Admission Control in UMTS Networks based on Approximate Dynamic Programming

This paper investigates, through simulation, the performance of five connection admission control (CAC) algorithms used in ATM networks, namely: PCR CAC, SCR CAC, AVG CAC, GCAC, and Norros CAC, when presented with synthetically generated homogeneous self-similar traffic sources. Various traffic and system parameters have been used. The simulation results show that statistical multiplexing gains both within a source and across sources should be exploited to improve network resource utilization. Source granularity, and variability have been shown to have the most impact on the CAC performance. The limited impact of the Hurst parameter shows that the long-range correlation structure of the traffic sources can be neglected in evaluating CAC performance, at least when the buffer size is small. The CAC algorithms should be more conservative when link capacity is low and more aggressive when link capacity is high. While none of the CAC algorithms performs satisfactorily in all scenarios, the Norrors CAC and AVG CAC perform better than the others.

Reliability and survivability are the two important attributes of cellular networks. In the existing literature, these measures were studied through the simulation. In this paper, we construct an analytical model to determine reliability and survivability attributes of third generation and beyond Universal Mobile Telecommunication Systems (UMTS) networks. Hierarchical architecture of UMTS networks is modeled using stochastic models such as Markov chains, semi-Markov process, reliability block diagrams and Markov reward models to obtain these attributes. The model can be tailored to evaluate the reliability and survivability attributes of other beyond third generation cellular networks such as All-IP UMTS networks and CDMA2000. Numerical results illustrate the applicability of the proposed analytical model. It is observed that incorporating fault tolerance increases the network reliability and survivability. The results are useful for reliable topological design of UMTS networks. In addition, it can help the guarantee of network connectivity after any failure, without over dimensioning the networks. Moreover, it might have some impact from the point of view of the design and evaluation of UMTS infrastructures.

Many public funding agencies adopt the one-stage call-based mode to select R&D projects. The funding decision-making in this mode is characterized by two primary features: 1) it is static, meaning that decision-makers solely concentrate on projects submitted within the current call, and 2) it is decentralized, indicating that funding decisions are made independently across diverse sectors/disciplines. As a result, the administrative burden on funding agencies is reduced. However, due to the budget constraint, the funding agencies may fail to fund better projects that emerge in future calls or appear in other sectors/disciplines. Therefore, we investigate whether a better project portfolio can be achieved by selecting public R&D projects in a dynamic and centralized manner. We formulate a Markov decision process (MDP) model for the dynamic centralized public R&D project portfolio selection problem. We develop an approximate dynamic programming (ADP) approach that combines learning-based Monte Carlo simulation and a two-stage rollout algorithm to efficiently solve the MDP model. Based on extensive computational experiments, we compare our ADP approach with a threshold heuristic that is representative of the static and decentralized funding mode, as well as two baseline algorithms. The results indicate that our ADP approach is effective, and it is beneficial to adopt the dynamic centralized decision-making mode in public R&D project portfolio selection. We also investigate our ADP approach utilizing a case study based on real-world data from the National Natural Science Foundation of China. Our ADP approach can be integrated into the decision support systems of funding agencies, enabling automated, dynamic, and centralized selection of public R&D projects.

This paper presents a methodology for evaluating the quality of service provided by a cellular network for background services, such as e-mail and text messaging. Data collected from drive testing were used as the means to evaluate different drive routes on a Universal Mobile Telecommunications System (UMTS) network. Although one type of cellular network was tested, this methodology may be readily adapted to fit other types of cellular networks.

This paper proposes an Approximate Dynamic Programming (ADP) approach for obtaining the optimal real-time operation strategy of microgrid with power-to-hydrogen (P2H) device. Firstly, the real-time operation model of microgrid with P2H is established, then a piece-wise linear function based approximate dynamic programming is proposed to solve the operation model. With the direction of the slope update and training policies under various training scenarios, the proposed ADP approach can obtain the approximate optimal real-time operation strategies to cope with uncertainties. Case studies verify the superiority of the proposed ADP approach compared with Model Predictive Control approach (MPC).

Although by default the Network Simulator 2 (NS2) does not implement the IEEE 802.16 networks, a few patches are available, that provide WiMAX specifications at different fidelity level. The ns2 environment is useful for system-level evaluation, but mainly with respect to wired networks. In order to provide an adequate QoS provisioning to different service flows and to prevent base station (BS) from running out of resources an appropriate connection admission control (CAC) algorithms needs to be considered. Since the introduction of IEEE 802.16e standard a lot of studies have focused on development of CAC. In this paper we present the ns-2 module with integrated Connection Admission Control support. Currently three admission control algorithms based on so called guard channel were implemented. In the final sections authors show the CAC performance as well as influence of various turbo-FEC schemes deployed in physical layer on the system level performance. Especially it is found that the nb-LDPC codes provide link level solution able to improve system level quality metrics.

One of the key objectives of Universal Mobile Telecommunications System (UMTS) is the realization of enhanced end-user experience through the provision of rich multimedia services, ensuring in parallel an economical delivery cost for service providers. Multimedia Broadcast/Multicast Services (MBMS) framework of UMTS epitomizes the increasing popularity of such applications by efficiently delivering multimedia traffic to a large number of users and optimizing the radio interface of UMTS networks. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more economic to deliver MBMS multicast traffic over point-to-point (PTP) or point-tomultipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies such as High Speed Downlink Packet Access (HSDPA) stresses the need for an advanced Counting Mechanism. To this direction, in this paper we propose a novel Power Counting Mechanism which performs optimal power resource utilization and incorporates the HSDPA broadband extension of UMTS for enhanced performance.

A distinguishing feature of the Universal Mobile Telecommunications System (UMTS) is the support of different levels of quality of service (QoS) as required by subscribers and their applications. To provide QoS, the UMTS backbone network needs an efficient QoS mechanism to provide the demanded level of services on UMTS network. We implement a model to investigate end-to-end quality of service (QoS) provisioning approaches for UMTS networks in a DiffServ IP network environment. The effort was put on QoS classes mapping from DiffServ to UMTS, Access Control, buffering and scheduling optimization. The DiffServ Code Point was utilized in the E2E UMTS QoS provisioning to differentiate different types of traffic. We hybridized our work by applying Resource reservation protocol (RSVP) in routers and hosts. The main advantages and drawbacks are discussed. We found that our proposed model (hybridized model (DiffServ/RSVP)) improves the end-to-end delay and end-to-end variation compared with DiffServ model only, and it is superior to DiffServ regarding to throughput, utilization and packet loss ratio. The overall work guarantees the E2E QoS parameters of each service class, especially for real-time applications and improved the bandwidth utilization. Simulation results show that DiffServ can be an effective candidate for UMTS backbone bearer service.

Abstract. An expanded effort is under the way to support the evolution of UMTS (Universal Mobile Telecommunication System). Apart from delivering high data rates, future UMTS releases will also require to provide high network performance in terms of system capacity, low radiated power, and high coverage. Well promising performance-enhancing technologies are smart antennas as well as multiuser detection. Although these new radio technologies have recently been subject to intense research, main UMTS network integration aspects with their specific constraints have been neglected in many cases. Especially the interaction with UMTS radio resource control being required to meet Quality of Service (QoS) constraints has to be included to assess the applicability of these technologies for UMTS. In this paper, we study the interaction of beamforming concepts as well as multiuser detection with load and power control. We also work out UMTS specific constraints like signal-to-interference-plus-noise ratio (SINR) operating points, pilot power pollution or channel estimation, all strongly limiting network performance. Results are shown for capacity gains and power reduction for all beamforming concepts of interest as well as linear multiuser detection schemes. The results show that fix as well as user-specific beamforming significantly improves network performance gains in downlink. In uplink multiuser detection indicates fairly modest system capacity gains, while it reduces tremendously mobile station power.

In this paper, novel connection admission control (CAC) algorithms that take into account the effect of mobility of users both inside and outside the cell in the downlink of third-generation mobile systems are developed. First, the system capacity, including the other-cell interference, subject to feedback between cells is studied. Then, effective bandwidth expressions for calls are obtained as a function of both their location in the cell as well as their class of traffic (i.e., voice versus data). Next, this formulation is used to derive two mobility-aware admission control algorithms, i.e., a priority CAC, where calls are accepted not only upon resource availability, but also through acceptance ratios that reflect their levels of priority, and a squeezing CAC, where elastic calls may be squeezed to a minimum agreed value, giving way to admit more calls in the system and to secure further ongoing mobile users. Using Markovian analysis, several performance measures are obtained, namely the blocking probability, the dropping probability, both intracell and intercell, as well as the overall cell throughput. The authors eventually investigate the performance of our CAC and show how to extend the Erlang capacity bounds, i.e., the set of arrival rates such that the corresponding blocking/dropping probabilities are kept below predetermined thresholds

Universal Mobile Telecommunication System (UMTS) is a third generation mobile communication technology based on wideband CDMA (WCDMA) and can facilitate the users in much better way as compared to the second generation of mobile communication. UMTS is superior to second generation in terms of bandwidth efficiency, quality of service, speech quality, speed and capacity. At present, more than 60 countries using WCDMA technology are operating commercially in 25 countries. In this paper, we focus on soft and hard handover issues in UMTS networks. In order to simulate a typical UMTS scenario we use OPNET modeler where a number of users are generating traffic and are free to move in various cells.

A network-assisted mobile VPN for securing users data in UMTS

Interconnection of different access network technologies is an important research topic in mobile telecommunications systems. In this paper, we propose an ns-3 architecture for simulating the interconnection of wireless local area network (WLAN) and Universal Mobile Telecommunications System (UMTS). This architecture is based on the architecture proposed by the Third Generation Partnership Project, being the use of virtual interfaces as its main innovation. In order to demonstrate the value of the proposed simulation framework, we implemented the UMTS and WLAN interconnection considering three joint radio resource management strategies for distributing arriving calls. From the simulations results, we can conclude that the proposed simulation architecture is suitable to test and evaluate performance aspects related to the interconnection and joint management of UMTS and WLAN technologies. Copyright © 2012 John Wiley & Sons, Ltd.

Optimal Exercise Patterns and Valuation of Employee Stock Options: An Approximate Dynamic Programming Approach

In this paper, we propose a new connection admission control (CAC) algorithm accommodating various classes of traffic, which can easily be implemented in mobile WiMAX system. The proposed CAC algorithm has three characteristics: first, the variation of air capacity is taken into account by measuring the distribution of modulation and coding scheme (MCS) levels offline; second, we estimate the mean and variance of frame occupancy ratio of each QoS flow based on declared traffic descriptors; and third, the admission region is determined to satisfy the target overflow probability in the bufferless model. Through numerical analysis, we show that the accuracy of the proposed CAC is satisfactory.