Wireless Communication System Components PDF

1-1 Components of a Wireless Communication System\ A wireless communication system is built from various types of\ basic components. The following are some of these basic types of\ components:\ *Transmitter:* The input to a wireless transmitter may be voice,\ video, data or other types of signal tha...

1-1 Components of a Wireless Communication System\ A wireless communication system is built from various types of\ basic components. The following are some of these basic types of\ components:\ *Transmitter:* The input to a wireless transmitter may be voice,\ video, data or other types of signal that is meant to be transmitted\ to one or more distant receivers. This signal is called the base band\ signal. The basic function of the transmitter is to modulate, or\ encode several base band signals onto a high frequency analog\ carrier signal. A modulated high frequency analog signal can be\ radiated and propagated more effectively and helps to make more\ efficient use of the radio frequency (RF) spectrum than the direct\ transmission of the individual base band signals.\ *Receiver:* The receiver receives modulated signals and reverses the\ functions of the transmitter component and thereby recovers the\ transmitted base band signal. The antenna of the receiver is usually\ capable to receiving the electromagnetic waves radiated from\ many sources over a relatively broad frequency range.\ *Antenna:* The functions of an antenna is to convert electric signal\ from a transmitter to a propagating electromagnetic RF wave; or\ conversely, to convert a propagating RF wave to electric signal in\ a receiver. In a *transceiver,* a transmitter and a receiver are colocated for supporting fullduplex communications. In this case, the\ same antenna is usually shared by both the transmitter and the\ receiver. There are mainly two types of antennas that are used on\ wireless networks: omnidirectional and directional. Omni¬\ directional antennas can receive and transmit over 360 degrees.\ \ ***Chapter 1 Fundamentals of Mobile Computing\ ***This can be compared to a light bulb that emits light all over. In\ contrast, a directional antenna is similar to a flashlight, which\ focusesIight in some direction.\ ***Filters:*** Filters are the key component present in all wireless\ transmitters and receivers. These are used to r\^ect interfering\ signals lying outside the operating band of receivers and\ transmitters. These also reject unwanted noise signals received or\ generated by the amplifier circuitry.\ ***Amplifiers:*** An amplifier amplifies the strength (usually voltage) of\ a signal. Important specifications of an amplifier include power\ gain and the noise figure. The noise figure of an amplifier is a\ measure of how much noise is added to the amplified signal by the\ amplifier circuitry. This is most critical in the front end of the\ receiver where the input signal is very weak and it is desirable to\ minimize the noise added by the receiver circuitry. Therefore, it is\ necessary that thefirst amplifier in the receiver circuit has as low a\ noise figure as possible.\ ***Mixers: K*** mixer is typically used to achieve frequency conversion\ at the transmitters and receivers. Frequency conversion is required\ because it is advantageous to transmit signals at a higher\ frequency. This is achieved by modulating a carrier waveform\ using the original baseband frequency. When a baseband signal is\ mixed appropriately with a high frequency on a carrier, it can be\ easily and efficiently radiated and becomes less susceptible to\ noise and attenuation. Therefore, the transmission range increases\ and the received signal quality improves. Further, multiple base\ band signals can be mixed with a carrier appropriately to\ efficiently utilize the spectral bandwidth. This forms the essence\ \ ***Chapter 1 Fundamentals of Mobile Computing\ ***of any signal modulation technique. When multiple baseband\ signals modulate multiple carrier frequencies and the different\ baseband signals are made to occupy nonoverlapping bandwidths\ over a frequency spectrum, abroadband signal is obtained.\ **1-2 Architecture of a Mobile Telecommunication System\ **A simplified architecture of a mobile telecommunication system\ has been shown in Fig. 1.1. It has three main components: the core\ network, the radio access network, and the mobile phones.\ **Base station\ Mobile\ Mobile\ Radio access network \-\-\--\ Figure 1.1** Architecture of amobile telecommunication system.\ The radio access network is primarily composed of the base\ stations which communicate with the mobile phones using radio\ frequency electromagnetic waves. The coverage area is structured\ into hexagonal cells. In each hexagonal cell, one base station is\ located. Two types of radio channels are usually involved in the\ \ *Chapter 1 Fundamentals of Mobile Computing\ *communication between a base station and the cell phones:\ control channels and voice channels. Control channels typically\ use frequency shift keying (FSK) and are used for transferring\ control messages between the mobile phone and the base station.\ Voice channels typically use frequency modulation (FM). A base\ station typically has two antennas of different characteristics. One\ antenna is used for receiving and the other for transmitting. Use of\ two different types of antennas at the base station increases the\ ability of the base station to receive the radio signal from mobile\ that use very low transmitter power levels. On the other hand,\ mobile handsets typically use the same antenna for both receiving\ and transmitting.\ As shown in Fig. 1.1, the core network interconnects the base\ stations, the ***mobile switching centre (MSC),*** and also provides an\ interface to other networks such as the traditional telephone\ network ***(PSTN)*** and the Internet. The interconnect used in thecore\ network is required to provide high-speed connectivity. Therefore,\ fibre optic cables are usually used as the backbone interconnect in\ the core network. In difficult terrain conditions, microwave\ communication can also be used. This interconnection in the core\ network must allow both voice and control information to be\ exchanged between the switching system and the base station. The\ MSC is connected to the landline telephone network to allow\ mobile telephones to be connected to standard landline telephones.\ The core network is responsible for transmitting voice calls, SMS\ (Short Message Service), etc. from one phone to another through\ switches. The core network also maintains a database that contains\ information about the subscribers and the information about billing.\ \ ***Chapter 1 Fundamentals of Mobile Computing\ *1-3 Wireless Networking Standards\ **Standardization is very important to the computer networking\ domain, since many protocols and devices need to interoperate in\ any practical networking solution. Further there can be various\ vendors manufacturing the networking equipment. In the absence\ of appropriate standards, it would become interoperate the products\ manufactured by different vendors. Mainly, three international\ standardization bodies are responsible for formulating networking\ standards: ITU, IEEE and ISO.\ The IEEE (Institute of Electrical and Electronics Engineers) is a\ nonprofit, technical professional association of members from over\ 150 countries. IEEE acts as a standard body. Standards are very\ important in networking since multiple devices that are often\ heterogonous and manufactured by different vendors need to\ communicate. IEEE proposes standard for new technologies and\ maintains old standards. IEEE created the 802 group to help\ standardize the LAN technology. 802.3 standard from this group\ defines the requirements that a product must meet for it to be\ considered \'Ethernet\'. Wireless Ethernet is defined by 802.1 1.\ 802.11 is further broken down into more specific certifications,\ such as 802.11a, 802.11b, and 802.11g. Each of these defines a\ different method for providing wireless Ethernet. Each protocol\ specifies various aspects of data transfer that distinguish it from the\ other protocols. 802.11 standards define rules for communication\ on wireless local area networks (WLANs). 802.11 was the original\ standard in this family, ratified in 1997. 802.11 defined WLANs\ that operate at 1-2 Mbps. This standard\ \ *Chapter 1 Fundamentals of Mobile Computing\ *is obsolete today, but its extensions are being used extensively.\ Popular extensions of the 802.11 standard include 802.11a, 802.11b\ and 802.11g. Each extension to the original 802.11 appends a\ unique letter to the name. For example, the standards 802.11a,\ 802.11b and 802.11g define different types of signal modulation and\ frequencies of operation.\ **TABLE 1.1 Wireless Networking Standards** ------------------------------------------------------------------- *Information* *Data rate* *Standard* --------------------------------------- -------------- ------------ This specification has been extended\ IEEE 802.1 1 Up to 2 ------------------------------------------------------------------- 802.11b.\ the 2.4 GHz\ Products that adhere to this standard\ considered \"Wi-Fi Certified.\" Eight\ channels. Less potential for RF\ than 802.11b and 802.11g. Better than\ at supporting multimedia voice, video\ large-image applications in densely\ user environments. Relatively shorter\ than 802.11b. Not interoperable with\ Up to 54\ in the 5 GHz\ band\ IEEE 802.11a\ (Wi-Fi)\ standar this to adhere that Product\ Not Certified.\" \"Wi- considered are\ interoperable with 802.11a. Requires\ access points than 802.11a for\ large areas. Offers high-speed access\ at up to 300 feet from base station. 14\ available in the 2.4 GHz band (only\ which can be used in the U.S. due to\ regulations) with only three non¬\ channel\ Up to 1 1\ **in** the 2.4\ band\ IEEE 802.11b\ (Wi-Fi)\ Products that adhere to this standard\ considered \"Wi-Fi Certified.\" May\ 802. 11b. Improved security\ 802.11b. wit Compatib 802.11. ove\ 14 channels available in the 2.4 GHz\ (only 11 of which can be used in the\ due to FCC regulations) with only\ overlapping\ Up to 54\ **in** the 2.4\ band\ IEEE 802.11g\ (Wi-Fi)\ Commonly referred to as WiMAX or\ commonly as WirelessMAN or the\ Standard, IEEE 802.16 is a\ fixed broadband wireless\ networks\ Specifies\ WiMAX in\ 10 to 66\ range\ IEEE 802.16\ (WiMAX)\ Commonly referred to as WiMAX or\ commonly as WirelessMAN or the\ Standard, IEEE 802.16 is a\ fixed broadband wireless\ networks\ Added\ for the 2 to\ GHz range.\ IEEE\ (WiMAX)\ No native support for IP, so it does\ TCP /IP and wireless LAN\ Not originally created to support\ LANs. Best suited for connecting\ phones and PCs in short\ Up to 2\ **in** the 2.45\ band\ Bluetooth\ \ *Chapter 1 Fundamentals of Mobile Computing* ---------------------------------------------------------------------------- *Information* *Data rate* *Standard\ ***HiperLAN/1** ---------------------------------------- ----------------- ----------------- **Only in Europe. HiperLAN is totally\ Up to 20** **requiring no configuration and no\ **in the 5 GHz\ controller. Does not provide real\ (Europe)** services. Relatively expensive to\ maintain. No guarantee of bandwidth.** **band** ---------------------------------------------------------------------------- **Only in Europe. Designed to cany\ IP packets, Firewire packets (IEEE\ digital voice (from cellular phones),\ quality of service than HiperLAN /1\ guarantees bandwidth.\ Up to 54\ in the 5 GHz\ band\ HiperLAN/2\ (Europe)\ OpenAir is the proprietary protocol\ Proxim. All OpenAir products are\ Proxim\'s module.\ Pre-802.11\ tocol, using\ quency\ and 0.8 and\ Mbps bit rate\ Open Air\ 1-4 Advantages of Wireless LANs over Wired LANs\ With wireless LANs, users can access shared information without\ looking for a place to plug in their network cable, and network\ managers can set up networks with much less effort. Wireless\ LANs offer the following advantages over traditional wired\ netwoiks:\ 1. *Mobility:* Wireless LAN systems can help users to get\ information at any place in their oiganization. This type of\ support and service are hard to implement with wired\ netwoiks\ *2. Simplicity and speedy deployment:* Installation procedure of a\ wireless LAN system is simple and eliminates the need to use\ wires through walls. Wireless LAN facility can be set up in an\ area in a matter of few hours.\ 3. *Flexibility:* Wireless technology allows the netwoik to be\ accessible where wire is difficult to lay. Consider an airport,\ the passengers can connect their computer to the netwoik just\ **\ ***Chapter 1 Fundamentals of Mobile Computing\ ***sitting at their seats.\ 4. *Cost effectiveness:* While the initial investment required for\ wireless LAN hardware can be higher than the cost of wired\ LAN hardware, but in the long-term cost benefits may accrue\ because frequent movements and dynamic changes are often\ required in a typical network.\ **1-5 What is Mobile Computing?\ **Mobile computing (sometimes called ubiquitous computing and\ also at times called nomadic computing) is widely described as the\ ability to compute remotely while on the move. This is a new and\ fast emerging discipline that has made it possible for people to\ access information from anywhere and at anytime. We can also\ view *mobile computing* as encompassing two separate and distinct\ concepts: mobile communication and computing.\ Computing denotes the capability to automatically carry out\ certain processing related to service invocations on a remote\ computer.\ Mobile communication, on the other hand, provides the\ capability to change location while communicating to invoke\ computing services at some remote computers.\ The main advantage of this type of mobile computing is the\ tremendous flexibility it provides to the users. The user need not\ be tethered to the chair in front of his desktop, but can move\ locally or even to far away places and at the same time achieve\ what used to be performed while sitting in front of a desktop.\ \ *Chapter 1 Fundamentals of Mobile Computing\ ***1-6 Mobile Computing vs. Wireless Networking\ **We must distinguish between mobile computing and wireless\ networking. These two terms are not synonymous. While mobile\ computing essentially denotes accessing information and remote\ computational services while on the move, wireless networking\ provides the basic communication infrastructure necessary to make\ this possible. Thus, we can say that mobile computing is based on\ wireless networking and helps one to invoke computing services\ on remote servers while on the move: be it be office, home,\ conference, hotel, and so on.\ It should be clear that wireless networking is an important\ ingredient of mobile computing, but forms only one of the\ necessary ingredients of mobile computing. Mobile computing\ also requires the applications themselves-their design and\ development, and the hardware at the client and server sides. In\ fact, we can say that mobile computing subsumes the area of\ wireless networking. Consequently, to be able to understand the\ subtle issues associated with mobile computing, in addition to\ studying the different aspects of mobile computing applications,\ their design and development, we need to have a good knowledge\ of the basics of wireless communications technologies. Wireless\ networking is increasingly replacing traditional networks because\ of the low setup time and low initial investment required to set up\ the wireless network. As we discuss later in this chapter, wireless\ networks appear in various forms such as WLANs (Wireless\ LANs), mobile cellular networks, personal area networks (PANs),\ and ad hoc networks, etc.\ pg.10\ *Chapter1 Fundamentals of Mobile Computing\ Wireless networks can be classified into two basic types. One is\ an extension of wired networks. It uses fixed infrastructures such\ as base stations to provide essentially single hop wireless\ communication with a wired network as illustrated in Fig. 1.2 or a\ two-hop wireless cellular communication with another mobile as\ explained earlier in Fig. 1.1.\ The other type of wireless network is an ad hoc network. An ad\ hoc network does not use any fixed infrastructure and is based on\ multi-hop wireless communication as shown in Fig. 1.3.\ One popular example of a fixed infrastructure wireless network\ is a Wireless LAN (WLAN) that implements the IEEE 802.11\ protocol. Observe from Fig. 2.1 that only the last hop is through\ the wireless medium. An access point (AP) provides the last hop\ connectivity of the mobile nodes\ ***Figure 1.2** *Wireless network based on fixed infrastructures.\ *pg.n\ *Chapter1 Fundamentals of Mobile Computing\ ***Figure 1.3** Wireless network having no fixed infrastructures\ Wireless networking of various types of devices using the\ Bluetooth technology, the Bluetooth technology can also be used to\ establish direct wireless connection of a cell phone with devices\ such as printers, cameras, scanners, laptop and desk computers.\ Bluetooth is gradually replacing cables and infrared as the\ dominant way of exchanging information between devices. One of\ the objectives of the Bluetooth technology is to enable users to\ easily connect to a wide range of personal computing and\ telecommunication devices, without the need to buy, carry, or lay\ out cables. In fact, the Bluetooth technology enables setting up of\ personal area networks (PANs) known as piconets and ad hoc\ networks known as scatter nets. It provides opportunities for rapid\ deployment of ad hoc connections, and the possibility of automatic,\ transparent connections between devices. It promises to eliminate\ the need to purchase additional or proprietary cabling and\ configuration exercises needed to connect the individual devices, to\ a wired network. All communication goes through APs which\ perform bridging\" between the wireless and the wired mediums. A\ station must be recognized by an AP to be able to connect to the\ pg- 12\ *Chapter1 Fundamentals of Mobile Computing\ *network. The AP may require authentication and this in turn is used\ as the basic means to keep out the unauthorized users. In an\ infrastructureless network, the communication between hosts\ occurs directly or via a few intermediate nodes that form the hops.\ For example, station A in Fig. 1.3 can communicate with station C\ using either the hops A-B, B-C or A-D, D-C.\ An ad hoc network is also known as a Mobile Ad hoc Network\ (MANET). It is a collection of mobile nodes that form a network\ on the fly without requiring the support of any fixed infrastructure.\ Wireless sensor networks are a special type of wireless ad hoc\ networks.\ **1-7 Characteristics of Mobile Computing\ **A computing environment is said to be \"mobile\", when either the\ sender or the receiver of information can be on the move while\ transmitting or receiving information. The following are some of\ the important characteristics of a mobile computing environment.\ *Ubiquity:* The dictionary meaning of ubiquity is *present everywhere.\ *In the context of mobile computing, ubiquity means the ability of a\ user to perform computations from anywhere and at anytime. For\ example, a business executive can receive business notifications\ and issue business transactions as long he is in the wireless\ coverage area.\ *Location awareness:* A hand-held device equipped with global\ positioning system (GPS) can transparently provide information\ about the current location of a user to a tracking station. Many\ applications, ranging from strategic to personalized services,\ require or get value additions by location based services For\ pg.13\ *Chapter 1 Fundamentals of Mobile Computing\ *example, a person travelling by road in a car, may need to find out\ a car maintenance service that may be available nearby. He can\ easily locate such a service through mobile computing where an\ application may show the nearby maintenance shop. A few other\ example applications include traffic control, fleet management and\ emergency services. In a traffic control application, the density of\ traffic along various roads can be dynamically monitored, and\ traffic can be directed appropriately to reduce congestions. In a\ fleet management application, the manager of a transport company\ can have up-to-date information regarding the position of its fleet\ of vehicles, thus enabling him to plan accurately and provide\ accurate information to customers regarding the state of their\ consignments. Location awareness can also make emergency\ services more effective by automatically directing the emergency\ service vehicles to the site of the call.\ ***Adaptation:*** Adaptation in the context of mobile computing implies\ the ability of a system to adjust to bandwidth fluctuation without\ inconveniencing the user. In a mobile computing environment,\ adaptation is crucial because of intermittent disconnections and\ bandwidth fluctuations that can arise due to a number of factors\ such as handoff, obstacles, environmental noise, etc.\ ***Broadcast:*** Due to the broadcast nature of the underlying\ communication network of a mobile computing environment,\ efficient delivery of data can be made simultaneously to hundreds\ of mobile users. For example, all users at a specific location, such\ as those near a railway station, may be sent advertising\ information by a taxi service operator.\ ***Personalization:*** Services in a mobile environment can be easily\ personalized according to a user\'s profile. This is required to let the\ Pg-14\ *Chapter1 Fundamentals of Mobile Computing\ *users easily avail information with their hand-held devices. For\ example, a mobile user may need only a certain type of\ information from specific sources. This can be easily done through\ personalization.\ **1-8 Structure of Mobile Computing Application\ **A mobile computing application is usually structured in terms of\ the functionalities implemented. The simple three-tier structure of\ a mobile computing application is depicted in Fig. 1.4. Figure 1.5\ shows a specific scenario of the types of functionalities provided\ by each tier. As shown in these figures, the three tiers are named\ presentation tier, application tier and data tier.\ We now briefly explain the roles of the three tiers of a mobile\ computing application.\ Presentation (Tier-1)\ Application (Tier-2)\ Data (Tier-3)\ **Figure** 1.4 The three tier structure of a mobile computing\ application.\ pg.15\ ***Chapter 1 Fundamentals of Mobile Computing\ *Database\ Figure 1.5** Functionalities provided by each tier structure of a\ mobile computing application.\ Presentation tier\ The topmost level of a mobile computing application concerns the\ user interface. A good user interface facilitates the users to issue\ requests and to present the results to the them meaningfully.\ Obviously, the programs at this layer run on the client\'s computer.\ This layer usually includes web browsers and customized client\ programs for dissemination of information and for collection of\ data from the user.\ Pg- 16\ *Chapter1 Fundamentals of Mobile Computing\ Application tier\ *This layer has the vital responsibility of making logical decisions\ and performing calculations. It also moves and processes data\ between the presentation and data layers. We can consider the\ middle tier to be like an \"engine\" of an automobile. It performs the\ processing of user input, obtaining information and then making\ decisions. This layer is implemented using technology like Java,\.NET services, cold fusion, etc. The implementation of this layer\ and the functionality provided by this layer should be database\ independent. This layer of functionalities is usually implemented\ on a fixed server.\ *Data tier\ *The data tier is responsible for providing the basic facilities of data\ storage, access, and manipulation. Often this layer contains a\ database. The information is stored and retrieved from this\ database. But, when only small amounts of data need to be stored,\ a file system can be used. This layer is also implemented on a\ fixed server.\ **1-9 Cellular Mobile Communication\ **In a cellular mobile system, the area of coverage is split into\ cells, Fig.1.6. Even though the cells have been shown to be non¬\ overlapping hexagons for simplicity, but in reality, cell shapes are\ irregular and do overlap to some extent. A base station (BS) is\ located at the center of each cell. The BS in a cell receives\ communications from all mobile handsets in the cell and forwards\ the data to the appropriate handset. Thus, a base station keeps track\ of the calls of all handsets in its cell. When a mobile handset while\ pg-17\ *Chapter1 Fundamentals of Mobile Computing\ *continuing a call, moves to another cell, the BS \"hands-off\" the\ call to the BS in the new cell. When a cell covers a crowded area\ having too many users, then the users can experience frequent call\ drops. To overcome this problem, such cells are split into smaller\ cells.\ **Figure 1.6** Cell structure in a cellular mobile communication\ system.\ Initially the focus of cellular mobile communication was to\ support voice communication. But today cellular phones provide\ many services based on data communication too. These include\ electronic mail, Internet access and running a variety of mobile\ applications. The term mobile communication has a much wider\ connotation than just cellular mobile communication, and includes\ wireless LANs and ad hoc networks. However, due to the\ overwhelming popularity of mobile phones, cellular\ communication and mobile communication are at times used\ interchangeably.\ **1-10 Generations of Cellular Communication Technologies\ **Pg- 18\ ***Chapter 1 Fundamentals of Mobile Computing\ ***Mobile communication technology has advanced at a very rapid\ pace over the last five decades. The gradual technology\ improvements over the last four decades can be roughly demarcated\ into four generations. Each generation essentially provides higher\ data rate and additional capabilities, as shown schematically in Fig.\ 1.7. This figure does not show the data rates of technologies before\ GSM, since these were analog techniques that did not support the\ data communications facility. The fourth generation (4G) of\ technology provides a substantial order of magnitude improvements\ in data speeds, but is not yet widely implemented. The important\ characteristics of the various generations of cellular mobile systems\ have been summarized in Table 1.2. As can be seen from the table,\ each passing generation of mobile cellular system brought about\ significant advancements to the technology, causing the quality of\ the services to improve and the number of service offerings to\ increase, and at the same time the cost to the customer to drop\ drastically. We briefly discuss these different generations of mobile\ cellular communication systems in the following\ **LTE** ---------- -------- --------- --------- ---------- **HSPA** **\#** **UMTS\ **EDGE\ **GPRS** \#** \#** ---------- -------- --------- --------- ---------- **GSM\ 1990 2000 2010\ Year of operation\ Figure 1.7** Summary of mobile technology advancements.\ Pg- 19\ *Chapter1 Fundamentals of Mobile Computing\ **1- First generation\ ***The first generation (1G) cellular system was designed in the late\ 1960s, but was commercially deployed in the early 1980s. The first\ commercial 1G system in the United States was known as Advanced\ Mobile Phone System (AMPS). It became operational in 1982 and\ supported only voice calls. This was a completely analog system. In\ an analog system, analog signals are transmitted by modulating\ them on a higher frequency carrier signal, without first converting\ the signal into digital form through quantization. In a completely\ analog system, it is difficult to support SMS and other data services.\ Also, the signals from different users cannot be intermixed on the\ same channel, and have to be transmitted in clearly separated\ channels.\ **TABLE 1.2 Comparison of the Characteristics Some Cellular\ Wireless Communication Systems\ ***Data\ speed\ Standards Important Features\ Period of\ commer¬\ cial use\ Genera¬\ tion\ *No direct\ support\ NMT,\ AMPS,\ TACS\ Analog transmissions, primarily\ restricted to voice\ 70\'s to\ 90\'s\ 1G\ 9.6 kbps GSM Digital transmissions, improved\ performance by letting multiple\ users share a single channel.\ 90\'s to\ 2000\ 2G\ 28 kbps\ or higher\ GPRS Enhanced multimedia and\ video, web browsing.\ 2001-\ 2005\ 2.SG\ 384 kbps\ or higher\ UMTS,\ HSPDA,\ EDGE,\ W-CDMA\ Enhanced multimedia and\ video capabilities.\ 2005-\ 2015\ 3G\ 100 Mbps\ or higher\ LTE,\ WiMAX\ Support interactive multimedia,\ voice, video, wireless internet\ other broadband services.\ 2010-? 4G\ pg. 20\ *Chapter 1 Fundamentals of Mobile Computing\ *In the 1G system, the available frequency spectrum was split\ into a number of sub-bands (or channels), each of which was used\ by a different caller. These systems typically allocated a 25 MHz\ frequency band for the signals to be sent from the base station to\ the handset (incoming signal), and a second different 25 MHz\ band for the signal transmitted from the handset to the base station\ (outgoing signal). Figure 1.8 shows a frequency band split into five\ sub-bands (channels). Though for simplicity, we have shown the\ different channels to be adjacent to each other, each channel was\ separated from the adjacent channels by a spacing of about 30\ kHz. This was called a guard band. The use of guard bands was\ one of the causes of inefficient spectrum usage and resulted in the\ reduced number of simultaneous calls that could be supported.\ This problem was overcome in the subsequent generations of\ technologies.\ The 1G systems were of multiple access type, since once a caller\ hanged up, another caller could use the same frequency. For this\ reason, the 1G technology was also called Frequency Division\ Multiple Access (FDMA). It was possible to reuse the same\ frequencies in the non-adjacent cells, because the transmitter power\ output was restricted. For example, the cells shown shaded in Fig.\ 1.8 could use the same set of frequencies.\ Pg-21\ *Chapter1 Fundamentals of Mobile Computing\ *Figure 1.8 Cell structure and frequency allocation of 1G systems.\ When a caller crossed a cell boundary, the channel being used\ might not be made available in the new cell as it might already be\ in use in some other cell. During handoff, a different channel was\ possible to be allocated in this case, otherwise the call got dropped\ if none were available. Beside the number of callers that could be\ accommodated being low, the voice quality was poor due to analog\ transmission. Also, it provided no security at all, since any one\ could hear a call by tuning into a channel.\ *2- Second generation\ *As already pointed out, the 1G technology had many disadvantages.\ The major drawback was the small number of simultaneous calls\ that could be made and the high risk of call drops during handoffs.\ Calls in 1G were expensive because of the inherent inefficient usage\ of the bandwidth spectrum and hence very few could afford to use\ a cell phone. Further, the 1G networks were not capable of\ providing several useful services such as caller identity and SMS.\ The disadvantages of 1G systems were overcome by the second\ generation (2G) cellular systems.\ pg. 22\ *Chapter 1 Fundamentals of Mobile Computing\ *The 2G systems encoded voice and other information digitally\ before transmitting them. Digital transmission has many\ advantages over analog transmissions. These include noise\ immunity and better bandwidth utilizations. The 2G system offered\ significant advancements in the evolution of the mobile cellular\ technologies. Hence the 2G technology rapidly replaced the 1G\ technology because of the drastic reductions in the cost of phone\ calls and availability of a wider range of services coupled with\ substantial improvements in the quality of services. Also, SMSs\ became possible.\ However, we must remember that the 2G technology is in many\ respects an extension of the 1G system and many of the principles\ involved in a 1G system also apply to 2G. For example, they both\ use the same cell structure. However, there are many differences.\ For example, they use different signal modulation techniques. 2G\ uses CDMA (Code Division Multiple Access) and TOMA (Time\ Division Multiple Access) as channel access technology, while 1G\ used FDMA.\ The 2G mobile system deployment started in the 1990s, and two\ competing standards existed. In North America, the IS-95 standard\ was adopted which used Code Division Multiple Access (CDMA)\ and could multiplex up to 64 calls per channel in the 800 MHz\ band. In Europe and elsewhere, operators adopted the Global\ System for Mobile Communication (GSM) standard, which used\ Time Division Multiple Access (TOMA) to multiplex up to 8 calls\ per channel in the 900 and 1800 MHz bands.\ The first commercial deployment of Global System for Mobile\ Communication (GSM) was done in 1992. It supported higher\ voice quality and provided data services such as SMS and e-mail.\ pg. 23\ *Chapter 1 Fundamentals of Mobile Computing\ *We will discuss the GSM system in more detail, later in this\ chapter. In 1993, another 2G system, known as CDMAone, was\ standardized and commercially deployed in South Korea and Hong\ Kong in 1995, followed by the United States of America in 1996.\ ***3- 2.5 Generation\ ***General Packet Radio Service (GPRS) is an extension of GSM and\ is considered to be the 2.5 generation technology. As indicated by\ the name, it is based on packet switching compared to circuit\ switching used in 2G. This was a significant improvement over 2G\ and helped to reduce call costs dramatically. GPRS data transfer is\ typically charged per megabyte of data transferred. This is in\ contrast to the traditional circuit switching systems where the\ customer is billed per minute of connection time, irrespective of\ whether the customer actually used the capacity or not. Another\ important advantage of GPRS is that it allows users to remain\ connected to the Internet without incurring additional charge and\ supports multimedia capabilities including graphics and video\ communications. GPRS deployments began in 2000, followed by\ EDGE in 2003. EDGE enhances the capabilities of GPRS, allows\ faster Internet browsing, and makes it possible to use streaming\ applications. Though this technology provided faster data rates over\ 2G systems, it is called 2.5G because it did not offer the multi¬\ megabit data rates which are the characteristics of the 3G system.\ ***4- Third generation\ ***The 3G systems are often referred to as IMT-2000 (International\ Mobile Telecommunications-2000) systems since this was made a\ global standard by ITU. The 3G systems support much higher data\ pg. 24\ *Chapter 1 Fundamentals of Mobile Computing\ *transmission rates and offer increased bandwidth, which makes\ them suitable for high-speed data applications as well as for high\ quality traditional voice calls. The 3G systems can be considered to\ be purely data networks, since voice signals are converted to digital\ data, this results in speech being dealt with in much the same way\ as any other form of data. The 3G systems use packet switching\ technology, and provide cheaper calls while giving better average\ call quality than that of the 2G systems, but they do require a\ somewhat different infrastructure compared to the 2G systems. The\ 3G networks made it possible for service providers to offer many\ innovative applications and services such as email, instant\ messaging and video telephony, multimedia gaming, live-video\ buffering, and location-based services among others. The first 3G\ network was deployed in Japan in 2001 by DoCoMo.\ UMTS (Universal Mobile Telephone System) is one of the 3G\ mobile systems that was developed within the ITU\'s IMT-2000\ framework. UMTS was developed mainly for the GSM networks,\ so that these could be easily upgraded to UMTS networks. In\ UMTS, coverage is provided by a combination of a variety of cell\ sizes ranging from \"in building\" *pico cells* to *global cells* provided by\ satellites.\ 5- *Fburth generation\ *A 4G system provides a faster data rate than that of 3G (at least 10\ times faster) and makes mobile broadband Internet access possible.\ The 4G system has made possible high speed Internet access from\ smartphones and laptops with USB wireless modems. A few\ applications that could not be supported in earlier generations of\ pg. 25\ *Chapter 1 Fundamentals of Mobile Computing\ ***the cellular phone systems, have now become possible in 4G\ including IP telephony, gaming services, high-definition mobile\ TV, video conferencing and 30 television. The 4G technology is\ expected to help solve the last mile problem that prevents the\ mobile users from running applications that are available on wired\ networks. There are at present two competing 4G standards:\ Mobile WiMAX standard and the Long Term Evolution (LTE)\ standard.\ *6- Fifth generation\ *Fifth generation cellular techniques have not yet been deployed\ and are still at a research and development phase. However, some\ of the characteristics of the 5th generation techniques are increased\ data transmission capability (1 Gbps). Connectivity to a large\ numberof devices due to the advent of the Internet of Things (loT)\ through MIMO (Multiple-Input and MultipleOutput) technologies.\ MIMO technologies deploy multiple antennas for transmission and\ reception, thereby effectively increasing the data rate.\ A summary of the important characteristics of the different\ generation wireless cellular technologies has been shown in Table\ 1.2. In the following section, we provide a brief overview of the\ working of a few cellular wireless technologies that are being\ popularly used at present In Table 1.3, we provide a comparative\ summary of the different transport protocols that are used across\ different generations cellular networks.\ **pg. 26\ *Chapter 1 Fundamentals of Mobile Computing\ *TABLE 1.3 Summary of Characteristics of Cellular Technologies ----------------------------------------------------------------------------------------- 5G\ 4G 3G 2G/2.5G\ 1G\ *Generatio* 2016-2020 2000-2005 1985- ------------------------ -------------- ----------- --------------- ------- ------------- 2010-2014 2005-2010 *Period* Simultaneous access\ Data and Fast data Used digital\ to different wireless\ Analog\ technologies.\ Main Complete wireless\ communication\ leading to wireless\ world wide web\ (WWWW). voice over\ radio voice\ features transfer service IP. and greater\ Voice Entir\ to digital\ packe\ signals.\ network\ Comparative\ capacity. secure. switc\ netw ----------------------------------------------------------------------------------------- 1 Gbps and higher 180-220\ to 1.5\ 2.5 Mbps 15-7 kbps 3 kbps Data\ IP Based/seamless\ combination of\ broadband¬\ wireless LAN\ (Proposed By)\ Digit\ broadband\ all, packe\ hig Very\ throughpu\ Digital\ broadband\ packet data\ Packet data\ system\ Analog\ voice\ cellular\ Techno¬\ logy\ Digital Information High\ audio and\ video\ Voice, SMS,\ Packet data\ facility\ Only\ voice\ facility\ Offered\ services\ Packet switching and message\ switching.\ Packet\ Switching\ Circuit\ hing with\ support for\ digital data\ Circuit\ switchin\ Switchin\ TABLE 1.4 Transport Technologies used Across Generations of\ Cellular Networks\ *Advantages and\ disadvantages\ Characteristic Generatio Full form Transport\ technology\ *Low\ requirement\ and low\ consumptio\ Low speed\ Voice and data\ transmission at\ upto 9.6 kbps\ 2G Time Division\ Multiple Access\ TDMA\ SMS restricted\ 160\ Voice and data\ transmission at\ upto 9.6 kbps\ 2G Global System for\ Mobile Communi¬\ cation\ GSM\ SMS restricted\ 160\ Data upto 115 2.SG General Packet\ Service\ GPRS\ Easier to adopt\ t compared\ WCDMA\ Data upto 384 3G Enhanced Data EDGE\ popular Less\ than GSM\ Data upto\ 144 kbps but\ successor EVDA\ at 2.4 Mbps\ 2G Code Division\ Multiple Access\ CDMA\ Widely Data upto 14 3G Wideband CDMA\ known as\ Mobile\ nication System.\ WCDMA\ (UMTS)\ Pg-27\ *Chapter 1 Fundamentals of Mobile Computing\ ***1-11 Global System for Mobile Communications (GSM)\ **GSM (Global System for Mobile Communications) is at present\ being used in India. It is possibly the most successful digital\ mobile system to have ever been used till now. An important\ characteristic of the GSM system is that it provides data services in\ addition to voice services, and yet is compatible to 1G systems.\ GSM networks operate in four different radio frequencies. Most\ GSM networks operate either in the 900 MHz or in the 1800 MHz\ frequency bands. Some countries in the American continent\ (especially the USA and Canada) use the 850 MHz and 1900 MHz\ bands because the 900 MHz and 1800 MHz frequency bands are\ already allocated for other purposes. The relatively rarely used 400\ MHz and 450 MHz frequency bands are assigned in some\ countries, notably Scandinavia where these frequencies were\ previously used for the first generation systems. In the 900 MHz\ band, the uplink frequency band is 890-915 MHz, and the\ downlink frequency band is 935-960 MHz.\ GSM provides three main categories of services. These are:\ (i) Bearer services\ (ii) Teleservices\ (iii) Supplementary services\ *Bearer services\ *Bearer services give the subscribers the capability to send and\ receive data to *I* from remote computers or mobile phones. For this\ reason, bearer services are also known as *data services* (see Box 2.1).\ These services also enable the transparent transmission of data\ between GSM and other networks like PSTN, ISDN, etc. at rates\ from 300 bps to 9600 bps. These services are implemented on the\ pg. 28\ *Chapter 1 Fundamentals of Mobile Computing\ *lower-three layers of the OSI reference model. Besides supporting\ SMS, e-mail, voice mailbox, and Internet access, this service\ provides the users with the capability to execute remote\ applications. GSM supports data transfer rates of up to 9.6 kbps.\ GSM provides both the voice-oriented teleservices and the non¬\ voice teleservices, as discussed below.\ : The main goal of GSM was to provide high quality\ digital voice transmission, offering the bandwidth of 3.1 kHz of\ analog phone systems. Special codecs are used for voice\ transmission, while other codecs are used for the transmission of\ analog data for communication with traditional computer modems\ used in fax machines.\ : The same number is used throughout an\ area. This service is free of cost and mandatorily provided by all\ service providers. This connection will automatically be set up\ with the closest emergency centre.\ a : This service offers transmission of text\ messages of sizes up to 160 characters. SMS services use the\ signalling channels, making possible the duplex system of the\ sending and receiving the SMSs messages.\ Fax: In this service, using modems fax data is transmitted as\ digital data over the analog telephone network according to the\ ITU-T Standards T.4 and T.30.\ pg. 29\ *Chapter 1 Fundamentals of Mobile Computing\ f* **Mobile Phone and Human Body X\ **Extensive research has been conducted to study the possible\ health effects of continuous exposure to low intensity RF fields\ produced by mobile phones. The overall evidence suggests that\ mobile phone usage of less than 10 years does not pose any\ increased risk of brain tumor. The effect of still longer use is\ unclear due to non-availability of data. Any conclusion therefore\ is uncertain and tentative. From the available data, however, it\ does appear that there is no increased risk for brain tumours in\ long-term users as well. Currently available studies on\ neurological effects and reproductive effects have not indicated\ any health risks at exposure levels below guidelines.\ Acoustic neuroma is a non-cancerous tumour that develops on the nerve\ that connects the ear to the brain. The tumour usually grows slowly. As\ it grows, it presses against the hearing and balance nerves. At first,\ there may be no symptoms or mild symptoms. They can include the\ following:\ Loss of hearing on one side\ Ringing in ears\ Dizziness and balance problems\ pg- 30\ Summary (Important Points)\ Mobile computing is a two-word terminology\ Mobile means moving\ Computing means using computer\ **Mobile Condition:** the set of properties that distinguishes the mobile user\ from the user of a typical stationary computing system.\ **Dimensions of Mobility:** the set of properties that distinguishes the mobile\ computing system and stationary computing system\ **Mobility Includes:\ ** Moving between different geographical locations\ Moving between different networks\ Moving between different applications\ **Mobility computing system differs from other systems in\ ** Functionality requirements\ \> Tasks that they are designed to perform\ \> Way that they are designed\ \> Way in which they are operated ------------------------------------------------------------------------- **Mobile Computing** **Wireless Communication** ------------------------------- ----------------------------------------- Perform process of computing\ The way or space that used to transfer\ with mobility (capability of\ signal over network moving) ------------------------------------------------------------------------- Devices of mobile computing need\ not to be connected over wireless\ Wireless communication systems are\ often used in mobile computing systems\ to facilitate network connectivity, but\ they are\ not mobile computing systems.\ Laptop computers, calculators,\ electronic watches, and many\ other devices are all mobile\ computing devices\ **Dimensions of Mobility:\ **1. Location awareness,\ 2. Wireless Connectivity,\ 3. Limited device capabilities (particularly storage and CPU),\ 4. Limited power supply,\ 5. Support a wide variety of user interfaces (Multimodal Uis),\ 6. Variety of Platforms,\ 7. Active Behavior.\ **1. Location Awareness\ **Acquiring position information and need connectivity to some network¬\ based infrastructure. ------------------------------------------------------------------------------------ Localization Location sensitivity -------------------------------------------- --------------------------------------- Often required in stationary applications\ Ability to obtain location information where users at different geographical\ and use this location information to\ locations can access a centralized\ offer features and functionality system. Ability of mobile application to\ How to collect location information?\ accommodate logic that allows the\ Entry by user (Not user friendly)\ selection of different bossiness logic,\ Triangulation\ level of work flow and interfaces based\ Proximity\ on location information.\ Scene analysis **Location Sensitivity Methods:\ Triangulation** ------------------------------------------------------------------------------------ Allow calculation of the location of a point that lies in the middle\ of three other points whose exact locations are known.\ Pg-31\ ** Proximity\ ***J* Measure the relative position of the unknown point to some\ known point\ ** Scene analysis\ ***J* Relies on image processing and graphical techniques\ ** GPS\ **Use Triangulation Technique but with more satellites \[Accuracy\ about 1 - 5 meters\]\ **2. Connectivity Challenges\ ** QoS (Quality of Service) tools are managed by network operators\ Provide info on:\ \> Available bandwidth\ \> Probability of connectivity loss\ \> Statistical traffic measurements\ Bad weather, solar flares, and variety of other climate conditions can\ negatively affect QoS.\ All mobile applications should know how to stop working when the\ application suddenly disconnects from the network and then resume\ working when it connects again.\ **3. Limited Device (Challenges)\ ** Size matters, Size limits\ - Sizecontributestomobility\ - Butitalsoaffects memoryand CPU capacities\ - Limited CPU, RAM andStorage\ **4. Power Challenges\ ** battery life is short\ For example, the brighter the display, the more battery power is used,\ so the user interface is indirectly coupled to the power supply.\ Mobility affect battery life\ Battery management is the OS job, not the App\'s job\ Platforms provide monitoring of the remaining power and other\ related power information\ Platforms allow multiprocessing and multithreading\ pg. 32\ **5. Multimodal Uis and varying user interfaces\ ** Stationary application users have more efficient user interface\ capabilities than mobile application\ Mobile User interfaces are difficult to design and implement for the\ following reasons\ \> Designers have difficulties learning the user\'s tasks.\ \> The tasks and domains are complex.\ \> The existing theories and guidelines are not sufficient.\ \> A balance must be achieved among the many different design\ aspects, such as standards, graphic design, technical writing,\ internationalization, performance, multiple levels of detail,\ social factors, and implementation time.\ **6. Varity of Platforms (platform proliferation)\ ** Due to commercial competence, every manufacture has his own\ platform (iOS, android)\ For implementation, writing native code is not recommended (use\ cross platforms)\ For designing, we use methodologies and tools, such as UML\ **7. Active transactions\ ** Mobile can act as active (online) or passive (offline) behavior\ Mobile always be in active and pushing mode within signal from base\ station\ Transactions\ Passive transaction\ Active transaction\ \> Synchronous\ \> Asynchronous\ Passive transactions\ The user must initiate all the transactions (stationary system)\ pg- 33\ Synchronous active transactions\ Transaction is initiated by system\ Require timely response from the user\ Interaction between system and user in sequential and serial manner\ Transactions are established between system and single user and may\ replicated for many users\ Asynchronous active transactions\ Transaction work just like messaging systems\ May be a composition of 1-n receivers or 1-n topics or 1-n messages\ Interaction between system and user in sequential and serial manner\ Transactions are being successful if responses from users are not\ received within some time frame specified by the system