A blessing or a curse?

Wireless sensor applications prosper best within the sphere of industry standards. Standards offer OEMs the freedom to purchase from a larger pool of suppliers and competitive pricing, a common technology which eases design decisions and inventory requirements and most importantly international standards that allow devices from different vendors to interoperate; a feature which is paramount in wireless applications that are marketed and used worldwide.

The benefits of communication standards are a top priority for large technology and consumer electronics companies; they require worldwide solutions, as they are loath to develop and certify different products (and different SKUs) for different regions in the world, as well as open standards with multiple chip and technology providers, to guarantee lowest cost and continuity of supply, thereby avoiding the single-source trap.

This ‘peace of mind’ aspect is the main blessing of standards that makes large companies big supporters. Without standards it would be difficult for machines or equipment to efficiently co-operate; it would be expensive to develop workarounds to make things talk to each other. Systems can be very complex, so every element of a large system that can be standardised essentially removes a significant uncertainty factor from the total system or, at least, isolates it and makes it manageable.

Furthermore a standard is usually based on a collective experience and cooperation which increases reliability and the long term availability. A good standard also creates an ecosystem of multiple vendors avoiding the single source trap (and at the same time, helps to drive down the cost), all helping to further bolster this peace of mind.

The challenge with standards, though, is that it usually takes a long time for a standard to come together and once it is completed it often feels like a compromise that doesn’t fully serve everyone’s interests. However, for wireless sensor communications for the Smart Home, there is one standard that has overcome the negotiations and delays, and prevails today. It is ZigBee..

It is important to recognise that there are ‘different horses for different courses’; there are two open IEEE-based standards for networking; WiFi and ZigBee, with WiFi primarily used for content sharing/distribution and ZigBee targeted at low data rate sense/control applications. There are also two open Bluetooth SIG based standards for peripheral connectivity: Bluetooth ‘Classic’ for content (audio connect to a phone, for example) and Ultra Low Power Bluetooth ‘Smart’ for sense and control (such as a heart rate monitor to a phone or watch).

In addition to these open standards, there are a few ‘proprietary standards’ that hit the market as pre-cursors to the open standards: ZWave (in the US), and EnOcean (in Europe) for ZigBee, and ANT+ for Bluetooth Smart.

ZWave, EnOcean, and also DECT-ULE, are sub-GHz, regional, quick to market technologies, while the majority of the industry is embracing open worldwide standards like WiFi, ZigBee and both flavours of Bluetooth.

WiFi or ZigBee?

For the home environment, the immediate question is: what networking technology will be best used in the home? One may think that WiFi and ZigBee are competing with each other. The reality, however, is that both technologies have their own place.

WiFi (based on IEEE 802.11) has been developed with a focus on a high speed data rate (100Mbit/s and beyond) optimised to distribute content through the home: from browsing the internet to downloading movies. WiFi connected devices are typically connected to the mains and energy consumption has therefore been a secondary criterion.

The focus of ZigBee (based on IEEE 802.15.4) has been very complementary to WiFi: developed for sense and control networks, the data rate (250kbit/s) has been secondary to the battery life, and therefore the battery life of ZigBee devices can easily be measured in years, or even exceeding the life time of the device it is used in. This is in contrast to the battery life of even ‘energy efficient’ WiFi implementations, usually expressed in weeks or months. This makes ZigBee the ideal candidate to complement WiFi in the home as the management network of choice (Figure 1).

Figure 1: GreenPeak Technologies believes Home Networks will use WiFi for content distribution and ZigBee for sense and control networks

The first open standard for wireless sensor applications is covered by IEEE 802.15.4. The IEEE standard 802.15.4 intends to offer the fundamental lower network layers of a type of wireless personal area network which focuses on low-cost, low-speed ubiquitous communication between devices. On the next communication layer, the ZigBee standard offers a superior solution for the rapidly evolving and growing Smart Home and Internet of Things market.

The ZigBee Alliance, an organisation with more than 400 members, maintains and publishes the ZigBee standard for wireless communication for a wide variety of application domains (home, consumer, smart energy/grid, building automation, retail automation, and several others). All these ZigBee protocols have one element in common: they all use the same underlying radio technology; the same 2.4GHz frequency band worldwide, and all comply with worldwide radio certification rules.

ZigBee can best be described as the low power WiFi. What WiFi provides for computers, TVs and other devices in distributing content through the home, ZigBee provides for all the small devices and gadgets in the home: light switches, thermostats, remote controls, security sensors, door locks, motion sensors and more.

The key characteristic for ZigBee is its long battery life. As it only needs to transmit tiny data packages, ZigBee is very low power and allows applications to run on batteries for many years. Often longer that the expected life span of the application, essentially making it maintenance free, since battery replacement will no longer be required.

ZigBee even supports energy harvesting, for example a wireless light switch that can be powered by simply flipping the switch. No battery at all is required because the actual motion of flipping a light switch generates enough energy to enable the switch’s ZigBee radio to send a signal across the room to an individual light, making it turn on or off.

Smart Home technologies

Today, leading large Multi-Service Operators (MSOs) are driving the Smart Home applications through a variety of innovative service offerings like security, energy management and home care. The number of Smart Home devices connecting to the internet is steadily growing by several millions per month.

ZigBee has already been chosen as the preferred technology by a number of service providers, such as Comcast, DirecTV and EchoStar. However, there are a handful of other wireless networking technologies that are also attempting to gain traction in the Smart Home networking market.

Below is an overview of the different technologies.

1. Probably the best known is ZWave, a proprietary technology from Sigma Designs in the USA, which uses various regional sub-GHz frequency bands in different parts of the world (USA, Europe, Japan, China). ZWave has achieved some early successes — in particular in the USA. It presents itself as a standard through the ZWave Alliance and is putting efforts in place to license its technology to other chip vendors.

2. In Europe, EnOcean is well known. It is a proprietary technology developed by EnOcean GmbH, a Munich, Germany based company. Like ZWave, it also uses various regional sub-GHz frequency bands for different parts of the world (USA, Europe, Japan, China). The wireless technology has been accepted as a standard under ISO (ISO/IEC 14543-3-10).

3. DECT-ULE is different. Not proprietary, it is an open protocol that is based on the original Digital European Cordless Telephony voice protocol. However, similar to both ZWave and EnOcean, it is very regionalised and uses various frequency bands in different parts of the world. Because of its connection oriented voice capabilities, it does not natively support networking, so therefore it is less suitable for sense and control networks. DECT-ULE technology is brought to market by a number of chip companies, including DSP Group and Dialog. It is interesting to note that in the past, efforts have been made to develop a version of DECT that could replace WiFi.

4. Bluetooth Smart is a low-power derivative of Bluetooth. It is an open standard that uses a worldwide frequency band (2.4GHz) and multiple large chip vendors provide this technology. However, Bluetooth Smart, just like Bluetooth, is a point-to-point connection technology, not a networking technology. So, it is very likely to follow the same market path as Bluetooth did: originally Bluetooth was proposed as a replacement for WiFi networking, but today, Bluetooth and WiFi are complementary technologies, used for complementary applications. In the same way, Bluetooth Smart and ZigBee are complementary technologies. For example: Bluetooth Smart is very suitable for Body Area Networks and ZigBee for Smart Home networking. One may well expect to see combo ZigBee-Bluetooth chips in the future, supporting both technologies.

Why ZigBee?

Figure 2: Using ZigBee, a wide variety of Smart Home ‘sentroller’ devices will not only talk to each other, but to end-users via a remote control, web interface and/or a smart phone

Today, ZWave, EnOcean and DECT-ULE are making regional progress. Bluetooth and Bluetooth Smart are open worldwide standards, but they are not networking technologies and therefore they play in different market segments, serving different sets of applications.

ZigBee however is an open standard networking technology standard (based on IEEE 802.15.4), supplied by more than 10 chip vendors. It is also complementary to WiFi; where WiFi pursues high data-rates to support internet content sharing and distribution, ZigBee is about long battery life. Furthermore, ZigBee uses the worldwide (2.4GHz) frequency band, meeting the requirements of the large worldwide product makers.

WiFi and Bluetooth are worldwide accepted open standards (based on IEEE 802.11 and 802.15.1). But a little over a decade ago, WiFi and Bluetooth went through a few years of market confusion, where they were pitted against each other and both had to compete with proprietary alternatives. For instance WiFi had to ‘battle’ with HomeRF, a proprietary networking technology that is now forgotten, and today Bluetooth is still battling somewhat with ANT+ for some applications.

Today the wireless networking and communications market is dominated by WiFi and Bluetooth, each in their own application domain. WiFi has become the technology for high speed, high data rate communications in our homes and throughout larger buildings, while Bluetooth has become the standard short range, low data rate ‘cable replacement’ technology connecting a wide range of devices from keyboards and mice to headsets.

When the market confusion is resolved, it seems likely that for low power networks the market will be dominated by ZigBee and Bluetooth Smart. ZigBee will be used for networked devices and sensors (e.g. Smart Home solutions) and Bluetooth Smart will be the answer for simple one-to-one connections (e.g. connecting a heart-rate monitor or a step-counter to, for instance, a cell phone).

As every home has its own specific home automation needs, defined by the occupants (be it a family with children or elderly people), by the construction (a large house, with a floor and cellar) and by the interest of the people who live there (comfort seekers or energy savers), the combination of these different profiles will result in different needs for home management applications.

Many of the technology solutions we need for the Smart Home are already available, but currently they do not share a common communication platform and are therefore not able to be integrated. A motion sensor used in the security system cannot be integrated in the light control system that switches off the lights when nobody is in a room.

Once we have all applications under the same open ZigBee communication standard, we can start thinking about integrating the different sensor applications and linking their intelligence to create the real smart home that no longer needs human intervention.

The smart and energy efficient home, monitored and controlled by one central application on your smart phone, will finally become a reality and introduce a connected ecosystem for everyday living.

Author profile: Cees Links is the CEO & Founder of GreenPeak Technologies. As a pioneer of the wireless data industry he was responsible for the first wireless LANs developed, and has been involved in the establishment of the IEEE 802.11 standardisation committee and the WiFi Alliance. He was also instrumental in helping to establish the IEEE 802.15 standardisation committee to become the basis for the ZigBee sense and control networking technology and standardisation.