no / This paper is focused on the design of an adaptive Connection Admission Control (CAC) algorithm for a Universal Mobile Telecommunication System (UMTS) based satellite system with variable link capacity. The main feature of the proposed algorithm is to maximize the resource utilization by adapting to the link conditions and the antenna gain of the users. The link quality of the user may vary depending on the weather condition, user mobility and any other propagation factors. The algorithm is compared against a non-adaptive admission control algorithm under different test cases. The proposed CAC algorithm is simulated using MATLAB and the performance results are obtained for a mix of multimedia traffic classes such as video streaming, web browsing, netted voice and email. The simulation results indicate a higher system performance in terms of the blocking ratio and the number of admitted connections.

Made available in DSpace on 2016-04-26T18:16:04Z (GMT). No. of bitstreams: 1 Renata Sertorio Fernandes.pdf: 2532547 bytes, checksum: 594e58a0c595ac136656cf253d17fd85 (MD5) Previous issue date: 2006-10-04 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This master degree main objective searched to evaluate the communication strategies of the marks of the companies of mobile telecommunication Tim and Vivo through theirs main manifestations, being considered as being exactly: names, logotypes, logomarks and slogans, these in turn, presented in the media printed. The objects of the analysis are announcements published in media printed, divulged in the two main ones reviewed weekly Brazilians: Veja e Época. Two of them, institutional advertisings (one of each company) are studied at great length, excessively they will be briefly analyzed. The mark and its manifestations are constituted by complex processes of meaning and directly are related to the language and the communication between company and consumers. The semiotics offers ways to investigate the existing potential of communication in the elements that constitute the representation of the mark, as well as its presentation through the different manifestations of marketing. The intention is to investigate the effect of the potential generated by the announcement advertising executive in general, and mainly for the mark through its main manifestations, in more specific way. From there, we ask: what strategies the companies promote to create and to keep this image to the consumers, by means of communications contracts established in the relation between sender and receiver / Esta dissertação de mestrado avalia as estratégias comunicativas das marcas das empresas de telecomunicação móvel Tim e Vivo em suas principais manifestações na mídia impressa: nome, logotipos, logomarcas e slogan. Os objetos da análise são anúncios publicados em mídia impressa, divulgados nas duas principais revistas semanais brasileiras: Veja e Época. Serão analisados em detalhe dois anúncios institucionais (um de cada empresa), entre outros, em que a análise incidirá de modo menos pontual. A marca e suas manifestações são constituídas por complexos processos de significação e estão diretamente relacionadas à linguagem e à comunicação entre empresa e consumidores. A semiótica peirceana oferece o enfoque metodológico para investigarmos o potencial comunicativo existente nos elementos que constituem a representação da marca, assim como sua apresentação através das diferentes manifestações de marketing. Trata-se de investigar os efeitos de sentido gerados pelos anúncios publicitários, e principalmente pela marca em suas principais manifestações. A partir daí, perguntamos: que estratégias as empresas promovem para criar e manter sua imagem perante os consumidores, por meio dos contratos comunicativos estabelecidos na relação entre emissor e receptor

Research Doctorate - Doctor of Philosophy (PhD) / The Radio Access Network (RAN) accounts for the major proportion of the UMTS system operating cost. Transmission from radio base station sites contributes a larger part of the RAN operating costs. Selection of suitable transport technologies and proper allocation of network resources are vital from an operator cost optimisation and the Quality of Experience (QoE) points of view. This thesis extensively investigated the performance of a RAN to support multimedia traffic on a HSDPA air interface. Transport network layer of a future RAN could be based on a number of transport protocols such as ATM, IP and Ethernet. With the increasing traffic volume and diversity the efficiencies of IP and Ethernet based RAN could increases significantly due to the use of larger payloads and simpler resource allocation techniques. Also, on IP and Ethernet based links relatively fewer overhead bits are transmitted compared to an ATM based link. Both the IP and Ethernet based links appear to perform better under heavy traffic load conditions. An IP based link could perform better than an Ethernet based link when an IP header compression technique is used. An Ethernet based link is an alternative transport technique for the UTRAN transport network due to its flexibility, economy and bandwidth efficiency. The HSDPA (High Speed Downlink Packet Access) is considered to be one of the initial evolutionary steps to enhance the data rate, and QoS of downlink data and multimedia services for the evolved UMTS network. It can provide high data rate up to 28.8 Mbps on the downlink shared channel using the packet access technique. A HSDPA network can dynamically adjust a connection data rate to match radio conditions to ensure the highest possible data rate for different type of traffic. Inappropriate RAN capacity allocation could lead to low radio resource or RAN resource utilizations. In this thesis, a Markov chain based analytical model has been developed to study the interaction between the air interface and the RAN for a HSDPA network. The analytical model was used to study interactions of RAN transport protocols, flow control techniques and the air interface transmission conditions. Further a simulation model was developed to investigate the relationship between the HSDPA air interface and its RAN parameters. Another important issue in the HSDPA network design is the scheduling algorithm used at the Node-B. A scheduling algorithm plays a key role in allocating a RAN’s network resources. Impacts of scheduling algorithms are studied in this work using a simulation model. Based on the study of the HSDPA air interface and its RAN parameter interactions this work has developed an adaptive resource management algorithm, which uses the measured air interface information to allocate the corresponding connection data rate on the Iub link. The developed algorithm reduces RAN resource requirements while increasing the air interface resource utilization and QoS of connections.

Orientador: Yuzo Iano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-11T08:32:05Z (GMT). No. of bitstreams: 1 Caetano_DiogoGara_M.pdf: 6545832 bytes, checksum: d1bdaa84e6d542ee7380aadc0423d44b (MD5) Previous issue date: 2007 / Resumo: O objetivo deste trabalbo foi estudar o desempenho de codificadores de canal com decodificação iterativa e diferentes esquemas de concatenação de codificadores para sistemas de TV digital móveis tais como: DVB-H e ISDB- T. Contribui-se com uma proposta de concatenação de codificadores para sistemas COFDM avaliada através de implementação computacional. Os resultados gerados nesta pesquisa demonstram ganhos de codificação em relação a sistemas padronizados de TV digital. Estes ganhos de codificação são referentes à utilização de codificadores BCH concatenados com codificadores Turbo e LDPC. As simulações ocorreram em canais com multipercurso, distribuição Rayleigh, ruído gaussiano branco e outros canais típicos de radiodifusão utilizados no Brasil para testes de TV digital / Abstract: The aim of this work is to study the performance of channel encoders with iterative decoder: and also different encoders concatenation schemes to mobile digital television standards ;; DVB-H and ISDB-T. The contribution of this work is a proposal of encoder concatenatic scheme for COFDM systems evaluated through software implementation. The final results I this work presents overall coding gain with respect to digital TV standards. The gain presenb in this work is regarded to the concatenation of BCH encoders with Turbo and LDPC encodel The simulations were performed over multipath, Rayleigh, A WGN and typical Brazili: broadcast channels used for digital TV trials / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

In this thesis we address the problem of providing end-to-end quality of service (QoS) to real-time and data connections in a third generation (3G) cellular network based on the Universal Mobile Telecommunication System (UMTS) standard. Data applications usually use TCP (Transmission Control Protocol) and the QoS is a minimum guaranteed mean throughput. For this one first needs to compute the throughput of a TCP connection sending its traffic through the UMTS network (possibly also through the wired part of the Internet). Thus we obtain closed form expressions for a TCP throughput in a UMTS environment. For downloading data at a mobile terminal, the packets of each TCP connection are stored in separate queues at the base station (node B). These are fragmented into Protocol Data Units (PDU). The link layer uses ARQ (Automatic Repeat Request). Thus there can be significant random transmission/queueing delays of TCP packets at the node B. On the other hand the link may not be fully utilized due to the delays of the TCP packets in the rest of the network. In such a scenario the existing models of TCP may not be sufficient. Thus we provide new approximate models for TCP and also obtain new closed form expressions of mean window size. Using these we obtain the throughput of a TCP connection for the scenario where the queueing delays are non-negligible compared to the overall Round Trip Time (RTT) and also the link utilization is less than one. Our approximate models can be useful not only in the UMTS context but also else where. In the second half of the thesis, we use these approximate models of TCP to provide minimum mean throughput to data connections in UMTS. We also consider real-time applications such as voice and video. These can tolerate a little packet loss (~1%) but require an upper Bound on the delay and delay jitter (≤ 150 ms). Thus if the network provides a constant bandwidth and the received SINR is above a specified threshold ( with a certain probability), QoS for the real-time traffic will be satisfied. The 3G cellular systems are interference limited. Thus wise allocation of power is critical in these systems. Hence we consider the problem of providing end-to-end QoS to different users along with the minimization of the downlink power allocation.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710¿1880 MHz), PCS (1850¿1990 MHz), UMTS (1920¿2170 MHz), WLAN (2400¿2500 MHz and 5000 ¿ 5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated. / UK Engineering and Physical Sciences Research Council (EPSRC)

行動通訊產業隨著日韓、西歐、亞太、北美和中國大陸陸續啟動B3G行動通訊的商業運轉，全球行動通訊服務和技術的發展進入嶄新的紀元，傳輸速度的大幅提昇，行動通訊服務商積極推動多媒體簡訊、行動音樂、行動影音、行動遊戲、行動訊息和企業數據應用等服務，寄望透過多元應用服務及創新經營模式提升顧客價值與獲利能力；另一方面，行動廣播、無線寬頻、網路電話等新興技術匯流至行動通訊領域，不僅催生行動通訊技術朝IMS和All-IP網路發展，並促使行動通訊服務商在行銷、服務、帳務和網路等層面朝向行動和固網雙網融合與數位匯流的願景佈局。在政府開放營運執照後，行動通訊服務業者皆投入巨額資金經營，期藉由傳輸速度快的優勢，可以發展出更多的行動加值服務內容，以期在語音營收成長飽和之下，創造另一營收來源；但是，行動通訊產業在大規模的投資下，未產生預期的效益，產業間渴望能讓產業創新的殺手級應用(Killer Application)，引導台灣行動通訊產業找到高獲利的藍海市場。本研究期望，透過分析行動通訊產業的價值供應鏈在營運發展過程中碰到的困境，及其面對創新的技術與商業模式如何評估與發展，在面對市場與技術的不確定性下，分析出產業價值鏈的廠商面對創新的競爭所必須思考的關鍵因素，提供台灣行動通訊業者經營業務的一些建議，以便協助台灣在行動通訊市場的產業創新能力，提昇業者對行動加值服務應用與行動通訊設備市場的創新決策正確性，以期推動台灣電信市場的蓬勃發展。 本研究以克雷頓‧克里斯汀生(Clayton M. Christensen)所提出的對突破性科技的看法，利用提出的破壞性創新及資源、流程與價值理論分析模式；以傑佛瑞‧墨爾(Geoffrey A. Moore)提出的技術採用生命周期(Technology Adoption Life Cycle)模式分析五種消費者,探討行動通訊產業如何分析電信業創新的鴻溝,如何邁向康莊大道。在訪談台灣行動通訊產業價值鏈的五家廠商中，就創新的驅動方式、創新的風險評估、如何管理創新與當前產業創新所面臨的問題與解決方案等議題，做充分意見交流，再經由文獻與理論探討、行動通訊產業市場的趨勢與分析、行動通訊產業技術的趨勢與分析，與台灣行動通訊產業個案分析後，最後作成結論與建議，並提出後續研究課題的建議。 經研究與分析台灣行動通訊產業的創新模式，了解行動通訊產業價值鏈創新發展過程中，所碰到過的困境及其後續改善之方案，並對台灣政府與行動通訊業者提出以下的結論與建議： 壹、結論: 一、技術驅動的創新重視程度通常是愈接近產業價值鏈的上游愈高；市場驅動的創新重視程度通常是愈接近產業價值鏈的下游愈高；突破性的創新可能發生於產業鏈中的每一環節。 二、突破性的創新需要同時處理產業鏈中的市場風險與技術風險，兩大天險必須要降低其中一項才容易創新成功；兩種風險都與財務因素息息相關。 三、創新常常來自邊陲，發展創新的組織需要不同於主流產品的績效目標與財務支援。 四、政府正確的產業監理政策常常是行動通訊產業的發展要件；產業生態系的活躍與否常取決於政府對產業的科技政策走向與合宜的法律。 貳、建議： 一、 政府方面: 1.基地台網路: 協調業者以共構的方式及加速整合寬頻接取技術以解決網路品質的問題。 2.技術平台與內容產業:制定適當的產業政策，以協助整合產業上中下游業者，以帶動產業研究與發展。 二、行動通訊營運商: 1.投入研究行動通訊的消費者行為: 行動通訊服務業者應投入資源研究本地消費者行為，以便洞悉創新的殺手級應用。 2.內容與服務平台:積極扮演內容服務開發與技術平台整合角色，以帶動內容產業的蓬勃發展創造「皆贏」的局面。 3.合宜費率: 根據消費者所獲得的行動通訊價值與成本動因計費。 / The mobile telecommunication industry along with Japan, Korea, Western Europe, Asia Pacific, North America and mainland China, it starts the B3G mobile telecommunications commercial subscriber service launch, the global mobile telecommunications service and the technology development enter a brand-new era. Following by the transmission speed of infrastructure network is improved rapidly, the mobile telecommunications service providers are positively to promote the multimedia services, mobile music, mobile video streaming, mobile gaming, mobile messaging and enterprise data service applications. We hope the penetration multi-dimensional applications to serve and innovate the business model to promote the customer value and profit ability. On the other hand, those emerging technologies, such as mobile broadcasting, wireless broadband, IP network telephony are converged to mobile telecommunications domain. Not only expedites the mobile telecommunications technology to IMS and the All-IP network development, but also urges the mobile telecommunications service provider in all aspects of marketing, service, billing and network infrastructures migrate to the wireless and wire-line network fusion and the vision of digital convergences. After the restriction of operation licenses released by government, the mobile telecommunications service providers invest a large amount of funds on new business development. Relying on the quick transmission speed superiority, may develop more mobile value-added service content. We expect to have more another revenue increasing objects while the voice-only service revenue mutuality. Nevertheless, the mobile telecommunications industry under the large-scale investment has not had the anticipated benefit, the industry hope we can let the industrial innovation to produce the “Killer Applications” that guides the Taiwan mobile telecommunications industry to find the high profitable blue sea market. The research expects that, by the penetration analysis mobile telecommunications industry value supply chain the difficult position which bumps into in transport business developing process, and how faces the innovative technology and the business model appraised and development, is facing the indefinite market and the technology, analyzes the industrial innovation the competitive strategy and the key success factors, provides Taiwan the mobile telecommunications entrepreneur to manage the business strategies and suggestions. In order to assist Taiwan in mobile telecommunications market industrial innovation ability, promotes the entrepreneur to the value-added service field and motivates the communication equipment market innovative decision-making accuracy, impels the Taiwan telecommunications market by the time the vigorous development. The research is based on the viewpoint of disruptive technology issued by Clayton M. Christensen to leverage the analysis model of disruptive innovations and resource, process and value theorem; analyzes the five types of consumers by Technology Adoption Life Cycle model issued by Geoffrey A. Moore to investigate how telecommunications industry analyzes the chasm of innovations and how to adopt the early majority of market. In the interview of 5 enterprises across Taiwan mobile telecommunications industrial value chain, we make good communications and share opinions about all the issues of the method of innovation driven, risk assessment on innovations, how to manage innovations, to face problems and resolutions on industrial innovation. By leveraging the entire reference thesis, issued papers and theorem, the trends of market, analysis of market, and technology issues in the mobile telecommunications industry, collaborate with case study of Taiwan mobile telecommunications industry to study and make comments and conclusions on this topic. Also, we provide the suggestions on governing policies, industry strategies, and further research direction. A.Conclusions: 1.Nearby the front end of industry value chain, technology driven innovations methodology is highly enhanced and focused; Nearby the rear end of industry value chain, market driven innovations methodology is highly enhanced and focused. Disruptive technology is possibly occurred in any section of industry value chain. 2.The two major risk factors, market and technology, need to be handled together while manage disruptive innovations. It would make success to assess at least one of two major risk factors and they are all related to financial variables. 3.Innovation is always occurred in the border of organizations which is supported by key performance indicator setting of different major products and necessary financial funding. 4.The mobile telecommunications industry grows by major inferences of correct governing policies and proper regulations issued by technology management department of government. B.Suggestions: 1.For government: a.Base Station System: Coordinate all operators to co-construct the system to speed the integration of broadband wireless access technology to resolve the network quality issues. b.Technology platform and content industry: Collaborate with the enterprises of industry chain to support the research and development by proper industry regulations. 2.For wireless operators: a.Research on wireless consumer behaviors: Coordinate all operators to invest subscriber behaviors and statistic analysis in local market to learn how to produce the killer applications. b.Content and service platform: Proactively involve the content service developing and technology platform integration to develop the content industry as win-win purpose. c.Proper subscriber fare: Charge wireless consumers by the value of requisition and cost driven factor.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), WLAN (2400-2500 MHz and 5000-5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated.

科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:11555149 研究代表者:都市域の総合的地震被災ポテンシャルの定量化に基づく地域防災カルテの作成 研究期間:1999-2001年度

Ο ταχύτατα εξελισσόμενος τομέας των δικτύων κινητών επικοινωνιών έχει επιφέρει μία ιδιαίτερα αυξανόμενη απαίτηση για ασύρματη, πολυμεσική επικοινωνία. Στη ραγδαία εξέλιξη του τομέα αυτού συμβάλουν τα μέγιστα και οι απαιτήσεις της σύγχρονης αγοράς για ένα ενοποιημένο και λειτουργικό σύστημα κινητής τηλεφωνίας παρέχοντας παράλληλα πληθώρα ευρυζωνικών υπηρεσιών ψηφιακού περιεχομένου στους πελάτες - χρήστες του. Είναι γεγονός ότι τα τελευταία χρόνια τα δίκτυα επικοινωνιών τρίτης γενιάς (3G) - Universal Mobile Telecommunication System (UMTS) γνωρίζουν μεγάλη άνθηση και η χρήση τους έχει επεκταθεί στις περισσότερες ευρωπαϊκές χώρες, όπως και στην Ελλάδα. Τα νέα αυτά κινητά δίκτυα αντικαθιστούν τα υπάρχοντα κινητά δίκτυα δεύτερης γενιάς και επιπλέον προσφέρουν προηγμένες υπηρεσίες στους κινητούς χρήστες. Ωστόσο, η αδήριτη ανάγκη για μεγαλύτερες (ευρυζωνικές) ταχύτητες πρόσβασης οδήγησε στην περαιτέρω ανάπτυξη των 3G δικτύων και στην υιοθέτηση νέων τεχνολογιών, με κυριότερο εκπρόσωπο τους την τεχνολογία High Speed Packet Access (HSPA). Η τεχνολογία HSPA αποτελεί τη φυσιολογική μετεξέλιξη του UMTS, η οποία πολλές φορές συναντάται και ως 3.5G ή 3G+, προκειμένου να δηλώσει την αναβάθμιση του 3G (UMTS) προτύπου. Ωστόσο, παρά το γεγονός ότι η τεχνολογία HSPA αναμένεται να προσφέρει τη δυνατότητα παροχής πληθώρας ευρυζωνικών υπηρεσιών, το 3rd Generation Partnership Project (3GPP), που αποτελεί τον οργανισμό που προτυποποιεί τις νέες τεχνολογίες και ορίζει τις προδιαγραφές τους, ήδη μελετά και επεξεργάζεται νέες τεχνολογίες που θα επικρατήσουν την αμέσως επόμενη δεκαετία στην αγορά των κινητών επικοινωνιών. Το νέο αυτό project αποκαλείται Long Term Evolution (LTE) και στοχεύει στην επίτευξη ακόμη υψηλότερων ρυθμών μετάδοσης σε συνδυασμό με την αξιοποίηση μεγαλύτερου εύρος ζώνης. Κύρια προοπτική του LTE αποτελεί η διασφάλιση της ανταγωνιστικότητας και η επικράτηση του προτύπου στο χρονικό ορίζοντα της επόμενης δεκαετίας. Κατά συνέπεια, η αγορά κινητών επικοινωνιών σταδιακά μεταλλάσσεται προς τη δημιουργία δικτύων κινητών επικοινωνιών επόμενης γενιάς, με απώτερο σκοπό την επίτευξη της αποκαλούμενης «Κινητής Ευρυζωνικότητας» (Mobile Broadband). Ταυτόχρονα με την εκτεταμένη εξάπλωση των δικτύων κινητών επικοινωνιών επόμενης γενιάς καθώς και τις αυξημένες δυνατότητες των κινητών συσκευών, οι πάροχοι πολυμεσικού περιεχομένου και υπηρεσιών ενδιαφέρονται όλο και περισσότερο για την υποστήριξη της πολυεκπομπής (multicasting) δεδομένων στα δίκτυα αυτά με σκοπό την αποτελεσματική διαχείριση και επαναχρησιμοποίηση των διαθέσιμων πόρων του δικτύου. Επιπρόσθετα, οι χρήστες των κινητών δικτύων έχουν πλέον την απαίτηση να προσπελαύνουν εφαρμογές και υπηρεσίες οι οποίες μέχρι σήμερα μπορούσαν να διατεθούν αποκλειστικά από τα συμβατικά ενσύρματα δίκτυα. Έτσι λοιπόν στις μέρες μας γίνεται λόγος για υπηρεσίες πραγματικού χρόνου όπως mobile TV, mobile gaming, mobile streaming κ.α. Ένα από τα σημαντικότερα βήματα των δικτύων κινητών επικοινωνιών προς την κατεύθυνση της παροχής νέων, προηγμένων πολυμεσικών υπηρεσιών είναι η εισαγωγή της υπηρεσίας Multimedia Broadcast / Multicast Service (MBMS). Η υπηρεσία MBMS έχει σαν κύριο σκοπό την υποστήριξη IP εφαρμογών πανεκπομπής (broadcact) και πολυεκπομπής (multicast), επιτρέποντας με αυτό τον τρόπο την παροχή υπηρεσιών υψηλού ρυθμού μετάδοσης σε πολλαπλούς χρήστες με οικονομικό τρόπο. Η multicast μετάδοση δεδομένων σε κινητά δίκτυα επικοινωνιών είναι μια σχετικά νέα λειτουργικότητα η οποία βρίσκεται ακόμη στο στάδιο των δοκιμών και της προτυποποίησης της. Ένας multicast μηχανισμός μεταδίδει τα δεδομένα μόνο μία φορά πάνω από κάθε ασύρματο σύνδεσμο που αποτελεί τμήμα των μονοπατιών προς τους προορισμούς-κινητούς χρήστες. Το κρισιμότερο σημείο που εντοπίζεται κατά τη multicast μετάδοση δεδομένων στα κινητά δίκτυα επικοινωνιών είναι ο αποτελεσματικός έλεγχος ισχύος. Οι σταθμοί βάσης των κυψελωτών αυτών δικτύων διαθέτουν περιορισμένους πόρους ισχύος, γεγονός που περιορίζει τη χωρητικότητα της κυψέλης (cell) και επιβάλλει τη χρήση μίας βέλτιστης στρατηγικής για την όσο το δυνατόν καλύτερη αξιοποίηση των διαθέσιμων πόρων ισχύος. Ο έλεγχος ισχύος στοχεύει στη μείωση της εκπεμπόμενης ισχύος, στην ελαχιστοποίηση του θορύβου στο κυψελωτό δίκτυο και κατά συνέπεια στη διασφάλιση μεγαλύτερης χωρητικότητας επιπλέον χρηστών. Ένα από τα βασικότερα στοιχεία του ελέγχου ισχύος στα δίκτυα κινητών επικοινωνιών επόμενης γενιάς κατά τη multicast μετάδοση πολυμεσικών δεδομένων αποτελεί η επιλογή του κατάλληλου καναλιού μεταφοράς για τη μετάδοση των δεδομένων στον κινητό χρήστη. Συγκεκριμένα, πρόκειται για ένα κρίσιμο ζήτημα το οποίο είναι ακόμα υπό εξέταση στο 3GPP. Προς την κατεύθυνση αυτή, στο MBMS πρότυπο έχουν αναπτυχθεί διάφοροι μηχανισμοί, με χαρακτηριστικό τον MBMS Counting Mechanism. Στόχος του μηχανισμού αυτού είναι η βελτιστοποίηση της ροής δεδομένων για την υπηρεσία MBMS, όταν αυτά διέρχονται από τις διεπαφές του UMTS/HSPA δικτύου. Ωστόσο, η υπάρχουσα μορφή του μηχανισμού αυτού, καθώς και των αρκετών άλλων μηχανισμών που έχουν προταθεί από το 3GPP, διακρίνεται από πολλές αδυναμίες που δεν επιτρέπουν την αποτελεσματική και μαζική μετάδοση πολυμεσικών δεδομένων. Τα σημαντικότερα προβλήματα των μηχανισμών αυτών είναι η απουσία ευρυζωνικών χαρακτηριστικών καθώς και η σπατάλη σημαντικού τμήματος των ούτως ή άλλως περιορισμένων πόρων ισχύος. Εν γένει, η επιλογή του κατάλληλου καναλιού μεταφοράς των πολυμεσικών δεδομένων στο ασύρματο μέσο είναι μια δύσκολη διαδικασία καθώς μια λανθασμένη επιλογή καναλιού μπορεί να οδηγήσει στην αστοχία μίας ολόκληρης κυψέλης. Γίνεται σαφές λοιπόν, ότι απαιτείται μία βελτιωμένη έκδοση των υπαρχόντων μηχανισμών για την αποτελεσματικότερη και οικονομικότερη μετάδοση πολυμεσικού περιεχομένου σε μεγάλο πλήθος χρηστών. Λαμβάνοντας υπόψη τα παραπάνω, στόχος της παρούσας διδακτορικής διατριβής είναι η μελέτη του ελέγχου ισχύος στα δίκτυα κινητών επικοινωνιών επόμενης γενιάς καθώς και η ανάπτυξη νέων μεθόδων/μηχανισμών για τη βελτιστοποίηση του. Ιδιαίτερο χαρακτηριστικό της διατριβής αυτής είναι η ενσωμάτωση και η «εκμετάλλευση» όλων των ιδιαίτερων χαρακτηριστικών της HSPA τεχνολογίας στην MBMS υπηρεσία. Προς αυτή την κατεύθυνση, στην παρούσα διδακτορική διατριβή αναλύονται και αξιολογούνται όλα τα υπάρχοντα κανάλια μεταφοράς του UMTS και της τεχνολογίας HSPA τα οποία μπορούν να χρησιμοποιηθούν για τη multicast μετάδοση MBMS υπηρεσιών. Η αξιολόγηση γίνεται με βάση την απαιτούμενη ισχύ που πρέπει να ανατεθεί από το σταθμό βάσης για καθένα από αυτά, και κατά συνέπεια με βάση το ρυθμό μετάδοσης τους, τον αριθμό των χρηστών που μπορούν να εξυπηρετήσουν, την ποιότητα υπηρεσιών για κάθε χρήστη, τη μέγιστη δυνατή κάλυψη της κυψέλης κ.α. Οι ιδιαίτερα αυξημένες απαιτήσεις των MBMS υπηρεσιών μας οδήγησαν στη συνέχεια στη διερεύνηση και αξιολόγηση ορισμένων τεχνικών μείωσης της εκπεμπόμενης ισχύος, με απώτερο σκοπό την αποδοτικότερη χρήση των πόρων του συστήματος κατά τη μετάδοση MBMS υπηρεσιών. Ενδεικτικά αναφέρουμε πως μία MBMS υπηρεσία με ρυθμό μετάδοσης 128 Kbps μπορεί να καταναλώσει έως και το 80% των πόρων ισχύος ενός σταθμού βάσης. Επομένως, γίνεται κατανοητό ότι η μετάδοση MBMS υπηρεσιών με τόσο υψηλούς ρυθμούς μετάδοσης καθίσταται δύσκολη έως και αδύνατη. Για την αντιμετώπιση αυτού του προβλήματος έχουν αναπτυχθεί τεχνικές, όπως η FACH Dynamic Power Setting, η Macro Diversity Combining και το Rate Splitting, ικανές να μειώσουν τα επίπεδα ισχύος κατά τη μετάδοση multicast δεδομένων στους MBMS χρήστες. Η διδακτορική αυτή διατριβή εξετάζει την αποδοτικότητα της χρήσης αυτών των τεχνικών εξοικονόμησης ισχύος και παρουσιάζει πειραματικά αποτελέσματα που αποκαλύπτουν το ποσό ισχύος που εξοικονομείται από κάθε μία τεχνική. Η αξιολόγηση τόσο των καναλιών μεταφοράς όσο και των τεχνικών μείωσης ισχύος θα οδηγήσει στην εύρεση ενός κατάλληλου σχήματος/μηχανισμού, ο οποίος θα εξασφαλίζει την αποδοτική εναλλαγή μεταξύ των διάφορων τύπων καναλιών κατά τη μετάδοση MBMS υπηρεσιών. Ο μηχανισμός αυτός, τον οποίο καλούμε MBMS Channel Assignment Mechanism (ή χάριν συντομίας «MCAM»), αναμένεται να εξασφαλίσει βελτιωμένη απόδοση σε σχέση με τους αντίστοιχους μηχανισμούς που έχουν προταθεί από το 3GPP, μείωση της καταναλισκόμενης ισχύος και κατά συνέπεια αύξηση της χωρητικότητας των κινητών δικτύων επόμενης γενιάς. Ωστόσο, το πιο αξιοπρόσεκτο πλεονέκτημα του προτεινόμενου μηχανισμού, που ουσιαστικά τον διαφοροποιεί από τις άλλες προσεγγίσεις, είναι ότι προσαρμόζεται στις αυξημένες απαιτήσεις των κινητών δικτύων επόμενης γενιάς για ταυτόχρονη παροχή πολλαπλών πολυμεσικών συνόδων. Το γεγονός αυτό μπορεί να επιτρέψει τη μαζική μετάδοση πολυμεσικών δεδομένων σε πληθώρα κινητών χρηστών, θέτοντας κατά τον τρόπο αυτό τον MCAM σαν έναν ισχυρό υποψήφιο για τα δίκτυα επόμενης γενιάς. / The rapid growth of mobile communications networks has involved an increasing demand for wireless, multimedia communication. The fast development of this area was mainly motivated by the requirements of modern market for a unified and functional system of mobile communications that, at the same time, may provide numerous broadband services to its users. More specifically, in the recent years, the usage of third generation (3G) - Universal Mobile Telecommunication System (UMTS) cellular networks has begun to rise in most European countries, as in Greece. 3G networks have replaced the second generation mobile networks and moreover, are in position of offering advanced services to mobile users. However, the need for higher (broadband) speeds led to the further development of 3G networks and to the adoption of new technologies, with main representative the High Speed Packet Access (HSPA) technology. HSPA constitutes the evolution of UMTS and is known as 3.5G or 3G+ in order to indicate the upgrade from UMTS. However, despite the fact that HSPA technology is expected to allow the provision of numerous broadband services, the 3rd Generation Partnership Project (3GPP), the authorized organization for the standardization of new mobile technologies, already examines new technologies that will prevail in the mobile communications industry over the next decades. This novel project is known as Long Term Evolution (LTE) and aims at achieving increased data rates and reduced latency compared to UMTS and HSPA networks. Therefore, the mobile communications industry progressively evolves to next generation networks, with main target the achievement of the so called “Mobile Broadband”. Simultaneously, multimedia content and service providers show an increased interest in supporting multicast data in order to effectively manage and re-use the available network resources. Additionally, more and more users require access to applications and services that until today could only be accessed by conventional wired networks. Thus, real time applications and services may face low penetration today; however, they are expected to gain high interest in future mobile networks. These applications actually reflect a modern, future way of communication among mobile users. For instance, mobile TV is expected to be a “killer” application for 3G’s. Such mobile TV services include streaming live TV (news, weather forecasts etc.) and streaming video (such as video clips). All the above constitute a series of indicative emerging applications that necessitate advanced transmission techniques. One of the most significant steps towards the provision of such demanding services is the introduction of Multimedia Broadcast/Multicast Service (MBMS). MBMS is a point-to-multipoint service in which data is transmitted from a single source entity to multiple destinations, allowing the networks resources to be shared. Actually, MBMS extends the existing UMTS infrastructure and efficiently uses network and radio resources, both in the core network and most importantly, in the air interface of UMTS, where the bottleneck is placed to a large group of users. Therefore, MBMS constitutes an efficient way to support the plethora of the emerging wireless multimedia applications and services such as IP video conferencing and video streaming. The main requirement during the provision of MBMS multicast services is to make an efficient overall usage of radio and network resources. This necessity mainly translates into improved power control strategies, since the base stations’ transmission power is the limiting factor of downlink capacity in UMTS networks. Under this prism, power control is one of the most critical aspects in MBMS due to the fact that downlink transmission power in UMTS networks is a limited resource and must be shared efficiently among all MBMS users in a cell. Moreover, power control aims at minimizing the transmitted power, eliminating in this way the intercell interference. However, when misused, the use of power control may lead to a high level of wasted power and worse performance results. In order to have efficient power control in MBMS, one of the most critical aspects is the selection of the transport channel for the transmission of MBMS multicast traffic. MBMS services can be provided in each cell by either multiple point-to-point (PTP) channels or by a single point-to-multipoint (PTM) channel. A wrong channel selection may result to a significant capacity decrease, thus, preventing the mass delivery of multimedia applications. It is worth mentioning that channel selection is still an open issue in today’s MBMS infrastructure mainly due to its catalytic role in MBMS performance. In the frame of MBMS power control and transport channel selection several approaches have been proposed, with main representative the 3GPP MBMS Counting Mechanism. However, none of these approaches performs optimal transport channel selection either due to the fact that some of them do not consider the power consumption as the selection criterion or because of the fact that they do not consider all the available transport channels (or combination of them) for the transmission of the MBMS data. All the above stress the need for an advanced version of these mechanisms that could deliver multimedia content to a large number of mobile users in a more efficient and economic way. After taking into account the above analysis, objective of this dissertation is the study of power control issues in next generation mobile communication networks and the development of new approaches/ mechanisms for its optimization. To this direction, this dissertation analyzes and evaluates all the available UMTS and HSPA transport channels that could be used for the transmission of MBMS multicast services. Moreover, this dissertation investigates and evaluates several power saving techniques that aim at the efficient usage of radio and network resources. Techniques, such as Dynamic Power Setting, Macro Diversity Combining and Rate Splitting are capable of decreasing the power consumption during the provision of MBMS services and may enable the mass market delivery of multimedia services to mobile users. The evaluation of the available transport channels and power saving techniques will lead to the development of a novel scheme/mechanism that will enable the efficient selection of transport channels for the transmission of MBMS services. The proposed mechanism, which we call MBMS Channel Assignment Mechanism (or «MCAM»), is expected to optimally utilize the available power resources of base stations to MBMS sessions running in the network, resulting in that way to an extensive increase on the system’s capacity. Therefore, MCAM may allow the mass provision of multimedia data to a large number of mobile users, which makes MCAM a strong candidate for next generation networks.