Wendong Hu

IEEE 802.22: The first cognitive radio wireless regional area network standard

This article presents a high-level overview of the IEEE 802.22 standard for cognitive wireless regional area networks (WRANs) that is under development in the IEEE 802 LAN/MAN Standards Committee.

NetBench: a benchmarking suite for network processors

Introduces NetBench, a benchmarking suite for network processors. NetBench contains a total of 9 applications that are representative of commercial applications for network processors. These applications are from all levels of packet processing; small, low-level code fragments as well as large application level programs are included in the suite. Using SimpleScalar simulator we study the NetBench programs in detail and characterize the network processor workloads. We also compare key characteristics such as instructions per cycle, instruction distribution, branch prediction accuracy, and cache behavior with the programs from MediaBench. Although the architectures are similar for MediaBench and NetBench suites, we show that these workloads have significantly different characteristics. Hence a separate benchmarking suite for network processors is a necessity. Finally, we present performance measurements from Intel IXP1200 Network Processor to show how NetBench can be utilized.

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.

On centralized and distributed frequency assignment in cognitive radio based frequency hopping cellular networks

Frequency Assignment is an important approach to mitigate multi-cell interference in cellular systems. In this paper, we consider frequency hopping as one possible frequency assignment approach. In particular we focus our attention on cognitive radio cellular systems as one of the very promising future access technologies, taking IEEE 802.22 as an example. While the optimal frequency assignment for such a system is conceptually straightforward as well as computationally complex, we demonstrate that usage of distributed methods leads to a significant loss of assignment efficiency. In addition, we suggest means of mitigating this adverse effect.