RF remotes: Consumer electronics’ next big thing

RF remotes: Consumer electronics’ next big thing

Radio-frequency home entertainment communications offer huge advantages

BY VICTOR BERRIOS and RYAN KELLY
Freescale Semiconductor
Austin, TX
www.freescale.com

During the short history of television remote controls, engineers have attempted several different technical schemes to make the remote more user-friendly. Early examples from the 1950s used wires, or a beam of light, or ultrasonic sound to change channels and control the volume, with obvious limitations. The photoelectric cells in the light beam, for example, could not tell the difference between a flashlight, an ordinary table lamp, or even sunlight, leading to some chaotic television viewing.

By the early 1980s, the industry had moved to IR remote controls, which have been the de facto standard ever since. The technology works fine, but with an increasing number of limitations including narrow field-of-vision, requirements for line-of-sight (LOS), and unidirectional communications. These drawbacks are magnified in today’s households that have many different components hidden behind furniture doors or walls as well as a dozen or more remotely targeted electronic devices spread throughout the house. The challenge is not just keeping track of multiple IR remote control units, but that IR cannot take advantage of an electronic home environment that is ripe for more advanced system-level control.

The RF factor

Radio-frequency home entertainment communications offer huge advantages over IR, including unlimited field of view and no LOS requirements. But what is moving the RF solution well beyond the capabilities of IR is the ability to perform bidirectional communications. These multiple communication paths take home entertainment control from the “point and push” world into the realm of full system-level control.

A ZigBee Remote Control system (based on the ZigBee RF4CE and IEEE 802.15.4 standards) offers features beyond simple commands from a handheld remote control. It is becoming the new standard by which entertainment systems communicate, entirely changing the way we watch, listen, and interact with our home entertainment systems.

The widely used 2.4 GHz is an unlicensed global frequency, making it a very cost effective option and it is used in a broad range of applications including Wi-Fi, cordless phones, microwave ovens, baby monitors, and any Bluetooth-enabled device. Many homes are likely to have several devices operating on the 2.4-GHz band, each with its own duty cycles and other application-specific requirements. It is, of course, essential that these devices do not interfere with each other.

ZigBee RF4CE takes advantage of 802.15.4’s built-in attributes to avoid signal interference in a crowded 2.4-GHz environment. It uses interference avoidance features including direct sequence spread spectrum (DSSS), or “signal spreading,” and carrier sense multiple access (CSMA). DSSS transmits the data more reliably because it distributes the signal energy over a larger frequency bandwidth (ZigBee RF4CE has 2-MHz-wide channels) so that any interference only affects part of the signal. CSMA is the principle of “listen first before you speak.”

It also has channel agility (operating over three 802.15.4 channels) that allows each node within the network to move immediately to a less-busy channel if the need arises. Depending on the circumstances, all three channels could be used by different nodes at the same time.

Setting it up

A ZigBee RF4CE-based network consists of one or more controller nodes and any number of target nodes, which may include items not normally associated with a home entertainment network. In addition to home entertainment systems, applications such as a light dimmer switch, ceiling fan, and thermostat controls can be included in the network.

To start, the controller node must be introduced, or “paired,” with each target node. For example, the remote’s pairing request is transmitted to the targeted node, a TV. During the request, the TV accepts the remote control, replying with its unique address so the remote can communicate directly with it going forward. Device pairing includes support for platform version, vendor ID, product ID, version exchange, and device capabilities information exchange, such as control commands. Once paired, the controller no longer needs to search huge lookup tables because the device to be controlled provides the remote with a list of all the supported public commands.

Once all the nodes in the network have been paired, the remote control can transmit commands on an address-to-address basis, so each target node will know how to respond. Commands can also be broadcast, meaning a single command can target multiple devices, thus reducing the amount of over-the-air traffic, saving battery life and avoiding possible interference.

The first public application profile for ZigBee RF4CE is ZigBee Remote Control, with commands separated into two categories: public and manufacturer-specific. The public commands are defined as standard commands available to all network users. These commands are functions each device is expected to perform power on, power off, volume up, volume down, etc. Since there is nothing proprietary about an “on” function or a volume control, standardization will simplify the memory requirements for both controller and target.

Manufacturer-specific commands offer vendors the freedom to generate value-added commands that can be understood only by their devices or by devices that they designate.

Not a typical remote control

With an IR remote, changing a TV’s color saturation or adjusting any other video parameters will likely result in a large “black set-up box” occupying most of the screen as you adjust the on-screen control sliders. To see full-screen results, you have to exit the configuration function and enter back in if the first adjustments were not satisfactory.

As you might expect, a ZigBee Remote Control remote changes everything. Taking advantage of the bidirectional communication capabilities, the remote can integrate a small LCD screen that provides multiscreen viewing capability. The “black box” with the video controls can be viewed on the remote while the TV image continues normally. Any picture adjustments can be viewed full screen and in real time.

The remote can be used in lieu of picture-in-picture viewing, or the viewer can use it to scroll through a cable programming guide without interfering with the TV image. The bidirectional capability of ZigBee Remote Control adds simple functions to the remote to enhance user experience such as a remote control location service where pushing a button on a TV that causes the remote to beep. The remote can also add considerable utility to any target device it controls because just as the remote can display and implement TV controls, it can also display controls or play lists for satellite radio, MP3 players and even offer controls for the air conditioning. And the possibilities are endless.

One remote to rule them all

Standard compliance testing can create an infrastructure that can ensure interoperability across components and makers. Building on the 2.4-GHz ZigBee RF4CE standard helps simplify the process for creating a worldwide RF entertainment control network standard and brings true system-wide control to the user.

Moving beyond the entertainment center, a ZigBee Remote Control entertainment control network can expand to interface with non-entertainment devices as well as bridge with other wireless networks, such as ZigBee Smart Energy or ZigBee Home Automation. A single remote device can control every aspect of the connected smart home and can be customized to satisfy different needs. The ultimate goal of a ZigBee Remote Control entertainment control network is more than just replacing an IR remote control it is building a foundation that enables a single remote control to control every electronic device and all the electronic systems in the next-generation digital home. ■