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This paper investigates the problem of source localization using a single sensor and multipath signals in a electromagnetic warfare (EW) context. Time difference of arrival (TDOA) and angle of arrival (AOA) measurements are used to localize transmitters. This approach is interesting in the sense that no a priori knowledge of scatterers is required. For this localization approach, the minimal number of components (emitters and reflectors) is determined. Attainable accuracies of our method for the different possible configurations are discussed using the Cramér-Rao lower bounds.

Recently it has been demonstrated that pulse width modulation (PWM) can represent a viable solution for the analog optical fronthaul alternative to standard radio over fibre, which still avoids the bandwidth expansion of the digital fronthaul. The PWM encodes the analog samples at the transmitter onto the duration of the on/off keyed optical signal, splitting the sampling and quantization of the radio signal between remote radio units (RRUs) and baseband units (BBUs). In particular in this contribution we demonstrate the capabilities of optical PWM for the transport of LTE signals to support the centralized access network (C-RAN) fronthaul in fibre optic link up to 10-km of standard single mode fibre. The generation and analysis of the radio signals is provided by software modules compliant with the LTE standard which allowed to analyse performance results for the different LTE carriers, channels and services. The PWM optical signal connecting RRUs to BBUs is generated by either directly modulating a DFB laser or an externally seeded reflective semiconductor optical amplifier (RSOA). Both devices could be exploited inside a wavelength division multiplexed passive optical network (WDM PON) architecture where the various RRU-to-BBU links are pooled through virtual point-to-point connections at different wavelengths. Keywords: WDM PON, fronthaul, PWM, RSOA, external-seeding. INTRODUCTIONNext generation (LTE and 5G) mobile communication networks are expected to cope with the ever-growing demand for high throughput, mobility and low latency which are changing the radio access networks (RANs) paradigm toward the centralized RAN (C-RAN). This architecture should be able to handle the growing demand of capacity and the increasing pervasivity of cellular systems. The C-RAN can be designed to support a large number of users taking advantage of mutual cooperation for interference mitigation and of a huge number of antennas for massive MIMO deployment [1]. In C-RANs the antennas, together with all the RF functionalities, are hosted at the cell sites in the remote radio heads (RRHs), which need to forward the signal to/from the BBUs through the fronthaul (FH) link. Due to the high available capacity preferred FH links exploit fiber optic transmission based on the common public radio interface (CPRI) protocol [2,3]. However digital FH leads to a bandwidth expansion not sustainable for next RAN requirements. Although CPRI compression or different RAN functional splits have been proposed a full-analog transmission, enabling the reduction of the bandwidth requirements, the latency and the hardware costs, will likely outperform other solutions. Recent strategies adopt multiple frequency-domain multiplexed (FDM) LTE signals assisted by analog and digital signal processing [4] or directly-modulated multiple intermediate frequency-over-fiber (IFoF) schemes [5]. On the other hand, analog radio-over-fiber (RoF) suffers from linear and nonlinear distortions (NLD) due to laser diode inherent nonlinearities, chromatic dispersion,...