Showing papers on "MIMO published in 1970"

Effects of Path Visibility on Urban MIMO Systems

Abstract: Multiple-Input Multiple-Output (MIMO) wireless communication technology is expected to improve the channel capacity over the limited bandwidth of existing networks. Since urban MIMO systems have complex propagation characteristics, the channel capacity cannot be estimated using a simple method. Hence, we introduce channel capacity characteristics to urban MIMO systems by using a combination of imaging and ray-launching methods as a ray-tracing scheme. A simulation based on these methods with variable parameters can reproducibly estimate various urban propagation characteristics and discriminate the effects of the urban model and antenna configurations. The characteristics of the Signal-to-Noise Ratio (SNR), the channel capacity, the spatial correlation, as well as the path visibility are then determined from the results of the simulation. The parameter called path visibility introduced in our previous study is considered again herein. We clarify that only this single parameter can be used to determine the channel capacity characteristics in urban MIMO scenarios. This parameter also provides guidance in determining the appropriate range for the base station (BS) height.

Hardware Development of Baseband Transceiver and FPGA-Based Testbed in 88 and 22 MIMO-OFDM Systems

Abstract: Multiple-input multiple-output orthogonal frequency multiplexing (MIMO-OFDM) is powerful in enhancing communication capacity or reliance. The IEEE802.11n standard defines use of four spatial streams in spatial division multiplexing (SDM). The task group of IEEE802.11ac will extend it to eight spatial streams. We present an 88 MIMOOFDM baseband transceiver compatible with the IEEE802.11ac specification. Two 88 MMSE MIMO detectors based on Streassen’s matrix inversion have been designed for real-time MIMO detection. To demonstrate MIMO-OFDM transmission, we have prototyped a FPGA-based testbed in 22 MIMOOFDM for field experiment and video transmission.

Proposal of Channel Estimation Method for ITS systems by using STBC MIMO-OFDM

Abstract: This paper proposes a new road-to-vehicle communication system for the future ITS by using the STBC MIMO-OFDM technique which can provide the safety and comfortable driving, and collection of variable information from the network in the realtime to the users on the vehicle. To realize the proposed STBC MIMO-OFDM system, it is required to estimate the channel frequency response at every symbol precisely in the time varying fading channel which is the typical operation conditions for the roadto-vehicle communications system. In this paper, we propose a novel channel estimation method by using the scattered pilots and null sub-carriers inserted into the data sub-carriers both in the frequency and time axes which enables the accurate channel estimation even in the higher time varying fading channel. From the computer simulation results, this paper demonstrates the effectiveness of proposed system which can achieve the higher transmission data rate with keeping the higher signal quality even under the higher mobile ITS environments.

A Novel Intercarrier Interference Cancellation for MIMO-OFDM Systems

Abstract: The main impairment of an orthogonal frequency division multiplexing (OFDM) systems is an intercarrier interference (ICI) effect caused by a frequency offset. A zero-padded technique designed for a conjugate cancellation scheme in MIMO-OFDM systems for ICI cancellation is proposed by padding zero between two consecutive symbols over a space-frequency domain. At the receiver, the ICI cancellation and space-frequency diversity combining techniques are proposed. In this paper, a performance analysis is investigated and analyzed. In comparison with the conventional complex conjugate scheme, the outage probability expressions of the proposed system and the repetition-coded conjugate cancellation scheme are derived for quasi-static Rayleigh fading channels. Simulation results show the close agreement with those obtained by theoretical analysis, which could be used to estimate the proposed system performance. Finally, simulation results in time-varying frequency-selective fading channels, a bit error rate (BER) performance of the proposed system is significantly improved over both the ordinary zero-padded MIMO-OFDM systems and the repetition-coded conjugate cancellation scheme when the frequency offset is not greater than 10% of subcarrier spacing. Furthermore, the proposed system is shown to be able to attain significant diversity gain.