Mutually Interfering Relay Channels

1
Towards Harnessing Relay Mobility in MANETs Rohit
Naini, Pierre Moulin - University of Illinois,
Urbana-Champaign
Introduction
Relay Channel as part of a MANET
Mutually Interfering Relay Channels

• The relay channel with single interferer
  though a good starting point , yields simplistic
  solutions.
• An actual Adhoc Network could potentially have
  several interfering transmissions.

Locations Should be Jointly Optimized
Relay
Relay
Sensors (Accelerometers)
Processing Module
Mobile Relays

• Sensors measure
• user activity
• Convert activities
• to calories burnt

Source
Destination
Compress and Forward rate vs Relay Position
Source
Calculations Log on PDA

• Mobility should be viewed as a resource in an
  Adhoc Network
• Exploring the potential held by mobility in a
  Relay Channel can provide valuable insights for
  larger networks

optimal location
Source
Destination
Destination

• This problem introduces aspects such as
  inter-nodal cooperation in different parts of the
  network.
• The joint-mobility of several nodes entitles a
  multiple objectives game-theoretic approach.
• Solving this problem would give valuable
  insight into interaction between coexistent
  non-cooperating network blocks

Source
Relay Position- Angular
Relay Position radial
Destination

• The transmissions from rest of the network are
  assumed to be from unknown Gaussian codebooks
• Correlation between noises at Relay and
  Destination are computed based on Relay position
  with respect to the position of interfering
  nodes.
• The throughputs of the three relay schemes are
  evaluated by varying the relay location

Interferer Locations (0.7,45),(0.7,72),(0.7,135
)
Relay Channel with Single Interferer

• Relay Channel capacity is unknown but
  surrogate performance metrics can be used
• Cut-set Bound
• Decode-Forward Rate
• Compress Forward Rate
• A Gaussian Channel model is employed with a
  corrected quadratic path loss
• External Interferer emits Gaussian signal with
  an unknown codebook
• Subject to mobility restrictions, optimal relay
  location/scheme can be chosen

Conclusion and Future Directions
Simulation Analysis and Discussion

• Interference management holds the key to
  improving Adhoc Network performance
• Mobility can be used to minimize the malicious
  impact of interference between the different
  parts of the network
• The usually sub-optimal Compress-Forward scheme
  proves helpful in a system marred with a high
  degree of interference
• Future Directions
• Understand the role of mobility in other adhoc
  network blocks.
• Devise mobility strategies for cooperative
  multi-hop relaying

• The optimal relay locations vary significantly
  based on the scheme being used
• For a Decode-Forward scheme, it is optimal for
  the relay to relocate itself away from the
  Interfering nodes
• For a Compress-Forward scheme, relay should
  relocate itself to a point with higher
  interference reception and good correlation to
  Destinations Noise
• Compress-Forward scheme exploits the noise
  correlation to allow cooperation between the
  Relay and Destination
• Compress-Forward is well suited when there is
  a relatively close interfering node with high
  power

Node Polar Co-ords Source (0,0) Destination
(1,0) Interferer (0.5,45)
Compress-Fwd
Cut Set Bound
Decode-Fwd