Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Increased QoS through a Degraded Channel using a Cross-Layered HARQ Protocol Elliot Ranger Brad Gaynor

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Topics Review Project Overview Simulation Plan Simulation Execution Future Work

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Previous Comments Won’t the protocol use more power to form a cluster? –Yes, but link integrity will increase –May result in lower energy consumption to the network Less energy drain on a single node More efficient routes discovered faster –But, will add overhead to the overall network (congestion) Where is the cluster intelligence? –Distributed in each node Nodes query their neighbors for assistance How/When does the cluster dissolve? –When a better route is discovered One node always gets the correction through Other metrics When do you stop sending FECs? –Same as existing HARQ protocols

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Review Take advantage of localized temporal uncertainty –A lower probability link may have a better chance of success at any given time A lower probability link may be incorrectly labeled as such Varying network topology Localized noise characteristics Send different FEC from multiple sources –Increases probability of receiving the correct message –Multiple transmit nodes relieve the strain on a single node

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Thesis Thesis: HARQ using multiple, collaborative nodes results in increased probability of message reception and extends the overall lifetime of the network.

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Project Overview Implementation –Prior work HARQ Turbo Codes –Cross-layer support Network Protocol Network/Data-link layer interface Simulation –Model network Topology Noise Mobility –Simulate implementation

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Simulation Scenarios Sim 1 - Simple Topology –Fixed Transmitter –Mobile Receiver –Results: errors due to path loss Sim 2 - ARQ –Same Network Topology –Add Automatic Repeat Request Sim 3 – Multiple Nodes –Add our approach of multiple collaborative nodes Sim 4 – HARQ –Add HARQ protocol Sim 5 – Complete Simulation –Our approach on a complete mobile ad-hoc network –Many nodes and events

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Sim 1 – Node & Process Models Node Models –Transmitter Packet Generator Radio Transmitter Antenna –Receiver Antenna Radio Receiver Packet Sink Process Model –Simple Source Generates Packets Interval Time Size of Packet Sends to Transmitter

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Sim 1 – Network Model Network Model –Describes Network Topology –Fixed Transmitter –Mobile Receiver Trajectory (Green Arrow) –Noise Model

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Sim 1 – Simulation Results Signal-to-Noise Ratio –Decreases as mobile receiver moves away from transmitter –Path Loss is modeled as 1/R 2 Bit Error Rate –Increases as mobile receiver moves away from transmitter

Tufts University. EE194-WIR Wireless Sensor Networks. March 3, 2005 Future Work In progress –Building a simple ACK/NACK protocol –Modeling noise & channel characteristics –Simulation 2+ Statistical models –Noise (Gaussian) –Bit Error (Model for receiver sensitivity) –Packet Loss (S/N + FEC gain) Mathematical models –Write models to describe the theory we are attempting to prove in simulation