MX2008005760A

MX2008005760A - Mobile station and handover control method

Info

Publication number: MX2008005760A
Application number: MXMX/A/2008/005760A
Authority: MX
Inventors: Ishii Minami; Nakamura Takehiro; Iwamura Mikio; Umesh Anil
Original assignee: Ntt Docomo Inc
Priority date: 2005-11-02
Filing date: 2008-05-02
Publication date: 2008-10-03

Abstract

A mobile station comprises a radio quality determining part (121a) that acquires a radio quality data indicative of the radio quality of a communication link between the mobile station and a base station;a handover determination part (161a) that determines the communication status in a peripheral cell when the radio quality data satisfies a predetermined condition;and a transmitting part (181) that transmits, based on a result of determining the communication status, a command for switching the connection from a first cell currently connected to the mobile station to a second cell that is different from the first cell or transmits the result of determining the communication status to a radio access network apparatus.

Description

MOBILE STATION AND CALL SWITCH CONTROL METHOD Field of the Invention The present invention relates to mobile stations and methods of control of handover or call switching.

BACKGROUND OF THE INVENTION In a conventional mobile communication system, in order to perform call switching, a mobile station UE measures the communication status of a link between the mobile station UE and the neighboring or neighboring cell. Next, based on the measurement result, a radio access network (hereinafter referred to as RAN) transmits to the mobile station UE a command that instructs the mobile station to change the connection of a cell. In this way, the mobile station UE changes the cell connection in response to the command of the RAN. Specifically, by using a compressed mode as shown in Figures 4A and 4B, the mobile station UE periodically measures, as the communication status of the neighboring cell, the communication status (a measurement value). of the propagation loss of the reception energy, the signal-to-interference ratio, and the like) of the link between the mobile station UE and the cell REF. 192845 neighbor Compressed mode is one of the methods used for measuring the communication status of the neighboring cell in order to perform call switching. The additional description of the compressed mode will be given with reference to Figures 4A and 4B. It is noted that Figure 4B is an enlarged view of a portion of Figure 4A. When the mobile station UE performs call transfer or switching, the mobile station UE measures the communication status of the neighboring cell. In general, the mobile station UE only includes a single communication device and therefore can not measure the communication status of the neighboring cell during data communication. Accordingly, in a link between the mobile station UE and a base station, the mobile station UE suspends transmission in a frame (stopping transmission of the base station) for a predetermined period and creates a separation or transmission space. In this way, the mobile station UE measures the communication status of the link between the mobile station UE and the base station controlling the neighboring cell. According to the 3GPP specification, for example, the communication status of a common pilot channel transmitted from a base station is measured as the communication status of the neighboring cell.

Conventionally, the mobile station UE transmits the measurement result of the communication states of a cell of its own and the neighboring cell to a RAN through a radio interface, on a regular basis or when a predetermined condition is satisfied (for example, the measurement value that exceeds a threshold). Based on these measurement results, the RAN determines that the mobile station UE needs to change the cell connection, of the cell with which the mobile station UE is currently connected, with a different cell. Then, the RAN transmits a command that instructs the mobile station UE to change the cell connection in an appropriate synchronization. When the command described above is received, the mobile station UE changes the cell connection. Therefore, call switching is performed in the conventional mobile communication system (refer, for example, to Document without Patent 1 and to Document without Patent 2). However, according to the conventional mobile communication system in the compressed mode shown, for example, in Figures 4A and 4B for the purpose of measuring the communication states of the cell itself and the neighboring cell, the mobile station UE is required to suspend transmission in the box (stopping transmission from the base station) during the predetermined period, at the link between the mobile station UE and the base station. So, the mobile station UE is required to create a transmission gap. Transmission separation causes the problem of deterioration in performance. In addition, in order to carry out the handover or call switching, the mobile station UE frequently measures the communication status of the neighboring cell and transmits the measurement result to the base station for each measurement. Therefore, a problem is created in which a large amount of resources is required. Document without Patent 1: 3GPP TSG-RAN TS25.212 v6.6.0 Document without Patent 2: "W-CDMA mobile communication system" edited by Keiji Tachikawa, p.140.

Brief Description of the Invention The present invention has been elaborated in. view of the above problems, and has the objective of providing a mobile station and a call switching control method, which can reduce the performance deterioration in the link between the mobile station and the base station when a call switching, and use fewer resources for the implementation of call switching.

A first aspect of the present invention is summarized as a mobile station, which includes a radio quality measurement unit that is configured to obtain the radio quality data indicating the radio quality of a communication link between the mobile station and a base station; a handoff or call switching measurement unit which is configured to measure the communication status of a neighboring cell, when the radio quality data complies with a predetermined condition; and a transmitter unit that is configured to send to a radio access network apparatus, based on the measurement result of the communication status, a command or the result of measurement of the communication status, the command instructs the network apparatus of radio access to change the connection of a cell, of a first cell with which the mobile station is currently connected to a second cell different from the first cell. A second aspect of the present invention is summarized as a method of call switching control of a mobile station, which includes: obtaining the radio quality data indicating the radio quality of a communication link between the mobile station and a radio station. base station; measure the communication status of a neighboring cell when the radio quality data meets a predetermined condition; and transmit to a network access device of radio, based on the measurement result of the communication status, a command or the measurement result of the communication status, the command instructs the radio access network to change the connection of a first cell with which the mobile station is connected, to a second cell different from the first cell.

Brief Description of the Figures Figure 1 is a general configuration diagram of a mobile communication system according to a first embodiment of the present invention. Figure 2 is a functional block diagram of a mobile station of the mobile communication system according to the first embodiment of the present invention. Figure 3 is a functional block diagram of the mobile station of the mobile communication system according to a second embodiment of the present invention. Figures 4A and 4B are diagrams of a compressed mode describing the conventional invention.

Detailed Description of the Invention (A mobile communication system according to the first embodiment of the present invention). A radio access network apparatus according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. In the example of Figure 1, a mobile station UE forms a link between the mobile station UE and a cell controlled by a radio base station Node B # 1. The mobile station UE is configured to measure the radio quality of the cell in which the mobile station UE is located and controlled by the radio base station Node B # 1. In addition, the mobile station UE is configured to measure the radio quality of a cell controlled by the radio base station Node B # 2. The mobile station UE is configured to transmit, to the radio base station Node B # 1, a CQI (Channel Quality Indicator) which signals the radio quality. In the example of Figure 1, the mobile station UE is connected to the cell controlled by the radio base station Node B # 1 by means of a link. However, when the radio base station Node B # 1 receives the CQI from the mobile station UE and when the CQI meets a predetermined condition, the radio base station Node B # 1 instructs the mobile station UE to start the measurement of the radio qualities of multiple links connecting the mobile station UE with the radio base station Node B # 1 and the radio base station Node B # 2, respectively. When the result of the measurement of the communication states, the radio base station Node B # 1 selects the most suitable cell to be connected to the mobile station UE and instructs the mobile station UE to change the cell connection. When the instruction described above is received, the mobile station UE changes the cell connection of the cell with which the mobile station UE is currently connected to a different cell. The mobile station UE is configured to perform a call switching as described above. An RNC radio network controller of the present invention is a device located at the higher level than the radio base station Node B, and is configured to regulate radio communication between the mobile station UE and the radio base station Node B. In the present embodiment, the radio network controller RNC and the radio base stations Node B are collectively called as a radio access network apparatus. It should be noted that in the radio access network apparatus according to the present invention, part of the instructions could be included in the radio network controller RNC and each of the other radio base stations Node B has similar functions . Figure 2 shows an example of a configuration schematic of the mobile station UE according to the present embodiment. As shown in Figure 2, the mobile station UE is provided with a receiving unit 111, a CQI measuring unit 121a, a CQI processing unit 121b, a comparison unit 131, the reference value database 141, a command processing unit 151, a call switching measurement unit 161a, a call switching signal generation unit 161b, a multiplexing unit 171, a transmitter unit 181 and a transmit and receive antenna 191. Note that each of these components will not necessarily be implemented as individual hardware. In other words, the components could be combined or they could be configured through a software process. The receiver unit 111 is configured to support downlink data coming from the radio access network through a downlink. In addition, the receiver unit 111 is configured to transfer to the CQI measurement unit 121a, a radio wave received through the downlink. The CQI measuring unit 121a is configured to receive the radio wave coming from the receiving unit 111. Furthermore, the CQI measuring unit 121a is configured to instantaneously measure the signal ratio with interference (hereinafter referred to as a SIR), reception power, loss of propagation or the like, and for transferring the radio quality data to the CQI processing unit 121b. In this regard, the reception power, the propagation loss, or the like, indicates the radio quality of a communication link between the mobile station UE and the radio base station Node B. Here, the term "CQI" is a collective term that covers sets of feedback information and is used to deal with high-speed variation in propagation (such as high-speed weakening) during communications. Specifically, the CQI includes the signal to interference ratio (hereinafter referred to as SIR) which is instantaneously measured by the mobile station UE, the instantaneous power of reception, the instantaneous loss of propagation, and the like. . Similarly, in the HSDPA (High Speed Downlink Packet Access) scheme, the mobile station UE is configured to measure an instantaneous SIR and to transmit a quantized CQI to the radio base stations Node B that controls the cell with which the mobile station UE is connected. Here, it is defined that a large CQI indicates a state favorable communication between the mobile station UE and the cell controlled by the radio base station Node B # 1, while a small CQI indicates an unfavorable communication state between them. The processing unit CQI 121b calculates the average CQI which indicates the average value of the instantly measured CQI data, and transfers the average CQI to the comparison unit 131. In this way, the comparison unit 131 is allowed to check the CQI average with the average CQI threshold value, while avoiding the excessive influence of an instantaneous variation on the radio quality data. Here, the average threshold value CQI is obtained from the reference value database 141. In this regard, the average CQI is not necessarily the average value of the CQI. Alternatively, other values such as the average CQI can be used, provided that the instantaneous variation in the radio quality data can be smoothed. The comparison unit 131 is configured to collate the average CQI obtained from the CQI processing unit 121b, with the average threshold value CQI which is obtained from the reference value database 141. When the average CQI is smaller than the value of average threshold CQI, the comparison unit 131 transfers to the processing unit of command 151, a measurement command that instructs the initiation of the measurement of the communication states of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located. On the other hand, when the average CQI is larger than the average CQI threshold value, the comparison unit 131 transfers to the command processing unit 151 a measurement completion command which instructs the completion of the measurement of the states of communication of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located The reference value database 141 includes the average threshold value CQI. The average CQI threshold value could be a predetermined value, or it could be a reference value calculated based on the previous average CQI. In addition, the average CQI threshold value used when the communication state measurement is initiated could differ from the average CQI threshold value when the measurement of the communication status is finished.- When a control command obtained from the comparison unit 131 be the measurement command, the command processing unit 151 is configured to transferring, to the call switching measurement unit 161a, the measurement command which instructs the call switching measurement unit 161 to initiate measurement of the communication states of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located. When the control command obtained from the comparison unit 131 is the measurement termination command, the command processing unit 151 is configured to transfer, to the call switching measurement unit 161a, the command for terminating the measurement. measurement that instructs the call switching measurement unit 161a to terminate the measurement of the communication states of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located. The call switching measurement unit 161a is configured to receive a control command from the command processing unit 151. When the control command received from the command processing unit 151 is the measurement command, the measurement unit call switch 161a is configured to initiate the measurement of the communication states of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located, and for transferring the measurement result of the call switching to the call switching signal generation unit 161b. When the control command received from the command processing unit 151 is the measurement termination command, the call switching measurement unit 161a is configured to terminate the measurement of the communication states of the links connecting the mobile station UE and each of the multiple cells in which the mobile station UE is located. The call switching signal generation unit 161b is configured to receive the result of the call switching determination of the call switching measurement unit 161a, and to transfer, to the multiplexing unit 171, the result of the determination of call switching or a call switching command. Here, the call switching command instructs the radio access network to make a call switching. The multiplexing unit 171 is configured to receive, from the call switching signal generation unit 161b, a call switching command together with the transmission data (such as user data or control data), or the measurement result of the call switching. Then, the unit multiplexing 171 performs a process of multiplexing the received data and converts the data into a signal having a radio frequency band and transfers the signal to the transmitter unit 181. The transmitter unit 181 is configured to amplify the signal obtained from the unit multiplexing 171 and for transmitting the amplified signal to the radio access network apparatus through the transmitting and receiving antenna 191. (Effects and advantages of the mobile communication system according to the first embodiment of the present invention). According to the above configuration, the mobile station UE does not need to frequently measure the communication state between the mobile station UE and the cell itself, and the communication state between the mobile station UE and the neighboring cell. Instead, only when the radio quality data meets the predetermined condition, the mobile station UE needs to measure the communication status between the mobile station UE and the cell itself and the communication state between the mobile station UE and the cell neighbor Therefore, the number of processes required to perform a call switching can be reduced. In other words, it is possible to provide a radio access network that can reduce the number of processes and resources required to perform call switching in a UE mobile station. In addition, the mobile station UE of the first embodiment of the present invention includes a CQI measuring unit 121a, a call switching measurement unit 161a and the transmitting unit 181. The CQI measuring unit 121a obtains the quality data of radius indicating the radio quality of the communication links between the mobile station UE and the radio base stations Node B. The call switching measurement unit 161a measures the communication status of the neighboring cell when the quality data radio meet the predetermined condition. In accordance with the measurement result of the communication state, the transmitting unit 181 sends to the radio access network apparatus the measurement result of the communication status or the command that instructs the radio access network apparatus to change the connection of a first cell to a second cell. Here, the first cell is the cell with which the mobile station UE is currently connected, and the second cell is the cell different from the first cell. According to this configuration, because the mobile station UE measures the radio quality of the communication link between the mobile station UE and the radio base station Node B, the mobile station UE can set the communication states of multiple cells with which the The mobile station UE is currently connected, without frequently using the result of measuring the communication status of the neighboring cell. Further, when the radio quality data complies with the predetermined condition, the mobile station UE can determine whether or not it will perform a call switching by measuring the communication status of the neighboring cell without using the compressed mode shown in FIG. Figure 4. In addition, the mobile station UE can perform call switching without interacting with the radio access network apparatus. In other words, according to the mobile station of the first mode, it is possible to reduce the deterioration in performance of the link between the mobile station and the base station when call switching is performed, and to use fewer resources of the mobile station to perform the call switching. (A mobile communication system according to a second embodiment of the present invention). A radio access network apparatus according to a second embodiment of the present invention will be described with reference to Figure 3. In the example of Figure 3, a process performed by the CQI processing unit 122b of the mobile station UE is mainly different from the network device of radio access of the first modality. Specifically, the CQI processing unit 122b is configured to obtain the transmission power or transmission rate information of the transmitting unit 182, to calculate the average value I of the transmission power or transmission rate information, and transfers the calculated average value I to a comparison unit 132. In this regard, the average value I is not necessarily the average value of the transmission power or transmission rate information. Alternatively, other values such as the average value I can be used, with the proviso that the value is not affected by the variation in each of the information of the transmission power and the transmission speed. The comparison unit 132 is configured to match the average value I obtained from the CQI processing unit 122b with the average value threshold value I obtained from the reference value database 142. As described with Prior to this, by using the information of the transmission power or the transmission rate as the CQI, the mobile station UE does not need to frequently measure the communication states of the cell itself and the neighboring cell. Instead, only when the radio quality data meets the predetermined condition, the mobile station UE needs to measure the communication states of the cell itself and the neighboring cell. In addition, the processes for performing call switching can be reduced.

Industrial Applicability As has been described in accordance with the present invention, it is possible to provide a mobile station and a call switching control method, which can reduce the deterioration in performance on the link between the mobile station and the mobile station. base when a 'call switching' is performed, and they use less * resources to perform call switching. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A mobile station, characterized in that it comprises: a radio quality measurement unit configured to obtain the radio quality data indicating the quality radio of a communication link between the mobile station and a base station; a call switching measurement unit is configured to measure the communication status of a neighbor cell, when the radio quality data complies with a predetermined condition; and a transmitter unit configured to send to the radio access network apparatus, based on the measurement result of the communication status, a command or the measurement result of the communication status, the command instructs the radio access network apparatus to change the cell connection of a first cell with which the mobile station is currently connected, to a second cell different from the first cell.
2. A method of call switching control of a mobile station, characterized in that it comprises: obtaining the radio quality data indicating the radio quality of a communication link between the mobile station and a base station; measure the communication status of a neighboring cell when the radio quality data meets a predetermined condition; and transmitting to a radio access network device, based on the measurement result of the communication status, a command or the measurement result the communication status, the command instructs the radio access network to perform a switching of called from a first cell with which the mobile station is connected, to a second cell different from the first cell.