2 . This makes it possible to easily realize both multiple connections and low delay.

1: base station 2: terminal 2s: multi-slot terminal 11: control unit 12: transmission/reception unit 13: storage unit 14: calculation unit 21: control unit 22: transmission/reception unit 23: storage unit 24: calculation unit 100: wireless communication system D : Terminal signal DC : Superimposed signal DS : Data signal G : Delay specified value RS : Reference signal S110 : Transmitting/receiving means S120 : Presence information confirming means S121 : Reporting means S122 : Comparing means S123 : Transmitting means S130 : Normal signal transmitting means S131 : Calculation means S132: Instruction signal transmission means S133: Classification means S133a: Classification means S134: Allocation means S135: Multi-slot transmission means S140: Post-processing means

Claims (5)

A wireless communication system that collects data signals from multiple terminals using non-orthogonal multiple access,
Based on a delay tolerance set in advance for each of the plurality of terminals, the data signal generated from some of the terminals among the plurality of terminals is superimposed and transmitted from some of the terminals to a base station. comprising transmitting and receiving means ,
The wireless communication , wherein the transmitting/receiving means comprises calculating means for calculating the number of superimposed data signals based on the number of the plurality of terminals and the allowable delay value set for each terminal. system. The transmitting/receiving means is
annunciation means for transmitting annunciation information including a specified delay value from the base station to the plurality of terminals ;
comparison means for comparing the specified delay value and the allowable delay value for each terminal;
A reference signal is transmitted to the base station from the first terminal set with the allowable delay value higher than the specified delay value, and from the second terminal set with the allowable delay value equal to or less than the specified delay value, the 2. The wireless communication system according to claim 1, further comprising transmitting means for transmitting the reference signal and the data signal to the base station. 3. The radio communication system according to claim 2, wherein said transmitting means is performed during random access communication. The transmitting/receiving means is
Classifying means for classifying a transmission power range for transmitting the data signal from the terminal to the base station into a plurality of multiplex slots;
allocation means for allocating each of the multiple slots to one multi-slot terminal from the plurality of terminals ;
and multi-slot transmission means for transmitting the data signal possessed by each multi-slot terminal to the base station using the transmission power corresponding to the multi-slot. 1. The wireless communication system according to claim 1. The classification means classifies the plurality of terminals based on at least one of a transmission power that the terminal can transmit, a type of the terminal, a distance between the terminal and the base station, and a topography where the terminal is provided. has classifying means for classifying into a plurality of classes,
The allocating means has a function of giving priority to a terminal having a low delay tolerance value set among a plurality of the terminals classified for each class, and allocating the terminal as the multi-slot terminal. Item 5. The wireless communication system according to item 4.

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