The maritime sector is an integral part of the growing blue economy, and accessible and affordable communication is a current goal. However, offshore areas lack adequate wireless connectivity. While Satellite and Very High Frequency (VHF) communication can be used, they come with limitations in cost and latency that hinder autonomous ship operations. In contrast, mobile networks can extend land-based communication over water, support Internet of Things (IoT) use cases, and enable seamless autonomous ship operations promising significant benefits for the maritime sector. However, the primary challenge lies in establishing reliable connectivity in coastal regions. Therefore, this paper explores the feasibility of using 5G-enabled drones and floating mobile base stations (FMBS) to establish mobile connectivity in coastal areas. Specifically, we examine the use of 5G FR-1 frequency (700MHz), which offers broader coverage, lower power consumption, and better support for IoT and fast-moving users (e.g., on ships and cruises). We present a case study to provide internet service along a predetermined route, i.e., from Kristiansand to Amsterdam. We also assess the appropriate maritime propagation model to evaluate the performance of the proposed solution and its feasibility for providing reliable and efficient connectivity. Our calculations provide insight into the number of drones needed to establish a mobile network in that particular route. Our study demonstrates the potential of using 5G-enabled drones and FMBS to improve mobile communication in the maritime sector.

The adoption of wireless technology for industrial wireless instrumentation requires high-quality communication performance. The use of transmission power control (TPC) can help address industrial issues concerning energy consumption, interference, and fading. This paper presents a TPC algorithm designed for industrial applications based on theoretical and empirical studies. It is shown that the proposed algorithm adapts to variations in link quality, and is hardware-independent and practical.

Wireless sensor networks for industrial automation applications must offer timely, reliable, and energy efficient communications at both low and high data rate. While traditional communication technologies between 2.4 GHz and 5 GHz are sometimes incapable to efficiently achieve the aforementioned goals, new communication strategies are emerging, such as millimeterWave communications. In this overview paper, the general requirements that factory and process automation impose on the network design are reviewed. Moreover, this paper presents and qualitatively evaluates the 60 GHz millimeterWave communication technology for automation. It is argued that the upcoming 60 GHz millimeterWave technology brings an enormous potential and can influence the design of the future communication infrastructures in factory and process automation.

Base station coordination has received much attention as a means to reduce the inter-cell interference in cellular networks. However, this interference reducing ability comes at the expense of increased feedback, backhaul load and computational complexity. The degree of coordination is therefore limited in practice. In this paper we explore the trade-off between capacity and feedback load in a cellular network with coordination clusters. Our main interest lies in a scenario with multiple fading users in each cell. The results indicate that a large fraction of the total gain can be achieved by a significant reduction in feedback. We also find an approximate expression for the distribution of the instantaneous signal-to-interference-plus-noise ratio (SINR) and propose a new effective scheduling algorithm.

In this paper we consider pure line-of-sight multiple-input multiple-output (MIMO) channels employing uniform linear antenna arrays. We investigate the influence of exact spherical wave propagation modeling versus approximate plane wave propagation modeling on the properties of the MIMO channel matrix. When the transmission distance increases, the properties of the singular values of the MIMO channel matrix given by the spherical wave model approach the properties given by the simpler plane wave model. We investigate this transition between the two channel models, which results in a new tool giving us analytical expressions describing when spherical wave modeling is necessary and when plane wave modeling gives sufficient modeling accuracy. The parameters of interest are the transmission distance, the frequency, the array orientation, and the array size. The tool introduced is general, in the sense that it supports different performance measures when deciding on the transition between the two models. As an example, we investigate underestimation of the mutual information in this paper. The results show that the spherical wave model should be applied e.g. in some practical WLAN scenarios where plane wave modeling is commonly applied today.

Multi-carrier OFDM-CDMA has a range of advantages that make ideal for high data rate wireless access system. A two-layer carrier interferometry (CI) phase coding approach is proposed for enhancing multi-user detection of the mm wavelength multi-carrier OFDM-CDMA based uplink broadband wireless access system (BWA). The proposed OFDM-CDMA scheme uses a two-layer CI phase coding structure, which comprises outer and inner CI modulations and is combined with the iterative interference cancellation and detection to boost the system capability in the high radio fading and strong multiple access interference environment. The orthogonal property of the CI signals is exploited to enhance diversities in time, frequency and spreading code domains, as well as to simplify signal processing. The proposed two-layer CI OFDM-CDMA scheme for the uplink BWA is mathematically analyzed. The effects of the frequency synchronization errors are studied. Numeric simulations are carried out to evaluate the system performance. The simulation results show the superior characteristics of the proposed two-layer CI phase coding scheme for the uplink BWA system compared to other schemes.

Multi-carrier OFDM-CDMA has a range of advantages that make it ideal for high data rate wireless access system. In this paper, a cross-layer multi-service random access and channel assignment approach is proposed for the uplink communication of the mm wavelength multi-carrier OFDM-CDMA BWA system. The OFDM-CDMA solution and the iterative interference cancellation and detection are applied at the system's physical layer to support multi-user multi-service capabilities and to improve the robustness against the flat and frequency selective fading. The proposed scheme grants the uplink random access connections and allocates the radio resources to the active multiservice subscriber stations by using the cooperation between base station and subscriber stations, as well as the diversities in spreading codes, subcarriers, time in OFDM symbols, and time division multiplex. A MAC protocol and its connection and channel assignment procedures are described. Numeric simulations of the uplink BWA system with the proposed random access and channel assignment scheme are carried out to evaluate the system's performance.

Multi-carrier OFDM-CDMA has a range of advantages that make ideal for high data rate wireless access system. A two-layer carrier interferometry (CI) phase coding approach is proposed for enhancing multi-user detection of the mm wavelength multi-carrier OFDM-CDMA based uplink broadband wireless access system (BWA). The proposed OFDM-CDMA scheme uses a two-layer CI phase coding structure, which comprises outer and inner CI modulations and is combined with the iterative interference cancellation and detection to boost the system capability in the high radio fading and strong multiple access interference environment. The orthogonal property of the CI signals is exploited to enhance diversities in time, frequency and spreading code domains, as well as to simplify signal processing. No pilot signal is needed. The proposed two-layer CI OFDM-CDMA scheme for the uplink BWA is mathematically analyzed, and its numeric simulations are carried out to evaluate the system performance. The simulation results show the superior characteristics of the proposed two-layer CI phase coding scheme for the uplink BWA system compared to other schemes.

In this paper we derive exact expressions for the mutual information (MI) probability density function and the MI cumulative distribution function of dual-branch multipleinput multiple-output (MIMO) systems (either two transmit (Tx) or two receive (Rx) antennas) communicating over a Ricean channel with no constraint on the rank of the line-of-sight (LOS) channel matrix. This is done both for the case where the channel is only known at the Rx, and for the case where the channel is known both at the Tx and the Rx. As an example, to evaluate the expressions, we employ uniform linear arrays and give expressions for the eigenvalues of the LOS channel matrix for the dual-branch case.

Huge popularity of mobile devices and Internet open new application field of wireless positioning and navigation systems, and this integration also brings new research issues. Currently the positioning and navigation systems are mostly based on satellite positioning systems, such as GPS. One serious drawback of these satellite based positioning and navigation systems is that they can only operate in outdoor environment. There are several approaches for wireless positioning, e.g. cell ID, DOA (directions of arrivals) or signal strength measurements, but these approaches can not meet requirements of wireless positioning, including latency, availability and accuracy. In this paper, we propose a new approach for Bluetooth positioning, which is based on the time offset acquisition of signals propagating over radio channel, and the forward-backward ranging. Through simulations and experiments, it shows that the new Bluetooth ranging approach could give high ranging accuracy with modest modifications of current Bluetooth technology.

This paper describes a technique for realizing a high-rank channel matrix in a line-of-sight (LOS) multiple-input multiple-output (MIMO) transmission scenario. This is beneficial for systems which are unable to make use of the originally derived MIMO gain given by independent and identically distributed (i.i.d.) flat Rayleigh fading subchannels. The technique is based on optimization of antenna placement in uniform linear arrays with respect to mutual information (MI). By introducing a new and more general 3-D geometrical model than that applied in earlier work, additional insight into the optimal design parameters is gained. We also perform a novel analysis of the sensitivity of the optimal design parameters, and derive analytical expressions for the eigenvalues of the pure LOS channel matrix which are valid also when allowing for non-optimal design. Furthermore, we investigate the approximations introduced in the derivations, in order to reveal when the results are applicable. The LOS matrix is employed in a Ricean fading channel model, and performance is evaluated with respect to the average MI and the MI cumulative distribution function. Our results show that even with some deviation from the optimal design, the LOS MEMO case outperforms the i.i.d. Rayleigh case in terms of MI.

In this paper we consider pure line-of-sight multiple-input multiple-output channels employing uniform linear antenna arrays. We investigate the influence of exact spherical wave propagation modeling versus approximate plane wave propagation modeling on the properties of the channel matrix. Our earlier work on 2 times 2 systems is extended to include arbitrary MIMO dimensions. As before, when transmission distance increases, the properties of the spherical wave model converge to the properties given by the simpler plane wave model. The investigation results in a new tool which gives us analytical expressions describing when spherical wave modeling is necessary and when plane wave modeling is sufficient. The parameters of interest are the transmission distance, the frequency, and the array size, and the results show that the spherical wave model should be applied e.g. in some practical WLAN scenarios where plane wave modeling is commonly applied today.

In wireless communications, bandwidth is a scarce resource. By employing link adaptation we achieve bandwidth-efficient wireless transmission schemes. Using a fixed number of codes we propose a variable-power transmission scheme for slowly flat-fading channels. Assuming that capacity-achieving codes for AWGN channels are available, we develop new combined discrete-rate discrete-power adaptation algorithms with limited feedback for wireless systems. The adaptation schemes are optimized in order to maximize the average spectral efficiency (ASE) for any finite number of available rates. We show that the new transmission schemes can achieve significantly higher ASE when compared to constant power schemes, almost reaching the upper bound of continuous power adaptation. Specifically, using just four rates and four power levels per rate results in a spectral efficiency that is within 1 dB of the continuous-rate continuous-power Shannon capacity. Further, the novel discrete transmission schemes reduce the probability of outage and are more robust against imperfect channel estimation and prediction.

We investigate the influence of exact spherical wave propagation modeling and approximate plane wave propagation modeling on the properties of a pure line-of-sight 2 times 2 multiple-input multiple-output channel. As transmission distance increases, the properties of the true spherical wave model converge to the properties given by the more simple plane wave model. We present a new model evaluation tool based on an analysis of the rank and singular values of the channel matrix, which can be employed to find the region where spherical wave modeling is necessary. The derivation results in new exact analytical expressions for which of the two models that should be applied, and the results based on mutual information show that the spherical wave model should be applied in many practical scenarios, e.g. indoor WLAN scenarios, where plane wave modeling is most frequently used today

This paper describes a technique for realizing a high rank channel matrix in a line-of-sight (LOS) multiple-input-multiple-output (MIMO) transmission scenario. This is beneficial for systems which can not make use of the originally derived MIMO gain given by independent and identically distributed (i.i.d.) flat Rayleigh fading channels. Typical applications are fixed wireless access and radio relay systems. The technique is based on optimization of antenna placement in a uniform linear array. By introducing a new and more general geometrical model than that applied in earlier works, additional insight into the optimal design parameters is gained. A novel analysis of the sensitivity of the optimal design parameters is performed. The LOS transmission matrix is used in a Rician fading channel model, and performance is evaluated with respect to ergodic capacity, outage capacity, and effective degrees of freedom. The results show that even with some deviation from optimal design, the LOS MIMO case outperforms the i.i.d. Rayleigh case in terms of Shannon capacity.

Recent publications on new improved convolutional codes claim different codes to be optimum under the optimum distance spectrum (ODS) criterion. This correspondence presents results from a study independent of the previous works, and seeks to clarify some inconsistencies. In addition, some new improved feed-forward convolutional encoders are presented.

In code division multiple-access (CDMA) systems, maximum total throughput assuming a matched filter receiver can be obtained by spreading with low-rate error control codes. Previously, orthogonal, bi-orthogonal and super-orthogonal codes have been proposed for this purpose. We present in this paper a family of rate-compatible low-rate convolutional codes with maximum free distance. The performance of these codes for spectrum spreading in a CDMA system is evaluated and shown to outperform that of orthogonal and super-orthogonal codes as well as conventionally coded and spread systems. We also show that the proposed low rate codes will give simple encoder and decoder implementations. With these codes, any rate 1/n, n/spl les/512, are obtained for constraint lengths up to 11, resulting in a more flexible and powerful scheme than those previously proposed.

The performance of an asynchronous code division multiple access (CDMA) system (uplink) employing very low-rate maximum free distance codes for combined coding and spreading is analyzed when successive or parallel interference cancellation is applied. An analytical approach to the evaluation of the bit error rate is presented and shown to give results close to simulations. Our results show that the code-spread system outperforms the conventionally coded and spread system. Without interference cancellation the single-user bound is never reached (except for one user). With two stages of parallel interference cancellation, a code-spread system with a load only slightly less than 1 bit/chip can obtain a bit error rate very close to that of a single-user system.

New rate-compatible convolutional (RCC) codes with high constraint lengths and a wide range of code rates are presented. These new codes originate from rate 1/4 optimum distance spectrum (ODS) convolutional parent encoders with constraint lengths 7-10. Low rate encoders (rates 115 down to 1/10) are found by a nested search, and high rate encoders (rates above 1/4) are found by rate-compatible puncturing. The new codes form rate-compatible code families more powerful and flexible than those previously presented. It is shown that these codes are almost as good as the existing optimum convolutional codes of the same fates. The effects of varying the design parameters of the rate-compatible punctured convolutional (RCPC) codes, i.e., the parent encoder rate, the puncturing period, and the constraint length, are also examined. The new codes are then applied to a multicode direct-sequence code-division multiple-access (DS-CDMA) system and are shown to provide good performance and rate-matching capabilities. The results, which are evaluated in terms of the efficiency for Gaussian and Rayleigh fading channels, show that the system efficiency increases with decreasing code rate.

The performance for sequential decoding on Rayleigh fading channels has been obtained theoretically and by simulations. The results show that sequential decoding of long constraint length convolutional codes is a good candidate coding scheme for data oriented services in future mobile communication systems. The applicability of such a coding and decoding scheme for future mobile systems is discussed.