WO2013161822A1

WO2013161822A1 - Communication terminal and measurement method

Info

Publication number: WO2013161822A1
Application number: PCT/JP2013/061935
Authority: WO
Inventors: 昌石原; 武志中森
Original assignee: 株式会社エヌ・ティ・ティ・ドコモ
Priority date: 2012-04-25
Filing date: 2013-04-23
Publication date: 2013-10-31
Also published as: JP2013229735A; JP6073569B2

Abstract

In the present invention, a communication terminal has: an information acquisition unit which acquires, from a wireless base station, frequency information indicating carrier frequencies in a serving cell that uses any among a predetermined plurality of system bandwidth capacities and each of neighboring cells that use any among the predetermined plurality of system bandwidth capacities; a measurement unit which measures a first radio quality with respect to the serving cell and a second radio quality with respect to the neighboring cells so as to obtain a difference in measurement values between the first and second radio qualities; and a correction unit which, if the carrier frequencies in the serving cell and each of the surrounding cells satisfy a predetermined relationship and the difference is greater than or equal to a predetermined value, corrects the measurement value of the first radio quality so as to reduce the difference.

Description

Communication terminal and measurement method

The present invention relates to a communication terminal and a measurement method.

(1) In the case of a mobile communication system provided with a plurality of cells, a mobile station or a user equipment (User Equipment: UE) continues communication by switching cells when moving from one cell to another cell. Is configured to do. Cell switching is called movement control or mobility control, and is called “cell reselection” or “handover” depending on the mode of switching. For example, it is assumed that the mobile station UE moves to a neighboring cell, and the reception power or reception quality of the signal from the neighboring cell becomes stronger than the reception power or reception quality of the signal from the serving cell. In such a case, the mobile station UE performs cell reselection or handover for neighboring cells. “Cell selection” is a process when the mobile station UE transitions from a serving cell to a neighboring cell in a standby state or an idle state. “Handover” is a process when the mobile station UE transitions from a serving cell to a neighboring cell during communication, that is, in a connected state (connected state).

(2) The mobile station UE needs to measure the reception power or reception quality of signals from the serving cell and the neighboring cells regardless of whether the mobile station UE is in a standby state or a connection state. The received power of the signal from the neighboring cell or serving cell is, for example, the received power (RSRP: Reference Signal Received Power) of the downlink reference signal (Reference Signal: RS) transmitted from the neighboring cell or serving cell, or all downlink data. A received signal strength indicator (Received Signal Strength Indicator: RSSI) that is received power may be used. The RSSI is an overall reception level observed in the mobile station UE, and is a reception level that includes not only the power of the desired signal from the own cell but also all of thermal noise, interference power from other cells, and the like. The reception quality may be expressed by, for example, RSRQ (Reference Signal Received Quality) which is a ratio or a relative ratio between RSRP and RSSI. RSRP, RSRQ, and the like are described in Non-Patent Document 1. The reference signal is a known signal that is known in advance between the transmitter and the receiver, and may be referred to as a reference signal, a pilot signal, a training signal, or the like.

(3) Received power and received quality are important parameters that serve as a basis for determining whether or not the mobile station UE should change cells, and thus need to be measured accurately. Suppose that the mobile station UE cannot accurately measure the reception power and reception quality of the serving cell or neighboring cells. For example, assume that the measured value is determined to be higher or lower than the actual value. In this case, the mobile station UE that should originally be in the area following the current serving cell transitions to a neighboring cell wastefully, or conversely, the mobile station UE that should move to the neighboring cell improperly tries to stay in the serving cell. It will be. As a result, there is a concern that service quality deteriorates for the user of the mobile station UE.

(4) In addition, in the standby state, the mobile station UE determines whether the mobile station UE is in or out of range based on the reception power and reception quality of the serving cell in addition to the measurement for celery selection. Is also going. For example, the mobile station UE compares the reception power and reception quality of the signal from the serving cell with a predetermined threshold, and if the reception power and reception quality of the signal from the serving cell are below the predetermined threshold, the mobile station UE is out of service In other cases, it is determined that the user is in the area. The predetermined threshold value used for the out-of-service area determination may be notified to the mobile station UE by signaling from the network (that is, the radio base station eNB). As an example, in the case of a long term evolution (LTE) mobile communication system, a predetermined threshold used for out-of-service area determination is called “Qrxlevmin” or “Qqualmin”.

(5) When the mobile station UE determines that the mobile station UE is out of the service area even though it is within the service area, the mobile station UE originally exists in an area where the mobile communication service can be provided. The mobile station UE cannot receive the mobile communication service. Conversely, when the mobile station UE determines that the mobile station UE is within the range even though it is out of the range, for example, it is determined that the mobile station UE is within the range even though the radio quality is originally so bad that communication is not established. Suppose. In this case, since the user apparatus cannot recognize being out of the service area, in addition to trying to receive the communication signal wastefully, there is a concern that the user cannot recognize that the user apparatus is out of service area. Therefore, from the viewpoint of accurately determining the out-of-service area and the in-service area, it is necessary to accurately measure the received power and the received quality.

(6) By the way, the measurement of received power and quality in the mobile station UE is not strictly defined in the standard specifications. For example, the bandwidth for measurement and the measurement interval (measurement period and interval) are as follows: It is implementation dependent. As an example, consider an LTE mobile communication system. The LTE system is a successor of the wideband code division multiple access (Wideband Code Division Multiple Access: W-CDMA) system and the high speed downlink packet access (High Speed Downlink Packet Access: HSDPA) system. In the case of the LTE scheme, downlink reference signals used for measurement by the mobile station UE are regularly and two-dimensionally distributed in both the frequency axis direction and the time axis direction. Non-patent document 2 describes the arrangement of reference signals (Reference Signal: RS). The mobile station UE measures received power and reception quality using the reference signal arranged in this way, but the mobile station UE can measure the bandwidth to be measured, the measurement interval, etc. within a range that satisfies a certain measurement accuracy. Can be set arbitrarily.

In a communication environment where a system band of a carrier frequency different from the carrier frequency of the serving cell is used in the neighboring cell, the mobile station residing in the serving cell accurately considers the amount of interference from the neighboring cell and accurately determines the reception quality, etc. It is desirable to be able to measure.

According to one embodiment of the present invention,
A communication terminal that communicates with a radio base station,
A first carrier frequency in a serving cell in which any one of a plurality of predetermined system bandwidths is used and a second carrier in a neighboring cell in which any of the plurality of predetermined system bandwidths are used An information acquisition unit for acquiring frequency information indicating a frequency from the radio base station;
The first radio quality for the serving cell and the second radio quality for the neighboring cell are measured, and the difference between the first measurement value of the first radio quality and the second measurement value of the second radio quality. Measuring unit for obtaining
When the first carrier frequency in the serving cell and the second carrier frequency in each of the neighboring cells satisfy a predetermined relationship and the difference is greater than or equal to a predetermined value, the first carrier frequency is set to be small. There is provided a communication terminal having a correction unit that corrects the first measurement value of radio quality.

According to another embodiment of the present invention,
A measurement method performed by a communication terminal communicating with a radio base station,
A first carrier frequency in a serving cell in which any one of a plurality of predetermined system bandwidths is used and a second carrier in a neighboring cell in which any of the plurality of predetermined system bandwidths are used Obtaining frequency information indicating a frequency from the radio base station;
The first radio quality for the serving cell and the second radio quality for the neighboring cell are measured, and the difference between the first measurement value of the first radio quality and the second measurement value of the second radio quality. A step of seeking
When the first carrier frequency in the serving cell and the second carrier frequency in the neighboring cell satisfy a predetermined relationship and the difference is equal to or greater than a predetermined value, the first carrier frequency is set to be small. Correcting a first measurement of radio quality is provided.

According to the present invention, in a communication environment where a system band having a carrier frequency different from the carrier frequency of the serving cell is used in the neighboring cell, the mobile station located in the serving cell appropriately considers the amount of interference from the neighboring cell. The reception quality can be accurately measured.

The figure which shows the specific example of a variable system bandwidth. The figure which shows the zone | band which a user apparatus measures. The figure which shows the frequency relationship between the cells of a different system bandwidth. The figure which shows the frequency relationship between the cells of a different system bandwidth. The figure which shows the signal relationship between the cells of a different system bandwidth. 1 is an overall view of a mobile communication system according to an embodiment of the present invention. The functional block diagram of the mobile station by embodiment of this invention. The flowchart which shows the operation example of the mobile station by embodiment of this invention. The flowchart which shows the operation example of the mobile station which performs non-service area determination. The flowchart which shows the operation example of the mobile station which performs celery selection. The flowchart which shows the operation example of the mobile station which performs a hand-over.

FIG. 1 shows various system bandwidths that can be used in the LTE scheme. As shown, there are various system bandwidths depending on the capabilities of the base station and the user equipment. Specifically, a variable system bandwidth of 6 to 100 resource blocks (1.4 to 20 MHz) can be used. For example, a system bandwidth of 6 resource blocks is used in a mobile communication system with LTE, and a system bandwidth of 15, 25, 50, 75, or 100 resource blocks is used in another mobile communication system of LTE. Good. A resource block (RB) is one transmission unit in the frequency direction, and the frequency bandwidth of one resource block is 180 kHz (refer to Non-Patent Documents 3 and 4 for this point). Note that the system bandwidth may also be referred to as a channel bandwidth (Channel Bandwidth).

As described above, in the LTE mobile communication system, the downlink reference signal RS used by the mobile station UE for measurement is regularly distributed in both the frequency axis direction and the time axis direction. Yes. As long as a certain measurement accuracy is satisfied, the mobile station UE can arbitrarily set a measurement band, a measurement bandwidth, a measurement period, and the like.

Generally, as the measurement bandwidth is wider and the measurement period is longer, the measurement accuracy tends to be improved, but more processing load and power are required. Furthermore, there is a limit to the improvement of measurement accuracy according to the radio quality. Therefore, it is desirable to devise so as to measure the radio quality in the serving cell and neighboring cells in the narrowest bandwidth and in the short time interval. For example, the mobile station UE is configured to measure radio quality using only a signal having a predetermined bandwidth (narrower than the system bandwidth) centered on the carrier frequency, thereby reducing the processing load. And can promote battery saving effect.

Specifically, a synchronization channel (SCH) and a physical broadcast channel (PBCH) are transmitted using 6 resource blocks at the center of each variable stem band from 1.4 MHz to 20 MHz. . In this way, the mobile station UE can receive the synchronization channel SCH and the broadcast channel PBCH by receiving signals for the central 6 resource blocks as shown in FIG. 2 regardless of the system bandwidth. Received power and reception quality can be measured.

However, when the radio quality greatly fluctuates within the range of the system bandwidth, that is, in an environment where the radio quality varies depending on the frequency band, if the measurement bandwidth is limited to the central 6 resource blocks, other cells The amount of interference from the camera cannot be measured properly. As a result, the mobile station UE cannot appropriately measure the radio quality, resulting in degradation of measurement accuracy. For example, as shown in FIG. 3, the system bandwidth of cell 1 is 20 MHz, the system bandwidth of cells 2 and 3 is 10 MHz, and the center frequency of the system band of each cell is in the positional relationship shown in the figure. Suppose that In this case, the center frequencies f ₁ -f ₃ of the system bands used in the cells 1-3 are different from each other, and two 10 MHz system bandwidths are included in the 20 MHz system bandwidth of the cell 1, Each of the two corresponds to cell 2 and cell 3. In the case of the example shown in FIG. 4, the system bandwidth of the cell 1 is 10 MHz, the system bandwidth of the cells 2 and 3 is 10 MHz, and the center frequency of the system band of each cell has a positional relationship as shown in the figure. ing. In this case, the center frequencies f ₁ -f ₃ of the system band used in each of the cells 1-3 are different from each other, and two 5 MHz system bandwidths are included in the 10 MHz system bandwidth of the cell 1, Each of the two corresponds to cell 2 and cell 3. In the example shown in FIGS. 3 and 4, one system band includes the entire other system band, but more generally, one system band includes a part of the other system band. Or may not be included at all.

Assume that cell 1 in the example shown in FIGS. 3 and 4 is a serving cell, and cells 2 and 3 are neighboring cells. In this case (specifically, f ₁ 6 resource blocks of frequencies centered at) a particular bandwidth of the center of the serving cell measured by carried out. Assume that the measurement target is reception quality. As described above, the reception quality RSRQ is a ratio between the reception power RSRP of the reference signal and the total reception power RSSI (RSRQ = RSRP / RSSI). In this case, the mobile station UE needs to measure not only the reception power RSRP of the reference signal from the serving cell 1 but also the power from the neighboring cells 2 and 3 (interference power when viewed from the serving cell 1). However, near the frequency f ₁ , the power of signals coming from the cells 2 and ₃ is much lower than the power at the frequencies f ₂ and f ₃ . For this reason, the reception quality measured in the vicinity of the frequency f ₁ looks good, but this is because the interference due to the other carrier frequencies f ₂ and f ₃ is not accurately reflected. This will be described with reference to FIG.

FIG. 5 specifically shows the system band of the cell 1-3 for the example shown in FIG. The system bandwidth of the cell 1 is 10 MHz, but the bandwidth that actually includes the communication signal is 9 MHz. Similarly, the system bandwidth of the cells 2 and 3 is 5 MHz, but the bandwidth in which the communication signal is actually included is 4.5 MHz. The mobile station UE needs to measure not only the received power RSRP of the reference signal from the serving cell 1 but also the power from the neighboring cells 2 and 3 (interference power when viewed from the serving cell 1) in order to measure the total received power RSSI. is there. However, since the vicinity of the frequency f ₁ is the boundary of the system band for the cell 2, the signal from the cell 2 is expected to be quite weak in the vicinity of the frequency f ₁ . Similarly, since the vicinity of the frequency f ₁ is the boundary of the system band for the cell 3 as well, the signal from the cell 3 is expected to be considerably weak in the vicinity of the frequency f ₁ . As a result, the reception quality RSRQ for the cell 1 in the vicinity of the frequency f ₁ shows a considerably good quality. However, when communication is performed in the serving cell 1, communication is performed not only in the vicinity of the frequency f ₁ but also over the entire bandwidth of 9 MHz. At frequencies other than the vicinity of the frequency f ₁ , for example, the frequencies f ₂ and f _3, etc., the signals from the cells 2 and 3 are received fairly strongly, and the reception quality in the serving cell 1 becomes worse than the value near the frequency f _1. . Thus, when the reception quality depending on the frequency at which the measurements are different, when it is determined necessity or out of service within the cell transition based on the apparent reception quality in the vicinity of the center frequency f ₁ good, cell transition There is a concern that it is not always possible to properly determine whether it is necessary or not and whether the area is outside the service area.

According to an embodiment of the present invention, a mobile station and a mobile station that compare measured values using the total received power RSSI of each of the serving cell and neighboring cells and determine whether to correct the measured value according to the comparison result A communication method is provided. By correcting the measurement value according to the comparison result, it is possible to provide a mobile station and a mobile communication method that can reduce processing load and power consumption while preventing deterioration in measurement accuracy.

A mobile station according to an embodiment of the present invention includes a measurement unit that measures radio quality of a serving cell and a neighboring cell, a carrier frequency management unit that manages a positional relationship between carrier frequencies of the serving cell and the neighboring cell, and information on the carrier frequency management unit. A measurement comparison unit that compares measurement results obtained by the measurement unit and a correction unit that determines whether or not the measurement value needs to be corrected according to the comparison result and corrects the measurement value that needs correction are provided.

The measurement method performed by the mobile station according to the embodiment of the present invention compares the measurement value with the step of measuring the radio quality of the serving cell and the neighboring cell, and compares the measurement result with the positional relationship of the carrier frequency of the serving cell and the neighboring cell. Accordingly, there is a step of correcting the measurement value.

According to the present invention, the measurement result is corrected according to the positional relationship of the carrier frequency of the serving cell and the neighboring cells and the comparison result of the measured value in an environment where the radio quality over the system bandwidth varies depending on the frequency band. As a result, even if the measurement is limited to the center specific bandwidth (for example, 6 resource blocks) without expanding the bandwidth to be measured, the reception quality is appropriately considered in consideration of interference from other cells. And the processing load and power consumption can be reduced while maintaining the measurement accuracy above a certain level.

Embodiments will be described from the following viewpoints with reference to the accompanying drawings. In the figures, similar elements are given the same reference numbers or reference signs.

1. 1. Mobile communication system 2. Mobile station 3. Example of operation for measuring reception quality 4. Example of operation for determining out-of-service area based on reception quality 5. Example of operation for performing cell reselection based on reception quality 6. Operation example for performing handover based on reception quality Effects of Embodiments The classification of these items is not essential to the present invention, and the items described in two or more items may be used in combination as necessary. It may apply to matters described in other items (unless inconsistent).

<1. Mobile communication system>
FIG. 6 schematically shows a mobile communication system according to an embodiment of the present invention. As an example, the mobile communication system is an LTE mobile communication system, but any suitable mobile communication system capable of using various system bandwidths may be used. For example, an LTE advanced (LTE-Advanced) mobile communication system may be used. The radio access scheme in the illustrated mobile communication system is an Orthogonal Frequency Division Multiplexing (OFDM) scheme for the downlink, and a single-carrier frequency division multiple access (Single-Carrier Frequency Division Multiplexing). : SC-FDMA) system.

The mobile station UE is typically a mobile phone, but may be another device. For example, the mobile station UE is a user device, an information terminal, a high-performance mobile phone, a smartphone, a tablet computer, a personal digital assistant (PDA), a portable personal computer, a palmtop computer, a laptop computer, etc. It is not limited.

In the illustrated mobile communication system, the radio base station eNB exchanges various signals with the mobile station UE. For example, the radio base station eNB, in the downlink, a physical broadcast channel PBCH, a synchronization channel SCH, a reference signal RS, a physical downlink control channel (Physical Downlink Channel: PDCCH), a physical downlink shared channel (Physical Downlink Shared Channel: PDSCH) and the like are transmitted to the mobile station UE.

On the other hand, the mobile station UE, in the uplink, a demodulation reference signal (DM-RS), a quality measurement reference signal (Sound Reference Reference Signal: SRS), a physical uplink control channel (Physical Uplink Channel: PUCCH), A physical uplink shared channel (Physical Uplink Shared Channel: PUSCH) or the like is transmitted to the radio base station eNB.

<2. Mobile station>
FIG. 7 shows a functional block diagram of the mobile station UE. FIG. 7 exemplifies a part particularly related to the present embodiment among various functional units or processing units provided in the mobile station. The illustrated mobile station UE includes a parameter acquisition unit 11, a carrier frequency management unit 12, a measurement unit 13, a measurement comparison unit 14, a measurement result correction unit 15, a filtering unit 16, a determination unit 17, and a notification unit. 18.

The parameter acquisition unit 11 acquires a parameter related to cell switching (specifically, a parameter related to mobility control) from the radio base station eNB. For example, the parameters related to mobility control include “EARFCN” indicating the carrier frequency of the neighboring cell, “Qrxlevmin” which is a predetermined threshold value used for the in-range / out-of-range determination. In addition, the parameters related to mobility control may include parameters “Qhyst”, “Qoffset”, “Trselection”, and the like that represent threshold values used for determination of celery selection. Furthermore, the parameters related to mobility control may include “Time-to-trigger”, which is a parameter related to handover control, hysteresis, offset, filter coefficient, and the like. Here, “Qhyst” is a positive offset given to the radio quality of the serving cell in the determination of celery selection, and “Qoffset” is a negative offset given to the radio quality of the serving cell in the determination of celery selection. It is. Further, “Treleselection” is a time-direction hysteresis used in the determination of celery selection, and is a parameter equivalent to “Time-to-trigger” in handover. The filter coefficient is notified to the filtering unit 16.

Based on the carrier frequency notified from the parameter acquisition unit 11, the carrier frequency management unit 12 stores the positional relationship of each carrier frequency in the frequency domain, and measures each carrier frequency according to the positional relationship. The measurement result comparison unit 14 is instructed to compare the results. The positional relationship of each carrier frequency in the frequency domain may indicate whether or not each carrier frequency is included in the same band based on “EARFCN” indicating the carrier frequency, for example. The determination of whether or not they are included in the same band may be made based on, for example, the degree of difference between carrier frequencies. “EARFCN” may be expressed by an absolute value that uniquely indicates the carrier frequency of each cell. Further, when determining whether or not a plurality of carrier frequencies are included in the same band, the frequency to be compared may be the carrier frequency of the serving cell or the carrier frequency of the neighboring cells. Further, it may be determined whether or not the carrier frequency of the neighboring cell exists in the system band of the serving cell, and whether or not the carrier frequency of the neighboring cell exists in a certain frequency range from the end of the system band of the serving cell. May be determined.

The measurement unit 13 measures the received power, radio quality, or reception quality in the serving cell and surrounding cells of the mobile station UE. The radio quality may be measured, for example, based on received power of signals (for example, reference signal RS) received from the serving cell and the neighboring cells of the mobile station UE. More specifically, the received power RSRP and the total received power RSSI of the reference signal may be measured, and the radio quality may be measured from their relative ratio RSRQ. The RSSI is an overall reception level observed in the mobile station UE, and is a reception level that includes not only the power of the desired signal from the own cell but also all of thermal noise, interference power from other cells, and the like. The measurement unit 13 may measure the radio quality at an appropriate time interval. The time interval (that is, the measurement interval) may be a long time such as 200 ms, or may be a short time such as 1 ms as long as the measurement accuracy can be maintained. Further, the measurement unit 13 may measure the radio quality at every intermittent reception (DRX) cycle. The measurement unit 13 measures wireless quality over a predetermined frequency range. For example, the radio quality may be measured within a range of 6 resource blocks near the center frequency. The range of 6 resource blocks is merely an example, and any appropriate value that is equal to or less than the system bandwidth may be used.

In the above description, the radio quality or the reception quality is expressed by the received power RSRP of the reference signal or the relative ratio RSRQ between the RSRP and the total received power RSSI, but this is not essential to the present invention. As the wireless quality, SIR (Signal to Interference Ratio), CQI (Channel Quality Indicator), or the like may be used instead of RSRP or RSRQ. The CQI is downlink radio quality information, and is specifically described in Non-Patent Document 5.

The measurement unit 13 notifies the filtering unit 16 and the measurement result comparison unit 14 of the measurement results of the radio quality in the serving cell and surrounding cells of the mobile station UE.

The measurement result comparison unit 14 compares the measurement value, which is the measurement result from the measurement unit 13, based on an instruction from the carrier frequency management unit 12, and notifies the measurement result correction unit 15 of the comparison result. For example, the total received power RSSI may be used as a measurement result used for measurement value comparison. The information notified to the measurement result correction unit 15 may be a difference in RSSI of each cell.

The measurement result correction unit 15 corrects the measurement value notified from the measurement unit 13 based on the information from the measurement result comparison unit 14. For example, it may be determined whether or not correction is performed depending on whether or not the difference between the measurement results notified from the measurement result comparison unit 14 exceeds a predetermined value. When the correction is performed, the measurement result correction unit 15 may perform the correction by adding the difference notified from the measurement result comparison unit 14 to the measurement value. Further, filtering according to the difference may be performed by the filtering unit 16.

For example, the serving cell is cell x, the neighboring cell is cell y, the measured value before correction of RSSI for the serving cell is D _x-1 , the measured value after correction is D _x, and the measured value of RSSI for the neighboring cell is D _y. And In this case, D _x may be corrected according to the following equation.

D _x = D _x-1 + d · k (1)
d = D _y −D _x−1 (2)
0 ≦ k ≦ 1 (3)
Here, d shows the difference of the measured value of RSSI with respect to a serving cell. k is a filter coefficient taking a value from 0 to 1. The filter coefficient k is a parameter that determines how much the measurement difference d contributes to the corrected measurement value Dx. The above mathematical formula is merely an example, and any appropriate correction that reduces the difference between the measurement values for the serving cell and the neighboring cells may be performed.

In addition to receiving the filter coefficient k (predetermined coefficient) from the parameter acquisition unit 11, the filtering unit 16 receives, from the measurement unit 13 or the measurement result correction unit 15, radio frequency measurement values in the serving cell and neighboring cells of the mobile station UE. Receive them and use them for filtering or averaging. For example, the index of the measurement timing at a certain time is “n”, the measurement result after filtering is “F _n ”, the filter coefficient is “k”, and the measurement result after filtering at the measurement timing of the previous time point is It is assumed that “F _n-1 ” and the measurement result in the measurement unit 13 is “M _n ”. In this case, filtering is performed so that the following relationship is established.

F _n = (1−a) · F _n−1 + a · M _n (4)
a = (1/2) ^{(k / 4)} (5)
a represents a forgetting factor. In addition, when calculating the measurement result “F _n ” after filtering, by adjusting the filter coefficient “a”, the latest measurement result “M _n ” in the measuring unit 13 and the past measurement result “F _n ” “F” are adjusted. The contribution ratio of “ _n−1 ” is adjusted.

The determination unit 17 receives the measurement result before filtering from the measurement unit 13 in addition to receiving the measurement result after filtering by the filtering unit 16. The determination unit 17 determines whether or not the mobile station UE is in the area (or whether it is out of the area) using the measurement result of the radio quality measured by the measurement unit 13. For example, in the standby state (Idle state), the determination unit 17 may receive the measurement result directly from the measurement unit 13 instead of the above-described filtering unit 16 and perform the in-range / out-of-range determination.

The determination unit 17 also determines whether or not to perform cell reselection or handover using the measurement result of the radio quality measured by the measurement unit 13. For example, the determination unit 17 may determine that cell reselection or handover should be performed when a predetermined condition is satisfied for a predetermined period or longer. The condition for determination may be expressed by the following mathematical formula. The predetermined period may be referred to as “Treletion”.

(Received power of signal from neighboring cells) + (Qhyst)> (Received power of signal from serving cell) (6)
The determination unit 17 determines whether or not the measurement result after filtering received from the filtering unit 16 should be notified. For example, the determination unit 17 may determine that the above measurement result should be notified when a predetermined condition is satisfied for a predetermined period or longer. The predetermined condition may be expressed by the following mathematical formula. The predetermined period may be referred to as “Time-to-trigger”.

(Received power of signal from neighboring cells) + (Hysteresis)> (Received power of signal from serving cell) (7)
When the determination unit 17 determines that the measurement result should be transmitted, the notification unit 18 notifies the radio base station eNB of the measurement result. Specifically, the notification unit 18 notifies the radio base station eNB of the measurement result via the physical uplink shared channel PUSCH. Note that the report of the measurement result may be referred to as a measurement report (Measurement Report).

<3. Example of operation for measuring reception quality>
An operation example of the mobile station UE according to the embodiment of the present invention will be described with reference to FIGS. FIG. 8 shows an example of a radio quality measurement procedure performed in the mobile station UE according to the embodiment of the present invention.

In step S100, the mobile station UE measures the radio quality. As described above, the mobile station UE measures the radio quality for each of the serving cell and the neighboring cells.

In step S101, the mobile station UE confirms the frequency positions of the carrier frequencies of the serving cell and the neighboring cells, and determines whether the carrier frequencies of the serving cell and the neighboring cells are located in the same band. If it is located in the same band, the flow proceeds to step S102.

In step S102, the mobile station UE determines whether or not there is a difference of a certain value or more between the RSSI of the serving cell and the RSSI of the neighboring cell. If there is a difference greater than or equal to a certain value, the flow proceeds to step S103.

In step S103, the mobile station UE corrects the RSSI of the serving cell and the RSSI of the neighboring cells.

In step S104, the mobile station UE filters the measurement result, and the flow for measuring the quality ends.

On the other hand, if it is determined in step S101 that the carrier frequencies of the serving cell and the neighboring cells are not located in the same band, the flow proceeds to step S104, and the measurement result is filtered. In step S102, if the difference between the RSSI of the serving cell and the RSSI of the neighboring cell is less than a certain value, the flow proceeds to step S104, and in this case, no correction is performed.

For example, it is assumed that the mobile station UE is in a cell 1 as shown in FIG. 3 and the cell 1 is a serving cell. In this case, the peripheral cells are cells 2 and 3. In step S101, the mobile station UE determines whether or not the bands of the serving cell and the neighboring cells are in the same band based on the positional relationship of the carrier frequencies f ₁ -f ₃ . In the case of the current example, since the carrier frequencies f ₁ -f ₃ are in the same band, the flow proceeds to step S102. The mobile station UE compares RSSI (RSSI ₁ ) for the serving cell 1 with RSSI (RSSI ₂ and RSSI ₃ ) for the neighboring cells ₂ and ₃ . The RSSI for the serving cell 1 is measured in the vicinity of the center frequency or the carrier frequency f ₁ (for example, within a frequency range of 6 resource blocks). Since the vicinity of the carrier frequency f ₁ is at the end of the system band of the cells 2 and 3, the signals from the cells 2 and 3 are very weak, and most of the RSSI ₁ is attributed to the signal from the cell 1. On the other hand, since the vicinity of the carrier frequency f ₂ is in the system band of the cell 1, it is expected that the RSSI ₂ includes not only the signal from the cell 2 but also the signal from the cell 1. Similarly, since the vicinity of the carrier frequency f ₃ is in the system band of the cell 1, it is expected that the RSSI ₃ includes not only the signal from the cell 3 but also the signal from the cell 1. Therefore, RSSI ₁ including only the signal from cell 1 is expected to be significantly different from RSSI ₂ including the signal from both cell 1 and cell 2. It is also expected that RSSI ₁ including only the signal from cell 1 is significantly different from RSSI ₃ including signals from both cell 1 and cell 3. For this reason, the flow proceeds from step S102 to step S103. In step S103, the mobile station UE corrects the RSSI (RSSI ₁ ) for the serving cell according to, for example, the above formulas (1) to (3). The corrected RSSI for the serving cell 1 is RSSI ₁ + k · d (0 ≦ k ≦ 1), and d = RSSI ₂ −RSSI ₁ (or d = RSSI ₃ −RSSI ₁ ). That is, the total received power RSSI for the serving cell 1 is corrected to increase, and as a result, the reception quality RSRQ (= RSRP / RSSI) for the serving cell 1 is corrected to be low. In this way, the influence of interference from the cells 2 and 3 that cannot be seen in the vicinity of the carrier frequency f ₁ can be appropriately reflected in the reception quality for the serving cell 1.

<4. Example of operation for determining out-of-service area based on reception quality>
FIG. 9 shows a procedure for determining whether the mobile station UE is in or out of range.

In step S201, the mobile station UE measures the received power of the signal from the serving cell. This received power is obtained by measuring according to the procedure shown in FIG. 8, being corrected as necessary, and filtered.

In step S202, the mobile station UE determines whether or not the received power of the signal from the serving cell is below a predetermined threshold S.

If the received power of the signal from the serving cell is less than the predetermined threshold S, in step S203, the mobile station UE determines whether the number of times that the received power of the signal from the serving cell is lower than the predetermined threshold S exceeds the predetermined number N. Determine whether or not. The mobile station UE counts the number of received powers below or above the predetermined threshold.

If the counted number exceeds the number N, in step S204, the mobile station UE determines whether the received power of the signals from the serving cell and the neighboring cells is below a predetermined threshold S for a certain period (for example, 10 seconds). Determine whether or not.

If no cell exceeding the predetermined threshold S is detected, it is determined in step S205 that the mobile station UE is out of range, and if a cell exceeding the predetermined threshold S is detected, the mobile station UE is determined to be within range.

<5. Example of celery selection based on received quality>
FIG. 10 shows an example of a procedure for performing celery selection in the mobile station UE.

In step S301, the mobile station UE measures received power of signals from the serving cell and neighboring cells. This received power is also determined by being measured according to the procedure shown in FIG. 8, corrected as necessary, and filtered.

In step S302, the mobile station UE determines whether or not the following mathematical formula is satisfied for the received power of signals from neighboring cells.
(Received power of signal from neighboring cell) + (Qhyst)> (Received power of signal from serving cell) (8)
When it determines with Formula (8) being satisfy | filled, in step S303, the mobile station UE performs celery selection so that it may be located in the applicable surrounding cell.

<6. Example of operation for performing handover based on reception quality>
FIG. 11 shows an example of a procedure for causing the mobile station UE to perform a handover.

In step S401, the mobile station UE measures received power of signals from the serving cell and the neighboring cells. This received power is also determined by being measured according to the procedure shown in FIG. 8, corrected as necessary, and filtered.

In step S402, the mobile station UE determines whether or not the following formula is satisfied for the received power of signals from neighboring cells.
(Received power of signal from neighboring cells) + (Hysteresis)> (Received power of signal from serving cell) (9)
When it determines with Formula (9) being satisfy | filled, the mobile station UE notifies the event for reporting the above-mentioned measurement result to a network. In the case of the LTE system, this event is called “event A3”.

Here, it is assumed that the values calculated by the following formulas (10) and (11) are used for the received power (radio quality) F _n of the signal. Specifically, the higher layer notifies the mobile station UE to perform the filtering process (L3 Filtering) shown in Equation (10) for the measurement value of the physical layer.

F _n = (1−a) · F _n−1 + a · M _n (10)
a = 1/2 ^{(k / 4)} (11)
The value of the filter coefficient “k” in Expression (11) is notified in advance from the radio base station eNB to the mobile station UE. In Equation (10), “n” is an index that specifies the measurement timing, “F _n ” is the measurement result after filtering, and “F _n−1 ” is the measurement timing at the previous time point. And “M _n ” is a measurement result in the measurement unit.

In step S403, when the network receives the report of the event A3, the network determines that the mobile station UE that has made the report should be handed over to the cell indicated by the event A3.

Note that, in the mobile communication system according to the above-described embodiment, a criterion for one type of radio quality is used. However, criteria for a plurality of types of radio quality may be used.

<7. Effect by Embodiment>
According to the mobile communication system according to the embodiment of the present invention, the mobile station UE can appropriately measure the radio quality even when the interference from other cells is different depending on the frequency band in the system band. It becomes. When the mobile station UE reports an appropriate measurement result to the network at an appropriate timing, it is possible to continue communication without causing communication interruption, and to suppress the load on the network and the current consumption of the mobile station UE, Furthermore, user convenience can be improved.

The features of the present embodiment described above may be expressed as follows.

The mobile station UE according to the present embodiment is a mobile station UE that communicates with a radio base station eNB, and includes a measurement unit 13 that measures radio quality of a serving cell and neighboring cells in the mobile station UE, and carrier frequency management that manages a carrier frequency. The measurement result comparison unit 14 that compares the measurement result notified from the measurement unit 13 based on the information from the unit 11, the information from the carrier frequency management unit 11, and the measurement result is corrected based on the information from the measurement result comparison unit The measurement result correction unit 15 uses the carrier frequency acquired from the parameter acquisition unit 12, and the measurement result correction unit 15 uses the carrier frequency acquired from the parameter acquisition unit 12 based on the information notified by the measurement result comparison unit 14. The measurement result is corrected.

The mobile station UE may further include a determination unit 17 that determines whether the mobile station UE is within the service area or out of service area using the measurement result of the radio quality measured by the measurement unit 13.

The mobile station UE may further include a determination unit 17 that determines whether or not to perform cell reselection using the measurement result of the radio quality measured by the measurement unit 13.

In the mobile station UE, using a predetermined coefficient, a filtering unit 16 that filters the measurement result of the radio quality measured by the measurement unit 13, and a determination that determines whether or not the filtered measurement result should be notified A part 17 may be further provided.

The mobile communication method according to the present embodiment has a step of measuring the radio quality of the serving cell and the neighboring cell in the mobile station, and the measurement result obtained by the step is based on the carrier frequency and the measurement result of the serving cell and the neighboring cell. , Correct the measurement results.

The operations of the radio base station eNB and the mobile station UE described above may be realized by hardware, may be realized by a software module executed by a processor, or may be realized by a combination of both. Software modules include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electronically Erasable and Programmable ROM, CD, ROM, CD, ROM, etc. It may be provided on any arbitrary storage medium. Such a storage medium is connected to the processor so that the processor can read and write information from and to the storage medium. The storage medium may be integrated in the processor. Further, the storage medium and the processor may be provided in an application specific integrated circuit (ASIC). The ASIC may be provided in the radio base station eNB and the mobile station UE. The storage medium and the processor may be provided in the radio base station eNB and the mobile station UE as discrete components.

As described above, the communication terminal and the measurement method have been described by way of examples. However, the present invention is not limited to the above examples, and various modifications and improvements can be made within the scope of the present invention. For example, the present invention may be applied to any appropriate mobile communication system that performs communication using any of a plurality of system bandwidths. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. In addition, although specific mathematical formulas have been used to facilitate understanding of the invention, these mathematical formulas are merely examples unless otherwise specified, and other mathematical formulas that yield similar results may be used. Good. The classification of items in the above description is not essential to the present invention, and the items described in two or more items may be used in combination as necessary, or the items described in one item may be used in different items. It may be applied to the matters described in (if not inconsistent). The boundaries between functional units or processing units in the functional block diagram do not necessarily correspond to physical component boundaries. The operations of a plurality of functional units may be physically performed by one component, or the operations of one functional unit may be physically performed by a plurality of components.

Hereinafter, specific embodiments of the present invention are listed as examples.

(Additional item 1)
A mobile station that communicates with a radio base station,
Comprising a parameter acquisition unit configured to acquire the carrier frequency of the serving cell and neighboring cells from the radio base station;
Comprising a measurement unit configured to measure the radio quality of a serving cell and a neighboring cell in the mobile station;
A carrier frequency management unit for managing the carrier frequency acquired by the parameter acquisition unit;
Based on the instruction to the carrier frequency management unit, comprising a measurement result comparison unit that compares the measurement result notified from the measurement unit,
Based on the information from the measurement result comparison unit, comprising a measurement result correction unit for correcting the measurement result notified from the measurement unit,
The mobile station characterized in that the measurement result correction unit is configured to correct a measurement result according to the carrier frequency and a measurement result comparison result.

(Appendix 2)
The mobile station according to attachment 1, further comprising a determination unit configured to determine whether the mobile station is within or out of service using the wireless quality measurement result measured by the measurement unit. May be.

(Additional Item 3)
The mobile station according to attachment 1, further comprising a determination unit configured to determine whether or not to perform cell reselection using the measurement result of the radio quality measured by the measurement unit. May be.

(Appendix 4)
The mobile station according to attachment 1, wherein a filtering unit configured to filter the measurement result of the radio quality measured by the measurement unit using a predetermined coefficient;
And a determination unit configured to determine whether or not the filtered measurement result should be notified.

(Appendix 5)
A step of obtaining the carrier frequency of the serving cell and the neighboring cell from the radio base station in the mobile station, the step of measuring the radio quality of the serving cell and the neighboring cell, the step of managing the carrier frequency and the step And comparing the measured results.
The mobile communication method according to claim 1, wherein the measurement result is corrected according to the comparison result of the measurement result.

This international patent application claims priority based on Japanese Patent Application No. 2012-100065 filed on April 25, 2012. The entire contents of Japanese Patent Application No. 2012-100065 are incorporated herein by reference. Incorporate.

DESCRIPTION OF SYMBOLS 11 Parameter acquisition part 12 Carrier frequency management part 13 Measurement part 14 Measurement comparison part 15 Measurement result correction | amendment part 16 Filtering part 17 Determination part 18 Notification part

Claims

A communication terminal that communicates with a radio base station,
A first carrier frequency in a serving cell in which any one of a plurality of predetermined system bandwidths is used and a second carrier in a neighboring cell in which any of the plurality of predetermined system bandwidths are used An information acquisition unit for acquiring frequency information indicating a frequency from the radio base station;
The first radio quality for the serving cell and the second radio quality for the neighboring cell are measured, and the difference between the first measurement value of the first radio quality and the second measurement value of the second radio quality. Measuring unit for obtaining
When the first carrier frequency in the serving cell and the second carrier frequency in the neighboring cell satisfy a predetermined relationship and the difference is equal to or greater than a predetermined value, the first radio is set so that the difference becomes small. A correction unit that corrects the first measurement value of quality.
The communication terminal according to claim 1, further comprising a filtering unit that averages the first measurement value of the first wireless quality corrected by the correction unit.
The communication terminal according to claim 2, further comprising a determination unit that determines that the communication terminal exists within or outside the communication system using the first measurement value averaged by the filtering unit.
The communication terminal according to claim 2, further comprising a determination unit that determines whether or not the communication terminal should change a serving cell using the measurement value averaged by the filtering unit.
The measurement unit measures the first radio quality in a first bandwidth including the first carrier frequency in the serving cell and includes a second bandwidth including the second carrier frequency in the neighboring cell. The communication terminal according to claim 1, wherein the second radio quality is measured.
A measurement method performed by a communication terminal communicating with a radio base station,
A first carrier frequency in a serving cell in which any one of a plurality of predetermined system bandwidths is used and a second carrier in a neighboring cell in which any of the plurality of predetermined system bandwidths are used Obtaining frequency information indicating a frequency from the radio base station;
The first radio quality for the serving cell and the second radio quality for the neighboring cell are measured, and the difference between the first measurement value of the first radio quality and the second measurement value of the second radio quality. A step of seeking
When the first carrier frequency in the serving cell and the second carrier frequency in the neighboring cell satisfy a predetermined relationship and the difference is equal to or larger than a predetermined value, the first carrier frequency is set to be small. Correcting the first measurement value of the radio quality of the method.