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Browse Prior Art Database

Method for Noise Floor based routing in Wireless Ad-Hoc Networks

IP.com Disclosure Number: IPCOM000032826D
Original Publication Date: 2004-Nov-12
Included in the Prior Art Database: 2004-Nov-12
Document File: 5 page(s) / 185K

Publishing Venue

Motorola

Related People

Kwan-Wu Chin: AUTHOR [+6]

Abstract

Existing ad hoc routing metrics do not give an indication how congested the wireless channel is at a particular node in the network, and hence do not allow for routing around any highly congested portion of the meshed network. For example if there are multiple nodes transmitting, a node may suffer severe interference due to transmission from nearby nodes. Moreover, once a link or route is chosen the resulting transmissions may reduce the effective bandwidth of other nodes in the vicinity. These problems are particularly serious in networks with single channels, which may include 4.9GHz MCLB incident scenes, or even large citywide mesh networks that are spectrum limited.

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Method for Noise Floor based routing in Wireless Ad-Hoc Networks

By Kwan-Wu Chin, Raad Raad, Darryn Lowe, Ramandeep Ahuja, Surender Kumar, Mario DeRango

 
 

PROBLEM       

Existing ad hoc routing metrics do not give an indication how congested the wireless channel is at a particular node in the network, and hence do not allow for routing around any highly congested portion of the meshed network.  For example if there are multiple nodes transmitting, a node may suffer severe interference due to transmission from nearby nodes.  Moreover, once a link or route is chosen the resulting transmissions may reduce the effective bandwidth of other nodes in the vicinity.  These problems are particularly serious in networks with single channels, which may include 4.9GHz MCLB incident scenes, or even large citywide mesh networks that are spectrum limited.

Figure 1 shows a conceptual view and resulting noise/interference level of two different traffic streams flowing through a wireless ad hoc network. Note that the term cluster is loosely defined as a set of nodes that affect each other’s perception of channel quality and experience similar noise/interference level. The shape of the cluster will primarily be determined by the flow of traffic.  We see that that nodes belonging to the middle (or purple) square will experience the highest level of noise/interference because both traffic streams are routed across them.  In a dense Mobile Ad-Hoc/Mesh Network, or even a Fixed Ad-Hoc/Mesh Network a routing protocol should avoid congested cluster of nodes and also determine whether routing traffic through a given route would cause an unacceptable increase in latency due to congestion delay.

In addition according to the paper,  “Kaixin Xu, Mario Gerla and Sang Bae (2002) How Effective is the IEEE 802.11 RTS/CTS Handshake in Ad-Hoc Networks? IEEE Globecom 2002”, the transmission range of RTS/CTS does not guarantee that hidden

nodes are not affected by a node’s transmission after receiving a CTS message.  This is because the interference range is much larger than the transmission range. 

Therefore, there is a need for a new routing metric that is sensitive to the causal effect of transmission of packets over a chosen path.  In other words, we want to choose a route that has acceptable interference before and after packet transmissions.

PROPOSED SOLUTION

This proposed solution enables each wireless ad hoc node to build a map called noise/interference map (or nMap) that indicates the observed noise/interference level on a given wireless channel.  This map is periodically updated in real-time to capture the current state of the wireless channel.

The nMap constructed by each node is then passed to other neighboring nodes in ROUTING ADVERTISEMENT messages which in turn include the received nMap in their ROUTING ADVERTISEMENT messages.  This enable each node to view the current noise/interference levels of nodes in a N hop range.  Each nodes will use...