142 research outputs found
Display probability of symbol errors for MQAM on Rician fading channel based on MGF method
We present a new method for calculating the probability of error per symbol (Symbol Error Probability, SEP) of M-ary Quadrature Amplitude Modulation (MQAM) over a slow, flat, identically independently distributed Rician fading channels. Since fading is one of the major constraints in wireless communications, the diversity modulation technique is used for the efficient transfer of message signals. Exact analysis of error probability per symbol for MQAM, transmitted over Rician fading channels, is performed by N branches of diversity reception using maximum ratio of signal-to-noise power (maximal-ratio-combining, MRC), where the information in the channel on the receiver side is known. We also analyzed the performances of MQAM over Rician fading channels are here also analyzed. Approximate formula is used to represent SEP for MQAM transmitted over Gaussian channels. Boundary condition for the approximation is M≥4 and 0≤SNR≤30 dB
Display probability of symbol errors for MQAM on Rician fading channel based on MGF method
We present a new method for calculating the probability of error per symbol (Symbol Error Probability, SEP) of M-ary Quadrature Amplitude Modulation (MQAM) over a slow, flat, identically independently distributed Rician fading channels. Since fading is one of the major constraints in wireless communications, the diversity modulation technique is used for the efficient transfer of message signals. Exact analysis of error probability per symbol for MQAM, transmitted over Rician fading channels, is performed by N branches of diversity reception using maximum ratio of signal-to-noise power (maximal-ratio-combining, MRC), where the information in the channel on the receiver side is known. We also analyzed the performances of MQAM over Rician fading channels are here also analyzed. Approximate formula is used to represent SEP for MQAM transmitted over Gaussian channels. Boundary condition for the approximation is M≥4 and 0≤SNR≤30 dB
Media-Based MIMO: A New Frontier in Wireless Communications
The idea of Media-based Modulation (MBM), is based on embedding information
in the variations of the transmission media (channel state). This is in
contrast to legacy wireless systems where data is embedded in a Radio Frequency
(RF) source prior to the transmit antenna. MBM offers several advantages vs.
legacy systems, including "additivity of information over multiple receive
antennas", and "inherent diversity over a static fading channel". MBM is
particularly suitable for transmitting high data rates using a single transmit
and multiple receive antennas (Single Input-Multiple Output Media-Based
Modulation, or SIMO-MBM). However, complexity issues limit the amount of data
that can be embedded in the channel state using a single transmit unit. To
address this shortcoming, the current article introduces the idea of Layered
Multiple Input-Multiple Output Media-Based Modulation (LMIMO-MBM). Relying on a
layered structure, LMIMO-MBM can significantly reduce both hardware and
algorithmic complexities, as well as the training overhead, vs. SIMO-MBM.
Simulation results show excellent performance in terms of Symbol Error Rate
(SER) vs. Signal-to-Noise Ratio (SNR). For example, a LMIMO-MBM is
capable of transmitting bits of information per (complex) channel-use,
with SER at dB (or SER
at dB). This performance is achieved using a single transmission
and without adding any redundancy for Forward-Error-Correction (FEC). This
means, in addition to its excellent SER vs. energy/rate performance, MBM
relaxes the need for complex FEC structures, and thereby minimizes the
transmission delay. Overall, LMIMO-MBM provides a promising alternative to MIMO
and Massive MIMO for the realization of 5G wireless networks.Comment: 26 pages, 11 figures, additional examples are given to further
explain the idea of Media-Based Modulation. Capacity figure adde
Asymptotic performance of M-ary signals on Rician fading diversity channels / by Hongwei Zhang.
In this thesis, we will study the average symbol error rate of M-ary signals on wireless Rician fading channels at high average signal-to-noise ratio (SNR) in both single-carrier and multicarrier orthogonal frequency division multiplexing (OFDM) systems. In the system discussed, diversity reception with maximal ratio combining (MRC) and equal gain combining (EGC) is adopted. A general theorem relates the asymptotic error rate to the multidimensional integral of the conditional error probability is presented. Two other theorems are presented for the special cases where the conditional error probability is function of the sum of received SNR's and the sum of received amplitudes corresponding to the cases using MRC diversity and EGC diversity respectively. Then theorems are provided to analyze the asymptotic error rate performance of M-ary signals including M-ary phase-shift keying (MPSK), M-ary pulse amplitude modulation (MPAM), and M-ary quadrature amplitude modulation (MQAM) signals in both single-carrier and multicarrier OFDM systems
Signal space cooperative communication with partial relay selection.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.Exploiting the available diversity from various sources in wireless networks is an easy way
to improve performance at the expense of additional hardware, space, complexity and/or
bandwidth. Signal space diversity (SSD) and cooperative communication are two promising
techniques that exploit the available signal space and space diversity respectively. This study
first presents symbol error rate (SER) analysis of an SSD system containing a single transmit
antenna and N receive antennas with maximal-ratio combining (MRC) reception; thereafter
it presents a simplified maximum-likelihood (ML) detection scheme for SSD systems, and
finally presents the incorporation of SSD into a distributed switch and stay combining with
partial relay selection (DSSC-PRS) system.
Performance analysis of an SSD system containing a single transmit antenna and multiple
receive antennas with MRC reception has been presented previously in the literature using the
nearest neighbour (NN) approximation to the union bound, however results were not presented
in closed form. Hence, closed form expressions are presented in this work. A new lower bound
for the SER of an SSD system is also presented which is simpler to evaluate than the union
bound/NN approximation and also simpler to use with other systems. The new lower bound is
based on the minimum Euclidean distance of a rotated constellation and is termed the minimum
distance lower bound (MDLB); it is also presented here in closed form. The presented bounds
have been validated with simulation and found to be tight under certain conditions.
The SSD scheme offers error performance and diversity benefits with the only penalty being an
increase in detector complexity. Detection is performed in the ML sense and conventionally,
all points in an M-ary quadrature amplitude modulation (M-QAM) constellation are searched
to find the transmitted symbol. Hence, a simplified detection scheme is proposed that only
searches m symbols from M after performing initial signal conditioning. The simplified
detection scheme is able to provide SER performance close to that of optimal ML detection in
systems with multiple receive antennas.
Cooperative communication systems can benefit from the error performance and diversity
gains of the spectrally efficient SSD scheme since it requires no additional hardware,
bandwidth or transmit power. Integrating SSD into a DSSC-PRS system has shown an
improvement of approximately 5dB at an SER of 10-4 with a slight decrease in spectral
efficiency at low SNR. Analysis has been performed using the newly derived MDLB and
confirmed with simulation
Coding in 802.11 WLANs
Forward error correction (FEC) coding is widely used in communication systems to correct transmis-
sion errors. In IEEE 802.11a/g transmitters, convolutional codes are used for FEC at the physical
(PHY) layer. As is typical in wireless systems, only a limited choice of pre-speci¯ed coding rates is
supported. These are implemented in hardware and thus di±cult to change, and the coding rates are
selected with point to point operation in mind.
This thesis is concerned with using FEC coding in 802.11 WLANs in more interesting ways that are
better aligned with application requirements. For example, coding to support multicast tra±c rather
than simple point to point tra±c; coding that is cognisant of the multiuser nature of the wireless
channel; and coding which takes account of delay requirements as well as losses. We consider layering
additional coding on top of the existing 802.11 PHY layer coding, and investigate the tradeo® between
higher layer coding and PHY layer modulation and FEC coding as well as MAC layer scheduling.
Firstly we consider the joint multicast performance of higher-layer fountain coding concatenated
with 802.11a/g OFDM PHY modulation/coding. A study on the optimal choice of PHY rates with and
without fountain coding is carried out for standard 802.11 WLANs. We ¯nd that, in contrast to studies
in cellular networks, in 802.11a/g WLANs the PHY rate that optimizes uncoded multicast performance
is also close to optimal for fountain-coded multicast tra±c. This indicates that in 802.11a/g WLANs
cross-layer rate control for higher-layer fountain coding concatenated with physical layer modulation
and FEC would bring few bene¯ts.
Secondly, using experimental measurements taken in an outdoor environment, we model the chan-
nel provided by outdoor 802.11 links as a hybrid binary symmetric/packet erasure channel. This
hybrid channel o®ers capacity increases of more than 100% compared to a conventional packet erasure
channel (PEC) over a wide range of RSSIs. Based upon the established channel model, we further
consider the potential performance gains of adopting a binary symmetric channel (BSC) paradigm for
multi-destination aggregations in 802.11 WLANs. We consider two BSC-based higher-layer coding
approaches, i.e. superposition coding and a simpler time-sharing coding, for multi-destination aggre-
gated packets. The performance results for both unicast and multicast tra±c, taking account of MAC
layer overheads, demonstrate that increases in network throughput of more than 100% are possible
over a wide range of channel conditions, and that the simpler time-sharing approach yields most of
these gains and have minor loss of performance.
Finally, we consider the proportional fair allocation of high-layer coding rates and airtimes in 802.11
WLANs, taking link losses and delay constraints into account. We ¯nd that a layered approach of
separating MAC scheduling and higher-layer coding rate selection is optimal. The proportional fair
coding rate and airtime allocation (i) assigns equal total airtime (i.e. airtime including both successful
and failed transmissions) to every station in a WLAN, (ii) the station airtimes sum to unity (ensuring
operation at the rate region boundary), and (iii) the optimal coding rate is selected to maximise
goodput (treating packets decoded after the delay deadline as losses)
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