Abstracts of Magazine FUJITSU 2011-7 (VOL. 62, NO. 4)

Special Issue: LTE

• Human-Centric ICT Society Opened Up by Broadband Wireless Access

"To create a human-centric intelligent society that brings prosperity and security to the lives of people through the use of ICT" is a new vision proposed by Fujitsu. This paper first demonstrates that "easing restrictions on use," "providing a smooth response" and "eliminating cumbersome manual procedures," as the features desired of networking functions, are key to realizing a human-centric ICT society. Of the broadband wireless access schemes that are pivotal to providing a smooth response, this paper presents WLAN, Mobile WiMAX and LTE in particular, and goes on to give a summary of their characteristics. Then, an example of the design of a wireless transmission area is presented to show that LTE offers a promising access link. To achieve more human-centric networking functions, a mechanism is required that controls users' requests and the timing to execute them based on an understanding of the conditions of users and wireless resources. Finally, as an approach to achieving this mechanism, a concept of virtualization control for wireless links reflecting the conditions of wireless resources dependent on user locations is described together with its expected effect.

• Next-Generation Mobile Network

The number of people using cell phones in the world has exceeded 4.5 billion and this figure is continuing to grow. For the past several years, mobile data traffic such as Internet access, the downloading of music, and video communication has been nearly tripling every year. With the popularity of smart phones, mobile data traffic will increase 200 times in the next 10 years to 2020. There are high expectations that Long Term Evolution (LTE), which is known as a 3.9G wireless system, will be a new service platform that can support such a huge amount of mobile data traffic. This paper describes the features, technologies and network architecture of LTE, which started commercial service in December 2010 in Japan, realizing high-speed wireless access.

• Evolved Packet Core (EPC) Network Equipment for Long Term Evolution (LTE)

Long Term Evolution/Evolved Packet Core (LTE/EPC) is a system that will follow on from 3G mobile system, and mobile operators around the world are planning to use it. Indeed, some operators have already started services with this latest technology. Fujitsu has been developing ESPGW, which is a gateway for EPC, together with Nokia Siemens Networks, and NTT DOCOMO has adopted it. LTE/EPC is standardized by 3GPP, and the maximum theoretical speed for radio is defined as 325.1 Mbps for downlink and 86.4 Mbps for uplink. Therefore EPC gateways have come to need a high throughput ability to handle such heavy LTE traffic. Based on Advanced TCA, Fujitsu's ESPGW offers high availability, reliability, scalability, high throughput, a large amount of bearers and many 3GPP-standardized features. In particular, ESPGW has high throughput performance to make good use of the LTE high capacity radio transmission, and thus meets the high performance requirements of large mobile operators.

• Evolved Node B on LTE System for NTT DOCOMO

Fujitsu has developed an evolved Node B (eNodeB) for the Long Term Evolution (LTE) mobile communication system of NTT DOCOMO. LTE provides at least 100 Mbps of transmission throughput per piece of user equipment, which is a protocol for 3.9G mobile communication. The eNodeB was developed while taking into consideration its miniaturization, improved maintainability, and easily functional extension in addition to the effective utilization of existing facilities. As a result, Fujitsu has miniaturized the eNodeB by aggregating and optimizing functions, given it a configuration that can be shared with 3G systems, and enhanced it by conducting only a software upgrade. This paper outlines the functions of this eNodeB, and the features of the installed hardware and software technologies.

• Outdoor LTE Infrastructure Equipment (eNodeB)

Fujitsu has developed outdoor LTE infrastructure equipment (eNodeB) based on the specifications in the 3rd Generation Partnership Project (3GPP). Thanks to the use of highly efficient and highly integrated devices, flexible software configuration technology and simple hardware architecture, this LTE infrastructure equipment is small, lightweight and has a low power consumption. This means it can be deployed easily and efficiently when a number of base stations are installed to cope with heavy traffic load in a mobile network. As a result, this equipment helps reduce capital investment and operating costs in our customers' networks and it also contributes to the environment. This paper describes an outline of this LTE infrastructure equipment and its features.

• High Efficiency Power Amplifier for LTE/W-CDMA System

Long Term Evolution (LTE) systems are attracting attention as next-generation mobile communication systems. Such systems have come to have high-speed data rates, and so base stations have urgent requirements for devices that are friendlier to the environment, easier to install and cheaper to run. Further, there are needs to reduce capital expenses and this can be done with the overlay service of W-CDMA/LTE, which uses antennas that are employed in the conventional 3G service and thus allows system introduction costs to be reduced. Conventional mobile communication systems are composed of a baseband portion and a radio frequency (RF) portion installed in the same building. In recent systems, the RF portion of more and more devices is housed in an outdoor case separate from the baseband portion, and they are connected with an optical fiber. This type of RF unit is generally called a remote radio head (RRH) device, while NTT DOCOMO calls it remote radio equipment (RRE). Fujitsu has developed multimode technology RRE which supports W-CDMA and LTE for NTT DOCOMO. To achieve small devices with low power consumption, the efficiency of the power amplifier (PA) has been improved by adopting digital pre-distortion (DPD) and GaN Doherty PAs. This paper describes the principle, methods of operation, characteristics, and configurations of such devices.

• GaN Device for Highly Efficient Power Amplifiers

Fujitsu has been developing gallium nitride high electron mobility transistors (GaN-HEMT) for small transmitter amplifiers for Long Term Evolution (LTE) base stations. The use of GaN-HEMT in highly efficient transmitter amplifiers has attracted much attention because of its high breakdown voltage characteristics. High efficiency amplifiers with high gain are needed to decrease the power consumption and size of base stations. This paper describes the development of high-power GaN-HEMT for LTE base stations. First, we introduce the advantages of GaN-HEMT and GaN-based power amplifiers. Then, issues to be solved in the early developing stage of GaN-HEMT are focused on and the current status is described. Efficiency data of power amplifiers are shown. Finally, the future outlook is discussed in detail.

• Management System for Mobile Networks

Fujitsu is working on the development of an integrated system to be used in the future for managing various communication networks. This paper introduces a system for managing one such communication network: a mobile network. It describes the current status of this development and how it could proceed in the future, based on the features of managing mobile networks. First, this paper gives a general introduction of systems for managing mobile networks, and then describes the features of managing networks and the problems involved. It goes on to explain the main points of various measures that can be used to solve these problems. Next, this paper explains the architectural concepts behind system and software configurations used to achieve these measures. It gives an overview of Self-Organizing Network (SON) that are characteristic of network management systems and that allow Fujitsu to differentiate itself from its competitors. The last part explains the concept of a system for managing mobile networks that can be used to develop an integrated management system.

• Development of LTE Baseband LSI and Express Card for Mobile Devices

Fujitsu has developed Express Card, a device for Long Term Evolution (LTE) systems. This device is provided for NTT DOCOMO's LTE system (called Xi), and it achieves a downlink speed of up to about 75 Mbps, which is more than ten times faster than the existing systems. In order to achieve a high data transmission rate with a device that is in the form of a card, state-of-the-art technologies have been applied such as current consumption reduction with thermal release technologies or breakthroughs in techniques for installing multiple antennas and LSIs onto a small and thin circuit board. This device uses an LSI developed as a communication platform which provides a fundamental communication function for future mobile devices for LTE systems. This paper also touches on several aspects of this communication platform and its future direction.

• SAW-less Transceiver LSI for LTE/W-CDMA/GSM Cellular Standards

A single-chip multi-mode multi-band CMOS transceiver was designed and implemented for 4G mobile platform. The transceiver supports both LTE FDD and TDD operation modes. It also supports 3G W-CDMA and 2G GSM/EGPRS operation with the same signal paths. The hardware supports FDD bands 1-21, TDD bands 33-40, W-CDMA bands I-VI and VIII-XI, and EGPRS bands Cell850, EGSM, DCS and PCS. The receiver has 9 primary and 5 diversity input ports that do not require external LNAs or interstage SAW filters. The automatic gain control system is fully autonomous. The transmitter has 8 output ports that do not require interstage SAW filters. An integrated transmit predistortion path reduces the impact of offset modulations. An integrated ARM7 core controls transceiver sequencing and enables a high level API that greatly reduces radio development time. Two industry standard digital interfaces provide compatibility to LTE basebands as well as 2G/3G basebands. It is fabricated in 90 nm CMOS technology.

• Radio Engineering Technology

Radio engineering technology is necessary to maximize the effectiveness of capital investment when a radio network is constructed for a mobile communication system. By improving this technology, it becomes possible to flexibly respond to changes in systems and optimize radio networks. Radio engineering technology is used in processes such as designing, tuning, and operating and maintaining radio networks. This paper explains a design technique that considers an LTE system, and introduces some of the results obtained in a field trial to confirm the technique's performance.

• Field Trial for LTE Mobile Network System

The Long Term Evolution (LTE) mobile network system is a wireless broadband infrastructure that supports the construction of a smart ubiquitous society. Fujitsu has conducted a field trial to verify this LTE system that provides a field-proven platform for the forthcoming Cloud age, so that it can be promptly established. In this field trial, 5 MHz bandwidth in the 1.7 GHz band was used to construct an end-to-end LTE system for the global market and the area design was checked and its performance evaluated. Throughput performance of up to 34.6 Mbps for downlink and 9.5 Mbps for uplink was achieved, which confirmed that the system had adequately high performance in the field. In addition, operations of applications conventionally used in fixed IP networks were checked in the LTE system to verify they are ready for the Cloud age. This paper describes the test results of the LTE field trial.

• Technology to Optimize Radio Access Networks: Self-Organizing Network (SON)

In next-generation mobile networks, technology for a Self-Organizing Network (SON) is being introduced to help new network services run economically. SON can reduce the Total Cost of Ownership (TCO) of network operators by managing and operating networks autonomously without the need for human intervention. Such management or operation includes network planning, network deployment and network operations for network optimization or fault management. There are some important considerations for introducing SON: it is possible to migrate SON's functionality while minimizing the impact on existing networks; the entire network can be optimized and not just wireless networks; and SON itself can evolve according to the network environment. The paper gives an overview of SON's concept, describes technologies to optimize radio access networks such as automatic load balancing or radio coverage optimization as examples of using SON, and introduces the system architecture needed for network optimization.

• Inter-Cell Interference Coordination (ICIC) Technology

Long Term Evolution (LTE) systems are a very promising technology for next-generation cellular systems and can realize a very high peak bit rate in downlink (up to 150 Mbps). However, at the cell border, the interference between adjacent cells possibly degrades the bit rate. Thus, Inter-Cell Interference Coordination (ICIC) is an important technology for alleviating this degradation and improving the bit rate at the cell border. In the standardization of LTE, interfaces between neighbor cells are specified in order to exchange information for ICIC. However, there is no specified way to use such interfaces and no specified control algorithm. Therefore, we have to develop an original algorithm for ICIC. This paper gives an outline of ICIC technology in the LTE system, and describes the ICIC control algorithm we have developed and its effect.

• Overview of Standardization of Next-Generation Mobile Systems

In 1998, standards bodies in Japan, Europe, North America, China and South Korea created the 3rd Generation Partnership Project (3GPP). Version 8 (called Release 8) of 3GPP was released in December 2008 as a set of specifications. This release formally specified Long Term Evolution (LTE), and also presented to the public new architecture for wireless networks and core networks, known as the Evolved Packet System (EPS). LTE supports packet communication services only and has a higher spectrum efficiency; thus, it has simpler architecture, higher data rates and ultra-low latency. However, the amount of data that networks have to cope with has increased in recent years with the increasing adoption of new devices such as smartphones, and it has become necessary to further expand system capacity. To find solutions to issues such as these, standardization activities including HetNet and centering on 3GPP have begun. This paper describes the future direction of these standardization activities for next-generation mobile communication systems, and the way Fujitsu's standardization activities are helping in this area.