Mutual interference among users can abruptly increase othercell interference and cause overload situation in coexisting WCDMA and HSDPA systems. Traffic overloading can degrade the performance of the systems. This letter proposes a new dynamic downlink load control (DDLC) algorithm to reduce performance degradation due to overload in the coexistence of WCDMA and HSDPA systems. With the proposed algorithm, the downlink load is controlled according to load states classified by two load-control thresholds, and traffic overloading is alleviated by dynamically adjusting the CQI values reported by users, based on the downlink load as well as channel variations. The proposed algorithm is simulated and results show that the DDLC scheme improves the performance of both WCDMA and HSDPA systems in terms of outage probability, total system throughput, and radio resource utilization.

This paper proposes a general expansion architecture for constructing large-scale multicast ATM switches with any type of small multicast switch, called the multicast Universal Multistage Interconnection Network (multicast UniMIN). The proposed architecture consists of a buffered distribution network that can perform cell routing and replication simultaneously, and a column of output switch modules (OSMs). The adoption of channel grouping and virtual first-in-first-out (FIFO) buffers results in high delay/throughput performance, and the distributed lookup table scheme for multicast addressing greatly reduces the size of a single lookup table. Analytical and simulation results show that high delay/throughput performance is obtained for both unicast and multicast traffic, and the proposed architecture yields an even better performance for multicast traffic than for unicast traffic. In addition, the multicast UniMIN switch has such good features as modular expandability, simple hardware, and no internal speed-up operation.

A dynamic pre-allocated connection (DPC) scheme is proposed to support fast handoff and to effectively utilize wireline links in a multi-connection call environment. Handoff can be quickly executed in real-time with reduced connection overhead, since the proposed scheme uses pre-allocated switched virtual connections (PSVCs). This dynamic resource management scheme increases link utilization due to statistical multiplexing effects. A path-loop elimination algorithm can be applied to remove duplicate resource usages. The DPC scheme in an environment of multi-connection calls is analyzed to obtain three probabilities; 1) new multi-connection call blocking probability, 2) multi-connection handoff call blocking probability, and 3) fast handoff failure probability.

An enhanced priority reservation algorithm for ATM multicast switches with a one-shot scheduling scheme is proposed. This algorithm is an input reservation method in which priority is selected among input ports considering the number of rejected copy requests and the blocked age of head-of-line (HOL) cells. The operation procedure of the proposed algorithm is described, and the average cell-delay and throughput performance is evaluated by simulation. The simulation results show that the proposed algorithm yields better performance than the conventional algorithms.

Reverse link performance analyses of single-code (SC) and multi-code (MC) CDMA systems in multipath fading environments are presented. The degree of orthogonality loss among multiple spreading code channels is characterized by introducing the orthogonality factor. This factor depends on the multipath delay power profiles of the propagation channel and the number of paths resolved at a Rake receiver. The link capacity and the signal power of both CDMA systems are then analyzed according to varying system parameters, including spreading bandwidth, traffic load, the orthogonality factor, and the number of spreading codes assigned to a user. Analytical results show that the SC-CDMA system provides a larger link capacity and MC users require more power than SC users. The dominant parameters affecting the performance difference are the spreading bandwidth and multipath delay power profiles.

Our previously proposed orthogonal code hopping multiplexing (OCHM) [1],[2] scheme is designed to accommodate a large number of bursty downlink users. However, it may undergo link quality degradation due to symbol perforations occurring when all code-collision symbol values are not identical. In this letter, a group-level random codeword hopping-pattern allocation (GRCHA) scheme is proposed to produce fewer symbol perforations than the previous symbol-by-symbol random codeword hopping (SRCH) of OCHM [1]. The proposed GRCHA scheme combined with the spatial filtering capability of switched-beam array antennas (SBAA) is expected to significantly reduce the symbol perforation probability in the OCHM scheme, and inter-beam softer handoff is applied to cope with high symbol perforation probability for users in overlapping beam areas of SBAA. The performance is evaluated by theoretical analysis and simulation in terms of the average symbol perforation probability. The proposed GRCHA scheme yields better performance than the SRCH scheme and the dedicated codeword allocation scheme, and the diversity gain of inter-beam softer handoff mitigates the effect of high symbol perforation probability for users in the overlapping beam areas.

This study is concerned with modeling an elastomer impact problem when a mass experiences a collision with the contact pad mounted on the underlying linear dynamic structure. The contact pad which consists of the viscoelastic material is modeled by a linear or nonlinear contact stiffness and the analytical form of frequency response obtained by a Fourier spectral analyzer is utilized in modeling the underlying dynamic structure. One linear model and one nonlinear model are introduced and their characteristics are analyzed. The result shows that the predicted impact forces match the measured responses fairly well.

The Resource Auction Multiple Access (RAMA) protocol was proposed by N. Amitay for fast resource allocations to mobile terminals. We have proposed an Enhanced RAMA (ERAMA) protocol yielding lower system delay and delay variations than does the RAMA protocol. In this paper, we model a two-stage queueing network to evaluate the performance of the proposed protocol in terms of mean access delay, mean buffering delay, talk spurt loss ratio, and channel utilization, under homogeneous voice connections. The analytical results yield upper estimates for the various performance indices, compared with those of the simulations.

Future broadband ATM networks are expected to accommodate various kinds of multi-media services with different traffic characteristics and quality of service (QOS) requirements. However, it is very difficult to control traffic by conventional mechanisms in this complex traffic environment. As an alternative approach, a multilayer perceptron neural network model is proposed as an intelligent control mechanism like "a traffic control policeman" in order to perform ATM connection admission control. This proposed neural control model is analyzed by computer simulations in a homogeneous and heterogeneous traffic environment and the result shows the effectiveness of this intelligent control mechanism, compared with that of an analytical method.

Channel holding time distributions in typical cross- and cigar-shaped urban microcells is determined. Practical low-tier-user behaviors in urban areas, such as turning at intersections, entering a buildings, as well as variable user speed and direction are considered. The results are useful in analyzing system traffic and in choosing the best cell shape in urban microcellular systems.

The blocking probabilities of n64Kb/s multi-slot calls are generally much higher than that of single slot calls. In order to improve these blocking probabilities of multi-slot calls, we propose a scheme to limit the number of time slots to be searched for lower rate calls. We analyze the performance of our scheme in a double-buffered time-space-time switching network which accommodates multi-slot calls as well as single-slot calls. The proposed method yields the reduced blocking probabilities of multi-slot calls, the increased traffic handling capacity and the reduced CPU processing load, compared with those of the conventional methods.

This letter proposes an improved timer-based location management scheme for packet-switched (PS) mobile communication systems. Compared to the conventional timer-based scheme with a single timer threshold, a new timer-based scheme with two timer thresholds is proposed to accommodate the bursty data traffic characteristics of PS service. The location update and paging costs of the proposed scheme are analyzed and compared with those of the conventional scheme. We show that the proposed scheme outperforms the conventional scheme in terms of total cost of both location update and paging with an appropriate selection of timer thresholds.

This paper is concerned with radio resource allocation in multiple-chip-rate (MCR) DS/CDMA systems accommodating multimedia services with different information rates and quality requirements. Considering both power spectral density (PSD) over a radio frequency (RF) band and the effect of RF input filtering on the receiver in MCR-DS/CDMA systems, criteria for capacity estimation are presented and the characteristics of co-channel interference between subsystems are investigated. System performance in MCR-DS/CDMA systems is strongly affected by radio resource assignment. A minimum power-increment-based resource assignment scheme for an efficient resource assignment scheme is proposed herein. The performance of this scheme is compared with that of a random-based resource assignment scheme in terms of blocking probability and normalized throughput. The minimum power-increment-based resource assignment scheme yields a better performance than the random-based resource assignment scheme for multimedia services.

A timer-based scheme is proposed to manage information within terminal and service profiles for both incall registration/deregistration of UPT users and incall registration resets of terminal owners. In the timer-based scheme, information related to incall registration for a UPT user in a terminal profile is deleted due to a timer expiration without accessing the terminal profile. The performance of the timer-based scheme is compared with the previously proposed request-based scheme in terms of; 1) total cost and, 2) the number of terminal profile accesses per unit time for a terminal. Even though provision of the timer-based scheme requires the modification of incoming call delivery procedure, the timer-based scheme can reduce both the total cost and the number of terminal profile accesses compared to the previously proposed request-based scheme.

An improved movement-based registration scheme reduces location update cost on conventional movement-based location update scheme but increases uncertainty of the position of a mobile terminal (MT). The effect of this uncertainty of the MT position on the paging cost of the improved movement-based registration scheme is analyzed. We show that the paging cost of the improved movement-based registration scheme in [2] is underestimated, especially for large values of movement threshold. The result shows that the underestimation cannot be ignored.

We propose and evaluate a single-bit adaptive step-size closed-loop power control (AS-CLPC) scheme which is adaptable to a dynamically changing radio channel. We also investigate the effect of the mobile terminal (MT) velocity on system performance when the proposed AS-CLPC scheme is employed. The proper power control constant of the AS-CLPC scheme is obtained by solving a polynomial equation. Compared with the IS-95 single-bit fixed step-size CLPC scheme, the proposed single-bit AS-CLPC scheme can reduce link margin (LM) by about 3 dB when the outage probability is below 0. 03 and a single fading path reception in the base station is assumed. System performance such as link availability and throughput can be improved by utilizing this proposed CLPC scheme in the outdoor radio propagation channel where time-selective fading occurs.

We analyze M,MMPP/G/1 finite queues with queue-length-threshold (QLT) scheduling policy and Bernoulli schedule where the arrival of type-1 customers (nonreal-time traffic) is Poisson and the arrival of type-2 customers (real-time traffic) is a Markov-modulated Poisson process (MMPP). The next customer to be served is determined by the queue length in the buffer of type-1 customers. We obtain the joint queue length distribution for customers of both types at departure epochs by using the embedded Markov chain method, and then obtain the queue length distribution at an arbitrary time by using the supplementary variable method. From these results, we obtain the loss probabilities and the mean waiting times for customers of each type. The numerical examples show the effects of the QLT scheduling policy on performance measures of the nonreal-time traffic and the bursty real-time traffic in ATM networks.

Reverse link performance analysis in single-code and multi-code CDMA systems is presented. Results show that the single-code system yields better performance than does the multi-code system in terms of link capacity and signal power. This improvement increases as spreading bandwidth is reduced and the number of spreading codes assigned to a user is increased.

In universal personal telecommunication (UPT) environments, UPT networks retain information related to incall/outcall registration in UPT user service profiles in order to provide incoming UPT calls for UPT users in any location who have registered at a terminal. As UPT networks support incall registration, terminal users can be different from terminal owners, and several UPT users can register for incoming calls on a single terminal. Therefore, appropriate third-party protection procedures are needed to protect the rights of terminal owners. A terminal profile database can be used to store information regarding terminal states and incall UPT users registered on a terminal in order to enable third-party protection procedures. In order to manage information within both the terminal profile and the service profile, we propose a request-based scheme for incall registration/deregistration of UPT users and incall registration resets of terminal owners. We evaluate the performance of the scheme in terms of; 1) total cost and, 2) the number of terminal profile accesses per unit time for a terminal.