302 research outputs found
Near-Capacity Turbo Coded Soft-decision Aided DAPSK/Star-QAM
Low-complexity non-coherently detected Differential Amplitude and Phase-Shift Keying (DAPSK) schemes constitute an ideal candidate for wireless communications. In this paper, we derive the soft-output probability formulas required for the soft-decision based demodulation of DAPSK, which are then invoked for Turbo Coded (TC) transmissions. Furthermore, the achievable throughput characteristics of the family of M-ary DAPSK schemes are provided. It is shown that the proposed 4-ring based TC assisted 64-ary DAPSK scheme achieves a coding gain of about 4.2 dBs in comparison to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme at a bit error ratio of 10?5
Performance Analysis of Coherent and Noncoherent Modulation under I/Q Imbalance
In-phase/quadrature-phase Imbalance (IQI) is considered a major
performance-limiting impairment in direct-conversion transceivers. Its effects
become even more pronounced at higher carrier frequencies such as the
millimeter-wave frequency bands being considered for 5G systems. In this paper,
we quantify the effects of IQI on the performance of different modulation
schemes under multipath fading channels. This is realized by developing a
general framework for the symbol error rate (SER) analysis of coherent phase
shift keying, noncoherent differential phase shift keying and noncoherent
frequency shift keying under IQI effects. In this context, the moment
generating function of the signal-to-interference-plus-noise-ratio is first
derived for both single-carrier and multi-carrier systems suffering from
transmitter (TX) IQI only, receiver (RX) IQI only and joint TX/RX IQI.
Capitalizing on this, we derive analytic expressions for the SER of the
different modulation schemes. These expressions are corroborated by comparisons
with corresponding results from computer simulations and they provide insights
into the dependence of IQI on the system parameters. We demonstrate that the
effects of IQI differ considerably depending on the considered system as some
cases of single-carrier transmission appear robust to IQI, whereas
multi-carrier systems experiencing IQI at the RX require compensation in order
to achieve a reliable communication link
Near-Capacity Turbo Coded Soft-decision Aided DAPSK/Star-QAM for Amplify-and-Forward based Cooperative Communications
Multilevel Differential Amplitude and Phase-Shift Keying (DAPSK) schemes do not require any channel estimation, which results in low complexity. In this treatise we derive the soft-output probability formulas required for a soft-decision based demodulation of high-order DAPSK, in order to facilitate iterative detection by exchanging extrinsic information with an outer Turbo Code (TC). Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. Compared to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme, the 4-ring based TC assisted 64-ary DAPSK arrangement has a power-efficiency improvement of 2.3 dB at a bit error rate (BER) of 10-5 . Furthermore, when the TC block size is increased, the system operates closer to the channel capacity. More specifically, when using a TC block length of 400 modulated symbols, the 64 DAPSK (4, 16) scheme is 7.56 dB away from its capacity curve, while it had a reduced gap as low as 2.25 dB, when using a longer TC block length of 40 000 modulated symbols. Finally, as a novel application example, the soft-decision M-DAPSK scheme was incorporated into an Amplify-and-Forward (AF) based cooperative communication system, which attains another 4.5 dB SNR improvement for a TC block length of 40 000 modulated symbols
Differential Diversity Reception of MDPSK over Independent Rayleigh Channels with Nonidentical Branch Statistics and Asymmetric Fading Spectrum
This paper is concerned with optimum diversity receiver structure and its
performance analysis of differential phase shift keying (DPSK) with
differential detection over nonselective, independent, nonidentically
distributed, Rayleigh fading channels. The fading process in each branch is
assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth,
but to have distinct, asymmetric fading power spectral density characteristic.
Using 8-DPSK as an example, the average bit error probability (BEP) of the
optimum diversity receiver is obtained by calculating the BEP for each of the
three individual bits. The BEP results derived are given in exact, explicit,
closed-form expressions which show clearly the behavior of the performance as a
function of various system parameters.Comment: 5 pages, 3 figures, to present at ISIT200
Differential Modulation for Short Packet Transmission in URLLC
One key feature of ultra-reliable low-latency communications (URLLC) in 5G is
to support short packet transmission (SPT). However, the pilot overhead in SPT
for channel estimation is relatively high, especially in high Doppler
environments. In this paper, we advocate the adoption of differential
modulation to support ultra-low latency services, which can ease the channel
estimation burden and reduce the power and bandwidth overhead incurred in
traditional coherent modulation schemes. Specifically, we consider a
multi-connectivity (MC) scheme employing differential modulation to enable
URLLC services. The popular selection combining and maximal ratio combining
schemes are respectively applied to explore the diversity gain in the MC
scheme. A first-order autoregressive model is further utilized to characterize
the time-varying nature of the channel. Theoretically, the maximum achievable
rate and minimum achievable block error rate under ergodic fading channels with
PSK inputs and perfect CSI are first derived by using the non-asymptotic
information-theoretic bounds. The performance of SPT with differential
modulation and MC schemes is then analysed by characterizing the effect of
differential modulation and time-varying channels as a reduction in the
effective SNR. Simulation results show that differential modulation does offer
a significant advantage over the pilot-assisted coherent scheme for SPT,
especially in high Doppler environments.Comment: 15 pages, 9 figure
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