Fujitsu’s Challenges for WiMAX System-on-a-Chip Solutions
V Tamio Saito V Makoto Awaga V Takeshi Takano (Manuscript received March 10, 2008)
Worldwide Interoperability for Microwave Access (WiMAX) is a promising candi- date for providing high-data-rate mobile broadband access systems around the world. This paper describes specific features of Mobile WiMAX, such as scalable orthogonal frequency division multiple access (OFDMA), adaptive modulation and coding, and smart antenna technologies, a system configuration, candidate applica- tions, and our challenges for WiMAX system-on-a-chip (SoC) solutions.
1. Introduction (MS: mobile station, SoC: system-on-a-chip, RF: In recent few years, the number of mobile radio frequency). Internet access users has been increasing very This paper summarizes Mobile WiMAX’s rapidly and requirements for high-data-rate specific PHY features, a WiMAX system configu- mobile broadband access systems are also ration, candidate applications for the system, and increasing. Worldwide Interoperability for our challenges for Mobile WiMAX SoC solutions. Microwave Access (WiMAX) is a promising candidate for high-speed mobile broadband 2. Mobile WiMAX specific PHY access. There are two flavors of standards features for WiMAX: IEEE 802.16-20041) a n d Here, we describe some PHY features that IEEE 802.16e-2005.2) IEEE 802.16-2004 is are specific to Mobile WiMAX. mainly focused on fixed wireless access technolo- gies while IEEE 802.16e-2005 is an amended 2.1 Scalable OFDMA version of IEEE 802.16-2004 that adds features Mobile WiMAX uses a scalable orthogonal and attributes to support mobility. In the frequency division multiple access (OFDMA) IEEE 802.16e-2005 standard, there are a lot of technology. A comparison between Fixed WiMAX parameters related to the media access control and Mobile WiMAX is shown in Figure 1. For (MAC) protocol and physical (PHY) layers. Fixed WiMAX, the size of the fast Fourier Therefore, to keep interoperability among devic- transform (FFT) is fixed to 2048 points. If es, an industry consortium called the WiMAX the signal bandwidth changes, the sub-carrier Forum develops guidelines known as system frequency spacing changes too. This means that profiles, which specify the frequency band, if the system changes the service bandwidth from PHY parameters, and MAC parameters to be 20 MHz to 10 MHz in a mobile environment, the used. We have already released commercial Doppler effects will change because there are products such as MS baseband SoC,3) MS RF different Doppler effects for the 20- and 10-MHz module4) and base stations5),6) for Mobile WiMAX bandwidths. To achieve the same performance
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for the systems, the channel estimation function tions from these modulation schemes and coding should be changed according to the bandwidth, schemes to achieve a high data rate, as shown in but this increases the circuit complexity. The Table 1. scalable OFDMA technology used in Mobile WiMAX avoids this phenomenon. The scalability 2.3 Smart antenna technologies is provided by adjusting the FFT size while fixing To enhance system performance, Mobile the sub-carrier spacing at 10.94 kHz. Since the WiMAX uses smart antenna technologies that sub-carrier spacing is fixed, the impact of the include beamforming, space-time coding (STC), Doppler effect is the same for systems using and spatial multiplexing (SM). For beamforming, different bandwidths. This approach enables the system uses multiple antennas to transmit one particular channel estimation method to be weighted signals to increase the system’s cover- applied to the entire range of environments. age and capacity. This enables a base station (BS) to get a feedback signal from an MS; then, the BS 2.2 Adaptive modulation and coding calculates the weight for each signal. The STC is To enhance the coverage and capac- a transmit diversity technology7) and the scheme ity of mobile applications, Mobile WiMAX uses two transmit antennas and one receive uses an adaptive modulation and coding antenna. The STC provides a spatial diversity (AMC) function in the system. Mobile WiMAX gain in the system and this technique reduces the supports quadrature phase shift keying (QPSK), fading margin. The SM8) achieves higher peak 16 quadrature amplitude modulation (16QAM), rates and increases the data throughput in a and 64QAM as mandatory in the downlink and link. With SM, multiple data streams are trans- supports QPSK and 16QAM as mandatory in mitted from multiple antennas. If two transmit the uplink. In addition, the system supports antennas and two receive antennas are used, the both convolutional coding (CC) and convolutional increase in data transmission rate is twice that turbo coding (CTC) with variable coding rate and in the best condition before. repetition coding. AMC can use various combina-
OFDMA: 802.16-2004 Scalable OFDMA: 802.16e-2005 • FFT size is fixed to 2048 for all bandwidths • Allocate the FFT size according to available • Interval of the sub-carriers becomes narrower frequency bandwidth as available bandwidth. • Interval of sub-carriers is fixed. • More difficult to keep performance
2048/20 MHz 2048/20 MHz
2048/10 MHz 1024/10 MHz 512/5 MHz 128/1.25 MHz
(a) Fixed WiMAX (b) Mobile WiMAX
Figure 1 Comparison between Fixed WiMAX and Mobile WiMAX.
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3. Mobile WiMAX system convergence, such as fixed-mobile conver- configuration gence (FMC) A next-generation packet-based network To deal with the issues of quality, security, configuration is shown in Figure 2. 3G/3.5G, and robustness LTE and WiFi/WiMAX systems are connected to To achieve autonomic control and an all-IP-based network (IP: Internet protocol). self-organization As described before, WiMAX has very flexible To satisfy these requirements, the Next functions for achieving a variety of services. To Generation Network (NGN) is a promising candi- support these features effectively, the all-IP date for the all-IP core network. core network should be flexible to handle their functions. Thus, the core network should satisfy 4. Candidate applications for the following requirements:9) Mobile WiMAX • Functionality to cope with the demand for This section describes some candidate appli- continuous broadband service cations for Mobile WiMAX. Mobile WiMAX • Ease of use and ease of service provision provides a high-data-rate service in the mobile To achieve new services provided through environment at a low cost. Some service models
Table 1 Mobile WiMAX PHY data rates with partial usage of sub-channels. 0ARAMETER $, 5, $, 5, 3YSTEM BANDWIDTH -(Z &&4 SIZE .ULL SUB CARRIERS 0ILOT SUB CARRIERS $ATA SUB CARRIERS 3UB CHANNELS 3YMBOL PERIOD 4S MICROSECONDS &RAME DURATION MILLISECONDS /&$- SYMBOLSFRAME $ATA /&$- SYMBOLS $,5, -OD #ODE RATE $, -BS 5, -BS $, -BS 5, -BS #4# X #4# X 103+ #4# X #4# X #4# #4# 1!- #4# #4# n n #4# n n 1!- #4# n n #4# n n
$, $OWNLINK 5, 5PLINK
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for Mobile WiMAX are shown in Figure 3. uses that can be considered: satellite and cable The first model is a fixed application in television (CATV) broadcasting through WiMAX which Mobile WiMAX is used as a fixed broad- and data transmission from a user’s personal band service such as a replacement for digital media assistant. This application is very suitable subscriber line (DSL) access. Of course, there for Mobile WiMAX because it needs a very high is Fixed WiMAX for this area. However, a lot of data transmission rate. For the voice-centric carriers would like to use Mobile WiMAX instead usage, voice-over-IP (VoIP) technology is applied of Fixed WiMAX. This is because Fixed WiMAX to the Mobile WiMAX system. Although the system currently is not so popular and the 2G/3G cellular communication systems already system cost is relatively high. have a legacy voice communication function The second model is a hot zone applica- in the system, WiMAX does not. Therefore, tion. For this purpose, there are three usage this function may be necessary to cover voice categories: data-centric, rich-media-centric, and applications. voice-centric. For data-centric usage, Mobile The third model is a hot zone with cellular WiMAX is used to keep the data transmission system application. This application is a combi- rate high when a notebook personal computer nation of Mobile WiMAX and a cellular system (PC) or personal digital assistant (PDA) is used. such as 2G or 3G. This application requires a This service is almost the same as the current dual-mode mobile phone, and the uncertain feasi- HSDPA/HSUPA (high-speed downlink/uplink bility of dual-mode technology and its high cost packet access) service in the 3G system. However might be a bottleneck. Mobile WiMAX can provide a higher data trans- One idea for a new mobile communica- mission rate at a relatively low cost. For the tion service using Mobile WiMAX is shown in rich-media-centric usage, there are two main Figure 4. This idea is for a user to send and
Service Circuit switched IP multimedia service Streaming service emulation service
Control/management Resource control/mobility management PSTN Internet Transport/access IP core network AGW xGSN 3G/3.5G xDSL/FTTx
RNC AGW AGW 3G-LTE WiFi/WiMAX HGW BTS BTS BTS BTS AP AP
BTS: Base station transceiver AGW: Access gateway RNC: Radio network controller LTE: Long term evolution xGSN: Serving/gateway GPRS support node FTTx: Fiber to the home/curb/premises, etc. HGW: Home gateway
Figure 2 Next-generation packet-based network configuration.
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!DOPTION 3ERVICE MODEL 5SERS USAGE !PPLICATION DEVICE TIME 0OOR 5SING 7I-!8 AS 3INGLE &IXED "" $ESKTOP &IXED ! BROADBAND SERVICE SUBSTITUTION NOTEBOOK 0# DE REPLACEMENT FOR $3,
5SING 7I-!8 TO KEEP $ATA CENTRIC HIGH DATA RATE TRANSMISSION WHILE " .OTEBOOK 0# 0$! HOT ZONE USING NOTEBOOK 0# AND 0$! '' IS STILL AVAILABLE BY MOBILE PHONE 4WO MAJOR USAGES (OT 3ATELLITE AND #!46 # 2ICH MEDIA CENTRIC BROADCASTING THROUGH 7I-!8 .OTE 0# 0-! 0$! ZONE 3INGLE (OME SERVER AS USERS 0-! DATA TRANSMISSION -OBILITY E 6O)0 USAGE INSIDE 7I-!8 6OICE CENTRIC NETWORK AND THE MOBILE PHONE $ 0$! MOBILE PHONE HOT ZONE COULD HAVE 7I-!8 6O)0 AND '' FUNCTION AT THE SAME TIME
7IDE HOT ZONE USAGE AND (OT -OBILE TELECOM % MAYBE THE REPLACEMENT FOR 0$! MOBILE PHONE ZONE SUBSTITUTE n SINGLE MESH '' SERVICE BY 7I-!8 $UAL MODEL MOBILE PHONE $UAL (OT ZONE -OBILE TELECOM WHICH COULD USE 7I-!8 E & SUBSTITUTE n SINGLE -OBILE PHONE NETWORK AND HAVE '' DUAL 'OOD '' '' SERVICE TOO
Figure 3 Service models of Mobile WiMAX.
• Personal life recorder • records scenes in personal life not with DSC/DVC, • but with cellular phone and transfer to home server
USB connection
Personal contents High-speed wireless IP infrastructure Home network (Mobile WiMAX, post 3G)
• Save any personal contents in home • High-resolution camera (5 megapixels or more) • server • Sophisticated image processing • Play them back anytime anywhere • H.264/AVC codec capability
DSC: Digital still camera DVC: Digital video camera
Figure 4 New mobile communication service.
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receive personal high-resolution pictures on a We plan to develop both baseband SoCs and RF Mobile WiMAX terminal to/from a home server LSIs for Mobile WiMAX terminals. For mobile located in his/her home. In the current situa- applications, it is very important to make these tion, to take a high-definition video picture, we SoCs or LSIs in a small size with very low use a digital still camera or digital video camera. power consumption. In 2007, we released the If the camera’s memory is full, we cannot record generation-1 baseband (BB) SoC (MB86K21) for any more until some data has been deleted. notebook PC applications such as PCMCIA cards However, if we can use wireless data trans- and USB-dongle WiMAX modules. The BB SoC mission for personal video recoding, then the has CardBus and USB interfaces for the module camera’s memory capacity becomes irrelevant. and uses 90-nm CMOS technology. We devel- Furthermore, this service enables playback of oped reference design kits (PC card type)10) and recorded personal videos. Via a Mobile WiMAX system development kits10) to enable custom- network, we can see personal videos that we ers to develop Mobile WiMAX products easily. recorded and stored on our home server wherev- We also performed a lot of interoperability tests er we are. Using a similar architecture, we can (IOTs), such as WiMAX Forum Plugfest and consider time-shift, location-shift TV-playback private IOTs, to confirm that our BB SoC works services, an on-demand package-less video rental well under the WiMAX Forum’s Mobile WiMAX service, and on-demand live video news service. System Profile version 1.5.0. For a generation-2 BB SoC, we use an 5. Fujitsu’s challenges for Mobile advanced 65-nm CMOS process to achieve high WiMAX SoC solutions performance and low power consumption. At To deploy Mobile WiMAX services on the the same time, we developed a generation-2 RF market, we must overcome the challenges of LSI and power management module (PMM) to developing Mobile WiMAX SoC solutions. Our create a complete solution that enables a custom- current roadmap for SoC is shown in Figure 5. er to make a PDA product or mobile-phone-type
Generation 3 • Wireless convergence • Ultralow power & small size
Generation 2 • Mobile multimedia terminal
Target application • Low power & small size
Generation 1 • Mobile WiMAX compliant • (MIMO wave 2) • Full reference design
2007 2008 2009
Figure 5 Roadmap of our SoC developments.
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WiMAX product. Regarding the RF LSI, we have already For the PMM, we applied a precise power announced the launch of the world’s smallest management scheme to achieve ultralow power RF module,4) MB86K71, for mobile devices. It consumption. The main features of the PMM are supports all of the RF circuitry necessary for as follows. Mobile WiMAX, including RF-IC, antenna switch- • Hierarchical power management scheme es, a power amplifier, filters, and an oscillator supported by new chip sets from Fujitsu. circuit, but still measures only 15 mm × 15 mm • During data communication, the clock (height: 1.5 mm). This generation-1 RF module gating scheme is mainly applied to the supports multiple-input multiple-output (MIMO) digital part of the WiMAX chip set. A power technology, thereby enabling high-speed and gating scheme is applied to the RF section, reliable wireless connections that are essential including the power amplifier, and analog for Mobile WiMAX devices. Furthermore, we front-end, e.g., the analog-to-digital and also verified that this RF module can be connect- digital-to-analog converters in the chip sets. ed to our previously released Mobile WiMAX • Fujitsu’s power gating scheme supports baseband chip MB86K21, enabling customers to “on-chip power switch integration” and achieve faster development and faster time to “auto-retention SRAM macros” (SRAM: market for Mobile WiMAX devices through the static random access memory). use of both chips. In addition, we plan to develop • In active mode, the entire power control a generation-2 RF LSI to further reduce the size scheme is executed on an ARM processor. and power consumption. • In standby mode, the entire power supply for the chip sets will be shut down, except 6. Conclusion for the PMM and power management unit Mobile WiMAX is a creditable candidate (PMU) in the SoC. system for providing high-speed-data access • The PMM supplies all the various voltages services to users. In this paper, we summa- needed for the WiMAX chip set using only a rized the specific features of Mobile WiMAX single battery as its power source. and a generic network configuration for a • It satisfies the requirement to reduce active next-generation core network. Then, we intro- and standby power automatically. duced candidate services for Mobile WiMAX. The main features of our generation-2 Finally, we mentioned our challenges for Mobile solution are as follows. WiMAX SoC solutions. We have already devel- • Low cost and full compliance with the oped both a BB SoC, MB86K21, and an RF IEEE 802.16e-2005 Mobile WiMAX standard module, MB86K71. These solutions enable a • Very small handset module customer to develop Mobile WiMAX products • RF, BB SoC, PMM, Flash, SDRAM, and all that are small and have low power consumption. passive components including built-in upper We will continue to develop the generation-2 BB and lower MAC (LMAC/UMAC) as firmware SoC and RF LSI to achieve even smaller and • Target profile: 2A/B/C, 3A, 5AL/BL/CL with lower-power-consumption solutions for customers. 20-MHz channel bandwidth • Host interface: SPI/SDIO References For generation 3, our target is to get a 1) Air Interface for Fixed Broadband Wireless Access Systems. IEEE STD 802.16-2004, October Mobile WiMAX terminal to coexist with WiFi/BT 2004. and various cellular phone systems such as 2.5G, 2) Air Interface for Fixed and Mobile Broadband Wireless Access Systems. IEEE STD 3G, and 3.5G.
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802.16e-2005, February 2006. 7) S. M. Alamouti: A Simple Transmit Diversity 3) Fujitsu: Fujitsu Announces Mobile WiMAX SoC Technique for Wireless Communications. IEEE Performance and Delivery Schedule. Journal on Selected Areas in Communications, http://www.fujitsu.com/us/news/pr/ 16, 8, p.1451-1458 (1998). fma_20070521-2.html 8) A. van Zelst: Space division multiplexing 4) Fujitsu: Fujitsu Launches World’s Smallest RF algorithms. Electrotechnical Conference, 2000. Module for Mobile WiMAX Devices. MELECON 2000, 10th Mediterranean, Vol.3, http://www.fujitsu.com/global/news/pr/ p.1218-1221, May 2000. archives/month/2008/20080207-01.html 9) K. Hayashi, T. Chujo, K. Kumatani, and A. 5) Fujitsu: Fujitsu Announces Global Launch of Hakata: Fujitsu’s Activities for Next-Generation Mobile WiMAX Base Station. Network. FUJITSU Sci. Tech. J., 42, 4, p.425-431 http://www.fujitsu.com/global/news/pr/ (2006). archives/month/2008/20080206-01.html 10) T. Arai, S. Yamamoto, and T. Saigo: System 6) Fujitsu: Fujitsu’s Compact Mobile WiMAX Base and Reference Design Kits for Mobile WiMAX Station Selected by UQ Communications. Terminals. FUJITSU Sci. Tech. J., 44, 3, http://www.fujitsu.com/global/news/pr/ p.249-255 (2008). archives/month/2008/20080303-03.html
Tamio Saito Takeshi Takano Fujitsu Laboratories Ltd. Fujitsu Laboratories Ltd. Mr. Saito received the B.S. degree Mr. Takano received the B.S. and M.S. in Electrical and Electronic Systems degrees in applied electronics from the Engineering and the M.S. degree University of Electro-Communications, in Electronic Engineering from the Tokyo, Japan in 1970 and 1973, respec- Nagaoka University of Technology, tively. He joined Fujitsu Laboratories Nagaoka, Japan in 1982 and 1984, Ltd., Kanagawa, Japan in 1973, where respectively. He joined Fujitsu he was engaged in research and Laboratories Ltd., in 1984 and en- development of satellite communica- gaged in research on microwave and tion systems. He is currently General millimeter-wave passive components, active components in- Manger of the NGW Project and a Fellow of Fujitsu Laboratories cluding MMIC design, an automotive collision avoidance radar Ltd. He is a member of the Institute of Electronics, Information system, a millimeter-wave wireless LAN system, and interfer- and Communication Engineers (IEICE) of Japan. ence canceller development for a W-CDMA/FDD system. He is currently Deputy General Manager of the NGW Project, Fujitsu Laboratories Ltd. His current interests include key technologies for broadband mobile access systems, such as WiMAX. He is a member of IEEE and IEICE.
Makoto Awaga Fujitsu Ltd. Mr. Awaga received the B.S. degree in electrical engineering from Ritsumeikan University, Kyoto, Japan in 1981. He joined Fujitsu Ltd., in 1981. He be- gan his career in system engineering for PCs. After spending six years in Fujitsu Microelectronics, Inc. (formerly Fujitsu Microelectronics of America) in technical marketing of microcontrollers and ASSPs in San Jose, he moved to the engineering division for graphics/multimedia in the Electronics Devices Group of Fujitsu Ltd. In June 2005, he started a new career as general manager of the mobile solution business. He is now general manager of the mobile solution division of Fujitsu Ltd., and has full responsibility for all mobile semiconductor products and solutions, including Mobile WiMAX LSI solutions and various baseband LSI products related to cellular communications. As an innovative and reliable semiconductor products and service provider, the company serves the digital consumer, mobile cellu- lar, networking, communications, automotive, security and other markets worldwide.
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