As we move forward towards the next generation of wireless pro tocols, the push for a better radio physical layer is ever increasing. Conventional radio architectures are limited to narrow operating regions and fails to adapt with changing technology. This is fur ther strengthened with the advent of cognitive radio, which needs a more versatile and flexible framework that is programmable within the timing constraints of a protocol. In this paper we present an architecture for Software Defined Cognitive Radio that caters to the specific baseband processing requirements in a changing environ ment. We aim to provide more flexibility by de-constructing the radio pipeline into a framework of user controlled kernels that can be reconfigured at run-time. This architecture provides the bare bones of a OFDM based radio physical layer that can adapt to per form a varied number of tasks in different radio networks. We also present a novel message based real-time reconfiguration method to transmit and receive a wide range of waveforms used in concurrent wireless protocols.
In this paper, we present an intelligent physical layer for cognitive mesh networks. It is well recognized that wireless mesh networks suffer from the inherent property of per hop delay attributed to store and forward routing and channel contention. We show that an intelligent physical layer coupled with efficient traffic engineering and channel allocation mechanism will reduce latency. In this paper, we discuss the evolution of an OFDM receiver, with sufficient software control to aid reconfigurability, capable of receiving and decoding information on different set of subcarriers, and also capable of switching the incoming signals to a different part of the available spectrum on the fly. Equipped with this enhanced receiver we propose a mechanism for wireless wormhole routing, which employs frequency domain switching between subchannels where each subchannel is defined by a set of subcarriers. The OFDM receiver handles three primitives: transmit, receive and relay rather than just transmit or receive. Instead of a contention based, store and forward routing, a relay oriented physical layer has been proposed to reduce latency. The processing pipeline at an intermediate node no longer involves higher layer processing, and the hardware relays the incoming signal on-the-fly to a different part of the spectrum allowing for a full duplex transmission as the transmitter can relay signals while it is receiving on a different subchannel.
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