Overview

Hydra is a flexible wireless network testbed being developed at UT Austin. Our focus is on networks that support multiple wireless hops and where the network, especially the MAC, takes advantage of sophisticated PHY techniques, such as OFDM and MIMO. We argue that for this domain simulation alone is not adequate and that working prototypes are needed to validate algorithms and protocols. Hydra nodes consist of a flexible RF front-end and a general purpose machine with a software based MAC and PHY. Using the frameworks of the Click modular router and GNU Radio and coding in C++ makes it relatively easy to implement working prototypes of crosslayer designs that require custom MACs and PHYs.

Block Diagram of a Hydra Node.

Each Hydra node is composed of a general purpose PC and programmable RF front-end. The RF front-end interfaces to the general purpose host through a USB 2.0 connection. The figure above shows the system configuration for a Hydra node. The RF front-end performs some basic filtering as well as upconversion and downconversion. All of the communication protocols for Hydra (i.e. network, MAC, and PHY) are implemented in a software framework that runs on a general purpose processor (GPP). Although an FPGA or ASIC implementation would provide better performance, the GPP complements our goals for low development time and accessibility (i.e. using a programming language with which most wireless researchers are famiiar). The use of a GPP also reduces cost. Click on the MAC, PHY, or RF sections of the figure above to learn more about the hardware and software used to implement the Hydra testbed.