Unlimited "sky": the coming of the era of software radio

Author: Kwan Tan wireless and Internet Group

Not long ago, I attended a class party.

Friends are learning the computer, then talk to me now. I said: "I was doing research on wireless. ”

"Oh, what standard?"

"What the standard is not," I said, "I was doing my own wireless physical layer.

”

"Oh, you now diverted to get hardware?" asked the friend is very surprised.

"No, no, I don't understand the hardware.

I just write software to do with software. "I tried to explain.

"It sounds cool.

However, this may? ... "

Over the past two years, similar dialogue around often.

Every time I speak to someone in my general purpose PC and use the software for all wireless underlying functionality (i.e., software defined radio), most people are so skeptical. I fully understand that such doubt is reasonable, because if two years ago, I would have the same suspect. In the people's common sense, common CPU is not designed to work with digital signal processing. Therefore, wireless underlying communication needs of high-speed signal processing should be hardware circuit and dedicated DSP processors. I just started research on software defined radio, best software-defined radio systems that achieve a few hundred Kbps narrowband data communications; and our goal is to high-speed broadband wireless communications systems, such as WiFi, 54Mbps broadband reached 20MHz data rate. This is two orders of magnitude above difference!

le="TexT-inDenT: 2em">Two years later, my Microsoft wireless and Internet Group has successfully developed a name of "Sora" software-defined radio system. Using ordinary commercial PC platform and generic wireless front, we succeeded in Sora for IEEE802.11a/b/g all physical layer and media access layer protocol, and can and commercial hardware adapter for seamless communication and achieve similar performance. The research results obtained the network community's top meeting NSDI2009 's best paper awards. In the autumn of 2009, we further in Sora platform on fourth-generation wireless communications standard 3GPPLTE uplink. This further illustrates the use of existing multi-core CPU, we not only can you implement existing wireless standard, but can also be used to achieve the standard in the future.

Figure 1 Sora logo.

Written by China Zhuan script SORA letters

Therefore, when the above dialogue here, I smiled and replied, "Yes, this is possible.

You know, the era of software-defined radio. ”

Tell you a new term: software defined radio

In a traditional wireless communication system, the key underlying operations, such as the physical layer of signal processing, and the media access layer control, are essentially use dedicated hardware chip.

However, the dedicated hardware chip once design production, you cannot modify it. Moreover, the design of a hardware chip cost is very high, so only a few large communications companies have the ability to design and produce communication chip. This greatly restricted the wireless technology research and development, makes the upgrading needs of wireless technology for ten years, or even longer period. While the idea of software radio is in common computing platforms (such as CPU), using a software program that does most of the underlying features of wireless. Because it is software, so you can easily modify and upgrade. And the development of general-purpose processors, much faster than proprietary hardware and processor. This is because the generic processor there is behind a vast market driving forces, Moore's law totalIn general the processor plays a major market.

However, a generic processor can perform high-speed wireless signal processing?, after all, the CPU is not design for signal processing applications.

In fact, prior to the Sora, there is a general view is that the CPU's speed is insufficient, and therefore must rely on dedicated hardware devices. But Sora changed people's views on software defined radio.

Sora secret

As mentioned earlier, in general the processor speed of the wireless signal processing is faced with great challenges.

First of all, high-speed broadband wireless signal requires a high sampling rate, and therefore requires high-speed i/o bandwidth. Now all common USB2.0 high speed serial interface can support the speed 400Mbps, in order to achieve the WiFi, we need at least 1.4Gbps speed; whereas in order to support the new 802 .11n, we need 5G ~ 10Gbps speeds. Secondly, how universal CPU architecture achieve high-speed digital signal processing algorithm is an open issue. Past simple calculation shows that implementation of 802 .11A requires the calculation of the amount already exceeds the available capacity of the latest CPU. This is why many people expressed doubts as to the software defined radio. Finally, a wireless system is a real-time system, hence requires software radio is capable of precise control of response time. This real-time requirements of accuracy in the nanosecond level. But now the real-time operating system can reach only a millisecond (there are three orders of magnitude difference!)

Sora system both hardware and software technology to address these challenges.

First of all, we developed a new PC input and output cards, called Wireless Control Board. Wireless Control Board has adopted the latest PCIe standard enables 10Gbps transmission rate above, therefore, can meet the needs of most of the wireless technology. Wireless Control Panel connected wireless transceiver antenna and PC, and high-speed transfer between them.

Figure 2Sora PCIe interface based wireless control panel

Secondly, we consider a wireless signal processing algorithms of realization of the strategy, and hardware implementation of a completely different way.

For example, CPU architecture, our extensive use lookup tables to speed up the algorithm; and this in hardware implementation is unthinkable, as in a traditional hardware wireless system, memory is a scarce resource. Sora full use of modern CPU's many features, such as cache and SIMD instructions, and at the same time you can take advantage of multiple CPU core parallel algorithm implementation. These software optimization techniques for greatly improving the signal-processing algorithms in CPU execution speed, so you can meet the requirements of real-time communications.

Finally, Sora adopts a very simple but effective way to achieve real-time support.

Sora can be multi-core system of several nuclear separated from the operating system. The CPU core is only used for software defined radio, and the operating system cannot be dispatched to these nuclear, software defined radio guaranteed real-time performance.

e="TexT-inDenT: 2em" align="center">

Figure 3 Sora software radio systems.

Taiwan-based exclusively on a PC

Sora-present: brave pioneer

September 2008, we have almost completed a software radio systems, the project team members are excited to get together to express their opinions, to give the system a good name.

Prior to this, we are the used MicrosoftResearch SoftwareRadio descriptive name. Discussion for a long time, have a good idea. At this time, because we use multi-core CPUs, so it has been proposed by Cora, but in the past have had too many research project called Cora. Then, suddenly, a colleague, followed by suggestions: "why not call Sora (SOftwareRadio's first two letters). " This all down and sobering, all boasting praise: the birth of a good name often came from the most simple of inspiration.

Back home, I searched on the Internet and found in Sora is Japanese for "sky".

At the same time, Sora is Disney animation game "Kingdom Hearts" in the hero. In the story, the sixteen-year-old brave boy, holding a "key cutters", save the world. These are just a metaphor for our Sora software radio systems of expectation, hope it will inspire more inspiration, open up another sky, so as to promote research on the entire wireless system.

Figure 4 to celebrate the Sora best paper Awards, we received bonuses making commemorative t-shirt.

Photo t-shirt back. Reads: you Sora, imagination is your limit.

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