Wiley.Developing.Software.for.Symbian.OS.2nd.Edition.Dec.2007 (779887), страница 3
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However, the exciting aspectof Symbian smartphones is that they are ‘open’, meaning that users canfurther customize their phone experience by downloading, installing,and uninstalling applications written by third-party developers (or by theusers themselves). Users can download applications from a PC to thesmartphone through a link such as USB, or Bluetooth technology, orover-the-air via the Internet.With the largest installed base of smartphones worldwide, SymbianOS offers a great opportunity for software developers to establish themselves in the mobile market by creating novel and exciting software forthe growing mass of smartphone users around the world.
There is agrowing list of Symbian applications available as freeware or as paiddownloads on numerous Internet sites (http://www.handango.com andhttp://www.epocware.com are good examples). They range from productivity, entertainment, navigation, multimedia, and communicationssoftware to programs that can count fast food calories, improve yourgolf swing, keep diaries, and calculate foreign currency exchange. Andbusiness opportunities aside, sometimes it’s just plain fun writing yourown code to run on your own smartphone.The purpose of this book is to help and inspire software developers tocreate good software for Symbian smartphones.1.1 Notes on this New EditionDeveloping Software for Symbian OS was first published in 2005, and inthe two years since then smartphones have continued their phenomenal2SMARTPHONES AND SYMBIAN OSgrowth rate. The number of Symbian OS smartphones shipped in 2006alone was 51 million – a 52% increase from the year before.
In the firsthalf of 2007, 47.9 million smartphones were shipped (a 39% increase onthe same period in 2006) and the total number of Symbian OS phonesin circulation now surpasses 145 million. Smartphones now make up9% of the total mobile market. Symbian continues to be the most widelyshipped smartphone OS. According to Canalys, Symbian’s share of thesmartphone OS market was 72.4% in Q2 2007.1 Many new Symbiansmartphones have been introduced that run on the latest versions ofSymbian OS, that is Symbian OS v9, which was a significant upgrade toprevious versions of the operating system.The main purpose of this edition is to update the original DevelopingSoftware for Symbian OS for Symbian OS v9. The basic programmingconcepts of Symbian OS have not changed, so much of the contentof the core programming chapters remains.
The main areas of changeinclude covering the new Symbian OS v9 software development kits(SDKs) and development environment changes, as well as the significantaddition of the platform security architecture to v9, which is used toprotect the integrity of the smartphone. Since it affects various aspects ofdevelopment, platform security is discussed in various places throughoutthis book as needed, and a new chapter has been added to the book todiscuss this subject in depth.In addition to updating the book for Symbian OS v9, we have madesure the book is updated in general for new developments that haveoccurred since the original book, and we have fixed a few errata reportedagainst the original.Before launching into programming for Symbian OS, this chapterintroduces the smartphone itself and gives an overview of its featuresand associated technologies.
Understanding the smartphone’s range offeatures helps you as a programmer to exploit these features to their fullpotential. (For more information about the typical features and designof a smartphone, please consult How Smartphones Work, published bySymbian Press in 2006.)I’ll also discuss the company Symbian Ltd, give an introduction toSymbian OS, and discuss how Symbian OS, as well as other operatingsystems, fit into the marketplace.1.2 Smartphone ConceptsA mobile phone that fits in your pocket and lets you communicatefrom and to anywhere in the world is an amazing invention.
Like mostinventions, mobile phones are built on a chain of prior technological advancements. Without advancements such as integrated circuits,1http://www.canalys.comSMARTPHONE FEATURES3microprocessors, semiconductor miniaturization, battery technology and,of course, the invention of telephone and radio, the modern cell phonewould not be possible.Smartphones combine the mobile phone with another stream of technology: the computer, which adds the ‘smart’ in smartphone. Computershave progressed from centralized mainframes to personal computers withuser-downloadable applications and graphical user interfaces.
With theintroduction of the Internet and email, the PC is a part of everyday life asa productivity, entertainment, and communication device. Laptops wereintroduced to allow PCs to be portable. Then came the mobile computingdevice known as the PDA – a true handheld computer.Since the PDA and the cell phone are both mobile devices, it’s onlynatural that we would want to combine them into one device. After all,you only have so much pocket and/or purse space! This is the basic ideaof a smartphone – but a smartphone is more than just a PDA combinedwith a cell phone. Smartphones also contain features such as a digitalcamera, video and music players, and GPS, thus combining other portabledevices as well.1.3 Smartphone FeaturesLike PDAs, smartphones can run applications such as organizers, games,and communications programs (e.g., email, browser).
They can, of course,also make telephone calls! The smartphone’s goal, however, is not just tolimit the number of devices you carry, but also to combine mobile phoneand computing technologies in a synergistic way. A simple example isthe ability to pull up a person’s contact information or even picture,hit a button and automatically dial the person’s phone number. Otherexamples include taking a picture, adding some text, and sending itinstantly to a PC or another smartphone user. There are many moreexamples of this – and certainly many that have not even been thoughtof yet.1.3.1 How Smartphones CommunicateSmartphones, like traditional cell phones, use radio to communicatewith base towers, which in turn act as gateways into landline-basedcommunication infrastructures.
While traditional cell phone systems arebased mainly on relaying voice communication between the wirelesshandset and the wired telephone infrastructure, smartphones providemore features that rely on network data transfer. After all, the basic conceptof the smartphone is to combine a mobile phone with a networked PDA.Improving data transfer is the current challenge for next generation mobilecommunications; unlike voice transfer, which requires a fixed bandwidth,the rule for data transfer is the faster the better.4SMARTPHONES AND SYMBIAN OSGenerations of mobile communicationWith faster data speeds come better services.
For example, when thebandwidth reaches a certain threshold, applications and services thattransfer real-time audio and video become possible. The industry goalsin wireless data communications have been categorized into generations – each generation includes a target data bandwidth as well as a setof data services available for it:First Generation (1G)Original analog cell phone technology.Second Generation (2G)Voice-centric digital systems with increased coverage and capacity.Introduces messaging.Third Generation Transitional (2.5G)Stepping stone to 3G. Introduces always-on network connections,bandwidths up to 170 Kbps, allowing better Internet browsing, email,and some audio video.
GPRS has been the dominant technology here.Third Generation (3G)/Fourth Generation (4G)Supports bandwidths up to 2 Mbps and 200 Mbps, respectively, forhigh-end services such as video teleconferencing.The topic of wireless communication protocols is vast and couldeasily take up another book. But let’s briefly cover some of the keycommunication technologies that apply to smartphones.GSMGSM, short for Global System for Mobile Communication, is a digital cell-based communication service that started in Europe, and hasquickly spread throughout most of the world. A notable exception is theUSA, where CDMA is the dominant standard; however, GSM is gainingpopularity there. GSM is the most supported protocol in smartphones.GSM was designed for circuit-switched voice communication.
Circuitswitched means that fixed bandwidth is reserved for each direction of aphone call for the entire duration of the voice call, whether you are talkingor not. Although originally designed for voice, GSM now has a variety ofhigher bandwidth data services (e.g., GPRS and EDGE) available, runningon top of the base GSM protocol. This allows for faster data transfer, aswe will see shortly.The following types of GSM exist, each using its own band in thefrequency spectrum: GSM 850, GSM 900, GSM 1800, and GSM 1900.The number indicates the frequency band, in MHz, that the protocol uses.Cell phones supporting GSM 900 and GSM 1800 will ensure coverage inEurope and many other areas outside the USA, while GSM 850 and GSM1900 are used in the USA (mostly GSM 1900).SMARTPHONE FEATURES5Fortunately, smartphones support multiple bands to ensure as wide acoverage as possible.
It’s common to have tri-band phones that supportGSM 900, GSM 1800, and GSM 1900 to ensure maximum internationalcoverage – although some still offer separate US models to reduce costs.A GSM phone uses a Subscriber Identification Module (SIM) to gainaccess to the GSM network. A SIM contains all the pertinent informationregarding a user’s account, including the services allowed. It is used toidentify the user to the GSM network for billing purposes.
The user canswitch their SIM from one GSM phone to another, provided that thephone is either not locked to a specific carrier, or locked to the carrierthat the SIM is associated with.CDMACDMA, which stands for Code Division Multiple Access, is a cell phonestandard that competes with GSM. CDMA currently dominates in theUSA and Korea, while GSM dominates virtually everywhere else. CDMAsupports a high-speed data mode called CDMA2000 1xRTT, which tendsto hover around 50–70 Kbps, bursting up to 144 Kbps.EV-DO is the high-speed, 3G version of CDMA.
EV-DO supportsrates up to 2.4 Mbps (with actual speeds averaging closer to 1 Mbps)and is adopted by many services including Verizon and Sprint in theUnited States.CSDCSD, short for Circuit Switched Data, is the most basic mode of transferring data over a circuit-switched connection like GSM. The connectionis established by dialing the number of an ISP, in the same manner thata dialup connection is started on a land-based telephone line using a PCmodem.
With CSD, you do not need any extra data plan like GPRS tosend data. You can use up your existing voice minutes.There are two major disadvantages to using CSD, however. First, ittakes a long time to connect since this involves dialing a number andwaiting for the server to answer the call. Second, it is slow; data transferspeed is only about 9.6 Kbps.In GSM-based smartphones, this mode is referred to as ‘Dial’ or simplyas GSM data. Earlier smartphones such as the Nokia 9290 rely entirelyon this mode of data communication.GPRSGPRS, short for General Packet Radio Service, is a wireless technologythat allows the smartphone user to quickly connect to the network andobtain good data rates. Connection time is fast since GPRS does notrequire any dialing (as CSD does), and the smartphone feels as if it isalways connected.6SMARTPHONES AND SYMBIAN OSProtocol-wise, GPRS runs on top of GSM.
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