Since the invention of the television (TV) in the early 20th century, its market has been constantly growing. The TV industry generated over 407 billion euros of revenue in 2014 and is projected to generate 474.6 billion euros in 2018 [1]. Today, there are more than 1,554 million TV households out of which 1,055 million use digital TV (including Terrestrial TV, Cable TV, satellite TV and IPTV). For the period between 2010 and 2014, the penetration rate of Digital TV increased from 40.5 percent to 67.2 percent [2].This thesis aims at optimizing the energy efficiency of digital broadcasting systems in general and of the second generation of the Digital Video Broadcasting Terrestrial (DVB-T2) standard in particular. The first generation DVB standard was released by the European DVB consortium in the early 90s, and DVB-T2 followed in 2008. DVB-T and DVB-T2 have been trialed, adopted or deployed in more than 150 countries worldwide, mainly in Europe, Asia (except China, Japan, Philippines and Sri Lanka) and Australia.DVB-T2, similar to many modern telecommunication systems (such as ADSL, Wi-MAX, Wi-Fi, DVB), adopted the Orthogonal Frequency Division Multiplexing (OFDM) technique for its robustness, high transmission rates, mobility and bandwidth efficiency. However, OFDM signals are characterized by high power fluctuations, which cause distortions at the output of nonlinear components of the transmission chain. The High Power Amplifier (HPA) is the main source of nonlinearities in a typical transmission system and has been shown to consume 55-60 percent of the total macro base station power in 4G Long Term Evolution (LTE) cellular networks according to the Energy Aware Radio and NeTwork Technologies (EARTH) project. The percentage of HPA power consumption is even higher in digital terrestrial TV networks where transmission power can reach 100 dBm (compared to 43 dBm for a 4G LTE macro base station).The power fluctuations of OFDM signals prevent the radio frequency designer to feed the signal at the optimal point of the HPA specifications. Moreover, these fluctuations lead to in-band and Out-Of-Band (OOB) distortions generating degraded Bit Error Rate (BER) performance and high adjacent channel interference respectively. This highlights the vast potential for energy savings by reducing the amount of signal fluctuations at the input of the HPA. The Peak to Average Power Ratio (PAPR) metric has been widely used to quantify power fluctuations. Many PAPR reduction techniques have been proposed in the literature. The DVB-T2 standard adopted two PAPR reduction techniques: the Active Constellation Extension (ACE) and the Tone Reservation (TR) technique. The ACE technique modifies the constellation points of the signal. The new constellation points are selected in a way to both reduce the PAPR of the transmitted signal and preserve the same Bit Error Rate. ACE suffers from multiple disadvantages: (1) it is not compatible with rotated constellations, which provide additional robustness when used; (2) its performance drops with large constellations; and (3) its implementation in the DVB-T2 standard requires two IFFT blocks and one FFT block to be computed sequentially, thus increases the processing delay caused by ACE.The TR technique reserves a set of sub-carriers for PAPR reduction. The TR implementation in DVB-T2 is based on a kernel created by setting all the subcarrier values to one. The time domain representation of the kernel has an impulse-like shape. TR iteratively reduces the PAPR by reducing one peak at a time. In each iteration the highest peak is detected, then a copy of the kernel is scaled, circularly shifted and its phase adjusted in such a way that the kernel’s peak and the signal’s peak coincide with opposite phases. The kernel is then added to the signal in time domain and the process is repeated until either the number of executed iterations exceeds a certain limit or the amplitude of the highest peak becomes lower than a predefined threshold. To the best of our knowledge at the time of writing, the TR algorithm has not been implemented by DVB-T2 modulator manufacturers since it does not offer the right performance complexity tradeoff (i.e. the number of iterations required to achieve reasonable PAPR reduction increases for large IFFT sizes, which translates into a longer processing delay and requires upgrades to the hardware of current market modulators). This thesis studies in detail the TR algorithm proposed in the DVB-T2 standard and proposes multiple novel techniques based on TR that increase the performance of TR and/or reduce its complexity.
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