JP2001326648A - Wireless data communication method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in the conventional wireless data communication methods that the data in units of packets are communicated in wireless manner between its own station and an opposite station that has deteriorated a communication efficiency, because a small packet length is fixed. SOLUTION: The wireless data communication method decides the length of a succeeding packet on the basis of the length of a packet, whose communication is finished to attain efficient communication at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless data communication method and apparatus suitable for performing packet communication with a mobile terminal such as a mobile phone.

[0002]

2. Description of the Related Art A packet used for data communication is obtained by adding information such as a header and an error correction code to data (division of data) to be communicated. These pieces of additional information are necessary for establishing packet communication, but are still extra information that is not a communication target. As the number of packets used to communicate a certain amount of data increases, the overhead increases and the communication efficiency decreases. In order to suppress the number of packets, for example, the packet length of the packet may be increased. However, when wireless is used for the communication path, there is a high possibility that packets will be lost or lost, and if the packet length is increased,
As a result, there is a high possibility that the packet will not be normally communicated. In particular, in mobile communication, the communication environment changes drastically, and a packet having a large packet length is easily affected.
If the packet is not transmitted normally, the packet will be retransmitted. Further, when the packet is lost, it is determined that the packet has not been normally communicated based on the elapse of the timeout period, so that the time during which communication is not substantially performed increases.
Therefore, when the communication state is unstable, if the packet length is increased, the communication efficiency may be reduced. For this reason, for example, in mobile communication using radio, the packet length is usually fixed at a small value so that retransmission does not occur as much as possible.

[0003]

However, if the packet length is fixed at a small value, the overhead is unavoidably increased. For example, JP-A-11-68873
JP-A-11-275110 and JP-A-11-275110 describe techniques for adjusting the packet length when the communication state deteriorates due to disconnection of a line. However, in these techniques, the packet length is also fixed. In some cases, communication efficiency was reduced. The present invention has been made in view of the above circumstances, and an object of the present invention is to always perform efficient communication by determining a packet size for each communication of a packet according to a communication environment. It is to provide a possible wireless data communication method and device.

[0004]

In order to achieve the above object, the present invention provides a wireless data communication method for performing wireless data communication in packet units between a self-station and a partner station. The wireless data communication method is characterized in that the length of the next packet is determined based on the length of the determined packet. With such a configuration, even if the communication state changes during data communication, it is possible to always determine a packet length that matches the communication state at that time and maintain high communication efficiency. In the above wireless data communication method, the length of a packet to be communicated next can be determined, for example, according to the following equation. P (k + 1) = P (k) + α × {A (k) −P (k)} where P (k): the packet length of the packet (time k) for which communication has been completed P (k + 1): the next packet ( Packet length at time k + 1) α: Smoothing constant A (k): Optimal packet length for communication at target time The optimal packet length A (k) in the above equation is, for example, communication of a completed packet. It can be determined based on time. In addition, the optimal packet length A
(K) can be determined based on the radio wave condition. In the above wireless data communication method, when there is a plurality of data to be communicated, if the communication is performed by preferentially selecting data having a size smaller than the length of the next packet, the length of the packet can be reduced. Even in the case of changing for each packet, it is possible to minimize an increase in the number of packets by dividing the data, and as a result, it is possible to further improve the communication efficiency.

The present invention also provides a wireless data communication apparatus for performing wireless data communication between a self-station and a partner station in packet units, based on the length of the completed packet. The wireless data communication apparatus is provided with a packet length determining means for determining a length. By the packet length determining means,
Even if the communication state changes during data communication, it is possible to always determine the packet length that matches the communication state at that point, and maintain high communication efficiency. In the above wireless data communication device, the packet length determining means determines the length of the next packet to be communicated according to, for example, the following equation. P (k + 1) = P (k) + α × {A (k) −P (k)} where P (k): the packet length of the packet (time k) for which communication has been completed P (k + 1): the next packet ( Packet length at time k + 1) α: Smoothing constant A (k): Optimal packet length for communication at target time The optimal packet length A (k) in the above equation is, for example, communication of a completed packet. It can be determined based on time. In addition, the optimal packet length A
(K) can be determined based on the radio wave condition. If the wireless data communication apparatus further includes data selection means for preferentially selecting and communicating data having a size smaller than the length of the next packet when there are a plurality of data to be communicated, Even when the length changes for each packet, it is possible to minimize the increase in the number of packets by dividing the data, and as a result, it is possible to further increase the communication efficiency.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
It should be noted that the following embodiments are examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is a block diagram illustrating a schematic configuration of a wireless data communication device Z1 according to an embodiment of the present invention, FIG. 2 is a diagram illustrating an example of a wireless data communication system to which the wireless data communication device Z1 can be applied, FIG. 3 is a flowchart showing a data communication procedure by the wireless data communication apparatus Z1, FIG. 4 is a view showing an example of the correspondence between the moving average and the standard deviation of the electric field strength time series value and the communication environment, and FIG. FIG. 4 is a diagram illustrating an example of a correspondence relationship with a packet length. FIG. 2 is a configuration example of a wireless data communication system using the wireless data communication device Z1 (FIG. 1) according to the present embodiment. This system includes a server 1 as a fixed station and a portable terminal 6 as a mobile station. A modem 2 is mounted (or connected) on the server 1 and is connected to a wireless base station 4 via a public line 3. The portable terminal 6 has a wireless communication device 5 mounted (or connected), and wireless data communication with the wireless base station 4 is possible. Here, the server 1 is, for example, a desktop personal computer equipped with a modem, and the mobile terminal 6 is, for example, a notebook personal computer connected to a mobile phone via a data card. A mobile phone having a data communication function for e-mail or the like is conceivable.

[0007] Wireless data communication apparatus Z according to the present embodiment
1 is mounted on, for example, the server 1 or the portable terminal 6 in the wireless data communication system, and as shown in FIG.
Packet length determining unit 13 (corresponding to packet length determining means),
It comprises a radio wave condition measuring unit 14 and a communication environment estimating unit 15. The application 11 is a program for requesting data communication, and is, for example, e-mail software or a WWW browser. The data transmission / reception control unit 12 performs overall control for data communication processing. The radio wave condition measuring unit 14 measures the electric field strength value at the start of data communication in a time series, and outputs the measurement result to the communication environment estimating unit 15. The communication environment estimating unit 15 estimates a communication environment at the start of data communication based on the time-series value of the electric field strength measured by the radio wave condition estimating unit 14.
Specifically, the communication environment is estimated based on, for example, the moving average and the standard deviation of the time-series values of the electric field strength and a predetermined correspondence relationship as shown in FIG. It is determined as a moving area, a stable stationary area, or the like. Here, since the communication environment estimation unit 15 estimates the communication environment based on a time series value instead of an instantaneous value of the electric field intensity, it is assumed that the radio wave intensity changes suddenly in a short time due to high-speed movement or the like. Even in wireless data communication by a mobile body, it is possible to accurately estimate a communication environment.

At the start of data communication, the packet length determining section 13 sets an initial packet length based on the communication environment estimated by the communication environment estimating section 15. Specifically, based on the correspondence table as shown in FIG. 5, the packet length corresponding to the communication environment estimated by the communication environment estimating unit 15 is set as the initial packet length. For example, if the communication environment is in a stable stationary area, the packet length determining unit 13 sets the initial packet length to 2048 bytes,
If it is in the weak electric field stationary area, the initial packet length is set to 1024 bytes. When data communication is started with the initial packet length set in this way, the packet length determining unit 13 returns a time required for communication of one packet (a response indicating that communication of a certain packet has been completed is returned). ) Is sequentially measured, and the packet length P (k + 1) of the next packet to be communicated is determined based on this communication time and the packet length P (k) of the packet that has already completed communication.
Specifically, the packet length P (k + 1) of the next packet is determined by the following equation (1) using, for example, the exponential smoothing method. P (k + 1) = P (k) + α × {A (k) −P (k)} (1) where α: smoothing constant A (k): optimal packet length for communication at the target time The optimal packet length A (k) in the equation (1)
Is a packet length calculated to maximize the amount of data that can be communicated within a predetermined target time, and is determined based on the measured communication time T of the packet and the target time.

If the target time is represented by τ, the optimal packet length A (k) is, for example, a packet length L that maximizes the data amount J expressed by the following equation (2). J = ∫ [τ / ((L / va) + T)] × L × f (va) dva (2) where, va: data communication speed of PDC layer (for mobile phone) f (va): probability This is the probability density function of the variable va. [] In the above equation (2) represents a Gaussian symbol, which is expressed by a target time τ when data is communicated in a packet having a packet length L.
Is the number of packets that can be sent within In actual wireless data communication, va is treated as a stochastic variable in consideration of the fact that the communication speed varies, and J is the data communicated within τ by multiplying by the probability density function of va and integrating. Will be expressed. If the packet length P (k + 1) of the packet to be transmitted next is determined according to the above equation (1), the packet length of each packet is made closer to the optimum packet length reflecting the communication environment. A packet length suitable for a communication environment can be selected for each packet, and efficient communication can always be performed.

Next, a series of data communication procedures (corresponding to the wireless data communication method according to the present invention) by the wireless data communication apparatus Z1 having the above configuration will be described with reference to the flowchart shown in FIG. When the user starts an application 11 such as e-mail software on the mobile terminal 6 and makes a data communication request such as mail transmission, the data transmission / reception control unit 12 determines the initial packet length to the packet length determination unit 13. The request is output to the communication environment estimating unit 15 as a request for estimating the current communication environment.
The communication environment estimating unit 15 receives the time-series value of the electric field strength from the radio wave condition measuring unit 14, and based on the moving average and the standard deviation of the time-series value and the preset correspondence as shown in FIG. For example, the communication environment at the present time is estimated in a form such as an unreachable area, a high-speed moving area, a stable stationary area, and the like, and the result is output to the packet length determining unit 13. The packet length determining unit 13 determines an initial packet length based on the current communication environment received from the communication environment estimating unit 15 and the correspondence as shown in FIG. Output to The data transmission / reception control unit 12 uses the initial packet length received from the packet length determination unit 13
1 starts communication of data output from step 1 (step S1).
1). When the data communication is started, the packet length determination unit 13 sequentially measures the time required for communication of one packet (step S3), and based on this, uses the above formulas (1) and (2). , The packet length P (k +
1) is determined (step S4). Then, the data transmission / reception control unit 12 determines the determined packet length P (k
+1), the data communication is continued (step S5). The processes of steps S3 to S5 are repeatedly performed until the data communication ends. As described above, according to the wireless data communication method and apparatus according to the present embodiment, a packet length suitable for a communication environment can be selected for each packet, and efficient communication can be performed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the wireless data communication method and apparatus according to the above embodiment, the optimum packet length A reflecting the communication environment is set.
The packet length P (k) of the packet that has completed communication with (k)
Is added to the packet length P (k), so that the packet length P (k + 1) of the next packet to be communicated is changed so that the largest amount of data can be communicated within the range of the communication environment. It was decided. In such a configuration, the packet length P (k + 1) of the packet to be communicated next changes sequentially. If the data to be communicated is larger than the data storage size determined by the packet length,
Since the data is divided, careless selection of data to be communicated may increase the number of packets even if the packet length is appropriately adjusted. FIG. 6 shows a configuration of a wireless data communication device Z1 'in which the wireless data communication device Z1 according to the above embodiment is modified to solve this problem. In FIG. 6, when there are a plurality of files (data) to be communicated, a communication file determination unit (corresponding to a data selection unit) 17 outputs a file having a smaller size than the packet length determined by the packet length determination unit 13. Is selected with priority, and the selected content is returned to the data transmission / reception control unit 12. Even if the packet length P (k + 1) of the next packet to be communicated changes successively, if a file having a smaller size is preferentially selected, the packet length P (k + 1) can be reduced. Nevertheless, it is possible to minimize the increase in the number of packets by selecting a large-sized file and dividing the file. If there are a plurality of files smaller in size than the determined packet length, or if all the files are smaller in size than the defined packet length, a file having a larger size is selected. This makes it possible to increase the possibility of selecting a smaller file when the packet length is further reduced during communication. If the sizes of all the files are larger than a predetermined packet length, a smaller file is selected. As a result, while minimizing the number of packets when performing communication with the packet length, when the packet length becomes larger during communication, it is possible to increase the communication efficiency by communicating large files. It becomes possible. The data communication processing procedure according to the wireless data communication apparatus Z1 'is included in the communication procedure (step S5) in FIG. When the packet length is determined in step S4, a file smaller in size is preferentially selected, and the file is communicated under the control of the data transmission / reception control unit 12. According to the wireless data communication method and apparatus according to the embodiment of the present invention, even when the length of a packet changes during communication, the increase in the number of packets due to the division of the packet is minimized. , So that the communication efficiency can be further improved. In the above embodiment, a file whose size is smaller than the packet length determined by the packet length determining unit 13 is selected. However, the optimal packet length A (k)
It is also possible to select a file smaller in size. In the above embodiment, the optimum packet length A (k) is obtained according to the above equation (2). However, the present invention is not limited to this. For example, instead of measuring the packet communication time in step S3 in FIG. Then, the radio wave condition may be measured, and the communication environment and the optimum packet length associated therewith may be determined from the measured radio wave condition in the same manner as at the start of communication.

[0012]

As described above, according to the present wireless data communication method and apparatus, even if the communication state changes during data communication, the packet length that always matches the communication state at that time is determined. High communication efficiency can be maintained. Furthermore, when there is a plurality of data to be communicated,
If data with a size smaller than the length of the next packet is preferentially selected for communication, even if the length of the packet changes for each packet, the data is divided to reduce the number of packets. It is possible to minimize the increase, and as a result, it is possible to further improve the communication efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a wireless data communication device Z1 according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a wireless data communication system to which the wireless data communication device Z1 can be applied.

FIG. 3 is a flowchart showing a data communication procedure by the wireless data communication device Z1.

FIG. 4 is a diagram showing an example of a correspondence relationship between a moving average and a standard deviation of electric field strength time series values and a communication environment.

FIG. 5 is a diagram showing an example of a correspondence relationship between a communication environment and an initial packet length.

FIG. 6 is a diagram showing a schematic configuration of a wireless data communication device Z1 ′ according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Application 12 ... Data transmission / reception apparatus 13 ... Packet length determination part 14 ... Radio wave condition measurement part 15 ... Communication environment estimation part 16 ... Communication file determination part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takanari Shirasaka 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Hiroshi Narasaki Nishi-ku, Kobe City, Hyogo Prefecture 1-5-5 Takatsukadai Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Naoki Tamura 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Kobe Steel, Ltd.Tokyo Head Office (72) Inventor Hidetaka Suzuki 3-6-2 Bingo-cho, Chuo-ku, Osaka-shi Tsukahon Kansainai, Ltd. (72) Inventor Masato Imon 3-6-1-2, Bingocho, Chuo-ku, Osaka-shi Tsukahon Kansaiuchi, Ltd. (72) Invention Person Hiroshi Yamazaki 3-6-2, Bingo-cho, Chuo-ku, Osaka-shi Tucar Phone Kansainai F-term (reference) 5K030 GA03 HA08 HB28 HC09 JA05 JA07 JT01 JT09 LA03 LB11 LC01 MB04 MB11 5K033 AA01 CB06 CB17 CC02 DA19 DB09 DB16 DB20 EA02 EA06 5K034 AA01 DD01 EE03 EE11 FF02 FF05 HH01 HH12 HH14 HH63 HH65 MM21 MM21 MM21 MM21 MM21 MM21 MM21 MM21 MM21 MM21 MM21 CC06 KK56

Claims (10)

[Claims] In a wireless data communication method for performing wireless data communication between a local station and a partner station in a packet unit, the length of the next packet is determined based on the length of a completed packet. A wireless data communication method, comprising: 2. The wireless data communication method according to claim 1, wherein the length of the next packet is determined according to the following equation. P (k + 1) = P (k) + α × {A (k) −P (k)} where P (k): the packet length of the packet (time k) for which communication has been completed P (k + 1): the next packet ( Packet length at time k + 1) α: Smoothing constant A (k): Optimal packet length for communication at target time 3. The wireless data communication method according to claim 2, wherein said optimum packet length A (k) is determined based on a communication time of a packet in which communication has been completed. 4. The wireless data communication method according to claim 2, wherein said optimum packet length A (k) is determined based on radio wave conditions. 5. The communication method according to claim 2, wherein when there are a plurality of data to be communicated, data having a size smaller than the length of the next packet is preferentially selected for communication. Wireless data communication method. 6. A wireless data communication apparatus for performing wireless data communication in packet units between a local station and a partner station, wherein a packet that determines the length of the next packet based on the length of a packet for which communication has been completed. A wireless data communication device comprising length determining means. 7. The wireless data communication apparatus according to claim 6, wherein said packet length determining means determines the length of the next packet according to the following equation. P (k + 1) = P (k) + α × {A (k) −P (k)} where P (k): the packet length of the packet (time k) for which communication has been completed P (k + 1): the next packet ( Packet length at time k + 1) α: Smoothing constant A (k): Optimal packet length for communication at target time 8. The wireless data communication apparatus according to claim 7, wherein said packet length determining means determines the optimum packet length A (A) based on a communication time of a packet for which communication has been completed. 9. The wireless data communication apparatus according to claim 7, wherein said packet length determining means determines said optimum packet length A (k) based on radio wave conditions. 10. The data processing apparatus according to claim 6, further comprising a data selection unit that, when there are a plurality of data to be communicated, preferentially selects data having a size smaller than the packet length. The wireless data communication device according to claim 1.