Math @ Duke

Publications [#235816] of Robert Calderbank
Papers Published
 Calderbank, AR; Fishburn, PC, Normalized second moment of the binary lattice determined by a convolutional code,
IEEE Transactions on Information Theory, vol. 40 no. 1
(1994),
pp. 166174 [doi]
(last updated on 2018/02/20)
Abstract: We calculate the perdimension mean squared error μ(S) of the twostate convolutional code C with generator matrix [1,1+D], for the symmetric binary source S = {0,1}, and for the uniform source S = [0,1]. When S = {0,1}, the quantity μ(S) is the second moment of the coset weight distribution, which gives the expected Hamming distance of a random binary sequence from the code. When S = [0,1], the quantity μ(S) is the second moment of the Voronoi region of the modulo 2 binary lattice determined by C. The key observation is that a convolutional code with 2v states gives 2v approximations to a given source sequence, and these approximations do not differ very much. It is possible to calculate the steady state distribution for the differences in these path metrics, and hence, the second moment. In this paper we shall only give details for the convolutional code [1,1+D], but the method applies to arbitrary codes. We also define the covering radius of a convolutional code, and calculate this quantity for the code [1,1+D].


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