On the Cooperative Relaying Strategies for Multi-Core Wireless Network-on-Chip

Quoc-Tuan Vien,Huan X Nguyen,Michael Opoku Agyeman,Mallik Tatipamula

doi:10.1109/access.2021.3049770

Abstract

Recently, hybrid wired-wireless Network-on-Chip (WiNoC) has been proposed as a suitable communication fabric to provide scalability and satisfy high performance demands of the exascale era of modern multi/many-core System-on-Chip (SoC) design. A well accepted low-latency wireless communication fabric for WiNoCs is millimeter wave (mm-Wave). However, the wireless channel of mm-Wave is lossy due to free space signal radiation with both dielectric propagation loss (DPL) and molecular absorption attenuation (MAA). This is exacerbated for edge situated cores and in macro-chips embodying thousands of cores. To this end, this article proposes efficient relaying techniques to improve the signal strength of the wireless channel in the WiNoCs using on-chip networking approaches under the realistic SoC channel conditions. First, we propose a realistic relay communication channel for the WiNoCs to characterise both MAA and DPL which have drastic effect on the performance. We then derive and show that the channel capacity for a single-relay WiNoC employing Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying protocols increases by up to 20% and 25%, respectively, compared to the conventional direct transmission. The AF protocol outperforms the DF mode for shorter transmissions between the relay and the destination cores, while the reverse is observed in other conditions. A hybrid protocol is then proposed to exploit the performance advantages of both relaying protocols to address the unbalanced distance between the cores, providing the maximal channel capacity close to the cutset bound. Finally, our approach is further validated in multi-relay WiNoCs where the communications of the remote cores is assisted by multiple intermediate cores along with the details of associated realistic channel model in emerging many-core SoCs.

Highlights

With growing and emerging multimedia applications which require a considerable enhancement of computation and interactive functionality, wire-based interconnects between cores in a Network-on-Chip (NoC) have been shown to be insufficient to meet the critical requirements of high performance, scalability and low latency, especially in this technological era of ever increasing number of cores [1], [2]
Inspired by the concept of cooperative relay in wireless networks, the Gaussian relay channel models are adopted for the communications between three on-chip wireless cores C1, C2 and C3 in a Wireless NoC (WiNoC) playing the roles of a source node, a relay node and a destination node, respectively
Considering high frequency band, dielectric material and gas compositions of the transmission medium within the chip package are taken into account in the developed channel model, based on which the channel capacity has been derived for the relay channel in a typical single-relay WiNoC employing DF and AF relaying protocols

Summary

INTRODUCTION

With growing and emerging multimedia applications which require a considerable enhancement of computation and interactive functionality, wire-based interconnects between cores in a Network-on-Chip (NoC) have been shown to be insufficient to meet the critical requirements of high performance, scalability and low latency, especially in this technological era of ever increasing number of cores [1], [2]. A full diversity can be achieved with the AF protocol when the destination receives different versions of the signal from the source and relay; the relay in this protocol amplifies and forwards the noises together with the signals to the destination These two relaying techniques have been well developed in the literature for wireless networks, their employment in the WiNoC, to the best of the authors’ knowledge, has not been investigated. A relay communication channel is proposed for the communications between wireless cores in a WiNoC taking into account the dielectric material and compositions of the transmission medium within the chip package, such as water vapour, oxygen, carbon dioxide, etc Such mixture of material substance at high frequency causes dielectric propagation loss (DPL), and molecular absorption attenuation (MAA) of the electromagnetic wave travelling between the cores, which have considerable impacts on the performance of the WiNoC.

RELATED WORKS

CHANNEL MODEL FOR POINT-TO-POINT

CAPACITY OF RELAY CHANNEL IN A WINOC

BOUNDS ON THE CHANNEL CAPACITY

Findings

CONCLUSION