Ray Tracing Modeling of Electromagnetic Propagation for On-Chip Wireless Optical Communications

Abstract

Multi-core processors are likely to be a point of no return to meet the unending demand for increasing computational power. Nevertheless, the physical interconnection of many cores might currently represent the bottleneck toward kilo-core architectures. Optical wireless networks on-chip are therefore being considered as promising solutions to overcome the technological limits of wired interconnects. In this work, the spatial properties of the on-chip wireless channel are investigated through a ray tracing approach applied to a layered representation of the chip structure, highlighting the relationship between path loss, antenna positions and radiation properties.

Multi-Level Analysis of On-Chip Optical Wireless Links

“…Therefore, the extension of the wireless solution to the optical domain represents an interesting topic of investigation, also in light of the minor attention so far devoted to OWiNoC [10,18,19]. A survey on the major studies and papers already published on wired and wireless NoC is summarized in Table 1 for the sake of brevity.…”

“…Physical Interconnection Networks-on-Chip (NoC) [1,5,20,21] Optical Networks-on-Chip (ONoC) [5,6,11,20,22] Wireless Networks Millimeter wave and THz (WiNoC) [4,5,8,17,23,24] Optical (OWiNoC) [9,10,18,19,24] A comprehensive performance assessment of a network-on-chip usually spans several different aspects such as the number of NoC elements (links, routing, switch elements) [2,23], the latency [2,12,17,24], the chip area [5,25], the communication distances [2], the data-rate [2], and the bit error probability (BEP) [2,22]. The analysis carried out in this paper is primarily focused on both the communication range and the BEP.…”

“…According to the chip layered representation, the electromagnetic waves springing out from the on-chip transmitting antenna are expected to bounce onto the interfaces between the layers, thus triggering multipath effects [8,10,14,16,18]. Assuming the antennas buried in a SiO 2 layer limited by two different, unbounded media on the lower and on the upper side [10,18], multipath is fundamentally generated by the multiple reflections between the interfaces ( Figure 5) and can be evaluated by means of the Ray Tracing (RT) approach discussed in [10]. It is worth pointing out that the RT modeling is particularly tailored to the investigation of the optical wireless channel, as geometrical optics is known to be an asymptotic theory, i.e., its accuracy increases at higher frequency.…”

“…It is worth pointing out that in both cases PG is on the average greater compared to what it would be in free space (dotted line in Figure 7), thus meaning that on-chip wireless communications can benefit from better propagation conditions than free space. As outlined in [10], this is the result of a sort of guiding effect triggered by the multiple reflections within the antenna layer up to a distance that depends on the antenna radiation properties, the material at the interfaces and the thickness of the layers [10]. Taking advantage of the computational agility of RT, the impact of materials, antennas and layers thickness on the optical wireless channel is further investigated in Figure 8.…”

“…In order to overcome the bottleneck of physical interconnections, Wireless Network on Chip (WiNoC) are being considered an interesting solution [3][4][5]8]. Since millimeter-wave antennas undergo obvious problems of on-chip integration, Optical Wireless Networks-on-Chip (OWiNoC) have been recently investigated [9,10], aiming at keeping the main benefits of WiNoC (short latency, simpler network design) but easing the antenna integration process. As wireless communications on-chip are expected to complement wired solutions, rather than to replace them [2,11], OWiNoC also benefit from full compatibility with optical, physical networks which may be also deployed on the same chip.…”