Jijun Luo

The road to IMT-advanced communication systems: State-of-the- art and innovation areas addressed by the WINNER + project

Phases I and II of the WINNER project contributed to the development, integration, and assessment of new mobile network techniques from 2004 to 2007. Some of these techniques are now in the 3GPP LTE and IEEE 802.16 (WiMAX) standards, while others are under consideration for LTE-Advanced and 802.16m. The WINNER+ project continues this forwardlooking work for IMT-advanced technologies and their evolution, with a particular focus on 3GPP LTE-advanced. This article provides an overview of the WINNER system concept and several of its key innovative components.

Network controlled mobility management with policy enforcement towards IMT-A

This paper introduces a framework of mobility management and call-handling based on policy enhancement towards the IMT-advanced systems. The function allocation and several selected mechanisms for the framework are described. The framework is based on the EU IST WINNER research project results and enables scalable service provisioning by setting the end user satisfaction and overall system performance as general goals. This paper aims to serve as a reference for the design of IMT-advanced systems.

Key technologies for IMT-advanced mobile communication systems

WINNER is an ambitious research project aiming at identification, development, and assessment of key technologies for IMT-advanced mobile communication systems. WINNER has devised an OFDMA-based system concept with excellent system-level performance for flexible deployments in a wide variety of operating conditions. The WINNER system provides a significant step forward from current 3G systems. Key innovations integrated into the system concept include flexible spectrum usage and relaying, adaptive advanced antenna schemes and pilot design, close to optimal link adaptation, hierarchical control signaling, and a highly flexible multiple access scheme. The end-to-end performance assessment results demonstrate that the WINNER concept meets the IMT-advanced requirements.

Inter GW Load Balancing for Next Generation Mobile Networks with Flat Architecture

With rapid growth of mobile users and developents of mobile equipments like cell phones, laptops and personal digits assistances (PDA), mobile networks have to meet dramatically increased service demands in the nearest future. The ever-increasing demands, such as the users expect to enjoy the service anywhere, anytime and the networks support a seamless mobility, driving the evolution of mobile networks at a fast pace. The next generation mobile network (LTE in 3GPP) is conducting research towards this goal. An IP protocol based flatter network architecture has been introduced in the next generation mobile networks (NGMN). In this network architecture, gateway (GW) is the only node which establishes a connection between RAN and external world. To provide capabilities of gateways catering for service demand at different stages, more advanced functions such as load balancing between gateways is proposed. Such mechanism will be used as a solution to avoid gateways congestion and optimize network performance for the future network. In this paper, based on the described flat architecture of the next generation mobile networks and some related concepts such as the pool of gateway, inter-GW load balancing approach has been introduced followed by performance evaluation. Simulation results show promising gains provided by the inter-GW load balancing mechanism for next generation systems.

Performance impact of flexible power arrangement in OFDMA based cellular communication networks

In the OFDMA-based downlink of wireless cellular communication networks, the intercell interference would be a key performance-limiting factor, especially for the cell edge users. To enhance the cell edge user performance, several flexible power allocation schemes have been proposed, e.g., the so-called soft frequency reuse scheme and the partial frequency reuse scheme. This paper analyzes those schemes in a very realistic multicell setting, investigates the layer 2 resource allocation algorithms that are associated to the physical layer setting, and finally gives results of the performance evaluation.

Location Determination using In-Band Signaling for Mobility Management in Future Networks

This paper covers positioning techniques for future cellular networks using orthogonal frequency division multiplexing communications signals. These methods are based on symbol- timing synchronization algorithms to find the starting point for the underlying in-band pilots in the preamble. Commonly used approaches as like the Schmidl-Cox algorithm and the Minn algorithm are discussed and investigated w.r.t. their positioning capabilities. Furthermore, they are extended to improve the performance in multipath environments and to achieve a sufficient accuracy with weak signals from neighboring out-of-cell base stations. Additionally, system-side applications that can make use of the estimated location information are analyzed.

Performance Impact of User Grouping on Fractional Power Loading in the OFDMA Downlink

In the OFDMA-based downlink of wireless communication networks, in order to counteract the strong influence of multi-cell interference on the cell edge users, the so-called fractional power loading strategy was proposed. The key idea is to divide the whole frequency band into two parts, one part has lower transmission power, the other has higher transmission power and is orthogonal in the neighboring cells. With such power allocation, a natural thinking is to schedule the cell edge users onto the high power band, and to schedule the cell center users onto the other. Such strategy leads to the partitioning of users into the cell center/edge user groups. This paper proposes a way to do dynamic user grouping, and compares the cell performance for elastic traffic, with and without the user grouping. Extensive system level simulations with multi-channel proportional fair scheduler are conducted to reveal the effect of user grouping on the scheduler performance and QoS fulfillment.

Access selection and mobility management in a beyond 3G RAN: The WINNER approach

Next generation communications will be composed of flexible, scalable and context-aware, secure and resilient architectures. The technologies will allow full mobility of the user and enable dynamic management policies that ensure end-to-end secure transmission of data and services across heterogeneous infrastructures and networks. The concept of ubiquitous and scalable system is applied in the IST WINNER II project to deliver optimum performance for different deployment scenarios from local area to wide area wireless networks. The integration of cellular and local area networks in a unique radio system will provide a great advantage to final users and operators, compared with the nowadays situation, where there are many standalone systems and users equipped with different subscriptions, radio interfaces and terminals. To this issue, the IST project WINNER II has defined three system modes suited to local, metropolitan and wide area respectively. This paper describes the mobility management and access selection schemes that are proposed for the WINNER system that is designed as a candidate Beyond 3G type of system. A radio resource management (RRM) architecture that fully enables the functionality of these schemes will also be presented. The RRM schemes are based on specially designed cooperation RRM algorithms for the successful coexistence and handover of WINNER with new and legacy systems. The paper describes the cooperation architecture and mobility management functionalities and the rules that are applied for the support of mobility within the above scenarios.

Media independent handover enabled advanced mobility management and its functional mapping

In this paper, we propose a suitable set of protocols schematically combining both radio handover and IP handover for heterogeneous network with the enhancement of relay nodes, that is considered as an important feature of the future radio network. Based on that, we develop the functional allocation of media independent handover entities for a 4G communication system developed by the European WINNER project. The allocation is suitable for decentralized radio resource and mobility management as proposed by the system architecture evolution. Performance evaluation of the handover signaling delay for media independent handover enabled relay enhanced cells is presented. Conclusions derived from this work serve as a reference for the design of future radio network and the associated protocols.

User Plane Protocol Optimization in Cellular Networks with Decode-and-Forward Type of Relay

The use of relay stations in the cellular network is a good candidate method to enhance the cell edge data rate, and to provide homogeneous QoS experience for users in different locations. We discuss the decode-and-forward type relay station within the context of the 3GPP RLC/MAC layers. The emphasis is on proper RLC layer operation for the relay-enhanced-cell (REC). RLC layer evolvement in the future high data rate radio access network will first be discussed, then its performance in REC will be investigated, with or without it being implemented on the relay station. Simulations are conducted on the downlink for the future OFDMA-based relay network, from which we finally draw significant conclusions.