Localization of wireless ad hoc and sensor networks has gained research attentions for several years. This paper proposes a hybrid localization scheme which exploits Received Signal Strength (RSS)-based ranging and Self Organizing Maps (SOM)-based range free localization methods to obtain the tradeoff between cost, power and location accuracy. By utilizing RSS-based distance estimation and connectivity information of 2-hop neighbors in learning steps of SOM-based localization, the proposed scheme achieves more accurate location estimates while reducing the number of learning steps. For the RSS-based distance estimation, a thorough empirical analysis of the radio propagation model has been presented. Solution for the impact of obstacles and irregular network shapes has also been incorporated in the proposed hybrid scheme. Results from extensive simulations prove that our proposed hybrid scheme outperforms several existing localization schemes in both isotropic and anisotropic network environments.

Localization of wireless ad hoc and sensor networks has gained much research attention for several years. This paper proposes a hybrid localization scheme which exploits Received Signal Strength (RSS)-based ranging and Self Organizing Maps (SOM)-based range free localization methods to obtain the tradeoff between cost, power and location accuracy. Distance information from RSS measurement has been utilized in the learning steps of SOM-based localization algorithm to get more accurate location estimates while reducing the number of learning steps. Methods on RSS uncertainty reduction and obstacle filtering are also incorporated in the proposed RSS-SOM scheme. Results from extensive simulations prove that our proposed hybrid solution outperforms several existing localization algorithms in both isotropic and anisotropic network environments with lower anchor utilization.

One problem with multicarrier CDMA systems is that they often produce large values of peak to average power ratio (PAPR). Here, the correlation properties of the user spreading codes are closely related to PAPR and hence suitable allocation of spreading codes can result in reduced PAPR. In this context, we analyze the PAPR characteristics of a very recently proposed orthogonal set of codes called "Orthogonal binary user codes" and compare them with the well known Walsh-Hadamard codes. In particular, we construct and present a user spreading code allocation table through suitable selection of code subsets from the orthogonal binary user codes that perform better than corresponding Walsh-Hadamard codes.

Several positioning systems to obtain precise location information have been researched. However, they have scalability and flexibility problems because they need completely configured space with a large number of sensors. To avoid the problems, we have proposed a self-organizing location estimation method that uses ad hoc networks and Self- Organizing Maps and needs no prepared space with a large number of sensors. In this paper and our demonstration, the proposed method and its characteristic are presented.

An adaptive multiple beam system, which has flexibility to adapt beam power to varying beam traffic, is proposed. The multiple beam transmitter, which is called "hybrid transponder" in this paper, consists of a pair of multiport hybrids and a set of amplifying elements. Power combining, isolation, and intermodulation characteristics of this multiport network are analyzed. Also, a new interbeam exchange and feeder link connection concept, which serves as the basis for an adaptive multiple beam system, is proposed. Finally, characteristics of an experimental 8-amplifier 8-port hybrid transponder are described.

The effects on CNR improvements are described for aK-band PCM-TDMA regenerative satellite relay system, using a multihorn antenna, whose horn powers are combined/divided with variable power combiners (VPCs)/dividers (VPDs). In conclusion, when the VPCs combination/VPDs division ratios are controlled according to the criterion maximizing the sum of uplink/downlink rain margins, both efficient on-board RF power utilization and regenerative effect enhancement can be accomplished remarkably.