Multiplex communications – Communication over free space – Message addressed to multiple destinations
Reexamination Certificate
1998-07-17
2001-10-23
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Communication over free space
Message addressed to multiple destinations
C370S338000, C370S390000, C370S469000, C455S453000
Reexamination Certificate
active
06307843
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to wireless networks, and more specifically to an ad hoc network in which mobile hosts are connected to each other via direct wireless links.
2. Description of the Related Art
An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized routing facility. Japanese Patent Laid-Open Specification Hei-8-37535 describes routing in an ad hoc network by having each mobile host maintain a routing table in which IP (network layer) addresses of destination hosts are mapped to IP addresses of transit hosts. When source and destination hosts are outside of the range of each other but within the range of a transit host, the latter acts as a router for routing packets between the source and destination hosts.
If mobile hosts were to use a number of wireless links to form an ad hoc network, these mediums would be identified by data link layer addresses in the routing table. Since the source host has no way of knowing which wireless link every other host is actually using, it will have to establish all wireless links and then broadcast a query packet to all destinations. However, this results in a low utilization efficiency of the network resource.
Another problem is that if mobile hosts having IP addresses of different network addresses were to form an ad hoc network, connections can only be established between mobile hosts of the same network address due to the lack of such routers and gateways of the type as used in wired backbone networks.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an ad hock network that allows efficient utilization of wireless links with which mobile hosts are interconnected.
According to a first aspect of the present invention, there is provided an ad hoc network comprising a plurality of mobile hosts interconnectable by a plurality of wireless links. Each of the mobile hosts comprises a link table having a plurality of entries each comprising a host name, a link identifier indicating one of the wireless links, a network layer address and a data link layer address. Each mobile host is responsive to an entered destination host name for detecting an entry of the link table in which the destination host name is contained, transmitting a frame containing the network layer and data link layer addresses of that entry on one of the wireless links which is indicated by the link identifier of that entry.
According to a second aspect, the present invention provides an ad hoc network comprising a plurality of mobile hosts interconnectable by a plurality of wireless links. Each of the mobile hosts comprises a link table having a plurality of entries each comprising a host name, a link identifier indicating one of the wireless links, a network layer address and a data link layer address. Each mobile host is responsive to an entered destination host name for making a search through the link table for an entry containing the destination host name. If such an entry is found, the mobile host transmits a frame containing the network layer and data link layer addresses of the entry on the wireless link indicated by the link identifier of the entry. Otherwise, the mobile host scans the wireless links, broadcasts a link table request message on one of the scanned wireless links, receives a remote link table containing the destination host name, and transmits a frame containing network layer and data link layer addresses of the remote link table on the wireless link on which the remote link table was received.
REFERENCES:
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patent: 5987011 (1999-11-01), Toh
patent: 6130892 (2000-10-01), Short et al.
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Hsu Alpus H.
NEC Corporation
Qureshi Afsar M.
Scully Scott Murphy & Presser
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