• Journal of KIISE:Information Networking
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• v.27 no.2
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• pp.206-218
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• 2000

Retransmissions on the DLC layer are essential to ABR service providing the low CLR (cell loss ratio) over the unreliable wireless channel with high bit error rate. In the wireless ATM, the DLC layer below ATM layer performs the retransmission and reordering of the cells to recover the cell loss over the wireless channel and by doing so, the effect of the wireless channel characteristics with high bit error rate can be minimized on the ATM layer which is designed under the assumption of the low bit error rate. We propose, in this paper, the schemes to reflect the changes of the transmission rate over the wireless channel on the ABR rate control. Proposed scheme can control the source rate to the changes of the transmission rate over the wireless channel and reduce the required buffer size in the AP (access point). In the simulation, we assume that the DLC layer can inform the ATM layer of the wireless channel quality as good or bad. Our simulation results show that the proposed schemes require the smaller buffer size compared with the existing scheme, enhanced dynamic max rate control algorithm (EDMRCA). It is also shown that the scheme with the intelligent DLC which adjusts the rate to the wireless channel quality not only provides the low CLR with smaller buffer requirement but also improves the throughput by utilizing the wireless bandwidth more efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1088-1097
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• 1999

In this paper we describe our investigation en ATM CLR(Cell Loss Rate) in the wireless ATM Networks, which consist of wireless access nodes and wireless links. A wireless access node is modelled as the ND/D/1queue. A wireless channel is modelled as channel with single and burst error characteristics, and it can be seen that the CLR degrades on a link with burst errors than on a link with single error. Because wireless channel can be approximated as the Rayleigh or Rician fading channel and wireless communication systems are power limited, it is customary that the CLR degrades on a link with burst errors than on a link with single error. So error control method should be used to improve performance degradation caused by burst errors. We consider the forward error correction(FEC) as error control scheme for CBR traffics to improve performance degradation caused by burst errors, and analyze performance of concatenated FEC scheme through the use of CLR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1195-1207
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• 1999

Wireless channel has high error rate and limited bandwidth. In order to guarantee the quality of service for multimedia through wireless channel, wireless ATM network requires the cell structure with error control schemes and an efficient medium access control protocol. In this paprt, an efficient medium access control protocol, which is considered of cell structure and the QOS, is proposed for wireless ATM networks. Many kinds of ATM cell structures are analyzed in terms of cell error rate and cell loss rate to choose the proper cell structures for this proposed MAC protocol. And a bandwidth allocation algorithm is also designed to satisfy the priority of services. The performance of proposed MAC protocol are evaluated in terms of channel utilization, call blocking and packet discard probability accotding to different kinds of cell structure through simulation.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.119-122
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• 1998

Wireless ATM(WATM) intends to provide a broad range of mobile multimedia services through wireless access by mobility extensions from the fixed ATM-based network. Recently, there have been active researches about new handover techniques to support terminal mobility in WATM. In this paper we classify path reestablishment schemes into full reestablishment, path rerouting with a static COS, path rerouting with a dynamic COS, and path extension. For a backward lossy handover procedure, we analyze and compare the performances of path reestablishment schemes in terms of delay, service disruption time and cell loss.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.527-539
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• 2001

The wireless asynchronous transfer mode (ATM) system has the advantage of providing the broadband services with various quality-of-service requirements to the mobile terminal efficiently by utilizing the ATM technology developed for the wired ATM system. The available bit rate (ABR) service among various ATM services utilizes the available bandwidth remaining in the ATM link, which allows the efficient bandwidth usage. During the handoff of the mobile terminal, however, the queue length in the access point (AP) which resides in the boundary of the wired ATM network and the wireless ATM network may increase abruptly. In this paper, we propose a scheme which prevents the buffer-overflow and buffer-underflow in the AP during the handoff of the wireless ABR connection in the wireless ATM system using binary feedback rate-based ABR traffic control. This scheme controls the source's cell generation rate during both handoff period and some time interval after the completion of the handoff procedure. The simulation results show that the proposed scheme prevents the buffer-overflow and buffer-underflow. The proposed scheme can contribute to increasing the throughput of the wireless ABR service during handoff by preventing the buffer overflow and underflow during handoff period.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.461-467
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• 2003

This paper proposes the method of mobility implementation for location searching in the intelligence wireless ATM networks that expand and apply standard broadband signaling capabilities, and analyze the performance based on the numerical algorithm. The existing B-ISDN UNI protocol stack demands the location search mechanism to determine the location of mobile terminal in the wireless ATM networks because it use single protocol through the fixed PTP interface or PTM interface that don't support terminal mobility. The proposed method make possible the dynamic mobility at a part of wireless access by minimizing the signaling load without a falling-off in system performance by using the intelligence network technology according to the expansion of ATM and B-ISDN signaling integration based on the fixed networks. We implemented the performance analysis by MFC modeling based on numerical algorithm, and realized the efficiency of expenses by carrying out the comparative signaling performance evaluation to measure the relative gains of location search service in the intelligence wireless ATM system. The obtained results have the flexibility to operate in the public B-ISDN network environment without a change of existing B-ISDN/ATM NNI signaling reference to support the wireless ATM access system, and can easily expand to correspond to terminal mobility and various multimedia services in the next broadband PCS.

• Journal of Digital Contents Society
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• v.3 no.1
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• pp.47-57
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• 2002

Recently, wireless networks have been pursuing multimedia data service as voice, data, image, video and various form of data according to development of information communication technology. It guarantees cell delivery delay of real time data in efficient real time multimedia data transfer. Also, it minimizes cell loss rate of non-real time multimedia data. In the wireless ATM, there are based on Asynchronous Transfer Mode(ATM). It implies that there are various service with difficult transmission rates and qualities in the wireless communication network. As a result, it is important to find out the ways to guarantee the Quality of Service(QoS) for each kind of traffic in wireless network. In this thesis, we propose an improved TCRM scheduling algorithms for transmission real-time multimedia data service in wireless ATM Networks. We appear real time multimedia scheduling policy that apply each different method to uplink and downlik to wireless ATM network. It can guarantee QoS requirements for each real time data and non-real time data. It also deals the fairness problem for sharing the scarce wireless resources. We solve fault of TCRM as inefficient problem of non-real data by using arbitrary transmission speed and RB(Reservation Buffer) through VC(Virtual Control) and BS(Base Station).

• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.88-96
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• 2001

Future mobile communication networks, which consist of ATM-based B-ISDN backbone networks and wireless ATM networks, will provide u user with broadband connection and QoS service. These network systems need the lossless handoff methods which support user mobility, satisfy ATM features such as ATM cell ordering and no ATM cell duplication and minimize buffer requirement for ATM cell buffering. In this paper we suggest a multicast-based handoff method to supp$\alpha$t lossless connection as well as to minimize buffer overhead. It establishes a dynamic multicast connection between source terminal and wireless member AP (access point)s. When the mobile terminal receives data packet correctly, it notifies the positive acknowledgement of the packet to all member APs. And member APs then release the MT related temporary buffer space for MT's future movement. Therefore member APs can eliminate unnecessary buffer usage and manage the buffer space efficiently. Analysis result shows that our handoff method has better performance in buffer requirement for lossless and seamless connection services over VCT (virtual connection tree) method and other dynamic multicast-based handoff methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2014-2026
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• 1997

In this paper, the performances of wireless asynchronous transfer mode (ATM) cell transmission in mobile work are analyzed. We adopt 16Star QAM as amodulation technique in wireless channel and considered Reed-Solomon, convolutional, and concatenated coding to improve the error rate performances, and also proposed the Partial Concatenated Coding (PCC) technique as UEP(unequal error protection) code for efficient transmission of ATM cell in the air interface. We consider Doppler's effect, Rician fading, and diversity technique of maximal-ratio combining (MRC) for mobile channel model. For performance measure, we analyze bit error rate, ATM cell loss probability, ATM cell error probability, and network performances of ATM cell transmission delay and throughput. The numerical results show that the adoption of PCC is a prospective way for the evolution of future wireless ATM network on mobile environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2230-2239
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• 1998

Recently, mobility support of connectionless mobile ATM data service has been mainly studied in wireless ATM communication network. this paper shows the network model for the mobility support of connectionless data service in ATM network, and proposes the methods to minimize COIP (care of IP address) acquisition processing time for MH(mobile host)migration. Th echaracteristics of proposed methods, COIP acquisition probability and IP data communication sequence of proposed model, are discussed in this paper.