Mobile Computing
How to beam up more bandwidth

Mobile Computing

Ever since the early episodes of Star Trek I’ve thought that people would love Captain Kirk’s communicator: a pocket-sized device that, as well as supporting simple communications, would give instant access to vast amounts of information.

It looks as though we’re getting closer to that ideal. PDAs and smartphones are often built on the same operating system. They both have considerable processing power and battery life and may use a variety of communications systems. For example, the Nokia 9500 can communicate via Bluetooth, 802.11b, infrared and USB as well as GSM, GPRS and Edge technology.

The Nokia 9500 also has enough processing power to handle encoded video. And now there are 3G mobiles that can support higher mobile data rates and video reception good enough to watch TV.

However, progress is still required on two fronts – processing power and network bandwidth. Moore’s Law should deal with the first problem, but the second is not so straightforward.

Present 3G networks can provide rates up to about 384kbit/s over a wide area, but this isn’t really enough. However, help is on the way.

In the 3G world, High-Speed Downlink Packet Access (HSDPA) will support faster rates, perhaps up to 10Mbit/s, but at the cost of using a lot of the cell capacity of the mobile operators. The first system tests will take place next year. The benefit of HSDPA is that it can be added to the existing 3G infrastructure.

A different tack is being taken by the IEEE 802 committee, which has formed a group, called 802.20, to define a standard for high-speed mobile data that will be able to support more users per square kilometre than existing systems.

It looks as though the new system will rely heavily on adaptive antennas. Each base station will have an array of antennas, allowing it to form multiple radio beams, one directed at each user. In addition, base stations will work together so that several beams intersect at the user’s location, providing a personal cell of good signal that moves with them. Any mobile not in the personal cell will not interfere and so the system’s capacity will be increased.

Some of the techniques being talked about are already available commercially from ArrayComm with its iBurst product, which is being tested in several countries.

The 3G vendors are not ignoring these developments, since 3G systems were designed to benefit from adaptive antennas. The result will be better services for customers and new applications to take advantage of the bandwidth.

However, those who dream about the transporter function of the Star Trek communicator will have to wait a good while yet.