Title :
Architectures for MIMO-OFDM Systems in Frequency-Selective Mobile Fading Channels
Author_Institution :
Dept. of Electr. Eng., California State Univ., Long Beach, CA, USA
Abstract :
Orthogonal frequency-division multiplexing (OFDM) is used in third and fourth generation and is being planned for fifth-generation (5G) systems. OFDM requires that the received subcarriers be orthogonal. However, various factors, such as residual carrier frequency offset due to Doppler shift in mobile fading channels, can lead to a loss in orthogonality between subcarriers, which results in intersymbol interference (ISI), intercarrier interference (ICI), and bit error rate (BER) degradation. In developing the conjugate cancelation (CC) scheme for mitigating these ISI and ICI of OFDM systems, we integrate the CC scheme together with a space-time (ST) system and form an STCC multiple-input-multiple-output (MIMO) scheme. This STCC system improves the BER without expending power or bandwidth or complexity. Additionally, a Walsh-Hadamard (WH) transform is employed as a precoder for this STCC system and forms a novel WHSTCC scheme. It provides a low peak-to-average power ratio (PAPR) at the transmitter and a significant diversity gain at the receiver. Simulations indicate that both STCC and WHSTCC schemes outperform the regular CC and ST systems in mobile fading channels. Both schemes are simple and are backward compatible, and they can serve as the baseband building block for reconfigurable 5G multiuser MIMO systems.
Keywords :
5G mobile communication; Doppler shift; Hadamard codes; Hadamard transforms; MIMO communication; OFDM modulation; Walsh functions; diversity reception; error statistics; fading channels; intercarrier interference; intersymbol interference; multi-access systems; precoding; radio receivers; radio transmitters; space-time codes; BER; CC scheme; Doppler shift; ICI; ISI; MIMO-OFDM system; PAPR; STCC multiple input multiple output scheme; WH transform; WHSTCC scheme; Walsh-Hadamard transform; bit error rate; conjugate cancelation scheme; diversity gain; fifth-generation system; frequency selective mobile fading channel; intercarrier interference; intersymbol interference; orthogonal frequency-division multiplexing; peak-to-average power ratio; precoder; reconfigurable 5G multiuser MIMO system; space-time system; Bit error rate; Fading; Mobile communication; Peak to average power ratio; Receivers; Transmitters; Inter-Carrier Interference; Intercarrier interference (ICI); MIMO-OFDM; Mobile Communication; Signal Processing; Space-Time; Walsh; mobile communication; multiple-input???multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM); signal processing; space???time (ST);
Journal_Title :
Circuits and Systems II: Express Briefs, IEEE Transactions on
DOI :
10.1109/TCSII.2015.2498300