M. Garcia Sanchez

Benefits of using Golay sequences in channel swept time cross-correlation sounders

Wideband radio channel sounders used for channel characterization purposes, are traditionally based on correlation of pseudorandom maximal length sequences. However, as it is shown in this paper, larger dynamic range can be achieved and wideband parameter estimation can be improved if Golay sequences are used instead. Results of the improvement achieved by using Golay sequences are confirmed by experimental wideband radio channel measurements carried out using both kinds of sequences.

Detection of malicious base station attacks through the carrier analysis

In 2G and 3G mobile standards there are vulnerabilities caused by the use of false Base Station (BS). In 3G security architecture offers protection against BS attacks, however when the User Equipment (UE) is configured in automatic GSM/3G mode this UE can accept connections coming from GSM/GPRS BSs that are configured as an attacker finally establishing a connection with such malicious BTS located within the UEs coverage area. Even without the use of a frequency jammer, potential attack danger exists because the connection between an UE and the fake BTS can be achieved if the BS is transmitting with more power than the real base station, and the UE enters in the handover process imposed by the 2G standard.

Experimental assessment of propagation models over sea for UHF and X bands

In this contribution we discuss the performance of two propagation models to characterize the propagation over sea at UHF and X frequency bands: two-ray model and log-distance. Experimental data were obtained for a calm sea scenario with two receiver antenna heights.

Development of 3D human tissues phantoms for analysis of frequency dispersion and human body interaction at 60GHz

Dispersive propagation could result of particular importance in the case of technologies involving human tissues. High-resolution systems as employed in medical imaging require the use of ultra wide band waveforms and for such pulses the medium is inherently dispersive. This will unavoidably lead the Brillouin or Sommerfield precursors to emerge even if they are not explicitly visible. However its analysis is not considered in body-centric radio channel characterization and models. For intra-body communications, the form and shape of the information-bearing transmitted signal is also an important factor to consider (Alejos, et al., JEMWA, 27(17), 2213–2220, 2013). Since the transmitted signal influences the formation and performance of the resulting precursor, we can conclude that a medium-matched signal can lead to optimal performance by combining the benefits of the precursor formation (larger amplitude) with minor impairments (lesser time duration broadening).

Stacked CPW-fed antenna for satellite applications with gain enhancement

This paper presents the design and implementation of a stacked CPW-fed antenna for satellite applications at Ku-, K-and Ka-bands for user terminals. The stacked structure combines two antennas. The base element consists of a CPW-fed patch antenna with modified CPW elements printed on Rogers TMM4 substrate. Above this base, a rectangular parasite patch was placed as a second layer using Arlon substrate with a high dielectric constant of 10.2. The two layers, base and parasitic patch, were separated by an air gap. This configuration reduces the antenna beam width and allows two-folding the antenna gain enhancement. The numerical simulations have been validated with experimental results.