JP2004297120A - Wireless terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless terminal device which can always maintain the reception level of a communication terminal in an optimum state. <P>SOLUTION: A wireless base station 51 decides the data transfer rate to the wireless terminal 1 by referring to the number of the wireless terminals executing data communications via the wireless base station 51, a data transfer rate request value transmitted from the wireless terminal 1, and the past data transfer rate request values. And, it transmits it to the wireless terminal 1. The CPU 10 of the wireless terminal 1 compares a decided value of the data transfer rate transmitted from the wireless base station 51 with the data transfer rate request value calculated by the wireless terminal 1 by a data transfer rate comparator 4. When the decided value of the data transfer rate of the wireless base station 51 is ≥ 60 % of the data transfer rate request value of the wireless terminal 1, the CPU 10 of the wireless terminal 1 starts the data communications with the wireless base station 51. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless terminal device that transmits moving image data and the like via a wireless packet network.
[0002]
[Prior art]
In recent years, the cdma2000 1x EV-DO system has been developed as a next-generation high-speed wireless communication system. In the cdma2000 1x EV-DO system, when the base station switches the modulation method of data transmitted to the terminal based on information for notifying the reception state received from the mobile communication terminal, the reception state of the terminal is good. It is possible to use a high communication rate with low error resilience but a high communication rate, and a low communication rate with high error resilience when reception conditions are poor.
[0003]
In the cdma2000 1x EV-DO system, the predicted downlink data communication speed (which directly indicates an extremely accurate data communication speed obtained in consideration of prediction and correction based on statistical data such as the past error rate of downlink data transmission, etc. The terminal has DRC (Data Rate Control Bit) as a table, and the terminal notifies the base station of the predicted downlink data communication speed based on this table.
The base station performs scheduling based on DRC information from all terminals, determines a terminal to transmit data on the downlink, and transmits data at a requested rate. This scheduling is to transmit data to the terminal with the best channel environment according to the radio wave reception conditions when there are multiple terminals in the same sector. And the base station can perform efficient data transmission. Thereby, the data communication at the various communication rates described above is performed.
[0004]
In the down direction (direction from the base station to the mobile communication terminal) of the cdma2000 1x EV-DO system, time is divided in units of 1/600 second, and communication with only one mobile communication terminal is performed within that time. In addition, time division multiplex access (TDMA; time division multiplex access) in which communication is performed with a plurality of mobile communication terminals by switching the mobile communication terminal of a communication partner with time is employed. This makes it possible to always transmit data to each mobile communication terminal with maximum power, and to perform data communication between mobile communication terminals at the highest communication speed.
[0005]
As described above, in the cdma2000 1x EV-DO system described above, the data communication speed in the direction from the base station to the mobile communication terminal greatly changes depending on the reception state (for example, received electric field strength, carrier-to-interference ratio = CIR) in the mobile communication terminal. It can be said that this is a best-effort wireless packet data communication system.
[0006]
However, the best-effort wireless packet network has a bit error rate, a packet loss rate, a packet delay time, and the like that are larger than those of a wired network due to the characteristics of wireless communication, and a wireless packet using an adaptive modulation scheme. In a network, there is a problem that a moving image streaming distribution is hindered because a data transmission bandwidth fluctuates rapidly.
[0007]
Therefore, in the conventional moving image distribution system, a distribution method using UDP (User Datagram Protocol) is mainly used. For example, as a distribution method to cope with fluctuations in the bandwidth of the network, a method of preparing several transmission patterns from a low transmission rate to a high transmission rate for moving image data and starting distribution from the lowest transmission rate, There is a method of transmitting and receiving some IP packets between a server and a client before starting distribution, measuring a data rate at which distribution is possible, and determining a distribution rate at the start.
[0008]
However, the method of starting distribution from the lowest rate has a drawback that it is necessary to start from the lowest rate even when the reception level is good, that is, when the network bandwidth is high. For this reason, the terminal side can see only from a poor quality image despite good reception conditions.
Further, the method of measuring the data rate before the start of the distribution has disadvantages in that extra packets need to be transmitted and received, and it takes time to actually transmit valid data.
[0009]
On the other hand, as a bit rate control during distribution, if the receiving side does not detect congestion, it changes to a higher rate than the current one, and if it detects congestion, it changes to a lower rate than the present one. is there. Detection of congestion is performed by packet loss on the receiving side. In other words, if a missing sequence number is detected on the receiving side, or if the data of the next sequence number does not reach the receiving side even after a certain period of time, the server requests retransmission to the server after detecting the missing sequence number. However, if data of the corresponding sequence number does not arrive within a certain time, congestion is detected (for example, see Patent Document 1).
[0010]
[Patent Document 1]
JP, 2002-300644, A
[Problems to be solved by the invention]
However, during distribution, in order to detect the missing sequence number from the actually received packet and measure the data rate, when moving from a place with a bad reception level to a place with a good reception level, congestion will be eliminated, Can only detect up to a certain point with a bandwidth higher than the data rate delivered to Therefore, after switching to a higher rate than the current state, the state of congestion is detected, and if there is no congestion, a method of increasing the distribution rate stepwise, such as a higher rate, is used, and the bandwidth is rapidly increased. When it becomes large, there is a drawback that it takes a long time to reach an optimum rate at which distribution is possible. Therefore, it takes a long time for a user to see a moving image of good image quality that can be obtained, and the reception level becomes poor before reaching the optimal rate, and as a result, good image quality cannot be obtained. There were cases.
[0012]
Also, when the mobile station moves from a place with a good reception level to a place with a bad reception level, the modulation method of wireless communication changes, so that the bandwidth of the wireless section becomes low and the arrival time of the packet becomes late. There is a disadvantage that it takes time to detect. For this reason, high-rate delivery data accumulates in a queue of a network or a wireless base station, and the time until the data of the switched rate arrives is delayed. On the other hand, on the terminal side, even though the bandwidth of the network is low, the packet does not arrive, so that a request is made to the server to retransmit the packet with the current high rate. Therefore, unnecessary data increases, and as a result, effective data passes only at a rate much lower than the actual bandwidth, and there is a problem that image quality deterioration such as a large drop of frames and stoppage of an image occurs.
SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and a wireless terminal device based on a wireless packet network that can always maintain a reception level of a communication terminal in an optimum state and perform stable moving image distribution. It is intended to provide.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a wireless terminal device according to claim 1 is a wireless terminal device that receives data of a data distribution server connected to a plurality of wireless base stations via an arbitrary wireless base station. Measuring means for measuring the quality of a received signal at the current position; request data transfer rate determining means for determining a requested data transfer rate required for one radio base station based on the quality of the received signal; Transmitting means for transmitting a rate to the one wireless base station; receiving data transfer rate detecting means for detecting a transfer rate of data received from the wireless base station; and the request data transfer rate and the received data transfer rate. Comparing means for comparing the received data transfer rate with the requested data transfer rate when the received data transfer rate is equal to or more than a predetermined value. Wherein the data communication is started from the data distribution server via.
[0014]
According to a second aspect of the present invention, in the wireless terminal device according to the first aspect, when there are a plurality of wireless base stations whose received data transfer rates are equal to or more than a predetermined value with respect to the requested data transfer rate, the received data transfer rate is highest. The data communication is started with a radio base station having a high rate.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a data transfer system according to one embodiment of the present invention. In FIG. 1, 1 is a wireless terminal, 6 is a base station controller, and 51 to 53 are wireless base stations.
The wireless terminal 1 includes a CPU 10 (reception data transfer rate detection unit) that controls each unit of the terminal, an RF processing unit 2 (measurement unit, transmission unit) that transmits and receives radio waves and measures signal quality, A data transfer rate calculation unit 3 (requested data transfer rate determining means) for calculating a transfer rate request value; and a data transfer for comparing a data transfer rate request value of the wireless terminal 1 with a data transfer rate value from the wireless base stations 51 to 53. A rate comparing section 4 (comparing means).
The RF processing unit 2 performs transmission and reception with a plurality of wireless base stations 51 to 53. The base station control device 6 connects to and manages the wireless base stations 51 to 53. Each of the wireless base stations 51 to 53 knows the number of a plurality of mobile phones that are performing data communication via the own base station.
[0016]
Next, the operation of the data transfer system having the above configuration will be described with reference to FIG. The wireless terminal 1 is wirelessly connected to the wireless base station 51. The RF processing unit 2 measures the intensity of the radio wave transmitted from the wireless base station 51 at the current position of the wireless terminal 1 600 times per second, and sends it to the data transfer rate calculation unit 3 via the CPU 10. The data transfer rate calculator 3 calculates a CIR (Carrier to Interference ratio) of the pilot signal from the value of the radio wave intensity, and uses a table having the CIR in advance to calculate a corresponding data transfer rate. Replace with the required value.
When the wireless terminal 1 starts data communication, the CPU 10 transmits the data transfer rate request value calculated by the data transfer rate calculator 3 and the content data request to the wireless base station 51 (step S101). The data transfer rate request value is transmitted on a dedicated channel.
[0017]
Next, the wireless base station 51 obtains information on the number of wireless terminals that are performing data communication via the own base station, the current data transfer rate request value of the wireless terminal 1 received in step S101, and the past data transfer rate. With reference to the request value (step S103), a data transfer rate for the wireless terminal 1 is determined, and slot allocation (scheduling) optimal for communication with the wireless terminal 1 is performed (step S105). Next, the wireless base station 51 notifies the wireless terminal 1 of the determined data transfer rate of the wireless base station 51 (step S107).
The CPU 10 of the wireless terminal 1 acquires the data transfer rate (data transfer rate determined value) notified from the wireless base station 51. Then, the data transfer rate comparison unit 4 compares the data transfer rate determination value with the data transfer rate request value obtained by the wireless terminal 1 (step S109).
[0018]
The comparison operation in the wireless terminal 1 in step S109 will be described with reference to FIG. When the data transfer rate determination value transmitted from the wireless base station 51 to the wireless terminal 1 is equal to or more than 60% of the obtained data transfer rate request value (step S201), the CPU 10 starts data communication with the wireless base station 51. (Step S211).
If it is less than 60% (“No” in step S201), the RF processing unit 2 of the wireless terminal 1 disconnects the physical line while maintaining the logical line connection with the wireless base station 51. If there is a next connectable wireless base station 52 (step S203), the CPU 10 causes the RF processing unit 2 to make a physical line connection with the wireless base station 52 (step S205). Then, the wireless base station 52 determines the data transfer rate of the wireless base station 52 to the wireless terminal 1 according to the procedure of FIG. 2 (step S207), and returns to the processing of step S201 to determine the data transfer rate of the wireless terminal 1 with the data transfer rate request value of the wireless terminal 1. Make a comparison.
If the connectable wireless base station cannot obtain a data transfer rate determination value of 60% or more (“No” in step S203), the connectable wireless base stations 51 to 53 determine the data transfer rate determined value. The physical line is reconnected to the wireless base station having the highest value of (step S209), and data communication is started (step S211). At this time, since the logical line connection (capacity exchange and acquisition of the wireless base station ID have been completed), the physical line reconnection is performed without delay.
[0019]
As described above, according to the present embodiment, at the start of or during data distribution, the wireless terminal compares the data transfer rate value obtained from the radio field intensity with the data transfer rate value from the wireless base station. By doing so, by searching for and connecting to a wireless base station that can satisfy the data transfer rate requested by the wireless terminal, it is possible to always receive stable moving image data.
[0020]
As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and may include a design change or the like without departing from the gist of the present invention.
[0021]
For example, in the above embodiment, the present invention may be applied to a portable personal computer or a PDA (Personal Digital Assistance) having a wireless communication function.
[0022]
【The invention's effect】
As is apparent from the above description, according to the present invention, at the start of data distribution or during distribution, the requested data transfer rate determined by the wireless terminal based on the quality of the received signal and the received data transfer rate from the wireless base station. By comparing the rates, the wireless terminal searches for a wireless base station that satisfies the data transfer rate requested by the wireless terminal and starts data communication, so that stable moving image data can always be received.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of a data transfer system according to an embodiment of the present invention.
FIG. 2 is an operation diagram of data exchange between a wireless terminal 1 and a wireless base station 5 in the embodiment.
FIG. 3 is a flowchart showing an operation of comparing data transfer rates in the wireless terminal 1 of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... CPU, 2 ... RF processing part, 3 ... Data transfer rate calculation part, 4 ... Data transfer rate comparison part, 10 ... Mobile telephone, 51-53 ... Radio base station, 6 ... Base station control device

Claims (2)

A wireless terminal device that receives data of a data distribution server connected to a plurality of wireless base stations via an arbitrary wireless base station,
Measuring means for measuring the quality of the received signal at the current position;
Request data transfer rate determining means for determining a request data transfer rate to request for one radio base station based on the quality of the received signal;
Transmission means for transmitting the request data transfer rate to the one radio base station,
Reception data transfer rate detection means for detecting a transfer rate of data received from the wireless base station;
Comparing means for comparing the requested data transfer rate and the received data transfer rate,
A wireless terminal device that starts data communication from a data distribution server via the one wireless base station when the received data transfer rate is equal to or more than a predetermined value with respect to the requested data transfer rate. 2. The data communication according to claim 1, wherein, when there are a plurality of radio base stations having the received data transfer rate equal to or higher than a predetermined value with respect to the requested data transfer rate, the data communication is started with the radio base station having the highest received data transfer rate. Wireless terminal device.

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