High-performance signal acquisition algorithms for wireless communications receivers

Due to the uncertainties introduced by the propagation channel, and RF and mixed signal circuits imperfections, digital communication receivers require efficient and robust signal acquisition algorithms for timing and carrier recovery, and interfer- ence rejection. The main theme of this work is the development of efficient and robust signal synchronization and interference rejection schemes for narrowband, wideband and ultra wideband communications systems. A series of novel signal acquisition schemes together with their performance analysis and comparisons with existing state-of-the- art results are introduced. The design effort is first focused on narrowband systems, and then on wideband and ultra wideband systems. For single carrier modulated narrowband systems, it is found that conventional timing recovery schemes present low efficiency, e.g., certain feedback timing recov- ery schemes exhibit the so-called hang-up phenomenon, while another class of blind feedforward timing recovery schemes presents large self-noise. Based on a general re- search framework, we propose new anti-hangup algorithms and prefiltering techniques to speed up the feedback timing recovery and reduce the self-noise of feedforward tim- ing estimators, respectively. Orthogonal frequency division multiplexing (OFDM) technique is well suited for wideband wireless systems. However, OFDM receivers require high performance car-rier and timing synchronization. A new coarse synchronization scheme is proposed for efficient carrier frequency offset and timing acquisition. Also, a novel highly accurate decision-directed algorithm is proposed to track and compensate the residual phase and timing errors after the coarse synchronization step. Both theoretical analysis and computer simulations indicate that the proposed algorithms greatly improve the performance of OFDM receivers. The results of an in-depth study show that a narrowband interference (NBI) could cause serious performance loss in multiband OFDMbased ultra-wideband (UWB) sys- tems. A novel NBI mitigation scheme, based on a digital NBI detector and adaptive analog notch filter bank, is proposed to reduce the effects of NBI in UWB systems. Simulation results show that the proposed NBI mitigation scheme improves signifi- cantly the performance of a standard UWB receiver (this improvement manifests as a signal-to-noise ratio (SNR) gain of 9 dB)

A Low Cost UWB Based Solution for Direct Georeferencing UAV Photogrammetry

Thanks to their flexibility and availability at reduced costs, Unmanned Aerial Vehicles (UAVs) have been recently used on a wide range of applications and conditions. Among these, they can play an important role in monitoring critical events (e.g., disaster monitoring) when the presence of humans close to the scene shall be avoided for safety reasons, in precision farming and surveying. Despite the very large number of possible applications, their usage is mainly limited by the availability of the Global Navigation Satellite System (GNSS) in the considered environment: indeed, GNSS is of fundamental importance in order to reduce positioning error derived by the drift of (low-cost) Micro-Electro-Mechanical Systems (MEMS) internal sensors. In order to make the usage of UAVs possible even in critical environments (when GNSS is not available or not reliable, e.g., close to mountains or in city centers, close to high buildings), this paper considers the use of a low cost Ultra Wide-Band (UWB) system as the positioning method. Furthermore, assuming the use of a calibrated camera, UWB positioning is exploited to achieve metric reconstruction on a local coordinate system. Once the georeferenced position of at least three points (e.g., positions of three UWB devices) is known, then georeferencing can be obtained, as well. The proposed approach is validated on a specific case study, the reconstruction of the façade of a university building. Average error on 90 check points distributed over the building façade, obtained by georeferencing by means of the georeferenced positions of four UWB devices at fixed positions, is 0.29 m. For comparison, the average error obtained by using four ground control points is 0.18 m

Wideband Broadcasting: A Power-Efficient Approach to 5G Broadcasting

(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this[EN] Efficient and flexible use of spectrum will be inherent characteristics of fifth-generation (5G) communication technologies with native support of wideband operation with frequency reuse 1, i.e. all transmit sites use all available frequency resources. Although not from the very first 5G release of 3GPP (Third Generation Partnership Project), it is expected that broadcast/multicast technology components will later be added and fully integrated in the 5G system. The combination of both wideband and frequency reuse 1 may provide significant gains for broadcast transmissions in terms of energy efficiency, since it is more efficient to increase capacity by extending the bandwidth rather than increasing the transmit power over a given bandwidth. This breaks with the traditional concept of terrestrial broadcast frequency planning, and paves the way to new potential uses of UHF (Ultra High Frequency) spectrum bands for 5G broadcasting. This paper provides an insight into the fundamental advantages in terms of capacity, coverage as well as power saving of wideband broadcast operation. The role of the network deployment, linked to frequency reuse in the UHF band, and its influence in the performance of a Wideband Broadcasting system are discussed. The technical requirements and features that would enable such power-efficient solution are also addressed.This work was supported in part by the European Commission under the 5G-PPP project 5G-Xcast (H2020-ICT-2016-2 call, grant number 761498). The views expressed in this contribution are those of the authors and do not necessarily represent the project. This work was also partially supported by the Ministerio de Educacion y Ciencia, Spain (TEC2014-56483-R), co-funded by European FEDER funds.Gimenez Gandia, JJ.; Gomez-Barquero, D.; Mogarde, J.; Stare, E. (2018). Wideband Broadcasting: A Power-Efficient Approach to 5G Broadcasting. IEEE Communications Magazine. 56(3):119-125. https://doi.org/10.1109/MCOM.2018.170067511912556