An Experimental Protocol Stack for Cognitive Radio Networks and
Its Integration with the Future Internet

Project Objectives:

This project started in 2006, and is supported under NSF NeTS-FIND, collaborating with Carnegie Mellon University, University of Kansas and Blossom Research/GNU. The 3-year project is aimed at building an experimental protocol stack for cognitive radio networks and integration with the future Internet.

Technology Rationale:

Adaptive networks of cognitive radios represent an important research opportunity for both wireless and networking communities.  Perhaps for the first time in the short history of networking, cognitive radios offer the potential for organic formation of infrastructure-less collaborative network clusters with dynamic adaptation at every layer of the protocol stack including physical, link and network layers.  This capability has significant implications for the design of network algorithms and protocols at both local/access network and global internetworking levels.  At the local wireless network level, an important technical challenge is that of defining a control protocol framework for cross-layer collaboration between radio nodes, and then using this control information to design stable adaptive networking algorithms that are not overly complex.  At the global internetworking level, ad hoc clusters of cognitive radios represent a new category of access network that need to be interfaced efficiently with the wired network infrastructure both in terms of control and data.  End-to-end architecture issues of importance include naming and addressing consistent with the needs of self-organizing network clusters, as well as the definition of sufficiently aggregated control and management interfaces between cognitive radio networks and the global Internet.

Technical Approach:

This project has two major thrusts: the first is to identify broad architectures and protocol design approaches for cognitive networks at both local network and the global internetwork levels.  This architectural study should lead to the design of control/management and data interfaces between cognitive radio nodes in a local network, and also between cognitive radio subnetworks and the global Internet.  The second thrust is to apply these architectural and protocol design results to prototype an open-source cognitive radio protocol solution (the CogNet stack) and use it for experimental evaluations on emerging cognitive radio platforms.  A number of architectural issues will be examined as we try to identify an efficient and complete solution - these include control and management protocols, support for collaborative PHY, dynamic spectrum coordination, flexible MAC layer protocols, ad hoc group formation and cross-layer adaptation.

The network architecture is shown in the figure below. The following cognitive radio networking capabilities as the baseline and will design our control protocol implementation:

• API for PHY layer adaptation (agility, change of modulation waveform), and support for collaborative PHY
• Spectrum coordination protocols that facilitate dynamic sharing among radio nodes using mechanisms such as etiquette policies or spectrum server
• Autoconfiguration - bootstrapping and topology discovery - protocols that can be used to establish network connectivity after a cognitive radio device is turned on or enters a new service area
• Flexible MAC framework that permits programmable functionality capable of dynamic selection of channel sharing modes based on observed network conditions and traffic demands
• Network layer protocols that support service discovery, naming, addressing and routing in ad hoc wireless constellations, including features that provide economic incentives for collaboration.  This network layer will interface with a cross layer network management overlay that can provide aggregated representations of the cognitive subnetwork state to the future Internet.

Results To Date and Future Work Plan:

The project started in 2006. On the hardware part, a USRP/GNU platform is being developed for software-defined radios. The USRP provides a set of RF daughterboards to perform analog RF up and down conversion, 1 million gates of FPGA, typically used to convert to and from complex baseband, 4 high speed A/Ds (64 MS/sec 12-bit), 4 high speed D/As (128 MS/sec 14-bit) and a USB 2.0 controller chip. For the network architecture and software support, a stack of control protocols is being designed which utilize a CSCC-based control plane to perform control functions for cognitive radio networks. The key components of the control protocol include bootstrapping, discovery, cross-layer routing and naming/addressing. The designed protocols will be first evaluated using ns2 simulations and they will later be implemented in the cognitive radio platform.