JP6146817B2 - Wireless network system, wireless data transfer method, and terminal device - Google Patents

Description

  According to the present invention, a terminal device that starts data transfer from outside the service area of a base station device (hereinafter referred to as “data transfer start terminal device”) wirelessly transfers data to the base station device via one or more other terminal devices. The present invention relates to a wireless network system, a wireless data transfer method, and a terminal device that improve a data arrival rate to a base station device in a network.

  When the link between the data transfer start terminal device and the base station device is interrupted, the data is replicated at each terminal device via one or more other terminal devices for which the link is secured. A wireless network system that performs data transfer from a transfer start terminal device to a base station device is known as a delay-tolerant network (Non-patent Document 1). The delay-tolerant network can cope with a large delay time and link interruption at the time of data transfer that could not be handled by TCP / IP.

FIG. 9 shows a data transfer method in a delay-tolerant network.
In FIG. 9, the data transfer start terminal device first confirms whether or not the base station device exists in another having a direct link with itself, and if the link with the base station device is secured, the base station device Data is transferred to the device and communication is terminated. If the link with the base station apparatus is not secured, the data transfer is started at the data transfer start terminal device, and a part of the copied data is transferred to another terminal device with the link secured. Similarly, if a link with the base station apparatus is not secured, the terminal apparatus that has received the data duplicates the data and transfers a part of the duplicated data to another terminal apparatus. By repeating this, data transfer from the data transfer start terminal device to the base station device is realized. In addition, when TTL (Time To Live) time elapses after data is generated at the data transfer start terminal device, the data and all data copied from the data are deleted from the network.

  Conventional techniques using such a data transfer method include ER (Epidemic Routing) (Non-Patent Document 2) and BSW (Binary Spray and Wait) (Non-Patent Document 3). Hereinafter, the terminal device on the data transfer side is referred to as “transfer source terminal device”, and the terminal device on the data transfer side is referred to as “transfer destination terminal device”.

K. Fall, “A Delay-Tolerant Network Architecture for Challengied Internets,” Proceedings of ACM SIGCOMM'03, pp.27-34, Aug. 2003 A.Vahdat and D.Beeker, “Epidemic Routing for Partially-Connected Ad Hoc Networks,” Technical Report CS-2000-06, Apr. 2000 T.Spyropoulos, K.Psounis, C.S.Raghavendra, “Spray and Wait: An E.cient Routing Scheme for Intermit-tently Connected Mobile Networks,” Proc. Of ACM SIGCOMM'05, pp.252-259, Aug. 2005

  Whenever a transfer destination terminal device appears within the data transferable range of the transfer source terminal device, the transfer source terminal device duplicates and transfers one piece of data to the transfer destination terminal device, and repeats this. That is, since the transfer source terminal device replicates data every time the transfer destination terminal device appears, there is a possibility that the copy data will increase without limitation in the network. As a result, since the terminal device holds the replicated data transferred from various data transfer start terminal devices, the number of replicated data held by one terminal device increases, and data drops frequently occur in the buffer of the terminal device. To do. As described above, ER has a problem that the data arrival rate of the base station apparatus decreases.

  The BSW transfers half of the duplicate data held by the transfer source terminal device to the transfer destination terminal device each time the transfer destination terminal device appears in the data transferable range of the transfer source terminal device. FIG. 10 shows a data transfer procedure in the BSW. As shown in FIG. 10 (1), the data transfer start terminal device generates L pieces of replicated data. Here, L is uniquely fixed in the system. Next, as shown in FIG. 10 (2), the transfer source terminal device transfers half L ′ / 2 of the L ′ copy data currently held to the transfer destination terminal device. Finally, as shown in FIG. 10 (3), the transfer source terminal device with L ′ = 1 performs data transfer only to the base station device, thereby transferring data from the data transfer start terminal device to the base station device. Is realized.

  In BSW, the data transfer start terminal device uniformly sets the maximum data replication number L for all users. When L is increased, the same problem as ER occurs. On the other hand, when L is reduced, the possibility that data transfer to the base station apparatus is not performed increases. Therefore, L must be set to an appropriate value empirically. However, even if an appropriate L value is set empirically, as shown in FIG. 11 (1), if the data transfer start terminal device is far from the base station device, the data is only in the range far from the base station device. Can only be transferred. Therefore, the time after the data is generated at the data transfer start terminal device exceeds the TTL time, the data is deleted from the network, and the probability that the data does not reach the base station device increases. On the other hand, if the data transfer start terminal device is close to the base station device, useless data replication increases as shown in FIG. 11 (2). For this reason, the number of replicated data held by one terminal device increases, and data drops frequently occur in the buffer of the terminal device. Therefore, the BSW has a problem that the data arrival rate is lowered similarly to the ER.

  The present invention considers the positional relationship between a data transfer start terminal device and a base station device, and can improve the arrival rate of data transferred from the data transfer start terminal device to the base station device. An object is to provide a method and a terminal device.

  According to a first aspect of the present invention, there is provided a wireless network system in which data transfer is started from a data transfer start terminal device that starts data transfer via one or more other terminal devices to transfer data to a base station device while replicating data. The number H of data transfers from the data transfer start terminal device to the base station device is estimated according to the distance d between the terminal device and the base station device, and the number of data transfers from the data transfer start terminal device is H-1 to H + 1. Means for estimating the total number of terminal devices existing within the ring-shaped range and setting the total number L of replicated data by the total number, and the transfer source terminal device according to the total number L of replicated data and the number of data transfers H Includes a means for setting the total number β of transfer destination terminal devices and transferring the replicated data to β transfer destination terminal devices.

  In the wireless network system of the first invention, the data transfer start terminal device obtains its own location information, calculates the distance d from the base station device, and divides by the maximum distance r that one terminal device can transfer data to Thus, the number of data transfers H is calculated.

In the wireless network system of the first invention, the data transfer start terminal device has a configuration in which the total number L of replicated data is obtained from the following equation based on the total number α of terminal devices existing in the communication range and the number of data transfers H: is there.
When H = 1: L = 1
When H ≧ 2: L = [4d (α + 1) / r]

In the wireless network system of the first invention, the transfer source terminal device is configured to obtain the total number β of transfer destination terminal devices by the following equation:
(Β ^{H + 2} −β ^H ) / (β−1) −L = 0
When the copy source data held by the transfer source terminal device is one or when the transfer destination terminal device is β-th, the transfer source terminal device does not transfer data to other than the base station.

  According to a second aspect of the present invention, there is provided a wireless data transfer method for transferring data from a data transfer start terminal device that starts data transfer to a base station device via one or more other terminal devices while replicating data. The number H of data transfers from the data transfer start terminal device to the base station device is estimated according to the distance d between the start terminal device and the base station device, and the number of data transfers from the data transfer start terminal device is H-1 to H + 1. Estimating the total number of terminal devices existing in the ring-shaped range and setting the total number L of replicated data by the total number, and the transfer source terminal device according to the total number L of replicated data and the number of times of data transfer H Sets the number β of transfer destination terminal devices, and transfers the replicated data to β transfer destination terminal devices.

  According to a third aspect of the present invention, there is provided a wireless network system terminal device that transfers data to a base station device while replicating data from a data transfer start terminal device that starts data transfer via one or more other terminal devices. The number H of data transfers from the data transfer start terminal device to the base station device is estimated according to the distance d between the data transfer start terminal device and the base station device, and the number of data transfers from the data transfer start terminal device to H-1 A means for estimating the total number of terminal devices existing within the ring-shaped range of H + 1 and setting the total number L of replicated data by the total number, and the transfer source according to the total number L of replicated data and the number of times of data transfer H The terminal device sets a number β of transfer destination terminal devices, and includes means for transferring the replicated data to β transfer destination terminal devices.

  The present invention sets the total number L of replicated data in accordance with the total number of terminal devices existing within a ring-shaped range in which the number of times of data transfer from the data transfer start terminal device is H-1 to H + 1. The data transfer rate from the data transfer start terminal device to the base station device can be improved by the transfer source terminal device setting the number β of transfer destination terminal devices according to L and the number of data transfer times H.

It is a figure which shows the positional relationship of a data transfer start terminal device and a base station apparatus. It is a figure which shows the structural example of the wireless network system of this invention. It is a figure which shows the data transfer procedure in this invention. It is a figure explaining the relationship between the transfer source terminal device and the transfer destination terminal device. It is a figure which shows the calculation method of distance d of a data transfer start terminal device and a base station apparatus. It is a figure which shows the structural example of the terminal device of the radio | wireless network system of this invention. It is a flowchart which shows the process sequence of the terminal device of the radio | wireless network system of this invention. It is a figure which shows the performance evaluation of this invention. It is a figure which shows the data transfer system in a delay tolerance network. It is a figure in the data transfer procedure in BSW. It is a figure which shows the subject of the data transfer in BSW.

  The present invention controls the data arrival rate from the data transfer start terminal device to the base station device by controlling the number of data replications and the number of terminals performing data transfer according to the distance between the data transfer start terminal device and the base station device. It is characterized by improvement.

  FIG. 1 shows the positional relationship between a data transfer start terminal device and a base station device in the wireless network system of the present invention.

In FIG. 1, when the distance from the data transfer start terminal device 1 to the base station device 2 is d, and the maximum distance that the terminal device can transfer data is r, the data from the data transfer start terminal device 1 to the base station device 2 The number of transfers (the number of hops) H is as follows. Note that the operator [S] used in this specification represents an integer greater than or equal to S and closest to S.
H = [d / r] (1)

FIG. 2 shows a configuration example of the wireless network system of the present invention.
In FIG. 2, 1 is a data transfer start terminal device, 2 is a base station device, and 3 is a terminal device other than the data transfer start terminal device. Assuming that the terminal device 3 is randomly present in the area between the data transfer start terminal device 1 and the base station device 2, the number of times of data transfer from the data transfer start terminal device 1 is within the area from H-1 to H + 1. If the data is transferred to all the terminal devices existing in, the remaining number of transfers to the base station device 2 is 1, so that the data can be transferred to the base station device 2 without fail. Hereinafter, a ring-shaped area in which the number of times of data transfer from the data transfer start terminal device 1 is H-1 to H + 1 is referred to as a ring area, and the number of times of data transfer from the data transfer start terminal device 1 is up to H-1. The area is called outside the ring area. That is, it can be expected to improve the data arrival rate up to the base station apparatus 2 by performing data transfer to all terminal apparatuses existing in the ring area.

  As another method for reliably transferring data from the data transfer start terminal device 1 to the base station device 2, each terminal device always grasps its own position by GPS (Global Positioning System), and the transfer source terminal device, Considering the positional relationship between the transfer destination terminal device and the base station device, a method of transferring data only to the transfer destination terminal device located in the direction from the transfer source terminal device toward the base station device can be considered. However, when the terminal device moves, it is necessary to always grasp its own position using GPS, and there is a problem that power consumption becomes remarkable. Therefore, in the present invention, the GPS is used only when the data transfer start terminal device 1 generates data.

FIG. 3 shows a data transfer procedure in the present invention.
In FIG. 3 (1), the data transfer start terminal device (transfer source terminal device) confirms its position using GPS when generating data. On the other hand, since the base station apparatus is fixedly present in the network, the data transfer start terminal apparatus is assumed to know the position of the base station apparatus in advance. At this time, the data transfer start terminal device calculates the distance d from the data transfer start terminal device to the base station device based on its own position confirmed by the GPS and the known position information of the base station device, and further calculates the equation (1 ) To calculate the number of times H of data transfer from the data transfer start terminal device to the base station device. Thereafter, the data transfer start terminal device determines the total number L of replicated data to be transferred in the network and the total number β of transfer destination terminal devices to which the transfer source terminal device can transfer data. A method for determining L and β will be described later.

Next, in FIG. 3 (2), when a certain transfer source terminal device holds L ′ copy data and a β′-th transfer destination terminal device capable of transferring data appears in the communication range, the transfer source terminal device D copy data is transferred to the transfer destination terminal device from the L ′ copy data held. D at this time is expressed by the following formula (2) or formula (3). That is, after the data transfer, D copy data held by the transfer source terminal device is reduced.
When β ′ <H−1: D = [L ′ / (β−β ′)] (2)
When H−1 ≦ β ′ ≦ H + 1: D = [(L′−1) / (β−β ′)] (3)

  Here, it should be noted that the transfer source terminal device transfers data only to the transfer destination terminal device that is a maximum distance r away from which data can be transferred. As shown in FIG. 4, the transfer destination terminal devices A and B that can transfer data at the time T when the transfer source terminal device tried to transfer data may not be transferred because there is a possibility of being closer to r. On the other hand, since the terminal device C that can newly transfer data at time T ′ after time T is a terminal device that has entered a distance capable of transferring data from a place farther than r, it is surely a terminal that is r far away. Yes, data transfer.

  According to the present invention, the minimum number of replicated data required in the network is zero for the transfer source terminal devices existing outside the ring area that cannot communicate directly with the base station device, and the ring that can communicate directly with the base station device. There is one transfer source terminal device in the area. This state is realized by equations (2) and (3). Equation (2) is the number of transfer data outside the ring area, and since the numerator is L ′, the transfer source terminal device existing outside the ring area shows that there can be finally zero duplicate data. ing. On the other hand, since the expression (3) is the number of transfer data in the ring area and the numerator is L′-1, the transfer source terminal device existing in the ring area finally leaves one copy data. It is shown that.

  As described above, when data transfer is repeated, the state in either the ring area or the outside of the ring area is either in FIG. 3 (3-1) or FIG. 3 (3-2). As shown in FIG. 3 (3-1), when the transfer source terminal device holds one copy data (L ′ = 1) or the transfer destination terminal device becomes β-th, the transfer source terminal device Data transfer is not performed except for the base station apparatus. On the other hand, as shown in FIG. 3 (3-2), when the number of replicated data held by the transfer source terminal apparatus becomes zero, the transfer source terminal apparatus ends the data transfer.

In the present invention, regarding the total number L of replicated data transferred in the network, the number of data transfers H from the data transfer start terminal device to the base station device and the total number of terminal devices existing within the communication range of the data transfer start terminal device Calculate from α. In order to avoid data drop as much as possible in the buffer of the terminal device, it is desirable that L is small. Therefore, if H = 1, the data transfer start terminal device can directly transfer data to the base station device in the future, and therefore asks for a communication opportunity with the base station device without performing data replication. If H ≧ 2, the data transfer start terminal device communicates with the base station device by transferring the replicated data to the transfer destination terminal device. At this time, in order to set L to the minimum number, one copy is transferred to the total number of terminals existing in the ring area, that is, the minimum number of duplicate data is transferred. At this time, the following equation holds. Here, it is assumed that the density at which the terminal devices exist is constant in the communication area.
(Α + 1): L = πr ² : π (d + r) ² −π (d−r) ² (4)

Therefore, L becomes the following equation.
When H = 1: L = 1 (5)
When H ≧ 2: L = [4d (α + 1) / r] (6)

In the present invention, the number β of transfer destination terminal devices that can transfer data by the transfer source terminal device is set as follows. First, the transfer source terminal device transfers the replicated data to the β transfer destination terminal devices. The β transfer destination terminal devices to which the duplicate data has been transferred from the transfer source terminal device become the next transfer source terminal device. That is, the transfer source terminal device also transfers the replicated data to the β transfer destination terminal devices. When this data transfer operation is repeated H times from the data transfer start terminal device, the number N (H) of terminal devices holding duplicate data is expressed by the following equation.
N (H) = 1 + β + β ² +... + Β ^H = (β ^{H + 1} −1) / (β−1) (7)

Using equation (7), the number of terminal devices Nring in the ring area is as follows.
Nring = N (H + 1) -N (H-1)
= (Β ^{H + 2} −β ^H ) / (β−1) (8)

Nring = L needs to be established in order to transfer one piece of replicated data to all terminal devices existing in the ring area. Therefore, the number β of transfer destination terminal devices is obtained from the following equation and rounded up to a positive integer.
(Β ^{H + 2} −β ^H ) / (β−1) −L = 0 (9)

  By using the above method, it is possible to transfer data one by one from the data transfer start terminal device to all terminal devices existing in the ring area. As a result, the data arrival rate from the data transfer start terminal device to the base station device can be improved.

In the above description, the terminal device that has become the transfer source terminal device at time T performs data transfer only to the transfer destination terminal device that has become newly transferable at time T ′ after time T. In the present invention, data transfer may be performed to a transfer destination terminal device capable of transferring data at time T under the replacement of the following equation. When r ′ is an expected value of the distance at which the terminal device can transfer data, Equation (2), Equation (3), and Equation (9) are changed into the following Equation (10), Equation (11), Equation (12), respectively. Replace with.
When β ′ <[(d−r) / r ′]: D = [L ′ / (β−β ′)] (10)
When [(d−r) / r ′] ≦ β ′ ≦ [(d + r) / r ′]:
D = [(L′−1) / (β−β ′)] (11)
(Β ^{[(d + r) / r} ′ ^{] + 1−} β ^{[(dr) / r} ′ ^{] + 1} ) / (β−1) −L = 0 (12)

(Other calculation methods of distance d between data transfer start terminal device and base station device)
In the above description, as a method for the data transfer start terminal device to know the distance d between the data transfer start terminal device and the base station device, the data transfer start terminal device has a GPS reception function as shown in FIG. It is assumed that the location of the base station device can be specified in advance. Other than this, there are the following methods.

  In the method shown in FIG. 5 (2), the data transfer start terminal device grasps its own position coordinates from the GPS information, and calculates d from the comparison with the position coordinates of the base station apparatus notified from the communication satellite. This is effective when the data transfer start terminal device has a GPS reception function and the location of the base station device cannot be specified in advance.

  In the method shown in FIG. 5 (3), d is estimated from the reception level of a radio wave having a constant intensity transmitted from the base station apparatus in the data transfer start terminal apparatus. This is effective when the data transfer start terminal device does not have a GPS reception function.

(Configuration example and processing procedure of terminal device of wireless network system of the present invention)
FIG. 6 shows a configuration example of a terminal device of the wireless network system of the present invention.
In FIG. 6, when the data duplication unit 12 inputs data to be transferred from the data input unit 11, the data duplication unit 12 duplicates L pieces of duplication data according to the distance between the terminal device and the base station device determined by the distance determination unit 13, Accumulate in the buffer unit 14. At this time, the initial value of TTL and β ′ = β are stored as information associated with the data in the header portion of the data accumulated in the buffer unit 14. Data received from the antenna 15 via the receiving unit 16 is accumulated in the buffer unit 14. The TTL counts down at regular intervals, and the data with TTL = 0 is deleted from the buffer unit 14. Further, every time data is transferred, the value of β ′ is decreased by 1, and the data for which β ′ = 1 is not transferred to any data other than the base station apparatus.

  The base station determination unit 17 monitors the link with the base station device, and when the link with the base station device is established, all the data in the buffer unit 14 is transmitted from the antenna 15 via the transmission unit 18 to the base station. Transfer to device. The transfer destination terminal determination unit 19 monitors the link with the transfer destination terminal device. When the link with the transfer destination terminal device is established, the transfer destination terminal determination unit 19 relates to two or more replicated data held in the buffer by the own terminal device. Check two items. (1) The same duplicate data as the relevant duplicate data is not held in the buffer of the transfer destination terminal device. (2) The replication data is not β ′ = 1. If these two items are confirmed, a part (D) of the duplicated data is transferred to the transfer destination terminal device. If these two items are not confirmed, the data transfer of the duplicate data is performed only to the base station apparatus.

  In the above (1), there is a method for determining whether or not two duplicate data are the same, by determining whether or not the combination of the transmission address, the reception address, and the protocol identifier in the header of the IP packet is the same. The transmission address, reception address, and protocol identifier are determined at the time of IP packet generation in the IP layer. At the time of data replication, the protocol identifier, transmission address, and reception address are also replicated. Therefore, if the combination of the transmission address, the reception address, and the protocol identifier is the same, it can be determined that the two replicated data are the same.

FIG. 7 shows a processing procedure of the terminal device of the wireless network system of the present invention.
In FIG. 7, when the link with the base station apparatus is established (S1: Yes), all the data in the buffer is transferred (S2). At this time, only one duplicated identical data may be transferred and all other identical data may be deleted from the buffer. When a link is established with a transfer destination terminal device other than the base station device (S3: Yes), the data in the buffer that is not held in the buffer of the transfer destination terminal device is searched as transfer target data. (S4) When the transfer target data is β ′ ≠ 1 (S5: Yes), D pieces are extracted from the transfer target data, and the extracted data is initialized to β ′ = β and transferred (S6). Further, β ′ is reduced by 1 for data to be transferred other than D pieces.

  FIG. 8 shows the performance evaluation of the present invention. Here, the data arrival rate when the number of terminals is changed from 100 to 1000 is used as an evaluation index. The data arrival rate is the ratio of the number of data arriving at the base station device to the total number of data created by all the data transfer start terminal devices. The comparison targets are EP and BSW. This shows that the present invention has a higher data arrival rate than the prior art.

The parameters used for the performance evaluation of the present invention are as follows.
Area area [m ² ]: 1000 × 1000
Data transfer range [m]: 100
Terminal buffer capacity [MB]: 5
Data size [MB]: 0.5 to 1.0
TTL [h]: 1

  In the above description, the data transfer from the data transfer start terminal device to the base station device has been described. However, even in the data transfer from the base station device to the data transfer start terminal device, the data source and destination are simply switched. The present invention can be applied.

DESCRIPTION OF SYMBOLS 1 Data transfer start terminal device 2 Base station device 3 Terminal devices other than data transfer start terminal device 11 Data input part 12 Data duplication part 13 Distance determination part 14 Buffer part 15 Antenna 16 Reception part 17 Base station determination part 18 Transmission part 19 Transfer Destination terminal determination unit

Claims (6)

In a wireless network system that performs data transfer from a data transfer start terminal device that starts data transfer via one or more other terminal devices to a base station device while replicating data,
The number of times H of data transfer from the data transfer start terminal device to the base station device is estimated according to the distance d between the data transfer start terminal device and the base station device, and data transfer from the data transfer start terminal device to the data transfer start terminal device is estimated. Means for estimating the total number of terminal devices existing in a ring-shaped range in which the number of times is H-1 to H + 1, and setting the total number L of replicated data by the total number;
A transfer source terminal device that sets a total number β of transfer destination terminal devices according to the total number L of the replicated data and the number of times of data transfer H, and means for transferring the replicated data to β transfer destination terminal devices. A wireless network system comprising: The wireless network system according to claim 1,
The data transfer start terminal device obtains the position information of the device itself, calculates the distance d from the base station device, and divides by the maximum distance r that can be transferred by one terminal device, so that the number of times of data transfer H A wireless network system, characterized in that: The wireless network system according to claim 1,
The data transfer start terminal device is configured to obtain the total number L of the replicated data by the following equation based on the total number α of terminal devices existing within the communication range and the number of times of data transfer H: When H = 1: L = 1
When H ≧ 2: L = [4d (α + 1) / r]
A wireless network system characterized by the above. The wireless network system according to claim 1,
The transfer source terminal device is configured to obtain the total number β of the transfer destination terminal devices by the following equation: (β ^{H + 2} −β ^H ) / (β−1) −L = 0
The transfer source terminal device is configured not to transfer data to other than the base station when the copy source data held by the transfer source terminal device is one or when the transfer destination terminal device is β-th. Wireless network system. In a wireless data transfer method for transferring data from a data transfer start terminal device that starts data transfer via one or more other terminal devices to a base station device while replicating data,
The number H of data transfers from the data transfer start terminal device to the base station device is estimated according to the distance d between the data transfer start terminal device and the base station device, and the number of data transfers from the data transfer start terminal device Estimating the total number of terminal devices existing within a ring-shaped range from H-1 to H + 1, and setting the total number L of replicated data by the total number;
The transfer source terminal device sets the number β of transfer destination terminal devices according to the total number L of the replicated data and the number of data transfers H, and transfers the replicated data to β transfer destination terminal devices. A wireless data transfer method comprising: In a terminal device of a wireless network system that performs data transfer from a data transfer start terminal device that starts data transfer via one or more other terminal devices to a base station device while replicating data,
The number H of data transfers from the data transfer start terminal device to the base station device is estimated according to the distance d between the data transfer start terminal device and the base station device, and the number of data transfers from the data transfer start terminal device Means for estimating the total number of terminal devices existing in a ring-shaped range from H-1 to H + 1, and setting the total number L of replicated data by the total number;
A transfer source terminal device that sets the number β of transfer destination terminal devices according to the total number L of the replicated data and the number of times H of data transfer, and means for transferring the replicated data to β transfer destination terminal devices. A terminal device comprising the terminal device.

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