Gerardo Gómez

Deployment of IP multimedia streaming services in third-generation mobile networks

In this article, an end-to-end quality of service framework for streaming services in 3G mobile networks is considered. Under this scenario, the interaction between UMTS and IETFs protocols and mechanisms for a streaming session is analyzed. By signaling flowcharts, it is shown that both groups of protocols and mechanisms can co-operate to provide seamless end-to-end real-time services. Specifically, the article proposes to make the IP multimedia subsystem aware of the real time streaming protocol, in order to extend its control from SIP to RTSP-based services, such as multimedia streaming services. Supported by this proposed framework, provisioning of audio streaming services over 3G mobile networks is also outlined.

Physical Layer Performance of Long Term Evolution Cellular Technology

Despite commercial 3G networks are starting to be fully operational and high speed data packet access (HSDPA) is on its way to be deployed, operators and manufacturers are already in a race towards 4G technologies. The road to 4G has a mandatory milestone in long term evolution (LTE) as it is a promising technology which will allow backwards compatibility besides a higher performance. Thus operators, manufacturers and research institutes are cooperating in the definition of LTE specifications. This paper presents a performance evaluation of LTE downlink physical layer according to the latest 3GPP specifications. Particularly, the main features at the LTE physical layer (like spatial multiplexing or adaptive modulation and coding) are described and analyzed.

End-to-end quality of service over cellular networks : data services performance and optimization in 2G/3G

List of Contributors. Foreword. Preface. Acknowledgements. 1 Introduction (John Cullen, Mattias Wahlqvist and Gerardo Gomez). 1.1 Mobile Services in Perspective. 1.2 Mobile Technology Evolution. 1.3 Motivation for QoS. References. 2 Cellular Wireless Technologies (Petteri Hakalin, Pablo Tapia, Juan Ramiro-Moreno, Raquel Rodriguez, Ma Carmen Aguayo-Torres and Rafael Sanchez). 2.1 Introduction. 2.2 GSM/GPRS/EDGE. 2.3 WCDMA/HSDPA. 2.4 IS-95/CDMA2000-1x, EV-DV, EV-DO. 2.5 WLAN. 2.6 Future Outlook. References. 3 Data Services Architecture and Standardization (Salvador Hierrezuelo, Alejandro Gil, Juan Guerrero, Raquel Rodriguez, Juan Torreblanca, Mattias Wahlqvist and Gerardo Gomez) 3.1 Introduction. 3.2 Services Architecture. 3.3 Data Protocols Characteristics. 3.4 SMS/MMS. 3.5 WAP. 3.6 Web. 3.7 Push-to-Talk over Cellular (PoC). 3.8 Network Gaming Services. References. 4 Quality of Service Mechanisms (Raquel Rodriguez, Daniel Fernandez, Hector Montes, Salvador Hierrezuelo and Gerardo Gomez). 4.1 What is Quality of Service? 4.2 IP-Based QoS. 4.3 QoS Architecture in 3GPP and 3GPP2. 4.4 QoS Policy Management. References. 5 End-to-End Service Performance Analysis (Rafael Sanchez, Gerardo Gomez, Pablo Ameigeiras, Jorge Navarro and Gabriel Ramos). 5.1 Introduction. 5.2 Service Performance Characterization. 5.3 Data Link Effects. 5.4 Transport and Application Layer Effects. 5.5 Impact of Network Dimensioning in the Service Performance. References. 6 Service Performance Verification and Benchmarking (Rafael Sanchez, Manuel Martinez, Salvador Hierrezuelo, Juan Guerrero and Juan Torreblanca). 6.1 Introduction. 6.2 Key Performance Indicators. 6.3 Trial Methodology. 6.4 Technology Benchmarking. 6.5 Performance Analysis Example. References. 7 Customer Experience Management (Brian Carroll). 7.1 Overview of Customer Experience Management. 7.2 CEM and Service Management. 7.3 Advantages CEM Brings to an Operator. 7.4 Summary. References. 8 Service Performance Optimization (Gerardo Gomez, Juan Torreblanca and Mattias Wahlqvist). 8.1 Introduction. 8.2 Network-Level Optimization. 8.3 Transport-Level Optimization. 8.4 Compression Techniques. 8.5 Performance Enhancing Proxies. References. Glossary. Index.

Towards a QoE-Driven Resource Control in LTE and LTE-A Networks

We propose a novel architecture for providing quality of experience (QoE) awareness to mobile operator networks. In particular, we describe a possible architecture for QoE-driven resource control for long-term evolution (LTE) and LTE-advanced networks, including a selection of KPIs to be monitored in different network elements. We also provide a description and numerical results of the QoE evaluation process for different data services as well as potential use cases that would benefit from the rollout of the proposed framework.

Physical-Layer Security in Free-Space Optical Communications

The communication between two legitimate peers in the presence of an external eavesdropper is studied from a physical-layer security perspective in the context of free-space optical (FSO) communications. We discuss viable mechanisms to eavesdrop the communication and study the effect of random optical irradiance fluctuations inherent to FSO communications on the probability of achieving a secure transmission. We observe that the joint effect of laser-beam divergence and turbulence-induced fading on the received irradiance, under certain conditions, allows an external eavesdropper close to the legitimate receiver to compromise the communication. Interestingly, we also observe that an eavesdropper placed close to the legitimate transmitter can easily compromise the communication by taking advantage of the larger attenuation suffered by the signal when propagating through the FSO link.

Analytical Modeling of Interference Aware Power Control for the Uplink of Heterogeneous Cellular Networks

Inter-cell interference is one of the main limiting factors in current heterogeneous cellular networks. Uplink fractional power control (FPC) is a well-known method that aims to cope with such a limiting factor and to save the battery life of the mobile terminals (MTs). In order to do that, the transmit power of each MT is adjusted as a function of a set of parameters that usually depend only on the link between MTs and serving base station (BS), such as the desired received power at the serving BS or the path loss between the MT and its serving BS. Contrary to these classical FPC schemes, in this paper, we use stochastic geometry to analyze a power control mechanism that keeps the interference generated by each MT under a given threshold. We also consider a maximum transmitted power and a partial compensation of the path loss. Our analysis reveals that such an interference aware method can reduce the average power consumption and increase the average spectral efficiency at once. In addition, the variance of the interference is reduced, thus improving the performance of adaptive modulation and coding schemes, since the interference can be better estimated.

YouTube QoE evaluation tool for Android wireless terminals

In this paper, we present an Android application which is able to evaluate and analyze the perceived quality of experience (QoE) for YouTube service in wireless terminals. To achieve this goal, the application carries out measurements of objective quality of service (QoS) parameters, which are then mapped onto subjective QoE (in terms of mean opinion score, MOS) by means of a utility function. Our application also informs the user about potential causes that lead to a low MOS as well as provides some hints to improve it. After each YouTube session, the users may optionally qualify the session through an online opinion survey. This information has been used in a pilot experience to correlate the theoretical QoE model with real user feedback. Results from such an experience have shown that the theoretical model (taken from the literature) provides slightly more pessimistic results compared to user feedback. Users seem to be more indulgent with wireless connections, increasing the MOS from the opinion survey in about 20% compared to the theoretical model, which was obtained from wired scenarios.

A next generation wireless simulator based on MIMO-OFDM: LTE case study

The complexity of next generation wireless systems is growing exponentially. The combination of Multiple-Input Multiple-Output (MIMO) technology with Orthogonal Frequency Division Multiplexing (OFDM) is considered as the best solution to provide high data rates under frequency-selective fading channels. The design and evaluation of MIMO-OFDM systems require a detailed analysis of a number of functionalities such as MIMO transmission modes, channel estimation, MIMO detection, channel coding, or cross-layer scheduling. In this paper we present a MIMO-OFDM-based simulator that includes the main physical and link layer functionalities. The simulator has been used to evaluate the performance of the 3GPP Long-Term Evolution (LTE) technology for different MIMO-OFDM techniques under realistic assumptions such as user mobility or bandwidth-limited feedback channel.

Multiuser Capacity and Fairness Evaluation of Channel/QoS-Aware Multiplexing Algorithms

In this work multiplexing of variable-rate sources over shared generic multiple fading channels is addressed. In general, the performance of existing multiplexing algorithms has been compared in very specific environments, making it difficult to draw general conclusions. In this article we propose a generic variable-rate multiuser and multichannel system model that can be applied to any orthogonal channel multiplexing mechanism (e.g., TDM, OFDM, CDM, or SDM) through parametric modeling. Based on the model, the performance of different multiplexing algorithms proposed in the literature is evaluated over moderately fast fading snared channels. Physical channel conditions, random traffic arrival, and QoS requirements are taken into consideration in the study. Multiuser capacity and fairness are assessed and evaluated for different channel-aware and/or QoS-aware user multiplexing algorithms. Results show the joint diversity gain and QoS in terms of the throughput and delay experienced by different user information flows

Performance evaluation of OFDMA wireless systems using WM-SIM platform

Orthogonal Frequency-Division Multiple Access (OFDMA) is becoming a very promising candidate for Long Term Evolution (LTE) and future Forth Generation (4G) technology specifications. This paper presents the work-in-progress development of an OFDMA wireless system model, which runs on top of the Wireless Mobile SIMulation platform (WM-SIM). The main physical (PHY) and Medium Access Control (MAC) functionalities at the radio interface have been implemented and evaluated. A multi-user downlink scheme, where a Base Station (BS) transmits variable-rate information to a set of mobile terminals, is assumed. Performance results show the accuracy of the simulations compared to theoretical estimations.