Base-Station And Handset Advances Keep 3G Rolling Out

April 12, 2007
Consumers are devouring an increasing amount of multimedia-driven services and products, made possible by advances in both wireless infrastructure and mobile devices.

After the downturn in the early part of this decade, it took many cellular carriers longer than expected to upgrade their mostly second-generation (2G) networks. The carriers simply lacked the funds to enhance their infrastructure. Since then, however, the market has stabilized. In fact, consumers are purchasing cell phones and services at an ever-increasing pace. Cellular carriers are now hastening to finish their third-generation (3G) network rollouts. To help them on this journey, a constant wave of products is being engineered for both the cellular infrastructure and the handset.

In the infrastructure arena, for example, Motorola, Inc. (Schaumburg, IL) just announced a base-station portfolio for next-generation code-division multiple access (CDMA). Beginning this year, the next-generation universal base station (UBS) and Picocell M810 will be deployed in mobile-communications service-provider networks with various frequencies and configurations (CDMA 1x and EVDO-Rev A). The Motorola UBS is available now for CDMA markets that support dual-mode voice/data applications. With its scalable, all-intellectual-property (IP) architecture, however, the UBS also is capable of supporting future technologies like Ultra Mobile Broadband. Because the unit is more compact than the previous generation, it is designed to address cellular operators’ future needs including the ability to add carriers from remote locations. The Picocell M810 provides capacity for up to eight carriers.

At the heart of the 3G infrastructure is the femtocell or 3G access point. In February, picoChip (Bath, UK) announced a High-Speed Uplink Packet Access (HSUPA)-femtocell reference design. The HSUPA specifications are part of Release 6 of the Universal Mobile Telecommunications Standard (UMTS). HSUPA increases the maximum theoretical 3G physical-layer link speed to 5.76 Mb/s. In addition, it significantly increases efficiency when used in conjunction with its downlink equivalent, High-Speed Downlink Packet Access (HSDPA). The new PC8209 design combines a modem that is fully compliant to 3GPP Release 6 for four users with a 200-m range. It supports 7-Mb/s HSDPA and 2-Mb/s HSUPA. The reference design includes all baseband processing (sample-rate, chip-rate, and symbol-rate operations) as well as a MAC-hs scheduler, operations-and-management (OAM) functionality, and protocol termination. The PC8209 product fully supports the 2-ms transmission-time-interval (TTI) specification.

Recently, picoChip announced a partnership with Tatara Systems (Acton, MA) to collaborate on all-IP solutions for the femtocell market. The interface between the femtocell and the core network is key to widespread deployment of an all-IP solution. As a result, this partnership will focus on developing an SIP/IMS-enabled femtocell reference design to ease the integration of femtocells into a mobile operator's network. The collaboration will leverage picoChip's products, which include the PC8208 HSDPA Femtocell modem reference design, and the Tatara Mobile Services Convergence products.

Of course, HSUPA and UMTS form just one path to 3G. Many CDMA mobile-phone service providers are instead leveraging the features of the Evolution-Data Optimized (EV-DO) standard. For example, QUALCOMM, Inc. (San Diego, CA) recently added a product that supports CDMA2000 1xEV-DO Revision B to its roadmap. With EV-DO Rev. B technology, high-performance devices could support forward-link data rates of up to 73.5 Mb/s. Lower-cost or pre-existing devices could support 4.9 Mb/s.

Over 5 MHz of spectrum, QUALCOMM's recent field tests of EVDO Rev. B technology resulted in average data rates of 9.3 Mb/s on the downlink. The company's new Mobile Station Modem (MSM) MSM7850 chip set provides support for EVDO Rev. B with full backward compatibility. A software upgrade release also is available. It enables QUALCOMM's Cell Site Modem (CSM) CSM6800 solution to support multi-carrier EVDO Rev. B.

Components like antennas are central to these impressive infrastructure products. For example, Alcatel-Lucent (Paris, France) has made its intelligent-antenna (IA) solution available to help 3G CDMA2000 operators upgrade their CDMA2000 1X networks. As a result, the carriers will be able to support greater volumes of voice traffic without the need for additional spectrum. The company's IA solution provides true per-user IA processing. Without such processing, a base station's antennas produce a wide-angle radio signal beam that transmits to all users in a given area. With per-user IA processing or beam forming, however, the base station sends a separate, dedicated, narrower beam to each active user. This beam adaptively follows the user as he or she moves through the base station's coverage area (see figure).

Through this transmission method, the approach makes more efficient use of spectrum while reducing interference. The Alcatel-Lucent IA processing techniques also are applied to the–reverse link” (i.e., the signal a base station receives from a mobile device when a voice or data call is active). The combination of IA processing at the base station—in both the signal transmission and reception of signals from mobile devices—makes overall system-capacity gains possible.

To leverage all of these infrastructure developments, the industry is witnessing the constant release of new technologies for mobile phones. In February, for example, Texas Instruments, Inc. (Dallas, TX) released the OMAP 3 architecture. The first OMAP 3-based device, the OMAP3430 processor, claims to be the first wireless processor to use 65-nm process technology. This application processor platform is based on the new ARM Cortex-A8 super scalar microprocessor core, which delivers three times more performance than the ARM11 core used in OMAP 2 processors.

The goal of the OMAP 3 architecture is to combine mobile entertainment with high-performance productivity applications. To reach this goal, the architecture houses an Image Video Audio (IVA) 2+ accelerator, which enables multi-standard (MPEG4, WMV9, RealVideo, H263, and H264) encode/decode at D1 (720 X 3 X 480 pixels) 30 frames/s. The high-definition (HD)-quality player allows users to download movies onto their phones and watch them on an HD monitor. In addition, an integrated image signal processor (ISP) provides image capture. The architecture also boasts composite and S-video TV output and XGA (1024 X 3 X 768 pixels), 16M-color (24-b-definition) display support. It includes a Flatlink 3G-compliant serial display and parallel display support.

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A new RF subsystem also is targeting handsets that incorporate advanced multimedia features like DVB-H, FM radios, MP3 players, digital cameras, and Web browsing. Yet Skyworks Solutions’– (Woburn, MA) Helios 3 subsystem targets Enhanced Data Rates for GSM Evolution (EDGE). The Polar Loop EDGE RF subsystem boasts a digital RF (DigRF) interface. At 5 X 3 X 5 mm, the SKY74218 DigRF EDGE Transceiver integrates a Polar Loop transmitter and receiver as well as four low-noise amplifiers (LNAs), a quadrature demodulator, and selectable-bandwidth digital baseband filters. The transceiver also generates a number of internal, general-purpose inputs/outputs (GPIOs), which are used for front-end-module (FEM) control.

The SKY77524 is a 6 X 3 X 6-mm transmit (Tx) and receive (Rx) front-end module (FEM) with an integrated coupler for quad-band GSM, GPRS, and EDGE applications. The device, which provides a complete Tx path from transceiver output to antenna, combines a power amplifier (PA), Tx harmonic filtering, and an integrated coupler. It also flaunts high-linearity, low-insertion-loss, pseudomorphic-high-electron-mobility-transistor (pHEMT) RF switches. The FEM enables a complete transmit voltage-controlled-oscillator-to-antenna (VCO-to-antenna) and antenna-to-receive surface-acoustic-wave filter solution. Together with the SKY74218, the SKY77524 creates the Helios 3 EDGE RF subsystem. These devices form an integral portion of the closed Polar Loop architecture, which autonomously splits amplitude and phase using traditional analog in-phase and quadrature (I/Q) signals.

EDGE also is the target of a quad-band PA module from RF Micro Devices, Inc. (Greensboro, NC). The RF3161 is designed to support EDGE transceivers that implement large-signal-polar-modulation (LSPM) transmit architectures. Impressively, it is housed in a 6 X 3 X 6 X 3 X 1-mm package. Because this fully integrated solution requires limited external component, no external routing is needed. It offers output power of +34.5 dBm for the 850- and 900-MHz GSM bands and +32.0 dBm for the DCS and PCS bands.

These products are just a tiny representation of the many developments that are spurning the cellular industry's transition to 3G and beyond. Sights are already being set on fourth-generation (4G) networks and services. This past December, NTT DoCoMo (Tokyo, Japan) conducted a field experiment of 4G radio access in Yokosuka, Kanagawa. The company achieved a maximum packet transmission rate of approximately 5 Gb/s in the downlink using 100-MHz frequency bandwidth to a mobile station moving at 10 km/h.

In this experiment, DoCoMo doubled the maximum speed of 2.5 Gb/s that it had reached on December 14, 2005. To do so, it increased the number of multiple-input multiple-output (MIMO) transmitting and receiving antennas from 6 to 12 each. It also used proprietary received signal-processing technology. Compared with the previous year's test, the 2006 experiment doubled the frequency spectrum efficiency—or the ratio of data transmission rate to channel bandwidth—– from 25 b/s/Hz to 50 b/s/Hz (5 Gb/s/100 MHz).

Clearly, the engineering groundwork is already being laid for 4G networks and services. Thanks to the consumer's hearty appetite for multimedia features and services, research and development into future networks should remain strong. The industry can therefore look forward to a steady stream of innovative products and services.

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