Reliable and secure communication schemes for wireless networks.

摘要

The focus of this dissertation is on reliable and secure communication schemes. This topic is motivated by the vast increase in the amount of data which is transmitted, compressed, and stored every day, in particular via wireless networks. The need for reliable and secure communications is more important than ever before. The dissertation studies properties of the so-called good codes, their performance and design with several communication schemes essential to reliability of wireless networks, and concludes with the study of rate achievable with good random codes when also perfect message confidentiality is desired.; We first focus on the class of good codes, including turbo, low-density parity-check, and repeat-accumulate codes. Their performance is characterized by a threshold behavior in a single channel model. We investigate the weight spectrum of good code sequences and derive a necessary and sufficient goodness condition for binary-symmetric and additive white Gaussian noise channels.; Next, we study the error probability performance of good codes for parallel communication channels. We investigate reliable channel regions which ensure reliable communications over parallel channels with good code ensembles. To construct reliable regions, we study the modified 1961 Gallager bound for parallel channels. By allowing codeword bits to be randomly assigned to each component channel, the average parallel-channel Gallager bound is simplified to be a function of code weight enumerators and channel assignment rates. Special cases of this bound, Union-Bhattacharyya, Shulman-Feder, Simplified-Sphere, and Modified Shulman-Feder parallel-channel bounds, allow for describing reliable channel regions using simple functions of channel and code spectrum parameters.; Finally, we focus on information-theoretic security for multi-terminal networks. We consider discrete memoryless interference and broadcast channels in which independent confidential messages are sent to two receivers. We also consider a two-user discrete multiple-access channel in which one user wishes to communicate confidential messages to a common receiver while the other user is permitted to eavesdrop. Confidential messages are transmitted to the desired receiver with perfect secrecy, as measured by the equivocation rate at the other receiver. We derive inner and outer bounds for the achievable rate regions for these three communication systems, achievable by good random binning codes.