Paul Odlyzko

Wireless in-building network architecture and protocols

The authors highlight the topology, architecture, and protocols developed for a wireless in-building network based on 18-GHz radio technology. They introduce the requirements of an in-building office environment that involves desktop computing applications and describe a microcellular topology with store-and-forward radio modules that uses time division duplex techniques to organize transmitting and receiving. Unique to the architecture and protocols are methods for coordinating devices with sectorized antennas, for providing high performance in terms of high throughput and low delay, and for compatibility with networking standards.<<ETX>>The topology, protocols and architecture for an 18-GHz wireless in-building network (WIN) aimed at office environments are described. The problems of controlling an array of directional antennas, using half-duplex radios and compensating for channel errors are addressed. The protocols provide robustness in the face of changing radio environment that requires no user intervention and provides low user delay and high system throughput.<<ETX>>

Performance analysis of a time division duplex broadband fixed wireless access system in the 5 GHz U-NII bands

In this paper we analyze the performance of a point-to-multipoint (PTM) time division duplex (TDD), time division multiple access (TDMA) broadband fixed wireless access (FWA) system in the 5 GHz U-NII Band. After a brief background on the 5 GHz radio and then the TDD/TDMA FWA system concept, we characterize throughput and system utilization, obtained from extensive simulations. Various traffic mixes have been modeled using a modified 3GPP2 traffic model. Additionally, analytical results for end-user performance is compared with the simulations results along with a discussion.

Simple asynchronous multiple access (SAMA) for ad hoc wireless networks in unlicensed bands

Effective spectrum sharing between non-interoperable radio devices as well as collocated but non-communicating radio networks is an important goal for the designers of RF spectrum. Apart from the traditional approach of selecting separate channels for distinct systems, there are methods such as spread spectrum, scheduling of transmissions in non-overlapping intervals to reduce collisions and also spatial diversity to reduce the effects of interference. The last two are the most promising methods to use to achieve multi-megabit data rates and high traffic densities. The listen-before-transmit (LBT) etiquette has been used with limited success in the past in decentralized RF environments to enable non-interoperable systems to share spectrum. We introduce the simple asynchronous multiple access (SAMA) scheme that combines some of the known channel access techniques in a novel way to achieve an implicit reservation effect that allows high throughput with modest overhead and low complexity without demanding interoperability or even explicit communications between the collocated systems. We analyze the throughput and spatial performance of SAMA. The analysis is based on the radio propagation law and the geometry of the users and antennas in the plane. It is aimed at establishing the fundamental performance bounds dictated by our basic assumptions. We cover the omni-directional antenna case and give preliminary results for the directional antenna.

MMIC Technology for Broadband Wireless Access

The increasing role and volume of data communications combined with the convenience of wireless access provide the motivation for the development of high speed, compact, affordable and portable high data rate digital radios that can be integrated with notebook computers and function for extended periods of time on battery power. Such radios can be constructed only as a result of an intense development effort in wireless communication systems and continued integration of hardware. High communication speeds dictate multi-megahertz channels which are more readily available at higher frequencies. Recent history of local and wide area wireless communications suggests the requirement for speeds of 10 Mbps or more, best implemented in the NII and HIPERLAN bands at 5 GHz and beyond.