Derek Gerlach

Base station transmitting antenna arrays for multipath environments

Abstract Adaptive transmitting antenna arrays can increase the capacity of mobile radio networks by reusing a channel among several users. To reuse bandwidth, a transmitting antenna array can exploit feedback information from the mobile receivers in order to track changes in the multipath environment. When the mobile is moving rapidly, the required feedback rates can become significant. We present a new method for transmission beamforming, which, by exploiting the subspace structure present in the spatial channel, requires much lower feedback data rates than previous methods. We consider antenna arrays at the base only, and the mobile has a single omnidirectional antenna.

Adaptive transmitting antenna methods for multipath environments

Adaptive transmitting antenna arrays hold great promise for increasing the capacity of mobile radio networks by reusing a channel among several users. To reuse bandwidth, a transmitting antenna array requires feedback information from the mobile receivers in order to track changes in the multipath environment. When the mobile is moving rapidly, the required feedback rates can become significant. We present a new method for transmission beamforming, which, by exploiting the subspace structure present in the spatial channel, requires much lower feedback data rates than previous methods.

VOFDM broadband wireless transmission and its advantages over single carrier modulation

In this paper we describe a coding, modulation, and spatial processing technique for fixed broadband wireless Internet access applications and provide examples of its performance. This technique is built on orthogonal frequency division multiplexing (OFDM) and is known as vector OFDM (VOFDM). We compare VOFDM with conventional single carrier modulation (SCM), and show that it provides substantial performance improvements over SCM.

Base station array receivers in cellular CDMA

A code-division multiple-access (CDMA) scheme using an array receiver is considered. This array receiver is a natural generalization of matched filtering with time functions to matched spaced-time filtering. Computer simulations and mathematical analysis show that the improvement in output SINR per element is simply the increase in energy received by the array, when there are many more users than array elements. When the number of users is less than the number of elements, the array has enough degrees of freedom to null undesired users and the SINR is then significantly greater and only limited by receiver and sky noise.<<ETX>>