35 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 Mâ„4 and 0â€SNRâ€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 Mâ„4 and 0â€SNRâ€30 dB
Performance of Fractionally Spread Multicarrier CDMA in AWGN as Well as Slow and Fast Nakagami-m Fading Channels
AbstractâIn multicarrier code-division multiple-access (MCCDMA), the total system bandwidth is divided into a number of subbands, where each subband may use direct-sequence (DS) spreading and each subband signal is transmitted using a subcarrier frequency. In this paper, we divide the symbol duration into a number of fractional subsymbol durations also referred to here as fractions, in a manner analogous to subbands in MC-CDMA systems. In the proposed MC-CDMA scheme, the data streams are spread at both the symbol-fraction level and at the chip level by the transmitter, and hence the proposed scheme is referred to as the fractionally spread MC-CDMA arrangement, or FS MCCDMA. Furthermore, the FS MC-CDMA signal is additionally spread in the frequency (F)-domain using a spreading code with the aid of a number of subcarriers. In comparison to conventional MC-CDMA schemes, which are suitable for communications over frequency-selective fading channels, our study demonstrates that the proposed FS MC-CDMA is capable of efficiently exploiting both the frequency-selective and the time-selective characteristics of wireless channels. Index TermsâBroadband communications, code-division multiple access (CDMA), fractionally spreading, frequency-domain spreading, multicarrier modulation, Nakagami fading, timedomain spreading
Design and performance evaluation of RAKE finger management schemes in the soft handover region
We propose and analyze new finger assignment/management techniques that
are applicable for RAKE receivers when they operate in the soft handover region.
Two main criteria are considered: minimum use of additional network resources and
minimum call drops. For the schemes minimizing the use of network resources, basic
principles are to use the network resources only if necessary while minimum call drop
schemes rely on balancing or distributing the signal strength/paths among as many
base stations as possible. The analyses of these schemes require us to consider joint
microscopic/macroscopic diversity techniques which have seldom been considered before
and as such, we tackle the statistics of several correlated generalized selection
combining output signal-to-noise ratios in order to obtain closed-form expressions for
the statistics of interest. To provide a general comprehensive framework for the assessment
of the proposed schemes, we investigate not only the complexity in terms of
the average number of required path estimations/comparisons, the average number
of combined paths, and the soft handover overhead but also the error performance of
the proposed schemes over independent and identically distributed fading channels.
We also examine via computer simulations the effect of path unbalance/correlation as
well as outdated/imperfect channel estimations. We show through numerical exam ples that the proposed schemes which are designed for the minimum use of network
resources can save a certain amount of complexity load and soft handover overhead
with a very slight performance loss compared to the conventional generalized selection
combining-based diversity systems. For the minimum call drop schemes, by
accurately quantifying the average error rate, we show that in comparison to the
conventional schemes, the proposed distributed schemes offer the better error performance
when there is a considerable chance of loosing the signals from one of the
active base stations
Adaptive Power Control for Single and Multiuser Opportunistic Systems
In this dissertation, adaptive power control for single and multiuser opportunistic
systems is investigated. First, a new adaptive power-controlled diversity combining
scheme for single user systems is proposed, upon which is extended to the multiusers
case. In the multiuser case, we first propose two new threshold based parallel multiuser
scheduling schemes without power control. The first scheme is named on-off
based scheduling (OOBS) scheme and the second scheme is named switched based
scheduling (SBS) scheme. We then propose and study the performance of thresholdbased
power allocation algorithms for the SBS scheme. Finally, we introduce a unified
analytical framework to determine the joint statistics of partial sums of ordered RVs
with i.i.d. and then the impact of interference on the performance of parallel multiuser
scheduling is investigated based on our unified analytical framework
Calculating the probability of error per symbol on the basis of MGF method using Rician fading for MFSK
U ovom radu se analizira verovatnoÄa greĆĄke po simbolu za M-arnu ne-koherentnu frekvencijsku modulaciju (M-ary Frequency Shift Keying, MFSK) signala u ambijentu frekvencijsko-neselektivnog sporog Rician fadinga i prijemnika zasnovanog na tehnici kombinovanja maksimalnog odnosa (Maximal Ratio Combining, MRC). VerovatnoÄe greĆĄke po simbolu su dobijene na osnovu numeriÄkog izraÄunavanja baziranog na funkciji generisanja momenta (Moment Generating Function, MGF). Pretpostavlja se da je informacija na prijemnoj strani kanala poznata. Analiza verovatnoÄe greĆĄke po simbolu za MFSK modulacionu tehniku izvrĆĄena je za razliÄite vrednosti Rician faktora K, diverziti reda N i nivoa modulacije M.In this paper is presented how to calculate the probability of error per symbol of M-ary non-coherent frequency modulation (M-ary Frequency Shift Keying, MFSK) over a slow, flat, identically independently distributed Rician fading channels. SEP is calculated by technique with maximal ratio combining diverzity, using the moment generating function. We assume that the information is known on the receiving side of the channel. Probabilities of error per symbol for the modulation technique are plotted for different values of Rician factor K, diverzity order N and modulation order M
Calculating the probability of error per symbol on the basis of MGF method using Rician fading for MFSK
U ovom radu se analizira verovatnoÄa greĆĄke po simbolu za M-arnu ne-koherentnu frekvencijsku modulaciju (M-ary Frequency Shift Keying, MFSK) signala u ambijentu frekvencijsko-neselektivnog sporog Rician fadinga i prijemnika zasnovanog na tehnici kombinovanja maksimalnog odnosa (Maximal Ratio Combining, MRC). VerovatnoÄe greĆĄke po simbolu su dobijene na osnovu numeriÄkog izraÄunavanja baziranog na funkciji generisanja momenta (Moment Generating Function, MGF). Pretpostavlja se da je informacija na prijemnoj strani kanala poznata. Analiza verovatnoÄe greĆĄke po simbolu za MFSK modulacionu tehniku izvrĆĄena je za razliÄite vrednosti Rician faktora K, diverziti reda N i nivoa modulacije M.In this paper is presented how to calculate the probability of error per symbol of M-ary non-coherent frequency modulation (M-ary Frequency Shift Keying, MFSK) over a slow, flat, identically independently distributed Rician fading channels. SEP is calculated by technique with maximal ratio combining diverzity, using the moment generating function. We assume that the information is known on the receiving side of the channel. Probabilities of error per symbol for the modulation technique are plotted for different values of Rician factor K, diverzity order N and modulation order M
Bit error rate estimation in WiMAX communications at vehicular speeds using Nakagami-m fading model
The wireless communication industry has experienced a rapid technological evolution from its basic first generation (1G) wireless systems to the latest fourth generation (4G) wireless broadband systems. Wireless broadband systems are becoming increasingly popular with consumers and the technological strength of 4G has played a major role behind the success of wireless broadband systems. The IEEE 802.16m standard of the Worldwide Interoperability for Microwave Access (WiMAX) has been accepted as a 4G standard by the Institute of Electrical and Electronics Engineers in 2011. The IEEE 802.16m is fully optimised for wireless communications in fixed environments and can deliver very high throughput and excellent quality of service. In mobile communication environments however, WiMAX consumers experience a graceful degradation of service as a direct function of vehicular speeds. At high vehicular speeds, the throughput drops in WiMAX systems and unless proactive measures such as forward error control and packet size optimisation are adopted and properly adjusted, many applications cannot be facilitated at high vehicular speeds in WiMAX communications. For any proactive measure, bit error rate estimation as a function of vehicular speed, serves as a useful tool. In this thesis, we present an analytical model for bit error rate estimation in WiMAX communications using the Nakagami-m fading model. We also show, through an analysis of the data collected from a practical WiMAX system, that the Nakagami-m model can be made adaptive as a function of speed, to represent fading in fixed environments as well as mobile environments
Distributed space-time coding including the golden code with application in cooperative networks
This thesis presents new methodologies to improve performance of wireless cooperative networks using the Golden Code. As a form of space-time coding, the Golden Code can achieve diversity-multiplexing tradeoff and the data rate can be twice that of the Alamouti code. In practice, however, asynchronism between relay nodes may reduce performance and channel quality can be degraded from certain antennas.
Firstly, a simple offset transmission scheme, which employs full interference cancellation (FIC) and orthogonal frequency division multiplexing (OFDM), is enhanced through the use of four relay nodes and receiver processing to mitigate asynchronism. Then, the potential reduction in diversity gain due to the dependent channel matrix elements in the distributed Golden Code transmission, and the rate penalty of multihop transmission, are mitigated by relay selection based on two-way transmission. The Golden Code is also implemented in an asynchronous one-way relay network over frequency flat and selective channels, and a simple approach to overcome asynchronism is proposed. In one-way communication with computationally efficient sphere decoding, the maximum of the channel parameter means is shown to achieve the best performance for the relay selection through bit error rate simulations.
Secondly, to reduce the cost of hardware when multiple antennas are available in a cooperative network, multi-antenna selection is exploited. In this context, maximum-sum transmit antenna selection is proposed. End-to-end signal-to-noise ratio (SNR) is calculated and outage probability analysis is performed when the links are modelled as Rayleigh fading frequency flat channels. The numerical results support the analysis and for a MIMO system
maximum-sum selection is shown to outperform maximum-minimum selection. Additionally, pairwise error probability (PEP) analysis is performed for maximum-sum transmit antenna selection with the Golden Code and the diversity order is obtained.
Finally, with the assumption of fibre-connected multiple antennas with finite buffers, multiple-antenna selection is implemented on the basis of maximum-sum antenna selection. Frequency flat Rayleigh fading channels are assumed together with a decode and forward transmission scheme. Outage probability analysis is performed by exploiting the steady-state stationarity of a Markov Chain model