In this paper, an in-vehicle power line channel mathematical multipath representation is proposed. The selected approach aims at describing the transmission of a signal on a possibly complex power network by means of a finite number of delayed echoes. Model parameters are computed via a well-defined step-by-step procedure from frequency-domain channel characteristics. The feasibility and strength of the method are demonstrated by means of a measurement campaign. Two-port scattering measurements have been carried out on a commercial automobile and the effect of the measurement setup has been considered in the analysis.

This paper focuses on the design of stopping rule criteria for duo-binary turbo codes. In particular, single-binary stopping rules are generalized and iteration/semi-iteration based criteria are developed. The proposed solutions are tested using the framework of HomePlug AV, which is the last generation technology for the in-home distribution of audio and video data over existing power-line wiring.

In this paper we derive two iterative joint precoding and power allocation methods for downlink MC-CDMA systems with multiple transmit antennas at the base station. The first method optimally solves the so called assigned target SINRs problem, i.e. determines the precoding coefficients and the minimum sum-power allocation under a constraint on the SINR of each user. The second method instead solves the maximum sum-rate problem, i.e. maximizes the system throughput under a constraint on the overall transmit power. The main result of this paper is that the proposed joint precoding and power control solutions provide an advantage with respect to suboptimal solutions for a fully loaded system, i.e. when the number of users is equal to the spreading factor times the number of transmit antennas. For lower loads, performance of the various schemes becomes closer.

In this paper a new bit-loading algorithm for the OFDM-based turbo coded HomePlug AV system is proposed. To better exploit the error correction capabilities of the turbo code, this algorithm tries to maximize the throughput while guaranteeing a target BER over a set of sub-carriers using a new metric based on the LLRs. The performance of the considered system, in terms of throughput and BER, is evaluated, using a realistic power-line channel model. Furthermore, data- aided channel and SNR estimates are investigated and their performance compared with the ideal case.

In this paper, as an alternative to post-detection techniques, we derive two iterative joint linear precoding and power allocation methods for downlink MC-CDMA systems with multiple transmit antennas at the base station. The first method optimally solves the so called assigned target SINRs problem, i.e. determines the precoding coefficients and the minimum sum-power allocation under a constraint on the SINR of each user. The second method instead solves the maximum sum-rate problem, i.e. maximizes the system throughput under a constraint on the overall transmit power. The main result of this paper is that the proposed joint precoding and power control solutions provide an advantage with respect to suboptimal solutions for a fully loaded system, i.e. when the number of users is equal to the spreading factor times the number of transmit antennas. For lower loads, performance of the various schemes becomes closer.

Time division duplex (TDD) systems based on orthogonal frequency division multiplexing (OFDM) have recently been proposed as potential candidates for next generation (4G) cellular networks. In this paper, as a multiple access scheme we propose an adaptive frequency division multiple access (AFDMA), where resources are assigned to users exploiting channel knowledge at the transmitter. In order to reduce the system overhead, the algorithm can also work on group of sub-carriers and OFDM symbols. The proposed solution is shown, through numerical results, to be superior to conventional allocation strategies, namely time division multiple access (TDMA) and FDMA. Furthermore, we also investigate a new power control algorithm based on a single-user discrete bit loading technique. Numerical results are reported for both downlink and uplink transmissions in a multi-cell environment supporting real-time traffic

In this paper, a convolutionally-coded uplink multi-carrier code-division multiple-access (MC-CDMA) system with multiple transmit and receive antennas is considered, over multipath Rayleigh fading channels. In this framework, a new iterative hybrid scheme based on the combination of a successive interference cancellation (SIC) and a vertical-BLAST detector is presented, to cope, respectively, with multiple-access interference and multiple-substream interference. Based on simulation results, the performance of the uplink MC-CDMA system, decoded by hard or soft-input decoding methods, is found to improve significantly by the use of antenna arrays in conjunction with the proposed multi-user receiver

This letter focuses on maximization of achievable throughput for uplink orthogonal frequency-division multiplexing code-division multiple-access (OFDM-CDMA) systems. In particular, a new pre-equalization technique is presented where all users employ spreading both in frequency (on sub-bands of the available spectrum) and time; moreover, bit and power loading is used at the mobile terminals to accomplish throughput maximization. To avoid interference among users, the proposed loading algorithm inherently inverts the channel amplitude on the sub-carriers of each sub-band, while the phase is adjusted separately.

A convolutional coded MC-CDMA system is considered for high-rate data transmission in a typical indoor environment with Rayleigh multipath fading. To mitigate the effect of multiple-access interference, new results, with iterative parallel and successive soft-interference cancellation schemes, that can benefit from information available through decoding, are presented, both for downlink and uplink transmissions. Based on the results, a combination of convolutional coding with soft successive interference cancellation (SIC) is found to be attractive also in the more critical fully loaded uplink scenario. Furthermore, in order to reduce the latency of SIC, a simplified receiver is presented where only a reduced number of users is canceled, based on a power criterion; on average, the latency of the system is halved, while the offered performance is still reasonably good.

In this paper the possibility of using pre-equalization on the uplink of a MC-CDMA system is investigated. Specifically, different single-user techniques are analyzed together with two approaches to limit the transmit power. Results of computer simulations show that pre-equalization is a very effective technique for the uplink and that several single-user techniques, with different degrees of complexity, can be applied.

A comparison in the performance between hard- and soft-decision Viterbi decoding, with application to the HIPERLAN/2 standard, is presented. The results show that when channel state information (CSI) is included in the generation of the soft-decision information, the soft-decision method greatly outperforms the hard method. Moreover, a simplified algorithm for the soft-output demapper for the 16-QAM and 64-QAM constellations is developed, which allows the complexity of the demapper to be maintained at almost the same level for all the possible modes of HIPERLAN/2.

The new Home Phoneline Networking Alliance (HomePNA) 2.0 system is an attractive proposition for home networking since it potentially allows transmission rates comparable to those of Ethernet, using the existing installed telephone wiring. However, although the transmission standard is designed to be variable rate (variable symbol rate and bits/symbol), not all combinations are mandatory and it is, therefore, instructive to determine the level of receiver complexity required to handle the optional higher rates. An accurate channel model is devised, characterizing the home phone line network around 7 MHz, which allows the performance of the HomePNA 2.0 physical layer to be evaluated. The very good agreement obtained between the measured and modeled channel responses, in both time and frequency domains, enables a high degree of confidence in the simulation results. Due to the considerable dispersion observed in some home phone line channels, a number of equalizer structures are proposed to improve performance in the receiver. These are compared for each of the two possible symbol rates. Computer simulations show that the performance of the system can be greatly improved at the lower rate with a low complexity equalizer, but at the higher rate, which is not mandatory, a much more complex equalizer is required.

Coherent detection of HIPERLAN Gaussian minimum-shift keying signals calls for complex and expensive receivers. However, when the channel delay spread is limited to at the most 50% of the symbol time and a reliable line-of-sight component of the radiated signal exists (Rician fading model), noncoherent detectors are capable of achieving a good performance. Based on the above motivations, we compare four different demodulation techniques, namely the following: (1) one-bit differential detector; (2) discriminator detector; (3) limiter discriminator detector; and (4) limiter discriminator integrator detector (LDID). The intersymbol interference introduced by these demodulators is nonlinear (with respect to the data symbols) and a decision-feedback equalizer (DFE) based on a mean square-error criterion may not be appropriate. Moreover, at this high speed, a DFE may be very complex to implement. Hence, we propose a new DFE design method that increases the eye-diagram aperture by removing the worst case interference. Performance of the above demodulators in the presence of a simple nonlinear DFE (with feedback part only) is computed in terms of the bit-error rate (BER) by means of the saddle-point approximation. This procedure, for static channels, turns out to be a very general tool with a simple and robust implementation. The same method can be applied, for multipath fading channels, to the BER evaluation as part of a semianalytic approach. The main conclusion from this work is that for LDID demodulators and in the presence of Rician fading channels with an average normalized root mean square delay spread of 0.3 and dual antenna diversity, the new equalizer lowers the outage probability from 60% to 10% at a BER of 10/sup -4/.

Noncoherent demodulators are very attractive for high performance radio LAN (HIPERLAN) systems because of their low implementation costs and their inherent robustness against frequency and carrier phase offsets. However, when the channel is time dispersive, the nonlinear intersymbol interference (ISI) introduced by these demodulators precludes the use of conventional linear equalization strategies. We present an alternative noncoherent receiver structure followed by a nonlinear equalizer, which includes a RAM and a Viterbi detector, capable of equalizing nonlinear multipath fading channels. In addition, we also present a new algorithm specifically for noncoherent demodulators, which allows estimation of all useful signal values at the input of the equalizer to be stored in the RAM. By means of computer simulations, we report the performance and computational complexity tradeoffs of the receiver/equalizer structure, including antenna diversity. We show that demodulators which consist of a complex receiver and a Viterbi detector are much more robust against multipath fading channels than traditional real noncoherent demodulators. The results suggest that in a typical HIPERLAN scenario, where the channel delay spread is less than 50 ns and a reliable line of sight component exists, it is feasible to combat multipath effects using noncoherent demodulation.