JP2011142602A - Wireless communication method and wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decide a packet distribution rate between multiplexed links while considering delay characteristics by link in link multiplexing of a plurality of wireless systems and to selectively use link switching or link multiplexing so as to satisfy target quality. <P>SOLUTION: A wireless communication method includes at least steps of: (S101) measuring throughput and a delay time of each wireless system and calculating a delay time difference between links; (S102) determining presence/absence of a wireless system which satisfies target quality independently on the basis of the measurement result; and (S106) if there is no wireless link satisfying the target quality independently as a result of the determination, comparing the delay time difference between the links with a threshold value, if the delay time difference is less than or equal to the threshold value, selecting a link-multiplexing mode to perform link multiplexing of the links, and on the other hand, if the delay time difference exceeds the threshold value, selecing a link-switching mode to perform link switching. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication method and a wireless communication apparatus that dynamically use heterogeneous wireless systems.

  2. Description of the Related Art Conventionally, there are two types of utilization methods of multi-mode terminals that support different types of wireless systems: link switching that always selects an optimal wireless link and link multiplexing that multiplexes multiple wireless links. Conventionally, studies focusing on link switching have been performed on the assumption that there are abundant radio resources. However, it is difficult to ensure a desired quality with one link when radio resources are tight, such as during congestion. Therefore, link multiplexing that bundles the remaining radio resources of a plurality of radio systems and provides desired quality is required.

  In this regard, a technique for integrating different wireless systems such as a wireless LAN and a mobile phone has been proposed. For example, Patent Document 1 discloses a technology for integrating different types of radio systems having different cell sizes such as a pico cell, a micro cell, and a macro cell by using a cognitive base station and a cognitive terminal. The cognitive base station and the cognitive terminal include a switch, a plurality of wireless modules, and a wireless environment recognition unit. The wireless environment recognition unit recognizes the wireless environment, and based on the recognition result, the link frame is transmitted to the switch. Specify the wireless module that is the distribution destination. The link frame is transmitted / received via the designated wireless module.

  Patent Document 2 proposes a method for notifying an index related to communication quality in accordance with fluctuations in the radio wave environment. Specifically, it is a technique that is closed to one radio system, measures a received CIR (Carrier to Interference Ratio), calculates a future predicted value, and outputs it. Also, Non-Patent Document 1 discloses a technique for defining the packet transmission rate for the multiplexed link by defining the transmission time for each packet as Air time cost for WiMAX and Wi-Fi.

JP 2008-085759 A JP 2004-253830 A

IEICE TRANS.COMMUN., VOL.E91-B.NO.10 OCTOBER 2008 `` Adaptive Multimedia Flow Splitting over WIMAX and Wi-Fi Links ''

  However, in link multiplexing, when there is a characteristic difference between links, problems such as the arrival order of packets going back and forth occur. This causes adverse effects such as occurrence of packet retransmission and resource consumption accompanying the retransmission. In order to avoid these problems, it is necessary to appropriately distribute packets according to the quality of the link. Moreover, it is preferable to execute link multiplexing after estimating the quality of the multiplexed link from the background of multiplexing limited radio resources.

  On the other hand, studies are being made on link multiplexing that provides desired quality by bundling the remaining radio resources of a plurality of radio systems. Patent Document 1 shows a mechanism for performing radio link multiplexing, but does not show a specific method. Non-Patent Document 1 calculates the rate of packet distribution to a plurality of radio links, but does not consider selection of links to be multiplexed, link quality fluctuations, and target quality settings. Patent Document 2 does not use an index from an application such as a delay time, and does not stand from the viewpoint of heterogeneous radio link control.

  The present invention has been made in view of such circumstances, and in link multiplexing of a plurality of radio systems, it is possible to determine a packet distribution rate between links to be multiplexed in consideration of delay characteristics for each link, and to achieve target quality. It is an object of the present invention to provide a wireless communication method and a wireless communication apparatus that can properly use link switching or link multiplexing so as to satisfy the above.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, the wireless communication method of the present invention is a wireless communication method for performing wireless communication by selecting at least one wireless link from a plurality of different wireless systems, and measuring the throughput and delay time of each wireless system. A step of calculating a delay time difference between the links, a step of determining whether there is a wireless system that satisfies the target quality independently based on a result of the measurement, and a result of the determination, If there is no wireless link that satisfies the above, a step of comparing a delay time difference between the links and a threshold value, and if the result of the comparison indicates that the delay time difference is less than or equal to the threshold value, link multiplexing of the links is performed. If the delay time difference exceeds the threshold value, the link switching mode for performing link switching is selected. A method, characterized by comprising the steps of: transmitting a signal in one mode of the selected link multimode or link switching mode, at least.

  As described above, when the delay time difference is equal to or smaller than the threshold, the link multiplexing mode for performing link multiplexing of each link is selected. On the other hand, when the delay time difference exceeds the threshold, the link switching mode for performing link switching is selected. Because signals are transmitted in either the selected link multiplexing mode or link switching mode, one or more radio systems are selected to meet the target quality, and link switching and link multiplexing are used properly It becomes possible. Further, when the delay time difference is equal to or smaller than the threshold value, the link multiplexing mode for performing link multiplexing of each link is selected, so that it is possible to secure the bandwidth and prevent the packet arrival order from being reversed.

  (2) Further, the wireless communication method of the present invention is characterized in that the link switching mode is selected when there is a wireless system that satisfies the target quality independently as a result of the determination.

  As described above, when there is a wireless system that satisfies the target quality alone as a result of the determination, the link switching mode is selected, so that link switching and link multiplexing can be used properly.

  (3) Further, the wireless communication method of the present invention uses a table showing characteristics between link delay time, CIR (Carrier to Interference Ratio), packet size, and simultaneous radio resource allocation ratio, and delays between the links. The time difference is calculated.

  With this configuration, it is possible to selectively use link switching and link multiplexing after selecting one or a plurality of wireless systems so as to satisfy the target quality.

  (4) Further, the wireless communication method of the present invention is characterized in that the contents of the table are updated in accordance with fluctuations in the CIR and the packet size.

  With this configuration, it is possible to perform processing in consideration of fluctuations with respect to CIR and packet size that fluctuate on a short time scale.

  (5) In the wireless communication method of the present invention, when the link multiplexing mode is selected, packets are distributed in consideration of the throughput and delay time of each link to be multiplexed.

  As described above, since the packets are distributed, it is possible to avoid a situation where an excessive packet is transmitted from any link and the arrival order of the packets is reversed. As a result, throughput can be improved.

  (6) The wireless communication method of the present invention is characterized in that an index is calculated using the throughput and delay time of each link, and packets are distributed based on the index.

In this way, an index determined by the throughput and delay time of each link is calculated, and packets are distributed based on the index. Therefore, excessive packets are transmitted from any link, and the arrival order of the packets is reversed. The situation can be avoided. As a result, throughput can be improved. This index may be calculated using, for example, the index BDP = Σ {(packet size Pi + overhead O _i ) × Delay _i } as the first index, and the index 2 = It may be calculated using Σ {(packet size P _i + overhead O _i ) ÷ Delay _i }. In the above equation, Σ {} is the sum of products of the packet size and delay time transmitted within the unit time.

  (7) The wireless communication device of the present invention is a wireless communication device that performs wireless communication by selecting at least one wireless system from a plurality of different wireless systems, and the throughput and delay time of each wireless system are determined. A wireless environment recognition unit that calculates a delay time difference between the links, and determines whether there is a wireless system that satisfies the target quality independently based on a result of the measurement, and a result of the determination, When there is no wireless system that satisfies the target quality alone, the delay time difference between the links is compared with a threshold, and if the result of the comparison is that the delay time difference is less than or equal to the threshold, the link of each link Transmission control for selecting a link switching mode for performing link switching when the link multiplexing mode for performing multiplexing is selected while the delay time difference exceeds the threshold value When, characterized in that it comprises a plurality of radio modules for transmitting signals on the basis of one mode of the selected link multimode or link switching mode.

  As described above, when the delay time difference is equal to or smaller than the threshold, the link multiplexing mode for performing link multiplexing of each link is selected. On the other hand, when the delay time difference exceeds the threshold, the link switching mode for performing link switching is selected. Because signals are transmitted in either the selected link multiplexing mode or link switching mode, one or more radio systems are selected to meet the target quality, and link switching and link multiplexing are used properly It becomes possible. Further, when the delay time difference is equal to or smaller than the threshold value, the link multiplexing mode for performing link multiplexing of each link is selected, so that it is possible to secure the bandwidth and prevent the packet arrival order from being reversed.

  According to the present invention, it is possible to selectively use link switching and link multiplexing after selecting one or a plurality of radio systems so as to satisfy the target quality. Furthermore, in link multiplexing, dynamic control is possible by using an index that takes into account quality fluctuations. Furthermore, since the packet distribution rate in consideration of the index is obtained and the packets are distributed to each link according to the packet distribution rate, order inversion can be suppressed, and link multiplexing that reduces retransmission can be performed.

It is a figure which shows the structure of the radio | wireless communications system of this invention. It is a block diagram which shows schematic structure of the base station apparatus 10 of this invention. It is a block diagram which shows schematic structure of the mobile station apparatus 100 of this invention. It is a figure which shows the relationship of the radio | wireless connection of the base station apparatus 10 (FIG. 2) and the mobile station apparatus 100 (FIG. 3) of this invention. It is a graph which shows the relationship between the packet size P and delay time Delay when CIR is changed in wireless systems, such as WiMAX and LTE. 6 is a graph showing a relationship between a packet size P and a delay time Delay when a radio resource allocation rate R is changed in a wireless system such as WiMAX and LTE. It is a graph showing the relationship between the radio resource allocation ratio R and the correction value f _{2 (R)} according to a first embodiment of the present invention. It is a graph which shows frequency distribution of the packet size P which concerns on the 2nd Embodiment of this invention. It is a graph which shows the cumulative frequency distribution of the packet size P which concerns on the 2nd Embodiment of this invention. It is a graph which shows the cumulative frequency distribution of CIR which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the procedure which uses properly link switching and link multiplexing in the 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. First, a system configuration that is a premise of the present invention will be described.

  FIG. 1 is a diagram showing a configuration of a wireless communication system of the present invention. As shown in FIG. 1, the network of the wireless communication system of the present invention includes a macro cell by a macro cell radio module 14a, a micro cell by a micro cell radio module 14b, a pico cell by a pico cell radio module 14c, a mobile station device 100, and a switch unit 13. (Hereinafter, the macro cell radio module 14a, the micro cell radio module 14b, and the pico cell radio module 14c are collectively referred to as a radio module 14). The macro cell is, for example, a cell of a cellular system that provides a mobile phone service. The microcell wireless module 14b forms a microcell that provides a communication area in a narrower range than the macrocell. The microcell is, for example, a cell conforming to “IEEE802.16” or “IEEE802.20”. The pico cell radio module 14c forms a pico cell that provides a communication area in a narrower range than the micro cell. The pico cell is, for example, a cell conforming to “IEEE802.11”. The micro cell and the pico cell are arranged in the macro cell.

  The macro cell radio module 14a, the micro cell radio module 14b, and the pico cell radio module 14c are installed at locations corresponding to the arrangement of each cell. Each wireless module 14a, 14b, 14c is connected to a separately provided switch unit 13 via a communication line. In FIG. 1, the other configurations (core network side interface 11, virtual MAC processing unit 12, wireless environment recognition unit 15) included in the base station device 10 are omitted. As shown in FIG. 1, the switch unit 13 accommodates only one macro cell. All the microcells and picocells included in the macro cell are accommodated in the same switch unit 13 as the macro cell. Thereby, one macro cell and all the micro cells and pico cells included in the macro cell are accommodated in the same switch unit 13 and processed in the same link layer.

  FIG. 2 is a block diagram showing a schematic configuration of the base station apparatus 10 of the present invention. As shown in FIG. 2, the base station apparatus 10 includes a core network side interface 11, a virtual MAC processing unit 12, a switch unit 13, a macro cell radio module 14a, a micro cell radio module 14b, a pico cell radio module 14c, and a radio environment recognition unit. 15 and sensor 16. The base station device 10 is connected to the core network of the wireless communication network via the core network side interface 11. Each base station apparatus 10 is mutually connected via a core network. Each base station apparatus 10 can be connected to a network outside a wireless communication network such as the Internet via a core network.

  In the present invention, the core network side interface 11 transmits and receives packets as network layer communication data to and from the core network. The virtual MAC processing unit 12 performs processing for establishing a link using a virtual MAC address. The virtual MAC address is a physical address and is uniquely assigned in advance to each of the base station apparatus 10 and the mobile station apparatus 100. The virtual MAC processing unit 12 of the base station device 10 establishes a link using the virtual MAC address with the virtual MAC processing unit of the mobile station device 100. The virtual MAC processing unit 12 generates a frame to be transmitted using this link. This frame is referred to as a “link frame” for convenience of explanation. A packet received from the core network is stored in the link frame. The virtual MAC processing unit 12 outputs the generated link frame to the switch unit 13. The virtual MAC processing unit 12 receives a link frame from the switch unit 13, extracts a packet from the link frame, and outputs the packet to the core network side interface 11.

  The switch unit 13 distributes the link frame input from the virtual MAC processing unit 12 to each wireless module 14, and outputs the link frame input from each wireless module 14 to the virtual MAC processing unit 12.

  The wireless module 14 has a unique MAC address. The MAC address unique to the wireless module 14 is referred to as a “real MAC address” for convenience of explanation in order to distinguish it from the virtual MAC address. The actual MAC address has been conventionally used. The wireless module 14 establishes a wireless link using a real MAC address with a wireless module of the same wireless communication method. A radio link is established on a frequency channel basis. The wireless module 14 generates a wireless frame to be transmitted using a wireless link. The radio frame stores the link frame received from the switch unit 13. The wireless module 14 extracts a link frame from the wireless frame received through the wireless link and outputs the link frame to the switch unit 13.

  The wireless environment recognition unit 15 recognizes the wireless environment and instructs the switch unit 13 on the distribution destination of the link frame input from the virtual MAC processing unit 12 based on the recognition result. The wireless environment recognition unit 15 acquires wireless information from each wireless module 14. Further, wireless information may be obtained from data observed with a sensor antenna (not shown). As radio information, for example, a value of RSSI (Received Signal Strength Indicator), background noise level, modulation method, amount of data waiting for transmission stored in the transmission buffer, and NACK signal indicating transmission failure are received from the other station. The number of times, the defect rate of radio frames received from the other station, and the like.

  The wireless environment recognition unit 15 determines the communication status of each wireless communication method based on the wireless information. For example, it is determined which wireless communication method is in a good communication state. Further, it is determined which frequency channel of which wireless communication system is in a good communication state. In addition, long-term statistical data and short-term statistical data are used to perform estimation processing for specifying a wireless communication system that may be able to obtain a good communication state in the future and the frequency channel. The wireless environment recognition unit 15 instructs the switch unit 13 on the distribution destination of the link frame input from the virtual MAC processing unit 12 based on the communication status of each wireless communication method. As a distribution destination of the link frame, one that is in a good communication state at present or a good communication state that will be obtained in the future, and instructing one or a plurality of wireless modules 14, Furthermore, one or a plurality of frequency channels in the wireless module 14 are indicated. Also, the distribution ratio may be determined based on the communication status of each wireless communication method and instructed to the switch unit 13.

  The switch unit 13 sequentially outputs the link frames received from the virtual MAC processing unit 12 to the distribution destination designated by the wireless environment recognition unit 15. When a distribution ratio is instructed from the wireless environment recognition unit 15, the link frame is distributed and output to each distribution destination according to the distribution ratio. In addition, although the base station apparatus 10 has the virtual MAC process part 12, it is not necessarily limited to this. As described above, the base station apparatus 10 controls the switch unit 13 so as to select an optimal wireless module based on information such as communication quality acquired by the wireless environment recognition unit 15.

  FIG. 3 is a block diagram showing a schematic configuration of the mobile station apparatus 100 of the present invention. As shown in FIG. 3, the mobile station device 100 includes a user network side interface 101, a virtual MAC processing unit 102, a switch unit 103, a macro cell radio module 104a, a micro cell radio module 104b, a pico cell radio module 104c, a radio environment It comprises a recognition unit 105 and a sensor 106. In FIG. 3, the mobile station apparatus 100 also has a configuration substantially similar to that of the base station apparatus 10 of FIG. In mobile station apparatus 100, the user-side interface performs network layer processing. In addition, although the mobile station apparatus 100 has the virtual MAC processing part 102, it is not necessarily limited to this. The mobile station device 100 controls the switch unit 103 so as to select an optimal wireless module based on information such as communication quality acquired by the wireless environment recognition unit 105.

  FIG. 4 is a diagram illustrating a wireless connection relationship between the base station apparatus 10 (FIG. 2) and the mobile station apparatus 100 (FIG. 3) according to the present invention. Between the base station apparatus 10 and the mobile station apparatus 100, connections are made between the same type of wireless modules. Note that the base station device 10 and the mobile station device 100 constitute a radio communication device, and the virtual MAC processing units 12 and 102 and the switch units 13 and 103 constitute a transmission control unit. Next, the contents of the radio link multiplexing system of the present invention will be described.

(First embodiment)
In the first embodiment, the base station apparatus 10 defines delay characteristics for each link as a function of several parameters, and holds them as an approximate expression or a table. By using the delay characteristic for each link, the index described in the third embodiment can be obtained.

<Delay time calculation method for each link>
FIG. 5A is a graph showing the relationship between the packet size P and the delay time Delay when the CIR is changed in a wireless system such as WiMAX or LTE. The horizontal axis represents the packet size P, and the vertical axis represents the delay time Delay. When the radio resource allocation rate R is a constant value, the larger the packet size P and the lower the CIR value, the longer the delay time. This is because, in the case of a low CIR, the transmission speed of the link is lowered and time is required for packet transmission. When the packet size P is small, the delay time shows a constant value regardless of the CIR value. This is because, up to a certain packet size P, transmission is possible with a certain delay time even if the transmission rate is low.

  FIG. 5B is a graph showing the relationship between the packet size P and the delay time Delay when the radio resource allocation rate R is changed in a wireless system such as WiMAX or LTE. The horizontal axis represents the packet size P, and the vertical axis represents the delay time Delay. When CIR is a constant value, the longer the packet size P and the higher the radio resource allocation rate R, the longer the delay time Delay is. This is because when the radio resource allocation rate R is high, the opportunity for transmission decreases and the effective throughput decreases. Similarly to FIG. 5A, the delay time shows a constant value up to a certain packet size P regardless of the radio resource allocation rate R.

The base station apparatus 10 actually measures the delay time shown in FIGS. 5A and 5B and holds this as a table. The base station apparatus 10 can obtain the delay time Delay by setting the packet size P, CIR, and the radio resource allocation rate R and referring to the stored table. Further, the delay time shown in FIGS. 5A and 5B can be obtained by an equation.
(Delay) = packet size P [bit] ÷ {f ₁ (CIR, P) [bit] ÷ T _PDU [time] × f ₂ (R)}… (1)

In a wireless system, a packet may be divided into PDUs (Protocol Data Units) for transmission, and the PDU size varies depending on the situation. f ₁ (CIR, P) indicates a PDU size [bit] when a packet with a packet size of P is transmitted when the carrier-to-interference power ratio is CIR. The base station apparatus 10 may hold f ₁ (CIR, P) as a table. T _PDU [time] indicates the time required to transmit one PDU.

In Expression (1), f ₂ (R) indicates a correction value. When the radio resource allocation rate R increases, that is, when the remaining resources decrease, the transmission opportunities decrease. This means that even if the transmission rate (instantaneous rate) of the link is high, the effective transmission rate cannot be ensured because the transmission opportunities decrease. Therefore, this correction is performed with f ₂ (R). f ₂ (R) represents a ratio, and 0 ≦ f ₂ (R) ≦ 1 is a range (no unit).

FIG. 5C is a graph showing the relationship between the radio resource allocation rate R and f ₂ (R) according to the first embodiment of the present invention. In FIG. 5C, the horizontal axis represents the radio resource allocation rate R, and the vertical axis represents f ₂ (R). When the radio resource allocation rate R is low, the radio resource has room, so the throughput of the mobile station device 100 does not decrease, and f ₂ (R) takes a value close to 1. As R increases, the throughput of mobile station apparatus 100 decreases, so f ₂ (R) decreases. In particular, when R is 100%, since there is no surplus radio resource, f ₂ (R) is 0 (in this case, Delay = ∞, and the radio system is considered to be incapable of communication, and is subject to this control. Excluded). The base station apparatus 10 may hold the characteristics of f ₂ (R) illustrated in FIG. 5C as a table.

  As shown in FIG. 5A, when the packet size P is equal to or smaller than a certain value, Delay is a constant value regardless of the CIR value. Therefore, if this is the case, a fixed value may be referred directly. By the processing shown in the first embodiment, it is possible to obtain a delay time Delay in units of packets. By using this delay time Delay, it is possible to grasp the delay time in units of packets.

(Second Embodiment)
The packet sizes P and CIR vary on a short time scale. In the second embodiment, an additional process when the packet sizes P and CIR, which are parameters for each link, when the delay characteristics for each link in the first embodiment are grasped will be described.

<Selection of packet size P>
The packet size P differs depending on the application and is set for each application. Therefore, if the application changes, the packet size P will change. It is also common for multiple applications to be used simultaneously. Even in such a case, the packet size P naturally varies. When the packet size P varies as described above, the P distribution of the packet size for each application is reflected in the delay time. Specifically, any of the following methods (P-1), (P-2), and (P-3) is adopted.

  Method (P-1): The longest packet size P is obtained from the P distribution of the packet size for each application, and the longest packet size P is set as the representative value (worst value) as the packet size P of the first embodiment.

  Method (P-2): First, the distribution of the packet size P is obtained by estimation (or actual measurement) from the application type.

  FIG. 6 is a graph showing a frequency distribution of the packet size P according to the second embodiment of the present invention. The horizontal axis represents the packet size P, and the vertical axis represents the frequency. From this frequency distribution, i packet sizes P at which the frequency reaches a peak are selected from the top and set to the packet size P of the first embodiment. For the same application, a delay time is obtained for each packet size. In FIG. 6, since there are two frequency peaks (i = 1, 2), two delay times are obtained.

  Method (P-3): First, as in method (P-2), the distribution of the packet size P is obtained by estimation (or actual measurement) from the application type.

  FIG. 7 is a graph showing the cumulative frequency distribution of the packet size P according to the second embodiment of the present invention. The horizontal axis represents the packet size P, and the vertical axis represents the cumulative degree. From this cumulative frequency distribution, an X% value (for example, X = 50), that is, a packet size P when the cumulative level reaches X% is obtained and set as the packet size P of the first embodiment.

<CIR selection>
CIR fluctuations are small in the stationary state of the mobile station device 100 and the line-of-sight state of the base station device 10, but are large in the moving state of the mobile station device 100 and the like. When the CIR fluctuates in this way, the CIR distribution is reflected in the delay time. Specifically, any one of the following methods (C-1), (C-2), and (C-3) is adopted.
Method (C-1): The instantaneous value of CIR is set to the CIR of the first embodiment.
Method (C-2): First, CIR distribution is observed.

FIG. 8 is a graph showing a cumulative frequency distribution of CIR according to the second embodiment of the present invention. From this cumulative frequency distribution, the Y% value (for example, Y = 90), that is, the CIR when the cumulative level reaches Y% is obtained, and this is set as the CIR of the first embodiment. Or after calculating | requiring the delay time with respect to a CIR instantaneous value, the Y% value is calculated.
Method (C-3): CIR variation is observed, and method C-1 and method C-2 are switched and used in accordance with the CIR variation.

<Combination example of packet size P selection method and CIR selection method>
Since variations in the packet sizes P and CIR can occur simultaneously, a combination of scheme P- # and scheme C- # is considered. Examples of combinations are shown in (case-1) and (case-2) below.

  CASE-1 (method P-1 & C-1): The delay time is obtained according to the first embodiment using the longest packet size P and the CIR instantaneous value. This combination has a small amount of statistical processing, but has a disadvantage of excessively estimating the delay time for a small packet.

  CASE-2 (method P-3 & C-2): Link characteristics are obtained according to the first embodiment using the X% value of the packet size P and the Y% value of the CIR. As described above, in the second embodiment, when the parameter used for obtaining the delay time for each link shown in the first embodiment fluctuates, secondary statistical processing is performed on the parameter. Thereby, it is possible to acquire a delay time in consideration of parameter variation.

(Third embodiment)
The delay time Delay _i for each link is acquired according to the first embodiment and the second embodiment. In this embodiment, by using an index that considers the throughput and delay time of the multiplexed links, a situation where an excessive number of packets are transmitted from one link and order reversal occurs is avoided. As an index, a bandwidth delay product BDP obtained by multiplying the throughput and the delay time is obtained according to Equation 2. From Equation 2, the sum of the product of the packet size including the overhead and the delay time per unit time is obtained as an index. Σ {} in the equation is the sum of products of packet size and delay time transmitted within a unit time.
Index BDP = Σ {(packet size Pi + overhead O _i ) × Delay _i } (2)

Here, i indicates the number (index) of the packet transmitted in the radio link. As the packet size P, the value after the additional processing shown in <Selection of packet size P> in the second embodiment may be used as a representative, or one packet size P may be monitored and used. The overhead O _i is a different value for each wireless system and may be held in a table. Delay _i is a value obtained in the first embodiment.

As described above, in the present embodiment, the base station apparatus 10 distributes packets so that the result obtained by multiplying the index BDP of each link by the distribution ratio matches. For the sake of explanation, assuming that the conditions are simplified and the overhead O _i = 0 and the packet size P is constant, the distribution ratio can be obtained only by the ratio of Delay _i . Assuming that the inverse of Delay _i is an index F _i , when Delay ₁ = 50 ms and Delay ₂ = 20 ms, F ₁ = 20 and F ₁ = 50, and the distribution ratio is obtained as follows. As a result, the base station apparatus 10 distributes 28.5% of the arrival packets to the link 1 and 71.5% to the link 2.
Distribution ratio 1 = F1 ÷ (F1 + F2) = 20 ÷ (20 + 50) = 28.5% ・ ・ ・ (3)
Distribution ratio 2 = F2 ÷ (F1 + F2) = 50 ÷ (20 + 50) = 71.5% ・ ・ ・ (4)

  Thus, in the third embodiment, the base station apparatus 10 obtains the packet distribution rate using the index BDP when performing link multiplexing. Thereby, the base station apparatus 10 absorbs the difference in delay time for each link.

(Fourth embodiment)
Since link multiplexing may cause problems such as order reversal, it is preferable to restrict its use. Therefore, in the fourth embodiment, whether to perform link switching or link multiplexing is determined according to the difference between the target quality of the throughput and delay time and the situation. When link multiplexing is used, multiplexing is performed by selecting an appropriate link. Specifically, the target delay time is set as Delay _Target , the target throughput is set as Thr _Target , the target jitter is set as Jitter _Target , and referring to these, the delay time Delay _i and the radio system i are the link characteristics of the radio system i. expected effective throughput Thr _i, or the link switching based on the jitter jitter _i, performs one of determination to the links multiplexed. Incidentally, Thr _i is determined according to Equation (5). Jitter _i is obtained as the variance of Delay _i .
Thr _i = f _1i (CIR, P) [bit] × f _2i (R)… (5)
Jitter _i = f _3i (Delay _i )… (6)

  FIG. 9 is a flowchart showing a procedure for properly using link switching and link multiplexing in the fourth embodiment of the present invention. First, the base station apparatus 10 measures the throughput, delay time, and jitter for each radio link (step S101). Next, the base station apparatus 10 compares them with the target quality and searches for a radio link that can satisfy the target quality alone. Judgment conditions are shown below (step S102).

(I) When only Delay _Target is set: Search for presence of a system that satisfies Equation (7).
Delay _i <Delay _Target … (7)
(Ii) When only Thr _Target is set: Search for the existence of a system that satisfies Equation (8).
Thr _i > Thr _Target … (8)
(Iii) When only Jitter _Target is set: Search for the existence of a system that satisfies Equation (9).
Jitter _i <Jitter _Target … (9)

  (Iv) When the target quality is set as a combination of (i), (ii), and (iii), a link that satisfies the combination conditions of Expressions (7), (8), and (9) is searched.

  Subsequently, when there are one or more radio links that satisfy the target quality independently (step S102: YES), the base station apparatus 10 shifts to a mode for switching the link between them (step S103). The base station apparatus 10 operates according to the link switching method with a link satisfying any one of (i), (ii), (iii), and (iv) in step S102 as a switching destination candidate. When the target quality is the best effort and when the target quality is only the throughput, even if there is a radio link that satisfies the target quality alone, the mode may be shifted to the link multiplexing mode. This aims at the effect of reducing the division loss of radio resources by bundling and utilizing the remaining radio resources of radio links in a congested state. In this case, a radio link that satisfies the condition (ii) of step S102 and whose congestion degree exceeds the threshold is selected as a multiplex candidate.

If there is no radio link that can be satisfied independently (step S102: NO), it is determined whether or not the quality target is only Thr _Target (step S104). When the quality target is only Thr _Target (step S104: YES), the mode shifts to the link multiplexing mode (step S105). In this case, a candidate link to be link-multiplexed is searched for the presence of a link satisfying the expression (10), and is selected from among them.
(ΣThr _i ) × α> Thr _Target … (10)
α: Correction coefficient indicating link multiplexing efficiency

If the quality target is not only Thr _Target (step S104: NO), multiple links satisfying the corresponding conditional expression from among the expressions (7), (8), and (9) are multiplexed with respect to the set quality target. Target candidate. In particular, as an option, when there are two or more candidate links, it is determined whether there is a pair of candidate links that satisfy Expression (11) (step S106).
min {abs (Delay _i -Delay _j )} ≦ Delay_diff _Target … (11)

  When there is a pair of wireless links satisfying the expression (11) (step S106: YES), the wireless link pairs are narrowed down to link multiplexing targets (step S105). This is to reduce the occurrence of sequence inversion by preferentially link-multiplexing a pair of links with a small delay time difference. If there is no link pair corresponding to the equation (11) (step S106: NO), the link multiplexing is stopped and the process proceeds to link switching (step S103). The base station apparatus 10 repeatedly executes the processing of steps S101 to S106, and adaptively uses link switching and link multiplexing appropriately.

  Thus, in the fourth embodiment, the base station apparatus 10 dynamically uses link switching and link multiplexing dynamically according to the target quality. This makes it possible to switch to a radio link that satisfies the target quality without using link multiplexing that causes packet order reversal. In addition, when link multiplexing is performed, one or a plurality of radio links that can satisfy the target quality are selected as candidates. Thereby, link multiplexing satisfying the target quality becomes possible.

(Fifth embodiment)
Next, a fifth embodiment will be described. In the fifth embodiment, an index 2 defined as in equation (2 ′) is used instead of equation (2) in the third embodiment.
Index 2 = Σ {(packet size P _i + overhead O _i ) ÷ Delay _i } (2 ′)

Here, as in the third embodiment, i is the number (index) of the packet transmitted in the wireless link. The value of packet size P _i + overhead O _i may be represented by an average value, or an average Delay _i corresponding to the value may be used. When using the equation (2 ′), the base station apparatus 10 distributes the packet so as to be proportional to the index 2. For example,
If the expected throughput of wireless link 1 is 5Mbps and the delay time is 100msec,
Wireless link 1 index 2 = 50 (5 [Mbit / s] ÷ 0.1 [s])
If the expected throughput of wireless link 2 is 10Mbps and the delay time is 50msec,
Wireless link 2 index 2 = 200 (10 [Mbit / s] ÷ 0.05 [s])
The distribution ratio of the radio link 1 and the radio link 2 is set to (1 to 4) so as to be proportional to the value of the index 2. Incidentally, including the formula (2 '), instead of Delay _i, multiplied by a coefficient, which was n-th power, also derived, such as with a function that increases monotonically with Delay _i.

  In the first to fifth embodiments, the link multiplexing method and the link switching / multiplexing in the base station apparatus 10 are described. The mobile station device 100 can also perform the control by providing the first to fourth embodiments.

DESCRIPTION OF SYMBOLS 10 Base station apparatus 11 Core network side interface 12 Virtual MAC processing part 13 Switch part 14a Macro cell radio module 14b Micro cell radio module 14c Pico cell radio module 15 Radio environment recognition part 16 Sensor 100 Mobile station apparatus 101 User network side interface 102 Virtual MAC processing unit 103 switch unit 104a macro cell radio module 104b micro cell radio module 104c pico cell radio module 105 radio environment recognition unit 106 sensor

Claims (7)

A wireless communication method for performing wireless communication by selecting at least one wireless link from a plurality of different wireless systems,
Measuring throughput and delay time of each wireless system, and calculating a delay time difference between each link;
Determining whether there is a wireless system that alone satisfies the target quality based on the measurement results;
As a result of the determination, if there is no radio link that satisfies the target quality alone, a step of comparing a delay time difference between the links and a threshold;
As a result of the comparison, if the delay time difference is less than or equal to the threshold value, a link multiplexing mode for performing link multiplexing of the links is selected. On the other hand, if the delay time difference exceeds the threshold value, link switching is performed to perform link switching. Selecting a mode;
Transmitting a signal in one of the selected link multiplexing mode and link switching mode.   The radio communication method according to claim 1, wherein when there is a radio system that satisfies the target quality alone as a result of the determination, the link switching mode is selected.   The delay time difference between the links is calculated using a table indicating characteristics between a link delay time, a CIR (Carrier to Interference Ratio), a packet size, and a simultaneous radio resource allocation rate. The wireless communication method according to claim 2.   4. The wireless communication method according to claim 3, wherein the contents of the table are updated in accordance with changes in the CIR and the packet size.   5. The radio communication method according to claim 1, wherein when the link multiplexing mode is selected, packets are distributed in consideration of throughput and delay time of each link to be multiplexed.   5. The wireless communication method according to claim 1, wherein an index is calculated using a throughput and a delay time of each link, and packets are distributed based on the index. A wireless communication device that performs wireless communication by selecting at least one wireless link from a plurality of different wireless systems,
A wireless environment recognition unit that measures the throughput and delay time of each wireless system and calculates a delay time difference between each link;
Based on the result of the measurement, it is determined whether there is a wireless system that satisfies the target quality alone. If there is no wireless link that satisfies the target quality alone, the delay between the links is determined. When the time difference is compared with a threshold value, and the result of the comparison is that the delay time difference is less than or equal to the threshold value, the link multiplexing mode for performing link multiplexing of each link is selected, while the delay time difference exceeds the threshold value A transmission control unit for selecting a link switching mode for performing link switching;
And a plurality of wireless modules that transmit signals based on one of the selected link multiplexing mode and link switching mode.

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