Showing papers in "IEEE Transactions on Vehicular Technology in 1995"
TL;DR: By partitioning the range of the received signal-to-noise ratio into a finite number of intervals, FSMC models can be constructed for Rayleigh fading channels and the validity and accuracy of the model are confirmed by the state equilibrium equations and computer simulation.
Abstract: The authors first study the behavior of a finite-state channel where a binary symmetric channel is associated with each state and Markov transitions between states are assumed. Such a channel is referred to as a finite-state Markov channel (FSMC). By partitioning the range of the received signal-to-noise ratio into a finite number of intervals, FSMC models can be constructed for Rayleigh fading channels. A theoretical approach is conducted to show the usefulness of FSMCs compared to that of two-state Gilbert-Elliott channels. The crossover probabilities of the binary symmetric channels associated with its states are calculated. The authors use the second-order statistics of the received SNR to approximate the Markov transition probabilities. The validity and accuracy of the model are confirmed by the state equilibrium equations and computer simulation. >
1,742 citations
TL;DR: This work considers the minimization of the total transmitted uplink power subject to maintaining an individual target CIR for each mobile and identifies synchronous and asynchronous distributed algorithms that find the optimal power vector and base station assignment.
Abstract: In cellular wireless communication systems, transmitted power is regulated to provide each user an acceptable connection while limiting the interference seen by other users. Previous work has focused on maximizing the minimum carrier to interference ratio (CIR) or attaining a common CIR over all radio links. However, previous work has assumed the assignment of mobiles to base stations is known and fixed. In this work, we integrate power control and base station assignment. In the context of a CDMA system, we consider the minimization of the total transmitted uplink power subject to maintaining an individual target CIR for each mobile. This minimization occurs over the set of power vectors and base station assignments. We show that this problem has special structure and identify synchronous and asynchronous distributed algorithms that find the optimal power vector and base station assignment. >
410 citations
TL;DR: A system to read automatically the Italian license number of a car passing through a tollgate using a CCTV camera and a frame grabber card to acquire a rear-view image of the vehicle is presented.
Abstract: A system for the recognition of car license plates is presented The aim of the system is to read automatically the Italian license number of a car passing through a tollgate A CCTV camera and a frame grabber card are used to acquire a rear-view image of the vehicle The recognition process consists of three main phases First, a segmentation phase locates the license plate within the image Then, a procedure based upon feature projection estimates some image parameters needed to normalize the license plate characters Finally, the character recognizer extracts some feature points and uses template matching operators to get a robust solution under multiple acquisition conditions A test has been done on more than three thousand real images acquired under different weather and illumination conditions, thus obtaining a recognition rate close to 91% >
258 citations
TL;DR: A new multiple access communications system based on the combination of multitone transmission and direct sequence spectrum spreading (DS/SS) is proposed because the associated larger symbol duration is favorable to combat the effects of multipath propagation.
Abstract: The paper proposes a new multiple access communications system based on the combination of multitone transmission and direct sequence spectrum spreading (DS/SS). Multitone transmission is proposed because the associated larger symbol duration is favorable to combat the effects of multipath propagation. The multiple access capability of the system is achieved by means of DS/SS which also helps to combat the presence of several paths. On the other hand, DS/SS is also attractive to decrease the multiple access interference. The performance of this system is investigated for a multipath, slowly Rician fading and frequency selective channel, and a suboptimal receiver based on matched filters. The multiple access interference is also taken into account, A model for the computation of the bit error probability is derived for QPSK modulation of the orthogonal tones by the spread symbols. The system performance is investigated for selection diversity and maximal ratio combining (RAKE reception). Then the influence of the number of tones is investigated for given bandwidth, bit rate and transmission power. The positive effect of a multitone spread spectrum transmission is demonstrated. >
251 citations
TL;DR: In this article, the mean signal level and envelope cross-correlation of 1800 MHz base station signals received in two-branch spatial and polarization diversity schemes were determined with the experimental base site located in two urban sites, a residential area, a rural area, and near a motorway.
Abstract: Determines the mean signal level and envelope cross-correlation of 1800 MHz base station signals received in two-branch spatial and polarization diversity schemes. Measurements have been conducted with the experimental base site located in (i) two urban sites, (ii) a residential area, (iii) a rural area, and (iv) near a motorway. In each location, the effect of the random orientation of a typical mobile radio telephone handset has been studied by examining the characteristics of signals received from a mobile collinear antenna inclined at angles of 0/spl deg/, 30/spl deg/, 45/spl deg/, 60/spl deg/, and 90/spl deg/ to the vertical. Furthermore, the diversity gain at 90% signal reliability has been evaluated for each diversity scheme by simulating selection, equal-gain and maximal-ratio combining techniques using the recorded signals as inputs. Results have shown that 20/spl lambda/ separation in the horizontal plane or 15/spl lambda/ in the vertical plane is sufficient to obtain a cross-correlation of less than 0.7 for most of the time at 1800 MHz. Similar cross-correlation results were obtained for polarization diversity. When the antenna is inclined at 45/spl deg/, a 6 dB degradation in signal level was recorded for space diversity schemes. However, the diversify gain is unaffected by tilt and remains unchanged at 5-6 dB for horizontal and 3.5-4.5 dB for vertical separation. For polarization diversity, only a little degradation is experienced because most of the energy lost on the vertical branch is recovered on the horizontal branch. The diversity gain is between 1-2 dB at 0/spl deg/ tilt and increases to 3-5.2 dB at 45/spl deg/. >
246 citations
TL;DR: It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls), and a transmit scheme which directs nulls against co-channel users within the cell is applied.
Abstract: In this paper we investigate the spectrum efficiency gain using transmitting antenna arrays at the base stations of a mobile cellular network. The proposed system estimates the angular positions of the mobiles from the received data, and allows multiple mobiles to be allocated to the same channel within a cell. This is possible by applying a transmit scheme which directs nulls against co-channel users within the cell. It is shown that multiple mobiles per cell is an efficient way of increasing capacity in comparison with reduced channel reuse distance and narrow beams (without directed nulls). The effect of the spatial spread angle of the locally scattered rays in the vicinity of the mobile is also investigated. >
220 citations
TL;DR: The performance of the proposed DCA technique has been derived by computer simulations in terms of call blocking and handover failure probabilities and comparisons with the classical fixed channel allocation (FCA) technique and other dynamic allocation algorithms recently proposed in the literature have been carried out to validate the proposed technique.
Abstract: This paper deals with an efficient dynamic channel allocation (DCA) technique applicable to terrestrial mobile cellular networks. A channel (or resource) is a fixed frequency bandwidth (FDMA), a specific time-slot within a frame (TDMA), or a particular code (CDMA), depending on the multiple access technique used. A cost function has been defined by which the optimum channel to be assigned on demand can be selected. In addition, a suitable mobility model has been derived to determine the effects of handovers on network performance. The performance of the proposed DCA technique has been derived by computer simulations in terms of call blocking and handover failure probabilities. Comparisons with the classical fixed channel allocation (FCA) technique and other dynamic allocation algorithms recently proposed in the literature have been carried out to validate the proposed technique. >
195 citations
TL;DR: It is shown how information in signal strength measurements can be exploited to improve the quality of handoff decisions, for both large and small cells, and an adaptive scheme for optimal averaging is outlined.
Abstract: The purpose of this paper is to show how information in signal strength measurements can be exploited to improve the quality of handoff decisions, for both large and small cells. Averaging of signal strength fluctuations is required. This leads to the following tradeoff problem for the averaging interval for the signal strength measurements. If the interval is too short, the fading fluctuations are not sufficiently smoothed out. If the interval is too long, delay in handoff increases. With this tradeoff in mind, we present a method to adaptively change the averaging interval. The method is based on estimating the maximum Doppler frequency, f D , as a means to obtain mobile velocity, the key to the tradeoff. A method used for estimating f D from the squared deviations of the signal envelope is outlined. Exact analysis for the f D estimate as a function of squared deviations of the logarithmically compressed signal envelope in Rayleigh fading is presented. An extension of the algorithm for robustness in a Rician fading environment is given. Sensitivity issues of the estimates are considered. An adaptive scheme for optimal averaging is outlined.
178 citations
TL;DR: In this paper, the application of coherent receiver antenna diversity (CRAD) to the more critical uplink of CDMA mobile radio systems with suboptimum joint detection (JD) techniques is investigated for maximal-ratio combining.
Abstract: In code division multiple access (CDMA) mobile radio systems, both intersymbol interference and multiple access interference arise which can be combated by using either elaborate optimum or favorable suboptimum joint detection (JD) techniques. Furthermore, the time variation of the radio channels leads to degradations of the receiver performance. These degradations can be reduced by applying diversity techniques. Using coherent receiver antenna diversity (CRAD) is especially attractive because only the signal processing at the receiver must be modified. In the present paper, the application of CRAD to the more critical uplink of CDMA mobile radio systems with suboptimum JD techniques is investigated for maximal-ratio combining. The authors study six different suboptimum JD techniques based on decorrelating matched filtering, Gauss-Markov estimation, and minimum mean square error estimation with and without decision feedback. These six suboptimum JD techniques which are well-known for single antenna receivers are extended for the application to CRAD. A main concern of the paper is the determining of the SNR performance of the presented JD techniques for CRAD and the achievable average uncoded bit error probabilities for the transmission over rural area, typical urban and bad urban mobile radio channels are determined.
166 citations
TL;DR: In this article, a method to quantify the RF exposure of the users of portable cellular phones in terms of specific absorption rate (SAR) is described, which involves a robotic system to accurately position an isotropic E-field probe within equivalent biological tissue.
Abstract: Describes a method to quantify the RF exposure of the users of portable cellular phones in terms of specific absorption rate (SAR). The method involves a robotic system to accurately position an isotropic E-field probe within equivalent biological tissue. The user of cellular phones is simulated by a simple human model (a phantom) consisting of a thin shell of fibreglass filled with a liquid having the complex dielectric constant of human brain tissue. The authors present the results of the dosimetric assays conducted using current and previous models of cellular telephones. The peak SAR values detected using the measurement method described are below the limits recommended by the National Council for Radiation Protection and Measurements (NCRP) Report 86 for the protection of humans exposed to RF electromagnetic energy. >
160 citations
TL;DR: In this article, a computer simulation was made to clarify the polarization dependence of the high-speed transmission characteristics of an indoor communications system operating at 60 GHz in a room within a modern office building.
Abstract: Measurements of polarization dependence of multipath-propagation characteristics were conducted at 60 GHz in a room within a modern office building. Delay profiles were measured using a swept frequency method with a high time-delay resolution of 2 ns. Directions of arrival of the multipath components reflected from walls were analyzed by rotating a narrow-beam receiving antenna with an angular resolution of 5 degrees. Results of this experiment showed that multipath delayed waves due to wall reflection can be effectively suppressed by employing circular polarization instead of linear polarization. Based on this experimental result, a computer simulation was made to clarify the polarization dependence of the high-speed transmission characteristics of an indoor communications system operating at 60 GHz. >
TL;DR: It is shown that the system is rather sensitive to small power control errors and that voice activity monitoring and sectorization are good methods to improve the performance of cellular DS CDMA systems.
Abstract: An analytical model is developed to evaluate the performance of a cellular slotted DS CDMA system in terms of user capacity, throughput, and delay for the reverse link, i.e., from mobile to base station, considering interference from both home cell and adjacent cells. The user capacity is studied for voice communications and the throughput and delay are inves- tigated for data communications. The effect of both imperfect power control and imperfect sectorization on the performance is investigated. It is shown that the system is rather sensitive to small power control errors and that voice activity monitoring and sectorization are good methods to improve the performance of cellular DS CDMA systems.
TL;DR: In this paper, the authors present an analytical framework and several new results, including convergence time and coefficient jitter, a bias effect that leads to extreme accuracy requirements in one coefficient, the effect of delay mismatch, and the mitigating effects of a filter inserted in one adaptation path.
Abstract: Feedforward linearization has advantages in bandwidth and generality over other linearization methods. However, it is based on the subtraction of nearly equal quantities, so its major parameters must adapt to changes in environmental or operating conditions. This paper is the first published analysis of adaptation behavior in feedforward amplifier linearizers. As such, it presents an analytical framework and several new results, including convergence time and coefficient jitter, a bias effect that leads to extreme accuracy requirements in one coefficient, the effect of delay mismatch, and the mitigating effects of a filter inserted in one adaptation path.
TL;DR: The paper suggests a very simple backoff scheme for slotted ALOHA and evaluates its performance in local wireless environments and gives a protocol parameter value which is highly recommendable from the practical viewpoint.
Abstract: Slotted ALOHA is widely used in local wireless communications not only by itself as a multiple access protocol but also as a component in many reservation protocols. The paper suggests a very simple backoff scheme for slotted ALOHA and evaluates its performance in local wireless environments. The authors analyze the system capacity in full load conditions and the throughput-delay characteristics in underload conditions. They conduct a computer simulation to evaluate the system performance in transient-state. They also give a protocol parameter value which is highly recommendable from the practical viewpoint. As an application example, they examine the packet reservation multiple access (PRMA) system with the suggested backoff scheme and compare its performance with that of the original PRMA system. >
TL;DR: One of the algorithms, called the SMIRA algorithm, has an outage probability that is very close to the minimum and a class of distributed power control algorithms that can achieve a balanced carrier-to-interference ratio with probability one are studied.
Abstract: Power control is an effective technique to reduce cochannel interference and increase capacity for cellular radio systems. Optimum centralized power control can minimize the outage probability, but requires the information of all link gains in real time, which is very difficult to successfully implement for a large system; besides, the computational complexity of an optimum power control algorithm makes it impractical for real implementations. In this paper, we propose some centralized power control algorithms with reasonable computational com- plexity. One of the algorithms, called the SMIRA algorithm, has an outage probability that is very close to the minimum. We also study a class of distributed power control algorithms that can achieve a balanced carrier-to-interference ratio with probability one. Among the class of algorithms, we found that the one proposed in (6) gives the minimum outage probability.
TL;DR: In this paper, the authors simulate call performance for users accessing channels in a regular cellular array with a base located at the center of each hexagon, and show that distributed power control and channel access can be combined in an access management policy that achieves satisfactory system capacity and provides desired call performance.
Abstract: Local autonomous dynamic channel allocation (LADCA) including power control is essential to accommodating the anticipated explosion of demand for wireless. The authors simulate call performance for users accessing channels in a regular cellular array with a base located at the center of each hexagon. The computer model includes stochastic channel demand and a propagation environment characterized by attenuation with distance as well as shadow fading. The study of LADCA shows that distributed power control and channel access can be combined in an access management policy that achieves satisfactory system capacity and provides desired call performance. The authors report: LADCA/power control is observed to be stable alleviating a major concern about users unaware of the signal to interference problems their presence on a channel might cause to others. There can be substantial inadvertent dropping of calls in progress caused by originating calls. Modeling user time dynamics is essential. LADCA contrasts very favorably with fixed channel allocation (FCA) in a comparative example. >
TL;DR: A method which aims at the reduction of signaling overhead on the radio link produced by the paging procedure through the application of a multiple step paging strategy which operates as follows.
Abstract: Location management procedures, in conjunction with the millions of users expected to subscribe to third generation mobile telecommunication systems, will generate a huge signaling load. In this paper, we propose a method which aims at the reduction of signaling overhead on the radio link produced by the paging procedure. The key idea is the application of a multiple step paging strategy which operates as follows: at the instance of a call terminating to a mobile user who roams within a certain location area, paging is initially performed in a portion of the location area (the paging area) that the so-called "paging related information" indicates. On no paging response, the mobile user is paged in the complementary portion of the location area-this phase can be completed in more than one (paging) step. Various "paging related information" elements (e.g. recent interaction information, high mobility flag, etc.) can be used and several "intelligent" paging strategies can be defined. Representative paging strategies are analyzed in terms of network performance and quality of service (paging signaling, paging delay, processing power requirements), via a simulation tool which models a realistic city area environment. >
TL;DR: The reported results show that DCA strategies in the considered class cope with large and sudden traffic fluctuations remarkably better than the FCA scheme does and that the advantage becomes more evident as the burstiness of the user mobility process increases.
Abstract: In this paper we refer to a specific class of Dynamic Channel Allocation (DCA) strategies, namely the interferencefree, timid, not-conditioned class. The main concern of this work is to verify if and to what extent strategies belonging to this class can offer better performance than Fixed Channel Allocation (FCA). The interest in this kind of strategies is motivated by their feasibility with current TDM technologies, the limited amount of information required to carry out channel assignments and their intrinsic stability. In this framework we present a simple, but very attractive DCA strategy, the so-called Geometric DCA (GDCA). A performance evaluation is carried out to compare some representative DCA strategies of the considered class, by using a user mobility model that accounts for the large fluctuations of the number of users in a cell coverage area expected in a microcellular environment. The effect of the non-null propagation time required by the information exchange in the DCA strategies is also taken into account. It emerges that the proposed GDCA allows better performance than more sophisticated strategies already proposed, at the expense of a frequency planning carried out only at network configuration. This is due to the ability of GDCA to exploit the a priori information to maintain a tight geometric packing of used carriers. The reported results also show that DCA strategies in the considered class cope with large and sudden traffic fluctuations remarkably better than the FCA scheme does and that the advantage becomes more evident as the burstiness of the user mobility process (hence of the offered traffic) increases.
TL;DR: In this article, a single-layer slotted leaky waveguide array antenna for mobile DBS reception is proposed, where the feed waveguide is in the same layer as the radiating waveguides.
Abstract: This paper proposes a single-layer slotted leaky waveguide array antenna for mobile DBS reception. A single-layer feed structure is proposed, where the feed waveguide is in the same layer as the radiating waveguides. This results in the simple fabrication of slotted waveguide arrays, suitable for mass production. Short radiating leaky waveguides are used to get a large beam-tilting angle of about 50/spl deg/ for the horizontal installation of the antenna and a beamwidth broad enough to dispense with mechanical steering in the elevation plane. A prototype antenna sized 30 cm by 21 cm has a maximum of 74% efficiency and more than 69% efficiency within the DBS band. It also has a broad l-dB beamwidth of 7.5/spl deg/ in the elevation plane, which enables clear DBS reception by a picture tube display over about one-third the area of Japan without elevation tracking. >
TL;DR: In this article, a three-dimensional uniform theory of diffraction (UTD) microcellular communications propagation model is presented, using multiple-image theory and a ray launching technique, applicable to a general city scene with various distributions of buildings, streets and open areas.
Abstract: A new three-dimensional uniform theory of diffraction (UTD) microcellular communications propagation model is presented, using multiple-image theory and a ray launching technique, applicable to a general city scene with various distributions of buildings, streets and open areas. The model includes contributions to the received signal from all possible propagation paths, including ground and wall reflections from diffracted and specularly reflected signals both in the line-of-sight (LOS) and out-of-sight (OOS) regions. Within the scope of the UTD model, the accuracy of the UTD model is limited mainly by the assumptions of characterizing the tall building walls as "smoothed-out" flat surfaces with average relative permittivity /spl epsiv//sub r/ and conductivity /spl sigma/. The building corners are modeled as conducting wedges characterized by /spl epsiv//sub r/ and /spl sigma/. Comparison between present calculations and published measurements for a side street and a parallel street in Ottawa shows good results. >
TL;DR: In this paper, an anti-multipath fading scheme employing a circular polarized wave for line-of-sight (LOS) indoor radio communications was proposed, and the received signal intensity variations and delay spread were investigated numerically using a 14-path propagation model and the usefulness was confirmed by comparing with a linear polarized wave transmission/reception under a same LOS condition.
Abstract: This paper presents an anti-multipath fading scheme employing a circular polarized wave for line-of-sight (LOS) indoor radio communications. The circular polarized wave transmission/reception significantly mitigates the multipath fading caused by reflections from walls, ceiling, and floor since the energies of single-bounce reflected waves do not appear at the receiver, thereby resulting in significant amplitude fade and delay spread reduction. The received signal intensity variations and delay spread are investigated numerically using a 14-path propagation model and the usefulness is confirmed by comparing with a linear polarized wave transmission/reception under a same LOS condition. >
TL;DR: This paper presents a new technique to determine the probability of outage, which allows the parameters of all Nakagami interferers to be arbitrary, and is more general and simpler to compute.
Abstract: Probability of outage is one of the major performance considerations in the design of cellular mobile radio systems, and Nakagami distribution is considered as one of the most appropriate models for practical mobile channels. Closed-form solutions for the probability of outage with multiple Nakagami interferers were recently published under the integer assumption on the fading parameters of both desired signal and interferers. Most of these restrictions, however, can be removed. In this paper, we present a new technique to determine the probability of outage, which allows the parameters of all Nakagami interferers to be arbitrary. In comparison with the previous results, the new formula is more general and simpler to compute. >
TL;DR: In this article, a ray model is developed to represent indoor microcell propagation by considering a direct ray plus rays which have undergone single and double reflections from the walls, and the signal variations and the amplitude of reflected rays with respect to the line of sight (LOS) ray as functions of mobile receiver position are predicted and used to assist in interpreting experimental results.
Abstract: Discusses millimeter waves for indoor microcellular communications. The results of propagation experiments conducted at 60.4 GHz (the oxygen absorption band) and 38.25 GHz to determine multipath characteristics in a number of indoor microcell channels employing omnidirectional antennas are presented. Cumulative distribution functions for received signal envelope, as well as corresponding power spectra are given. In addition, a comparison between the fading statistics measured at 60.4 GHz and 38.25 GHz under similar conditions is made. The change in multipath characteristics due to the presence of different building materials is also illustrated. A ray model is developed to represent indoor microcell propagation by considering a direct ray plus rays which have undergone single and double reflections from the walls. Specular floor-reflected and ceiling-reflected rays are included when the antennas radiation pattern does not preclude them. Using this simple model, the signal variations and the amplitude of reflected rays with respect to the line of sight (LOS) ray as functions of mobile receiver position are predicted and used to assist in interpreting experimental results. Theoretical results are found to be in good agreement with measured ones, with the model also being used to predict structure-induced root mean square (rms) delay spread along receiver routes in an indoor microcell environment. This parameter is a measure of multipath conditions in a mobile radio channel and is inversely proportional to the maximum usable data signalling rate of a channel. >
TL;DR: In this paper, the behavior of the Rice factor and local mean power in a multi-storied building at 1.9 GHz was studied. But the outage probability was not analyzed.
Abstract: Narrow-band propagation measurements were conducted at two floors of a multi-storied building at 1.9 GHz to study the behavior of the Rice factor and local mean power. To evaluate the influence of the Rice factor on a pico-cellular system, the outage probability is calculated for two different cases: (i) Rician fading for the desired and interfering signals with different Rice factors; (ii) desired signal with Rician fading and interfering signals with Rayleigh fading with a different local mean power for each interfering signal. Finally, a pico-cellular structure is determined as an illustration. >
TL;DR: The authors provide constructions based on orthogonal latin squares that guarantee different sets of users will interfere in successive slots to improve re-use of time/frequency slots in a cellular radio system.
Abstract: To improve re-use of time/frequency slots in a cellular radio system, it is desirable for the average interference levels seen by all users to be made approximately equal. The authors provide constructions based on orthogonal latin squares that guarantee different sets of users will interfere in successive slots. When signal to interference ratios are independent from successive symbols, channel codes can provide a large diversity gain which is far in excess of the gain against additive noise. Consequently, coding with interleaving fits together very naturally with this construction. The authors illustrate how to achieve large performance improvement using convolutional codes with low decoding delay in a slow hopped system. >
TL;DR: In this article, an experimental passive infrared system was designed and developed to detect and monitor vehicular road traffic, which uses infrared pyroelectric sensors to sense vehicles passing through its field of view.
Abstract: An experimental passive infrared system was designed and developed to detect and monitor vehicular road traffic. The system uses infrared pyroelectric sensors to sense vehicles passing through its field of view. In conjunction with computerized signal processing and correlation techniques the sensor information can then be used to count the number of vehicles passing and compute their speed and length. Laboratory and field tests results indicate that this technology should be cost effective, weather resistant and have the potential for a variety of sophisticated traffic monitoring applications. >
TL;DR: An efficient method for accurately calculating the mean and variance of power sums with two log-normal components with Gaussian probability density functions using the technique of transformation and the trapezoidal rule is presented.
Abstract: An efficient method for accurately calculating the mean and variance of power sums with two log-normal components is presented. It involves numerical quadrature with integrands consisting of Gaussian probability density functions. Only the technique of transformation and the trapezoidal rule are used in the evaluation. The whole computational work and roundoff error are much lower than the one by Schwartz and Yeh (1982). Because of its high efficiency, no least-squares fit is necessary. >
TL;DR: Novel 2-D TCM schemes that attain diversity of order two even for a trellis structure that includes parallel paths with one symbol per edge are developed and assessed via computer simulation for some representative TCM-QAM schemes.
Abstract: The design of trellis coded modulation (TCM) schemes for QAM constellations to counteract simultaneous flat fading and additive white Gaussian noise (AWGN) is considered. Motivated by the results of Divsalar and Simon (see IEEE Trans. Commun., vol.36, p.1004, 1988), and incorporating some recent ideas from Boulle and Belfiore (1992), we develop novel 2-D TCM schemes that attain diversity of order two even for a trellis structure that includes parallel paths with one symbol per edge. An algorithm is described that transforms codes designed for the AWGN channel into codes that achieve significant gains over flat fading channel, while preserving their coding gain over AWGN channel. Their performance is assessed via computer simulation for some representative TCM-QAM schemes under the assumption of uncorrelated fading and perfect channel state information (CSI). Finally, the effects of finite interleaving as well as imperfect CSI on code performance are investigated. >
TL;DR: In this paper, a method to choose an appropriate sampling rate for the predistorter is presented and different filter approximations and orders are examined for different amplifier configurations by means of simulation.
Abstract: The reconstruction filters are a major source of error in digital predistortion linearizers for RF power amplifiers. This paper presents a method that enables these filters to be designed for lowest filter complexity and minimum degradation of the linearizer performance. Furthermore, a method to choose an appropriate sampling rate for the predistorter is presented. Different filter approximations and orders are examined for different amplifier configurations by means of simulation. Of the filters tried, low-ripple Chebyshev and Butterworth filters perform best. It is demonstrated that it is possible to account for reasonable filter misalignment with only a small degradation in performance. It is also shown that the effect on the modulation is small with respect to intersymbol interference. >
TL;DR: In this paper, a new approach for approximating the time variant radio channel impulse response, given an arbitrary Doppler power density spectrum, based on a harmonic decomposition of stochastic processes, is presented.
Abstract: Based on a harmonic decomposition of stochastic processes, a new approach for approximating the time variant radio channel impulse response, given an arbitrary Doppler power density spectrum is presented. The basic idea is to use a Fourier expansion with uncorrelated coefficients to approximate the actual radio fading process. An upper bound on the mean square error between the actual and approximated fading as a function of the number of terms in the expansion is also given. The proposed method is particularly adapted for simulating broadband radio channels. >