• Journal of Korea Multimedia Society
• /
• v.10 no.9
• /
• pp.1153-1164
• /
• 2007

One of the most challenging technical issues in mobile communication for multimedia is Quality of Service (QoS) management of handover calls. This paper proposes a 2-level handover control system to copy with this problem. A 2-level handover control system consists of resource reservation and call admission control modules. The resource reservation module divides the network resource into Hard and Soft reserved resource. The Hard reserved resource is only for the handover calls while the Soft reserved resource is for both the handovers and the new calls. And also, the resource reservation module classifies handovers into primary and secondary handovers based on often they occur. The call admission control module deals with the primary and secondary handover calls in different ways. The new calls can use Soft reserved resource only if there is sufficient amount available in the Hard reserved resource. Proposed system is evaluated using an M/M/c/c queueing model. It is shown that proposed system allows more efficient utilization of network resource without degrading QoS comparing with the legacy handover control systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.3A
• /
• pp.217-224
• /
• 2010

In this paper, we propose a hard handover algorithm for a base station's self-optimization, one of the automatic operational technologies for the 3GPP LTE systems. The proposed algorithm simultaneously considers a mixed target sell selection method for optimal selection and a multiple parameter based active hysteresis method with the received signal strength from adjacent cells and the cell load information of the candidate target cells from information exchanges between eNBs through X2 interface. The active hysteresis method chooses optimal handover hysteresis value considering the costs of the various environmental parameters effect to handover performance. The algorithm works on the optimal target cell and the hysteresis value selections for a base station's automatic operational optimization of the LTE system with the gathered informaton effects to the handover performance. The simulation results show distinguished handover performances in terms of the most important performance indexes of handover, handover failure rate and load balancing.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.12A
• /
• pp.1200-1208
• /
• 2008

In TD-SCDMA systems based on TDD, when mobiles move to cell from cell, Baton Handover was used to maintain an ongoing call. But baton handover has a great demand for the equipment and system. Then both hard handover and baton handover are used alternativly in real systems. But ratio of handover success in real system is 95% which is too low to be used in systems. This paper proposes to employ Soft Handover in TD-SCDMA systems which has performed in WCDMA systems. Also we carry out the simulation, which get result of the BER performance between baton handover method and proposed handover method. The proposed method is forward to be better performance than those of the baton and hard handover.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.9
• /
• pp.1596-1612
• /
• 2011

Coordinated Multi-Point (CoMP) transmission / reception is being studied in Long Term Evolution-Advanced (LTE-A) for future evolution of the $3^{rd}$ Generation Partnership Project (3GPP) LTE. Support of soft handover is essential for improving the performance of cell edge users. CoMP provides a natural framework for enabling soft handover in the LTE system. This paper evaluates the soft handover gain in LTE-A downlink. Mathematical analysis of signal to interference plus noise ratio (SINR) gain and the handover margins for soft handover and hard handover are derived. CoMP system model is developed and an inter-cell and intra-cell interference model is derived, taking into account the pathloss, shadowing, cell loading, and traffic activity. Reference signal received power (RSRP) is used to define the triggers and the measurements for soft handover. Our results indicate that parameter choices such as handover margin and the CoMP set size impact CoMP performance gain.

• 한국정보통신설비학회:학술대회논문집
• /
• 2004.08a
• /
• pp.160-164
• /
• 2004

본 논문은 CDMA 통신망과 WLAN 통신망 사이에서 이동단말기에 적용할 수 있는 MCHO 방법에 의한 핸드오버 기술을 구현한다. MCHO에 의한 핸드오버는 단말기에서 하드 핸드오버와 소프트 핸드오버 모두를 선택적으로 적용할 수 있다. 구현된 각각의 핸드오버에 환경에서 통신 채널을 유지하고, 전송상태를 유지하기 위한 핸드오버의 절차와 그에 따른 전송상태를 비교한다. 본 논문에서 구현한 핸드오버 기술은 원격 데이터 관측, 실시간 데이터 관측, 연속 데이터관측 등의 응용과 관련 연구에 도움이 될 것으로 기대된다.

• Proceedings of the IEEK Conference
• /
• 2002.07b
• /
• pp.1098-1100
• /
• 2002

Inter-RNC(radio network controller) and inter-BSC(base station center) hard handovers involve rerouting. Thus additional delay time for the new bearer setup and reroute determination should be considered. For theses kinds of handovers we propose a new scheme and coined it as ICHP(Inter-Cluster Handover Prediction). When a call approaches a boundary cell of a cluster, ICHP prepares for the handover by performing resource reservations and reroute computation in advance. Performance analysis shows that ICHP provides faster handover and that it lowers the blocking probability.

• Journal of the Korea Society for Simulation
• /
• v.11 no.1
• /
• pp.45-58
• /
• 2002

In the wireless communication systems of the next generation, the hard handover may frequent]y occur between the existing 2G(2nd generation) and the 3(1(3rd generation). When it occurs between the 2G and the 3G, the call setup procedure will be added to MT(Mobile Terminal), the relay bases in 2G and 3G, and the switches. It causes total time to handle the hangover to increase. Therefore, the forced termination probability may be increased since relative time decreases. In this paper, we propose a method to decrease the forced termination. The method execute the handover procedure with speed and direction of the MT preestimated in the inner cell when MT enters the boundary cell.

• ETRI Journal
• /
• v.36 no.5
• /
• pp.761-771
• /
• 2014

Long-Term Evolution employs a hard handover procedure. To reduce the interruption of data flow, downlink data is forwarded from the serving eNodeB (eNB) to the target eNB during handover. In cellular networks, unbalanced loads may lead to congestion in both the radio network and the backhaul network, resulting in bad end-to-end performance as well as causing unfairness among the users sharing the bottleneck link. This work focuses on congestion in the transport network. Handovers toward less loaded cells can help redistribute the load of the bottleneck link; such a mechanism is known as load balancing. The results show that the introduction of such a handover mechanism into the simulation environment positively influences the system performance. This is because terminals spend more time in the cell; hence, a better reception is offered. The utilization of load balancing can be used to further improve the performance of cellular systems that are experiencing congestion on a bottleneck link due to an uneven load.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.2
• /
• pp.91-99
• /
• 2009

Mobile WiMAX is an emerging technology that can provide ubiquitous Internet access. To provide seamless service in mobile WiMAX environment, delay or disruption in dealing with mobility must be minimized. However offering seamless services on IEEE 802.16e networks is very hard due to long handover latency both in layer 2 and 3. In this paper, we propose a fast cross-layer handover scheme based on prediction algorithm. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency can be reduced. The experiments conducted with system parameters and propagation model defined by WiMAX Forum demonstrate that the proposed method predicts the future signal level accurately and reduces the total handover latency.

• Journal of Broadcast Engineering
• /
• v.15 no.4
• /
• pp.487-497
• /
• 2010

In this paper, we propose a hard handover scheme which adaptively decides important handover parameters such as hysteresis and time-to-trigger values considering the load difference between the target and serving cells. First of all, the hysteresis value can be automatically adjusted according to the load difference, thus it is used to decide the handover trigger time. As a result, through the adaptive hysteresis scheme, handover drop rate is improved. However, this adaptive hysteresis scheme has a problem that the ping-pong effect, which occurs due to the frequent movement of mobile stations at the cell boundary, is increased. Therefore, to solve this problem, we propose a novel adaptive time-to-trigger scheme with the time-to-trigger which is in inverse proportion to the hysteresis value already established by the adaptive hysteresis scheme which adapts to the changing load difference between the target and serving cells. The simulation results show that the proposed adaptive time-to-trigger scheme based on the adaptive hysteresis is better than existing schemes in terms of handover drop rate and ping-pong generation.