An Exploration on Quantity and Layout of Wireless Nodes for Hybrid Wireless Network-on-Chip

As the scaling of integration, massive remote communication has become the main bottleneck of system performance for network-on-chip (NoC). Most packets have to travel long distances from source to destination, leading to long latency and severe contention. Hybrid Wireless NoC(HWiNoC) has emerged as a popular method to handle remote transmission in NoC, in which packets can be modulated to wireless channel and delivered to remote nodes in just one hop. However wireless nodes introduces non-trivial overhead. In this paper, we explore the quantity and layout of wireless nodes in HwiNoC. We first define three optimization rules, with the main optimization targets being minimizing Maximum Distance(MD), Average Distance(AD) and Sum of Distance from each nodes to wireless nodes(SD) respectively. We further decide the optimal wireless count to ensure the maximum performance gain per wireless node, and propose a novel heuristic to find a near optimal target layout. Experiment results show that minimizing AD and SD outperforms minimizing MD by 6.21% and 8.19% in terms of average packet latency under synthetic traffic patterns, while minimizing AD exhibits more stability than the other two rules. And our heuristic layout introduces less than 1% performance loss in terms of AD and SD compared with the enumerated optimal layout, while the calculate complexity is reduced from O(N!) to O(N).