Channelization for Multi-Standard Software-Defined Radio Base Stations

As the number of radio standards increase and spectrum resources come under more pressure, it becomes ever less efficient to reserve bands of spectrum for exclusive use by a single radio standard. Therefore, this work focuses on channelization structures compatible with spectrum sharing among multiple wireless standards and dynamic spectrum allocation in particular. A channelizer extracts independent communication channels from a wideband signal, and is one of the most computationally expensive components in a communications receiver. This work specifically focuses on non-uniform channelizers suitable for multi-standard Software-Defined Radio (SDR) base stations in general and public mobile radio base stations in particular. A comprehensive evaluation of non-uniform channelizers (existing and developed during the course of this work) shows that parallel and recombined variants of the Generalised Discrete Fourier Transform Modulated Filter Bank (GDFT-FB) represent the best trade-off between computational load and flexibility for dynamic spectrum allocation. Nevertheless, for base station applications (with many channels) very high filter orders may be required, making the channelizers difficult to physically implement. To mitigate this problem, multi-stage filtering techniques are applied to the GDFT-FB. It is shown that these multi-stage designs can significantly reduce the filter orders and number of operations required by the GDFT-FB. An alternative approach, applying frequency response masking techniques to the GDFT-FB prototype filter design, leads to even bigger reductions in the number of coefficients, but computational load is only reduced for oversampled configurations and then not as much as for the multi-stage designs. Both techniques render the implementation of GDFT-FB based non-uniform channelizers more practical. Finally, channelization solutions for some real-world spectrum sharing use cases are developed before some final physical implementation issues are considered

Arquiteturas paralelas avançadas para transmissores 5G totalmente digitais

The fifth generation of mobile communications (5G) is being prepared and should be rolled out in the early coming years. Massive number of Radio-Frequency (RF) front-ends, peak data rates of 10 Gbps (everywhere and everytime), latencies lower than 10 msec and huge device densities are some of the expected disruptive capabilities. At the same time, previous generations can not be jeopardized, fostering the design of novel flexible and highly integrated radio transceivers able to support the simultaneous transmission of multi-band and multi-standard signals. The concept of all-digital transmission is being pointed out as a promising architecture to cope with such challenging requirements, due to its fully digital radio datapath. This thesis is focused on the proposal and validation of fully integrated and advanced digital transmitter architectures that excel the state-of-the-art in different figures of merit, such as transmission bandwidth, spectral purity, carrier agility, flexibility, and multi-band capability. The first part of this thesis introduces the concept of all-digital RF transmission. In particular, the foundations inherent to this thematic line are given, together with the recent advances reported in the state-of-the-art architectures.The core of this thesis, containing the main developments achieved during the Ph.D. work, is then presented and discussed. The first key contribution to the state-of-the-art is the use of cascaded Delta-Sigma (∆Σ) architectures to relax the analog filtering requirements of the conventional All-Digital Transmitters while maintaining the constant envelope waveform. Then, it is presented the first reported architecture where Antenna Arrays are directly driven by single-chip and single-bit All-Digital Transmitters, with promising results in terms of simplification of the RF front-ends and overall flexibility. Subsequently, the thesis proposes the first reported RF-stage All-Digital Transmitter that can be embedded within a single Field-Programmable Gate Array (FPGA) device. Thereupon, novel techniques to enable the design of wideband All-Digital Transmitters are reported. Finally, the design of concurrent multi-band transmitters is introduced. In particular, the design of agile and flexible dual and triple bands All-DigitalTransmitter (ADT) is demonstrated, which is a very important topic for scenarios that demand carrier aggregation. This Ph.D. contributes withseveral advances to the state-of-the-art of RF all-digital transmitters.A quinta geração de comunicações móveis (5G) está a ser preparada e deve ser comercializada nos próximos anos. Algumas das caracterı́sticas inovadoras esperadas passam pelo uso de um número massivo de font-ends de Rádio-Frequência (RF), taxas de pico de transmissão de dados de 10 Gbps (em todos os lugares e em todas as ocasiões), latências inferiores a 10 mseg e elevadas densidades de dispositivos. Ao mesmo tempo, as gerações anteriores não podem ser ignoradas, fomentando o design de novos transceptores de rádio flexı́veis e altamente integrados, capazes de suportar a transmissão simultânea de sinais multi-banda e multi-standard. O conceito de transmissão totalmente digital é considerado como um tipo de arquitetura promissora para lidar com esses requisitos desafiantes, devido ao seu datapath de rádio totalmente digital. Esta tese é focada na proposta e validação de arquiteturas de transmissores digitais totalmente integradas e avançadas que ultrapassam o estado da arte em diferentes figuras de mérito, como largura de banda de transmissão, pureza espectral, agilidade de portadora, flexibilidade e capacidade multibanda. A primeira parte desta tese introduz o conceito de transmissores de RF totalmente digitais. Em particular, os fundamentos inerentes a esta linha temática são apresentados, juntamente com os avanços mais recentes do estado-da-arte. O núcleo desta tese, contendo os principais desenvolvimentos alcançados durante o trabalho de doutoramento, é então apresentado e discutido. A primeira contribuição fundamental para o estado da arte é o uso de arquiteturas em cascata com moduladores ∆Σ para relaxar os requisitos de filtragem analógica dos transmissores RF totalmente digitais convencionais, mantendo a forma de onda envolvente constante. Em seguida, é apresentada a primeira arquitetura em que agregados de antenas são excitados diretamente por transmissores digitais de um único bit inseridos num único chip, com resultados promissores em termos de simplificação dos front-ends de RF e flexibilidade em geral. Posteriormente, é proposto o primeiro transmissor totalmente digital RF-stage relatado que pode ser incorporado dentro de um único Agregado de Células Lógicas Programáveis. Novas técnicas para permitir o desenho de transmissores RF totalmente digitais de banda larga são também apresentadas. Finalmente, o desenho de transmissores simultâneos de múltiplas bandas é exposto. Em particular, é demonstrado o desenho de transmissores de duas e três bandas ágeis e flexı́veis, que é um tópico essencial para cenários que exigem agregação de múltiplas bandas.Apoio financeiro da Fundação para a Ciência e Tecnologia (FCT) no âmbito de uma bolsa de doutoramento, ref. PD/BD/105857/2014.Programa Doutoral em Telecomunicaçõe

Paraunitary oversampled filter bank design for channel coding

Oversampled filter banks (OSFBs) have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder's synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided

Polyphase filter with parametric tuning

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

Exploração de transmissores integralmente digitais em cenários C-RAN

In order to accommodate the ever-growing demand for higher transmission rates, the next generation of mobile telecommunications (5G) will need larger bandwidths, as well as, new frequencies with available spectrum capable of accommodate such bandwidths. The rise in frequency is being pointed out as a solution for this problem, however, the low coverage areas presented by these frequency bands (mmWave) will require a new way of implementing base stations. Those, in their turn, will exist in higher numbers and closer together. It is where that the new radio access network architecture, C-RAN, may allow for the ful lment of these requirements, besides also allowing for the reduction in cost of each base station as well as providing an increase in its energy e ciency. This dissertation aims to create a point-to-point optical link based on All- Digital Transmitters (ADT) capable of being used for data transmission in the fronthaul. Taking advantage of recent developments in ADT, it is now possible to create one with large bandwidths. Besides, the eld programmable gate arrays (FPGAs) have been providing each time higher processing capacity using each time less energy, making the nal product cheaper and more e cient. Recurring to delta-sigma modulation ( M), a reduction in the complexity of the remote radio head (RRH) can be achieved. In this work the optical link that will be used to transport the data through the fronthaul will be based on an SFP. However, other techniques of radio over bre (RoF) can be used to enable, for example, optical upconversion. From the conclusion of this work, a point-to-point optical link based on an ADT was achieved with an Error Vector Magnitude (EVM) always lower than 5%. Also, from this work, two optical upconversions were developed with an output frequency range from 27 GHz up to 63 GHz.De modo a acompanhar a sempre crescente exigência de maiores taxas de transmissão, a próxima geração de telecomunicações móveis (5G) irá necessitar de maiores larguras de banda, bem como novas frequências de transmissão com espectro livre capaz de acomodar tais larguras de banda. A subida em frequência é apontada como uma solução para este problema, contudo as baixas áreas de cobertura apresentadas por estas bandas de frequência (mmWave) irão necessitar de uma nova forma de implementar estações base. Estas, por sua vez, terão de existir em maior número e mais próximas. É aqui que a nova arquitetura de redes de acesso radio, C-RAN, pode permitir cumprir com estes requisitos, além de poder baixar o custo de cada estação base e aumentar a sua eficiência energética. Esta dissertação tem como objetivo a criação de uma ligação ponto a ponto baseada em transmissores integralmente digitais (ADTs) capaz de ser usada para a transmissão de dados no fronthaul. Aproveitando os desenvolvimentos recentes nos ADT, a criação de um transmissor integralmente digital com largura de banda elevada é agora possível. Além disto, os agregados de células lógicas reprogramáveis (FPGAs) têm vindo a fornecer cada vez uma maior capacidade de processamento, usando menos energia, tornando o produto final, mais barato e mais eficiente. O recurso à modelação deltasigma ( M) no ADT poderá reduzir consideravelmente a complexidade da cabeça remota de rádio (RRH). Neste trabalho a ligaçãao ótica que irá ser usada para enviar os dados no fronthaul será baseada num SFP, mas outras técnicas de rádio sobre fibra (RoF) poderão ser também usadas de forma a possibilitar, por exemplo, upconversion ótico. Da conclusão deste trabalho resulta uma ligação ponto a ponto baseada num ADT com um Error Vector Magnitude (EVM) sempre abaixo dos 5%, bem como duas arquiteturas de upconversion ótico com uma gama possível para o sinal de saída que pode variar entre os 27 GHz e os 63 GHz. uma maior capacidade de processamento, usando menos energia, tornando o produto nal, mais barato e mais e ciente. O recurso a modelação deltasigma ( M) no ADT poder a reduzir consideravelmente a complexidade da cabeça remota de radio (RRH). Neste trabalho a ligação otica que ir a ser usada para enviar os dados no fronthaul ser a baseada num SFP, mas outras t ecnicas de r adio sobre bra (RoF) poderão ser também usadas de forma a possibilitar, por exemplo, upconversion otico. Da conclusão deste trabalho resulta uma ligação ponto a ponto baseada num ADT com um Error Vector Magnitude (EVM) sempre abaixo dos 5%, bem como duas arquiteturas de upconversion otico com uma gama possível para o sinal de saída que pode variar entre os 27 GHz e os 63 GHz.POCI-01-0247-FEDER- 024539; POCI-01-0145- FEDER-016432Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Efficiency in audio processing : filter banks and transcoding

Audio transcoding is the conversion of digital audio from one compressed form A to another compressed form B, where A and B have different compression properties, such as a different bit-rate, sampling frequency or compression method. This is typically achieved by decoding A to an intermediate uncompressed form, and then encoding it to B. A significant portion of the involved computational effort pertains to operating the synthesis filter bank, which is an important processing block in the decoding stage, and the analysis filter bank, which is an important processing block in the encoding stage. This thesis presents methods for efficient implementations of filter banks and audio transcoders, and is separated into two main parts. In the first part, a new class of Frequency Response Masking (FRM) filter banks is introduced. These filter banks are usually characterized by comprising a tree-structured cascade of subfilters, which have small individual filter lengths. Methods of complexity reduction are proposed for the scenarios when the filter banks are operated in single-rate mode, and when they are operated in multirate mode; and for the scenarios when the input signal is real-valued, and when it is complex-valued. An efficient variable bandwidth FRM filter bank is designed by using signed-powers-of-two reduction of its subfilter coefficients. Our design has a complexity an order lower than that of an octave filter bank with the same specifications. In the second part, the audio transcoding process is analyzed. Audio transcoding is modeled as a cascaded quantization process, and the cascaded quantization of an input signal is analyzed under different conditions, for the MPEG 1 Layer 2 and MP3 compression methods. One condition is the input-to-output delay of the transcoder, which is known to have an impact on the audio quality of the transcoded material. Methods to reduce the error in a cascaded quantization process are also proposed. An ultra-fast MP3 transcoder that requires only integer operations is proposed and implemented in software. Our implementation shows an improvement by a factor of 5 to 16 over other best known transcoders in terms of execution speed