Rakon are market leaders for one of the most critical components in every femtocell – the oscillator that provides very accurate timing and synchronisation. Their pioneering low cost and high accuracy designs have been an essential part as the industry strives to drive costs down while meeting tight technical specifications.
We hear a lot about the latest chipset designs for femtocells, which all lead to lower cost and higher performance. Equally important to the low cost and high performance of a femtocell is the timing solution provided by the crystal oscillator. Rakon have dominated the market share for TCVCXOs – the specially designed low cost oscillators used in femtocells – but is this about to change?
I met up with Mary Carbin and Andrew Miles, Business Development Managers, to hear the latest about Rakon’s success in the femtocell market and how they expect it to develop.
A bit of background about Rakon
Founded in 1967 in Auckland, New Zealand and now run by the sons of the original owner, Rakon had the foresight of the huge market size that GPS devices would create. They developed timing solutions for GPS equipment and quickly gained a reputation for quality. Their approach required intensive measurement and calibration of each quartz crystal, identifying and allowing for the natural flaws and quirks of nature. Investing heavily in high volume production lines, they were able to manufacture up to 7 million units a month and have been shipping in volume for many years.
In 2007, Rakon acquired C-MAC, a European competitor based in both France and the UK. Unusually, this company had an in-house ASIC design team which meant they could combine the electronic control of temperature and voltage within a unique integral component. Their Pluto chip met the high “Stratum 3” level performance specifications and became the defacto standard.
Rakon’s operations are currently spread across several worldwide locations, with design of the TCXO (as used in femtocells) remaining in the UK and design of the OCXO (as used in macrocells) based in France. Manufacturing is distributed between the UK, New Zealand, India and Chengdu in China which provides security of supply and manufacturing capacity. The Femtocell oscillators were initially manufactured in Lincoln, UK and are the first genuinely dual-site product, now being manufactured in parallel in NZ.
Rakon’s involvement with Femtocells
Working closely with Picochip, Rakon joined the Femto Forum at the outset. It quickly became clear that an OCXO with a unit cost of $30 or more wasn’t going to achieve the low total costs for a residential femtocell. The Pluto TCXO could meet the demanding 100 part per billion accuracy required, and promised significantly lower costs (in volume).
Rakon enjoy some 85% of the femtocell TCXO market share today. With their additional production capacity in New Zealand, they believe they are well placed to satisfy the rapidly growing demand forecast. They recognise the huge responsibility that their large market share brings, and ensure that they can honour their commitments by holding stocks and manufacturing capacity.
Their membership of the Femto Forum has allowed them greater insight into the state of the market and what operators are doing. This in turn has allowed them to validate their order pipeline, avoid double counting and match investment to meet market demand.
With the growing volume of femtocells being shipped, new entrants are appearing with similar products that also meet the tight tolerances required. These include some of the well known Japanese manufacturers such as Epson Toyocom (ETC), [Update: Since renamed Miyazaki Epson Corporation in 2013], Taiwanese manufacturer Taitien who were reported to be supplying Sercomm and Gemtek, and US supplier Pletronics.
It is common for femtocell manufacturers to require at least two different vendors for critical components to ensure certainty of supply. This is best practice to avoid supply problems should these occur, whether due to technical, commercial, manufacturing capacity or other unforeseen issues.
Parts from a second source may be pin compatible or may require design changes, meaning that the choice of suppliers is made early in the design cycle.
Crystal Ageing Compensation – A unique selling point?
Nature takes its course with quartz crystals, and over a period of years their individual characteristics change. Rakon claim that one of their technology's unique attributes is how effectively it maintains an oscillator's specified stability during this ageing process, adapting the control algorithm and voltages appropriately. This increases the reliable operating lifetime of the femtocell, so that performance doesn’t degrade after a period of years.
The bottom line is that the end customer remains satisfied with effective operation of their femtocell products for a longer lifetime.
How will LTE change the demands for TCXOs?
The main technical difference that LTE will introduce which affects the timing solution is a much tighter phase noise requirement. This is critical to achieve maximum throughput at short range. The timing solution not only has to be frequency accurate to 100 parts per billion (as for 3G), but must also achieve consistent phase accuracy.
As you may know, the mobile phone standards for GSM, WCDMA and LTE can all run asynchronously. However there is a feature called MBMS (Mobile Broadband Multicast Service – tutorial on the 3G version here) which can “simulcast” a common transmission to all users. This would require synchronised femtocells, leading to a few microseconds tolerance and much more demanding synchronisation.
The synchronisation requirement will make it difficult for femtocells to be used with DSL – they can’t just be plugged into a router and connected over any 3rd party broadband. Either they will need to be integrated with the DSL modem and operate closely with the wireline DSL provider (some attributes in the DSLAM are essential); alternatively, other options such as GPS, FTTH or even listening to other nearby macrocells might be an easier option to implement.
Regardless of which timing source is used, a TCXO will still be needed to maintain an accurate reference clock during glitches and short outages.
What about TDD mode for LTE?
This option is being promoted strongly for use in China and India. The basestations must be accurate to 3 microseconds synchronisation and know it – if any do transmit when out of sync, it could interfere with other cellsites in the local area.
How quickly are LTE femtocell products appearing?
We’re seeing the industry investing in public area LTE femtocells first, rather than residential products. These are higher capacity femtocells which will support larger numbers of users, and may use an oscillator with longer hold times. Size and cost may be less extreme than for the lowest cost residential products. Fuelled in part by the needs of this market, we've developed their new Mercury family of oscillators - the world's first OCXOs based on an integrated circuit.
There are also combined 3G and LTE femtocell product designs emerging which can share the same TCXO to save cost.
Many ODM and OEM vendors are entering the market, and there are new entrants emerging with LTE designs who we haven’t previously seen as femtocell vendors. Not all of the 3G femtocell companies are developing LTE products as quickly, so there may be a different market share split between 3G and LTE as this evolves.
No doubt we will continue to see further innovative femtocell designs with a wide range of configurations to meet different customer needs. Rakon will continue to be at the forefront to meet the technical challenges of the industry.
- TCXO – Temperature Controlled Crystal Oscillator
- TCVCXO – Temperature Compensated Voltage Controlled Crystal Oscillator
- OCXO – Oven Compensated Crystal Oscillator
Small Cell Forum white paper on Femtocell Synchronisation and location