Weighted Sum Rate Maximization for Downlink OFDMA with Subcarrier-pair based Opportunistic DF Relaying

This paper addresses a weighted sum rate (WSR) maximization problem for downlink OFDMA aided by a decode-and-forward (DF) relay under a total power constraint. A novel subcarrier-pair based opportunistic DF relaying protocol is proposed. Specifically, user message bits are transmitted in two time slots. A subcarrier in the first slot can be paired with a subcarrier in the second slot for the DF relay-aided transmission to a user. In particular, the source and the relay can transmit simultaneously to implement beamforming at the subcarrier in the second slot. Each unpaired subcarrier in either the first or second slot is used for the source's direct transmission to a user. A benchmark protocol, same as the proposed one except that the transmit beamforming is not used for the relay-aided transmission, is also considered. For each protocol, a polynomial-complexity algorithm is developed to find at least an approximately optimum resource allocation (RA), by using continuous relaxation, the dual method, and Hungarian algorithm. Instrumental to the algorithm design is an elegant definition of optimization variables, motivated by the idea of regarding the unpaired subcarriers as virtual subcarrier pairs in the direct transmission mode. The effectiveness of the RA algorithm and the impact of relay position and total power on the protocols' performance are illustrated by numerical experiments. The proposed protocol always leads to a maximum WSR equal to or greater than that for the benchmark one, and the performance gain of using the proposed one is significant especially when the relay is in close proximity to the source and the total power is low. Theoretical analysis is presented to interpret these observations.Comment: 8 figures, accepted and to be published in IEEE Transactions on Signal Processing. arXiv admin note: text overlap with arXiv:1301.293

Low feedback downlink MIMO channel estimation for distributed FBMC systems using SNR measurements

In this paper, we present a new method to estimate the MIMO channel in a distributed MIMO system using FBMC modulation (Filter Bank based Multicarrier). As opposed to previously presented methods, it is not based on the existence of pilots and therefore avoids the necessity of auxiliary pilots or similar methods. Besides, it requires a very low amount of feedback. Only the SNR observed by the different users need to be fed back periodically. It is intended for the estimation of the downlink MIMO channel in a distributed beamforming system where the basestations can cooperate to some extent. It is based on the concept of adding small, controlled, perturbations to the transmitted signals and observing the related changes to the SNR at the receivers. It is shown in this paper that, based on a limited amount of SNR measurements from the receivers, it is possible to accurately estimate the MIMO channels, both in amplitude and phase. It is also shown that the proposed method exhibits the best performance in a tracking mode.info:eu-repo/semantics/publishe

Filtered orthogonal matching pursuit: applications

info:eu-repo/semantics/publishe

A Sub-mW Cortex-M4 Microcontroller Design for IoT Software-Defined Radios

We present an Internet-of-Things (IoT) software-defined radio platform based on an ultra low-power microcontroller. Whereas conventional wireless IoT radios often implement a single protocol, we demonstrate that general-purpose microcontrollers running software implementations of wireless physical layers are a promising solution to increase interoperability of IoT devices. Yet, since IoT devices are often energy-constrained, the underlying challenge is to implement the digital signal processing of the radio in software while maintaining an overall very low power consumption. To overcome this problem, we propose an ultra low-power microcontroller architecture with an ARM Cortex-M4 processor for the protocol-specific computations and a hardware digital front-end for the generic signal processing. The proposed architecture has been prototyped in 28nm FDSOI and the physical layers of the well-known LoRa and Sigfox protocols have been implemented in software. Thanks to the efficient hardware/software partitioning and an ultra-low power digital implementation, experimental evaluations of the microcontroller prototype show sub-mW power consumptions (32 – $332~\mu \text{W}$ ) for the digital signal processing of the software-defined radios

Frequency selective channel equalization for filter bank multi-carriers modulation

The filter bank multicarrier modulation (FBMC) is a transmission technique better suited for new concepts such as dynamic access spectrum management (DASM) and cognitive radio. It is used to improve the efficiency of mobile radio and wireless communication networks, because it allows reaching a high data rate and improving spectral efficiency. The FBMC principle exploits the concept of better waveform localization in both time and frequency domains, unlike orthogonal frequency division multiplexing...info:eu-repo/semantics/publishe

Secrecy capacity of FBMC-OQAM modulation over frequency selective channel

This letter studies the Information-theoretic secrecy capacity of an Offset-QAM-based filterbank multicarrier (FBMC-OQAM) communication over a wiretap frequency selective channel. The secrecy capacity Is formulated as an optimization problem which has a closed-form solution In the high signal-to-noise ratio (SNR) regime. Two of the most common equalization strategies In FBMC-OQAM are considered, namely, single-tap and multi-tap equalization. For the sake of comparison, we also consider the secrecy capacity of a generic modulation and a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) modulation. As a result, we find that FBMC-OQAM Is particularly competitive for medium-to-long burst transmissions.SCOPUS: ar.jinfo:eu-repo/semantics/publishe