Research Article A Multiple-Access Time and Frequency Spectrum-Spreading Modulation Samer S. Saab , Joe Khalife, and Rayana H. Jaafar Department of Electrical and Computer Engineering, Lebanese American University, Byblos, Lebanon Correspondence should be addressed to Samer S. Saab; ssaab@lau.edu.lb Received 13 June 2018; Revised 30 September 2018; Accepted 8 October 2018; Published 25 October 2018 Academic Editor: Andr´ e de Almeida Copyright © 2018 Samer S. Saab et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this paper a novel modulation scheme called Carrier Interleaved Multiple Access (CIMA) is proposed. CIMA provides an alternative for multiple-access modulation accommodating resistance to noise and channel interference. Te approach is based on polar signaling modulated with an FM-like composite sinusoidal function. Te user assigned frequency deviation and modulation index are strictly related and unique. Te latter parameters are generated using a nontraditional pseudorandom noise generator (PRNG). Tis PRNG provides CIMA with low interference capability between cochannels and adjacent channels. CIMA can be considered for a single-user or multiple-access technique. Selected CIMA characteristics are presented. In order to numerically illustrate the efectiveness of the proposed modulation scheme, the performance of CIMA is compared with the conventional direct- sequence spread spectrum binary phase-shif keying (DSSS-BPSK) modulation. 1. Introduction Wireless communications connect more devices than people and the trend is only increasing in both venues. Te number of connected devices per person rose to 1.84 in 2010 [1], and it is expected that we will have seven trillion devices connected wirelessly by 2020 [2]. Over the past ten years smartphones and tablet PCs resulted in a signifcant increase in the number of devices connected to the internet. However, other prospec- tive wireless applications such as vehicle-to-vehicle commu- nication, applications based on the use of radio frequency identifcation (RFID), wireless electric meters, and other applications not yet envisaged may evolve. Consequently, an increase in investigation activities towards various and novel wireless communication schemes associated with diferent applications is desired. Common characteristics for wireless communication systems remain to include spectral efciency, security, and interference resistance. Spread spectrum techniques are employed for secure communications, increasing resistance to interference, noise, and jamming. Diferent techniques of spread spectrum include frequency-hopping spread spectrum (FHSS), direct- sequence spread spectrum (DSSS), time-hopping spread spectrum (THSS), chirp spread spectrum (CSS), and in some cases combinations of these forms. For example, in Multicarrier Direct-Sequence CDMA (MC-DS-CDMA) time and frequency spreading is used [3]; also lattice reduction theory and aided multiple user detection is applied to a spread spectrum system leading to near-far efect suppression [4]. A conventional spread spectrum system employs pseudo- noise (PN) code generators while other schemes employ nondeterministic spreading codes generated from a random input data stream such as the self-encoded spread spectrum (SESS) [5]. Ultra-wideband (UWB) is another modulation technique [6] that possesses similar characteristics to spread spectrum. It is based on transmitting short duration pulses and is applied to short-range wireless communication. In order to improve its performance, DSSS techniques have been introduced to UWB systems [7]. Another technique is the chaotic communication where a noise-like, aperiodic, chaotic signal is employed to modulate the information signal. Diferent chaos modulation techniques have been proposed (see, e.g., [8, 9] and references therein). In Diferential Chaos Shif Keying (DCSK), index modulation is integrated to improve the system’s data rate and energy efciency such as permutation index DCSK (PI-DCSK) [10] and Commutation Code Index DCSK (CCI-DCSK) [11]. Recently, Code Index Hindawi Wireless Communications and Mobile Computing Volume 2018, Article ID 8920746, 10 pages https://doi.org/10.1155/2018/8920746