This thesis looks at the problem of designing a coding strategy for interference channels with rate-limited transmitter cooperation. We first consider a simple communication model in which the classic two-user Gaussian interference channel is augmented by rate-limited conferencing links between the transmitters. The main contribution is a partial zero-forcing precoding strategy based on a shared-private rate splitting scheme at the transmitter, in which each transmitter communicates part of its message to the other transmitter, and subsequently partially pre-subtracts the interfering signal using a zero-forcing precoder. We extend the proposed strategy to a class of multiuser interference channels, and outline a distributed algorithm to compute the precoder coefficients. The partial zero-forcing precoding strategy is shown to be particularly effective in certain high SNR/INR regimes, and simulation results for a multicell system highlight the cooperation gain due to the proposed strategy.

This thesis looks at the problem of designing a coding strategy for interference channels with rate-limited transmitter cooperation. We first consider a simple communication model in which the classic two-user Gaussian interference channel is augmented by rate-limited conferencing links between the transmitters. The main contribution is a partial zero-forcing precoding strategy based on a shared-private rate splitting scheme at the transmitter, in which each transmitter communicates part of its message to the other transmitter, and subsequently partially pre-subtracts the interfering signal using a zero-forcing precoder. We extend the proposed strategy to a class of multiuser interference channels, and outline a distributed algorithm to compute the precoder coefficients. The partial zero-forcing precoding strategy is shown to be particularly effective in certain high SNR/INR regimes, and simulation results for a multicell system highlight the cooperation gain due to the proposed strategy.

This thesis investigated the role of interference in general cognitive functioning. Study 1 explored the relationships among interference control, memory, and fluid intelligence. Studies 2 and 3 explored the possibility that interference is controlled by suppressing the interfering information rather than, for example, facilitating the target information. Study 1 tested the hypothesis that individual differences in the ability to regulate interference are responsible for the correlation between memory tasks and fluid intelligence. Participants completed common measures of working memory, long-term memory, fluid intelligence, and interference regulation. In structural equation models, controlling for interference regulation ability largely accounted for the correlation between the memory tasks and fluid intelligence. These results suggest that efficient interference control is critical to cognitive functioning. Study 2a tested the hypothesis that interference is regulated by suppressing competing responses. In Phase 1 of a three-phase paradigm, participants performed a vowel-counting task that included pairs of orthographically similar words (e.g., allergy/analogy). In Phase 2 participants solved word fragments (e.g., a _ l _ _ gy) that resembled both words in an earlier pair, but could be completed only by one of these words. Phase 3 measured the consequence of having resolved interference in Phase 2 by asking participants to read a list of words, including the rejected competitors, as quickly as possible. Relative to participants in control conditions that did not require interference resolution these interference condition participants were slower to name competitor words. Study 2b showed that while competitors are suppressed during interference resolution, a complementary facilitative process does not directly enhance accessibility of targets. Finally, Study 3 tested the hypothesis that older adults have impaired suppression abilities. Older adults were tested in the same paradigm used in Studies 2a and 2b. In contrast to younger adults, older adults showed no suppression of competitors. This result supports the theory that some age related memory deficits stem from impaired suppression processes.

This thesis investigated the role of interference in general cognitive functioning. Study 1 explored the relationships among interference control, memory, and fluid intelligence. Studies 2 and 3 explored the possibility that interference is controlled by suppressing the interfering information rather than, for example, facilitating the target information. Study 1 tested the hypothesis that individual differences in the ability to regulate interference are responsible for the correlation between memory tasks and fluid intelligence. Participants completed common measures of working memory, long-term memory, fluid intelligence, and interference regulation. In structural equation models, controlling for interference regulation ability largely accounted for the correlation between the memory tasks and fluid intelligence. These results suggest that efficient interference control is critical to cognitive functioning. Study 2a tested the hypothesis that interference is regulated by suppressing competing responses. In Phase 1 of a three-phase paradigm, participants performed a vowel-counting task that included pairs of orthographically similar words (e.g., allergy/analogy). In Phase 2 participants solved word fragments (e.g., a _ l _ _ gy) that resembled both words in an earlier pair, but could be completed only by one of these words. Phase 3 measured the consequence of having resolved interference in Phase 2 by asking participants to read a list of words, including the rejected competitors, as quickly as possible. Relative to participants in control conditions that did not require interference resolution these interference condition participants were slower to name competitor words. Study 2b showed that while competitors are suppressed during interference resolution, a complementary facilitative process does not directly enhance accessibility of targets. Finally, Study 3 tested the hypothesis that older adults have impaired suppression abilities. Older adults were tested in the same paradigm used in Studies 2a and 2b. In contrast to younger adults, older adults showed no suppression of competitors. This result supports the theory that some age related memory deficits stem from impaired suppression processes.

This study investigated the influence of training on interference in younger and older adults using the Eriksen flanker task. Does flanker interference differ with age and, as practice progresses, does the pattern of interference change? Younger and older adults were given five sessions of training on the flanker task over five successive days. On each trial, participants saw a central target letter flanked vertically by two flanker letters; the flankers could be either compatible or incompatible with the target. Participants were to respond to the identity of the central letter, ignoring the flanker letters. Although older adults were slower overall than younger adults in responding, the two groups showed virtually identical overall benefits from practice. Critically, the two age groups showed equivalent and constant interference due to incompatible flankers at all stages of practice. In the flanker paradigm, aging slows response execution without affecting attention within a trial or learning across trials.

I studien undersöktes effekten av bakgrundljud på prestationen i en räkneuppgift. Två experiment genomfördes för att testa effekten av tre bakgrundstal: irrelevanta tal, yrkesbeteckningar och tal uppspelade baklänges. Dessutom ingick en kontrollbetingelse utan bakgrundstal. Hypotesen var att de irrelevanta talen skulle störa prestationen mest. Experiment 1 visade ingen effekt av bakgrundsljuden och stödde alltså inte hypotesen. I experiment 2 användes en svårare räkneuppgift och bakgrundstalen presenterades i en högre takt. Talen störde då prestationen mer än baklängestalen och yrkesbeteckningarna, och prestationen i kontrollbetingelsen var bättre än i någon av ljudbetingelserna. Skillnaden mellan talen och baklängestalen var däremot inte signifikant. Resultatet var i linje med att störningen förklaras av interference by process.

In the direct sequence-code division multiple access (DS-CDMA) system, which uses direct sequence spread spectrum (DSSS) technique to perform multiple-access, the major limitation of the system capacity is the capability of interference rejection. In this system, multiuser receivers usually divided into two groups, the first group is called the ¡§centralized receiver,¡¨ because it must know the information of total users, including the spreading sequence of each user, channel response, etc. Due to the complexity of computation, this kind of receivers is suitable for the base station. The second group is called the ¡§decentralized receiver,¡¨ because it only needs to know the information of desired user, therefore, it is very suitable for mobile station. The decentralized receiver can be further separate into two kinds: data-aided and non-data-aided receivers. Usually, the non-data-aided receiver is also called the blind receiver; our proposed interference cancellator belongs to this blind one. This thesis mainly discusses the performance of our proposed interference cancellator in different conditions. There is a novel interference detector which can efficiently detect strong interferers in our proposed interference cancellator. When strong interferers exist, the received signal will be passed through the interference-blocking transformer, which exploits the subspace approach to block strong interference. After interference cancelled, conventional de-spreading technique is used to obtain the desired data. In this thesis, besides the complete mathematical analysis of our proposed interference cancellator, computer simulations are also used to observe its performance behavior in different conditions. The simulation results exhibit that this interference cancellator has good performance in different conditions, and due to have the property of low complexity, our proposed interference cancellator is very suitable for the mobile station. Finally, we make a conclusion for this blind interference cancellator, and expect to realize a mature multiuser receiver based on this technique in the future.

We present design and fabrication of ring cavity semiconductor lasers and single ring filter with simple fabrication processes. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the lasers. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, and 2x2 Multi-Mode Interference (MMI) with different splitting ratio(50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to control the output of specific wavelength. Therefore we can obtain filter and lasers with the property of wavelength selection. We also design two kinds of special waveguides to achieve low reflectivity. One is a tapered spiral waveguide tail. The other waveguide is expanded in a curve and then cut off at the Brewster¡¦s angle. In loop mirror, two curvature radius(260,160£gm) were introduced to study bending loss and material loss. In single ring filter, we design two kinds of resonator lengths(1479,1385£gm) and the corresponding Free Spectrum Range (FSR) are 63.4, 67.75GHz, respectively. In fabrication, owing to the unstable dry etch condition for InGaAlAs, we adopted multi-step etch technology. In the part of curved waveguide, we also use this method to make deep-etching to increase the difference of refractive index between waveguide and the outside part. Finally, we use the etch solution (HBr:HCl:H2O2:H2O=5:4:1:70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device.

The purpose of this research is to present design and fabrication of resonant loop-mirror Fabry-Perot lasers. Single filter has simple fabrication processes and good potential for intergration. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the laser. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, 2x2 Multi-Mode Interference (MMI) with different splitting ratio (50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to reflect specific wavelength at particular position. Therefore we can obtain semiconductor laser with property of wavelength-selection filter. In this design of the mask, we add a mask of deep-etch around MMI in order to decrease the loss of higher mode inside MMI. In the part of devices design, we apply multi-step technology for wet etch to obtain necessary depth. Finally, we use the etch solution (HBr¡GHCl¡GH2O2¡GH2O¡×5¡G4¡G1¡G70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device. In the part of planarization, we can adhere dummy wafers to surround the main sample and extend the total area. If we can fill the gap flat, the problem of high edge by spinning will be solved. However, we were not able to fill the gap.

This study uses vertical mirror optical waveguide reflector and bending waveguide to fabricate semiconductor ring resonators. By using multimode interference couplers with specific width and length that generate distinctive energy distribution to achieve the power splitting of 85:15. We integrate vertically deep etching turning mirror to reflect optical mode, and reduce the component size to 37.6%. In fabrication process, this study applies multiple wet etching technique to form the waveguide structure. First, we use wet etching technique to etch ridge waveguide and turning mirror, and then perform deep etching in the periphery of bending and turning region to reduce the bending loss. Finally, the etching mask is lifted off, and the wafer is polished and sliced for measurement. After measuring the signal, we can compute waveguide loss by Fabry-perot resonant situation. The waveguide loss is 59.6dB/cm. Power splitting of 90:10 is achieved. The free spectral range (FSR) is 72GHz for the ring resonators.