[1] D. Raychaudhuri, N. B. Mandayam, J. B. Evans, B. J. Ewy, S. Seshan, P. Steenkiste, "CogNet - An Architectural Foundation for Experimental Cognitive Radio Networks within the Future Internet,"
In Proc. of MobiArch’06 December 2006.

[2] X. Jing and D. Raychaudhuri, "Global Control Plane Architecture for Cognitive Radio Networks,"  In Proc. IEEE CogNet’07 Workshop (with IEEE ICC) June 2007.

[3] D. Raychaudhuri,  X. Jing, I. Seskar, K. Le and J. B. Evans, "Cognitive Radio Technology: From Distributed Spectrum Coordination to Adaptive Network Collaboration," Accepted for publication in Pervasive and Mobile Computing (PMC) Journal, 2008.

[4] D. Raychaudhuri and X. Jing, "A spectrum etiquette protocol for efficient coordination of radio devices in unlicensed bands,"  In Proc. PIMRC 2003, Beijing, China, September, 2003.

Cognitive Radio Networks (CogNet)

Project Objectives:
This project (which is a part of NSF’s “FIND” future Internet research initiative) aims to develop an architectural foundation for the integration of emerging cognitive radio networks with the global Internet. This is a joint project involving collaboration between WINLAB at Rutgers University, University of Kansas, CMU and a startup company, Blossom Research, involved in developing the software defined GNU radio platform. The project consists of two integrated research thrusts. The first is to identify broad architecture and protocol design approaches for cognitive networks at both local network and at global inter-network levels. This architectural study aims to design the control/management and data interfaces between cognitive radio nodes in a subnetwork, and between cognitive radio subnetworks and the global Internet. The second thrust is to apply these architectural results towards prototyping a comprehensive cognitive radio protocol solution (the CogNet stack) and use it for experimental evaluations on emerging cognitive radio platforms.

Technology Rationale:
Emerging software-defined cognitive radios represent a potentially disruptive technology in the wireless field, with many potential benefits including ultra-high speed radio transmission, dynamic spectrum sharing, robust cross-layer adaptation and collaborative networking. The first generation of cognitive radio hardware has started to emerge, and it is therefore important to design the corresponding protocol and software framework that will enable use of the technology in wireless networks.

Technical Approach:
The CogNet protocol design considers the unique requirements of cognitive radio networks which adapt to dynamically changing spectrum usage conditions, physical topology/density, and end-user service requirements. Key design objectives for the cognitive radio protocol stack include:

• Adaptation of physical-layer radio parameters (frequency agility, change of modulation waveform, power/rate control);

• Integrated support for dynamic spectrum coordination between collocated cognitive radio nodes;

• Auto-configuration protocols to establish network connectivity after a cognitive radio device is turned on or enters a new service area;

• Flexible medium access control (MAC) framework that permits programmability of channel sharing modes based on observed network conditions and traffic demands;

• Efficient integration of cross-layer control information in the cognitive radio network with end-to-end protocols used in the wired Internet.

In a collaborative wireless network, radio nodes avoid interference at the PHY and MAC layers by opportunistically forming or joining an ad hoc network which carries data packets over multiple radio hops, each operated at relatively high speed and low power. The CogNet protocol architecture is based on the concept of a “global control plane (GCP)” which uses a separate physical channel for control messaging. The CogNet control plane shown in the figure below incorporates several key components including a radio bootstrapping function, a discovery process to provide global awareness of radios within a subnetwork, a data path setup protocol for establishing multi-hop path for collaborative data forwarding, and a naming/addressing scheme for allocating network addresses and name-to-address translation.

CogNet Protocol Architecture

The data plane shown in the figure has an agile physical layer which can sense spectrum opportunities and rapidly move to newly available bands. The flexible MAC layer supports for switching between different media access mechanisms to achieve the best performance under different network topology and traffic conditions, e.g., in a sparse network, CSMA-based MAC may be appropriate, while in a dense network, it is preferable to use a TDMA-like MAC for scheduling to avoid excessive channel contention. The GCP provides a generic framework to exchange control information to implement these and other network adaptation functions. Details of the generic GCP protocol, including bootstrapping, discovery, naming/addressing and data path setup were given in last year’s progress report and are not repeated here. During this reporting period, we focused on using the GCP protocol framework to implement two important cognitive radio scenarios, specifically (a) dynamic spectrum coordination between co-located cognitive radio nodes; and (b) MAC adaptation by a group of collaborating cognitive radio nodes participating in an ad hoc network. A significant part of this year’s effort was spent on implementing the above mentioned GCP usage scenarios on the ORBIT radio grid testbed and related GNU radio platforms. Further details are provided in the progress summary section that follows.

Results To Date and Future Work Plan:

A specific protocol architecture has been designed for the above requirements, based on the concept of a “global control plane” (GCP) for dissemination of control information between cognitive network nodes. The proposed CogNet architecture has been evaluated using ns2 simulations, and is currently being validated via real-time prototyping on the ORBIT radio grid testbed at Rutgers. This GCP-based control protocol has been used to implement dynamic spectrum coordination in dense multi-radio environments as reported in a recent DySpan08 paper [Jing, et al]. The key adaptive medium access control (MAC) component for this protocol stack has been prototyped successfully using GNU radio platforms at CMU, and this capability is now being integrated into the overall CogNet software running on the ORBIT radio grid testbed. A GNU open source release of the CogNet software is planned at the conclusion of this project in late 2009.

Prof. D. Raychaudhuri
732-932-6857 Ext. 638

ray (AT) winlab (DOT) rutgers (DOT) edu    

GNU/USRP2 Board used for cognitive radio experiments


Microsoft Cognitive Radio Workshop Presentation

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