Capacity modeling for admission control in WiMAX networks

WiMAX networks support QoS reservation of resources by allowing a new flow to apply for admittance in the system. Thus, there is a need for an accurate estimation of the available capacity to be shared by incoming connections. Admission control algorithm must ensure that, when a new QoS resource reservation is accepted, reservations already present in the system continue having their QoS guarantees honored. Its efficiency is then expressed in terms of accuracy and computational complexity which is the focus of the work in this thesis. Different approaches are presented to compute the aggregated allocated capacity in WiMAX networks and, based on their limitations, the E-Diophantine solution has been proposed. The mathematical foundations for the designed approach are provided along with the performance improvements to be expected, both in accuracy and computational terms, as compared to three alternatives of increasing complexity. The different solutions considered are validated and evaluated with OPNET’s WiMAX simulator in a realistic scenario. Finally, the multi-hop relay case is analyzed: a capacity model description is provided together with a conjectured reuse of the admission control algorithm designed

Cross-layer RaCM design for vertically integrated wireless networks

Includes bibliographical references (p. 70-74).Wireless local and metropolitan area network (WLAN/WMAN) technologies, more specifically IEEE 802.11 (or wireless fidelity, WiFi) and IEEE 802.16 (or wireless interoperability for microwave access, WiMAX), are well-suited to enterprise networking since wireless offers the advantages of rapid deployment in places that are difficult to wire. However, these networking standards are relatively young with respect to their traditional mature high-speed low-latency fixed-line networking counterparts. It is more challenging for the network provider to supply the necessary quality of service (QoS) to support the variety of existing multimedia services over wireless technology. Wireless communication is also unreliable in nature, making the provisioning of agreed QoS even more challenging. Considering the advantages and disadvantages, wireless networks prove well-suited to connecting rural areas to the Internet or as a networking solution for areas that are difficult to wire. The focus of this study specifically pertains to IEEE 802.16 and the part it plays in an IEEE vertically integrated wireless Internet (WIN): IEEE 802.16 is a wireless broadband backhaul technology, capable of connecting local area networks (LANs), wireless or fixed-line, to the Internet via a high-speed fixed-line link

Quality-Oriented Mobility Management for Multimedia Content Delivery to Mobile Users

The heterogeneous wireless networking environment determined by the latest developments in wireless access technologies promises a high level of communication resources for mobile computational devices. Although the communication resources provided, especially referring to bandwidth, enable multimedia streaming to mobile users, maintaining a high user perceived quality is still a challenging task. The main factors which affect quality in multimedia streaming over wireless networks are mainly the error-prone nature of the wireless channels and the user mobility. These factors determine a high level of dynamics of wireless communication resources, namely variations in throughput and packet loss as well as network availability and delays in delivering the data packets. Under these conditions maintaining a high level of quality, as perceived by the user, requires a quality oriented mobility management scheme. Consequently we propose the Smooth Adaptive Soft-Handover Algorithm, a novel quality oriented handover management scheme which unlike other similar solutions, smoothly transfer the data traffic from one network to another using multiple simultaneous connections. To estimate the capacity of each connection the novel Quality of Multimedia Streaming (QMS) metric is proposed. The QMS metric aims at offering maximum flexibility and efficiency allowing the applications to fine tune the behavior of the handover algorithm. The current simulation-based performance evaluation clearly shows the better performance of the proposed Smooth Adaptive Soft-Handover Algorithm as compared with other handover solutions. The evaluation was performed in various scenarios including multiple mobile hosts performing handover simultaneously, wireless networks with variable overlapping areas, and various network congestion levels

Spectrum Sharing Methods in Coexisting Wireless Networks

Radio spectrum, the fundamental basis for wireless communication, is a finite resource. The development of the expanding range of radio based devices and services in recent years makes the spectrum scarce and hence more costly under the paradigm of extensive regulation for licensing. However, with mature technologies and with their continuous improvements it becomes apparent that tight licensing might no longer be required for all wireless services. This is from where the concept of utilizing the unlicensed bands for wireless communication originates. As a promising step to reduce the substantial cost for radio spectrum, different wireless technology based networks are being deployed to operate in the same spectrum bands, particularly in the unlicensed bands, resulting in coexistence. However, uncoordinated coexistence often leads to cases where collocated wireless systems experience heavy mutual interference. Hence, the development of spectrum sharing rules to mitigate the interference among wireless systems is a significant challenge considering the uncoordinated, heterogeneous systems. The requirement of spectrum sharing rules is tremendously increasing on the one hand to fulfill the current and future demand for wireless communication by the users, and on the other hand, to utilize the spectrum efficiently. In this thesis, contributions are provided towards dynamic and cognitive spectrum sharing with focus on the medium access control (MAC) layer, for uncoordinated scenarios of homogeneous and heterogeneous wireless networks, in a micro scale level, highlighting the QoS support for the applications. This thesis proposes a generic and novel spectrum sharing method based on a hypothesis: The regular channel occupation by one system can support other systems to predict the spectrum opportunities reliably. These opportunities then can be utilized efficiently, resulting in a fair spectrum sharing as well as an improving aggregated performance compared to the case without having special treatment. The developed method, denoted as Regular Channel Access (RCA), is modeled for systems specified by the wireless local resp. metropolitan area network standards IEEE 802.11 resp. 802.16. In the modeling, both systems are explored according to their respective centrally controlled channel access mechanisms and the adapted models are evaluated through simulation and results analysis. The conceptual model of spectrum sharing based on the distributed channel access mechanism of the IEEE 802.11 system is provided as well. To make the RCA method adaptive, the following enabling techniques are developed and integrated in the design: a RSS-based (Received Signal Strength based) detection method for measuring the channel occupation, a pattern recognition based algorithm for system identification, statistical knowledge based estimation for traffic demand estimation and an inference engine for reconfiguration of resource allocation as a response to traffic dynamics. The advantage of the RCA method is demonstrated, in which each competing collocated system is configured to have a resource allocation based on the estimated traffic demand of the systems. The simulation and the analysis of the results show a significant improvement in aggregated throughput, mean delay and packet loss ratio, compared to the case where legacy wireless systems coexists. The results from adaptive RCA show its resilience characteristics in case of dynamic traffic. The maximum achievable throughput between collocated IEEE 802.11 systems applying RCA is provided by means of mathematical calculation. The results of this thesis provide the basis for the development of resource allocation methods for future wireless networks particularly emphasized to operate in current unlicensed bands and in future models of the Open Spectrum Alliance

Lightweight mobile and wireless systems: technologies, architectures, and services

1Department of Information and Communication Systems Engineering (ICSE), University of the Aegean, 81100 Mytilene, Greece 2Department of Information Engineering and Computer Science (DISI), University of Trento, 38123 Trento, Italy 3Department of Informatics, Alexander Technological Educational Institute of Thessaloniki, Thessaloniki, 574 00 Macedonia, Greece 4Centre Tecnologic de Telecomunicacions de Catalunya (CTTC), 08860 Barcelona, Spain 5North Carolina State University (NCSU), Raleigh, NC 27695, US

Cross-Layer RaCM Design for Vertically Integrated Wireless Networks

IEEE 802.16 wireless metropolitan area network (WMAN) technology is an improvement on its wireless local area network (WLAN) counterpart, namely IEEE 802.11, in that it provides longer range and higher bandwidth capabilities. More importantly, it specifies a connection-oriented medium access control layer (MAC) and scheduling services to support quality of service (QoS) in IEEE 802.16 networks. However, in the standard, scheduling and connection admission control (CAC) mechanisms are left unspecified, leaving this for network operators to decide. This allows implementers to create market and performance advantages, making it a rich field of research and performance analysis. Typically, researchers studying scheduling and admission control in such wireless networks consider these resource and connection management (RaCM) algorithms in isolation: They investigate (1) schedulers while fixing the admission control processes or using static connection scenarios and (2) admission controllers while fixing the scheduling processes. We hypothesize that there exists an interdependent relationship between RaCM components which is an essential aspect to cross-layer inter-RaCM algorithm design. In order to prove our hypothesis that you cannot consider the scheduler and the CAC in isolation, where it involves the performance of IEEE 802.16 networks, we require a performance model: Analytic modelling is an ideal solution but the system is far too complex. Experimental test beds are expensive, making hardware experimentation another impractical solution. The only other feasible solution is simulation. General simulation environments, such as NS2 and OMNeT++, offer IEEE 802.16 libraries and some degree of development community support. However, for several reasons, as we shall discuss, we developed our own deep simulator – a discrete-event simulation model of an IEEE vertically integrated wireless Internet scenario. In particular, we concentrate our effort on the fixed IEEE 802.16 WMAN (802.16-2004), simulating admission control and scheduling processes exactly. Both the machine model and workload model play an integral part in obtaining useful performance data: Our machine model includes particular MAC and physical layer (PHY) functions of the standard, such as framing, adaptive modulation and coding, fragmentation, and so on, as well as the admission control and scheduling algorithms. For the workload model, we developed a Markov Modulated Arrival Process (MMAP) by combining existing traffic models of different Internet applications, such as VoIP, P2P, etc. Each application is associated with one of the IEEE 802.16 traffic categories (TCs). The MMAP generates both connection– and packet level data, maintaining traffic volume ratios, as reported by previous studies of Internet application traffic volumes. Performance metrics of delay and jitter are calculated per TC connection. This allows a comparison of the quality of experience (QoE) of an individual user for the duration of a connection. At the connection level, we report the blocking probability. By simulating the RaCM with various admission control and scheduling configurations, we were able to show that there is a significant difference in performance when using different CAC and scheduler combinations. Although hardly surprising, it is still proof that one cannot simply consider either in isolation, as is done in various performance studies reported in the literature. This interdependent relationship should be considered when designing complementary admission control and scheduling algorithms

Base Station controlled load balancing with handovers in Mobile WiMAX

Tämän diplomityön päätavoitteena on tutkia, kuinka kuorman tasaus voidaan suorittaa tukiaseman aloitteesta yhteysvastuun vaihdoilla mobiili WiMAX:ssa ja selvittää menetelmän potentiaalia edistää resurssien käyttöä sekä palvelun laatua koko systeemissä. Tavoitteena on myös tutkia alustavasti sitä, miten turvakaistoja voitaisiin varata ns. pelastavalle yhteysvastuun vaihdolle mobiili WiMAX:ssa, kuinka tämä vaikuttaisi kuorman tasaukseen ja kuinka nämä lähestymistavat voitaisiin yhdistää. Diplomityö sisältää koosteen IEEE 802.16e radiorajapintateknologian ja WiMAX Forum liityntäverkkoarkkitehtuurin tärkeimmistä elementeistä kuorman tasauksen ja yhteysvastuun vaihdon suhteen sekä kirjallisuuskatsauksen kuorman tasauksesta, sekä pelastavan yhteysvastuun vaihdon ja liikenteen priorisoinnista. Näiden perusteella suunniteltiin mobiili WiMAX:lle räätälöity resurssien käyttöön perustuva peruskuormantasausalgoritmi. Tämän lisäksi tehtiin muutama alustava ehdotus perusalgoritmia edistävistä menetelmistä. Näihin kuuluivat esimerkiksi kuorman tasauksen laukaisuun tarkoitetun kynnyksen automaattinen säätäminen, useiden kynnysten käyttäminen sekä resurssien varaukseen perustuva laukaisu, missä kuorman tasaus voidaan laukaista turvakaistojen suhteen. Lopuksi perusalgoritmi evaluoitiin staattisessa ympäristössä. Vaikka suoritetut simulaatiot eivät olleet laajamittaisia, perusalgoritmin parametreista ja yleisestä suorituskyvystä saatiin hyödyllistä informaatiota. Vaikka algoritmi suoriutui hyvin simuloidussa ympäristössä, aikaisemmin suunnitelluille edistäville menetelmille todettiin yleisesti ottaen selvä tarve. Tämän diplomityön pitäisi luoda hyvä pohja yhteysvastuun vaihtoon perustuvan kuorman tasauksen edelleen kehittämiselle ja evaluoinnille mobiili WiMAX:ssa. Tutkimuksen perusteella päädyttiin siihen johtopäätökseen, että kuorman tasaus yhteysvastuun vaihdolla voi olla todella tehokas tapa vapauttaa resursseja suurimmassa osassa ympäristöistä, mutta että turvakaistojen käyttöä tulisi silti harkita.The purpose of this thesis is to examine how load balancing with Base Station initiated directed handovers could be conducted in Mobile WiMAX and the potential it has to enhance Resource Utilization and QoS system wide. An additional goal of the thesis is also to conduct preliminary research on how guard bands for rescue handovers could be used in Mobile WiMAX, how this would affect load balancing and how these two approaches could be combined. The thesis includes a background study on the key system aspects of the IEEE 802.16e radio interface technology and WiMAX Forum Access Network Architecture in terms of load balancing and handovers and a literary review on load balancing, and system wide handover and traffic prioritization. Based on the gained knowledge a basic Resource Utilization based load balancing algorithm tailored for Mobile WiMAX is designed. Few preliminary enhancement proposals are also made in terms of e.g. automatic tuning of the triggering threshold, multiple threshold based triggering and Resource Reservation based triggering where load balancing can be triggered in relations to the reserved guard for rescue handovers and higher priority traffic. Finally preliminary evaluation of the basic algorithm in a static environment is conducted. Although the simulations are not extensive, beneficial information is obtained of the basic parameters of the algorithm and of the overall performance of the algorithm. Even though the basic algorithm performed well in the simulated environment, a clear need was recognized for the enhancements introduced earlier. All in all this thesis should form a very good basis for the further development and evaluation of handover based load balancing in Mobile WiMAX. Based on the study it was concluded that load balancing with directed handovers can be a very efficient way to release resources in most cases but the use of rescue handover guard bands should still be considered

Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks

In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users’ needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications