• 한국통신학회논문지
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• 제25권12B호
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• pp.2109-2119
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• 2000

In this paper, the Packet CDMA Reservation ALOHA protocol is proposed to support the multi-traffic services such as voice and videophone services with handoff calls, high-rate data and low-rate data services efficiently on the multi-rate transmission in uplink cellular systems. The frame structure, composed of the access slot and the transmission slot, and the proposed access permission probability based on the estimated number of contending users for each service are presented to reduce MAI. The assured priority to the voice and the videophone handoff calls is given through higher access permission probability. And through the proposed code assignment scheme, the voice service can be provided without the voice packet dropping probability in the CDMA/PRMA protocols. The code reservation is allowed to the voice and the videophone services. The low-rate data service uses the available codes during the silent periods of voice calls and the remaining codes in the codes assigned to the voice service to utilize codes efficiently. The high-rate data service uses the assigned codes to the high-rate data service and the remaining codes in the codes assigned to the videophone service. Using the Markov-chain subsystem model for each service including the handoff calls in uplink cellular systems, the steady-state performances are simulated and analyzed. After a round of tests for the examples, through the proposed code assignment scheme and the access permission probability, the Packet CDMA Reservation ALOHA protocol can guarantee the priority and the constant QoS for the handoff calls even at large number of contending users. Also, the data services are integrated efficiently on the multi-rate transmission.

• 한국콘텐츠학회논문지
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• 제6권9호
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• pp.1-8
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• 2006

CDMA 시스템에서 핸드오프 호를 최소화하는 것은 사용자 만족도 평가에 매주 중요한 요인이다. 본 논문에서는 셀의 영역을 정규 영역과 소프트 핸드오프 영역으로 분할하고, 각각의 영역에서 서로 다른 가드채널 수를 갖게 함으로서 핸드오프 호를 최소화할 수 있음을 보인다. 이를 위하여 SRN을 기반으로 하여 정규영역과 소프트 핸드오프 영역으로 분할된 셀을 모델링하고, 성능 분석을 수행한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.341-344
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• 2001

H.323 proposes to use Mobile IP and H.323 ad hoc conference signaling to provide Handoff function to an H.323 mobile terminal. But the H.323 ad hoc conference signaling has a drawback. It requires an H.323 terminal to do a complex conference signaling which takes a longer signaling time. In this paper, we propose an GK architecture that provides Handoff function effectively using 3$^{rd}$ P'||'||'||'||'||'&'||'||'||'||'||'R(Third party initiated Pause and Rerouting) signaling which are done through H.245 logical channel. The GK which is implementing 3$^{rd}$ P'||'||'||'||'||'&'||'||'||'||'||'R signaling only requires an H.323 endpoint to do the H.323 basic signaling in reestablishing media channel and gives the faster Handoff signaling. To do this, our GK has derived H.245 control channel using tunneling f3r all H.323 calls including the fast connect calls which enable terminals communicate each other if they doesn't have H.245 control channel .municate each other if they doesn't have H.245 control channel .

• 전자공학회논문지S
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• 제35S권1호
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• pp.39-51
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• 1998

In this paper, we propose signaling procedures amon network elements for a connection rerouting method which can reduce inter-switch handoff processing delay reduces the delay in the connection re-routing by reserving VPI/VCIs for possible inter-switch handoff calls in advance. Additionally, we mathematically analyze the signaling procedures and then suggest solutions to the relations with cluser size, network topoloty, handoff-request rete and handoff delay. With simulation, the solutions are validated. From numerical examples, we concluded taht handoff delay, one of the handoff QoSs, can be satisfied by adjusting the cluster size and network topology according to the handoff -request rate of service area. With our proposed signaling and analytic methods, we concluded that the connection rerouting method using cluster-sectoring effectively reduces the delay of inter-switch handoff processing than dynamic connection rerouting method. Our solutions are useful in guaranteeing the requested handoff delay (especially, inter-switch handoff delay) when the connection rerouting method is applied to ATM-based wireless/wired integrated network.

• 한국정보과학회논문지:정보통신
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• 제29권4호
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• pp.352-357
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• 2002

CDMA셀룰러 시스템에서는 이동국이 한 셀에서 다른 셀로 이동할 때에 핸드오프영역에서 인접한 땅 셀의 채널을 신호를 동시에 점유함으로써 끊김 없는 연결을 가능하게 한다. 이 경우에 핸드오프 영역에 있는 이동국은 현재 셀의 신호 수신 지역을 벗어나지 않아도 양 기지국와 연결을 유지하는데 이것은 채널 효율성에 낭비를 가져온다. 따라서 핸드오프 율은 채널 효율성을 평가하는 중요한 요소이다. 본 논문에서는 CDMA셀룰러 시스템에서 이동국의 이동 속도와 방향을 기반으로 핸드오프 확률과 핸드오프 호수를 구하는 방식을 제안하였다.

• International Journal of Contents
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• 제1권1호
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• pp.45-49
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• 2005

If the service provider provides mobile service with mobile switching centers that use different handoff message format, the soft-handoff between mobile switching centers is not available and the hard-handoff scheme is used instead. When this occurs, calls are often disconnected or there is an interruption of service. This can be very annoying to a mobile user. We propose the handoff subsystem of the ATM switch which provides the soft-handoff between wireless cells under the control of different MSCs. The proposed handoff subsystem transforms the handoff message format of the source MSC to that of the destination MSC. It also provides efficient routing scheme that distributes handoff packets to balance the traffic load.

• 한국통신학회논문지
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• 제22권5호
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• pp.1075-1082
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• 1997

In this paper, we propose a channel assignment scheme for reducing call blocking rate in a base station(BS) of DS-CDMA cellular systems. The proposed scheme can e applied to the case where the capacity of reverse radio link is enough, but not are the available traffic channels performing the digital modulation and demodulation functions between a mobile station and the base station. The proposed scheme takes advantage of the feature of soft handoff in which a mobile station keeps its communication link even if one of the two communication links is released. The scheme estimates the mean and variance of the received power level measured at the base station before assigning a traffic channel for a new call request. The BS makes decision based on the estimated balues whether the new call request will be accepted or not. If it is decided that the capacity of reverse radio link is enough, but all traffic channels are not available, then the BS increases the soft handoff parameter T_DROP to release the traffic channels of mobile stations loactedin soft handoff area. The BS assigns the released traffic channel to anew call or a handoff call. The performance of the proposed channel assignment scheme is evaluated by computer simulation. The results show that the call blocking rate for new calls and handoff calls is reduced.

• 한국경영과학회지
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• 제25권1호
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.

• 산업경영시스템학회지
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• 제29권4호
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• 전자공학회논문지 IE
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• 제46권3호
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• pp.42-47
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• 2009

본 연구에서는 CDMA 시스템에서 신규 호의 차단률 및 핸드오프 호의 절단률에 따라 각 셀의 대역폭을 가변시켜 신규 호와 핸드오프 호를 처리하는 가변등가대역 개념을 이용한 호 수락 제어 방법을 사용하였다. 핸드오프 호를 위해서는 무선자원을 예약해 두며, 자원이 부족할 경우 신규 호와 핸드오프 호를 일정한 시간 동안 버퍼에 대기하도록 하여 가용자원이 발생하였을 때 대기 중인 호부터 처리하도록 하였다. 버퍼의 사용유무에 따른 시스템의 성능을 분석하였다.