WO2025022631A1 - Terminal device, base station device, and communication system - Google Patents

Abstract

This terminal device comprises: a measurement unit that measures the reception power of a signal from a base station device; a reception unit that receives threshold value information including a threshold value; and a control unit that calculates an offset value according to reference transmission power used as a reference in the calculation of the threshold value and maximum transmission power, calculates an adjusted threshold value obtained by adding the offset value to the threshold value, and controls the number of times of repeated transmission and transmission power of a first message to be transmitted at the start of a wireless connection according to the reception power and the adjusted threshold value.

Description

Terminal device, base station device, and communication system

The present invention relates to a terminal device, a base station device, and a communication system.

In today's networks, traffic from mobile devices (e.g., smartphones and feature phones) accounts for the majority of wireless resources. Furthermore, the traffic used by mobile devices is expected to continue to expand in the future.

In addition to traffic used by mobile devices, IoT (Internet of things) services are being developed for use in, for example, transportation systems, smart meters, and monitoring systems for devices. For this reason, networks are being required to support services with diverse requirements. In order to accommodate such diverse services, the 5th generation mobile communications (5G or NR (New Radio)) communication standards (e.g., non-patent documents 11 to 28) are being formulated to support many use cases classified as eMBB (Enhanced Mobile Broadband), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communication) in addition to the standard technologies of 4G (4th generation mobile communications) (e.g., non-patent documents 1 to 10).

In addition, the working group of the international standardization project, the 3rd Generation Partnership Project (3GPP (registered trademark): 3rd Generation Partnership Project) is continuously studying and standardizing the extension technologies for the above communication standards.

In 3GPP, uplink synchronization is established, for example, by executing a random access procedure. Random access procedures include, for example, a contention-based random access procedure (CBRA: Contention Based Random Access) and a contention-free random access procedure (CFRA: Contention Free Random Access). In addition, random access procedures include, for example, a two-step random access procedure and a four-step random access procedure (Non-Patent Document 6 or 21).

The 3GPP working group is studying a technology for repeat transmission of the Physical Random Access Channel (PRACH) in terminal devices in order to improve the success rate of PRACH reception in base station devices during random access procedures.

Technologies related to random access procedures are described, for example, in the following documents:

3GPP TS 36.133 V17.10.0 3GPP TS 36.211 V17.3.0 3GPP TS 36.212 V17.1.0 3GPP TS 36.213 V17.5.0 3GPP TS 36.214 V17.0.0 3GPP TS 36.300 V17.4.0 3GPP TS 36.321 V17.5.0 3GPP TS 36.322 V17.0.0 3GPP TS 36.323 V17.2.0 3GPP TS 36.331 V17.4.0 3GPP TS 37.324 V17.0.0 3GPP TS 37.340 V17.5.0 3GPP TS 38.133 V17.10.0 3GPP TS 38.201 V17.0.0 3GPP TS 38.202 V17.3.0 3GPP TS 38.211 V17.5.0 3GPP TS 38.212 V17.5.0 3GPP TS 38.213 V17.6.0 3GPP TS 38.214 V17.6.0 3GPP TS 38.215 V17.3.0 3GPP TS 38.300 V17.5.0 3GPP TS 38.321 V17.5.0 3GPP TS 38.322 V17.3.0 3GPP TS 38.323 V17.5.0 3GPP TS 38.331 V17.5.0 3GPP TS 38.420 V17.2.0 3GPP TS 38.423 V17.5.0 R1-2306069

However, the details of repeated transmission of PRACH in a terminal device have not been determined. For example, if the number of repetitions is increased, a corresponding amount of radio resources will be required, and the utilization efficiency of radio resources will decrease. For example, if there is capacity to increase the transmission power of the terminal device, it may be possible to achieve a PRACH reception success rate equivalent to that of repeated transmission while suppressing the decrease in utilization efficiency of radio resources by increasing the transmission power of the terminal device without increasing the number of repetitions. However, a control method that takes into account the relationship between radio resource efficiency and the PRACH reception success rate has not been determined for repeated transmission of PRACH in a terminal device in this way.

Therefore, one disclosure provides a terminal device, a base station device, and a communication system that perform PRACH repeated transmission processing that efficiently uses radio resources.

The device has a measurement unit that measures the received power of a signal from a base station device, a receiving unit that receives threshold information including a threshold, and a control unit that calculates an offset value according to a reference transmission power used as a reference in calculating the threshold and a maximum transmission power, calculates an adjustment threshold by adding the offset value to the threshold, and controls the transmission power and the number of repeated transmissions of a first message to be transmitted at the start of a wireless connection according to the received power and the adjustment threshold.

The present disclosure provides a method for performing PRACH repeated transmission processing that efficiently uses radio resources.

FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 10. FIG. 2 is a diagram showing an example of the configuration of the base station device 200. As shown in FIG. FIG. 3 is a diagram illustrating an example of the configuration of the terminal device 100. FIG. 4 is a diagram illustrating an example of a first method of PRACH transmission control processing. FIG. 5 is a diagram illustrating an example of a second method of PRACH transmission control processing. FIG. 6 is a diagram illustrating an example of a third method of PRACH transmission control processing. FIG. 7 is a diagram showing an example of the received power at the base station device 200 in each of Case 1 and Case 2. In FIG. FIG. 8 is a diagram illustrating an example of a fourth method of PRACH transmission control processing.

[First embodiment]
A first embodiment will be described.

<Regarding wireless communication system 10>
FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 10. The wireless communication system 10 has a base station device 200 and terminal devices 100-1 and 100-2. The wireless communication system 10 is a system that controls the transmission power and the number of repeated transmissions of the PRACH used in the random access procedure based on, for example, the received power of radio waves measured by the terminal devices 100-1 and 100-2. Repeated transmission of the PRACH means, for example, that the terminal device 100-1 and/or the terminal device 100-2 transmit the same preamble a certain number of times. Here, the certain number of times may be at least any value of 2, 4, or 8. The base station device 200 may notify the terminal device 100-1 and/or the terminal device 100-2 of the resources used for repeated transmission of the PRACH. The terminal device 100-1 and/or the terminal device 100-2 may perform repeated transmission of the PRACH using a part or all of the resources used for repeated transmission of the PRACH notified by the base station device 200. A part or all of the PRACH included in the repeated transmission of the PRACH may be transmitted using different resources in the time domain. The base station device 200 can obtain a gain by receiving a part or all of the PRACH transmitted by the repeated transmission of the PRACH from the terminal device 100-1 and/or the terminal device 100-2 and combining (Soft combine). The repeated transmission of the PRACH may be referred to as multiple PRACH transmissions. The number of repetitions may be the number of repetitions of the repeated transmission of the PRACH. Unless otherwise specified, the repeated transmission may be the repeated transmission of the PRACH.

The terminal devices 100-1 and 2 (hereinafter sometimes referred to as terminal devices 100) are communication devices that wirelessly connect to the base station device 200 and transmit and receive data (wireless communication), and are, for example, smartphones or tablet terminals. When the terminal device 100 wirelessly connects to the base station device 200, it executes a random access procedure. In the random access procedure, the terminal device 100 transmits a PRACH to the base station device 200. The number of repeated transmissions of the PRACH and the transmission power are determined by the control of the base station device 200 and/or path loss. The terminal device 100 may determine the number of repeated transmissions of the PRACH and the transmission power according to the received power of the signal from the base station device 200 under the control of the base station device 200.

The base station device 200 is a device that is wirelessly connected to the terminal device 100 and performs wireless communication, and is, for example, an eNodeB (eNB) or a gNodeB (gNB). The base station device 200 controls the transmission power and the number of repeated transmissions of the PRACH transmitted by the terminal device 100.

The base station device 200 forms a cell within which communication with the terminal device 100 is possible. In FIG. 1, the base station device 200 forms communication ranges C1 to C3 in one or more cells. The communication range may be referred to as coverage. The communication ranges C1 to C3 indicate the ranges within which wireless connection is possible (assumed to be successful) using the random access procedure of the terminal device 100. The boundaries of each communication range are set, for example, by the reception power of the signal from the base station device 200 at the terminal device 100. The reception power of the terminal device 100 located within each communication range is X or more for communication range C1, Y or more for communication range C2, and Z or more for communication range C3. As a specific example, the communication range C1 is a range in which a terminal device 100 with a reception power of -100 dBm or more can wirelessly connect, the communication range C2 is a range in which a terminal device 100 with a reception power of -103 dBm or more can wirelessly connect, and the communication range C3 is a range in which a terminal device 100 with a reception power of -106 dBm or more can wirelessly connect. The base station device 200 configures the communication range assuming the reception power at the terminal device 100, and controls the number of repeated transmissions of the PRACH and the transmission power depending on which communication range the terminal device 100 is located within. The reception power may also be derived based on the SSB-RSRP. The communication range may also be referred to as a cell.

<Configuration example of base station device 200>
2 is a diagram showing an example of the configuration of the base station device 200. The base station device 200 includes a CPU (Central Processing Unit) 210, a storage 220, a memory 230, and a wireless communication circuit 250.

Storage 220 is an auxiliary storage device such as a flash memory, HDD (Hard Disk Drive), or SSD (Solid State Drive) that stores programs and data. Storage 220 stores a wireless communication control program 221 and a PRACH transmission control program 222.

Memory 230 is an area into which programs stored in storage 220 are loaded. Memory 230 may also be used as an area in which programs store data.

The wireless communication circuit 250 is a device that performs wireless communication with the terminal device 100. The base station device 200 transmits and receives signals (messages) to and from the terminal device 100 via the wireless communication circuit 250.

The CPU 210 is a processor that loads the programs stored in the storage 220 into the memory 230, executes the loaded programs, configures each component, and realizes each process.

The CPU 210 executes the wireless communication control program 221 to construct a notification section and a base station control section, and to perform wireless communication control processing. The wireless communication control processing is processing for controlling wireless communication with the terminal device 100. In the wireless communication control processing, the base station device 200 wirelessly connects to the terminal device 100 and transmits and receives signals (messages).

The CPU 210 executes the PRACH transmission control program 222 to construct a notification unit and a base station control unit, and performs PRACH transmission control processing. The PRACH transmission control processing is processing for controlling the transmission power (transmission output) and the number of repeated transmissions when the terminal device 100 transmits a PRACH of a random access procedure. In the PRACH transmission control processing, the base station device 200 transmits a threshold value of the reception power of the terminal device 100, which is used to determine the transmission power and the number of repeated transmissions of the terminal device 100.

<Configuration example of terminal device 100>
3 is a diagram illustrating an example of the configuration of the terminal device 100. The terminal device 100 includes a CPU 110, a storage 120, a memory 130, and a wireless communication circuit 150.

Storage 120 is an auxiliary storage device such as a flash memory, HDD, or SSD that stores programs and data. Storage 120 stores a wireless communication program 121 and a PRACH transmission program 122.

Memory 130 is an area into which programs stored in storage 120 are loaded. Memory 130 may also be used as an area in which programs store data.

The wireless communication circuit 150 is a device that performs wireless communication with the base station device 200. The terminal device 100 transmits and receives signals (messages) to and from the base station device 200 via the wireless communication circuit 150.

The CPU 110 is a processor that loads the programs stored in the storage 120 into the memory 130, executes the loaded programs, configures each component, and realizes each process.

The CPU 110 executes the wireless communication program 121 to construct a measurement unit, a receiving unit, and a control unit, and to perform wireless communication processing. The wireless communication processing is processing for performing wireless communication with the base station device 200. In the wireless communication processing, the terminal device 100 wirelessly connects to the base station device 200 and transmits and receives signals (messages). In the wireless communication processing, the terminal device 100 receives, for example, a synchronization signal transmitted by the base station device 200, and measures the received power.

The CPU 110 executes the PRACH transmission program 122 to construct a receiver and a controller, and performs PRACH transmission processing. The PRACH transmission processing is a process for transmitting a PRACH to the base station device 200 when executing a random access procedure. In the PRACH transmission processing, the terminal device 100 determines the transmission power of the PRACH and the number of repeated transmissions under the control of the base station device 200.

<PRACH transmission control process>
The base station device 200 may control the transmission power and the number of repeated transmissions of the PRACH of the terminal device 100 by transmitting a threshold value of the reception power to the terminal device 100. Various methods of the PRACH transmission control process will be described below. The PRACH transmission control process is executed, for example, when the terminal device 100 transmits the PRACH once with the above-mentioned transmission power but does not reach the base station device 200 or is expected not to reach the base station device 200. In addition, the PRACH transmission control process is executed, for example, when the terminal device 100 is present within the communication area of the base station device 200.

<PRACH transmission power>
First, the PRACH transmission power and maximum transmission power that are the basis of each method of the PRACH transmission control process will be described.

The PRACH transmission power is calculated, for example, taking into consideration the maximum transmission power of the terminal device 100, the power notified from a higher layer (for example, the power required on the receiving side), and the path loss between the terminal device 100 and the base station device 200. For example, the smaller value of the maximum transmission power of the terminal device 100 or the value obtained by adding the path loss to the power notified from the higher layer is calculated as the PRACH transmission power. The calculation of the PRACH transmission power is performed, for example, by the base station device 200 or the terminal device 100.

The maximum transmission power of the terminal device 100 is the maximum value of the transmission power that the terminal device 100 can transmit, and is calculated, for example, taking into account the power class and MPR (Maximum power reduction) of the terminal device 100. For example, the maximum transmission output is calculated as the smaller value of the maximum transmission power according to the power class of the terminal device 100, or the maximum transmission power due to MPR restrictions. The calculation of the transmission power of the PRACH is performed, for example, by the base station device 200 or the terminal device 100.

<1. First method>
A first method of the PRACH transmission control process will be described. The first method is a method for determining the number of repeated transmissions using a first threshold, a second threshold, and a third threshold. The base station device 200 may notify the terminal device 100 of the first threshold, the second threshold, and the third threshold at a predetermined timing. Each threshold is notified to the terminal device 100 by, for example, a SIB (System Information Block).

FIG. 4 is a diagram showing an example of the first method of PRACH transmission control processing. In the following figures, repeated transmission is referred to as "Repetition", "None" indicates that repeated transmission is not performed (transmitted once), and "x number" indicates the number of repeated transmissions. Furthermore, the received power used in the following explanation is, for example, the received power (SSB-RSRP) of the synchronization signal transmitted by the base station device 200. Furthermore, "greater than or equal to" and "less than or equal to" used in the following explanation may be replaced with "greater than" and "less than or equal to".

The terminal device 100 may not perform repeated transmission when the received power is equal to or greater than the first threshold (range E1). Furthermore, the terminal device 100 may determine the number of repeated transmissions to be two when the received power is less than the first threshold and equal to or greater than the second threshold (range E2). Furthermore, the terminal device 100 may determine the number of repeated transmissions to be four when the received power is less than the second threshold and equal to or greater than the third threshold (range E3). Furthermore, the terminal device 100 may determine the number of repeated transmissions to be eight when the received power is less than the third threshold (range E4).

In the first method, the number of repetitions can be set according to the received power. On the other hand, in the first method, repeated transmission may be performed even if the transmission power of the PRACH of the terminal device 100 has not reached the maximum transmission power. Since repeated transmission uses more radio resources than a single transmission, the efficiency of radio resource usage may decrease.

<Second method>
A second method of the PRACH transmission control process will be described. The second method is a method of determining the number of repeated transmissions using a second threshold and a third threshold. The base station device 200 may notify the terminal device 100 of the second threshold and the third threshold without notifying the first threshold. Each threshold is notified to the terminal device 100 by, for example, an SIB. The terminal device 100 recognizes that the PRACH transmission control process is performed by the second method by not notifying the first threshold.

FIG. 5 is a diagram showing an example of the second method of PRACH transmission control processing. When the received power is equal to or greater than the second threshold (range E5), the terminal device 100 performs the following processing. Note that in the following figures, black squares indicate received power P1 in the terminal device 100-1, and white squares indicate received power P2 in the terminal device 100-2. Also, unless otherwise noted, each method will be explained using an example in which received power P1 and received power P2 are the same value.

If the transmission power of the PRACH is not the maximum transmission power, the terminal device 100 does not perform repeated transmission, and performs processing to increase the transmission power of the PRACH. For example, the terminal device 100 performs processing to increase the transmission power of the PRACH to the maximum transmission power. In addition, the terminal device 100 may, for example, increase the transmission power of the PRACH by a predetermined power, may increase it in stages, or may immediately increase it to the maximum transmission power.

On the other hand, when the transmission power of the PRACH is the maximum transmission power, the terminal device 100 may determine the number of repeated transmissions to be two. When the transmission power of the PRACH is the maximum transmission power, the terminal device 100 may determine the number of repeated transmissions to be equivalent to the range E5.

Furthermore, when the received power is less than the second threshold and greater than or equal to the third threshold (range E3), the terminal device 100 determines the number of repeated transmissions to be four.Furthermore, when the received power is less than the third threshold (range E4), the terminal device 100 determines the number of repeated transmissions to be eight.

In the second method, there are cases where it is possible to suppress a decrease in the efficiency of radio resource usage caused by repeated transmission even when the transmission power of the PRACH of the terminal device 100 has not reached the maximum transmission power. However, when the maximum transmission power of each of the multiple terminal devices 100 is different, the reception power at the base station device 200 differs for each terminal device 100 even if the number of repetitions is the same.

For example, a case will be described in which the maximum transmission power of the terminal device 100-1 is 23 dBm, the PRACH transmission power is 23 dBm, and the reception power P1 belongs to range E5, and the maximum transmission power of the terminal device 100-2 is 20 dBm, the PRACH transmission power is 20 dBm, and the reception power P2 belongs to range E5. In this case, both the terminal device 100-1 and the terminal device 100-2 determine the number of repetitions to be 2.

Because terminal device 100-1 and terminal device 100-2 have the same reception power, their distances from base station device 200 are similar and they can be assumed to be located in the same cell. Although terminal device 100-1 and terminal device 100-2 have the same number of repeated transmissions (2), their PRACH transmission powers are different, and the PRACH reception powers at base station device 200 are different, which may result in unfairness between the terminal devices, with the PRACH of terminal device 100-1 being easier to reach.

<Third Method>
The third method will be described. The third method is a method in which an offset is further considered in addition to the second method. In the third method, in order to equalize the reception power in the base station device 200, for example, in order to reduce the transmission power difference of the PRACH, the number of repetitions of the terminal device 100 with a small transmission power of the PRACH is made larger than the number of repetitions of the terminal device 100 with a large transmission power. As a result, the gain of the transmission power of the PRACH due to the increase in the number of repetitions of the terminal device with a small transmission power of the PRACH becomes large, and the reception power in the base station device 200 can be increased. The gain of the transmission power of the PRACH due to multiple transmissions may be, for example, about 3 dB for two repeated transmissions, about 6 dB for four repeated transmissions, and about 9 dB for eight repeated transmissions, as a theoretical value. Here, the gain of the transmission power of the PRACH may be the gain of the reception power after the base station device 200 receives and combines (Soft combine) the repeated transmission of the PRACH transmitted from the terminal device 100. Furthermore, the gain of the transmission power of the PRACH may be the sum of the received powers after the base station device 200 receives and soft combines the repeated transmissions of the PRACH transmitted from the terminal device 100 .

FIG. 6 is a diagram showing an example of a third method of PRACH transmission control processing. In the third method, the base station device 200 determines the second threshold and the third threshold using a certain transmission power of the terminal device 100 as a reference. This certain transmission power serving as a reference is called the reference transmission power. The reference transmission power may be the standard transmission power.

The terminal device 100 may acquire the reference transmission power, the second threshold, and the third threshold. The reference transmission power, the second threshold, and the third threshold are notified, for example, by SIB. Furthermore, the reference transmission power may be, for example, a value stored in advance by the terminal device 100, or may be a fixed value.

The terminal device 100 compares the maximum transmission power of the device with the reference transmission power and calculates an offset value. The offset value is the reference transmission power minus the maximum transmission power. The calculated offset value is added to the second and third thresholds. Processing other than adding the offset value to the thresholds is, for example, the same as in the second method. Below, the processing for each will be explained using as examples a terminal device 100-1 whose maximum transmission power and reference transmission power are the same, and a terminal device 100-2 whose maximum transmission power and reference transmission power are different. The reference transmission power is, for example, 23 dBm.

The terminal device 100-1 has a transmission power of 23 dBm and a maximum transmission power of 23 dBm. Because the maximum transmission power of the terminal device 100-1 is the same as the reference transmission power, the terminal device 100-1 calculates the offset value as 0 dB. In other words, the terminal device 100-1 uses the second threshold and the third threshold as they are.

The terminal device 100-1 determines that the number of repeated transmissions will be two, because the received power P1 is equal to or greater than the second threshold (range E5) and the transmission power is the maximum transmission power of 23 dBm.

The terminal device 100-2 has a transmission power of 20 dBm and a maximum transmission power of 20 dBm. Because the maximum transmission power of the terminal device 100-2 is 3 dB lower than the reference transmission power, the terminal device 100-2 calculates the offset value as +3 dB. Note that if the maximum transmission power is higher than the reference transmission power, the offset value will be a negative value. The terminal device 100-2 adds the offset value to the second threshold and the third threshold, and calculates the second threshold and the third threshold after the offset adjustment.

The terminal device 100-2 determines the number of repeated transmissions to be four because the received power P2 is less than the second threshold after offset adjustment and is equal to or greater than the third threshold (range E3).

In the third method, as described above, terminal device 100-1 and terminal device 100-2 have the same reception power but different maximum transmission power, and therefore different numbers of repeated PRACH transmissions. Terminal device 100-1 transmits once with a transmission power of 23 dBm (no repeated transmissions), while terminal device 100-2 transmits twice with a transmission power of 20 dBm. Terminal device 100-2 has a transmission power equivalent to 23 dBm, which is an additional 3 dB gain in transmission power due to the two transmissions, and can transmit PRACH with the same transmission power as terminal device 100-1.

In the third method, the process when the PRACH transmission power is not the maximum transmission power and the number of repeated transmissions is four or more (when the number is less than the second threshold) will be described. The process that the terminal device 100 can take is, for example, the following two cases.

Case 1: Do not repeat transmissions, but increase the PRACH transmission power (e.g., increase to maximum transmission power).

Case 2: Repeated transmissions are performed according to the threshold value with the PRACH transmission power unchanged.

Figure 7 shows examples of the received power in the base station device 200 for each of Case 1 and Case 2. As a prerequisite, the first threshold is none, the second threshold is -103 dBm, and the third threshold is -106 dBm. Furthermore, the terminal device 100-1 has a received power of -100 dBm, a PRACH transmission power of 22 dBm, and a maximum transmission power of 23 dBm. Furthermore, the terminal device 100-2 has a received power of -105 dBm, a PRACH transmission power of 27 dBm, and a maximum transmission power of 29 dBm. Furthermore, in Case 1, the terminal device 100 increases the transmission power to the maximum.

Because the received power of the terminal device 100-1 is equal to or greater than the second threshold and is not the maximum transmission power, the terminal device 100-1 increases the PRACH transmission power by +1 dB and transmits the PRACH at the maximum transmission power. In this case, the received power (estimated value or theoretical value) at the base station device 200 is -77 dBm (calculation formula: -100 + 1 + 22).

On the other hand, the terminal device 100-2 determines that the number of repeated transmissions is four because the received power is less than the second threshold and greater than or equal to the third threshold.

When processing case 1, the terminal device 100-2 does not perform repeated transmission, but increases the PRACH transmission power by +2 dB and transmits the PRACH at the maximum transmission power. In this case, the received power (estimated value or theoretical value) at the base station device 200 is -76 dBm (calculation formula: -105 + 2 + 27).

When processing case 2, the terminal device 100-2 repeats PRACH transmission four times without changing the PRACH transmission power. Because the PRACH transmission power has a gain of +6 dB due to these four repetitions, the received power (estimated value or theoretical value) at the base station device 200 in this case is -72 dBm (calculation formula: -105 + 6 + 27).

The received power of the PRACH of the terminal device 100-1 at the base station device 200 is -77 dBm, and therefore -76 dBm in case 1 is closer to the -72 dBm in case 2, so from the perspective of fairness, case 1 is preferable.

In this way, for example, the gain from transmitting four times is a large value of 6 dB, so increasing the transmission power as in case 1 may ensure greater fairness. Therefore, unless there are other specific conditions, the terminal device 100 may prioritize increasing the transmission power over repeated transmission.

Also, for example, when the maximum transmission power is large and the transmission power is a relatively small value, the gain of multiple transmissions may be smaller than the increase in transmission power. In this case, the terminal device 100 may select case 2. In this way, the terminal device 100 may calculate the reception power at the base station device 200 as shown in FIG. 7 and select case 1 or case 2.

When the terminal device 100 can obtain the transmission output, maximum transmission power, and reception power of another terminal device 100, it may calculate the reception power of the other terminal device 100 at the base station device 200 and select a case that is close to that value. Also, the base station device 200 may calculate the reception power and notify the terminal device 100 of which case to select.

<Fourth method>
The fourth method is a method in which, when the first threshold value is notified to the terminal device 100, the offset of the third method is also applied to the first threshold value.

FIG. 8 is a diagram showing an example of a fourth method of PRACH transmission control processing. In the fourth method, the base station device 200 determines the first threshold, the second threshold, and the third threshold based on the reference transmission power.

The terminal device 100 acquires the reference transmission power, the first threshold, the second threshold, and the third threshold. The reference transmission power, the first threshold, the second threshold, and the third threshold are notified, for example, by SIB. The reference transmission power may be, for example, a value stored in advance by the terminal device 100, or may be a fixed value.

The terminal device 100 compares the maximum transmission power of the device with the reference transmission power and calculates an offset value. The calculated offset value is added to the first threshold, the second threshold, and the third threshold. Processing other than adding the offset value to the thresholds is, for example, the same as in the first method. Below, the processing for each will be explained using as examples a terminal device 100-1 whose maximum transmission power and reference transmission power are the same, and a terminal device 100-2 whose maximum transmission power and reference transmission power are different. The reference transmission power is, for example, 23 dBm.

The terminal device 100-1 has a transmission power of 23 dBm and a maximum transmission power of 23 dBm. Because the maximum transmission power of the terminal device 100-1 is the same as the reference transmission power, the terminal device 100-1 calculates the offset value to be 0 dB. In other words, the terminal device 100-1 uses the first threshold, the second threshold, and the third threshold as they are. Because the received power P1 of the terminal device 100-1 is less than the first threshold and greater than or equal to the second threshold (range E2), and the transmission power is the maximum transmission power of 23 dBm, the terminal device 100-1 determines that the number of repeated transmissions will be two.

The terminal device 100-2 has a transmission power of 20 dBm and a maximum transmission power of 20 dBm. Because the maximum transmission power of the terminal device 100-2 is 3 dB lower than the reference transmission power, it calculates the offset value as +3 dB. The terminal device 100-2 adds the offset value to the first threshold, the second threshold, and the third threshold, and calculates the first threshold, the second threshold, and the third threshold after the offset adjustment. Because the received power P2 of the terminal device 100-2 is less than the second threshold after the offset adjustment and is equal to or greater than the third threshold (range E3), it determines the number of repeated transmissions to be 4.

In the fourth method, as described above, the terminal device 100-1 and the terminal device 100-2 have the same reception power but different maximum transmission power, and therefore the number of repeated transmissions of PRACH transmission is different. The terminal device 100-1 transmits twice with a transmission power of 23 dBm, and the terminal device 100-2 transmits four times with a transmission power of 20 dBm. The terminal device 100-1 transmits twice with a transmission power gain of 3 dB, resulting in a transmission power equivalent to 26 dBm. On the other hand, the terminal device 100-2 transmits four times with a transmission power gain of 6 dB, resulting in a transmission power equivalent to 26 dBm. As a result, the PRACH transmission power of the terminal device 100-1 and the terminal device 100-2 becomes equal, and fairness is ensured.

[Other embodiments]
The above-mentioned embodiments may be used in combination or alone. For example, the terminal device 100 and the base station device 200 may support only one of the first method to the fourth method. Also, for example, the terminal device 100 may execute the fourth method (or the first method) when the first threshold is notified, and the third method (or the second method) when the first threshold is notified. Furthermore, the base station device 200 may notify the terminal device 100 in advance which method to use.

In addition, in each method, if the received power is less than the second threshold and the transmission power is not the maximum transmission power, repeated transmission may not be performed and the transmission power may be increased. In this case, the number of repetitions may be reduced (for example, from four transmissions to two transmissions, or from eight transmissions to four transmissions), and the transmission power may be further increased. The number of repetitions and the transmission power may be determined, for example, according to the gain from repeated transmission.

10: Wireless communication system 100: Terminal device 110: CPU
120: Storage 121: Wireless communication program 122: PRACH transmission program 130: Memory 150: Wireless communication circuit 200: Base station device 210: CPU
220: Storage 221: Wireless communication control program 222: PRACH transmission control program 230: Memory 250: Wireless communication circuit

Claims (10)

A measurement unit for measuring a received power of a signal from a base station device;
A receiving unit that receives threshold information including a threshold;
a control unit that calculates an offset value according to a reference transmission power used as a reference in calculating the threshold and a maximum transmission power, calculates an adjustment threshold by adding the offset value to the threshold, and controls the transmission power and the number of repeated transmissions of a first message to be transmitted at the start of a wireless connection according to the reception power and the adjustment threshold;
A terminal device having the above configuration. When the threshold information does not include a first threshold and the received power is equal to or greater than a second adjustment threshold obtained by adding the offset value to a second threshold that is smaller than the first threshold, the control unit:
When the transmission power of the first message is smaller than the maximum transmission power, the repeated transmission is not performed, and a first process is performed to increase the transmission power;
The terminal device according to claim 1 , wherein, when the transmission power of the first message is equal to the maximum transmission power, the second process of repeatedly transmitting the first message is performed. When the threshold information includes the first threshold, the control unit:
The terminal device according to claim 2 , wherein the repeated transmission is not performed when the received power is equal to or greater than a first adjustment threshold obtained by adding the offset value to the first threshold, and the repeated transmission is performed when the received power is less than the first adjustment threshold. When the threshold information includes the first threshold, the control unit:
When the received power is less than the first adjustment threshold and is equal to or greater than the second adjustment threshold, the number of repeated transmissions is set to N (N is an integer equal to or greater than 2);
The terminal device according to claim 3 , wherein when the received power is less than the second adjustment threshold, the number of times of the repeated transmission is set to M times (M is an integer equal to or greater than 3) which is greater than the N times. the wireless connection includes a random access procedure;
The terminal device according to claim 1 , wherein the first message includes a Physical Random Access CHannel (PRACH). The terminal device according to claim 1 , wherein the threshold information includes the reference transmission power. The terminal device according to claim 1 , wherein the reference transmission power is a fixed value that is stored in advance in the terminal device and the base station device. The terminal device according to claim 1 , wherein the threshold information includes a first threshold, a second threshold smaller than the first threshold, and a third threshold smaller than the second threshold. A base station control unit that calculates a threshold value using a reference transmission power serving as a reference;
a notification unit that notifies a terminal device of threshold information including the threshold;
the base station control unit causes the terminal device to calculate an adjustment threshold by adding an offset value corresponding to the reference transmission power and the maximum transmission power of the terminal device to the threshold, and controls the number of repeated transmissions and the transmission power of a first message transmitted by the terminal device at the start of a wireless connection according to the reception power of a signal from the base station device in the terminal device and the adjustment threshold.
Base station equipment. The terminal device measures the received power of a signal from the base station device;
The base station device calculates a threshold value using a reference transmission power serving as a reference, and notifies the terminal device of threshold information including the calculated threshold value;
the terminal device receives the threshold information, calculates an offset value according to the reference transmission power and a maximum transmission power, calculates an adjustment threshold by adding the offset value to the threshold, and controls the number of repeated transmissions and the transmission power of a first message to be transmitted at the start of a wireless connection according to the reception power and the adjustment threshold.
Communication systems.

Images