Large-scale multiple antenna fixed wireless systems for rural areas

Abstract

Multi-user multiple-input multiple-output (MU-MIMO) has a potential to realize cost effective high data rate internet access to the homes in rural areas. We propose the novel Ngara Access system where the central access point (AP) is equipped with a uniform circular array (UCA) installed on a high tower while each UT is equipped with a directional antenna free of clutter, providing predominantly line-of-sight (LoS) channel environment. Using a three dimensional geometric optics based channel model, we provide bit error probability simulation results which show that the spectral efficiency of the proposed system can be improved linearly as a function of the number of antenna elements at AP, without increasing the total transmitting power, provided a half wavelength antenna spacing is maintained and user groups of four or more are used to avoid ill-conditioned channel. Hardware demonstrators based on the proposed system have achieved the system spectral efficiency of 20 bits/s/Hz in an actual rural environment and of 67 bits/s/Hz in a laboratory environment at a lower UHF band.

Highly spectrally efficient Ngara Rural Wireless Broadband Access Demonstrator

“…The proposal of using MU-MIMO-OFDM to improve the spectrum efficiency is not new (one of the earliest proposal was made in 1999 [6]), however, the latter two methods are the new contribution by CSIRO. It has been shown by simulation that the spectrum efficiency of both the uplink and downlink can be improved linearly as a function of the number of antenna elements at the AP, without increasing the total transmitting power [4]. We note that this is possible without so called "multipath rich" environment, due to the large spatial separation of the UT antennas.…”

“…Detailed analysis on the performance of the Demonstrator in various environments is left as a future work. Some analytical results based on computer simulation can be found in [4]. UT units were located uniformly in two sides of a rectangular room while the AP was located in the center.…”

“…Commonwealth Scientific and Industrial Research Organisation (CSIRO) proposed the use of multi-user multiple-input multiple-output orthogonal frequency division multiplexing (MU-MIMO-OFDM) for increasing the spectrum efficiency of fixed wireless multiple access systems in rural areas [4], [5]. With the proposed method, the AP is equipped with multiple antennas while UTs are each equipped with a single antenna.…”

A Fast Low Complexity Method for Optimal Zero-Forcing Beamformer MU-MIMO System

“…The main complexity is the calculation of the dual cost as in (9). Each time, we need to calculate the vector , (16) Note that the vector is already calculated and is required to be calculated only once. Denote by the number of times the dual cost is required to be calculated for the step size search algorithm.…”

“…The base station array considered is a uniform planar circular array consisting of a ring with ideal dipole antennas and interelement spacing equal to , where is the wavelength of the radio frequency carrier. The wireless channel between each base station array antenna and a user antenna is modeled as in [16] and [17]. The channel is comprised of a direct line of sight propagation path and a ground reflected propagation path.…”