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Date: 08-08-15

FPGA ingredient: Must in 4G/5G wireless, cloud and data centers

There are three important physical blocks in the electronics hardware. They are Analog, RF and the rest is digital logic circuitry to encode and decode the audio, video and such human Interface and sensor interface data, and also to create/wrap and unwrap the packets of digitized data, along with the core-computing. If you keep the analog input and physical RF transceiver out of your electronic hardware, the rest is just billions of logic gates wired to perform some combinational logic and sequential logic and also to store data temporarily. You can make use of permanently wired logic functions in the form of traditional processor/CPU and use software programs to deliver the digital data-output the way you want, or use a programmable silicon/field programmable gate array (FPGA) which basically rewire the logic blocks and deliver the digital-data output the way you want. For electronics engineer, this concept is not something new. If you look at very earlier 8-bit computer motherboards, there used to be a lot of discrete logic gate chips (74xx series) and also 8085 or 68K processor on the same board. Some part of the digital data processing used to be done on logic gates and much of it on the 8-bit processor. With the advancement of Moore's law, the performance of processor has increased so fast, the relevance of hard wired logic lost its scope in terms of cost and time spent. However there was always demand for hardwired logic circuitry called glue logic. That gave birth to a new concept called programmable logic device(PLD), where the physical connections between the gates can be programmed to achieve a particular logic function, it was a success in the market.

Now electronic engineers by default use PLD for gluelogic for most of the applications. Then came the even more advanced programmable silicon FPGA, which can pack a lot more gates and implement complex logic functions. Initially FPGAs were very-expensive, and consume lot more power and also limited in number of gates. Like how the traditional processors got benefited from higher integration, today's FPGAs also pack billions of gates. Now except for the analog and RF , all the logic functionality in a complex SOC can be implemented on FPGA integrated IC. For some reason if SOC designer decide to use MIPS architecture instead of ARM processor architecture, it is just running a piece of C/RTL code and programming FPGA chips in just a few seconds to become a SOC of different kind. And most importantly the power consumption of FPGA chips has come down significantly in the nodes of 28 nm and down. The cost of FPGA still a issue, but only for high volume applications.

4G/5G kind of a communication systems need to be ready for any kind of digital media standards and also communication protocols which continue to evolve. This writer spoke to Giles Peckham, Regional Marketing Director, Xilinx Europe to learn the latest trends in use of FPGA in wireless, data centres. Below are some of the points shared by Mr. Giles :

On mobile communication challenges such as exponential growth in data, capacity and coverage issues, operational efficiency:
Giles Peckham: At the moment we have an exponential growth in data driven largely by video. Ericsson finds in its analysis, around 40- 60% of its network's capacity is consumed by video. Certainly there are lot of mobile traffic video downloads ,YouTube, and other forms of communication such as instant communication and so on. Moving to Internet of things and other areas, there is vastly increased identity of data.

While increasing the capacity and coverage, there is also need to be more efficient about how we do these things, so you got trends like software defined networks and network function virtualisation including cloud-based processing which driving changes in the architecture for systems to deal with each challenges.
Off course, overriding goal for our customers is to reduce not only the CAPEX and also the OPEX expenses, they're looking to reduce the bill of materials costs, overall cost of ownership, hardware efficiency and to improve the transmission efficiency. We have 5G on the horizon integrating things like Internet of things, device to device communication where humans are not involved, machine to machine communication is being part of that and integration of that into current networks, and than on top of that new technologies in radio access and the new techniques some of which are applied to the baseband. So very big change of networks is required here, it's not about making the network cheaper and bigger.

Actually moving from 4G LTE into LTE advanced, we are finding new technology changes driving things like carrier aggregation. There is pre-5G coming before 5G, it is precursor to what 5G will deliver, a wider variety of ability to support different network communication.

The necessity of FPGA:
Giles Peckham:Different radio access technologies such as 3G 4G integrated with now things like Wi-Fi and Bluetooth, the 3G and 4G also evolve with the MIMO and so on. Its really the rapid change in the technology and the user need to have a standard piece of equipment for porting all of these different technologies which is where this FPGA come in as very strong value proposition. One thing the customer recognise very early on, the current system which is deployed in the field, the ability of FPGA to enable them to have a standard line card which they could program for different applications. Indeed it could be installed in a remote radio unit and reprogrammed over the network to perform a different function due the rereprogramming ability of FPGA. This happens without sending an individual out in a van to shut down the network, change the card, repair the network, saving all that downtime which is very expensive for them. They can do all that on-the-fly by reprogramming these cards, so there is a lot more reusability of line cards.

This is all about the concept of Software defined networks (SDN) or network function virtualisation (NFV).

Use of FPGAs in data centers:
Giles Peckham: Data centers are looking for low-power processing solutions and at the same time they have been asked to increase the performance. Things like search engines for instance, using dedicated piece of hardware for search functions. The dedicated piece of hardware is far more efficient in terms of performance per Watt. FPGA's performance per watt is lot better than a ASSP or general-purpose processor.

It's basically identifying the hotspots while running the code and then creating a hardware coprocessor in a FPGA to offload that function on to it. Basically FPGA serve as accelerators.

Hardware is now less harder and more softer: If you are a software developer you don't need to become a hardware expert to program the FPGA using RTL code. There are programming environments to convert your C language into RTL and into FPGA implementation. In the past we need a hardware engineer to translate from C to RTL and use that to design to program an FPGA and now that is no longer necessary we will talk about that in our next article.

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