pseudolite indoor geolocation system. A C-CDMA pseudolite indoor geolocation system consists of four C-CDMA pseudolites and one or more C-CDMA receivers. The purpose of this paper is to provide the requirements for building C-CDMA pseudolites and a C-CDMA receiver.First, the pseudolite is assumed stationary and the geolocation information consists of the transmitter position and time. For each pseudolite this information is 4-ary encoded data at a symbol rate of 1 KHz. For example, an encoded geolocation signal is spread using a Kasami sequence which runs at a rate of 1.023 MHz and then the signal is modulated on [10 15 20 25] MHz carrier signals each one of which corresponds to each of pseudolite respectively via a Quadrature Phase-Shift Keying (QPSK) modulator to resist interference encountered in an indoor geolocation environment. A total of four pseudolites are simulated to enable a geolocation solution for the receiver. The spreading modulation is that of a Variable Binary Offset Carrier (VBOC) VBOC(2,1,) which we have examined previously to provide a better spectrum utilization than the BOC(2,1) and definitely much better than the PSK.Second, the receiver consists of four channels each one of which is assigned to a single transmitter. On each receiving channel the received signal is down-converted, de-spread using the Kasami sequence, demodulated and decoded.Third, the channel consists of the following models: a realistic indoor path loss, realistic Rayleigh and Rician fading channels, receiver thermal noise, phase frequency offset, and additive white Gaussian noise. The system will include the ability to perform distance measurement; to take into consideration the effect of transmitter clock stability on position accuracy; such effects will include the transmitter and receiver oscillator drift (short term stability) on positioning accuracy; the signal processing on the receiver design will include techniques for detecting an extremely week Line-of-Sight (LOS) signal and for maintaining lock on the LOS signal in the presence of severe multipath. Journal of Geolocation, Geo-information, and Geo-intelligence 47It is expected that this paper will provide the required overview for first designing the system components utilizing as much as possible commercial of the shelf components and provide the framework for Giftet Software solution products one of which is a global software solutions for a C-CDMA pseudolite indoor geolocation system to operate under heavy multipath and low signal to noise ratio environment. Simulation results in MATLAB and Simulink are provided.
This paper describes the development and evaluation of an indoor localization algorithm using Visual Simultaneous Localization and Mapping (VSLAM) aided by gyroscope sensor information. Indoor environments pose several challenges which could cause a vision only system to fail due to tracking errors. Investigation revealed significant feature loss in a vision only system when traversing plain walls, windows and staircases. However, the addition of a gyroscope helps in handling such difficult conditions by providing additional rotational information. A portable system consisting of an Inertial Measurement Unit (IMU) and a stereo camera has been developed for indoor mapping. The images and gyroscope rates acquired by the system are stored and post-processed using a new Gyroscope Assisted Scalable Visual Simultaneous Localization and Mapping Algorithm (GA-ScaViSLAM). The algorithm has been evaluated for data-sets collected in the Atwater Kent building, Worcester Polytechnic Institute. This algorithm was found to be more robust in comparison to the vision only system. The Ga-ScaViSLAM was found to have an error (rms) of 0.6 m in the indoor environment over a total path length of 77m.
This paper describes a method for automated test generation and evaluation for realtime expert systems. This method supports dynamic testing, where test inputs are generated randomly within the constraints specified by a Test Specification Language. This allows the discovery of "unintended functionalities," which may not be possible either through static testing or expert-supplied test cases. Automated test generation also allows rapid regeneration of test suites as the system evolves through various prototypes and versions. The Test Specification Language provides constructs for dealing with real-time constraints. Sample specifications and results implemented within the Activation Framework software development tool are also described. 0 1994 John Wiley & Sons, Inc.
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