Twin tree hierarchy: a regularized approach to construction of signature matrices for overloaded CDMA. Issue 17 (10th October 2016)

• Record Type: Journal Article
• Authors: Singh, Amiya; Singh, Poonam; Amini, Arash; Marvasti, Farokh
• Is Part Of: Wireless communications and mobile computing. Volume 16:Issue 17(2016)
• Page Start: 3070
• Page End: 3088
• Publication Date: 2016-10-10
• Subjects: overloaded CDMA -- uniquely decodable codes -- orthogonality -- multiple access interference (MAI) -- twin tree hierarchy -- decoder -- bit error rate (BER); Wireless communication systems -- Periodicals; Mobile communication systems -- Periodicals; 621.38205
• DOI: 10.1002/wcm.2732
• Languages: English
• ISSNs: 1530-8669

Abstract

Abstract: Overloaded code division multiple access being the only means of the capacity extension for conventional code division multiple access accommodates more number of signatures than the spreading gain. Recently, ternary Signature Matrices with Orthogonal Subsets (SMOS) has been proposed, where the capacity maximization is 200 % . The proposed multi‐user detector using matched filter exploits the twin tree hierarchy of correlation among the subsets to guarantee the errorless recovery. In this paper, we feature the non‐ternary version of SMOS (i.e., 2 k ‐ary SMOS) of same capacity, where the binary alphabets in all the k constituent (orthogonal) subsets are unique. Unlike ternary, the tree hierarchy for 2 k ‐ary SMOS is non‐uniform. However, the errorless detection of the multi‐user detector remains undeviated. For noisy transmission, simulation results show the error performance of the right child for each subset of 2 k ‐ary to be significantly improved over the left. The optimality of the right child of the largest (Hadamard) subset is also discovered. At higher loading, for larger and smaller subsets the superiority is reported for the 2 k ‐ary and ternary, respectively, and the counter‐intuitive deviations observed for the lower loading scenarios are logically explained. For the overall capacity maximization being 150 %, superiority is featured by the 2 k ‐ary, but beyond, it becomes a conditional entity. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : This paper introduces the non‐ternary version of construction of signature matrices with orthogonal subsets for overloaded CDMA with a maximum capacity of 200%. The construction of the proposed signature matrices with orthogonal subsets, similar to its ternary counterpart, is also driven by the twin tree hierarchy of correlation among its constituent subsets. The paper, as a whole, focuses on comparing the variation of the twin tree hierarchy and error performance of the signature elements of different subsets for noisy transmission.