En esta tesis doctoral se plantea la mejora de la capacidad de transmisión en las redes HDR-WPAN ( redes WPAN con elevada tasa binaria) empleando el estándar MB-OFDM (OFDM sobre múltiples bandas) en canales UWB con modulación adaptativa realizando una adaptación discreta de la tasa de bits transmitidos por subportadora. La tesis comienza con un análisis en el dominio del tiempo y de la frecuencia de los dos modelos de canal UWB propuestos en IEEE: IEEE 802.15.3a y 802.15.4a. El objetivo consiste en determinar la distribución estadística que mejor se aproxima a la amplitud de cada una de las subportadoras, para posteriormente definir la métrica a emplear en la evaluación del estado y dinámica del canal UWB. En la modulación adaptativa se requiere que el transmisor se adapte a la variabilidad del canal. El análisis se puede realizar de dos formas: - Asumiendo adaptación perfecta (estimación ideal), lo que implica que el transmisor siempre conoce la dinámica y estructura del canal. - Considerando un error (estimación imperfecta del canal) en la adaptación debido a la incertidumbre en el conocimiento del canal. El método de estimación del canal UWB empleado en la tesis se fundamenta en el conocimiento del coeficiente de correlación en potencia entre las subportadoras de datos y la subportadora piloto. A partir de la información sobre el estado del canal, u una vez definida la métrica que permite su evaluación, se calculan las prestaciones de la modulación adaptativa. Esta evaluación se realiza a través de expresiones cerradas para la capacidad media, la probabilidad de error de bit media y la probabilidad de bloqueo, así como la obtención de la distribución y estadísticos del error de estimación en el caso de estimación imperfecta del canal. Por otro lado, a partir de la distribución estadística de la amplitud de cada una de las subportadoras en frecuencia del canal UWB, se obtienen resultados respecto a la variación de potencia del canal en función del ancho de banda . / Llano Ramírez, G. (2010). Modelado en frecuencia del canal UWB y su aplicación en el análisis de técnicas de modulación adaptativa en sistemas MB-OFDM UWB para redes WPAN [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8429

A high-throughput low-power Soft-Output Viterbi decoder designed for the convolutional codes used in the ECMA-368 UWB standard is presented in this thesis. The ultra wide band (UWB) wireless communication technology is supposed to be used in physical layer of the wireless personal area network (WPAN) and next generation Blue Tooth. MB-OFDM is a very popular scheme to implement the UWB system and is adopted as the ECMA-368 standard. To make the high speed data transferred over the channel reappear reliably at the receiver, the error correcting codes (ECC) are wildly utilized in modern communication systems. The ECMA-368 standard uses concatenated convolutional codes and Reed-Solomon (RS) codes to encode the PLCP header and only convolutional codes to encode the PPDU Payload. The Viterbi algorithm (VA) is a popular method of decoding convolutional codes for its fairly low hardware implementation complexity and relatively good performance. Soft-Output Viterbi Algorithm (SOVA) proposed by J. Hagenauer in 1989 is a modified Viterbi Algorithm. A SOVA decoder can not only take in soft quantized samples but also provide soft outputs by estimating the reliability of the individual symbol decisions. These reliabilities can be provided to the subsequent decoder to improve the decoding performance of the concatenated decoder. The SOVA decoder is designed to decode the convolutional codes defined in the ECMA-368 standard. Its code rate and constraint length is R=1/3 and K=7 respectively. Additional code rates derived from the "mother" rate R=1/3 codes by employing "puncturing", including 1/2, 3/4, 5/8, can also be decoded. To speed up the add-compare-select unit (ACSU), which is always the speed bottleneck of the decoder, the modified CSA structure proposed by E.Yeo is adopted to replace the conventional ACS structure. Besides, the seven-level quantization instead of the traditional eight-level quantization is proposed to be used is in this decoder to speed up the ACSU in further and reduce its hardware implementation overhead. In the SOVA decoder, the delay line storing the path metric difference of every state contains the major portion of the overall required memory. A novel hybrid survivor path management architecture using the modified trace-forward method is proposed. It can reduce the overall required memory and achieve high throughput without consuming much power. In this thesis, we also give the way to optimize the other modules of the SOVA decoder. For example, the first K-1 necessary stages in the Path Comparison Unit (PCU) and Reliability Measurement Unit (RMU) are IX removed without affecting the decoding results. The attractiveness of SOVA decoder enables us to find a way to deliver its soft output to the RS decoder. We have to convert bit reliability into symbol reliability because the soft output of SOVA decoder is the bit-oriented while the reliability per byte is required by the RS decoder. But no optimum transformation strategy exists because the SOVA output is correlated. This thesis compare two kinds of the sub-optimum transformation strategy and proposes an easy to implement scheme to concatenate the SOVA decoder and RS decoder under various kinds of convolutional code rates. Simulation results show that, using this scheme, the concatenated SOVA-RS decoder can achieve about 0.35dB decoding performance gain compared to the conventional Viterbi-RS decoder.

The advent of software radio technology has enabled radio developers to design and implement radios with great ease and flexibility. Software radios are effective in experimentation and development of radio designs. However, they have limitations when it comes to high-speed, high-throughput designs. This limitation can be overcome by introducing a hardware element to the software radio platform. Enhancing GNU Radio for Hardware Accelerated Radio Design project implements such a scheme by augmenting an FPGA co-processor to a conventional GNU Radio flow. In this thesis, this novel platform is evaluated in terms of performance of a radio design, as well as hardware and software system requirements. A simple and efficient Zigbee receiver design is presented. Implementation of this receiver is used as a proof-of-concept for the effectiveness and design methodology of the modified GNU Radio. This work also proposes a scheme to extend this idea for design of ultra-wideband radio systems based on multiband-OFDM. / Master of Science