| 1. |
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| 2. |
- Dellborg, M, et al.
(author)
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Changes in the use of medication after acute myocardial infarction : Possible impact on post-myocardial infarction mortality and long-term outcome
- 2001
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In: Coronary Artery Disease. - : Lippincott Williams & Wilkins. - 0954-6928 .- 1473-5830. ; 12:1, s. 61-67
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Journal article (peer-reviewed)abstract
- Objective: To describe the change in the use of medication after acute myocardial infarction (AMI) and discuss its possible impact on risk and risk indicators for death. Patients: All patients discharged alive after hospitalization for AMI at Sahlgrenska Hospital (covering half the community of Goteborg, i.e. 250 000 of 500 000 inhabitants) during 1986-1987 (period I) and at Sahlgrenska Hospital and Ostra Hospital (covering the whole community of Goteborg, 500 000 inhabitants) during 1990-1991 (period II). Methods: Overall mortality was retrospectively evaluated during 5 years of follow-up. Results: In all, 740 patients were included in the study during period I and 1448 during period II. The 5-year mortalities were 44.1% for period I patients and 39.3% for period II patients (P = 0.036). The relative risk of death for period II patients was 0.78 [95% confidence interval (CI) 0.67-0.89, P = 0.0005] after adjustment for differences at baseline. There was a significant interaction with a history of congestive heart failure; improvement in duration of survival was found only for patients without such a history. During period I, only 3% of patients were administered fibrinolytic agents, compared with 33% of patients during period II (P < 0.0001). During period I, aspirin was prescribed for 13% of patients discharged from hospital compared with 79% during period II. Other changes in treatment on going from period I to period II included increases in prescription of [beta]-blockers and angiotensin converting enzyme inhibitors. After adjustment for various risk indicators for death, relative risk of death for those administered fibrinolytic agents was 0.60 (95% CI 0.18-2.02) for patients in the period-I cohort and 0.68% (95% CI 0.51-0.91) for those in the period-II cohort. Adjusted relative risk of death for those prescribed aspirin upon discharge from hospital was 0.81 (95% CI 0.52-1.25) for period-I patients and 0.71 (95% CI 0.56-0.91) for period-II patients. The adjusted relative risk of death for those administered [beta]-blockers was 0.72 (95% CI 0.55-0.96) for period-I patients and 0.70 (95% CI 0.55-0.90) for period-II patients. Conclusion: Increased use of fibrinolytic agents and aspirin for AMI as well as a moderate increase in use of [beta]-blockers and angiotensin converting enzyme inhibitors was associated with a parallel reduction in age-adjusted mortality during the 5 years after discharge from hospital. However, this improvement was seen only for patients without histories of congestive heart failure.
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| 3. |
- Herlitz, Johan, et al.
(author)
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Impact of a history of hypertension on symptoms and Quality of Life prior to and at five years after coronary artery bypass grafting
- 2000
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In: Blood Pressure. - : Informa Healthcare. - 0803-7051 .- 1651-1999. ; 9:1, s. 52-63
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Journal article (peer-reviewed)abstract
- AIM: To describe symptoms and other aspects of health-related quality of life (QoL) prior to and 5 years after coronary artery bypass grafting (CABG) in relation to a history of hypertension. METHODS: Patients who underwent CABG in western Sweden were approached prior to surgery and 5 years after the operation. Health-related QoL was estimated with the Physical Activity Score, the Nottingham Health Profile and the Psychological General Well-Being Index. RESULTS: In patients with a history of hypertension (n = 740) the 5-year mortality was 16.9% versus 12.4% among patients with no history (n = 1257; p = 0.004). Of 1717 patients available for the survey, 876 (51%) responded both prior to and 5 years after CABG. Of these, 36% had a history of hypertension. Compared with the situation prior to surgery there was an improvement in both hypertensive and non-hypertensive patients in terms of physical activity, symptoms of dyspnea and chest pain and other estimates of health-related QoL. However, physical activity and dyspnea improved less in hypertensive than in non-hypertensive patients. CONCLUSION: Five years after CABG, a marked and significant improvement in terms of symptoms and other aspects of health-related QoL was observed among both hypertensive and non-hypertensive patients. However, improvement in physical activity was less marked in patients with a history of hypertension. Overall, a history of hypertension seemed to have a minor impact on improved well-being 5 years after coronary surgery. However, because of the limited response rate the results may not be applicable in a non-selected CABG population.
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| 4. |
- Herlitz, Johan, et al.
(author)
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Improvement and factors associated with improvement in quality of life during 10 years after coronary artery bypass grafting
- 2003
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In: Coronary Artery Disease. - : Lippincott Williams & Wilkins. - 0954-6928 .- 1473-5830. ; 14:7, s. 509-517
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Journal article (peer-reviewed)abstract
- AIM: To describe (1) the improvement in various aspects of quality of life (QoL) and (2) predictors of improvement, during 10 years after coronary artery bypass grafting (CABG). PATIENTS AND METHODS: All patients who underwent CABG in western Sweden between June 1988 and June 1991 without simultaneous valve surgery and with no previous CABG were approached with an inquiry prior to and 5 and 10 years after the operation. QoL was measured with three different instruments: (1) Nottingham health profile (NHP), (2) psychological general well-being index (PGWBI) and (3) physical activity score (PAS). RESULTS: There was a significant improvement in QoL with all three instruments from before to 10 years after the operation. The mean improvements +/-SD were for NHP, - 4.2+/-17.0 (P<0.0001), for PGWBI, +9.7+/-17.6 (P<0.0001) and for PAS, -0.96+/-1.23 (P<0.0001). However, there was also a deterioration with all three instruments between 5 and 10 years after surgery. The mean deteriorations +/-SD were for NHP, +4.4+/-12.8 (P<0.0001), for PGWBI, -4.6+/-14.8 (P<0.0001) and for PAS, +0.44+/-0.94 (P<0.0001). Independent predictors for an improvement in QoL with at least one of the instruments were low preoperative QoL, a younger age, being a man, high functional class (New York Heart Association), no hypertension, proximal left anterior descending coronary artery stenosis, short extracorporeal circulation time, use of internal mammary artery and a short postoperative time in the intensive care unit. CONCLUSION: There is a higher estimated QoL 10 years after CABG than before, despite the fact that the patients are 10 years older. However, there is also a deterioration in QoL between 5 and 10 years after surgery. Predictors of improvement during the 10 years included age, sex, previous history, localization of stenosis, type of graft and preoperative and postoperative factors.
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| 5. |
- Herlitz, Johan, et al.
(author)
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Mortality, mode of death and risk indicators for death during 5 years after coronary artery bypass grafting among patients with and without a history of diabetes mellitus
- 2000
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In: Coronary Artery Disease. - : Lippincott Williams & Wilkins. - 0954-6928 .- 1473-5830. ; 11:4, s. 339-346
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To describe mortality, mode of death, risk indicators for death and symptoms of angina pectoris among survivors during 5 years after coronary artery bypass grafting (CABG) among patients with and without a history of diabetes mellitus. METHODS: All patients in western Sweden who underwent CABG without concomitant valve surgery and who had no previous CABG between June 1988 and June 1991 were entered prospectively in this study. After 5 years, information on deaths that had occurred was obtained for the analysis. RESULTS: In all, 1998 patients were included in the analysis; 242 (12%) had a history of diabetes. Among the non-diabetic patients, 5-year mortality was 12.5%; the corresponding relative risk for diabetic patients was 2.1 (95% confidence interval 1.6 to 2.9). A history of diabetes was an independent risk indicator of death; there was no significant interaction between any other risk indicator and diabetes. Independent risk indicators for death among diabetic patients were: current smoking, renal dysfunction and left ventricular ejection fraction < 0.40. Compared with non-diabetic patients, those with diabetes more frequently died in hospital, died a cardiac death, or had death associated with the development of acute myocardial infarction and with symptoms of congestive heart failure. Among survivors, diabetic patients tended to have more angina pectoris 5 years after CABG than did those without diabetes. CONCLUSION: During a period of 5 years after CABG, diabetic patients had a mortality twice that of non-diabetic patients. The increased risk included death in hospital, cardiac death and death associated with development of acute myocardial infarction and with symptoms of congestive heart failure.
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| 6. |
- Herlitz, Johan, et al.
(author)
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Mortality, risk indicators for death and mode of death in younger and elderly patients during 5 years coronary artery bypass graft.
- 2000
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In: Clinical Cardiology. - : John Wiley & Sons, Inc.. - 0160-9289 .- 1932-8737. ; 23:6, s. 421-426
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Journal article (peer-reviewed)abstract
- BACKGROUND: The number of elderly patients who may be candidates for coronary artery bypass graft (CABG) for severe coronary artery disease has increased. Cardiac surgery in the elderly is a high-risk procedure because many of these patients have concomitant systemic disease and other disabilities. HYPOTHESIS: The study was undertaken to evaluate mortality, risk indicators for death, and mode of death in younger and elderly patients during 5 years after CABG. METHODS: The study included all patients in western Sweden who underwent CABG without concomitant valve surgery and without previously performed CABG between June 1988 and June 1991. In all, 2,000 patients, of whom 953 (48%) were > or = 65 years, were divided into two age groups (< 65 years and > or = 65 years). RESULTS: Compared with the younger patients, the elderly had a relative risk of death of 2.3 (95% confidence interval 1.8-3.0). The increased risk of death in the elderly was significantly more marked in men, in patients with more severe angina pectoris, and in patients without a history of cerebrovascular diseases. The mode and place of death appeared similar regardless of age; neither was there marked difference in symptoms of angina pectoris among survivors 5 years after CABG. CONCLUSION: Compared with patients < 65 years, the elderly have more than twice as high a risk of death during the subsequent 5 years, and this risk is higher in men, in patients with severe symptoms of angina pectoris, and in those with no history of cerebrovascular disease.
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| 7. |
- Herlitz, Johan, et al.
(author)
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Mortality, risk indicators for death, mode of death and symptoms of angina pectoris during 5 years after coronary artery bypass grafting in men and women
- 2000
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In: Journal of Internal Medicine. - : Wiley-Blackwell Publishing Ltd.. - 0954-6820 .- 1365-2796. ; 247:4, s. 500-506
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Journal article (peer-reviewed)abstract
- AIM: To describe mortality, risk indicators of death, mode of death and symptoms of angina pectoris during 5 years after coronary artery bypass grafting in women and men. SAMPLE: All patients in western Sweden who underwent coronary artery bypass grafting without concomitant valve surgery and without previously performed coronary artery bypass grafting between June 1988 and June 1991. RESULTS: In all, 2000 patients participated in the evaluation, 381 (19%) of whom were women. Compared to men, who had a 5-year mortality of 13.3%, women had a relative risk of death of 1.4 (95% CI 1.0-1.8; P = 0.03). Renal dysfunction interacted significantly (P = 0.048) with gender, in that the differences were more marked in patients without renal dysfunction. When adjusting for differences at baseline, the relative risk of death amongst women was 1.0 (95% CL 0.7-1.3). Compared to men, women had an increased risk of in-hospital death and death associated with stroke. However, amongst the patients who died, the place and mode of death appeared to be similar in women and men. Amongst survivors after 5 years, women had more symptoms of angina pectoris than men. CONCLUSION: During 5 years after coronary artery bypass grafting, women had an increased mortality compared to men; renal dysfunction seemed to interact with female gender regarding mortality. Women had a higher risk of in-hospital death and death associated with stroke. However, the adjusted relative risk of death during 5 years was equal in women and men. Amongst survivors, women suffered more from angina pectoris than men.
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| 8. |
- Herlitz, Johan, et al.
(author)
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Physical activity, symptoms of chest pain and dyspnea in patients with ischemic heart disease in relation to age before and two years after coronary artery bypass grafting
- 2001
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In: Journal of Cardiovascular Surgery. - : Edizioni Minerva Medica. - 0021-9509 .- 1827-191X. ; 42:2, s. 165-173
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Journal article (peer-reviewed)abstract
- BACKGROUND: To describe limitation of physical activity, cause of limitation of physical activity and symptoms of dyspnea and chest pain in relation to age before and 2 years after coronary artery bypass grafting (CABG). METHODS: All patients from Western Sweden who underwent CABG without concomitant procedures during 3 years in 1989-1991 answered questionnaires before, and 2 years after the operation. Patients were divided into 3 age groups of equal size i.e. 32-59 years, 60-67 years and > or = 68 years. RESULTS: In total, 2121 patients participated in the evaluation. The overall 2 year mortality in the 3 age groups was 3.8%, 6.8% and 12.2% (p<0.001). Limitation of physical activity was significantly associated with age prior to surgery but not thereafter. Improvement in physical activity, following CABG, was significant in all age groups. The proportion of patients being free of dyspnea increased markedly regardless of age. The number of chest pain attacks was associated with age after CABG, i.e. fewer attacks in the elderly, but such an association was not found prior to surgery. Improvement in number of chest pain attacks was more marked in the elderly. CONCLUSIONS: Physical activity improved similarly in all age groups after CABG. Attacks of chest pain, although significantly reduced in all age groups, seemed more effectively reduced in the elderly.
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| 9. |
- Herlitz, Johan, et al.
(author)
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Relief of symptoms and improvement of health-related quality of life five years after coronary artery bypass graft in women and men.
- 2001
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In: Clinical Cardiology. - : John Wiley & Sons, Inc.. - 0160-9289 .- 1932-8737. ; 24:5, s. 385-392
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Journal article (peer-reviewed)abstract
- BACKGROUND: Severe coronary artery disease can be successfully treated with coronary artery bypass graft (CABG), with considerable improvement in the symptoms of angina pectoris. Approximately three of four patients are free of ischemic events for 5 years; however, increased survival is demonstrated only in selected subgroups with advanced coronary artery disease, and this effect has not been established in elderly patients. HYPOTHESIS: The study was undertaken to determine the relief of symptoms and improvement in other aspects of health-related quality of life (QoL) during 5 years after CABG in women and men. METHODS: Patients who underwent CABG in western Sweden were approached prior to and 5 years after surgery. Health-related QoL was estimated with Physical Activity Score (PAS), Nottingham Health Profile, and Psychological General Well-Being Index. RESULTS: Women (n = 381) had a 5-year mortality of 17% compared with 13% for men (n = 1,619; NS). After 5 years, 1,719 patients (survivors) were available for the survey; of these, 876 (51%) answered the inquiry both prior to and after 5 years. Both women and men improved markedly and highly significantly, both with respect to symptoms and other aspects of health-related QoL. Women suffered more than men in terms of limitation of physical activity, dyspnea, chest pain, and others aspects of health-related QoL. There was a significant interaction between time and gender, with more improvement in men with regard to chest pain when walking uphill or quickly on level ground, when walking on level ground at the speed of other persons their own age, when under stress, and in windy and cold weather. For those parameters as well as for PAS, improvement was more marked in men than in women. In the other aspects of health-related QoL, there was no interaction between time and gender. CONCLUSION: Five years after CABG, limitation of physical activity, symptoms of dyspnea, and chest pain were reduced, and various aspects of health-related QoL had improved in both women and men. In general, women suffered more than men both prior to and after CABG; however, in some aspects the improvement was more pronounced in men. Because of the limited response rate, the results may not be applicable to a nonselected population who had undergone CABG.
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| 10. |
- Herlitz, Johan, et al.
(author)
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Relief symptoms and improvement of quality of Life five years after coronary artery bypass grafting in relation to preoperative ejection fraction
- 2000
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In: Quality of Life Research. - : Springer Netherlands. - 0962-9343 .- 1573-2649. ; 9:4, s. 467-476
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Journal article (peer-reviewed)abstract
- AIM: To describe the relief of symptoms and improvement in Quality of Life (QoL) 5 years after coronary artery bypass grafting (CABG) in relation to preoperative ejection fraction (EF). METHODS: Patients who underwent CABG between 1988 and 1991 in western Sweden were approached with an inquiry prior to surgery and 5 years after the operation. Quality of Life was estimated with three different instruments: Physical activity score, Nottingham Health Profile and Psychological General Well-being Index. RESULTS: Among all patients who underwent CABG (n = 1904) the 5-year mortality rate was 27% in those with EF < 0.40 and 12% in those with EF > or = 0.40 (p < 0.0001). In all, 849 patients, of whom 58 (7%) had EF < 0.40 participated in the evaluation. Neither physical activity, symptoms of chest pain, dyspnea nor any indices of QoL were significantly associated with preoperative EF. Improvement in physical activity, symptoms of chest pain and dyspnea and various estimates of QoL appeared similar and marked regardless of preoperative EF. CONCLUSION: Among survivors there was no association between preoperative EF and symptoms or various estimates of QoL 5 years after CABG. Improvement in symptoms and QoL were not dependent on preoperative EF.
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| 11. |
- Karlsson, Per Erik, 1957, et al.
(author)
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New critical levels for ozone effects on young trees based on AOT40 and simulated cumulative leaf uptake of ozone
- 2004
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In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:15, s. 2283-2294
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Journal article (peer-reviewed)abstract
- Leaf or needle ozone uptake was estimated for young trees at seven experimental sites across Europe using a stomatal conductance simulation model. Dose-response relationships based on cumulative leaf uptake of ozone (CUO) were calculated using different hourly ozone flux thresholds and these were compared to dose-response relationships based on daylight AOT40, which is currently used within the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP). Regression analysis showed that the CUO-biomass response relationships were highly significant for both coniferous and broadleaf trees, and independent of which ozone flux threshold was applied. On the basis of this regressions analysis, an hourly flux threshold of 1.6 nmol m(-2) s(-1) (COO > 1.6) is proposed as the most appropriate for all species categories in deriving dose-response relationships. The analysis indicated that the current critical level for ozone impacts on European forests of AOT40 10 ppm h may not protect the most sensitive receptors and that critical levels for AOT40 and CUO > 1.6 of 5 ppm h and 4 mmol m(-2), respectively, are more appropriate. The research identified weaker dose-response relationships for the CUO exposure index compared with AOT40. Distinguishing between sensitive and less sensitive species substantially improved the CUO-biomass response relationships although, still, to a lesser extent than when exposure was expressed as AOT40. (C) 2004 Elsevier Ltd. All rights reserved.
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| 12. |
- Brogren, M, et al.
(author)
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Optical properties, durability, and system aspects of a new aluminium-polymer-laminated steel reflector for solar concentrators
- 2004
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In: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 82:3, s. 387-412
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Journal article (peer-reviewed)abstract
- A newly developed aluminium-polymer-laminated steel reflector for use in solar concentrators was evaluated with respect to its optical properties, durability, and reflector performance in solar thermal and photovoltaic systems. The optical properties of the reflector material were investigated using spectrophotometer and scatterometry. The durability of the reflector was tested in a climatic test chamber as well as outdoors in Alvkarleby (60.5degreesN, 17.4degreesE), Sweden. Before ageing, the solar weighted total and specular reflectance values were 82% and 77%, respectively, and the reflector scattered light isotropically. After I year's outdoor exposure, the total and specular solar reflectance had decreased by less than 11%. However, after 2000 h in damp heat and 1000 W/m(2) simulated solar radiation, the optical properties had changed significantly: The light scattering was anisotropic and the total and specular solar reflectance values had decreased to 75% and 42%, respectively. The decrease was found to be due to degradation of the protective polyethylene terephthalate (PET) layer, caused by UV radiation and high temperature. The conclusions are that the degradation is climate dependent and that PET is not suitable as a protective coating under extreme conditions, such as those in the climatic test chamber. However, the results from outdoor testing indicate that the material withstands exposure in a normal Swedish climate.
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| 13. |
- From Attebring, M, et al.
(author)
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Are patients truthfull about their smoking habits? A validation of self-report about smoking cessation with biochemical markers of smoking activity amongst patients with ischaemic heart disease.
- 2001
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In: Journal of Internal Medicine. - : Wiley-Blackwell Publishing Ltd. - 0954-6820 .- 1365-2796. ; 249:2, s. 145-151
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Journal article (peer-reviewed)abstract
- AIMS: To validate self-report about smoking cessation with biochemical markers of smoking activity amongst patients with ischaemic heart disease. PATIENTS AND METHODS: Outpatients at the Division of Cardiology, 75 years of age or younger, who had been Hospitalized at Sahlgrenska University Hospital in Göteborg due to an ischaemic event and who consecutively participated in a nurse-monitored routine care programme for secondary prevention, from 6 February 1997 to 5 February 1998. Data concerning smoking habits were collected through interviews. Two chemical markers, cotinine in plasma and carbon monoxide (CO) in expired air, validated self-reports concerning smoking cessation. RESULTS: 260 former smokers were validated. In the vast majority of the study population, the anamnestic information concurred with the chemical marker. However, 17 patients had chemical markers that contradicted their self-report with raised CO (n = 6) and/or raised cotinine levels (n = 13) without alternative nicotine delivery. CONCLUSION: Most patients with coronary artery disease relating information concerning cessation of smoking are truthful. A few patients, however, seem to conceal their smoking. Testing by chemical markers may be questionable for ordinary care but should, however, be included in studies concerning the association between smoking and health.
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| 14. |
- Gardtman, M, et al.
(author)
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Has an intensified treatment in the ambulance of patients with acute severe left heart failure improved the outcome?
- 2000
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In: European journal of emergency medicine : official journal of the European Society for Emergency Medicine. - : Lippincott Williams & Wilkins, Ltd.. - 0969-9546 .- 1473-5695. ; 7:1, s. 15-24
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate short- and long-term outcome prior to and after the introduction of a more intensified treatment in the ambulance of patients with acute severe heart failure. Consecutive patients with acute severe heart failure transported by the mobile coronary care unit (MCCU) in the community of Göteborg prior to and after the introduction of an intensified treatment (nitroglycerine, continuous positive airway pressure (CPAP) and furosemide). One hundred and fifty-eight patients were evaluated during each period. The median age was 77 and 76.5 years, respectively, and 52% and 42% were women. The proportion of patients given nitroglycerine in the ambulance was 4% and 68% in the two periods; the proportion of patients treated with furosemide was 13% and 84%, respectively. CPAP was used in less than 1% during period 1 and in 91% during period 2. On admission of the ambulance 60% had fulminant pulmonary oedema during period 1 versus 78% during period 2 (p<0.0001). On admission to hospital the opposite was found, 93% during period 1 versus 76% during period 2 (p<0.0001). The median serum creatinine kinase (CK-MB) maximum activity was 13 microkat/l during period 1 and 8 microkat/l during period 2 (p = 0.007). However, the mortality during the first year remained high during both periods (39.2% and 35.8%, p = 0.64). It is concluded that a more intensive treatment in the ambulance of patients with acute severe heart failure seems to have resulted in an improvement in symptoms during transport and less myocardial damage. However, no significant improvement in long-term mortality was observed.
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| 15. |
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| 16. |
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| 17. |
- Herlitz, Johan, et al.
(author)
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Characteristics and outcome of patients with ST-elevation infarction in relation to whether they received thrombolysis or underwent acute coronary angiography : are we selecting the right patients for coronary angiography?
- 2003
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In: Clinical Cardiology. - : John Wiley & Sons, Inc.. - 0160-9289 .- 1932-8737. ; 26:2, s. 78-84
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Journal article (peer-reviewed)abstract
- BACKGROUND: During the last decade, there has been an on-going debate with regard to whether percutaneous coronary intervention (PCI) or thrombolysis should be preferred in patients with ST-elevation acute myocardial infarction (AMI). Some studies clearly advocate PCI, while others do not. HYPOTHESIS: The study aimed to describe the characteristics and to evaluate outcome of patients with suspected ST-elevation or left bundle-branch block infarction in relation to whether they received thrombolysis or had an acute coronary angiography aiming at angioplasty. METHODS: The study included all patients admitted to Sahlgrenska University Hospital in Göteborg, Sweden, with suspected acute myocardial infarction who, during 1995-1999, had ST-elevation or left bundle-branch block on admission electrocardiogram (ECG) requiring either thrombolysis or acute coronary angiography. A retrospective evaluation with a follow-up of 1 year after the intervention was made. RESULTS: In all, 413 patients had thrombolytic treatment and 400 had acute coronary angiography. The patients who received thrombolysis were older (mean age 70.3 vs. 64.1 years). Mortality during 1 year of follow-up was 20.9% in the thrombolysis group and 16.6% in the angiography group (p = 0.12). Among patients in whom acute coronary angiography was performed, only 85% underwent acute percutaneous coronary intervention (PCI). There was a mortality of 12.1 vs. 41.7% among those who did not undergo acute PCI. Development of reinfarction, stroke, and requirement of rehospitalization was similar regardless of type of initial intervention. The thrombolysis group more frequently required new coronary angiography (36.9 vs. 20.6%; p<0.0001) and new PCI (17.8 vs. 11.9%; p = 0.01). Despite this, after 1 year symptoms of angina pectoris were observed in 27% of patients in the thrombolysis group and in only 14% of those in the angiography group (p = 0.0002). CONCLUSION: In a Swedish university hospital with a high volume of coronary angioplasty procedures, we found no significant difference in mortality between patients who had thrombolysis and those who underwent acute coronary angiography. However, requirement of revascularization and symptoms of angina pectoris 1 year later was considerably less frequent in those who had undergone acute coronary angiography. However, distribution of baseline characteristics was skewed and efforts should be focused on the selection of patients for the different reperfusion strategies.
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| 18. |
- Herlitz, Johan, et al.
(author)
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Five year mortality in patients with acute chest pain in relation to smoking habits
- 2000
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In: Clinical Cardiology. - : John Wiley & Sons, Inc.. - 0160-9289 .- 1932-8737. ; 23:2, s. 84-90
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Journal article (peer-reviewed)abstract
- BACKGROUND: Smoking is one of the major risk indicators for development of coronary artery disease, and smokers develop acute myocardial infarction (AMI) approximately a decade earlier than nonsmokers. In smokers with established coronary artery disease, quitting smoking has been associated with a more favorable prognosis. However, most of these studies comprised younger patients, the majority of whom were males. HYPOTHESIS: The purpose of the study was to determine mortality, mode of death, and risk indicators of death in relation to smoking habits among consecutive patients admitted to the emergency department with acute chest pain. METHODS: In all, 4,553 patients admitted with acute chest pain to the emergency department at Sahlgrenska University Hospital during a period of 21 months were included in the analyses and were prospectively followed for 5 years. RESULTS: Of these patients, 36% admitted current smoking. They were younger and had a lower prevalence of previous cardiovascular diseases than did nonsmokers. The 5-year mortality was 19.4% among smokers and 24.9% among non-smokers (p < 0.0001). However, when adjusting for difference in age, smoking was associated with an increased risk [relative risk (RR) 1.51; 95% confidence interval (CI) 1.32-1.74; p < 0.0001]. Among patients presenting originally with chest pain, the increased mortality for smokers was more pronounced in patients with non-acute than acute myocardial infarction (AMI). Among patients who died, death in smokers was less frequently associated with new-onset myocardial infarction (MI) and congestive heart failure. Among those who smoked at onset of symptoms and were alive 1 year later, 25% had stopped smoking. Patients with a confirmed AMI who continued smoking 1 year after onset of symptoms had a higher mortality (28.4%) during the subsequent 4 years than patients who stopped smoking (15.2%; p = 0.049). CONCLUSION: In consecutive patients admitted to the emergency department with acute chest pain, current smoking was significantly associated with an increased risk of death during 5 years of follow-up. Among patients who died, death in smokers was less frequently associated with new-onset MI and congestive heart failure than was death in nonsmokers.
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| 19. |
- Herlitz, Johan, 1949, et al.
(author)
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Five-year mortality in patients with acute chest pain in relation to smoking habits.
- 2000
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In: Clinical cardiology. - 0160-9289. ; 23:2, s. 84-90
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Journal article (peer-reviewed)abstract
- Smoking is one of the major risk indicators for development of coronary artery disease, and smokers develop acute myocardial infarction (AMI) approximately a decade earlier than nonsmokers. In smokers with established coronary artery disease, quitting smoking has been associated with a more favorable prognosis. However, most of these studies comprised younger patients, the majority of whom were males.
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| 20. |
- Herlitz, Johan, et al.
(author)
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Limitation of physical activity, dyspnea and chest pain prior to and two years after coronary artery bypass grafting in relation to preoperative ejection fraction
- 2000
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In: Scandinavian Cardiovascular Journal. - : Informa Healthcare. - 1401-7431 .- 1651-2006. ; 34:1, s. 65-72
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Journal article (peer-reviewed)abstract
- To investigate the relationships between limitation of physical activity and dyspnoea and chest pain before and 2 years after coronary artery bypass grafting (CABG) and preoperative left ventricular ejection fraction (LVEF), questionnaires were issued to all patients from Western Sweden who underwent CABG during 1988-1991. The analysis comprised 985 patients. Physical activity improved significantly after CABG regardless of the preoperative LVEF. No significant association was found between LVEF and degree of limitation of physical activity before or after surgery. Dyspnoea and chest pain improved markedly, irrespective of LVEF. There was significant association between freedom from dyspnoea and LVEF preoperatively (less dyspnoea with higher LVEF), but not after CABG. The frequency of chest-pain attacks was not related to LVEF, before or after the operation. Thus physical activity, dyspnoea and chest pain improved in the 2 years after CABG irrespective of preoperative LVEF. Absence of dyspnoea was related to LVEF before, but not after surgery, and there was no association between preoperative LVEF and frequency of anginal attacks before or after CABG.
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| 21. |
- Herlitz, Johan, et al.
(author)
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Long term prognosis after CABG in relation to preoperative left ventricular ejection fraction
- 2000
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In: International Journal of Cardiology. - : Elsevier Ireland Ltd. - 0167-5273 .- 1874-1754. ; 72:2, s. 163-171
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Journal article (peer-reviewed)abstract
- AIM: To evaluate the mortality rate, risk indicators for death, mode of death and symptoms of angina pectoris during 5 years after coronary artery by pass grafting (CABG) in relation to the preoperative left ventricular ejection fraction (LVEF). PATIENTS: All patients in western Sweden who underwent CABG without concomitant valve surgery and without previously performed CABG between June 1988 and June 1991. RESULTS: In all 1904 patients were included in the analysis, of whom 173 (9%) had a LVEF < 40%. Patients with LVEF > or = 40% had a 5-year mortality of 12.5%. LVEF < 40% was associated with an increased risk of death (RR 2.3; 95% cl 1.7-3.1). There was no significant interaction between age, sex or any other factor in terms of clinical history and LVEF. However, left main stenosis was a strong independent predictor of death among patients with LVEF < 40% but not in those with a higher LVEF. Patients with a low LVEF more frequently died a cardiac death and a death associated with myocardial infarction (AMI). Furthermore they more frequently died in association with congestive heart failure and ventricular fibrillation. Among survivors, symptoms of angina pectoris were similar regardless of the preoperative LVEF. CONCLUSION: Patients with a low preoperative LVEF have a more than two-fold increased risk of death during 5 years after CABG. Their increased risk of death includes cardiac death, death associated with AMI, congestive heart failure and ventricular fibrillation.
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| 22. |
- Herlitz, Johan, et al.
(author)
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Prognosis after acute myocardial infarction continues to improve in the reperfusion era in the community of Göteborg
- 2002
-
In: American Heart Journal. - : Mosby, Inc.. - 0002-8703 .- 1097-6744. ; 144:1, s. 89-94
-
Journal article (peer-reviewed)abstract
- BACKGROUND: The objective of this study was to compare the prognosis of nonselected patients who had an acute myocardial infarction (AMI) during 2 time periods in the thrombolytic era and to describe coronary heart disease (CHD) mortality rates in the community of Göteborg during 1990 to 1995. METHODS: Patients aged <75 years who were hospitalized in the community of Göteborg for AMI during 1990 to 1991 (period 1) and 1995 to 1996 (period 2) were compared in terms of history, treatment for AMI, and outcome. Information on CHD mortality rates in the community of Göteborg was gathered from the National Registry of Deaths. RESULTS: The numbers of patients in the 2 cohorts were 926 and 861, respectively. The incidence rate for AMI per 100,000 inhabitants and year was 200 for period 1 and 183 during period 2. During period 2, there was an increased use of percutaneous transluminal coronary angioplasty, coronary artery bypass grafting, angiotensin-converting enzyme inhibitors, heparin, and intravenous nitroglycerin. On the other hand, there was a decreased use of thrombolytic agents, diuretic agents, digitalis, long-acting nitrates, calcium-channel blockers, and lidocaine. The hospital case-fatality rates were 9.4% during period 1 and 6.0% during period 2 (P =.01). The adjusted risk ratio for period 2 versus period 1 was 0.65, with 95% confidence limits of 0.45 to 0.94. The mortality rate over a period of 3 years was 26.5% during period 1 and 17.8% during period 2 (P <.0001). The adjusted risk ratio for period 2 versus period 1 was 0.67, with 95% confidence limits of 0.54 to 0.82. Among inhabitants aged 30 to 74 years in the community of Göteborg, the CHD mortality rate decreased in 1995 as compared with 1990 (age-adjusted odds ratio 0.79, 95% confidence limits 0.68 to 0.92). CONCLUSIONS: For consecutive patients aged <75 years who were hospitalized for AMI in the community of Göteborg, we found that in the thrombolytic era, major changes in medical and nonmedical treatment still took place associated with a continuing decrease in mortality rates during 3 years of follow-up. A similar reduction of CHD mortality rates was seen in the same age group within the community of Göteborg.
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| 23. |
- Holmberg, Torgny, et al.
(author)
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Fair scheduling of uplink traffic in HiperAccess
- 2003
-
In: 9th Asia-Pacific Conference on Communications (IEEE Cat. No.03EX732). - 0780381149 ; , s. 1198-1204
-
Conference paper (peer-reviewed)abstract
- In HiperAccess, the scheduling problem takes two forms; firstly, the base station reserves capacity on the uplink for the different terminals, and secondly, the terminals schedule their respective traffic in its assigned share of the channel capacity. Further, the base station generally has less and older information than the terminals, hence, the base station and the terminals may act differently for a given scenario. In view of this, scheduling traffic with quality of service (QoS) demands can be very difficult. In this paper, we propose a terminal scheduler capable of serving real-time and best-effort traffic with demands on QoS. Further, a new measure of fairness which is well suited for time-slotted systems is proposed
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| 24. |
- Holmberg, Torgny, et al.
(author)
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Scheduling deadline driven packet flows in HiperAccess
- 2003
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In: Proceedings of the Eighth IEEE Symposium on Computers and Communications. ISCC 2003. - 076951961X ; , s. 108-113
-
Conference paper (peer-reviewed)abstract
- Wireless communication systems are by nature and by regulations limited in bandwidth and hence capacity. Services with high demands on quality of service (QoS) will enforce high demands on the available capacity. This observation motivates the development of schedulers that can deliver the required QoS as well as being resource efficient. In this paper, we provide expressions of the worst case delivery time for schedulers based in the first in first out (FIFO) and the earliest due-date (EDD) principles which are applied to the HiperAccess point-to-multipoint radio communication system. Further, we propose modifications of the schedulers, which are more resource efficient at the expense of rare deadline misses. Despite the deadline misses, the modified scheduling algorithms can still provide an average delivery time well within the required deadline
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| 25. |
- Natt och Dag, Johan, et al.
(author)
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A Feasibility Study of Automated Support for Similarity Analysis of Natural Language Requirements in Market-Driven Development
- 2002
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In: Requirements Engineering. - : Springer Science and Business Media LLC. - 0947-3602 .- 1432-010X. ; 7:1, s. 20-33
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Journal article (peer-reviewed)abstract
- In market-driven software development there is a strong need for support to handle congestion in the requirements engineering process, which may occur as the demand for short time-to-market is combined with a rapid arrival of new requirements from many different sources. Automated analysis of the continuous flow of incoming requirements provides an opportunity to increase the efficiency of the requirements engineering process. This paper presents empirical evaluations of the benefit of automated similarity analysis of textual requirements, where existing information retrieval techniques are used to statistically measure requirements similarity. The results show that automated analysis of similarity among textual requirements is a promising technique that may provide effective support in identifying relationships between requirements.
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| 26. |
- Omland, T, et al.
(author)
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N-Terminal Pro-B-Type Natriuretic Peptide and Long-Term Mortality in Acute Coronary Syndromes
- 2002
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In: Circulation. - : American Heart Association. - 0009-7322 .- 1524-4539. ; 106:20, s. 2913-2918
-
Journal article (peer-reviewed)abstract
- ackground— B-type natriuretic peptide (BNP) is a predictor of short- and medium-term prognosis across the spectrum of acute coronary syndromes (ACS). The N-terminal fragment of the BNP prohormone, N-BNP, may be an even stronger prognostic marker. We assessed the relation between subacute plasma N-BNP levels and long-term, all-cause mortality in a large, contemporary cohort of patients with ACS. Methods and Results— Blood samples for N-BNP determination were obtained in the subacute phase in 204 patients with ST-elevation myocardial infarction (MI): 220 with non-ST segment elevation MI and 185 with unstable angina in the subacute phase. After a median follow-up of 51 months, 86 patients (14%) had died. Median N-BNP levels were significantly lower in long-term survivors than in patients dying (442 versus 1306 pmol/L; P<0.0001). The unadjusted risk ratio of patients with supramedian N-BNP levels was 3.9 (95% confidence interval, 2.4 to 6.5). In a multivariate Cox regression model, N-BNP (risk ratio 2.1 [95% confidence interval, 1.1 to 3.9]) added prognostic information above and beyond Killip class, patient age, and left ventricular ejection fraction. Adjustment for peak troponin T levels did not markedly alter the relation between N-BNP and mortality. In patients with no evidence of clinical heart failure, N-BNP remained a significant predictor of mortality after adjustment for age and ejection fraction (risk ratio, 2.4 [95% confidence interval, 1.1 to 5.4]). Conclusions— N-BNP is a powerful indicator of long-term mortality in patients with ACS and provides prognostic information above and beyond conventional risk markers.
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| 27. |
- Omland, T, et al.
(author)
-
Serum homocysteine concentration as an indicator of survival in patients with acute coronary syndromes
- 2000
-
In: Archnet-IJAR. - : American Medical Association. - 1994-6961 .- 1938-7806. ; 160:12, s. 1834-1840
-
Journal article (peer-reviewed)abstract
- Background Circulating homocysteine levels are predictive of survival in patients with stable coronary artery disease. The prognostic value of serum homocysteine levels, obtained in the acute phase in patients with myocardial infarction or unstable angina, is unknown. Objective To test the hypothesis that circulating homocysteine levels, obtained during the first 24 hours following hospital admission in patients with acute coronary syndromes, are predictive of long-term mortality. Methods To test this hypothesis we performed a prospective inception cohort study at a teaching hospital in Gothenburg, Sweden. A total of 579 patients (179 women and 400 men; median age, 67 years) were included (Q-wave myocardial infarction in 163 patients, non– Q-wave myocardial infarction in 210 patients, unstable angina pectoris in 206 patients). Main Outcome Measure All-cause mortality. Results During a median follow-up of 628 days, 65 patients died. The serum homocysteine level (mean [SD]) was significantly lower in long-term survivors (n=514) than in nonsurvivors (n=65) (12.3 [7.0] vs 14.3 [5.9] µmol/L; P=.003). The relative risk (all-cause mortality) for patients with homocysteine levels in the upper quartile was 2.4 (95% confidence interval, 1.5-4.0) compared with that of patients in the 3 lower quartiles. After adjustment for relevant confounders, the relative risk estimate remained significant (relative risk=1.69; 95% confidence interval, 1.02-2.80). In a stepwise model the homocysteine level provided prognostic information additional to that of patient age, diabetes mellitus, and diuretic usage prior to hospital admission (P=.03). Conclusion The serum homocysteine level on hospital admission is an independent predictor of long-term survival in patients with acute coronary syndromes.
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| 28. |
- Persson, Henrik, et al.
(author)
-
Evaluating the effects on enhanced intersystem connectivity
- 2004
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In: Proceedings - 5th World Wireless Congress. ; , s. 247-252
-
Conference paper (peer-reviewed)abstract
- Future mobile terminals will be able to use several types of wireless systems and have the possibility to change between different operators, while maintaining there original connection. This will impact the operators way of conduct business locally as well as globally. The different wireless systems will form hierarchical networks, where the systems have different coverage areas and bandwidth offerings. In this paper a model of hierarchical networks is presented, consisting of different kinds of wireless systems, such as WLAN and UMTS. The analyse of the hierarchical model shows that an increasing coverage area of any of the networks with higher bandwidths, will manifold the usage of these systems. Results from the study also show that as the number of applications and services increase, there will be a distinct shift towards hot spot systems at the expense of the wide area coverage systems. However, this will also dramatically increase the number of intersystem handovers, in both directions.
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| 29. |
- Persson, Henrik, et al.
(author)
-
Maintaining QoS by utilizing hierarchical wireless systems
- 2003
-
In: 9th Asia-Pacific Conference on Communications (IEEE Cat. No.03EX732). - 0780381149 ; , s. 292-296
-
Conference paper (peer-reviewed)abstract
- Future wireless networks, the systems beyond 3G, will be a combination of different wireless systems. With only one terminal a user should be able to connect to different type of operators, technologies and systems. The issue is also to make the terminal staying online connected, when these changes are made. Both intrasystem handovers and intersystem handovers should be supported by such terminals. The systems will form a hierarchical cell structure, that offer the users several technologies and different type of QoS-levels and bandwidths. To analyze this type of hierarchical cell structure a model has been created, and to verify the model calculations on a Markov-chain have been made. Using the transition probabilities we have calculated the state probabilities, to verify the results from the simulations made of our model. The analytical model and the simulation shows a very good agreement. The results show that the model could be used to show how the WLAN usage will behave as the number of WLANs and WLAN users increase
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| 30. |
- Persson, Henrik, et al.
(author)
-
Performance analysis of hierarchical wireless systems
- 2003
-
In: 2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484). - 0780379543 ; , s. 2217-2221
-
Conference paper (peer-reviewed)abstract
- For future usage of services and applications, it would be beneficial to be able to use only one terminal for their communication needs. The intention is also that the terminal should stay connected even if it has to change technology, system and/or operator. This means that a user will need to have a terminal, which can use different types of wireless systems. As well as that the systems have the opportunity to make seamless handovers not only intratechnology but also intertechnology. The future wireless networks should have transparent roaming, meaning consistent service availability, across networks. This paper also analyses how the progress and extension of the WLAN technology, affects the operators and the users of mobile applications and services. The analyze shows that the total number of handovers will decrease making it easier for both operators and users. At the same time the usage of WLAN technology, with the proposed enhanced user behavior, could increase hundredfold. A moderate extension of the WLAN coverage from 20 to 30 percent of city coverage, greatly effects the time a user utilize the WLAN
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| 31. |
- Persson, Henrik, et al.
(author)
-
Real and potential handover problems in future wireless networks
- 2002
-
In: Wireless 2002. Fourteenth International Conference on Wireless Communications. ; , s. 347-355
-
Conference paper (peer-reviewed)abstract
- Wireless communications are really poised to see major improvements in terms of network capabilities. The next generation of wireless services, besides improving the overall capacity, will create new demand and usage patterns, which will in turn, drive the development and continuous evolution of services and infrastructure. Future wireless networks should have transparent roaming, meaning having a consistent service which is available across networks, independent of the network, across all networks throughout the world. For this to be reality, one of the main obstacles to overcome is handover procedures. The requirements and prioritisation procedures for seamless handover are given and examples are discussed. Existing handover techniques are analyzed as well as potential problem of future wireless inter-network handovers
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| 32. |
- Uddling, Johan, 1972, et al.
(author)
-
Biomass reduction of juvenile birch is more strongly related to stomatal uptake of ozone than to indices based on external exposure
- 2004
-
In: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 38:28, s. 4709-4719
-
Journal article (peer-reviewed)abstract
- In order to test the hypothesis that ozone-induced limitation of biomass production in juvenile silver birch (Betula pendula Roth) is driven by stomatal uptake of ozone (O-3) rather than external exposure, biomass reduction was related to the cumulative uptake of O-3 through stomata over an uptake cut-off threshold of x nmol O-3 m(-2) s(-1) (CUO > x), to the accumulated exposure to O-3 over a threshold of y nmol mol(-1) during daylight hours (daylight AOTy) or during 24 h (24 h AOTy), and to the sum of daytime concentrations exceeding 60 nmol mol(-1) (SUM06). The analysis included data from nine different experiments conducted in Sweden, Finland and Switzerland. Stomatal uptake of O-3 was estimated using a stomatal conductance (g,) model including g, response functions for photosynthetic photon flux density, water vapour pressure deficit of the air and air temperature. Experiment-specific maximum g(s) (g(max)) as well as g(s) in darkness (g(dark)) were assessed through local measurements. Biomass reduction Was more strongly related to CUO > x than to SUM06 and daylight or 24 h AOTy, but the difference between CUO > x and 24 h AOTy was small. The better performance of CUO > x was dependent on the use of site- and experiment-specific g(max) and g(dark) values, and there was a positive relationship between g(max) and biomass reduction per unit AOT40. Daylight AOTy and SUM06 could not account for the growth limiting impact of nocturnal O-3 uptake in the Swiss experiments. A sensitivity analysis revealed that the CUO > x estimates were largely insensitive to the estimate of the conductance for non-stomatal leaf surface deposition of O-3, as a result of turbulent conditions at the experimental plots. In summary, we conclude that CUO > x was more successful in accounting for the variation in biomass reduction in juvenile birch as compared to indices based on external exposure, if g(max) and g(dark) were locally parameterised. (C) 2004 Elsevier Ltd. All rights reserved.
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| 33. |
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| 34. |
- Widell, Niklas, et al.
(author)
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Gateway-based call admission in distributed object oriented systems
- 2000
-
In: Proceedings fifteenth Nordic Teletraffic Seminar, NTS-15, Lund University, August 22-24, 2000.
-
Conference paper (other academic/artistic)abstract
- Many applications in telecommunications will depend on distributed systems to provide enough capacity. In a distributed system a service is split up into a number of modules (often called objects) that can be placed at different nodes or processors in a network. A service can be seen as a number of invocations of the objects in a certain order. There are a number of performance problems which have to be solved. How shall objects be distributed on the nodes? How shall the load be distributed among the nodes for a given object distribution? How shall the distributed system be protected from temporary overload situations? In our paper we investigate these questions for distributed systems where requests for service arrive to a gateway from which they distributed to the nodes of the system. We assume that the object distribution is given and we concentrate on protecting the system using three different external load control mechanisms: Percent Thinning, Call Gapping and Tokens. Using simulations, we nd that Tokens provide the best system protection.
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| 35. |
- Zander, Roland, et al.
(author)
-
A layer assignment and resource reservation scheme for hierarchical cell structures
- 2004
-
In: NETWORKING 2004, Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications. Proceedings (Lecture Notes in Computer Science). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540219590 ; 3042, s. 1508-1513
-
Conference paper (peer-reviewed)abstract
- To provide for a high QoS in a cellular network, each call should be assigned to its preferred cell and priority given to already ongoing calls. Herein, a combined speed-sensitive layer selection method and dynamic guard channel scheme, called CLARR, for use in hierarchical networks, is introduced. To reduce the complexity, partially the same speed estimation and measurement procedures are applied for both tasks. The main features of CLARR are the use of dwell time feedback control in the layer selection method and the grouping of calls depending on previous movement patterns. The measurements needed for making mobility predictions are performed separately for calls of different groups.
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| 36. |
- Zander, Roland, et al.
(author)
-
A measurement-based dynamic guard channel scheme for handover prioritization in cellular networks
- 2002
-
In: NETWORKING 2002. Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications. Second International IFIP-TC6 Networking Conference. Proceedings (Lecture Notes in Computer Science Vol.2345). - 3540437096 ; , s. 1245-1251
-
Conference paper (peer-reviewed)abstract
- The introduction of guard channels in a cellular network is a method for giving priority to on-going calls by having channels exclusively reserved for handover purposes. Herein, an adaptive measurement-based dynamic guard channel scheme is introduced. The proposed scheme uses the number of on-going calls in adjacent cells and measurements of handover probabilities to determine the amount of guard channels to allocate in a cell. To improve the efficiency of the scheme, the calls are divided into groups depending upon mobility and latest visited cell, where separate measurements are performed for every single group. Simulations showed that the proposed scheme seems to be very efficient
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| 37. |
- Zander, Roland, et al.
(author)
-
A rate-based bandwidth borrowing and reservation scheme for cellular networks
- 2004
-
In: IEEE Vehicular Technology Conference. - 1550-2252. ; 60:2, s. 1123-1128
-
Conference paper (peer-reviewed)abstract
- In the third generation cellular networks and beyond, a wide variety of different services are/will be provided by the operators. Out of QoS reasons, it is preferable to give higher priority to certain connection types. These include calls carrying delay-sensitive services and already ongoing calls. In this paper, a prioritization method combining bandwidth borrowing and reservation, called BBR, is introduced. BBR monitors the rate-adaptiveness of the ongoing calls in a cell. Simultaneously, advanced movement predictions are applied to estimate the arrival rate to each cell. If it is determined that the use of bandwidth borrowing (temporarily reducing the data rate of other calls in the same cell) is not sufficient to support the high priority calls that are expected to arrive, a portion of the assigned bandwidth to the cell is exclusively reserved for these calls to prevent call dropping. The scheme enables the operator to increase the average user satisfaction in the network. This is achieved by defining appropriate penalty functions for blocking, dropping and bandwidth reduction of a call.
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| 38. |
- Zander, Roland, et al.
(author)
-
A zone-based bandwidth reservation scheme for UMTS
- 2004
-
In: IEEE Vehicular Technology Conference. - 1550-2252. ; 59:4, s. 1993-1998
-
Conference paper (peer-reviewed)abstract
- It is out of QoS reasons advisable for cellular operators to give higher priority to already ongoing connections than new call attempts. This can be achieved by having bandwidth in each cell exclusively reserved for these calls. Herein, a method for dynamically determining the size of the reserved bandwidth in UMTS networks, called Zone-based Reservation Scheme (ZRS), is introduced. For this purpose, ZRS applies advanced subscriber movement predictions. The prediction accuracy is improved by grouping the calls according to previous movement patterns and speed, where data are collected separately for each group. To handle the soft capacity property of UMTS, ZRS considers both intra- and intercellular movements. This is achieved by dividing the cell areas into zones and tracking every cell zone ID alteration for all ongoing calls. ZRS can be implemented together with most call admission control schemes.
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| 39. |
- Zander, Roland, et al.
(author)
-
Introducing Handover Prioritization in Channel Borrowing Without Locking (CBWL)
- 2003
-
In: Proceedings of the IASTED International Conference on Wireless and Optical Communications. - 0889863741 ; 3, s. 429-434
-
Conference paper (peer-reviewed)abstract
- In order to improve the offered quality of service in a cellular network, load balancing between cells with momentarily different traffic loads can be applied. This can be accomplished through channel borrowing techniques where a cell requiring extra capacity borrows a channel from a less loaded cell in the same region. However, the borrowing of a channel results in an alteration of the channel reuse pattern. To prevent channels from being locked in some of its dedicated cells due to unacceptable interference levels caused by borrowing, a method where borrowed channels are transmitted with reduced power, called Channel Borrowing Without Locking (CBWL), can be applied. In CBWL, borrowed channels are only capable of serving calls in the proximity of the base station, meaning that an intracellular handover is required if one of these calls move to the outer cell area. In this paper, different handover prioritization methods applicable to CBWL are discussed. It is shown that the efficiency of these methods are highly dependent on the CBWL parameter settings.
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