Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks

This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then optimize an AMC scheme which directly satisfies a prescribed packet loss rate constraint at the data-link layer. The results indicate that utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the spectral efficiency compared with the system that employs AMC alone at the physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme outperforms the fixed rate counterpart when the transmission modes at the source and relay are chosen based on the channel statistics. This in turn quantifies the possible gain achieved by joint design of AMC and ARQ in wireless relay networks.Comment: 5 pages, 4 figures, To appear in the Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems (ISWCS), Rykevick, Island, Oct 200

Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks

This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then optimize an AMC scheme which directly satisfies a prescribed packet loss rate constraint at the data-link layer. The results indicate that utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the spectral efficiency compared with the system that employs AMC alone at the physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme outperforms the fixed rate counterpart when the transmission modes at the source and relay are chosen based on the channel statistics. This in turn quantifies the possible gain achieved by joint design of AMC and ARQ in wireless relay networks.Comment: 5 pages, 4 figures, To appear in the Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems (ISWCS), Rykevick, Island, Oct 200

Short Communication Residence time distribution in the extra capillary space of hollow fiber bioreactors

The residence time distribution (RTD) in the extracapillary space (ECS) of hollow fiber bioreactors (HFBRs) has been studied using a high molecular weight protein, bovine serum albumin, as a tracer. The RTD measurements have been carried out at different conditions of flow in the ECS and the intracapillary space (ICS). The RTD results obtained give an indication of the flow patterns existing in the ECS. The implications of these studies on cell cultivation as well as product recovery from HFBRs have been discussed

Study of Intraventricular Hemorrhage in VLBW Neonates Admitted in Al-Zahra Hospital, Tabriz, Iran

Introduction and Aim: Intra-ventricular hemorrhage (IVH) is an important predictor of adverse neurodevelopmental outcome. IVH risk factor identification may conduct improvement of quality of care in Neonatal Intensive Care Units. The aim of the current study was to determine possible risk factors associated with IVH in VLBW neonates admitted in our hospital. Patients and Methods: All neonates with birth weight below 1500 gr admitted to NICU. Cranial ultrasonography was done for premature neonates weighed <1000 g in 3 to 5 days and in 1 month again. In premature infants weighed >1000 g, sonography was done in 7 days and 30 days of life respectively. If there is any conditions such as apnea, seizure, significant decrease in level of hemoglobin, increased head circumference, increased oxygen consumption, and other significant changes another sonography was done again. Exclusion criteria were cerebral malformations, metabolic disturbances, chromosomal anomalies, central nervous system infection, and genetic syndromes. Data was analyzed by SPSS ver 16.0 (SPSS Inc, Chicago, IL, USA) Results: In this study 64 cases with IVH and 110 without IVH were included. Mean of gestational age was 28.78±2.08. From neonates, 54.6% were boys and 45.4% were girls. Vaginal delivery and cesarean section was done in 56 (32.2%) and 118(67.8%) cases respectively. Mean±SD of pH in cases with IVH and without IVH was 7.19±0.22 and 7.30±0.12 respectively(p=0.001). Mean ±SD of pco2 in cases with IVH and without IVH was 65.15±29.89 and 49.88±40.89 respectively(p=0.001). Mean of 5th min APGAR score in patients required CPR was 7.36±1.57 and in patients without CPR was 8.68±1.25(P=0.001). From cases with IVH, hydrocephaly was detected in 20 cases. From cases without IVH, hydrocephaly was detected in 6 cases. Result of chi-square showed significant correlation between IVH and prematurity( X2=21.94, df=1, P<0.001). From cases with IVH, 18 cases (28.1%) expired. From cases without IVH, 11 cases(10%) expired(X2=9.398, df=1, P=0.002). Results of chi-square test showed that there were a correlation between IVH and PDA, pressure support, surfactant therapy, inotrop drug administration, vaginal delivery, neonatal resuscitation, and antenatal corticosteroid therapy(p<0.05). Hyaline membrane disease, history of preclampsia in mother was significantly higher in cases without IVH(Chi-square, p<0.05). Conclusion: PDA, pressure support, surfactant therapy, inotrop drug administration, vaginal delivery, neonatal resuscitation, and antenatal corticosteroid therapy were significantly higher in cases with IVH. Hyaline membrane disease and preeclampsia in mother was significantly higher in cases without IVH.Keywords: Intraventricular hemorrhage, APGAR, low birth weight, hyaline membrane disease, corticosteroid, surfactant, inotrop, pre-eclampsi

Halal dating: changing relationship attitudes and experiences among young British Muslims

Young Muslims in the UK are making space to gain greater control over their personal lives through the diction of ‘halal’ and ‘haram’ when reflecting on and negotiating personal relationships. This article explores the significance of ‘halal dating’ within the lived experiences and sexual relationships of young British Muslims. It draws upon 56 in-depth interviews conducted with young (16–30 years) British Muslims of Pakistani heritage. This research shows that, contrary to popular stereotype and widespread expectations, many young British Muslims do date, or have dated. By entertaining the idea that certain forms of dating may be halal, these young Muslims are finding and claiming agency to make relationship choices of their own