Wi-FM Resolving Neighborhood Wireless Affairs by Listening to Music - - PowerPoint PPT Presentation

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Wi-FM Resolving Neighborhood Wireless Affairs by Listening to Music - - PowerPoint PPT Presentation

Nov 16, 2022 382 likes •722 views

Wi-FM Resolving Neighborhood Wireless Affairs by Listening to Music Marcel Flores, Uri Klarman, and Aleksandar Kuzmanovic ICNP 2015 1 The home network Many 802.11 devices. Many 802.11 networks! Many are poorly configured.

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Wi-FM

Resolving Neighborhood Wireless Affairs by Listening to Music

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Marcel Flores, Uri Klarman, and Aleksandar Kuzmanovic

ICNP 2015

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The home network

  • Many 802.11 devices.
  • Many 802.11 networks!
  • Many are poorly configured.
  • Overlapping Wi-Fi channels.
  • Controlled by many different

“operators.”

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An example

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Sender A Sender B

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An example

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Sender A Sender B

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Crossing the lines…

  • How can neighbors interact?
  • Can’t require APs to explicitly communicate.
  • Can’t depend on any kind of AP based signal.
  • We will solve this using an ambient radio signal for

coordination.

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What kind of coordination?

  • We are not interested in packet level scheduling.
  • Don’t want to alter 802.11 itself.
  • Would like an approach that allows efficient sharing

when the networks are busy.

  • This will be achieved with block scheduling.

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FM radio

  • Ubiquitous in the United States and Europe.
  • Penetrates Buildings (unlike GPS).
  • Cheap and prevalent antennas.
  • Already included on many Wifi/BT chipsets.
  • Comes with included digital signal (RDS).

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Radio Data System

  • Designed to provide additional meta-information about a

radio broadcast.

  • Program name, alternative frequencies, etc.
  • Broadcast alongside FM signal at the 3rd harmonic of

19kHz pilot.

  • Includes a well defined structure.

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SLIDE 9

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103

PI CODE CRC GID

25 51 77 Data Data

CRC

A B C D

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Block layout Repeating code

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How do we use it?

  • Use RDS bits as our base unit of time.
  • Data rate of 1187.5 bps.
  • Use structure to synchronize to RDS signal.
  • Implement non-exclusive scheduling in terms of the

blocks.

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How do senders schedule?

  • Sample the channel, determine which blocks are
  • ccupied by other senders.
  • Determine a fair share.
  • Choose the least contested blocks.
  • Repeat process to ensure continued fairness.

25 51 77 103

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Our implementation

  • NooElec DVB-T USB radio.
  • GnuRadio using RTL SDR .
  • Testbed:
  • Arch Linux 3.17.3, on 3.3 Ghz

Intel i5 processor.

  • TP Link TL-WDN3800 802.11n

card, Ath9k driver.

  • Modified “plug” qdisc to control

traffic.

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Delay between nodes

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`

Delay between nodes is well under 1ms.

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Sync time

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WiFM maintains a near perfect sync rate

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Neighborhood coordination

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Sender A Sender B

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25 51 77 103 Bit Index 10 20 30 40 50 60 70 80 Packets Sender A Available 25 51 77 103 Bit Index 5 10 15 20 25 30 35 40 Packets

Sender A

(a)

25 30 35 40 45 ckets

Sender A Sender B

Neighborhood coordination

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Sender A Available

(a)

25 51 77 103 Bit Index 5 10 15 20 25 30 35 40 45 Packets

Sender A Sender B

Sender A Sender B

(b)

30 40 50 60 70 Packets

Sender A Sender B

Neighborhood coordination

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Bit Index Sender A Sender B

(b)

25 51 77 103 Bit Index 10 20 30 40 50 60 70 Packets

Sender A Sender B

Sender A Sender B

(c)

Neighborhood coordination

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All nodes are scheduled on non-overlapping blocks.

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Throughput gain

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Throughput gains achieved 80% of the time.

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Neighborhood coordination

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More complex arrangements are possible.

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Throughput gain

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Greater gains are achieved.

`

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Summary

  • Used FM Radio as an external coordination mechanism.
  • First to provide a neighborhood coordination

mechanism for use across networks.

  • Demonstrated implementation which relies on

straightforward coordination process.

  • Showed throughput gains in testbed experiments.

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Thank you!

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Extras

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Related work

  • A large body of work exists on performing TDMA with

802.11 networks.

  • Inn the realm of enterprise/managed networks, don’t

apply to home networks.

  • Significant work in general synchronization.
  • Including the use of RDS.
  • We are the first to consider neighborhood setting.

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Testbed arrangement

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Negative schedules

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Negative schedules

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25 51 77 103 Bit Index 10 20 30 40 50 60 70 80 Packets Sender 1 Light 25 51 77 103 Bit Index 5 10 15 20 25 30 35 40 Packets

Sender A

25 51 77 103 Bit Index 5 10 15 20 25 30 35 Packets

Sender 1 Sender 2 Sender 3

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Negative schedules

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Latency improved by nearly 40ms

10 20 30 40 50 60 70 80 Latency (ms) 0.0 0.2 0.4 0.6 0.8 1.0 CDF of Flows

Light Light + Heavy WiFM With Both

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Negative schedules

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Negative schedules

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