Chan H.A.,Huawei |
Yokota H.,KDDI |
Xie J.,University of Northern Carolina |
Seite P.,Orange Group |
Liu D.,China Mobile
Journal of Communications | Year: 2011
Cellular networks have been hierarchical so that mobility management have primarily been deployed in a centralized architecture. More flattened network architecture for the mobile Internet is anticipated to meet the needs of rapidly increasing traffic from the mobile users and to reduce cost in the core network. Distributing the mobility management functions as opposed to centralizing them at the root of the network hierarchy is more compatible with a flat network architecture. Mobility management may be distributed at different levels: core level, access router level, access level, and host level. It may also be partially distributed or fully distributed. A distributed mobility management architecture avoids unnecessarily long routes, is more scalable with the increasing number of mobile users, and is a convenient platform for dynamic mobility management which means providing mobility support to mobile users only when they need the support. Dynamic mobility management can avoid waste of resources and also reduce signaling overhead and network cost. The desired distributed and dynamic mobility management needs to solve existing problems, meet the needs of changes in traffic and network architecture, and be simple and inexpensive to deploy. This paper surveys existing mobility management solutions in mobile Internet, explains the limitations of a centralized mobility management approach, and discusses potential approaches of distributing mobility management functions. The issues and challenges in the design of distributed and dynamic mobility management are also described. © 2011 ACADEMY PUBLISHER.
Mehling W.E.,University of California at San Francisco |
Gopisetty V.,University of California at San Francisco |
Bartmess E.,University of California at San Francisco |
Acree M.,University of California at San Francisco |
And 6 more authors.
Spine | Year: 2012
Study Design.: Prospective cohort study. Objective.: To assess the prognosis of patients presenting with acute low back pain (LBP) in a primary care setting in the United States. Summary of Background Data.: Practice guidelines for acute LBP based on return-to-work outcomes underestimate the development of chronic pain in the primary care setting. Because of differences in inclusion criteria, chronic pain definitions, and national health systems, prognostic cohort studies have reported a wide range of results limiting interpretation and generalization. Current data from carefully designed prognostic studies of acute LBP are lacking for the US primary care system. Methods.: Members of a large health service organization were enrolled after seeking medical care for acute LBP, with or without sciatica, of up to 30 days duration, with no episode in the past 12 months and no history of spine surgery. We conducted phone interviews at baseline, 6 months, and 2 years. Based on receiver operating characteristic analyses, a combination of global perceived recovery with pain intensity was used as primary outcome for chronic pain. Recurrence and multiple secondary outcomes were assessed to allow for comparison with other studies. Results.: Six hundred five patients had an average pain intensity of 5.6 (numeric rating scale=0-10) and disability of 15.8 (Roland-Morris scale=0-24). Eight percent had declared sick leave between pain onset and baseline interview. Thirteen percent of 521 patients (86% follow-up) experienced chronic pain at 6 months and 19% of 443 patients at 2 years. At 6 months, 54% had experienced at least 1 LBP recurrence, and 47% in the subsequent 18 months. Conclusion.: The prognosis of strictly defined acute LBP, with or without sciatica, is less favorable than commonly stated in practice guidelines based on failure to return to work. Broad initiatives to develop new means for the primary and secondary prevention of recurrent and chronic LBP are urgently needed. © 2012 Lippincott Williams & Wilkins.