mx-mac: a mobility-aware mac protocol for medical applications

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01062 Dresden, Germany. Email: {Jianjun.Wen ... wakes up and replies to sender with its address ... Case 5: Handover Phase A new free receiver wakes up and ...

Department of Computer Science Institute for Systems Architecture, Computer Networks Group

MX-MAC: A MOBILITY-AWARE MAC PROTOCOL FOR MEDICAL APPLICATIONS Motivation

Contributions

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Wireless sensor nodes employed in medical application are not always static

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Stochastic link quality estimation model to detect link quality during run time

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Mobility of nodes may lead to frequently link disconnection and establishment, which potentially increase packet loss and latency

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Lightweight Neighbor discovery algorithm to search for new receivers after detecting weak link quality

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Single packet transmission scheme is not sufficient for some applications which require large amount of packets in burst

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Seamless Handover without link disruption. It keeps link connection while discovering new links.

A Mobility-Aware MAC Protocol for Medical Applications

MX-MAC

Seamless Handover Process ·

Case 1: Initial Phase sending preambles to discover new receiver

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Case 2: Early ACK Phase new receiver wakes up and replies to sender with its address information

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Case 3: Normal Phase Transmitting messages to specific receiver in burst

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Case 4: Neighbor Discovery Phase sender continues transmitting message to original receiver while discovering new receiver by embedding handover request to destination address

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Case 5: Handover Phase A new free receiver wakes up and replies to the handover request

Link Quality Estimation and Decision Mechanism Predition

RSSI Partition

Decision

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10 consecutive RSSI values as one slot

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Employ LMS adaptive filter to predicate link quality

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Partition RSSI range into 5 link quality levels, each level has 20 dBm width

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Affordable computational complexity. It requires only 17 multiplications and 15 additions for one prediction

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Using probability method to determine link quality level

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handover Immediate Handover

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Take both current link quality level and predicted one into account

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Two static receivers deployed in a distance of 30m. The mobile node walked from R1 towards R2 at a normal speed (1.5 m/s)

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Integrate with time-based and trend-based algorithm

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Handover happened when link quality became weak

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Predefined rule-based decision module

No additional configuration

Evaluation Packt Loss ·

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Distance is the main factor that affects link quality Handover mechanism can reduce packet loss

Single-Hop Latency ·

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Seamless handover mechanism introduces little latency In neighbor discovery phase, waiting ACK timer is the main factor of latency

Contact: Jianjun Wen, Waltenegus Dargie TU Dresden, Department of Computer Science, Computer Networks Group 01062 Dresden, Germany Email: {Jianjun.Wen, Waltenegus.Dargie}@tu-dresden.de

Ping Pong Handover ·

The distance between R1 and R2 was 40m

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Handover occurred back and forth in the middle area of R1 and R2

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