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Attracted by the advantages of Non-Orthogonal Multiple Access (NOMA) in accommodating multiple users within the same resources, this paper jointly addresses the resource allocation and power control problem for Machine Type Devices (MTDs) in a Hybrid NOMA system. Particularly, we model the problem using a Mean Field Game (MFG) framework underlying a Multi-Armed Bandit (MAB) approach. Firstly, the devices invoke the MAB tool to arrange themselves into multiple NOMA coalitions. Then, within each coalition, the MTDs apply the MFG approach to autonomously adjust their transmit power based on limited feedback received from the Base Station (BS). Simulation results are given to illustrate the equilibrium behavior of the proposed resource allocation algorithm and to underline its robustness compared to existing works in the literature.

Reliability is one of the promised features by the LoRaWAN technology. In this paper, we investigate the cost of reliable uplink communication in terms of latency and energy-consumption in a large scale LoRaWAN. We resort to markov chain to model latency and energy consumption for both class A and class B LoRaWAN end-devices. Results prove that reliable uplink communication in large scale LoRaWAN considerably affects latency and energy consumption. For example, in a best case scenario of 1000 end-devices, an uplink packet requires an average of$4620s$to be acknowledged, and$124J$of energy consumption.

Attracted by the advantages of Non-Orthogonal Multiple Access (NOMA) in accommodating multiple users within the same resource, this paper investigates the power allocation problem for Machine Type Devices (MTDs) in a Hybrid NOMA system. Particularly, we consider a densely deployed network in which the devices are divided into orthogonal coalitions. Firstly, the power control problem is modeled as a differential game. Then, we formulate the proposed game as a Mean Field Game (MFG) in order to handle massive Internet of Things (IoT) access scenarios. Furthermore, we design an iterative algorithm that paves the way for distributed control in which the devices can appropriately regulate their transmit power in response to brief information received from the Base Station (BS). The analysis of the proposed approach is conducted through coupled equations, namely the Hamilton-Jacobi-Bellman (HJB) and the Fokker-Planck-Kolmogorov (FPK). Our simulation results prove the convergence of the proposed power control strategy and spotlight the robustness of our formulated MFG.

The steady expansion of the number of wireless devices and the ubiquity of the networks give rise to various interesting challenges for the future sixth generation (6G) of wireless communication systems. Particularly, the operators have to handle massive connectivity among Machine Type Devices (MTDs) and increasing demand for eMMB through limited spectrum resources. Non-Orthogonal Multiple Access (NOMA) has been spotlighted as an emerging technology to meet the above-mentioned challenges. In this paper, we consider a densely deployed network in which users are divided into NOMA coalitions. Firstly, we model the power allocation problem as a differential game. Then, we extend the formulated game using a Mean Field Game (MFG) theoretic framework by considering the effect of the collective behavior of devices. Furthermore, we derive a distributed power control algorithm that enables the users to appropriately regulate their transmit power according to brief information received from the BS. Indeed, the analysis of the proposed approach is governed by the two fundamental Hamilton- Jacobi-Bellman (HJB) and Fokker-Planck-Kolmogorov (FPK) equations. Numerical results are presented to analyze the equilibrium behaviors of the proposed power control algorithm and to demonstrate the effectiveness of the formulated MFG compared to existing works in the literature.

Long Range Wide Area Network (LoRaWAN) technology is knowing an impressive growth. It is considered by many researchers as the new era of Internet of Things (IoT) communication. Several studies focus on evaluating the LoRaWAN performance according to many features such as coverage, scalability, and communication reliability. However, these studies assume that LoRaWAN end-devices are already activated by the network server. Thus, the performance of LoRaWAN activation procedure, referred as Over-The-Air Activation (OTAA), is not widely treated.In this paper, we elaborate an experimental analysis of the OTAA procedure performance using a real field LoRaWAN deployment. Our objective is to analyse the end-device activation delay and power consumption at large scale LoRaWAN. To achieve this goal, we design an experimental scenario of 30 end-devices competing for being activated by sending network join-requests. Upon its activation, each end-device transmits unconfirmed data at high rate, which simulates a large-scale LoRaWAN where hundreds of end-devices send their join-requests concurrently. Results show that OTAA procedure incurs high activation delays and power consumption, especially in large scale where the network traffic is high. This is due to three main factors: collisions, the back-off retransmission mechanism and join-request duty-cycle.

Non-Orthogonal Multiple Access (NOMA) is an interesting candidate to tackle the massive access challenges in Beyond 5G (B5G) systems. However, arranging Machine Type Devices (MTDs) into NOMA clusters and allocating resources to these clusters is a non-trivial task. In this paper, we consider a Hybrid NOMA system where every NOMA cluster is allocated an orthogonal sub-carrier and propose a game theoretical framework based on a bi-level game in order to achieve joint channel selection and power allocation for MTDs. Indeed, the proposed approach is composed of a non-cooperative power control game underlying a cooperative Hedonic game that enables MTDs to self-organize into coalitions. Furthermore, we propose two low-complexity algorithms that enable us to obtain a Nash-Stable partition where MTDs decide autonomously the appropriate Resource Block (RB) and the transmit power to use in order to deliver their packets. Our simulation results show that the proposed bi-level game allows the devices to achieve a high successful packet transmission rate while consuming less energy.

Pilot contamination is considered as a bottleneck in the massive multi-input multi-output (MIMO) systems. In a previous work, we proposed a novel iterative algorithm, dubbed channel Zooming Algorithm (CZA), to ensure the mitigation of pilot contamination effect. For this, we assumed that each cell is assigned a set of orthogonal pilot sequences and that these same pilot sequences are reused in other cells. In this paper, we propose a novel strategy of pilot design, based on the divide-and-conquer approach (DCA), aiming to halve the contamination power observed by the channel estimate and to conquer the remaining pilot contamination through the iterations of the CZA. More precisely, instead of being contaminated by a given number of contaminants, as in the initial approach of the CZA, the user, in the proposed approach, is contaminated by a twice the number of contaminants, while halving the pilot contamination power coming from each one of them. We confirm the effectiveness of the proposed scheme with analytical and simulation results and show that the CZA algorithm is more efficient and faster to eliminate the contamination in this case.

The channel access technique of LoRaWAN hinders the thorough utilization of channel capacity since it was not designed to exclusively limit or even avoid collisions, but rather with simplicity and energy consumption in mind. As a consequence, in presence of plenty of active nodes, the overall performance offered by a LoRaWAN Network can be poor. In this paper, we propose a new synchronized Uplink transmission scheme to improve the performance of data transmissions for LoRaWAN class B end-devices which are suitable for IoT applications with low latency requirements and regular traffic. In contrast to related works, our proposal is defined without modifying the fundamentals of the original ALOHA based channel access technique, but simply takes advantage of Class B downlink synchronization. Our preliminary analysis based on an analytic model shows an enhancement of performances regarding data transmission success.

In most of the real-life application scenarios, where Wireless Sensor Networks (WSNs) are deployed, the energy is a limited and valuable resource. Many energy-based strategies were proposed in the literature to reduce the power consumption of sensor nodes and thus enhance the network lifetime. When those algorithms are developed and tested with some well-known network simulators like NS3, OPNET, the energy estimation aspect is not a key criterion, because these simulators have their own specific energy models. By implementing these algorithms in a real sensor node, the energy consumption can be measured and compared to the results provided by other previously implemented approaches. This paper proposes a method for estimating the energy consumption of a low power wireless node panStamp NRG 2.0. The proposed model calculates the consumed energy of the system, at run time for different operation cycles. Besides, since the biggest amount of energy is consumed during the communication, this paper aims to characterize the power consumption in the transmission state. A proper metric of the energy consumed per byte transmission pattern of the packets is provided. The results can be used to derive not only the energy consumption for other protocols but also the energy needed to transmit one byte as well as the payload size are given.

Conventional orthogonal frequency division multiplexing (OFDM) may turn to be inappropriate for future wireless cellular systems services, because of extreme natural and artificial impairments they are expected to generate. Natural impairments result from higher Doppler and delay spreads, while artificial impairments result from multisource transmissions and synchronization relaxation for closed-loop signaling overhead reduction. These severe impairments induce a dramatic loss in orthogonality between subcarriers and OFDM symbols and lead to a strong increase in intercarrier interference (ICI) and intersymbol interference (ISI). To fight against these impairments, we propose here an optimization of the transmit/receive waveforms for filter-bank multicarrier (FBMC) systems, with hexagonal time-frequency (TF) lattices, operating over severe doubly dispersive channels. For this, we exploit the Ping-pong Optimized Pulse Shaping (POPS) paradigm, recently applied to rectangular TF lattices, to design waveforms maximizing the signal-to-interference-plus-noise ratio (SINR) for hexagonal TF lattices. We show that FBMC, with hexagonal lattices, offers a strong improvement in SINR with respect to conventional OFDM and an improvement of around 1 dB with respect to POPS-FBMC, with rectangular lattices. Furthermore, we show that hexagonal POPS-FBMC brings more robustness to frequency synchronization errors and offers a 10 dB reduction in out-of-band (OOB) emissions, with respect to rectangular POPS-FBMC.

In this paper, we consider a downlink coordinated multi-cells multi-users network, in which each User Equipment (UE) knows its Channel State Information (CSI) perfectly and feeds back its quantized composite channel to the distributed Base stations (BSs) through a limited feedback. We propose a cooperative beamforming design, considering quantized composite channels, that reduces the inter-cell interference for both cases of perfect and outdated quantized CSI and an optimal power allocation that maximizes the system sum rate. Furthermore, we propose a bit labelling of codebooks, used for channel quantization, that outperforms the random labelling under channel feedback errors and delay. We analyze also the sum rate loss due to the outdated and quantized channel knowledge at the transmitter.

Because of its spectrum-sharing nature, a CR network inevitably operates in interference-intensive environments. One challenge is how to maintain the interferences generated by the cognitive transmissions to the primary network below an acceptable threshold level. In this paper, we firstly propose an efficient primary users identification, using compressive sensing (CS). Our focus is on the angular sparsity of the received signal given an unknown number of primary user source signals impinging upon the antenna array from different directions of arrival (DOA). Given multiple snapshots, multiple measurement vectors (MMV) are available at the secondary base station and considered for primary channel detection over the angular domain using the regularized M-FOCUSS algorithm. Then, we develop novel methods for paths separation and primary channels estimation based on their autocorrelation matrix properties. Through simulations, we show that the recovery performance of the proposed approach in terms of false alarm and average minimum square error (MES) between the true and the estimated primary channel, is better than the conventional maximum to minimum eigenvalue (MME) detector.

In this paper, we consider a downlink Multiple-Input-Multiple-Output (MIMO) underlay cognitive radio network where unlicensed Secondary Users (SUs) share the Primary Users (PUs) spectrum. We assume that the channels from the Secondary Base Station (SBS) to each receiver are known to the SBS. We propose a beamforming matrix design to ensure that the transmitted signal does not cause harmful interference to the PUs and SUs. Furthermore, we study the optimal power allocation that maximizes the sum rate of the secondary system when the channel is not perfectly known at the SBS. Simulations results show the performance of our system in terms of sum rate of the secondary users in both cases of perfect and imperfect knowledge of Channel State Information (CSI) at the SBS.

In this paper, we investigate limited feedback precoding for stacked space-time architectures over Rayleigh fading MIMO channels, for the cases where the components are taken from orthogonal or algebraic non-orthogonal designs. Stacked constructions allow to achieve high spectral efficiency. Our precoding approach enables an efficient decoding of the component codes and an improvement of the array gain. We use at the receiver a VBLAST signal processing which is based on a successive component interference suppression. For selecting the optimum precoding matrix among grassmannian codebook matrices, we consider a criterion based on maximizing the minimum signal to interference and noise ratio over all components of the stacked design. Simulations show that limited feedback precoding for a stacked algebraic design performs better than precoding for the cases of stacked Alamouti design and of spatial multiplexing scheme for the same number of transmit and receive antennas, the same spectral efficiency and the same number of bits on the feedback link.

In this paper, we investigate the selection of cooperative relays in a cellular mobile network. We take into account the effect of the resource sharing of each relay by its served users on the relay selection strategy. At first, we propose a novel selection strategy of one cooperative relay considering both Amplify and Forward (AF) and Decode and Forwards (DF) protocols. Then, we extend our study to the case of selection of two cooperative relays in an attempt to improve the spatial diversity gain. The performances of the proposed selection algorithms are analyzed in terms of number of users assisted by cooperation and residual powers at the relays.

This paper investigates space-frequency (SF) coding for non-coherent (NC) Multiple Input Multiple Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) fading links, where neither the transmitter nor the receiver knows the channel. Our strategy consists in distributing the convolutional encoded and interleaved bits over the different transmit antennas, OFDM tones and OFDM symbols. The combination of the convolutional coding and bit interleaving with the SF coding can exploit the maximum spatial/frequency diversity over frequency-selective channels. In order to reduce the decoding complexity, we divide the OFDM symbol into several groups and apply differential encoding and decoding between adjacent groups. The proposed NC SF matrix is designed as a combination of a differential Cayley code and a systematic NC SF code, which leads to a simple decoding rule over the multipath channel. We show through asymptotic Pairwise Error Probability (PEP) analysis and simulation results that our encoding strategy can provide full diversity gain and achieves better performance in terms of spectrum efficiency and symbol error rate than all three the systematic NC-SF coding, the Cayley differential SF coding and our proposed SF coding without convolutional encoding and bit interleaving.

Cognitive radio is an exciting emerging technology that has the potential of dealing with the stringent requirement and scarcity of the radio spectrum. Such revolutionary and transforming technology represents a paradigm shift in the design of wireless systems as it will offer the ability of radio sensing, self adaptation and dynamic spectrum sharing. In this paper, we are interested in the case where secondary users are allowed to communicate concurrently with primary users provided that they do not create harmful interference to the licensed users. More precisely, the secondary transmission will depend on a variable cost that reliably quantifies the interference power generated by the secondary user at the primary base stations. Here, we aim to improve the unlicensed system performance in terms of throughput. For this aim, we propose to use an adaptive modulation as well as an energy optimization at the unlicensed user in order to maximize its data rate. We show that the system throughput depends on several parameters such as the maximum allowed cost and the number of base stations in the primary network, the secondary user location and its transmission energy.

In this paper, we define a multi-access interference (MAI) cost that can assess the extra interference, inherent to relaying use and perceived by the whole cellular network. This MAI cost shadows an implicit and smart power control for CDMA uplink communications. In fact, this cost takes into account not only the reception quality required at the serving base station but also the global interference generated to all others base stations in the cellular system. Here, the optimization goal aims to enhance the system performance, in terms of Packet-Error-Rate (PER), for a required quality of service (QoS). The optimization approach is achieved for both Decode-and-Forward (DF) and Incremental DF relaying schemes, carried out on packet-by-packet basis. A variety of simulation results are obtained using the analytical expressions of Packet-Error-Probability (PEP) that we derive for both DF and IDF schemes. By way of an example, for a target PER of 10-2, our optimized IDF scheme could afford more than 13 dB gain, in terms of MAI cost reduction, over the direct transmission scheme. Furthermore, simulation results underline that the optimized IDF relaying is more powerful than the optimized DF scheme and provides as much as 3 dB gain for some relay positions.

In this paper, we propose a novel approach for cooperative systems performance optimization. We are interested on the uplink CDMA communications, known to be both intra-cell and inter-cell interference limited. More precisely, we define a multi-access interference (MAI) cost that reliably quantifies the additional interference generated by a relayed communication to the whole cellular system. For CDMA uplink communications, this MAI cost hides an implicit and smart power control that takes into account not only the reception quality required at the serving base station but also the interference generated to the whole network. Here, the optimization process aims to improve the system performance, in terms of Packet-Error-Rate (PER) for a certain required quality of service (QoS). The optimization process is carried for both Selective Relaying (SR) and Incremental Selective Relaying (ISR) schemes, on packet-by-packet basis. A variety of simulation results are carried using analytical expressions of Packet-Error-Probability that are derived for SR and ISR schemes. We show that, for a target PER of 10-2, our optimized ISR scheme could provide up to 14 dB gain, in terms of MAI cost reduction, over the direct transmission scheme. Additionally, results highlight that our optimized ISR relaying is always more powerful than the optimized SR scheme and provides as much as 4 dB gain in the most favorable cases.

The use of single-antenna terminals for coherent cooperative wireless communications has received more attention in literature than for non-coherent communications. But acquiring knowledge of the fading coefficients in a cooperative scheme is very challenging in a fast fading case. In this paper, we develop several cooperative schemes suited for systems which do not require channel state information at either relays or destination. We analyze the performance of these schemes in terms of diversity gain and error probability. The diversity gained with an equal gain combiner at the destination is investigated too. The proposed cooperative schemes are compared to the literature and are shown to achieve significant performance gain depending on the type of relaying protocol.

This paper deals with the problem of code design for non-coherent frequency-selective Multiple Input Multiple Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) fading links, where neither the transmitter nor the receiver knows the channel. A simple and classical approach for non coherent (NC) coding for MIMO-OFDM system consists of coding across antennas and time slots on each OFDM subcarrier. Only, this approach does not permit to exploit the diversity of frequency-selective channels. In our aim to exploit this diversity, we propose in this paper a strategy that consists of coding across antennas and OFDM subcarriers (space-frequency coding) within a single OFDM symbol. Our space-frequency (SF) codes are based on NC Grassmann space-time (ST) codes obtained via an exponential map from coherent ST codes. We determine the asymptotic Pairwise Error Probability (PEP) for each scheme in order to evaluate the diversity and the coding gains. Simulations show that compared with the classical approach, our NC-SF codes can get more diversity gain and better symbol error performance.

In this paper, we consider a cooperative network with one source, one destination and two relays to bring cooperative diversity. We assume the link between the source and the destination is so bad that we do not consider it. We propose a decode-and-forward (DAF) strategy based on the Alamouti space-time (ST) code. The two relays must recover the transmitted sequence and forward it to the destination. We consider fast time varying channels between the cooperative users and the destination and our objective is to estimate these two channels in order to recover the information sequence at the destination. We propose a data-aided decision-directed Maximum A Posteriori (MAP) iterative channel estimation algorithm. It can profit from an optimum initialization by means of the MAP data-aided channel estimation. Besides, we adapt this iterative receiver to the case where the destination is equipped with two receive antennas to bring more diversity. The validity of the proposed algorithms is highlighted by simulation results.

In this paper, we consider the problem of maximum a posteriori (MAP) equalization of the received signal over a frequency selective channel when the channel is not perfectly known at the receiver. The derivation of the MAP criterion in this case leads to an expression for which no exact implementation exists in the literature. In this paper, we propose to solve the problem by using the expectation-maximization (EM) algorithm. The algorithm we propose has linear-time complexity per iteration. Simulations show that few iterations are required to reach the performance of the MAP equalizer with perfect channel knowledge.

We construct a new family of space-time codes suited for multiple-antenna non-coherent communications over Rayleigh flat fading channels. These codes use all the complex degrees of freedom of the system, i.e. (M times(1-M/T)) symbols per channel use, where T is the code length and M is the number of transmit antennas. Their codewords belong to the Grassmann manifold GTldrM(C), the set of the M-dimensional vector subspaces of CT. Our codes are built from space-time codes for coherent systems via a non linear map (parameterization) called the exponential map. The relationships between some properties of the non-coherent space-time codes and their corresponding coherent codes are investigated. We also propose a simplified decoding for these classes of unitary space-time codes. We analyse the performance of these codes in terms of complexity and error probability and we compare them with some current best propositions, in particular training-based codes. The performance of our codes is substantially equivalent or slightly better than the one of training-based codes, under GLRT (Generalized Likelihood Ratio Test) decoding. When a simplified decoder is applied at the receiver, the error probability curves of the two propositions seem to be basically equivalent in the SIMO case with small block size, high spectral efficiency and high number of receive antennas, and in the 2times2 MIMO case with low spectral efficiency. In the other cases the training codes with simplified decoding seem to outperform our proposition.

We consider multiple-antenna non-coherent communications over Rayleigh flat fading channels and single-antenna non-coherent systems with unknown channel phase. For both systems, we propose some sub-optimal simplified decodings for the class of unitary space-time codes obtained via the exponential map (I. Kammoun and J.-C. Belfiore, Nov. 2003). To this aim, we use the geometrical interpretation of these codes as sets of points over the Grassmann manifold G/sub TM/. We compare these codes with other propositions in the literature, for which a simplified decoder exists.