Radio frequency identification (RFID) is a technology with numerous benefits in applications where objects have to be identified automatically. However, cost, fragile tags, collision and reading errors are some of issues to be concerned with in an RFID implementation. Mainly, this paper proposes a method for tag identification and a method for the selection of the binary codes to program on the tags in order to facilitate the identification process. For the identification method a heuristic based on Hamming distance is developed where the basic idea is to utilize the information obtained in consecutive read attempts to help identify a tag. For the selection method three models based on Hamming distance are also developed which strive to find the set with the greatest dissimilarity among the codes. Computer simulations are performed to verify the validity of the proposed methods.
A Position Location (PL) scheme for mobile users on the outskirts of coverage areas is presented. The proposed methodology makes it possible to obtain location information with only two land-fixed references. We introduce a¨general formulation and show that maximum-likelihood estimation can provide adequate PL information in this scenario. The Root Mean Square (RMS) error and error-distribution characterization are obtained for different propagation scenarios. In addition, simulation results and comparisons to another method are provided showing the accuracy and the robustness of the method proposed. We study accuracy limits of the proposed methodology for different propagation environments and show that even in the case of mismatch in the error variances, good PL estimation is feasible.
SUMMARYSmart antennas are a suitable technology to increase the capacity of cellular systems. However, under severe channel conditions, the capacity gain may be small. This work presents a general methodology for the analysis of the effect of the angular power dispersion on the capacity gain for a CDMA system when using smart antennas. System capacity is expressed in terms of a supportable mean number of subscribers per angular sector and it is shown that maximum and mean number of subscribers criteria can be considered equivalent. Formulations for a single cell as well as for multi-tier scenarios are presented. Omni-directional case and non-spread scenarios are shown to be particular cases of the methodology introduced. Capacity is determined for a smart antenna system, both for general antenna beam patterns and general spread characteristics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.