Patent Application
20070008918
1. Field of the Invention
The present invention relates to a system and method for forming an ad-hoc multihopping network of movable devices. The present invention utilizes the knowledge of channel and link quality at the application layer to enable a movable device to create connections with other movable devices and to maintain reliable connections with the other movable devices in an autonomous and heuristic fashion. More particularly, the system and method comprise ad hoc radios in a network of movable devices, to which is presented routing and link quality data at the application layer.
2. Description of the Related Art
Wireless communication networks, such as mobile wireless telephone networks, have become increasingly prevalent over the past decade. These wireless communications networks are commonly referred to as “cellular networks”, because the network infrastructure is arranged to divide the service area into a plurality of regions called “cells”. A terrestrial cellular network includes a plurality of interconnected base stations, or base nodes, that are distributed geographically at designated locations throughout the service area. Each base node includes one or more transceivers that are capable of transmitting and receiving electromagnetic signals, such as radio frequency (RF) communications signals, to and from mobile user nodes, such as wireless telephones, located within the coverage area. The communications signals include, for example, voice data that has been modulated according to a desired modulation technique and transmitted as data packets. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format, which enables a single transceiver at a first node to communicate simultaneously with several other nodes in its coverage area.
In recent years, a type of mobile communications network known as an “ad-hoc” network has been developed. In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet. Details of these advanced types of ad-hoc networks are described in U.S. patent application Ser. No. 09/897,790 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, filed on Jun. 29, 2001, in U.S. patent application Ser. No. 09/815,157 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, filed on Mar. 22, 2001, and in U.S. patent application Ser. No. 09/815,164 entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, filed on Mar. 22, 2001, the entire content of each being incorporated herein by reference.
An application of wireless communication technology which has been the focus of much research is movable devices and, more particularly, robotics. In particular, for example, search and rescue robots are being developed for public safety and for homeland security. Moreover, researchers have focused, for example, on the practical limitations of movable devices that move away from a control point and, ultimately, can face unreliable radio links. In this regard, conventional movable devices can fall out of working range of a control station and lose communications with the control station when Line Of Sight (LOS) is lost between the movable device and the control station. Current routing and link layer implementations, in this regard, do not have enough information to perform adequately in all situations.
Accordingly, there remains a need for a system or method of deploying a movable ad hoc device network which presents routing and link quality data to the application layer.
These and other objects, advantages and novel features of the invention will be more readily appreciated from the following detailed description when read in conjunction with the accompanying drawings, in which:
As can be appreciated by one skilled in the art, the nodes 102, 106 and 107 are capable of communicating with each other directly, or via one or more other nodes 102, 106 or 107 operating as a router or routers for packets being sent between nodes, as described in U.S. patent application Ser. Nos. 09/897,790, 09/815,157 and 09/815,164, referenced above.
As shown in
Each node 102, 106 and 107 further includes a memory 114, such as a random access memory (RAM) that is capable of storing, among other things, routing information pertaining to itself and other nodes in the network 100. As further shown in
The use of ad hoc radios in networks of movable devices has the potential to extend communications between devices in these networks, for example, by repeating or relaying the communications through intermediate nodes. Additionally, channel and link quality information can be used to enable a moveable device to create connections with other devices. “Movable devices”, in this regard, can be any robot, vehicle, instrumentality, or any other controllable device. For purposes of this description, the term “movable device” will be used.
As will now be discussed, the present invention provides a wireless movable device that determines the link and channel quality of a link between itself and another device, such as an ad-hoc multihopping device, such that the movable device is adapted to determine when it has traveled too far from the ad-hoc device to maintain a reliable link to the ad-hoc device, and wherein the movable device, upon determining the loss of a reliable link to the ad-hoc device, seeks out a location at which a reliable link exists with the ad-hoc device or with another ad-hoc multihopping device.
The present invention also provides a system of wireless movable devices. The system comprises, for example, a first movable device that is adapted to determine the link and channel quality of a link between the first movable device and a first ad-hoc multihopping device, such that the first movable device is capable of determining when it has traveled too far from the first ad-hoc device to maintain a reliable link to the first ad-hoc device. The first movable device, upon determining the loss of a reliable link to the first ad-hoc device, is adapted to seek out a location at which a reliable link exists with the first ad-hoc device or with another ad-hoc multihopping device, and stops at that location. A second movable device, having a link with the first movable device, determines the link and channel quality of a link between itself and the first movable device. The second movable device is capable of determining when it has traveled too far from the first movable device to maintain a reliable link to the first movable device. The second movable device, upon determining the loss of a reliable link to the first movable device, seeks out a location at which a reliable link exists with the first movable device or with another ad-hoc multihopping device, and stops at that location.
The present invention also provides a method for operating wireless movable devices, the method comprising: deploying a first movable device that is adapted to determine the link and channel quality of a link between itself and a first device, such as a first ad-hoc multihopping device. The first movable device is operated to determine when it has traveled too far from the first ad-hoc device to maintain a reliable link to the first ad-hoc device, and, when the first movable device determines the loss of a reliable link to the first ad-hoc device, the first movable device is operated to seek out a location at which a reliable link exists with the first ad-hoc device or with another ad-hoc multihopping device, and the first movable device is moved to that location.
A network including movable device will be described with regard to
As illustrated in
While the above-described scenario pertains to movable devices 120-1 seeking to stay in contact with a control station 125, it can clearly be extended to enable movable devices to find and maintain good quality links with other movable devices in a network. In a scenario in which a “swarm” of movable devices (e.g., robots) is searching a terrain, each movable device may have more than one option in terms of routes. Accordingly, it will not always be necessary for the movable devices to move to create a better communications link. Conversely, it may be necessary for several movable devices to move to create and maintain the communications network.
While conventional movable devices use link quality metrics in layer 2 and layer 3 of the stack, the present invention allows for the use of radio metrics in higher layers of the protocol stack. In this regard, any suitable sets of metrics can be provided or visible at the high layers utilized in the present invention, such as, for example, link quality, congestion, throughput, priority, and battery life. Moreover, any suitable algorithm can be employed at the high layers utilized in the context of the present invention so that the metrics can be more readily understood and acted upon by additional applications.
“Intelligent” radios can also be used in the context of the present invention. In particular, as technology allows the devices to change the modulation and bandwidth on the fly, the devices can start to add application layer considerations that are not possible with the limited knowledge that is available at the lower layers in the stack. For instance, a movable device may be going out of range where it can maintain a high speed data link. An option to maintain the link would be to change the modulation to a lower data rate. However, it may be possible for the mobile device to look to the option of acquiring more bandwidth in order to maintain the data rate with the lower modulation. This may require knowledge about the location and other spectrum users in the location, as well as the price of bandwidth, QOS constraints or other policy rules and regulations. Accordingly, it is advantageous to provide the additional information to the upper layers in the stack, so that such information can be readily access by additional applications.
Although only a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.
