Magneto-inductive Passive Relaying in Arbitrarily Arranged ... · Ad-Hoc and Sensor Networking Symposium, ICC 2017, Paris AHSN-IS04: Ad Hoc Networks G. Dumphart, E. Slottke, A. Wittneben

Ad-Hoc and Sensor Networking Symposium, ICC 2017, Paris

AHSN-IS04: Ad Hoc Networks G. Dumphart, E. Slottke, A. Wittneben May 24, 2017 1

Magneto-inductive Passive Relaying in Arbitrarily Arranged Networks

Concept: presence of resonant

relay coils improves the link

SotA: regular arrangements

lead to large gains [6]-[8] (in the paper)

Our Vision: passive relaying in

arbitrarily arranged networks

Open: gains and behavior?

Passive Relaying

Applications: NFC, WPT,

WSNs in harsh environments

Passive Relaying: nearby

idle nodes serve as relays

extends usable range

Magneto-Inductive PHY

First analysis of near-field

passive relaying in arbitrary

arrangements

Channel gain derived for the

general passive relaying case

with full network coupling

Effects of arbitrary geometry:

Gain governed by sum of

non-co-phased terms

Frequency-selective fading

Optimization for improved

relay utilization:

Frequency tuning

Relay load switching:

large and reliable gains

Contributions




Arbitrary network geometry:

no distinct path(s)

Model Tx-Rx link as

two-port, incorporating the

effect of full relay coupling

loaded relays (𝑁 × 𝑁)

Two-port

FormulationCircuit

Analysis

Gain over Two-Port

Maximum power gain

over two-port, achieved

with simultaneous

conjugate matching:

coupling to

relays (2 × 𝑁)coupling w/o relays




Relay Density

10 / dm3

Non-co-phased summands f-selective fading

coupling w/o relays

Coil Ø L R f

24 mm 3.7 𝜇H 1 Ω 13.56 MHz

Simulation Parameters

Example Spectra of Relaying Channels

Regular relay geometry

Arbitrary relay geometry

Two-port Transimpedance

Arbitrary relay geometry

no

relays

no relays

500 mm

Considered Tx-Rx

arrangements:

Coaxial

Misaligned

(shown) mostly

large gains

small gains

or losses




Practical relay gains are limited to the

compensation of Tx-Rx misalignment

Further gains (i.e. highly co-phased terms) unlikely

Optimize relay utilization

Statistics for Random Arrangements

Relay Density

10 / dm3

Non-co-phased summands f-selective fading

Coil Ø L R f

24 mm 3.7 𝜇H 1 Ω 13.56 MHz

Simulation Parameters

500 mm

Considered Tx-Rx

arrangements:

Coaxial

Misaligned

(shown)

coupling w/o relays

Two-port Transimpedance




reposition relays:

unattractive for

applications ✘

Channel Gain Optimization: Degrees of Freedom & Results

f - tuning

genetic load

switching

all resonant

no relays

after load switching

(genetic algorithm)

all relays resonant

(no optimization)

f - tuning

Load Opt.

Adaptive

Impedance

Load Switching: {open circuit, resonant}

Lower

Complexity

frequency tuning:

choose 𝜂 −maximizing

operation frequency

load switching: 2𝑁 possible

switching states find high−𝜂state with genetic algorithm




Low-Complexity Switching Schemes

f - tuning

genetic load

switching

all resonant

no relays

Reliability Evaluation via Data Rates

By 𝜂 −maximizing exhaustive search, set …

… 1 relay resonant, other N-1 open circuited

compensates Tx-Rx misalignment

… 1 relay open circuited, other N-1 resonant

shuts down most destructive relay

Average Rate

1% Outage Rate

Even without optimization, the outage rate

benefits from passive relaying,

With load switching, the outage rate

approaches the avg. rate (channel hardening)

Documents

Magneto-inductive Passive Relaying in Arbitrarily Arranged ... · Ad-Hoc and Sensor Networking Symposium, ICC 2017, Paris AHSN-IS04: Ad Hoc Networks G. Dumphart, E. Slottke, A. Wittneben