Interference analysis for optical wireless communications in Network-on-Chip (NoC) scenarios

Optical wireless (OW) communications, besides being of great interest for indoor and outdoor applications, have been recently proposed as a powerful alternative to the existing wired and wireless radio frequency (RF) interconnects in network-on-chips (NoCs). Design and analysis of networks with OW links require a careful investigation of cross-link interference, which impacts considerably the efficiency of systems that reuse the same channel for multiple transmissions. Yet, there is no comprehensive analysis of interference for OW NoCs, and the analyses of crosstalk in optical waveguide communications usually rely on synchronous data transmissions. A novel framework for the analysis of on-chip OW communications in the presence of cross-link cochannel interference and noise is proposed, where asynchronous data transmissions are considered. Self-beating of interfering signals is also considered, which was often neglected in previous literature. The bit error probability (BEP) for arbitrary number of interfering sources is derived as a function of signal-to-noise ratio (SNR), interference powers, detection threshold and pulse shaping, using both exact and approximation methods. The proposed analysis can be applied to both noise- and interference-limited cases, and enables a system designer to evaluate reuse distance between links that share the same optical carrier for simultaneous communication in NoCs

Interference Analysis for Optical Wireless Interconnections

Optical wireless (OW) links have been recently proposed as an interconnection technology for multiple processing cores operating in parallel on the same chip. OW communication is also a mature option for indoor and outdoor applications. Design and analysis of networks with optical wireless links require a careful investigation of cross-link interference which plays a key-role on the performance and efficiency of systems that reuse the same channel for multiple parallel transmissions. In this paper we analyze the bit-error rate performance of OW links for on-chip applications with cross-link cochannel interference. As a novelty with respect to known literature on crosstalk in optical communications we consider asynchronous data transmission and address the system performance in case of heavy interference. Analytical methods are used to derive error probabilities as a function of signal-to-noise ratio (SNR), crosstalk power ratio, detection threshold, pulse shaping. Both exact and tight approximation methods are considered. As shown in the results, robustness against interference increases with asynchronous transmission, RZ pulse shaping and suitable design of detection threshold. It is also shown how the proposed analysis can be used to evaluate the reuse distance between two parallel links simultaneously transmitting in the same direction

On-chip optical wireless interconnections with plasmonic nanoantennas

Plasmonic nanoantennas integrated with silicon waveguides are a suitable solution for the implementation of on-chip wireless communications at optical frequencies. The use of optical wireless links simplifies on chip network design, mitigating switching and routing issues, while avoiding electro-optical conversion. In this work, we investigate the performance of multiple parallel on-chip optical interconnections by taking into account cross-link interference, which arises when the links reuse the same optical frequency. This analysis combines two approaches: FDTD simulation to evaluate both the radiation diagram of the antennas used in the optical links and the near-field coupling between transmit and receive neighbor antennas, and system-analysis to evaluate interference effects on link error probability. The results obtained will enable us to design the distances among parallel interconnections in order to preserve acceptable bit error probability

Adaptive Communications for Stochastic Networks

Wireless networks have crucial needs for increasing efficiency in the spectrum usage. Adaptive communication is a key enabler for enhancing the spectral efficiency (SE) of wireless networks. This paper develops a framework for design and analysis of stochastic wireless networks, in which nodes employ diversity techniques and are randomly distributed in space. The signal-to-interference-plus-noise ratio (SINR) distribution is determined for finite and infinite stochastic networks at the output of the optimum combiner (OC). The statistics of the SINR at the OC output are used to design adaptive communication systems with diversity in the presence of small- A nd large-scale fading, interference, and noise. Slow adaptive modulation for any diversity order is analyzed in the presence of an interference field modeled as a Poisson point process. The results are applied to evaluate the benefits of adaptive modulation techniques with diversity for maximizing the SE in a stochastic network

Demonstration of optical wireless links for on-chip communications

This work presents experimental results of on-chip optical communications between dielectric antennas realized on a Silicon on Insulator technology. The observed fast fading effects call for ray-tracing modeling of the propagation channel

Multi-Level Analysis of On-Chip Optical Wireless Links

Networks-on-chip are being regarded as a promising solution to meet the on-going requirement for higher and higher computation capacity. In view of future kilo-cores architectures, electrical wired connections are likely to become inefficient and alternative technologies are being widely investigated. Wireless communications on chip may be therefore leveraged to overcome the bottleneck of physical interconnections. This work deals with wireless networks-on-chip at optical frequencies, which can simplify the network layout and reduce the communication latency, easing the antenna on-chip integration process at the same time. On the other end, optical wireless communication on-chip can be limited by the heavy propagation losses and the possible cross-link interference. Assessment of the optical wireless network in terms of bit error probability and maximum communication range is here investigated through a multi-level approach. Manifold aspects, concurring to the final system performance, are simultaneously taken into account, like the antenna radiation properties, the data-rate of the core-to core communication, the geometrical and electromagnetic layout of the chip and the noise and interference level. Simulations results suggest that communication up to some hundreds of μm can be pursued provided that the antenna design and/or the target data-rate are carefully tailored to the actual layout of the chip

The GRETA architecture for energy efficient radio identification and localization

This paper presents an overview of the innovative solutions developed within the Italian project GRETA (GREen TAgs and sensors with ultra-wide-band identification and localization capabilities), whose aim is the development of a distributed and comprehensive system for identification, localization, tracking and monitoring in indoor scenarios. The system is based on hybrid UWB-UHF RFID tags, and the realization and experimental validation of novel tag prototypes based on environmentally friendly materials is a major achievement of the project