Channel estimation in MIMO-OFDM spatial multiplexing using Least Square method

Abstract

In this paper, channel estimation for Spatial Multiplexing (SM) is investigated for MIMO-OFDM system. Due to the channel characteristic of the transmission system is always changed by the time and its importance in wireless transmission to reconstruct the transmitted signals, the channel needs to be known as well as possible. Pilot symbols are used to gather knowledge about the channel and try to estimate it. The channel estimation based on the pilot symbol is called pilot aided channel estimation. In this research, Least Square (LS) method was chosen for initial channel estimation. By using applicable proposed system design, channel state information is estimated through the use of channel information before in subcarriers with no pilot symbols. Zero forcing (ZF) algorithm is used to detect and separate the received signal. The result shows that channel estimation would be better by increasing SNR. Normalized Mean Square Errror (NMSE) value of the channel reached 5xlO· 5 for SNR 25 dB. The value of BER reached 3xlO· 4for SNR 25 dB. The estimated channel capacity has the values that closed to the known channel capacity.

Enhanced Adaptive Channel Estimation Technique for MIMO-OFDM Wireless Systems

“…is the maximum eigen value of the correlation matrix. And error signal is expressed as: (4) Where is the desired value and is the filtered output or estimated value which can be expressed as: (5) As the value of u is increased, convergence speed is increased but the performance is degraded as less data is taken for processing. Value of u has to be adjusted according to the environment.…”

“…Moreover it provides ISI free communication due to the use of CP (cyclic prefix) which is just the repetition of tail of the symbol at the front part of the symbol. OFDM acts as a standard for many wireless applications like Digital Video Broadcasting (DVB), Digital Audio Broadcasting (DAB) [1] [2], WIMAX, Wireless Local Area Network (WLAN) and ADSLs [1] [5].…”

“…STBCs are used to increase the diversity gain in MIMO systems. Channel capacity and multiplexing gain is increased by spatial multiplexing (SM) [5].The challenging problem for wireless systems is channel estimation. In wireless systems channels are dynamic in nature as compared to guided media.…”

“…Moreover this type of channel estimation technique increases the complexity at the receiver. Although pilot based channel estimation (CE) consumes bandwidth more than blind type but it is a good candidate for fast time varying channels [5]. Adaptive CE algorithms are gaining more attention these days.…”

Channel State Information Estimation In MIMO-OFDM Wireless Systems

“…Moreover it provides ISI free communication due to the use of CP(cyclic prefix) which is just the repetition of tail of the symbol at the front part of the symbol. OFDM acts as a standard for many wireless applications like Digital Video Broadcasting (DVB), Digital Audio Broadcasting (DAB) [1] [2], WIMAX, Wireless Local Area Network (WLAN) and ADSLs [1] [5].…”