By Alf Helge Omre, Business Development Manager, Bluetooth low energy wireless technology, Nordic Semiconductor

The IR remote control is a senior citizen. The 50-year-old technology is struggling in the multimedia age, but in the absence of a worthy successor, the CE industry won’t let IR fade away. However, with the Bluetooth SIG’s recent announcement of remote control support in the upcoming Bluetooth low energy specification, that’s about to change.

Bluetooth wireless technology owes a lot to the ubiquitous infrared (IR) remote control. Humble and affordable devices, IR remote controllers have done more to educate consumers about the benefits of short-range ‘wireless’ than any other technology.

When IR remotes were originally launched in the late 1950s, the concept of being able to control a consumer electronics (CE) product from the sofa without wires was virtually unknown (although RCA had launched a remote control based on ultra sound some years before). Yet, by the end of the century, IR became so pervasive it was not unusual for a household to play host to ten different remotes.

Fifty years is an incredibly long time for a technology to endure. And while the IR remote control has evolved, the underlying technology remains the same. That’s testament to its reliability, simplicity and cheapness and explains why the vast majority of CE manufacturers still rely on this optical veteran to provide the interface between their products and customers.

But while changing channels and adjusting the volume might have been enough to keep consumers happy the 1970s and 80s, with a few more functions to keep them quiet in the 90s and early 2000s, today’s IR remotes are showing their limitations alongside the latest digital products.

End users now expect a high level of intuitive functionality when controlling any consumer electronics (CE) product. Unfortunately, multi-layered menus, ‘live’ two-way status displays (for example, track playing information), HID refresh rates for track ball or joystick navigation and the ability to operate reliably regardless of whether physical objects happen to be in the way or if the user is in another room, are beyond the capability of IR remote controls.

Yet RF remote controls can do all this and more, so why hasn’t this technology pushed IR aside? The answer is because CE companies are yet to see RF as a natural successor to IR. While competent proprietary RF technology alternatives certainly exist, in comparison to IR, these lack interoperability and the second sourcing required to form the competitive market the CE makers demand.

Bluetooth low energy wireless technology is about to change all that. Remotes equipped with Bluetooth low energy chips will have all the advantages of RF technology at slightly more cost than IR. This, however, will be more than compensated for by lots of useful added functionality and comprehensive interoperability. And, in the medium term the cost differential will practically be eliminated.

Moreover, Bluetooth low energy wireless technology will extend remote RF control functionality to watches, mobile phones, PDAs and more, to give end users an array of ubiquitous portable devices with which to control their CE appliances.

RF remotes to date

RF has made inroads into the remote control market in some specialist applications, for example MP3 player docks. Here users want a ‘live’ menu of whatever is being played displayed on the remote control because the display on the MP3 player is too small to be read across a room. They also want to be able to drill down into various nested folders of stored content in a way that closely mimics how this would be done on the actual MP3 player.

Aside from this application, it’s surprising that RF has not penetrated more applications because RF has several inherent advantages over IR. For example, contemporary ultra-low power (ULP) consumption RF transceivers like the nRF24L01+ from Nordic Semiconductor can be powered for months or even years in remote control applications by AA or AAA batteries, and offer 10 metre (plus) ranges while operating in the global licence free 2.4GHz band. And RF offers high bandwidth bi-directional communication through walls and doors (albeit with a reduction in range). In comparison, IR has limited range and is restricted to line-of-sight-operation. And, while it is possible to create bi-directional communication with IR, it’s far from an ideal solution. The cost rapidly escalates and there are performance challenges caused by (light) interference and low data rates.

Unfortunately, the big disadvantage of today’s RF remotes is that the radios and protocols are proprietary, effectively ending any possibility that a mainstream CE manufacturer will embrace the technology for fear of being held hostage by a single supplier.

That’s not to say that IR remotes are themselves truly interoperable. They don’t, for example, adhere to the Infrared Data Association (IrDA) protocols that are commonly used for fast communication between, for example, PDAs and mobile phones. All too often, the remote that comes with the DVD player from one manufacturer typically won’t work with the TV from another. That’s why most home coffee tables groan under the weight of five or six separate remotes.

However, so-called ‘universal’ IR remotes are available. These devices can be ‘trained’ to operate all the IR devices in the house to offer true interoperability. (This is because most IR remotes use frequency or format variations of just a few base protocols allied to a library of commands that map a button to a particular function that a universal remote can quickly decode and memorise.)

This convenience, however, comes at a price – typically upwards of US$100. Consumers are yet to be convinced a universal remote is worth that outlay. Potential vendors of RF remote controls should take note: new RF remotes must offer useful additional functionality to justify the initial extra cost over the cheap IR remote controls currently supplied by the CE makers.

In summary, to displace IR, RF must do the following:

• Deliver the ‘next generation’ functionality that IR can’t;
• Become less expensive;
• Offer genuine interoperability;
• Be available from many vendors.

RF remote control using Bluetooth low energy

Bluetooth low energy has its roots in an initiative led by Nokia in October 2006. The Finnish mobile handset manufacturer joined with a group of like-minded companies, including Nordic Semiconductor, to form the Wibree initiative, in order to encourage the development of an ultra-low power wireless connectivity specification. In June 2007, the Bluetooth SIG announced Wibree’s fledgling spec would form the basis of Bluetooth low energy wireless technology (formerly known as ultra low power Bluetooth). Nordic Semiconductor is now an associate member of the Bluetooth SIG, and has contributed core expertise in ultra-low power RF design to the forthcoming specification for Bluetooth low energy wireless technology

This specification details a short-range RF communication technology featuring ultra-low power consumption, a lightweight protocol stack and integration with Bluetooth wireless technology. (However, it is important to note that Bluetooth low energy will not communicate with legacy Bluetooth chips adhering to the current v2.1 + EDR standard or older versions. Communication will require Bluetooth chips to be revised to include additional circuitry and software to ensure compatibility with Bluetooth low energy. It is expected that this revision will become common in ‘dual-mode’ devices as the addition of Bluetooth low energy to existing Bluetooth devices requires minimal effort. (See sidebar “Inside Bluetooth low energy wireless technology” for definitions of dual- and ‘single-mode’ devices.)) The full specification is currently being drafted for release in the second half of 2009.

Bluetooth low energy will be power and cost optimised to provide compact, low cost and ultra-low power (ULP) transceivers for sport, wellbeing and HID product categories. What’s more, Bluetooth low energy wireless technology will feature a stack meeting the requirements of the consumer products industry for interoperable, universal remote controls. Bluetooth low energy will be available as an open standard, encouraging many vendors to manufacture the chips, thus ensuring the multiple sources of supply the CE makers crave. (See sidebar “Trusting the Bluetooth brand”.)

“Remote controls were identified as one of the key markets when we were designing this specification,” says Mike Foley, PhD, executive director of the Bluetooth SIG. “Every customer is aware of the frustration of owning a handful of different, incompatible remote controls. By bringing the experience of the Bluetooth community to bear on a low cost, interoperable solution, we hope to make that frustration a distant memory.”

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, whether it’s 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 conventional IR remote controls, each Bluetooth low energy remote control always uses a secure, unique link to the device it’s controlling. It’s also fast, interference immune and bi-directional.

Lowering the power

While RF has some inherent advantages over IR as a modern remote control solution, there are some engineering challenges to overcome when developing the optimum RF remote control.

In summary, these are:

• Low power consumption – so that batteries last a reasonable time;
• Low latency – so that the user is unaware of any delay between button press on the remote and the response from the appliance being controlled even if the transceiver has to wake up from an ULP ‘deep sleep’ mode;
• The ability to control several devices simultaneously in a point-to-multipoint Personal Area Network (PAN) – so that the user is able to employ just one remote for all appliances.

Nordic-Fig1Figure 1: ULP RF operation will be critical to maintain reasonable battery life for a remote control with high duty-cycle operation. (Courtesy: Bluetooth SIG.)

The amount of data typically transmitted by a remote is small, dictating than the remote doesn’t have to be ‘on’ for very long each time a button is pressed. In addition, users don’t press buttons very often, perhaps 50 to 100 times a day. Consequently, IR remotes have a very low duty cycle and exhibit battery life measured in months or even years; RF devices need to match this benchmark to meet consumer aspirations. (However, note that while this is the case today, it’s not difficult to imagine a bi-directional link being used to carry more data as manufacturers come up with new functions. (For example, interactive menus on the remote itself – see figure 1.) When this happens the duty cycle will dramatically increase and ULP operation will be critical to maintain reasonable battery life.)

According to the Bluetooth SIG’s provisional figures for ‘single-mode’ Bluetooth low energy silicon, it has two characteristics that meet the ULP requirements for remote controls: a modest peak current requirement and wide bandwidth. The Bluetooth SIG says the chip’s peak current consumption will be less than 15mA when transmitting at 0dBm (sufficient for a range of up to 10 metres while obeying the authorities’ power restrictions for operation in the licence-free 2.4GHz band) and slightly less than this when receiving. (See Table 1.)

Nordic-Table1Table 1: Provisional specifications of Bluetooth low energy chips

In addition, the Bluetooth SIG says Bluetooth low energy chips will have a bandwidth of 1Mbps. This bandwidth has been carefully chosen because years of field experience with ULP proprietary technology has shown that 1Mbps is the optimal trade-off in exactly the kind of wireless applications Bluetooth low energy wireless technology will target. The trade-off is between transmit power – which goes up with increasing bandwidth – and duty cycle – which decreases with increasing bandwidth for a given amount of data. For example, Bluetooth low energy chips running at 1Mbps only have to transmit at the peak current of 15mA for one quarter of the time of a typical IEEE 802.15.4 radio running at 250kbps and a transmission current of 28mA, to send the same amount of data. (Although some lower power, higher bandwidth IEEE 802.15.4 radios are available.)

Putting the RF transceiver into a deep sleep mode if it is inactive for long periods can further reduce power consumption in the remote. While figures for Bluetooth low energy’s sleep modes have yet to be released, a comparison with a similar ULP RF proprietary technology like that from Nordic Semiconductor shows it’s likely a ‘stand-by’ mode will consume tens of microamps and a deep sleep (or ‘power down’ mode) will consume perhaps 900 nanoamps. This level of power consumption is low enough for a pair of AA batteries to last for months or years. (To put this in perspective the self-discharge current of an AA battery is around one microamp.)

A fast response

However, low power consumption in the remote control is only part of the challenge. Several countries, including Australia, Japan and the US, are voluntarily adopting the International Energy Agency’s One-Watt program. This program is designed to encourage manufacturers to develop products – such as TVs and DVDs - that consume less than one watt when in standby mode (and, almost inevitably, that target will become lower in time). Achieving this target allows the product to be Energy Star certified, an important selling point for environmentally conscious consumers.

Appliances with a one watt or less standby restriction will have little power to spare for the built-in RF transceiver required to ‘pair’ with an RF remote control. This means that the transceiver in the appliance will have to spend much of its life in a stand-by mode to save power, waking up periodically to check if the remote is trying to communicate.

It turns out there is a linear trade-off between power consumption and the frequency with which the transceiver in the TV or DVD wakes up to check for transmissions; the more often the transceiver wakes up, the higher the power consumption. However, a Bluetooth low energy chip will be able to wake up, for example, every 10ms, listen for transmissions (consuming around 15mA for very short period) and then return to a deep sleep state while maintaining an average current consumption as little as some tens of microamps.

The start-up time for a Bluetooth low energy chip has yet to be revealed, but a Nordic proprietary RF chip with a comparable architecture has an equivalent start-up time from deep sleep of 2.5ms, an insignificant time after a button on the remote is pressed from the user’s perspective. However, there is more to establishing communication than this; for example, if the receiving chip in the appliance to be controlled happens to be in a stand-by state at the time the remote control button is pressed the transmission will fall on deaf ears.

Nonetheless, by repeatedly polling the receiver, the remote’s transceiver’s communication will eventually coincide with the waking mode of the receiver. Even if this doesn’t happen after the first 10ms interval – perhaps due to interference from other 2.4GHz transmitters in the vicinity such as a home Wi-Fi network – it is likely to be received the second or, at worst, the third time. Consequently, the maximum latency when both chips start from deep sleep or standby modes is likely to be less than 50ms. In comparison, the minimum latency of an IR remote between button press and response from the unit being controlled is between 70 and 110ms.

One of the major advantages of Bluetooth wireless technology, the bigger brother of Bluetooth low energy, is that it was designed from the beginning to operate as a Personal Area Network (PAN) with one master controlling up to seven slaves. Bluetooth low energy will build on that legacy. The Bluetooth low energy chip in the remote control will be the ‘master’ with its retinue of ‘slaves’ being the TV, DVD player, MP3 dock, hi-fi, games console and the other CE appliances typical of the modern home. A consumer will be able to use a single remote confident that it will instantly communicate with any of the seven devices with which it is paired (providing all types of device adhere to the Bluetooth low energy specification).

As Mike Foley of the Bluetooth SIG explains: “A major drawback of other proposed standards for remote controls is that they easily become confused when working with multiple consumer devices. Bluetooth low energy technology provides the ability for remote controls to talk to multiple devices with total assurance that they will control the correct piece of equipment.”

The remote control on your wrist

Bluetooth wireless technology’s ubiquity in portable products such as cell phones, PDAs and laptops provides a platform for Bluetooth low energy wireless technology to change remote control from dedicated device to an extremely useful added function of existing portable products (as these portable products migrate to dual-mode plus Bluetooth low energy). In other words, it promises to change the way people use remote controls.

Nordic-Fig2Figure 2: ULP RF transceivers can be powered by coin cell batteries and allow sports watches – like this model from Suunto - to communicate with heart rate monitors and shoe-mounted speed & distance monitors. (Courtesy: Suunto.)

Consider, for example, the 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 & distance monitors (see figure 2), a sports watch with a Bluetooth low energy chip will also be able to operate as a remote control for a suitably Bluetooth-equipped mobile phone or MP3 player. And a Bluetooth low energy equipped-sports watch will also be able to talk to the Bluetooth chip in a mobile phone to let the user know who’s calling, display e-mails, SMS and much more. Hands up who wants one?

Because Bluetooth low energy wireless technology enables interoperability, a suitably equipped mobile phone or MP3 player will be able to control the TV, DVD, hi-fi and more. A compact device that everybody carries everywhere with them already will suddenly be able to replace a multitude of clunky remotes.

In a second 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 Bluetooth single-mode low energy chip-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 mobile phone will connect wirelessly with the Bluetooth low energy chip in the set-top box and/or TV, and the week’s viewing will be automatically programmed.

The wireless remote control has a history spanning five decades. IR has done the heavy lifting thus far, but the future belongs to RF. RF’s advantages over IR make it the only technology that can meet the aspirations of tomorrow’s consumers and CE equipment makers. Bluetooth low energy wireless technology has the technical capabilities and interoperability to be the best RF solution. The technology will liberate the remote control from a dedicated device to become a function of the portable devices we already carry in our pockets or wear on our wrists. What’s more, not only will Bluetooth low energy be the obvious choice for the new remote control standard, it will also be the missing link enabling a merger between PC and TV.

Posted by Janine E. Mooney, Editor

December 1, 2011