A New CAC Policy Based on Traffic Characterization in Cellular Networks

The Call Admission Control (CAC) method presented in this paper is based on the statistical properties of the network’s traffic variables. It probabilistically estimates the time until the release of a seized channel: the admission control depends on the computed mean remaining time averaged along all channels at a specific instant and on a time threshold. The policy produces a smooth transition between the QoS metrics, giving the operator the freedom to design the network at the desired QoS point. Another valuable property is that the algorithm is straightforward and fed only by simple teletraffic metrics: distribution and the first and second moments of Channel Holding Time (CHT). Simplicity is important for a CAC method because decisions for accepting or rejecting calls must be computed quickly and frequently.Peer Reviewe

Mobile Networks

The growth in the use of mobile networks has come mainly with the third generation systems and voice traffic. With the current third generation and the arrival of the 4G, the number of mobile users in the world will exceed the number of landlines users. Audio and video streaming have had a significant increase, parallel to the requirements of bandwidth and quality of service demanded by those applications. Mobile networks require that the applications and protocols that have worked successfully in fixed networks can be used with the same level of quality in mobile scenarios. Until the third generation of mobile networks, the need to ensure reliable handovers was still an important issue. On the eve of a new generation of access networks (4G) and increased connectivity between networks of different characteristics commonly called hybrid (satellite, ad-hoc, sensors, wired, WIMAX, LAN, etc.), it is necessary to transfer mechanisms of mobility to future generations of networks. In order to achieve this, it is essential to carry out a comprehensive evaluation of the performance of current protocols and the diverse topologies to suit the new mobility conditions

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

Resource allocation in cellular CDMA systems with cross- layer Optimization

Ph.DDOCTOR OF PHILOSOPH

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments

Handover management strategies in LTE-advanced heterogeneous networks.

Doctoral Degree. University of KwaZulu-Natal, Durban.Meeting the increasing demand for data due to the proliferation of high-specification mobile devices in the cellular systems has led to the improvement of the Long Term Evolution (LTE) framework to the LTE-Advanced systems. Different aspects such as Massive Multiple-Input Multiple Output (MIMO), Orthogonal Frequency Division Multiple Access (OFDMA), heterogeneous networks and Carrier Aggregation have been considered in the LTE-Advanced to improve the performance of the system. The small cells like the femtocells and the relays play a significant role in increasing the coverage and the capacity of the mobile cellular networks in LTE-Advanced (LTE-A) heterogeneous network. However, the user equipment (UE) are faced with the frequent handover problems in the heterogeneous systems than the homogeneous systems due to the users‟ mobility and densely populated cells. The objective of this research work is to analyse the handover performance in the current LTE/LTE-A network and to propose various handover management strategies to handle the frequent handover problems in the LTE-Advance heterogeneous networks. To achieve this, an event driven simulator using C# was developed based on the 3GPP LTE/LTE-A standard to evaluate the proposed strategies. To start with, admission control which is a major requirement during the handover initiation stage is discussed and this research work has therefore proposed a channel borrowing admission control scheme for the LTE-A networks. With this scheme in place, resources are better utilized and more calls are accepted than in the conventional schemes where the channel borrowing is not applied. Also proposed is an enhanced strategy for the handover management in two-tier femtocell-macrocell networks. The proposed strategy takes into consideration the speed of user and other parameters in other to effectively reduce the frequent and unnecessary handovers, and as well as the ratio of target femtocells in the system. We also consider scenarios such as the one that dominate the future networks where femtocells will be densely populated to handle very heavy traffic. To achieve this, a Call Admission Control (CAC)-based handover management strategy is proposed to manage the handover in dense femtocell-macrocell integration in the LTE-A network. The handover probability, the handover call dropping probability and the call blocking probability are reduced considerably with the proposed strategy. Finally, the handover management for the mobile relays in a moving vehicle is considered (using train as a case study). We propose a group handover strategy where the Mobile Relay Node (MRN) is integrated with a special mobile device called “mdev” to prepare the group information prior to the handover time. This is done to prepare the UE‟s group information and services for timely handover due to the speed of the train. This strategy reduces the number of handovers and the call dropping probability in the moving vehicle.Publications and conferences listed on page iv-v

Improving relay based cellular networks performance in highly user congested and emergency situations

PhDRelay based cellular networks (RBCNs) are the technologies that incorporate multi-hop communication into traditional cellular networks. A RBCN can potentially support higher data rates, more stable radio coverage and more dynamic services. In reality, RBCNs still suffer from performance degradation in terms of high user congestion, base station failure and overloading in emergency situations. The focus of this thesis is to explore the potential to improve IEEE802.16j supported RBCN performance in user congestion and emergency situations using adjustments to the RF layer (by antenna adjustments or extensions using multi-hop) and cooperative adjustment algorithms, e.g. based on controlling frequency allocation centrally and using distributed approaches. The first part of this thesis designs and validates network reconfiguration algorithms for RBCN, including a cooperative antenna power control algorithm and a heuristic antenna tilting algorithm. The second part of this thesis investigates centralized and distributed dynamic frequency allocation for higher RBCN frequency efficiency, network resilience, and computation simplicity. It is demonstrated that these benefits mitigate user congestion and base station failure problems significantly. Additionally, interweaving coordinated dynamic frequency allocation and antenna tilting is investigated in order to obtain the benefits of both actions. The third part of this thesis incorporates Delay Tolerate Networking (DTN) technology into RBCN to let users self-organize to connect to functional base station through multi-hops supported by other users. Through the use of DTN, RBCN coverage and performance are improved. This thesis explores the augmentation of DTN routing protocols to let more un-covered users connect to base stations and improve network load balancin

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

Contribución a la gestión de recursos en redes de acceso celulares. Modelos analíticos y evaluación de prestaciones

Desde sus inicios hace algo más de veinte años, la telefonía móvil celular ha experimentado un enorme crecimiento e importantes transformaciones y, todavía hoy, se encuentra en una fase de cambio y crecimiento. A diferencia de lo que ocurre en una red fija, en la que la enorme capacidad de transmisión que aporta la fibra óptica relega a un segundo plano la gestión eficiente de esta capacidad, el medio de transmisión en la interfaz radio de las redes móviles es un bien escaso. Aunque los avances tecnológicos permiten ampliar el rango de frecuencias utilizables y conseguir una mayor eficiencia espectral, el aumento del tráfico junto a la aparición de nuevos usos y servicios hacen que la gestión eficiente de los recursos radio continúe siendo de gran importancia. El control de admisión (CA) es un mecanismo importante para la gestión de los recursos radio. Aunque el estudio de las técnicas de CA recibió un impulso importante en el contexto de la red digital de servicios Integrados de banda ancha (RDSI-BA), las redes móviles tienen ciertas características específicas que hacen que el CA sea más complejo: las ya referidas limitaciones del espectro, las características propias del canal radio que resultan en un comportamiento aleatorio y, sobre todo, la movilidad de los terminales. En este trabajo se estudia el CA en relación con la movilidad: para admitir una nueva sesión se deben tener ciertas garantías -al menos en un sentido estadístico- de que la red tendrá recursos suficientes para mantener, con la calidad de servicio (QoS) requerida, tanto esa nueva sesión como las ya existentes en ese momento, y ello teniendo en cuenta que durante la vida de una sesión, ésta -el terminal- puede cambiar de área de cobertura (célula), y los recursos deberán estar disponibles allí donde vaya el terminal. Aunque el interés por este tema no es nuevo, continúa vigente, pues para atender la creciente demanda de capacidad, una de las formas pasa por reducir el tamaño de las células....Pla Boscà, V. (2005). Contribución a la gestión de recursos en redes de acceso celulares. Modelos analíticos y evaluación de prestaciones [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/2001Palanci