In the future PCS (personal communication system), it is needed to use wireless and wired resources most efficiently, because of the increase of users and various multimedia traffics. Therefore, there have been much researches on CDMA (code division multiple access) whose frequency reuse is most efficient. Here, if one of PCS subsystems is broken down because of system, power, or network failure, it is impossible to serve PCS user terminals anymore. To solve this problem, the integrated network management function is required to examine each subsystem periodically or non-periodically, and handle each error properly, and inform network manager or PCS service management center of error occurrence. In this paper, we consider standard SNMP (simple network management protocol) and CMIP (common management information protocol) as the management protocol of PCS land mobile network. Also, we present the overall structure of management information taking CDMA PCS characteristics into consideration. Since there were little considerations for characteristics specific to cellular environment in the conventional network management systems, we add the CDMA PCS-specific management informations to each agent systems. Thereafter, we present the optimum network management protocol stack for PCS environment which provides TMN (telecommunications management network) interfaces among each subsystems as well as including wired networks.

A Virtual Cellular Network (VCN) is a wireless cellular network wherein a single Mobile Station (MS) can communicate simultaneously with more than one Base Station (BS). In this paper, we analyze handoff for two kinds of VCN: a 'Distributed Resource-control VCN' (DR-VCN) and a 'Centralized Resource-control VCN' (CR-VCN). A VCN can take advantage of the fact that the same data is received by multiple base stations. The DR-VCN is a system in which every BS controls its own channels, while the CR-VCN is a system wherein a central station controls all system channels. Results from analysis and simulation show that both the new call drop rate and handoff refusal rate of the CR-VCN are much lower than those of the DR-VCN.

CPCH is an uplink common channel that is used by 3GPP to support reliable packet transport. In this paper, we propose a new access scheme by using the discrimination of backoff timer for providing a prioritized service. We also present a simple system model of CPCH for EPA and use it to derive mathematical results. The results show that multi-class services with different priorities can be served effectively and easily by the proposed scheme.

The capacity analysis of CDMA forward link is required to allocate high data-rate users. To solve this problem, we analyze the capacity of the CDMA forward link based on optimum power control. In a multi-cell environment, the intracell interference and intercell interference are derived. To show the capacity impact of high data-rate users, we introduce a location dependent factor, which is the ratio of intercell interference to intracell interference. Considering the location dependent factor, we propose a coordinated allocation scheme that can be used to allocate high data-rate users in sectorized cells. As a result, we show the capacity impact of high data-rate users according to location variations. The outage probability can be decreased when the coordinated allocation scheme is applied.

We propose a new data link protocol with an adaptive frame length control scheme for satellite networks. The wireless communication channel in satellite networks is subject to errors that occur with time variance. The frame length of the data link layer is another important factor that affects throughput performance in dynamic channel environments. If the frame length could be chosen adaptively in response to changes in the dynamically varying satellite channel, maximum throughput could be achieved under both noisy and non-noisy error conditions. So, we propose a frame length control scheme that acts adaptively to counter errors that occur with time variance. We model the satellite channel as a two-state Markov block interference (BI) model. The estimation of the channel error status is based on the short-term bit error rate and the duty cycle of noise bursts. Numerical and computer simulation results show that the proposed scheme can achieve high throughput for both dense and diffuse burst noise channels.

We propose a new closed-loop power control scheme for wireless mobile communication systems using an adaptive step size. The proposed scheme selects the basic power control step size by considering the speed of the mobile station and a variable step size by using instantaneous companding logic based on power control command bit patterns. We show its improved performance in view of the standard deviation of received power at the base station in consideration of channel BER.

In this paper, the average error-rate characteristics are investigated as the number of users increases in the digital cellular DS/CDMA (Direct Sequence/Code Division Multiple Access) systems. Then, the performances of the various error control schemes applied to the data service of digital cellular DS/CDMA systems are compared and analyzed. That is, the performances of the conventional error control schemes such as Go-back-N ARQ (Automatic Repeat Request) and Selective-Repeat ARQ are analyzed in the circumstance of digital cellular DS/CDMA system. Also, the improved error control schemes which utilize the variable window size and/or variable data packet size are proposed and evaluated in order to improve the performances of the conventional error control scheme such as Quick-Repeat ARQ and WORM ARQ schemes in the digital cellular DS/CDMA system environments. According to the simulation results, the performances of the improved scheme with variable window and variable frame size are superior to those of the conventional scheme in the view of throughput and delay characteristics due to the robustness to the fading channel impairments.

In this paper, we consider conventional signaling link fault tolerance and error correction mechanisms to provide reliable services of mobile multimedia telecommunication network based on ATM (Asynchronous Transfer Mode) technology. Also, we propose an efficient signaling protocol interworking architecture and a reliable distributed interworking network architecture between SS7 based FPLMTS and ATM networks. Besides, we evaluate the performance of proposed method through computer simulation. According to the results, proposed signaling architecture shows efficient and fast fault restoration characteristics than conventional MTP-3/3b based network. Functional signaling protocol stack and network architecture of proposed fast rerouting mechanism provide reliable and efficient restoration performance in view of interworking between SS7 based FPLMTS and ATM networks.

Intelligent paging uses the sequential paging technique with additional user information in order to reduce the paging delay cost and the paging load cost. Our proposed paging scheme uses distribution density information of users as required additional user information. This letter addresses an optimal paging sequence and introduces formulas to calculate the paging costs. These formulas are necessary to evaluate the performance of location management. The paging delay cost and the paging load cost for the proposed paging scheme and two other paging schemes are calculated and numerical analyses for these paging schemes are performed. Results show how the paging delay cost and the paging load cost vary as either the paging request arrival rates or the number of cells in an LA increases. The proposed paging scheme is more efficient in view of both the paging delay cost and the paging load cost.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

A loop architecture of DQDB with slot reuse (LDQDB-SR) segmented by erasure nodes was studied to overcome the performance limitation due to the nature of the unidirectional bus architecture of DQDB with slot reuse. The LDQDB-SR adopts the destination slot release and an inter-segment bandwidth regulation based on the distributed queuing system of DQDB. This network suffers not only from severe throughput deterioration due to a high regulation cost and an excessive transit delay but also from unfairness in bandwidth sharing, especially under an overload condition. In this paper, we introduce an enhanced loop architecture of DQDB with slot reuse (ELDQDB-SR) to improve the performance of LDQDB-SR. The ELDQDB-SR uses a quota-based inter-segment bandwidth regulation mechanism to effectively control the bandwidth use of each segment. Each station selects the bus that minimizes the number of erasure nodes on the path to destination stations. Fairness control methods of DQDB are reviewed and the alpha-tuning mechanism is modified to achieve a fair bandwidth distribution among stations within each segment. Simulation results show that the ELDQDB-SR gives an enhanced throughput level and also maintains good fairness under overload conditions.

In this paper, we propose and evaluate the performance of Wireless ATM MAC layer protocol to support efficiently various ATM traffics, such as CBR, VBR, ABR and UBR, in wireless ATM network environments for reverse and forward link. The proposed MAC protocol could extend efficiently the service discipline of ATM traffics from wired network to wireless ATM network environments. Thus, available bandwidth, which is remained except the bandwidth for CBR and VBR traffics, could be effectively allocated to ABR and UBR traffics. Especially, in view of reverse link, two-phase scheduling algorithm supports successfully variable characteristics of VBR traffic. And, in view of forward link, 'Wireless Dynamic Weighted Earliest Deadline First' scheduling algorithm minimizes the mean cell delay and required buffer size. Simulation results show that proposed method provides effective performance in wireless ATM environments.

In this paper, efficient data transmission methods in wire and wireless interworking environments are studied in the case of handover occurring. To provide efficient mobile data service based on TCP, the wire and wireless interworking module with analysis function of TCP frame header protects the duplicated transmission of TCP frames. Also, by using the forwarding mechanism of status information and buffered data in the interworking module, it is possible to recover frame loss occurring in handover quickly. According to simulation results, proposed method has better performance than conventional method in view of throughput and delay. The reason is due to the fact that duplicated transmission is prevented and data recover is performed very quickly because buffered data is forwarded without loss in the case of handover.

To support efficiently the high-speed service and the multimedia service in mobile communication environments, network architecture is generally based on small cell radius structure to increase the wireless channel capacity. In a small cell radius structure based mobile network environment, a mobile station with large mobility should perform frequent handover. Thus, advanced handover mechanism should be provided, and must be done fastly. For these reasons, we suggest the efficient handover mechanism based on forward handover method in this paper. Proposed handover mechanism could support fast handover procedure, and is performed by using optimized path. Also, proposed handover mechanism could support QoS (Quality of Service) attribute of multimedia traffic during handover procedure. We evaluated the performance of proposed handover mechanism, and analysis results show that the suggested forward handover mechanism has less blocking ratio and lower delay than conventional backward handover mechanism.

As mobile communication systems have been widespread and the needs for new service grows, IMT-2000 systems have largely been researched and developed for standardization. Among them, Wideband CDMA (WCDMA) solution is standardized in the 3rd Generation Partnership Project. In WCDMA system, voice and high data rate services are supported through dedicated traffic channels, however other packet based services with short duration are provided by using common channels. Data users are allowed to transmit a short message based on a contention manner via the reverse common channels. The basic Common Packet Channel (CPCH) mechanism has been proposed and adopted for accessing common channels. It consists of three phases: Random Access Phase, Collision Resolution Phase, and Data Transmission Phase. To enhance the resource usage efficiency, the CPCH mechanisms with channel assignment or status monitoring have been proposed. They can improve the performance, however increase the system complexity. Up to now, performances of the CPCH mechanisms have been discussed and studied based on computer simulations. Numerical results have been obtained by using S-G analysis, but they are different from simulation results. In this paper, we analyze the CPCH mechanisms by using the Equilibrium Point Analysis (EPA). And we compare computer simulation results with analytical results.

Hierarchical constellations offer a different property of robustness to the multiple bits that construct a symbol according to channel errors. We apply the characteristics of hierarchical constellations to a multi-user cellular system that has limited modulation levels, in order to improve cell capacity. We propose an adaptive resource allocation scheme based on the hierarchical constellation in which a symbol is shared by multiple users and each bit in a symbol is allocated adaptively according to the channel condition of each user. The numerical results show that the proposed resource allocation scheme provides mobile users with higher modulation levels so that the cell capacity is improved.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

We herein describe an autonomous peer discovery scheme for Device-to-Device (D2D) communications. With the increasing popularity of D2D communications, an efficient means of finding the neighboring node, i.e., peer discovery, is required. To this end, we propose a new autonomous peer discovery scheme that uses azimuth spread (AS), delay spread (DS), and shadow fading of the uplink pilot from each mobile station (MS). Given that AS, DS, and shadow fading are spatially correlated, nodes that have similar values must be neighbors. The proposed scheme filters out the MSs that are unlikely to be neighbors and uses the Kolmogorov-Smirnov (K-S) test to improve the accuracy of neighbor discovery. Unlike previous peer discovery schemes that incur additional signaling overheads, our proposal finds neighboring nodes by using the existing uplink pilot transmission from MSs such that neighboring peers can be found autonomously. Through analysis and simulation, we show that neighboring MSs can be found accurately with low latency.

Recent technology innovations have increased the study on wireless LAN (Local Area Network). Also, improved computing power of end user has needed the distributed communication environment. However, conventional access protocols (TDMA, CSMA/CA and CDMA) have some problems such as the degradation of channel utilization, necessity of control station and code reuse. Therefore, we propose new multiple access scheme, Hybrid Reservation CDMA based on our previous work, DR-CDMA. Proposed method for distributed/central wireless LAN architecture provides, distributed channel access mechanism, code reuse method and internetworking method with conventional wire-based LAN. In proposed mechanism, efficient channel utilization could be obtained by minimizing overhead. Also, variable length frame from upper layer could be transmitted without segmentation. Moreover, nodes are serviced based on priority. In view of management, insertion of new node could be done easily in proposed HR-CDMA in proposed method due to its variable length property which can encapsulate conventional LAN frame. According to computer simulation, it has been shown that performances of proposed method are better than those of reservation TDMA bitmap protocol with respect to delay and throughput characteristics in the distributed environments as well as interworking environments between wire and wireless LAN.

We point out the unstable operation of reverse traffic management in the cdma2000 1xEV-DO system, and propose a new rate control scheme that controls the reverse traffic load more precisely. The proposed scheme is modeled as a multidimensional Markov process and compared with the conventional scheme. The analysis results show that the proposed rate control scheme has a lower overload probability and higher reverse link throughput than the conventional one.