14,263 research outputs found
Space-Time Frequency Block Codes in LTE-DSRC Hybrid Vehicular Networks
In vehicular communication systems, Dedicated Short Range
Communication (DSRC) is said to provide fast communication and high security
between vehicles. Simultaneously, Long-Term Evolution (LTE) is used due to its
high bandwidth, low latency, and high spectrum efficiency. The DSRC and LTE
hybrid model has gained much attention as it is feasible and simpler in design
and deployment. In fact, multiple-input multiple-output (MIMO) systems have
been widely used in modern wireless communication systems to enhance data
throughput, reliability, and coverage. This paper proposes a MIMO LTE-DSRC
hybrid system using space-time frequency block codes (STFBC). This paper
focuses on the physical layer performance of the LTE-DSRC hybrid uplink
structure. The DSRC Orthogonal Frequency Division Multiplexing (OFDM)
transmitter and LTE Single Carrier Frequency Division Multiplexing (SCFDM)
receiver are used for the uplink transmission. A study on bit error rate (BER),
pairwise error probability (PEP), and channel-to-interference ratio (CIR) of
the 2x2 MIMO LTE-DSRC system is conducted. The numerical results show that this
proposed method improves the error rate performance with a gradual increase in
signal-to-noise ratio (SNR) compared to the baseline systems
Cooperative Symbol-Based Signaling for Networks with Multiple Relays
Wireless channels suffer from severe inherent impairments and hence
reliable and high data rate wireless transmission is particularly challenging to
achieve. Fortunately, using multiple antennae improves performance in wireless
transmission by providing space diversity, spatial multiplexing, and power gains.
However, in wireless ad-hoc networks multiple antennae may not be acceptable
due to limitations in size, cost, and hardware complexity. As a result, cooperative
relaying strategies have attracted considerable attention because of their abilities
to take advantage of multi-antenna by using multiple single-antenna relays.
This study is to explore cooperative signaling for different relay networks,
such as multi-hop relay networks formed by multiple single-antenna relays and
multi-stage relay networks formed by multiple relaying stages with each stage
holding several single-antenna relays. The main contribution of this study is the
development of a new relaying scheme for networks using symbol-level
modulation, such as binary phase shift keying (BPSK) and quadrature phase shift
keying (QPSK). We also analyze effects of this newly developed scheme when it
is used with space-time coding in a multi-stage relay network. Simulation results
demonstrate that the new scheme outperforms previously proposed schemes:
amplify-and-forward (AF) scheme and decode-and-forward (DF) scheme
MIMO Underwater Visible Light Communications: Comprehensive Channel Study, Performance Analysis, and Multiple-Symbol Detection
In this paper, we analytically study the bit error rate (BER) performance of
underwater visible light communication (UVLC) systems with binary pulse
position modulation (BPPM). We simulate the channel fading-free impulse
response (FFIR) based on Monte Carlo numerical method to take into account the
absorption and scattering effects. Additionally, to characterize turbulence
effects, we multiply the aforementioned FFIR by a fading coefficient which for
weak oceanic turbulence can be modeled as a lognormal random variable (RV).
Moreover, to mitigate turbulence effects, we employ multiple transmitters
and/or receivers, i.e., spatial diversity technique over UVLC links.
Closed-form expressions for the system BER are provided, when equal gain
combiner (EGC) is employed at the receiver side, thanks to Gauss-Hermite
quadrature formula and approximation to the sum of lognormal RVs. We further
apply saddle-point approximation, an accurate photon-counting-based method, to
evaluate the system BER in the presence of shot noise. Both laser-based
collimated and light emitting diode (LED)-based diffusive links are
investigated. Since multiple-scattering effect of UVLC channels on the
propagating photons causes considerable inter-symbol interference (ISI),
especially for diffusive channels, we also obtain the optimum multiple-symbol
detection (MSD) algorithm to significantly alleviate ISI effects and improve
the system performance. Our numerical analysis indicates good matches between
the analytical and photon-counting results implying the negligibility of
signal-dependent shot noise, and also between analytical results and numerical
simulations confirming the accuracy of our derived closed-form expressions for
the system BER. Besides, our results show that spatial diversity significantly
mitigates fading impairments while MSD considerably alleviates ISI
deteriorations
- …