Master the fundamentals of digital communications systems with this accessible and hands-on introductory textbook, carefully interweaving theory and practice. The just-in-time approach introduces essential background as needed, keeping academic theory firmly linked to practical applications. The example-led teaching frames key concepts in the context of real-world systems, such as 5G, WiFi, and GPS. Stark provides foundational material on the trade-offs between energy and bandwidth efficiency, giving students a solid grounding in the fundamental challenges of designing digital communications systems. Features include over 300 illustrative figures, 80 examples, and 130 end-of-chapter problems to reinforce student understanding, with solutions for instructors. Accompanied online by lecture slides, computational MATLAB® and Python resources, and supporting data sets, this is the ideal introduction to digital communications for senior undergraduate and graduate students in electrical engineering.

This article examines the problem of interference in automotive radar. Different types of automotive radar as well as mechanisms and characteristics of interference and the effects of interference on radar system performance are described. The interference-to-noise ratio (INR) at the output of a detector is a measure of the susceptibility of a radar to interference. The INR is derived from different types of interfering and victim radars and depends on the location of both as well as parameters such as transmit power, antenna gain, and bandwidth. In addition, for victim radar with beamscanning, INR depends on the location of the target the victim radar is attempting to detect. Analysis is presented to show the effects of various interference scenarios on the INR. A review of the current state of the art in interference mitigation techniques previously deployed as well as areas of research currently being addressed is then provided. Finally, important future research directions are suggested.

In this paper we describe measurements of wireless propagation characteristics to develop path loss models in industrial environments. The models for path loss we develop are two-slope models in which the path loss is a piecewise linear relation with the log distance. That is, the path loss is a inverse power law with two regions, two exponents and a break point, that are optimized to find the best fit to the measured data. Second, the multipath power delay profile is determined. We use a reference measurement and the CLEAN algorithm for processing the measurements in order to determine an estimate for the impulse response of the channel. From this the delay spread of the channel can be determined. Finally we discuss the performance of Zigbee receivers. We compare the performance of different receiver structures for the O-QPSK type of modulation used as one Zigbee physical layer.

This paper considers optimal multiband transmission under hostile jamming, where both the authorized user and the jammer are power-limited and operate against each other. The strategic decision making of the authorized user and the jammer is modeled as a two-party zero-sum game, where the payoff function is the capacity that can be achieved by the authorized user in the presence of the jammer. First, we investigate the game under AWGN channels. It is found that: either for the authorized user to maximize its capacity, or for the jammer to minimize the capacity of the authorized user, the best strategy for both of them is to distribute the transmission power or jamming power uniformly over all the available spectrum. The minimax capacity can be calculated based on the channel bandwidth and the signal-to-jamming and noise ratio, and it matches with the Shannon channel capacity formula. Second, we consider frequency selective fading channels. We characterize the dynamic relationship between the optimal signal power allocation and the optimal jamming power allocation in the minimax game, and then propose an iterative water pouring algorithm to find the optimal power allocation schemes for both the authorized user and the jammer.

In this paper, we study the bandwidth efficiency (throughput) and the energy efficiency of relay networks considering both the physical layer and the medium access control (MAC) layer. Due to wireless signal power attenuation with transmission distance, using a relay for packet transmissions can lead to more energy-efficient wireless networking at the expense of requiring multihop transmissions. To understand the potential benefits of using a relay, the energy-throughput tradeoff needs to be analyzed. In a decentralized wireless network, not only the physical layer but also the MAC layer should be considered. At the physical layer, the transmit power determines the area which contains nodes that might be contending for channel access at the MAC layer. At the MAC layer, gaining access to the channel entails transmitting various signals at the physical layer. This uses energy and takes time, which impacts the bandwidth efficiency. We analyze the energy consumption and the throughput of relay networks as a function of the transmit power. We determine the conditions in which wireless communication using a relay has better energy efficiency or bandwidth efficiency than direct transmission.

In this paper, we investigate the performance improvements of single band full duplex device to device communication that can transmit and received on the same frequency band in cellular networks. In cellular networks, two separate frequencies are used to enable simultaneous transmission and reception for half duplex radios. Recently, full duplex radios that allows a wireless node to simultaneously transmit and receive in one frequency band were proposed. It was shown that it was effective for short-range communications. As such, full duplex communication is adequate for device to device (D2D) communication, which is usually a short range communication. Device to device communication is an underlay scheme for cellular networks that enables peer-to-peer local services with limited impact on the primary cellular network. When user devices are closer to each other than the base station, D2D communication can improve the bandwidth efficiency of the communication between the users. When full duplex communication is adopted for D2D communication, it requires only one frequency band for two way communication between the local users. It improves the bandwidth efficiency for D2D communication. We propose a simple full duplex D2D communication protocol and analyze the bandwidth performance gain of the protocol compared to the legacy cellular communication scheme.

In this paper we investigate the impact of pulse jamming on Alamouti space-time block codes (STBC). We find the worst case duty cycle of a pulse jammer that maximizes the bit-error-rate (BER). We show that, like the single antenna case, with pulse jamming the BER is an inverse linear function of the signal-to-jammer power ratio (SJR). In addition, we study the transmit antenna correlation effects on the STBC system performance in terms of BER and find the corresponding optimal jamming strategy. We find that as the correlation increases, the BER maximizing duty cycle of a pulse jammer increases. As an anti-jamming technique that mitigates the jamming effects, we concatenate convolutional codes with the STBC system. The numerical result shows that convolutional codes improves the BER of the system by as much as 30 dB at 10 -- 5 BER at the expense of lowering the data rate.

In this paper we propose a simple relay enabled medium access (SRMAC) protocol that enables cooperative relay transmissions. Due to the wireless signal power attenuation with distance, using a relay in a wireless network can make wireless networking more bandwidth efficient at the expense of requiring multiple transmissions for a single packet. Standard MAC protocols such as the IEEE 802.11 MAC protocol, while useable with relaying, however are not designed explicitly for relay communication. When IEEE 802.11 MAC protocol is used for cooperative communication such a relaying, each packet transmission would need to separately contend for the channel via a channel access procedure which can use significant resources (both energy and bandwidth). Because using a single relay requires two transmissions, an efficient medium access control (MAC) protocol that supports two hop transmission is needed. We introduce a protocol, SRMAC, which is a simple cooperative MAC protocol that utilizes information from the physical layer for the MAC operation of relay networks. We consider the bandwidth efficiency of SRMAC protocol considering both the physical layer and MAC layer. The SRMAC protocol includes the possibility of both cooperative transmission and direct transmission. With SRMAC, cooperative transmission (relaying) can be dynamically chosen when it is more beneficial than direct transmission. The SRMAC protocol can improve the throughput by up to 20% compared to conventional MAC protocols.

In this paper, we present multi-hop relay communication strategies for half-duplex decode-and-forward relay networks. The model for the channel that we consider includes pathloss, shadowing, and fast fading. For this channel model, we propose a full spatial reuse multi-hop (FSRM) relay communication scheme, which allows relays to transmit their data using every other time slot. With the FSRM scheme, the end-to-end rate reduction factor of multi-hop relay communication is fixed at 1/2, regardless of the number of hops. We analyze the outage probability of the proposed scheme for a directional antenna system and an omnidirectional antenna system. For a directional antenna system, the analysis reveals that the FSRM scheme achieves a lower outage probability than the traditional orthogonal multi-hop relaying scheme. For an omnidirectional antenna system, we find the SNR region of the proposed scheme that achieves better performance. We further analyze various power allocation methods to manage interference and determine the optimal operation scheme in terms of the SINR.

In this paper, we consider a half-duplex decode-and-forward multi-hop relay network. The model for the channel that we consider includes path loss, shadowing, and fast fading. For this system and channel model, we find the outage probability for the multi-hop relay communication strategy that allows a packet to follow any path through the relays in the network. Based on the outage probability and the rate that used in the network, we find the exact throughput of the system. From this understanding of the system throughput, we find the optimal operating rate and the optimal number of hops that maximize the throughput. We also consider a system in which the relays have buffers that allow them to delay transmission and transmit when the channel conditions are favorable. We compare the system throughput of this buffer-equipped multi-hop relay network with the conventional multi-hop relay network without buffers.

Half duplex radios use two separate frequency bands to enable simultaneous transmission and reception. Recently, full duplex radio that allows a wireless node to transmit and receive simultaneously in one frequency band was proposed. We propose a MAC protocol for full duplex radio networks, FD-MAC, which is a simple and efficient protocol compatible with IEEE 802.11 MAC protocol. We analyze the performance of full duplex wireless networks with FD-MAC considering both the physical layer and the MAC layer.

Carbon-fibre prepregs have found widespread use in lightweight applications. They are based on a carbon-fibre fabric impregnated with reactive epoxy resin. Prepreg materials are generally pre-cured so that they have a higher molecular weight than typical resins in order to reduce resin flow, which facilitates storage and later processing properties.The measurements were carried out using commercially available materials and follow the published DMA investigations of the same material [1]. TMDSC was used to find the correlation between curing conditions, the degree of cure and glass transition temperature. TMDSC has the advantage over standard DSC that it enables better determination of the glass transition temperature, which is often accompanied by an exothermic curing reaction, and thus overshadowed. The influence of the amplitude of temperature modulation was tested in preliminary experiments. For non-cured material a glass transition temperature of approximately 0 degrees C was determined; whereas for the totally cured material it was approximately 230 degrees C. The changes in degree of cure, temperature of actual glass transition and post-reaction are given as a function of curing time at 180 degrees C. The correlation between actual glass transition temperature and degree of cure is derived. (C) 2013 Elsevier Ltd. All rights reserved.

Carbon fibre prepregs have found widespread application in lightweight constructions. They are based on a carbon fibre fabric impregnated with reactive epoxy resin. Measurements were carried out using commercially available prepreg material. For Dynamic Mechanical Analysis (DMA), a single cantilever measuring device was applied. The DMA results were refined by additional DSC measurements. The measurements were carried out with dynamic heating in the temperature range -90 to 280 degrees C. The heating rates were 1 and 2 K/min, respectively. A glass transition of the uncured material (I-g0) near 1 degrees C, and crosslinking-induced vitrification and devitrification at the maximal glass transition temperature of the cured material (T-gmax) in the temperature range 220 to 230 degrees C were found. The activation energies for the glass transitions were determined using an Arrhenius plot. By detailed consideration of the influence of the frequency on the DMA data, indications for gelation were deduced. (C) 2012 Elsevier Ltd. All rights reserved.

In this paper we study the bandwidth efficiency (throughput) and energy efficiency of relay networks considering both the physical layer and the medium access control (MAC) layer. Due to the wireless signal power attenuation with transmission distance, adopting a relay for packet transmissions leads to more energy efficient wireless networking at the expense of requiring multi-hop transmissions. To understand benefits of using a relay, the energy-throughput tradeoff needs to be analyzed. In a decentralized wireless network, not only the physical layer but also the MAC layer should be considered because the physical layer affects the MAC layer and the MAC layer overhead is not negligible. However, the energy-throughput tradeoffs for relay networks considering both the physical layer and the MAC layer has not been studied yet. We analyze the energy consumption and the throughput of relay networks with transmit power control. We determine the conditions in which wireless communication using a relay has better energy efficiency or bandwidth efficiency than direct transmission.

In this paper we investigate the bandwidth (throughput) and energy efficiency considering both the physical layer and the medium access control (MAC) layer in multi-hop relay wireless networks. For a given distance between the source and the destination, as the number of relays increases the overhead necessary to operate the MAC protocol increases. However, the energy needed for a given throughput decreases when the distance between relays decreases. Thus there is an optimal number of relays that optimizes both the throughput and the energy efficiency. We analyze how the number of relays used between the source and the destination affects the throughput and the energy consumption. The energy-throughput relationship incorporating both the physical layer and the MAC layer was considered in the analysis and optimization of the number of relays. Based on the analysis we provide general criteria for the optimal number of relays.

In this paper, we use a realistic energy consumption model for wireless networks to analyze the energy and bandwidth performance of wireless networks with transmit power control. Transmit power affects the performance at the physical layer. When the transmit power increases, the capacity at the physical layer increases accordingly, which reduces the energy consumption and increases throughput. Transmit power also affects the performance of the medium access control (MAC) layer. When the transmit power of nodes increases, contention for channel access increases, which leads to more energy consumption and lower throughput. An energy consumption model that is linked with the bandwidth performance analysis is crucial for understanding the performance of wireless networks. We propose a simple energy consumption model and analyze the energy-throughput tradeoff of distributed wireless network considering both the physical layer and the MAC layer. We show that there exist an optimal transmit power that achieves either the minimum energy consumption or maximum throughput.

In this paper, we investigate opportunistic buffer-equipped, multi-antenna relay networks with a decode-and-forward relaying strategy. The channel that we are considering includes three key wireless channel effects: path loss, shadowing, and fast fading. We first analyze the direct communication outage probability, and based on that, analyze the opportunistic relay network's outage probability. For an opportunistic relay selection protocol, we consider max-max relay selection (MMRS), where two relays are involved in the relaying: one for the source data reception and the other for transmission to the destination. As a relay selection method, we suggest dual-timer relay selection (DTRS), which reduces channel estimation overhead and solves the full-buffer problem of a reception relay and the empty-buffer problem of a transmission relay in the MMRS protocol. Along with the DTRS protocol, we further investigate the optimal relay selection period for maximizing the throughput while avoiding selection overhead.

This paper explores the application of compressive sensing (CS) for ultra wide band (UWB) communication. Channel estimation is an important aspect for any communication system and especially for UWB systems in order to appropriately collect the energy from the multipath channel. UWB generally requires a high sampling rate since the bandwidth is large. Channel estimation using CS is studied along with its impact on reducing the sampling rate for an ADC to reduce power. Practical issues regarding the effect of quantization on channel estimation are addressed and a hardware implementation for CS based on the Walsh-Hadamard transform (WHT) allowing sub-Nyquist sampling is proposed. To separate the effect of channel estimation with CS, the performance of the sub-Nyquist ADC is studied in a noiseless and multipath free channel and design decisions are discussed. Comparison with the Nyquist ADC shows that using the sub-Nyquist ADC reduce power by a factor of about 6×. For the proposed hardware, two receiver architectures based on matched filtering and filtering in the compressed domain (so-called “smashed filtering”) are studied. It is found that with a perfect channel smashed filtering performs better than matched filtering. Finally the effect of channel estimation on the proposed hardware is studied along with two different recovery algorithms namely basis pursuit and matching pursuit.

We consider the problem of channel estimation for ultrawideband communication in a multipath channel using compressed sensing techniques. The receiver when using a compressed sensing approach consists of a number of correlators processing the received signal with random projection vectors. The theory is based on Gaussian distributed vectors. We have compared the performance of using orthogonal Hadamard vectors with that of using a random projection matrix in compressed sensing procedures. We have also compared the performance of systems with different parameters for Gaussian and Hadamard projections vectors such as number of pilots, number of projection vectors and different coding schemes. Moreover, we are investigating different receiver structures resulting in different complexity of the receivers. We show that the sampling rate can be reduced significantly with only a slight degradation in the performance.