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LTE

2012-1 (Vol.48, No.1)

This special issue on LTE covers the following topics:
– Radio access technology toward a human-centric society
– Technologies making up an LTE network infrastructure system
– Express Card terminal and associated device technologies
– Radio engineering technology for installing base stations and related field trials
– Self-organizing network (SON) and inter-cell interference coordination (ICIC) technologies for improving network performance.
Fujitsu's contributions to LTE standardization activities are also described in this issue.

2012-1 (Vol.48, No.1) Contents

1. Preface (535 KB): Fujitsu has played a leading role in the development of mobile-network infrastructure systems and mobile terminals starting from the research and development stage. Higher transmission speeds in the mobile network should drive the creation of new human-centric services and applications bringing about a revolution in mobile communications. Looking forward, Fujitsu will continue to develop advanced technologies to enhance the mobile network while contributing to the development of next-generation mobile systems and the provision of diverse and compelling mobile services. ---[Hiroshi Nagatomi, Corporate Executive Advisor]

2. Broadband Wireless Access Supporting a Human-Centric ICT Society (1.30 MB ): Fujitsu is promoting a new vision: "Use information and communications technology (ICT) to create a human-centric intelligent society that brings prosperity and security to peoples' lives." This paper first presents some characteristics of networking functions that are key to realizing such a human-centric ICT society, including "easing constraints on use," "providing smooth responses," and "eliminating cumbersome procedures." It then examines the use of wireless local area network (WLAN), Mobile Worldwide Interoperability for Microwave Access (Mobile WiMAX), and Long Term Evolution (LTE) technologies for providing broadband wireless access, which is the key to providing smooth responses, and summarizes their characteristics. Examination in light of the increasing volume of information flow revealed that LTE is the most promising. Achieving more human-centric networking functions requires a mechanism able to understand the state of wireless resources available to the user and to control the timing and execution of user requests accordingly. An approach is presented to developing such a mechanism, one that virtualizes the wireless access link and that controls it in accordance with changes in the wireless resources available as the user changes location. The effects that can be expected from this approach are discussed. ---[Hiroyuki Seki, Keiichi Nakatsugawa]

3. Next-Generation Mobile Network (946 KB): The number of people using mobile 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 smartphones, mobile data traffic will increase 200 times in the 10 years up 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. ---[Tsuguo Kato]

4. Evolved Packet Core (EPC) Network Equipment for Long Term Evolution (LTE) (737 KB): Long Term Evolution/Evolved Packet Core (LTE/EPC) is a system that will follow on from the 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 LTE/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 Mb/s for downlink and 86.4 Mb/s 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. ---[Toshiki Hayashi]

5. Evolved Node B on LTE System for NTT DOCOMO (952 KB): Fujitsu has developed an evolved Node B (eNodeB) for the Long Term Evolution (LTE) mobile communication system of NTT DOCOMO in Japan. LTE provides at least 100 Mb/s 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 easy 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. ---[Hiroaki Watanabe, Satoru Hirasawa, Kyousuke Suzuki, Ryuichi Karino]

6. Outdoor LTE Infrastructure Equipment (eNodeB) (1.34 MB ): Fujitsu has developed outdoor Long Term Evolution (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. ---[Kimio Watanabe, Mamoru Machida]

7. High-Efficiency Power Amplifier for LTE/W-CDMA System (1.04 MB ): Long Term Evolution (LTE) systems are attracting attention as next-generation mobile communication systems. Such systems have come to transfer and manage large volumes of data at high speed. Therefore, 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 size and power consumption. This can be done with the overlay service which supports both W-CDMA and LTE systems, and 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. The RRH is also known as 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. ---[Yoshiaki Kumagai, Yasuhito Funyu, Hiroaki Maeda]

8. GaN Device for Highly Efficient Power Amplifiers (1.11 MB ): 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 operating at high voltage for LTE base stations. First, we introduce the advantages of GaN-HEMT in terms of its physical properties 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. ---[Toshihide Kikkawa, Kazukiyo Joshin, Masahito Kanamura]

9. Management System for Mobile Networks (1.06 MB ): 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 is a characteristic of network management systems and that allows Fujitsu to differentiate itself from its competitors. The last part explains the concept of a system to integrate communication management systems that have been individually developed. ---[Kazutoshi Kawamura, Masao Murata, Shouji Higuchi, Fumiyasu Kurokochi]

10. Development of LTE Baseband LSI and ExpressCard Terminal for Mobile Devices (794 KB): Fujitsu has developed ExpressCard device for Long Term Evolution (LTE) systems. This device is provided for Xi "crossy," an LTE service offered by NTT DOCOMO in Japan, and it achieves a downlink speed of up to about 75 Mb/s, 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 baseband LSI and its future direction. ---[Nobuhide Maruo, Makoto Saotome]

11. SAW-less Transceiver for 4G/3G/2G Cellular Standards (1.47 MB ): A single-chip multi-mode multi-band CMOS transceiver was designed and implemented for the 4G mobile platform. The transceiver supports both Long Term Evolution (LTE) frequency division duplexing (FDD) and time division duplexing (TDD) operation modes. It also supports 3G Wideband Code Division Multiple Access (W-CDMA) and 2G global system for mobile communication (GSM)/enhanced general packet radio service (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 low-noise amplifiers (LNAs) or interstage surface acoustic wave (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 application programming interface (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. ---[Patrick Rakers, Daniel B. Schwartz, Mahib Rahman, James Mittel]

12. Radio Engineering Technology (1.08 MB ): Radio engineering technology is necessary for maximizing the effectiveness of capital investment when constructing a radio network for a mobile communications system. Improving this technology enables optimization of the radio network and more flexible response to changes in the system requirements. Radio engineering technology is used in the design, tuning, operation, and maintenance of radio networks. This paper introduces and explains methods for designing Long Term Evolution systems and presents results obtained in field trials conducted to evaluate their performance. ---[Mitsuhiro Ono, Satoru Tawara, Satoshi Makino]

13. Field Trial for LTE Mobile Network System (1.44 MB ): The Long Term Evolution (LTE) mobile network system is slated to become the wireless broadband infrastructure for constructing the smart ubiquitous society. Fujitsu has conducted a field trial toward the early implementation of an LTE system as a field-proven platform for the cloud era. An end-to-end LTE system targeting the global market was set up using a 5-MHz bandwidth in the 1.7-GHz band, and measurements were taken to assess system performance and the applicability of LTE system operations for the coming cloud era. The achievement of a maximum throughput of 34.6 Mb/s for the downlink and 9.5 Mb/s for the uplink shows that the LTE system has sufficient performance for use in the field. Testing of applications traditionally used in a fixed Internet protocol network showed that they could also run well on an LTE system. This article presents and discusses the results of this field trial. ---[Hiroyuki Kiyanagi, Morihiko Minowa]

14. Use of Self-Organizing Networks to Optimize Radio Access Networks (1.10 MB ): Self-organizing networks (SONs) are collections of control and management methods and optimization algorithms that are attracting attention as a means of achieving economical services in the next-generation mobile network. The aim with them is to reduce the total cost of ownership (TCO) by having traditionally manual tasks like design, configuration, optimization, and operation/monitoring performed autonomously on the network side as much as possible. When a SON is introduced, it is important that the SON functions be applied with minimal impact on the existing network, that the entire network be optimized and not just the radio network, and that the SON itself be enhanced as needed. This article outlines the SON concept, describes the technologies of automatic load balancing and coverage/capacity optimization as SON use cases for optimizing a radio access network, and describes a system architecture for implementing SON. ---[Ryuichi Takechi, Koji Ogawa, Masato Okuda]

15. Inter-Cell Interference Coordination (ICIC) Technology (959 KB): Long Term Evolution (LTE) is a promising standard for next-generation cellular systems targeted to have a peak downlink bit rate of 150 Mb/s. However, as adjacent cells use the same frequency, interference between adjacent cells may degrade the bit rate at cell edges, preventing sufficient throughput from being obtained. Inter-cell interference coordination (ICIC) is a promising technology for alleviating this degradation and improving the bit rate at cell edges. In the LTE standard, an interface between adjacent base stations is specified for exchanging ICIC information. However, no methods or control algorithms have been specified for using this interface, leaving it to base station vendors to develop them on their own. This paper outlines ICIC technology in the LTE system, describes the original ICIC algorithm we have developed, and discusses its evaluation. ---[Dai Kimura, Hiroyuki Seki]

16. Standardization Activities for Next-Generation Mobile Communications Systems (1.04 MB ): The 3rd Generation Partnership Project (3GPP) founded in 1998 by standardization organizations in Japan, Europe, North America, China, and South Korea released a set of specifications called Release 8 in December 2008. This release formally specified Long Term Evolution (LTE) technology and presented the evolved packet system (EPS), a new architecture covering the radio access and core networks. By supporting only packet communications and achieving more flexible frequency spectrum usage, LTE enables mobile communications at even higher bit rates and wider bandwidths. The explosive increase in new terminals like smartphones, however, is dramatically increasing the amount of data that the network must handle, making it necessary to further expand system capacity. To address these new issues, standardization activities for the Heterogeneous Network (HetNet) system and other new systems have begun, centered on 3GPP. This article describes standardization trends for next-generation mobile communications systems and Fujitsu's contributions to standardization activities. ---[Akishige Noda]

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