Prasun Chowdhury

A Fair and Efficient Packet Scheduling Scheme for IEEE 802.16 Broadband Wireless Access Systems

This paper proposes a fair and efficient QoS scheduling scheme for IEEE 802.16 BWA systems that satisfies both throughput and delay guarantee to various real and non-real time applications. The proposed QoS scheduling scheme is compared with an existing QoS scheduling scheme proposed in literature in recent past. Simulation results show that the proposed scheduling scheme can provide a tight QoS guarantee in terms of delay, delay violation rate and throughput for all types of traffic as defined in the WiMAX standard, thereby maintaining the fairness and helps to eliminate starvation of lower priority class services. Bandwidth utilization of the system and fairness index of the resources are also encountered to validate the QoS provided by our proposed scheduling scheme.

Cross Layer QoS Support Architecture with Integrated CAC and Scheduling Algorithms for WiMAX BWA Networks

In this paper, a new technique for cross layer design, based on present Eb/N0 (bit energy per noise density) ratio of the connections and target values of the Quality of Service (QoS) information parameters from MAC layer, is proposed to dynamically select the Modulation and Coding Scheme (MCS) at the PHY layer for WiMAX Broadband Wireless Access (BWA) networks. The QoS information parameter includes New Connection Blocking Probability (NCBP), Hand off Connection Dropping Probability (HCDP) and Connection Outage Probability (COP). In addition, a Signal to Interference plus Noise Ratio (SINR) based Call Admission Control (CAC) algorithm and Queue based Scheduling algorithm are integrated for the cross layer design. An analytical model using the Continuous Time Markov Chain (CTMC) is developed for performance evaluation of the algorithms under various MCS. The effect of Eb/No is observed for QoS information parameters in order to determine its optimum range. Simulation results show that the integrated CAC and packet Scheduling model maximizes the bandwidth utilization and fair allocation of the system resources for all types of MCS and guarantees the QoS to the connections.

Load Balancing with Reduced Unnecessary Handoff in Energy Efficient Macro/Femto-cell based BWA Networks

The hierarchical macro/femto cell based BWA networks are observed to be quite promising for mobile operators as it improves their network coverage and capacity at the outskirt of the macro cell. However, this new technology introduces increased number of macro/femto handoff and wastage of electrical energy which in turn may affect the system performance. Users moving with high velocity or undergoing real-time transmission suffers degraded performance due to huge number of unnecessary macro/femto handoff. On the other hand, huge amount of electrical energy is wasted when a femto BS is active in the network but remains unutilized due to low network load. Our proposed energy efficient handoff decision algorithm eliminates the unnecessary handoff while balancing the load of the macro and femto cells at minimal energy consumption. The performance of the proposed algorithm is analyzed using Continuous Time Markov Chain (CTMC) Model. In addition, we have also contributed a method to determine the balanced threshold level of the received signal strength (RSS) from macro base station (BS). The balanced threshold level provides equal load distribution of the mobile users to the macro and femto BSs. The balanced threshold level is evaluated based on the distant location of the femto cells for small scaled networks. Numerical analysis shows that threshold level above the balanced threshold results in higher load distribution of the mobile users to the femto BSs.

A tradeoff pricing strategy using AHP for revenue maximization in WiMAX networks

Pricing plays a crucial role in trading any resource or service in the existing Broadband Wireless Access system i.e. WiMAX. Through a proper pricing strategy, a wireless service provider would like to achieve the highest revenue, while the end users would like to achieve the highest satisfaction from service usage. In order to make it feasible, in this paper we propose a tradeoff policy between the user satisfaction and profit of the service providers. In addition, we also propose a Call Admission Control (CAC) mechanism to control various level of Quality of Service (QoS) guarantee of the WiMAX service classes viz. UGS, rtPS, nrtPS and BE. Analytic Hierarchy Process (AHP) is used to prove the consistency of the assumed order of preference of the various QoS parameters for each service classes. Simulation results shows that our proposed tradeoff price maximizes the revenue of the service providers as it provides more user satisfaction or higher level of QoS guarantee to the end users.

An Efficient Quality of Service Scheduling Strategy for IEEE 802.16 Broadband Wireless Access Systems

In this paper, an efficient QoS scheduling strategy is proposed for IEEE 802.16 BWA systems that satisfies both throughput and delay guarantee to the applications such as video and audio streaming, online gaming, video conferencing, Voice over IP (VoIP), File Transfer Protocol (FTP) and Web Browsing. The proposed QoS scheduling strategy is compared with an existing QoS scheduling scheme proposed in literature in recent past. Simulation results show that the proposed scheduling architecture can provide a tight QoS guarantee for all types of traffic as defined in the standard hence maintain fairness and helps to eliminate starvation of lower priority class services.

An Improved Call Admission Control Mechanism with Prioritized Handoff Queuing Scheme for BWA Networks

Nowadays, due to increased demand for using the Broadband Wireless Access (BWA) networks in a satisfactory manner a promised Quality of Service (QoS) is required to manage the seamless transmission of the heterogeneous handoff calls. To this end, this paper proposes an improved Call Admission Control (CAC) mechanism with prioritized handoff queuing scheme that aims to reduce dropping probability of handoff calls. Handoff calls are queued when no bandwidth is available even after the allowable bandwidth degradation of the ongoing calls and get admitted into the network when an ongoing call is terminated with a higher priority than the newly originated call. An analytical Markov model for the proposed CAC mechanism is developed to analyze various performance parameters. Analytical results show that our proposed CAC with handoff queuing scheme prioritizes the handoff calls effectively and reduces dropping probability of the system by 78.57% for real-time traffic without degrading the number of failed new call attempts. This results in the increased bandwidth utilization of the network.

Queue size analysis of QoS-aware Weighted Hybrid Packet Scheduling Scheme for BWA networks

The increasing demand for multimedia communication over wireless platform necessitates the QoS-aware packet scheduling schemes in Broadband Wireless Access (BWA) networks. This paper deals with the analysis of queue size of QoS-aware Weighted Hybrid Packet Scheduling Schemes (WHPSS) for heterogeneous traffic classes in BWA networks. By categorizing the heterogeneous traffics of BWA networks into several classes (i.e. Class-1, Class-2, Class-3) depending upon their QoS requirement, we analyze the effect of queue size in WHPSS using three dimensional Continuous Time Markov Chain (CTMC) model. The analysis has been carried out with respect to the several performance parameters such as queuing delay, packet loss rate and throughput. This paper aims to observe the effect of queue size for each traffic flow to maximize the throughput of the network under the specified constraint of queuing delay and packet loss rate. Thus, the analysis helps to determine suitable queue size in the BWA network under varied traffic condition satisfying the required QoS constraints.

Design and implementation of a cognitive channel allocation algorithm for BWA system

The practical feasibility of any proposed algorithm could be tested only by hardware implementation of the algorithm. However, in cases involving wireless infrastructure based networks, hardware implementation may be very costly and time consuming. Hence, software simulations are used for these cases. In this paper, we have discussed the approach to be taken to implement any algorithm in any real time simulator. As a test case, we have implemented a simple infrastructure based centralized cognitive channel allocation algorithm for WiMAX BWA system under QualNet 5.0 software. The performance of the algorithm is then validated in terms of Spectrum Utilization and System Throughput for both Poisson and Pareto Arrival Rate of the end users. The results are further compared with results obtained from MATLAB 7.3.0. Unlike MATLAB, the impact of the lossy environment and layered architecture of the nodes is embedded in the results obtained from Qualnet. A fall of 4% in Spectrum Utilization and 3.8% in Throughput is observed in Qualnet compared to MATLAB.

Buffered non-random channel access method for better QoS of cognitive users

Cognitive Radio Networks allow opportunistic spectrum usage by the cognitive users leading to better spectrum utilization. The spectrum utilization however depends on the channel access method adopted and the access of the channel by the primary and the cognitive users. In this paper, a non-random channel access method with dedicated channels for the primary users has been proposed which buffers the requesting cognitive users when all channels are busy. A four dimensional Continuous Time Markov Chain (CTMC) has been developed to analyze our proposed algorithm. The performance of the algorithm has been compared with the existing non-random channel access method and about 71% improvement has been achieved in the Call Blocking Probability while the Channel Utilization and Call Dropping Probability remains almost unchanged.

Load Balancing with Reduced Unnecessary Handoff in Hierarchical Macro/Femto-cell WiMAX Networks

The hierarchical macro/femto cell WiMAX networks are observed to be quite promising for mobile operators as it improves their network coverage and capacity at the outskirt of the macro cell. However, this new technology introduces increased number of macro/femto handoff which inturn may affect the system performance. Users moving with high velocity or undergoing real-time transmission suffers degraded performace due to huge number of unnecessary macro/femto handoff. Our proposed handoff decision algorithm eliminates the unnecessary handoff while balancing the load of the macro and femto cells. The performance of the proposed algorithm is analyzed using Continuous Time Markov Chain (CTMC) Model. In addition, we have also contributed a method to determine the balanced threshold level of the received signal strength (RSS) from macro base station (BS). The balanced threshold level provides equal load distribution to the macro and femto BSs. The balanced threshold level is evaluated based on the distant location of the femto cells for small scaled networks. Numerical analysis shows that threshold level above the balanced threhold results in higher load distribution to the femto BSs.