京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第20741号 / 情博第655号 / 新制||情||113(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 原田 博司, 教授 守倉 正博, 教授 大木 英司 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

Previous approach for narrowband interference cancellation based on compressed sensing (CS) in wideband receivers uses orthogonal projections to project away from the interference. This is not effective in the presence of nonlinear LNA (low noise amplifier) and finite bit ADCs (analog-to-digital converters) due to the fact that the nonidealities present will result in irresolvable intermodulation components and corrupt the signal reconstruction. Cancelling out the interferer before reaching the LNA thus becomes very important. A CS measurement matrix with randomly placed zeros in the frequency domain helps in this regard by removing the effect of interference when the signal measurements are performed before the LNA. Using this idea, under much idealized hardware assumptions impressive performance is obtained. The use of binary sequences which makes the hardware implementation simplistic is investigated in this thesis. Searching sequences with many spectral nulls turns out to be nontrivial. A theoretical approach for estimating probability of nulls is provided to reduce significant computational effort in the search and is shown to be close to actual search iterations. The use of real binary sequences (generated using ideal switches) obtained through the search does not do better compared to the orthogonal projection method in the presence of nonlinear LNA.

Interference limits the throughput of modern wireless communication networks, and thus the successful mitigation of interference can have a significant impact on network performance. Successive interference cancellation (SIC) has emerged as a promising physical layer method, where multiple packets received simultaneously need not be treated as a ``collision'' requiring retransmission; rather, under certain conditions, all of the packets can be decoded. Obviously, using SIC can thus serve as an important design element that can provide higher performance for the network. However, it also requires a rethinking of the way that traditional routing and scheduling algorithms, which are designed for a traditional physical layer, are developed. In order to consider routing and scheduling over a physical layer employing SIC, some tools such as the oft-employed conflict graph need to be modified. In particular, a notion of links interfering with other links ``indirectly'' is required, and this issue has been ignored in many past works. Therefore, considering the dependencies and interferences between links, a joint routing and scheduling algorithm that employs an understanding of the SIC that will be employed at the physical layer is presented and shown to surpass previous algorithms. We know that the maximum throughput scheduling problem is NP-hard. On the other hand, even if we can reach maximum throughput scheduling, while being throughput efficient, it can result in highly unfair rates among the users. Hence, proportional fairness is developed in the proposed algorithm.

Climate change pressures fossil-driven vehicles into electrification to sustain a healthy planet and environment for its inhabitants. Air traffic contributes to the ongoing climate crisis, and electric aircraft is taking its toll on the avionics market. The electrification of aircraft is complex and requires specialists and researchers to engage in the subject to haste the process of electric aircraft becoming commercial.  The electrification of aircraft comes with challenges in electromagnetic compatibility (EMC). Part of the aim of this study was to get a broad view of what EMC problems electric aircraft are facing. The leading purpose was to understand electric drive with brushless DC (BLDC) motors and to design and construct an active cancellation filter (ACF) for reducing harmonic noise in electric propulsion systems. A literature study including recent research on EMC issues onboard, outside of, and within the system of electric aircraft deepened the view of the specifications and limits in the electronic design of the airplane. The literature study also covered electric propulsion using BLDC motors and ACF topologies for suppressing harmonics originating from the power inverter in the electric propulsion system.  Measurements on a Cypress motor kit with a BLDC motor showed ringings on the motor phase voltages. The parasitic drain-source capacitances in the MOSFETs of the motor inverter caused the ringings, and damping resistors managed to overcome the ringings in simulations and when measured. However, adding damping resistors line-to-line on the motor phase was determined to be ineffective, but the knowledge of the ringings and how to manage them will become relevant for future work. This study proposed an ACF and a hybrid filter for attenuating harmonics caused by a square wave. The proposed hybrid filter was the ACF filter with an LC filter added to it. Simulations showed that the ACF suppresses harmonics up to 2 MHz, and the hybrid filter had no impact. The measured results showed that the ACF and hybrid filter suppress harmonics up to 10 MHz, and beyond 10 MHz, the filters stop the attenuation of harmonics. The purpose of the hybrid filter was to eliminate harmonics in the higher frequency band, where the performance of the ACF started to lack. However, the hybrid filter showed no influence on the ACF performance, which might have been due to software issues with the Fourier transform.  Although the filters did attenuate harmonics from the voltage pulse source, it could not be stated whether the ACF and hybrid filter topology will perform the same when applied to the drive system of an electric aircraft. Future work will determine how the filters perform on the Cypress motor kit, and eventually, with electric aircraft.

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Upphävande av ett naturreservat innebär inte alltid att reservatet upphävs helt, utan det kan även innebära förändringar av reservatets syfte eller ändringar i naturreservatsföreskrifterna. Upphävande av naturreservat kan vara nödvändigt av olika skäl och får ske endast i undantagsfall och efter noggrann bedömning där två olika faktorer vägs samman. Dels förekomsten av synnerliga skäl för upphävande samt möjligheten att kompensera för förlust av naturvärden. Denna studie undersöker förutsättningarna för upphävande av naturreservat generellt och förutsättningarna för upphävande av naturreservatet Pålsjö skog i Helsingborg. Genom en analys av lagstiftning, förarbeten och domar relaterade till upphävandet av naturreservat får man en djupare förståelse för den juridiska ramen och tidigare praxis. Aktiv deltagande och observationer av Helsingborgsteamet och Stadsbyggnadsnämnden i Helsingborg ger insikt i deras perspektiv, arbetsprocess och utmaningar. Slutsatsen från studien är att definitionen och tillämpningen av "synnerliga skäl" och "kompensation" inom naturvårdsområdet är komplexa och föremål för diskussion och tolkning. "Synnerliga skäl" avser exceptionella omständigheter som motiverar upphävande av naturreservat, medan "kompensation" handlar om att balansera eller motverka förlusten av naturvärden i samband med upphävanden. Det finns utmaningar med att fastställa rättvisa och effektiva kompensationsåtgärder samt bedöma värdet av förlorade naturvärden. Återskapande av den ursprungliga biologiska mångfalden och naturliga processer efter upphävande av naturreservat är svårt. Kompensation kräver noggrann planering och förvaltning för att ha en positiv och hållbar effekt på naturmiljön. Förbättringar kan göras genom att utveckla tydliga riktlinjer och rättsliga principer för kompensationsåtgärder samt involvera experter och berörda parter i beslutsprocessen. Att uppnå balans mellan naturvärden och samhällets utvecklingsbehov är viktigt. Genom fortsatt diskussion och utforskning av dessa begrepp kan vi arbeta mot förbättrad naturvård och bevarande av våra värdefulla naturresurser. / The revocation of a nature reserve does not always mean the complete revocation of the reserve, but it can also involve changes to the purpose of the reserve or amendments to the nature reserve regulations. Revoking a nature reserve may be necessary for various reasons and can only occur in exceptional cases and after careful consideration, weighing two different factors. These factors include the existence of exceptional reasons for revocation and the possibility of compensating for the loss of natural values. This study examines the conditions for revoking nature reserves in general and the conditions for revoking the Pålsjö Skog nature reserve in Helsingborg specifically. Through an analysis of legislation, preparatory works, and court judgments related to the revocation of nature reserves, a deeper understanding of the legal framework and past practices is obtained. Active participation and observations of the Helsingborg team and the Urban Planning Committee provide insights into their perspectives, working processes, and challenges. The conclusion of the study is that the definition and application of "exceptional reasons" and "compensation" within the field of nature conservation are complex and subject to discussion and interpretation. "Exceptional reasons" refer to exceptional circumstances that justify the revocation of a nature reserve, while "compensation" involves balancing or counteracting the loss of natural values associated with revocations. There are challenges in determining fair and effective compensation measures and assessing the value of lost natural values. Restoring the original biodiversity and natural processes after the revocation of a nature reserve is difficult. Compensation requires careful planning and management to have a positive and sustainable impact on the natural environment. Improvements can be made by developing clear guidelines and legal principles for compensation measures and involving experts and stakeholders in the decision-making process. Achieving a balance between natural values and the development needs of society is important. Through continued discussion and exploration of these concepts, we can work towards improved nature conservation and preservation of our valuable natural resources.

No / A proposed method for cancelling or reducing the effect of the transmitted power within the transceiver MIMO unit is investigated and discussed using a feedback signal process between the elements. Several parameters including the level of feedback power mismatch, the transmitted power and the received power are considered in this work to test the performance of the system in term of the bit error rate (BER) versus signal to noise ratio (SNR). A new software programme using MATLAB is implemented to evaluate the proposed method. The results showed that the performances of the system are heavily dependent on the amount of the transmitted power, the received power, and the mismatch in the feedback component.

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