Abstract
In this paper, we present an experimental study on the performance of spatial interference alignment (IA) in indoor wireless local area network scenarios that use orthogonal frequency division multiplexing (OFDM) according to the physical-layer specifications of the IEEE 802.11a standard. Experiments have been carried out using a wireless network testbed capable of implementing a 3-user MIMO interference channel. We have implemented IA decoding schemes that can be designed according to distinct criteria (e.g., zero-forcing or MaxSINR). The measurement methodology has been validated considering practical issues like the number of OFDM training symbols used for channel estimation or feedback time. In case of asynchronous users, a time-domain IA decoding filter is also compared to its frequency-domain counterpart. We also evaluated the performance of IA from bit error ratio measurement-based results in comparison to different time-division multiple access transmission schemes. The comparison includes single- and multiple-antenna systems transmitting over the dominant mode of the MIMO channel. Our results indicate that spatial IA is suitable for practical 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
Aligned signals as well as signals from other schemes are sent — in a single transmission cycle — during this second stage in order to evaluate the performance of the Interference alignment (IA) approach and to compare such performance to that exhibited by other alternative approaches, all of them experiencing the same channel realization
We have firstly pointed out that time-domain IA decoding must be applied in totally asynchronous scenarios to cancel out the interference before time synchronization, and we have proposed a simple design for such decoders
Summary
Interference management is a key issue in the design of wireless systems. 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. A large number of theoretical results have shown IA to be a very promising technique, there is still lack of experimental over-the-air (OTA) results evaluating its actual performance in real wireless scenarios. This scarcity of experimental results is mainly due to the high
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