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In this paper, a joint adaptive modulation and multiple-input multiple-output (MIMO) transmission scheme is considered. An efficient use of radio resources shall be based on channel state information at the transmitter (CSIT) to adjust the modulation order and MIMO transmission mode. A new suboptimal algorithm is proposed for link adaptation in a MIMO-OFDMA cellular system under spatially correlated...
This paper gathers some of the authors' work with the family of the elliptically contoured distributions and its application to the analysis of performance in communication systems. Specifically, the Pearson type VII distribution is used to derive a closed-form expression for the BER in an LTE uplink system over a Rayleigh fading channel. ECDs possess many nice properties similar to those of multivariate...
In this work, we derive analytical expressions for the maximum attainable user rate by accomplishing a probabilistic delay constraint in an uncorrelated Rayleigh channel. These rates are derived for two representative scheduling schemes, round robin (RR) and best channel (BC) allocation, but presented tools can be applied to any scheduling policy. On the basis of the effective bandwidth theory, the...
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.
The capacity with probabilistic delay constraint CDt,epsiv expresses the maximum source rate that may be supported in a wireless system with a probability epsiv of exceeding certain delay bound Dt. In a previous paper by the authors (see Proc. IEEE GLOBECOM, November 2007), CDt,epsiv was calculated for a Rayleigh channel carrying a constant rate flow. In this work, the potential of the effective...
A fine time tracking system is presented for orthogonal frequency division multiplexing (OFDM) systems working in multipath fading channels. Due to the channel variability, coarse timing is the most common sampling synchronization level performed in these environments. However, in case of slow time variant channels, fine time tracking can help in some way to the channel equalization, improving the...
The use of finite state Markov chains (FSMC) for the simulation of the Rayleigh channel has been generalized in the last years. Several parameters influence the construction of the chain. The chain can be defined in terms of the complex channel response, the envelope of the received signal or the Signal to Noise Ratio. Moreover the partition method has to be selected among various options. This paper...
A blind method for jointly estimating and correcting time, carrier frequency and sampling clock frequency synchronization in OFDM based systems is proposed. The algorithm is particularlly suitable for low-cost terminal implementations, since it provides a great efficiency in terms of hardware complexity. Its performance has been tested on a real system, taking 3GPP-LTE as target technology and FPGAs...
This paper presents a FPGA implementation of an OFDMA modem for the physical layer of LTE technology, suitable for both uplink and downlink transmission. The designed structure achieves a low area occupation while fulfilling LTE requirements.
This paper shows an efficient implementation of symbol synchronization and frequency equalization algorithms for OFDM (orthogonal frequency division multiplexing) based systems. The aim is to have a low complexity realization that can be implemented on a FPGA (Field Programmable Gate Array), to obtain an area-efficient receiver. The algorithms are described theoretically, and hardware considerations...
In the world of wireless communications, OFDM is one of the most used multicarrier techniques today. The main reasons for that are the multipath immunity that provides and the easy implementation of FFT, but OFDM systems are sensitive to timing synchronization errors. This paper shows a novel synchronization algorithm for the IEEE 802.16-2004 standard. The proposed method performs frame detection...
Resource allocation techniques are determinant to achieve high spectral efficiency in wireless systems and to provide QoS guarantees and fairness to the system users. In this work, several scheduling algorithms are evaluated over a packetized multiuser adaptive OFDMA system with spatial diversity MIMO. Multiuser capacity and fairness are assessed for different channel-aware and/or QoS-aware user multiplexing...
In this work the evaluation of LS channel estimation algorithm for MIMO-OFDM system is carried out. The evaluation has been made using specific pilot design rules that guarantee a bounded error level for the estimation. The method is used to estimate the channel matrix. The quality of the method is evaluated, not for a specific channel but in diverse surroundings of mobile representative channels...
In this paper, a simulator for indoor power-line channels is presented. Its behavioral model includes both the long-and short-time variation of the channel. The long-time variation is due to the electrical appliances switching and is modeled in a statistical way. The cyclic short-time variation is related to the presence of the mains voltage and is characterized modeling the channel response as a...
A wireless resource allocation algorithm based on utility functions is presented. Distinct utility functions dependent on the specific traffic class and the numerical QoS requirements are combined and maximised, so that different treatment is provided to each data flow. This approach is applied to allocate subcarriers and slots of an adaptive OFDMA scheme for services with heterogeneous QoS requirements...
This paper analyzes the performance, of a frequency division multiple access (FDMA) scheme for indoor broadband power-line communications based on discrete multitone (DMT) modulation. Bit-rate loss due to multiple access interference (MAI) is assessed for a synchronous and an asynchronous scheme. Improvements obtained by means of pulse-shaping at the transmitter and windowing at the receiver in the...
We present an adaptive modulation policy that provides delay-throughput balance for data packet transmission over flat fading channels. The proposed policy is based on uninterrupted data transmission (zero-outage) and achieves low packet-delay while satisfies certain average BER constraints. Such delay and BER control is not an obstacle to achieve an average spectral efficiency close to that obtained...
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