Stanford University Interim Channel Research Articles

Comparative studies on multi-carrier transmission schemes in mountainous and dense forest environment

Earthquakes, forest fires, mudslides and other natural disasters occur frequently in recent years. They usually occur in the mountainous and dense forests, where local communication facilities do not exist or have been destroyed by the disasters. Adverse geographical environment poses a huge challenge to emergency communications and rescue. This paper presents comparative studies on multi-carrier transmission schemes in the mountainous and dense forest environment. The comprehensive communication performance for various multi-carrier waveform schemes, has been extensively analyzed by using the Stanford University Interim channel model. Simulation results show that the pruned discrete Fourier transform spread filter bank multi-carrier scheme exhibits generally the best performance in terms of transmission rate and distance for most operation modes.

BER Analysis of SWT Based OFDM ON LTE

We proposed to use singular wavelet transform (SWT) in OFDM based LTE because the SWT based system does not require a cyclic prefix, so spectrum efficiency is increased. SWT is used to analyze signals by the coefficients of SWT in both time and frequency domain. In order to investigate the bit error rate performance a practical channel model is required. Many channel models are proposed to mimic a real world scenario. Out of which Stanford university interim (SUI) channel provides best results so we replaced AWGN channel with SUI channel. We investigated the performance of bit error rates of SWT based OFDM in LTE for different modulation techniques such as QPSK, 64 QAM, 128 QAM under SUI 3 Channel model using SWT based haar and db2 transform. BER is reduced by 2 times when compared to the existing system.

Performance of adaptive MIMO switching for cognitive MC-CDMA system

The future 5G wireless network will be identified by flexibility design, high combination of services, and higher data rate. In this treatise, we present the performance evaluation physical layer design for multi-carrier code-division-multiple-access (MC-CDMA) system for cognitive radio network (CRN) employing link adaptive multiple-input multiple- output (MIMO). CRN in conjunction with MIMO promises to achieve massive amelioration in system bandwidth. We consider link adaption scheme (LAS) which will select modulation scheme and MIMO profile based on channel parameters. CRN is a device in wireless communication which can sense the idle unused spectrum and allocate the spectrum dynamically to base station. We utilize sub-band frequency of CRN for multi-carrier communication and to extract for user-specific spreader in CDMA system. Further, we realize iterative decoder at the receiver to achieve better error-rate performance for CRN based MIMO MC-CDMA system with less signal-to-noise ratio (SNR). Furthermore,We study the performance of adaptive MIMO scheme with CRN defined MC-CDMA for Stanford University Interim channel model specifications. We discern through computer simulations that CRN based MC-CDMA system with adaptive MIMO scheme achieves significant performance enhancement both in error-rate and data rate.

Ber Performance Analytical Approach for Conventional DFT and DWT for Different Modulation Techniques using SUI Channel in OFDM

Orthogonal Frequency Division Multiplexing (OFDM) is of the strong prospects as a future wireless communication system. Improved spectral efficiency has been found in OFDM based on DFT, has a good orthogonality but inter symbol interference (ISI) and inter carrier interference (ICI) degrade the performance. ISI and ICI can be improved by using cyclic prefix (CP). About 20% of bandwidth is consumed by CP. For preferable performance DWT based OFDM gives better outlook than DFT based OFDM.. Three advantages of using DWT are desirable signal to noise ratio, desirable data rate and below per power requirement are given by wavelet based OFDM. Comparison of performances of BER using practical channel model known as Stanford University Interim (SUI) is given in this paper. Consideration to QPSK, 4QAM, 8QAM, 16-QAM, 32QAM, 64-QAM, 128QAM and 256 QAM has been given in modeling. Channel condition and modulation are the precursors given for the selection of particular performance.

Robust Neural Network based Multiuser Detector in MC-CDMA for Multiple Access Interference Mitigation

The aim of this paper is to design a multiuser detector technique using artificial Neural Network under multiple access interference mitigation. To improve the performance of Multi Carrier Code Division Multiple Access (MC-CDMA) under multiple access interference, we have used a multilayered perceptron model of Neural Network that has three layers namely, input layer, hidden layer and output layer. The Neural Network is further trained by Levenberg-Marquardt algorithm. This algorithm uses the error function as key factor based on which the weights are adjusted to get the desired output. The Bit Error Rate (BER) performance of the system has been evaluated under Rayleigh and Stanford University Interim (SUI) channels for Binary Phase Shift Keying (BPSK) and Quadrature Amplitude Modulation (QAM) techniques. The proposed Neural Network based receiver is compared with Equal Gain Combining (EGC) and Maximal Ratio Combining (MRC) with varying number of users and Signal to Noise Ratio (SNR). Under SUI channel conditions and for a BER of 10 -3 , the Neural Network based receiver shows an improvement of 1 dB and 8 dB than EGC and MRC receivers, respectively.

Coded Downlink Multi-user MC-CDMA System using Transmitter Pre-processing: Performance Results

In this treatise, we evaluate the error-rate (ER) performance of turbo-coded multi-carrier code division multiple access scheme (MC-CDMA) for downlink (DL) transmission. The transmitter pre-processing (TP) technique is a promising signal processing technique, which is carried out at the transmitter side to reduce the burden of each mobile station (MS) in the context of DL communication. We formulate minimum mean-square-error-aided TP matrix using noisy feedback of vector-quantized estimated channel information (CI) for frequency-division duplexing system. Clearly, we estimate the CI and perform vector quantization (VQ) at each MS and transmit the index of the quantized value through dedicated low rate noisy channel. Finally, we acquire CI of all active users using known estimation algorithm in order to build TP. We realize time-frequency domain signature sequence to support more user population. In particular, we analyze the ER performance of coded MC-CDMA system with TP for Stanford University Interim channel model. The ER curve shows that coded MC-CDMA system based on TP approach provides better performance with less signal-to-noise ratio while offering low complexity of MS. In addition, performance curve shows that there is an improvement in the ER performance when perfect CI is utilized to build TP matrix compared with noise-contaminated VQ-CI.

Performance of a turbo-coded downlink IDMA system using transmitter pre-processing

In this study, we investigate the bit error rate (BER) performance of a multi-user transmitter pre-processing (MUTP) aided, turbo-coded interleave division multiple access (IDMA) scheme over correlated frequency-selective channels for downlink (DL) communication. We realize MUTP using a zero forcing (ZF) approach. Further, we build the pre-processing matrix using the channel state information of all of the active users. To be specific, we evaluate the BER performance of a coded ZF-MUTP assisted IDMA system for a realistic channel model based on Stanford University Interim channel and Long term Evolution channel specifications; the MUTP is based on both an equal power approach and a maximum-signal-to-noise ratio (MSNR) approach. From our simulation results, we observe that our considered system with a MSNR power allocation regime provides better performance in terms of the achievable BER than the equal power approach, while offering a low complexity receiver for DL transmission.

Performance of Dual-Polarized DSTTD-IDMA system over correlated frequency selective channels

In this correspondence, we present the performance of Dual-Polarized double space–time transmit diversity (DSTTD) aided multiple-input multiple-output (MIMO) interleave division multiple access (IDMA) scheme over correlated frequency-selective channels for downlink communication. DSTTD system is realized by employing two space–time block code units at the base station (BS). We employ two Dual-Polarized antennas both at the BS and mobile stations. We consider maximum-likelihood ratio detection algorithm at the receiver to detect the signals and to mitigate the effects of multiple access interference and multi stream interference. We implement iterative type turbo decoding algorithm to enhance bit error rate (BER) performance. We evaluate the performance of Dual-Polarized DSTTD-IDMA system based on Stanford University Interim channel models and Long-Term Evaluation channel model. Our simulation results reveal that DSTTD-IDMA system with Dual-Polarized antenna requires higher SNR than uni-polarized antennas. However, it provides the advantage of replacing two uni-polarized antennas by a single Dual-Polarized antenna.

Neural network-based adaptive multiuser detection schemes in SDMA–OFDM system for wireless application

Neural network applications in adaptive multiuser detection (MUD) schemes are suggested here in the context of space division multiple access–orthogonal frequency division multiplexing system. In this paper, various neural network (NN) models like feed forward network (FFN), recurrent neural network (RNN) and radial basis function network (RBFN) are adopted for MUD. MUD using NN models outperforms other existing schemes like genetic algorithm--assisted minimum bit error rate (MBER) and minimum mean square error MUDs in terms of BER performance and convergence speed. Among these NN models, the FNN MUD performs efficiently as RNN in full load scenario, where the number of users is equal to number of receiving antennas. In overload scenario, where the number of users is more than the number of receiving antennas, the FNN MUD performs better than RNN MUD. Further, the RBFN MUD provides a significant enhancement in performance over FNN and RNN MUDs under both overload and full load scenarios because of its better classification ability due to Gaussian nonlinearity. Extensive simulation analysis considering Stanford University Interim channel models applied for fixed wireless applications shows improvement in convergence speed and BER performance of the proposed NN-based MUD algorithms.

Coverage Availability for the IEEE 802.16 System over the SUI Channels with Rayleigh Fading

The coverage probability and range of IEEE 802.16 systems depend on different wireless scenarios. Evaluating the performance of IEEE 802.16 systems over Stanford University Interim (SUI) channels is suggested by IEEE 802.16 specifications. In order to derive an effective method for forecasting the coverage probability and range, this study uses the SUI channel model to analyze the coverage probability with Rayleigh fading for an IEEE 802.16 system. The BER of the IEEE 802.16 system is shown in the simulation results. Then, the maximum allowed path loss can be calculated and substituted into the coverage analysis. Therefore, simulation results show the coverage range with and without Rayleigh fading. Keywords—OFDM, coverage, SUI channel, IEEE 802.16

Coverage probability analysis of IEEE 802.16 system with smart antenna system over Stanford University Interim fading channels

The IEEE 802.16 system, a promising wireless communication system, has a maximum transmission range of 50 km according to the IEEE 802.16 standard. In reality, the transmission range and coverage probability of an IEEE 802.16 system vary for different wireless scenarios. Evaluating the transmission range and coverage probability of an IEEE 802.16 system prior to implementation is important. Hence, the Stanford University Interim (SUI) channel model in IEEE 802.16 specifications is suitable for evaluating the performance of IEEE 802.16 systems. To generate an effective method for predicting coverage, this study uses the SUI channel model to analyse the coverage probability of an IEEE 802.16 system. Furthermore, this study utilises a smart antenna system (SAS) to enhance IEEE 802.16 system performance. In terms of different antenna heights of the Base Transceiver Station and Customer Premises Equipment, the performance evaluation results show that the cell radius with the SAS is at least 30 more than that without the SAS.

Unequal protection using adaptive burst profile selection for WiMAX video streaming

It is proposed that in a compact urban region fixed WiMAX (IEEE 802.16d) burst profiles can be adaptively selected according to the picture type of packets from an arriving encoded video stream. Because additional protection of anchor picture packets reduces the data rate, an algorithm dynamically selects less favourable burst profiles for less important packets. Under the stringent Stanford University Interim channel model, this simple scheme achieves as much as 10 dB gain in video quality at the receiver.