JP2005354646A - Radio communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of terminals for switching base stations as much as possible. <P>SOLUTION: The radio communication apparatus having a communication means for performing wireless data communication with base stations is provided with: a calculation means for calculating a base station switching probability; and a switching means for switching a base station of a communicating party for the communication means based on the base station switching probability. When a channel load of a base station under communicating exceeds a threshold and a channel load of a base station switched to communicate may not exceed the threshold, the switching means switches the base station of the communicating party for the communication means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication apparatus including a communication unit that wirelessly performs data communication with a base station.

  When multiple wireless LAN base stations are installed in the same area and traffic concentrates on a specific base station during emergency communications, some terminals switch connections to base stations with low traffic This can eliminate concentration. Here, in detecting traffic concentration and switching timing control, it is desirable that the control can be performed by distributed control between terminals as much as possible in order to reduce the load on the fixed network.

  As an existing method for realizing this, the connection is switched to a base station in which a terminal connected to the base station is more vacant. Here, the switching probability is the same for all terminals.

  However, in general, various communication connections such as voice, video, data communication, and control communication are mixed as a communication connection handled by a terminal connected to a base station, and the data rate varies depending on the type of traffic. For example, several tens of kbps for voice communication, several tens of kbps to several Mbps for video communication, and several hundred kbps to several tens of Mbps for data communication are common.

  In the prior art, when traffic concentration occurs, each communication connection is switched with the same probability regardless of the data rate. Therefore, many communication connections with a low data rate such as voice may switch. it is conceivable that. However, switching the connection causes a temporary deterioration in communication quality on the terminal side, so the number of terminals to be switched needs to be kept as small as possible.

In addition, there exist the following as what is considered to be related to this invention (refer patent document 1, 2, 3).
JP 2000-295650 A JP 2000-165946 A JP 2003-60657 A

  An object of the present invention is to provide a technique for suppressing the number of terminals for switching base stations as much as possible.

  The present invention has been made in order to solve the above problems, and is a wireless communication apparatus including a communication unit that wirelessly performs data communication with a base station, and a calculation unit that calculates a base station switching probability; Switching means for switching a communication partner base station of the communication means based on the base station switching probability.

  According to the present invention, the base station switching probability is calculated (for example, according to the formula 1 of the embodiment), and the communication partner base station is switched based on the base station switching probability. Therefore, for example, the number of terminals to be switched is minimized as much as possible by calculating the base station switching probability according to the formula including the data rate Ri of the communication connection handled by itself as in the formula 1 shown in the embodiment. It becomes possible.

  In the above wireless communication device, for example, the channel load of the base station with which it is communicating exceeds the threshold, and the channel load of the base station with which it is switching to exceed the threshold If not, the switching unit switches the communication partner base station of the communication unit.

  In this way, only when the channel load of the base station with which the self is communicating exceeds the threshold and the channel load of the base station to which the self is trying to communicate does not exceed the threshold, It is possible to switch. That is, useless switching can be prevented.

  In the wireless communication apparatus, for example, when the base station switching probability exceeds a random value, the switching unit switches a communication partner base station of the communication unit. This is an example of the switching condition. Therefore, you may make it switch on other conditions.

  The present invention can be specified as a vehicle equipped with the wireless communication device.

  The present invention can be specified as the invention of the communication method as follows.

  A communication method in a wireless communication apparatus comprising a communication means for wirelessly communicating data with a base station, the step of calculating a base station switching probability, and a communication partner of the communication means based on the base station switching probability And a step of switching base stations.

  Further, the present invention can be specified as the invention of a program as follows.

  A wireless communication device comprising a communication means for wirelessly communicating data with a base station, a calculation means for calculating a base station switching probability, and a switching for switching a communication partner base station of the communication means based on the base station switching probability A computer-readable program for functioning as a means.

  According to the present invention, since the base station switching probability is calculated and the communication partner base station is switched based on the base station switching probability, for example, an appropriate formula for calculating the base station switching probability (for example, the embodiment) By using Equation 1), it is possible to keep the number of terminals to be switched as small as possible.

(System overview)
A wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an outline of a wireless communication system according to an embodiment of the present invention. This is based on the assumption that base stations for wireless LAN hotspots (registered trademark) A and B operated by different operators are installed in the same area (hereinafter, the wireless LAN hotspot is simply abbreviated as hot). Called a spot). Note that the wireless LAN hotspot refers to a space in which a wireless LAN access point is installed and a wireless Internet connection service is provided to an unspecified number of users.

  The number of frequency channels used by one base station is one channel for both uplink and downlink, and the two base stations in FIG. 1 use different frequency channels.

On the other hand, each vehicle shown in FIG. 1 includes a terminal 1 to a wireless LAN transceiver 10, 20.
5 (see FIG. 2) is mounted. In addition, although FIG. 1 illustrates the terminals 1 to 5, this is for convenience of explanation, and the number of terminals is not limited to these.

  The terminals 1 to 5 are mobile terminals (hereinafter simply referred to as terminals) such as in-vehicle computers and so-called car navigation systems, and control devices such as a CPU that controls the overall operation of the terminals, and a memory (whichever is connected) via a bus or the like. 2) and two wireless LAN transceivers 10, 20 and the like. Each of the wireless LAN transceivers 10 and 20 may be detachably attached to the terminal in the form of a card, may be incorporated in the terminals 1 to 5, or may be connected to the terminals 1 to 5 in other forms. May be.

  In general, there are two operation modes of a wireless LAN transceiver: an infrastructure mode (hereinafter abbreviated as an infrastructure mode) connected to a base station, and an ad hoc mode connected to another terminal without going through the base station. One wireless LAN transceiver 10 is set to the infrastructure mode. When it is desired to establish a communication connection with a server or other terminal placed on a fixed network, the terminal connects to one of the hot stations A and B. The other wireless LAN transceiver 20 is set to the ad hoc mode and is connected to surrounding terminals.

  The wireless LAN transceiver 20 set to the ad hoc mode can perform multi-hop communication. The network realized by this is called an ad hoc network here. A broken-line circle in FIG. 1 indicates a communication range of the wireless LAN transceiver 20 of each terminal in the ad hoc network. The ad hoc network is used as a means for exchanging information regarding traffic of base stations between terminals.

In the system of this embodiment, the inventive scheme operates only at the terminal, and the base station is not involved in the operation. For simplicity of explanation, it is assumed that all terminals are stationary. (Definition of terms)
Terms relating to the system example shown in FIG. 1 and terms relating to operating parameters are defined below.
(Definition of terms related to system examples)
The maximum throughput (unit: bps) of the base station refers to the maximum value of the number of bits of packets that can be transmitted / received per unit time by the base station. Hereinafter, it is expressed as Thmax. For example, in IEEE802.11b, when the packet size is 1500 bytes, the maximum throughput is about 5 Mbps.

  The data rate (unit: bps) of a communication connection refers to the number of bits of a packet that a terminal transmits / receives per unit time in one communication connection. In order to simplify the explanation, in this embodiment, it is assumed that the data rate of the communication connection is constant from the start to the end of communication. In the following, the sum of the data rates of communication connections set by the terminal I (= 1... 5) in FIG.

The channel load (no unit) of the base station is a value obtained by dividing the sum of the data rates of all communication connections currently handled by the base station by the maximum throughput of the base station. In the following, the channel loads of the base stations of hot spots A and B shown in FIG. 1 are represented by ρA and ρB, respectively.
(Definition of terms related to operating parameters)
The high load state threshold (no unit) refers to a value set in advance to determine whether or not the base station is in a high load state that saves a lot of traffic based on the channel utilization rate of the base station. When the channel load of a base station exceeds this value, the base station is determined to be highly loaded, and each terminal starts a base station switching operation, as will be described later. Hereinafter, the high load state threshold value is represented by ρth.

Next, the operation of the radio communication system having the above configuration will be described with reference to the drawings. FIG. 3 is a flowchart for explaining the operation in the wireless communication system of the present embodiment. The parameters shown in FIG. 1 are used as parameters and numerical examples in the flowchart.
(1) Each terminal 1 to 5 measures the channel loads (also referred to as channel utilization rates) ρA and ρB of the base station A or B to which it is connected for every period T (S100). Specifically, each of the terminals 1 to 5 is set so that the wireless LAN transceiver 20 of its own infrastructure mode can receive packets that are not addressed to itself (for example, set to an eavesdropping mode), and the base station to which it is connected Measure the data rate of the communication connection handled by. Then, for each predetermined time interval T (for example, 5 seconds), the channel load averaged over the time T is measured. In addition, the timing of the time for measuring is different for each of the terminals 1 to 5.

For example, in FIG. 1, since each of the terminals 1 to 4 is connected to the base station A, the sum of the data rates of all communication connections currently handled by the base station A is divided by the maximum throughput of the base station A. Is obtained as the channel load ρA. In FIG. 1, since the terminal 5 is connected to the base station B, a value obtained by dividing the sum of the data rates of all communication connections currently handled by the base station B by the maximum throughput of the base station B is obtained. Obtained as channel load ρB
(2) Immediately after S100, each of the terminals 1 to 5 notifies other terminals of the measured channel load value of the base station using an ad hoc network (also referred to as an advertisement) (S101). This is performed by the wireless LAN transceiver 20 set to the ad hoc mode. For example, it is conceivable to broadcast a packet including a measured base station channel load ρA (or ρB), a base station identifier, and a measurement time with a predetermined number of hops set.

Similarly, each of the terminals 1 to 5 receives the channel load value ρB or ρA of the base station transmitted from the other terminals 1 to 5. Thereby, each terminal 1-5 knows the value of the channel load of the base station to which the terminal itself is not connected.
(3) Next, each of the terminals 1 to 5 is preset with the channel load ρA (or ρB) of the base station to which the terminal is connected and the channel load ρB (or ρA) of the other base station. The high load state threshold value ρth is compared (S102). If it is determined that one of the base stations is in a high load state, the process proceeds to S103, and if not, the process returns to S100.

For example, if a numerical example of the channel load ρA or ρB of the base station is as shown in FIG. 1 and the value of the high load state threshold ρth is 0.6, each of the terminals 1 to 5 It is determined that the base station of the spot A is in a high load state, and the terminals 1 to 4 connected to the base station A proceed to S103.
(4) The terminals 1 to 4 that have determined that the base station of the hot spot A to be connected is in a high load state will not cause the base station B to be in a high load state when the terminal switches the connection to the base station B. It is checked whether or not (S103). Therefore, it is checked whether or not (ρB + (Ri / Tmax) <ρth) holds for the total data rate Ri of each terminal i (i = 1, 2, 3, 4). If not, the process returns to S100. For example, in the example of FIG. 1, since the above equations are satisfied for all of the terminals 1 to 4, all of them proceed to S <b> 104. In addition, (rho) B used here is what each terminal 1-4 received from the terminal 5 by S101.
(5) Next, each of the terminals 1 to 4 calculates the base station switching probability Pswitch of its own terminal using the following equation 1.

Ri represents the data rate of the communication connection handled by the terminal i. Rk represents the data rate of the communication connection satisfying S102 and S103 among the communication connections handled by all the terminals connected to the base station A including the terminal i. The values of Ri and Rk can be acquired by the operation of S100.
(6) Then, a random number is generated in the interval [0, 1], the random number is compared with Pswitch (S105), and if the random number is smaller than Pswitch, the process proceeds to S106 (S105: Yes), and the base station to be connected (S106). Otherwise, the process returns to S100 (S105: No).

  Table 1 shows the base station switching probabilities of the terminals 1 to 4 determined by these operations.

  In the conventional method in which terminals are switched with the same probability, for example, when terminals 3 and 4 perform switching, the high load state of base station A cannot be resolved unless two or more terminals perform switching. On the other hand, in this embodiment, as shown in the table above, there is a high possibility that one of the terminals 1 and 2 performs switching. In this case, if one of the terminals 1 and 2 is switched, the base station A is not in a high load state, so the remaining terminals do not need to be switched, and the number of terminals to be switched can be reduced. Become.

  As described above, according to the system of the present embodiment, a plurality of radio base stations A and B are installed in the same area, and a plurality of terminals 1 to 4 and 5 are connected to these radio base stations. If the traffic volume of a specific base station is higher than a predetermined threshold value, a terminal connected to that base station will connect to another base station with a low traffic volume with a certain probability. By switching between, the traffic volume between base stations is equalized.

  In the existing scheme, all terminals perform switching with the same probability, while in the inventive scheme, terminals handling a communication connection with a large data rate perform base station switching with a higher probability. The total number of terminals that perform base station switching is reduced.

  In general, the operation of switching the connection base station causes a temporary deterioration in communication quality on the terminal side, but this method is effective in that the number of occurrences can be reduced.

  That is, it is possible to reduce the number of terminals to be switched by switching a connection base station with a higher probability that a terminal handling a communication connection with a large data rate has a higher probability than a terminal handling a small communication connection.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, said embodiment is only a mere illustration in all points. The present invention is not construed as being limited by these descriptions.

  According to the present invention, since the base station switching probability is calculated and the communication partner base station is switched based on the base station switching probability, for example, an appropriate formula for calculating the base station switching probability (for example, the embodiment) By using Equation 1), it is possible to keep the number of terminals to be switched as small as possible.

It is a figure for demonstrating schematic structure of the radio | wireless communications system which is one Embodiment of this invention. It is a figure for demonstrating schematic structure of a terminal. It is a flowchart for demonstrating operation | movement of the radio | wireless communications system which is one Embodiment of this invention.

Explanation of symbols

10 Wireless LAN transceiver 20 Wireless LAN transceiver

Claims (6)

A wireless communication device comprising a communication means for wirelessly communicating data with a base station,
A calculating means for calculating a base station switching probability;
Based on the base station switching probability, switching means for switching the communication partner base station of the communication means,
A wireless communication device comprising:   When the channel load of the base station with which the base station is communicating exceeds a threshold, and the channel load of the base station to which the self is trying to communicate does not exceed the threshold, the switching means includes the communication The wireless communication apparatus according to claim 1, wherein the communication partner base station of the means is switched.   The radio communication apparatus according to claim 1 or 2, wherein when the base station switching probability exceeds a random value, the switching unit switches a communication partner base station of the communication unit.     A vehicle equipped with the wireless communication device according to claim 1. A communication method in a wireless communication device comprising a communication means for wireless data communication with a base station,
Calculating a base station switching probability;
Based on the base station switching probability, switching the communication partner base station of the communication means,
A wireless communication method comprising: A wireless communication device comprising a communication means for wireless data communication with a base station,
A calculation means for calculating a base station switching probability;
Based on the base station switching probability, switching means for switching a communication partner base station of the communication means,
A computer readable program to function as a computer.

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