The increase of distributed renewable electricity generators, such as solar cells and wind turbines, requires new energy management systems where real-time measurements and communication between end users, suppliers and utilities are vital. To address this need, we propose a common service architecture that allows houses with renewable energy generation and smart energy devices to plug into a distributed energy management system, integrated with the public power grid. The presented architecture facilitates end-users to optimize their energy consumption, enables power network operators to better balance supply and demand, and creates a platform where new market players (e.g. ESCOs) can easily provide new services. This service architecture has been implemented and is currently evaluated in a field trial with 21 users, of which we present the initial results.

In order to deliver intelligent context-aware services (e.g. notifications of nearby points of interest), location based services are getting a lot of interest. However, deploying these services efficiently is currently hampered by the lack of enabling platforms, especially platforms taking advantage of easy service composition and flexible management. In this paper we detail the design of pCASE, a platform for enabling context aware services. This platform allows easy deployment in both home and business premises and flexible management of complex services taking into account context information such as location and presence. A use case is presented: an intelligent call redirection service which dynamically (re)routes communication sessions depending on the location, occupation and social networks of users.

In response to fierce competition, telecom service providers re-engineer their IT and telecommunications services environment in order to offer a wide range of new value-added services faster and more cost efficiently. These organizations are adopting a service-oriented paradigm in order to rationalize the OSS and BSS infrastructure, introduce self-service systems and manage 3/sup rd/ party business-to-business interactions. This paper investigates how service-oriented principles introduced in the business domains can extend into the telecom services domain. An approach for telecommunications service creation in a SOA through service orchestration is detailed and illustrated by a use case for triple play (3P).

While the Java programming language and the J2EE platform are increasingly popular for implementing business logic on backend platforms, new emerging Java technologies such as JAIN SLEE and SIP Servlet are focusing on the development of low latency Java applications. As J2EE mainly focuses on enterprise applications with complex long lasting transactions, this technology is considered unsuitable for applications with low latency and high throughput characteristics. This paper compares these telecom oriented Java technologies to J2EE both in terms of functionality and through a detailed performance evaluation. JVM performance tuning has been studied as well and is explained in the paper. We performed a SIP proxy benchmark with strict low latency requirements of which the results are presented. Furthermore, design guidelines for J2EE applications are discussed to optimize for low latency behavior together with an interpretation of the obtained performance results.

Per-tone equalization has recently been proposed as an alternative receiver structure for discrete multitone-based systems improving upon the well-known structure based on time-domain equalization. Fast initialization of all the equalizer coefficients has been identified as an open problem. In this letter, a recursive initialization scheme based on recursive least squares with inverse updating is presented for the per-tone equalizers. Simulation results show convergence with an acceptably small number of training symbols. Complexity calculations are made for per-tone equalization and for the case where tones are grouped. It is demonstrated with an example that in the latter case, initialization complexity becomes sufficiently low and comparable to complexity during data transmission.

A new echo cancellation structure for discrete multitone systems is presented, where each used tone has its own per-tone echo canceller in addition to a per-tone equalizer, which provides an alternative to currently employed time domain and time/frequency domain approaches. The per-tone approach enables us to optimize the signal-to-noise ratio for each tone separately by solving a minimum mean-square error problem for each tone, with implicit so-called joint shortening. Complexity during data transmission is compared for time domain, time/frequency domain, and per-tone echo cancellation. Structures with reduced complexity are derived for an interpolated and a decimated rate setup. Finally, simulation results for an asymmetric digital subscriber line setting demonstrate improved performance over time domain (or time/frequency domain) echo cancellation.

This paper is devoted to the design and the steady-state performance analysis of a data-aided or decision-directed timing recovery scheme for filter bank-based multicarrier transmission with equalization. The symbol synchronizer is obtained from a Mueller and Muller approach extended to multiband transmission. A simple synchronizer is first proposed which can be derived from an approximate likelihood function. Then, possible improvements are discussed. Timing jitter variances are computed and discussed for high bit-rate transmission over copper wires.

In classical discrete multi tone receivers, the equalizer structure consists of a (real) time domain equalizer (TEQ) combined with (complex) 1-taps frequency domain equalizers. Recently, an alternative receiver was introduced based on a separate per tone equalization, where the SNR on each tone and hence the bitrate is maximized. In this paper, a new adaptive initialization scheme for this per tone equalizer (PTEQ) is introduced, based on a combination of Least Mean Squares (LMS) and Recursive Least Squares (RLS) with inverse updating. It will be shown that the proposed method exhibits only slightly slower convergence compared to full RLS with inverse updating, while complexity as well as memory cost are reduced considerably.

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.

A new echo canceller for discrete multitone (DMT) systems is presented where each used tone has its own per tone echo canceller (PT-EC) in addition to a per tone equalizer (PT-EQ). This enables us to optimize the signal-to-noise ratio (SNR) for each tone separately by solving a minimum mean square error (MMSE) problem for each tone. Simulation results confirm improved performance over time domain echo cancellation.

An alternative receiver structure is presented for discrete multitone-based systems. The usual structure consisting of a (real) time-domain equalizer in combination with a (complex) 1-tap frequency-domain equalizer (FEQ) per tone, is modified into a structure with a (complex) multitap FEQ per tone. By solving a minimum mean-square-error problem, the signal-to-noise ratio is maximized for each individual tone. The result is a larger bit rate while complexity during data transmission is kept at the same level. Moreover, the per tone equalization is shown to have a reduced sensitivity to the synchronization delay.

The performance degradation of filter-bank-based multicarrier transmission due to timing errors is investigated. The receiver is made of a fractionally spaced linear or decision-feedback equalizer designed for some sampling phase. The actual sampling phase is different and the impact of the difference on the performance is investigated. Sampling phase offset and jitter are considered. Besides, assuming the sampling phase error can be estimated the efficiency of various types of interpolation is investigated.

In discrete multi-tone (DMT) systems, demodulation of the QAM modulated sinusoids is achieved by a fast Fourier transform (FFT) on blocks of samples generated from the received continuous-time signal. A clock difference between transmitter and receiver, annihilates the orthogonality of the carriers. Therefore, a receiver using asynchronous sampling must perform timing correction in the discrete-time domain. A new digital timing synchronization method is presented which is based on temporal and frequency domain digital signal processing. Correction of the sample clock offset is done in the time domain whereas DMT symbol timing alignment is done in the frequency domain. The method alleviates the need for accurate free running Xtals generating the sample clocks and can be used for high rate DMT systems like for instance the emerging very high rate digital subscriber loop (VDSL) transceivers.

This paper examines a decision-directed timing recovery scheme for filter-bank-based multicarrier transmission. The symbol synchronizer is obtained from a maximum-likelihood approach and uses the digital equalization filters. The algorithm is first derived, the performances of the scheme (timing offset and timing jitter) are then computed, and computational results are provided for high bit-rate transmission over copper wires. Finally, different improvements are discussed.

This paper is devoted to a decision-directed timing recovery scheme for filter bank based multicarrier transmission. The symbol synchronizer is obtained from a maximum-likelihood approach and uses the equalizer outputs. The algorithm is first derived and computational results for the resulting timing error are provided for high bit rate transmission over copper wires. Finally, different improvements are discussed.

In this contribution the transmission of M-PSK and M-QAM modulated orthogonal frequency division multiplexed (OFDM) signals over an additive white Gaussian noise (AWGN) channel is considered. The degradation of the bit error rate (BER), caused by the presence of carrier frequency offset and carrier phase noise is analytically evaluated. It is shown that for a given BER degradation, the values of the frequency offset and the linewidth of the carrier generator that are allowed for OFDM are orders of magnitude smaller than for single carrier systems carrying the same bit rate.>

Investigates the bit error rate (BER) performance of a passband single-carrier QAM transceiver for asymmetric digital subscriber lines (ADSL), with additive white Gaussian noise (AWGN) and self far-end crosstalk (FEXT) as the main disturbances. The major difference with previous contributions on ADSL performance is that the authors present a simple approximate analytical expression fur the signal-to-noise ratio (SNR) margin, which clearly shows the effect of various cable and system parameters (such as loop length, transmit power, QAM constellation size, bit rate, ...) on ADSL performance. From this expression, they determine the optimum constellation size and the maximum achievable bit rate as a function of the loop length.>