Outage probability of the MIMO Gaussian free-space optical channel with PPM

Abstract

The main drawback in communicating via the freespace optical channel is the detrimental effect the atmosphere has on a propagating laser beam. Atmospheric turbulence causes random fluctuations in the irradiance of the received laser beam, commonly referred to as scintillation. We investigate the mitigation of scintillation through the use of multiple lasers and multiple apertures, thereby creating a multiple-input multiple output (MIMO) channel. We adopt a quasi-static block fading model and study the outage probability of the channel under the assumption of orthogonal pulse-position modulation. Non-ideal photodetection is also assumed such that the combined shot noise and thermal noise are considered as signal-independent additive Gaussian white noise. Assuming perfect receiver channel state information (CSI), we compute the signal-to-noise ratio exponents for the cases when the scintillation is lognormal, exponential and gamma-gamma distributed, which cover a wide range of atmospheric turbulence conditions. Furthermore, we illustrate very large gains when CSI is also available at the transmitter.

Nearest Neighbor Decoding in MIMO Block-Fading Channels With Imperfect CSIR

“…Suppose that is used to evaluate the Gallager error exponent (10). Then, it follows from [5], [12], [29] that is equal to , and for sufficiently large , (12) and (18) converge and we obtain that [5] (19) (20) which is the information outage probability [3]. The above results show the convergence of the random coding achievability and converse to the outage probability as the block length increases to infinity.…”

“…One has to note that the convergence in (20) holds when the capacity-achieving distribution for a given alphabet , is used to construct codebooks. For a fixed input distribution , the probability in (19) only characterizes random coding achievability bound to the average error probability; it does not imply anything on the converse bound for any given code.…”

“…Note that the perfect CSIR condition is easily recovered by letting to infinity. Finally, the results are applicable to a wide-range of fading distributions including Rayleigh, Rician, Nakagami-, Nakagami-and Weibull fading models; it can also be directly extended to optical wireless scintillation channels based on lognormal-Rice and gamma-gamma distributions [20]- [22].…”

Asymptotic Performance Analysis of Free-Space Optical Links with Transmit Diversity

“…The selection principle varies with different transmit-diversity schemes. In a MISO FSO system with repetition coding (RC) [17][18][19][20], all N laser sources are selected to transmit data synchronously. In Dual-TLS and Group-TLS systems, part of the N laser sources participate in sending optical signals.…”

“…Therefore, the concept of spatial diversity in FSO differs from that in traditional RF communications. As introduced in [11], spatial diversity in FSO systems can be realized via the use of multiple apertures at the receiver (receive diversity) [12], multiple beams at the transmitter (transmit diversity) [13][14][15], or a combination of the two [16][17][18][19][20][21][22][23]. Receive diversity and transmit diversity are usually referred to as SIMO (Single-Input Multiple-Outputs) and MISO (Multiple-Inputs Single-Output) respectively.…”