Route Discovery Latency in Wireless Mesh Networks

Solution Overview

Problem

On-demand routing protocols in wireless mesh networks, such as AODV, face significant route discovery latency when finding the best route between source and destination nodes, which is critical for real-time applications like voice and video communications.

Innovation Solution

Introducing an 'Intermediate Reply' (IR) flag in Route Request (RREQ) messages allows the first intermediate node with a valid route to respond with a Route Reply (RREP), establishing a temporary forward route, while downstream nodes suppress responses, enabling the destination node to select the best route based on end-to-end metrics and send a new RREP to establish the optimal path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the destination only flag is set in the RREQ by the source node, then the route discovery latency is large, but the up-to-date best route between the source node and the destination node is eventually discovered

Engineering Contradiction:

Improveroute qualityVSAvoidroute discovery latency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent segments the route discovery process into two phases: a fast phase where intermediate nodes can reply with RREP messages to establish temporary routes quickly, and a slow phase where only the destination node replies to ensure the best route is found. This is achieved by introducing a new flag in the RREQ message that controls whether intermediate nodes are allowed to reply, allowing the system to switch between the two phases as needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent makes the RREQ message dynamic by introducing a new flag that can be set or cleared by the source node based on the requirements of the current route discovery operation. This flag dynamically controls the behavior of intermediate nodes, allowing them to reply or not reply based on the current phase of route discovery, thus resolving the contradiction between speed and quality.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If the destination only flag is not set by the source node, then the source node can discover a route to the destination node more quickly, but the best end-to-end route may not be discovered

Engineering Contradiction:

Improveroute discovery latencyVSAvoidroute quality

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent segments the route discovery process into two phases: a fast phase where intermediate nodes can reply with RREP messages to establish temporary routes quickly, and a slow phase where only the destination node replies to ensure the best route is found. This is achieved by introducing a new flag in the RREQ message that controls whether intermediate nodes are allowed to reply, allowing the system to switch between the two phases as needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent makes the RREQ message dynamic by introducing a new flag that can be set or cleared by the source node based on the requirements of the current route discovery operation. This flag dynamically controls the behavior of intermediate nodes, allowing them to reply or not reply based on the current phase of route discovery, thus resolving the contradiction between speed and quality.

Inventive Principle:

Principle #15Dynamics

3Loss of time

If an intermediate node generates a RREP message, then the source node can discover a route more quickly, but the cached route in the intermediate node may not be the best route to the destination node

Engineering Contradiction:

Improveroute discovery latencyVSAvoidroute optimality

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent segments the route discovery process into two phases: a fast phase where intermediate nodes can reply with RREP messages to establish temporary routes quickly, and a slow phase where only the destination node replies to ensure the best route is found. This is achieved by introducing a new flag in the RREQ message that controls whether intermediate nodes are allowed to reply, allowing the system to switch between the two phases as needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses the new flag in the RREQ message as an intermediary mechanism to control the behavior of intermediate nodes. This flag acts as a mediator that determines whether intermediate nodes should reply with RREP messages or simply forward the RREQ, thus controlling the trade-off between speed and route optimality without requiring changes to the intermediate nodes themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8064416B2Route selection in wireless networks

Publication Date: 2011.11.22 INTERDIGITAL CE PATENT HOLDINGS SAS

AI summary

A method and apparatus are described for locating a route between a source node and a destination node in an on-demand wireless network including flooding the wireless network with a route request message by the source node and receiving a route reply message responsive to the route request message from a first intermediate node having a valid route to the destination node, wherein the first intermediate node responds to the route request message based on a condition of a flag in the route request message. Also described are a method and apparatus for locating a route between a source node and a destination node in an on-demand wireless network including receiving a route request message from the source node and responding to the route request message with a route reply message by a first intermediate node having a valid route to the destination node, wherein the intermediate node responds to the route request message based on a condition of a flag in the route request message.