Reconfigurability in FPGAs

Field Programmable Gate Arrays (FPGAs) are composed of configurable logic elements interconnected by configurable switch matrices. FPGAs configuration is contained in a configuration bitstream, which contains every function and switch position to be configured for implementing a given design. Nowadays FPGAs allow processing partial bitstreams, reconfiguring just a sector of the FPGA while the remaining logic stays unaffected. When evolving a circuit on an FPGA, one can consider the logic cell as the basic element; thus, evolving each logic cell configuration and the whole connectionism schema. However, doing that implies a huge search space to explore and can easily prevent the evolution algorithm to find a solution. A common technique to constraint the search space is to define a basic block as a set of logic cells. In this way each basic block can be an artificial neuron, a fuzzy rule, or a more complex cell in a general way. Another option is to constraint the connectionism: with layered architectures, constraining connectionism to a certain neighborhood, or just defining a fixed connectionism.

Hardware, like software, can be designed modularly, by creating subcomponents and then higher-level components to instantiate them. In many cases it is useful to be able to swap out one or several of these subcomponents while the FPGA is still operating. Normally, reconfiguring an FPGA requires it to be held in reset while an external controller reloads a design onto it. Partial reconfiguration allows for critical parts of the design to continue operating while a controller either on the FPGA or off of it loads a partial design into a reconfigurable module. Partial reconfiguration also can be used to save space for multiple designs by only storing the partial designs that change between designs.

A common example for when partial reconfiguration would be useful is the case of a communication device. If the device is controlling multiple connections, some of which require encryption, it would be useful to be able to load different encryption cores without bringing the whole controller down.

Partial reconfiguration is not supported on all FPGAs. In current versions of software, Xilinx supports partial reconfiguration on Virtex II, Virtex II Pro, and Virtex 4 FPGA lines. A special software flow with emphasis on modular design is required. Typically the design modules are built along well defined boundaries inside the FPGA that require the design to be specially mapped to the internal hardware.

Introduction to Wireless Sensor Networks

A Wireless Sensor Network (WSN) is a computer network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.

In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery. The size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust. The cost of sensor nodes is similarly variable, ranging from hundreds of dollars to a few cents, depending on the size of the sensor network and the complexity required of individual sensor nodes. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth

Wireless Sensor Networks (WSN) have wide and varied applications. A smart sensor is a collection of integrated sensors and electronics. When these types of sensors are used in WSNs, very powerful, versatile networks can be created and used in situations where traditional wired networks fail. These sensor networks can be used for emission monitoring systems in the harsh environment of automobile exhaust systems or in large buildings for more consistent climate control. Research is already being conducted with respect to low-power dissipation for deep space missions. While the space station research is concentrating on direct networks, this would be an excellent case were the flexibility of wireless networking could be aptly applied.

Before we can use WSN in these applications, however, we need to overcome several obstacles, including limited energy, computational power, and communication resources available to the sensors in the network.

A wireless smart sensor network node can include MEMS components such as sensors, RF components, actuators, or CMOS building blocks such as interface pads, data fusion circuitry, specialized and general purpose signal processing engines or micro-controllers. These individual nodes can be resource-aware – expose their system resources to other node over the network and manage to reduce participation in the network, and resource-adaptive – can adapt to the environment that they are in and change the way they communicate with other nodes. More important than the individual data in a wireless sensor network is the aggregate data that the network contains, for this gives a clear, multi-dimensional view of the sensing environment.

Federal Communication Commission explains Software Defined Radio as “A radio that includes a transmitter in which the operating parameters of the transmitter, including the frequency range, modulation type or maximum radiated or conducted output power can be altered by making a change in software without making any hardware changes”. Software defined radio technology is achieving rapidly growing acceptance as a military communications platform because of its security advantages and its ability to be reconfigured to meet specific mission parameters. Programmable logic offers the performance, flexibility, and cost-effectiveness required for SDR systems.

Introduction:

Consider a problem where in you are using wireless fax, the protocol often differs from country to country which implies different hardware for different countries. Due to the present day advances in silicon ,a probable solution would be to use a single Software Defined Radio set with an all-inclusive software range can be used in any mode, anywhere in the world.

The equipment needed would be just changing the service type, the mode, and the modulation protocol involves selecting and launching the requisite computer program. Making sure the batteries are adequately charged if portable operation is needed.

In a nut-shell, the problem is to provide a single radio transceiver for all the applications such as:

1.Cordless telephone

2.Cell phone

3.Wireless fax

4.Wireless e-mail system

5.Pager

6.Wireless videoconferencing unit

7. Wireless Web browser

8. Global Positioning System unit and other functions