Long Term Evolution “LTE” is considered to be one of the most
important and latest communication technologies falling under the fourth
generation of cellular communications technology 4G. LTE supports
high-speed and large bandwidth which makes it
a great candidate to
providing the potential to improve the Quality of Service "QoS"
associated with specific types of data transfer. As a consequence,
researchers have paid their attentions to this type of networks. In fact, it
was a great challenge for researchers to achieve a good level of QoS for
all users as the LTE provides Audio and Data transmission to users at the
same time.
يعتبر التعاون بين المحطات القاعدية في نظم الاتصالات النقالة الحديثة من مثل LTE أو (Long-Term Evolution) وكذلك LTE-Advanced (4G) من أهم التقنيات التي تسمح بتحسين التغطية ونوعية الخدمة المقدمة للمستخدمين. يهدف هذا البحث إلى اقتراح خوارزميات عملية للتعا
ون بين المحطات القاعدية على الوصلة الهابطة (Downlink) في هذا النوع من الأنظمة وسبر أداء هذه الخوارزميات من خلال بعض نتائج المحاكاة.
تعتمد الخوارزميات المقترحة على إعادة الإرسال الهجين (HARQ: Hybrid Automatic Repeat reQuest) بناءً على قرار مشترك بين المحطات المتعاونة يُتخذ في ظل معرفة معينة عن حالة القنوات اللاسلكية. تقدم إعادة الإرسال الموزعة، أي المعتمدة على التعاون، أداءً أفضل من حيث معدل الخطأ على المعطيات والتأخير الزمني لإيصالها بشكل صحيح، وذلك مقارنةﹰ بإعادة الإرسال من محطة واحدة بدون تعاون.
Handover technique in LTE networks suffers from Ping-pong Handover, which can be defined as a call is handed over to a new eNB and it then is handed back to the source eNB (evolved NodeB) within pre-defined and short time. Ping-pong handover can redu
ce the quality connection and
increases the number of handovers which in turn raise the network load and generally degrade the network performance. The work aims to present a novel approach to reduce the undesirable effects of ping-pong handover in beyond third Generation Mobile Networks.
The study guided to suggest an algorithm to select whether the user movement belongs to ping-pong type of movement or not and propose a technique to reduce the number of ping-pong handovers in Networks.
The suggested algorithm is based on performing the handover process in two steps (separated by timer). First step starts the handover preparation and execution as soon as the received signal strength from the target eNodeB becomes higher than that received from the source eNodeB. And delay the completion part of the HO technique for a time equal to the timer value. The research focused on the ping-ping phenomenon taking into account maintained the dropped calls rates at lowest levels. The optimal timer values are determined based on the width of overlapping area, user velocity and type of eNodeB. Moreover, the effects of tilting antennae on the probability of ping-pong handover are studied. Analysed and simulated results (using Matlab and TRIAS) showed that the timer values of the proposed algorithm reconciled with the mathematical results. Also, results clarified that tilting eNBs’ antennas decrease the probability of dropped calls. Comparison results illustrated that there is a significant reduction in the probability of ping-pong HOs, without any increasing in the probability of dropped calls for different scenarios. In future work, the proposed algorithm can be evolved and applied to heterogeneous networks and LTE advanced.
Research paper on the TCP protocol and its handling of bottlenecks, with a simple comparison between several copies of the protocol.
