Abstract
In October 2005, the next generation mobile communication system was officially named as the International Mobile Telecommunications-Advanced (IMT-Advanced) by the ITU Radiocommunication Sector (ITU-R). Wideband multiple input and multiple output (MIMO) channel models in multiple propagation environments are fundamental for IMT-Advanced systems and such research has been initiated since 2003. The research challenges come from the fact that the wider bandwidth (20–100 MHz) and the advanced multiple antenna technology have been proposed for the IMT-Advanced system, thus leading to higher sampling rates and multiple spatial propagation channels. In this review, four aspects of wideband MIMO channel measurement and modeling are discussed: (1) radio channel measurement procedure and equipment; (2) large scale fading models; (3) small scale fading models; and (4) MIMO channel models. In particular, the large scale fading affected by the carrier frequency is investigated for urban macrocells and it shows that the higher carrier frequency results in greater loss for non-line-of-sight (NLoS) conditions in the cities of China, for which the frequency dependent factor is 32.1. Moreover, the dense and the obviously higher buildings also lead to a larger angle spread (AS) of both the angle of arrival and angle of departure in urban macrocell scenarios. The results indicate that there is the potential to explore the MIMO technique for an IMT-Advanced system with larger ASs, which would lead to the high system capacity. The progress on MIMO models is described and some methods for simplifying geometry-based stochastic channel models (GBSM) are proposed. Finally future research topics on channel measurement and modeling are identified.
Highlights
In October 2005, the generation mobile communication system was officially named as the International Mobile Telecommunications-Advanced (IMT-Advanced) by the ITU Radiocommunication Sector (ITU-R)
Their achievements are included in the European Cooperation in Science and Technology 207 (COST 207) and ITU-R M.1225 [9,10], which are widely used in the development and evaluation of the second and the third generation mobile communication systems
(3) Based on the measured data, we found low correlation between the K-factor, angle of arrival (AoA) and angle of departure (AoD), etc., and five methods for simplifying geometry-based stochastic channel models (GBSM) are proposed, and a cluster deleting scheme that would reduce the simulation time by as much as 40% when a 25 dB clipping threshold is adopted for the “Indoor line of sight (LoS)” case
Summary
Research on the characterization of radio propagation is based on field measurements. PropSound CS developed by Elektrobit of Finland and RUSK developed by MEDAV of Germany have been viewed as two of the most representative MIMO channel measurement items of equipment in the world. Due to the non-ideal cross-correlation characteristics of PN codes, performance degradation occurs at low signal to noise ratios (SNRs) Taking these factors into consideration, in 2005 we hired a PropSound CS to conduct channel measurements in indoor hotspots and outdoor scenarios. By using a channel sounder, CIRs can be acquired, which describe the channel propagation properties and provide the data basis for extracting other statistical parameters. These parameters and models are usually categorized into large scale and small scale fading.
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