Ofdm Simulation Research Papers - Academia.edu (original) (raw)

To reduce the occurrence of high peak-to-average power ratio (PAPR), this paper introduces prolate-binary sequences, and their application in orthogonal frequency division multiplexing (OFDM) systems that implement selected mapping (SLM). Through computer simulation, it is shown that the proposed prolate-binary sequences offer combined improved PAPR reduction performance, and reduced computational complexity compared with Riemann-binary sequences.

- by and +1
- •
- Computational Complexity, Orthogonal Frequency Division Multiplexing (OFDM), Long Term Evolution (LTE), Ofdm Systems

Performance of pilot-aided channel estimation
techniques such as the Least Squares (LS) method depends on
not only on the signal-to-noise ratio (SNR), channel conditions
and pilot ratio, but also on the choice of interpolation method
for deriving channel estimates at non-pilot subcarriers. This
paper investigates the bit-error-rate (BER) performance of
linear, spline and Piecewise Cubic Hermite Interpolating
Polynomial (PCHIP) interpolation methods in LS channel
estimation over the three extended ITU channel profiles defined
for Long Term Evolution (LTE) testing. Simulation results
show that applying the linear interpolation method produces
the best BER performance over the fading channel with the
smallest multipath delay spread. It is also shown that the choice
of best interpolation method actually depends on the SNR in
some of the fading channel profiles.

- by Paolo Banelli
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- OFDM, Time-Varying Channel, Ofdm Simulation

Frame synchronization is a critical factor for effective operation of Orthogonal Frequency Division Multiplexing (OFDM) schemes. This paper studies the frame synchronization of OFDM based wireless systems and proposes a new method for IEEE 802.16 (WiMAX) to improve its performance. The preamble, which is used in this method, is consists of two identical halves, and our method uses the correlation between these two parts in a new efficient form. Our metric calculates the start point within two levels. It finds some possible points as start point in the first level and removes the irrelevant candidates at the second level. The performance of proposed metric and existing ones is compared in terms of mean square error (MSE) and probability of correct detection in AWGN and multipath fading channels. Simulation results show that the proposed method has better performances than famous methods, which were proposed by Schmidl, Minn, Park, Kim, Meng, and in both AWGN and multipath fading Rayleigh channels. Also, compared to new methods with more accurate performance, proposed method has egual performance with less complexity.

This paper studies control format indicator (CFI) estimation methods in 4G-LTE communication systems. CFI is an essential control signal in LTE, and must be correctly detected at the receiver to avoid degraded system performance. The standard method of CFI detection involves the use of the Maximum Likelihood (ML) estimation criterion. Unfortunately, ML decoding performance relies on accurate channel estimation, and as a consequence may result in poor CFI decoding when channel estimates are poor. To improve CFI detection in severe fading channel conditions, a time-domain decision rule that requires no channel estimation, is proposed. Results show that when compared with the ML approach, the proposed method reduces the probability of CFI estimation error in the form of reduced block error rate.

- by Saheed Adegbite and +1
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- Orthogonal Frequency Division Multiplexing (OFDM), Long Term Evolution (LTE), LTE physical layer, Data Recovery

The paper describes how to improve channel estimation in Single Carrier Frequency Division Multiple Access (SC-FDMA) system, using a Hybrid Artificial Neural Networks (HANN). The 3 rd Generation Partnership Project (3GPP) standards for uplink Long Term Evolution Advanced (LTE-A) uses pilot based channel estimation technique. This kind of channel estimation method suffers from a considerable loss ofbitrate due to pilot insertion; all data frame sent contains reference signal. The HANN converts data aided channel estimator to semi blind channel estimator. To increase convergence speed, HANN uses some channel propagation Fuzzy Rules to initialize Neural Network parameters before learning instead of a random initialization, so its learning phase ismore rapidly compared to classic ANN.HANN allows more bandwidth efficient and less complexity. Simulation results show that HANN has better computational efficiency than the Minimum Mean Square Error (MMSE) estimator and has faster convergence than classic Neural Networks estimators.

One of the orthogonal frequency division multiplexing (OFDM) schemes is the Time Domain Synchronous OFDM (TDS-OFDM) scheme, in which, the guard intervals between consecutive OFDM symbols contain Pseudo Noise (PN) sequences which are known to the receiver and are used for channel estimation and synchronization. In this paper, a joint channel estimation algorithm is proposed for TDS-OFDM scheme, the proposed algorithm is based on using a Data-Dependent Superimposed Training (ST) sequence to improve the channel estimation accuracy in TDS-OFDM by utilizing two sources for channel estimation, the PN sequence at the guard interval and the ST sequence added to the data-dependent sequence. Furthermore, a simple linear combination algorithm is used to combine the two channel estimation results. The simulation results of the proposed algorithm show improvement in the estimation accuracy and bit error rate (BER) with little excess in the receiver complexity while, conserving same spectral efficiency as conventional TDS-OFDM scheme.

The UMTS network is complementary to GSM and GPRS. The GSM network covers the features required for voice-type services in a circuit mode, the network brings GFPRS the first features to the introduction of services such as packet data, and UMTS networks complement these by
offering voice and data services on an additional packet. UMTS is thus an extension of GPRS and also works in packet mode. The transmission speed offered by UMTS networks to 2Mbit/s. UMTS infrastructure enables expansion of frequencies as well as changes in data coding. In this
paper, the use of OFDM signals in the UMTS access network UTRANFDD and 64QAM modulation allowed us to improve the rate 2Mbit/s to 22.5 Mbit/s. The results, including improved throughput to 22.5Mbit/s, show us that the power frequency spectrum of a
single OFDM signal is centered around the fundamental frequency, but the spectral width of the power spectrum of the OFDM signals is higher than that of the power spectrum is a function that is typically used in UMTS. We also noted that the greater the number of carriers increases, the more important
the spectral width is. The multicarrier modulation was based, in our case, on the choice of the multiplexing of signals without noise and with noise.

This paper focuses on the channel estimation in OFDM system and it implemented by using pilot type channel estimation by hybrid LS-LMMSE. A LTE system is basically MIMO-OFDM system, where a cyclic prefix is inserted at the beginning of each OFDM symbol in order to suppress both inter-carrier interference (ICI) and inter symbol interference (ISI). The inserted CP is usually longer or equal to the channel length but in some cases, the CP can be shorter. In case of LS and LMMSE channel estimation technique, simulation results shows that LMMSE performs better than LS estimator where cyclic prefix is equal to or longer than the channel length. In other case, LMMSE gives better performance than LS only for low SNR values and for high SNR value, LS gives better performance. Therefore, a hybrid LS-LMMSE channel estimation technique is to reduce the effect of the channel length on system. Simulation results for hybrid system shows its true efficiency and specially for the case where the channel length exceeds the cyclic prefix length.

- by IAEME Publication
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- Hybridity, MIMO Systems, Ion Channels, Ofdm Simulation

The high data transmission rates in the communication channel is a recent growing demand which is achieved by using the multiple input multiple output systems because of their unique properties.. The OFDM systems that adopt the cyclic require only one inverse discrete Fourier transform (IDFT) operation at the low-complexity by means of increasing the transmission diversity in MIMO pilot sequences which minimize the mean square error (MSE) of the channel estimate in traditional MIMO systems are inapplicable to CDD minimum MSE of both the least square (LS) channel estimate and the MMSE channel estimate in CDD systems. The derived criteria are then used to develop a general methodology for determining the sequence. Significantly, the proposed design methodology enables the status of the channel to be estimated using single OFDM symbol. We have compared the performances of channel estimation algorithm by measuring bit error rate vs. SNR with BPSK, QPSK 16

Filter bank multicarrier (FBMC) is considered a competitive waveform candidate for 5G that can replace orthogonal frequency division multiplexing (OFDM). However, channel estimation (CE) is a big challenge in FBMC because it suffers from intrinsic interference which is due to the orthogonality of the subcarrier functions in the real field only. In this paper, we investigate a proposed modified interference approximation scheme (M-IAM) by approximating the intrinsic interference from the neighbouring pilots to accommodate the complex channel frequency and thus improving CE performance besides simplifying its processing. The M-IAM scheme has a larger pseudo pilot magnitude than other conventional preamble schemes, namely the interference approximation method (IAM) with its versions (IAM-C) and (E-IAM-C); in addition to the novel preamble design (NPS). In addition, the proposed (M-IAM) scheme is characterized by the lower transmitted power needed. The CE performance of the M-IAM is investigated through 512 and 2048 subcarriers via different types of outdoor and indoor multipath fading channels that are time-invariant such as IEEE 802.22, IEEE 802.11, Rician, and additive white Gaussian noise (AWGN), as well as time-varying channels such as Rayleigh and Vehicular A (Veh-A). Simulation results demonstrate that the proposed M-IAM scheme achieves a lower bit error rate (BER), lower normalized mean square error (NMSE) and lower peak-to-average power ratio (PAPR) over the conventional preamble schemes under the aforementioned channel models. The proposed scheme has the advantage of saving the transmitted power, a requirement that could match 5G low power requirements. KEYWORDS Filter bank multicarrier (FBMC), intrinsic interference, preamble based channel estimation methods

Chaotic-Binary (CB) sequences have been successfully
employed in selected mapping (SLM) schemes to reduce peak-toaverage
power ratio (PAPR) in Orthogonal Frequency Division Multiplexing
(OFDM) systems. However, construction and implementation
of CB sequences on a Digital Signal Processor (DSP) require a
significant number of complex computations and therefore put additional
constraints on limited DSP resources. This paper presents and
investigates the PAPR reduction capabilities of Binary-Polynomial
(BP) sequences whose coefficients are selected from numbers in a
Fibonacci series. Simulations compare PAPR reduction performance
and the computational complexity of the proposed sequences over
CB sequences. Results show that the proposed BP sequences offer
comparable PAPR reduction performance to CB sequences but have
the advantage of significantly reduced computational complexity.