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This paper considers a distributed storage system, where multiple storage nodes can be reconstructed simultaneously at a centralized location. This centralized multi-node repair (CMR) model is a generalization of regenerating codes that allow for bandwidth efficient repair of a single-failed node. This paper focuses on the tradeoff between the amount of data stored and repair bandwidth in the CMR model. In particular, repair bandwidth bounds are derived for the minimum storage multi-node repair (MSMR) and the minimum bandwidth multi-node repair (MBMR) operating points. The tightness of these bounds is analyzed via code constructions. The MSMR point is characterized by codes achieving this point under functional repair for the general set of CMR parameters, as well as with codes enabling exact repair for certain CMR parameters. The MBMR point, on the other hand, is characterized with exact repair codes for all CMR parameters for systems that satisfy a certain entropy accumulation property. Finally, the model proposed here is utilized for the secret sharing problem, where the codes for the multi-node repair problem are used to construct communication efficient secret sharing schemes with the property of bandwidth efficient share repair. [ABSTRACT FROM AUTHOR]

This paper applies multiple-input multiple-output (MIMO) transmission methods to multiwire communication systems. Using channel matrices generated from a binder MIMO channel model, a performance assessment of digital subscriber line (DSL) technology based on MIMO transmission methods finds that symmetric data rates of more than 1 Gbps are achievable over four twisted pairs (category 3) for a 300 m range. Similar results are also obtained for a ‘quad’ cable. To achieve this data rate, this paper proposes that the source and load be excited using common mode. [ABSTRACT FROM AUTHOR]

In this paper, we develop optimal energy-bandwidth allocation algorithms in fading channels for multiple energy harvesting transmitters. We first assume that the side information of both the channel states and the energy harvesting states is known for $K$ time slots a priori, and the battery capacity and the maximum transmission power in each time slot are bounded. The network consists of N$ transmitter-receiver pairs and the objective is to maximize the sum-rate of all communication links over the K$ time slots by assigning the transmission power and bandwidth for each transmitter in each slot. The problem is formulated as a convex optimization problem with constraints, where N$ is the number of the receivers, making it hard to solve with a generic convex solver. An iterative algorithm is proposed based on efficiently solving two subproblems in each iteration, that has an overall complexity of {\cal O}(NK^2). The convergence and the optimality of this algorithm are also shown. Moreover, a heuristic algorithm is also proposed for energy-bandwidth allocation based on causal information of channel and energy harvesting states. Simulation results show that the proposed causal and noncausal algorithms can make efficient use of the harvested energy and the available bandwidth. And they achieve significantly higher rates than some heuristic policies for energy and bandwidth allocation. [ABSTRACT FROM AUTHOR]

Mitigation of interference among adjacent radio systems is a topic of growing interest as the spectrum occupation increases. Site-shielding techniques appear as a method of improving millimeter-wave wireless communication system design, allowing frequency reuse and reducing cochannel interference. The viability of applying such techniques to systems operating in frequency bands around 40 GHz is the aim of this paper. Several propagation mechanisms are experimentally studied, including transmission across building obstacles, depolarization, reflection, and diffraction. The performance of some theoretical models of the different scattering mechanisms has been compared with measurement results. The measuring and processing procedures have also been improved. Values of the dielectric parameters of the materials in this frequency band have been obtained and are given in this paper. The attenuation results indicate that various materials, such as mortar, brick, and concrete walls, that present large values of attenuation in decibels per centimeter, can be used to shield base stations, reducing the frequency reuse distance in radio cellular networks. It can also be concluded that there is a significant diffracted field in the shadow region of brick corners. [ABSTRACT FROM AUTHOR]

This paper proposes a cross-layer optimization framework for the wireless sensor networks. In a wireless sensor network, each sensor makes a local observation of the underlying physical phenomenon and sends a quantized version of the observation to a central location via wireless links. As the sensor observations are often partial and correlated, the network performance is a complicated and nonseparable function of individual data rates at each sensor. In addition, due to the shared nature of wireless medium, nearby transmissions often interfere with each other. Thus, the traditional "bit-pipe" model for network link capacity no longer holds. This paper deals with the joint optimization of source quantization, routing, and power control in a wireless sensor network. We follow a separate source and channel coding approach and show that the overall network optimization problem can be naturally decomposed into a source coding subproblem at the application layer and a wireless power control subproblem at the physical layer. The interfaces between the layers are precisely the dual optimization variables. In addition, we introduce a novel source coding model at the application layer, which allows the efficient design of practical source quantization schemes at each sensor. Finally, we propose a dual algorithm for the overall network optimization problem. The dual algorithm, when combined with a column-generation method, allows an efficient solution for the overall network optimization problem. [ABSTRACT FROM AUTHOR]

Computer communication systems are complex systems in which both computing power and communications capabilities play a key role. Examples of such systems range from worldwide data and voice communications networks to local area networks, and even encompass the more recent multiprocessor computer systems. In the past, the design and development of such systems has been done in a fairly ad hoc manner. However, it is increasingly apparent that in order to understand and develop sucy systems, it is necessary to have a more systematic approach to designing and studying such systems.

FlexRay offers high-speed reliable transmission in the vehicle domain. Thus, it is one of the most popular in-vehicle communication protocols for the applications that are safety-critical or applications with very low transmission time requirement. Due to the real-time constraint, the worst case end-to-end delay (EED) for such applications transmitting over a shared bus must be known. This paper addresses the problem of computation of EED for a given set of tasks with precedence constraint and corresponding messages, which are scheduled with slot multiplexing for event-triggered communication over the dynamic segment of FlexRay. First, computing precise delay has been shown to be an intractable problem. Subsequently, motivated by the intractability, an efficient estimation technique has been proposed to compute approximate EED. Unlike the common practice of considering the network in isolation, we present a comprehensive timing analysis, which considers the effects of task execution as well. Moreover, EED is allowed to be greater than interactivation time of task graph. The extensive simulation has been performed on the test cases generated with uniform as well as normal distribution. Note to Practitioners—In the past few decades, due to the large-scale use and sophistication of automotive electronic systems, various in-vehicle communication networks and protocols are also evolving. FlexRay is one such in-vehicle communication protocol, which provides the mechanism for the fault-tolerant high-speed communication over FlexRay bus. FlexRay is widely being employed for safety-critical applications in the automotive domain. For such applications, often the timing constraint is imposed with a bound on the worst case EED. Thus, timing properties of the designed network must be verified before applying it on the real domain such that the worst case EED for the propagation of an event at sensor end to actuator end is known. The proposed estimation technique can be used to compute approximate EED for an application scheduled with other applications over the dynamic segment of FlexRay. In addition, various guidelines for designing the network in order to reduce overestimation have also been presented. [ABSTRACT FROM AUTHOR]

Impulse Radiating Antenna (IRA) is a highly efficient antenna that has a number of applications in both civilian and military sectors. These antennae produce fast rising pulses in a narrow beam that can give rise to high intensity electromagnetic fields having a wide impact on electrical and electronic systems. One such area where the impact becomes prominent is the present day telecommunication network. This system consists of buried coaxial cables connected to sensitive equipments at their terminations. Henceforth, there could be situations where the incident IRA field can interfere with the cables laid in the area. As the cables pass over different regions with varied soil texture and characteristics, the proportion of the IRA field incident on it will vary, that is dependent upon the nature of the soil in which the cable is buried. This paper reports the response of different types of soils to incident IRA fields and the induced voltage in a cable buried in such soils. A case study of different types of soils is also included in the paper. It is found that the soils in industrial areas are more prone to electromagnetic interference from IRA rather than in a highly moist ground. [ABSTRACT FROM AUTHOR]

This paper obtains the first degrees of freedom (DoFs) bound that is provably sensitive tonetworkcoherence time, i.e., coherence time in an interference network, where all channels experience the same coherence patterns. This is accomplished by a novel adaptation of the aligned image sets bound and settles various open problems noted previously by Naderi and Avestimehr and by Gouet al.For example, a necessary and sufficient condition is obtained for the optimality of 1/2 DoF per user in a partially connected interference network, where the channel state information at the receivers (CSIRs) is perfect, the channel state information at the transmitters (CSITs) is instantaneous but limited to finite precision, and the network coherence time is $T_{c}=1$. The surprising insight that emerges is that even with perfect CSIR and instantaneous finite precision CSIT, the network coherence time matters, i.e., it has a DoF impact. [ABSTRACT FROM AUTHOR]

In a cognitive radio network, the spectrum that is allocated to primary users can be used by secondary users if the spectrum is not being used by the primary user at the current time and location. The only consideration is that the secondary users have to vacate the channel within a certain amount of time when- ever the primary user becomes active. Thus, the cognitive radio faces the difficult challenge of detecting (sensing) the presence of the primary user, particularly in a low signal-to-noise ratio region, since the signal of the primary user might be severely attenuated due to multipath and shadowing before reaching the secondary user. In this paper, a blind sensing algorithm is derived, which is based on oversampling the received signal or by employing multiple receive antennas. The proposed method combines linear prediction and QR decomposition of the received signal matrix. Then, two signal statistics are computed from the oversampled received signal. The ratio of these two statistics is an indicator of the presence/absence of the primary signal in the received signal. Our algorithm does not require the knowledge of the signal or of the noise power. Moreover, the proposed detection algorithm in this paper is blind in the sense that it does not require information about the multipath channel distortions the primary signal has undergone on its way to reaching the secondary user. Simulations have shown that our algorithm performs much better than the commonly used energy detector, which usually suffers from the noise uncertainty problem. [ABSTRACT FROM AUTHOR]

This paper presents two algorithms, namely clustered simple polling and neighbor relay polling, for solving the typical "silent node" problem in automatic meter reading (AMR) systems using power-line communications (PLC)-access networks. These schemes are tested through computer simulations to be both effective and efficient in overcoming the "silent node" problem in AMR systems. The construction of the PLC-access network model in this paper is based on the actual structure of the PLC-access networks of Singapore public residential buildings. Also, a two-state transition Markov model is used to simulate a meter unit with such a "silent node" problem in a PLC network. The processing time model is established on a meter topology of three-level clustering. By using these models for our computer simulations, the performance of our proposed schemes can be evaluated in terms of reliability and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, the impact of user mobility and the handover process on the performance of interference adaptive (IA) dynamic channel allocation (DCA) schemes is investigated. Among the hundreds of papers that can be found in the literature dealing with DCA (IEEE Pers. Commun., vol. 3, no. 3, p. 10, Jun. 1996), only very few analyze their performance by taking into proper consideration all the aspects related to user mobility: the speed of mobiles, the handover process, the radio channel fluctuations, and the forced terminations. The results we show in this paper have been achieved by means of a simulation tool that takes propagation, mobility, handover, power control, directed retry (DR), interference, traffic, and channel allocation into account. Moreover, some simplified analytical descriptions are given to discuss the behavior of the blocking probability when varying the speed of users. We compare the performance of well-known totally distributed IA-DCA schemes (least interference algorithm and least interference and threshold algorithm) (IEEE J. Sel. Areas Commun., vol. 14, no. 5, p. 698, May 1996) to that of a partially distributed algorithm. The comparison to fixed channel allocation is also considered, and the role of DR is emphasized. To emphasize the role played by the speed of the terminals, two different mobility models are considered; the numerical results show that the satisfaction probability changes when taking user mobility into account, whereas the blocking probability is scarcely affected by the mobile speed; the latter statement is compared to previous results from the literature, and it is in good agreement. [ABSTRACT FROM AUTHOR]

IEEE 802.15.4 is an emerging standard specifically designed for low-rate wireless personal area networks (LR-WPAN) with a focus on enabling the wireless sensor networks. It attempts to provide a low data rate, low power, and low cost wireless networking on the device-level communication. In this paper, we have established a realistic environment for the preliminary performance evaluation of the IEEE 802.15.4 wireless networks. Several sets of practical experiments are conducted to study its various features, including the effects of 1) the direct and indirect data transmissions, 2) CSMA-CA mechanism, 3) data payload size, and 4) beacon-enabled mode. The data throughput, delivery ratio, and received signal strength indication (RSSI) are investigated as the performance metrics. The results show that IEEE 802.15.4 has better performance in non-beacon mode. Some issues that could degrade the network performance are also discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper discusses the requirements on the numerical precision for a practical Multiband Ultra-Wideband (UWB) consumer electronic solution. To this end we first present the possibilities that UWB has to offer to the consumer electronics market and the possible range of devices. We then show the performance of a model of the UWB baseband system implemented using floating point precision. Then, by simulation we find the minimal numerical precision required to maintain floating-point performance for each of the specific data types and signals present in the UWB baseband. Finally, we present a full description of the numerical requirements for both the transmit and receive components of the UWB baseband. The numerical precision results obtained in this paper can then be used by baseband designers to implement cost effective UWB systems using System-on-Chip (SoC), FPGA and ASIC technology solutions biased toward the competitive consumer electronics market. [ABSTRACT FROM AUTHOR]

This paper considers the power-control problem for a fading channel in an information-theoretic framework. We derive power-control schemes to optimize ergodic capacity, outage capacity, and capacity with a service outage constraint. The novelty in the paper lies in the use of a two-time-scale fading process and its implications for the channel-state information available at the transmitter. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel mathematical investigation on the dispersion-limited optical communication channel. We tackle the problem using a comprehensive approach that is based on the optimization of the energy transfer from the input to the output of the channel. We solve the optimization problem deriving a fundamental integral equation, which we are able to solve analytically. We show that the dispersion-limited optical channel has a very interesting equivalence to the ideal lowpass filter. This equivalence allows us to derive new bounds on the maximum achievable bit rate on the channel with limited intersymbol interference (ISI). In particular, we demonstrate that by suitably increasing the memory of the modulator and using the optimal pulses derived in this paper, one can transmit with limited ISI over a channel with arbitrarily high dispersion. [ABSTRACT FROM AUTHOR]

The idea of proxying network connectivity has been proposed as an efficient mechanism to maintain network presence on behalf of idle devices, so that they can “sleep.” The concept has been around for many years; alternative architectural solutions have been proposed to implement it, which lead to different considerations about capability, effectiveness and energy efficiency. However, there is neither a clear understanding of the potential for energy saving nor a detailed performance comparison among the different proxy architectures. In this paper, we estimate the potential energy saving achievable by different architectural solutions for proxying network connectivity. Our work considers the tradeoff between the saving achievable by putting idle devices to sleep and the additional power consumption to run the proxy. Our analysis encompasses a broad range of alternatives, taking into consideration both implementations already available in the market and prototypes built for research purposes. We remark that the main value of our work is the estimation under realistic conditions, taking into consideration power measurements, usage profiles, and proxying capabilities. [ABSTRACT FROM AUTHOR]

In a wireless network, while the signal attenuation due to the distance-related path loss is minimum between a node and its nearest neighbor, this is not the case for the overall attenuation when the fading effect is also taken into account. Hence, the communication best neighbor (CBN) of a node is defined as the neighbor of that node with which it has the highest channel power gain. Recently, the statistics of the physical neighborhood index of the CBN have been derived for a general fading environment in which the nodes have two-dimensional Poisson distribution. In this paper, the statistics of the distance between a node and its CBN as well as the joint CBN distance-index statistics are obtained for the same scenario. Then, the analytical expressions are specialized for the case where the communication channels follow the generalized gamma fading model. Also, the results are verified and illustrated by computer simulations and numerical results. Further, it is shown how the obtained analytical results can be used to identify the CBN more efficiently by limiting the search region and the number of neighbors that are examined. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a combined full duplex (FD)- and half duplex (HD)-based transmission and channel acquisition model for an open-loop multiuser multiple-input multiple-output (MIMO) systems. Assuming residual self-interference at the base station (BS), the idea is to utilize the FD mode during the uplink (UL) training phase in order to achieve simultaneous downlink (DL) data transmission and UL CSI acquisition. More specifically, the BS begins serving a user when its CSI becomes available, while at the same time, it also receives UL pilots from the next scheduled user. We investigate both zero-forcing (ZF) and maximum ratio transmission MIMO beamforming techniques for the DL data transmission in the FD mode. The BS switches to the HD mode once it receives the CSI of all users and it employs ZF beamforming for the DL data transmission until the end of the transmission frame. Furthermore, we derive closed-form approximations for the lower bounded ergodic achievable rate relying on the proposed model. Our numerical results show that the proposed FD–HD transmission and channel acquisition approach outperforms its conventional HD counterpart and achieves higher data rates. [ABSTRACT FROM AUTHOR]

Millimeter wave (mmWave) communications is a promising approach to satisfy the increasing high data rate requirement of next generation mobile communications. This paper studies the downlink coverage performance of mmWave cellular networks with imperfect beam alignment. An enhanced antenna model is adopted to model the directional antenna beamforming pattern, in which the mainlobe beamwidth and directivity gain can be expressed as functions of the number of elements in the antenna array. After deriving the probability density function of the distance between mobile station and its serving base station (BS), the directivity gain with imperfect beam alignment is obtained as a discrete random variable. Then, a computationally tractable expression is obtained for the coverage probability of mmWave cellular networks. This generalized expression can be applied in different blockage regimes, e.g., general blockage regime, full-blockage regime, and nonblockage regime with or without beam alignment errors. Numerical results show that small beam alignment errors will not deteriorate the coverage performance significantly, and the antenna array with the less number of elements provides higher robustness against the beam alignment errors. Moreover, when the beam alignment error is small enough, the coverage performance can be improved by increasing the BS intensity and the number of elements in the antenna array. [ABSTRACT FROM AUTHOR]

This paper discusses challenges and opportunities for thermal management of information and communications technologies equipment, with a particular focus on telecommunications equipment. This paper identifies the key drivers for network traffic growth and how these increasing traffic demands are driving innovations in telecommunications, requiring the development of new and novel thermal management technologies to meet the product performance and reliability requirements. Application areas discussed include photonics, wireless networking, extreme heat density applications, and liquid cooling, with spatial scales ranging from individual transistors up to data center and telecom central offices. A perspective on the anticipated technology trends, key technical challenges, and opportunities for innovation and impact is also presented. [ABSTRACT FROM AUTHOR]

Part II. Introduces a series of articles on multiple-input multiple-output communication systems.

This paper proposes a domain corpus independent vocabulary generation algorithm in order to improve the coverage of vocabulary for embedded Continuous Speech Recognition (CSR). A vocabulary in CSR is normally derived from a word frequency list. Therefore, the vocabulary coverage is dependent on a domain corpus. We present an improved way of vocabulary generation using Part-Of-Speech (POS) tagged corpus and knowledge base. We investigate 152 POS tags defined in a POS tagged corpus and word-POS tag pairs. We analyze all words paired with 101 among 152 POS tags and decide on a set of words which have to be included in vocabularies of any size. The other 51 POS tags are mainly categorized with noun-related, Named Entity (NE)-related and verb-related POSs. We introduce a domain corpus independent word inclusion method for noun-, verb-, and NE-related POS tags using knowledge base. For noun-related POS tags, we generate synonym groups and analyze their relative importance using Google search. Then, we categorize verbs by lemma and analyze relative importance of each lemma from a pre-analyzed statistic for verbs. We determine the inclusion order of NEs through Google search. The proposed method shows at least 28.6% relative improvement of coverage for a SMS text corpus when the sizes of vocabulary are 5K, 10K, 15K and 20K In particular, the coverage of 15K size vocabulary generated by the proposed method reaches up to 97.8% with the relative improvement of 44.2%. [ABSTRACT FROM AUTHOR]

Inspired by recent promotions of wireless location services and applications, this paper develops a simple model for detecting a mobile caller location with low implementation complexity and promising accuracy. The model that is described in this paper employs the geometrical transformation method with single propagation delay measurement. Depending on the number of available surrounding base transceiver stations (BTS5), a set of the pseudodistances and pseudodistance differences is provided through the geometrical distances between the home and multiple foreign BTSs, which is called the geometrical transformation method. Accordingly, the mobile caller location can be detected using the circular location technique and the hyperbolic location technique. The major benefit of the proposed model is that during a call to detect the mobile caller's location, the use of geometrical transformation allows us to overcome the location handover problem. A forcing handover in a Global System for Mobile Communications (GSM) network or a three-way soft handover in a Universal Mobile Telecommunications System (UMTS) network, for example, occurs when detecting the location when a standard model that is based on the measurement of the propagation delay is utilized. Comparing the standard model with the proposed model, the former needs at least three propagation delays that were simultaneously measured from at least three BTSs, whereas the latter needs only a single propagation delay that was measured from the home BTS. Moreover, in the case where we do not have a priori information of a non-line-of-sight (NLOS) error, a deterministic parameter that is related to the propagation delay is defined. This parameter is shown as limited a priori information for calibrating the coarse resolution in the proposed location model, which is caused by the NLOS error. To have significant findings, we conduct a practical experiment in an urban environment based on a 1.8-GHz commercial cellular network. In the five-BTS case where the location error is less than 300 m, the probability of location error that the proposed model with a bit period of 1/2 achieved is greater than 0.85. Although the performance of the proposed location model does not satisfy the U.S. Federal Communications Commission Enhanced 911 (FCC E-911) requirements, it is a good solution for the deployment of wireless location services and applications. [ABSTRACT FROM AUTHOR]

All currently available code-division multiple-access (CDMA) technologies used in second-generation and third-generation mobile cellular systems are interference limited and can be appropriately called first-generation CDMA, whereas next-generation CDMA should provide a nearly interference- free performance. This paper addresses the issues on spreading code generation that is suitable for next-generation CDMA systems. The real environment adaptation linearization (REAL) approach is proposed to generate perfectly orthogonal complementary (POC) codes characterized by multiple access interference (MAI)-free and multipath interference (MI)-free operation. The REAL approach takes into account almost all major impairing factors in real applications, such as multipath propagation, asynchronous transmission, random data signs, and burst traffic, such that a CDMA system using them can offer an interference- resist operation. Two important conclusions are drawn in this paper: First, implementation of an interference-free CDMA will not be possible unless using complementary codes, such as the POC codes. Second, to enable interference-free CDMA, the flock size of the signature codes should preferably be equal to the set size of the codes. A fast algorithm to generate supercomplementary codes (a subset of POC codes) is also presented, and their ideal orthogonality is explicitly proven. [ABSTRACT FROM AUTHOR]

In this paper, we deal with an amplify-and-forward (AF) cooperative strategy in slot-based, block-fading environments. In contrast with previous schemes, which assume a constant channel during the cooperative frame (several slots), here, we relax this constraint and assume a classical quasi-static block-fading channel (constant for one slot). This additional degree of freedom modifies the behavior of the conventional nonorthogonal AF (NAF) schemes and generates a new block-fading NAF (BFNAF) protocol, where the source can usefully retransmit the same data during the cooperative slot. This new protocol is interesting at low spectral efficiencies, where diversity against fading is more important. To overcome performance degradation, which characterizes cooperative schemes at low signal-to-noise ratios (SNR5), an adaptive version of the considered schemes is also proposed, where cooperation is activated according to the outage behavior of the direct link. Moreover, an optimal hybrid protocol that allows intelligent switching between noncooperation, NAF, and BFNAF protocols is also proposed. Another issue that is discussed throughout this paper is the optimal power allocation of the investigated schemes. The proposed power-allocation strategy uses as an optimization criterion the well-defined asymptotic expressions of the outage probabilities, which are averaged over the fading statistics. The minimization (and avoidance for the nonhybrid protocols) of the required data feedback makes it suitable for practical ad hoc networks with crucial power constraints. The enhancement of the proposed schemes and the efficiency of the power allocation policy are shown by theoretical analysis and simulation results. [ABSTRACT FROM AUTHOR]

Rainfall rate is the main cause of fades in the frequency bands above 10 GHz. To optimize the planning of satellite and terrestrial radio communication systems operating on these frequency bands, it is essential to have a detailed knowledge of the temporal and spatial distributions of the rainfall rate. For this reason, it is necessary to develop experimental networks, which provide adequate data to study, prevent, and compensate the rain fade. In this paper, an experimental instrumentation network is presented. This network comprises weather stations that are capable of measuring rainfall rate; temperature, and humidity; a weather radar; and three radio links. This paper first introduces the rationale and the state of the art in meteorological sensors and describes the experimental network for automatic data acquisition as a distributed process system. The design of the experimental network is explained in detail. Finally, the interest in millimeter wavelength for broadband applications is outlined, and some research lines from the collected data are presented. [ABSTRACT FROM AUTHOR]

In this paper, we present a unified asymptotic symbol error rate (SER) analysis of linearly modulated signals impaired by fading and (possibly) non-Gaussian noise, which in our definition also includes interference. The derived asymptotic closed-form results are valid for a large class of fading and noise processes. Our analysis also encompasses diversity reception with equal gain and selection combining and is extended to binary orthogonal modulation. We show that for high signal-to-noise ratios (SNRs) the SER of linearly modulated signals depends on the Mellin transform of the probability density function (pdf) of the noise. Since the Mellin transform can be readily obtained for all commonly encountered noise pdfs, the provided SER expressions are easy and fast to evaluate. Furthermore, we show that the diversity gain only depends on the fading statistic and the number of diversity branches, whereas the combining gain depends on the modulation format, the type of fading, the number of diversity branches, and the type of noise. An exception are systems with a diversity gain of one, since their combining gain and asymptotic SER are independent of the type of noise. However, in general, in a log-log scale for high SNR the SER curves for different types of noise are parallel but not identical and their relative shift depends on the Mellin transforms of the noise pdfs. [ABSTRACT FROM AUTHOR]

This paper presents a method of determining electromotive force and battery internal resistance as time functions, which are depicted as functions of state of charge (SOC) because Soc = f(t). The model is based on battery discharge and charge characteristics under different constant currents that are tested by a laboratory experiment. This paper further presents the method of determining the battery soc according to a battery modeling result. The influence of temperature on battery performance is analyzed according to laboratory-tested data, and the theoretical background for calculating the SOC is obtained. The algorithm of battery SOC indication is depicted in detail. The algorithm of the battery SOC "online" indication considering the influence of temperature can be easily used in practice by a microprocessor. An NiMH battery is used in this paper to depict the modeling method. In fact, the method can also be used for different types of contemporary batteries, as well as Li-ion batteries, if the required test data are available. [ABSTRACT FROM AUTHOR]

In this paper, an efficient design of dual mode deinterleaver for both IEEE 802.16 and digital video broadcasting (DVB) standards is presented. The paper first proposes a systematic data allocation method for the design of matrix transposer which can be used to realize the block deinterleaver adopted by IEEE 802.16 based on the multi- bank memory architecture. In addition, multiple input/output data can be grouped together in order to further reduce the memory access frequency such that the required number of banks and ports for the memory can be both reduced. Similarly, the multi-bank memory design approach can also be applied for the byte-level convolutional deinterleaver adopted in DVB system by realizing the multiple delay branches as the circular buffer. Finally, these two different deinterleaving standards can be further integrated . into a single design suitable for those dual-mode communication systems. Our implementation results show that the dual mode deinterleaver can run up to 150 Mhz, and consume about 38.5k gates. The same design methodology can also be applied for the design of interleavers. [ABSTRACT FROM AUTHOR]

Probabilistic Boolean networks (PBNs) have beer recently introduced as a paradigm for modeling genetic regulatory networks. One of the objectives of PBN modeling is to use the network for the design and analysis of intervention strategies aimed at moving the network out of undesirable states, such a those associated with disease, and into desirable ones. To date a number of intervention strategies have been proposed in the context of PBNs. However, all these techniques assume perfect knowledge of the transition probability matrix of the PBN. Such an assumption cannot be satisfied in practice since the presence of noise and the availability of limited number of samples will prevent the transition probabilities from being accurately deter mined. Moreover, even if the exact transition probabilities from be estimated from the data, mismatch between the PBN model am the actual genetic regulatory network will invariably be present Thus, it is important to study the effect of modeling errors on the final outcome of an intervention strategy and one of the goals of this paper is to do precisely that when the uncertainties are in the entries of the transition probability matrix. In addition, the paper develops a robust intervention strategy that is obtained by minimizing the worst-case cost over the uncertainty set. [ABSTRACT FROM AUTHOR]

The determination of intermodulation products is an ever pervasive problem to the radar and satellite community—its eminence will continue to manifest itself as data rates increase, as transmitters are required to handle increasing numbers of multiple carriers, and as amplifiers are pushed to operate closer to their nonlinear regions (to circumvent the need of adding the extra weight and cost of a more linear amplifier). To study the intermodulation effects, fast Fourier transform (FFT)-based techniques are often employed. By definition, Δ = F8/N defines the frequency resolution for the discrete Fourier transform (DFT). It is typically desired to design Δ to be as small as possible to allow for a very fine frequency resolution. Doing this requires that F8, be minimized and/or N be selected as large as possible. Minimizing F8, has its pitfalls since high-order harmonics may violate the Nyquist criteria. Selecting N to be as large as possible introduces unreasonably long simulation times. This may be the case when large values of N are very near or exceed the maximum allowable array size of a digital computer. Breaking this nexus is the focus of this paper, which introduces a computationally efficient technique that will allow the frequency and amplitude of the intermodulation terms to be precisely computed. [ABSTRACT FROM AUTHOR]

This paper proposes a low-complexity multicarrier- code-division-multiple-access (MC-CDMA) space-time receiver with full-interference-suppression capabilities. First, we derive a complete model of the interference which takes into account multiple-access, intersymbol, and intercarrier interferences. Based on this model, we introduce a new multicarrier-interference- subspace-rejection (MC-ISR) receiver and analyze its performance in an unknown time-varying Rayleigh channel with multipath, carrier offset, and cross correlation between subcarrier channels. We also propose a realistic implementation of this receiver, which includes an efficient strategy for carrier-offset recovery in a multicarrier- and multiuser-detection scheme. In addition, based on the Gaussian assumption, we derive a link-/system-level performance analysis of the MC-ISR over the two MC-CDMA air-interface configurations, which are the multitone CDMA and the multicarrier direct-sequence CDMA, and validate it by simulations. The gains in the throughput, which are attainable by the MC-ISR, are significant and evaluated in this paper as functions of the air-interface configuration, the number of subcarriers, and the modulation order. [ABSTRACT FROM AUTHOR]

Estimation of electromagnetic (EM)-field emissions from broadband power-line communication systems (BPLC) is necessary, because at its operating frequencies, the radiated emissions from BPLC systems act as sources of interference/crosstalk to other radio-communication systems. Currently, the transmission-line (TL) system used for BPLC is complex, involving arbitrarily/irregularly distributed branched networks, arbitrary termination loads, varying line lengths, and line characteristic impedance. In order to study the electromagnetic-compatibility (EMC) issues associated with the radiated emissions of such complex BPLC networks, knowledge of current and voltage distributions along the length of the power-line channels is needed. This paper attempts to derive and present generalized expressions for either the current or voltage distribution along the line (whose TL parameters are known) between the transmitting and receiving ends for any line boundary condition and configuration based on the TL theory. The expressions presented in this paper could be beneficial for direct calculation of EM emissions from BPLC systems. [ABSTRACT FROM AUTHOR]

The power line has been proposed as a solution to deliver broadband services to end users. Various studies in the recent past have reported a decrease in channel capacity with an increase in the number of branches for a given channel type whether it is an indoor or low-voltage (LV) or medium-voltage (MV) channel. Those studies, however, did not provide a clear insight as to how the channel capacity is related to the number of distributed branches along the line. This paper attempts to quantify and characterize the effects of channel capacity in relation to the number of branches and with different terminal loads for a given type of channel. It is shown that for a power spectral density (PSD) between —90 dBm/Hz to —30 dBm/Hz, the channel capacity decreases by a 20-30 Mb/s/branch, 14-24 Mb/s/branch, and a 20-25 Mb/s/branch for an MV channel, LV channel, and indoor channel, respectively. It is also shown that the channel capacity is minimum when the load impedance is terminated in characteristic impedances for any type of channel treated here. It is shown that there could be a significant loss in channel capacity if a ground return was used instead of a conventional adjacent conductor return. The analysis presented in this paper would help in designing appropriate power-line communication equipment for better and efficient data transfer. [ABSTRACT FROM AUTHOR]

Optimization of complex systems demands advanced methods that are implemented in specialized software. Multiple combinations of optimization methods, objective functions, and constraints further complicate the problem of developing this software, making it hard to create, maintain, and evolve. To overcome this problem, this paper presents a new development methodology based on ideas of Aspect-Oriented Programming (AOP). This new methodology supports a clean separation of concerns, and keeps dependencies to a minimum. The optimization method is self-contained and completely independent from the rest of the system; for each optimization scenario, the solution binds the optimization with the concrete problem at run-time. This approach improves the ability to deal with several different objective functions and constraints, providing flexibility, maintainability, and usability to the development and evolution effort without degradation of the computational time. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of bit-interleaved coded multiple beamforming (BICMB). We provide interleaver design criteria such that BICMIB achieves full spatial multiplexing of min(N, M) and full spatial diversity of NM with N transmit and M receive antennas over quasi-static Rayleigh flat fading channels. If the channel is frequency selective, then BICMB is combined with orthogonal frequency division multiplexing (OFDM) (BICMB-OFDM) in order to combat ISI caused by the frequency-selective channels. BICMB-OFDM achieves full spatial multiplexing of min(N, M), while maintaining full spatial and frequency diversity of NML for an N × M system over L-tap frequency-selective channels when an appropriate convolutional code is used. Both systems analyzed in this paper assume perfect channel state information both at the transmitter and the receiver. Simulation results show that, when the perfect channel state information assumption is satisfied, BICMB and BICMB-OFDM provide substantial performance or complexity gains when compared to other spatial multiplexing and diversity systems. [ABSTRACT FROM AUTHOR]

This paper presents the capacity region of frequency-selective Gaussian interference channels under the condition of strong interference, assuming an average power constraint per user. First, a frequency-selective Gaussian interference channel is modeled as a set of independent parallel memoryless Gaussian interference channels. Using nonfrequency selective results, the capacity region of frequency-selective Gaussian interference channels under strong interference is expressed mathematically. Exploiting structures inherent in the problem, a dual problem is constructed for each independent memoryless channel, in which both mathematical and numerical analysis are performed. Furthermore, three suboptimal methods are compared to the capacity-achieving coding and power allocation scheme. Iterative waterfilling, a suboptimal scheme, provides close-to-optimum performance and has a distributed coding and power allocation scheme, which are attractive in practice. [ABSTRACT FROM AUTHOR]

As is well known, multiple-antenna systems can improve the reliability and maximize the spectral efficiency of radio channels. A way to measure the effectiveness of a multiple-antenna system is by evaluating the bit error rat (BER) for a specific channel. In this paper, we present BER calculations for a realistic channel simulation instead of assuming Rayleigh or Ricean fading with a specific K-factor. Specifically, we extract statistics based on data from an in-house full-wave electromagnetic solver and proceed to obtain BER across the channel. Based on the developed tools, we demonstrate how one can increase the reliability of wireless systems. [ABSTRACT FROM AUTHOR]

Conventional multiuser diversity maximizes the system throughput but results in an unfair scheduling of the system resources across users. Proportional fair scheduling types of systems achieve strict fairness among different users, but this fairness comes at the cost of a significant system capacity penalty. In this paper, we propose two forms of a hybrid multiuser scheduling scheme that provides a flexible balance/tradeoff between the system achievable capacity and the fairness among users. Our results show that the capacity versus fairness tradeoff can be achieved by grouping users and then using a two-step selection process. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel spatial multiplexing (SM) scheme for transmission over flat-fading multiple-input multiple-output (MIMO) channels, which allows simple maximum-likelihood decoding at the receiver with small feedback information. We begin with a real-valued representation of the complex-valued system model, and show that we can achieve orthogonality between transmitted signals by applying a proper rotation to transmitted symbols. Compared with other closed-loop methods, the proposed scheme significantly reduces the processing complexity at both transmitter and receiver as well as the feedback overhead. We also combine the proposed orthogonalization method with antenna-selection techniques, and then discuss a criterion based on the minimum Euclidean distance between received vectors for selecting the optimal subset of multiple transmit antennas. Using geometrical properties of the receive constellations, we also present a simple antenna-selection metric for the proposed SM systems. Simulation results demonstrate that our SM system performs close to the optimum closed-loop system with much-reduced complexity. [ABSTRACT FROM AUTHOR]

Ultrawideband (UWB) technology is characterized by transmitting extremely short duration radio impulses. To improve its multiple-access capability, the UWB technology can be combined with traditional spread-spectrum techniques. This paper demonstrates the influence of spatial and temporal diversities on the performance of direct-sequence (DS) UWB multiple-access systems in dense multipath environments. Numerical results show that the bit error rate performance of the DS-UWB system can be improved significantly by increasing the number of antenna array elements and/or by adding more multipaths coherently at the receiver. Furthermore, this paper studies the impact of array geometry on system performance and shows that a rectangular array can capture more energy and thus can offer better performance than a uniform linear array. [ABSTRACT FROM AUTHOR]

This paper studies finite-terminal random multiple access over the standard multipacket reception (MPR) channel. We characterize the relations among the throughput region of random multiple access, the capacity region of multiple access without code synchronization, and the stability region of ALOHA protocol. In the first part of the paper, we show that if the MPR channel is standard, the throughput region of random multiple access is coordinate convex. We then study the information capacity region of multiple access without code synchronization and feedback. Inner and outer bounds to the capacity region are derived. We show that both the inner and the outer bounds converge asymptotically to the throughput region. In the second part of the paper, we study the stability region of finite-terminal ALOHA multiple access. For a class of packet arrival distributions, we demonstrate that the stationary distribution of the queues possesses positive and strong positive correlation properties, which consequently yield an outer bound to the stability region. We also show the major challenge in obtaining the closure of the stability region is due to the lack of sensitivity analysis results with respect to the transmission probabilities. Particularly, if a conjectured ‘sensitivity monotonicity’ property held for the stationary distribution of the queues, then equivalence between the closure of the stability region and the throughput region follows as a direct consequence, irrespective of the packet arrival distributions. [ABSTRACT FROM AUTHOR]

In distributed multiple access control protocols, two categories of overhead are usually associated with contention resolution. One is channel idle overhead, where all contending stations are waiting to transmit. Another is collision overhead, which occurs when multiple contending stations attempt to transmit simultaneously. Either idle overhead or collision overhead being large, contention resolution algorithm would be inefficient. Prior research work tries to minimize both the idle and the collision overheads using various methods. In this paper, we propose to apply ‘pipelining’ techniques to the design of multiple access control protocol so that channel idle overhead could be (partially) hidden and the collision overhead could be reduced. While the concept of pipelined scheduling can be applied to various MAC protocol designs in general, in this paper, we focus on its application to IEEE 802.11 DCF. In particular, an implicitly pipelined dual-stage contention resolution MAC protocol (named DSCR) is proposed. With IEEE 802.11, the efficiency of contention resolution degrades dramatically with the increasing load due to high probability of collision. Using the implicit pipelining technique, DSCR hides the majority of channel idle time and reduces the collision probability, hence, improves channel utilization, average access delay, and access energy cost over 802.11 significantly both in wireless LANs and in multihop networks. The simulation results, as well as some analysis, are presented to demonstrate the effectiveness of DSCR. [ABSTRACT FROM AUTHOR]

This paper reports an extension of parametric harmonic balance (PHB) to efficiently analyze mixers excited by communications signals. In the case of digitally modulated signals, PHB is demonstrated in this paper, exhibiting reduced simulation times and memory resources. For validation purposes, a high electron-mobility transistor mixer has been constructed and characterized with single- and two-tone 2-GHz input RF signals, and also the output spectra under Universal Mobile Telecommunications System-wide-band code-division multiple-access signal excitations above the 1-dB compression point have been obtained. In addition to its fast convergence properties, the presented simulations demonstrate a very good agreement with experimental results. The close correspondence between calculated and measured spectral regrowth permitted a reliable prediction of adjacent channel power rejection. [ABSTRACT FROM AUTHOR]

This paper is on optical performance monitors for applications in dense wavelength-division multiplexing (DWDM) communication systems. Two algorithms for estimation of central wavelength and signal power of DWDM channels, on the basis on raw measurement data provided by a low resolution spectrometric transducer, are compared. The first algorithm is based on the use of a curve-fitting and constrained-optimization technique; the second on application of a superposition of simple feed forward neural networks. The comparison is carried out using semisynthetic data. Conclusions are drawn concerning the applicability of compared algorithms in engineering practice. [ABSTRACT FROM AUTHOR]

In two recent papers, the performances of dual-branch postdetection switch-and-stay combining (SSC) for non-coherent orthogonal binary frequency-shift keying (BFSK) and noncoherent orthogonal M-ary frequency-shift keying (MFSK) operating in the present of slow flat fading modeled by Rayleigh, Nakagami-m, and Rician distributions have been analyzed. In this paper, we show that these previous analyses for the Nakaga mi-m fading model, which are restricted to integer values of m, are incorrect, and we derive the correct bit-error rate (BER) performances of BFSK and MFSK with dual-branch SSC in Nakagami-m fading for all values of m. Optimum switching thresholds that minimize the BER of BFSK and MFSK with postdetection SSC in Nakagami-m fading are obtained. The performance of postdetection SSC is compared with the performance of predetection SSC, and it is shown that postdetection SSC outperforms predetection SSC for all values of signal-to-noise ratio (SNR). We also show that for a given BER, the performance gain of postdetection SSC over predetection SSC has been overestimated by several decibels in SNR in previous publications. [ABSTRACT FROM AUTHOR]

In this paper, we study a cellular mobile communications network with multiple cells and multiple classes of calls. The different classes of calls have different call holding times and residence time distributions. We consider a protocol mechanism under which a blocked call in a cell is either disconnected from the network or is deemed as a handoff call in a neighboring cell. Under this protocol, we prove that the stationary distribution of this cellular mobile network has a product form. This allows us to derive explicit expressions for handoff rates of each class of calls from one cell to another and the disconnecting probabilities for each class of new and handoff calls. Our numerical results show how these measures depend on the mobility of the mobile terminals in each cell and on the numbers of reserved channels. [ABSTRACT FROM AUTHOR]

The iterative decoding structure and component maximum a posteriori decoders used for decoding binary concatenated codes can be extended to the nonbinary domain. This paper considers turbo codes over nonbinary rings, specifically ternary, quaternary, penternary, hexernary, and octernary codes. The best rate-1/2 component codes are determined using a practical search algorithm. The performance of the resulting rate-1/3 turbo codes on an additive white Gaussian noise channel using q-ary phase-shift keying modulation is given. [ABSTRACT FROM AUTHOR]

In February 2002, the Federal Communications Commission allocated 7500 MHz of spectrum for unlicensed use of commercial ultra-wideband (UWB) communication devices. This spectral allocation has initiated an extremely productive activity for industry and academia. Wireless communications experts now consider UWB as available spectrum to be utilized with a variety of techniques, and not specifically related to the generation and detection of short RF pulses as in the past. There are many differences between real-world behavior of narrow-band and UWB systems. All wireless systems must be able to deal with the challenges of operating over a multipath propagation channel, where objects in the environment can cause multiple reflections to arrive at the receiver (RX). For narrow-band systems, these reflections will not be resolvable by the RX when the narrow-band system bandwidth is less than the coherence bandwidth of the channel. The large bandwidth of UWB waveforms, instead, significantly increases the ability of the RX to resolve the different reflections in the channel. The UWB channel model developed by the IEEE 802.15.3a standard body is described in this paper. For highly dispersive channels, an orthogonal frequency-division multiplexing (OFDM) RX is more efficient at capturing multipath energy than an equivalent single-carrier system using the same total bandwidth. OFDM systems possess additional desirable properties, such as high spectral efficiency, inherent resilience to narrow-band RF interference, and spectral flexibility, which is important because the regulatory rules for UWB devices have not been finalized throughout the entire world. This paper describes the design of a UWE system optimized for very high bit-rate, low-cost, and low-power wireless networks for personal computing (PC), consumer electronics (CE), and mobile applications. The system combines OFDM modulation technique with a multibanding approach, which divides the spectrum into several sub-bands, whose bandwidth is approximately 500 MHz. The system described in this paper has been selected by several key industry organizations [Mulitband OFDM Alliance, WiMedia, Wireless Universal Serial Bus (USB)] because of its very good technical characteristics for the diverse set of high performance short-range applications that are eagerly anticipated for CE, PC, and mobile applications. [ABSTRACT FROM AUTHOR]