Base station, user equipment, and methods thereof

Abstract

To reduce a data size necessary for notifying radio resource settings for a coverage improvement level from a base station to user equipment (UE).SOLUTION: UE configured to perform radio communication according NB-IoT receives, from a base station, system information including a first value of the RA-response window size and a multiplier corresponding to a coverage improvement level. The UE transmits a random access (RA) preamble in the coverage improvement level, and receives a RA response (RAR) from the base station in a RA response window with a length indicated by a second value of the RA-response window size. Here, the second value is derived by multiplying the first value included in the system information by the multiplier, and the multiplier is also set as a value corresponding to the number of repetition of the RAR in a random access procedure.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system that performs communication control to improve coverage. [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP (registered trademark)) is standardizing technologies to address the degradation of communication quality caused by the recent rapid increase in mobile traffic and to achieve even faster communication speeds. Furthermore, it is also standardizing technologies to avoid the increase in control signaling load caused by the expected connection of a huge number of Machine-to-Machine (M2M) devices to Long Term Evolution (LTE) networks or LTE-Advanced networks. Here, an M2M device refers to a device that communicates without human intervention. M2M devices are installed in various devices, such as machines (e.g., vending machines, gas meters, electricity meters, automobiles, railroad vehicles, and ships) and sensors (e.g., sensors related to the environment, agriculture, and traffic). In LTE and LTE-Advanced, communication by M2M devices is called Machine Type Communication (MTC), and a device that performs MTC is called an MTC device (MTC User Equipment (MTC UE)).

[0003] M2M service providers need to distribute a huge number of M2M devices to the market, but there are limitations on the cost they can spend per M2M device. Therefore, M2M devices must be low-cost and capable of communicating with low power consumption. One use case for MTC UEs is when they are installed or statically installed within a building. In this case, the wireless quality of the MTC UE may be consistently low, necessitating technologies to improve coverage compared to conventional mobile UEs (e.g., mobile phones, smartphones, tablet computers, and notebook personal computers (notebook PCs)). Furthermore, functional limitations imposed by cost reduction include low maximum transmit power, a limited number of receive antennas (e.g., only one receive antenna), lack of support for high-order modulation schemes (e.g., 64 quadrature amplitude modulation (64QAM)), and narrowband available wireless bandwidth (e.g., 1.4 MHz), which reduces the maximum transmission rate of the MTC UE.

[0004] Therefore, 3GPP is standardizing techniques for improving or enhancing the communication characteristics (i.e., coverage) of MTC UEs, which are expected to be inferior to those of normal UEs (Non-Patent Document 1). An example of a technique for improving the coverage of MTC UEs under consideration by 3GPP is described below. The coverage improvement techniques (coverage enhancement processes) for MTC UEs described below can also be referred to as processes for improving or enhancing the communication characteristics or communication quality of MTC UEs. The UE states to which these special coverage improvement techniques are applied are called Coverage Enhancement (CE) Mode, Coverage Extension (CE) Mode, Enhanced Coverage Mode (ECM), or Extended Coverage Mode (ECM).

[0005] The characteristics improved by the coverage enhancement technology include the reception characteristics of the Physical Broadcast Channel (PBCH), the transmission characteristics of the Physical Random Access Channel (PRACH) preamble (i.e., the detection characteristics in the radio base station (evolved NodeB (eNB))), the reception characteristics of the Physical Downlink Control Channel (PDCCH), the reception characteristics of the Physical Downlink Shared Channel (PDSCH), the transmission characteristics of the Physical Uplink Control Channel (PUCCH), and the transmission characteristics of the Physical Uplink Shared Channel (PUSCH). The PBCH is a downlink broadcast channel used by the eNB to transmit broadcast information common to the cell. The PRACH is an uplink physical channel used by the UE for initial access (i.e., random access) to the eNB. The PDCCH is a downlink physical channel used by the eNB to transmit, for example, scheduling information (DL assignment) for downlink data and radio resource allocation information (UL grant) for uplink data. The PDSCH is a downlink physical channel used by the UE to receive system information and data. The PUSCH is an uplink physical channel used for data transmission by the UE.

[0006] One of the processes under consideration for improving the reception performance of the PBCH is to repeat transmission of broadcast information via the PBCH a predetermined number of times more than usual (see Non-Patent Document 2). One of the processes under consideration for improving the transmission performance of the PRACH is to repeat transmission of the PRACH (i.e., preamble) a predetermined number of times (see Non-Patent Document 3). Furthermore, one of the processes under consideration for improving the reception performance of the PDSCH and the transmission performance of the PUCCH and PUSCH is to repeatedly transmit the PDSCH, PUCCH, and PUSCH over multiple subframes (see Non-Patent Document 4). Furthermore, one of the processes under consideration for improving the reception performance of the M-PDCCH, which is a PDCCH that transmits L1 / L2 control information for MTC UEs, is to repeatedly transmit the M-PDCCH over multiple subframes. These processes are expected to improve the communication performance of MTC UEs, which are expected to be worse than that of normal UEs. When downlink data is scheduled by repeated transmission of M-PDCCH, it is being considered to transmit the data in a subframe subsequent to the subframe in which the last repeated transmission of M-PDCCH is performed.Furthermore, it is being considered to include the number of repetitions of the M-PDCCH (the number of repetitions actually planned) in downlink control information (DL Control Information) included in the M-PDCCH.

[0007] The number of transmission repetitions and reception repetitions required to improve communication performance depends on the location of each MTC UE and the path loss between each MTC UE and the eNB. Therefore, coverage enhancement techniques provide multiple coverage enhancement (CE) levels. Coverage enhancement (CE) levels are also called enhanced coverage levels, coverage extension levels, extended coverage levels, or repetition levels (e.g., PRACH repetition levels). Furthermore, a one-to-one relationship or a predetermined relative relationship may be preset between the CE level and the repetition level.

[0008] For example, coverage enhancement technology provides three CE levels in addition to normal coverage and zero coverage extension. The multiple CE levels are associated with different transmission and reception repetitions. The transmission and reception repetitions used for higher CE levels are greater than those used for lower CE levels. The greater the path loss between the MTC UE and the eNB, the higher the CE level assigned to the MTC UE. In some implementations, the MTC UE measures the Reference Signal Received Power (RSRP) from the eNB or the estimated path loss between the MTC UE and the eNB, determines (estimates) the required CE level based on the measured RSRP or path loss, and transmits a random access channel (RACH) preamble according to the maximum transmission repetition number associated with the determined CE level (see Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2015 / 021315 [Non-patent literature]

[0010] [Non-Patent Document 1] 3GPP TR 36.888 V12.0.0 (2013-06), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Study on provision of low-cost Machine-Type Communications (MTC) User Equipments (UEs) based on LTE (Release 12)”, June 2013 [Non-patent document 2] 3GPP R1-135943, Vodafone, “Way Forward on P-BCH for MTC enhanced coverage”, 3GPP TSG RAN WG1 #75, San Francisco, USA, 11-15 November 2013 [Non-patent document 3] 3GPP R1-135944, Vodafone, “Way Forward on PRACH for MTC enhanced coverage”, 3GPP TSG RAN WG1 #75, San Francisco, USA, 11-15 November 2013 [Non-patent document 4] 3GPP R1-136001, Vodafone et al. “Way forward on PDCCH, PDSCH, PUCCH and PUSCH for MTC enhanced coverage”, 3GPP TSG RAN WG1 #75, San Francisco, USA, 11-15 November 2013 Summary of the Invention [Problem to be solved by the invention]

[0011] An eNB needs to inform an MTC UE that supports coverage enhancement technology of radio resource configurations for multiple CE levels. For example, the eNB includes radio resource configurations for initial access (i.e., random access) by an idle MTC UE in system information for the MTC UE (i.e., System Information Block x-bis (SIB x-bis)), such as SIB 1-bis or SIB2-bis, and transmits the information within the cell. If the system information needs to explicitly include multiple radio resource configurations for multiple CE levels, the data size of the system information increases.

[0012] One of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, method, and program that contributes to reducing the data size (i.e., signaling overhead) required for a base station to notify a wireless terminal of multiple radio resource configurations for multiple coverage improvement levels. It should be noted that this objective is only one of multiple objectives to be achieved by the multiple embodiments disclosed in this specification. Other objectives or problems and novel features will become apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0013] In a first aspect, a base station includes a memory and at least one processor coupled to the memory, the at least one processor configured to transmit a first value associated with normal coverage or a first coverage enhancement level for a first radio resource configuration information element and information on a conversion factor to a wireless terminal, the conversion factor value obtained from the information on the conversion factor being used by the wireless terminal to derive a second value associated with a second coverage enhancement level for the first radio resource configuration information element from the first value.

[0014] In a second aspect, a method in a base station includes transmitting a first value associated with normal coverage or a first coverage enhancement level for a first radio resource configuration information element and information on a conversion factor to a wireless terminal, the conversion factor value obtained from the information on the conversion factor being used by the wireless terminal to derive from the first value a second value associated with a second coverage enhancement level for the first radio resource configuration information element.

[0015] In a third aspect, a wireless terminal includes a memory and at least one processor coupled to the memory. The at least one processor is configured to execute at least one module. The at least one module includes a receiving module and a calculating module. The receiving module is configured to receive from a base station a first value associated with normal coverage or a first coverage enhancement level for a first radio resource configuration information element. The calculating module is configured to derive a second value associated with a second coverage enhancement level for the first radio resource configuration information element by converting the first value using a conversion factor value.

[0016] In a fourth aspect, a method in a wireless terminal includes: (a) receiving from a base station a first value associated with normal coverage or a first coverage enhancement level for a first radio resource configuration information element; and (b) deriving a second value associated with a second coverage enhancement level for the first radio resource configuration information element by converting the first value using a conversion factor value.

[0017] In a fifth aspect, a program includes a group of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to the second or fourth aspect described above. [Effects of the Invention]

[0018] According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that contribute to reducing the data size (i.e., signaling overhead) required for a base station to notify a wireless terminal of multiple radio resource settings for multiple coverage improvement levels. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 illustrates an example configuration of a wireless communication network according to some embodiments. [Figure 2] FIG. 4 is a sequence diagram showing an example of a transmission operation of system information according to the first embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of repeated transmission of a RACH preamble. [Figure 4] FIG. 10 is a diagram illustrating example values of radio resource configuration information elements for multiple CE levels. [Figure 5] 5 is a flowchart showing an example of the operation of the wireless terminal according to the first embodiment. [Figure 6] FIG. 4 is a diagram illustrating a first example of calculation for deriving a radio resource configuration information element by a radio terminal according to the first embodiment. [Figure 7] FIG. 10 is a diagram illustrating a second example of calculation for deriving a radio resource configuration information element by a radio terminal according to the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating a third example of calculation for deriving a radio resource configuration information element by a radio terminal according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating a fourth example of calculation for deriving a radio resource configuration information element by a radio terminal according to the first embodiment. [Figure 10] FIG. 2 is a diagram illustrating an example of a random access procedure according to the first embodiment. [Figure 11] FIG. 1 is a block diagram illustrating an example configuration of a wireless terminal according to some embodiments. [Figure 12] FIG. 1 is a block diagram illustrating an example configuration of a base station according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0021] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different purposes or problems and to achieving different effects.

[0022] The following embodiments are described primarily with respect to the Evolved Packet System (EPS) that includes LTE and SAE (System Architecture Evolution). However, these embodiments are not limited to the EPS and may be applied to other mobile communication networks or systems, such as 3GPP UMTS, 3GPP2 CDMA2000 systems (1xRTT, HRPD (High Rate Packet Data)), global system for mobile communications (GSM (registered trademark)) / General packet radio service (GPRS) systems, and WiMAX systems.

[0023] First Embodiment Fig. 1 shows an example of the configuration of a wireless communication network according to some embodiments including this embodiment. In the example of Fig. 1, the wireless communication network includes one or more wireless terminals (i.e., MTC UEs) 1 and a base station (eNB) 2. Each MTC UE 1 has at least one radio transceiver and is configured to perform cellular communication with the eNB 2. The eNB 2 manages a cell 21 and is configured to perform cellular communication with each of the multiple MTC UEs 1 using a cellular communication technology (e.g., Evolved Universal Terrestrial Radio Access (E-UTRA) technology).

[0024] The eNB2 shown in FIG. 1 may be a Baseband Unit (BBU) used in a Centralized Radio Access Network (C-RAN) architecture. In other words, the eNB2 shown in FIG. 1 may be a RAN node connected to one or more Remote Radio Heads (RRHs). In some implementations, the eNB2 as a BBU is responsible for control plane processing and user plane digital baseband signal processing. Meanwhile, the RRHs are responsible for analog Radio Frequency (RF) signal processing (e.g., frequency conversion and signal amplification). Note that the C-RAN is sometimes referred to as a Cloud RAN. The BBU may also be referred to as a Radio Equipment Controller (REC) or a Data Unit (DU). The RRHs may also be referred to as Radio Equipment (RE), Radio Unit (RU), or Remote Radio Unit (RRU).

[0025] In the example of FIG. 1, MTC UE 1A is located farther from eNB 2 than MTC UE 1B, and therefore is expected to experience greater propagation loss and degraded wireless quality. MTC UE 1C is installed inside a building (e.g., a building), and is expected to experience worse wireless quality than when installed outdoors. Furthermore, if each MTC UE 1 has limited capabilities or functions compared to UEs that perform human-type communications such as voice calls and web browsing, such as smartphones and tablet computers, the degradation of wireless quality is expected to be even more pronounced. Therefore, the MTC UE 1 according to this embodiment supports the above-described coverage improvement technology.

[0026] As already explained, to improve cell coverage in the downlink (DL), repetition of DL transmissions, e.g., repeated transmission of system information, M-PDCCH, and PDSCH, can be used, and to improve cell coverage in the uplink (UL), repetition of UL transmissions, repeated transmission of RACH preambles, PUCCH, and PUSCH can be used.

[0027] MTC UE1 may support multiple CE modes (or ECMs). In some implementations, MTC UE1 may support CE modes (or ECMs) for the RRC_IDLE state and other CE modes (or ECMs) for the RRC_CONNECTED state. Additionally or alternatively, MTC UE1 may support multiple CE modes (or ECMs) for the RRC_IDLE state and multiple CE modes (or ECMs) for the RRC_CONNECTED state. In some implementations, multiple coverage enhancement levels are defined for each CE mode (or each ECM). Additionally or alternatively, in some implementations, multiple CE modes provide different coverage enhancement levels.

[0028] 2 shows an example of a system information transmission operation (process 200) according to this embodiment. In step 201, the eNB2 transmits system information (e.g., SIB1-bis, SIB2-bis) in the cell 21. The eNB2 may repeatedly transmit the system information (SIB1bis, SIB2-bis) according to the coverage enhancement configuration for DL of the cell 21.

[0029] The system information transmitted in step 201 includes information indicating explicitly or implicitly that a coverage enhancement solution is supported in the cell, and control information (coverage enhancement configuration) required for the coverage enhancement solution. In particular, the system information includes a value (hereinafter referred to as a "base value") associated with normal coverage (zero coverage extension) or a first coverage enhancement (CE) level (e.g., CE level 1) for a first radio resource configuration information element (IE). The first radio resource configuration IE is an IE that needs to be set to a different value for each CE level. For example, the first radio resource configuration IE may relate to at least one of a UL message, a UL physical channel, a DL message, and a DL physical channel that are repeatedly transmitted in the random access procedure.

[0030] In some implementations, the first radio resource configuration IE may include at least one of the following IEs related to RACH configuration: ·numberOfRA-Preambles; ·maxNumPreambleAttemptCE; ·numRepetitionPerPreambleAttempt; ·ra-ResponseWindowSize; ·mac-ContentionResolutionTimer; maxHARQ-Msg3Tx; and ·numRepetitionPerRA-Response.

[0031] The "numberOfRA-Preambles" IE indicates the total number of random access preambles (RACH preambles) that can be used for contention-based random access. The "maxNumPreambleAttemptCE" IE indicates the maximum number of PRACH attempt attempts (per CE level). The "numRepetitionPerPreambleAttempt" IE indicates the number of preamble transmission repetitions (per CE level) per PRACH attempt. The "ra-ResponseWindowSize" IE indicates the duration of the random access (RA) response window. The "mac-ContentionResolutionTimer" IE indicates the timer value of the MAC contention resolution timer to wait for the receipt of a Medium Access Control (MAC) Contention Resolution message for RA Contention Resolution from the eNB2 after sending the third message (Msg3) of the random access procedure, i.e., the RRC Connection Request message, to the eNB2. The "maxHARQ-Msg3Tx" IE indicates the maximum number of Hybrid Automatic Repeat Request (HARQ) retransmissions of the third message (Msg3) of the random access procedure, i.e., the RRC Connection Request message. The "numRepetitionPerRA-Response" IE indicates the number of repetitions (per CE level) of M-PDCCH transmissions used to transmit the second message (Msg2) of the random access procedure, i.e., the Random Access Response (RAR) message, or the number of repetitions of the RAR message transmission. Note that these IE names are merely examples, and other names may be used for these IEs.

[0032] Figure 3 shows an example of repeated RACH preamble transmission by MTC UE1 supporting coverage enhancement technology. In the example shown in Figure 3, MTC UE1 repeats preamble transmission four times per PRACH attempt, for a maximum of 20 PRACH attempts. If one attempt fails, MTC UE1 increases the transmission power of the RACH preamble according to a power ramping scheme and starts the next attempt.

[0033] Figure 4 shows example values of the radio resource configuration information element for multiple CE levels. In the example of Figure 4, the value of the "maxNumPreambleAttemptCE" IE associated with the lowest CE level (i.e., CE level 1) is 20, and the value of the "numRepetitionPerPreambleAttempt" IE is 4. This corresponds to the example shown in Figure 3. On the other hand, for higher CE levels, both the maximum number of PRACH attempt attempts and the number of preamble transmission repetitions per PRACH attempt increase. That is, the value of the "maxNumPreambleAttemptCE" IE associated with CE level 2 is 60, and the value of the "numRepetitionPerPreambleAttempt" IE is 10. Furthermore, the value of the "maxNumPreambleAttemptCE" IE associated with CE level 3 is 120, and the value of the "numRepetitionPerPreambleAttempt" IE is 20.

[0034] In some implementations, the first radio resource configuration IE may include at least one of the following IEs related to PRACH configuration: prach-ConfigIndex; and ·prach-FreqOffset.

[0035] The "prach-ConfigIndex" IE indicates a value (i.e., R_Slot) that defines when the MTC UE1 should transmit the random access preamble within the frequency / time grids. The "prach-FreqOffset" IE indicates a frequency offset value that identifies the physical resource block (PRB) available for RACH access.

[0036] The 3GPP specifications define a set or one-dimensional array of a predetermined number (e.g., eight) of values that can be set in each radio resource configuration IE. These values are arranged, for example, in ascending or descending order, and each value is associated with an index value indicating its rank in the ascending or descending order. Therefore, each radio resource configuration IE indicates an index value representing one of the values included in this set or one-dimensional array. For example, in 3GPP Release 12, the RA response window size is in subframe units and can be set to eight values: 2, 3, 4, 5, 6, 7, 8, and 10 subframes. Therefore, the "ra-ResponseWindowSize" IE has a length of three bits, and a three-bit index value indicates one of these eight values.

[0037] The MTC UE1 receives from the eNB2 a base value associated with a normal coverage extension (CE level 0) or a first CE level (e.g., CE level 1) for the first radio resource configuration IE, and derives a value (second value) associated with another CE level (e.g., a second CE level (e.g., CE level 2)) for the first radio resource configuration IE from the received base value. Thus, the MTC UE1 does not need to receive from the eNB2 an additional IE that explicitly indicates the second value associated with the second CE level for the first radio resource configuration IE.

[0038] More specifically, MTC UE1 uses a conversion factor value to derive a second value associated with a second CE level (e.g., CE level 2) from the base value received from eNB2. The conversion factor may simply be referred to as a factor. To support the derivation of the second value in MTC UE1, in some implementations, eNB2 may further include the conversion factor value in the system information transmitted in step 201 of FIG. 2. Alternatively, in some implementations, eNB2 may further include information indirectly indicating the conversion factor value or information for deriving the conversion factor value in the system information transmitted in step 201 of FIG. 2. For example, the information indirectly indicating the conversion factor value may be an index specifying one value from a set including multiple predetermined candidate values. For example, the information for deriving the conversion factor value may include one or more parameters to be substituted into a predetermined conversion factor calculation formula. That is, the eNB2 may transmit information about the conversion factor (e.g., the value of the conversion factor itself, information indirectly indicating the value of the conversion factor, or information for deriving the value of the conversion factor) to the MTC UE1. The information about the conversion factor is used by the MTC UE1 to obtain the value of the conversion factor. In this case, the conversion factor and the procedure for deriving (calculating) the second value using the conversion factor are defined so that the data size of the information about the conversion factor is smaller than the data size required to explicitly transmit values associated with the second CE level for one or more radio resource configuration IEs from the eNB2 to the MTC UE1.

[0039] Prior to step 201, eNB2 may calculate a value of a conversion factor to be transmitted to MTC UE1. Specifically, eNB2 may determine a value of a first radio resource configuration IE for each of one or more second CE levels (e.g., CE levels 1-3), and calculate a value of the conversion factor for each second CE level using the determined IE value and a base value of the first radio resource configuration IE (e.g., IE value for CE level 0).

[0040] In another implementation, the MTC UE1 may be configured to pre-store a default value of the conversion factor in its memory, and may use the default value to derive the second value from the base value of the first radio resource configuration IE if the conversion factor is not explicitly transmitted from the eNB2.

[0041] 5 is a flowchart showing an example of an operation (process 500) of the MTC UE1. In step 501, the MTC UE1 receives system information from the eNB2, the system information including a base value for a first radio resource configuration IE. As already described, the base value for the first radio resource configuration IE is a value of the first radio resource configuration IE associated with normal coverage (zero coverage extension) or a first CE level (e.g., CE level 1). The system information may further include a conversion factor used to derive a second value associated with a second CE level for the first radio resource configuration IE from the base value.

[0042] In step 502, the MTC UE1 derives values of first radio resource configuration IEs associated with the second CE level by converting base values of first radio resource configuration IEs associated with the normal coverage (or the first CE level) using the value of the conversion factor. For example, the first radio resource configuration IE includes one or more RACH configuration IEs (e.g., ra-ResponseWindowSize and mac-ContentionResolutionTimer). In this case, the MTC UE1 uses the value of the conversion factor to derive second values associated with the first CE level (or the second CE level) from the base values of one or more RACH configuration IEs associated with the normal coverage (or the first CE level).

[0043] MTC UE1 may measure the received power (RSRP) of the reference signal from eNB2 or the estimated path loss between MTC UE1 and eNB2, and determine the required CE level based on the measured RSRP or path loss. In step 503, if MTC UE1 requires the second CE level, MTC UE1 performs a random access procedure according to the second values of the first radio resource configuration IEs (e.g., ra-ResponseWindowSize and mac-ContentionResolutionTimer) derived in step 502.

[0044] Next, several examples of conversion factors and several examples of procedures for deriving (calculating) the second value of a radio resource configuration IE using the conversion factor from a base value of the radio resource configuration IE will be described. In a first example shown in FIG. 6, the conversion factor represents a multiplier factor. Furthermore, in the first example, one conversion factor (multiplier) value is used to derive two or more values associated with a second CE level for two or more radio resource configuration IEs (e.g., ra-ResponseWindowSize and mac-ContentionResolutionTimer). Therefore, in the first example, the eNB2 only needs to transmit one conversion factor value instead of transmitting two or more values associated with a second CE level for two or more radio resource configuration IEs. This enables the first example to reduce the data size required for notifying a wireless terminal of multiple radio resource configurations for multiple CE levels from a base station. Note that the conversion factor in the first example may also be referred to as a scaling factor, coefficient, or scaling coefficient.

[0045] More specifically, in the example of Figure 6, MTC UE1 receives the values of the "ra-ResponseWindowSize" IE and the "mac-ContentionResolutionTimer" IE for normal coverage (i.e., zero coverage extension or CE level 0) from eNB2 via SIB (601). In Figure 6, the RA response window size for normal coverage (ra-ResponseWindowSize) is 2 subframes (sf2), and the length of the contention resolution timer for normal coverage (mac-ContentionResolutionTimer) is 8 subframes (sf8).

[0046] The MTC UE1 further receives from the eNB2 three conversion factor (i.e., multiplier) values associated with three CE levels (CE levels 1, 2, and 3) (602). In FIG. 6, the conversion factor (multiplier) values for CE levels 1, 2, and 3 are 2, 3, and 4, respectively. Note that the MTC UE1 may receive from the eNB2 only the conversion factor value corresponding to one required CE level among the three CE levels.

[0047] MTC UE1 multiplies each of the two or more IE values (601) for normal coverage by the conversion factor (multiplier) value (603), allowing MTC UE1 to derive two or more IE values for CE level 1, 2, or 3 (604). Note that MTC UE1 may calculate only the value corresponding to one required CE level out of the three CE levels.

[0048] In the second example shown in FIG. 7, IE values for two or more CE levels are calculated using one conversion factor value. That is, the MTC UE1 not only calculates a second value of the radio resource configuration IE associated with a second CE level using a base value of the radio resource configuration IE and the conversion factor value, but also calculates a third value of the radio resource configuration IE associated with a third CE level using the base value and the conversion factor value. Therefore, in the second example, the eNB2 only needs to transmit one conversion factor value instead of transmitting two or more values associated with the second and third CE levels for the first radio resource configuration IE. This allows the second example to reduce the data size required for the base station to notify the wireless terminal of multiple radio resource configurations for multiple CE levels.

[0049] In more detail, in the example of Figure 7, MTC UE1 receives the value of the "ra-ResponseWindowSize" IE for normal coverage (i.e., zero coverage extension or CE level 0) from eNB2 via SIB (701). In Figure 7, the RA response window size (ra-ResponseWindowSize) for normal coverage is 2 subframes (sf2).

[0050] MTC UE1 also receives from eNB2 (702) the value of one conversion factor (i.e., base multiplier factor) used to determine IE values for three CE levels (CE level 1, 2, 3). In FIG. 7, the value of the conversion factor (base multiplier factor) is 2.

[0051] The MTC UE1 multiplies the value of the radio resource configuration IE for normal coverage (701) by the value of a conversion factor (base multiplier) (703). This allows the MTC UE1 to derive an IE value for CE level 1 (704). Furthermore, when determining an IE value for CE level 2, the MTC UE1 multiplies the IE value for CE level 1 by the value of the conversion factor (base multiplier). That is, in the example of FIG. 7, the value of the conversion factor (base multiplier) directly or indirectly specifies a scale ratio between the IE value for normal coverage and the IE values of two or more CE levels. This allows the MTC UE1 to calculate IE values for two or more CE levels based on the value of one conversion factor (base multiplier).

[0052] In a third example shown in Fig. 8, the conversion factor represents an offset. In the third example, similar to the first example described above, the value of one conversion factor (offset) is also used to derive two or more values associated with a second CE level for two or more radio resource configuration IEs (e.g., ra-ResponseWindowSize and mac-ContentionResolutionTimer). Therefore, similar to the first example described above, the third example can reduce the data size required for a base station to notify a wireless terminal of multiple radio resource configurations for multiple CE levels.

[0053] More specifically, in the example of Figure 8, MTC UE1 receives the values of the "ra-ResponseWindowSize" IE and the "mac-ContentionResolutionTimer" IE for normal coverage (i.e., zero coverage extension or CE level 0) from eNB2 via SIB (801). In Figure 8, the RA response window size for normal coverage (ra-ResponseWindowSize) is 2 subframes (sf2), and the length of the contention resolution timer for normal coverage (mac-ContentionResolutionTimer) is 8 subframes (sf8).

[0054] The MTC UE1 further receives from the eNB2 three conversion factor (i.e., offset) values associated with three CE levels (CE levels 1, 2, and 3) (802). In FIG. 8, the conversion factor (offset) values for CE levels 1, 2, and 3 are 2, 4, and 6, respectively. Note that the MTC UE1 may receive from the eNB2 only the conversion factor value corresponding to one required CE level among the three CE levels.

[0055] MTC UE1 adds (803) a conversion factor (offset) value to each of two or more IE values (801) for normal coverage, thereby enabling MTC UE1 to derive (804) two or more IE values for CE level 1, 2, or 3. Note that MTC UE1 may calculate only a value corresponding to one required CE level out of the three CE levels.

[0056] In the fourth example shown in Fig. 9, IE values for two or more CE levels are calculated using one conversion factor value, as in the second example described above. Therefore, the fourth example can reduce the data size required for a base station to notify a wireless terminal of multiple radio resource configurations for multiple CE levels, as in the second example described above. However, in the fourth example, a base offset is used as the conversion factor.

[0057] In more detail, in the example of Figure 9, MTC UE1 receives the value of the "ra-ResponseWindowSize" IE for normal coverage (i.e., zero coverage extension or CE level 0) from eNB2 via an SIB (e.g., SIB2-bis) (901). In Figure 9, the RA response window size (ra-ResponseWindowSize) for normal coverage is 2 subframes (sf2).

[0058] MTC UE1 further receives from eNB2 the value of one conversion factor (i.e., base offset) used to determine IE values for three CE levels (CE level 1, 2, 3) (902). In FIG. 9, the value of the conversion factor (base offset) is 2.

[0059] The MTC UE1 adds the value of the conversion factor (basic offset) to the value of the radio resource configuration IE for normal coverage (901) (903). This allows the MTC UE1 to derive the IE value for CE level 1 (904). Furthermore, when determining the IE value for CE level 2, the MTC UE1 adds the value of the conversion factor (basic offset) to the IE value for CE level 1. That is, in the example of FIG. 9, the value of the conversion factor (basic offset) indirectly specifies the scale ratio between the IE value for normal coverage and the IE values of two or more CE levels. This allows the MTC UE1 to calculate IE values for two or more CE levels based on the value of one conversion factor (basic offset).

[0060] The fifth example is a variation of the first example, in which the conversion factor represents a divisor factor. In the fifth example, as in the first example, a single conversion factor (divisor) value is used to derive two or more values associated with the second CE level for two or more radio resource configuration IEs. In some implementations, the MTC UE1 divides each of the two or more IE values for normal coverage by the conversion factor (divisor) value for each CE level. This allows the MTC UE1 to derive two or more IE values for each CE level. The fifth example may be used to determine a value for an IE (e.g., maxNumPreambleAttemptCE) that decreases as the CE level increases.

[0061] The sixth example is a variation of the second example, in which the conversion factor represents a base divisor factor. In the sixth example, similar to the second example, IE values for two or more CE levels are calculated using a single conversion factor value. In some implementations, MTC UE1 divides the IE value for normal coverage by the conversion factor (i.e., base divisor). This allows MTC UE1 to calculate IE values for two or more CE levels based on the single conversion factor (base divisor) value. The sixth example may be used to determine a value for an IE (e.g., maxNumPreambleAttemptCE) that decreases as the CE level increases.

[0062] The seventh example is a modification of the first example, in which the conversion factor represents an exponent of an integer m (power of m). When the conversion factor is a positive integer k, the second value of the radio resource configuration IE is a value obtained by multiplying the base value of the radio resource configuration IE by the kth power of m. The value of the base m of the exponent may be specified in the 3GPP specifications or the like. That is, the value of the base m of the exponent may be stored in advance in the memory of the MTC UE1. For example, when the base m is 2 and the value of the conversion factor for CE level 1 is 3, the value of the radio resource configuration IE for CE level 1 is obtained by multiplying the base value of the radio resource configuration IE for normal coverage (CE level 0) by the third power of 2, i.e., 8 times the base value. In the seventh example, as in the first example, the value of one conversion factor (exponent) is commonly used to derive two or more values associated with second CE levels (e.g., CE level 1) for two or more radio resource configuration IEs.

[0063] The first to seventh examples described above may be modified as appropriate. Also, a method different from the first to sixth examples may be used to derive the second value of the radio resource configuration IE from the base value using a conversion factor.

[0064] For example, in the above-described first to seventh examples, the value of the conversion factor is a multiplier, offset, divisor, or exponent for multiplication, addition, or division of a specific value (e.g., the number of subframes) indicated by the base value (e.g., the index value) of the radio resource configuration IE. Alternatively, the value of the conversion factor may be a multiplier, offset, divisor, or exponent for multiplication, addition, or division of the base value (e.g., the index value) of the radio resource configuration IE itself. For example, the base value (e.g., the index value) of the radio resource configuration IE itself may be multiplied by the multiplier value as the conversion factor. In this case, the specific value (e.g., the number of subframes) represented by the converted index value is used for each CE level.

[0065] The first to seventh examples described above may be used in combination as appropriate. For example, when the values of multiple IEs are calculated using the same conversion factor, the role of the conversion factor (i.e., the calculation method for deriving the IE value) may be different for each IE. For example, the value of the conversion factor may be used as a multiplier for multiplication to obtain the value of a certain IE, and the value of the conversion factor may be used as an offset for addition to obtain the value of another IE.

[0066] In some implementations, the value of the conversion factor for determining the value associated with the second CE level for the first radio resource configuration IE may be shared with the value associated with the second coverage enhancement level for a second radio resource configuration IE different from the first radio resource configuration IE. For example, the MTC UE1 may use one or both of the value of the “numRepetitionPerPreambleAttempt” IE indicating the number of preamble repetitions at the second CE level (PRACH preamble repetition level) and the value of the “numRepetitionPerRA-Response” IE indicating the number of RA response repetitions at the second CE level (RAR repetition level), both received from the eNB2, as a conversion factor for determining the values associated with the second CE level for the “ra-ResponseWindowSize” IE and the “mac-ContentionResolutionTimer” IE. Additionally or alternatively, MTC UE1 may use one or both of the values of the IEs indicating the repetition level of the third message (RRC Connection Request message) and the fourth message (Contention Resolution message) of the random access procedure at the second CE level received from eNB2 as a conversion factor for determining a value of the “mac-ContentionResolutionTimer” IE associated with the second CE level. In these two examples, the coefficient (proportionality coefficient) relating one or both of the PRACH preamble repetition level and the RAR repetition level to the ra-ResponseWindowSize may be the same as the coefficient (proportionality coefficient) relating one or both of the repetition level of the third message and the repetition level of the fourth message to the mac-ContentionResolutionTimer.

[0067] In some implementations, other values may be used in addition to the conversion factor to determine the value of the IE corresponding to the required CE level in the MTC UE1. For example, the value of the IE may be derived using the repetition level of the corresponding signal (preamble, message) and the conversion factor. For example, the value of ra-ResponseWindowSize for the second CE level (e.g., CE level 1, 2, or 3) may be multiplied by the value of the ra-ResponseWindowSize for the first CE level (e.g., CE level 0) by the value of the PRACH preamble repetition level for the second CE level (e.g., CE level 1, 2, or 3), and then multiplied (or added or divided) by the conversion factor to derive the value of ra-ResponseWindowSize for the second CE level. In this case, the conversion factor may be the interval between repeated transmissions of the RACH preamble or the interval between repeated transmissions of the RAR message (M-PDCCH or PDSCH).

[0068] Furthermore, when the same conversion factor is applied to multiple IEs, the values of the IEs may be derived using the repetition levels (number of repetitions) of the corresponding signals (preambles, messages) and the same conversion factor. For example, the value of ra-ResponseWindowSize for the second CE level (e.g., CE level 1, 2, or 3) may be multiplied by the value of the PRACH preamble repetition level or the value of the RAR repetition level, and then multiplied (or added or divided) by the value of the conversion factor to derive the value of ra-ResponseWindowSize for the second CE level. Similarly, the value of mac-ContentioResolutionTimer for the first CE level (e.g., CE level 0) may be multiplied by either or both of the repetition level value of the third message (RRC Connection Request message) and the repetition level value of the fourth message (Contention Resolution message) for the second CE level (e.g., CE level 1, 2, or 3), and then multiplied (or added or divided) by the same conversion factor to derive the value of mac-ContentioResolutionTimer for the second CE level.

[0069] In some implementations, the value of the conversion factor may be a CE level value, such as a value (e.g., 1) indicating a required CE level (e.g., CE level 1) or a value obtained by converting this value according to a predetermined conversion formula.

[0070] In some implementations, IE values may be derived using a conversion factor only for some CE levels (e.g., CE level 1) among multiple CE levels, and IE values for the remaining CE levels (e.g., CE level 1 and CE level 2) may be derived from the IE value for the part of the CE levels (e.g., CE level 1) according to a predetermined rule. For example, the IE value for CE level 2 may be twice the IE value for CE level 1, and the IE value for CE level 3 may be three times the IE value for CE level 1. Alternatively, the IE value for CE level 2 may be the IE value for CE level 1 plus an "offset + 2," and the IE value for CE level 3 may be the IE value for CE level 1 plus an "offset + 3." Alternatively, the IE values may be derived using a value corresponding to the difference (e.g., ratio or difference) in repetition levels between CE levels. For example, if the repetition level of CE level 1 is 2 and the repetition level of CE level 2 is 4, the IE value of CE level 2 may be set to 4 / 2 times the value of CE level 1, i.e., twice the value.

[0071] The above-described first, third, fifth, and seventh examples illustrate examples in which one conversion factor value is set (or used) for each of two or more radio resource configuration IEs. The second, fourth, and sixth examples illustrate examples in which one conversion factor value is set (or used) for each of two or more CE levels. Alternatively, in some implementations, one conversion factor value may be set (or used) for each radio resource configuration IE and for each CE level. In this case, it is preferable that the conversion factor is defined so that the bit length of the IE indicating the conversion factor is smaller than the bit length of the radio resource configuration IE.

[0072] 10 is a diagram showing an example of a random access procedure (process 1000) according to this embodiment. In step 1001, MTC UE1 determines (estimates) the required CE level based on a measurement of the reception quality (e.g., RSRP) of a signal from eNB2 or a measurement (estimate) of the path loss between UE1 and eNB2.

[0073] In step 1002, the MTC UE1 receives system information (SIB) transmitted from the eNB2 while applying a coverage enhancement technique (e.g., repeated transmission of system information (SIB)) corresponding to the determined CE level. The system information includes a base value associated with the first CE level (e.g., CE level 1) or a normal coverage for a first radio resource configuration IE (e.g., one or more RACH configuration IEs), and further includes information on a conversion factor for deriving a value of the first radio resource configuration IE associated with the second CE level (e.g., CE level 2). As already described, the information on the conversion factor may include, for example, the value of the conversion factor itself, or may be information indirectly indicating the value of the conversion factor or information for deriving the value of the conversion factor.

[0074] In step 1003, the MTC UE1 converts the base value of the first radio resource configuration IE associated with the normal coverage (or the first CE level) using the value of the conversion factor. The value of the conversion factor can be obtained from the information about the conversion factor received from the eNB2. Thus, the MTC UE1 derives the value of the first radio resource configuration IE associated with the determined required CE level.

[0075] Thereafter, the MTC UE1 performs a random access procedure according to the derived value of the first radio resource configuration IE (eg, one or more RACH configuration IEs) (steps 1004 to 1006).

[0076] In step 1004, if random access is not successful even after the maximum number of RACH preamble attempts for the determined (estimated) CE level (e.g., CE level 1) is reached, MTC UE1 may start transmitting RACH preambles using settings for the next CE level (e.g., CE level 2). At this time, MTC UE1 may derive settings corresponding to the next CE level (e.g., CE level 2), such as the values of the “ra-ResponseWindowSize” IE and the “mac-ContentionResolutionTimer” IE, when changing the CE level, or may derive values corresponding to multiple CE levels together in advance.

[0077] In addition, MTC UE1 may start measuring the RA response window according to the "ra-ResponseWindowSize" IE from three subframes after the first or last subframe of a repeat transmission within one RACH preamble transmission attempt in step 1004. The "ra-ResponseWindowSize" IE indicates the time MTC UE1 should wait for receiving a random access response (RAR) in step 1006 after transmitting the RACH preamble in step 1004. Also, MTC UE1 may start measuring the MAC contention resolution timer according to the "mac-ContentionResolutionTimer" IE from either the first or last subframe of a repeat transmission of the third message (Msg3) of the random access procedure. The "mac-ContentionResolutionTimer" IE indicates the time MTC UE1 should wait for receiving a Contention Resolution message (and confirming the content) after transmitting the third message (Msg3).

[0078] In step 1005, eNB2 detects a random access (RA) preamble (RACH preamble) transmitted from MTC UE1. For example, eNB2 determines the CE level of MTC UE1 based on the radio resource on which the RA preamble is detected. Then, eNB2 performs coverage improvement operations, including repeated reception of the RA preamble and repeated transmission of the RA response, according to values of multiple IEs (e.g., a “numRepetitionPerPreambleAttempt” IE and an “ra-ResponseWindowSize” IE) corresponding to the determined CE level of MTC UE1. In some implementations, eNB2 may calculate values of multiple IEs corresponding to the determined CE level of MTC UE1 based on the value of a conversion factor for the determined CE level of MTC UE1. In other implementations, eNB2 may calculate values of multiple IEs corresponding to the determined CE level of MTC UE1 by referencing a look-up table that stores values of multiple IEs corresponding to each CE level.

[0079] In the above specific example, a method for deriving values corresponding to each CE level for existing radio parameters (IEs in an RRC message) in a random access procedure has been described. Similarly, the above derivation method may be used to derive values corresponding to each CE level for newly defined radio parameters (IEs in an RRC message) for coverage enhancement technologies. For example, the above derivation method may be applied to an IE indicating the maximum number of RACH preamble attempts per CE level (i.e., maxNumPreambleAttemptCE) and an IE indicating the maximum number of repetitions per RACH preamble attempt (i.e., numRepetitionPerPreambleAttempt). In this case, the eNB2 may transmit an IE value corresponding to the lowest CE level (e.g., CE level 1) in the system information, and the UE1 may derive IE values corresponding to one or more higher CE levels (e.g., CE level 2 or higher) using the above conversion factor.

[0080] The above-mentioned random access procedure may be applied not only to initial access when the UE transitions from the RRC_IDLE state to the RRC_CONNECTED state, but also to random access in the RRC_CONNECTED state. Furthermore, in the case of random access by an execution command (PDCCH Order) from the eNB2, the execution command may include at least one of a base value and a conversion factor.

[0081] Next, exemplary configurations of the MTC UE1 and eNB2 according to this embodiment will be described below. FIG. 11 is a block diagram showing an exemplary configuration of the MTC UE1. A radio frequency (RF) transceiver 1101 performs analog RF signal processing for communication with the eNB2. The analog RF signal processing performed by the RF transceiver 1101 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1101 is coupled to an antenna 1102 and a baseband processor 1103. That is, the RF transceiver 1101 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1103, generates a transmit RF signal, and provides the transmit RF signal to the antenna 1102. The RF transceiver 1101 also generates a baseband receive signal based on the receive RF signal received by the antenna 1102 and provides the baseband receive signal to the baseband processor 1103.

[0082] The baseband processor 1103 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and packet communication).

[0083] For example, in the case of LTE and LTE-Advanced, the digital baseband signal processing by the baseband processor 1103 may include signal processing of a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer, and a PHY layer. Also, the control plane processing by the baseband processor 1103 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0084] The baseband processor 1103 may include a modem processor (e.g., a Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a Central Processing Unit (CPU) or a Micro Processing Unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1104, which will be described later.

[0085] The application processor 1104 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 1104 may include multiple processors (multiple processor cores). The application processor 1104 executes a system software program (operating system (OS)) and various application programs (e.g., communication applications that acquire metering data or sensing data) read from the memory 1106 or a memory not shown, thereby realizing various functions of the MTC UE1.

[0086] In some implementations, the baseband processor 1103 and the application processor 1104 may be integrated on a single chip, as indicated by the dashed line (1105) in Figure 11. In other words, the baseband processor 1103 and the application processor 1104 may be implemented as a single System on Chip (SoC) device 1105. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0087] The memory 1106 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1106 may include multiple physically independent memory devices. The volatile memory may be, for example, static random access memory (SRAM), dynamic RAM (DRAM), or a combination thereof. The nonvolatile memory may be mask read only memory (MROM), electrically erasable programmable ROM (EEPROM), flash memory, a hard disk drive, or any combination thereof. For example, the memory 1106 may include an external memory device accessible from the baseband processor 1103, the application processor 1104, and the SoC 1105. The memory 1106 may also include an internal memory device integrated within the baseband processor 1103, the application processor 1104, or the SoC 1105. Furthermore, the memory 1106 may include memory within a universal integrated circuit card (UICC).

[0088] The memory 1106 may store one or more software modules (computer programs) 1107 including instructions and data for performing the processes by the MTC UE 1 described in the above embodiments. In some implementations, the baseband processor 1103 or the application processor 1104 may be configured to read and execute the software modules 1107 from the memory 1106 to perform the processes by the MTC UE 1 described in the above embodiments.

[0089] 12 is a block diagram showing an example configuration of a base station (eNB) 2 according to the above embodiment. Referring to FIG. 12, the eNB 2 includes an RF transceiver 1201, a network interface 1203, a processor 1204, and a memory 1205. The RF transceiver 1201 performs analog RF signal processing for communication with the wireless terminal 1. The RF transceiver 1201 may include multiple transceivers. The RF transceiver 1201 is coupled to an antenna 1202 and the processor 1204. The RF transceiver 1201 receives modulation symbol data (or OFDM symbol data) from the processor 1204, generates a transmit RF signal, and provides the transmit RF signal to the antenna 1202. The RF transceiver 1201 also generates a baseband receive signal based on the receive RF signal received by the antenna 1202 and provides the baseband receive signal to the processor 1204.

[0090] The network interface 1203 is used to communicate with network nodes (e.g., a Mobility Management Entity (MME) and a Serving Gateway (S-GW)). The network interface 1203 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series.

[0091] The processor 1204 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. For example, in the case of LTE and LTE-Advanced, the digital baseband signal processing by the processor 1204 may include signal processing of a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. Furthermore, the control plane processing by the processor 1204 may include processing of an S1 protocol, an RRC protocol, and a MAC CE.

[0092] The processor 1204 may include multiple processors. For example, the processor 1204 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing.

[0093] The memory 1205 is configured by a combination of volatile memory and nonvolatile memory. The volatile memory is, for example, SRAM or DRAM, or a combination thereof. The nonvolatile memory is, for example, MROM, PROM, flash memory, or a hard disk drive, or a combination thereof. The memory 1205 may include storage located remotely from the processor 1204. In this case, the processor 1204 may access the memory 1205 via the network interface 1203 or an I / O interface (not shown).

[0094] The memory 1205 may store software modules (computer programs) 1206 including instructions and data for performing the processes of the eNB2 described in the above embodiments. In some implementations, the processor 1204 may be configured to read and execute the software modules 1206 from the memory 1205 to perform the processes of the eNB2 described in the above embodiments.

[0095] As described with reference to FIGS. 11 and 12 , each of the processors included in the MTC UE1 and eNB2 according to the above-described embodiments executes one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs can be stored and provided to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), compact disc read only memories (CD-ROMs), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash ROMs, and random access memories (RAMs)). The programs may also be provided to a computer by various types of transitory computer-readable media. Examples of the temporary computer-readable medium include an electric signal, an optical signal, and an electromagnetic wave. The temporary computer-readable medium can provide the program to the computer via a wired communication path such as an electric wire or an optical fiber, or via a wireless communication path.

[0096] <Other embodiments> The above-described embodiments have been mainly described with respect to radio resource configuration IEs (e.g., RACH configuration IE and PRACH configuration IE) related to random access. However, the method of deriving an IE value for a specific CE level using a conversion factor described in the above-described embodiments can be widely used when different radio resource configurations are required depending on the coverage enhancement (CE) level. For example, the method described in the above-described embodiments may be used to derive a value of the radio resource configuration IE (e.g., the number of transmission (reception) repetitions) required when an MTC UE1 in an RRC_CONNECTED state transmits UL user data on a PUSCH, transmits L1 / L2 control information on a PUCCH, receives system information or DL user data on a PDSCH, and receives L1 / L2 control information on an M-PDCCH at a specific CE level.

[0097] The above-described embodiment has been mainly described with reference to a case where eNB2 transmits information about conversion factors in system information. However, the information about conversion factors may also be transmitted in a signal (e.g., RRC signaling, MAC signaling) in which eNB2 transmits individual control information to MTC UE1. For example, the information about conversion factors may be transmitted from eNB2 to MTC UE1 in an RRC Connection Reconfiguration message or a MAC Control Element. Note that when MTC UE1 receives information about conversion factors in system information and individual control information, it may preferentially use the value of the conversion factor obtained from the information about conversion factors notified in the individual control information (i.e., overwrite the value of the conversion factor obtained from the system information with the value of the conversion factor obtained from the individual control information).

[0098] The operations of the MTC UE1 and eNB2 regarding the derivation of IE values using conversion factors described in the above embodiments may be used to derive values of timers that require different lengths depending on the Coverage Enhancement (CE) level. Specific examples of timers that use different timer values for multiple CE levels include, for example, (1) timers related to control such as call processing (i.e., RRC, NAS), (2) timers related to Layer 2 (i.e., PDCP, RLC, MAC) control, and (3) timers that measure in the RRC_IDLE state.

[0099] For example, the timer (1) above may be a timer (i.e., timer T300) used to determine whether the RRC connection establishment is successful or failed. The MTC UE1 starts the timer (i.e., timer T300) from the time when it transmits the RRC Connection Reestablishment Request message, and stops the timer when it receives a response (i.e., RRC Connection Setup message or RRC Connection Reject message) from the eNB2.

[0100] Additionally or alternatively, the timer (1) may be a timer (i.e., timer T311) for determining whether the search for a suitable cell has succeeded or failed. The MTC UE1 starts the timer (i.e., timer T311) when the RRC Connection Reestablishment procedure is initiated, and stops the timer when a suitable cell has been detected (selected).

[0101] Additionally or alternatively, the timer (1) may be a timer (i.e., timer T304) for determining whether the handover is successful or unsuccessful. The MTC UE1 starts the timer (i.e., timer T304) upon receiving an RRC Connection Reconfiguration message including the Mobility Control Info IE (i.e., a handover command), and stops the timer upon successfully completing the random access procedure to the target cell.

[0102] For example, the timer in (2) above may be a timer used for MAC layer control. Specific examples of timers used for MAC layer control include timers related to discontinuous reception control (DRX) in the UE (e.g., OnDurationTimer, drx-InactivityTimer, drx-RetransmissionTimer, HART RTT Timer), timers measuring a period during which a scheduling request (SR) is prohibited (e.g., sr-ProhibitTimer, logicalChannelSR-ProhibitTimer), timers related to a report of uplink buffer capacity (Buffer Status Report (BSR)) (e.g., PeriodicBSR-Timer, RetxBSR-Timer), and timers related to a report of remaining uplink transmission power (Power Headroom Report (PHR)) (e.g., periodicPHR-Timer, prohibitPHR-Timer).

[0103] Additionally or alternatively, the timer (2) may be a timer used for controlling the RLC layer. Specific examples of timers used for controlling the RLC layer include a timer (T-Reordering) used for detecting loss of RLC PDUs and for controlling the order of RLC PDUs in DL data reception, and a timer (T-StatusProhibit) for measuring the period during which transmission of information indicating the reception status of DL data (STATUS PDU) is prohibited.

[0104] Additionally or alternatively, the timer (2) may be a timer used for controlling the PDCP layer. A specific example of a timer used for controlling the PDCP layer includes a timer (discardTimer) that determines whether or not to discard untransmitted data in UL data transmission.

[0105] For example, the timer (3) may be a timer used in the cell reselection process by the MTC UE1 in the RRC_IDLE state. Specifically, the timer (3) may be a timer that measures the duration (i.e., T-Reselection) during which the conditional expression for triggering cell reselection is satisfied.

[0106] The timers may start counting from either the beginning or end of repeated transmission of the associated (i.e., triggering) signal (message), or from either the beginning or end of repeated reception of the associated signal (message).

[0107] In the above-described embodiment, the wireless terminal 1 may be a non-MTC UE, that is, the above-described embodiment can be widely applied to communication between a UE and an eNB that supports coverage enhancement techniques including repeated transmission (or reception).

[0108] Furthermore, the above-described embodiments are not limited to LTE, LTE-Advanced, and their improvements, but may also be applied to communications between wireless terminals and base stations supporting coverage enhancement technologies in other wireless communication networks or systems.

[0109] For example, the above-described embodiments may be applied to a coverage improvement technology in a system called Narrow Band - Internet of Things (NB-IoT) under consideration by 3GPP. NB-IoT aims to accommodate low-cost and ultra-low-power IoT terminals (e.g., 10-year operation without battery replacement) in a cellular network. NB-IoT is very similar to Rel-13 MTC in terms of its purpose and the characteristics of the target terminals, and reuse of 3GPP Release 13 (Rel-13) MTC technology for NB-IoT is under consideration. Therefore, the above-described embodiments may be applied to NB-IoT. While a Rel-13 MTC UE transmits a RACH preamble during random access, in NB-IoT, it is under consideration that the UE transmit a message (e.g., a contention-based message) instead of a preamble on the PRACH. Thus, while improvements to Rel-13 MTC for NB-IoT or the introduction of features not present in Rel-13 MTC into NB-IoT are under consideration, the above-described embodiments are applicable to NB-IoT regardless of these differences.

[0110] Furthermore, the above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0111] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0112] (Appendix A1) A base station, Memory and at least one processor coupled to the memory; Equipped with The at least one processor is configured to transmit, to a wireless terminal, a first value associated with normal coverage or a first coverage enhancement level for a first radio resource configuration information element and information regarding a conversion factor; a value of the conversion factor obtained from the information about the conversion factor is used by the wireless terminal to derive from the first value a second value associated with a second coverage enhancement level for the first radio resource configuration information element. Base station.

[0113] (Appendix A2) the first radio resource configuration information element includes two or more radio resource configuration information elements; the second value includes two or more values associated with the second coverage enhancement level for the two or more radio resource configuration information elements; the conversion factor value being commonly used by the wireless terminal to derive the two or more values from the first value. A base station as described in Appendix A1.

[0114] (Appendix A3) the value of the conversion factor is used by the wireless terminal to derive from the first value a third value associated with a third coverage enhancement level for the first radio resource configuration information element in addition to the second value. A base station as described in Appendix A1.

[0115] (Appendix A4) the value of the conversion factor directly or indirectly specifies a scale ratio between the first value, the second value, and the third value; Base stations as described in Appendix A3.

[0116] (Appendix A5) the conversion factor value includes a multiplier value; the second value is calculated by multiplying the first value by the multiplier value; The base station according to any one of appendices A1 to A4.

[0117] (Appendix A6) the conversion factor value includes an offset value; the second value is calculated by adding the offset value to the first value; The base station according to any one of appendices A1 to A4.

[0118] (Appendix A7) the value of the conversion factor is also used as a value associated with the second coverage enhancement level for a second radio resource configuration information element different from the first radio resource configuration information element; The base station according to any one of appendices A1 to A4.

[0119] (Appendix A8) the first radio resource configuration information element includes at least one parameter related to a random access procedure; The at least one parameter is: (a) a parameter defining frequency and time resources available for transmitting a random access preamble; (b) a parameter indicating the total number of random access preambles; (c) a parameter indicating the maximum number of attempts to transmit a random access preamble; (d) a number of repetitions of transmitting a random access preamble per attempt to transmit a random access preamble; (e) a parameter indicating the duration of a random access response window; (f) a parameter indicating the duration of a contention resolution timer; (g) a maximum number of repetitions of transmitting a random access response by the base station; and (h) a parameter indicating the maximum number of retransmissions of a third message in response to receiving a random access response. The base station according to any one of appendices A1 to A7.

[0120] (Appendix A9) the at least one processor is further configured to calculate a value of the conversion factor to be transmitted to the wireless terminal using the first value and the second value, and transmit the calculated value of the conversion factor to the wireless terminal. The base station according to any one of appendices A1 to A8.

[0121] (Appendix B1) A wireless terminal, Memory and at least one processor coupled to the memory; Equipped with the at least one processor is configured to execute at least one module; The at least one module comprises: a receiving module configured to receive from a base station a first value associated with a normal coverage or a first coverage enhancement level for a first radio resource configuration information element; a calculation module configured to derive a second value associated with a second coverage enhancement level for the first radio resource configuration information element by converting the first value with a conversion factor value; Equipped with Wireless terminal.

[0122] (Appendix B2) the first radio resource configuration information element includes two or more radio resource configuration information elements; the second value includes two or more values associated with the second coverage enhancement level for the two or more radio resource configuration information elements; the calculation module commonly uses the value of the conversion factor to derive the two or more values from the first value. 2. A wireless terminal as described in Appendix B1.

[0123] (Appendix B3) the calculation module jointly uses the value of the conversion factor to derive from the first value, in addition to the second value, a third value associated with a third coverage enhancement level for the first radio resource configuration information element. 2. A wireless terminal as described in Appendix B1.

[0124] (Appendix B4) the value of the conversion factor directly or indirectly specifies a scale ratio between the first value, the second value, and the third value; 1. A wireless terminal as described in Appendix B3.

[0125] (Appendix B5) the at least one processor is configured to receive from the base station information regarding the conversion factor to obtain the value of the conversion factor. A wireless terminal according to any one of appendices B1 to B4.

[0126] (Appendix B6) the conversion factor value includes a multiplier value; the second value is calculated by multiplying the first value by the multiplier value; A wireless terminal according to any one of appendices B1 to B5.

[0127] (Appendix B7) the conversion factor value includes an offset value; the second value is calculated by adding the offset value to the first value; A wireless terminal according to any one of appendices B1 to B5.

[0128] (Appendix B8) the value of the conversion factor is also used as a value associated with the second coverage enhancement level for a second radio resource configuration information element different from the first radio resource configuration information element; A wireless terminal as described in Appendix B5.

[0129] (Appendix B9) The at least one module further comprises: an estimation module configured to estimate a coverage enhancement level to which the wireless terminal should comply; a communication module for communicating with the base station according to a value of the first radio resource configuration information element associated with the estimated coverage enhancement level; Equipped with the calculation module calculates the second value as a value of the first radio resource configuration information element associated with the estimated coverage enhancement level. A wireless terminal according to any one of appendices B1 to B8.

[0130] (Appendix B10) the first radio resource configuration information element includes at least one parameter related to a random access procedure; The at least one parameter is: (a) a parameter defining frequency and time resources available for transmitting a random access preamble; (b) a parameter indicating the total number of random access preambles; (c) a parameter indicating the maximum number of attempts to transmit a random access preamble; (d) a number of repetitions of transmitting a random access preamble per attempt to transmit a random access preamble; (e) a parameter indicating the duration of a random access response window; (f) a parameter indicating the duration of a contention resolution timer; (g) a maximum number of repetitions of transmitting a random access response by the base station; and (h) a parameter indicating the maximum number of retransmissions of a third message in response to receiving a random access response. A wireless terminal according to any one of appendices B1 to B9.

[0131] This application claims priority based on Japanese Patent Application No. 2015-217963, filed November 5, 2015, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0132] 1. Wireless Terminal Equipment (UE) 2 Base station (eNB) 1101 radio frequency (RF) transceiver 1103 Baseband Processor 1104 Application Processor 1106 Memory 1201 RF Transceiver 1204 processor 1205 memory

Claims

1. means for broadcasting system information including a first value of ra-ResponseWindowSize and at least one multiplier corresponding to a coverage enhancement level; means for receiving a Random Access (RA) preamble at the coverage enhancement level from User Equipment (UE) that performs wireless communication according to Narrow Band-Internet of Things (NB-IoT); means for transmitting an RA response (RAR) to the UE in response to the received RA preamble; Equipped with the RAR is received within an RA response window of a length indicated by a second value of the ra-ResponseWindowSize; the second value of the ra-ResponseWindowSize is derived by multiplying the first value of the ra-ResponseWindowSize by the at least one multiplier corresponding to the coverage enhancement level; The at least one multiplier is also set to a value corresponding to the number of repetitions of the RAR in the random access procedure. Base station.

2. broadcasting system information including a first value of ra-ResponseWindowSize and at least one multiplier corresponding to a coverage enhancement level; receiving a Random Access (RA) preamble at the coverage enhancement level from User Equipment (UE) communicating wirelessly in accordance with Narrow Band-Internet of Things (NB-IoT); and sending an RA response (RAR) to the UE in response to the received RA preamble; Equipped with the RAR is received within an RA response window of a length indicated by a second value of the ra-ResponseWindowSize; the second value of the ra-ResponseWindowSize is derived by multiplying the first value of the ra-ResponseWindowSize by the at least one multiplier corresponding to the coverage enhancement level; The at least one multiplier is also set to a value corresponding to the number of repetitions of the RAR in the random access procedure. A method for a base station.

3. A User Equipment (UE), means for receiving system information from a base station, the system information including a first value of ra-ResponseWindowSize and at least one multiplier corresponding to a coverage enhancement level; means for transmitting, by the UE performing wireless communication in accordance with Narrow Band-Internet of Things (NB-IoT), a Random Access (RA) preamble at the coverage enhancement level; means for receiving an RA response (RAR) from the base station within an RA response window having a length indicated by a second value of the ra-ResponseWindowSize in response to transmitting the RA preamble; Equipped with the second value of the ra-ResponseWindowSize is derived by multiplying the first value of the ra-ResponseWindowSize by the at least one multiplier corresponding to the coverage enhancement level; The at least one multiplier is also set to a value corresponding to the number of repetitions of the RAR in the random access procedure. UE.

4. 1. A method for User Equipment (UE), comprising: receiving system information from a base station, the system information including a first value of ra-ResponseWindowSize and at least one multiplier corresponding to a coverage enhancement level; transmitting, by the UE communicating wirelessly in accordance with Narrow Band-Internet of Things (NB-IoT), a Random Access (RA) preamble at the coverage enhancement level; and receiving an RA response (RAR) from the base station within an RA response window of a length indicated by a second value of the ra-ResponseWindowSize in response to transmitting the RA preamble; Equipped with the second value of the ra-ResponseWindowSize is derived by multiplying the first value of the ra-ResponseWindowSize by the at least one multiplier corresponding to the coverage enhancement level; The at least one multiplier is also set to a value corresponding to the number of repetitions of the RAR in the random access procedure. method.

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