Hannes Ekström

Bio: Hannes Ekström is an academic researcher from Ericsson. The author has contributed to research in topics: Network packet & Quality of service. The author has an hindex of 16, co-authored 30 publications receiving 1617 citations.

Technical solutions for the 3G long-term evolution

Abstract: Work has started in the 3GPP to define a long-term evolution for 3G, sometimes referred to as super-3G, which will stretch the performance of 3G technology, thereby meeting user expectations in a 10-year perspective and beyond. The fundamental targets of this evolution - to further reduce user and operator costs and to improve service provisioning - will be met through improved coverage and system capacity as well as increased data rates and reduced latency. This article presents promising technologies to fulfil these targets, including OFDM, multi-antenna solutions, evolved QoS and link layer concepts, and an evolved architecture. Furthermore, the results of a performance evaluation are presented, indicating that the requirements can indeed be reached using the proposed technologies.

QoS control in the 3GPP evolved packet system

Abstract: In this article we describe the QoS concept of the evolved packet system, which was standardized in 3GPP Release 8. The concept provides access network operators and service operators with a set of tools to enable service and subscriber differentiation. Such tools are becoming increasingly important as operators are moving from a single to a multi-service offering at the same time as both the number of mobile broadband subscribers and the traffic volume per subscriber is rapidly increasing. The "bearer" is a central element of the EPS QoS concept and is the level of granularity for bearer-level QoS control. The network-initiated QoS control paradigm specified in EPS is a set of signaling procedures for managing bearers and controlling their QoS assigned by the network. The EPS QoS concept is class-based, where each bearer is assigned one and only one QoS class identifier by the network. The QCI is a scalar that is used within the access network as a reference to node-specific parameters that control packet forwarding treatment. This class-based approach, together with the network-initiated QoS control paradigm, gives network operators full control over the QoS provided for its offered services for each of its subscriber groups.

The 3G Long-Term Evolution - Radio Interface Concepts and Performance Evaluation

Abstract: 3GPP is in the process of defining the long-term evolution (LTE) for 3G radio access, sometimes referred to as Super-3G, in order to maintain the future competitiveness of 3G technology. The main targets for this evolution concern increased data rates, improved spectrum efficiency, improved coverage, and reduced latency. Taken together these result in significantly improved service provisioning and reduced operator costs in a variety of traffic scenarios. This paper gives an overview of the basic radio interface principles for the 3G long-term evolution concept, including OFDM and advanced antenna solution, and presents performance results indicating to what extent the requirements/targets can be met. It is seen that the targets on three-fold user throughput and spectrum efficiency compared to basic WCDMA can be fulfilled with the current working assumptions. More advanced WCDMA systems, employing e.g. advanced antenna solutions may however achieve similar performance gains. Enhancements for reduced latency and IP optimized architectures and protocols are further applicable to both LTE and WCDMA.

Efficient header handling involving GSM/EDGE radio access networks

Abstract: To facilitate handing of headers for Internet-transmissible packets, a radio access network sends to a mobile station (MS) a message which downloads configuration options for each of corresponding plural header adaptation strategies. The mobile station (MS) elects one of the plural header adaptation strategies and includes the elected strategy in a return message, whereby the radio access network configures a radio bearer for packets to be transmitted between the radio access network and the mobile station. In a first illustrated mode of implementation of the invention, the radio access network is a GSM/EDGE radio access network, with the downloading message being a radio bearer setup message and the return message sent from the mobile station to the radio access network being a radio bearer setup complete message. In a second illustrated mode of implementation of the invention, the message that downloads configuration options for each of plural header adaptation strategies is a handover command message for handing over control of the mobile station from a source radio access network to a target radio access network. In this second mode, the message which informs which of the plural strategies is elected is a handover complete message. The plural header adaptation strategies can include header compression (useful, e.g., for a multimedia service); header removal (useful, e.g., for a spectrum efficient voice packet voice bearer that reuses codec-specific channel coding); and no header adaptation.

Link adaptation for point-to-multipoint channel

Abstract: A network node (28) of a wireless telecommunication network (20) uses a first coding scheme (selected from plural possible coding schemes) for encoding of a point-to-multipoint (PTM) transmission carried to plural mobile stations (30) on a common downlink channel (32). The mobile stations (30) receiving the point-to-multipoint transmission on the common downlink channel (32) evaluate the link quality of the point-to-multipoint transmission. Feedback from the plural mobile stations (30) regarding the link quality of the point-to-multipoint transmission is provided to the network node (28) on a common uplink channel (36). A controller (48) at the network node (28) monitors information received on the common uplink channel for feedback regarding the link quality of the point-to-multipoint transmission. The controller (48) at the network node (28) uses the feedback to determine whether to change from the first coding scheme to a second coding scheme for the encoding of the point-to-multipoint transmission to the plural mobile stations (30).

Single carrier FDMA for uplink wireless transmission

Abstract: Single carrier frequency division multiple access (SC FDMA), a modified form of orthogonal FDMA (OFDMA), is a promising technique for high data rate uplink communications in future cellular systems. SC-FDMA has similar throughput performance and essentially the same overall complexity as OFDMA. A principal advantage of SC-FDMA is the peak-to-average power ratio (PARR), which is lower than that of OFDMA. SC FDMA is currently a strong candidate for the uplink multiple access scheme in the long term evolution of cellular systems under consideration by the third generation partnership project (3GPP). In this paper, we give an overview of SC-FDMA. We also analyze the effects of subcarrier mapping on throughput and PARR. Among the possible subcarrier mapping approaches, we find that localized FDMA (LFDMA) with channel-dependent scheduling (CDS) results in higher throughput than interleaved FDMA (JFDMA). However, the PARR performance of IFDMA is better than that of LFDMA. As in other communications systems there are complex tradeoffs between design parameters and performance in an SC-FDMA system

Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey

Abstract: Future generation cellular networks are expected to provide ubiquitous broadband access to a continuously growing number of mobile users. In this context, LTE systems represent an important milestone towards the so called 4G cellular networks. A key feature of LTE is the adoption of advanced Radio Resource Management procedures in order to increase the system performance up to the Shannon limit. Packet scheduling mechanisms, in particular, play a fundamental role, because they are responsible for choosing, with fine time and frequency resolutions, how to distribute radio resources among different stations, taking into account channel condition and QoS requirements. This goal should be accomplished by providing, at the same time, an optimal trade-off between spectral efficiency and fairness. In this context, this paper provides an overview on the key issues that arise in the design of a resource allocation algorithm for LTE networks. It is intended for a wide range of readers as it covers the topic from basics to advanced aspects. The downlink channel under frequency division duplex configuration is considered as object of our study, but most of the considerations are valid for other configurations as well. Moreover, a survey on the most recent techniques is reported, including a classification of the different approaches presented in literature. Performance comparisons of the most well-known schemes, with particular focus on QoS provisioning capabilities, are also provided for complementing the described concepts. Thus, this survey would be useful for readers interested in learning the basic concepts before going into the details of a particular scheduling strategy, as well as for researchers aiming at deepening more specific aspects.

Simulating LTE Cellular Systems: An Open-Source Framework

Abstract: Long-term evolution (LTE) represents an emerging and promising technology for providing broadband ubiquitous Internet access. For this reason, several research groups are trying to optimize its performance. Unfortunately, at present, to the best of our knowledge, no open-source simulation platforms, which the scientific community can use to evaluate the performance of the entire LTE system, are freely available. The lack of a common reference simulator does not help the work of researchers and poses limitations on the comparison of results claimed by different research groups. To bridge this gap, herein, the open-source framework LTE-Sim is presented to provide a complete performance verification of LTE networks. LTE-Sim has been conceived to simulate uplink and downlink scheduling strategies in multicell/multiuser environments, taking into account user mobility, radio resource optimization, frequency reuse techniques, the adaptive modulation and coding module, and other aspects that are very relevant to the industrial and scientific communities. The effectiveness of the proposed simulator has been tested and verified considering 1) the software scalability test, which analyzes both memory and simulation time requirements; and 2) the performance evaluation of a realistic LTE network providing a comparison among well-known scheduling strategies.

Multiple-antenna techniques for wireless communications - a comprehensive literature survey

Abstract: The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. With an enormous amount of yearly publications, the field of multiple-antenna systems, often called multiple-input multiple-output (MIMO) systems, has evolved rapidly. To date, there are numerous papers on the performance limits of MIMO systems, and an abundance of transmitter and receiver concepts has been proposed. The objective of this literature survey is to provide non-specialists working in the general area of digital communications with a comprehensive overview of this exciting research field. To this end, the last ten years of research efforts are recapitulated, with focus on spatial multiplexing and spatial diversity techniques. In particular, topics such as transmitter and receiver structures, channel coding, MIMO techniques for frequency-selective fading channels, diversity reception and space-time coding techniques, differential and non-coherent schemes, beamforming techniques and closed-loop MIMO techniques, cooperative diversity schemes, as well as practical aspects influencing the performance of multiple-antenna systems are addressed. Although the list of references is certainly not intended to be exhaustive, the publications cited will serve as a good starting point for further reading.

Simulating the Long Term Evolution physical layer

Abstract: Research and development of signal processing algorithms for UMTS Long Term Evolution (LTE) requires a realistic, flexible, and standard-compliant simulation environment. To facilitate comparisons with work of other research groups such a simulation environment should ideally be publicly available. In this paper, we present a MATLAB-based downlink physical-layer simulator for LTE. We identify different research applications that are covered by our simulator. Depending on the research focus, the simulator offers to carry out single-downlink, single-cell multi-user, and multi-cell multi-user simulations. By utilizing the Parallel Computing Toolbox of MATLAB, the simulator can efficiently be executed on multi-core processors to significantly reduce the simulation time.