Ricard Aquilue

Circuital and Modal Characterization of the Power-Line Network in the PLC Band

With present day measurement techniques, it is very difficult to accurately model the power- line network (PLN), as seen from its power-line terminals, both in terms of impedance and noise. In this paper, a new circuital model (that considers line-ground and neutral-ground signals) and a new modal model (that considers common and the differential mode signals) for characterizing the low voltage PLN are presented. These models, which treat impedance and noise in a unified way, are composed by a three-impedance pi-network and two voltage sources. These models, which are complete and rigorous, are very interesting to desing PLC modems matched to the PLN for maximal power transfer, to compute the energy conversion between common mode and differential mode produced by asymmetries in the PLN, and to know the levels of differential mode noise that will affect a PLC receiver. These models have been experimentally validated.

Scattering Parameters-Based Channel Characterization and Modeling for Underground Medium-Voltage Power-Line Communications

Power-line communications (PLC) technologies rely on the power grid for data transmission. Since the communications channel is already deployed, this communication alternative is specially interesting for the power grid owner (i.e., the electrical utility). The medium-voltage (MV) distribution network, located after the last step-down electrical substation with typical levels from 6 to 25 kV, directly feeds large consumers and small ones through several transform stations. The growing interest on MV-PLC technology, the natural aggregation point for data coming and going into the low-voltage (LV) network, faces the same issue that the LV-PLC technology did (and does): standardization. In this way, a properly implemented channel model will allow the design of suitable modulation and access methods. This paper proposes a deterministic channel model for the MV underground network transfer function, based on a complete set of measurements performed in an MV urban ring. Moreover, the characterization of the MV-PLC channel elements as well as the noise scenario and access impedance have been carried out.

High-Voltage Multicarrier Spread-Spectrum System Field Test

High-voltage (HV) power lines have been used as a communications medium since the 1920s. Those point-to-point links were typically based on single-sideband amplitude modulation. These days, the state of the art in HV power-line carrier (PLC) communications comprises the combination of analog systems, mainly for teleprotection tasks, and digital systems, used for voice and data transmission. Beside traditional core services (monitoring, operation management, and limitation and removal of failures), electrical utilities would like to satisfy the increasing need of new internal applications. In that way, quadrature amplitude modulation and, most recently, multicarrier modulation (MCM)-based modems are beginning to play an important role in HV PLC systems. Although the typical 4-kHz bandwidth has been recently increased up to 32 kHz, this paper proposes a low-power 256-kHz bandwidth multicarrier-spread-spectrum (MC-SS)-based physical layer. Based on channel measurements, the MC-SS symbol has been designed and tested in order to increase the user bit rate while delivering reduced power spectral density and bit-error rate.

Contiguous frequency-time resource allocation and scheduling for wireless OFDMA systems with QoS support

The orthogonal frequency division multiple access (OFDMA) scheme has been selected as a potential candidate for many emerging broadband wireless access standards. In this paper, a new joint scheduling and resource allocation scheme is proposed for the OFDMA systems using contiguous subcarrier permutation. The proposed resource allocation algorithm provides contiguous sets of frequency-time resource units following a rectangular shape yielding a reduction on the required burst signalling. The joint scheduling and resource allocation process is divided into two phases: the QoS requirements fulfilment and the input buffers emptying status. For each phase, a specific prioritization function is defined in order to obtain a trade-off between the fairness and the spectral efficiency maximization. The new prioritization scheme provides a reduction of 50% of the 99th percentile from the delivered packets delay in case of non real-time services, and 30% of the packet loss rate in case of real-time services compared to the proportional fair scheduling function. On the other hand, it is also demonstrated that using the rectangular data packing algorithm, the number of required bursts per frame can be reduced up to a few tenths without compromising the performance.

Urban underground medium voltage channel measurements and characterization

Power line communications (PLC) technologies rely on the power grid for data transmission. Since the communications channel is already deployed, this communication alternative is specially interesting for the power grid owner, i.e., the electrical utility (EU). Focusing on the MV distribution network, located after the last step-down electrical substation, with typical levels from 6 to 25 kV, feeds directly large commercial or industrial consumers and domestic and small commercial consumers through several transformer stations. The growing interest on MV-PLC technology, the natural aggregation point for data coming and going into the LV network, faces the same issue that the LV- PLC technology did (and does): standardization. In this way, a properly implemented channel model will allow the design of suitable modulation and access methods This paper presents a complete set of measurements done in a MV urban underground ring and proposes a deterministic model for the MV-PLC transfer function.

High voltage channel measurements and field test of a low power OFDM system

High voltage (HV) power lines have been used as a communications medium since the 1920s. Those point to point links were typically based on single-sideband amplitude modulation. Nowadays, the state of the art in HV power line carrier (PLC) communications comprises the combination of analog systems, mainly for teleprotection tasks, and digital systems, used for voice and data transmission. Beside traditional core services (monitoring, operation management, and limitation and removal of failures), electrical utilities would like to satisfy the increasing need of new internal applications. In that way, quadrature amplitude modulation and, most recently, multicarrier modulation (MCM) based modems are beginning to play an important role in HV PLC systems. Although the typical 4 kHz bandwidth has been recently increased up to 32 kHz, this paper proposes a low-power 256 kHz bandwidth orthogonal frequency division multiplexing (OFDM) based physical layer. Based on channel measurements, the OFDM symbol has been designed and tested in order to increase the user bit rate while keeping both the power spectral density and bit error rate low.

A Low Complexity Multicarrier Proposal for Medium Rate Demanding Automatic Meter Reading Systems

In automatic meter reading (AMR) technology, electrical utilities (EUs) have been exploiting their own infrastructure to bill their customers in an efficient and economical way using power line communications (PLC) technologies. Since the amount of data that has to be send is quite low related to the available time to perform this task, AMR applications have been demanding low bit rates. At this moment, EUs are exploring and demanding other services as load and alarm management, remote monitoring and disconnections, etc. In this context, the low voltage PLC modems should provide more throughput while keeping the cost of the hardware low. In this paper, a low complexity multicarrier modulation is proposed in order to exploit the CENELEC A band.

Multicarrier Symbol Design for HF Transmissions from the Antarctica Based on Real Channel Measurements

Last fifteen years improvements in HF digital systems have made ionospheric communications a true alternative to low bit rate, long distance links, especially in the polar caps where alignment with geostationary satellites is not always possible. Our previous research efforts were focused on using pseudo-noise (PN) sequences and orthogonal frequency division multiplexing (OFDM) pilot symbols to evaluate the 7900 miles link from the Spanish Antarctic Base Juan Carlos I to Spain, crossing the equatorial belt. In this paper we face the problem of designing the OFDM physical layer. Two multicarrier transmission schemes are proposed and compared based on channel measured transfer functions and noise plus interference records. Special attention is paid to pilot pattern design in order to maximize the system performance while assuring high power and bandwidth efficiency. The quality and throughput in real transmissions from the Antarctica, as well as the evolution of BER in front of interferences, are studied