Lowering the cost of femtocell oscillators

rakonRakon are the leading supplier of crystal oscillators for femtocells, which are perhaps the most significant cost component after the broadband chipset.  We've profiled the company and gained some insights into the measures being taken to reduce cost whilst still meeting the stringent specifications required.

 

Where do Rakon originate from and what do they do?

Rakon is a global company headquartered in New Zealand. Its primary business is designingand  manufacturing crystaloscillators, and are a major supplier for GPS handheld devices. Founded in1967, the company went public in 2006 and acquired the oscillator division ofC-MAC in 2007, which included design and manufacturing facilities in the UK andFrance.

We've described the various types of crystal oscillators used for femtocells elsewhere. The common term is TCXO -temperature compensated crystal oscillator - which combines a calibrated andmeasured resonator (a quartz crystal) with a temperature sensor and frequency compensationcircuit. By knowing the temperature/frequency profile of the resonator, astable frequency source can be delivered.

The original femtocell oscillators

Their original product came from their New Zealand factory -a part codenamed "Barracuda" which had a frequency tolerance of around 0.1 ppm(parts per million). This compares favourably with handset frequency crystalsthat are typically 3ppm (30 times less accurate).

Tolerances have been relaxed

The latest 3GPP release 8 specifications have relaxed thetolerances for femtocells: whilst picocells must maintain 0.1 ppm, femtocellsare now 0.25ppm.

However, many operators are still demanding 0.1 ppm orbetter rather than the 0.25 ppm allowed by Release 8. There are still costimplications of requiring the tighter frequency tolerance, which is why it'sbeen relaxed. So if operators do want to see cheaper femtocell products, theyneed to accept the wider tolerances too.

Rakon now using a completely new product

Rakon acquired a European company (the Frequency ControlProducts division of C-MAC) in 2007, and are now using one of their designs andmanufacturing locations for their latest femtocell TXCO products. Theirproduct, based on a proprietary integrated circuit called Pluto, is made in theUK.

They plan to sell this into the femtocell market at around$5 in volume. There is a perception today that Rakon is an expensive/premiumsupplier - products with similar specifications ship at prices around $10 in othermarkets. This compares with handset TXCOs that sell in volume for $0.70 (3ppmtolerance) or TXCOs for GPS devices for $1.50 (0.5ppm tolerance).

With broadband chipsets coming down in price dramatically,the TXCO could become the top single cost item after the baseband processor.

Dual sourcing

As with any sensible product design, most femtocell vendorshave chosen two TXCO suppliers, but Rakon believe they are getting most of thevolume shipped today. They have high product quality and consistency.

A crystal isn't enough on its own

In addition to the physical product, their customers arelooking for a complete solution to achieve and maintain the frequencytolerances over the long term. This includes system engineering advice andcomplementary software which manages the timing and synchronisation. There is avariety of techniques to track and maintain long term frequency accuracy, andby combining these, their customers achieve a scalable, cost effective solutionthat meets their requirements.

With forecasts of millions of femtocells in the next few years, we'll see whether Rakon can maintain their technical lead and continue to dominate the market for femtocell timing solutions.


[Thanks to Andrew Miles and Philip Davies at Rakon for answering our questions for this article.] 

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