Binary-Tree Encoding for Uniform Binary Sources in Index Modulation Systems

Justin Coon, Mihai-Alin Badiu, Ye Liu, Ferhat Yarkin, Shuping Dang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The problem of designing bit-to-pattern mappings and power allocation schemes for orthogonal frequency-division multiplexing (OFDM) systems that employ subcarrier index modulation (IM) is considered. We assume the binary source conveys a stream of independent, uniformly distributed bits to the pattern mapper, which introduces a constraint on the pattern transmission probability distribution that can be quantified using a binary tree formalism. Under this constraint, we undertake the task of maximizing the achievable rate subject to the availability of channel knowledge at the transmitter. The optimization variables are the pattern probability distribution (i.e., the bit-to-pattern mapping) and the transmit powers allocated to active subcarriers. To solve the problem, we first consider the relaxed problem where pattern probabilities are allowed to take any values in the interval [0,1] subject to a sum probability constraint. We develop (approximately) optimal solutions to the relaxed problem by using new bounds and asymptotic results, and then use a novel heuristic algorithm to project the relaxed solution onto a point in the feasible set of the constrained problem. Numerical analysis shows that this approach is capable of achieving the maximum mutual information for the relaxed problem in low and high-SNR regimes and offers noticeable benefits in terms of achievable rate relative to a conventional OFDM-IM benchmark.
Original languageEnglish (US)
Pages (from-to)1270-1285
Number of pages16
JournalIEEE Journal of Selected Topics in Signal Processing
Issue number6
StatePublished - May 2 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by EPSRC grant numbers EP/R511742/1 and EP/N002350/1. The authors also wish to acknowledge the support of the Telecommunications Research Laboratory of Toshiba Research Europe Ltd.


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