Recently, indoor positioning systems (IPSs) have been designed to provide location information of persons and devices. The position information enables location-based protocols for user applications. Personal networks (PNs) are designed to meet the users' needs and interconnect users' devices equipped with different communications technologies in various places to form one network. Location-aware services need to be developed in PNs to offer flexible and adaptive personal services and improve the quality of lives. This paper gives a comprehensive survey of numerous IPSs, which include both commercial products and research-oriented solutions. Evaluation criteria are proposed for assessing these systems, namely security and privacy, cost, performance, robustness, complexity, user preferences, commercial availability, and limitations. We compare the existing IPSs and outline the trade-offs among these systems from the viewpoint of a user in a PN.

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Dynamic Spectrum Access (DSA) radio devices look for temporarily unoccupied frequency bands and attempt to communicate in them. It is envisioned that DSA can substantially increase the capacity of wireless networks by broadening the utilization of radio resources. Given the ubiquitous use of Internet's Transport Control Protocol (TCP), it can be expected that TCP will be used in DSA networks in the future. Whether TCP can efficiently provide stable end-to-end transmissions over DSA links, given their dynamic and unpredictable nature, remained unclear. Therefore, we have studied by simulation the ability of various TCP flavors to efficiently utilize DSA links. We have performed simulations using the TCP stack from the Linux operating system. Our simulations show that modern TCPs can efficiently make use of the dynamic capacity of DSA links for bulk data transmission, under a wide range of conditions, but only if certain requirements are met. We also analytically determine the effect of Primary User (PU) detection errors on TCP performance and conclude that the dominating component responsible for TCP throughput reduction in a DSA environment is the observation time, not, as one might expect, PU detection errors.

The objectives of spectrum sensing are twofold: to start with, CR users ought not cause unsafe interference to PUs by either switching to an available band or limiting its interference with PUs at an acceptable level and, second, CR users ought to efficiently identify and exploit the spectrum holes for required throughput and quality-of service (QoS). probability of false alert, which denotes the probability of a CR user declaring that a PU is present when the spectrum is in reality free, and probability of detection, which denotes the probability of a CR user declaring that a PU is present when the spectrum is indeed occupied by the PU. In this paper review the different methods of spectrum sensing.

Quality of service (QoS) support in Mobile Ad-hoc NETworks (MANETs) is a challenging task. Most of the proposals in the literature only address certain aspects of the QoS support, e.g., QoS routing, QoS medium access control (MAC) and resource reservation. However, none of them proposes a QoS model for MANETs. Meanwhile, two QoS models have been proposed for the Internet, viz., the Integrated Services (IntServ) model and the Differentiated Services (DiffServ) model, but these models are aimed for wired networks.In this paper, we propose a flexible QoS model for MANETs (FQMM) which considers the characteristics of MANETs and combines the high quality QoS of IntServ and service differentiation of Diff-Serv. Salient features of FQMM include: dynamics roles of nodes, hybrid provisioning and adaptive conditioning. Preliminary simulation results show that FQMM achieves better performance in terms of throughput and service differentiation than the besteffort model. 0-7803-571 8-3/00/$10.00 02000 IEEE.