Parallel overloaded CDMA crossbar for network on chip

Abstract

For high performance of Network on Chip (NoC), Code Division Multiple Access (CDMA) technique is used recently due to its fixed communication delay, reduced area utilisation and low power consumption. The CDMA system uses Walsh based spreading code which improves the bandwidth efficiency. On the contrary, it is not effective when the number of nodes present in the system increases. Overloaded CDMA (OCDMA) is presented for such large network systems. In this paper, OCDMA crossbar is modified and advanced with parallel encoding and decoding operation using orthogonal gold codes for improving the speed of crossbar thereby obtaining high performance in NoC switch. A modified crossbar consisting of extra processing elements is used to enhance the performance of NoC based System on Chip (SoC) system. This work is simulated on Xilinx tool and implemented in Vertex-6 (XC6VLX760) Field Programmable Gate Array (FPGA) device. The proposed work is implemented for four ports, eight ports and sixteen ports with deterministic X-Y routing algorithm in 3 3 NoC design with mesh topology. This NoC switch shows 9.79% improvement in delay and shows 20.76% improvement in power consumption when compared to the existing CDMA NoCs for 8 bit data packet.switch has five input port, five output port (four directional and one local) and crossbar with control module (arbiter). The four bi-directional ports are connected with neighboring switches for transfer of data between the source and destination [4]. The local port is used as a processing element (PE) and is responsible for communication between the port and crossbar.This paper proposes a new method for NoC with fixed latency, reduced system cost and power consumption. Recently, CDMA is used to transfer data between the input and output in NoC switch [5]. Fig.1 depicts the structure of CDMA NoC switch. NoC switch has neither solid design nor standard protocol and hence can be designed flexibly to meet the user requirements. The proposed method is implemented for NoC switch using a CDMA crossbar with 2-D mesh topology and 3 3 NoC designed with deterministic X-Y routing algorithm. The routing of data initially searches along the X-direction of destination router and proceeds to the Y-direction. Depending on the destination availability, the distance between the source and destination switch is calculated and transferred to the neighboring switches. Since each port has FIFO buffer, store and forward packet switching [6] is used for the proposed work. The crossbar is the key module for NoC switch as it affects the switch performance and provides multiple access for the data packets. The primary multiple access technique, Time Division Multiple Access (TDMA) is simple but not efficient for CMP. In TDMA only one port sends the data packet simultaneously leaving the other ports to wait until it releases the physical link, thereby increasing the packet latency. Space Division Multiple Access (SDMA) a dedicated path is created between the ports. CDMA is another traditional multiple access techniq...

Enhanced overloaded code division multiple access for network on chip

“…Moreover, this design can be implemented with minimal delay employing parallelisation techniques similar to the ones proposed in Refs. [13,24].…”

Aggregated CDMA Crossbar With Hybrid ARQ for NoCs

“…The parallel overloaded CDMA (OCDMA) crossbar is presented in [18]. In this work, the overloaded CDMA crossbar is modified with a parallel encoding/decoding circuit using Gold codes for increasing the channel utilization and improving the crossbar throughput.…”