Wireless USB: no more cables between peripheral and pc.

Wireless USB: USB over a UWB-connection

Before we get into Wireless USB however, first we’ll have short introduction on the basics of Wireless USB, i.e. USB itself. USB was - and is - the standard for connecting peripherals to the pc. Since its introduction more than 2 billion USB products have been sold and this number still increases heavily. Many statistics show that USB has been one of the most successful, if not the most successful, way of interconnecting devices throughout the history of the pc. The reasons for this success have been plentiful: cheap connectors and cabling, compact- and fool-proof plugs, (relatively) unlimited expandability, moderate power requirements, speed, “plug-and-play” ease of use, etc. To meet the need for larger bandwidth version USB 1.1 (12 Mbit/s) was introduced after the original version 1.0 of only 1,5 Mbit/s. Some years later USB 2.0 was introduced: a connection boasting a bandwidth of 480 Mbit/s which offers ample performance up to this day.

At the beginning of the 21^st century we saw a shift in the concept of communication, namely the demand for wireless connections. The urge for wireless freedom, short- and long range, develops. To meet the latter, IEEE already had an answer: WiFi. In its incarnations 802.11a and 802.11b, it already caters to the demand for wireless networks in the middle- to long distance. For short distances however the demand remains unanswered. Infrared is not at all capable to exchange large amounts of data, 4 Mbit/s at the time against 16 Mbit/s nowadays. Ericsson is making efforts with Bluetooth, but does not get past the point of low-speed integration of telecom gadgets. Bluetooth 1.0 has a maximum of 1 Mbit/s and Bluetooth 2.0 theoretically hits the ceiling at a rate of 3 Mbit/s. All things considered: apart from USB it was about time for a sturdy protocol regarding wireless connection.

At the USB Implementers Forum, an organization which promotes the support for USB, they started noticing this. At that moment the goals for Wireless USB were being set. Why create something from scratch when you can further expand on an already successful concept? In other words: while developing a wireless USB-connection, the current USB technology ideally should be preserved. Both the cabled- and wireless variety should be mutually compatible. To summarize the most important criteria: the present architecture should be preserved and the performance should be 480 Mbit/s, as is the case with USB 2.0.

We have to view the above summarized performance criteria separately from the wireless part of the equation: the carrier on which the USB-signal travels through the air. In this respect criteria such as energy consumption and security play important roles. Because of the choice for an open standard, the USB Implementers Forum called upon the IEEE – the international organization for standards, which is well known for its 802.11 WiFi specification. The forum was particularly interested in the 802.15 3a standard. This standard describes wireless communication with high bandwidth (ultra wide band) over relatively short distances. The IEEE 802.15 specifications apply to personal area networks (PAN) whereas those of the 802.11 apply to local area networks (LAN).

At that same time the TG3a workgroup – TG3a is an acronym for the IEEE 802.15.3a Task Group – was quite busy with the fulfillment of the supplied criteria. Eventually two candidates emerge for the concrete implementation of the ultra wide band IEEE 802.15.3a standard. The WiMedia Alliance adopts the so called Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB. Whereas its opponent, the UWB Forum, chooses Direct Sequence UWB (DS-UWB).

After long deliberation IEEE 802.15.3a is cancelled in January 2006 because the two candidates could not reach an agreement over the standard, and the USB Implementers Forum subsequently opts for the WiMedia Alliance. This is understandable given the fact that within the WiMedia Alliance the most prominent players regarding Wireless USB are represented. Intel, Microsoft, HP, Samsung and Sony are just a few of the MB-OFDM UWB promoters. As of that moment the specification for Wireless USB were laid down and we can now sit back and wait for the first products to appear. Before we go into that however, let’s have a look at the implementation of Wireless USB and its implications on our daily use of the pc.