This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright © 2012 John Wiley & Sons, Ltd.

An open ITS platform combining interactive satellite services with other communication channels is being developed and evaluated in field trials within the SafeTRIP project [1]. Prototyping and in-field validation of a novel waveform for messaging return channel over satellite for land mobile is an important objective of the project. The overall system architecture has recently been standardized by ETSI under the name of S-MIM (S-band Mobile Interactive Multimedia). The messaging protocol, described in the Part 3 of the standard, is based on the Enhanced Spread Spectrum Aloha (E-SSA). Its main asset resides in the low power required at the transmitter, which will allow the reuse of off-the-shelf power amplifiers and low-cost omnidirectional antennas. This paper will present a comprehensive summary of previous E-SSA performance analysis from simulations and the first field trials results using the E-SSA waveform. The presented results have been derived from static and mobile field trials carried out in Germany with fully functional E-SSA modulator and demodulator prototypes and the EUTELSAT10A satellite. Results for the static and mobile performance of the E-SSA demonstrator with an omni-directional antenna under Line-of-sight (LOS) conditions are presented. The measured Packet Error Rates of transmissions via satellite at different terminal power levels confirm the theoretical link budget calculations for single and multiple simultaneously transmitting terminals. The degradation due to fading effects of the transmission channel under mobile conditions has been measured during the trials to approx. 3 dB. The resulting overall required transmitter power in the multi-user scenario of the trials setup has been only -3 dBW to reach a high QoS under mobile conditions. This value confirms the suitability of the E-SSA waveform for interactive mobile services for the mass market

This paper describes the simulated system performances of the enhanced spread spectrum ALOHA (E-SSA) random access scheme in a realistic mobile satellite multibeam scenario operating in S-band. The E-SSA random access scheme has been selected for supporting messaging services in the ETSI S-band Mobile Interactive Multimedia (S-MIM) standard. Finally, the operation and the performance of E-SSA is elaborated in the context of a terrestrial gap-filler component complementing the satellite coverage in densely populated areas. It is shown that the terrestrial network is able to off-load traffic from the satellite component while ensuring continuity of service in areas that cannot be covered by a satellite only system. ‡ Although orthogonal frequency division multiplexing (OFDM) technology might be even more efficient in such frequency selective environments; it appears less suitable for use in random access schemes. MHz is available in S-band for mobile satellite communications. In Europe, two licenses were given to Inmarsat and Solaris for operating in such bandwidth, each one having an allocation of a 15-MHz band. ¶ We ignore here the effect on capacity deriving from the limitation of an on-board feeder link (satellite-to-gateway) radio frequency power. This is justified for a bent-pipe star satellite architecture where a sufficiently large gateway antenna makes the feeder downlink carrier to noise ratio much higher than the user-to-satellite uplink. E-SSA SYSTEM LEVEL PERFORMANCE † † † The residual (noncanceled) power is dominated by the power in the other signals paths (which were not correctly detected and thus canceled). For example, in Rec. ITU-R M.1225 Vehicular Channel A model, the four weakest paths (out of a total of six paths) contribute to 27% of the overall received signal power. So assuming we were only able to correctly detect the two strongest paths, we would have a 27% residual (not canceled) power. 498 G. GALLINARO ET AL.

Wireless sensor networks (WSN) are large scale networks of unattended devices, aimed at monitoring environmental parameters. Their extremely scarce hardware resources constitute a huge limitation to the use of standard security protocols to secure communications, so that custom ones must be designed. In this article we describe the development of a novel access control system for WSN based on a distributed threshold scheme. Our model gives support for mobility and limits the needed communication and consequent energy drain, which is a fundamental parameter for the lifetime of WSN.

An intelligent transport system open platform integrating the S-band Mobile Interactive Multimedia messaging return channel protocol over satellite (based on Enhanced Spread Spectrum Aloha) has been developed and tested under real environment conditions within the framework of SafeTRIP, an FP7 EU-funded project. This paper presents the first field trials results using the S-band Mobile Interactive Multimedia technology. The introduced forward and return link outcomes have been derived from mobile field trials carried out in the surroundings of the German Aerospace Center (DLR) in Germany. Finally the validation of the system performances has been realized thanks to the use of a traffic emulator that can simulate a large population of Enhanced Spread Spectrum Aloha terminals