Software Defined Radios The future of wireless technology

Software Defined Radios The future of wireless technology By Zac Lessard

Software Defined Radios what are they? ? n n A radio in which some or all of the physical layer functions are software defined. This is contrasted with older radios where all of their functionality is determined by hardware.

Five Tiers of SDR technology n n n Tier 0 – Pure hardware radios Tier 1 – Software “controlled radios Tier 2 - modulation methods, band selection between wide or narrow, security mechanisms and controls such as hopping pattern management, and wave form selection are all handled by software

Four Tiers Cont. n n Tier 3 – fully programmable radios. Tier 4 - radios are the absolute model of perfection, and they exist only on paper. They are the absolute pinnacle of anything wireless technology could ever even begin to approach. These radios are capable of anything a user can imagine, from storing money transfer information on smart cards, to receiving satellite transmissions in real time.

The history of SDR SPEAKeasy phase I A government program with the following goals: to develop a radio that could function anywhere between 2 Mhz and 2 Ghz, to be able to communicate with the radios used by ground forces as well as air force and naval radios in addition to satellites to develop a new signal format within 2 weeks with no prior preparation To use parts and software from multiple contractors at once n

SPEAKeasy Phase I n n When the project was tested at TF-XXI Advanced Warfighting Exercise it was deemed a success. One problem was that the cryptography engine could not keep up well enough to maintain several connections at once.

SPEAKEasy Phase II n n Phase II made use of an open architecture known as Software communication architecture. This phase of the project was focused on refining the phase one project for use in the field, minimizing the device form factor and getting the system ready for use in the field. 15 months since the start of the project a fully functioning radio was produced. It was so successful that no further development was needed.

Phase II Cont n n This radio only had a range between 4 MHz and 400 MHz data rates between 75 bps and 10 Mbps. 22 different wave forms in addition to GPS and cellular communications. four channels programmed into it at once as well as cellular and GPS at the same time.

A final contributor Joint Tactical Radio System n n n Unlike the other projects that ran from 19921995, JTRS was started in 1998. Goals: to create a radio that will work in harmony with many different other radios, both civilian and military, built in encryption, and wideband networking software to allow the system to form ad hoc wireless networks. The key architecture used in this projected is the Software Communications Architecture(SCA).

Software Communications Architecture

SDR What does it take to make one? n n n Software Defined Radios are made up of: programmable gate arrays Digital Signal processors General processors An antenna A digital to analog converter and an analog to digital converter

How do they work? n n n In the case of a receiver The antenna receives a signal and passes it through the analog to digital converter. The result from the converter is passed to the digital signal processors. The software is left in charge of every other function for establishing and maintaining a connection, such as modulation/demodulation, frequency selection, and encryption. A transmitter simply works opposite to the way a receiver does.

One Example

SDR, Why Use It? n n n Flexibility Can be updated on the fly Interoperability Easier to upgrade by a non-technician using an update bundle. Minimal infrastructure requirements for use in the field Effective for setting up ad-hoc networks

SDR the downsides n n n SDR is often referred to as a silver bullet to many networking problems without any attention being paid to the effort involved. For example, the problem with trying to set up a single unifying network. The competitor’s paradox. The potential for knocking out other networks with accidental misconfiguration by a user. Problems with multiple service levels, and fraud.

Downside Cont n n n Security Issues in: Authentication Authorization Misuse Verification of validity of software updates

Downsides Cont n n Implementation and switchover costs: The upfront unit costs are higher than with ordinary hardware radios. Sometimes customers pay for more flexibility than they actually need. The sunk cost associated with legacy equipment that is no longer used

Limited advancement n n n Even with Software Defined Radio technology advancing rapidly, many of the technologies it is built upon are not advancing nearly as quickly. Moore’s law has helped immensely with processing and memory. Limits on front-end technologies and RF capabilities.

Where could SDR technology Lead? • • The ultimate potential of SDR technology is realized within adaptive array antennas. These intelligent antennas first must detect which direction a signal is coming from, and then adapt its radiation pattern to allow for optimum communication conditions through the use of beam forming. Beam forming is using several antennas together to utilize constructive interference to generate an approprate radiation pattern SDR technology allows a radio to be controlled entirely by software, from this point, system learning and algorithms can be introduced into the radios using methods already applied in artificial intelligence

MIMO n n n Multiple Input Multiple Output devices. These are a class of intelligent antenna. This type of device uses an array of intelligent antennas at both ends of the link. This will allow both the sender and the receiver to adapt to changing environmental conditions and ultimately to create the optimum communication environment.

In Conclusion n Software Defined Radios employ a technology that will ultimately bring a great deal of flexibility and adaptability to the networks of the future. As many benefits as they provide, the technology still has a long way to go before it finds its way into cellular handsets that can exploit the absolute potential of SDR serves as an enabling technology for intelligent radios and MIMO devices.

Any Questions?

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