Simulative Analysis of a Multi-Cell Admission Control Algorithm in WCDMA Networks

Adaptive admission control algorithm in a QoS-aware Web system

During last few years the development of concepts concerning how to accommodate continuous and bursty traffic has gained a lot of attention. The flexibility of the W-CDMA (wideband code division multiple access), which has been specified as a possible radio interface in the third generation cellular systems, can simplify the management of variant data rate traffic. An admission control (AC) algorithm is necessary in order to regulate the access of mobile terminals based on the amount of radio resources requested and available in the network. In this context, the AC must be able to control the quality of all active connections, usually expressed in terms of signal-to-interference ratio (SIR). We propose and analyze different AC strategies for W-CDMA cellular systems. The ideal AC scheme, which provides the maximum network capacity, is investigated in this paper. Since the ideal algorithm is not realizable in real systems the design of practical schemes is the goal of this project.

In this paper we propose a Differentiated Services Based Admission Control and Routing Algorithm for IPv6 (ACMRA). The basic DiffServ architecture lacks an admission control mechanism, the injection of more QoS sensitive traffic into the network can cause congestion at the core of the network. Our Differentiated Services Based Admission Control and Routing Algorithm for IPv6 combines the admission control phase with the route finding phase, and our routing protocol has been designed in a way to work alongside DiffServ based networks. The Differentiated Services Based Admission Control and Routing Algorithm for IPv6 constructs label switched paths in order to provide rigorous QoS provisioning. We have conducted extensive simulations to validate the effectiveness and efficiency of our proposed admission control and routing algorithm. Simulation Results show that the Differentiated Services Based Admission Control and Routing Algorithm for IPv6 provides an excellent packet delivery ratio, reduces the control packets' overhead, and makes use of the resources present on multiple paths to the destination network, while almost each admitted flow shows compliance with its Service Level Agreement.

Due to huge popularity of wireless service, public transport vehicles (PTV) might provide wireless Internet service through Mobile Local Area Network (MLAN) where mobile router (MR) is the main controlling element. MR can ask necessary resources to cellular base stations so that it can provide the guaranteed service of on-board users. The other users, non-PTV users, might observe variations of available resource in the cellular networks. If the admission control is performed by using the current available resource information then the network might see huge call interruption ratio (CIR) whenever the available resource for non-PTV users decrease. Therefore, it is necessary to propose an efficient admission control algorithm for these networks. In this paper, we propose a probabilistic admission control (PAC) algorithm for providing guaranteed service to PTV calls and reducing fluctuation in the wireless networks. Admission control is applied only for non-PTV calls not PTV calls. The admission decision of non-PTV calls depends not only current traffic conditions such as available resource but also admission probability. We have proposed two call interruption thresholds: max and min. If the observed CIR is less than min then admission probability is 1. On the other hand, if the observed CIR is greater than max then admission probability is 0. If the CIR is between min and max then admission probability will be in between 0 and 1. The relationship between CIR and admission probability is linear. Our scheme tries to serve PTV calls even by interrupting one or more non-PTV calls. The performance of this algorithm is evaluated through discrete event simulation. The arrival process of non-PTV and PTV calls is Poisson. Each non-PTV call needs one Bandwidth Unit (BU), and the PTV calls need different number of BUs at different time. The performance metrics of our scheme are CBP of PTV, CBP of non-PTV, CIR, and fluctuation in terms of total serving calls. Simulation results show that CIR can be maintained precisely between min and max. Moreover, the proposed algorithm can provide the guaranteed service to PTV calls, minimize CBP of non-PTV calls, and minimize fluctuation. Results also show that there is a trade off between CIR and CBP of non-PTV calls.

The crucial issues for service providers in wireless cellular networks include providing guaranteed quality of service (QoS), minimizing dropping rate (DR) for handoff calls, reducing the blocking rate (BR) for new calls and most importantly ensuring efficient utilization of network resources to maximize profits. This paper proposes an adaptive call admission control (CAC) algorithm for a wideband code division multiple access (WCDMA) network. The proposed algorithm utilizes three major concepts: cell breathing by considering the distance of a new and handoff call from a base station, bandwidth degradation of multimedia calls to provide priority for voice and video calls and transfer of ongoing calls to other cells to provide the highest priority to voice calls. This work is useful in the case when a voice or video call cannot be accepted into a cell due to unavailability of bandwidth and also when a new or handoff voice call cannot be accepted because the cell has already reached its maximum number of calls. Simulation results are presented for relations between call blocking, dropping probability and bandwidth utilization for different types of traffic (i.e. multimedia, video and voice calls).

In This work we investigate the utilization of non-dedicated, opportunistic resources in a desktop environment to provide statistical assurances to a class of QoS sensitive, soft real-time applications. Supporting QoS in such an environment presents unique challenges: (1) soft real-time tasks must have continuous access to resources in order to deliver meaningful services. Therefore the tasks will fail if not enough idle resources are available in the system. (2) Although soft real-time tasks can be migrated from one machine to another, their QoS may be affected if there are frequent migrations. In this paper, we define two new QoS metrics (task failure rate and probability of bad migrations) to characterize these QoS failures/degradations. We also design admission control and resource recruitment algorithms to provide statistical guarantees on these metrics. Our model based simulation results show that the admission control algorithms are effective at providing the desired level of assurances, and are robust to different resource usage patterns. Our resource recruitment algorithm may need long time of observations to provide the desired guarantee. But even with moderate observations, we can reduce the probability of a bad migration from 12% to less than 4%, which is good enough for most real applications.

This paper describes and tests a distributed bandwidth broker that has been implemented in NS simulator. It focuses on the admission control algorithm, its advantages and drawbacks. Also, the bandwidth broker is tested, managing the IP Premium service and we compare 2 different implementations of the service. Finally it approaches the problem of the optimal location of a bandwidth broker in a backbone network. For this purpose, a new model is proposed that evaluates each node and finally selects the most capable node where the base bandwidth broker should be located.

More advanced receiver structures than the conventional single antenna Rake can be used to improve the signal-to-noise (SNR) ratios, which is especially beneficial in order to utilize the high bit rates provided by the HSDPA concept in Wideband Code Division Multiple Access (WCDMA) network. In WCDMA system, orthogonal Walsh---Hadamard sequences are used as channelization codes. In frequency-selective fading channels the orthogonality of channelization codes disappears and intra-cell multiple access interference (MAI) arises. In order to mitigate the effect of MAI, chip-level equalization has shown to be a simple and effective solution. The effectiveness of chip equalization, however, degrades at the cell borders where the inter-cell interference dominates rather than MAI. Dual antenna reception is a straight-forward solution to mitigate that performance drop. In this paper, we present an analysis of the expected gains of advanced receivers over conventional single antenna Rake receiver in realistic situations by using a dynamic WCDMA system-level tool. Considered advanced receivers include single and dual antenna Linear Minimum Mean Squared Error (LMMSE) chip-level equalizers and dual antenna Rake receiver. The network performance with advanced receivers is studied also from a more practical point of view by assuming that the penetration of advanced HSDPA terminal receivers is gradually increased in the network.

In this paper we propose Admission Control and Multipath Routing Algorithm for Differentiated Services (DiffServ) based Networks (ACMRA). The basic DiffServ architecture lacks the admission control mechanism thus injecting more QoS sensitive traffic into the network can cause congestion at the core of the network. ACMRA combines the admission control with route finding phase and our routing protocol has been designed in a way to work alongside DiffServ based networks. ACMRA constructs label switched paths in order to provide low delay, low jitter and to some extend guaranteed bandwidth. We have done extensive simulations to validate the effectiveness and efficiency of our proposed admission control and routing algorithm. Simulation results have confirmed that ACMRA provides splendid packet delivery ratio, reduced overhead, it makes use of resources present on multiple paths to the destination network and each admitted flow shows compliance with its Service Level Agreement (SLA).

The challenge of the adaptive modulation and coding (AMC) scheme is to make a decision when to switch between different modulation and coding scheme. This is difficult because the performance of the AMC system is very sensitive to channel quality estimation errors and other channel impairments. In this paper, block error rate (BLER) performance of the wideband code division multiple access (WCDMA) system using AMC techniques are studied with nonideal channel and signal-to-interference-and-noise ratio (SINR) estimation and with the presence of multiuser interference. Also, the throughput of the adaptive system is simulated.

A distributed algorithm, where only one user for each cell is involved in the adjustment of weight and power, is proposed for joint diversity and power control in wireless networks. We prove that the power and weight of this algorithm converge to the optimal power and weight that minimize the total power consumption. In addition, we also prove some properties that facilitate the operation of the admission control in which the distributed algorithm is incorporated. Two approaches are proposed for the admission control: 1) the admission criterion and 2) the admission control algorithm. The proposed admission criteria are realized by considering a set of inequalities, whereas the proposed admission control algorithm is based on the connection removal. It is shown that the number of inequalities for the proposed admission criteria can be reduced from the number of users to the number of base stations so that the computational complexity of the proposed admission criteria can largely be reduced. In addition, we have found in the simulation results that the proposed admission control algorithm outperforms other admission control algorithms in terms of the average execution time and computational complexity.

In this paper, we investigate a call-admission and handoff-control framework for multi-tier cellular networks. We first propose and compare Call-Admission Control (CAC) algorithms based on the cell-dwelling time, by studying their impact on the handoff-call dropping and new-call blocking probabilities and the channel partitioning between the two tiers. Our results show that a simple, cell-dwelling-time-insensitive algorithm performs better under various mixes of user mobilities and call types. Moreover, there is an optimal channel partition of the overall spectrum between the tiers which minimizes the dropping and blocking probabilities for the two different CAC algorithms studied in this paper. Once the call is admitted into the network, we propose and compare various handoff- queuing strategies to reduce the call dropping probability. We show that implementing a queuing framework in one of the tiers (especially the upper, i.e., macrocellular, tier), results in a significant reduction in the dropping probability.

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.

Resource allocation and admission control algorithm based on non-cooperation game in wireless mesh networks

In Wideband Code Division Multiple Access (WCDMA) networks the Signaling Radio Bearer (SRB) is transmitted downlink to inform the user i.a. when it needs to make a handover. When transmitting e.g. Voice over IP (VoIP) on High Speed Downlink Packet Access (HSDPA) SRB is mapped on HSDPA user data channel, high-speed downlink shared channel (HS-DSCH) in order to maximize voice capacity. The lack of support for soft handover (SHO) of HS-DSCH may compromise the reception of SRB and thus also a possible incoming serving HSDPA cell change command especially at the cell borders. This can lead to serious VoIP service degradation due to prolonged camping on a poor cell and in the worst case even to call dropping, if the cell change command is not received before VoIP call drop criterion is met. This paper considers the performance of SRB transmission on source cell HS-DSCH during a handover process. Also a strategy of transmitting the serving cell change command from the target cell is analyzed. The study is done by the means of fully dynamic system simulations and they consider both macro-cell and manhattan scenarios. The results show that a relatively low SRB/handover error rate is experienced in a macro cell scenario but in a more challenging manhattan scenario the error rate is higher. Transmitting the serving cell change command from the target cell HS-SCCH results in similar handover failure rates in manhattan scenario than using SRB on HS-DSCH in macro-cell scenario when static power allocation for HS-SCCH is in use.