JP2005101815A - Mobile communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a problem that quality deterioration occurs in contents such as images and sounds by performing a handover while executing an application (for example, downloading of moving image data or streaming service) in a mobile communication terminal. Provide a terminal.
Signal quality between a first radio base station 11 that is currently communicating and a second radio base station 12 that is a candidate for handover is transmitted to a mobile communication terminal 25 that is to perform a handover. Means for comparing the number of connected communication terminals (number of accommodated communication terminals) acquired from the first radio base station and the second radio base station 12 that is a candidate for handover, and the signal quality On the basis of the comparison result and the comparison result of the number of connected communication terminals, and a means for determining the necessity of handover control and a radio base station to be handed over.
[Selection] Figure 1

Description

  The present invention relates to a mobile communication terminal, and in particular, by executing handover (switching of a radio base station) during execution of an application (for example, downloading of moving image data or a streaming service), quality of image or audio information is improved. The present invention relates to a mobile communication terminal that can avoid the problem of deterioration.

  In recent years, mobile communication terminals such as mobile phones (also simply referred to as “communication terminals”) transmit and receive data and images as well as moving image data in addition to conventional voice call services, as communication terminals become more sophisticated. Various applications such as moving image data download service and streaming service have begun to be provided for mobile phone services. With such diversification of applications, mobile communication networks are required to transmit a larger amount of data on the downlink. In order to respond to such needs, a high-speed packet communication network using a “1xEV-DO (1x Evolution Data Only)” system that improves the transmission efficiency of a downlink from a radio base station to a mobile communication terminal has been proposed. .

  Hereinafter, high-speed packet communication performed between the radio base station and the mobile communication terminal in the 1xEV-DO system will be described. A packet used in the 1xEV-DO system is configured by adding a header including a pilot signal and control information to the head of a data portion in which data addressed to each user is time-division multiplexed. The control information includes assignment information indicating assignment of communication resources to each mobile communication terminal.

  First, the radio base station transmits a packet including a pilot signal to each mobile communication terminal accommodated in its own cover area. Each mobile communication terminal measures downlink channel quality (for example, CIR (desired wave-to-interference wave ratio)) based on a pilot signal included in the received signal. Each mobile communication terminal stores a table indicating the correspondence relationship between downlink channel quality and the optimal communication mode when transmitting packets with the channel quality. Each mobile communication terminal refers to this table. Then, a communication mode capable of performing high-speed packet communication most efficiently with the measured line quality is selected. The communication mode is a combination of a slot length allocated to transmission data, a transmission data coding rate, a modulation method, and a spreading factor. Each mobile communication terminal transmits a signal (data rate control signal: DRC signal) indicating the selected communication mode to the radio base station. Other mobile communication terminals accommodated in the radio base station similarly transmit DRC signals to the radio base station.

  The radio base station refers to the DRC signal transmitted from each mobile communication terminal, and preferentially allocates communication resources from mobile communication terminals with good channel quality. As a result, since the data is transmitted at a higher transmission rate for mobile communication terminals with good line quality, the time required for communication can be shortened, and for mobile communication terminals with poor line quality, the transmission rate can be reduced. Since data is transmitted, error tolerance can be increased. In this way, determining the allocation of transmission slots according to the channel quality in the radio base station of the 1xEV-DO system is called scheduling.

  The radio base station assigns slots to transmission data according to communication resource allocation, performs encoding processing, modulation processing, spreading processing, etc., and configures transmission frames by time-division multiplexing transmission data addressed to each mobile communication terminal Then, the transmission frame is transmitted to each mobile communication terminal. At this time, control information (allocation information) indicating allocation of communication resources to each mobile communication terminal is inserted into the header of the head of the transmission frame. The mobile communication terminal can demodulate data addressed to itself by knowing the communication mode by referring to the allocation information. As described above, in the conventional 1xEV-DO system, data transmission efficiency is enhanced as a whole system by preferentially allocating communication resources from portable communication terminals having good channel quality.

  As a service using the high-speed wireless packet communication network as described above, a video streaming service such as VOD or live streaming is considered. In general, in a video streaming system, a video distribution server transmits content data to a video client through a transmission path. The video distribution server includes an encoding unit, a transmission unit, and a transmission control unit. The encoding unit converts the information from the video distribution source into, for example, an MPEG-4 stream and sends it to the transmission unit. The transmission unit segments the received stream data according to the lower transmission protocol and sends it to the transmission path. The transmission control unit performs transmission start / stop, transmission rate control, and the like.

  In order to ensure real-time performance of data reproduction during streaming, RTP (Realtime Transport Protocol) defined by RFC1889 and RTCP (RTP Control Protocol), which is a control protocol, are used as a data transmission protocol. The video distribution server can predict the reception rate on the client side using this RTCP information, and streaming is performed using a variable rate control method for controlling the transmission rate of the server using this RTCP information. In particular, when a video streaming service is realized on a 1xEV-DO system with a large transmission band variation, variable-rate streaming in which the transmission rate of the server is switched in accordance with the varying band is effective.

  In the communication system as described above, as shown in FIG. 4, the mobile communication terminal is moving toward the area of the second radio base station while communicating in the area of the first radio base station. Handover control will be described.

  The mobile communication terminal in communication with the first radio base station receives signals from a plurality of connectable radio base stations (second radio base station in the example shown in FIG. 4), and determines the signal quality on the network side. To inform. The radio base station (switching station) that manages the line management transmits from the first radio base station to the second radio base station to which the mobile communication terminal will connect in the future, depending on the situation notified from the mobile communication terminal. Command to send the same signal that is being transmitted.

The mobile communication terminal receives the same signal transmitted from the two radio base stations, compares the two signal qualities, and the signal quality of the signal from the second radio base station is the signal quality of the first radio base station. When it becomes higher, the wireless base station to be connected is switched from the first wireless base station to the second wireless base station, and communication is continued (handover).
The 1xEv-DO system is disclosed in the following patent document.
JP 2002-353876 A

  By the way, for example, a mobile communication terminal receiving a video streaming service from a variable-rate streaming server (video distribution server) in the 1xEV-DO network described above is second from the area of the first wireless base station in communication. Consider the case of moving toward the area of the wireless base station.

  At this time, if there are more mobile communication terminals accommodated in the second radio base station and communicating with the second radio base station than the mobile communication terminals communicating with the first radio base station, the received signal quality If the handover is performed by judging from the above, the transmission rate between the second radio base station and the handed over mobile communication terminal after the handover decreases due to the influence of the scheduling at the radio base station described above. When such a decrease in transmission rate occurs, a difference occurs between the transmission rate of the streaming server (video distribution server) and the transmission rate of the wireless section, data retention occurs in the wireless base station, and data delay occurs in the mobile communication terminal. There arises a problem that the quality of the video content being generated is deteriorated.

  The present invention has been made to solve such a problem, and its purpose is to perform a handover while executing an application (for example, downloading of moving image data or a streaming service) on a mobile communication terminal. An object of the present invention is to provide a mobile communication terminal that can avoid the problem of quality deterioration in contents such as images and sounds.

  The present invention has been made to solve the above problems, and the mobile communication terminal of the present invention includes a mobile communication terminal connected to a communication network via a radio base station, the mobile communication terminal, each radio base station, In the communication network system in which each wireless base station monitors the number of connected communication terminals accommodated in its own station and provides information on the number of connected communication terminals to the portable communication terminal. Means for measuring communication quality between a radio base station in data communication and each radio base station that is a candidate for handover; and a radio base station that is in communication and each radio base that is a candidate for handover Based on the means for comparing the number of connected communication terminals acquired from a station, the measurement result of the communication quality, and the acquired number of connected communication terminals, Characterized in that it comprises a means for determining a radio base station to be Ndooba.

  In addition, when determining whether the handover control is necessary or the radio base station to be handed over, the mobile communication terminal according to the present invention can communicate with each radio base station based on the information on the number of connected communication terminals. The data transfer rate is predicted and calculated and compared.

  In addition, the mobile communication terminal of the present invention is characterized in that when determining whether the handover control is necessary or a radio base station to be handed over, the type of application currently being executed is added as a determination condition. .

In the mobile communication terminal of the present invention, the communication quality between the currently communicating wireless base station and each wireless base station that is a candidate for handover is measured, and the currently communicating wireless base station and the candidate for handover are The number of connected communication terminals acquired from each wireless base station is acquired. Then, based on the measurement result of the received signal quality and the number of connected communication terminals, the necessity of handover control or a radio base station to be handed over is determined.
As a result, it is possible to predict the degree of congestion of the handover destination wireless line before executing the handover, and to avoid the deterioration of the quality of the application image and sound due to the decrease in the effective rate after the handover.

Further, in the mobile communication terminal of the present invention, based on the information on the number of connected communication terminals acquired from the radio base station, the data transfer rate between each radio base station is predicted and calculated, and based on the prediction calculation result The necessity of handover control and the radio base station to be handed over are determined.
As a result, the data transfer rate (reception rate) of the handover destination wireless line can be predicted before the handover is executed, and the deterioration of the image and voice quality of the application due to the decrease in the effective rate after the handover can be avoided.

In the portable communication terminal of the present invention, when determining whether or not handover control is necessary, the application type currently being executed is further added as a determination condition.
As a result, whether or not handover control is necessary and the radio base station to be handed over can be selected according to the type of application, in addition to the degree of congestion of the handover destination radio channel.

  First, the outline of the present invention will be described. A communication system in which the mobile communication terminal of the present invention is used has an adaptive modulation scheme that determines a connection time and a modulation scheme based on a data transfer rate request (DRC) from each mobile communication terminal connected to a radio base station. It is a best-effort wireless packet data communication system that uses and performs scheduling according to the number of terminals connected in the same cell to share the bandwidth.

  The mobile communication terminal according to the present invention can communicate with a wireless base station that is in communication with a wireless base station that is in communication with a wireless base station that is in communication with a wireless base station that is in communication. Information on the number of mobile communication terminals (number of accommodated communication terminals) connected to each radio base station is acquired from the base station. Then, the mobile communication terminal predicts the data transfer rate (reception rate) with each radio base station from the received signal quality of the terminal itself and the information on the number of connected mobile communication terminals, and the best data transfer rate A wireless base station that can be expected to be selected is selected as a connection destination, and handover is performed.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a wireless packet data communication system in which the mobile communication terminal of the present invention is used, and is a diagram illustrating an example of a video streaming system.

  The video distribution server 4 is connected to a wired communication network 1 such as the Internet, for example, and content data encoded using an encoding means such as MPEG-4 is transmitted through the communication network 1 to the mobile communication terminals 21 to 26. To client terminals. The video distribution server 4 receives feedback information regarding the reception status from the mobile communication terminals 21 to 26 as clients, and controls the transmission rate from the video distribution server 4 according to the reception status of the mobile communication terminals 21 to 26. Has a variable rate distribution function.

  The server 5 functioning as an exchange station enters between the communication network 1 and the wireless networks 2 and 3, selects the wireless base stations 11 and 12 that accommodate the mobile communication terminals 21 to 26, and determines the data distribution route. . The radio base stations 11 and 12 transmit / receive information to / from the mobile communication terminals 21 to 26 in the area through a radio line. Further, DRC information is received from the mobile communication terminals 21 to 26 accommodated in the area, and scheduling is performed based on the DRC information. At this time, each of the radio base stations 11 and 12 holds information on the number of mobile communication terminals that are currently connected (accommodated), and in response to requests from the mobile communication terminals 21 to 26, “number of connected communication terminals (accommodated communication) The number of terminals) ”is transmitted. In FIG. 1, five mobile communication terminals 21 to 25 are accommodated (connected) in the area of the first radio base station 11 (wireless network 2), and the area of the second radio base station 12 In the (wireless network 3), two mobile communication terminals 25 and 26 are accommodated (connected).

  The mobile communication terminals 21 to 26 have functions of transmitting and receiving data to and from the radio base stations 11 and 12, receiving data from the video distribution server 4, and decoding and displaying the received encoded data. The mobile communication terminals 21 to 26 monitor the reception status of data from the video distribution server 4 and periodically transmit the information to the video distribution server 4. In addition, the mobile communication terminals 21 to 26 obtain information on the “number of connected communication terminals (accommodated communication terminals)” of each base station from the connectable radio base stations 11 or 12, and the “number of connected communication terminals” It has a function of switching the radio base station 11 or 12 for communication based on information and channel quality of the downlink (for example, CIR (desired wave to interference wave ratio)).

  Next, in the system configuration as shown in FIG. 1, the mobile communication terminal 25 is in the area of the first radio base station 11 and communicates with the first radio base station while A flow of handover control when moving toward an area will be described with reference to FIG.

  It is assumed that the mobile communication terminal 25 is communicating with the first wireless base station 11 and is receiving video streaming data from the video distribution server 4 (step S101).

  The mobile communication terminal 25 obtains the CIR (1) value based on the signal received from the first radio base station 11 currently communicating (step S102). In addition, a pilot signal is received from a radio base station that can receive the pilot signal (here, the second radio base station) (steps S103 and S104), and based on the pilot signal received from the second radio base station 12 A CIR (2) value is calculated (step S105), and this is monitored together with the CIR (1) value of the first radio base station currently communicating.

  When the calculated CIR (2) value of the radio base station (here, the second radio base station 12) that can receive the pilot signal is equal to or greater than the CIR (1) value (or there is a CIR (2) value) When the threshold is equal to or greater than the threshold, the second radio base station 12 is set as a handover candidate radio base station (Step S106).

  When the second radio base station 12 that is a candidate for handover is detected, the mobile communication terminal 25 notifies the first radio base station 11 and the second radio base station 12 that are currently communicating with the “number of connected communication terminals (accommodated). The number of communication terminals) "is requested (step S107).

  The first wireless base station 11 and the second wireless base station 12 that have received the “request for number of connected communication terminals” from the mobile communication terminal 25 send the “number of connected communication terminals (accommodated communication) to the mobile communication terminal 25. The number of terminals) is transmitted (steps S108 to S111). The mobile communication terminal 25 that has received the information on the “number of connected communication terminals” uses the information on the “number of connected communication terminals” acquired from each radio base station (here, the second radio base station 12) to transfer data. A prediction calculation of a rate (reception rate) is performed (step S112).

  When the data transfer rate predicted from the number of mobile communication terminals connected to the second radio base station 12 is predicted not to greatly decrease from the current data transfer rate, a handover is executed and the signal quality is high. If the transmission rate predicted from the number of connected mobile communication terminals is expected to drop sharply compared to the current transmission rate, handover is not performed and the connection with the first radio base station 11 is maintained. (Step S113, step S114).

  That is, for the first radio base station 11 and the second radio base station 12, the signal quality and the “number of mobile communication terminals” connected to the respective base stations are compared, and the second radio base station When the signal quality for 12 is high and the data rate predicted from the number of connected mobile communication terminals is not expected to drop significantly, a handover is executed. In addition, when the data transfer rate predicted from the number of connected mobile communication terminals with high signal quality is predicted to be drastically reduced compared to the current transmission rate, handover is not performed, and the first radio base Control is performed to maintain the connection with the station 11.

  As for the method of transmitting the “number of connected communication terminals”, in addition to the method of transmitting in response to a request from the mobile communication terminal, a message periodically notified to each mobile communication terminal, for example, “1xEV-DO Information on “number of connected communication terminals” may be embedded in a broadcast message such as “sector parameter message” or “QuickConfig message”.

  It is also possible to perform handover by recognizing the type of application being executed on the mobile communication terminal side. For example, when comparing the case of the video streaming service and the case of VoIP, it becomes possible to perform handover even when only a relatively low data transfer rate can be expected in the case of VoIP.

  It is also possible to use a method of notifying the user when a situation occurs in which a handover occurs and performing the handover according to the user's selection.

  FIG. 3 is a block diagram showing an example of the configuration of the mobile communication terminal according to the present invention. The mobile communication terminal 100 of the present invention is a radio having a transmitter and a receiver serving as a line interface with a radio base station. Unit 101 and antenna 101a, control unit 102 for controlling the entire mobile communication terminal, operation unit 103 having a numeric keypad and direction keys, a display unit 104 for outputting and displaying character information and image information, and a voice input unit 105 for capturing voice information A voice output unit 106 for outputting the received voice information, and a storage unit 107 for storing application programs and data files.

  The control unit 102 includes a processing program unit 110, and functions directly related to the present invention include a signal quality monitoring processing unit 111, a connected communication terminal number information acquisition processing unit 112, a data transfer rate calculation processing unit 113, A data transfer rate comparison processing unit 114, a handover control processing unit 115, and the like are included.

  The signal quality monitoring processing unit 111 calculates a CIR value from the pilot signal received from each radio base station that is a candidate for handover, and the CIR value of the radio base station that is currently communicating with the radio base station that is a candidate for handover. Monitor (compare) the CIR value. Further, the connected communication terminal number information acquisition processing unit 112 requests the wireless base station currently communicating and the wireless base station that is a candidate for handover to transmit the information of “number of connected communication terminals (accommodated communication terminals)”. , Information on “number of connected communication terminals” is acquired.

  In addition, the data transfer rate calculation processing unit 113 performs data communication with each radio base station based on the information of “number of connected communication terminals (number of accommodated communication terminals)” acquired from each radio base station that is a candidate for handover. Predict and calculate the transfer rate (reception rate). Further, the data transfer rate comparison processing unit 114 compares the data transfer rate (reception rate) obtained by the data transfer rate calculation processing unit 113, and determines the necessity of handover control and the radio base station to be handed over. . In addition, the handover control processing unit 115 performs handover control for performing channel connection with a radio base station that is a handover target.

  Although the embodiment of the present invention has been described above, the mobile communication terminal of the present invention is not limited to the above-described illustrated examples, and various modifications can be made without departing from the gist of the present invention. Of course.

It is a figure which shows the structural example of the communication system in which the portable communication terminal of this invention is used. It is a figure which shows the flow of the handover process in the portable communication terminal of this invention. It is a block which shows the structural example of the portable communication terminal of this invention. It is a figure for demonstrating the conventional handover control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Communication network 2, 3 Wireless network 4 Video distribution server 5 Server 11 1st wireless base station 12 2nd wireless base station 21-26 Portable communication terminal 100 Portable communication terminal 101 Radio | wireless part 101a Antenna 102 Control part 103 Operation part 104 Display unit 105 Audio input unit 106 Audio output unit 107 Storage unit 110 Processing program unit 111 Signal quality monitoring processing unit 112 Connected communication terminal number information acquisition processing unit 113 Data transfer rate calculation processing unit 114 Data transfer rate comparison processing unit 115 Handover control processing Part

Claims (3)

A mobile communication terminal is connected to a communication network via a radio base station, a handover control is performed between the mobile communication terminal and each radio base station, and a connection communication terminal that each radio base station accommodates in its own station The mobile communication terminal in a communication network system that monitors the number and provides information on the number of connected communication terminals to the mobile communication terminal,
Means for measuring communication quality between a radio base station in data communication and each radio base station that is a candidate for handover;
Means for acquiring the number of connected communication terminals acquired from the radio base station in data communication and each radio base station that is a candidate for handover;
Means for determining the necessity of handover control during communication or a radio base station to be handed over based on the measurement result of the communication quality and the acquired number of connected communication terminals. Terminal. When determining the necessity of the handover control or the radio base station to be handed over,
The mobile communication terminal according to claim 1, wherein the data transfer rate between each radio base station is predicted and compared based on the information on the number of connected communication terminals. When determining the necessity of the handover control or the radio base station to be handed over,
The mobile communication terminal according to claim 1, wherein the type of application currently being executed is added as a determination condition.

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