Combining SDM-Based Circuit Switching with Packet Switching in a Router for On-Chip Networks

Abstract

A Hybrid router architecture for Networks-on-Chip “NoC” is presented, it combines Spatial Division Multiplexing “SDM” based circuit switching and packet switching in order to efficiently and separately handle both streaming and best-effort traffic generated in real-time applications. Furthermore the SDM technique is combined with Time Division Multiplexing “TDM” technique in the circuit switching part in order to increase path diversity, thus improving throughput while sharing communication resources among multiple connections. Combining these two techniques allows mitigating the poor resource usage inherent to circuit switching. In this way Quality of Service “QoS” is easily provided for the streaming traffic through the circuit-switched sub-router while the packet-switched sub-router handles best-effort traffic. The proposed hybrid router architectures were synthesized, placed and routed on an FPGA. Results show that a practicable Network-on-Chip “NoC” can be built using the proposed router architectures. 7 × 7 mesh NoCs were simulated in SystemC. Simulation results show that the probability of establishing paths through the NoC increases with the number of sub-channels and has its highest value when combining SDM with TDM, thereby significantly reducing contention in the NoC.

Centralized parallel multi-path multi-slot allocation approach for TDM NoCs

“…The dynamic connection allocation techniques can be divided into two categories: i) centralized [6]- [10] and ii) distributed allocation [3], [11], [12]. The centralized allocation is done by a central module.…”

Parallel probe based dynamic connection setup in TDM NoCs

“…Dynamic path searching methods can be divided into centralized [2], [8] and distributed solutions [9], [10]. In centralized solutions a special node is used to schedule all the connections in the network.…”

“…Traditionally, distributed solutions in TDM NoCs are implemented with configuration packets [9]. Configuration packets such as setup, tear-down and Ack/Nack, require a separate Best Effort (BE) network during the connection establishment procedure.…”

“…For distributed dynamic solutions [5], [9], the BE NoC is not only used for delivering configuration packets, but also for path searching. Centralized dynamic solutions also depend on a BE NoC [8] for delivery of configuration information.…”

“…3) Path searching algorithms: Unlike other distributed path setup solutions [9], our probe based solution imposes no constraint on the routing algorithm. Hence, any probe searching algorithm with reasonable hardware cost is applicable.…”