Software Manager in System Optimization Technology Center (SOTC), Intel Corporation. Kerry has been working with Intel for eight years, four years in open source mobile OS software stack on IA, which includes Android optimization and MeeGo SDK. Before joining Intel, Kerry worked in Motorola on mobile platform and 2G wireless base-station software developments. Kerry holds a master degree in electronics engineering.
Architect of System Software Optimization Center, Intel Corporation. Xiao-Feng has been working with Intel for 12 years, with extensive technical experience in parallel system, compiler design and runtime technologies, where he has authored about 20 academic papers and 10 U.S. patents. Two years ago, Xiao-Feng initiated the evaluation and optimization efforts for best Android user experience on Intel platforms. Before he joined Intel, Xiao-Feng was a technical manager in Nokia Research Center. Xiao-Feng holds a PhD degree in computer science, and is a member of Apache Software Foundation. His personal homepage can be found at http://people.apache.org/~xli.
Engineering manager of Open Source Technology Center, Intel Corporation. Bingwei has been working in Intel for 11 years, with abundant experience in Linux OS, open source software and system engineering. His working scope spans from enterprise to client platforms and now is focused on Mobile OS. Bingwei holds a master degree of computer science.
Senior software engineer from Intel’s Open Source Technology Center. He has been with Intel for 7 years working on a variety of projects, including virtualization, manageability, OSV enabling, etc. Most recently Yong has been working on power management for a wide range of mobile operating systems such as Moblin, Meego, Tizen and Android. Yong graduated from Beijing University of Aeronautics and Astronautics and holds a master degree of computer science. He enjoys sports and reading in his spare time.
Engineering Manager in Intel's Open Source Technology Center leading a team on Mobile OS and HTML5 tools development. Before that, as a research engineer, Jackie was focused on wireless network and energy efficient communications. Prior to joining Intel in 2004, Jackie was in Chinese Academy of Sciences developing embedded operating system and smartphone products. Jackie received his M.S. and B.S. in Engineering Mechanics from Beijing University of Aeronautics and Astronautics in 2002 and 1999 respectively. He has two US patent applications.
Mobile OS Architecture Trends - Part II Published: September 30, 2013 • Service Technology Magazine Issue LXXVI PDF
Abstract: This is the second article in a two-part article series. Read the first part of this article here.
Power Management (PM)
Power management has always been a key challenge to mobile OS designers and will be even more so moving forward. Power demands are increasing rapidly on mobile devices as more and more power hungry applications are developed for mobile platforms. However, battery capacity growth could never keep up in the meantime due to both the slow development in battery technologies and the fact that people want more sleek and compact form factors that could fit into a pocket. Power management is becoming an increasingly complex problem on mobile devices and a holistic approach needs to be employed to address it.
Processor Power Management
Mobile operating systems have been making steady progress in the power management area in the last decade. Initially the focus of mobile OS power management work had been on processor power management since the processor had long been the most significant consumer of total platform power. Modern processors support dynamic frequency and voltage scaling such as Enhanced Intel SpeedStep® Technology. Such processor capabilities enabled mobile operating systems to adjust processor frequency and/or voltage dynamically at runtime based on the demand of computing power required by the workload that is currently running on the processor. This saves a significant amount of processor power while it is active since consumed power is proportional to the square of core voltage and frequency. The cpufreq subsystem in the Linux kernel is an example of managing processor power while it is active. In addition to dynamic frequency and voltage scaling, modern processors typically support multiple processor idle states with varying amounts of power consumed in those idle states. The deeper the idle state, the more power could be saved although at the expense of longer entry and exit latency. A mobile OS could direct the processor to enter an appropriate idle state based on predicted idleness and QoS constraints posed by other subsystems and user space. Linux's cpuidle subsystem is an example of power managing a processor while it is idle.
Device Power Management
The focus of mobile OS power management work has shifted to device power management. In particular, a mechanism has been introduced to manage the power of I/O devices at runtime. Runtime power management for I/O devices could automatically put I/O devices into whatever appropriate low power states they support when the corresponding devices are detected as idle at runtime. In addition to managing the power of I/O devices while they are idle, there are some technology innovations to save I/O device power while they are active. For example, modern GPUs are starting to support dynamic voltage and frequency scaling similar to that found on CPUs. GPU dynamic voltage and frequency scaling could reduce power consumption by as much as 50 percent for mobile 3D graphics in some cases. In addition, I/O devices are becoming smarter in the sense that they can work on their own without CPU intervention. For example, technologies like panel self-refresh could save a significant amount of power while the image is static in the cases like when a user is reading a book on a mobile device. The display panel could keep rendering from its local memory in this case and many hardware components that traditionally must be working while rendering display could be shut down, including CPU, memory, display engine and display port.
Mobile OS Power Management Cases
Android gained momentum and became popular before the infrastructure of device runtime power management was introduced into the Linux kernel and it came up with another approach called opportunistic suspend in order to achieve the goal of extending battery life on Android devices. Without device runtime power management capabilities, Android tries to suspend the system aggressively whenever there is no interesting work going on. This is indicated by no one holding a wakelock.
Windows 8 introduced a new system power state called connected standby. Unlike traditional S3 standby, which halts all system activities, the system is still running though in an extremely low power state and this enables users to stay up to date with the latest information such as their e-mails. Windows 8 connected standby is based on processor idle power management and device runtime power management technologies.
Software hygiene is the most challenging problem for both suspend- and idle- based power management approaches, and the battery life depends very much on application behaviors on such systems. A recent study says that free Android applications waste 75 percent of power on ads by holding a wakelock in the background, thus block system suspend. This is also true for Windows 8, where one power-unfriendly application staying busy for no good reason will prevent the entire system from entering connected standby power state. Some people expect the system power management to be more robust even in the face of such power-unfriendly applications by introducing more capable mechanisms, while others think that putting such a mechanism in place will only lead to the proliferation of more ill-behaved applications.
Another major trend of mobile operating systems is the openness. In this context, the openness of mobile operating systems means the level of opportunity and freedom that people have to use, contribute to, customize, and innovate for the mobile OS for their purposes. There is already work[REF-6] that has studied the openness from the developers' perspective. The work has identified the facets that decide the developers' perception of the platform openness. Here we study the trend of openness from the ecosystem perspective, As we believe the openness matters to enable and foster the mobile ecosystem.
Openness to Players of the Mobile Ecosystem
The players of the mobile ecosystem include manufacturers (OEMs) who make and sell mobile devices, the service providers (operators) who provide network connection and other value-added services, consumers (end users), the ISVs who develop commercial applications, and developers from communities who develop applications and even contribute on mobile OS development and evolution if the mobile OS is open-sourced.
The openness of mobile operating systems implies different things to different players in the mobile ecosystem. For operators, the openness of the mobile OS determines how easy their services can be ported, migrated, deployed, and run smoothly across the devices. For mobile device manufacturers, the openness determines how much they can customize the mobile OS itself to run across platforms and differentiate their devices from others, and even more importantly, the openness determines how easily they can build devices with a consistent user experience. For ISVs and community developers, the openness determines how easily they can develop new applications with their creative ideas and how their investment on application development can be maximized through programming once running across devices. For the end users or consumers of mobile devices, the openness means how easily they can get more applications, like the rich applications downloaded from the stores, without worrying too much about inconsistency of user experience and incompatibility of applications across devices. The openness may also give people the chance to participate in the development and evolution of the mobile OS itself during the life cycle of the mobile OS.
Evolution of Mobile OS Openness
A couple of years ago, most mobile devices were feature phones, and people mostly used the phones for voice calls, as a phonebook, and for text messages. For consumers, the applications they could play were limited to the applications built in devices when the devices were shipped out from the factory. For application developers or third-party ISVs, they didn't have access to any level of source code without a contract with the OS owner. Such a mobile OS was a purely closed system and was typically owned by a mobile device maker. For operators, they had to work closely with OS developers to enable their services, because only the people who developed the mobile OS knew how to develop applications.
Later, as the mobile phone started to transition from feature phone to smart phone, people expected the smart phone to be able to do more, like browsing the Web and playing music/video, rather than just making calls, storing contact information, and sending text messages. To encourage more developers to develop more applications to meet people's needs, the creators of mobile operating systems simply provided sets of APIs and related tools like SDKs, so that people could develop all kinds of applications for mobile devices. With such openness, application developers gained the freedom to develop applications for mobile operating systems, so it became possible for consumers to buy and install more applications rather than being limited to the pre-built applications. Because application developers and consumers benefitted from such openness, it became almost a "must-have" for most mobile operating systems to provide a set of APIs and an SDK. The iOS from Apple is one of the great examples of a mobile OS providing such a level of openness. In recent years more and more mobile operating systems have made all source code public, in addition to providing APIs and SDKs. Anyone could have the chance to view all source code, contribute to the code, evolve, and customize the mobile OS itself. Compared with the level of openness of just providing APIs and SDK, the open-source mobile OS can provide some additional freedom. For mobile device makers, they may have the freedom to build their own mobile OS based on the open source OS to run on their platforms across devices. For operators, they can easily build and deploy their services across devices running the open source OS and its variants. For developers, the open source mobile OS provides everything they need to easily build their applications. Eventually the end users of mobile devices can benefit from this level of openness, as they have more choices of applications and more devices to choose to run the applications. Lastly, everyone has the freedom to participate in evolving and shaping the open source mobile OS, which is very attractive to the talents from communities around the world. Android OS is another great example of an open source mobile OS. Its great success and segment share growth in the smart phone market during the past few years have indicating to the industry just how successful it has been and how fast it has been growing as an open source mobile OS.
As a summary, the openness of future mobile operating systems is one of the key factors to make mobile platforms friendly to the mobile ecosystem, especially to be attractive to application developers and consumers. Mobile OS openness is a requirement of computing continuum, which expects most software to be built once and running everywhere with a consistent user experience to end users.
The cloud has been widely used by mobile users and most of the cloud services are presented as Web sites and accessed by the browser running on the mobile browsers. More and more cloud services have been provided through web applications, which are installed from an application store and run like native applications on the mobile client. Either with a browser or standalone web application, the following areas should be considered in mobile OS design.
HTML5 capability is essential for web applications to integrate cloud services well and to provide a good user experience.
The HTML5 test web site[REF-9] scores HTML5 support of browsers on various mobile devices. We can see in Table 2 that iOS, Android, and Windows Phone are all improving their browser's capability to support HTML5. Google made Chrome work on Android 4.0 and showed its ambition to have the lead browser in mobile operating systems. Tizen, the new participant in the mobile OS campaign even got the highest score on its development device released in the first Tizen Developer Conference. We can easily see the intense race of HTML5 support between mobile operating systems.
The third-party browsers are in difficult situation and need a strategy to have their own host mobile OS. Opera and Firefox are in such a situation. Due to the fact that they have less control of mobile OS development, they won't be able to win easily if the built-in browser is capable enough for HTML5 support. Firefox has been looking for Boot To Gecko as its host mobile OS. A video on YouTube[REF-10] also shows the preview of Opera OS on Asus EeePC .
The mobile OS vendors view HTML5 support as more and more important and are making it a core competency. The browser vendors are also looking for the possibility to make it default in the mobile OS.
The web application defines the client side applications developed with web technologies. It provides rich features by providing APIs for client side development. The web application can be installed and run even offline on the devices. The web application can access local devices and resources as a native application and can be sold in an application store, which benefits much from the cloud service delivery and billing.
The web application is more than a URL accessed from a browser. The related capabilities are being defined in several working groups in W3C. The Web Applications Working Group is the central place related to those works.[REF-11]
To enable web applications, the mobile OS needs to provide a web application platform, which includes web runtime, web framework, and development tools:
As a trend, the mobile OS has to provide a capable and high performance web runtime, a rich web framework, and flexible development tools.
Security is always an important topic for cloud computing. For HTML5 cloud integration in mobile operating systems, the following features must be present:
HTML5 is well known for its cross-platform capability. But in reality, different mobile operating systems provide different HTML5 support, and the standardization of HTML5 is still ongoing. PhoneGap has been developed to address the cross-platform HTML5 support by providing its own device APIs. Apple iOS, Android, and Windows Phone all have supported PhoneGap. It is evolving and following W3C. Other Web API providers are also trying to make them into the HTML5 standard in W3C.
The trend is to have a unified HTML5 standard but that is not easy. Mobile OS vendors will implement their ideas in their own way before they go to standard. Apple, Google, and Microsoft are all active participants in the W3C standard definition. For other mobile OS vendors, either following W3C or joining the definition is the trend to make their mobile operating systems survive.
The performance is complained about most by mobile application developers when they start to build applications with HTML5. The optimization for mobile devices is the most important work to do for HTML5 to really succeed in the mobile area. We consider the following to be the most important areas to do work in optimization for mobile operating systems:
Besides the powerful capabilities provided by HTML5, the seamless integration between the cloud and client is even more important. It is not only for web applications but also for native applications. Important reasons for integration include:
Discussion and Summary
In this section, we first discuss the major mobile operating systems in the market today, and then summarize this article.
Apple has been the leader in mobile OS design. Its iPhone* and iPad* have prevailed across the world in only a few years. Both products feature the Apple iOS.
User experience: iOS provides good performance and is normally set as the benchmark for other mobile operating systems. Apple is continuously enhancing the UX performance. The iPhone 4S has much better performance boost than its previous generations, especially the Internet and browser.[REF-1] With more new features added, it adds more performance requirements. An unofficial study[REF-1] showed the UX performance drops after the upgrade from iOS 4.x to 5.x on iPhone 3GS.
Power management: iOS power optimization seems not able to catch up with the increasing demands on power for new features. Arieso, a mobile network management company, estimates that iPhone 4S users consume twice as much data as the previous iPhone model due to increasing use of online services like the virtual personal assistant Siri, which definitely consumes much more power.[REF-3]
Openness: iOS is perceived as a closed mobile OS. Research work[REF-6] defines a concept of perceived platform openness (PPO), where a platform's openness degree is decided by its developers' perception.
Cloud readiness: iOS 5.0 with HTML5 support makes it a good cloud client and the iCloud has been integrated by default as storage.
Android is currently a popular operating system for mobile devices and is developed by the Open Handset Alliance led by Google. The goal of the Android Open Source Project is to create a successful real-world product that improves the mobile experience for end users.[REF-16]
User experience: The Android user experience team defined a set of design principles[REF-17] with three overarching goals: "Enchant me," "Simplify my Life," and "Make me amazing."[REF-18] State-of-the-art Android and iOS devices achieved similar results in a set of battery life benchmark tests.[REF-19]
Power management: Android aggressively suspends devices to save power whenever nothing blocks suspend by holding a wakelock.[REF-20] However, Android allows third-party applications to run in the background, which might hold such a wakelock for no good reason and thus suck power quietly.
Security: Each application runs in a sandbox environment to enforce security in Android and this is done by assigning each application a unique user ID and running that application as that user in a separate process.[REF-21]
Openness: Google releases the Android code as open source under Apache license and the Android Open Source Project is where Android development and maintenance happen. However, Google typically partners with a selected manufacturer to make a flagship device for each new version of Android and only makes the new code publicly available after that device has been released. Fragmentation has become more and more a big concern in the Android ecosystem. Android maintains the Android compatibility program and offers the compatibility test suites to guarantee applications developed for Android run on every Android device.
Cloud readiness: Although Google has a huge lead in the cloud area, it has not put together a comprehensive solution as Apple does with iCloud yet.
Microsoft Windows Phone
Microsoft has released its latest redesigned mobile OS called Windows Phone. Based on their design change between Windows Mobile 6.5 and Windows Phone 7, some characteristics of the newer OS are exposed.
User experience: With touchscreen-based user interaction replacing the previous stylus input, Microsoft decided to break the application compatibility between Windows Phone and Windows Mobile.[REF-23] Similar to Android's AppWidget design, Windows Phone invents the concept of Live Tiles for the home screen.[REF-28]
Power management: Similar to its design security, Windows Phone's design for battery life can largely benefit from its Windows CE and Windows Mobile experience. One special consideration is that Windows Phone chooses black as the main default color theme, because black pixels do not emit any light, hence saving power for the OLED screen.[REF-32]
Security: Windows Phone's design is shifted from the original Windows Mobile's enterprise-oriented design to an end-user–oriented one. The security experience accumulated for the enterprise product should be still useful.[REF-31]
Openness: Before Windows Phone was available in the market, Microsoft released its SDK to enable the developers to program for the new OS.[REF-24] Windows Phone Marketplace has provided its services to 35 different countries/regions.[REF-25] The current programming languages are C# and Visual Basic. These are not a surprise to any Windows developers, so the language learning curve is expected to be flat.
Cloud readiness: Windows Phone is approaching cloud readiness at a fast pace. Windows Phone 8 integrates Internet Explorer 10 that is claimed to have full HTML5 support and supports parallel page loading in multiple tabs. [REF-29] Besides that, Skype is deeply integrated into the OS.[REF-26] One new concept in Windows Phone are hubs, which aggregate various similar service features into one hub. This is supposed to greatly improve the phone's user experience with cloud services.[REF-27] Furthermore, the software framework design of Windows Phone includes two parts: Screen and Cloud. The Cloud part is especially designed for "Developer Portal Services" and "Cloud Service."
In this article, we have investigated the major aspects of mobile OS design based on the analysis model we have developed, including user experience, battery life, cloud readiness, security, and openness. These should be the areas of focus for next-generation mobile OS design.
The future mobile OS also depends on the available hardware design. We believe a successful mobile system is a result of co-design between software and hardware, together with the progress of the Internet.
Copyright © 2013 Intel Corporation. All rights reserved.