Multicast-Aware High-Performance Wireless Network-on-Chip Architectures

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Today's multiprocessor platforms employ the network-on-chip (NoC) architecture as the preferable communication backbone. Conventional NoCs are designed predominantly for unicast data exchanges. In such NoCs, the multicast traffic is generally handled by converting each multicast message to multiple unicast transmissions. Hence, applications dominated by multicast traffic experience high queuing latencies and significant performance penalties when running on systems designed with unicast-based NoC architectures. Various multicast mechanisms such as XY-tree multicast and path multicast have already been proposed to enhance the performance of the traditional wireline mesh NoC incorporating multicast traffic. However, even with such added features, the multihop nature of the wireline mesh NoC leads to high network latencies and thus limits the achievable system performance. In this paper, to sustain the high-bandwidth and high-throughput requirements of emerging applications, we propose the design of a wireless NoC (WiNoC) architecture incorporating necessary multicast support. By integrating congestion-aware multicast routing with network coding, the WiNoC is able to efficiently handle heavy multicast injections. For applications running with a broadcast-heavy Hammer cache coherence protocol, the proposed multicast-aware WiNoC achieves an average of 47% reduction in message latency compared with the XY-tree-based multicast-aware mesh NoC. This network level improvement translates into a 26% saving in full-system energy delay product.