Abstract
In this paper we present an experimental study on the performance of spatial Interference Alignment (IA) in broadband indoor wireless local area network scenarios that use Orthogonal Frequency Division Multiplexing (OFDM) according to the IEEE 802.11a physical-layer specifications. Experiments have been carried out using a wireless network testbed made up of six nodes equipped with Multiple-Input Multiple-Output (MIMO) radio interfaces. This setup allows the implementation of a 3-user MIMO interference channel. We have implemented different IA decoding schemes that operate either before or after the Fast Fourier Transform block. IA has been experimentally evaluated comparing both approaches to analyze its performance in synchronous and asynchronous transmissions. Our results indicate that spatial IA performs satisfactorily in practical broadband indoor scenarios in which wireless channels often exhibit relatively large coherence times.
Highlights
Interference management is a key issue in the design of wireless systems
We start by studying the performance of pre-Fast Fourier Transform (FFT) and post-FFT Interference Alignment (IA) decoders when users transmit without any coordination
As expected, when there is no coordination among users, post-FFT decoding is not capable of successfully detecting the desired frame due Error Vector Magnitude (EVM) for pre-FFT and post-FFT IA decoding in asynchronous transmission [dB]
Summary
When several users transmit over the same wireless resources, orthogonal access techniques, such as Frequency-Division or Time-Division Multiple Access (FDMA and TDMA, respectively), are traditionally applied to avoid interference among them. IA was further evaluated in [3], where the authors conducted an experimental study over measured indoor and outdoor Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) channels. They characterized the effect of spatial correlation and subspace distance, and showed that IA is able to achieve the maximum available Degrees of Freedom (DoF) over realistic channels. We use the IEEE 802.11a Wireless Local Area Network (WLAN) physical-layer standard [7] as a benchmark to evaluate the performance of spatial IA in a 3-user 2 × 2 MIMO-OFDM indoor channel
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