The Cambridge-based Olivetti Research Ltd unit of Ing C Olivetti & Co SpA claims to have the world’s first prototype radio Asynchronous Transfer Mode system running at its labs. According to the company, the radio Asychronous Mode network currently runs in the 2.45GHz ISM band, where operation is licence-free at low power levels. A raw data rate of 10Mbps is used to give sufficient bandwidth for a number of mobiles running compressed video applications, said Olivetti, and the hardware is based around a range of low-end Asychronous Mode switches and network interface cards that use Advanced RISC Machines Ltd’s processor. The mobile network is split into a large number of small areas called pico-cells, each served by a base station. All base stations operate on the same frequency and are interconnected via the lab’s wired Asynchronous Transfer Mode network. In terms of in-band data, the base stations are, Simple cell relays that translate the header formats from the radio Asynchronous Transfer Mode data to the wired network. According to Olivetti, the radio data cells differ only slightly from fixed Asynchronous Transfer Mode data cells. A preamble is added to the front of the header to enable the receiver to lock on and a checksum is added to the back of the payload. Each time a cell is received the checksum is validated and an acknowledgement returned to the transmitter. Because the wired network has a higher bandwidth than the wireless one, control and management is initiated from the former. Base station functions and mobility management are also decoupled to reduce the complexity of the base station, said the company. Mobiles are allocated a Mobile Representative, to handle all the management and control tasks associated with mobility. While the research is still at an early stage, the company says it expects commercial products within two years.
