Public wireless communications will increasingly extend into wireless LAN environments in order to meet the ubiquitous access, high data rate, and local services demands of future Internet appliances. This article offers architectural guidelines for relatively large-scale IP-based WLAN environments configured to accept public access by mobile/portable appliances. By relying on IP-level service mechanisms at the access point, independent of the wireless medium access technology, the WLAN can simultaneously support different air interfaces, franchises for multiple service providers with effective authentication and billing, and a multisegment LAN environment including handoffs. QoS across the air interface is not addressed; this article rather concerns architecture of the wired LAN environment in which wireless access points are imbedded, and its capabilities for QoS and support of the business model.

The development of rapid algorithms for computation of the discrete Fourier transform has encouraged the use of this transform in the design of communication systems. Here we describe and analyze a data transmission system in which the transmitted signal is the Fourier transform of the original data sequence and the demodulator is a discrete Fourier transformer. This system is a realization of the frequency division multiplexing strategy known as “parallel data transmission”, and it is constructed in this manner so that the data demodulator, after analog to digital conversion, may be a computer program employing one of the fast Fourier transform algorithms. The system appears attractive in that it may be entirely implemented by digital circuitry. We study the performance of this system in the presence of typical linear channel characteristics. It is shown, via computer simulation and computation of the variances of errors, how the system corrects linear channel distortion.