Youssef Nasser

Recent Advances in Indoor Localization: A Survey on Theoretical Approaches and Applications

The availability of location information has become a key factor in today’s communications systems allowing location based services. In outdoor scenarios, the mobile terminal position is obtained with high accuracy thanks to the global positioning system (GPS) or to the standalone cellular systems. However, the main problem of GPS and cellular systems resides in the indoor environment and in scenarios with deep shadowing effects where the satellite or cellular signals are broken. In this paper, we survey different technologies and methodologies for indoor and outdoor localization with an emphasis on indoor methodologies and concepts. Additionally, we discuss in this review different localization-based applications, where the location information is critical to estimate. Finally, a comprehensive discussion of the challenges in terms of accuracy, cost, complexity, security, scalability, etc. is given. The aim of this survey is to provide a comprehensive overview of existing efforts as well as auspicious and anticipated dimensions for future work in indoor localization techniques and applications.

System Level Evaluation of Innovative Coded MIMO-OFDM Systems for Broadcasting Digital TV

Single-frequency networks (SFNs) for broadcasting digital TV is a topic of theoretical and practical interest for future broadcasting systems. Although progress has been made in the characterization of its description, there are still considerable gaps in its deployment with MIMO technique. The contribution of this paper is multifold. First, we investigate the possibility of applying a space-time (ST) encoder between the antennas of two sites in SFN. Then, we introduce a 3D space-time-space block code for future terrestrial digital TV in SFN architecture. The proposed 3D code is based on a double-layer structure designed for intercell and intracell space time-coded transmissions. Eventually, we propose to adapt a technique called effective exponential signal-to-noise ratio (SNR) mapping (EESM) to predict the bit error rate (BER) at the output of the channel decoder in the MIMO systems. The EESM technique as well as the simulations results will be used to doubly check the efficiency of our 3D code. This efficiency is obtained for equal and unequal received powers whatever is the location of the receiver by adequately combining ST codes. The 3D code is then a very promising candidate for SFN architecture with MIMO transmission.

Blind spectrum sensing using symmetry property of cyclic autocorrelation function: from theory to practice

Spectrum sensing has been identified as the key step of the cognition cycle and the most important function for the establishment of cognitive radio. In this paper, a blind cyclostationary feature detector, which is based on the symmetry property of cyclic autocorrelation function (SP-CAF), is implemented and tested using universal software radio peripheral platform and GNU Radio open-source software development toolkit. Performance of the SP-CAF is compared to the classical energy detector via various tests conducted in real scenarios where both detection algorithms are employed to blindly sense the spectrum for opportunistic access. This study shows that the blind cyclostationary feature detector outperforms the classical energy detector while guaranteeing acceptable complexity and low sensing time. Moreover, different experimental results indicate that the blind sensing detector can achieve high detection probability at a low false alarm probability under real channel conditions and low signal-to-noise ratio.

Wireless Body Area Network (WBAN): A Survey on Reliability, Fault Tolerance, and Technologies Coexistence

Wireless Body Area Network (WBAN) has been a key element in e-health to monitor bodies. This technology enables new applications under the umbrella of different domains, including the medical field, the entertainment and ambient intelligence areas. This survey paper places substantial emphasis on the concept and key features of the WBAN technology. First, the WBAN concept is introduced and a review of key applications facilitated by this networking technology is provided. The study then explores a wide variety of communication standards and methods deployed in this technology. Due to the sensitivity and criticality of the data carried and handled by WBAN, fault tolerance is a critical issue and widely discussed in this paper. Hence, this survey investigates thoroughly the reliability and fault tolerance paradigms suggested for WBANs. Open research and challenging issues pertaining to fault tolerance, coexistence and interference management and power consumption are also discussed along with some suggested trends in these aspects.

Sensitivity of OFDM-CDMA Systems to Carrier Frequency Offset

This paper presents the impact of a carrier frequency offset on the performance of 2 dimensional spreading OFDM-CDMA systems. This is measured by the degradation of the Signal to Interference plus Noise Ratio (SINR) obtained after despreading and equalization. Using some properties of random matrix and free probability theories, a new expression of the SINR is derived. It is independent of the actual value of the spreading codes while still accounting for the orthogonality between codes. This model is validated by means of Monte-Carlo simulations. It is also exploited to compare the sensitivities of MC-CDMA and MC-DS-CDMA systems to carrier offset in a frequency selective channel. This work is carried out for zero forcing (ZF) and minimum mean square error (MMSE) equalizers.

Efficient MIMO-OFDM Schemes for Future Terrestrial Digital TV with Unequal Received Powers

This article investigates the effect of equal and unequal received powers on the performances of different MIMO-OFDM schemes for terrestrial digital TV. More precisely, we focus on three types of non-orthogonal schemes: the BLAST scheme, the linear dispersion (LD) code and the Golden code, and we compare their performances to that of Alamouti scheme. Using two receiving antennas, we show that for moderate attenuation on the second antenna and high spectral efficiency, Golden code outperforms other schemes. However, Alamouti scheme presents the best performance for low spectral efficiency and equal received powers or when one antenna is dramatically damaged. When three antennas are used, we show that Golden code offers the highest robustness to power unbalance at the receiving side.

Lattice Reduction-aided Minimum Mean Square Error K-Best detection for MIMO systems

The Multiple-Input Multiple-Output (MIMO) with a Spatial-Multiplexing scheme is a topic of high interest for the next generation of wireless communications systems. In this paper, we propose to approach the Maximum Likelihood (ML) performance through the combination of a neighbourhood study and a Lattice Reduction (LR)-aided solution. Moreover, by introducing a neighbourhood study in the reduced domain, we propose in this paper a novel equivalent metric that is based on the combination of the LR-aided Minimum-Mean Square Error solution. We show that the proposed metric presents a relevant complexity reduction while maintaining near-ML performance. In particular, the corresponding computational complexity is polynomial in the number of antennas while it is shown to be independent of the constellation size. For a 4×4 MIMO system with 16-QAM modulation on each layer, the proposed solution is simultaneously near-ML and ten times less complex than the classical neighbourhood-based K-Best solution.

A novel combined PAPR reduction and channel estimation approach for OFDM systems

In this paper, a novel combination of peak-to-average power ratio (PAPR) reduction and channel estimation techniques for orthogonal frequency division multiplexing (OFDM) systems is addressed. In order to reduce the spectrum efficiency loss due the insertion of dedicated pilots for PAPR reduction issues, we propose to use some pilots dedicated for channel estimation to reduce the PAPR value. These pilots follow particular laws which allow their blind detection at the receiving side and avoid sending side information. At the receiver, based on these properties, the pilots are detected and channel estimation is then performed. The proposed laws operate in discrete domain to mitigate the performance degradation due to residual estimation error in continuous domain. Simulation results performed using the new DVB-T2 standard parameters show that the proposed approach gives better performance and higher spectral efficiency when compared to conventional Tone Reservation (TR) method.

SINR based network selection strategy in integrated heterogeneous networks

Future integrated wireless and mobile network are emerging to offer a wide range of services anywhere at any time. In these networks, each mobile terminal equipped with heterogeneous interfaces will be able to perform the corresponding user services using any available network. To select a network, users can choose the most suitable one according to the predetermined preferences. Several factors may be considered to select a network such as bandwidth availability, power consumption, received signal strength and cost. The interference represents also an important factor in this environment. In this paper, we consider a new network selection strategy based on the estimated Signal to Interference-plus-Noise Ratio (SINR) value in an integrated heterogeneous wireless network. This strategy always allows users to select the network that has a higher SINR value from all the available networks during its communication. We analyze the system performance in terms of the blocking probabilities of calls on the whole service area. Our results are compared with other strategies found in the literature.

Global Ergodic Capacity Closed-Form Expression of Coexisting DVB-LTE-Like Systems

In this paper, we analyze the problem of deploying small cellular cells into a large broadcast cell in the framework of the convergence between the Long Term Evolution (LTE) and the Digital Broadcasting Video (DVB) technologies. In this work, a non- cooperative deployment of these technologies is considered in the sense that cellular and broadcast networks interfere on each other. In literature, there is no work dealing with the ergodic capacity of full cross-interfering links in a DVB-LTE convergence scenario. Our contribution lies in two folds: i) the global ergodic capacity is derived in closed-form with Rayleigh fading channel on each link. This derivation allows us to evaluate the global data rate of the DVB and LTE in a spectral overlap scenario. ii) The analytical forms allow the evaluation of the influence of system parameters on the global and broadcast data rate, e. g. mobile and broadcast power, distance between the broadcast receiver and the LTE base station.