Wireless LAN system

• US 6,031,863 A
• Filed: 03/19/1996
• Issued: 02/29/2000
• Est. Priority Date: 03/20/1995
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Jusa, Hidehiko, Shida, Masaaki
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US08/618,116
• Time in Patent Office: 1,442 Days
• Field of Search: 375/200, 375/202, 375/203, 375/356, 370/328, 370/338, 370/350, 455/502, 455/517
• US Class Current: 375/132
• CPC Class Codes: H04B 1/7156 Arrangements for sequence synchronisation
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 72/044 based on the type of the allocated resource
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

The wireless LAN system has an information-carrying capacity which is several times the transmission rate obtained by a single cell. The wireless LAN system properly notifies hopping information even if an error in transmission arises. Hopping control is carried out on a master base-station device 10a and slave base-station devices 10b and 10c based on a synchronizing frame generated from hopping timing of the master base-station device 10a. After completion of the hopping control, each base-station device 10 starts to send hopping information to radio terminals 2 present in the same cell. Radio terminals 2, which are in the same cell as one of the base stations 10, work under the base-station device 10.

Claims

1. A wireless LAN system having a plurality of cells each comprising a base-station device and one or more radio terminals serving under the base-station device and wherein said base-station device and said one or more radio terminals in each of said plurality of cells perform mutual communications using a low-speed frequency hopping/spread spectrum system while frequencies are hopped at regular intervals by said cells and individual base-station devices in said cells are mutually connected to one another, each base-station device comprising:

means for assigning inherent hopping patterns at each cell;

means for generating a cue for providing synchronization between base-stations devices from a hopping timing;

synchronism control means for enabling communications between the respective base-station devices in the cells in accordance with the cue, generated by said means for generating the cue, thereby providing hopping synchronization between the base-station devices;

wherein each base-station device further comprises means for communicating with other base-station devices to divide said respective base-station devices in said plurality of cells into a single master base-station device and base-station devices other than said master base-station into slave base-station devices;

wherein with respect to said master base-station device, said synchronism control means of said master base-station device provides the hopping synchronization between said master base-station device and said one or more radio terminals serving under said master base-station device in accordance with the cue generated by said means for generating the cue and notifies a hopping synchronous request to said each slave base-station device; and

wherein with respect to said slave base-station device, said synchronism control means provides the hopping synchronization between said slave base-station device and said one or more radio terminals serving under said slave base-station device in response to the hopping synchronous request notified from said master base-station device.

2. A wireless LAN system according to claim 1, wherein said synchronism control means of said master base-station device measures a time that has elapsed before the occurrence of the next hopping timing for said master base-station device in accordance with the cue generated by said means for generating the cue and sets it as a synchronous correction time for said master base-station device, and when a time corresponding to the difference between the hopping interval and the synchronous correction time for said master base-station device has elapsed after completion of a predetermined number of hops, said synchronism control means performs the hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said master base-station device belongs, and;

said synchronism control means of said slave base-station device measures a time that elapsed before the occurrence of the next hopping timing for said slave base-station device in response to the hopping synchronous request notified from said master base-station device and sets it as a synchronous correction time for said slave base-station device, and when a time corresponding to the difference between the hopping interval and the synchronous correction time has elapsed after completion of the predetermined number of hops, said synchronism control means performs the hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said slave base-station device belongs.

3. A wireless LAN system according to claim 2, wherein said synchronism control means sends hopping information, including the synchronous correction time and a synchronous control start hopping number indicative of the number of hops counted before the hopping synchronization is provided, to said one or more radio terminals in said cell to which said master base-station device belongs;

and

when each of said radio terminals receives the hopping information and the number of hops for initiation of the synchronous control indicates a hopping synchronization at the next hopping, said radio terminal performs the hopping from the leading frequency of the inherent hopping pattern for said cell to which said master base-station device belongs, when a time corresponding to the difference between the hopping interval and the synchronous correction time for said master base-station device has elapsed from the head of the next hopping.

4. A wireless LAN system according to claim 3, wherein said synchronous control means notifies the hopping information to said one or more radio terminals in said cell to which said master base-station device belongs a plural number of times.

5. A wireless LAN system according to claim 2, wherein said synchronism control means sends hopping information, including the synchronous correction time and a synchronous control start hopping number indicative of the number of hops counted before the hopping synchronization is provided, to said one or more radio terminals in said cell to which said slave base-station device belongs;

and

when each of said radio terminals receives the hopping information and the number of hops for initiation of the synchronous control indicates a hopping synchronization at the next hopping, said radio terminal performs the hopping from the leading frequency of the inherent hopping pattern for said cell to which said slave base-station device belongs, when a time corresponding to the difference between the hopping interval and the synchronous correction time for said intended base-station device has elapsed from the head of the next hopping.

6. A wireless LAN system according to claim 5, wherein said synchronous control means notifies the hopping information to said one or more radio terminals in said cell to which said slave base-station device belongs a plural number of times.

7. A wireless LAN system having a plurality of cells each comprising a base-station device and one or more radio terminals serving under the base-station device and wherein said base-station device and said one or more radio terminals in each of said plurality of cells perform mutual communications using a low-speed frequency hopping/spread spectrum system while frequencies are hopped at regular intervals by said cells and individual base-station devices in the cells are mutually connected to one another, wherein each base-station device comprises:

means for assigning inherent hopping patterns to said cell to which the corresponding base-station device belongs, at said each cell;

means for generating a cue for providing synchronization between base-station devices from a hopping timing;

base-station-device-to-base-station devices synchronism control means for enabling communications between the respective base-station devices in said other cells in accordance with the cue generated by said means for generating the cue to thereby provide hopping synchronization between the base-station devices;

wherein each of said base-station devices further comprises means for communicating with other base-station devices to divide said respective base-station devices in said plurality of cells into a single master base-station device and at least one slave base-station device;

wherein in a cell containing said master base-station device, said base-station device-to-base-station device synchronism control means provides the hopping synchronization between said master base-station device and said one or more radio terminals serving under said master base-station device in accordance with the cue generated by said means for generating the cue and notifies a hopping synchronous request to said at least one slave base-station device; and

wherein in a cell containing said at least one slave base-station device, said base-station device-to-base-station device synchronism control means provides the hopping synchronization between said slave base-station device and said one or more radio terminals serving under said slave base-station device in response to the hopping synchronous request notified from said master base-station device.

8. A wireless LAN system according to claim 7, wherein said base-station device-to-base-station device synchronism control means of said master base-station device measures a time that elapsed before the occurrence of the next hopping timing of said master base-station device in accordance with the cue generated by said means for generating the cue and sets it as a synchronous correction time for said master base-station device, and when a time corresponding to the difference between the hopping interval and the synchronous correction time has elapsed after completion of a predetermined number of hops for initiation of synchronous control, said base-station device-to-base-station device synchronism control means performs hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said master base-station device belongs.

9. A wireless LAN system according to claim 8, wherein said base-station device-to-base-station device synchronism control means sends hopping information, including the synchronous correction time and the number of hops for initiation of the synchronous control to said one or more radio terminals in said cell to which said master base-station device belongs, a plural number of times.

10. A wireless LAN system according to claim 7, wherein said base-station device-to-base-station device synchronism control means of said slave base-station device measures a time that elapsed before the occurrence of the next hopping timing for said slave base-station device in response to the hopping synchronous request notified from said master base-station device and sets it as a synchronous correction time, and when a time corresponding to the difference between the hopping interval and the synchronous correction time has elapsed after completion of a predetermined number of hops for initiation of synchronous control, said base-station device-to-base-station device synchronism control means performs the hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said slave base-station device belongs.

11. A wireless LAN system according to claim 10, wherein said base-station device-to-base-station device synchronism control means sends hopping information, including the synchronous correction time and the number of hops for initiation of the synchronous control to said one or more radio terminals in said cell to which said slave base-station device belongs, a plural number of times.

12. A method of controlling base-station devices employed in a wireless LAN system having a plurality of cells each comprising the base-station device and one or more radio terminals serving under the base-station device and wherein said base-station device and said one or more radio terminals in each cell perform mutual communications using a low-speed frequency hopping/spread spectrum system while frequencies are hopped at regular intervals by said cells and individual base-station devices in the cells are mutually connected to one another, said method causing said base-station device to perform the steps of:

communicating with other base-station devices to divide said respective base-station devices in said plurality of cells into a single master base-station device and at least one slave base-station device, and assigning inherent hopping patterns at said each cell;

wherein if the base-station device is said master base-station device, generating a cue for providing synchronization between base-station devices from hopping timing, providing the hopping synchronization between said master base-station device and said one or more radio terminals serving under said master base-station device in accordance with the generated cue for providing synchronization and notifying a hopping synchronous request to said at least one slave base-station device; and

wherein if said base-station device is said at least one slave base-station device, providing the hopping synchronization between said slave base-station device and said one or more radio terminals serving under said slave base-station device in response to the hopping synchronous request notified from said master base-station device.

13. A method according to claim 12, wherein said hopping synchronous request includes hopping information including a synchronous correction time and a synchronous control start hopping number indicative of the number of hops counted before the hopping synchronization is provided, and

when each of said radio terminals receives the hopping information and the number of hops for initiation of the synchronous control indicates a hopping synchronization at the next hopping, said radio terminal performs the hopping from the leading frequency of the inherent hopping pattern for said cell to which said master base-station device belongs, when a time corresponding to the difference between the hopping interval and the synchronous correction time for said master base-station device has elapsed from the head of the next hopping.

14. A method according to claim 13, wherein said hopping information is provided to said one or more radio terminals in said cell to which said master base-station device belongs a plural number of times.

15. A method according to claim 13, wherein said hopping synchronous request includes hopping information including a synchronous correction time and a synchronous control start hopping number indicative of the number of hops counted before the hopping synchronization is provided, and

when each of said radio terminals receives the hopping information and the number of hops for initiation of the synchronous control indicates a hopping synchronization at the next hopping, said radio terminal performs the hopping from the leading frequency of the inherent hopping pattern for said cell to which said slave base-station device belongs, when a time corresponding to the difference between the hopping interval and the synchronous correction time for said slave base-station device has elapsed from the head of the next hopping.

16. A method according to claim 15, wherein said hopping information is provided to said one or more radio terminals in said cell to which said slave base-station device belongs a plural number of times.

17. In a wireless LAN system having one or more cells each comprising a base-station device and one or more radio terminals serving under the base-station device and wherein said base-station device and said one or more radio terminals in each cell perform mutual communications using a low-speed frequency hopping/spread spectrum system while frequencies are hopped at regular intervals by said cells based on inherent hopping patterns, said base-station device comprising:

means for generating a cue for providing hopping synchronization; and

hopping synchronism control means for providing the hopping synchronization between said corresponding base-station device and said one or more radio terminals serving under said corresponding base-station device, based on the cue generated by said means for generating the cue for providing hopping synchronizing;

said hopping synchronism control means comprising;

hopping synchronizing means for measuring a time that elapsed before the occurrence of the next hopping timing of said corresponding base-station device in accordance with the cue generated by said hopping synchronization generating means and setting it as a synchronous correction time, and performing the hopping from the leading frequency of the inherent hopping pattern for said cell to which said corresponding base-station device belongs, when a time corresponding to the difference between the hopping interval and the synchronous correction time for said corresponding base-station device has elapsed after completion of a predetermined number of hops for initiation of synchronous control; and

means for notifying hopping information including the synchronous correction time and the number of hops for initiation of the synchronous control to said one or more radio terminals in said cell to which said corresponding base-station device belongs; and

when each radio terminal receiving the hopping information therein and the number of hops for initiation of the synchronous control indicates a hopping synchronization at the next hopping, each of said radio terminals performs the hopping from the leading frequency of the inherent hopping pattern when a time corresponding to the difference between the hopping interval and the synchronous correction time for said corresponding base-station device has elapsed from the head of the next hopping.

18. A base-station device for use in a wireless LAN system having a plurality of cells each comprising one or more radio terminals serving under the base-station device, the base-station device comprising:

means for assigning inherent hopping patterns to said cell to which the base-station device belongs;

means for generating a cue for providing synchronization between the base-station device and other base-station device in different cells by using a hopping timing;

synchronism control means for enabling communications between the base-station device and the other base-station devices in accordance with the cue generated by said means for generating the cue to thereby provide hopping synchronization between the base-station device and the other base-station device;

wherein said base-station device further comprises means for communicating with said other base-station devices to divide said respective base-station devices in said plurality of cells into a single master base-station device and at least one slave base-station device;

wherein if said base-station device is said master base-station device, said synchronism control means provides the hopping synchronization between said base-station device and said one or more radio terminals serving under said base-station device in accordance with the cue generated by said means for generating the cue and notifies a hopping synchronous request to said at least one slave base-station device; and

wherein if said base-station device is said at least one slave base-station device, said synchronism control means provides the hopping synchronization between said base-station device and said one or more radio terminals serving under said base-station device in response to the hopping synchronous request notified from said master base-station device.

19. A base-station device according to claim 18, wherein said synchronism control means of said master base-station device measures a time that elapsed before the occurrence of the next hopping timing of said master base-station device in accordance with the cue generated by said means for generating the cue and sets it as a synchronous correction time for said master base-station device, and when a time corresponding to the difference between the hopping interval and the synchronous correction time has elapsed after completion of a predetermined number of hops for initiation of synchronous control, said synchronism control means performs hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said master base-station device belongs.

20. A base-station device according to claim 19, wherein said synchronism control means send hopping information, including the synchronous correction time and the number of hops for initiation of the synchronous control to said one or more radio terminals in said cell to which said master base-station device belongs, a plural number of times.

21. A base-station device according to claim 18, wherein said synchronism control means of said slave base-station device measures a time that elapsed before the occurrence of the next hopping timing for said slave base-station device in response to the hopping synchronous request notified from said master base-station device and sets it as a synchronous correction time, and when a time corresponding to the difference between the hopping interval and the synchronous correction time has elapsed after completion of a predetermined number of hops for initiation of synchronous control, said synchronism control means performs the hopping from the leading frequency of the inherent hopping pattern for said corresponding cell to which said slave base-station device belongs.

22. A base-station device according to claim 21, wherein said synchronism control means sends hopping information, including the synchronous correction time and the number of hops for initiation of the synchronous control to said one or more radio terminals in said cell to which said slave base-station device belongs, a plural number of times.

23. A method of controlling base-station devices in a wireless LAN system having a plurality of cells each comprising the base-station device and one or more radio terminals serving under the base-station device and wherein said base-station device and said one or more radio terminals in each cell perform mutual communication using frequency hopping spread spectrum system and each base-station device is mutually connected to another base-station, said method causing said base-station device to perform the steps of:

hopping frequencies at regular intervals in each cell according to a hopping pattern common to said plurality of cells in order of frequencies and shifting from the hopping pattern of other cells;

periodically transmitting a control frame to other base-station devices in the wireless LAN system during operation; and

adjusting the hopping timing in response to reception of said control frame transmitted by another base-station device.

24. A method according to claim 23, said method further causing said base-station device to perform the step of adjusting hopping timing by switching the frequency to a next hop after a first period from transmitting said control frame, wherein said adjusting step in response to the reception of the control frame includes the step of switching the frequency to the next hop.

25. A base-station device for use in a wireless LAN system having a plurality of cells each comprising one or more radio terminals serving under said base-station device, wherein the base-station device and said one or more radio terminals in each cell perform mutual communication using frequency hopping spread spectrum system and the base-station device is mutually connected to another base-station, said base-station device comprising:

means for hopping frequencies at regular intervals in each cell according to a hopping pattern common to said plurality of cells in order of frequencies and shifting from the hopping pattern of other cells;

means for periodically transmitting a control frame to other base-station devices in the wireless LAN system during operation; and

means for adjusting the hopping timing in response to reception of said control frame transmitted by another base-station device.

26. The base-station device according to claim 25, wherein said means for adjusting the hopping timing includes means for switching the frequency to a next hop after a first period from transmitting said control frame and means for switching the frequency to the next hop upon receiving the control frame.