Adaptive bit allocation for DMT-based systems is critical for preventing performance degradation due to poor allocation of bits given challenging channel conditions. In this paper, we extend the bit removal greedy algorithm to a multi-user environment. It has been proved that the proposed algorithm converges faster than the traditional multiuser greedy algorithm.

Higher levels of Dynamic Spectrum Management (DSM) are strongly desired; however, we still need methods that are compliant with the current spectrum management specifications and DSM-proven, at the same time. Therefore, we propose a simple yet efficient pre-Level-2 DSM algorithm to protect legacy xDSL systems from new technology implementations (e.g. VDSL2). We show by extensive simulations how effective our proposed algorithm performs over different scenarios. We have also evaluated the penalty (performance) function for VDSL2 lines. We have found that VDSL2 lines suffer from performance degradation in the order of up to ~4.5 Mbps, depending on the primary access network (PAN) length and the cable in use. We have also shown that previous methods as followed in [17, 18, 19] correspond to a specific case of our proposed algorithm.

Bit and power allocation remains a challenge in multiuser multicarrier systems though optimal and suboptimal algorithms have been proposed. In this paper, we optimize the multiuser bit removal greedy algorithm by allowing removing bits in parallel, so reducing the computation time of the algorithm and making it attractive for real implementations. It has been proved that the proposed algorithm converges faster than both the traditional multiuser greedy algorithm and the multiuser bit removal greedy algorithm. This is another approach in comparison to other centralized and distributed algorithms like Optimum Spectrum Balancing (OSB) and Convex Approximation Distributed Spectrum Balancing (CA-DSB).

In this paper we discuss the performance of different profiles of VDSL2 systems in a frequency range up to 12 MHz (band- plan 998 and 997, corresponding to the European region) using two different noise scenarios: VDSL2 Mix and VDSL2 only. The use of different power levels at the downstream is evaluated in these scenarios and it is found that there is no need to use maximum power. As operators are commonly interested to achieve higher data rates, we have selected profile 12a as the most suitable when dealing with frequencies up to 12 MHz while consuming 4 times less power at the downstream than profile 8 b and leading to similar performance in the scenarios herein described. The impact of using different cables has been evaluated for both the downstream and upstream direction. An analysis on boosted and non-boosted masks is also provided. A method to evaluate the upstream performance per band has been used in order to obtain the contribution of each upstream band versus the loop length. With this approach and keeping in mind the dependency of the cable when evaluating performance (e.g. TP150 0.5 mm cable), it has been shown that US2 dies out after 700 m, US1 after 1600 m and USO provides more or less a constant performance contribution in the VDSL2 only scenario for band-plan 998. The same behavior for these upstream bands but in different ranges is expected for other type of cables (also for other band- plans, i.e. 997, which is presented in annex B).

Ultra-wideband (UWB) impulse radio is a promising technique for low-power bio-medical communication systems. While a range of analog and digital UWB architectures exist, the mostly-digital approach without analog down-conversion enables better technology scaling and signal processing flexibility. Furthermore, recently proposed sub-sampling schemes and advances in high-speed ADC circuit design are helping to make this approach more feasible at low power. However, architectures that directly sample the received signal are more vulnerable to sampling jitter. Currently, there does not exist a model describing the impact of sampling jitter making it difficult to determine appropriate tolerances or to establish the feasibility of digital architectures. To address this problem, we have developed a model of sampling jitter and derived a generic bit error rate expressions for a digital UWB modem with sampling jitter, additive noise, and imperfect channel estimation in a generic multipath environment. We then use this model to investigate the performance of sub-sampled digital UWB in a body area network. This paper explains this analytical model and compares it with simulations results for communication around the body.

In order to identify if a subscriber loop is suitable for a certain digital subscriber line (DSL) service, the transfer function of the loop has to be estimated. Several measurement techniques exist, however single-ended line testing (SELT) is often preferred by the telecom operators because all necessary measurements can be done at the central office. The SELT data is typically interpreted in the time domain. This paper presents a new approach by doing the identification in the frequency domain. It starts by explaining the drawbacks of the time domain approach. The paper explains how these are avoided by using a frequency domain identification algorithm. Measurement results show this is a viable alternative to the classical time domain identification.

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. Furthermore, ultra-wideband is a promising air interface for short-range low data rate communication scenarios matching the requirements of wireless bio-medical applications. However, the performance and complexity tradeoffs of ultrawideband systems has never been assessed for the special features of the body area propagation channel. To address this problem, we have measured electromagnetic wave propagation around the body and developed a statistical model. Using this model, we evaluate the performance of optimal and sub-optimal RAKE receivers. This paper describes the resulting communication performance versus complexity for ultra wideband RAKE receivers in a body area propagation environment.

Using ultra-wideband (UWB) wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no detailed models describing the UWB radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have measured radio propagation around the body in a typical indoor environment and incorporated these results into a simple model. We then implemented this model on a computer and compared experimental data with the simulation results. This paper proposes a simple statistical channel model and a practical implementation useful for evaluating UWB body area communication systems.

Using wireless sensors placed on a person to continuously monitor health information is a promising new application. However, there are currently no models describing the radio channel around the human body making it difficult to design a suitable communication system. To address this problem, we have simulated electromagnetic wave propagation around the body and incorporated these results into a simple model. We then compared this model with measurements taken around the human torso and with previous studies in the literature. This paper proposes a simple statistical channel model useful for evaluating both UWB and (after resampling) narrow-band body area communication systems.

In order to qualify a subscriber loop for xDSL transmission, the channel capacity has to be estimated, which depends on the transfer function of the network. A method is provided to estimate the transfer function of the subscriber loop only measuring the one-port scattering parameter at the central office. We consider three types of networks according to their topology: a single line, a homogeneous network with a bridged tap, and a cascade of two line sections. For each type of network a parametric model is derived of its one-port scattering parameter and transfer function based on the physical line model VUB0. The model for the scattering parameter is used to identify the network based on the corresponding measurements by means of a maximum-likelihood estimator. The estimated parameters are substituted in the transfer function model, which is needed for the capacity estimation. The proposed models and estimators are validated by measurements and simulations. For the measurements, which were performed with a network analyzer, three types of twisted-pair cables were used: British Telecom (BT), Deutsch Telekom (FT), and Belgacom.

This contribution proposes a new family of methods to reduce the peak-to-average power ratio (PAR) in discrete multi-tone (DMT) and orthogonal frequency division multiplexing (OFDM) systems. This method avoids the use of extra inverse fast Fourier transformations (IFFT) as were used in some previously published techniques, but instead is based on transformations in the time domain of the original sequence available at the output of the IFFT processor. The improved statistics of peak power in the optimized transmit signal are demonstrated by simulation results.