JP2005065182A - Radio terminal control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio terminal control method which can ease electric wave interference by electric wave from a radio terminal in an area where two or more radio LANs which use a spectrum direct spreading method, are arranged. <P>SOLUTION: Base stations (11-19) of each radio LAN control radio terminals connected to the own station, in an area (10) where two or more radio LANs which use a direct spread spectrum method are arranged. The base station of each radio LAN acquires a communication channel of other station and a receiving level of the own station for the other station, inspects existence of other station with communication area which overlaps communication area (11A-19A) of the own station based on the acquired receiving level, and notifies about electric wave interference to each other station. Each base station which receives the notification directs reduction of transmission power to two or more radio terminals connected with the own station. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of controlling a wireless terminal connected to a base station in a wireless LAN, and more particularly, to a wireless terminal wireless terminal control method using a direct sequence spread spectrum (DSSS) as a physical layer communication system. About.

  Conventionally, a wireless LAN that performs wireless communication between a personal computer or a portable terminal having a wireless communication function and a base station installed in a company or a residence is known. In each network, for example, as shown in FIG. 9, wireless terminals 1 a and 1 b connected to the base station 1 communicate with each other at a power level equivalent to that of the base station 1 using a frequency of a communication channel assigned in advance. Further, regarding wireless LAN, there is a technique described in Patent Document 1 described later, for example. Here, in order to reduce the burden on each base station in a plurality of networks, a message communicated between base stations in adjacent networks is relayed to the receiving base station by the transmitting wireless terminal.

By the way, in recent years, wireless LANs conforming to IEEE802.11b, which employs a direct spectrum spread method, are widely used. IEEE802.11b prescribes wireless communication using a frequency in the 2.4 GHz band. According to the prescription, for example, in the case of Japan, first to fourteenth communication having a frequency band of about 22 MHz per channel. Channels are provided at center frequency intervals of about 5 MHz. In general, in an area where a plurality of wireless LANs are arranged, different communication channels are assigned for each network in order to prevent radio wave interference between each other. An interval of at least 4 channels is required between the networks.
JP-T-2001-513968

  However, as described above, even if an interval of 4 channels or more is provided between adjacent networks, the number of channels that can be allocated is limited, and therefore, in an area where many networks are crowded, the mutual channel interval is narrow. It is inevitable. Further, for example, as shown in FIG. 10, even if the base station 4 and the base station 5 are arranged so that the communication areas in which the radio waves of the base station can reach do not overlap, there is no sufficient interval between the communication channels of both. The terminals 4a and 5a connected to each of the terminals may affect the communication area of the other base station near the boundary of the communication area, causing data destruction and a decrease in communication speed.

  The present invention has been made in view of the above problems, and a wireless terminal control method capable of alleviating radio wave interference due to radio waves from a wireless terminal in an area where a plurality of wireless LANs using a direct spectrum spread method are arranged The purpose is to provide.

  The present invention relates to a method for controlling a wireless terminal connected to a base station of each wireless LAN in an area where a plurality of wireless LANs using a direct spectrum spread system are provided. Collecting the communication channel of the other station and the reception level of the own station with respect to the other station, and checking whether there is another station having a communication area overlapping with the communication area of the own station based on the collected reception level. When a plurality of other stations are detected by the above, each other station whose mutual communication channel interval is less than a predetermined value is detected from the other stations, and the other station is notified of the radio wave interference. Each base station that receives the notification instructs a plurality of wireless terminals connected to the base station to reduce transmission power.

  According to the wireless terminal control method of the present invention, each wireless LAN base station notifies each other station that radio wave interference between other stations may occur in its own communication area, and receives this notification. Since the base station instructs the wireless terminal of its own station to control the power, even if it is not possible to provide a sufficient channel interval with the adjacent network, the influence of radio waves from the wireless terminal of the adjacent network can be reduced. Can be relaxed.

[Example]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram for explaining an embodiment of a wireless terminal control method according to the present invention. In the present embodiment, when constructing a wireless network covering the area 10, APs 11 to 19 serving as base stations of a plurality of wireless LANs are arranged as shown in FIG. The APs 11 to 19 are connected to each other via a wired LAN so that they can communicate with each other. In each wireless LAN having APs 11 to 19 as base stations, conventionally known IEEE802.11b using a direct spectrum spread system (DSSS) is applied as communication in the physical layer.

  The operation between the APs 11 to 19 provided in the area 10 will be described with reference to the flowchart of FIG. The APs 11 to 19 obtain the communication channels of other stations via the wired LAN after activation. Also, all channels are periodically scanned by radio, the reception level is detected from the beacon signal that can be received by the own station, and recorded together with the communication channel (step S1).

  FIG. 3A is an example of a list recorded in the AP 11, and FIG. 3B is an example of the AP 14. The value of “signal level” shown in the figure indicates that the greater the numerical value, the higher the radio wave intensity that can be received. In the list of FIG. 3A, it can be seen that the signal level of the AP 12 using the “fourth channel (4ch)” is “20”. In the next record related to AP13, the signal level is "0", which indicates that AP11 cannot receive the beacon signal from AP13. That is, as shown in FIG. 1, it is intended that the communication areas 11A and 13B do not overlap.

  Subsequently, each of APs 11 to 19 uses a list as shown in FIGS. 3A and 3B to check whether there are a plurality of other stations having overlapping communication areas in its own communication area. It is determined whether there are a plurality of signal levels other than “0” in the list (step S2). If there are not a plurality of such other stations, the process is terminated assuming that there is no radio wave interference between the other stations in the area (step S2: No). For example, in the list of FIG. There are a plurality of base stations whose signal levels are other than “0”, such as AP14 and AP15. Similarly, AP11, AP12, AP15, AP17, and AP18 are detected for AP14 from the list of FIG.

  The APs 11 to 19 confirm whether or not there is an interval of 4 channels or more between the respective communication channels for the detected plurality of other stations (step S3). This is to check the possibility of radio wave interference between other stations in the communication area of the own station. In this embodiment, interference is possible if the channel interval between other stations is 4 or more based on IEEE802.11b. It is considered that there is no sex (step S3: No). The determination threshold for the channel interval is not limited to the above “4”, and can be set as appropriate as long as the channel interval can avoid radio wave interference.

  When the channel interval is specifically verified, for example, with respect to AP11, in the list of FIG. 3A, for the AP12, AP14, and AP15 whose signal levels are other than “0”, AP12 and AP15, and the channel interval between AP14 and AP15. Are 3 channels each. Therefore, it is determined that there is a possibility of radio wave interference between these areas. In addition, regarding the AP 14 in FIG. 3B, other stations such as the AP 11 and the AP 12 whose channel interval is less than “4” are detected, and it is determined that radio wave interference can occur in each of them. When the determination of the channel interval is completed, the APs 11 to 19 notify the other stations with the possibility of radio wave interference (step S4).

  Next, the operation of the base stations AP11 to 19-19 that have received notification regarding radio wave interference will be described with reference to the flowchart shown in FIG. Here, the AP 11 is taken as an example, and it is assumed that a plurality of wireless terminals CLs 101 to 124 are present in the communication area 11A as shown in FIG.

  First, when receiving a notification regarding radio wave interference from any other station, the AP 11 performs test communication for recognizing a wireless terminal connected to the own station. During this time, the CLs 101 to 124 existing in the communication area 11A confirm the reception level between the terminals, and record this as arrangement information of the own terminal. And after completion | finish of test communication, AP11 collects arrangement | positioning information from each of CL101-124, and forms a list as shown in FIG. 6 (step S11). In forming this list, the relative reception levels between the CLs 101 to 124 are tabulated for each terminal. In the illustrated example, the average value of the reception levels for other terminals is used as the total value. The higher the total value, the closer to the station.

  Subsequently, the AP 11 forms a list as shown in FIG. 7 for the degree of perspective from the own station to each of the CLs 101 to 124 based on the total values in the list of FIG. 6 (step S12). In the list shown in the figure, the signal level, which is the total value, is divided into three stages of “50” to “40”, “30” to “20”, and “10” to “0”. Arrangement levels of “near”, “middle”, and “far” indicating the degree of perspective from the station are assigned. In the example shown in FIG. 7, the arrangement level is divided into three stages, but the division method is not limited to this and can be set as appropriate.

  Furthermore, AP11 sets the communication route for each CL101-124 to communicate with an own station using the list | wrist of FIG. 7 (step S13). When setting a communication route, a wireless terminal with a placement level of “near” is set to communicate directly with its own station, and with respect to other terminals, the order of the placement level, that is, “far-middle” Search for a route in which the terminal relays a message to and from the AP 11 in the order of “close”. For example, when searching for the communication route of the CL 101 whose arrangement level is “far”, the route from the CL 101 to the AP 11 via the terminal having the arrangement level “intermediate” and the terminal “near” is obtained.

  The procedure for setting the communication route of the CL 101 will be described in detail. First, in order to search for a terminal that can directly communicate with the CL 101, a wireless terminal whose arrangement level is “intermediate” is extracted from the list of FIG. Here, CL102, CL104, CL106, etc. correspond. And a terminal with a high reception level in CL101 is selected from among them. In this selection, the reception level of the above-mentioned CL102, CL104, and CL106 is referenced from the record of CL101 using the list of FIG. 6, and the one with the highest value is selected. If multiple high values are detected, select them appropriately. Here, in the record of CL101 in FIG. 6, the reception levels of CL102 and CL106 are high, and CL102 is selected. At this stage, the route “CL101-CL102” is determined.

  Next, in order to determine a terminal that relays between CL 102 and AP 11, in the same manner as described above, the list of FIG. 7 has a “close” arrangement level, and the list of FIG. Select a terminal with a high reception level. Then, since CL107 corresponds, this CL107 is determined as the next relay terminal of CL102.

  As a result, a communication route “CL101-CL102-CL107-AP11” is determined. The AP 11 sets a communication route for all of the CLs 101 to 124 by the above procedure. FIG. 8 shows an example of a communication route for all terminals.

  When the communication route is set, the AP 11 obtains a minimum level of transmission power that allows communication between adjacent terminals on the communication route with respect to the CLs 101 to 124 (step S14). At that time, the calculation is performed using the reception level between terminals in the list of FIG. Then, the CL 101 to 124 are notified of the minimum level transmission power value to instruct power control, and the communication route is notified to notify the relay route after power reduction (step S15).

  When receiving the power control instruction, the CLs 101 to 124 perform power control and reduce the transmission power to the notified power level. Thereby, the influence of the radio wave from the wireless terminal can be mitigated with respect to the communication area 11A of the AP 11 and the other station area that may cause radio wave interference.

  Further, when the transmission power is reduced, it becomes difficult for a terminal having a disposition level of “far” or a terminal of “middle” to deliver radio waves to the AP 11. Therefore, these terminals use the communication route notified from the AP 11 to communicate with the AP 11 via other wireless terminals on the route. For example, when the CL 101 transmits a message to the AP 11, the CL 101 refers to the communication route and passes the message to the CL 102. Then, the CL 102 that has received the message transfers it to the CL 107, and the message is delivered to the AP 11 by this CL 107. Therefore, even if the range in which radio waves reach is narrowed by reducing transmission power, other terminals on the communication route relay the message, so that the message can be properly propagated to the destination.

  In the above embodiment, when an instruction to reduce the transmission power is given, an example in which a power value of the minimum level that can be communicated between adjacent terminals on the communication route is notified, but regarding the setting of this reduction level, In the present invention, other methods can be used instead of the above embodiment. For example, regarding transmission power reduction, a specific power value or a specific reduction rate is prepared in advance in the base station, and when receiving notification that radio wave interference between communication areas may occur, those values are set for each terminal. Notify Thereby, power control can be instructed quickly to each terminal.

It is explanatory drawing for demonstrating the Example of the radio | wireless terminal control method which concerns on this invention. It is a flowchart which shows the operation | movement procedure between the base stations of an Example. It is explanatory drawing for demonstrating the list | wrist which each base station of an Example produces regarding another station. It is a flowchart which shows the operation | movement procedure with respect to the radio | wireless terminal of each base station of an Example. It is explanatory drawing for demonstrating the example of arrangement | positioning of the radio | wireless terminal connected to the base station of an Example. It is explanatory drawing for demonstrating the relative reception level between the radio | wireless terminals of an Example. It is explanatory drawing for demonstrating the arrangement | positioning level of each radio | wireless terminal of an Example. It is explanatory drawing for demonstrating the example of a setting of the communication route with respect to the base station of an Example. It is explanatory drawing for demonstrating the communication area of the base station in the conventional wireless LAN. It is explanatory drawing for demonstrating the radio wave interference between the conventional wireless LANs.

Explanation of symbols

10 area 11-19 base station (AP)
11A-19A Communication area 101-124 Wireless terminal (CL)

Claims (6)

A method of controlling a wireless terminal connected to a base station of each wireless LAN in an area provided with a plurality of wireless LANs using a direct spectrum spread method,
The base station of each wireless LAN collects the communication channel of the other station and the reception level of the own station with respect to the other station, and the other station having a communication area overlapping with the communication area of the own station based on the collected reception level. When there is a plurality of other stations detected by the inspection, each other station whose mutual communication channel interval is less than a predetermined value is detected from the other stations, and notification of radio wave interference to each other station And
The base station control method, wherein each base station that has received the notification regarding the radio wave interference instructs a plurality of base stations connected to the base station to reduce transmission power.   Each base station that has received the notification regarding the radio wave interference collects a relative reception level between the wireless terminals from each wireless terminal connected to the own station, and arranges each wireless terminal with respect to the own station based on the collected reception level. The information is aggregated, a communication route between the own station and each wireless terminal is set using the result of the aggregation, and each wireless terminal is instructed to communicate with the own station along the communication route. Item 2. The wireless terminal control method according to Item 1.   When each base station instructs each wireless terminal to reduce transmission power, each base station obtains a minimum level of transmission power that can be communicated between adjacent wireless terminals in the communication route, and determines the transmission 3. The wireless terminal control method according to claim 2, wherein a power level is notified to the wireless terminal.   The base station, when each base station instructs each wireless terminal to reduce transmission power, the base station notifies each wireless terminal of a preset level of specific transmission power. Wireless terminal control method.   3. The radio terminal according to claim 2, wherein when each of the base stations aggregates the arrangement information, the reception level for each radio terminal is divided in stages, and a predetermined arrangement level is assigned to each divided stage. Control method. 6. The base station according to claim 5, wherein when each of the base stations sets the communication route, the base station searches for a route relayed by another wireless terminal along the order of the arrangement level between the wireless terminal and the own station. Wireless terminal control method.

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