Multi-user interference mitigation under limited feedback requirements for WCDMA systems with base station cooperation

One of the techniques that has been recently identified for dealing with multi-user interference (MUI) in future communications systems is base station (BS) cooperation or joint processing. However, perfect MUI cancellation with this technique demands severe synchronization requirements, perfect and global channel state information (CSI), and an increased backhaul and signaling overhead. In this paper, we consider a more realistic layout with the aim of mitigating the MUI, where only local CSI is available at the BSs. Due to synchronization inaccuracies and errors in the channel estimation, the system becomes partially asynchronous. In the downlink of wideband code division multiple access based systems, this asynchronism stands for the loss of the orthogonality of the spreading codes allocated to users and thus, for an increase in the MUI level of the system. In this contribution, we propose a framework for mitigating the MUI which builds in three main steps: definition of a cooperation area based on the channel characteristics, statistical modeling of the average MUI power experienced by each user and a specific spreading code allocation scheme for users served with joint processing. This code allocation assigns spreading codes to users in such a way that minimum average cross-correlation between active users can be achieved. Interestingly, these steps can be performed with a limited amount of extra feedback from the user's side

Power allocation strategies for distributed precoded multicell based systems

Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improve system fairness, and increase capacity. In this article, we propose power allocation techniques for the downlink of distributed, precoded, multicell cellular-based systems. The precoder is designed in two phases: first the intercell interference is removed by applying a set of distributed precoding vectors; then the system is further optimized through power allocation. Three centralized power allocation algorithms with per-BS power constraint and diferente complexity trade-offs are proposed: one optimal in terms of minimization of the instantaneous average bit error rate (BER), and two suboptimal. In this latter approach, the powers are computed in two phases. First, the powers are derived under total power constraint (TPC) and two criterions are considered, namely, minimization of the instantaneous average BER and minimization of the sum of inverse of signal-to-noise ratio. Then, the final powers are computed to satisfy the individual per-BS power constraint. The performance of the proposed schemes is evaluated, considering typical pedestrian scenarios based on LTE specifications. The numerical results show that the proposed suboptimal schemes achieve a performance very close to the optimal but with lower computational complexity. Moreover, the performance of the proposed per-BS precoding schemes is close to the one obtained considering TPC over a supercell.Portuguese CADWIN - PTDC/ EEA TEL/099241/200

MID TERM RESULTS AFTER OPEN HEART SURGERY IN HEMODIALYSIS PATIENTS AWAITING KIDNEY TRANSPLANT: DOES CARDIOVASCULAR SURGICAL INTERVENTION PRIOR TO TRANSPLANTATION PROLONG SURVIVAL?

PubMed ID: 26719549The aim of this study was to compare the mid and long term postoperative outcomes between the hemodialysis-dependent patients awaiting kidney transplantat who underwent open heart surgery in our department during the last five years, and those who did not receive a renal transplant, to determine the predictors of mortality, and assess the possible contribution of post heart surgery kidney transplantation to survival. The patients were separated into two groups: those who underwent a transplantation after open heart surgery were included in the Tp+ group, and those who did not in the Tp- group Between June 2008 and December 2012, 127 dialysis dependent patients awaiting kidney transplant and who underwent open heart surgery were separated into two groups. Those who underwent transplantation after open heart surgery were determined as Tp+ (n=33), and those who did not as Tp- (n=94). Both groups were compared with respect to preoperative paramaters including age, sex, diabetes mellitus (DM), hypertension (HT), hyperlipidemia (HL), obesity, smoking, chronic obstructive pulmonary disease (COPD), peripheral vascular disease (PVD), left ventricle ejection fraction (EF), Euroscore; operative parameters including cross clamp time, perfusion time, number of grafts, use of internal mammary artery (IMA); postoperative parameters including revision, blood transfusion, ventilation time, use of inotropic agents, length of stay in the intensive care unit and hospital, and follow up findings. Problems encountered during follow up were recorded. Predictors of mortality were determined and the survival was calculated. Among the preoperative parameters, when compared with the Tp- group, the Tp+ group had significantly lower values in mean age, presence of DM, obesity, PVD, and Euroscore levels, and higher EF values. Assessment of postoperative values showed that blood transfusion requirement and length of hospital stay were significantly lower in the Tp+ group compared to the Tp- group, whereas the length of follow up was significantly higher in the Tp+ group. The use of inotropic agents was significantly higher in the Tp- group. A logistic regression analysis was made to determine the factors affecting mortality. Revision (p=0.013), blood transfusion (p=0.017), ventilation time (p=0.019), and length of stay in the intensive care unit (p=0.009) were found as predictors of mortality. Survival rates at years 1, 2 and 3 were 86.1%, 81%, 77.5% in the Tp- group, and 96.0%, 96.3%, 90.4% in the Tp+ group. Median survival rate was 41.35±2.02 in the Tp- group, and 49.64±1.59 in the Tp+ group which was significantly higher compared to the Tp- group (p=0.048). Chronic renal failure is among the perioperative risk factors for patients undergoing open heart surgery. Transplantation is still an important health issue due to insufficiency of available transplant organs. Patients with chronic renal failure are well known to have higher risks for coronary artery disease. A radical solution of the cardiovascular system problems prior to kidney transplantation seems to have a significant contribution to the post transplant survival

A WiMAX-based implementation of network MIMO for indoor wireless systems

It is well known that multiple-input multiple-output (MIMO) techniques can bring numerous benefits, such as higher spectral efficiency, to point-to-point wireless links. More recently, there has been interest in extending MIMO concepts tomultiuser wireless systems. Our focus in this paper is on network MIMO, a family of techniques whereby each end user in a wireless access network is served through several access points within its range of influence. By tightly coordinating the transmission and reception of signals at multiple access points, network MIMO can transcend the limits on spectral efficiency imposed by cochannel interference. Taking prior information-theoretic analyses of networkMIMO to the next level, we quantify the spectral efficiency gains obtainable under realistic propagation and operational conditions in a typical indoor deployment. Our study relies on detailed simulations and, for specificity, is conducted largely within the physical-layer framework of the IEEE 802.16e Mobile WiMAX system. Furthermore,/nto facilitate the coordination between access points, we assume that a high-capacity local area network, such as Gigabit Ethernet,/nconnects all the access points. Our results confirm that network MIMO stands to provide a multiple-fold increase in spectral/nefficiency under these conditions

"Only volunteers"? Personal motivations and political ambiguities within Refugees Welcome to Malmö civil initiative

Between 7 September and 12 November 2015, approximately 800 volunteers met up to 1000 refugees a day under the banner of Refugees Welcome to Malmö, at Malmö Central train station as the first point of the asylum seekers’ arrival in Sweden. Based on in-depth interviews, this chapter analyzes the volunteers’ motivations, experiences and ambiguities, against the background of a specific historical, organizational and local context in which this grassroots initiative emerged. Special attention is paid to the volunteers’ perceptions of their work and to collaborations and conflicts with other actors in the field. The analysis of the volunteers’ positions toward the politicization of a civil initiative points to the need for city context-sensitive research on the changing constellations of actors who provide support to refugees