Gary Marrs, senior field application engineer at Lantronix, discusses some of the benefits that wireless technology can bring to a wide range of businesses.
Companies are increasingly turning to wireless technology to connect serial devices and avoid the high costs associated with cable installations. Low-cost wireless links reduce installation and maintenance costs and provide mobility. However, designing an effective wireless network requires an understanding of today's complex wireless technologies, their benefits, and their trade-offs.
Technical information is needed to help understand the wireless technologies for embedded systems. So what is the motivation to go wireless and what are the various wireless networking standards available?
Investing in wireless is worthwhile
Local Area Networks (LANs) run on wire cable which are expensive to install and difficult to reconfigure for production changes. They do not allow for easy mobility and cables cannot go into certain areas - for example, a factory floor.
WLANs (wireless LANs) are revolutionising the way we work and do business. Data applications running over wireless networks are becoming pervasive in our daily lives. Transforming the business process and removing road blocks to productivity, wireless networks are being used across a wide variety of industries:
- Industrial automation
Productivity improvements, inventory management and quality control are common challenges for manufacturing facilities today. Manufacturing equipment must be attached to essential devices such as quality control equipment and operator displays. Wireless networks offer the solution to such challenges.
Wireless applications are particularly attractive to industries where certain functions are difficult to perform because of large areas, harsh operating conditions, or other restrictions.
The medical industry seeks productivity gains due to staff shortages. Increasingly, medical departments are building convincing wireless return on investment (ROI) models. Use of computer-based practices is expected to expand and wireless communications networks are essential to their success.
With increasing competition, retailers are seeking ways to improve productivity, reduce costs and generate incremental revenue. WLANs and the applications that run over them, are proven. A popular example includes multimedia kiosks that employ audio, video and graphics to run point-of-sale (POS) applications. Improving timeliness makes the flow of information more seamless; these wireless systems therefore improve customer satisfaction and increase profitability.
Businesses of all types are finding that wireless networks meet the high availability and capacity requirements needed for their specific applications. Once a decision is made to deploy a wireless system, the overriding question becomes one of standards.
Table 1 summarises today's popular wireless-networking standards. The sections that follow describe these standards in greater detail.
|StandardData Rate||Frequency Band||Modulation Scheme||Typical Range||Pros/Cons|
|IEEE 802.11||Up to 2 Mbps||2.4 GHz||FHSS or DSSS||20 m||This specification has been extended into 802.11b|
|IEEE 802.11a||Up to 54 Mbps||5 GHz||OFDM||40 ft at 54 Mbps,
300 ft at 6 Mbps
|IEEE 802.11b||Up to 11 Mbps||2.4 GHz||DSSS with CCK||100 ft at 11 Mbps,300 ft at 1 Mbps|
|IEEE 802.11g||Up to 54 Mbps||2.4 GHz||OFDM above 20 Mbps, DSSS with CCK below 20 Mbps||50 ft at 54 Mbps, 150 ft at 11 Mbps|
Wireless LAN standards
The 802.11 standard comprises a family of standards – some sanctioned and others working their way through the approval process.
The 802.11 standard is based on the same standards framework as Ethernet. This provides a high level of interoperability and ensures that Ethernet/WLAN internetworking functions and devices can easily be implemented.
IEEE WLAN standards are listed and compared in the following table.
|Standard Approved||July 1997||September 1999||September 1999||June 2003|
|Available Bandwidth||83.5 MHz||300 MHz||83.5 MHz||83.5 MHz|
|Unlicensed Frequencies of Operation||2.4-2.4835 GHz DSSS, FHSS||5.15-5.35 GHz OFDM,5.725-5.825 GHz OFDM||2.2-2.4835 GHz DSS||2.2-2.4835 GHz DSS or OFDM|
|Number of Non-overlapping Channels||3 (indoor/outdoor)||4 indoor (UNII1), 4 indoor/outdoor (UNII2), 4 outdoor (UNII3)||3 (indoor/outdoor)||3 (indoor/outdoor)|
|Data Rate per Channel||2, 1 Mbps||54, 48, 36, 24, 18, 12, 9, 6 Mbps||11, 5.5, 2, 1 Mbps||54, 36, 33, 24, 33, 12, 11, 9, 6, 5.5, 2, 1 Mbps|
|Modulation Type||DQPSK (2 Mbps DSSS), DBPSK (2 Mbps DSSS), 4GFSK (2 Mbps FHSS), 2GFSK (1 Mbps FHSS)||BPSK (6, 9 Mbps), QPSK (12, 18 Mbps), 16-QAM (24, 36 Mbps), 64-QAM (48, 54 Mbps)||DQPSK/CCK (11, 5.5 Mbps), DQPSK (2 Mbps), DQPSK (1 Mbps)||OFDM/CCK (6, 9, 12, 18, 24, 36, 48, 54 Mbps), OFDM (6, 9, 12, 18, 24, 36, 48, 54 Mbps), DQPSK/CCK (5.5, 11, 22, 33 Mbps), DQPSK (2 Mbps), DBPSK (1 Mbps)|
802.11a (OFDM in the 5 GHz Band)
The 802.11a standard is an extension to the 802.11 standard and specifies operation in the 5 GHz UNII band using orthogonal frequency division multiplexing (OFDM). By moving to the 5 GHz frequency band and using OFDM modulation, the IEEE 802.11a standard provides the following benefits over 802.11b:
- It increases the maximum data transfer rate per channel from 11 Mbps to 54 Mbps
- It increases the number of non-overlapping channels
The 802.11a standard is not without its drawbacks. Since its inception, wireless networking requirements have changed drastically, with a greater need for interoperability and security. The European Telecommunications Standards Institute (ETSI) interoperability requirements were omitted from the 802.11a standard and compatibility trade-offs had to be made.
Because 802.11a and 802.11b operate in different frequency bands, products that follow either one of these standards are not compatible.
802.11b (High Rate DSSS in the 2.4 GHz Band)
The 802.11b standard is an extension to the 802.11 standard and covers devices that operate in the unlicensed 2.4 GHz RF band, from 2.4 to 2.483 GHz.
It uses DSSS transmission technology, with a chipping code that increases the signal's bandwidth to improve resistance to interference and frequency-selective fading. See the 802.11g section for 802.11g interoperability.
802.11g (DSSS at 2.4 GHz / OFDM at Higher Speeds)
The 802.11g standard's backward compatibility protects customer investments in various ways. To benefit from speeds up to 54 Mbps, both the access point and the device with which it communicates must be 802.11g compliant.
Because every 802.11g client and access point must be able to fall back and operate exactly like an 802.11b device, migration to 802.11g technology can be smooth and easy. As new 802.11g access points are installed, 802.11b access points can remain in service and be fully interoperable with newer 802.11g clients.
The 802.11g standard also specifies optional modulation types that are intended to improve efficiency in an all-802.11g installation.
The 802.11b standard WLAN infrastructure can also be upgraded to higher speeds easily, without having to install additional access points in many new locations for covering a given area.
The 802.11g standard technology supports higher data rates at longer ranges than 802.11a. The combination of OFDM and the superior wall-penetrating power of 2.4 GHz give 802.11g a clear advantage over other high-speed WLAN technologies. The ability to provide high-throughput coverage for a comparatively large area is an important cost factor.
In a mixed wireless network environment, it is important to select standards-based wireless products that are interoperable. The main measure of 802.11 equipment interoperability is the Wireless Fidelity (Wi-Fi) certification program and any products approved as Wi-Fi Certified by the Wi-Fi Alliance are certified as interoperable with each other.
The Wi-Fi interoperability program also tests for association and roaming capabilities, throughput, and required features such as 64-bit encryption.
As a short-range (10 metre) frequency-hopping protocol that links devices, Bluetooth is designed to operate in noisy RF environments. Using a fast acknowledgement and frequency hopping scheme to make the link robust, Bluetooth operates by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems in the same frequency band, Bluetooth hops faster and uses shorter packets.
Because Bluetooth shares the 2.4 GHz radio spectrum with 802.11b, there is a potential for interference with consumer appliances that operate in the same spectrum, such as cordless phones and microwave ovens.
Understanding wireless connectivity and bringing it to embedded solutions is daunting, time-consuming and expensive. The effort can be reduced by using a wireless embedded device server that provides a 'drop-in' solution. This adds wireless connectivity to products while slashing development costs and accelerating time to market. Lantronix WiPort is an example of such a device – a fully integrated module that can be easily added to OEM products without expensive RF and software development. By adding WiPort to your design, you can now add wireless connectivity within months, not years.
Increasingly, wireless LANs are playing a key role in revolutionising the use of technology across a growing range of industries. Designers who want to capitalise on this growth need a convenient, cost-effective and easy-to-install solution for adding wireless connectivity to their embedded designs.
Designers should look for easily installed solutions that boast high performance with a small footprint. These can add to your bottom line by reducing development time, risk and cost.