Impact of Clustering in Indoor MIMO Propagation Using a Hybrid Channel Model

EURASIP Journal on Advances in Signal Processing, Dec 2005

The clustering of propagating signals in indoor environments can influence the performance of multiple-input multiple-output (MIMO) systems that employ multiple-element antennas at the transmitter and receiver. In order to clarify the effect of clustering propagation on the performance of indoor MIMO systems, we propose a simple and efficient indoor MIMO channel model. The proposed model, which is validated with on-site measurements, combines the statistical characteristics of signal clusters with deterministic ray tracing approach. Using the proposed model, the effect of signal clusters and the presence of the line-of-sight component in indoor Ricean channels are studied. Simulation results on channel efficiency and the angular sensitivity for different antenna array topologies inside a specified indoor scenario are also provided. Our investigations confirm that the clustering of signals significantly affects the spatial correlation, and hence, the achievable indoor MIMO capacity.

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Impact of Clustering in Indoor MIMO Propagation Using a Hybrid Channel Model

EURASIP Journal on Applied Signal Processing Impact of Clustering in Indoor MIMO Propagation Using a Hybrid Channel Model Zhongwei Tang 0 Ananda Sanagavarapu Mohan 0 0 Microwave and Wireless Technology Research Laboratory, Information and Communication Group, Faculty of Engineering, University of Technology , Sydney, L24/B1, P.O. Box 123, Broadway NSW 2007 , Australia The clustering of propagating signals in indoor environments can influence the performance of multiple-input multiple-output (MIMO) systems that employ multiple-element antennas at the transmitter and receiver. In order to clarify the effect of clustering propagation on the performance of indoor MIMO systems, we propose a simple and efficient indoor MIMO channel model. The proposed model, which is validated with on-site measurements, combines the statistical characteristics of signal clusters with deterministic ray tracing approach. Using the proposed model, the effect of signal clusters and the presence of the line-of-sight component in indoor Ricean channels are studied. Simulation results on channel efficiency and the angular sensitivity for different antenna array topologies inside a specified indoor scenario are also provided. Our investigations confirm that the clustering of signals significantly affects the spatial correlation, and hence, the achievable indoor MIMO capacity. and phrases; angle sensitivity; channel efficiency; indoor propagation; signal clusters; MIMO; Ricean K factor; ray tracing 1. INTRODUCTION The multiple-input multiple-output (MIMO) technique is being tipped as one of the most significant breakthroughs in wireless communications for achieving high data-rates without increasing the channel bandwidth [ 1, 2, 3, 4 ]. In view of its significance, the MIMO technique is considered for inclusion into the forthcoming IEEE 802.11n WLAN standard. MIMO systems have the ability to turn multipath propagation into a benefit for users by employing multiple antennas at both the transmitter and receiver to exploit multipath fading, in order to maximize data throughput. The underlying mathematical nature of MIMO, where the data is transmitted over a matrix rather than a vector channel, creates new and enormous opportunities beyond just diversity or array gain benefits. This has prompted new research on channel modelling, antenna design, coding schemes and signal processing, and so forth. In MIMO systems, the channel transfer matrix is a key component that includes the coupling information between the transmitter and the receiver and their interaction with the surrounding physical environment, through the spatial and angular features of RF propagation. It has been reported that the correlation of the channel transfer matrix due to directional multipath propagation tends to decrease MIMO performance [ 5, 6, 7 ] for both indoor and outdoor MIMO systems, when time diversity is not considered [ 8 ]. Thus, the characteristics of the transmit and receive arrays, such as antenna polarization [ 9 ], antenna element separation [ 10 ], and array topology and orientations [ 11 ] can play a major role in determining the achievable MIMO capacity. It has also been reported [ 12, 13 ] that the presence of the line-of-sight (LOS) component in Ricean channels also reduces the achievable MIMO capacity. As the antenna characteristics and channel correlations affect the achievable spectrum efficiency, antenna selection assumes importance for obtaining the optimized capacity [ 14, 15 ]. On the other hand, in indoor propagation environments, it has been well-established that multipath waves tend to be clustered in both angular and temporal domains [ 16, 17, 18, 19 ]. Moreover, the clustering propagation is found to be detrimental to indoor MIMO performance as it increases the spatial correlation between subchannels [ 20, 21 ]. When antenna arrays are employed at both the transmitter and receiver in indoor environments, the correlation between antenna elements is a function of the signal clusters, whose characteristics are determined by the physical features of a given indoor environment as well as the locations of the transmitter and receiver. Since antennas are key components in MIMO systems, it is important to understand the impact of antenna array topology and orientation on achievable capacity in clustering indoor environments. Many realistic indoor environments are Ricean scenarios since it is common for a strong line-of-sight component between the transmitter and receiver to exist. Thus an investigation on the effect of Ricean K factor on the achievable MIMO capacity assumes practical importance. Further, the subchannel efficiency in indoor environments is not fully addressed. Therefore, a comprehensive investigation on the impact of signal clustering on indoor MIMO performance is expedient for the efficient design and deployment of highperformance wireless systems. To this end, it is essential to exploit the MIMO channel (...truncated)


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Zhongwei Tang, Ananda Sanagavarapu Mohan. Impact of Clustering in Indoor MIMO Propagation Using a Hybrid Channel Model, EURASIP Journal on Advances in Signal Processing, 2005, pp. 896950, Volume 2005, Issue 11, DOI: 10.1155/ASP.2005.1698