Design and analysis of scheduling algorithms for next generation broadband wireless access systems

Efficient utilization of network resources is a key goal for emerging Broadband Wireless Access Systems (BWAS). This is a complex goal to achieve due to the heterogeneous service nature and diverse Quality of Service (QoS) requirements of various applications that BWAS support. Packet scheduling is an important activity that affects BWAS QoS outcomes. This thesis proposes a new packet scheduling mechanism that improves QoS in mobile wireless networks which exploit IP as a transport technology for data transfer between BWAS base stations and mobile users at the radio transmission layer. In order to improve BWAS QoS the new packet algorithm makes changes at both the IP and the radio layers. The new packet scheduling algorithm exploits handoff priority scheduling principles and takes into account buffer occupancy and channel conditions. The packet scheduling mechanism also incorporates the concept of fairness. The algorithm also offers an opportunity to maximize the carriers’ revenue at various traffic situations. Performance results were obtained by computer simulation and compared to the well-known algorithms. Results show that by exploiting the new packet scheduling algorithm, the transport system is able to provide a low handoff packet drop rate, low packet forwarding rate, low packet delay, ensure fairness amongst the users of different services and generates higher revenue for the telecom carriers. Furthermore this research proposes a new and novel measure named “satisfaction factor to measure the efficacy of various scheduling schemes and finally this s research also proposes four performance measurements metric for NodeB’s of Next Generation Wireless Network

Soft Handoff in MC-CDMA Cellular Networks Supporting Multimedia Services

An adaptive resource reservation and handoff priority scheme, which jointly considers the characteristics from the physical, link and network layers, is proposed for a packet switching Multicode (MC)-CDMA cellular network supporting multimedia applications. A call admission region is derived for call admission control (CAC) and handoff management with the satisfaction of quality of service (QoS) requirements for all kinds of multimedia traffic, where the QoS parameters include the wireless transmission bit error rate (BER), the packet loss rate (PLR) and delay requirement. The BER requirement is guaranteed by properly arranging simultaneous packet transmissions, whereas the PLR and delay requirements are guaranteed by the proposed packet scheduling and partial packet integration scheme. To give service priority to handoff calls, a threshold-based adaptive resource reservation scheme is proposed on the basis of a practical user mobility model and a proper handoff request prediction scheme. The resource reservation scheme gives handoff calls a higher admission priority over new calls, and is designed to adjust the reservation-request time threshold adaptively according to the varying traffic load. The individual reservation requests form a common reservation pool, and handoff calls are served on a first-come-first-serve basis. By exploiting the transmission rate adaptability of video calls to the available radio resources, the resources freed from rate-adaptive high-quality video calls by service degradation can be further used to prioritize handoff calls. With the proposed resource reservation and handoff priority scheme, the dynamic properties of the system can be closely captured and a better grade of service (GoS) in terms of new call blocking and handoff call dropping probabilities(rates) can be achieved compared to other schemes in literature. Numerical results are presented to show the improvement of the GoS performance and the efficient utilization of the radio resources

Measurement-based Admission Control for Real-Time Traffic in IEEE 802.16 Wireless Metropolitan Area Network

To support real-time applications, we present a Measurement-based Admission Control (MBAC) scheme with Modified Largest Weighted Delay First (M-LWDF) scheduling algorithm. The objective of the admission control scheme is to admit new real-time application call into the system without jeopardizing the maximum average packet delay bound. Measured values of the average packet delay from the network are used for the admission decision. As long as a new call can obtain the requested service and the packet delay of existing calls are not risked by admitting it, the new call will be accepted into the network. In addition, M-LWDF scheduling algorithm is introduced to efficiently allocate network resource. Simulation results show that the proposed MBAC scheme maintains good packet delay bound

Final report on the evaluation of RRM/CRRM algorithms

Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin

Opportunistic scheduling algorithms in downlink centralized wireless networks.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.As wireless spectrum efficiency is becoming increasingly important with the growing demands for wideband wireless service scheduling algorithm plays an important role in the design of advanced wireless networks. Opportunistic scheduling algorithms for wireless communication networks under different QoS constraints have gained popularity in recent years since they have potentials of achieving higher system performance. In this dissertation firstly we formulate the framework of opportunistic scheduling algorithms. Then we propose three new opportunistic scheduling schemes under different QoS criteria and situations (single channel or multiple channel). 1. Temporal fairness opportunistic scheduling algorithm in the short term. We replicate the temporal fairness opportunistic scheduling algorithm in the long term. From simulation results we find that this algorithm improves the system performance and complies with the temporal fairness constraint in the long term. However, the disadvantage of this algorithm is that it is unfair from the beginning of simulation to 10000 time slot on system resource (time slots) allocation - we say it is unfair in the short term. With such a scheme, it is possible that some users with bad channel conditions would starve for a long time (more than a few seconds) , which is undesirable to certain users (say, real-time users). So we propose the new scheme called temporal fairness opportunistic scheduling algorithm in the short term to satisfy users ' requirements of system resource in both short term and long term. Our simulation results show that the new scheme performs well with respect to both temporal fairness constraint and system performance improvement. 2. Delay-concerned opportunistic scheduling algorithm. While most work has been done on opportunistic scheduling algorithm under fairness constraints on user level, we consider users' packet delay in opportunistic scheduling. Firstly we examine the packet delay performance under the long term temporal fairness opportunistic scheduling (TFOL) algorithm. We also simulate the earliest deadline-first (EDF) scheduling algorithm in the wireless environment. We find that the disadvantage of opportunistic scheduling algorithm is that it is unfair in packet delay distribution because it results in a bias for users with good channel conditions in packet delay to improve system performance. Under EDF algorithm, packet delay of users with different channel conditions is almost the same but the problem is that it is worse than the opportunistic scheduling algorithm. So we propose another new scheme which considers both users' channel conditions and packet delay. Simulation results show that the new scheme works well with respect to both system performance improvement and the balance of packet delay distribution. 3. Utilitarian fairness scheduling algorithm in multiple wireless channel networks. Existing studies have so far focused on the design of scheduling algorithm in the single wireless communication network under the fairness constraint. A common assumption of existing designs is that only a single user can access the channel at a given time slot. However, spread spectrum techniques are increasingly being deployed to allow multiple data users to transmit simultaneously on a relatively small number of separate high-rate channels. Not much work has been done on the scheduling algorithm in the multiple wireless channel networks. Furthermore in wire-line network, when a certain amount of resource is assigned to a user, it guarantees that the user gets some amount of performance, but in wireless network this point is different because channel conditions are different among users. Hence, in wireless channel the user's performance does not directly depend on its allocation of system resource. Finally the opportunistic scheduling mechanism for wireless communication networks is gaining popularity because it utilizes the "multi-user diversity" to maximize the system performance. So, considering these three points in the fourth section, we propose utilitarian fairness scheduling algorithm in multiple wireless channel networks. Utilitarian fairness is to guarantee that every user can get its performance requirement which is pre-defined. The proposed criterion fits in with wireless networks. We also use the opportunistic scheduling mechanism to maximize system performance under the utilitarian fairness constraint. Simulation results show that the new scheme works well in both utilitarian fairness and utilitarian efficiency of system resource in the multiple wireless channel situation

Fuzzy Assisted Handoff Algorithm for Micro and Macro Cellular System

Handoff is an essential part of any Mobile Communication Network. Efficient handoff algorithms provide cost-effective way for enhancing the capacity and QOS of cellular system. The work reported here in presents multi-criteria based hard handoff algorithm for micro and macro-cellular architecture. Fuzzy technique has been used as optimization engine. The fuzzy handoff algorithm based on Received Signal Strength (RSS), absolute threshold value, hysteresis level, slope ratios and speed of Mobile Terminal (MT) have been previously developed for conventional cellular networks. In this work the handoff algorithm has been improved by considering two new parameter, signalling delay and angle of motion of MT along with velocity as our input criteria. Two fuzzy models named Mamdani and Sugeno have been used for processing the input criteria. Further, ANFIS has also been used to tune the Sugeno model for parameter adjustment. The proposed fuzzy inference scheme uses triangular and trapezoidal membership function for fuzzification. The types of defuzzification method used are centriod and weighted average formula for Mamdani and Sugeno model respectively. Extensive simulation analysis has been used to validate the proposed technique. The results show that fuzzy is a viable option for handoff

Comparison of vertical handover decision-based techniques in heterogeneous networks

Industry leaders are currently setting out standards for 5G Networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature because no single network type is capable of optimally meeting all the rapid changes in customer demands. Heterogeneous networks are typically characterized by some network architecture, base stations of varying transmission power, transmission solutions and the deployment of a mix of technologies (multiple radio access technologies). In heterogeneous networks, the processes involved when a mobile node successfully switches from one radio access technology to the other for the purpose of quality of service continuity is termed vertical handover or vertical handoff. Active calls that get dropped, or cases where there is discontinuity of service experienced by mobile users can be attributed to the phenomenon of delayed handover or an outright case of an unsuccessful handover procedure. This dissertation analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using the OMNeT++ discrete event simulator. The loose coupling type network architecture is adopted and results of the simulation are analysed and compared for the two major categories of handover basis; multiple and single criteria based handover methods. The key performance indices from the simulations showed better overall throughput, better call dropped rate and shorter handover time duration for the multiple criteria based decision method compared to the single criteria based technique. This work also touches on current trends, challenges in area of seamless handover and initiatives for future Networks (Next Generation Heterogeneous Networks)

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

SCHEDULING IN PACKET SWITCHED CELLULAR WIRELESS SYSTEMS

In cellular wireless networks where users have independent fading channels, throughput for delay tolerant applications has been greatly increased on the downlink by using opportunistic schedulers at the base station. These schedulers exploit the multiuser diversity inherent in cellular systems. An interesting question is how opportunistic schedulers will provide Quality of Service(QoS) guarantees for a mix of data traffic and traffic from delay-sensitive multimedia applications. In the first part of this dissertation, we completely characterize the scheduled rate, delay and packet service times experienced by mobile users in a packet switched cellular wireless system in terms of a configurable base station scheduler metric. The metric used has a general form, combining an estimate of a mobile user's channel quality with the scheduling delay experienced by the user. In addition to quantifying the scheduler performance, our analysis highlights the inherent trade-off between system throughput and the delay experienced by mobile users with opportunistic scheduling. We also use this analysis to study the effect of prioritized voice users on data users in a cellular wireless system with delay constrained opportunistic scheduling. Our statistical analysis of the forward link is validated by extensive simulations of a system architecture based on the CDMA 1xEV-DO system. The increase in data traffic from mobiles to the base station has led to a growing interest in a scheduled reverse link in the 1xEV-DO system. We address the reverse link scheduling problem in a multi-cell scenario with interference constraints both within and outside the cell. This approach leads to a co-operative scheduling algorithm where each base station in a cellular network maximizes the sum of mobile data transmission rates subject to linear constraints on (1) the maximum received power for individual mobiles(2) the total interference caused by scheduled mobiles to (a) traffic and control channels of other mobiles within the cell and (b) mobiles in neighboring cells. Simulations of the reverse link structure based on the 1xEV-D0 system highlight the distinct advantages of this algorithm in ensuring predictable inter-cell interference and higher aggregate cell throughputs