Optical wireless GEO satellite-to-ground downlinks: rateless codes as solution for scintillation fading

Scintillation fading can corrupt a satellite-to-ground optical wireless links with burst errors. Rateless codes, suitable for erasure channel, are able to eliminate or to reduce these communication errors. We analyzed the performances of three different rateless codes in a simulated Geo satellite-to-ground downlink.

Joint Space-Time Alamouti Synchronous W-CDMA LMMSE equalization

A linear chip-level model for multi-antenna space-time coded wideband CDMA reconfigurable receivers

Transmitter side reconfigurability is currently mostly implemented via adaptive modulation and coding. In the scenario of multiple antenna transmission which is foreseeable for fourth generation wireless mobile communications, a new level of reconfigurability might employ transmission scheme adaptation, i.e. dynamically switching between spatialmultiplex and space-time coded transmission. This paper presents a generalized linear model for the received signal in a multi-antenna CDMA signaling scheme on frequency-selective fading MIMO channels. The proposed model is unprecedented in that it supports general complex space-time codes as well as spatial-multiplex multiantenna transmission and it…

Joint Equalization and Detection for Space-Time Block Coded High-Speed CDMA Downlink over Frequency Selective Channels

Phase lock loop false lock avoidance in presence of global navigation satellite system signal

In this paper we analyse the operation of a fully digital Phase Lock Loop (PLL) in a false lock regime, using real data. The issue has been noticed while we were testing performance of our software receiver in a moving user scenario. While the phenomenon of false lock has been described in other papers about PLLs, our intent is to describe a practical, and in our opinion interesting, issue we encountered and how we got over it.

A software receiver adaptive phase lock loop method

The aim of this paper is to introduce a new and relatively simple algorithm which is capable to tune the parameters of the loop filter in a phase lock loop, like the one that can be found in a global navigation satellite system receiver. The parameters are chosen while the system is running, in order to make the bandwidth of the filter adaptive with respect to the signal dynamic and strength. A wider bandwidth is obtained to make the filter more reactive when searching the carrier, while the bandwidth gets narrower when the system is in the tracking state, in order to cut off as much noise as possible. The algorithm is based on the observation of the estimated variance of the phase lock loo…

Fading mitigation coding techniques for space to ground free space optical communications (Euro Med Telco 2014)

In this manuscript, a Geostationary satellite-toground Free Space Optics (FSO) downlink channel model has been implemented, which is able to predict temporal irradiance fluctuations caused by scintillation at a wide range of turbulence conditions and for different values of the zenith angle. In order to mitigate fading events that occur in FSO communications, we have also tested the performance of three different families of Rateless Codes (Luby Transform, Raptor and RaptorQ) into our model and found that RaptorQ is the best candidate to mitigate errors in FSO links.

Fading mitigation coding techniques for space to ground free space optical communications