WITH A HUGE ASSORTMENT OF SERVER, EMBEDDED, AND CONSUMER-ELECTRONICS DESIGNS ALREADY IN ITS PORTFOLIO, THE LINUX OPERATING SYSTEM DIVES INTO THE EXPLODING WORLDWIDE MOBILEPHONE MARKETPLACE.
Featuring free source code, no licensing fees, and zero per-unit royalties, the Linux operating system has captured the attention of product developers around the globe. To date, Linux has done remarkably well in the Web-server and embedded-systems markets and has built a reputation as a stable, reliable, and crashproof operating system compatible with a wide range of processors. This solid reputation, along with its modular architecture, has also turned Linux into the fastest growing operating system for today’s hottest convergence device: the mobile phone.
The growth of Linux in the mobile market has been nothing short of spectacular. Two research companies, Evans Data Corp and The Diffusion Group, both report that by the end of 2005, almost a quarter of all mobile feature phones shipped worldwide were based on the Linux operating system. This phenomenal growth has been mostly at the expense of the market-leading Symbian operating system. Symbian’s smartphone market share had dropped from almost 80% to approximately 50% by the end of last year. To further illustrate the rapid deployment of Linux-based devices, Motorola has suggested that Linux will drive more than 50% of the phones it ships within two years. “Motorola is a firm believer in the power of open platforms and the promise of Linux for mobile,” says Greg Besio, Motorola’s corporate vice president for mobile-devices software.
Linux market penetration varies depending on location. “The fastest growing Linux volumes are found in Asia, with Panasonic and NEC, and in the United States, with Motorola,” says Philippe Robin, ARM’s Linux-product manager. “Europe has been slower to adopt Linux due to the domination of Nokia’s Symbian operating system.” Although these markets are saturated for single-function voice services, Linux allows for increased revenues with new applications and services. New markets are also tempting for Linux developers. For example, The Diffusion Group reports that despite less than 50% coverage today, the entire population of India should be covered by mobile networks by the end of 2009. This additional coverage would extend the number of mobile subscribers from 100 million today to 348 million.
MORE FEATURES, LESS SPACE You can directly attribute the rise in Linux popularity with designers to the buying public’s insatiable appetite for more features in a smaller package. Mobile-phone users are no longer content with a device that has only a single function, so manufacturers must constantly pack more and more features into every new product to compete for market share. In addition to the cellular phone itself, mobile multifunction devices include various combinations of multimedia recorders, players, shortrange digital communications, messaging, position-location electronics, and thousands of application programs for work-related information management and personal amusement. With the high volumes and thin profit margins associated with mobile phones, design teams are evaluating and adopting the Linux operating system to tackle the complex software burden.
Linux is modular and allows developers to construct a small, tailored software set that fits the memory footprint of each device, thus eliminating some of the code overhead present in proprietary, multiuse operating systems. Linux also supports a vast arsenal of microprocessors, making it ideal for the diversity of the mobilephone market. Because Linux has been ported to most popular embedded processors, software limitations don’t force developers into hardware decisions. Designers can start production with a lowpriced microprocessor that meets current needs and easily upgrade to a more powerful CPU as the device requirements and features expand.
Another Linux advantage is a worldwide team of developers dedicated to chasing down and correcting every internal bug or problem in the kernel. Some of these developers are hobbyists working for nothing, and companies with Linux products support other such developers. Either way, Linux problems get a lot of attention and are usually resolved rapidly. No matter who corrects a bug, the fixes are proposed for incorporation into the next revision of the kernel. Silicon manufacturers also contribute to the open-source community. “Although ARM does not generate revenue from Linux, we have a continuing commitment to support open source,” Robin says. “ARM contributes architectural support to the Linux-kernel development, promotes standardization initiatives, and provides early access to technology to promote adoption by the opensource community.” ARM also maintains a Linux Wiki (www.linux-arm.org) for the latest developer information.
Linus Torvalds first released Linux in October 1991, and he remains its author and trademark holder. The basic architecture of the Linux kernel includes memory management, process scheduling, a file system, and a communications interface. The memory manager enables multiple programs to securely share the system memory, and the process scheduler ensures that programs have fair access to the CPU. The virtual file system hides the details of the hardware and presents a common file interface to the developer. The Linux kernel updates periodically to include patches and suggestions from the user community. You can find information on and download the latest version of the kernel at www.kernel.org.
CONTROLLING PATCHES One possible danger that mobilephone vendors foresee in an opensource Linux environment is the potential for fragmentation. If a developer modifies the Linux kernel to solve an integration problem, that action creates two different and possibly incompatible versions of Linux. When the next official Linux update comes out, the developer will have to search through the revised code to reincorporate the modifications or continue to use the old version. So far, the Linux community has been successful in preventing multiple versions through an elaborate system of upgrade proposals and releases.
Mobile-phone software also has unique requirements that the Linux kernel does not address. For example, the user interface is undefined, although multiple open-source implementations are available to designers. Mobile operating software may also need power management, reduced boot-up time, and possible realtime operation. Call-management and data-communications routines are extremely important in a mobile-phone environment but are as yet unavailable as open-source components.
The Linux Phone Standards (LiPS) Forum and the Open Source Development Labs (OSDL) have recently teamed up to address these deficiencies and define standards that promise to turn Linux into a plug-and-play mobilephone platform. Motorola, NEC, NTT DoCoMo, Panasonic Mobile Communications, Samsung Electronics, and Vodafone recently announced plans to work toward a global, open, Linuxbased software platform for mobile devices. They hope to provide an API (application- programming-interface) specification, architecture, open-source code, rules for third-party software, and a conformance test suite.
The Linux licensing agreement has positive and sometimes negative consequences in the highly competitive mobile market. On the positive side, you can download a free copy of Linux, adapt it to your product, and sell as many units as you want without paying royalties. Yet Linux is not public-domain software; it is licensed under the GNU General Public License (GPL), which contains specific rules for its use. If you modify and distribute GPL software, your modifications automatically fall under the GPL, and you must give the source code to anyone who asks for it. Your application programs and device drivers may remain proprietary as long as they are separate and distinct from the Linux kernel and contain no GPL code. This code isolation is a constant source of anxiety among developers, especially in small-footprint mobile systems in which all software links together in a single ROM image.
FREE SOFTWARE REVENUE With the software available for free, Linux vendors have adopted multiple business models to ensure sustained revenue. Some vendors offer product- development or consulting services, and others offer telephone-support services similar to those that traditional operating-system suppliers provide. Still others have packaged Linux and their own proprietary add-ons or development tools into a distribution disk for sale to designers. For example, Monta- Vista offers the Linux for Mobile Devices (Mobilinux) operating system for wireless handsets and mobile products with requirements for power management, hard real-time performance, fast start-up, and a small footprint. Similarly, PalmSource recently revealed tails of its Linux-based mobile-phone operating system, which can run legacy Palm OS application binaries, Java applications, and native Linux applications. Norway-based Trolltech has also announced a hardware-reference design and custom Linux distribution for mobile phones. And finally, Wind River Systems, supplier of the popular VxWorks real-time operating system, has launched the Platform for Consumer Electronics, Linux Edition, which targets mobile phones, set-top boxes, personal video recorders, and other small-footprint consumer-electronics devices.
Although Linux may not yet be the perfect operating system for every mobile-phone application, it has enough built-in features and future promise to lure scores of phone developers into its camp. Developers can go it alone or select commercial vendors providing custom software distributions, subscription support packages, development tool kits, and reference designs to augment the free Linux core. With these benefits and a worldwide army of developers ready to resolve integration issues, Linux has a bright future in the mobile-phone industry.
FOR MORE INFORMATION You can find a list of relevant vendors and organizations at the Web version of this article at www.edn.com/061109g1.hhI
