JP2002076993A - Mobile-station equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain mobile-station equipment for radio LAN which can maintain the quality of transmitted data at a high level. SOLUTION: A wireless physics control section 8 has a function of performing frequency switching while maintaining synchronization with one frequency band even when communications are made in the frequency band. The state, etc., of a radio wave in each frequency band acquired by the frequency switching is stored on a table provided in a statistic information monitoring and controlling section 5. The optimum frequency band to communications in each frequency band can be known by analyzing the contents of the table. Synchronous connection is made by performing the frequency switching from the known optimum frequency band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile station device in a wireless LAN, and more particularly to a wireless LAN employing an FH-SS system (frequency hopping spread spectrum communication system).
In the mobile station device.

[0002]

2. Description of the Related Art FIG. 6 shows an FH-compliant device conforming to IEEE 802.11 (American Electrical and Electronic Engineers Association 802.11 Committee).
FIG. 2 is a block diagram showing a configuration of a conventional mobile station device in a wireless LAN adopting the SS system. In FIG. 6, a conventional mobile station device includes a data communication control unit 1 for transmitting and receiving data, and a frequency for performing synchronization acquisition and holding in each frequency band switched by frequency switching according to a hopping pattern. A synchronization control unit 2, a wireless physical control unit (MAC driver) 3 for performing the above-described frequency switching control and wireless control for data transmission and reception, and a beacon (synchronization) after being synchronously connected to a base station (access point) in one frequency band. A connection and roaming processing unit 4 for discriminating and managing which base station it is connected to based on information such as a connection partner and a connection frequency band included in data for capturing and maintaining synchronization, and a transfer speed of a beacon. .

FIG. 7 is a diagram for explaining the operation when the conventional mobile station apparatus shown in FIG. 6 connects to a base station in one frequency band. In FIG. 7, the mobile station apparatus shown in FIG. 6 performs frequency switching according to a hopping pattern, and establishes a synchronous connection with a base station in a frequency band in which a beacon can be received at regular intervals. Even after the synchronous connection, a beacon is transmitted and received in order to maintain synchronization in the frequency band, so that the wireless communication state is kept stable while sequentially monitoring the synchronously connected frequency band.

Another conventional technique is disclosed in Japanese Patent Application Laid-Open No.
There is a wireless mobile terminal disclosed in 8133. When a handover occurs, the wireless mobile terminal disclosed in the above publication receives control signals of a plurality of base stations existing in the vicinity, detects and stores the identification code and the received electric field strength. The base station having the highest received electric field strength is selected as the base station of the communication destination among the base stations that can be searched within the predetermined time. After completion, the base station is selected as a base station for communication. As a result, the time required to search for a base station to communicate with at the time of handover is reduced, and the time during which communication is interrupted is reduced.

[0005]

In the conventional mobile station apparatus shown in FIG. 6, a beacon is transmitted and received even after synchronous connection in one frequency band as described above, but this is for monitoring the connection state. However, synchronization acquisition and synchronization holding cannot be performed in other frequency bands, and the radio wave condition in other frequency bands cannot be grasped. Therefore, after synchronous connection with the base station in one frequency band, the frequency until the reception level of the frequency band falls below the threshold and it is determined that the connection should be cut off, or until the connection is actually cut off. Synchronous connection with another frequency band higher than the reception level of the band is not possible. Therefore, there is a very high possibility that a reception error occurs in the mobile station apparatus, and it is difficult to maintain the quality of transmission data at a high level.

[0006] In the above-mentioned conventional mobile station apparatus, roaming (Roami) is performed in an environment where a plurality of base stations exist.
ng) can be performed, but if the terminal is synchronously connected to the base station in one frequency band as described above, the radio wave condition in another frequency band cannot be grasped. Therefore, connection with the base station is made in the first frequency band in which synchronization acquisition and synchronization can be maintained by frequency switching. However, as a matter of course, it cannot be determined whether the base station connected synchronously is the most suitable base station for communication. In order to be able to determine this, it is necessary to know where and how many base stations can be connected synchronously. For this purpose, connection with all target base stations must be performed while switching the frequency. Therefore, when performing roaming, it takes a considerable amount of time to find a base station that is the most suitable connection partner for communication, and there is a disadvantage that seamless roaming processing cannot be realized.

[0007] In addition, the wireless mobile terminal disclosed in the above publication has a handover function using a predetermined fixed frequency band. It cannot be applied to mobile communication that performs frequency switching.

[0008] A first object of the present invention is to provide a mobile station device in a wireless LAN which can maintain the quality of transmission data at a high level.

A second object of the present invention is to provide a mobile station device in a wireless LAN that can realize a seamless roaming process.

[0010]

A mobile station apparatus according to the present invention comprises:
When starting a wireless connection with an access point, a wireless physical control means for performing first frequency switching for sequentially switching a plurality of frequency bands in accordance with a hopping pattern, and performing synchronization capture and holding based on an output of the wireless physical control means. A mobile station device in a wireless LAN employing a frequency hopping spread spectrum communication system, wherein the wireless physical control unit communicates in one of the plurality of frequency bands. And frequency switching means for performing a second frequency switching to sequentially switch the plurality of frequency bands according to the hopping pattern, the frequency synchronization control means, while maintaining synchronization in the one frequency band, the frequency The synchronization acquisition and the synchronization holding are performed based on the output of the switching means.

Further, the mobile station device has a table for storing radio wave conditions of each of the plurality of frequency bands obtained from the output of the frequency synchronization control means, and the plurality of the plurality of frequency bands are based on the contents of the table. A frequency band optimal for communication is selected from among frequency bands, and when the one frequency band currently being communicated and the optimal frequency band for communication are the same, communication in the one frequency band is continued. When the one frequency band currently being communicated is different from the optimal frequency band for the communication, a statistical information monitoring control means for performing the first frequency switching from the optimal frequency band for the communication is further included. Features.

The operation of the present invention is as follows. The wireless physical control unit has a function of performing frequency switching while maintaining synchronization with this frequency band even during communication in one frequency band. The radio wave condition of each frequency band obtained by the frequency switching is stored in a table in the statistical information monitoring control unit. By analyzing the contents of this table, it is possible to know the most suitable frequency band for communication among the respective frequency bands. Frequency switching is performed from the obtained optimal frequency band, and synchronous connection is performed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 illustrates an I according to an embodiment of the invention.
FIG. 7 is a block diagram showing a configuration of a mobile station device in a wireless LAN adopting the FH-SS system conforming to EEE 802.11, and portions equivalent to those in FIG. 6 are denoted by the same reference numerals.
In FIG. 1, the mobile station device according to the present embodiment includes a data communication control unit 1, a connection and roaming processing unit 4, a statistical information monitoring control unit 5, a monitoring control unit 6, a frequency synchronization control unit 7, And a physical control unit 8.

Here, the radio physical control unit 8 has a function of performing first frequency switching control and data transmission / reception radio control as performed in the conventional mobile station apparatus shown in FIG. In addition, the radio physical control unit 8 further has a function of performing second frequency switching control and data transmission / reception radio control even during communication in one frequency band.

However, the second frequency switching is performed within a range where the frequency synchronization control unit 7 can keep the synchronization with the frequency band currently being communicated to a minimum. That is, if the second frequency switching during communication is performed at the switching interval of the first frequency switching during connection, synchronization with the frequency band currently being communicated cannot be maintained. Therefore, the switching interval of the second frequency switching is set shorter than the switching interval of the first frequency switching, and is limited to an interval sufficient to grasp the radio wave condition of the surrounding frequency band.

Even if the frequency synchronization control unit 7 cannot maintain synchronization with the frequency band currently being communicated due to the second frequency switching and a disconnection state occurs, the frequency synchronization control unit 7 starts from the first frequency band of the hopping pattern. Instead of starting the second frequency switching, the second frequency switching is restarted from the frequency band immediately before disconnection to establish a synchronous connection.

If the synchronous connection cannot be established even after the second frequency switching is performed for one cycle, the first frequency switching is performed to establish the synchronous connection.

The monitoring controller 6 determines which of the first frequency switching and the second frequency switching should be used for frequency switching.

In the first frequency switching at the time of connection, the radio wave condition of each frequency band acquired from the beacon, etc.
In addition, the radio physical control unit 8 notifies the statistical information monitoring control unit 5 of the radio wave condition and the like of each frequency band acquired from the beacon by the second frequency switching during communication. The notified radio wave condition of each frequency band is stored in a table in the statistical information monitoring control unit 5, and the statistical information monitoring control unit 5 grasps the radio wave condition of each frequency band based on the contents of this table.

When the synchronous connection is disconnected or roaming occurs due to radio wave interference or movement of the mobile station device, the statistical information monitoring and control unit 5 switches the frequency for restarting the connection based on the contents of the table. Select the starting frequency band.

FIG. 2 is a diagram showing an example of a table in the statistical information monitoring control unit 5. In FIG. 2, for each of the bands A to F, which are frequency bands, the reception sensitivity and the BSS (Basic Service Set) having the highest reception sensitivity are shown.
, An order of the receiving sensitivity, and the presence or absence of noise are managed so as to be identified in a list.

The statistical information monitoring controller 5 grasps and analyzes the current radio wave condition of each frequency band based on the contents of the table. Thereby, it is possible to select an optimal frequency band for performing communication in a short time.

Further, the mobile station apparatus according to the present embodiment can search for its own location. Based on the contents of the table shown in FIG. 2, the mobile station device can identify which base station in the plurality of BSS areas is closest to itself and where it is. FIG. 3 is a diagram for explaining the correspondence of the position search of the mobile station. In FIG. 3, the base station A is most suitable for synchronous communication for the mobile station, and the base station C is barely capable of synchronous communication with the base station C.
It exists within the BSS area (BSS-A) of the base station C and near the boundary of the BSS area (BSS-C) of the base station C. Also, since the mobile station cannot be synchronized with the base station B, the BSS area (BSS-B) of the base station B
Does not exist.

FIG. 4 is a diagram for explaining an operation when the mobile station apparatus according to the embodiment of the present invention is connected in one frequency band. In FIG. 4, the mobile station apparatus according to the present embodiment performs first frequency switching according to a hopping pattern,
Synchronous connection with the base station is made in a frequency band in which a beacon can be received at regular intervals. Even after the connection, a beacon is transmitted and received in order to maintain synchronization in the frequency band, thereby maintaining the stability of the wireless communication state while sequentially monitoring the frequency band connected in synchronization.

After the synchronous connection, the second frequency switching is performed while adjusting the time until the frequency switching is started according to the communication state. Since the second frequency switching is started from the frequency band during communication and is intended only to acquire the surrounding radio wave condition, the switching interval is one of the switching intervals of the first frequency switching at the time of connection. About / 4.

FIG. 5 is a flowchart for explaining the operation of the mobile station apparatus according to this embodiment. In FIG.
First, scanning (scanning; processing of acquiring a beacon) for synchronous connection is started by first frequency switching at the time of connection (step S1). This scanning is also performed in the conventional mobile station apparatus shown in FIG. 6, and the switching interval is adjusted so that a synchronous connection with a communicable frequency band is possible.

Also, when a frequency band that can be synchronously connected is found for high-speed connection as in conventional control, scanning may be stopped and communication may be started. Scanning is performed in the frequency band. Therefore, when the scanning is not completed in all the frequency bands (step S2, No), the scanning result of the scanned frequency band is stored in a table in the statistical information monitoring controller 5 (step S3). Then, the process shifts to the next frequency band according to the hopping pattern (step S4), and scanning is performed in this frequency band (step S1).

When the scanning is completed in all the frequency bands by repeating this (step S2, Yes), the statistical information monitoring control unit 5 determines the radio wave condition of each frequency band based on the scanning result stored in the table. Is analyzed (step S5). Here, since the mobile station device has not performed communication yet (step S6, No), the first frequency switching is performed from the frequency band optimal for communication, which is the result of analyzing the radio wave condition of each frequency band, and the synchronous connection is performed. (Step S
7).

After a while, the process returns to step 1 to start scanning again, but it should be noted that the frequency switching interval here is about １ ／ of the first frequency switching interval at the time of connection. is there. As a result, it is possible to maintain synchronization with one frequency band that is connected synchronously in step S7 and is currently communicating.

When the scanning is completed in all frequency bands (step S2, Yes), the radio wave condition of each frequency band is analyzed as described above (step S5). Here, since the mobile station device is communicating (step S6, Yes),
It is confirmed whether or not the radio wave condition of the frequency band currently in communication is more optimal than the radio wave condition of another frequency band (step S8). If the current situation is optimal (step S9, Ye
s) The communication in the currently communicating frequency band is continued. After a while, the process returns to step 1 to start the scanning again. The frequency switching interval here is also about １ ／ of the first frequency switching interval at the time of connection.

If it is determined in step 9 that the current condition is not optimal (step S9, No), the first frequency is switched from another frequency band that is optimal for communication and synchronous connection is made (step S7). After a while, the process returns to step 1 and starts scanning again. The frequency switching interval here is also one of the normal frequency switching intervals for connection.
It is about / 4.

[0032]

A first effect of the present invention is that the quality of transmission data can be maintained at a high level. The reason is that, even when communicating in one frequency band, by scanning each frequency band, the radio wave condition of the communicating frequency band is compared with the radio wave condition of other frequency bands, and communication is performed. This is because communication is performed in an optimal frequency band.

The second effect of the present invention is that a seamless roaming process can be realized. The reason is that the radio wave condition around the mobile station is grasped in advance, so that when performing roaming, the frequency can be switched from the optimal frequency band. This is because they can be found earlier.

A third advantage of the present invention is that security in wireless communication can be improved. The reason is that by scanning each frequency band, it is possible to grasp the interference state of radio waves, and when transmitting or receiving important information, make sure that the radio waves are not affected by other radios in advance It is because it understands.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a mobile station device in a wireless LAN employing an FH-SS system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a table in a statistical information monitoring control unit 5;

FIG. 3 is a diagram for explaining correspondence of location search of the mobile station device according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining an operation when the mobile station device according to the embodiment of the present invention is connected in one frequency band.

FIG. 5 is a flowchart illustrating an operation of the mobile station device according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional mobile station device in a wireless LAN adopting the FH-SS system.

FIG. 7 is a diagram for explaining an operation when a conventional mobile station device connects in one frequency band.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Data communication control part 4 Connection and roaming control part 5 Statistical information monitoring control part 6 Monitoring control part 7 Frequency synchronization control part 8 Radio physical control part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04L 12/28 H04L 11/00 310B H04Q 7/28 H04Q 7/04 K F term (reference) 5K022 EE04 EE36 5K033 AA05 CA00 CB15 DA19 DB11 DB12 EA02 EA06 EA07 5K042 AA01 AA06 DA13 DA19 FA15 JA04 NA03 5K047 AA11 BB01 JJ06 MM13 MM24 5K067 AA23 BB21 CC10 DD25 EE02 EE10 EE72 FF16 FF23 HH22 HH23 JJ37 JJ52 LL01

Claims (2)

[Claims] When starting wireless connection with an access point, a wireless physical control means for performing first frequency switching for sequentially switching a plurality of frequency bands according to a hopping pattern, and a synchronous compensation based on an output of the wireless physical control means. A wireless LAN including frequency synchronization control means for acquiring and maintaining synchronization, and employing a frequency hopping spread spectrum communication system
Wherein the radio physical control means, when communicating in one frequency band of the plurality of frequency bands, the second frequency that sequentially switches the plurality of frequency bands according to the hopping pattern Frequency switching means for performing switching, wherein the frequency synchronization control means maintains synchronization in the one frequency band, and performs the synchronization capture and the synchronization maintenance based on an output of the frequency switching means. Mobile station device. 2. A table for storing radio wave conditions of each of the plurality of frequency bands obtained from an output of the frequency synchronization control means, and communication is performed in the plurality of frequency bands based on the contents of the table. The most suitable frequency band is selected, and when the one frequency band currently in communication and the optimal frequency band for the communication are the same, the communication in the one frequency band is continued, and the 2. The apparatus according to claim 1, further comprising: a statistical information monitoring control unit configured to perform the first frequency switching from a frequency band optimal for the communication when one frequency band is different from a frequency band optimal for the communication. The mobile station device as described in the above.