MANETs are attractive because they provide instant network formation without the need for connection planning and routing node administration. The result is ease of deployment, speed of deployment, and decreased dependence on a fixed infrastructure. For example, nodes are mobile and connected dynamically in an arbitrary manner based on the proximity of one node to another and are therefore subject to frequent disconnection.
Wireless links have significantly lower capacity than wired links because they are affected by additional error sources that result in degradation of the received signal and high bit error rates. Mobile nodes may rely on battery power and therefore be energy constrained. Mobile nodes are more autonomous and less capable of centralized administration. The mobile nodes in a network must share common radio frequencies and are therefore prone to greater interference from each neighboring node. One important network component is its routing protocol.
The routing protocol is the mechanism by which message packets are directed and transported through the network from the message source to its destination. An important routing protocol objective is to maximize network performance while minimizing the cost of the network itself in accordance with its capacity.
Dynamic connections and the arbitrary manner in which nodes are connected in a MANET create a challenge to the routing method. Factors which impact the ability of the routing protocol to accomplish its objectives include hop count, delay, throughput, loss rate, stability, jitter, density, frequency of communications, and frequency of topology changes mobility rate. The routing protocol must also guard against message packet duplication and communication loops. For example, if two network nodes, A and B, were to retransmit every message packet they received; A would first send a message packet to B which would then retransmit it back to A, and so on.
Any new message packets introduced into the network would also loop and eventually the network would be completely saturated with continuously looping message packets. However, STP and its variants, such as Rapid Spanning Tree Protocol and Multiple Spanning Trees Protocol, do not perform well in networks where the quality or availability of connections between routing nodes is dynamic and subject to frequent change. For example, STP relies upon a root node to organize and create a logical tree that spans all of the nodes in the network with only one active path.
This routing pathway information is disseminated from the root node to all other routing nodes. Any changes to the network topology, including changes in link quality and the addition or subtraction of a pathway or network node must be organized by the root node and a new logical tree created and disseminated to all routing nodes. Because of this, STP and other protocols which rely upon root node techniques do not perform well in dynamic network environments and can cause network reliability issues due to unacceptable periods of interrupted communications while the network routing is rediscovered and disseminated to all routing nodes.
In order for a routing node to forward a message packet, the routing protocol must know the network address of the next network node in the message packet's path. Network addresses can either be explicitly stated in the header or wrapper of the message packet, or predetermined and maintained in a table by each routing node. In the former, called source routing, there is no need to maintain a table at every routing node because every packet contains the address of every network node the packet needs to traverse. In the latter, called table-driven routing, the next routing node address is taken from a table based on the packet destination address and other criteria defined by a routing protocol.
In table-driven routing, such as Optimized Link State Protocol OLSR and Wireless Routing Protocol WRP , each routing node must continuously evaluate and maintain information on routes to every other node in the network and periodically exchange this information with other routing nodes.
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Some MANET routing protocols include variations for on-demand routing using reactive mechanisms, where routes are found when they are needed and thus reduce the amount of overhead traffic by avoiding the need to frequently exchange state information. Additionally, there are other hybrid, hierarchical, and location-based protocols that have been proposed. AODV is based on a distance vector routing method and uses a route table to find the next network node in the route.
However, the AODV protocol assumes that each link is symmetric and is not well adapted to networks having asymmetric pathways between routing nodes. DSR is based on a source routing method and while supporting asymmetric pathways between routing nodes, it imposes the overhead of communicating the entire route map with every message packet.
It is to be understood that both the following summary and the detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Neither the summary nor the description that follows is intended to define or limit the scope of the invention to the particular features mentioned in the summary or in the description. In some embodiments, it is an object of the present invention to develop a MANET Node Device, network routing protocols and administrative systems that support rapid and robust adaptation to the factors impacting the efficient propagation of message packets through a mobile wireless network.
There is also a need for a MANET Node Device that minimizes the need for skilled installation and administration of the network by implementing protocols, techniques, mechanisms, and processes to self-initialize and auto-configure the network for optimized network reliability and availability, channel analysis and selection, security and other network services. There is also a need for a MANET Node Device that can select and use multiple radio transceiver channels while minimizing the impact of interference on message packet throughput.
There is a further need to integrate these protocols, techniques, mechanisms, and processes in a way that the MANET Node Devices are portable and usable in harsh physical environments and situations. According to these and other objectives, and to overcome limitations of the prior systems and other limitations that will be apparent upon reading and understanding the present application, the present invention is directed to a system and method for reliable data communication in a wireless network, especially when the routing nodes are mobile and the connections can be dynamic and arbitrary.
The preferred embodiment of the present invention includes a MANET Node Device having a power-efficient computing platform, enabling it to function under portable battery power. For example, a radio transceiver which supports IEEE approved or proposed standards The computing platform, radios and related electronics are encased in housing which reduces the egress and ingress of radio frequency interference RFI and mitigates the buildup of internal heat.
The present invention includes a message packet routing protocol implemented at OSI Layer 2. The protocol uses a hybrid path discovery technique comprised of both proactive and reactive path discovery methods and thus enables fast failover to alternate pathways while adding minimal protocol overhead.
For example, the proactive path discovery techniques of the message routing protocol include causing an introductory message to be generated by a MANET Node Device when a STA associates with an AP, as well as the reading, analysis and storage of reverse route information. Reactive path discovery techniques include a discovery request message that is sent by a MANET Node Device when a local table entry exists for the message destination. The MANET routing protocol also includes path cost calculations which encourage a preference for higher bandwidth connections, while emphasizing communications reliability.
The MANET routing protocol also includes Layer 2 flood control mechanisms for mitigating flood attacks and reducing the bandwidth impact of certain legitimate flood messages such as the MANET routing protocol discovery request messages and address resolution protocol arp requests used by Internet Protocol version 4 IPv4. The routing protocol includes detecting at least one data packet entering a port on the MANET Node Device and reading the associated message packet header information. The information in the header is then compared with information contained in a table stored and maintained locally by the MANET Node Device.
By way of example, the local table includes information related to at least destination address, source address, port, path cost, timestamp, source sequence number SSN , and alternate port and path cost for the MIP port connections available on the network. Based on the comparison, a data packet can be either dropped or prepared for transmission via a port connection on the MANET node. The protocol header is comprised of information related to the destination address, source address, source sequence number SSN , protocol identifier information, path cost, Ethertype, time-to-live and protocol flags.
ISBN 13: 9781402050657
At least some of the current information in an existing local table is updated based on the examination of the protocol header on a data packet received over a MIP connection from another MANET Node Device. The preferred embodiment of the system also provides multifunctional usage of radio transceivers in which each radio transceiver can provide both AP services for communicating with STAs and MIP connection services for node to node routing of message packets.
A routing protocol management application on the MANET Node Device prevents MIP connections from occurring between radio transceivers on the same MANET Node Device while still allowing message packets arriving on one radio transceiver to be forwarded out of the other transceiver, if the routing protocol's costing algorithm indicates. Automated management and startup processes are provided in which network and radio transceiver settings within the MANET Node Device are automatically configured. For example, wireless channel selection is automated through the startup process to accomplish the primary goal of choosing a radio transceiver channel with the strongest connection to a neighboring MANET Node Device, and the secondary goal of choosing the least noisy channel in order to reduce over use of frequencies.
At least one radio transceiver is configured for communications with other MANET Node Devices on the network and at least one radio transceiver can also be configured for AP communications with wireless STAs seeking access to the network. The radio transceiver channel assignments on the MANET Node Device can be automatically reconfigured based on changes in network operating conditions or manually configured by a network operator through an administrative process. In some embodiments, the system also connects the MANET Node Device network to other wireless and wired networks and enabling the exchange of message packets between the networks.
The MANET Node Device is equipped with at least one Ethernet interface or at least a second radio transceiver that is configured to establish a bridge, router or NAT router connection to another network.
For example, an Ethernet interface or a second radio transceiver on the MANET Node Device can be automatically or administratively configured to establish a bridge connection to another network through a wired or wireless connection. The MANET Node Device listens to all message traffic on both networks, and forwards each message packet to the network that is not the one from which the message packet was heard.
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The MANET Node Device associates stations with a particular network connection, and can then forward message packets in a more efficient manner, transmitting only over the appropriate connection. For example, a radio transceiver in the MANET Node Device can be administratively configured to establish either a peer-to-peer connection to a wireless ad hoc network or a STA connection to an AP on another wireless network. This connection can be configured to provide routing and networking functions such as Network Address Translation NAT , static ingress port forwarding, and static egress port forwarding to enable the forwarding of message packets from one network to another.
An administration system connects the MANET Node Devices with a software application that presents information to the administrative user about the current status of connections, security and performance of the MANET Node Device network and provides the administrative user with a means to affect changes to the current status.
More specifically, the administration system provides a graphical and tabular representation of the current topology of the wireless network, including objects representing each MANET Node Device, each associated station, and each MIP and AP connection.
Also by Liljana Gavrilovska
Additional status details are available to the administrative user that identify the specific channels used by a connection, signal and noise measurements, network address assignments, operational time, software versions, port configurations, access control settings, intrusion detection settings and state, among others. The graphical user interface provides access to this information through a combination of graphical representation, window tabs, pull-down menus and mouse over popups. The administrative user may affect changes to current settings and default configurations, override automatic settings, initiate built in testing, rearrange graphical display elements, manage security parameters, and other network administration functions.
An onboard testing and evaluation mechanism provides operator feedback regarding the functionality of hardware and software as well as the current status of wireless MIP connections to neighboring MANET Node Devices. More specifically, the testing and evaluation mechanism consists of a display, for example a multicolor Light Emitting Diode LED ; a user interface, for example a switch to provide power to the LED; and control software.
As further example, the LED will emit a continuous red light if an error state occurs and the LED will emit a blinking red light during a user initiated software update. A bi-directional frequency translator transverter downconverts and upconverts MANET Node Device radio transceiver signals to RF bands other than those provided by the radio transceiver.
The transverter interacts with the signal from the transceiver to either convert the transceiver transmit signal up to a higher frequency and convert the receive frequency down to the transceiver receive frequency, or convert the transceiver transmit signal down to a lower frequency and convert the receive frequency up to the transceiver receive frequency. The transverter, coupled with a low-noise amplifier appropriate for the frequencies being converted up or down to, provides a means to operate the MANET Node Device in frequencies with certain desirable characteristics, such as better propagation through obstacles.
A path cost algorithm encourages a preference for higher bandwidth connections, though it does not guarantee the connection with the maximum throughput.
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