Towards wireless personal networks
Along with the advance of wireless communication technology, the personally centred communication paradigm has evolved to meet the concept of Wireless Personal Area Network (WPAN). Tethered to an individual, the Personal Operating System (POS) introduced by WPAN enables personal devices to communicate in an ad hoc manner, as well as with other devices within its communication range. To fully exploit the available spectrum for wireless communication systems, the orthogonal frequency division multiplexing (OFDM) scheme was introduced within the PACWOMAN project. Chosen for the outgoing communication through the WPAN gateway, OFDM will enable terminals to handle a wide range of different applications, from voice communication to high-speed data transfer. The strength of the OFDM resides in its spectrum efficiency (bps/Hz) and importantly, its ability to cover multipath channels, which appear in wireless environments. Computationally demanding and therefore power consuming, it was not until recently that technological advancements made it possible to build mobile OFDM devices with an adequate operation time. Researchers at the University of Lund sought to design a flexible application specific integrated circuit (ASIC) that would enable OFDM transmitters to be configured to function with different standards. A signal mapper and a signal-reordering unit that can insert a cyclic prefix and reorder data flow through a Fast Fourier Transform (FFT) processor were included in the OFDM chip. When focus was turned from transmitter to transceiver, a higher level of performance optimisation achieved hardware savings. More than half of the memory needed to insert a cyclic prefix could be removed if a bidirectional FFT processor and cyclic suffix was used. In addition to lower latency and less hardware, the number of memory accesses was also reduced and thus power consumption. The proposed scheme has sacrificed backwards compatibility to existing standards for flexibility; however it could be a promising candidate for future OFDM systems. This line of research work will be continued to investigate whether the flexibility in the OFDM transmitter can be matched in the receiver.
