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Subsystems and Systems

MIMO and the Battle Between LTE and WiMAX™

Executive Interview: Andy Botka and Carla Feldman, Agilent Technologies with MWJ European Editor -Richard Mumford

February 4, 2009
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Agilent Technologies has launched the N5106A PXB MIMO Receiver Tester for quicker, more accurate testing of Multiple-Input-Multiple-Output (MIMO) receivers earlier in the design cycle. In supporting 2 by 2, 2 by 4 and 4 by 2 MIMO with a bandwidth of 120 MHz the tester delivers up-to-date, versatile signal creation and channel emulation capabilities for the latest LTE and WiMAX standards. The company’s Andy Botka and Carla Feldman discuss the product’s development and applications with Microwave Journal’s Richard Mumford as well as the broader issue of LTE and WiMAX development.

Andy Botka is vice president and general manager, Signal Sources Division. He began his career in 1987 with Hewlett-Packard Corporation as an applications engineer and subsequently held a wide variety of posts in HP and Agilent. These include taking up his first leadership position as product manager for HP’s Microwave Instrument Division (MID) in 1992, followed three years later by a move to Hong Kong to take over marketing management for MID in Asia. He took up his current position in 2007.

Carla Feldman is Wireless Business Unit marketing manager. She joined the company in 1985 and held a variety of positions in product marketing and management in her 15 year tenure within the test and measurement sector of Hewlett-Packard Company and Agilent Technologies, focused on RF/microwave spectrum analysis, optical and digital parametric analysis. Feldman left the company in 2000 but rejoined to take up her current position in 2007.

MWJ – Explain the thinking behind the development of the new MIMO receiver tester.

Botka – Both LTE and WiMAX apply OFDMA and MIMO technology, to improve system capacity. There is a lot of similarity between the two but the way they have chosen to implement their solutions differs significantly.

Agilent specifically architected the PXB with wideband modulation and MIMO in mind. It is inherently a multichannel baseband generator with fading. Basically, what we have done is to bring together what were previously separate pieces in a test system and coordinated them in a way that is easy to use, reconfigure and calibrate. Our belief is that it will help our customers to dramatically reduce their time to market.

Also, MIMO is evolving, as any engineering endeavour would, starting out with lower order systems, but the potential for higher order MIMO, also exists. The practicality and the economics however are yet to be proven. PXB is architected to expand to cover these higher order systems as the market need grows. Agilent’s position is to provide the best engineering tools to our customers removing the barrier to adoption.

Feldman – It was also developed to work seamlessly with the RF equipment investment that had been made for both WiMAX and LTE, so that existing products are not obsolete and can be used in conjunction with the PXB to expand the capability.

Botka – When we bring a new product like this to market, we want to make sure that it plays well with what is already in use. It brings a different level of performance, a different level of integration and a different level of accuracy. However, the Agilent MXA, MXG, ESG products that exist in almost all R&D labs already can be utilised as a companion product to the PXB. And the software investment that we have made in LTE and WiMAX carries forward. So, the same software for signal generation – Signal Studio – and the same software for analysis, which is the vector signal analyser software VSA 89600 can be utilised in these configurations, depending on the problem that is being addressed.

MWJ - In the long term do you see LTE or WiMAX being the dominant technology?

Botka – They both have advantages but fundamentally the problem they are trying to solve and the way they are trying to solve it is similar. WiMAX has a technology head start, but LTE has an infrastructure head start. In the long term beyond 3.9G I would not be surprised if there were some coexistence of these standards in the market, with an LTE variant and a WiMAX variant existing in next generation systems beyond 3.9G. I think most of our customers are evaluating both standards.

Feldman – It also depends on geography. You have some countries that currently have a cellular infrastructure versus emerging countries that are trying to exploit the internet quickly. To get into the world economy it is probably less expensive to deploy WiMAX than a huge cellular infrastructure. We see such places adopting WiMAX faster than somewhere in the US for example. It is not just a WiMAX versus LTE question – you have to consider what technology works best for the particular location.

Botka– Customers working on proprietary systems such as military communications will start with a WiMAX or LTE standard then modify it to meet their needs. The modification could be in terms of which carrier frequency they are using or in terms of additional security.

Feldman – I think there is a pause in the WiMAX market at the moment in order to see what is going to really happen. It has come to the point where it has been developed and is at the stage where it is being tested to see if it is going to go into full scale manufacturing. Whereas LTE is a little bit behind but is catching up. We need to get to 3.9G so we have seen the development of the LTE standard accelerate over the past year.

We are seeing HSPA, and EDGE Evolution as margin plays on the road to 3.9G and demand for those intermediate standards in the cellular ecosystem.

Botka – Demand is definitely growing for LTE.

MWJ - How imminent is the implementation of LTE or WiMAX?

Botka – The difficulty in trying to predict absolute calendar times is that at present I don’t know of any technical impediments to the implementation of WiMAX systems but my suspicion is that the bigger driver would be economic and political in some locations in the world.

No matter what the economic and political situation Agilent’s job is to focus on providing the best engineering tools to make sure that the engineer is not in the critical path of the technology roll out. I think both WiMAX and LTE have made significant investment in the engineering of those new standards. The technology and expertise behind making each of these work is incredible. I have confidence that they will come to market roughly in line with the last published roll-out schedule from the standards bodies.

MWJ – Which technology has the lead at present?

Botka – WiMAX development started sooner and was more intense but recently we have seen LTE ramping up very aggressively. Like previous standards the maturity curve is an S shape and at present the rate of change of WiMAX has stabilised and has started to roll over while LTE is still growing.

The deployment follows an S curve and the engineering effort follows a similar curve. As much as one and a half to two years ago we saw commercial products from our EEsoff Division being used to design and simulate physical layer (PHY). Then our hardware began to be used to turn on and validate those implementations and now we have conformance test systems, drive test systems and the ability to cover the entire life cycle of the development of the standard. One of the unique benefits Agilent has is that it can see and have solutions for the entire life cycle and we are connected across organisations, both within our company and the greater external community to make sure that that the test capabilities are seamless.

MWJ – How easy is this to achieve?

Botka –It is a challenge to find the balance, the balance being specificity and optimisation of a solution versus commonality and linkages, both to other organisations and within product functionality. Agilent strives for excellence as a partner to its customers and that includes making our organisational boundaries invisible in order to support our customers across their development lifecycle.

MWJ – Agilent has representatives on both the WiMAX Forum® and 3GPP. How important is it to be active on these standards bodies and what role do you play?

Feldman – Agilent is an active player in over 30 standards bodies, WiMAX and 3GPP are among them. We are intensively involved in the development of the revisions of the specifications. Working on these standards bodies requires the delicate balance of the technologists with the measurement expert to ensure that the outcome is something that is commercially viable. Our measurement experts strive to work with the technologist to deliver products that can be measured and tested for ultimate market deployment and use.

As a representative on these standards bodies it also enables us to know what is going into the standards and enables us to be able to modify our software to hit the standard’s releases in a very timely, market based manner.

Botka – What we really bring to these forums is our leadership in intellectual property related to measurement. When you look at a very large standard document it is hard sometimes to know what is feasible and the price point of a solution that would need to be deployed to validate that the system is going to work. Sometimes the reality is that the level of certainty required to meet the spec as originally written is not economically feasible. What we offer is our guidance and expertise in recommending other ways of approaching the problem.

Although we have individuals on these standards bodies and working groups, the benefits is that the individual has a vast network of people behind them that they can draw on upon in many technical areas that may need to be addressed.

MWJ – With all these technical brains on these standards bodies is there the danger that a technological route can be taken that is simply not commercially viable?

Botka – The example in technological history that often gets used is VHS versus BETA. BETA was the best technical solution but VHS won! The economics behind VHS trumped the technology benefit of BETA. So, yes I think it is important not to lose sight of the fact that the solution has to provide value to the end user customer and the service provider. Developers have to be working on something that has a realistic chance of getting to market.

MWJ – So, is WiMAX VHS or BETA?

Botka – Good try but no comment!

If you look at the way devices are evolving, the economics of emerging countries around the world really lean towards a WiMAX solution versus the countries that already have an extensive wireless network established, where this existing infrastructure would upgrade fairly easily to LTE. I travel quite a bit and I am intrigued by the idea of having a phone that works everywhere in the world. There is the drive for some ability to have a mobile device engage with the network anywhere in the world, so adding another radio link to a handset is certainly not beyond the ability of engineering capabilities.

There is a potential that both come to market and both have success. I can’t see that as being a significant technical issue.

MWJ – Tell me more about the development of MIMO?

Feldman – MIMO is a technology that is being used for both WiMAX and LTE. It utilizes the diverse scattering found in urban environments to create multiple distinct data channels at the same time and frequency. These distinct data channels are what give MIMO the capacity improvements over single channel technologies. Most of the tools that we are producing are suitable for both. We don’t discriminate until getting to the protocol layers where there are some unique areas in which they differ.

Botka – MIMO is a technology that is being evaluated on a number of different standards. Both LTE and WiMAX have written MIMO into the specifications. MIMO can be utilised for many other applications. We try to create high performance hardware that is software reconfigurable. In this case the Agilent PXB is user reconfigurable from the front panel and can be used for MIMO receiver test for LTE one day and then MIMO receiver test for WiMAX the next. We are trying to be more flexible in modelling what our customers are telling us they need to do.

When customers make capital purchases like this, whether they can articulate their specific needs or not they are looking for the ability to use what they buy today and tomorrow. That is one of the reasons why we have architected this product in a way that is user upgradable to handle higher level MIMO in the future.

One of the real benefits that Agilent brings to solving these problems is all the way from the front end of R&D through installation, maintenance and deployment. We have a set of well coordinated solutions for LTE and WiMAX. The idea is, we don’t take one point in the customer’s development lifecycle, and our intent is to partner with them throughout the entire process. Parts of our organisation focus on different aspects but we transfer IP or knowledge between the groups thus accelerating our ability to support the customer and reduce their time to market, which ultimately benefits the customer.

WiMAX, Fixed WiMAX, Mobile WiMAX, WiMAX Forum, the WiMAX Forum logo, WiMAX Forum Certified, and the WiMAX Forum Certified logo are trademarks of the WiMAX Forum. All other trademarks are the properties of their respective owners.

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