understanding zigbee rf4ce...the zigbee smart energy , zigbee home automation , zigbee light link...

© 2014 ZigBee Alliance. All rights reserved. www.zigbee.org1

Understanding ZigBee RF4CE

October 2014

© 2014 ZigBee Alliance. All rights reserved. www.zigbee.org

Understanding ZigBee RF4CE October 2014

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Foreword

Since its inception, the ZigBee Alliance has worked with a singular focus: create a muchneeded global wireless language capable of giving voices to the myriad of everydaydevices that surround us as we go about our daily lives – also sometimes referred at as“The Internet of Things”. This focus has been aimed at devices often overlooked in an IT-centric world, such as light switches, thermostats, electricity meters and remote controls,as well as more complex sensor devices found abundantly in the health care, commercialbuilding and industrial automation sectors. By connecting these devices, this Machine-to-Machine (M2M) network or Internet of Things is created that offers exceptional efficiency,convenience, security and control and a whole new way for people to interact with theirenvironment. As a result, ZigBee Alliance members have created a smart set of wirelessstandards that enable this new class of networks and offer extraordinary control,expandability, energy efficiency, security, ease-of-use and the ability to use ZigBeetechnology in any country around the world.

Today, organizations use ZigBee standards-based wireless sensor networks to deliverinnovative solutions for a variety of areas including consumer electronic device control,energy management and efficiency, health care, telecom services, consumer electronicdevices, home and commercial building automation, as well as industrial plantmanagement. By choosing ZigBee, they also benefit from the Alliance’s competitive andstable supply chain. With a comprehensive set of attributes, the non-profit, openmembership and volunteer-driven Alliance has become a thriving ecosystem with severalhundred members. As an ecosystem, the Alliance offers everything prospective productand service companies need to develop the most dynamic ZigBee products and services.



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Executive Summary

Infrared (IR) remote controls have been around since the late 1970s and used to be thetechnology of choice for control of many devices. With the rapid growth of sophisticatedconsumer electronics devices offering new features and content choices, more advancedremote control technology has been brought to market to enable robust products withinnovative new features. ZigBee RF4CE was launched in 2008 to specifically address theneeds of this new era of remote controls. It enables a robust two-way and non-line-of-sight communication technology to free consumers from pointing a remote at an exacttarget, allowing them to more easily and accurately control entertainment equipment.

Consumer electronics based on ZigBee RF4CE is part of a growing ZigBee presence inhomes. This latest release of the ZigBee Remote Control 2.0 standard (ZRC 2.0) offers newfeatures enabling consumers with the state-of-the art remote control technology;

• Validation based binding to ease the binding process by eliminating the needfor involvement, i.e. a button press, on the consumer equipment;

• Binding proxy for quick binding with a device or a group of devices withassistance of alternative means (e.g. UPNP, HDMI-CEC, NFC, barcodes);

• IR code upload to dynamically configure IR codes for hybrid IR-RF remote controls;

• Standards based two-way communication heart beat to enable “find myremote” feature and upload of new firmware image and meta data;

• Bridging capability to enable ZigBee RF4CE to become a remote control in the ZigBee Home Automation network;

• Dynamic re-mapping of remote control keys/commands by the consumer equipment;

• HID command bank for the most common ZigBee Input Device standard (ZID) use-cases;

• Enhanced security enabling security key update after a successful binding

The new features are enabled yet keeping the compatibility with already deployedstandards based ZigBee Remote Control 1.x (ZRC 1.x) devices.

ZigBee has emerged as the preferred solution in several major markets: energy, homeautomation, lighting control, and healthcare. The ZigBee Smart Energy™, ZigBee HomeAutomation™, ZigBee Light Link™ and ZigBee Health Care™ standards address each ofthose verticals and are focused on improving consumers’ lives by enhancing comfort andconvenience, helping them save time and money, improve energy efficiency and liveindependent longer. ZigBee RF4CE complements the aforementioned standards and isspecifically addressing the needs for a low-latency (fast response), low energy (longbattery life) and cost efficient solutions for interaction and control with consumerelectronics devices.



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Table of Contents

Technical SummaryIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Network topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

The ZigBee RF4CE Network layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.4 GHz Band Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Channel Agility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Node Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Power Saving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

NWK Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Transmission Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Binding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Pairing, Configuration and Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Infrared (IR) Code Download . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

The ZigBee RF4CE Application Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Heartbeat for Effective Two-Way Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

ZigBee Remote Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

ZigBee Input Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Bridging ZigBee Remote Control and ZigBee Home Automation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

List of Figures

Figure 1 – Example ZigBee RF4CE Network Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 2 – The ZigBee RF4CE Specification Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 3 – General Schematic View of a NWK Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 4 – Binding Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9


TECHNICAL SUMMARYIntroductionThe ZigBee RF4CE specification defines a simple,robust, low-cost and low-latency communicationnetwork that allows wireless connectivity in consumerelectronics applications. ZigBee RF4CE is built on theIEEE 802.15.4 standard by providing a simplenetworking layer and includes support for two ZigBeeAlliance-developed standards, ZigBee Remote Controland ZigBee Input Device, that can be used to createmulti-vendor interoperable solutions for use withinthe home.

Some of the characteristics of a ZigBee RF4CEnetwork are:

• Operation in the 2.4GHz frequency bandaccording to IEEE 802.15.4.

• Co-existence with other 2.4 GHztechnologies is built-in through techniquesas defined in the IEEE radio channel accessscheme.

• Channel agile solution operating over threechannels.

• Power-management mechanism for alldevice classes.

• Simple and intuitive discovery and pairingmechanism with full applicationconfirmation.

• Multiple star topology with inter-PANcommunication.

• Various transmission options includingunicast, broadcast, acknowledged,unacknowledged, secured and un-secured.

• Security key generation mechanism withoption to renew key after pairing isestablished.

• Utilizes the industry standard AES-128security scheme.

• Support for two publicly availablestandards: ZigBee Remote Control andZigBee Input Device.

• Support for custom features withmanufacturer specific profiles.

• Seamless integration with other ZigBeestandards in the Smart Home throughdefined bridging mechanisms

Network topologyA ZigBee RF4CE personal area network (PAN) iscomposed of two types of devices: a target device (ornode) and a controller device (or node). A targetdevice has full PAN coordinator capabilities and canstart a network on its own.A controller device can join networks started by targetdevices by pairing with the target. Multiple ZigBeeRF4CE PANs form a ZigBee RF4CE network and devicesin the network can communicate between ZigBeeRF4CE PANs. In order to communicate with a targetdevice, a controller device first switches to the channeland assumes the PAN identifier of the destinationZigBee RF4CE PAN. It then uses the network address,allocated through the pairing procedure, to identifyitself on the ZigBee RF4CE PAN and thus communicatewith the desired target device.

Figure 1: Example ZigBee RF4CE Network Topology

Figure 1 illustrates an example ZigBee RF4CE topologywhich includes three target devices: a TV, a DVD and aSet Top Box (STB) and each target device creates itsown ZigBee RF4CE PAN. The TV, DVD and STB alsohave dedicated remote controls which are paired toeach appropriate target device. A multi-functionremote control, capable of controlling all three targetdevices itself, is added to the network by successivelypairing to the desired target devices.

As a consequence, this ZigBee RF4CE network consistsof three separate ZigBee RF4CE PANs: one managedby the TV (PAN 1), containing the TV remote controland the multi-function remote control; a second


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managed by the STB (PAN2), containing the STBremote control and the multi-function remote control;and a third managed by the DVD (PAN3), containingthe DVD remote control and the multi-function remotecontrol.

ArchitectureThe ZigBee RF4CE architecture is defined in terms of anumber of blocks or layers in order to simplify thespecification. Each layer is responsible for one part ofthe specification and offers services to the next higherlayer and utilizes services from the next lower layer.The interfaces between the layers serve to define thelogical links that are described in this specification. Thelayout of the layers is based on the open systemsinterconnection (OSI) seven-layer model.

Figure 2: The ZigBee RF4CE Specification Architecture

Figure 2 illustrates the ZigBee RF4CE stack architecture.The ZigBee RF4CE specification is designed to be builton top of the IEEE 802.15.4 standard MAC and PHYlayers and provides networking functionality, while theZigBee Remote Control and/or ZigBee Input Devicecan interface to the end-user application. Manufacturerspecific extensions to standards can be defined bysending vendor-specific data frames within thestandard. In addition, manufacturer specific profilescan also be defined.

The ZigBee RF4CE Network layerThe ZigBee RF4CE Network (NWK) layer provides twoservices: the NWK layer data service, interfacing to theNWK layer data entity (NLDE) and the NWK layermanagement service, interfacing to the NWK layermanagement entity (NLME). These services areaccessed through the NWK layer data entity serviceaccess point (SAP) (NLDE-SAP) and the NWK layermanagement entity SAP (NLME-SAP). The NWK layerdata service enables the transmission and reception ofNWK protocol data units (NPDUs) across the MAC dataservice. The NWK layer management service permitsservice discovery, pairing, un-pairing, receiver control,device initialization and network information base(NIB) attribute manipulation.

2.4 GHz Band FrequenciesA ZigBee RF4CE device operates in the worldwideavailable 2.4GHz frequency band, as specified by IEEE802.15.4. However, to provide robust, low-latencyservice against other common sources of interferencein this band, only a subset of channels is used –channels 15, 20 and 25. A target device can choose tostart its network on the best available channel atstartup time and so a ZigBee RF4CE network mayoperate over one or more of the available threechannels.

Channel AgilityAll ZigBee RF4CE devices support channel agilityacross all three permitted channels. As describedabove, a target device selects its own initial channelbased on the channel conditions during startup.During the course of the life of the target device,however, the channel conditions may vary and thetarget device can elect to switch to another channel tomaintain a high quality of service.

Each device paired to the target records the channelwhere communication is expected. However, in theevent that the target switches to another channel, thedevice can attempt transmission on the other channelsuntil communication with the target is reacquired. Thedevice can then record the new channel accordinglyfor the next time communication is attempted.


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Node InitializationA ZigBee RF4CE device initializes itself according towhether it is a target or a controller. Controller devicessimply configure the stack according to this model andstart operating normally. Target devices configure thestack and then attempt to start a network. To do this,the target device first performs an energy detectionscan that allows it to obtain information on the usageof each available channel, thereby allowing it to selecta suitable channel on which to operate. The targetdevice then performs an active scan allowing it todetermine the identifiers of any other IEEE 802.15.4PANs (ZigBee RF4CE or other ZigBee networks)operating on the selected channel, thus allowing aunique PAN identifier to be selected for its network.The target device then begins operating normally.

Power SavingPower saving is an important consideration for aZigBee RF4CE device. The specification defines apower-save mechanism that allows both controllerdevices as well as target devices to manage theirpower consumption by entering a power-savingmode. The power saving mechanism is under thecontrol of each ZigBee RF4CE standard. A device canmanage its receiver in a number of ways:

• The receiver can be enabled until further notice (e.g. when a TV comes out of standby).

• The receiver can be enabled for a finiteperiod (e.g. when a TV enters standby mode and wants to engage the powersaving-mode).

• The receiver can be disabled until furthernotice (e.g. when a remote control enters adormant state due to none of its buttonsbeing pressed). When the power savingmode is engaged, the receiver is enabledfor an application-defined duration (known

as the active period) and then disabled. Thismechanism is then repeated at anapplication-defined interval (known as theduty cycle). Other devices can stillcommunicate with a device in power-saving mode by targeting thetransmission during the active period. Theresult is a device that periodically enablesits receiver for only a short time, allowingit to conserve power while remainingactive on the network.

NWK FramesThe ZigBee RF4CE NWK layer defines three frametypes: standard data, network command and vendor-specific data. Standard data frames transportapplication data from either standards or manufacturerspecific profiles. Network command frames transportframes that allow the network layer to accomplishcertain tasks such as discovery or pairing. Vendor-specific data frames transport vendor-specificapplication data. The general NWK frame format isillustrated in Figure 3.

The fields of the general NWK frame are:• Frame control: control information for the frame

• Frame counter: incrementing counter todetect duplicates and prevent replay attacks (security)

• Profile identifier: the application frameformat being transported

• Vendor identifier: to allow vendorextensions

• Frame payload: contains the application frame

• Message integrity code: to provideauthentication (security)


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Figure 3: General Schematic View of a NWK Frame.


Transmission OptionsThe ZigBee RF4CE specification defines a number oftransmission options that can be used by anapplication and combined as appropriate. Eachtransmission can be sent secured or un-secured.

• Acknowledged: Originator data isconfirmed by the recipient

• Unacknowledged: Originator data is notconfirmed by the recipient

• Unicast: Originator data is sent to a specificrecipient

• Broadcast: Originator data is sent to allrecipients

• Multiple channel: Originator attemptstransmission using frequency re-acquisitionmechanism

• Single channel: Originator attemptstransmission on the expected channel

BindingThe binding process creates a logical associationbetween two RF4CE nodes, aka a pairing link. Nodeswithin a ZigBee RF4CE network may only exchangedata messages directly with other devices on thenetwork after the binding process has completedsuccessfully. The binding process consists of multiplesteps illustrated in Figure 4.

Figure 4: Binding Process

DiscoveryA ZigBee RF4CE device can perform discovery in anattempt to find other suitable devices for pairing.Discovery can be attempted repeatedly on all threechannels for a fixed duration or until a sufficientnumber of responses have been received. Servicediscovery is only available to devices that are notcurrently in power-saving mode. During discovery, anumber of pieces of information are exchangedbetween both devices. This information is passed tothe application, which can then make a decisionwhether it should respond.The information exchanged is as follows:

• Device capabilities: The type of the device(i.e. target or controller), whether thedevice is mains or battery powered andlevel of security.

• Vendor information: The ZigBee RF4CEallocated vendor identifier and a freeformvendor string specifying vendor specificidentification (e.g. a serial number).

• Application information: A short user-defined string which describes theapplication functionality of the device (e.g.“lounge TV”), a device type list specifyingwhich types of device are supported (e.g. acombo device may support both “TV” and“STB” functionality) and a profile identifierlist specifying standard or manufacturerspecific profiles supported by the device.

• Requested device type: The type of devicebeing requested through the discovery (e.g.a multifunction remote control may besearching for “TV” functionality).

• Class descriptor(s): A mechanism toindicate the state and importance of thedevice used to rank discovery responsesbefore pairing. For example, a STB that isjust turned on with an empty pairing tablewill be a more likely candidate for pairingcompared to a STB with a significantuptime and existing pairing

• Filters: The originator of the discovery canset filters (vendor ID, min/max classdescriptors and signal strength) to avoidexcessive number of responses


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Discovery

Pairing

Configura�on

Valida�on


Pairing, Configuration and ValidationOnce a device has determined, through discovery, thatthere is another device within communication rangeoffering compatible services, it can set up a pairing linkin order to begin communication.

The ZRC1.x profile required a “push button” stimuluson the target device to start the pairing process.ZRC2.0 enables pairing without a stimulus on thetarget device. After successful discovery of otherdevices within communication range, the pairingoriginator ranks the devices based on their classdescriptor(s) to find the best pairing candidate. Itattempts pairing with the highest ranked device, if notsuccessful, it attempts paring with the second highestranked device, and so on. This pairing is temporary andused for configuration and interactive validation. Notethat security is enabled for the temporary pairing toensure an encrypted communication channel for theconfiguration and validation phases.

The configuration phase is used to exchange attributesto determine the specific functionality supported byeach of the two devices. Typical attributes exchangedare profile version, supported profile capabilities(heartbeat, key-remapping, IR upload etc), supportedcommand banks, specific command bank codes etc.

After configuration and once validation is successful,e.g. the pairing originator enters the correct PIN codedisplayed on the target device (STB/TV), the bindingprocess is completed.

If the binding was successful, both devices store apairing link in their respective pairing tables. Thisallows an originator to communicate with a target anda target to communicate back to an originator. Eachentry in the pairing table contains all the informationnecessary for the network layer to transmit a frame tothe target device. This removes the burden ofaddressing, etc. from the application layer which cansimply supply an index into the pairing table in orderto communicate with another device.

Each entry in the pairing table contains the followinginformation:

• Pairing reference• Source network address• Destination logical channel• Destination IEEE address• Destination PAN identifier• Destination network address• Recipient device capabilities• Recipient frame counter• Security link key

Proxy binding offers a mechanism to bypass thediscovery process and obtain the necessaryinformation (IEEE address and PAN ID) by other meansto bind directly with the intended equipment. Acouple of examples;

• STB and remote control is equipped withNFC. The IEEE address and PAN ID isexchanged out-of-band over the NFC link tostart the binding process directly betweenthe STB and remote control.

• STB is connected to other media centerequipment. After a successful binding of aremote with the STB, the STB can obtain theIEEE and PAN ID of the other equipmentout-of-band (HDMI-CEC, UPNP, etc). Thisinformation is sent to the remote controllerin-band so the remote controller can binddirectly with all media center equipment.From the user’s perspective, they are able tobind with all devices in their media centerafter completing a single binding.

• This optional feature can also be utilized inwarehouses to scan the barcodes of thetargets to allow the remote control toautomatically bind upon first use

SecurityThe ZigBee RF4CE specification provides acryptographic mechanism to protect thetransmissions. This mechanism provides the followingsecurity services:

• Data confidentiality: To ensure that the datacontained in a ZigBee RF4CE transmission canonly be disclosed to the intended recipient.


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• Data authenticity: To ensure that theintended recipient of a ZigBee RF4CEtransmission knows that the data was sentfrom a trusted source and not modifiedduring transmission.

• Replay protection: To ensure that a securetransmission cannot simply be repeated byan attacking device if overheard.

128-bit cryptographic keys are generated by each endof a pairing link and stored in the pairing table forfuture use. The keys can be updated at the userdiscretion if desired and supported by the application.

Infrared (IR) Code DownloadMany ZigBee RF4CE remote controls include an IRdatabase for control of legacy consumer electronicsequipment. An IR database for controlling TV, STB andAudio/Visual equipment is quite large due to the largeavailability of protocols and manufacturerscustomizations, and as such, consumes valuableresources on the remote control. Customers may alsorequest an IR protocol to control equipment notincluded in the database at production time.

ZRC2.0 defines a standards based solution foruploading IR codes to the remote control. This way,the IR database can be stored on the target device or in the cloud as opposed to on the remote, and only the necessary IR codes are uploaded to theremote control.

Heartbeat for Effective Two-WayCommunicationIR (Infrared) remote control use-cases are limited tosimple control due to the generally one-way nature ofthe communication technology. The two-waycommunication feature of ZigBee RF4CE is not onlyused to acknowledge sent packets for increasedreliability, it can also be used to expand the remotecontrol application scenarios.

ZRC2.0 defines a standard based solution for effectivecommunication between a remote control andconsumer equipment. A remote control is in its lowestpower mode most of the time to save battery

consumption and only wakes up to process a useraction like a button press. The heartbeat mechanismenables the consumer equipment to send a messageto the remote control, yet keeping the remotecontrol in its lowest power mode most of the time.The remote control basically checks in with theconsumer equipment at a negotiated interval toretrieve the message.

Examples of application features using the heartbeatmechanism;

• “Find my remote” where a user e.g. push abutton on the consumer equipment if theremote is lost and the remote sends a signal(e.g. sounds a buzzer) when triggered;

• Upload of new remote control firmwarewithout user interaction to enable newapplication features;

• Upload of actual information (e.g. sportsscores, stock tickers, etc.) for advancedremote controllers with LCD user interface.

The ZigBee RF4CE Application LayerThe application layer of a ZigBee RF4CE device iscomposed of a profile component and an application-specific component. The profile component can bethought of as a common language that devicesimplementing the profile exchange to accomplishcertain tasks, e.g. switching the channel on a TV, andallows for interoperability between devices. Theapplication component is provided by the end-manufacturer in order to add specific functionality tothe commands request through the profile.

One important aspect of the application standardsdeveloped by the ZigBee Alliance is their unified pairingmechanism. This enables controller and target devices todiscover and pair in an agnostic manner as long as theyshare a common profile.

The ZigBee RF4CE specification defines two standardsdeveloped by the ZigBee Alliance, ZigBee Remote Controland ZigBee Input Device, but also permits vendors toeither extend these standards or to define completelyproprietary ones called manufacturer specific profiles.


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ZigBee Remote ControlThe ZigBee Remote Control standard defines commandsand procedures to enable consumer electronics devices(e.g. a TV, STB, DVD or CD player) to be controlled bybasic or advanced remote control devices.

The standard’s commands are based on the HDMICEC specification and covers commands such asvolume up/down, channel up/down, power on/off,mute, select, guide, ok, 0-9, etc. It also includessupport for common Human Interface Device (HID)operations like mouse (remote controller pointingdevices), keyboards, and ZigBee Home Automationcommands. Consumer electronics devices can alsoquery the control device for the list of commandsthat it supports. This enables a STB or a TV tocustomize its menu system based on the capabilitiesof the control device.

A button on the remote control is typically mappedto one specific command. It is possible to easily re-map the button/command from the target device ifdesired. This enables a remote control to bedynamically configured depending on the context,for example, some keys are re-mapped if you enter agaming application.

A command sent from the control device to the targetdevice also contains a code indicating the specificbutton “action taken by the user”

• User control pressed: This code is used tospecify the first command sent due to abutton press on the control device.

• User control repeated: This code is used tospecify that the command is sent due to abutton being continually held down on thecontrol device

• User control released: This code is used tospecify that the button on the controldevice is released for the specific command

As an example, this allows users to hold down thevolume up button to continually increase the volumeto a desired level. ZigBee Remote Control specifies thetiming requirements for each of the user controlledpressed/repeated/released commands.

ZigBee Remote Control provides an easy migrationpath from IR-based remotes to advanced controldevices with little, if any, change to the user interfaceor remote control buttons.

ZigBee Input DeviceThe ZigBee Input Device standard defines commandsand procedures to enable consumer electronicsdevices (e.g. a TV, STB, DVD or CD player) to becontrolled by the new generation of advanced inputcontrol devices. This standard is modeled after theubiquitous USB Human Interface Device (HID)specification and enables input devices like keyboards,motion-controlled pointing devices, touchpad etc.

A controller device supporting ZigBee Input Device isreferred to as an input class device, and a target devicesupporting the standard is referred to as an adapterclass device.

Although the ZigBee Input Device is modeled after theUSB HID specification, it is important to notice that theinterface between an adapter and the consumerelectronics equipment does not need be a physicalUSB interface. The standard is merely using theconcepts of USB HID specification for deviceconfiguration and command reporting over the ZigBee RF4CE link.

A mandatory configuration phase is entered after apairing between two devices is established. In thisphase, the input class device will describe itscapabilities and command reporting descriptors to theadapter class device. The standard defines a collectionof command reporting descriptors for commonly usedinput devices like a keyboard and mouse. Additionally,it provides a mechanism for the device to define itscustom command reporting descriptors.

ZigBee Input Device provides three communicationmethods (a.k.a. pipes) between the input device andthe adapter:

• Control pipe: This is a mandatory bi-directional pipe enabling an input device tosend commands or for an adapter to pollthe class device for data. Commands are


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sent using the unicast/acknowledged/multichannel or broadcast transmissionoption. Keyboard commands are typicallysent using this pipe.

• Input interrupt pipe: This is a mandatory pipe enabling an input device to send low-latency or asynchronous commands to an adapter.Commands are sent using a combination of the unicast/unacknowledged/singlechannel and unicast/acknowledged/multichannel transmit options. Theunicast/unacknowledged/single channeltransmit option ensures low-latencydelivery of commands, while theunicast/acknowledged/ multichanneltransmit option reacquires the ZigBeeRF4CE channel in the case it iscompromised and the adapter has movedto a different channel. Mouse data aretypically sent using this pipe.

• Output interrupt pipe: This is an optionalpipe enabling the adaptor to transfer low-latency or asynchronous commands to theinput device.

ZigBee RF4CE enables bi-directional communicationand the ZigBee Input Device standard defines aconsistent way to enable adapters to send commandsto input devices.

This can be used to locate a lost input device such as aremote control, or send social media status, stockmarket alerts or real-time sports scores to be displayedon the input device.

Next-generation consumer electronics devices provideuser interfaces and services that require input devicesbeyond a simple push-button remote controller.Among other things, consumers want to update theirsocial media status, surf the web, search the video-on-demand catalog or TV guide for their favoriteactress/actor, or play a casual game. ZigBee InputDevice enables development of input control devicesthat can accomplish these tasks in an easy andstandardized manner.

Bridging ZigBee Remote Control andZigBee Home AutomationZigBee is the industry preferred technology forcreating smarter homes to enhance the comfort,convenience, security and energy management for thecustomer. Devices like thermostats, lights, alarmsystems, etc. are utilizing the ZigBee HomeAutomation standard for low-cost and low-poweroperation, in addition to mesh networking technologyfor whole-home coverage.

A STB may also include functionality for configuration,control and monitoring of a ZigBee Home Automationnetwork in addition to providing video services. Thisenables the rich user interface capabilities available ona STB for control of the home automation devicesthrough the ZigBee RF4CE remote controller.

There are two possible options• The remote controller communicates withthe STB using standard RF4CE messagesbased on HDMI CEC or HID commands tonavigate to the home automation menuand to control the devices on the network,e.g. set the temperature of a thermostat orconfigure the alarm system. The STB willtranslate the user interface action to aZigBee Home Automation command andsend the message to the appropriate deviceon the ZigBee network

• The remote controller communicates withthe STB using messages from the ZRC2.0 HAcommand bank which are then relayed tothe ZigBee network. This enables a moreadvanced remote controller, e.g. withspecific home automation buttons or LCDscreen, to control the home automationdevices without STB user interfaceinteraction


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understanding zigbee rf4ce...the zigbee smart energy , zigbee home automation , zigbee light link...

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