Abstract
In this paper, we investigate a class of new multiple-input multiple-output (MIMO) transmission schemes, dubbed space time line code (STLC), in the context of different mobility situations. We extend its original structure into space and frequency domains and propose a novel frequency line code (SFLC) for combining with orthogonal frequency division multiplexing (OFDM) in order to achieve potential diversity gains in time-varying multipath fading channels. Specifically, at the transmitter, the STLC/SFLC-OFDM scheme exploits the channel state information (CSI) to linearly encode successive modulated symbols in the time/frequency domain to achieve full diversity gain. At the receiver, it can retrieve the transmit symbols without full CSI, thanks to its special structure. We analyse the impact of time-variant channels to STLC and SFLC to show the expected performance degradation in practical channel, especially in the case of different mobile speeds. Our analysis and simulations show that the BER performance degrades with increasing correlation coefficient, which makes STLC-OFDM more robust in channels with abundant multipath spread, and SFLC-OFDM more robust in channels with high mobility speed. Meanwhile, a guideline is provided for switching when the communication environment changes. Finally, we carry out the practical implementation of STLC-OFDM and SFLC-OFDM schemes and characterize their performance with both computer simulations and an experimental testbed.
Highlights
Multiple-input multiple-output (MIMO) [1], [2] is an important and widely used technique for 4G and 5G wireless communications, which theoretically multiplies the link capacity by using multiple antennas at the transmitter and receiver, to exploit spatial diversity and spatial multiplexing
The major contributions of this paper are as follows: 1) We extend the concept of space time line code (STLC) to the frequency domain and propose space-frequency line coded (SFLC), which is capable of efficiently combining the classic orthogonal frequency division multiplexing (OFDM) technique
Fast channel variation in the time domain causes performance degradation of STLC-OFDM, so it fails to adapt the high mobility environment. To alleviate this time-domain problem by exploiting the frequency-domain resource, we propose a new scheme as space-frequency line coded OFDM
Summary
Multiple-input multiple-output (MIMO) [1], [2] is an important and widely used technique for 4G and 5G wireless communications, which theoretically multiplies the link capacity by using multiple antennas at the transmitter and receiver, to exploit spatial diversity and spatial multiplexing. C. Wu et al.: Space-Time/Frequency Line Coded OFDM: System Design and Practical Implementation computation complexity of the receiver. When operating in frequency selective fading channels, the multipath inter channel interference (ICI) will induce the performance degradation of STLC, as in STBC [3]. To address this issue, we consider a space-frequency line coded (SFLC) scheme, which is a more reliable technique, to attain bandwidth efficiency and ISI suppression in this scenario. Notation: · F denotes the Frobenious norm of a matrix. |·| represents the magnitude of a complex quantity or the cardinality of a given set. (·)T, (·)∗ and (·)H refer to the transpose, conjugate and Hermitian transpose of a vector/matrix, respectively. min(x) returns the value of the smallest element of x
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