Enhanced Connectivity Drives Wireless Standards

Oct. 22, 2009
Beyond the desire to send and receive increasing amounts of data over cellular and broadband networks, consumers are looking to wirelessly monitor their homes, their bodies, and more.

Five or more years ago, it seemed that a new wireless standard was being proposed almost monthly. Much debate has focused on which standards would outlast the others, proving themselves to be the optimal solutions for given applications. Yet the landscape has not changed very much since then. The IEEE 802.11x standards continue to evolve to meet the needs of the wireless-local-area-network (WLAN) market. Bluetooth has cornered the wireless-headset market and is making inroads into some new areas. IEEE 802.15.4, in which ZigBee has its roots, has seemingly become the de-facto solution for applications like remote appliance control in the home. In fact, the only wireless technologies generating buzz these days are Long Term Evolution (LTE) and mobile WiMAXboth of which are designed to carry generous amounts of data. Although many debate whether both technologies are needed, the increasing demand for wireless connectivity ensures roles for a variety of standards and technologies within homes and across the globe.

Mobile WiMAX and LTE are similar in that they are both rooted in orthogonal- frequency-division-multiplexing (OFDM) technologies. In addition, they were created to aid the increased transmission of wireless data over Internet Protocol (IP) networks. Many favor LTE for its superior speed compared to mobile WiMAX, although IEEE 802.16m promises to match or exceed the data rates offered by LTE. At ITU Telecom World in Geneva, Switzerland earlier this month, both the WiMAX Forum and executives from 50 suppliers and operators endorsed the IEEE's submission to ITU-R, which proposes an IEEE 802.16m-based architecture for IMT-Advanced. The WiMAX Forum also announced that it will finalize its WiMAX Release 2 specification in parallel with IEEE 802.16m and IMT-Advanced, ensuring that WiMAX Release 2 networks and devices will remain backward compatible with legacy WiMAX Release 1 systems based on IEEE 802.16e.

According to the ITU-R's definition, which reflects aggregate throughput delivered to multiple users in a practical deployment, the IEEE's IMT-Advanced proposal documents the following: Using 4x2 multiple-input, multipleoutput (MIMO) configurations in the urban microcell scenario with only a single 20-MHz TDD channel available system-wide, the IEEE 802.16m system can support both 120-Mb/s downlink and 60-Mb/s uplink rates per site simultaneously. In addition, higher data rates can be obtained with additional spectrum resources or more complex antenna schemes. The WiMAX Release 2 profile also will incorporate these capabilities for improved voiceover- Internet-protocol (VoIP) capacity, spectral efficiency, latency characteristics, handover speed, cell range, and coverage with support for wider operating bandwidth in both time-division- duplexing (TDD) and frequencydivision- duplexing (FDD) formats. The WiMAX Forum expects to see WiMAX Release 2 available commercially in the 2011 to 2012 timeframe.

In Russia, WiMAX Release 2.0 is already being tested by Yota in conjunction with its partner, Samsung Electronics. Yota plans to install the mobile WiMAX Release 2.0 solution from Samsung on its network by the end of next year. Samsung demonstrated its IEEE 802.16m-based solution at ITU Telecom World, which comprised the Samsung U-RAS Flexible base stations with upgraded modules, the existing mobile WiMAX handset, and the prototype of a new handset developed for mobile WiMAX Release 2.0. The demonstration showcased the full backward compatibility between mobile WiMAX Release 2.0 (IEEE 802.16m) and the IEEE 802.16e technologies. Mobile WiMAX operators can supposedly upgrade to mobile WiMAX Release 2.0 simply by updating several circuit-board sections and the software in their base stations.

Recently, the WiMAX Forum announced that the number of IEEE 802.16e WiMAX deployments has reached approximately 504 networks in 145 countries with 15 new deployments added in August. Regionally, Africa led with 109 deployments and Central/ Latin America closely followed with 102. The Asia Pacific and Eastern European regions reached 79 deployments each while Western Europe hosts 68 networks. North America and the Middle East grew to 49 and 18 deployments, respectively. In addition to an increase in the number of networks tracked by the WiMAX Forum, many of the already established WiMAX networks continue to expand rapidly. Yota, for example, expects to reach 200,000 subscribers this month. Clear, Sprint, and Comcast all have made strides toward expanding their networks with multiple city launches planned by the end of 2009. In addition, UQ Communications plans to cover more than half of the Japanese population by the end of December.

Such deployments are supported by product developments like the new WiMAX transceiver from Maxim Integrated Products. Aimed at subscriber applications, the single-chip MAX2839AS covers 2.3 to 2.7 GHz in a 3.5-x-5.1-mm wafer-level package (Fig. 1). Using a dual-receiver architecture, it vows to mitigate RF channel fading by as much as 10 dB compared to a single-receiver architecture. By leveraging the firm's silicon-germanium (SiGe) BiCMOS process, the transceiver's two receivers flaunt a low noise figure at 2.3 dB, 81 dBm sensitivity for a 64-QAM signal at a 5-MHz channel bandwidth, and a 95-dB gain range that is digitally controlled in 1-dB steps. Each device is factory calibrated to achieve better than 35 dB error vector magnitude (EVM), 45 dBc sideband suppression, and carrier leakage of 40 dBc. The transmitter features a 62-dB gain control range, which is digitally controlled in 1-dB steps. It delivers a 0-dBm linear output with a 64-QAM signal, greater than 45 dBc of sideband suppression, and more than 36 dB EVM while meeting a 70 dBc spectral mask.

As evidence of mobile WiMAX's continued viability, visitors to the WiMAX Pavilion at ITU Telecom World experienced mobile broadband through a live indoor demonstration as well as a 30-min. driving tour with live streaming video and music along with location awareness via the Global Positioning System (GPS). Interestingly, that show also was the site of the world's first live 2.6-GHz timedivision- duplex-LTE (TD-LTE) drive demonstration.

During Motorola's Home and Networks Mobility TD-LTE drive tour, visitors rode in the firm's LTE van to experience the reallife performance of TD-LTE including mobility and hand-over and a number of demanding applications. Such applications included high-definition (HD) video streaming on the downlink and uplink, GPS navigation, VoIP, video conferencing, and high-speed Internet browsing. Within the van, a TD-LTE device received and transmitted the over-the-air (OTA) data including HD video and high-speed data from and to the application servers and high-speed data from and to the Internet. Motorola's TD-LTE solution is comprised of second-generation OFDMbased products, which include a base controller unit (BCU2) that supports TD-LTE, FDD-LTE, and WiMAX and a remote radio unit (RRU) that supports both WiMAX and LTE (Fig. 2). At the China Mobile Communications Corp. exhibition booth, Motorola also provided a TD-LTE demonstration that showcased downlink throughput of over 100 Mb/s.

Many companies are now backing LTE including US carrier Verizon. In fact, the firm recently opened the lab at the Verizon Wireless LTE Innovation Center in Waltham, MA. The experience center of the LTE Innovation Center is anticipated to open in the first half of 2010. Verizon also introduced a virtual LTE Innovation Center, in which device developers can access an online portal to discover support services for participants at the Verizon Wireless LTE Innovation Center.

According to ABI Research, a minimum of 12 mobile operators are planning to launch LTE services next year. Aside from Verizon Wireless, the first launches in the US are expected to be from MetroPCS Wireless and US Cellular. Japan's first LTE networks will be from NTT-DoCoMo and KDDI while TeliaSonera, Tele2, and Telenor are among the carriers with LTE roadmaps in Europe. Although China Mobile has LTE in its sights, it does not plan to launch until 2011.

Although it has not formally committed to any deployments, Telefnica just made headlines by commissioning six advanced LTE pilot trials. The firm has chosen Alcatel-Lucent, Ericsson, Huawei, NEC, Nokia Siemens Network, and ZTE to test their respective LTE technologies in six different countries. The trials include both laboratory tests and the installation of e-node Bs in the field. The countries selected for testing are Spain, the United Kingdom, Germany, the Czech Republic, Brazil, and Argentina.

Because LTE has not rolled out yet, development is going at a furious pace on both the infrastructure and handset sides. To help LTE and 4G base-station manufacturers reduce board space and material costs, for example, Analog Devices, Inc. debuted a series of integrated radio-frequency integrated circuits (RFICs). By combining multiple discrete functional blocks into one device, the ADRF660x series of mixers and ADRF670x series of modulators enable smaller, higher-density radio card form factors (see "Integrated Devices Arm Infrastructure Radios," September 2009).

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On the handset side, NTT DoCoMo, Inc., NEC Corp., Panasonic Mobile Communications Co. Ltd., and Fujitsu Ltd. are making progress with their joint development of a mobile-terminal platform dubbed "LTE-PF." In fact, the companies have completed the development of an LTE-PF chipset engineering sample and are now evaluating its main functions. LTE-PF is a core system comprising software for baseband processing and other basic functions in mobile communication devices (Fig. 3).

Of course, test equipment must precede the rollout of equipment for new technologies. Companies like Agilent Technologies, Rohde & Schwarz, Tektronix, Anritsu, and Keithley Instruments have already jumped on the 4G bandwagon. Just this month, the first LTE protocol-conformance test cases were successfully verified by Anite and LG Electronics. LG uses Anite's LTE solution, which provides a suite of development tools for UE designers, to develop its devices in advance of LTE networks being available.

A lot of progress also is being made in the areas of wireless personal-area and local-area networks (WPANs and WLANs). In 2008, for example, the Bluetooth Special Interest Group formally announced its intent to harness the speed of IEEE 802.11 with an innovative method of radio substitution. This "alternate MAC/ PHY" allows the Bluetooth protocols, profiles, security, and pairing to be used in consumer devices while achieving faster throughput with momentary use of a secondary radio already present in the device. This past April, the Bluetooth SIG released the new Bluetooth high-speed specification, Version 3.0 + HS, to enable consumers to take advantage of higher data rates.

In WLAN news, the Wi-Fi Alliance has begun product testing for its Wi- Fi-certified n program shortly after finalizing the IEEE 802.11n standard. It updated its twoyear- old Wi-Fi-certified IEEE 802.11n draft 2.0 program to add testing for some popular optional features that are now more widely available in Wi-Fi equipment. Those features include the following: test support for the simultaneous transmission of as many as three spatial streams, packet aggregation (A-MPDU) to make data transfers more efficient, and space-time block coding (STBC)a multiple-antenna encoding technique to improve reliability in some environments. In addition, channel coexistence measures are included for "good neighbor" behavior when using 40-MHz operation in the 2.4-GHz band. Devices can now be designated "Wi- Fi-certified dual-stream n" or "Wi-Fi certified multi-stream n" to indicate that they have passed tests for specific performance-enhancing features.

In July, the ZigBee Alliance announced that it will draft a standard for energy-harvesting devices. According to David Cohen, Director of Marketing at California Eastern Laboratories, the firm's latest MeshConnect Extended Range Module enables networks to operate at long, open distances without having to saturate the area with many radios. It also allows solid mesh connections to be maintained in noisy, indoor, urban, and/or RF-harsh environments.

The MeshConnect Extended Range Module provides +20 dBm output power, which translates into a range of over two miles. It also promises to provide more reliable transmission with fewer nodes. With receiver sensitivity of 103.5 dBm, the module's +123-dBm link budget ensures high-quality connections even in harsh environments. In addition, data rates to 1 Mb/s help engineers satisfy the demands of higherbandwidth networks while an on-chip voice codec opens the door to voicetransmission applications.

ZigBee does face a rival in the EnOcean Alliance. This consortium of companies has an energy-harvesting standard that is open and interoperable with existing standards. According to IDTechEx, EnOcean has applied to the IEC to become an official global standard for energy-harvesting devices. It already has success in Europe and is now gaining ground in North America. Clearly, controversy in the wireless market is not dead. As history has shown, however, no player should be counted out of the game too early. Standards organizations have far-reaching resources and the ability to tweak their technologies to meet evolving communications needs. As individuals become increasingly accustomed to being wirelessly connected through almost every aspect of their livesfrom monitoring their home-energy usage to watching their blood pressurewireless standards and technologies will play an increasingly vital role.

About the Author

Nancy Friedrich | Editor-in-Chief

Nancy Friedrich began her career in technical publishing in 1998. After a stint with sister publication Electronic Design as Chief Copy Editor, Nancy worked as Managing Editor of Embedded Systems Development. She then became a Technology Editor at Wireless Systems Design, an offshoot of Microwaves & RF. Nancy has called the microwave space “home” since 2005.

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