Improving and distributing key management on mobile networks

We address the problem of mobile network key management and authentication that negatively affects the handoff performance, adds overhead to the system in terms of key exchange signaling, authentication, and key distribution. We aim to improve the efficiency of the key management subsystem and to reduce investment pressure on core network elements. We address all these problems successfully. Our novel SKC key management mechanism is the best key management mechanism among the ones we found in reducing signaling load from the KD and making the mobility system independent of the AP-KD link delay. It is a significant contribution to the mobile network key management with fast handoffs when separate keys for APs are required and has many useful applications. Our novel receiver and sender ID binding protocol with symmetric keys is new and shows analogy with Identity Based Cryptography. It is a generalization of the identity binding that SKC is using. Furthermore, our distributed AAA architecture with SKC, certificates, and hardware-based security is a disruptive proposal and show how the mobile network KD can be distributed to the edge nodes. Our quantitative analysis and comparison of SKC and LTE key management is new and not seen before. Our research affected the LTE Security standardization and contributes to the research and development of home base stations, community and municipal Wi-Fi access points

QoS Abstraction Layer in 4G Access Networks

Tese de Mestrado. Redes e Serviços de Comunicação. Faculdade de Engenharia. Universidade do Porto. 200

Future Mobile Communications: LTE Optimization and Mobile Network Virtualization

Providing QoS while optimizing the LTE network in a cost efficient manner is very challenging. Thus, radio scheduling is one of the most important functions in mobile broadband networks. The design of a mobile network radio scheduler holds several objectives that need to be satisfied, for example: the scheduler needs to maximize the radio performance by efficiently distributing the limited radio resources, since the operator's revenue depends on it. In addition, the scheduler has to guarantee the user's demands in terms of their Quality of Service (QoS). Thus, the design of an effective scheduler is rather a complex task. In this thesis, the author proposes the design of a radio scheduler that is optimized towards QoS guarantees and system performance optimization. The proposed scheduler is called Optimized Service Aware Scheduler (OSA). The OSA scheduler is tested and analyzed in several scenarios, and is compared against other well-known schedulers. A novel wireless network virtualization framework is also proposed in this thesis. The framework targets the concepts of wireless virtualization applied within the 3GPP Long Term Evolution (LTE) system. LTE represents one of the new mobile communication systems that is just entering the market. Therefore, LTE was chosen as a case study to demonstrate the proposed wireless virtualization framework. The framework is implemented in the LTE network simulator and analyzed, highlighting the many advantages and potential gain that the virtualization process can achieve. Two potential gain scenarios that can result from using network virtualization in LTE systems are analyzed: Multiplexing gain coming from spectrum sharing, and multi-user diversity gain. Several LTE radio analytical models, based on Continuous Time Markov Chains (CTMC) are designed and developed in this thesis. These models target the modeling of three different time domain radio schedulers: Maximum Throughput (MaxT), Blind Equal Throughput (BET), and Optimized Service Aware Scheduler (OSA). The models are used to obtain faster results (i.e., in a very short time period in the order of seconds to minutes), compared to the simulation results that can take considerably longer periods, such as hours or sometimes even days. The model results are also compared against the simulation results, and it is shown that it provides a good match. Thus, it can be used for fast radio dimensioning purposes. Overall, the concepts, investigations, and the analytical models presented in this thesis can help mobile network operators to optimize their radio network and provide the necessary means to support services QoS differentiations and guarantees. In addition, the network virtualization concepts provides an excellent tool that can enable the operators to share their resources and reduce their cost, as well as provides good chances for smaller operators to enter the market

Performance of handover in long term evolution

Tässä diplomityössä tutkitaan LTE:n (Long Term Evolution) yhteydellisen tilan solunvaihdon vaikutusta tiedostonsiirtoon, suoratoistoon, sekä internetpuheluihin. Analyysi perustuu Soneran tuotantoverkossa suoritettuihin mittauksiin, joissa tutkittiin viivettä, datakatkosta ja hävinnyttä datamäärää. Solunvaihdon vaikutusta puheluihin tutkitaan laadullisella käyttäjätutkimuksella. Työssä esitetään ensin kirjallisuuskatsaus LTE:stä. Katsaus pohjautuu järjestelmän spesifikaatioihin, laitevalmistajien julkaisuihin, sekä tieteellisiin tutkimuksiin. Eniten huomiota kiinnitetään liikkuvuuden hallintaan. Solunvaihtoprosessi käsitellään signalointitasolla. Tämän jälkeen esitetään mittaustulokset ja niiden analyysi. Lopuksi esitetään johtopäätökset, sekä ehdotetaan mahdollisia kohteita jatkotutkimukselle. Mittaustulokset osoittavat, että tavallisella solunvaihdolla ei ole vaikutusta palveluiden suorituskykyyn. Dataa ei häviä solunvaihdon aikana. 95%:ssa tapauksista päätelaite on kokonaan verkosta irti kytkettynä alle 50 ms, ja käyttäjän kokema datakatko on alle 75 ms. Näin ollen käyttäjä ei koe laadun heikentymistä, elleivät radio-olosuhteet sitä aiheuta. Käyttäjätutkimuksen tulokset osoittavat, että tavallinen solunvaihto ei aiheuta laadullista häiriötä loppukäyttäjälle. Keskusverkon avustaman solunvaihdon huomattiin hävittävän dataa. Tämä ei ole spesifikaatioiden mukaista. Datan häviäminen aiheutti TCP:n (Transmission Control Protocol) uudelleenlähetyksiä, joista 26% johtui uudelleenlähetysajastimen laukeamisesta. Käyttäjätutkimuksen mukaan kyseinen solunvaihto aiheuttaa lyhyen häiriön puheluun. Häiriö on kuitenkin laadultaan vähäinen.This thesis studies the effect of intra-system handover in Long Term Evolution to the performance of popular services and protocols. Protocols examined include file transfer using Transmission Control Protocol (TCP), streaming, and internet phone calls. The analysis is based on measurements conducted in a live production network in Helsinki. The measurements include delay, data pause and data loss. Additionally, the effects of handover to voice quality are studied with a qualitative user survey. The thesis first presents a literature review of Long Term Evolution based on the system specifications, white papers and scientific studies. Most detail is given to mobility management. The handover process is studied at the level of signalling messages. Measurement results and their analysis are then discussed. Finally, conclusions and opportunities for further study are given. The measurement results show that the normal handover has minimal effect on the service performance. No data is lost because of the handover. In 95% of the cases the device is disconnected from the network for under 50 ms, and the data pause experienced is less than 75 ms. Thus, the end user will not experience any disturbance other than that resulting from low radio conditions. The results of the voice call user survey confirm that the normal handover is not audible to the end user. The core network assisted handover was found to lose data during handover, not according to the specifications. This caused TCP retransmissions, of which 26% were triggered because of a retransmission timeout. The user survey established that this type of handover is also audible to the user, but the overall quality impairment is not significant

Deployment and operational aspects of rural broadband wireless access networks

Broadband speeds, Internet literacy and digital technologies have been steadily evolving over the last decade. Broadband infrastructure has become a key asset in today’s society, enabling innovation, driving economic efficiency and stimulating cultural inclusion. However, populations living in remote and rural communities are unable to take advantage of these trends. Globally, a significant part of the world population is still deprived of basic access to the Internet. Broadband Wireless Access (BWA) networks are regarded as a viable solution for providing Internet access to populations living in rural regions. In recent years, Wireless Internet Service Providers (WISPs) and community organizations around the world proved that rural BWA networks can be an effective strategy and a profitable business. This research began by deploying a BWA network testbed, which also provides Internet access to several remote communities in the harsh environment of the Scottish Highlands and Islands. The experience of deploying and operating this network pointed out three unresolved research challenges that need to be addressed to ease the path towards widespread deployment of rural BWA networks, thereby bridging the rural-urban broadband divide. Below, our research contributions are outlined with respect to these challenges. Firstly, an effective planning paradigm for deploying BWA networks is proposed: incremental planning. Incremental planning allows to anticipate return of investment and to overcome the limited network infrastructure (e.g., backhaul fibre links) in rural areas. I have developed a software tool called IncrEase and underlying network planning algorithms to consider a varied set of operational metrics to guide the operator in identifying the regions that would benefit the most from a network upgrade, automatically suggesting the best long-term strategy to the network administrator. Second, we recognize that rural and community networks present additional issues for network management. As the Internet uplink is often the most expensive part of the operational expenses for such deployments, it is desirable to minimize overhead for network management. Also, unreliable connectivity between the network operation centre and the network being managed can render traditional centralized management approaches ineffective. Finally, the number of skilled personnel available to maintain such networks is limited. I have developed a distributed network management platform called Stix for BWA networks, to make it easy to manage such networks for rural/community deployments and WISPs alike while keeping the network management infrastructure scalable and flexible. Our approach is based on the notions of goal-oriented and in-network management: administrators graphically specify network management activities as workflows, which are run in the network on a distributed set of agents that cooperate in executing those workflows and storing management information. The Stix system was implemented on low-cost and small form-factor embedded boards and shown to have a low memory footprint. Third, the research focus moves to the problem of assessing broadband coverage and quality in a given geographic region. The outcome is BSense, a flexible framework that combines data provided by ISPs with measurements gathered by distributed software agents. The result is a census (presented as maps and tables) of the coverage and quality of broadband connections available in the region of interest. Such information can be exploited by ISPs to drive their growth, and by regulators and policy makers to get the true picture of broadband availability in the region and make informed decisions. In exchange for installing the multi-platform measurement software (that runs in the background) on their computers, users can get statistics about their Internet connection and those in their neighbourhood. Finally, the lessons learned through this research are summarised. The outcome is a set of suggestions about how the deployment and operation of rural BWA networks, including our own testbed, can be made more efficient by using the proper tools. The software systems presented in this thesis have been evaluated in lab settings and in real networks, and are available as open-source software