Product How-To: RF remotes view for IR's crown

by Chim Chan, Nordic Semiconductor , TechOnline India - May 14, 2010

The IR remote control is a simple, cost effective method of controlling electronic appliances, but it is also a 30-year-old technology that’s showing its age. RF is a better alternative for modern consumers and the competitors are lining up for the designer’s attention.

Using IR (infrared) for consumer remote controls was an inspired choice in the late 1970s. It solved all the reliability, range and complexity issues of more costly ultrasonic devices (which struggled to catch on) and proved so good that over thirty years later we’re still using IR to control the majority of CE products shipped worldwide.

But IR’s durability is also proving to be its downfall. At its inception, IR was designed to do a few simple functions such as adjust volume or switch between TV channels; it was never envisaged that it would have to cope with the multimedia, multi-menu, multi-function demands of modern CE products. For example, IR remote controls are unable to support the kind of “seamless” navigation promised by a scroll wheel, track pad or track ball because of limitations in the frequency of report rate between the remote control and appliance.

Fortunately, RF (radio frequency) remotes – previously considered too expensive, complex and tough on batteries – are finally promising to fulfil their potential. Once users experience the benefits of RF they don’t want to go back to IR.

Several alternative RF technologies – available now, or soon to be released – are competing for the RF market. These separate into proprietary (such as the products available from the company I work for, Nordic Semiconductor) and standards-based alternatives such as the forthcoming Bluetooth low energy and RF4CE (based on the IEEE802.15.4 media access control/physical (MAC/PHY) layer1).

RF: Remote control for the multimedia age

RF is not a new technology for remote control. For example, in 1903, Leonardo Torres Quevedo presented his “Telekino” at the Paris Academy of Science before obtaining patents in France, Spain, the UK and the US. The Telekino consisted of a remotely controlled robot executing commands transmitted by radio2.

But IR became the technology of choice for controlling TVs (and later most other household appliances) because it was simple, inexpensive and reliable. However, as the functionality of modern CE products has increased, the disadvantages of IR have become more of a problem. Perhaps the biggest of these disadvantages is the relatively slow refresh rate – the time it takes for a command to be repeated, for example, when scrolling down a list of programs on an Electronic Program Guide (EPG). At best this is around 75 ms, but more typically stretches to 110 ms or more if there is any light interference present.

The slow refresh rate prevents the incorporation of scroll wheels, track pads or track balls into IR remote controls (hence the reason why they often have so many buttons). This limits what the CE makers have been able to do with the graphical user interfaces (GUIs) on their products and explains why they remain basic and not particularly user friendly.

In comparison, the refresh rate of a modern, short range, 2.4GHz radio transceiver is of the order of few milliseconds. Wireless mice, which require a refresh rate of 8 to 16 ms, are a good example of a technology that takes advantage of this low latency and demonstrate smooth and rapid reaction to the wireless command.

Seamless navigation allows CE makers to radically change the GUI on their equipment. This is becoming a pressing requirement as CE products converge into a single unit that stores the family’s music, film and photo library as well as providing access to the Internet. While not the only way to manage lots of content, the scroll wheel on Apple’s iPod is a good example of smooth navigation through menus and control of audio and video files. With RF, the remote control manufacturers will similarly be able to change a clunky box with dozens of buttons into a compact unit with an elegant interface to control the next generation of CE devices.

IR remote controls feature low power consumption (primarily due to modest peak currents and low duty cycles where the unit sits idle for 99.995 percent of the time (based on a usage of around 50 key presses per day)). Consequently, consumers have come to expect a battery life of many months from a couple of AA cells.

Modern 2.4GHz transceivers – whether proprietary, Bluetooth low energy- or IEEE802.15.4-compliant devices – can easily match this electrical performance. The transceivers send data for a very short time only and then re-enter an ultra-low power sleep mode as quickly as possible. A combination of peak transmission current of tens of milliamps for just a few hundred microseconds followed by extended periods in a nanoamp sleep mode results in average currents in the microamps range. This is economical enough to ensure the battery life of a typical RF remote control is similar (or better) than the IR devices they will replace.

Other advantages of RF are less pronounced, but could become more important as CE products evolve. For example, whereas today users are generally positioned in front of the TV when they wish to scan the EPG, guaranteeing line-of-sight access, and requiring only short range, it’s not difficult to imagine a future where that changes. When the “media center” in one room is used to distribute content to different rooms in the house users need an RF remote control that works around corners and has a range of tens of metres.

But while it’s easy to see that RF remote control is a better choice for modern multimedia applications, what’s not so obvious is the best choice of technology. Designers can select from proprietary solutions such as Nordic’s proven 2.4GHz transceivers or interoperable solutions such as Bluetooth low energy or RF4CE.

Proprietary RF

Proprietary transceivers can offer a reliable and short development path to RF remote control for applications as simple as operating an air conditioning unit through to controlling a multimedia CE product. And because proprietary transceivers only have to communicate with themselves, they can be designed to specifically meet the requirements of particular end applications (whereas standards-based specifications have to be designed to be interoperable with a wide range of applications which introduces inevitable compromises). For these reasons, proprietary solutions have made inroads into the RF remote control sector.

In addition, proprietary solutions also tend to be updated more frequently than standards-based technologies that are often effectively “frozen” for several years until an updated version is officially sanctioned. Consequently, proprietary products generally outperform standards-based alternatives in all the key parameters of a wireless link.

For example, Nordic’s nRF24LE1 2.4 GHz GFSK (Gaussian Frequency Shift Keying) single chip transceiver integrates a transceiver core and mixed signal 8-bit microcontroller with flash memory into a 4 by 4mm package and is a proven proprietary hardware option for RF remote control. (See figure 1 for an RF remote control reference design incorporating an nRF24xxx transceiver.)

Figure 1: Proprietary remote control reference design

But the hardware is only one part of an effective RF remote control. The other part is the embedded software protocol responsible for managing how the radio sends and receives data and manages environmental factors such as interference from other 2.4GHz sources operating nearby.

Nordic’s supplies “off-the-shelf” optimised RF remote control software - such as its Gazell RF stack - for a bi-directional communication link with frequency hopping capabilities. It requires minimal memory space and can be set to either a low latency mode (with an average latency, even in the vicinity of other, potentially interfering, 2.4GHz sources, of 3.5ms – more than adequate for the smooth navigation discussed above) or, if both ends of the link are battery-powered, an ultra-low power mode to extend battery life in both ends of the link. In this mode, latency can be increased to reduce the average current consumption on the host (the equipment being controlled) side. The average latency can be extended up to 50ms - still less than a typical IR remote control’s latency of between 75 and 125ms – extending battery life.

{pagebreak}Meeting the demand for interoperability

The downsides of a proprietary solution are that it can’t be guaranteed to control a product other than the one for which is was designed to operate, and the technology is owned by a single supplier. In contrast IR can be made to operate with appliances from different manufacturers (although this often requires the consumer to spend time “programming” the remote with new commands).

Many manufacturers are not concerned about interoperability because they envisage their remote only ever being used with the product for which it was supplied. These manufacturers are typically concerned with the best performance for the price – a strength of proprietary solutions because they can by optimised for a particular task. Consequently, proprietary solutions will continue to carve a prosperous niche in the remote control sector.

However, a lack of interoperability and fear of being held hostage by a single supplier or a potentially dead-end technology has hindered the uptake of proprietary RF remote controls by the major CE makers. These manufacturers are looking for guaranteed interoperability and the type of multi-vendor ecosystem assured by an open standard.

A single RF remote control complying with an open standard will be able to be “paired” with many different CE appliances using a simple operation taking just a few seconds. Each pairing will be unique and thereafter the remote will “instantly” (within 30ms) work with the unit – for example, TV, DVD player, hi-fi or games console – that the user wants to control. (There will be no need for the tedious programming required with an “interoperable” IR remote control.) The six or seven bulky remotes typically overloading the average consumer’s coffee table will be replaced with one elegant device.

The Bluetooth SIG and the RF4CE Consortium are addressing the market with their respective versions of interoperable, low power RF specifications that any chip vendor (provided they join the appropriate group) can use as the basis for their silicon for RF remote controls.

The Bluetooth SIG plans to offer an ultra-low power coin cell (watch battery) variant called Bluetooth low energy technology – due for imminent release – which will include a specialised profile for interoperable RF remote controls.

Bluetooth low energy is a 2.4 GHz short-range wireless technology featuring ultra-low power consumption, lightweight protocol stack and the promise of seamless communication with Bluetooth wireless technology. (However, it is important to note that Bluetooth low energy will not communicate with legacy Bluetooth chips up to and including the current v2.1 + EDR and v3.0 standard).

Communication will require existing Bluetooth chips to be revised to include additional “dual mode” circuitry and software to ensure compatibility with Bluetooth low energy. It is anticipated that this modification will require minimal additional design effort, chip area and cost.

Dual mode Bluetooth low energy chips will then be able to communicate with any product equipped with a “single mode” Bluetooth low energy device. The latter will be power and cost optimised to provide compact, low cost ULP transceivers and will feature a software stack “profile” tuned to the requirements of the consumer products industry for interoperable, universal remote controls. Other early profiles will include human interface devices (HID) and proximity for watches and cell phones. Bluetooth low energy will be available as an open standard, encouraging multiple vendors to manufacture the chips, ensuring multiple sources of supply (see figure 2.)


Figure 2: Bluetooth low energy wireless technology features dual-mode and single-mode implementations
Click on image to enlarge.

The Bluetooth SIG says the standard will allow the remote control to be designed as a low cost, non-intelligent peripheral. The target receiver product, such as a TV, DVD player, set-top box, or media player, can control the operation of the remote control so that it learns to work with each new device that’s purchased. Unlike IR remotes, Bluetooth low energy controllers will employ a secure, fast and bi-directional link with the device under control.

My company, Nordic Semiconductor is an associate member of the Bluetooth SIG, and has contributed core expertise in ultra-low power RF design to the forthcoming Bluetooth low energy specification. It plans to be among the first to release a single mode Bluetooth low energy chip meeting the version 1.0 specification and recently announced the release of samples and Prototype Development kit for its µBlue (“MicroBlue”) products (see figure 3 for a schematic of the chip’s stack) at Bluetooth SIG meetings in London and Beijing. (See http://www.tinyurl.com/y9k33w0.)

Figure 3: The first product in Nordic's μBlue range will include the nRF8001 - a single mode slave chip suitable for watches, sensors and remote controls

µBlue is a single modeBluetooth low energy transceiver that can run on small coin cell batteries for months or years (depending on the application). The first product in Nordic’s µBlue range will include the nRF8001 – a single mode slave chip suitable for watches, sensors and remote controls – scheduled to be made generally available after the official version 1.0 release of the Bluetooth low energy specification.

{pagebreak}The ZigBee option

Panasonic, Philips, Samsung and Sony Corporation founded the RF4CE initiative in mid-2008 “to address increased demand for advanced functionality not currently available through IR or other proprietary wireless technologies”. In March this year the consortium teamed up with the ZigBee Alliance, the association driving development of ZigBee wireless technology.

RF4CE is based on the IEEE 802.15.4 2.4GHz radio (MAC/PHY) that is also the hardware basis of the ZigBee standard. The upper layers of the RF4CE protocol are defined specifically for remote control. Several chip vendors already manufacture 802.15.4 radios that are capable of being used as the hardware for remote controls and operating at the microamp average currents required for good battery life.

The alliance says it plans to incorporate version 1.0 of the RF4CE specification into its suite of global sensor and control network solutions. The specification is designed for a wide range of products, including home entertainment devices, garage door openers and keyless entry systems. The first public profile specification will enable bi-directional interaction and control of home entertainment equipment. IEEE802.15.4 devices employ Direct Sequence Spread Spectrum (DSSS) technology for interference immunity. The RF4CE protocol is available as a free download from the ZigBee Alliance’s website. (See http://www.tinyurl.com/yh9fg6s.)

Picking a winner

RF’s advantages over IR make it certain that it will become the technology of choice for all but the least expensive remote controls. But which technology will be the most successful replacement for IR is still an open question. Proprietary solutions will almost certainly continue to carve out a sizeable niche where performance and cost are critical and interoperability is not. But on the interoperable side, things are less certain.

On paper, both the Bluetooth SIG and the RF4CE Consortium have decent technology at their disposal. RF4CE has perhaps taken an early lead by basing its hardware on an existing standard while the Bluetooth SIG is still ironing out the intricacies of its Bluetooth low energy technology. RF4CE also has the backing of some of the biggest names in consumer electronics and many vendors manufacture the hardware. Sony, for example, already supplies IEEE802.15.4-based remote controls (using the company’s own proprietary protocol) with its high-end LCD TVs. That said, IEEE802.15.4-based technology’s has struggled to meet market penetration predictions. It remains to be seen if the RF sector too will witness a battle.

In contrast, the 12,000-member the Bluetooth SIG, while perhaps not the quickest at releasing its standards, does have an excellent reputation for delivering on its promises of interoperability. Its standards (Bluetooth versions 1.0, 2.0, 2.1, 2.1 + EDR and the forthcoming version 3.0) have all proven to reliably wirelessly connect products from hundreds of different manufacturers (the result of months of beta testing at “unplugfests” before release).

However, perhaps Bluetooth’s major advantage over its rival is its enviable installed base – something that ZigBee can never hope to match. Shipments of Bluetooth radios into products such as mobile phones, headsets and PCs surpassed 1 billion units in 2006 and are on track to reach 2 billion soon.

This means that Bluetooth low energy will be able to communicate with the dozens of products that are likely to migrate to dual mode Bluetooth chips – not least of which is the cell phone. And Bluetooth’s ubiquity in other portable products such as PDAs and laptops provides a platform for Bluetooth low energy to change remote controllers from a dedicated device to an extremely useful added function of existing portable products. In other words, it promises to change the way people use remote controls (see figure 4).

Figure 4: Bluetooth low energy promises to change the way people use remote controls

For example, imagine a smart phone with mobile browsing capabilities. These devices will inevitably migrate from conventional Bluetooth connectivity to dual-mode devices that will be able to communicate directly with single mode-equipped devices. It’s not hard to imagine a user browsing the web while on the move for the schedules of their favourite TV programmes. Then, with one press of a button when the user returns home, the Bluetooth dual mode chip in the cell phone will connect wirelessly with the single mode chip in the set-top box and/or TV, and the week’s viewing will be automatically programmed. If the user then wants to modify their selection, there will be no need to retrieve the traditional remote control from the back of the sofa, the user can simply make the changes by controlling the EPG directly from their cell phone.

In a second example, consider a sports watch powered by a CR2032 3V type coin cell battery. Apart from being able to connect to a range of peripheral devices, such as heart rate monitors or speed and distance monitors, a sports watch with a Bluetooth low energy chip will also be able to operate as a remote control for a suitablyBluetooth-equipped mobile phone, MP3 player, portable computer or CE product. In Japan, this has already got watch manufacturers very excited.

That said, the RF4CE alliance might yet have some tricks to reveal, so it’s impossible at this stage to predict which technology will win through in the long run. What’s more certain is the future of remote control is going to be RF, and IR will soon become a fond but fading memory – much like VHS video players, compact audio cassettes and black and white television.

References:

1. Philips, Samsung, Sony, ZigBee Alliance press release; “ZigBee and RF4CE set new course for consumer electronic remote controls”, issued March 3, 2009.

2. Wikipedia; http://ww.en.wikipedia.org/wiki/Remote_Control

About the Author:

Chim Chan is Regional Sales Manager in India with Nordic Semiconductor. Nordic Semiconductor is a leading manufacturer of proprietary 2.4GHz ULP silicon solutions and a member of the group developing the Bluetooth low energy wireless specification. The company expects to be among the first to market single mode devices meeting the specification. For more information on these products, go to Nordic Semiconductor or contact Chim at chim.chan@nordicsemi.no.

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