Hannes Ekström

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.

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

An Evolved 3GPP QoS Concept

Simple and cost efficient means for providing and controlling quality of service (QoS) are important for 3GPP operators. This is particularly important for operators planning to provide a wide range of IP-based services across 3GPP broadband shared channels. We point out shortcomings of todays (Rel. 5) 3GPP QoS concept and, based on these, explain why that demand is currently not met. Based on a set of requirements identified for an evolved 3GPP QoS concept, we propose four small additions to the 3GPP specifications. The resulting evolved QoS concept is a realization of DiffServ for 3GPP access networks enhanced with the integration with session admission control. Operator QoS control is exercised from the policy charging rule function (PCRF) and through pre-configuration via the management plane. The evolved QoS concept provides a 3GPP operator with capabilities beyond those found in state-of-the-art fixed broadband access networks

End-to-end performance of WCDMA enhanced uplink

In this paper we study the end-to-end performance of the enhanced uplink of WCDMA. We present results for latency and TCP performance on both uplink and downlink when using the enhanced uplink. The results show that the enhanced uplink can significantly improve the end-to-end performance of both for up- and downlink oriented traffic when compared to the uplink provided by 3GPP R5. The expected performance depends strongly on the configuration of the enhanced uplink, especially on the HARQ operating point.

Searching for mobile mice and elephants in GPRS networks

In this paper, we provide statistics on large-scale traffic measurements that have been made in a live cellular GPRS network. We show that the current GPRS traffic is dominated by HTTP- and WAP-based applications, and further show in what direction (uplink and/or downlink) the ensuing traffic is transmitted as well as statistics on the length of the flows on a per application basis. We find that the results differ compared to those found in similar measurement studies that have been carried out in the fixed Internet. In particular, our results suggest that flows are shorter in cellular networks, and that the so-called mice and elephant effect, whereby a small part of the flows make up a majority of the bytes transferred, is not prevalent in GPRS networks. Instead, extremely short flows account for the majority of the total flows and bytes transferred. We also discuss the impact of this finding on future research on TCP loss recovery.

Buffer management for the interactive bearer in GERAN

In this paper, we describe and evaluate a novel active queue management scheme that has been designed to optimize the transport of TCP-based traffic over GERAN 3rd generation wireless links. By means of simulations, we found that this scheme outperforms traditional passive and popular RED queuing schemes both in terms of link utilization and in terms of the amount of queuing delay introduced.

Queue management for TFRC-based traffic in 3G networks

We study the performance of TFRC-based traffic running across a 3G network. The goal is to evaluate the impact of three different queue management schemes on the end-to-end performance provided by TFRC. We show that drop-on-full queuing is absolutely inappropriate for TFRC traffic running over 3G links since it leads to burst packet drops and oscillatory behaviour in TFRC. Although, this is mostly avoided with RED (Random Early Discard) queuing, we find large initial probing phases of TFRC when using RED. With a simpler active queue management scheme we propose, PDPC, this probing phase is significantly reduced.