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The long-term evolution of 3G

Ericsson Review, no. 02, 2005

Written by: Erik Dahlman, Hannes Ekström, Anders Furuskär, Jonas Karlsson, Michael Meyer, Stefan Parkvall, Johan Torsner and Mattias Wahlqvist

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The Third Generation Partnership Project (3GPP) has begun charting the long-term evolution of 3G to ensure the competitiveness of 3G technology during the next 10 years and beyond. The fundamental aims of this evolution - to further improve service provisioning and reduce user and operator costs - will be met through improved coverage and system capacity and by improving data rates and reducing latency.

The authors describe technologies that promise to provide these improvements, including orthogonal frequency-division multiplexing (OFDM), multi-antenna solutions, evolved quality-of-service (QoS) and link-layer concepts, and an evolved system architecture. The authors also present the results of a performance evaluation which confirms that the long-term requirements can indeed be fulfilled.

Background and targets
Third-generation mobile systems (3G) based on WCDMA radio-access technology are being deployed on a broad scale all around the world. A first step in enhancing or evolving this technology entails introducing high-speed downlink packet access (HSDPA) and an enhanced uplink (E-UL), giving a radio-access technology that is highly competitive.

However, knowing that user and operator requirements and expectations will continue to evolve, the 3GPP has begun considering the next major step or evolution of the 3G standard (sometimes called Super 3G) to ensure the long-term competitiveness of 3G. The 3GPP recently launched a Study Item entitled Evolved UTRA and UTRAN. The study will investigate means of achieving major leaps in performance in order to improve service provisioning and reduce user and operator costs.

It is generally assumed that there will be a convergence toward the use of internet protocols, and all future services will be carried on top of IP. Therefore, the focus of the evolution is on enhancements to the packet-switched (PS) domain. In particular, the 3GPP aims to deliver a set of specifications for evolved 3G radio access in 2007. Initial product availability is envisioned around 2009-2010.

The main objectives of the evolution are to further improve service provisioning and reduce user and operator costs. More specifically, some key performance and capability targets for the long-term evolution are

  • the potential to provide significantly higher data rates compared to HSDPA and E-UL, with target peak data rates of more than 100Mbps over the downlink and 50Mbps over the uplink;
  • improved coverage - that is, high data rates with wide-area coverage;
  • the potential to significantly reduce latency in the user plane in the interest of improving the performance of higher layer protocols (for example, TCP) as well as reducing the delay associated with control plane procedures (for instance, session setup); and
  • greater system capacity - threefold capacity compared to current standards.

One other key requirement of the long-term evolution is to allow for a smooth migration to these technologies. This can be ensured by giving

  • operators the ability to deploy the new system in existing (already paid for) spectrum. This puts technical requirements on spectrum flexibility, allowing deployment in many different allocations of spectrum (2G and 3G);
  • operators the ability to reuse sites and investments in site and transmission equipment;
  • operators the ability to maintain their base of end users by smooth service phase-ins and phase-outs. This puts requirements on service continuity and mobility between systems;
  • operators the ability to deploy the new technology in areas where it is profitable. Elsewhere, they can rely on existing systems for coverage and, to some extent, capacity. This puts requirements on mobility between systems; and
  • manufacturers the ability to reuse investments in development. This results in stable and competitively priced equipment and shorter time to market.

To reach the performance and capability targets, 3GPP must consider some new radio-transmission technologies as well as updates and modifications to the architecture of the 3G radio network. Ericsson believes that the following building blocks can help fulfill the stated targets:

  • simplified system architecture;
  • evolved QoS and link-layer concepts;
  • the use of adaptive multilayered OFDM (AML-OFDM) as a new radio-access technology; and
  • advanced multi-antenna solutions.