Anders Furuskär

LTE: the evolution of mobile broadband

This article provides an overview of the LTE radio interface, recently approved by the 3GPP, together with a more in-depth description of its features such as spectrum flexibility, multi-antenna transmission, and inter-cell interference control. The performance of LTE and some of its key features is illustrated with simulation results. The article is concluded with an outlook into the future evolution of LTE.

Technical solutions for the 3G long-term evolution

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.

EDGE: enhanced data rates for GSM and TDMA/136 evolution

Two of the major second-generation standards, GSM and TDMA/136, have built the foundation to offer a common global radio access for data services. Through use of a common physical layer, EDGE, both standards will have the same evolutionary path toward providing third-generation services. EDGE is currently subject to standardization in TIA TR45.3 and ETSI SMG, a process which will be finalized at the end of 1999. Compared to the existing data services in GSM and TDMA/136, EDGE will provide significantly higher user bit rates and spectral efficiency. EDGE can be introduced in these systems in a smooth way, using existing frequency plans of already deployed networks. This article gives the rationale behind the development of the EDGE concept, presents the EDGE technology, and addresses performance by means of system simulations.

LTE-Advanced - Evolving LTE towards IMT-Advanced

This paper provides a high-level overview of some technology components currently considered for the evolution of LTE including complete fulfillment of the IMT-advanced requirements. These technology components include extended spectrum flexibility, multi-antenna solutions, coordinated multipoint transmission/reception, and the use of advanced repeaters/relaying. A simple performance assessment is also included, indicating potential for significantly increased performance.

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

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

Relation between base station characteristics and cost structure in cellular systems

A simple method for estimating the costs of building and operating a cellular mobile network is proposed. Using the empirical data from a third generation mobile system (WCDMA), it is shown that the cost is driven by different factors depending on the characteristics of the base stations deployed. When the site density increased, the operational and transmission costs tend to dominate rather than the radio equipment and site costs. The results also show how, for different capacity requirements, the costs can be minimized by a proper selection of macro, micro and pico base stations. In many scenarios, the macro base stations yield the lowest cost, indicating that the coverage (cell range) is an important parameter when designing wireless systems.

Multiservice allocation for multiaccess wireless systems

This paper discusses principles for allocating multiple bearer services onto different subsystems in multiaccess wireless systems. Based on the included subsystems multiservice capacities, under certain constraints near-optimum subsystem service allocations that maximize combined multiservice capacity are derived through simple optimization procedures. These favorable service allocations are either extreme points where services, as far as possible, are allocated to the subsystems best at supporting them, or they are characterized by the relative efficiency of supporting services being equal in all subsystems. The consequences of this include that services should typically be mixed in subsystems with convex capacity regions and isolated in subsystems with concave capacity regions. Simple user assignment algorithms based on this are also discussed. Additionally, illustrating the main findings of the analysis, some system examples are given, including a case study with combined global system for mobile communications (GSM) and wideband code-division multiple-access (WCDMA) systems. The gain of using the proposed service allocation principles compared to a reference case of maintaining equal service mixes in all subsystems depends on the shape of the subsystem capacity regions; the more different the capacity regions, the larger the gain. In the GSM and WCDMA case study, capacity gains of up to 100% in terms of supported data users for a fixed voice traffic load are achieved.

Downtilted Base Station Antennas - A Simulation Model Proposal and Impact on HSPA and LTE Performance

This paper proposes a low-complexity model for vertical antenna radiation patterns, e.g. for inclusion in system- level simulations. They can be seen as extensions to the horizontal radiation pattern model used in 3GPP simulation scenarios. The model is verified against and compared to predicted and measured data from real networks. The impact on system-level performance is also investigated. It is seen that using the proposed model, simulated geometry distributions and soft handover statistics closely matching those of real networks may be achieved. The analysis also concludes that many real networks have better cell isolation than what is modeled by the 3GPP antenna model. As a consequence, the horizontal radiation pattern model significantly under-estimates the system level performance in such networks. Furthermore, the proposed model is used to assess the LTE and HSPA system-level performance for realistic scenarios.

System performance of EDGE, a proposal for enhanced data rates in existing digital cellular systems

The use of alternative modulation to provide Enhanced Data rates for Global Evolution (EDGE) is currently being standardized for GSM by the European Telecommunications Standards Institute (ETSI), and is also adopted for IS-136 evolution by the Universal Wireless Communications Consortium (UWCC) in the US. This paper analyzes the system performance of the EDGE concept. Two scenarios are studied: one where EDGE is introduced in an existing GSM system with 3/9 frequency reuse, and one where EDGE is introduced as an IS-136 overlay, using a very limited amount of spectrum and 1/3 frequency reuse. Both capacity and coverage results are provided. Simulations show that the introduction of EDGE significantly increases the user bit rates in both coverage and interference limited systems compared to standard GSM. The spectral efficiency is also increased considerably. It is also shown that spectral efficiencies exceeding 0.45 bps/Hz/site can be achieved when EDGE is introduced in an IS-136 system using a 1/3 frequency reuse pattern. Further, coverage simulations indicate that existing sites can be reused when EDGE is introduced.

Comparison of link quality control strategies for packet data services in EDGE

EGPRS is the packet radio service of EDGE, the common evolutionary path for the two second generation cellular standards GSM and TDMA/136. In this paper, methods for adapting the transmission rates and robustness to different environments and to the sometimes rapidly varying radio conditions experienced in such systems are evaluated. A discussion comparing different solutions together with supporting simulation results lead to the proposed solution for EGPRS.