JPH1198217A - Broadcast period switching method, its system and record medium recorded with program for execution of the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce wait time until data are acquired by discriminating whether or not information whose acquisition is desired is included in plural information sets, repeatedly sent by a 1st transmission means of a server and allowing the server to change a transmission period of the information, when the information is not included and the client makes an information acquisition request of the information by a 2nd transmission means. SOLUTION: An acquisition request reception section 11 receives a data acquisition request from the user, gives it to a discrimination section 12 to discriminate whether or not the data requested by the user have been broadcasted. When they have not been broadcasted, the request is given to an acquisition request transmission section 13. When they are discriminated to have been broadcasted, the requests is given to an information selection section 17. An information selection section 16 receives data broadcast with a server side equipment 3, and the received data are given to the information selection section 17. The information selection section 17 extracts data requested among broadcast data received via the information reception section 16 and gives the data to a result display section 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information providing system that integrates broadcast-type communication and on-demand type communication in an information providing system capable of shortening a waiting time until a client acquires data. The present invention relates to a broadcast cycle switching method and apparatus and a recording medium on which a program for executing the method is recorded.

[0002]

2. Description of the Related Art Conventionally, database search and WWW (Wo
ld Wide Web), data is stored in the server side device in advance, and only necessary data is acquired from the server side device in response to a request from the client side device, and is stored in the client side device. There is known a data distribution method for providing the data.

This system is called an on-demand communication system. A data acquisition request transmitted from a client device to a server device and data provided from the server device to the client device are one. Corresponds to one. That is, in this on-demand communication method, only data requested by the user is transmitted from the server-side device to the client-side device via a communication path such as a network, so that unnecessary data (a request from the user is unnecessary). No data) flows through the communication path and does not waste limited communication resources.

On the other hand, as means for providing information to a large number of people, transmission of information such as video and audio using radio waves, such as television broadcasting and radio broadcasting (AM, FM), has been realized. . In recent years, in the traffic congestion information providing service VICS, traffic information has been provided to receiving terminals mounted on vehicles using FM radio waves.

[0005] Also, Broadcast Disks (S. Acharya, M. Fr.) being studied at Brown University in the United States.
anklin and S. Zdonik: “Dissemination-based Data Del
ivery Using Broadcast Disks, ”IEEE Personal Commun
ication, Vol. 2, No. 6, Dec. 1995.) proposes a method of changing the transmission order of information to be broadcast using the access status of information from a user. Hereinafter, these systems are referred to as broadcast communication systems. In this broadcast-type communication, information can be provided to a larger number of users by broadcasting the information than the transmission capacity.

Next, this data is periodically broadcasted in "B
The feature of the method by "roadcast Disks"
This will be described with reference to the system configuration shown in FIG. This FIG.
, The system includes one server-side device 103 and a plurality of client-side devices 101 (only one is shown in FIG. 8).

As a result, "Broadcast Dis"
In the method using “ks”, data in the server-side device 103 is periodically broadcast to the client-side device 101, so that data can be provided to many client-side devices 101. Also, the broadcast cycle of each data is determined by the rate at which the data is accessed, and by shortening the broadcast cycle of the data at a high access rate,
Reduce the waiting time before acquiring data. However, the broadcast cycle of data that is accessed at a low rate becomes long.

[0008] That is, "Broadcast Disk"
s "periodically broadcasts all the data stored in the database. Then, by shortening the cycle of data frequently accessed from the client-side apparatus 101 and broadcasting the data, the waiting time until the client-side apparatus 101 acquires data is shortened. FIG. 9 shows an example of data broadcast at this time. In this example, it takes one second to transmit one piece of data, and when there are five pieces of data A, B, C, D, and E in the descending order of the rate of access per unit time, the data is periodically transmitted. Shows that it is being broadcast. From this, it can be understood that each cycle is 2 seconds for A, 6 seconds for B and C, and 12 seconds for D and E.

An equation for calculating the expected value of the waiting time until data acquisition when the cycle at which each data is broadcast and the rate at which the data is acquired per unit time is known is shown below. The expected value of the waiting time can be calculated by multiplying the expected value of the waiting time until the data k is obtained by the rate at which the data is obtained per unit time, and adding all of them.

[0010]

(Equation 1) W: Expected value of waiting time until data acquisition P _k : When data k is acquired per unit time T _k : Expected value of waiting time until data k is acquired k: Data ID N: Data Next, a calculation example will be described. It is assumed that the number of times and the ratio of accessing each data are the values shown in Table 1. Then, as shown in FIG. 9, frequently accessed A has the shortest cycle, B and C have the second shortest cycle, and D and E have the longest cycle. The expected value of the waiting time at this time can be calculated as follows.

Waiting time = (50/100) × 1 + (20/100) × 3 × 2 + (5/100) × 6 × 2 = 0.5 + 1.2 + 0.6 = 2.3 (2) Result of calculation The waiting time is 2.3 seconds. Similarly, A ~
The expected value of the waiting time when all five data items up to E are broadcast at the same cycle is 2.5 seconds. Therefore, by changing the broadcasting cycle according to the access rate, the expected waiting time is changed. It can be seen that the value can be shortened.

[0012]

[Table 1] Next, an information providing system that combines broadcast communication and on-demand communication will be described. The above "Broa
In the method using "dcast Disks", all data is broadcast, and therefore, when the number of data to be broadcast is large, the broadcast cycle becomes long. As a result, there is a problem that even if the broadcast cycle of data that is accessed at a high rate is shortened, the waiting time until the client-side device acquires the data becomes longer as a whole system. In order to solve this, an information providing method combining broadcast-type communication and on-demand type communication has been proposed (Japanese Patent Application No. 8-308539).
No. “Information transmission system (Tanabe, Hakomori, Inoue)”).

FIG. 10 shows the configuration of an information providing system that combines broadcast-type communication and on-demand type communication, and the contents of the processing of each mechanism will be described below.

First, the client-side device 101 includes an acquisition request receiving unit, a determination unit, an acquisition request transmitting unit, a request collecting unit, a communication unit, an information receiving unit, an information selecting unit, and a result display unit. Is composed of a request receiving unit, a request collecting unit, an information searching unit, a switching unit, an information mixing unit, and an information broadcasting unit.

The switching unit of the server-side device 103 merely determines whether or not to broadcast the data. For example, based on the rate at which the client-side device 101 accesses the data stored in the server-side device 103. To select data to be broadcast. At this time, the data to be broadcast is broadcast only once in the stream, and all data are broadcast in the same cycle. As a result, the broadcast data mixing unit transmits all data provided to the client-side device 101 in one stream.
For example, it is assumed that there are five data A to E. And
If A and B are broadcast and the remaining three data C, D, and E are transmitted in response to a request from the client device 101, the transmission is as shown in FIG.

At this time, the expected value of the waiting time until the client-side device 101 acquires data is calculated using the following equations (1) to (5). Then, the number k of broadcast data is determined so that the value of W becomes the smallest.

(A) The expected value of the waiting time in the entire system The expected value of the waiting time in the entire system is the data to be broadcasted (hereinafter referred to as broadcast data) and the data to be transmitted on demand (hereinafter referred to as ON data). Demand data) is obtained by multiplying the expected value of each waiting time by the ratio of accessing each data.

[0018]

(Equation 2) W: the expected value of the waiting time P _i: If the data i (broadcast data, on-demand data) is accessed W _b: expected value W of the waiting time of the broadcast data i _o: expected value k of on-demand data latency : Number of broadcast data (b) Expected value of broadcast data wait time Since the broadcast cycle of all broadcast data is the same, the expected value of wait time is half of the cycle T in which broadcast data is broadcast.

W _b = T / 2 × 1 / S (4) T: broadcast cycle S: number of slots per unit time (c) Expected value of waiting time for on-demand data Expected value is calculated based on a queuing model calculate. The transmission slot for on-demand data is a slot obtained by removing a slot allocated for broadcast data from a slot of one cycle.

[0020]

(Equation 3) ρ: On-demand slot usage rate λ _i : Data i access rate Q: Number of requests generated per unit time S _b : Number of broadcast data slots per unit time For example, at the rate shown in Table 1. When data is being accessed, the relationship between the number of data to be broadcast and the waiting time until the client-side device acquires the data is as follows: one data acquisition request is generated per unit time; Assuming that one slot is used to transmit one data and the time required to transmit one slot is 1 second, the equation (5) is calculated from the equation (3), as shown in Table 2. become. Therefore, when the number of broadcast data is set to one, the expected value of the waiting time is minimized, so that the broadcast of the data A is determined.

[0021]

[Table 2] The features of the information providing system that combines the broadcast communication and the on-demand communication are described below.

(A) The number of data to be broadcasted is reduced by broadcasting data that is accessed at a high rate and transmitting other data in response to an on-demand request from the client device. As a result, the broadcast cycle is shortened, so that the waiting time until the client device acquires data can be shortened.

(B) Since non-broadcast data is provided on demand, a large amount of data can be provided to the client device.

[0024]

However, each of the above-mentioned methods has the following problems to be solved.

(A) The broadcast cycle cannot be changed according to the rate at which data is accessed.

In an information providing system in which broadcast-type communication and on-demand type communication are combined, the broadcast cycle of all data to be broadcast is the same broadcast cycle T, as shown in FIG. The ratio of access to the broadcast data is different, but this cannot be considered in the conventional system. For example, the broadcast cycle of the data whose access rate is the fifth and sixth is the same as that of the data whose rate is the highest. As a result, despite the fact that data is acquired most frequently, the waiting time before acquiring that data is the same as other data.

(B) The amount of calculation for determining the broadcast cycle is large.

The expected value of the waiting time can be shortened by changing the broadcasting cycle in accordance with the rate at which data is accessed.
However, since the method using “Broadcast Disks” has the following problems, it is impossible to realize a mechanism for determining a broadcast cycle using the same method in an information providing system that combines broadcast-type communication and on-demand communication. .

(A) Since a specific method of determining the broadcast cycle of each data is not shown, automation cannot be performed.

(B) When trying to determine the broadcast cycle using the above equation (1), the number of combinations of data and broadcast cycle increases. Therefore, when the server device broadcasts a lot of data, it is not possible to calculate an expected value of a waiting time until data is acquired for each combination and determine a combination that takes the minimum value. Have difficulty. Also, no solution for this is described.

In an information providing system combining broadcast-type communication and on-demand type communication, if the broadcast cycle is simply determined according to the rate at which data is accessed, "Br
Similar to the method using "oadcast Disks", a problem arises in that the amount of calculation is large. Here, when the broadcast cycle is changed for each data, an example in which the number of combinations of the broadcast cycle and the data is specifically calculated for the amount of calculation in the information providing system that combines the broadcast communication and the on-demand communication will be described. . Here, A, B, C,
There are five types of data, D and E, which are the largest in an information providing system that combines broadcast-type communication and on-demand type communication.
The period is fixed (five slots in this example), and it takes one second to transmit one slot, and one data is transmitted in one slot. When there is a possibility that five data items A to E are broadcast, n of the five data items A to E are broadcasted in k slots among the five slots having the longest period (FIG. 12). reference).

[0032]

(Equation 4) Therefore, 3906 combinations can be made, and it is necessary to calculate the waiting time for each of the combinations.

While the number of slots is small and the type of data is small, the number of combinations is small and the amount of calculation is small.
As the number of slots and the type of data increase, the number of combinations increases, making it difficult to calculate in a short time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to reduce a waiting time until a client device acquires data in an information providing system integrating broadcast-type communication and on-demand communication. It is an object of the present invention to provide a broadcast cycle switching method and apparatus capable of performing the method and a recording medium on which a program for executing the method is recorded.

[0035]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present invention provides a method for transmitting a plurality of pieces of information and a plurality of pieces of information repeatedly transmitted from a first transmitting means on a server side. In the broadcast cycle switching method in the information providing system when the client can respectively receive information transmitted in response to a request from the client from the second transmission means, the information desired to be acquired by the client is the first information of the server. It is determined whether or not the information is included in a plurality of pieces of information repeatedly transmitted from the transmitting unit. When it is determined that the information is not included, the client transmits the information to the server by the second transmitting unit. When an acquisition request is made, the server sends a transmission cycle of information repeatedly transmitted from the first transmission unit according to a request frequency from a client. And it is required to change.

According to the first aspect of the present invention, the server has a first transmitting means for repeatedly transmitting a plurality of information, and a second transmitting means for transmitting the information in response to a request from the client. In an information providing system in which broadcast-type communication and on-demand type communication are integrated, when the information desired by the client is not included in a plurality of information repeatedly transmitted from the first transmission unit of the server, the client From the second transmission means, the server makes a request to acquire information, and the server changes the transmission cycle of the information repeatedly transmitted from the first transmission means according to the request frequency from the client. The waiting time until the side device acquires data can be reduced.

According to a second aspect of the present invention, a plurality of information repeatedly transmitted from the first transmission means on the server side and information transmitted in response to a request from the client from the second transmission means are transmitted to the client. In the broadcast cycle switching device in the information providing system when each of the information can be received, the client determines whether or not the information desired to be acquired is included in a plurality of information repeatedly transmitted from the first transmission unit of the server. And when it is determined that the information is not included, the client makes a request to the server to acquire information by the second transmitting means, and the server makes the request for the information according to the request frequency from the client. The gist of the present invention is to include a switching unit that switches a transmission cycle of information repeatedly transmitted from one transmission unit.

According to the present invention, the server has first transmitting means for repeatedly transmitting a plurality of information, and second transmitting means for transmitting the information in response to a request from the client, When the information desired by the client is not included in the plurality of information repeatedly transmitted from the first transmission means of the server, the second
Requesting information acquisition by the transmitting means, and the server switches and changes the transmission cycle of the information repeatedly transmitted from the first transmitting means according to the request frequency from the client, The waiting time until the client device acquires the data can be reduced.

In order to realize the above, a means for calculating an expected value of a waiting time until the client-side device acquires data, and further, when an optimum broadcast cycle is determined by using this calculation means, the broadcast cycle of the broadcast cycle is calculated. In order to reduce the amount of calculation of the expected value of the determination and the waiting time, means for determining the broadcast cycle based on the ratio of the rate at which data is accessed may be provided.

Further, according to the present invention, a plurality of information repeatedly transmitted from the first transmitting means on the server side and information transmitted in response to a request from the client from the second transmitting means are transmitted to the client. In the recording medium recording the broadcast cycle switching program in the information providing system when each of the information can be received, the client includes information desired to be acquired in a plurality of information repeatedly transmitted from the first transmission unit of the server. And if it is determined that the information is not included,
The client makes a request to the server to acquire information by the second transmission unit, and the server changes a transmission cycle of information repeatedly transmitted from the first transmission unit according to a request frequency from the client. The gist is that the broadcast cycle switching program is recorded on a recording medium.

According to the present invention, since the broadcast cycle switching program is recorded as a recording medium,
By using the recording medium, its distribution can be improved.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a first embodiment of an information providing system that combines broadcast-type communication and on-demand type communication according to the present invention.
FIG. 3 is a block diagram showing a configuration of the embodiment.

As shown in FIG. 1, an information providing system including a broadcast cycle switching device according to the present embodiment includes a client device 1 and a server device 3 connected to the client device 1 via a network or the like. And an information database 5 attached to the server-side device 3.

The client device 1 includes an acquisition request receiving unit 11, a determination unit 12, an acquisition request transmitting unit 13, a request collecting unit 14, a communication unit 15, an information receiving unit 16, and an information selecting unit 1.
7 and a result display unit 18. The server-side device 3 includes a request receiving unit 31, a request collecting unit 32, and an information searching unit 3.
3. It is composed of a variable broadcast data switching unit 35, an information mixing unit 37 and an information broadcasting unit 39.

Next, the operation of each unit in the client device 1 will be described.

The acquisition request receiving unit 11 receives a data acquisition request from a user, and the received request is passed to the determination unit 12. The determination unit 12 determines whether or not the data requested by the user is being broadcast. If the determination unit 12 determines that the broadcast is not being broadcast, the request is passed to the acquisition request transmission unit 13. If it is determined that the broadcast is being performed by the determination unit 12, the request is passed to the information selection unit 17. The information receiving unit 16 receives data broadcast by the server-side device 3, and the received data is passed to the information selecting unit 17. As a result, the information selection unit 17
The data requested to be obtained by the user is extracted from the broadcast data received via the information receiving unit 16, and the requested data is passed to the result display unit 18. Result display section 1
8 presents the acquired data to the user via a display screen or the like.

The acquisition request transmission unit 13 transmits a data acquisition request to the server device 3 through the communication unit 15.

Next, the operation of each unit in the server-side device 3 will be described.

The request receiving unit 31 receives a data acquisition request from the user from the client device 1 and passes it to the information search unit 33. The information search unit 33 searches the database 5 for data requested by the user, and passes the search result to the information mixing unit 37. The information mixing unit 37 forms a broadcast stream by mixing data to be broadcast and data requested by a user (that is, data not to be broadcast). The information broadcast unit 39 transmits all data to be provided to the client-side device 1 in one stream. The variable broadcast data switching unit 35 selects data to be broadcast based on the rate at which the client-side device 1 accesses data stored in the server-side device 3.

Hereinafter, the variable broadcast data switching unit 35 will be described in detail. This variable broadcast data switching unit 35
Is a switching unit that uses a variable broadcast cycle in an information providing system that combines broadcast-type communication and on-demand type communication, and can change the data broadcast cycle in accordance with the rate at which the data is accessed. Therefore, the broadcast cycle of frequently accessed data can be shortened, and as a result, the waiting time until the client device 1 acquires the data can be shortened.

Hereinafter, the variable broadcast data switching unit 3 will be specifically described.
5 will be described.
FIG. 2 shows an example in which data to be broadcast is assigned to a slot in the variable broadcast data switching unit 35.

In FIG. 2, A is broadcast in a T / 2 cycle, and B and C are broadcast in a T cycle. D, E, and F are transmitted in response to an on-demand request. in this way,
The variable broadcast data switching unit 35 switches between broadcast data and on-demand data, and in one broadcast stream, data broadcast at different broadcast cycles and data transmitted in response to an on-demand request from a user. Can be transmitted together.

Next, the switching section variable type broadcast data switching section 35
Will be described. Here, when calculating the expected value of the waiting time in the variable broadcast data switching unit 35, the amount of calculation is reduced by determining the broadcast cycle using the ratio of the ratio of accessing data.
This makes it possible to determine a set of data to be broadcast in a short period of time and a broadcast cycle of each data even when the access rate of data changes, and to cope with a dynamic environmental change.

The set of data to be broadcast among the data sets held by the server device 3 and the broadcasting cycle of each data are represented by a data set N in which the data sets held by the server device 3 are arranged in descending order of the rate of data access. , And the maximum broadcast cycle (slot: T).

Step a: A slot S (hereinafter referred to as a broadcast slot) to be allocated to data to be broadcast in the maximum broadcast cycle T is appropriately determined. Step b: An appropriate number of k data is selected from the largest ratio in the data set N, and is set as a set of data to be broadcast (hereinafter referred to as broadcast data). Step c: Find the ratio of the rate at which k pieces of broadcast data are accessed. Step d: The broadcast slots S are allocated to k pieces of broadcast data according to the ratio in that case. Step e; Since the broadcast cycle of each broadcast data can be determined by allocating slots to each broadcast data, the expected value of the waiting time is calculated. Step f: The expected value of the waiting time in step e is S = 1,
, T, k = 1, 2,..., N are calculated for all combinations. Step g: A combination having the smallest expected value is selected from the combination of S and k, and is set as a broadcast cycle and broadcast data.

For example, data is accessed from the client device 1 at the rate shown in Table 1 and the maximum broadcast cycle T
Is set to 5 slots and the number of broadcast slots S is set to 3 (at this time, the remaining 2 slots are slots for transmitting on-demand data), and each data (k = 1, 2,
3), the broadcast cycle is assigned as shown in Table 3.

Hereinafter, a process until the assignment is determined will be described using an example in which the number k of broadcast data is two in the number of broadcast data shown in Table 3.

Step h: The number S of broadcast slots is set to 3.

Step i: The broadcast data number k is set to 2.

Step j: According to Table 1, the ratio of the access ratio is 5: 2.

Step k; Therefore, the number of broadcast slots to be allocated can be calculated by solving the following two equations. That is, the number of slots allocated to data A is 3 ×
5/7 = 2.14... In addition, since the broadcast slot is an integer, two decimal places are allocated to data A by truncating the decimal part. Then, the remaining one slot is allocated to data B.

5: 2 = x: y (x indicates the ratio of slots allocated to data A, y indicates the ratio of slots allocated to data B.) x + y = 3 (the number of broadcast slots must be 3 slots) According to this method, the number of broadcast slots S and the number of broadcast data k
Is determined, the broadcast cycle of the broadcast data of each data is determined by the rate at which the data is accessed, so that it is not necessary to calculate all combinations of the broadcast cycle. In the above example, the number of combinations of the number of broadcast slots, the number of broadcast data, and the broadcast cycle is as follows, where the number of broadcast slots is S _b = 15.

(Equation 5) Therefore, there are 15 combinations, and the number of combinations is smaller than when all combinations are calculated (3906 combinations). Furthermore, if the broadcast cycle and the number of broadcast slots are determined, the expected value of the waiting time until data acquisition can be calculated quickly.

[0064]

[Table 3] Next, the configuration of the variable broadcast data switching unit 35 will be described with reference to FIG. The variable broadcast data switching unit 35 includes a broadcast cycle determination unit 351, a database 352, an expected value calculation unit 3
53 and a broadcast data determination unit 354.

Next, the function of each unit constituting the variable broadcast data switching unit 35 will be described with reference to FIG. First, the broadcast cycle determination unit 351 determines the cycle of broadcasting each data using the ratio of access to each data stored in the database 352 and the number of slots for broadcast data. Hereinafter, this method is referred to as a broadcast cycle determination method. The determined combination is passed to the expected value calculation unit 353. Note that the rate of data access can be determined by adding on-demand data requests from the client-side device 1 and then stopping broadcasting at regular intervals to count on-demand requests from the client-side device 1. Can be obtained.

The expected value calculation unit 353 calculates the waiting time until data acquisition using the ratio of each data accessed and the broadcast cycle of each data. The calculation result is passed to the broadcast data determination unit 354. Further, the broadcast data determination unit 3
54 selects a combination having the smallest expected value from the expected values calculated by combining the broadcast cycle, the broadcast slot, and the broadcast data.

Next, a method of calculating the waiting time when the broadcast cycle is changed will be described.

Here, the expected value of the waiting time when the broadcast cycle of each data is changed is calculated using the following equation based on the rate at which the data is accessed.

First, the expected value of the waiting time of the entire system is calculated. The expected value of the waiting time of the whole system is
It is obtained by multiplying the expected value of the waiting time of each of the broadcast data and the on-demand data by the rate at which each data is accessed.

[0070]

(Equation 6) W: expected value of waiting time N: type of data that can be provided by the server-side device k: type of broadcast data (determined by a method of determining a broadcast cycle) _Pi : data i (broadcast data, on-demand data) is accessed B _i : the expected value of the waiting time of the broadcast data i W _o : the expected value of the waiting time of the on-demand data Next, the expected value of the waiting time of the broadcast data when the broadcast cycle is made variable is calculated. Since the broadcast data is evenly arranged in one cycle, the expected value of the waiting time is obtained in half of the cycle in which the broadcast data is broadcast. Incidentally, F _i is shown below, is the number distribution of the broadcast data shown in step e of determination procedure of the broadcast cycle described above.

[0071]

B _i = (T / 2) × (1 / F _i ) × (1 / S) (9) T: the longest broadcast cycle of the broadcast cycle of broadcast data F _i ; On the other hand, the number of times the broadcast data i is broadcast S: the number of slots per unit time Next, the expected value of the waiting time of the on-demand data will be described.

Here, the expected value is calculated based on the queue model. The on-demand data transmission slot is a slot obtained by removing a slot allocated for broadcast data from a slot of one cycle.

[0073]

(Equation 8) ρ: On-demand slot usage rate λ _i : Data i access rate Q: Number of requests generated per unit time S _i : Number of broadcast data slots per unit time Next, a broadcast cycle determination method will be described. I do.

First, the following policy is given to determine the broadcast cycle.

(A) The number of slots T obtained by combining a slot for transmitting on-demand data and a broadcast slot
give. This T is the maximum cycle of the broadcast data.

(B) A set of broadcast data is determined, and the number of slots to be allocated to broadcast data among T slots is determined. Then, the number of broadcast slots is allocated to each broadcast data based on the ratio of the rate at which the broadcast data is accessed. For example, if two slots are allocated to certain data, T
The slot of / 2 becomes the broadcast cycle of the data, and if three slots are allocated, the T / 3 slot becomes the broadcast cycle of the data.

Next, an algorithm for determining a broadcast cycle will be described with reference to FIG.

First, in step S1, the value of the ratio of access to broadcast data is fetched from the memory for the type of broadcast data, and the ratio of the ratio of access to the broadcast data is determined. Next, in step S3, broadcast slots are allocated using the ratio of the ratio obtained previously to the number of broadcast slots given by the higher-level program or the caller. Further, in step S5, after the broadcast slots are allocated to each broadcast data, the number of broadcast slots is adjusted. In other words, if broadcast slots are allocated to each broadcast data at the access ratio based on the maximum length of the broadcast slots,
The assigned number may not be an integer. In that case,
Assign after rounding down the decimal point. In this way,
If the total number of broadcast slots allocated to each broadcast data is less than the number of slots initially given for broadcast slots, the shortage is allocated to the broadcast data with the highest access ratio.

Next, an example of calculating the expected value of the waiting time will be described.
In calculating the expected value of the waiting time, the following conditions were set. That is, the number N of data is set to ten,
All slots (the maximum length of one cycle) T were set to 20 slots (however, when the broadcast cycle of all broadcast data is the same, T is assumed to be 10 slots). Further, the total number of requests Q per unit time from the user is set to two, and the data access ratio can be automatically acquired at a certain timing (for example, every minute). Further, all data are assumed to be the same size, one slot is used to transmit one data, and it takes one second to transmit this one slot. Note that the request processing time in the server-side device is set to 0.

The rate at which data is accessed is defined as the number of requests for data from the client device 1 per unit time with respect to the total number of requests per unit time. It is assumed that there are three types of patterns shown in Table 4 as patterns of the access ratio. Actually, since the access ratio changes depending on the request situation from the client-side device 1, the three types of ratios set here are only examples. Then, a calculation was performed to find out which combination of data has the smallest expected value of the waiting time in each access pattern.

[0081]

[Table 4] Next, a calculation result will be described with reference to FIG. In FIG. 6, compared to the case where the broadcast cycle of all data is the same,
The waiting time until data is obtained is shorter when the broadcasting cycle is made different. The expected value of the waiting time is minimized in each of the numbers of broadcast data when the broadcast cycle of each broadcast data is set to the broadcast cycle shown in Table 5. In Table 5, T indicates the largest broadcast cycle among broadcast cycles of broadcast data, 0 indicates that the data is on-demand data, and Δ indicates that data cannot be transmitted.

[0082]

[Table 5] From the calculation results, in each pattern, the expected value of the broadcast cycle and the waiting time of the broadcast data set and each broadcast data is:
It is as follows.

Pattern 1: Data A and B are broadcast, and the broadcast cycle is T / 9 slots for data A and T / 4 slots for data B. That is, when data A is arranged in 9 slots and data B is arranged in 4 slots in T = 20 slots, the expected value of the waiting time becomes the minimum and becomes 1.54 seconds.

Pattern 2: four data A to D are broadcast, and the broadcasting cycle is T / 9 slot for data A, T / 4 slot for data B, T / 2 slot for data C,
Data D is a T / 2 slot. That is, T = 20
When 9 slots for data A, 4 slots for data B, 2 slots for data C, and 2 slots for data D are arranged in the slot, the expected value of the waiting time becomes minimum, and
4 seconds.

Pattern 3: Seven data from data A to G are broadcast, and the broadcast cycle is T / 6 slots for data A, T / 3 slots for data B, T / 3 slots for data C, and T for data D. / 2 slots, data E is T / 2 slots, data F is T / 2 slots, and data G is T slots. That is, data A during T = 20 slots
Is 6 slots, data B is 3 slots, data C is 3 slots, data D is 2 slots, data E is 2 slots, data F is 2 slots, and data G is 1 slot. Minimum, 3.57
Seconds.

Next, the flow of processing in the variable broadcast data switching unit 35 will be described in detail with reference to FIG.

First, in step S11, the determination unit of the broadcast cycle determination unit 351 initializes a variable BS that gives the number of broadcast slots for transmitting broadcast data (BS = 0).
I do. Next, in step S12, the number of broadcast slots BS is increased by one in order to increase the rate at which broadcast data is transmitted, and in step S13, it is checked whether or not the broadcast slot exceeds the size of the entire slot. (Condition 1). If it exceeds, the process proceeds to step S22, and the broadcast data determination unit 354 selects a combination having the smallest expected wait time in order to determine the broadcast data. If not, the process proceeds to step S14, where the broadcast data set setting unit initializes a variable BN that gives the type of data to be broadcast in order to determine another combination of the number of broadcasts.

Subsequently, in step S15, the number of data sets NB to be broadcasted is increased, and in step S16, it is checked whether the number of broadcast data exceeds the number of slots allocated for slot broadcasting (condition 2). If not, the process proceeds to step S17 to determine another combination.

In step S17, the access ratio of each data is divided by the smallest access ratio among the data to be broadcast in order to obtain the ratio of the number of broadcasts of each data to be broadcast by the broadcast cycle designation section. Subsequently, in step S18, a broadcast slot is allocated to each broadcast data based on the ratio of the ratio obtained in step S17, and the process returns to step S15.

On the other hand, when the broadcast data exceeds the number of slots in step S16, the process proceeds to step S19, where the expected value calculator calculates the expected value of the waiting time of the on-demand data. Subsequently, in step S20, the expected value of the waiting time of the broadcast data is calculated, and in step S21, each expected value is multiplied by the access ratio of each data, and the obtained values are added.
The expected value of the waiting time is obtained, and the process returns to step S12.

As described above, after selecting the combination of the broadcast data having the smallest expected value of the waiting time and the number of slots for broadcasting in step S22, the broadcast data currently being broadcast is newly recalculated in step S23. As a result, by comparing the obtained combinations of broadcast data, it is determined whether or not the broadcast data currently being broadcast needs to be changed (condition 3). If there is a need to change, the process proceeds to step S24, where the currently broadcast data is changed, and if not, the process in the variable broadcast data switching unit 35 ends.

As described above, according to the present embodiment, the following effects can be obtained.

(A) The broadcast cycle of data can be changed according to the rate at which data is accessed.

(B) Since the broadcast cycle is determined based on the ratio of the rate at which data is accessed, the amount of calculation can be reduced.

(C) The communication band for on-demand and the communication band for broadcasting can be optimally allocated in accordance with the rate at which the client-side device accesses data.

(D) The expected value of the waiting time until the client device acquires data can be shortened.

(E) By recording the broadcast cycle switching program on a recording medium, the distribution of the program can be enhanced by using the recording medium.

[0098]

As described above, according to the present invention, the server changes the transmission cycle of the information transmitted according to the request frequency from the client, so that the client acquires the information desired to be acquired. In this case, the server can reduce the amount of information required for calculating the expected value of the waiting time, and can reduce the amount of calculation for the distribution of the number of information, the transmission cycle, and the like. . In addition, by recording such a program on a recording medium, the distribution of the program can be enhanced by using the recording medium.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an information providing system according to the present invention.

FIG. 2 is a diagram illustrating a manner in which data to be broadcast is allocated to slots in a variable broadcast data switching unit.

FIG. 3 is a block diagram illustrating a detailed configuration of a variable broadcast data switching unit illustrated in FIG. 1;

FIG. 4 is a diagram schematically showing a flow of processing in a variable broadcast data switching unit.

FIG. 5 is a diagram schematically illustrating a procedure for determining a broadcast cycle using a ratio of an access ratio.

FIG. 6 is a diagram illustrating a calculated value of an expected value of a waiting time.

FIG. 7 is a diagram showing in detail a flow of processing in a variable broadcast data switching unit.

FIG. 8 is a block diagram showing a conventional system configuration.

FIG. 9 is a diagram illustrating an example of data to be broadcast.

FIG. 10 is a block diagram showing a configuration of a conventional information providing system that combines broadcasting and on-demand.

FIG. 11 is a diagram showing transmission of broadcast data and on-demand data.

FIG. 12 is a diagram for explaining how to assign data to be broadcast to slots.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 client-side device 3 server-side device 5 information database 11 acquisition request receiving unit 12 discriminating unit 13 acquisition request transmitting unit 14 request collecting unit 15 communication unit 16 information receiving unit 17 information selecting unit 18 result display unit 31 request receiving unit 32 request collecting Unit 33 information retrieval unit 35 variable broadcast data switching unit 37 information mixing unit 39 information broadcasting unit

Continuation of the front page (72) Inventor Shio Inoue NTT Data Communication Corporation, 3-3-3 Toyosu, Koto-ku, Tokyo

Claims (5)

[Claims] 1. A method in which a client can receive a plurality of information repeatedly transmitted from a first transmission unit on a server side and information transmitted in response to a request from a client from a second transmission unit. In the broadcast cycle switching method in the providing system, the client determines whether or not the information desired to be obtained is included in a plurality of pieces of information repeatedly transmitted from the first transmission unit of the server, and the information is included. When it is determined that there is no request, the client makes a request to acquire information from the server by the second transmitting means, and the server repeatedly transmits the information from the first transmitting means according to the request frequency from the client. A broadcast cycle switching method characterized by changing a transmission cycle of information to be transmitted. 2. Information when a client can receive a plurality of information repeatedly transmitted from a first transmission unit on a server side and information transmitted in response to a request from a client from a second transmission unit. In the broadcast cycle switching device in the providing system, the client determines whether or not the information desired to be acquired is included in a plurality of pieces of information repeatedly transmitted from the first transmitting unit of the server, and the information is included. When it is determined that there is no request, the client makes a request to acquire information from the server by the second transmitting means, and the server repeatedly transmits the information from the first transmitting means according to the request frequency from the client. A switching unit for switching a transmission period of the information to be transmitted. 3. The switching unit measures a waiting time until the client acquires the information desired to be acquired, and is repeatedly transmitted from the first transmitting unit with reference to the measured waiting time. 3. The broadcast cycle switching device according to claim 2, wherein the information transmission cycle is switched. 4. The broadcast cycle switching device according to claim 2, wherein said switching means determines the distribution of the transmission cycle according to a ratio of the request frequency from the client in order to reduce the amount of calculation. 5. Information when the client can receive a plurality of information repeatedly transmitted from the first transmission means on the server side and information transmitted in response to a request from the client from the second transmission means. In a recording medium recording a broadcast cycle switching program in a providing system, the client determines whether or not the information desired to be obtained is included in a plurality of pieces of information repeatedly transmitted from a first transmission unit of the server. When it is determined that the information is not included, the client makes a request to the server to acquire information by the second transmission unit, and the server transmits the first transmission according to a request frequency from the client. A recording medium storing a broadcast cycle switching program for changing a transmission cycle of information repeatedly transmitted from the means.