Search

In this paper, we present an efficient architecture of the adaptive beamforming satellite system based on the planar (square) array antenna. It is consisted of an Angle-of-Arrival (AOA) estimator for estimating AOAs of signals, an adaptive beamformer for suppressing interference signals and enhancing the desired signals, a signal processing & D/B unit for saving and processing data obtained from the received signal, and a transmission beamformer for transmitting signal information. Also, we provide computer simulation results to evaluate the performance of the presented system with different sizes of the square antenna array.

Radio frequency identification (RFID) is an important and essential components of ubiquitous computing, with the development of wireless communication technologies and mobile computing environment. Recently, RFID becomes the mainstream application that helps fast handling and uniquely identifying the physical objects. It utilizes the electromagnetic energy for data transmission from a tag to a reader in the presence of arbitrary interference and noise. In order to employ the portable mobile RFID reader, a tag-collision problem between two or more adjacent tags should be considered. In this paper, we present the operation of RFID system in which numerous tags are present in the interrogation zone of a single reader at the same time. Since there may exist a number of tagged objects in the narrow area, multiple RFID tags may interfere each other, caused to degrade the data reliability and efficiency of the RFID system. In order to suppress interference signals from multiple neighboring tags, we present an application of Gold code for RFID communication system, which uses spread spectrum technique. In this RFID system, data bits are spreaded in each tags with the unique Gold code and the spreaded data bits are despreaded in the reader with the same Gold code. The performance analysis of the considered RFID anti-collision system is illustrated via computer simulation examples.

Tire Pressure Monitoring System (TPMS) is an auxiliary safety system for recognizing the condition of tires based on the pressure and temperature data transmitted from the sensor unit installed on a tire of the vehicle. Using TPMS, a driver can frequently check the state of tires and it aids to maintain the optimum running condition of the vehicle. Since TPMS must utilize the wireless communication technique to transmit data from a sensor unit to a signal processing unit installed in the vehicle, it suffers from interference signals caused by various external electrical or electronic devices. In order to suppress high-power interference signals, we employ beamforming techniques based on the uniform linear antenna array. As the number of the antennas is increased, the performance of the interference suppression is improved. However, there is the limit of the number of antennas, installed in the center of a vehicle, because of its size. In this paper, we compare and analyze the performance of the beamformer, when reducing the interelement spacing of antennas, to increase the number of the receiving antennas. For the performance analysis of the beamformers, we consider the switching beamformer and minimum-variance distortionless-response (MVDR) beamformer for TPMS, recently proposed.

A TPMS(Tire Pressure Monitoring System) is a wireless communication system designed to monitor the pressure and temperature of pneumatic tires of a vehicle. In order to provide the aid in protecting a driver, this system reports tire pressure information to the driver of the vehicle. Since the wireless communication technique should be employed to transmit the TPMS data from each tire to signal processing unit in the vehicle, it suffers from interference signals from external electrical or electronics equipments. In this paper, we propose the TPMS interference cancellation technique based on GSC(Generalized Sidelobe Canceler), which does not have only the excellent performance like MVDR(Minimum-Variance-Distortionless-Response) but also has the low computational complexity comparing with MVDR. The performance of interference suppression is conformed by computer simulation examples.

A TPMS is a wireless communication system designed to monitor its condition inside the pneumatic tires on various types of vehicles. These systems report the tire pressure information to the driver of the vehicle. While wireless communications is used to transmit the measurement data from TPMS sensors to a central processing unit in the vehicle, it suffers from the various interferences such as sensors of each tire or outside electrical equipments. Based on the conventional beamformer, a switching beamforming technique is proposed to minimize the interference and efficiently receive valid data. Moreover, in order to minimize the interference and reduce power consumption for communication, a system with unique Gold Code is presented for each tire. The performance of interference suppression is illustrated by computer simulations.

A nonblocking photonic switch can be used to implement a tapped delay line with a large number of adaptive weights and a wide range of time delays. An advantage of using optical tapped delay lines for adaptive filtering is that the operating frequency can be quite high, in the 10-100 GHz range. We present a sparse reconfigurable adaptive filter (SRAF) based on a photonic switch with an input/output connection architecture that can be represented by a matrix of adaptive weights. This unique parallel structure can be reconfigured in an adaptive manner to implement a sparse filter impulse response for use in many applications. We consider an adaptive algorithm for this filter that chooses the input and output delays using a cross-correlation-based approach and connects these delays by weights that are adapted using a gradient algorithm. An alternative adaptive algorithm is also considered that is based on a system identification formulation where the weights are first adapted, and then the appropriate delay combinations are chosen. A search algorithm for implementing the connection constraint required by the SRAF is also discussed whereby each input is connected to only one output at any moment. Computer simulation examples are presented to illustrate the behavior of the filter for a system identification model.

The global positioning system (GPS) was designed to provide location estimates for various civilian and military applications using at least four satellites. Since GPS signals have a low signal-to-noise ratio (SNR), they also have a low signal-to-jammer ratio so that the accuracy of location estimates is influenced by cochannel interference and intentional jammers. We propose a low-complexity blind adaptive receiver that is based on a novel modified despreader and the constant modulus (CM) array. This system is capable of nulling directional interference and capturing the GPS signal of interest without requiring explicit angle-of-arrival (AOA) information. We also consider the multiple satellite problem and extend the proposed receiver to capture several GPS signals of interest. Representative computer simulation examples are presented to illustrate the performance of the multicomponent system for the suppression of different jammer types.

The global positioning system (GPS) is a one-way satellite-based navigation system employing spread-spectrum techniques that is widely used for commercial and military applications. Although the very low signal-to-noise ratio (SNR) is handled by the large spreading gain, GPS is susceptible to high-power interference signals and various types of jammers. We propose multicomponent receiver architectures for GPS interference suppression. A conventional antenna system is first considered which utilizes a minimum-variance distortionless-response (MVDR) beam former and assumes that the GPS signal angle of arrival (AOA) and the antenna model are known at the receiver. However, this receiver is sensitive to AOA estimation errors and can have a high computational complexity. This sensitivity problem is eliminated by a multicomponent system based on a multistage matched filter (MF). Since this MF receiver also has a high computational complexity because the jammer AOAs must be estimated, we introduce a blind interference canceler based on the constant modulus (CM) array that is insensitive to AOA estimation errors and has a low computational complexity. Computer simulations are provided to illustrate the performance of the various systems for interference suppression in example signal scenarios.

The Tire Pressure Monitoring System (TPMS) displays the state of a tire on a display to inform a driver of the relevant information, by means of a sensor installed on the tire of the vehicle. When the data measured from the tire are wirelessly transmitted to a receiving antenna located in the center of the vehicle, the exact transmission of data is affected by the interference from various external electronic and electrical devices. In this paper, we suggest a minimum variance distortionless response (MVDR) beamformer based on the angle-of-arrival (AOA) vector for suppressing external interference and receiving accurate data. Although the MVDR beamformer effectively suppresses the interference, it has high computational complexity because of the calculation of an autocorrelation matrix. In order to address this issue, we also suggest a generalized sidelobe canceler (GSC) beamformer which does not have the same performance of the interference suppression to MVDR but also has low computational complexity. Since the signal from each tire can cause interference to others, we consider utilizing a unique Gold Code to each tire to minimize intertire interference and reduce power consumption of a battery installed in each tire.

The interference suppression technique is one of core techniques for the wireless sensor communications. In this paper, we focus on the Tire Pressure Monitoring System (TPMS) interference suppression among the wireless sensor communication techniques. The TPMS is an auxiliary safety device for measuring pressure and temperature, wirelessly transmitting the data to the central processing unit (CPU) of a vehicle and displaying the state of a tire on a display to inform a driver of the relevant information, by means of a sensor installed on the tire of the vehicle. When the data measured from the tire are wirelessly transmitted to a receiving antenna located in the center of the vehicle, exact transmission of data is affected by the interference from various external electronic and electrical devices. In this paper we suggest a minimum-variance distortionless-response (MVDR) beamformer based on the angle-of-arrival (AOA) vector for suppressing external interference and receiving accurate data. Although the MVDR beamformer effectively suppresses the interference, it has high computational complexity because of calculation of an auto-correlation matrix. In order to address this issue, we also suggest a generalized sidelobe canceler (GSC) beamformer which does not have the similar performance of the interference suppression to MVDR, but also has low computational complexity. Since the signal from each tire can cause interference to others, we consider utilizing a unique Gold Code to each tire to minimize inter-tire interference and reduce power consumption of a battery installed in each tire. The performance of the proposed interference suppression technique is verified through computer simulation.

A sparse reconfigurable adaptive filter (SRAF) for a photonic switch consists of a large number of input and output delays, sparse reconfigurable connections, and adaptive weights. Recently, it was shown that a modified system-based (MSB) algorithm for the SRAF is more efficient than conventional algorithms such as previously introduced cross-correlation-based (CCB) and system-based (SB) approaches. In this paper, we propose a connection constraint for the MSB algorithm that chooses the most effective elements among the entire connection matrix. The proposed method allows any input to be connected to any output with an arbitrary weight, and is more efficient than the approaches mentioned above due to its reduced computational complexity. We provide a computer simulation example to demonstrate the performance of the connection-constraint algorithm for a system identification application.

The Tire Pressure Monitoring System (TPMS) is a wireless communication system designed to monitor the condition of a vehicle tire, based on the transmitted data from the tire sensor. This system reports the tire pressure or temperature information of tires to a driver. While wireless communications is used to transmit the measurement data from TPMS sensors to a central processing unit in the vehicle, it suffers from various interferences such as signal of each tire sensors or outside electrical equipments. In this paper, we propose a switching beamformer based on the conventional beamformer to suppress the outside interference signals and to efficiently receive effective data. In order to suppress interferences due to sensors of each tire and to save the power consumption for the communication, we assign the unique gold code to each tire. Moreover, we propose the data architecture of the duplex wireless communication for the TPMS to maximize the power efficiency of the battery. The performance of the proposed system is illustrated by computer simulations.

Adaptive algorithms can be an important component of a sparse reconfigurable adaptive filter (SRAF) for photonic switches. In this paper, we propose a modified system-based (MSB) algorithm that not only has good performance for white and non-white input signals, but also has a reduced computational complexity compared with conventional approaches such as the previous cross-correlation-based (CCB) and system-based (SB) algorithms. In order to improve the convergence rate of the system, the MSB algorithm separately updates each row or column of the switch weight matrix. We also consider a specific structure for the intermediate desired signals, and present a computer simulation example to demonstrate the performance of the proposed SRAF algorithm for a system identification application.

The Global Positioning System (GPS) is one of the core technologies for the Location Based Service (LBS), and has various applications from the leisure business to the military. LBS requires accurate location information of an object, which GPS estimates using at least four satellites. In order to enhance the GPS signal quality, angle-of-arrival (AOA) information is required, but these are difficult to estimate because the system operates with a low signal-to-noise ratio (SNR) and in the presence of high-power interference. In this paper, we explore an extension of a recently proposed GPS AOA estimation technique based on a modified despreader for multiple GPS signals. Since the extended estimator does not require a singular value decomposition (SVD), unlike conventional AOA estimation algorithms such as Multiple Signal Classification (MUSIC), it has a relatively low computational complexity. Also, this technique does not need to choose the GPS AOAs from all estimated AOAs because those of the interference signals are not estimated. We demonstrate the performance of the GPS AOA estimation algorithm for multiple satellites via a computer simulation example.

The Global Positioning System (GPS) is designed to estimate the locations of users or objects, and has a variety of civilian and military applications. Although angles-of-arrival (AOAs) may be required to enhance the desired GPS signals, it is difficult to estimate explicit AOA information because a GPS signal has a low power relative to the noise level. In this paper, we propose a GPS AOA estimation method based on a modified despreader and the constant modulus (CM) array cost function. This technique has a low computational complexity compared with other AOA estimation methods, such as the Multiple Signal Classification (MUSIC) algorithm, because it does not require a singular value decomposition (SVD). It also has good estimation performance in low signal-to-noise ratio (SNR) environments.

The multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) is one of core technologies for the third generation (3G) and fourth generation (4G) communication systems. The efficient channel estimation scheme with relatively low estimation error is required for the MIMO-OFDM communication system. In this paper, we propose a channel estimation scheme based on the adaptive algorithm such as the least-mean-square (LMS) and a preamble signal architecture considering the guard subcarrier, which is suitable to MIMO-OFDM. The proposed algorithm which estimates channels in the time-domain has not only the low channel estimation error but the low peak-to-average power (PAPR) comparing to conventional techniques such as the least-square (LS). Computer simulation results are provided to illustrate the performance of the proposed algorithm for the channel estimation.

The Global Positioning System (GPS) requires at least four satellites to achieve the best accuracy for location estimation. Since a conventional despreader can recover only one GPS signal, multiple despreaders are usually required for separating multiple GPS signals. In this paper, we explore an extension of a recently proposed GPS receiver that consists of a conventional despreader and a so-called null despreader, along with the multistage constant modulus (CM) array, to detect multiple GPS signals. This system does not require explicit direction-of-arrival (DOA) information about the GPS signals in order to reject directional interference. We present a computer simulation example to illustrate the jammer suppression performance of the proposed system for multiple GPS signals

The Global Positioning System (GPS) utilizes low- power spread-spectrum signals and thus is vulnerable to various types of high-power interference sources. In this paper, we propose a blind adaptive GPS receiver that is based on a new despreader and the one-stage constant modulus (CM) array. The despreader consists of a conventional GPS despreader and a so- called null despreader which together modify the received signal so that the CM array can extract the GPS signal of interest. The beamformer rejects jammers without explicit direction-of- arrival (DOA) information of any of the signals. A computer simulation example is presented to illustrate the performance of the proposed receiver for different types of jammer signals.

The Global Positioning System (GPS) utilizes low-power spread-spectrum signals which are vulnerable to many kinds of high-power interference signals and jammers. We propose a low-complexity blind adaptive receiver that is based on a novel modified despreader and the one-stage constant modulus (CM) array. This system is capable of nulling directional interference and capturing the GPS signal of interest without requiring explicit angle-of-arrival (AOA) information. Computer simulations are provided to illustrate the performance of the multicomponent receiver for a combination of different types of jamming signals.

A nonblocking photonic switch can be used to implement a tapped delay line with a large number of coefficients and a wide range of time delays. In this paper, we present a sparse reconfigurable adaptive filter (SRAF) based on a photonic switch with an input/output connection architecture that can be represented by a matrix of adaptive weights. This unique parallel structure can be reconfigured in an adaptive manner to implement a sparse filter impulse response for a variety of applications. The appropriate choice of time delays is determined from a cross-correlation function between the filter input and a desired response signal that depends on the particular application. A computer simulation example illustrates the performance of the algorithm for modeling a bandpass filter characteristic.

The Global Positioning System (GPS) was designed to provide location estimates for various civilian and military applications using at least four satellites. Since GPS signals have a low signal-to-noise ratio, they also have a low signal-to-jammer ratio, and thus the accuracy of these estimates is influenced by cochannel interference and intentional jammers. In this paper, we explore an extension of a recently proposed blind multicomponent jammer rejection system, which is based on a modified despreader, to extract multiple GPS signals. This extended system also operates blindly to null directional interference and capture all GPS signals of interest without requiring explicit knowledge of their angles-of-arrival. A representative computer simulation example is presented Io illustrate the performance of the multicomponent system for the suppression of different jammer types.

The Global Positioning System (GPS) is a satellite-based navigation network employing spread-spectrum techniques that is widely used for commercial and military applications. Although the large spreading gain of GPS allows for operation in very low signal-to-noise ratio environments, the received signals are vulnerable to various types of narrowband and wideband interference. In this paper, we propose a blind multi-component adaptive receiver based on the constant modulus (CM) array that cancels the high-power interference and recovers the GPS signal of interest without using a priori direction-of-arrival information or training data. The performance of the system at the output of each component is illustrated via computer simulations for an example signal scenario. Expressions for the output signal-to-interference-plus-noise ratio are also provided in order to investigate the steady-state properties of the system.

The Global Positioning System (GPS) is a one-way satellite communication system that is widely used for both civilian and military applications. Because of the relatively low power of the received signals, GPS is highly susceptible to a variety of intentional and unintentional interferers. In this paper we examine a multistage space-time adaptive-processor (STAP) that is used to improve the detection capability of a GPS receiver for a wide range of jamming scenarios. Depending on the type of interference, the stages incorporate structures such as a notch filter, a beamformer and a blind linear interference canceler. Computer simulations are provided to illustrate the performance of the multistage receiver for wideband and narrowband interferers.