Slide 1

Presented By:

Madhushri N Kumar

1CR14LDC06

Ally Friendly Jamming

Agenda

Introduction

What is jamming

Ally Friendly Jamming

Illustration

Generation of Jamming Signals

Synchronization of Ally Jamming Signals

Introduction of pilot frequency

Detecting and recovering transmissions

Dealing with multiple jammers

Dealing with multiple transmitters

Limitations

conclusion

Introduction

Wireless Communication technology is widely deployed and increasingly adopted.

Ease of installation and reduced operational cost.

Efforts on adopting wireless communication in emerging and mission critical applications.

Desirable to provide protection to the network.

Jamming in wireless communication is threat.

What is Jamming?

Transmission of radio signals that disrupt communications by decreasing the signal noise ratio.

Effects

* channel busy

* transmission delayed

* new packets dropped when buffer is full

* unable to decode by the receiver.

Ally friendly Jamming

Disables unauthorised devices and allows authorised devices

Uses secret keys

Three technical challenges:

*Irresolvable interference.

*Synchronisation

* multiple ally jammers

Illustration

Ally jammer (Aj) and authorised users A1, A2 share a secret key

Generation of ally jamming signals

Epoch index,

The key and the epoch index to generate jamming symbols.

Synchronization with ally jamming signals

Introduction of Pilot frequencies

Pilot frequency is a 1hz wide frequency.

Used to compensate for frequency offset as well as identify ally jammers.

A pilot frequency is injected along the psuedo random jamming signals into the channel.

Authorized device use this pilot frequency to identify the associated ally jammer.

Detecting and Recovering Transmissions

Initial synchronization is done soon when the authorized device joins the network.

Resynchronization has to be done periodically.

If no transmissions, the channel coefficients tend to be stable.

If authorized transmissions, the stability of channel coefficients is corrupted by the received signal.

Dealing with Multiple Ally Jammers

Synchronization with multiple ally jammers

Ally Jammers are detected by computing FFT.

Authorized transmission detection and recovery.

Channel coefficient is stable for no authorized transmission.

On detection of authorized transmission, the channel coefficient corrupts.

Applying the channel coefficients to estimate the received ally jamming signals, the transmitted signal can be detected.

Dealing with multiple authorized Transmitters.

Ally Jamming signals occupy the channel, MAC protocol cannot be applied.

Transmission detection techniques are used.

Channel coefficients are computed between itself and multiple ally jammers.

If channel coefficients are stable- no ongoing transmission.

If channel coefficients is found corrupted- authorized transmitters will back-off for a random time.

Limitation

Fast identification of Ally Jammers

The attacker can inject the pilot frequency to mislead the authorized receivers

Fast Synchronization

Shifting correlation based synchronisation is expensive in computation

Ally friendly Jamming with MIMO devices

More studies are required for MIMO devices case

Conclusion

A mechanism that jams unauthorized wireless communication and maintain legitimate communication at the same time.

It is achieved by sharing secret keys among authorized devices and ally jammers.

Future work includes enhancing the robustness of ally friendly Jamming attacks.

THANK YOU

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