George A. Vlantis

COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - Dynamic Frequency Hopping Communities for Efficient IEEE 802.22 Operation

One of the key challenges of the emerging cognitive radio-based IEEE 802.22 wireless regional area networks (WRANs) is to address two apparently conflicting requirements: ensuring QoS satisfaction for WRAN services while providing reliable spectrum sensing for guaranteeing licensed user protection. To perform reliable sensing, in the basic operation mode on a single frequency band (non-hopping mode), one must allocate quiet times, that is, periodically interrupt data transmission that could impair the QoS of WRAN. This critical issue can be addressed by an alternative operation mode proposed in 802.22 called dynamic frequency hopping (DFH), where WRAN data transmission is performed in parallel with spectrum sensing without interruptions. DFH community, as described in this article, is a mechanism that coordinates multiple WRAN cells operating in the DFH mode, such that efficient frequency usage and reliable channel sensing are achieved. The key idea of DFH community is that neighboring WRAN cells form cooperating communities that coordinate their DFH operations

Efficient, flexible, and scalable inter-network spectrum sharing and communications in cognitive IEEE 802.22 networks

Although avoiding harmful interference to licensed incumbents is the prime concern of the system design for the emerging IEEE 802.22 standard, another key design challenge to cognitive radio based 802.22 systems is how to dynamically share the scarce spectrum among the collocated 802.22 network cells so that performance degradation, due to mutual co-channel interference, is effectively mitigated. This paper describes a distributed, cooperative, and real-time spectrum sharing protocol called On-Demand Spectrum Contention (ODSC) that employs interactive MAC messaging on an inter-network communication channel to provide efficient, scalable, and fair inter-network spectrum sharing among the coexisting 802.22 cells. Additionally, in order to support ODSC and other inter-network coordination functions in 802.22, we introduce a beacon-based inter-network communication protocol called the Beacon Period Framing (BPF) protocol that realizes a reliable, efficient, and scalable over-the- air inter-network communication channel utilizing the occupied RF channels of the network cells.

NPSE: A High Performance Network Packet Search Engine

This paper describes the NPSE, a high-performance SRAM-based network packet search engine which has the primary application of supporting IPv4 and IPv6 forwarding. It is based on a high-speed hardware implementation of a tree-based storage and retrieval algorithm, which is memory and power-efficient compared to traditional CAM-based look-up methods.