Recent Advances on Telematics Engineering

Agüero, R.; Payeras Capella, MM.; Lloret, J.; Femenias, G. (2017). Recent Advances on Telematics Engineering. Mobile Networks and Applications. 22(6):1065-1067. https://doi.org/10.1007/s11036-017-0836-71065106722

Frequency-hopping trellis-coded 8-DPSK for indoor communications

A TDMA (time-division multiple-access) slow frequency hopping-trellis-coded 8-DPSK (differential phase-shift keying) scheme is proposed for indoor mobile radio communications. In order to assess the performance of this scheme, a GWSSUS (Gaussian wide-sense stationary uncorrelated scattering) continuous channel model with an exponential power delay profile has been adopted. This channel model allows one to analyze transmission rates much lower than the inverse of the RMS (root mean square) delay spread. Bit error rate (BER) is obtained, through Monte Carlo computer simulation, as a function of signal-to-noise ratio and with normalized frequency-hopping separation and number of hopping-frequency channels as parameters. It is found that the degradation of the system BER performance with respect to the null-correlation case is, for normalized frequency-hopping separations greater than 0.15, hardly significantPeer ReviewedPostprint (published version

Trellis-coded 8-DPSK with postdetection combining diversity for digital land mobile radio

The performance of rate 2/3 postdetection combining diversity TCM-8DPSK systems is analyzed. A simulated Rayleigh mobile radio channel and the presence of cochannel interferers are assumed. Only the case where an ideal interleaving/deinterleaving process is used to further combat the Rayleigh fading is considered. Bit error rate (BER) is obtained through computer simulation as a function of signal-to-noise ratio (SNR) and carrier-to-interference average power ratio. Results obtained for the QDPSK and TCM-8DPSK schemes are considered as a reference to determine the performance improvements introduced by the coding diversity set-upPeer ReviewedPostprint (published version

Switched-diversity trellis-coded 8-DPSK for mobile radio applications

Peer ReviewedPostprint (published version

Short-Term Power Constrained Cell-Free Massive-MIMO Over Spatially Correlated Ricean Fading

This paper considers short-term power constrained cell-free massive multiple-input multiple-output (MIMO) scenarios where a large set of multi-antenna access points (APs) provide service to a group of single-antenna mobile stations (MSs) on a spatially correlated multipath environment. Based on a probabilistic approach, the spatially correlated propagation links are modeled using either Ricean or Rayleigh fading channel models that combine a deterministic line-of-sight (LOS) propagation path with a small-scale fading caused by non-line-of-sight (NLOS) multipath propagation. Assuming the use of minimum mean square error (MMSE) channel estimates, closed-form expressions for the downlink (DL) achievable spectral efficiency of a cellfree massive MIMO network with short-term power constraints (i.e., a vector normalized conjugate beamformer (NCB)) are derived and benchmarked against that provided by the conventional cell-free massive MIMO network with long-term power constraints (i.e., the conventional conjugate beamforming (CB)). These expressions, encompassing the effects of spatial antenna correlation, Ricean/Rayleigh fading and pilot contamination, are then used to derive both pragmatic and optimal max-min peruser power allocation strategies and to gain theoretical insight on the performance advantage provided by the use of short-term power constraints instead of the conventional long-term power constrained approach.This work was supported in part by the Agencia Estatal de Investigacion (AEI) of Spain under Grants TEC2017-90093-C3-2-R and TEC2017-90093-C3-3-R, and in part by the European Regional Development Fund (ERDF) funds of the European Union (EU) (AEI/FEDER, UE)

Throughput Analysis and Optimization of Multi-layer FFR-aided OFDMA Networks

[EN] In OFDMA networks, the use of universal frequency reuse plans improves cell capacity but causes very high levels of inter-cell interference (ICI), particularly affecting users located in the cell-edge regions.In order to mitigate ICI while achieving high spectral efficiencies, fractional frequency reuse (FFR) shows a good tradeoff between cell-edge throughput and overall cell spectral efficiency.Recently, multi-layer FFR-aided OFDMA-based designs, splitting the cell into inner, middle and outer layers have been proposed and studied with the aim of increasing the spectrum utilization and improving the user fairness throughout the cell.This paper presents an analytical framework allowing the performance evaluation and optimization of multi-layer FFR designs in OFDMA-based networks.Tractable mathematical expressions of the average cell throughput as well as the layer spectral efficiency have been derived for both proportional fair (PF) and round robin (RR) scheduling policies.Work supported by the Agencia Estatal de Investigacion and Fondo Europeo de Desarrollo Regional (AEI/FEDER, UE) under project ELISA (subproject TEC2014-59255-C3-2-R), Ministerio de Economía y Competitividad (MINECO), Spain, and the Conselleria d’Educacio, Cultura i Universitats (Govern de les Illes Balears) under grant FPI/1538/2013 (co-financed by the European Social Fund). The research leading to these results has also received funding from ”la Caixa” Banking Foundation.Garcia-Morales, J.; Femenias, G.; Riera-Palou, F.; Thompson, JS. (2018). Throughput Analysis and Optimization of Multi-layer FFR-aided OFDMA Networks. En XIII Jornadas de Ingeniería telemática (JITEL 2017). Libro de actas. Editorial Universitat Politècnica de València. 140-147. https://doi.org/10.4995/JITEL2017.2017.6582OCS14014

Downlink scheduling and resource allocation for 5G MIMO-multicarrier: OFDM vs FBMC/OQAM

OAPA The definition of the next generation of wireless communications, so-called 5G networks, is currently underway. Among many technical decisions, one that is particularly fundamental is the choice of the physical layer modulation format and waveform, an issue for which several alternatives have been proposed. Two of the most promising candidates are: (i) orthogonal frequency division multiple (OFDM), a conservative proposal that builds upon the huge legacy of 4G networks, and (ii) filterbank multicarrier/offset quadrature amplitude modulation (FBMC/OQAM), a progressive approach that in frequency selective channels sacrifices subcarrier orthogonality in lieu of an increased spectral efficiency. The comparative merits of OFDM and FBMC/OQAM have been well investigated over the last few years but mostly, from a purely physical layer point of view and largely neglecting how the physical layer performance translates into user-relevant metrics at the upper-layers. This paper aims at presenting a comprehensive comparison of both modulation formats in terms of practical network indicators such as goodput, delay, fairness and service coverage, and under operational conditions that can be envisaged to be realistic in 5G deployments. To this end, a unifying cross-layer framework is proposed that encompasses the downlink scheduling and resource allocation procedures and that builds upon a model of the queueing process at the data-link control layer and a physical layer abstraction that can be chosen to model either OFDM or FBMC/OQAM. Extensive numerical results conclusively demonstrate that most of the apriori advantages of FBMC/OQAM over OFDM do indeed translate into improved network indicators, that is, the increase in spectral efficiency achieved by FBMC/OQAM makes up for the distortion caused by the loss of orthogonality.Peer ReviewedPostprint (published version