In this paper we study widely-linear precoding techniques to mitigate in-phase/quadrature-phase (IQ) imbalance (IQI) in the downlink of large-scale multiple-input multiple-output (MIMO) systems. We adopt a real-valued signal model which takes into account the IQI at the transmitter and then develop widely-linear zero-forcing (WL-ZF), widely-linear matched filter (WL-MF), widely-linear minimum mean-squared error (WL-MMSE) and widely-linear block-diagonalization (WL-BD) type precoding algorithms for both single-and multiple-antenna users. We also present a performance analysis of WL-ZF and WL-BD. It is proved that without IQI, WL-ZF has exactly the same multiplexing gain and power offset as ZF, while when IQI exists, WL-ZF achieves the same multiplexing gain as ZF with ideal IQ branches, but with a minor power loss which is related to the system scale and the IQ parameters. We also compare the performance of WL-BD with BD. The analysis shows that with ideal IQ branches, WL-BD has the same data rate as BD, while when IQI exists, WL-BD achieves the same multiplexing gain as BD without IQ imbalance. Numerical results verify the analysis and show that the proposed widely-linear type precoding methods significantly outperform their conventional counterparts with IQI and approach those with ideal IQ branches. Index TermsIQ imbalance, large-scale MIMO, widely-linear signal processing, downlink precoding W. Zhang is with Jiangsu University, China. He was with CETUC, PUC-Rio, Brazil.

This study identifies several novel susceptibility genes for MMD. The association with homocysteine metabolism and the immune system enrichment of susceptibility gene expression suggest that therapeutic interventions targeting these pathways may be effective approaches for MMD treatment.

Background: Moyamoya disease (MMD) develops mostly in Asian countries including Japan, Korea, mainland China and Taiwan. However, there are few detailed demographic and clinical data about Chinese patients with MMD. Currently, the most effective treatment in adult patients with MMD is unknown. There have only been a few small case series reporting on encephaloduroarteriosynangiosis (EDAS) in an adult population. Here we describe the clinical features, surgical treatment and long-term outcome of adults with MMD treated at a single institution in China. Methods: Our cohort included 470 adult patients with MMD. The demographic and clinical characteristics were obtained by retrospective chart review and long-term outcome was evaluated using the stroke status. The modified Rankin Scale (mRS) was used to determine the neurological functional outcome. Univariate and multivariate logistic regression analyses were performed to determine risk factors for postoperative morbidity and functional outcome. The risk of subsequent stroke was determined using the Kaplan-Meier method and Cox regression was used to determine risk factors for postoperative or subsequent strokes. Results: The median age for the onset of symptoms was 36.8 (range, 18–59) years. The ratio of female to male patients was 1:1 (231/239). Familial occurrence of MMD was 2.3%. The most common initial symptom was a cerebral ischemic event. The incidence of postoperative ischemic events or hemorrhage was 5.9% (9.8% of patients). Older age at symptom onset, posterior cerebral artery (PCA) involvement and the presence of transient ischemic attack (TIA) were identified as predictors of adverse postoperative events. The Kaplan-Meier estimate stroke risk was 10.1% in the first 2 years, and the 5-year Kaplan-Meier risk of stroke was 13% after surgery for all patients treated with surgical revascularization. Older age at symptom onset, PCA involvement and the presence of TIA were identified as predictors of postoperative or subsequent strokes. Overall, 73.2% of patients had an independent life with no significant disability, with the strongest predictor being the preoperative mRS score. Conclusion: Clinical characteristics of adult MMD in China are different from those in other Asian countries. EDAS in adult patients with MMD carries a low risk, is effective at preventing future ischemic events and improves quality of life.

Background: There was few detailed demographic and clinical data about Chinese patients with moyamoya disease. Here we describe the clinical features, surgical treatment, and long-term outcome of pediatric patients with moyamoya disease at a single institution in China. Methods: Our cohort included 288 pediatric patients with moyamoya disease. The demographic and clinical characteristics were obtained by retrospective chart review and long-term outcome was evaluated using the stroke status. Univariate and multivariate logistic regression analyses were performed to determine the risk factors for clinical outcome. The risk of subsequent stroke was determined using the Kaplan-Meier method. Results: The median age for the onset of symptoms was 8.0 years. The ratio of female to male patients was 1:1. Familial occurrence of moyamoya disease was 9.4%. The incidence of postoperative complications was 4.2%. Postoperative ischemic events were identified as predictors of unfavorable clinical outcome, while older age of symptom onset was associated with a favorable clinical outcome. The Kaplan-Meier estimate stroke risk was 5% in the first 2 years, and the 5-year-Kaplan-Meier risk of stroke was 9% after surgery for all patients treated with surgical revascularization. Overall, 86% of patients had an independent life with no significant disability. Conclusion: This long-term survey demonstrated that most surgically treated pediatric patients with MMD maintain good outcomes. Our results indicate that an early diagnosis and active intervention before the establishment of irreversible hemodynamic change are essential to achieve a favorable clinical outcome.

Background and Purpose-Here we describe the clinical features and outcomes of patients with moyamoya disease who were surgically treated at a single institution in China. Methods-Our cohort included 802 patients with moyamoya disease. Demographic and clinical characteristics were obtained by retrospective chart review; follow-up information and outcome were obtained through clinical visits, telephone, or letter interview. We used the Kaplan-Meier methods to estimate stroke risk by treatment status. Results-The median age for the onset of symptoms was 28 (range, 0.5-77) years. Two definite peaks in age distribution were found. The ratio of women to men was 1:1 (398/404). Familial occurrence of moyamoya disease was 5.2%. The initial symptom was ischemia, hemorrhage, or others in 564, 113, and 125 patients, respectively. Twenty-nine of the 802 patients (3.6%) received conservative management. The remaining 773 patients (96.4%) underwent neurosurgical revascularization procedures, and 502 of these were bilateral. The median follow-up after surgery (nϭ773) or conservative management (nϭ26) was 26.3 months (range, 6.0 -101.9 months). Most subsequent ischemic events appeared in the first 2 years after surgery. The Kaplan-Meier estimated stroke risk was 10.1% in the first 2 years, and the 5-year-Kaplan-Meier risk of stroke was 12.7% after surgery for all patients treated with surgical revascularization. Conclusions-This study on the clinical features of moyamoya disease in mainland China indicated bimodal incidence distribution with women-to-men ratios of 1:1 and lower rate of hemorrhages in adults compared with in children. Patients had low rates of postoperative ischemic or hemorrhagic strokes, and the majority of patients had preserved functional status after revascularization. (Stroke. 2012;43:56-60.)