CBSE (UGC)-NET Wireless Communications
Wireless communications have become synonymous with relatively short range radio communications that are able to replace wired installations. Standards including Bluetooth, Wi-Fi or IEEE 802.11, Ultra Wide Band, Zigbee and many more all fall into this category. Recent years have seen a phenomenal level of growth, to the extent that they are common place for many applications, and they are one of the fastest growing areas of the electronics industry.
Even though the technology is growing rapidly some standards have already gone by the board. One notable example is HomeRF. Despite this new standards and technologies are being introduced to meet the demands of new sectors of this growing industry.
For many years there has been a variety of short range wireless systems. These have normally not conformed to world wide specifications and often they were developed for individual applications. However the development of integrated circuit technology started to open far greater possibilities. Not only were costs reducing, but the capabilities were increasing.
Before any further developments could take place other enablers needed to be set in place. One of the major changes took place in radio licensing. It had been a requirement to possess a licence for most radio transmissions. This had been a requirement to ensure that use of the radio spectrum was regulated in a way that prevented undue interference to other users. Then in 1985 the Federal Communications Commission (FCC) in the USA opened up some small portions of the spectrum for licence free communications applications. The bands that were used were the 900 MHz, 2.4 GHz, and 5.8 GHz Industrial, Scientific, and Medical (ISM) bands. These portions of the spectrum were allocated to a variety of non-communications applications including microwave ovens. As such they were already used by non-licensed users, but for communications purposes it was stated that any new systems that were implemented would have to avoid the other transmissions and successfully communicate in the presence of the interference.
One of the first wireless technologies to be standardised across the industry was Bluetooth. It traces its origins back to a concept that came out of Ericsson in 1994. The original intention was to make a wireless connection between something like an earphone and a cordless headset and the mobile phone. However the idea developed as the possibilities of interconnections with a variety of other peripherals such as computers printers, phones and more were realised. Using this technology, the possibility of quick and easy connections between electronic devices should be possible.
In order that the technology could move forward and be accepted as an industry standard, Ericsson opened the technology up. As a result of this, in Feb 1998, five companies (Ericsson, Nokia, IBM, Toshiba and Intel) formed a Special Interest Group (SIG) to further advance the work that Ericsson had begun, hoping to develop an industry standard. The group consisted of market leaders in the fields of telephony and computing-the two main areas they wished to address. Then in May 1998, Bluetooth was publicly announced with the first specification following on with the first release of the standard in July 1999. Later more members were added to the group with four new companies, Motorola, Microsoft, Lucent and 3Com, joining the group. Since then more companies have joined and the specification has grown and is now used in a large variety of products.
The name of the standard originates from the Danish king named Harald Blatand who was king of Denmark between 940 and 981 AD. His name translates to be “Blue Tooth” and this was used as his nickname. A brave warrior, his main achievement was that of uniting Denmark under the banner of Christianity, and then uniting it with Norway that he had conquered. The Bluetooth standard was named after him because it endeavours to unite personal computing and telecommunications devices.
There were some initial offerings for wireless LANs, but these were proprietary solutions developed by individual companies.
Inspired by the success of Ethernet, used for wire based local area networks, a number of vendors realised that it would be necessary to develop an industry standard. By adopting this approach a much greater market would be opened up:
A number of manufacturers approached the Institute of Electrical and Electronics Engineers (IEEE) in the USA. Having successfully launched the Ethernet standard under the 802.3 committee, they set up another committee with the designation 802.11, but it took until 1997 before a recommendation could be agreed. It allowed for data transfer at a rate of 2 Mbps using either frequency hopping or direct sequence spread spectrum. The standard was published in 1997 to enable development to start. Even at this early stage there were two variants, 802.11a (operating in the 5.8 GHz ISM band) and 802.11b (operating in the 2.4 GHz ISM band). These standards were ratified in December 1999 and January 2000 respectively.
Of the two specifications it was 802.11b that started to be developed first. Its lower frequency meant that production costs were less. Nevertheless the 802.11b specification was very long, running to over 400 pages. In view of this complexity compatibility problems were encountered. To help solve these six companies (Intersil, 3Com, Nokia, Aironet, Symbol and Lucent) formed the Wireless Ethernet Compatibility Alliance (WECA) in August 1999.
The aim was that WECA would certify the products. To denote that products were compatible a number of brand names were investigated. Of these the clear winner was Wi-Fi. Although initially it did not stand for anything in particular, the idea was added later that it should stand for Wireless Fidelity, implying that a product from one manufacturer would interface with one from another.
The idea of Wi-Fi products just started to capture the market as the downturn of 2001 hit, and this slowed development somewhat.
Despite this further development of the standards took place as the need for higher speeds along with compatibility with the 802.11b standard were seen. Accordingly another 802.11 standard was developed. Offering a maximum data rate of 54 Mbps, but operating on the 2.4 GHz band and completely backward compatible with 802.11b, it was launched in the summer of 2003.
With the rapidly growing use of Wi-Fi, an increasing number of “hotspots” were set up in airports, cafes hotels and many other places. Its use grew indicating the convenience of using the standard.
The working group for this standard was launched in 1998 and developed a single specification, the Shared Wireless Application Protocol (SWAP), for a broad range of interoperable consumer devices. The working group grew to more than 100 companies. However in January 2003 the group was disbanded because of competition from some of the other standards that were more widely available and could compete on cost.
Despite the problems with HomeRF, the global market for wireless devices is still growing rapidly and other technologies and standards are being launched to meet the demands of these markets. WiMax and Zigbee are two.