The performance of Reed-Solomon codes on a bursty-noise channel

Abstract-Multilevel pulse amplitude modulation (M -PAM) is gaining momentum for high-capacity and power-efficient cloud computing. Compared to the classic on-off keying (OOK) modulation, high-order PAM yields better spectral efficiency but is also more susceptible to physical layer degradation effects. We develop a cross-layer analysis framework to examine PAM transmission performance in data center network environments supporting both optical multicasting and wavelength routing. Our analysis is conducted on a switch architecture based on an arrayed-waveguide grating (AWG) core and distributed broadcast domains, exhibiting different physical paths, and random, uncontrolled crosstalk noise. Reed-Solomon coding with rate adaptation is incorporated into PAM transceivers to compensate for impairments. Our Monte Carlo simulations point to the significant impact of AWG crosstalk on higher-order PAM in wavelength-reuse architectures and the importance of code rate adaptation for signals traversing multiple routing stages. According to our study, 8-PAM offers the highest effective bit rates for signals terminating in one broadcast domain and performs poorly when considering interdomain connectivity. On the other hand, the impairment-induced degradation of interdomain capacity for 4-PAM can be limited to 20.4%, making it better suited for connections spanning two broadcast domains and a crosstalkrich stage. Our results call for software-defined PAM transceiver designs in support of both modulation order and code rate adaptation.Index Terms-Arrayed waveguide grating (AWG), bit error rate (BER), data center, forward error correction (FEC), goodput, optical multicast, physical layer, pulse amplitude modulation (PAM).

Section: Pam Performance Evaluation Resultsmentioning

confidence: 99%

PAM Performance Analysis in Multicast-Enabled Wavelength-Routing Data Centers

Rastegarfar

Szczerba

et al. 2017

“…Then, an interleaver is considered to make the errors independent at the input of the outer RS decoder. Finally, the BER at the output of the exploited outer RS decoder with no decoding failures is obtained by [55,Eq. (16)- (19)] assuming negligible probability of undetected errors.…”

Section: Numerical Resultsmentioning

confidence: 99%

Rate-Adaptive Coded Modulation for Fiber-Optic Communications

Beygi

Agrell

Kahn

et al. 2014

Abstract-Rate-adaptive optical transceivers can play an important role in exploiting the available resources in dynamic optical networks, in which different links yield different signal qualities. We study rate-adaptive joint coding and modulation, often called coded modulation (CM), addressing non-dispersion-managed (non-DM) links, exploiting recent advances in channel modeling of these links. We introduce a four-dimensional CM scheme, which shows a better tradeoff between digital signal processing complexity and transparent reach than existing methods. We construct a rate-adaptive CM scheme combining a single low-density paritycheck code with a family of three signal constellations and using probabilistic signal shaping. We evaluate the performance of the proposed CM scheme for single-channel transmission through long-haul non-DM fiber-optic systems with electronic chromaticdispersion compensation. The numerical results demonstrate improvement of spectral efficiency over a wide range of transparent reaches, an improvement over 1 dB compared to existing methods.Index Terms-Fiber-optic communications, four-dimensional set partitioning, non-dispersion managed links, nonlinear channel model, probabilistic shaping, rate-adaptive coded modulation.

“…To investigate the impact of physical-layer impairments on the transmission rate for different modulation orders, we deploy a forward error correction (FEC) code with rate adaptation. We use a Reed-Solomon code with block length of 255 bytes [34], i.e., RS(255, k), where k is chosen by the switch controller after calculating the pre-FEC BER such that the post-FEC BER becomes less than 10 −12 . The larger the pre-FEC BER, the smaller the value of k, and the lower the effective bit rate per transmitter.…”

Section: Cross-layer Performance Analysismentioning

confidence: 99%

Overcoming the Switching Bottlenecks in Wavelength-Routing, Multicast-Enabled Architectures

Keykhosravi

Rastegarfar

Peyghambarian

et al. 2019

Modular optical switch architectures combining wavelength routing based on arrayed waveguide grating (AWG) devices and multicasting based on star couplers hold promise for flexibly addressing the exponentially growing traffic demands in a cost-and powerefficient fashion. In a default switching scenario, an input port of the AWG is connected to an output port via a single wavelength. This can severely limit the capacity between broadcast domains, resulting in interdomain traffic switching bottlenecks. An unexplored solution to this issue is to exploit multiple AWG free spectral ranges (FSRs), i.e., to set up multiple parallel connections between each pair of broadcast domains. In this paper we i) study, for the first time, the influence of the FSR count on the throughput of a multistage switching architecture and ii) propose a generic and novel analytical framework to estimate the blocking probability. We assess the accuracy of our analytical results via Monte Carlo simulations. Our study points to significant improvements with a moderate increase in the number of FSRs. We show that an FSR count beyond four results in diminishing returns. Furthermore, to investigate the trade-offs between the network-and physical-layer effects, we conduct a cross-layer analysis, taking into account pulse amplitude modulation (PAM) and rate-adaptive forward error correction (FEC). We illustrate how the effective bit rate per port increases with an increase in the number of FSRs.Index Terms-Arrayed waveguide grating (AWG), blocking probability, coupler, free spectral range (FSR), multicast, physical layer, scheduling, switch architecture.