C. Gomez-Calero

A 2

The increasing interest in MIMO (Multiple-Input Multiple-Output) systems has given rise to a prolific research activity in recent years. Both theoretical and practical issues have been studied. However, so far few MIMO testbeds or prototypes have been built for DVB-T or future standards. In this paper, a novel 2 × 2 MIMO testbed specifically designed for evaluating the performances of a DVB-T2 MIMO system is presented. The description of signal processing is detailed including a new scheme to estimate the MIMO channel matrix. Finally, measurement results with different polarization schemes are presented for typical scenarios, obtaining higher capacity in LoS situations using polarization diversity.

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In this paper, the influence of the features of the propagation channel in the performance of energy-efficient routing algorithms for wireless sensor networks is studied. Although there are a lot of works regarding energy-efficient routing protocols, almost no reference to realistic propagation channel models and influence is made in the literature. Considering that the propagation channel may affect the efficiency of the different energy-efficient routing algorithms, different propagation scenarios are proposed in this work, from the most simplistic free-space propagation model to more complex ones. The latter includes the effects of multipath propagation, shadowing, fading, etc. In addition, spatial diversity transmission/reception models are considered to mitigate the effects of hard propagation fading. Some results are provided comparing the performance of several energy-efficient routing algorithms in different scenarios.

2 MIMO DVB-T2 System: Design, New Channel Estimation Scheme and Measurements With Polarization Diversity

A new testbed specifically designed for evaluation and measurement of MIMO systems is presented. A flexible and reconfigurable system was implemented, where some system parameters such as sampling frequency and power gain are selectable via software. Also multiple antenna configurations are considered. A user interface was developed in order to simplify testing of algorithm. Thus, the user does not need to design the MIMO scheme or algorithm considering real-time constrains or requirements of the specific platform. On the other hand, real implementation effects and realistic scenarios are included in the system, which allows a more complete study of algorithms. An example with a conventional MIMO algorithm was performed in order to validate the implemented testbed.

Erratum to: On the Influence of the Propagation Channel in the Performance of Energy-Efficient Geographic Routing Algorithms for Wireless Sensor Networks (WSN)

An OFDM-MIMO testbed based on a SDR platform with very flexible antenna positioning system has been designed and presented for WLAN applications. Antenna positioning allows the proper spatial characterization of radio channel links in real scenarios where future wireless networks will be deployed. Some measurements in real indoor scenarios proving reconfigurable antennas are been carried out leading to some interesting results that will be presented in the conference.

New test-bed for evaluation of antenna and system performance for MIMO systems

The increasing interest in MIMO (Multiple-Input Multiple-Output) systems has given rise to a prolific research activity in this topic in recent years. Several aspects have been studied, including both theoretical and practical issues. However, so far few MIMO testbeds or prototypes have been done for DVB-T or future standards. In this paper, a novel 2 × 2 MIMO testbed has been realized which has been specifically designed for evaluating the performances of a DVB-T2 MIMO system.

A wideband OFDM MIMO measurement system for antenna evaluation

Dual-polarized antennas have been proposed as an interesting option to implement MIMO systems in realistic user terminals. In order to study the MIMO channel characteristics when multiple polarizations are considered, a measurement campaign was carried out by using a custom MIMO testbed. Both single and dual-polarized antennas were used, and several scenarios were measured, including indoor and outdoor transmitter location. The capacity analysis showed that the dual-polarized antennas offer a higher diversity for both indoor and outdoor to indoor scenarios when the receiver is moved along corridor routes. However, when the antenna gain is also considered, the achieved capacity for indoor office-like scenarios was slightly lower for the dual-polarized antennas, due to the lower antenna gain of the used elements.

A 2×2 novel MIMO testbed for DVB-T2 systems

The introduction of new generations of mobile communication systems, such as the current 3G and the future 4G, along with the provision of multimedia services, has exponentially increased the number of users demanding higher data rate. This fact has aroused the interest in studying possible solutions to improve system performance without making use of new frequency band allocations in the already crowded frequency spectrum. As an interesting option, wireless communication systems with Multiple-Inputs and Multiple-Outputs (MIMO) in which many antennas are used for transmission and reception have received increasing attention from the research community over the past few years (Paulraj et al., 2004, Goldsmith et al., 2003).

Comparison of mimo single and multi-polarized measured channels in indoor WLAN scenarios

Communication systems employing any kind of diversity scheme can provide valuable advantages for improving power reception and increasing multiplexing and diversity gain. In this paper, single and dual-polarized arrays are used for DoA (direction-of-arrival) estimation using multiple antennas at the receiver side. Polarization diversity at the received side increases the sensitivity for receiving power coming from different directions. This diversity scheme partially resolves the effect caused by the depolarization losses that suffer signals due to the interaction with the existing scatters in the environment. DoA estimations using polarization information are presented and compared to analyze the effect of depolarization losses in indoor environments. An extended version of the common well-known MUSIC algorithm to manage two polarization components was used. (5 pages)