This paper presents a new algorithm applied to compensate for the influence of jamming in data transmission. A new metric of system optimization has been adopted from the blind equalization criterion previously proposed by the author. The algorithm is used for blind signal source separation and signal detection. Thus, extraction of a useful signal can be performed from the mixture of useful and jamming signals. Selected simulation results are presented showing the performance of the proposed receiver in the MIMO system.

This paper presents a new and simple algorithm applied to detect jamming in OFDM transmission. A new metric is proposed for jamming detection. It can be used in both the time and frequency domains. It can also be implemented separately in each physical resource block, enabling the detection of passband jamming. Selected simulation results are presented showing the performance of the physical downlink shared channel in the MIMO 5G system configuration in the presence or absence of jamming.

This paper describes the results of investigations of autonomous resource re-selection for the Cellular-Vehicle-to-Everything (C-V2X) Mode 4 applied in LTE. We have investigated the system-level performance of the Sensing-based Semi-Persistent Scheduling (S-SPS) algorithm that 3GPP has standardized as a resource allocation scheduler. The S-SPS with Adaptive Modulation (AM) and Adaptive Modulation and Collision Detection (AMCD) resource re-selection algorithms are the algorithms newly proposed in this paper to improve the Packet Reception Ratio (PRR) and resource Collision Ratio (CR). It is known that S-SPS faces failures in resource re-selection and causes collision problems when multiple transmitters re-select the same resource at the same time or when channel load is increased for the same transmission range. In the literature, adaptive modulation has been previously introduced to solve this collision problem in IEEE 802.11p by managing the Distributed Congestion Control (DCC). This paper proposes AM and AMCD algorithms in C-V2X Mode 4, depending on the Channel Busy Ratio (CBR) and the probability of resource re-selection P to solve the channel load collision and resource collision problems by broadcasting the collided resource locations to announce the source of these collisions. We show that AMCD is a promising method of maintaining efficient and reliable vehicular communications by re-selecting resources with proper modulation when the Re-selection Counter (RC) applied in the MAC layer reaches zero, and when the current resource is assigned as a collided resource by surrounding vehicles. The AMCD algorithm has shown better performance than the AM algorithm in resource re-selection, and it is more reliable in broadcasting awareness messages.

This paper reports the results of investigations of autonomous resource selection for the Cellular-Vehicle-to-Everything (C-V2X) Mode 4 of LTE. We have investigated the system-level performance of sensing based Semi-Persistent Scheduling (S-SPS) algorithm that has been proposed by 3GPP for resource allocation scheduling and our newly proposed Extended-Estimation and Reservation Resource Allocation (E-ERRA) algorithm. It is known that S-SPS faces collision problems in resource allocation. The ERRA algorithm previously introduced by the authors has solved this collision problem by pre-allocating the first received packet that has the same value of the Random Counter (RC). RC gets a value generated randomly when the reselection is needed and is decreased by one in each broadcast cycle. Furthermore, the extension of ERRA (E-ERRA) introduced in this paper is aimed at solving the problem of the lost reserved resources when the vehicle with preallocated resources has just left or appeared in the broadcast range before the re-selection process. E-ERRA specifies an alternative list of resources to use when this problem appears. It has been proven that E-ERRA is a promising way to support efficient and reliable vehicular communications by choosing and announcing the next resource allocation. The decrease in the collision ratio (CR) and increase of the packet reception ratio (PRR) that are shown in the paper indicate that E-ERRA performs substantially better than S-SPS in reliable broadcasting and resource allocation for vehicle transceivers operating in C-V2X Mode 4.

Professional applications of UAVs require fast and reliable communication for the streaming of data from a variety of sensors located on board, as well as for telemetry and control. In this paper we present a project of downlink and uplink high-speed communication which enables control and data reception in rapidly changing propagation conditions in urban outdoor-to-outdoor (LOS and NLOS) and outdoor-to-indoor scenarios. The selected solutions for modulation, channel coding, synchronization and SNR estimation resulting high-performance transmission. The design assumptions have been verified by simulations using carefully selected radio channel models. The proposed design has been implemented in software-defined radio technology using the limited resources of an FPGA and microcontroller board.

The paper considers the practical limitations of a cooperative adaptive cruise control algorithm for driving in a platoon of cars which communicate in conformance with the IEEE 802.11p standard. These limitations stem from the limited accuracy of sensors applied in vehicle control algorithms and from the maximum acceleration and deceleration of several classes of cars. The speed, acceleration, distance and relative speed sensors applied on board cars connected via wireless 802.11p communication links are considered. We show how these inaccuracies influence the overall platoon performance expressed in the form of an allowable physical distance between subsequent cars that ensures platoon stability and no car crashes. The sophisticated simulation package developed by the authors has been used in investigations which helped to determine the cases where limitations and inaccuracies substantially influence the platoon performance.

This paper introduces the Virtual Leader-Predecessor Following (VLPF) information flow topology to support communication between vehicles moving in a long platoon under the constant distance policy. The virtual leaders in the proposed VLPF architecture are spread across the platoon with specified density and act as local leaders for a certain number of cars following them. Such a topology ensures that distances between vehicles and their local leaders are small enough to guarantee reliable wireless communication, and thus enables much higher platoon lengths. At the same time, the proposed solution does not introduce any additional communication overhead or delays.

In this paper, the decentralized resource selection for Cellular Vehicle to Everything (C-V2X) communication is investigated. The immunity against packet collisions and selection of resource allocation are examined. It is found that the improvement of collision ratio and packet reception ratio (PRR) with the estimation and reservation of resource allocation, is the best way to improve the message broadcasting reliability. However, Sensing-based Semi-Persistent Scheduling (S-SPS), has been proposed for C-V2X Mode 4. The S-SPS faces several serious problems, like half duplex errors, hidden terminal errors, and packet collision errors. We propose an algorithm to enhance the performance aimed at decreasing the collision ratio and increasing PRR. The idea is that each vehicle lists all resource locations of the received packets that have the same random counter. This allows each terminal to estimate which resource location will be free in the next resource selection. Also, the announced next location in the list will be the current location when the random counter reaches zero. This way the vehicle does not need to depend on the sensing process, and resources utilization is improved. Our simulations show a significant improvement in the performance of our proposed algorithm as compared to S-SPS.

This paper investigates the ability of modified cooperative adaptive cruise control to support high-density car platooning. We first use a simplistic communication model to study the impact of actuation lag, message periodicity, and communication delay on the minimum feasible inter-car spacing. We then use a detailed IEEE 802.11p simulation model to evaluate platooning performance in realistic highway scenarios. Different highway traffic intensities are simulated to observe the impact of increasing contention on the wireless channel with two different transceiver configurations: a single-transceiver operating on the common safety channel and a dual-transceiver operating, simultaneously, on the common safety channel and a dedicated service channel.

This paper investigates block error rate (BLER) performance and computational complexity of candidate channel coding schemes for ultra-reliable low latency communication (URLLC) in 5G. The considered candidates are the same as those identified in 3GPP: turbo, LDPC, polar, and convolutional codes. Details of code constructions and decoding algorithms are provided with computational complexity analysis. Code construction parameters, number of iterations, and list sizes are selected to provide a fair comparison among candidate coding schemes. Simulation results on BLER are shown for several code rates and small-to-moderate block sizes. The results reveal that polar and LDPC codes outperform turbo codes for short block sizes of 40 bits, while the opposite is true for medium block sizes of 200 bits. None of the schemes is a clear winner at all considered block sizes and coding rates. Other aspects like implementation complexity, latency, and flexibility will also be important when deciding the URLLC coding scheme.

In this paper we present an efficient method of peak- to-average power ratio (PAPR) minimization in the space-time block coded (STBC) MIMO orthogonal frequency division multiplexing (OFDM) transmission. The developed system is based on 802.11p standard designed for the communication between vehicles and between vehicles and infrastructure. The presented algorithm belongs to the family of selective mapping (SLM) methods. Since SLM algorithms require that side information is transmitted to the receiver, in the proposed solution pilot tones are used for this purpose.

This paper studies the two-way wireless relaying with multiple antennas at the nodes, where data transfer takes place between the base station (BS) and the mobile station (MS) with the help of the relay station (RS). We consider the decode-and-forward protocol which is divided into two phases: Multiple Access phase and Broadcast phase. The main focus of this work is on the broadcast phase during which two data blocks received by the RS have to be sent to the BS and MS using the same channel resources. It may be achieved by incorporating network coding, where the binary sum of two data blocks is broadcast to both end nodes. In this paper, we demonstrate that when multiple antennas are available at the transmitter and receiver, applying network coding is not the optimal solution. We present a novel approach that exploits the MU-MIMO scheme and together with the proposed SVD precoding algorithm and interference cancellation receiver, provides a significant performance improvement. In the proposed scheme, we assume full channel state information at the transmitter (CSIT), which in a time division duplex (TDD) system may be obtained by exploiting the reciprocity of the wireless channel. The performance of the considered scenario is analyzed and verified through multi-link level simulations.

The paper is devoted to the studies on modifications of mapping of the OVSF channelization codes onto the data and control channels in HSUPA, aiming at increasing the uplink data rates. Appropriate selection of mapping can result in a link throughput gain of up to 28% as compared with the standard HSUPA transmission. An intensive HSUPA link level simulation campaign has been performed to investigate many possible mappings, to optimize the ratios of traffic to pilot channel powers and to measure parameters of the transmitted signal such as the peak-to-average power ratio and the cubic metric. The most important and representative results are summarized in this paper.

The effective method of two-way relaying for TDD (Time Division Duplex) wireless systems is described. In a traditional two-way relaying without network coding four time slots are needed in the TDD mode to exchange data blocks between two stations, e.g. mobile (MS) and base (BS) stations via a relay station (RS). In the proposed solution the number of slots is reduced to two only - the multiple access and broadcasting slots. Substantial savings in the transmission time resources are achieved thanks to the application of the MIMO technique used by the relay station in the multiple access phase and simple network coding in the broadcasting slot. Contrary to well known solutions, in the proposed system network coding is performed on the decoded information blocks received by the RS from both end stations which participate in two-way relaying. Such an approach results in high performance of each constituent link between the end stations and the RS, which leads to the high overall system performance. Simulation experiments are reported showing satisfactory performance of the proposed two-way relaying system.

We suggest applying constellation shaping to reduce the peak and average power of orthogonal frequency division multiplexing (OFDM) signals using quadrature amplitude modulation (QAM) in all subcarriers without clipping or reducing the data rate. Adopting the successful shell mapping algorithm for high data rate transmission over telephone channels, as described in the V.34 Recommendation of ITU-T, we build a shell mapping algorithm for multidimensional constellation in the frequency domain for OFDM communication systems with N subcarriers. We give closed-form expressions of the functions needed to apply the constellation shaping algorithm for any N being a power of two. No side information needs to be transmitted and the data rate remains the same as for the basic OFDM system. Our simulation results show that we are able to reduce the peak and mean power by about 1 dB for OFDM signals with N = 16. For a higher number of subcarriers, we expect that we obtain more freedom in power minimization and the resulting gain will be higher. The only price to be paid is the enhanced complexity of the system by an amount that is rather acceptable.

The paper presents a novel computationally and memory efficient structure of an HPA predistorter based on piece-wise linear approximation of the HPA inverse characteristics. The adaptation algorithm is derived and representative simulation results are presented showing good quality of the proposed HPA predistorter and its adaptation algorithm

Simple methods of the estimation of that part of the frequency offset, which is a multiple of the subcarrier spacing in the OFDM (orthogonal frequency division multiplexing) systems have been proposed. Described methods are aimed at burst transmission systems and take use of only one preamble symbol also required for the timing offset estimation. The methods are based on the frequency domain search for the unused subcarriers in the received signal spectrum. The proposed algorithms are immune to a constant phase shift (e.g. caused by timing errors). The estimation range depends on the algorithm but in general can be made as large as desired (but less than a half of the signal bandwidth). Simulation results show that the proposed algorithms estimate an integer part of the frequency offset in the AWGN channel even in the presence of some amount of the intercarrier interference (ICI). Satisfactory performance has been obtained also for OFDM transmission on multipath channels.

The data driven frequency-domain echo canceller (EC) for a multicarrier modulation system is considered. An EC in such a system has to deal with both the interchannel and intersymbol interference occurring in the echo signal. For this reason, the main disadvantage of the data driven EC structure is the large computational complexity. Here, the solution of the computational complexity problem is presented. It is based on assumption that in practice, interchannel interference has a limited range. The number of operations per symbol as a measure of the EC computational complexity is given. Simulation results present echo attenuation in the frequency-domain EC, operating in the orthogonally multiplexed quadrature amplitude-shift keying system. Modifications of the proposed EC structure and its computational complexity in the systems with pulse shaping are discussed.

Application of linear predictors is considered for maximum likelihood sequence estimation of digital signals corrupted by intersymbol interference and colored noise. After general derivation of the cost function a few receiver versions are presented. The simulation results for trellis coded signals transmitted over a two-path channel introducing deep selective fade are presented. The proposed receivers when applied in mobile TDMA radio are aimed to cope with intercell and interchannel interference which in case of many interferers can be modeled as colored Gaussian noise.

Automatic control of the step size and filter length is presented for a transversal blind equalizer which is driven by the "stop-and-go" decision directed algorithm. The proposed method results in substantial shortening of the convergence time.>

Several space diversity techniques for a maximum-likelihood sequence estimation receiver applied to digital mobile radio are considered and compared. Space diversity reception helps to overcome the frequency selective fading that is a common problem in mobile radio environment. Many papers have been devoted to the space diversity techniques but only few of them consider the diversity reception combined with the MLSE receiver. For such a receiver two groups of structures can be specified-combining/selection at the "sample level" and combining/selection at the "metric level". For each group the authors investigate a few particular structures. They also define new criteria for the optimal combining. All the structures are compared by means of the computer simulation and the results are presented for typical channel models.

The DFE & ML receiver is presented for data transmission systems using QAM modulation. A substantial improvement in performance results as compared to other one- or two-stage receiver structures at relatively low computational complexity.

The two-stage equalizer of A. Gersho and T. L. Lim is analyzed, and simulation results of its performance, as well as derivation of the lower bound of the probability of error at the output of the canceller, are presented. They indicate that the overall performance of the canceller critically depends on the performance of the first-stage equalizer. Thus, a decision-feedback equalizer is proposed as the first-stage equalizer.

The paper presents an equalization scheme based on the two-stage equalizer originally introduced by Proakis. Mostly additions are required for implementation of the equalizer structure and the adaptation algorithm. The equalizer can be applied to data transmission Systems which use four-phase modulation, especially in 1200/2400 bit/s modems, thus replacing the fixed equalizer recommended by CCITT. The results presented in the paper deal with the analog and digital implementation of the proposed equalizer. Its performance is compared to the performance of the conventional transversal equalizer, a decision-feedback equalizer, an ideal linear canceller, and an ideal QPSK system.