This work aims at improving indoor positioning systems (IPS) by integrating multiple radio frequency techniques, namely received signal strength indiction (RSSI), Angle of Arrival (AoA), and a combination of both, within the bluetooth low energy (BLE) 5.1 framework. While AoA stands out for its precision, low energy consumption, and cost-effectiveness, RSSI is characterized by its simplicity and widespread availability. By resorting to a database of real RSSI and AoA measurements from a BLE 5.1 target node in a$14\times 8$-m environment, our work employs the Kalman filter (KF) to improve the accuracy of multilateration, AoA combined with RSSI, and AoA-only algorithms. Moreover, we consider one more step in our IPS where the aforementioned KF-filtered outputs are then fused through a track fusion model. Results demonstrate that the proposed scheme, which we refer to as angle-RSSI fusion localization (ARFL), significantly improves localization accuracy compared to other techniques. In particular, it reduces up to 81.61% in the average position error when compared to multilateration with KF. This advanced IPS offers a cost-effective and precise solution suitable for various applications in industries, such as healthcare, commerce, and logistics.

In this letter, we investigate the Age of Information (AoI) of a power domain nonorthogonal multiple access (NOMA) network, where multiple Internet of Things (IoT) devices transmit to a common gateway in a grant-free random fashion. More specifically, we consider a framed setup composed of multiple time slots, and resort to the Q-learning algorithm to properly define, in a distributed manner, the time slot and the power level each IoT device transmits within a frame. In the proposed AoI-QL-NOMA scheme, the Q-learning reward is adapted with the aim of minimizing the average AoI of the network, while only requiring a single feedback bit per time slot, in a frame basis. Our results show that AoI-QL-NOMA significantly improves the AoI performance compared to some recently proposed schemes, without significantly reducing the network throughput.

This paper introduces an enhancement to the Long-Range Frequency-Hopping Spread Spectrum (LR-FHSS), a modulation within the LoRaWAN specification, particularly useful in dense networks supported by satellite gateways. LR-FHSS replicates headers and payload fragments across different physical channels, but the distinct transmission strategies for headers and payloads can lead to uneven success rates and degrading performance. To address this, we propose a scheme that allocates orthogonal physical channels for headers and payloads. Through analytical and simulation results, considering factors such as payload size and the number of users, we identify the optimal distribution of channels between headers and payloads to maximize success probability. The proposed scheme significantly improves performance, supporting up to 50% more users at the same reliability level as the standard LR-FHSS.

We propose and evaluate age of information (AoI)-aware multiple access mechanisms for the Internet of Things (IoT) in multi-relay two-hop networks. The network considered comprises end devices (EDs) communicating with a set of relays in ALOHA fashion, with new information packets to be potentially transmitted every time slot. The relays, in turn, forward the collected packets to an access point (AP), the final destination of the information generated by the EDs. More specifically, in this work we investigate the performance of four age-aware algorithms that prioritize older packets to be transmitted, namely max-age matching (MAM), iterative max-age scheduling (IMAS), age-based delayed request (ABDR), and buffered ABDR (B-ABDR). The former two algorithms are adapted into the multi-relay setup from previous research, and achieve satisfactory average AoI and average peak AoI performance, at the expense of a significant amount of information exchange between the relays and the AP. The latter two algorithms are newly proposed to let relays decide which one(s) will transmit in a given time slot, requiring less signaling than the former algorithms. We provide an analytical formulation for the AoI lower bound performance, compare the performance of all algorithms in this set-up, and show that they approach the lower bound. The latter holds especially true for B-ABDR, which approaches the lower bound the most closely, tilting the scale in its favor, as it also requires far less signaling than MAM and IMAS.

The increasing number of connected devices in machine-type applications, such as the Internet of Things (IoT), leads to the coexistence of heterogeneous services in Beyond 5G (B5G) networks, where users with diverse requirements share physical resources. In this article, we apply a channel allocation method to assign grant-based (GB) users to channels. This method, named max-matching diversity (MMD), leads to a frequency diversity gain that equals the number of available channels, reducing the outage of GB users. In the same network resource that serves a GB user, one grant-free (GF) user is allocated through a distributed contention protocol that considers the Quality-of-Service (QoS) of the GB user, performing the pairing that causes the minimum interference, so that the presence of a GF user is transparent to the GB user. Both users admitted to the same physical resource operate in either nonorthogonal multiple access (NOMA) or rate-splitting multiple access (RSMA), depending on the channel gains. Exact expressions for the outage probability of this semi-grant-free (SGF) system are provided and compared to simulation results, showing that the SGF transmissions with MMD-aided GB users strategy reduces the outage and increases the achievable rate of both users.

In this work, we apply an asynchronous contention resolution-aided ALOHA protocol to the recently proposed long-range frequency hopping spread spectrum (LR-FHSS) scheme, which is an amendment of widespread chirp spread spectrum (CSS)-based long-range (LoRa) modulation patented by Semtech. More specifically, we modify the so-called asynchronous contention resolution diversity ALOHA (ACRDA) protocol to comply with LR-FHSS requirements and improve LR-FHSS performance against collisions. In the proposed scheme, only the gateway requires modifications, while the ACRDA operation is transparent from the end-devices perspective, which follows the regular LR-FHSS operation. Our results, obtained using a discrete event simulator, show that the proposed scheme outperforms regular LR-FHSS in various aspects, such as average network success (up to 60% improvement in the scenarios considered), goodput (2× better) and number of supported devices for a target reliability level (more than 2×). Finally, we also evaluate the impact on the performance of the proposed scheme of parameters such as the window and the step sizes, showing that a relatively small window size (~2× the time-on-air of a single message) is sufficient to approach the asymptotic maximum network success achieved by an infinite window.

We evaluate the outage probability and the energy efficiency (EE) of a long range (LoRa) network when the end devices (EDs) are capable of exchanging messages with a device-to-device (D2D) technology. Our proposal is to assess the performance of the network when operating under the concept of network-coded cooperation (NCC), where the EDs are capable of transmitting linear combinations of more than one frame (including frames of another ED), performed over a nonbinary finite field. We consider both connection and collision probabilities when modeling the outage probability of an ED, as well as a realistic power consumption model to evaluate the EE. Our results indicate that the proposed scheme, which we refer to as NCC-LoRa, provides considerable gains in terms of both outage probability and EE when compared to a regular LoRa network, even when considering the additional consumption of D2D communication.

Age of Information (AoI) has turned to be an outright metric to evaluate information freshness in Internet of Things (IoT) networks. In this work, we evaluate the average AoI of an uplink IoT monitoring network where multiple end devices have independent status updates to transmit to a common access point (AP). More specifically, we propose the so-called successive interference cancellation (SIC)-aided age-independent random access (AIRA-SIC) scheme, where the AP performs SIC aiming at recovering collisions of multiple packets that are transmitted simultaneously by different devices in a slotted ALOHA fashion. Our results show that the proposed scheme not only achieves considerably lower AoI levels than the standard AIRA but also outperforms a recently proposed threshold-based age-dependent random access (ADRA) scheme, where the channel access probability (CAP) of each device is dynamically adapted based on each devices’ AoI. Finally, we provide some insights on the optimal CAP that minimizes the network average AoI, as well on the influence of imperfect channel state information (CSI) in the performance of the proposed scheme.

In this work, we study the coexistence in the same Radio Access Network (RAN) of two use cases present in the Fifth Generation (5G) of wireless communication systems: enhanced Mobile BroadBand (eMBB) and massive Machine-Type Communications (mMTC). eMBB services are requested for applications that demand extremely high data rates and moderate requirements on latency and reliability, whereas mMTC enables applications for connecting a massive number of low-power and low-complexity devices. The coexistence of both services is enabled by means of network slicing and Non-Orthogonal Multiple Access (NOMA) with Successive Interference Cancellation (SIC) decoding. Under the orthogonal slicing, the radio resources are exclusively allocated to each service, while in the non-orthogonal slicing the traffics from both services overlap in the same radio resources. We evaluate the uplink performance of both services in a scenario with a multi-antenna Base Station (BS). Our simulation results show that the performance gains obtained through multiple receive antennas are more accentuated for the non-orthogonal slicing than for the orthogonal allocation of resources, such that the non-orthogonal slicing outperforms its orthogonal counterpart in terms of achievable data rates or number of connected devices as the number of receive antennas increases.

The 5G systems feature three generic services: enhanced Mobile BroadBand (eMBB), massive Machine-Type Communications (mMTC) and Ultra-Reliable and Low-Latency Communications (URLLC). The diverse requirements of these services in terms of data-rates, number of connected devices, latency and reliability can lead to a sub-optimal use of the 5G network, thus network slicing is proposed as a solution that creates customized slices of the network specifically designed to meet the requirements of each service. Under the network slicing, the radio resources can be shared in orthogonal and non-orthogonal schemes. Motivated by Industrial Internet of Things (IIoT) scenarios where a large number of sensors may require connectivity with stringent requirements of latency and reliability, we propose the use of Non-Orthogonal Multiple Access (NOMA) to improve the number of URLLC devices that are connected in the uplink to the same base station (BS), for both orthogonal and non-orthogonal network slicing with eMBB devices. The multiple URLLC devices transmit simultaneously and across multiple frequency channels. We set the reliability requirements for the two services and evaluate the pairs of achievable sum rates. We show that, even with overlapping transmissions from multiple eMBB and URLLC devices, the use of NOMA techniques allows us to guarantee the reliability requirements for both services.

In this work we resort to the Bluetooth Low Energy (BLE) beaconing mechanism to propose an hybrid indoor positioning system (H-IPS) that fuses both multilateration (MLT) and fingerprinting (FP) RSSI-based approaches. The aim is to estimate the localization of an indoor target node, which is assumed to follow a uniform motion model. We adopt Kalman Filtering (KF) to diminish the MLT and FP errors while performing a track-to-track fusion (TTF) of the two KF outputs to further improve the performance. Our results indicate that the proposed H-IPS improves the estimation accuracy when individually compared to the standalone FP scheme in up to 46% in the considered scenarios, while the standalone MLT is outperformed in approximately 54%. Moreover, we also provide some insights on the influence of parameters such as the FP grid size, number of access points (APs) and number of samples on the accuracy of the proposed scheme. Finally, we show that the probability that the distance error of the proposed H-IPS is lower than 2 m is 92%, while for the FP and MLT the same probability is 43% and 47%, respectively.

In this paper, we consider a scenario where two multiple-aperture legitimate nodes (Alice and Bob) communicate by means of free-space optical communication in the presence of a multiple-aperture eavesdropper (Eve), which is subject to pointing errors. Two different schemes are considered depending on the availability of channel state information (CSI) at Alice: 1) the adaptive scheme, where Alice possesses the instantaneous CSI with respect to Bob and 2) the fixed-rate scheme, where such information is not available at Alice. The performance of the aforementioned schemes is evaluated in terms of a recently proposed metric named effective secrecy throughput (EST), which encompasses both the reliability and secrecy constraints. By constraining the system to operate below a given maximum allowed secrecy outage probability, we evaluate the EST analytically and through numerical results, showing that the use of multiple apertures at Alice is very important toward achieving the optimal EST.

In this paper, we consider a vehicular network and propose the application of directional antennas to a recently proposed information-theoretic location verification system (LVS), aiming at increasing the system capability in correctly detecting malicious nodes. In the proposed LVS with directional antennas (LVS-DA), we adopt a more realistic dual-slope large-scale fading model that is suitable to vehicular networks. The performance of the proposed scheme is evaluated analytically for some specific number of directional antennas and confirmed by numerical results, showing that the proposed LVS-DA scheme is capable of considerably increasing the system capability in detecting malicious nodes when compared with other recently proposed schemes, under different scenarios.

We evaluate the effective secrecy throughput of the multiple-input multiple-output multiple-antenna eavesdropper (MIMOME) wiretap channel with antenna selection at the legitimate transmitter. The optimal target secrecy rate that maximizes the effective secrecy throughput is obtained and confirmed by numerical results. Differently from previous works, we constrain the maximum allowed secrecy outage probability (SOP) and show that, the single-input single-output multi-antenna eavesdropper (SISOME) scheme recently proposed in the literature presents a much lower resilience to the decrease of the maximum allowed SOP than that obtained by MIMOME scheme.

Presents corrections made to the paper, “Energy Efficiency-Spectral Efficiency Trade-Off of Transmit Antenna Selection” (Rayel, O.K., et al; IEEE Trans. Commun., vol. 62, no. 12, pp. 4293–4303, Dec. 2014).

We evaluate the secrecy outage probability of a two-user network-coded cooperative network in the presence of an eavesdropper. We show through theoretic and numerical analyses that the secrecy can be increased through the use of network coding when compared to the direct transmission and traditional cooperative techniques.

We investigate the energy efficiency-spectral efficiency (EE-SE) trade-off of transmit antenna selection/maximum ratio combining (TAS) scheme. A realistic power consumption model (PCM) is considered, and it is shown that using TAS can provide significant energy savings when compared to multiple-input multiple-output (MIMO) in the low to medium SE region, regardless the number of antennas, as well as outperform transmit beamforming scheme (MRT) for the entire SE range. For a fixed number of receive antennas, our results also show that the EE gain of TAS over MIMO becomes even greater as the number of transmit antennas increases. The optimal value of SE that maximizes the EE is obtained analytically, and confirmed by numerical results. Moreover, the influence of receiver correlation is also evaluated and it is shown that considering a non-realistic PCM can lead to mistakes when comparing TAS and MIMO.

In this paper, the use of network coding is exploited to improve the cooperative diversity order of multi-source multi-hop networks with line topology. We elaborate on a previous system model by allowing user nodes to be arbitrarily located along the line network, to have the ability to perform network decoding, and to be able to listen to upstream nodes. The recently introduced generalized dynamic-network codes (GDNC) are shown to be the best performing scheme under several distinct circumstances. Computer simulation results support the superiority of the GDNC scheme, and suggest that the connection between network coding and classical channel coding, initiated in a previous work, can once again be proved useful by reducing the design of network codes for arbitrarily located nodes to the design of classical block codes with unequal error/erasure protection.

In this paper, we apply nonbinary network coding to a multiple access cooperative vehicular ad hoc network (VANET), where the vehicles have independent information to transmit to a common destination. We consider that all the users in the network are provided with multiple antennas (MIMO), so that the benefits of both space-time codes and cooperative communication are used to increase the network diversity order and consequently provide more reliable communication. A Nakagami-m fading model is considered, aiming to evaluate the reliability of the proposed scheme mainly in scenarios where the channel condition is critical (sub-Rayleigh scenario with m<;1). The network outage probability is obtained analytically, and confirmed by numerical results.

In this letter, we evaluate the energy efficiency of a wireless network-coded cooperative system where multiple nodes cooperatively transmit their information to a common destination. The energy consumption of the transmission and reception circuits is taken into account. It is shown that network coding can provide significant energy savings compared to direct transmission and traditional cooperation techniques. We consider a Nakagami- m fading model, so that the influence of a line-of-sight is also investigated. The optimal number of users that minimizes the energy consumption is obtained analytically, and confirmed by numerical results. Using this number to organize the nodes in clusters can provide considerable energy savings and decrease the network encoding/decoding complexity.

In this work, we propose an adaptive distributed network-channel coding for a cooperative multiple access channel where M users cooperatively communicate with a common base station. The scheme is based on the recently proposed generalized dynamic-network codes (GDNC), in which the network code design that maximizes the diversity order was recognized as equivalent to the design of linear block codes over a nonbinary finite field under the Hamming metric. The aim here is to increase the system average code rate without reducing its diversity order, making use of a small quantity of feedback. The average rate and the diversity order are obtained analytically, and computer simulations are shown to agree with the analytical results.

In this work, network coding is employed to obtain maximum diversity order in a network where the users have independent information to transmit to a common base station. We elaborate on the recently proposed generalized dynamic network codes (GDNC), which can only achieve part of the maximum diversity order when the inter-user channels are subject to outages. In particular, by allowing the users to perform network decoding, in this paper we show that maximum diversity order can be achieved. Results are restricted to the 2-user case, although some discussion regarding the general case is provided.

In this contribution, we investigate Near-Capacity Multi-user Network-coding (NCMN) based systems using an Irregular Convolutional Code, a Unity-Rate Code and M-ary Phase-Shift Keying. In the NCMN based systems, we consider a multiuser network in which the users cooperatively transmit independent information to a common base station (BS). Extrinsic Information Transfer (EXIT) charts were used for designing the proposed NCMN scheme. The design principles presented in this contribution can be extended to a vast range of NCMN based systems using arbitrary channel coding schemes.

In this contribution, Near-capacity Non-coherent Cooperative Network-coding aided Multi-user (NNCNM) systems are designed with the aid of Extrinsic Information Transfer (EXIT) charts for the sake of approaching the Differential Discrete-input Continuous-output Memoryless Channel (D-DCMC)-based capacity. The proposed sub-frame-based network coding solution allows the system to significantly mitigate the effects of large-scale fading on each frame. Hence, NNCNM systems operating in large-scale fading environments are capable of approaching the D-DCMC capacity of the less hostile single link channel incurring the small-scale fading, but no shadow fading.

In this work, we propose and analyze a construction of adaptive network codes for a multiple access network under independent block-fading assumption. We aim to increase the system average transmission rate of the recently proposed generalized dynamic-network codes (GDNC) without reducing its diversity order, making use of a small amount of information fed back by the base station. The average rate and the diversity order are obtained analytically, and computer simulations of the diversity order are shown to agree with the analytical results.

In this work, we propose and analyze a generalized construction of distributed network codes for a network consisting of M users sending different information to a common base station through independent block fading channels. The aim is to increase the diversity order of the system without reducing its code rate. The proposed scheme, called generalized dynamic-network codes (GDNC), is a generalization of the dynamic-network codes (DNC) recently proposed by Xiao and Skoglund. The design of the network codes that maximizes the diversity order is recognized as equivalent to the design of linear block codes over a nonbinary finite field under the Hamming metric. The proposed scheme offers a much better tradeoff between rate and diversity order. An outage probability analysis showing the improved performance is carried out, and computer simulations results are shown to agree with the analytical results.