Chapter 1 Fundamentals of Mobile Computing PDF

Chapter 1 Fundamentals of Mobile Computing ### 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 b...

Chapter 1 Fundamentals of Mobile Computing ### 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 co-located 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. This can be compared to a light bulb that emits light all over. In contrast, a directional antenna is similar to a flashlight, which focuses light in some direction. - **Filters**: Filters are the key component present in all wireless transmitters and receivers. These are used to reject 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 the first amplifier in the receiver circuit has as low a noise figure as possible. - **Mixers**: A 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 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, a broadband signal is obtained. ### **1-2 Architecture of a Mobile Telecommunication System** A simplified architecture of a mobile telecommunication system has been shown in Figure 1.1. It has three main components: the core network, the radio access network, and the mobile phones. *** A diagram showing the architecture of a mobile telecommunication system. This diagram shows a mobile phone connected to a base station using a cellular network and is connected to another base station using a cellular network followed by a switch connected to a core network. The core network is connected to a PSTN, the Internet, and a subscriber database. *** 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 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 Figure 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 the core 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. ### 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 802.11. 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 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. | Information | Data rate | Standard | |-----------------------------------|-----------|------------------| | This specification has been extended 802.11b. 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 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 2 in the 2.4 GHz band Up to 54 in the 5 GHz band | IEEE 802.11 IEEE 802.11a (Wi-Fi) | | Products that adhere to this standard considered "Wi-Fi Certified." May 802. llb. 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 11 in the 2.4 band | IEEE 802.11b (Wi-Fi) | | Products that adhere to this standard considered "Wi-Fi Certified." May 802. llb. 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 66 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 | | Only in Europe. HiperLAN is totally requiring no configuration and no controller. Does not provide real services. Relatively expensive to maintain. No guarantee of bandwidth. | Up to 20 in the 5 GHz band | HiperLAN/1 (Europe) | | Only in Europe. Designed to carry 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 networks: * **Mobility**: Wireless LAN systems can help users to get information at any place in their organization. This type of support and service are hard to implement with wired networks * **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. * **Flexibility**: Wireless technology allows the network to be accessible where wire is difficult to lay. Consider an airport, the passengers can connect their computer to the network just sitting at their seats. * **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. ### **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. ### **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 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 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 Figure 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. *** A diagram showing the three tier structure of mobile applications - Presentation, Application, and Data. The presentation tier lists: Find the sales total, Five total sales. The Application tier lists: Find the list of sales made in last year, Query. The Data tier lists: Database, Storage. *** We now briefly explain the roles of the three tiers 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. - **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, Figure 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 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. *** A diagram showing the cell structure in a cellular communication system. This diagram shows a hexagonal grid pattern, where each hexagon represents a `cell`, with a base station in the center of each cell. The `cell` is the smallest geographical area covered by a base station. *** 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** 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 Figure 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 *** A graph showing the evolution of Data speed, on the Y-axis and Year of Operation on the X-axis. The Y-axis shows the data speed starting at 100kb till 1Gb and the X-axis shows the Year of Operation starting at 1990 till 2005. This graph shows the different technologies that were introduced, the different data speeds, and the year of operation. This includes - GSM operating in the years 1990-1995, GPRS operating in the years 1998-2005, EDGE operating in the year 2000-2005, UMTS operating in the year 2000-2010, HSPA operating in the years 2005-2010, and LTE operating in the year 2010-2015. *** #### **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. | Data speed | Standards | Important Features | Period of Commercial use | Generation | |------------|----------|----------------------------------------------------------------------|--------------------------|-------------| | 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 | GPRS | Enhanced multimedia and video, web browsing. | 2001-2005 | 2.5G | | 384 kbps | UMTS, EDGE, W-CDMA | Enhanced multimedia and video capabilities. | 2005-2015 | 3G | | 100 Mbps | LTE, WiMAX | Support interactive multimedia, voice, video, wireless internet other broadband services. | 2010-? | 4G | In the IG 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. *** A diagram showing the cell structure and frequency allocation of the IG system - `cell` structure and frequency allocation. The diagram shows a hexagonal grid pattern, where each hexagon represents a `cell`, with a base station in the center of each cell. There are five frequencies allocated to different channels in each cell. The frequency allocated to each channel is shown in the diagram. *** The IG 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 Figure 1.8 could use the same set of frequencies. 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 IG 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 IG 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. 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.  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 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- Fourth 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 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 number of devices due to the advent of the Internet of Things (IoT) 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. | 5G | 4G | 3G | 2G/2.5G | 1G | Generation | |---------------------------------|-------------------------------------------|---------------------------------------|---------------------------------------------|---------------|--------------| | 2016-2020 | 2010-2014 | 2005-2010 | 2000-2005 | 1985- | Period | | Simultaneous access to different wireless technologies. Complete wireless communication leading to wireless world wide web (WWWW). | Data and voice over IP. Entir packe fast data transfer and greater network capacity. | Digital radio Voice to digital signals. Comparative secure. | Used digital radio Voice to digital signals. | Analog voice service | Analog Main service features | | 1 Gbps and higher IP Based/seamless combination of broadband-wireless LAN (Proposed By) | 180-220 to 1.5 Digit broadband all, packe high throughput | 2.5 Mbps Digital broadband packet data High audio and video | 15-7 kbps Packet data system. Voice, SMS, Packet data facility hing with digital data | 3 kbps Data analog voice cellular | Data Techno-logy | | Digital Information | Packet switching and message switching. | Packet switching. | Circuit switching. | Circuit switching. | Only offered services Switchin | ### **TABLE 1.4 Transport Technologies used Across Generations of Cellular Networks** | Advantages and disadvantages | Characteristic | Generation | Full form | Transport technology | |--------------------------------|------------------------------------------|------------|------------------------------------|-----------------------| | Low requirement and low consumptio | Voice and data transmission at upto 9.6 kbps | 2G | Time Division Multiple Access | TDMA | | Low speed SMS restricted 160 | Voice and data transmission at upto 9.6 kbps | 2G | Global System for Mobile Communication | GSM | | SMS restricted 160 | Data upto 115 | 2.5G | General Packet Service | GPRS | | Easier to adopt compared to WCDMA | Data upto 384 | 2.5G | Enhanced Data GSM | 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 Communication System. | WCDMA (UMTS) | ### **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: * Bearer services * Teleservices * 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 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