Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-07-28
2001-01-16
Le, Thanh Cong (Department: 2749)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S453000, C455S062000, C455S509000
Reexamination Certificate
active
06175739
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a channel selection method to be applied to a wireless communication system wherein a plurality of wireless channels are used by a plurality of wireless stations, each selected dynamically according to usage of the wireless channels checked by each of the wireless stations, and particularly relates to the channel selection method which enables a dynamic and appropriate channel selection even when but few available wireless channels are left to be selected.
In conventional connection-less wireless communication systems to be applied to a wireless LAN (Local Area Network), for example, such as described in “Wireless LAN Medium Access Control and Physical Layer Specifications”, Draft Standard IEEE 802.11, P802.11D2.0, (July 1995), (hereafter called the first prior document), a wireless channel is commonly used by a base station connected to a wired network and one or more mobile stations connected with the base station for configuring a wireless link of a wireless communication system, and a wireless channel is fixedly assigned to each base station considering propagation characteristics and the traffic prediction of each base station. The mobile station designates a wireless channel assigned to a base station of a zone where the mobile station actually exists, manually or according to a control signal which is periodically or continuously transmitted from the base station.
However, when the wireless channels are assigned fixedly for each of the base stations according to the propagation characteristics and the traffic prediction, there may occur interferences between base stations whereto the same wireless channel is assigned, if the actual propagation characteristics or the actual communication traffic is changed from the prediction.
For dealing with this problem, we proposed a dynamic channel selection method in a paper entitled “A Proposal of Packet DCA for a Wireless LAN System”, B-652, p. 136, Proceedings of the Communication Society Congress 1996, IEICE, (hereafter called the second prior document), wherein an appropriate channel selection according to actual propagation characteristics and communication traffic is realized by enabling a wireless station to select a wireless channel not used by other wireless stations dynamically and independently, for establishing a new wireless link.
However, the channel selection method proposed in the second prior document is based on an assumption that a sufficient number of wireless channels are prepared so that there are always left some channels not used by other wireless stations and available for the new wireless link to be established, and there is no description concerning the case where no available channel is left unused. Therefore, there may arise wireless links whereto any wireless channel can be assigned, when the number of available wireless channels is insufficient.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide a channel selection method of a wireless communication system which enables a wireless station to select a wireless channel dynamically even when there are but an insufficient number of wireless channels, by resolving above problem of the dynamic channel allocation.
In order to achieve the object, a channel selection method of the invention for establishing a wireless link of a wireless communication system by dynamically selecting a wireless channel to be used for the wireless link from a plurality of wireless channels prepared for the wireless communication system comprises:
a channel search step of checking whether any one of the plurality of wireless channels is left unused by other wireless stations of the wireless communication system or not;
a sharing channel selection step of selecting a wireless channel to be shared from wireless channels under use of the other wireless stations, said sharing channel selection step being performed when every of the plurality of wireless channels is found to be under use of one of the other wireless stations at the channel search step; and
a link establishment step of establishing the wireless link by sharing the wireless channel selected at the sharing channel selection step.
Therefore, the wireless station can establish the new wireless link even when no wireless channel is left unused, by designating a wireless channel to be shared dynamically from wireless channels under use of other base stations, enabling at the same time to improve efficiency of channel resources of the wireless communication system.
Furthermore, the link establishment step comprises a step of registering sharing information of the wireless channel to be shared in a sharing information register provided in the wireless station, and the wireless station reports the sharing information to a sharing wireless station which is using the same wireless channel whereof the sharing information is registered in the sharing information register of the wireless station by way of the same wireless channel, periodically during the sharing information is registered. The wireless station also registers the sharing information in the sharing information register thereof when the sharing information is reported from another wireless station of the wireless communication system.
Therefore, both the wireless station and the sharing wireless station can always confirm sharing status of their using wireless channel by exchanging the sharing report with each other periodically, and so, they can recognize release of the sharing status for clearing the sharing information by counting a number of the sharing reports received in a certain time interval.
Furthermore, the wireless station clears the sharing information registered in the sharing information register thereof when the sharing report is not received from any other wireless station of the wireless communication system during a predetermined time period, and the wireless station switches the wireless channel used for the wireless link into an unused one of the wireless channels when the unused one is found by performing the channel search step periodically during the sharing information is registered in the sharing information register thereof.
Therefore, sharing of a wireless channel can be minimized dynamically in accordance with communication traffic in the wireless communication system according to the invention.
REFERENCES:
patent: 5749055 (1998-05-01), Dahlin
patent: 5812952 (1998-09-01), On et al.
patent: 6041239 (2000-03-01), Reed et al.
“Wireless LAN Medium Access Control and Physical Layer Specifications”, Draft Standard IEEE 802.11, P802.11D2.O, (Jul. 1995).
“A Propsal of Packet DCA for a Wireless LAN System”, by Ishii et al., B-652, p. 136, Proceedings of the Communication Society Congress 1996, IEICE.
Ishii Kenichi
Osawa Tomoki
Cong Le Thanh
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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