Implications of Implementing HDTV Over Digital Subscriber Line Networks

This thesis addresses the different challenges a telecommunications company would face when trying to implement an HDTV video service over a Digital Subscriber Line (DSL) connection. Each challenge is discussed in detail and a technology, protocol, or method is suggested to overcome that particular challenge. One of the biggest challenges is creating a network architecture that can provide enough bandwidth to support video over a network that was originally designed for voice traffic. The majority of the network connections to a customer premises in a telephony network consists of a copper pair. This type of connection is not optimal for high bandwidth services. This limitation can be overcome using Gigabit Ethernet (GE) over fiber in the core part of the network and VDSL2 in the access part of the network. For the purposes of this document, the core portion of the network is considered to be an area equal to several counties or approximately 50 miles in radius. The core network starts at the primary central office (CO) and spreads out to central offices in suburbs and small towns. The primary central office is a central point in the telecom operator\u27s network. Large trunks are propagated from the primary central office to smaller central offices making up the core network. The access portion of the network is considered to be an area within a suburb or small town from the central office to a subscriber\u27s home. Appendix A, located on page 60, contains a network diagram illustrating the scope of each of the different portions of the network. Considerations must also be given for the internal network to the residence such as category 5 (Cat5) cable or higher grade and network equipment that can provide up to 30 Megabits per second (Mbps) connections or throughput. The equipment in the telecommunications network also plays a part in meeting the challenge of 30 Mbps bandwidth. GE switches should be used with single mode fiber optic cable in the core part of the network. Digital Subscriber Line Access Multiplexers (DSLAM) with the capability to filter Internet Group Management Protocol (IGMP) messages should be used in the access part of the network to facilitate bandwidth utilization. Placement of this equipment and how the data is aggregated is another issue to consider when implementing HDTV service. Another major challenge facing the implementation of HDTV over DSL networks is controlling quality of service (QoS) throughout the network. Class of Service (CoS) and Differentiated Services (DiffServ) is a method of QoS that would enable video packets to have a higher priority and less delay than other data packets. The consumer could have data, video, and voice traffic all over the same DSL connection. Data, video and voice packets would need to have a different priority in order to maintain appropriate QoS levels for each service. The use of advanced technology in video encoding will be essential to the success of the video service. MPEG-2, MPEG-4, and Windows Media 9 are just a few of the video encoding technologies that could be used to reduce the necessary bandwidth for HDTV. The advancement of this technology is essential to allow telecommunications providers to offer HDTV. Another challenge for the telecom operator concerns the security of the network and service after implementation. Theft of service will be another area that the telecomm operator will be forced to resolve. The cable operators currently face this issue and lose millions of dollars in revenue. Authentication, IP filtering and MAC address blocking are a few possible solutions to this problem

Analysis of the impact of impulse noise in digital subscriber line systems

In recent years, Digital subscriber line (DSL) technology has been gaining popularity as a high speed network access technology, capable of the delivery of multimedia services. A major impairment for DSL is impulse noise in the telephone line. However, evaluating the data errors caused by this noise is not trivial due to its complex statistical nature, which until recently had not been well understood, and the complicated error mitigation and framing techniques used in DSL systems. This thesis presents a novel analysis of the impact of impulse noise and the DSL framing parameters on transmission errors, building on a recently proposed impulse noise model. It focuses on errors at higher protocol layers, such as asynchronous transfer mode (ATM), in the most widely used DSL version, namely Asymmetric DSL (ADSL). The impulse noise is characterised statistically through its amplitudes, duration, inter-arrival times, and frequency spectrum, using the British Telecom / University of Edinburgh / Deutsche Telekom (BT/UE/DT) model. This model is broadband, considers both the time and the frequency domains, and accounts for the impulse clustering. It is based on recent measurements in two different telephone networks (the UK and Germany) and therefore is the most complete model available to date and suited for DSL analysis. A new statistical analysis of impulse noise spectra from DT measurements shows that impulse spectra can be modelled with three spectral components with similar bandwidth statistical distributions. Also, a novel distribution of the impulse powers is derived from the impulse amplitude statistics. The performance of a generic ADSL modem is investigated in an impulse noise and crosstalk environment for different bit rates and framing parameters. ATM cell and ADSL frame error rates, and subjective MPEG2 video quality are used as performance metrics. A new modification of a bit loading algorithm is developed to enable stable convergence of the algorithm with trellis coding and restricted subtone constellation size. It is shown that while interleaving brings improvement if set at its maximum depth, at intermediate depths it actually worsens the performance of all considered metrics in comparison with no interleaving. No such performance degradation is caused by combining several symbols in a forward error correction (FEC) codeword, but this burst error mitigation technique is only viable at low bit rates. Performance improvement can also be achieved by increasing the strength of FEC, especially if combined with interleaving. In contrast, trellis coding is ineffective against the long impulse noise error bursts. Alien as opposed to kindred crosstalk degrades the error rates and this is an important issue in an unbundled network environment. It is also argued that error free data units is a better performance measure from a user perspective than the commonly used error free seconds. The impact of impulse noise on the errors in DSL systems has also been considered analytically. A new Bernoulli-Weibull impulse noise model at symbol level is proposed and it is shown that other models which assume Gaussian distributed impulse amplitudes or Rayleigh distributed impulse powers give overly optimistic error estimates in DSL systems. A novel bivariate extension of the Weibull impulse amplitudes is introduced to enable the analysis of orthogonal signals. Since an exact closed-form expression for the symbol error probability of multi-carrierQAM assuming Bernoulli-Weibull noise model does not exist, this problem has been solved numerically. Multi-carrier QAM is shown to perform better at high signal-to-noise ratio (SNR), but worse at low SNR than single carrier QAM, in both cases because of the spreading of noise power between subcarriers. Analytical expressions for errors up to frame level in the specific case of ADSL are then derived from the impulse noise model, with good agreement with simulation results. The Bernoulli-Weibull model is applied to study the errors in single-pair highspeed DSL (SHDSL). The performance of ADSL is found to be better when the burst error mitigation techniques are used, but SHDSL has advantages if low bit error rate and low latency are required

Transmisión multiportadora sin prefijo cíclico para comunicaciones radio de alta capacidad

Este trabajo fin de grado está orientado en una de las líneas de investigación seguidas en la actualidad para conseguir aumentar la capacidad de los sistemas de comunicaciones. Se ha centrado el trabajo en el marco de la modulación multiportadora Orthogonal Frequency Division Multiplexing (OFDM) por ser una de las técnicas más utilizadas en la actualidad en sistemas de banda ancha. El objetivo será aumentar la tasa de transmisión de un sistema de comunicaciones suprimiendo o reduciendo el prefijo cíclico, Cyclic Prefix (CP), perteneciente a OFDM. Se analizan y muestran las consecuencias en forma de interferencias que se tienen como resultado de no utilizar un CP mayor que la respuesta al impulso del canal. Las interferencias que se han encontrado son las denominadas como ISI (Inter-Symbol Interference) por no introducir un intervalo de guarda suficiente entre los símbolos OFDM e ICI (Inter-Carrier Interference) por la pérdida de ortogonalidad entre las subportadoras, provocando estas unos pésimos resultados en el sistema. Para poder combatir estos efectos se explicará y se implementará un algoritmo de cancelación de interferencias llamado “Cancelación residual de ISI” (RISIC). Este algoritmo consiste en realizar una combinación de cancelación de cola y una reconstrucción cíclica. Se ha analizado si los resultados obtenidos compensan el aumento de complejidad introducida en el sistema. Además, en este trabajo se investiga cómo esta técnica puede ser implementada en estándares actuales como Wimax (Worldwide Interoperability for Microwave Access) o LTE (Long Term Evolution), y así poder conseguir mayores velocidades de transmisión de datos.This final degree project deals with the research lines followed at present for increasing the capacity of communications systems. We have focused our work in multicarrier modulation Orthogonal Frequency Division Multiplexing (OFDM) for being one of the techniques used today in broadband systems. The goal that we want to achieve will be to increase the transmission rate of a communication system by eliminating or reducing the Cyclic Prefix (CP) pertaining to OFDM. Consequences are analyzed and displayed in the form of interference effects as result as not using a CP higher than the channel impulse response. The interferences that have been found are named ISI (Inter-Symbol Interference). This is because ISI doesn't introduce enough guard interval between OFDM symbols and ICI (Inter-Carrier Interference) for the loss of orthogonality between subcarriers and it provokes dismal system results. To combat these effects will be discussed and implemented an algorithm called interference cancellation "Residual ISI Cancellation" (RISIC). This algorithm is to perform a combination of tail cancellation cyclic reconstruction. We have analyzed if the results outweigh the increased complexity introduced into the system. In addition, this final degree project investigates how this technique can be implemented in existing standards such as WiMAX (Worldwide Interoperability for Microwave Access) or Long Term Evolution (LTE), so you can achieve higher data transmission speeds.Ingeniería de Sistemas de Comunicacione

OFDM con prefisso ciclico parziale

Nelle trasmissioni digitali multiportanti di tipo OFDM, al fine di limitare effetti di interferenza tra blocchi e tra diversi sottocanali, viene inserito un prefisso ciclico in ogni sottoblocco. Tale CP riduce però l'efficienza del sistema. Sono stati proposti alcuni algoritmi di equalizzazione per limitare l'inefficienza dovuta al C

Super-High-Frequency /SHF/ communications system performance on ATS. Volume 1 - System summary

Super high frequency communication systems performance on ATS - Vol.

Orthogonal multicarrier modulation for high-rates mobile and wireless communications

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN037085 / BLDSC - British Library Document Supply CentreGBUnited Kingdo