Juan J. Sanchez-Sanchez

BER Analysis for Zero-Forcing SC-FDMA Over Nakagami-m Fading Channels

In this paper, we present an analytical study of the bit error rate (BER) for single-carrier frequency-division multiple access (SC-FDMA) transmission over frequency-selective fading channels when zero-forcing frequency-domain equalization is applied. SC-FDMA, which can be described as a precoded version of orthogonal frequency-division multiple access (OFDMA), is regarded as a promising candidate for next mobile communication systems due its favorable envelope characteristics and low peak-to-average-power ratio (PAPR), compared with that of OFDMA. We focus on Nakagami-m fading channels and provide a method to calculate BER values with a single numerical computation. We provide a closed-form expression for the BER with binary phase-shift keying (BPSK) and square M-ary quadrature amplitude modulation (M-QAM) under the assumption of independence among channel frequency responses for allocated subcarriers.

A next generation wireless simulator based on MIMO-OFDM: LTE case study

The complexity of next generation wireless systems is growing exponentially. The combination of Multiple-Input Multiple-Output (MIMO) technology with Orthogonal Frequency Division Multiplexing (OFDM) is considered as the best solution to provide high data rates under frequency-selective fading channels. The design and evaluation of MIMO-OFDM systems require a detailed analysis of a number of functionalities such as MIMO transmission modes, channel estimation, MIMO detection, channel coding, or cross-layer scheduling. In this paper we present a MIMO-OFDM-based simulator that includes the main physical and link layer functionalities. The simulator has been used to evaluate the performance of the 3GPP Long-Term Evolution (LTE) technology for different MIMO-OFDM techniques under realistic assumptions such as user mobility or bandwidth-limited feedback channel.

Closed-Form BER Expression for Interleaved SC-FDMA with M-QAM

One of the novelties of the forthcoming LTE technology is the use of SC-FDMA as the transmission technique in the uplink. In this paper a study of the BER in an interleaved SC-FDMA system over a fading channel is presented. This study provides the mathematical grounds to obtain a closed-form expression for the BER for BPSK and square M-QAM. Results are validated by means of comparison with simulations.

Performance of LTE in Vehicle-to-Vehicle Channels

Vehicle-to-vehicle (V2V) communications have seen growing attention in the last few years. In this work, we address the use of the 3GPP Long Term Evolution (LTE) standard technology applied to V2V. We employ empirical models for the V2V channel, and show results from comprehensive computer simulations, based upon both the uplink (UL) and downlink (DL) standards for LTE. We provide results for 10 MHz and 20 MHz channels, in terms of BER, BLER, spectral efficiency and throughput, using multiple MIMO modes. Results show the attractive feasibility of the LTE technology in V2V communication systems.

Spectral Efficiency of Interleaved SC-FDMA With Adaptive Modulation and Coding Over Nakagami-

Because it achieves similar performance to that of orthogonal frequency-division multiple access (OFDMA) with much more favorable envelope characteristics and lower peak-to-average power ratio (PAPR), single-carrier frequency-division multiple access (SC-FDMA) was chosen as the uplink transmission technology for Long Term Evolution (LTE) and LTE-Advanced systems. This choice has provoked a growing interest in this transmission technology; therefore, there is extensive literature on its performance in terms of bit error rate (BER) and PAPR. However, research on its spectral efficiency has been scarce until now. This paper aims to help fill this gap with an analytical study of the spectral efficiency in SC-FDMA when adaptive modulation and coding (AMC) and linear frequency-domain equalization are applied. This paper therefore computes the spectral efficiency for zero-forcing (ZF) and minimum-mean-square-error frequency-domain equalization (MMSE-FDE) for different Nakagami-m fading channels.

m

The sum of ratios of two complex Gaussian random variables appears frequently in the mathematical analysis of telecommunication systems when zero-forcing equalization is applied. This paper is focused on the study of one of those systems: a simple Orthogonal Frequency Division Multiplexing (OFDM) relay network. The reason behind the election of this particular scenario is the recent interest on employing relay networks in wireless and mobile broadband systems to increase the coverage and throughput in a cost-effective way. Thus, the probability distribution of enhanced noise, made up by the sum of ratios of complex Gaussian random variables, is used to obtain a closed-form expression for the BER in the scenario under study.

Fading Channels

Orthogonal Frequency Division Multiplexing (OFDM) advantages, such as flexible user and rate allocation or easy intersymbol interference compensation, explain its expansion. OFDM has shown resistance to multipath fading. However, OFDM suffers from high Peak to Average Power Ratio (PAPR) which may be particularly troublesome in certain environment such as satellite communications. Single Carrier Orthogonal Frequency Division Multiple Access (SC-FDMA) has become an alternative to OFDM due to its low PAPR. Described as a precoded version of OFDM, its performance is worse than that of OFDM for Rayleigh channels. In this work, the SC-FDMA performance over a simplified model for Land Mobile Satellite (LMS) channels is investigated for different Rice factor K, average delays, and allocated subcarriers. It is shown that, besides its lower PAPR, SC-FDMA outperforms OFDM due to the existence of a Line Of Sight (LOS) able to increase SC-FDMA resistance to fading further than that of OFDM.

Sum of Ratios of Complex Gaussian RVs and Its Application to a Simple OFDM Relay Network

Since many years the Gaussian or normal distribution has been a useful tool to model data observations in fields as physics or astronomy. In communication systems, for instance, this distribution is widely used to model thermal noise. However, there exist many natural physical phenomena that exhibit tails decay following a power law that cannot be modelled by the classical Gaussian distribution. In many of these cases, Students t distributions can be useful for modelling these kind of data because they allow heavy tails which are more realistic. This study provides a brief introduction to those distributions and their convolutions, which are distributed according to the Behrens–Fisher distributions. The goal is to highlight the potential application of non-Gaussian distributions to the analysis of communication systems. With this purpose, the authors present their work applying those distributions to describe the enhanced noise when zero-forcing (ZF) equalisation is used to compensate the effects of a selective fading Rayleigh channel. Obtained results allows the analysis of enhanced noise in three different scenarios: an orthogonal frequency division multiplexing (OFDM) transmission, an OFDM-based relay network and a single carrier frequency division multiple access (SC-FDMA) transmission.

Link level performance of Single Carrier Frequency Division Multiple Access (SC-FDMA) for Land Mobile Satellite (LMS) channel

Wireless networking is coming to the airport surface environment in the near future. This will begin with the Aeronautical Mobile Airport Communication System (AeroMACS), deployed in the 5 GHz MLS Extension (E-MLS) band, from 5.091‣5.15 GHz. The AeroMACS system is based upon the IEEEs 802.16e wireless networking standard, customized for the airport surface by the RTCAs special committee SC-223. The implemented subset of 802.16 technologies is conventionally known as WiMAX. The primary competitor to WiMAX is the Third Generation Partnership Projects Long Term Evolution (LTE) standards. The LTE and WiMAX standards share much in common, but LTEs initial release is typically regarded as being superior to WiMAX in terms of multiple performance criteria. In this work, we explore the performance of LTE in the airport surface environment, using measurement-based models for the airport surface channel. Our results employ a sophisticated LTE simulator along with the empirical channel models. We provide results in terms of error probability, spectral efficiency, and throughput for several multiple-input/multiple-output (MIMO) antenna modes of operation. The MIMO modes we employ include 1 × 2 receiver diversity, 2 × 1 space-frequency coding for transmit diversity, and 2 × 2 spatial multiplexing, all in comparison to conventional (1 × 1) processing. Multiple modulation formats are also employed. We investigate performance in several channel conditions (line of sight, obstructed), and include correlations among the MIMO channels to make results realistic. Our results can be viewed as numerical benchmarks for AeroMACS, and also show the very attractive performance attainable with LTE.

Application of student's t and behrens-fisher distributions to the analysis of enhanced noise after zero-forcing frequency domain equalisation

In this paper, a method for estimating cell capacity from network measurements in a multiservice long-term evolution (LTE) system is presented. Unlike previous work, the proposed method takes into account multiple service-specific constraints, including both delay and throughput constraints. For this purpose, services are first classified by their quality-of-service (QoS) class identifier (QCI). Then, several multivariate linear regression equations are used to estimate the value of the different service-specific QoS indicators from network performance statistics collected on a cell basis. The output of the method is the maximum value of a previously selected traffic capacity indicator per cell ensuring that all QoS constraints are fulfilled. Method assessment is based on data taken from a live LTE network. Results show that cell capacity estimation is robust, provided that enough data are available for each service.