Channel Knowledge Research Articles

Multi-Layer Precoding: A Potential Solution for Full-Dimensional Massive MIMO Systems

Massive MIMO systems achieve high sum spectral efficiency by simultaneously serving large numbers of users. In time division duplexing systems, however, the reuse of uplink training pilots among cells results in channel estimation errors, which causes downlink inter-cell interference. Handling this interference is challenging due to the large channel dimensionality and the high complexity associated with implementing large precoding/combining matrices. In this paper, we propose multi-layer precoding to enable efficient and low-complexity operation in full-dimensional massive MIMO, where a large number of antennas are used in two dimensions. In multi-layer precoding, the precoding matrix of each base station is written as a product of a number of precoding matrices. Multi-layer precoding: 1) leverages the directional characteristics of large-scale MIMO channels to manage inter-cell interference with low channel knowledge requirements and 2) allows for an efficient implementation using hybrid analog/digital architectures. We present and analyze a specific multi-layer precoding design for full-dimensional massive MIMO systems. The asymptotic optimality of the proposed design is then proved for some special yet important channels. Numerical simulations verify the analytical results and illustrate the potential gains of multi-layer precoding compared with other multi-cell precoding solutions.

IQ Imbalance Compensation for Generalized Frequency Division Multiplexing Systems

Generalized frequency division multiplexing (GFDM) with a flexible structure is one of the promising candidates for the fifth generation wireless communication system. This letter presents a compensation scheme of in-phase and quadrature (IQ) imbalance caused by radio frequency front-end for GFDM. The motivation behind this letter is to relax the requirement on time-invariant channel in the process of estimating IQ imbalance parameters. A low computational complexity approach is proposed to directly estimate IQ imbalance parameters without any prior knowledge of channel. Meanwhile, the structure of training sequences that avoid channel estimation is derived. Simulation results confirm that the proposed method can reduce the effects of IQ imbalance and provide reliable performance even over severe IQ imbalance environment.

Time is Ripe for Knowledge Synthesis: (Re)inventing Technologies, Outlets, and Incentives

This panel symposium gathers five former AOM presidents to discuss how we can create a knowledge synthesis ecosystem, by (re)inventing our technologies, outlets and research incentives. It is timely to revisit Herbert Simon (1967)¡¯s concern of persistant gaps between ¡°the world of practice¡± and the ¡°sciences¡± of business scholarship given this year¡¯s theme of ¡°At the Interface¡±. Although we have much reason to celebrate the introduction of top scientific journals in management for their impact on the research climate and contributions to our knowledge ecosystem, we should also acknowledge several deficiencies that make knowledge accumulation via academic journal publication exceedingly difficult to achieve. One of the most salient consequences of the weak connection between management scholarship and practical knowledge is perhaps the difficulty in enacting ¡°evidence-based management¡± as a way to improve the quality of teaching and application activities. Questions our panelists will address include, but are not limited to: 1) Many mature fields related to professions (e.g., medicine, law, engineering, etc.), strive to balance new knowledge creation and existing knowledge synthesis, in order to constantly channel knowledge flows between practice and science. How do we embrace this model in our management field? 2) How can we encourage more knowledge synthesis to close the gap between increasingly fragmented new knowledge and the practical need for comprehensive guidance to enact the goal of evidence-based management? 3) Many critics of the field call for research that combines science-based principles as well as being actionable. However, how do we manage the increasing complexity in both science and action, which seems to call for a (re)focus on each and a (re)division of labor in two opposite directions (e.g., specialization vis-¨¤-vis integration)? How do we draw experiences from similar and more mature fields such as engineering, medicine, and law? 4) What new technologies are available or should be created to facilitate knowledge synthesis? What new publication outlets should be (re)invented to host these technologies? What new forms of publications might be available that would enable constant updates and integration of academic findings? 5) Who are, and who should be, responsible for inventing, hosting, and maintaining these new outlets? 6) How do we evaluate the quality (and publishability) of synthesis-based research? If it is related to performance prediction, how do we measure a research¡¯s comprehensiveness in predicting performance measures? And what performance measures should we adopt, given that science-based principles are supposed to be value-neutral? 7) What research incentives should business schools (re)invent to divert some of scholars¡¯ attention, energy, and resources into inventing/learning these new technologies and contributing into these new outlets? 8) How would these new initiatives on knowledge synthesis complement, rather than compete with, the current top scientific journal-centric system, whose role in new knowledge creation is always critical?

Multi-Cell Massive MIMO Systems With Hardware Impairments: Uplink-Downlink Duality and Downlink Precoding

In this paper, we propose a new framework for uplink-downlink duality in multi-cell multi-user multiple-input multiple-output systems suffering from residual hardware impairments (HWIs) at the base stations and the user terminals. We apply the proposed uplink-downlink duality framework to derive a multi-cell interference and HWI aware minimum mean square error (MCHA-MMSE) precoder which also takes channel state information estimation errors into account. We use results from random matrix theory to derive an analytical expression for the downlink power allocation for the proposed MCHA-MMSE precoder in the large system limit, which only depends on the channel's second order statistics. In contrast to the conventional MMSE precoder, the proposed MCHA-MMSE precoder takes inter-cell interference, pilot contamination, and residual HWIs into account and therefore achieves substantially higher sum rates. The proposed MCHA-MMSE precoder exploits statistical channel knowledge, but does not require data exchange between base stations via backhaul links. In order to reduce the computational complexity, the matrix inversion required for the computation of the MCHA-MMSE precoder is approximated by a matrix polynomial leading to a new polynomial-expansion MCHA-MMSE precoder. Using results from the random matrix theory, we derive closed-form expressions for the asymptotically optimal coefficients of the matrix polynomial, which only depend on the channel's second order statistics.

A knowledge-based approach to mapping degraded meadows on the Qinghai–Tibet Plateau, China

ABSTRACTThe spatially unique properties of degraded meadows (heitutan) on the Qinghai–Tibet Plateau offer an excellent opportunity in assessing the utility and effectiveness of various knowledge in their automatic and accurate mapping from satellite imagery. After a Landsat Operational Land Imager image was K-means clustered to produce a degradation severity map, it was also used to generate a normalized difference vegetation index (NDVI) map that was subsequently converted to a degradation severity map, as well. Both maps were further refined with spatial knowledge derived from topographic data and the image via onscreen digitization. It is found that elevation is a more useful knowledge than channel in refining the image-derived results. It can reduce the area of K-means clustering results by 37% through exclusion of non-genuine heitutan at a very high elevation. This knowledge is especially beneficial to severe and slight heitutan. Channel knowledge is less effective by reducing the mapped heitutan by 15%, with a similar pace of reduction across all three classes of degradation severity. However, it is more useful in refining the NDVI-derived results than with the K-means results as all sparsely vegetated areas were indiscriminately lumped together. Both K-means clustering and NDVI produced drastically different results, but they converge closely with each other with a disparity of only 6% between them after the application of the spatial knowledge. Both methods achieved a similar overall mapping accuracy around 70%. Slope gradient and aspect are of limited use to the mapping due to lack of distinction between degraded heitutan and intact meadows. More research should focus on the universality of the knowledge and the impact of scale on the findings.

The Role of Host Country Networks in Foreign Investment Location Decisions: Interfaces All Over

Extent theory emphasizes the role of host country factors and home-host countries’ ‘distance’ on the choice of foreign investment location (FIL). This study argues host country networks constitute a third set of drivers of FIL choice. Host country networks in general (HCN), and more specifically host country investment networks (HCINs) are fundamental to multinational enterprises’ (MNEs) FIL choices. HCINs signal the potential benefits of investing in the hst country and channel knowledge and information about investment opportunities in that country and potential partners. HCINs also channel information and knowledge about third countries within the HCIN facilitating the evaluation of future investments into these third countries. HCINs also increase the attractiveness of the host country as a ‘regional’ base. We hence argue that the relative propensity to invest into a host country (RPI) is positively associated with HCIN. This hypothesis is tested using nearly half a million firm investment data aggregated to measure the impact of HCIN on RPI between more than 24,000 country dyads. The results support the importance of HCN to FIL choices.

A Survey on Robust Interference Management in Wireless Networks

Recent advances in the characterization of fundamental limits on interference management in wireless networks and the discovery of new communication schemes on how to handle interference led to a better understanding towards the capacity of such networks. The benefits in terms of achievable rates of powerful schemes handling interference, such as interference alignment, are substantial. However, the main issue behind most of these results is the assumption of perfect channel state information at the transmitters (CSIT). In the absence of channel knowledge the performance of various interference networks collapses to what is achievable by time division multiple access (TDMA). Robustinterference management techniques are promising solutions to maintain high achievable rates at various levels of CSIT, ranging from delayed to imperfect CSIT. In this survey, we outline and study two main research perspectives of how to robustly handle interference for cases where CSIT is imprecise on examples for non-distributed and distributed networks, namely broadcast and X-channel. To quantify the performance of these schemes, we use the well-known (generalized) degrees of freedom (GDoF) metric as the pre-log factor of achievable rates. These perspectives maintain the capacity benefits at similar levels as for perfect channel knowledge. These two perspectives are: First,scheme-adaptationthat explicitly accounts for the level of channel knowledge and, second,relay-aided infrastructure enlargementto decrease channel knowledge dependency. The relaxation on CSIT requirements through these perspectives will ultimately lead to practical realizations of robust interference management techniques. The survey concludes with a discussion of open problems.

Artificial Noise-Aided Physical Layer Security in Underlay Cognitive Massive MIMO Systems with Pilot Contamination

In this paper, a secure communication model for cognitive multi-user massive multiple-input multiple-output (MIMO) systems with underlay spectrum sharing is investigated. A secondary (cognitive) multi-user massive MIMO system is operated by using underlay spectrum sharing within a primary (licensed) multi-user massive MIMO system. A passive multi-antenna eavesdropper is assumed to be eavesdropping upon either the primary or secondary confidential transmissions. To this end, a physical layer security strategy is provisioned for the primary and secondary transmissions via artificial noise (AN) generation at the primary base-station (PBS) and zero-forcing precoders. Specifically, the precoders are constructed by using the channel estimates with pilot contamination. In order to degrade the interception of confidential transmissions at the eavesdropper, the AN sequences are transmitted at the PBS by exploiting the excess degrees-of-freedom offered by its massive antenna array and by using random AN shaping matrices. The channel estimates at the PBS and secondary base-station (SBS) are obtained by using non-orthogonal pilot sequences transmitted by the primary user nodes (PUs) and secondary user nodes (SUs), respectively. Hence, these channel estimates are affected by intra-cell pilot contamination. In this context, the detrimental effects of intra-cell pilot contamination and channel estimation errors for physical layer secure communication are investigated. For this system set-up, the average and asymptotic achievable secrecy rate expressions are derived in closed-form. Specifically, these performance metrics are studied for imperfect channel state information (CSI) and for perfect CSI, and thereby, the secrecy rate degradation due to inaccurate channel knowledge and intra-cell pilot contamination is quantified. Our analysis reveals that a physical layer secure communication can be provisioned for both primary and secondary massive MIMO systems even with the channel estimation errors and pilot contamination.

The Effect of Pungent and Tingling Compounds from Piper nigrum L. on Background K+ Currents.

Black peppercorns (Piper nigrum L.) elicit a pungent and tingling oral impression. Their pungency is partially explained by the agonist activity of some of their active principles, especially piperine, on TRP channels. However, we recently showed that piperine, as well as other pungent compounds, also possess a marked effect on two-pore domain (KCNK, K2P) K+ channels. Members of this family play a key role in maintaining the resting membrane potential of excitable cells. Interestingly, tingling compounds have been shown to induce neuronal excitation by inhibiting KCNK channels. We addressed the question of whether it was plausible that KCNK channels could constitute a physiologically relevant target for the sensory active compounds present in black peppercorns. Because previous studies have demonstrated that mouse trigeminal neurons respond to several pungent compounds, to which humans are also sensitive, we used a primary culture of mouse trigeminal neurons to investigate whether the effect of piperine on these cell types could also be mediated by KCNK channels. We observed that even in the presence of classical TRP-antagonists, piperine was still able to activate a fraction of trigeminal neurons. Furthermore, our results showed that piperine is capable of inducing neuronal depolarization by a mechanism that does not require extracellular Na+ or Ca2+. This depolarization was mediated by the inhibition of a background K+ conductance, most likely corresponding to the KCNK channels of the TASK subfamily. We then performed a screening with 12 other pungent and/or tingling chemosensates isolated from black peppercorns. These compounds were evaluated on Xenopus laevis oocytes expressing the human orthologues of KCNK3, KNCK9 and KCNK18, which we previously showed to be inhibited by piperine. Remarkably, almost all of the isolated chemosensates inhibited the basal activity of hKCNK3, with 1-(octadeca-2E,4E,13/12Z-trienoyl)pyrrolidine acting as one of the most potent natural blockers for hKCNK3 found to date. Our results suggest that KCNK channels, especially KCNK3, are likely to play a complementary role to TRP channels in the complex orosensory impression elicited by black peppercorns, while they also help to expand the pharmacological knowledge of KCNK channels.

CLINICIAN SENSITIZATION ON INTEGRATED DISEASE SURVEILLANCE AND RESPONSE IN FEDERAL MEDICAL CENTRE OWO, ONDO STATE, NIGERIA, 2016

Background: For effective Integrated Disease Surveillance and Response (IDSR) all health care workers involvement is required. Most trainings have often neglected the clinicians. Aim: This study aimed to identify gaps requiring capacity building in preventing infectious disease outbreak among health care workers in Federal Medical Centre, Owo, Ondo State.Methods: A cross sectional study of clinicians at the Federal Medical Centre, Owo was done. Data was collected using semi structured interviewer administered questionnaire. Data collected were analysed with SPSS version 21. Summary statistics was conducted to identify training need requirements.Results: The mean age of participant was 43 ± 5.9 years, 14(70%) were male. Respondents who have worked for 10 years and above were 12(60%). In all, 5(25%) respondent understood disease surveillance to be systematic collection of data and analysis in order to prevent diseases. Regarding respondent’s knowledge of notifiable diseases. Only 4(20%) of the respondents knew malaria as a notifiable disease, Cholera knew by 11(55%), Ebola by 15(75%) and Lassa by 13(65%). The main factor identified to be affecting prompt disease notification in Federal Medical Centre, Owo was lack of adequate training 12(60%) while communication gap was identified by 7(35%). In all, 18(90%) felt they do not know all that they needed about disease surveillance. Conclusion: Rapid notification of infectious diseases is essential for prompt public health action and for monitoring of disease trends. Trainings that will improve the level of knowledge of clinician and communication channels will improve disease surveillance and notification.

Forty Years of Sodium Channels: Structure, Function, Pharmacology, and Epilepsy.

Voltage-gated sodium channels initiate action potentials in brain neurons. In the 1970s, much was known about the function of sodium channels from measurements of ionic currents using the voltage clamp method, but there was no information about the sodium channel molecules themselves. As a postdoctoral fellow and staff scientist at the National Institutes of Health, I developed neurotoxins as molecular probes of sodium channels in cultured neuroblastoma cells. During those years, Bruce Ransom and I crossed paths as members of the laboratories of Marshall Nirenberg and Philip Nelson and shared insights about sodium channels in neuroblastoma cells from my work and electrical excitability and synaptic transmission in cultured spinal cord neurons from Bruce's pioneering electrophysiological studies. When I established my laboratory at the University of Washington in 1977, my colleagues and I used those neurotoxins to identify the protein subunits of sodium channels, purify them, and reconstitute their ion conductance activity in pure form. Subsequent studies identified the molecular basis for the main functions of sodium channels-voltage-dependent activation, rapid and selective ion conductance, and fast inactivation. Bruce Ransom and I re-connected in the 1990s, as ski buddies at the Winter Conference on Brain Research and as faculty colleagues at the University of Washington when Bruce became our founding Chair of Neurology and provided visionary leadership of that department. In the past decade my work on sodium channels has evolved into structural biology. Molecular modeling and X-ray crystallographic studies have given new views of sodium channel function at atomic resolution. Sodium channels are also the molecular targets for genetic diseases, including Dravet Syndrome, an intractable pediatric epilepsy disorder with major co-morbidities of cognitive deficit, autistic-like behaviors, and premature death that is caused by loss-of-function mutations in the brain sodium channel NaV1.1. Our work on a mouse genetic model of this disease has shown that its multi-faceted pathophysiology and co-morbidities derive from selective loss of electrical excitability and action potential firing in GABAergic inhibitory neurons, which disinhibits neural circuits throughout the brain and leads directly to the epilepsy, premature death and complex co-morbidities of this disease. It has been rewarding for me to use our developing knowledge of sodium channels to help understand the pathophysiology and to suggest potential therapeutic approaches for this devastating childhood disease.

Secure Alamouti MAC Transmissions

We investigate the physical layer security of synchronous multiple access transmissions using the Alamouti space-time block code in fading channels where multiple users communicate with a single intended receiver in the presence of an eavesdropper. We propose an artificial-noise-aided technique to secure the transmissions by having the Alamouti users collaborate with each other, without exchanging information, to degrade the eavesdropper’s channel. Unlike previous work, which assumes that the transmitters have complete knowledge of the legitimate as well as the eavesdropper’s channels, our proposed technique requires no communications between the users, minimal knowledge of the legitimate channel, and no channel knowledge regarding the eavesdropper.

Binary Fading Interference Channel With No CSIT

We study the capacity region of the two-user binary fading (or erasure) interference channel, where the transmitters have no knowledge of the channel state information. We develop new inner bounds and outer bounds for this problem. We identify three regimes based on the channel parameters: weak, moderate, and strong interference regimes. Interestingly, this is similar to the generalized degrees of freedom of the two-user Gaussian interference channel, where transmitters have perfect channel knowledge. We show that for the weak interference regime, treating interference as erasure is optimal while for the strong interference regime, decoding interference is optimal. For the moderate interference regime, we provide new inner and outer bounds. The inner bound is based on a modification of the Han–Kobayashi scheme for the erasure channel, enhanced by time-sharing. We study the gap between our inner bound and our outer bounds for the moderate interference regime and compare our results to that of the Gaussian interference channel. Deriving our new outer bounds has three main steps. We first create a contracted channel that has fewer states compared with the original channel, in order to make the analysis tractable. We then prove the correlation lemma that shows an outer bound on the capacity region of the contracted channel and also serves as an outer bound for the original channel. Finally, using the conditional entropy leakage lemma, we derive our outer bound on the capacity region of the contracted channel.

Leveraging One-Hop Information in Massive MIMO Full-Duplex Wireless Systems

We consider a single-cell massive MIMO full-duplex wireless communication system, where the base-station (BS) is equipped with a large number of antennas. We consider the setup where the single-antenna mobile users operate in half- duplex, while each antenna at the BS is capable of full-duplex transmissions, i.e., it can transmit and receive simultaneously using the same frequency spectrum. The fundamental challenge in this system is intra-cell inter-node interference, generated by the transmissions of uplink users to the receptions at the downlink users. The key operational challenge is estimating and aggregating inter-mobile channel estimates, which can potentially overwhelm any gains from full-duplex operation. In this work, we propose a scalable and distributed scheme to optimally manage the inter-node interference by utilizing a "one- hop information architecture". In this architecture, the BS only needs to know the signal-to-interference-plus-noise ratio (SINR) from the downlink users. Each uplink user needs its own SINR, along with a weighted signal-plus-noise metric from its one-hop neighboring downlink users, which are the downlink users that it interferes with. The proposed one-hop information architecture does not require any network devices to comprehensively gather the vast inter-node interference channel knowledge, and hence significantly reduces the overhead. Based on the one-hop information architecture, we design a distributed power control algorithm and implement such architecture using overheard feedback information. We show that, in typical asymptotic regimes with many users and antennas, the proposed distributed power control scheme improves the overall network utility and reduces the transmission power of the uplink users.

Code-Multiplexing-Based One-Way Detect-and-Forward Relaying Schemes for Multiuser UWB MIMO Systems

In this paper, we consider decode-and-forward (DF) one-way relaying schemes for multiuser impulse-radio ultrawideband (UWB) communications. We assume low-complexity terminals with limited processing capabilities and a central transceiver unit (i.e., the relay) with a higher computational capacity. All nodes have a single antenna differently from the relay in which multiple antennas may be installed. In order to keep the complexity as low as possible, we concentrate on noncoherent transceiver architectures based on multiuser code-multiplexing transmitted-reference schemes. We propose various relaying systems with different computational complexity and different levels of required channel knowledge. The proposed schemes largely outperform systems without relay in terms of both bit error rate (BER) performance and coverage.

Joint MMSE Transceiver Designs for MIMO AF Relaying Systems With Direct Link

In this paper, we provide minimum mean-squared error-based source-relay-destination transceiver designs for multiple-input multiple-output amplify-and-forward relaying systems, where direct link between the source and the destination is non-negligible. In an earlier work, a local optimal technique was introduced which employs a projected gradient method and an interior point method. Since these methods may have quite high computational complexity, we investigate a new local optimal solution for the source-relay-destination transceiver which has low complexity. To this end, we first introduce the optimal closed-form solution for the relay transceiver for given source and destination filters. Then, for given relay and destination transceivers, the optimal source precoder design is derived, which requires only 1-D bisection search. Based on these solutions, we propose a joint optimization algorithm which iteratively finds a local optimal solution. Also, we introduce a simple non-iterative algorithm which computes filters in closed-forms with low complexity. Furthermore, since perfect channel knowledge may not be feasible in practical systems, a joint transceiver technique which is robust to channel uncertainties is provided. It is confirmed by simulation results that the proposed schemes outperform conventional techniques with significantly reduced complexity.

Practical Framework for Downlink MU-MIMO for LTE Systems

The performance of multi-user multiple input multiple output (MU-MIMO) LTE systems critically depends on how the interference is estimated and managed. In this letter, we propose a practical framework for interference estimation for LTE networks. Moreover, we present a practical suboptimal non-iterative method for managing the interference through utilizing the interference knowledge. Furthermore, we consider the non-ideality of MU-MIMO precoding resulting from limited channel knowledge. Finally, we evaluate the proposed framework benefits through comparisons with other techniques.

Secure Degrees of Freedom Region of the Two-User MISO Broadcast Channel With Alternating CSIT

The two user multiple-input single-output (MISO) broadcast channel with confidential messages (BCCM) is studied, in which the nature of channel state information at the transmitter (CSIT) from each user can be of the form $I_{i}$ , $i=1,2$ where $I_{1}, I_{2}\in \{\mathsf {P}, \mathsf {D}, \mathsf {N}\}$ , and the forms $\mathsf {P}$ , $\mathsf {D}$ , and $\mathsf {N}$ correspond to perfect and instantaneous, completely delayed, and no CSIT, respectively. Thus, the overall CSIT can alternate between nine possible states corresponding to all possible values of $I_{1}I_{2}$ , with each state occurring for $\lambda _{I_{1}I_{2}}$ fraction of the total duration. We assume that perfect and instantaneous CSI is available at the all receivers. The main contribution of this paper is to establish the secure degrees of freedom (s.d.o.f.) region of the MISO BCCM with alternating CSIT with the symmetry assumption, where $\lambda _{I_{1} I_{2}}=\lambda _{I_{2}I_{1}}$ . The main technical contributions include developing 1) novel achievable schemes for MISO BCCM with alternating CSIT with security constraints, which also highlight the synergistic benefits of inter-state coding for secrecy; 2) new converse proofs via local statistical equivalence and channel enhancement; and 3) showing the interplay between various aspects of channel knowledge and their impact on s.d.o.f.

Hybrid MMSE Precoding for Millimeter-Wave (mmW) Multi-user Massive MIMO Systems

Millimeter-wave (mmWave) cellular systems is considered to be the key enabling technology for the future 5G wireless communication systems because of its high data rates, low latency, high system capacity, and huge available bandwidths. However, in order to meet the increasing demand, mmWave communications need to overcome certain challenges including high path loss and interference which can be reduced by applying large antenna arrays to achieve high beamforming gains. Although multi-user beamforming can improve spectral efficiencies, full digital beamforming strategies used in the conventional microwave systems increase the hardware cost and consumes high power for large number of antennas in mmW systems. In this paper, a multi-user hybrid precoding structure is proposed for mmWave massive-MIMO channels utilizing MMSE precoders at the BS with perfect channel knowledge. Simulations show that the sum-rate obtained by the proposed hybrid precoding scheme is nearly similar to the single-user rate and also performs better compared to other hybrid precoding approaches.

Non-Coherent MIMO Scheme Based on OFDM-MFSK

We propose a non-coherent transmission system based on orthogonal frequency division multiplexing (OFDM) for use in low-power applications. The proposed system uses ${M}$ -ary frequency shift keying (MFSK) and employs two transmitting and two receiving antennas, with encoding performed across the space, frequency and time domains. For the resulting scheme, we develop a novel optimal non-coherent detector that produces soft bit information for a state-of-the-art error correction decoder. The proposed solution eliminates the need for channel knowledge and enables a simple receiver structure. Simulation results demonstrate up to 8 dB of coding gain for the proposed scheme compared to single-antenna OFDM-MFSK. When compared with coherent systems based on OFDM and binary phase shift keying, the designed scheme offers a receiver sensitivity gain of 9 dB and beyond.