Search

5G antenna arrays are being designed to generate a dedicated stream of data for every single user. This results in more capacity and speed over the network along with the least possible latency rate. Depending upon the direction of the user demanding internet access, the beam can be steered in that direction. Meanwhile, the occurrence of side lobes in such systems can be menacing. The smart antenna is a pivotal technology for modern cellular communication. It helps the user's signal to determine the direction of arrival It also estimates antenna arrays using an adaptive signal processing algorithm that produces a radiation beam for communication. This work presents beamforming for uniform linear smart antenna array using leaky least mean square algorithm and side lobe level reduction using array synthesis methods like Tchebycheff and Taylor distribution. Multiple interferers are considered for the smart antenna. Here, one of the aims is to reduce side lobe levels nearer to the main beam which can enhance more efficient frequency reuse in a cellular network. Side lobe level is reduced up to about 16 dB that enacted for signal-to-noise ratio to 20 dB. [ABSTRACT FROM AUTHOR]

5G applications such as the Internet of Things, high-resolution video streaming, robotic cars, smart cities, and telehealth care have a universal presence nowadays. These applications mandate higher data rates, large bandwidth, increased capacity, low latency and high throughput. The key element to meet this demand is to apply efficient frequency reuse and scheduling strategies based on adaptive beamforming. Employing efficient frequency reuse and scheduling techniques based on adaptive beamforming will significantly increase the cellular system capacity by eighteen times and substantially reduce the consumption power levels and interference. In cellular networks, the performance of the adaptive beamforming algorithms is severely degraded by the presence of interfering signals. In this paper, we introduce a beamforming-based algorithm for 5G applications named Direction Finding for Beamforming and Synthesizing. This algorithm combines the Direction of Arrival (DOA), adaptive beamforming, and radiation pattern synthesizing. The proposed algorithm uses the DOA technique to feed the adaptive beamforming algorithms with estimations of the desired user direction, desired user signal, and the interfering signals with their directions as initial values. In addition, we use the adaptive beamforming process to supply the radiation pattern synthesizing algorithms with an initial radiation pattern, and the required positions of nulls. At the beamformer output, we evaluate our proposed mechanism in terms of error convergence, tracking capabilities, and the obtained radiation pattern characteristics. At the synthesizer output, we carry out analysis in terms of the convergence speed and the resultant radiation pattern attributes to investigate the efficiency of the proposed algorithm. The simulation results show that our proposed algorithm has significantly fast convergence, reliable tracking capabilities, and radiation patterns with very low Side Lobe Levels. [ABSTRACT FROM AUTHOR]

Optimizing the current distribution of an evenly spaced antenna array has shown to be an efficient approach for reducing side lobe levels. In this article, the Tchebyscheff distribution-based antenna array synthesis approach is combined with an adaptive signal processing algorithm for beamforming and side lobe level reduction in smart antennas in various fading situations. The performance of smart antennas in uniformly spaced linear, planar, circular, and semi-circular arrays are evaluated. The presence of Rayleigh and Rician channels is examined in the network. The least mean square (LMS) and normalised least mean square (NLMS) algorithms are applied as adaptive algorithms. In fading environments, the NLMS algorithm with Tchebyscheff distribution outperforms than the LMS algorithm with Tchebyscheff distribution, with a side lobe level decrease of 11.23 dB. The lowest side lobe achieved with the NLMS algorithm with Tchebyscheff distribution is − 45.59 dB for uniform planar array. [ABSTRACT FROM AUTHOR]

This paper presents a resilient localization scheme for wireless sensor networks (WSNs). It suits well in estimation of node position under a corrupted radio environment. Position computation is based on information of angle-of-arrivals (AoA) and references obtained from a few mobile anchors. In the network, anchors are equipped with smart antennas and global positioning system receivers. They broadcast signals in a synchronous and periodic fashion. The neighboring nodes having the signals with received signal strength values above a prescribed threshold level, respond with their respective IDs. Anchors evaluate AoA information from these signals using estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm. Next, they forward beacon messages, containing their references and estimated angles, to the corresponding nodes and move along random trajectories. After receiving three sets of such data, at least, nodes can initiate selective segregation of the inconsistent position estimations. Simulation results attaining higher degree of localization accuracy validate its competency over the existing schemes. [ABSTRACT FROM AUTHOR]

A new kind of smart antenna capable of automatically switching its main beam to track a moving target is presented. The antenna, which is suitable for mobile communication in long straight spaces, such as railways or highways, integrates a sensing element, signal processing element, and radiating element. The sensing element works based on a frequency-modulated continuous wave and delivers a beat frequency signal containing environmental information to the signal processing element, which is used to control the excitation of the radiating element. To verify the efficiency of the proposed antenna, a prototype is fabricated and implemented in a real corridor scenario. Furthermore, the error vector magnitude (EVM) along the test path is investigated to evaluate the system performance when using the proposed antenna. The results show that this kind of smart antenna is capable of improving mobile communication quality and decreasing energy consumption. Therefore, it is a promising candidate for mobile communication. [ABSTRACT FROM AUTHOR]

In this work, we propose a fast conjugate gradient method (CGM) for beamforming, after thoroughly analyzing the performances of the least mean square (LMS), the recursive least square (RLS), and the sample matrix inversion (SMI) adaptive beamforming algorithms. Various experiments are carried out to analyze the performances of each beamformer in detail. The proposed conjugate gradient method does not use the Eigen spread of the signal correlation matrix as in the case of the LMS and the RLS methods. It computes antenna array weights orthogonally for each iteration. Hence the convergence rate and the null depths of the proposed method are much better than the LMS, the SMI the RLS and the classical CGM. Also, the simulation results confirm that this method has a speed improvement of about 60% over the classical conjugate gradient method. This aspect significantly reduces the processor burden and saves a lot of power during the beamforming process. Hence the proposed method is superior compared to the LMS, the RLS, the SMI, and classical CGM and most suitable for high-speed mobile communication. [ABSTRACT FROM AUTHOR]

In this paper, the concept of blind algorithm with automatic gain control (AGC) is introduced in adaptive antenna system for signal optimization with an aim to estimate the desired response in adaptive fashion. Blind algorithm with AGC is a hybrid two-stage adaptive filtering algorithm; sequentially combining constant modulus algorithm (CMA) and Bessel least mean square (BLMS) algorithm. Blind Bessel beamformer with AGC does not require external reference signal to update its weight vectors and step size for convergence but updates itself from own reference signal obtained from the output of CMA. Similarly, step size is obtained from the correlation matrix which is the product of the signals induced in array elements of antenna. BLMS is the modified version of LMS algorithm; based on the non-uniform step size exploiting the asymptotic decay property of Bessel function of the first kind. The output of CMA provides input and reference signals for BLMS that makes it blind. The contributions of this paper include the development of novel blind theory concept and presentation of an AGC method in order to make the Bessel beamformer blind which can update itself electronically through the correlation matrix depending on the signal array vector with the aim to make the signal power constant. [ABSTRACT FROM AUTHOR]

Wireless communication is one of the fastest growing fields of communication industry. Cellular phones have shown the drastic exponential growth from the last decade and this growth has reached about one billion mobile phone users worldwide. Certainly, mobile phones have become one of the most importants components of daily life and a critical business tool in all countries. Huge gap between a vision for future wireless communication systems and the current system's performance represents that massive research work has to be carried out to make future communication system vision a reality. In this paper, all most all the types of beamforming and direction of arrival schemes for wireless communications have been presented. This paper also presents the comprehensive study of smart antenna systems, its advancement in recent years and futuristic scope. [ABSTRACT FROM AUTHOR]

In the antenna array signal processing, a lot of interest has been given towards large number of samples which is asymptotic case. In certain cases like automotive radar applications only few or in the worst condition one sample (snapshot) of radar sensor is available for the direction finding. Hence single snapshot based direction of arrival (DOA) algorithms are required for such cases. Two such methods, namely, single snapshot root-multiple signal classification (MUSIC) and single snapshot estimation of signal parameters via rotational invariance technique (ESPRIT) algorithms using uniform linear array (ULA) are proposed. The experimental results clearly show that the proposed methods with single snapshot and the classical methods with 100 snapshots have almost similar performance. This results in ten times increase in execution. Hence the proposed methods are computationally efficient and can be used in advanced radar communications where latency is an important issue. [ABSTRACT FROM AUTHOR]

Forthcoming wireless systems are developed to support greater data rate and extra coverage area. This can be achieved with the help of multiple input multiple output and smart antenna techniques. One of the major rapidly emerging areas of communication is the smart antenna system which aids in attaining better coverage by increasing the signal strength only in the chosen direction. With effective optical beamforming techniques, the smart antenna systems demonstrate to be more competent in terms of excellence of signals in wireless communication. In this paper, a succinct outline of the smart antenna, an analysis and the comparison of different architectures of optical signal processing beamforming network (OSPBFN) is presented. The performance of OSPBFN is analyzed and the comparison is done for different architectures with the antenna radiation parameters. This paper can enhance the understanding of the ongoing research work in the area of OSPBFN. [ABSTRACT FROM AUTHOR]

Space-time channel models are very important in evaluation of smart antenna system. In this paper, several space-time channel models that are often used in smart antenna system are presented and the properties of each model are analyzed. At the same time, the situations for each model are discussed. DOA, time delay and Doppler spectrum are discussed specially, while computer simulation is also done. Clarke model is thought as a special one. [ABSTRACT FROM AUTHOR]

The complexity of deployment and high implementation costs impede proliferation of real time location systems, depriving society of the benefits in terms of safety that these systems are capable of providing. The people tracking system presented in this article prioritizes ease of installation and adaptability to new low cost devices in emerging market against location accuracy to suit large scenarios that lack own infrastructure. The system has been implemented in a large playground to provide to the guardians of monitored children information about location and alert when an output of the controlled area is detected. Wireless channel characterization has been performed by means of deterministic 3D ray launching technique in order to assess the radioplanning process in the implemented network. This article describes the system and how it has been deployed in the validation scenario. [ABSTRACT FROM AUTHOR]

Smart antenna systems are rapidly emerging as one of the key technologies that can enhance overall wireless communications system performance. The purpose of this paper is to develop a novel adaptive beamforming system from two adaptive algorithms that are known in the literature as spatial filters. Our adaptive beamforming algorithm is a combination of the direct matrix inversion (DMI) and the recursive least square (RLS). This combination is called DMI-RLS and is used to calculate iteratively the optimum weights of smart antenna array and to ensure a possible faster convergence. Simulation data used for a uniform linear array antenna as an application verifies the accuracy of the analytical results. The performance of the DMI-RLS algorithm is also compared with the conventional RLS algorithm ones. From the simulation results, we noticed that, in the main, the performances of the DMI-RLS algorithm are sturdier than those of the conventional RLS algorithm. [ABSTRACT FROM AUTHOR]

To improve the capacity of initial ranging (IR) users simultaneously accessing into network and enhance the performance of the IR, a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna. The beamforming weight vectors provided by the antenna array are introduced for the IR users, and the procedures of the multiuser parameter estimation and the interference cancellation are designed. The proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference. Simulation results show that the proposed method has a much better performance than the available successive multiuser detection and interference cancellation algorithm and accommodates more active ranging users simultaneously accessing into a cell. [ABSTRACT FROM AUTHOR]

In a wireless sensor network (WSN), after gathering information, tiny sensor nodes need to transmit data to a sink. It is important to guarantee that each node can communicate with a sink. Due to the multi-hop communication of WSNs, an essential condition for reliable transmission is completely connectivity of a network. Adaptive or smart antenna (SA) techniques in WSNs have been a topic of active research in recent years. These techniques have been shown to be effective with respect to decreasing energy consuming via specified regions which are formed by the SA beams. In this paper, we propose a probabilistic technique to determine the network connectivity probability of the SA integrated WSN. We employ the geometric shape model to evaluate the network connectivity probability of the WSN using the SA beam specifications. The sensor node density to satisfy the desired network connectivity is determined in terms of the beam-width of the antenna array and node transmission range. The analytical results agree with the simulation results by less than 4.7 % error in the average. [ABSTRACT FROM AUTHOR]

In this paper, a simplified sidelobe reduction technique for uniform concentric circular antenna arrays (UCCA) is proposed. This technique is based on modifying some conventional windows to control the amplitude feeding instead of using adaptive techniques which require excessive processing and calculations and suffer from the lack of practical application especially for UCCA. The modified windows are applied to individual rings of the array that will taper the corresponding current amplitudes. The resulted sidelobe level, beamwidth and stability for amplitude errors are discussed for the different proposed windows where it shows a sidelobe reduction to about 49 dB as in the case of Binomial UCCA while the Hamming window shows the most immunity to tapered amplitude errors. [ABSTRACT FROM AUTHOR]

Smart antenna is now commonly used in communication systems due to its high advantages. In order to improve the performance of smart antenna operation, efficient design of beam forming pattern is required based on the subjected antenna parameters. In the previous works, beam forming techniques were proposed using hybridization of soft computing techniques, however the precision has not been considered in terms of direction of arrival (DOA). This paper includes DOA while deriving the beam forming pattern of smart antenna. To estimate precise DOA, the MUSIC algorithm is improved by introducing a tuned correlation matrix after solving the objective model for the matrix. Thus estimated DOA pattern is more precise as the unwanted side lobes are suppressed when compared to the conventional DOA pattern. Based on the estimated DOA pattern, the antenna beam forming pattern is derived as per the required direction of angles. The experimental results show the performance of the proposed beam forming technique over the previous techniques. [ABSTRACT FROM AUTHOR]

In this paper, a novel multiple antenna system framework, which combines smart antennas (SA) with multiple-input-multiple-output (MIMO) at the transmitter, is proposed. The downlink capacity of the single-user SA-MIMO wireless systems is investigated. The joint optimization problem corresponding to the capacity is deduced. After that, upper bounds of the capacity are given in general case and in the case of equal power allocation, respectively. Furthermore, in the case of equal power allocation and the same direction of departure from one transmit smart antenna to all antenna arrays at the receiver the closed-form expression of the capacity is obtained. Some numerical results are given to show that smart antennas can bring significant capacity gain for the MIMO systems due to the smart antennas gain, without additional spatial degrees of freedom, especially at high SNR with strong correlation among the MIMO channel links or at low SNR. [ABSTRACT FROM AUTHOR]

This study presents an implementation of the standard smart antenna (SA) application programming interface (API) and Transceiver API developed by the wireless innovation forum's (WINNF) smart antenna working group (SAWG). The API is implemented using the open-source SCA implementation-embedded (OSSIE) developed at Virginia Tech. Our implementation verified that the SA API can be utilized in software communication architecture (SCA)-based software defined radio (SDR) systems. We also verified that the Transceiver API can be realized with a real radio frequency (RF) transceiver module such as universal software radio peripheral2 (USRP2). The SA API enables various functions of multi-antenna systems such as beamforming and multiple input multiple output (MIMO) of spatial multiplexing. These are core technologies prevalent in 4G mobile communication systems. In order to support multi-antenna structures, the Transceiver API has first been extended for multichannel use. The paper details how the API is extended using OSSIE and the current status of the API as a standard within the Wireless Innovation Forum. [ABSTRACT FROM AUTHOR]

The application research on smart antenna (SA) for CDMA system is consists of two parts in general. One part is the research on mathematical methods in SA technology, i.e., how to isolate the array manifold parameter $${e^{ja_m }}$$ and then to get the weighting coefficient w for the SA receiving signal $${S(t)e^{ja_m }}$$ . The estimation of DOA is included in the above handling process. The other is how to extract the signal $${S(t)e^{ja_m }}$$ from SA receiver, which should be the focus of the research of SA application. Utilizing the feature of mid-amble sequence of TD-SCDMA system, a novel DOA estimation method based on mid-amble sequence (MDOA) is presented in this paper, by which the array manifold $${e^{ja_m }}$$ can be extracted directly from the SA receiving signal. Making use of the array manifold parameter $${e^{ja_m }}$$ obtained by the MDOA method, the simulation of downlink beam-forming shows that the proposed MDOA method is feasible. This method will result in the research of mathematical methods used in SA being completely abandoned. Also, a usable SA receiver for TD-SCDMA with beam-forming by amplitude weighting in base-band is given as well as the correctness proof by using spectrum searching method in base-band. [ABSTRACT FROM AUTHOR]

In the broadband signal processing, the array has different relative aperture for the different frequency bins, which results in waveform distortion. Moreover, the greater the bandwidth is, the more serious the distortion becomes. It is valuable to study the Frequency-invariant beam patterns (FIBPs) for receiving broadband signals without distortion. Based on the array dimensions, this paper will summarize some new methods to design a broadband beamformer with an FIBP. There will be two categories: One-dimensional arrays and Multi-dimensional arrays. For one-dimensional array, there are sampling rate method, minimax frequency invariant beamforming, etc. For multi-dimensional array, there are Bessel function method, Bessel function and phase mode method, and so on. Finally, we will discuss the pros and cons of every method. [ABSTRACT FROM AUTHOR]

In this paper, we introduce Adaptive Beamforming (AB) and Distributed Beamforming (DB) as two efficient techniques for Intelligent WiMAX (I-WiMAX). I-WiMAX is a new maritime communication system, consisting of Smart Radio (SR) principles and mobile WiMAX based on the IEEE 802.16e standard. Adopting AB, the same spectrum can accommodate more users by directing the main beam towards desired users while antenna pattern nulls towards others. To reduce the channel interferences caused by spectrum reusing, the Null Broadening (NB) method is required for downlink beamforming of I-WiMAX. A new NB method is presented in this paper with iterative weights computing for different OFDM subcarriers. Considering the spatial channel model seen at Subscriber Stations (SS) based on the von Mises distribution, the coverage range of one Base Station (BS) is dramatically enlarged by employing the NB technique. Meanwhile, assuming those SS which are within the coverage range as nodes of a relay network, the DB technique is introduced to forward signals to distant SS by forming the main beams towards them instead of deploying more BS to increase the communication range. It is proven in this paper that DB can successfully do the job. To reuse the spectrum, two DB methods are presented by directing different beams towards different required directions at the same time. With the AB and DB techniques, reliable I-WiMAX links can be established for long distances, with more optimum spectrum use and less infrastructure. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of estimation of direction of arrivals (DOA) of a multiple ultra-wideband (UWB) pulse postion modulation signals incident on a smart antenna in the presence of white Gaussian noise. We transform the received signal into frequency domain in order to split the array output into multiple frequency channels. Corresponding frequency channels data of the array is arranged into a model similar to narrowband DOA estimation. Iterative quadratic maximum likelihood algorithm is applied to yield DOA estimates. These separate estimates at different frequencies are combined into a single estimate of DOA for each source in an appropriate manner. The performance of the proposed method is studied via extensive computer simulations. It is seen that the technique can successfully resolve the DOA of the closely-spaced UWB signals. [ABSTRACT FROM AUTHOR]

In cellular mobile communication systems using coded modulations, the spectrum efficiency of the system is related to the number of available codes. Recently, large area synchronous (LAS) CDMA codes, which exhibit a region called interference free window (IFW) within some delay-spread, have been accepted as one of fourth-generation (4G) wireless communication systems. However, the number of synthesized LAS codes is very low due to the low duty ratio of the sequence. In this paper, a dynamic space coded multiple access (DSCMA) scheme which utilizes the spatial diversity from smart antenna system is proposed to overcome the low spectrum efficiency in LAS CDMA system. In the DSCMA a modified version of LAS codes called LAS even ternary (LAS-ET) codes is proposed. These codes are used together with a novel algorithm called dynamic space code (DSC), which will decrease the code length so that the spectrum efficiency can be increased. By taking advantage of dynamic code reuse assignment in spatial diversity, the spectrum efficiency of the DSCMA can be further increased significantly. [ABSTRACT FROM AUTHOR]

This article proposes an analytical model for evaluating the number of simultaneous communications that can be sustained by an ad-hoc network in which the nodes are equipped with fully adaptive smart antennas. The presented mathematical framework adopts realistic models for the antenna radiation pattern and the channel behavior, and is able to take into account the network topology and the characteristics of the medium access control (MAC) protocol in the spatial domain. The model is employed to investigate the impact of the spatial channel model and of the angular spread on network performance. Additionally, this article examines the influence of the transmission policy of the control and data packets of the MAC layer on the number of simultaneous communications. [ABSTRACT FROM AUTHOR]

A beamforming algorithm is introduced based on the general objective function that approximates the bit error rate for the wireless systems with binary phase shift keying and quadrature phase shift keying modulation schemes. The proposed minimum approximate bit error rate (ABER) beamforming approach does not rely on the Gaussian assumption of the channel noise. Therefore, this approach is also applicable when the channel noise is non-Gaussian. The simulation results show that the proposed minimum ABER solution improves the standard minimum mean squares error beamforming solution, in terms of a smaller achievable system’s bit error rate. [ABSTRACT FROM AUTHOR]

In wireless communication environment, the time-varying channel and angular spreads caused by multipath fading and the mobility of Mobile Stations (MS) degrade the performance of the conventional Direction-Of-Arrival (DOA) tracking algorithms. On the other hand, although the DOA estimation methods based on the Maximum Likelihood (ML) principle have higher resolution than the beamforming and the subspace based methods, prohibitively heavy computation limits their practical applications. This letter first proposes a new suboptimal DOA estimation algorithm that combines the advantages of the lower complexity of subspace algorithm and the high accuracy of ML based algorithms, and then proposes a Kalman filtering based tracking algorithm to model the dynamic property of directional changes for mobile terminals in such a way that the association between the estimates made at different time points is maintained. At each stage during tracking process, the current suboptimal estimates of DOA are treated as measurements, predicted and updated via a Kalman state equation, hence adaptive tracking of moving MS can be carried out without the need to perform unduly heavy computations. Computer simulation results show that this proposed algorithm has better performance of DOA estimation and tracking of MS than the conventional ML or subspace based algorithms in terms of accuracy and robustness. [ABSTRACT FROM AUTHOR]

A Matrix Inversion Normalized Least Mean Square (MI-NLMS) adaptive beamforming algorithm was developed for smart antenna application. The MI-NLMS which combined the individual good aspects of Sample Matrix Inversion (SMI) and the Normalized Least Mean Square (NLMS) algorithms is described. Simulation results showed that the less complexity MI-NLMS yields 15 dB improvements in interference suppression and 5 dB gain enhancement over LMS algorithm, converges from the initial iteration and achieves 24% BER improvements at cochannel interference equal to 5. For the case of 4-element uniform linear array antenna, MI-NLMS achieved 76% BER reduction over LMS algorithm. [ABSTRACT FROM AUTHOR]

A novel Least Squares Constant Modulus (LSCM) beam-forming algorithm in smart antenna Multi-Carrier Code Division Multiple Access (MC-CDMA) system is proposed in this paper. It adaptively beam-forms the multi-carrier antenna array signal using the LSCM Algorithm (LSCMA), and in the meantime, the beam-formed signals on every sub-carrier are combined by using Orthogonal Restore Combination (ORC), Equal Gain Combination (EGC) or Maximum Ratio Combination (MRC). Then the decision of the combined signals and the spread-code of the expected user are used to re-construct the signals on every sub-carrier. At last, the difference between the re-constructed signal and the output signal of the beam-former is used to control the coefficients of the beam-former. The bit error probability of the proposed algorithm is analyzed. We simulated and compared it with the conventional LSCM beam-forming algorithm. Simulation results show that the proposed algorithm is superior to the latter in Bit Error Rate (BER). [ABSTRACT FROM AUTHOR]

In this paper, a theoretical analysis of Time Division Duplex-Code Division Multiple Access (TDD-CDMA) uplink capacity constraint is presented when employing the smart antenna techniques. The evaluation formulations of capacity and load for multi-services are proposed. In order to maximize the throughput, the objective of optimization is proposed, and an advanced uplink resource management algorithm is developed. The proposed algorithm based on the least interference admission control scheme focuses on the maximum throughput for the circuit switched multi-services. The simulation results show that the proposed strategy has a significant improvement in throughput when the optimum admission control threshold is set. [ABSTRACT FROM AUTHOR]

The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system. [ABSTRACT FROM AUTHOR]

Copyright of e & i Elektrotechnik und Informationstechnik is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a generalized multipath separability condition for subspace processing and derives a novel COD (Combined Oversampling and Displacement) algorithm to utilize both spatial and temporal diversities for path separation, DOA (Direction of Arrival) estimation and signal recovery. A unique advantage lies in its ability to cope with the situation where the number of multipaths is larger than that of antenna elements, which has not been treated in the traditional approaches. COD strategy solves the antenna deficiency problem by combining vertical expansion with temporal oversampling and horizontal expansion with spatial displacement. We provide a detailed analysis on the theoretical footings for COD factorization and multipath separability conditions, which naturally leads to COD path separation and DOA estimation algorithms. Another advantage of COD factorization hinges upon its ability to generate a multiplicity of eigenvalues which greatly facilitates a SIMO channel equalization formulation useful for signal recovery. This paper also proposes a frequency-domain total-least-square algorithm for SIMO equalization procedure. Finally, simulation results on path separation, DOA estimation and signal recovery are demonstrated. [ABSTRACT FROM AUTHOR]

Quadratic programming models for integrated space-time interference suppression in CDMA systems are proposed in this paper. The models integrate the advantages of smart antenna and RAKE receiver, mitigate multiuser access interference (MAI) and interchip interference (ICI), and combine multipath components. The zero-forcing conditions are derived. Neural network implementation of the models is also studied. [ABSTRACT FROM AUTHOR]

The paper describes an optimal dynamic channel assignment algorithm for smart antennas. This algorithm can deal with the Spatial Division Multiple Access (SDMA) and traditional channel multiple accesses (FDMA, TDMA, or CDMA) simultaneously to enlarge the capacity of communication systems. This algorithm has several merits, including less computer time, the largest capacity, and avoidance of co-channel interference. The paper also describes the idea of a spatial channel pattern, in which several users can share a channel. Several simulation results are presented in the paper. [ABSTRACT FROM AUTHOR]

The incorporation of directional sensitivity, provided by so-called adaptive antennas is useful in suppressing interfering signals that arise from spatially distinct mobile sources. The problem is that in a cellular radio environment where multipath exists, the standard adaptive antenna using reference signals may not properly lock on the desired signal. This is because the signal correlation matrix processed by the antenna may then be close to singular and standard algorithms fail. Also, most standard algorithms need to cooperate with the receiver for the spatial discrimination of signals. A smart antenna utilizing a blind algorithm is of interest since the antenna may not need to get any feedback from a receiver for the adjustment of weight coefficient for spatial processing and can stand alone to be plugged into any kind of receiver structure. In this paper, we address the convergence property of a Constant Modulus Algorithm which is a blind algorithm and, if employed, can provide no need for an antenna to cooperate with a receiver attached. By identifying a relationship between the weight coefficients and output signal amplitude, we also evaluate the performance of such a stand-alone antenna plus a CDMA matched filter reception. Our results show that for a three element CM array, the BER of a desired user with the other interfering users is much better than a conventional correlation receiver for a single user case since the array suppresses interferences and achieves array gain in SNR. [ABSTRACT FROM AUTHOR]