Alamouti-type space-time coding for free-space optical communication with direct detection

Abstract

In optical communication systems employing direct detection at the receiver, intensity modulations such as on-off keying (OOK) or pulse-position modulation (PPM) I. System ModelConsider an optical communication system with two transmit antennas and one receive antenna as shown in Fig. 1. This model inherently assumes that both transmitters are simultaneously observed by the receiver, thus implying a large receiver field of view (FOV). This, in turn, implies a larger collected background radiation that could seriously degrade system performance. Therefore, care must be exercised to limit background through the use of appropriate spatial filtering prior to detection. For example, if the link distance is R m and the receiver FOV is θ rad, then the separation of the two transmitters cannot exceed approximately θR m. Thus, if R = 1 km and θ ∼ = 10 mrad, then the transmitters would have to be less than 10 m apart for the scheme to work. This model is applicable to urban "last mile" links where multiple transmitters and receivers can be envisioned for mitigating link outage due to turbulence, scattering, and occasional blockage.

On the Optimality of the Selection Transmit Diversity for MIMO-FSO Links with Feedback

“…RC was also analyzed in [3] for systems corrupted uniquely by AWGN. In [4], [5], non-negative totally-real space-time codes (STC) were proposed for FSO systems corrupted by Gaussian noise. In [1], a selection transmit diversity (STD) scheme was proposed for Multiple-Input-Single-Output (MISO) FSO links in the presence of AWGN while ignoring the shot noise.…”

Self Healing MIMO Transreceiver Module On-Chip

“…It reads the input frames given by the user and converts into a framing sequence. The Arm processor is configured to act as a error detection and correction unit for the physical layer [6]. The hardware (Figure 3) functions as a self-healing physical layer implementation in future embedded web server.…”

Contrasting space-time schemes for MIMO FSO systems with non-coherent modulation

“…On the other hand, most of the orthogonal ST block codes (OSTBCs) can be modified to be adapted to IM/DD FSO systems. For instance, for the case of two transmitter beams, a modified Alamouti scheme [15] is proposed in [16] which is adapted to IM/DD optical systems by introducing a bias to overcome unipolar signaling used in these systems. This idea is then generalized in [17] to ON-OFF keying (OOK) modulation with any pulse shape.…”

“…1. As OSTBC, we consider the modified Alamouti scheme, proposed in [16]. We notice that the RC scheme remains the best.…”