Research On Topology And Routing Algorithm In Hierarchical NoC

Network on chip(NoC)is an important means to further improve the communication efficiency of multiprocessor system on chip,but with the increase of the number of on chip processing units,the density and distance of the nodes on the network limits the performance improvement,therefore,the researchers proposed a hierarchical NoC interconnection structure.This paper focuses on the research on hierarchical NoC topology and routing algorithm.In order to further improve the communication efficiency of the top network in hierarchical NoC,we proposed a hierarchical NoC topology based on top network diagonalization according to the analysis of the existing hierarchical NoC technology;For the problem of increasing network delay caused by excessive NoC relay nodes,we propose a hybrid Ring-Torus hierarchical NoC topology;For the problem of poor load balancing of deterministic shortest routing algorithm in hierarchical NoC,a hybrid adaptive routing algorithm based on virtual channel assignment is proposed.The specific research work is as follows.In order to further improve the communication efficiency of the top network in hierarchical NoC,we proposed a hierarchical NoC topology based on top network diagonalization.The structure is designed with two levels: the bottle network is connected with Mesh structure responsible for the communication between local nodes;on the top network,we add two diagonal links to the Mesh structure which provides express lane for the remote nodes to further reduce the network latency.The experimental simulation shows that the latency of HDXY structure is lower than Mesh and CHMesh structure in the network with 16 and 64 nodes.And the improvement is higher in the larger network.For the problem of increasing network delay caused by excessive NoC relay nodes,we propose a hybrid Ring-Torus hierarchical NoC topology.The structure is cluster connected and combines the features of Torus and Ring structure.There are no relay nodes in the structure;each router in the structure has three ports: one for the communication between clusters and two for the communication within cluster.It largely reduces the network delay.The experimental simulation shows that the delay of RT structure is lower than Mesh and tNo C in the network with 16 and 64 nodes network with synthetic traffic mode,only in 16 nodes network with Rent traffic,the delay of the RT structure is higher than tNoC structure.For the problem of poor load balancing of deterministic shortest routing algorithm in hierarchical NoC,we propose a hybrid adaptive routing algorithm based on virtual channel assignment-HAR algorithm.HAR algorithm has two stages: adaptive routing and deterministic routing.The routing process assigns different virtual channels for each stage.The routing is in the channel index descending order and it ensures that the routing algorithm is deadlock free.According to the experimental simulation,the saturation throughput of HAR algorithm is increased by 43.2% and 6.2% compared with deterministic routing under the synthesized and Rent traffic mode.