Got no wires to hold me down

It’s hard to look back at the past twenty years and believe the difference communications has made on our lives. In 1989 most of us had a home phone and that was all. Very few people even had a PC at home and cell phones and Internet connection were very scarce and expensive.

Since then cell phones and the Internet have boomed; a survey last year by the Telegraph in the UK estimated 90% of people now have a cell phone, and over 50% have Internet access. These numbers seem to be average for the developed world, and even low in some cases where physical constraints impaired widespread implementation of a telephone network, for example in Finland.

It has reached the point that today every device seems to have some type of connectivity option, and this trend is set to continue well into the future. This article will look at wireless networking options, and in particular the short range device to device networking that is set to show the biggest rate of growth in the near future.

Initially, apart from mobile communications, the only other example of wireless networking that was popular was variations of the IEE802.11 standard for connecting IT equipment. Even then it is only fairly recently that WiFi was fast and reliable enough to equal the performance wired networking protocols.

Many applications are unsuitable for wired networking, or for those which could potentially use wired solutions, the implementation can be time consuming and costly. Wireless networks have also enabled some applications which wouldn’t be considered previously. For example, remote sensors can now run off batteries and communicate to a central controller. Previously this would have required a mains supply and/or an engineer to visit the location and take readings. These sensors may only take readings infrequently and do not require large data transfers.

Standards such as WiFi, which are used extensively in IT networks, require their own mains supply for the radio to operate, which makes them unsuitable for applications like the one mentioned above. As such, a new generation of standards have emerged to fulfil the requirements of short range, low power networks. Special interest groups and individual manufacturers all have developed their own standards which all have different traits and are suitable for different applications.

Most of these short range standards operate on ISM channels, as communication devices using these bands must tolerate any interference from ISM equipment. These bands are typically used for unlicensed operation, since unlicensed operation typically needs to be tolerant of interference from other devices anyway. There is no one single solution for all short range, low power applications, as they have varying requirements.

Bluetooth

Bluetooth is a short-range communications technology intended to replace cables while maintaining high levels of security. The key features of Bluetooth technology are robustness, low power, and low cost. The Bluetooth specification defines a uniform structure for a wide range of devices to connect and communicate with each other.

So far the Bluetooth standard has been used mostly to connect cell phones and other mobile devices to each other and IT equipment. But this is changing as variations of the standard emerge for higher speed data transfer and better levels of security.

The original Bluetooth specification used GFSK modulation frequency hopping on 79 frequencies to minimize interference and contention. In its basic mode, a gross data rate of up to 1Mbit/s to a range of 10m could be achieved. Later iterations of the standard have added new functionality.

For example, Bluetooth 1.2 allows faster connection and discovery and also improved resistance to interference. Bluetooth 2.0 enhances the data rate up to 3Mbit/s, giving a usable bandwidth of 2.1Mbit/s. The latest specification, Bluetooth 2.1, increases security options and introduces easier connection with NFC technology.

By keeping all the new iterations of the Bluetooth standard backward compatible and adding these new features for data rates, connectivity, security and an enhanced range of up to 100m, Bluetooth can now take on more varied and complex role.

Zigbee

According to the Zigbee Alliance, ZigBee was created to address the need for a cost-effective, standards-based wireless networking solution that supports low data-rates, low-power consumption, security, and reliability. After what seemed like a slow start, Zigbee has been gaining in popularity, initially mainly in industrial networks.

ZigBee is based on the IEEE 802.15.4-2006 standard and operates in the unlicensed 2.4GHz, 915MHz and 868MHz ISM bands. In the 2.4 GHz band there are 16 ZigBee channels, with each channel requiring 5MHz of bandwidth. Data bandwidth is a mazimum of 250kbit/s per channel in the 2.4GHz band, 40kbit/s per channel in the 915MHz band, and 20kbit/s in the 868MHz band. The transmission range is between 10 and 75m, although it is heavily dependent on the particular environment.

The lower data rate compared to Bluetooth makes Zigbee applicable for a totally different set of applications. One potential killer application may be home area networks, especially in the expected boom application of utility monitoring. Because the typical applications for Zigbee are generally not time critical, a low duty cycles can be used to ensure that power used is kept to a maximum.

Wibree

Wibree is a wireless standard which was initially adapted from Bluetooth by Nokia. The protocol is intended to become an open standard for short range and ultra low power consumption. From June, 2007 Wibree was incorporated into the Bluetooth specification, and can be described as Bluetooth low energy technology.

Wibree is designed to complement Bluetooth technology in supported devices, while being smaller and more energy-efficient than Bluetooth. Wibree operates in 2.4GHz ISM band with gross data transfer rate of 1Mbit/s and range of 10m. The main areas Wibree is intended to target include wrist watches, wireless keyboards and toys.

Z-Wave

Developed by Danish company Zensys, the Z-Wave standard is designed for remote control applications in residential and light commercial environments. The Z-Wave RF system is optimized for low-overhead commands such as on-off and raise-lower, with the ability to include device metadata in the communications.

Z-Wave uses the 900 MHz ISM band, avoiding the popular 2.4GHz frequency and therefore it is more impervious to interference from the common household wireless electronics that operate in that frequency. Using GFSK modulation, Z-wire has a data transfer bandwidth of between 9.6Kbit/s and 40Kbit/s with a range of approximately 30m depending on environment.

Applications in which Z-Wire technology is expected to be embedded or retrofitted are lighting, home access control, entertainment systems and appliances.

SimpliciTI

TI’s proprietary SimpliciTI RF networking protocol targets simple, small RF networks with less than 100 nodes. These networks typically contain battery-operated devices, which require long battery life, low data rate and low duty cycle, and have a limited number of nodes talking directly to each other.

The protocol was designed for easy implementation with minimal microcontroller resource requirements (4K FLASH, <512byte RAM). Since SimpliciTI network protocol is designed for simple RF networks, it offers a good complement to ZigBee. The SimpliciTI network protocol supports a wide range of low-power applications including alarm and security, automated meter reading, home automation and active RFID.

Provided as source code, SimpliciTI is provided license free, without royalties and developers are encouraged to adapt the protocol to their specific application needs.

SMAC/Synkro

SMAC and Synkro are Freescale’s proprietary protocols based on IEEE 802.15.4. SMAC works with Freescale's transceivers with 8-bit MCU control. The protocol is intended to be used for fast product development and system evaluation. Low-cost applications that require basic primitives, such as transmit, receive and power and channel selection are examples of what SMAC can do. SMAC supports star and peer-to-peer networks, but more complex approaches can be developed, creating network layers or adding repeater nodes. SMAC can fit into 4-8 Kbyte, depending on the extra elements added.

Synkro starts with 802.15.4, but incorporates improvements in interference avoidance by adding channel agility and low latency transmissions. Synkro was created to control, monitor and automate consumer electronic products including televisions, DVD players and recorders, set top boxes, audio video receivers and remote control.

MiWi

Miwi and MiWi P2P are Microchip proprietary wireless protocols. The protocols use small, low-power digital radios based on IEEE 802.15.4 that are designed for low data transmission rates, short distance, cost constrained networks. The MiWi protocol stacks are small foot-print alternatives (3K-17K) to ZigBee (40K-100K) and are useful for cost-sensitive applications with limited memory. Although the stacks can all be downloaded for free there is an obligation to use them only with Microchip microcontrollers.

Standard	company	Frequency Band	Bit Rate	Range	description
Wibree	Nokia	2.4G	1M	<10M	applications where low power design is very critical. working parallel and complement with Bluetooth
Z-Wave	Zensys	868.42M/908.42M	40K	100M	about half cost of Zigbee,not suitable for Audio/Video data transfer.
SimpliciTI	TI	1G/2.4G	less than 100 nodes, a perfect complement to ZigBee, lower cost and low-power .
MIWI	microchip	2.4G	based on the IEEE 802.15.4 specification,for low-power, low data rate, cost sensitive application
SMAC and Synkro	Freescale	2.4G	SMAC: Based on the 802.15.4 PHY, provide PP and star networks ,Synkro:RF remote control based on 802.15.4 ,no line-of-sight restrictions and supports two way communication.