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ALTTC BSNL Training Report A Report Submitted in the Partial Fulfillment of the Requirements for the Degree of B.Tech in Electronics and Communication Engineering by Sonal Bansal 1133231023 Under the Guidance of Mr. S.K. Gupta ELECTRONICS AND COMMUNICATION DEPARTMENT MAHARAJA AGARSAIN INSTITUTE OF TECHNOLOGY, GHAZIABAD – 245304, INDIA June, 2014

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A report that is close to the field of Telecommunication and gives the basic idea on various technology used in this field.

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  • ALTTC BSNL Training Report A Report Submitted in the Partial Fulllment of the Requirements for the Degree of B.Tech in Electronics and Communication Engineering by Sonal Bansal 1133231023 Under the Guidance of Mr. S.K. Gupta ELECTRONICS AND COMMUNICATION DEPARTMENT MAHARAJA AGARSAIN INSTITUTE OF TECHNOLOGY, GHAZIABAD 245304, INDIA June, 2014
  • UNDERTAKING I declare that the work presented in this report ti- tled ALTTC BSNL Training Report, submitted to the Electronics and Communication Engineering De- partment, Maharaja Agarsain Institute of Technology, Ghaziabad, for the award of the B.Tech degree in Electronics and Communication Engineering, is my original work. I have not plagiarized or submitted the same work for the award of any other degree. In case this undertaking is found incorrect, I accept that my degree may be unconditionally withdrawn. June, 2014 Ghaziabad (Sonal Bansal) ii
  • CERTIFICATE Certied that the work contained in the report titled ALTTC BSNL Training Report, by Sonal Bansal, Registration Number 1133231023 has been carried out under my supervision and that this work has not been submitted elsewhere for a degree. June, 2014 (Mr. S.K. Gupta) ALTTC BSNL, Ghaziabad iii
  • Acknowledgment It would not have been possible to write this report without the help and support of almighty God and kind people around me, to only some of whom it is possible to give particular mention here. Above all, I am truly indebted and thankful to my parents and my family for their personal support and great patience at all times. My family has given me their unequivocal support throughout, as always, for which my mere expression of thanks does not sufce. This report would not have been possible without the help, support and patience of my training incharge, Mr. S.K. Gupta. His advice and unsurpassed knowledge has been invaluable, for which I am extremely grateful. I was privileged to experience a sustained enthusiastic involved interest from his side. I would like to acknowledge the academic and technical support of ALTTC BSNL, Ghaziabad and its staff. I am thankful for their valuable support and guidance. Last, but not the least, I would like to thanks everyone who has contributed for the successful completion of my training. - Sonal Bansal iv
  • Contents Acknowledgment iv 1 Introduction 1 1.1 Voice Signal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Switching System Fundamentals . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Trunking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.4 Call Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.5 A Typical Telephone Exchange-OCB-283 . . . . . . . . . . . . . . . . . 3 2 Corporate Network 4 2.1 Security of Corporate Network . . . . . . . . . . . . . . . . . . . . . . . 5 3 Signalling In Telecommunications 7 3.1 ISDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 Signalling System Number 7 . . . . . . . . . . . . . . . . . . . . . . . . 8 4 Pulse Code Modulation Principle 9 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.2 Basic requirements for PCM system: . . . . . . . . . . . . . . . . . . . . 10 v
  • 5 Dense Wavelength Division Multiplexing 13 5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.2 Challenges of Todays Telecommunication Network . . . . . . . . . . . . 14 5.3 Optical Fiber Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3.1 Optical Fiber Transmission . . . . . . . . . . . . . . . . . . . . . 14 5.3.2 Classication of Optical Fiber . . . . . . . . . . . . . . . . . . . 15 5.3.3 Optical Fiber in the DWDM . . . . . . . . . . . . . . . . . . . . 15 5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6 GSM Architecture and Technology 17 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.1.1 Mobile Station . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1.2 The Base Station Subsystem . . . . . . . . . . . . . . . . . . . . 19 6.2 The Network and Switching Subsystem . . . . . . . . . . . . . . . . . . 19 6.2.1 The Mobile services Switching Center (MSC) . . . . . . . . . . . 19 6.2.2 The Gateway Mobile services Switching Center (GMSC) . . . . . 19 6.2.3 Home Location Register (HLR) . . . . . . . . . . . . . . . . . . 20 6.2.4 Visitor Location Register (VLR) . . . . . . . . . . . . . . . . . . 20 6.2.5 The Authentication Center (AuC) . . . . . . . . . . . . . . . . . 20 6.2.6 The Equipment Identity Register (EIR) . . . . . . . . . . . . . . 20 7 Base Transceiver Station 21 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 8 Introduction oF 3G Communication 23 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.2 Architecture Model of 3G Network . . . . . . . . . . . . . . . . . . . . . 24 9 CDMA Technology 25 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9.2 Advantage of CDMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.3 Disadvantage of CDMA . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.4 Difference between CDMA and GSM . . . . . . . . . . . . . . . . . . . 26 vi
  • References 28 vii
  • List of Figures 1 Corporate Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 Frequency Division Multiplexing . . . . . . . . . . . . . . . . . . . . . . 10 3 Time Division Multiplexing . . . . . . . . . . . . . . . . . . . . . . . . 10 4 Quantization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5 Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6 Optical Fiber Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 15 7 Network of GSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8 Base Transceiver Station . . . . . . . . . . . . . . . . . . . . . . . . . . 21 9 Overview of BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 10 Architecture of 3G Network[1] . . . . . . . . . . . . . . . . . . . . . . . 24 xiii
  • Chapter 1 Introduction Telephone is a telecommunication device that is used to transmit and receive electroni- cally or digitally encoded speech between two or more people conversing[1]. It is one of the most common household appliances in the world today. Telecommunication networks carry information signals among entities, which are ge- graphically far apart. An entity may be a computer or human being, a teleprinter, a data terminal and so on. The entities are involved in the process of information transfer that may be in the form of a telephone conversation or a le transfer between two computers or message transfer between two terminals etc. With the rapidly growing trafc and untargeted growth of cyberspace, telecommuni- cation becomes a fabric of our life. The future challenges are enormous as we anticipate rapid growth in terms of new services and number of users. What comes with the chal- lenge is a genuine need for more advanced methodology supporting analysis and design of telecommuniction architectures. Telecommunication has envolved with a growth at an explosive rate in the recent years and will undoubtedly continue to do so. The communication switching system enables the universal connectivity. The univer- sal connectivity is realized when any entity in one part of the world can communicate 1
  • with any other entity in another part of the world. In many ways telecommunication acts as a substitute for the increasingly expensive physical transportation. 1.1 Voice Signal Characteristics The range of frequencies used by a communication device determines the communication channel, communicating devices, and bandwidth or information carrying capacity. The most commonly used parameter that characterizes an telephone system, the frequencies it passes are restricted to between 300 to 3400 Hz[2]. 1.2 Switching System Fundamentals Telecommunication switching systems generally perform three basics function:- They transmit signals over separate channels to convey the identify of the called address, and ring the called station. They establish connections through a switching network for conversational use dur- ing the entire call. They process the signal information to control and supervise the establishment and disconnection of the switching network connection. Switching techniques Space and time division are the two basics techniques used in establishing connections:- When an individual conductor path is established through a switch for the duration of a call, the system is known as space division. When the transmitted speech signals are sampled and the samples multiplexed in time so that high-speed electronic devices may be used simultaneously by several calls, the switch is known as time division. 2
  • 1.3 Trunking In telecommunication systems, trunking is aggregation of multiple user circuits into a single channel. The aggregation is achieved using some form of multiplexing[3]. 1.4 Call Routing Routing in the PSTN (public switched telephone network) is the process used to route telephone calls across the PSTN. This process is the same whether the call is made be- tween two phones in the same locality, or across two different continents. Thus the ob- jective of routing is to establish a successful connection between any two exchanges in the network. By selecting routes that meet the constraints set by the user trafc and the network, routing determines which network resources should be used to transport which user trafc[4]. 1.5 A Typical Telephone Exchange-OCB-283 The Alcatel E10 system is located at the heart of the telecommunication networks con- cerned. It is made up of three independent functional units:- Subscriber Access Subsystem Connection and Control Operation and Maintenance 3
  • Chapter 2 Corporate Network A corporate network is a closed and private computer network that affords secure commu- nication between geographically dispersed LANs of an enterprise. These point to point connection have delivered through leased lines. A corporate network is also dened as a group of computers, connected together in a building or in a particular area, which are all owned by the same company[1]. 4
  • Figure 1: Corporate Network 2.1 Security of Corporate Network Protect PC workstations over your network with Corporate Network Security. This net- work based password protected security software lets you impose access restrictions to all your PC workstations you have in your corporate network to stop users from tampering with them. The workstations are controlled from a single administrators computer from 5
  • almost everywhere you have access to the TCP/IP- based network or Internet. Corporate Network Securitys features Complete bullet-proof protection of the remote computers you have on your net- work. Executable patches can be easily uploaded to all your remote computers and exe- cyted remotely. You do not need to physically visit your workstations when you need to change security settings or install patches. 6
  • Chapter 3 Signalling In Telecommunications The term signaling, when used in telephony, refers to the exchange of control information associated with the establishment of a telephone call on a telecommunications circuit. An example of this control information is the digits dialed by the caller, the callers billing number, and other call-related information. When the signalling is performed on the same circuit that ultimately carry the conver- sation of the call, it is termed Channel Associated Signalling (CCS). In contrast, SS7 signalling is termed Common Channel Signalling (CCS) in that the path and facility used by the signalling is separate and distinct from the telecommunica- tions channels that will ultimately carry the telephone conversation. In the PSTN one channel of a communication link is typically used for the sole pur- pose of carrying signaling for establishment and tear down of telephone calls. The re- maining channels are used entirely for the transmission of voice data. In most cases, a single 64Kbits/s channel is sufcient to handle the call setup and call clear-down trafc numerous voice and data channels. CCS offers the following advantage over CAS, in the context of the PSTN:- Faster call setup 7
  • No falsify interference between signaling tones by network and speech frequency. No security issues related to the use of in-band signalling with CAS. CCS allows the transfer of additional information along with the signalling trafc providing features such as caller ID. The most common CCS signaling method in use today are Integrated Services Digital Network (ISDN) and Signalling System 7 (SS7). 3.1 ISDN ISDN signaling is used primarily on trunks connecting enduser Private Branch Exchange (PBX) system to a central ofce. 3.2 Signalling System Number 7 SS7 is a set of telephony signaling protocols which are used to set up most of the worlds public switched telephone network telephone calls. The main purpose is to set up and tear down telephone calls. Other uses include number translation, prepaid billing mechanisms, short message service (SMS), and a variety of other mass market services[5]. 8
  • Chapter 4 Pulse Code Modulation Principle 4.1 Overview Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, Compact Discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps[3]. Multiplexing techniques: There are basically two types of multiplexing techniques:- 1). Frequency Division Multiplexing 2). Time Division Multiplexing 1). FDM principle- Frequency Division Multiplexing (FDM) is inherently an analog technology. FDM achieves the combining of several signals into one medium by sending signals in several distinct frequency ranges over a single medium[6]. In the gure it is clear that how three different signals are tnransmiting over a single medium. 9
  • Figure 2: Frequency Division Multiplexing 2). TDM principle- Basically, Time Division Multiplexing involves nothing more than sharing a transmission medium by a number of circuits in time domain by establishing a sequence of time slots during which individual channels (circuits) during which individual channels are transmitted. Thus the entire bandwidth is periodically available to each channel[7]. Figure 3: Time Division Multiplexing 4.2 Basic requirements for PCM system: Filtering Sampling Quantization Encoding Line coding 10
  • Filtering Filters are used to limit the speech signal to the frequency band 300-3400 hz. Sampling In signal processing, sampling is the reduction of a continuous signal to a discrete signal. A common example is the conversion of a sound wave (a continuous signal) to a sequence of samples (a discrete time signal). A sample refers to a value or set of values at a point in time and/or space. A sampler is a subsystem or operation that extracts samples from a continuous signal. Sampling theorem If a band limited signal is sampled at regular intervals of time and at a rate equal to or more than twice the highest signal frequency in the band, then the signal contains all the information of the original signal, Or Fs is greter then 2fH where fH is the highest fre- quency in the signal and Fs is the sampling frequency. Let us say that our voice signals are band limited to 4khz and let the sampling frequency be 8 khz. Time period of sampling Ts = 1 sec/8000 Or Ts= 125 micro seconds. In a 30 channel PCM system, Ts i.e. 125 mi- croseconds are divided into 32 parts. That is 30 time slots are used for 30 speech signals, one time slot for signaling of all the 30 channels and one time slot for synchronization b/w transmitter and receiver. Time available per channel would be 3.9 microsec[3]. Quantization Quantizing is a process of breaking down a continuous amplitude range into a nite num- ber of amplitude values or steps. A sampled signal exists only at discrete times but its amplitude is drawn from a continuous range of amplitudes of an analog signal. The - nite no. of amplitude intervals is called the quantizing interval. Relation between Binary Codes and No. of levels:- Because the quantized samples are coded in binary form, quan- tization intervals will be in powers of 2. If we have a 4 bit code, then we can have 24=16 levels. Practical PCM systems use an 8 bit code with a rst bit as sign bit. This means we 11
  • have 28= 256 levels. (128 levels in the positive direction and 128 levels in the negative direction). Figure 4: Quantization Encoding Conversion of quantized analog levels to binary signal is called encoding. To represent 256 steps, 8 level code is required. Figure 5: Encoding 12
  • Chapter 5 Dense Wavelength Division Multiplexing DWDM is a bre optic transmission technique that employs multiple light wavelengths to transmit data in parallel through a single-ber[1]. 5.1 Overview DWDM systems in enabling service providers to accommodate consumer demand for ever increasing amounts of bandwidth. DWDM is a crucial components of optical networks hat allows the transmission of a e-mail, video, multimedia, data and voice-carried in different formats like Internet protocol (IP), over the optical layer. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical ber. Each channel carries a time division multiplexed (TDM) signal. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical ber. DWDM is also sometimes called wave division multiplexing (WDM). 13
  • Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together. Specically, Internet (IP) data, Synchronous Optical Network data (SONET), and asynchronous transfer mode (ATM) data can all be travelling at the same time within the optical ber[8]. 5.2 Challenges of Todays Telecommunication Network To understand the importance of DWDM and optical networking, these capabilities must be discussed in the context of the challenges faced by the telecommunications industry. The forecasts of the amount of bandwidth capacity needed for networks were calculated on the presumption that a given individual would only use network bandwidth six minutes of each hour. In fact, today many people use the bandwidth equivalent of 180 minutes or more each hour. Therefore, an enormous amount of bandwidth capacity is required to provide the ser- vices demanded by consumers. At the transmission speed of one Gbps.If one million families decide they want to see video on Web sites and samples the new emerging video application, then network transmission rates of terabits required. 5.3 Optical Fiber Layer Optical Fiber is new medium, in which information (voice, Data or Video) is transmitted through a glass or plastic ber, in the form of light[9]. 5.3.1 Optical Fiber Transmission Optical ber transmission can be understand by following diagram:- 14
  • Figure 6: Optical Fiber Transmission 5.3.2 Classication of Optical Fiber Index Multi-mode Fiber It contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. A digital pulse suffers less dispersion. Single-Mode Fiber It has a narrow core (eight microns or less), and the index of refraction between the core[1] and the cladding changes less than it does for multi-mode bers. Light thus travels parallel to the axis, creating little pulse dispersion. Telephone and cable television networks install millions of kilometers of this ber every year. 5.3.3 Optical Fiber in the DWDM Single mode bers are preferred for longer distance and higher bandwidth application including DWDM.WDM is the practice of dividing the wavelength capacity of an optical ber into multiple channels in order to send more than one signal over the same ber. 15
  • 5.4 Conclusion Optical networking provides the backbone to support existing and emerging technologies with almost limitless amounts of bandwidth capability. Such are as follow:- Speed: Fiber optic networks operate at high speeds - up into the gigabits. Bandwidth: large carrying capacity. Distance: Signals can be transmitted further without needing to be refreshed or strengthened. Resistance: Greater resistance to electromagnetic noise such as radios, motors or other nearby cables. Maintenance: Fiber optic cables costs much less to maintain. 16
  • Chapter 6 GSM Architecture and Technology 6.1 Introduction The GSM technical specications dene the different entities that form the GSM net- work by dening their functions and interface requirements[10]. The GSM network is presented in gure:- Figure 7: Network of GSM 17
  • A GSM network consists of several functional entities, whose functions and interfaces are dened[1]. The GSM network can be divided into following broad parts:- The Mobile Station (MS) The Base Station Subsystem (BSS) The Network Switching Subsystem (NSS) The Operation Support Subsystem (OSS) 6.1.1 Mobile Station A mobile station consists of two main elements: The Terminal There are different types of terminals distinguished principally by their power and appli- cation: The xed terminals are the ones installed in cars. Their max allowed output power is 20 W. The GSM portable terminals can also be installed in vehicles. Their max allowed output power is 8W. Hand-held terminals can emit up to 2W. The evolution of tech- nologies allows decreasing the max allowed power to 0.8W. The SIM The SIM is a smart card that identies the terminal. By inserting the SIM in the terminal, user can have an access to all the subscribed services. The SIM card is protected by a 4 digit PIN (Personal Identication Number). In order to identify the subscriber to the system, the SIM contains some parameters of the user such as its International Mobile Subscriber Identity (IMSI). 18
  • 6.1.2 The Base Station Subsystem The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception. The BSS can be divided into two parts:- The Base Transceiver Station The BTS corresponds to the transceivers and antennas used in each cell of the network. The BTS is placed in the center of the cell. Each BTS has between one and sixteen transceivers depending on the density of users in the cell. The Base Station Controller The BSC controls the group of BTS and manages their radio resources. A BSC is princi- pally in charge of hand-overs, frequency hopping, exchange functions and control of the radio frequency power levels of the BTS[11]. 6.2 The Network and Switching Subsystem Its main role is to manage the communications between the mobile users and other users, such as mobile users, ISDN users, xed telephony users etc. It also includes data bases needed in other to store information about the subscribers and to manage their mobility. The components of NSS are:- 6.2.1 The Mobile services Switching Center (MSC) It is the central component of NSS. The MSC performs the switching functions of the network. It also provides connection to the other network. 6.2.2 The Gateway Mobile services Switching Center (GMSC) A gateway is a node interconnecting two networks. The GMSC is the interface between mobile cellular network and the PSTN. It is in charge of routing calls from the xed 19
  • network towards the GSM user. The GSMC is often implemented in the same machines as the MSC. 6.2.3 Home Location Register (HLR) The HLR is considered as a very important database to store information of the sub- scribers belonging to the covering area of a MSC. It also stores the current location of these subscribers and the services to which they have access. The location of subscribers corresponds to the SS7 address of the Visitor Location Register(VLR) associated to the terminal. 6.2.4 Visitor Location Register (VLR) The VLR contains information from a subscribers HLR necessary in order to provide the subscribed services to visiting users. When a subscriber enters the covering area of a new MSC, the VLR associated to the MSC will request information about the new subscriber to its corresponding HLR. 6.2.5 The Authentication Center (AuC) The AuC register is used for security purpose. It provides parameters needed for authen- tication and encryption functions. These parameters help to verify the users identity. 6.2.6 The Equipment Identity Register (EIR) The EIR is also used for security purposes. It is a register containing information about the mobile equipment. More particularly, it contains a list of all valid terminals. A terminal is identied by its International Mobile Equipment Identity (IMEI). The EIR allows then to forbid calls from stolen or unauthorized terminals (e.g. a terminal which does not respect the specications concerning the output RF power). 20
  • Chapter 7 Base Transceiver Station 7.1 Introduction Figure 8: Base Transceiver Station A base transceiver station (BTS) is a piece of equipment that facilitates wireless com- munication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), computers with wireless Internet connectivity. The network can be that of any of the wireless communication technologies like GSM, CDMA, wireless lo- cal loop,Wi-Fi, WiMAX or wide area network (WAN) technology. BTS is also referred 21
  • to as the radio base station (RBS), node B (in 3G Networks) or simply, the base station (BS). For discussion of the LTE standard the abbreviation eNB for evolved node B is widely used. Though the term BTS can be applicable to any of the wireless communi- cation standards, it is generally associated with mobile communication technologies like GSM and CDMA. In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have equipment for encrypting and de- crypting communications, spectrum ltering tools (band pass lters), etc. antennas may also be considered as components of BTS in general sense as they facilitate the function- ing of BTS. Typically a BTS will have several transceivers (TRXs) which allow it to serve several different frequencies and different sectors of the cell (in the case of sectorised base stations). A BTS is controlled by a parent base station controller via the base station con- trol function (BCF). The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations. The BCF provides an operations and maintenance (OM) connection to the network management system(NMS), and manages operational states of each TRX, as well as software handling and alarm collection. The basic structure and functions of the BTS remains the same regardless of the wireless technologies[12]. Figure 9: Overview of BTS 22
  • Chapter 8 Introduction oF 3G Communication 8.1 Introduction 3G is the next generation of wireless network technology; it is also known as UMTS (Universal Mobile Telecommunication System) that provides high speed bandwidth (high data transfer rates) to hand-held devices[13]. The high data transfer rates will allow 3G networks to offer multimedia services combining voice and data. Specically, 3G wireless networks support the following maximum data transfer rates:- 2 M bits/second to stationary devices. 384 Kbits/second for slowly moving devices, such as a handset carried by a walking user. 128 Kbits/second for fast moving devices, such as handset in moving vehicles. UMTS is amalgamations of both packet are circuit switched technologies. It has si- multaneously been designed to have the upgradeability features of earlier mobile systems such as GSM and CDMA. In addition, it is expected that, IP multimedia will be and integral part of thw UMTS standards. 23
  • 8.2 Architecture Model of 3G Network Figure 10: Architecture of 3G Network[1] 24
  • Chapter 9 CDMA Technology 9.1 Introduction Code division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, which is where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies. To permit this to be achieved without undue interference between the users, CDMA employs spread spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA is used as the access method in many mobile phone standards and WCDMA (the 3G standard used by GSM carriers), which are often referred to as simply CDMA. The technology is used in ultra-high-frequency (UHF) cellular telephone systems in the 800-MHz and 1.9-GHz bands. CDMA employs analog-to-digital conversion (ADC) in combination with spread spectrum technology[14]. The original CDMA standard, also known as CDMA One and still common in cellular telephones in the U.S., offers a transmission speed of only up to 14.4 Kbps in its single channel form and up to 115 Kbps in an eight-channel form. CDMA2000 and Wideband 25
  • CDMA deliver data many times faster. 9.2 Advantage of CDMA Increased cellular communications security. Simultaneous conversations Increased efciency, meaning that the carrier can serve more subscribers. Smaller phones Low power requirements and little cell-to-cell coordination needed by operators. Extended reach-benecial to rural users situated far from cells. 9.3 Disadvantage of CDMA Due to its proprietary nature, all of CDMAs aws are not known to the engineering community. CDMA is relatively new, and the network is not as mature as GSM. CDMA cannot offer international roaming, a large GSM advantage. 9.4 Difference between CDMA and GSM The GSM stands for global system for mobile communication and CDMA for code di- vision multiple accesses. GSM is a form of multiplexing, which divides the available bandwidth among the different channels. Most of the times the multiplexing used are either TDM (Time Division Multiplexing) or FDM (Frequency Division Multiplexing). On the other hand CDMA is a type of multiple access scheme (which means allotting the given bandwidth to multiple users) and makes use of spread spectrum technique which is essentially increasing the size of spectrum. In CDMA each user is provided a unique 26
  • code and all the conversations between 2 users are coded. This provides a greater level of security to CDMA users then the GSM ones[15]. 27
  • References [1] Hand out on ALT Vocational Training, ferbury 2013-2014. [2] Voice fundamentals, in http://www.uoverip.com/voice-fundamentals-human- speech-frequency/, 2001. [3] youtube http://www.youtube.com/watch?v=YJmUkNTBa8s. [4] webopedia http://www.webopedia.com/TERM/R/routing.html. [5] telecom.net http://telecom.tbi.net/history1.html#hierarchy. [6] Harold P.E. Stern and Sanny A. Mahmound, Communication System Analysis and Design, prentice Hall, 2006. [7] Wikipedia http://en.wikipedia.org/wiki/Time-division_ multiplexing. [8] searchtelecom http://searchtelecom.techtarget.com/ definition/dense-wavelength-division-multiplexing. [9] craig Fredenrich http://computer.howstuffworks.com/ fiber-optic.htm. [10] Wikipedia http://en.wikipedia.org/wiki/GSM. 28
  • [11] techopedia http://www.techopedia.com/definition/24191/ base-station-controller-bsc. [12] techopedia http://www.techopedia.com/definition/2927/ base-transceiver-station-bts. [13] Draft summary minutes decisions and action from 3GPP Organizatiom Partners Meeting, Tokyo, in http://en.wikipedia.org/wiki/3GPP, vol. 6, October, 2001. [14] Margaret Rouse http://searchtelecom.techtarget.com/ definition/CDMA. [15] Sasche Sagan http://www.pcmag.com/article2/0,2817,2407896, 00.asp. 29