Path gain algebraic formulation for the scalar linear network coding problem

  • Authors:
  • Abhay T. Subramanian;Andrew Thangaraj

  • Affiliations:
  • Department of Management Science and Engineering, Stanford University, Stanford, CA;Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai, India

  • Venue:
  • IEEE Transactions on Information Theory
  • Year:
  • 2010

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Abstract

In the algebraic view, the solution to a network coding problem is seen as a variety specified by a system of polynomial equations typically derived by using edge-to-edge gains as variables. The output from each sink is equated to its demand to obtain polynomial equations. In this paper, we propose a method to derive the polynomial equations using source-to-sink path gains as the variables. In the path gain formulation, we show that linear and quadratic equations suffice; therffore, network coding becomes equivalent to a system of polynomial equations of maximum degree 2. We present algorithms for generating the equations in the path gains and for converting path gain solutions to edge-to-edge gain solutions. Because of the low degree, simplification is readily possible for the system of equaltions obtained using path gains. Using small-sized network coding: problems, we show that the path gain approach results in simpler equations and determines solvability of the problem in certain cases. On a larger network (with 87 nodes and 161 edges), we show how the path gain approach continues to provide deterministic solutions to some network coding problems.