CHAPTER 1INTRODUCTION TO TELECOMMUNICATION1.1 DEFINITION OF TELECOMMUNICATIONTelecommunication is the transmission of information over significant distance to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded drumbeats, lung-blown horns, or sent by loud whistles, for example. In the modern age of electricity and electronics, telecommunications now also includes the use of electrical devices such as thetelegraph,telephone, andteleprinter, as well as the use of radio andmicrowave communications, as well asfiber opticsand their associated electronics, plus the use of theorbiting satellitesand the Internet.In modern times, this process almost always involves the sending of electromagnetic waves by electronic transmitters but in earlier years it may have involved the use of smoke signals. Today, telecommunication is widespread and devices that assist the process, such as the television, radio and telephone, are common in many parts of the world. There is also a vast array of networks that connect these devices, including computer networks, public telephone networks, radio networks and television networks. Computer communication across the Internet, such as e-mail and instant messaging, is just one of many examples of telecommunication.CDMA is the only one of the three technologies that can efficiently utilize spectrum allocation and offer service to many subscribers without requiring extensive frequency planning. All CDMA users can share the same frequency channel because their conversations are distinguished only by digital code, while TDMA operators have to coordinate the allocation of channels in each cell in order to avoid interfering with adjacent channels. The average transmitted power required by CDMA is much lower than what is required by analog, FDMA and TDMA technologies.

1.2 CLASSIFICATION

Telecommunication

WirelessWireline

DLCPRIBRIILLMPLSLLNPLCCDMA

GSM

Figure 1.1 Classification of Telecommunication

1.2.1 GSMGSM (Global System for Mobile communication) is a digital mobile telephony system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. GSM networks operate in a number of different frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G). Most 2G GSM networks operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz frequency bands were already allocated. Most 3G GSM networks in Europe operate in the 2100 MHz frequency band.

1.2.2 CDMACDMA (Code-Division Multiple Access) refers to any of several protocols used in so-called second-generation (2G) and third-generation (3G) wireless communications. As the term implies, CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth. 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. Audio input is first digitized into binary elements. The frequency of the transmitted signal is then made to vary according to a defined pattern (code), so it can be intercepted only by a receiver whose frequency response is programmed with the same code, so it follows exactly along with the transmitter frequency. There are trillions of possible frequency-sequencing code, which enhances privacy and makes cloning difficult. The CDMA channel is nominally 1.23 MHz wide. CDMA networks use a scheme called soft handoff, which minimizes signal breakup as a handset passes from one cell to another. The combination of digital and spread-spectrum modes supports several times as many signals per unit bandwidth as analog modes. 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.CDMA uses a radically different approach. It assigns each subscriber a unique "code" to put multiple users on the same wideband channel at the same time. Both the mobile station and the base station, to distinguish between conversations use the codes, called pseudo-random codes. Depending on the level of mobility of the system, it provides 10 to 20 times the capacity of AMPS, and 4 to 7 times the capacity of TDMA.

Figure 1.2 CDMA technique

Figure 1.3 CDMA users separated by codes

CDMA is the only one of the three technologies that can efficiently utilize spectrum allocation and offer service to many subscribers without requiring extensive frequency planning.All CDMA users can share the same frequency channel because their conversations are distinguished only by digital code, while TDMA operators have to coordinate the allocation of channels in each cell in order to avoid interfering with adjacent channels. The average transmitted power required by CDMA is much lower than what is required by analog, FDMA and TDMA technologies.

1.3 CDMA TECHNOLOGYCDMA technology is most developing technology in nowadays world. Earlier it was only used for military purpose because of its message security property but now we are using it for commercial use also. RELIANCE and TATA, both service providers are using this technology. We are using CDMA technology because of its great advantages which are listed here under.CDMA technology has numerous advantages including: 1. Coverage 2. Capacity 3. Clarity 4. Cost 5. Compatibility

Here we will take brief description of each advantage of the CDMA technology:1.3.1 CDMA Coverage CDMA's features result in coverage that is between 1.7 and 3 times that of TDMA: Power control helps the network dynamically expand the coverage area. Coding and interleaving provide the ability to cover a larger area for the same amount of available power used in other systems.1.3.2 CDMA CapacityCDMA capacity is ten to twenty times that of analog systems, and it's up to four times that of TDMA. Reasons for this include: CDMA's universal frequency reuse. CDMA users are separated by codes, not frequencies. Power control minimizes interference, resulting in maximized capacity. CDMA's soft handoff also helps increase capacity. This is because a soft handoff requires less power.

Figure 1.4 Comparison of various techniques1.3.3 CDMA ClarityOften CDMA systems can achieve "wire line" clarity because of CDMA's strong digital processing. Specifically, The rake receiver reduces errors. The variable rate vocoder reduces the amount of data transmitted per person, reducing interference. The soft handoff also reduces power requirements and interference. Power control reduces errors by keeping power at an optimal level. CDMA's wide band signal reduces fading.

1.3.4 CDMA CostCDMA's better coverage and capacity result in cost benefits: Increased coverage per BTS means fewer BTS are needed to cover a given area. This reduces infrastructure costs for the providers. Increased capacity increases the service provider's revenue potential. CDMA costs per subscriber have steadily declined since 1995 for both cellular and PCS applications. 1.3.5 CDMA CompatibilityCDMA phones are usually dual mode. This means they can work in both CDMA systems and analog cellular systems. Some CDMA phones are dual band as well as dual mode. They can work in CDMA mode in the PCS band, CDMA mode in the cellular band, or analog mode in an analog cellular network.

1.4CDMA WORKINGAs the name suggest this technique uses mathematical codes to allow multiple access Instead of using frequencies or time slots, as do traditional technologies. However, because the conversations taking place are distinguished by digital codes, many users can share the same bandwidth simultaneously. The advanced methods used in commercial CDMA technology improve capacity, coverage and voice quality, leading to a new generation of wireless networks. CDMA receivers, conversely, separates communication channels by a pseudo-random modulation that is applied and removed in the digital domain. Multiple users can therefore occupy the same frequency band. This universal frequency reuse is crucial to CDMA's distinguishing high spectral efficiency. Central to the cellular concept is frequency reuse, which is critically dependent upon the fact that the carrier wave power decreases with increasing distance. With this information, a cellular division of frequency channels can be implemented. The channel is allocated to another radio station far enough apart where signals won't interfere with each other. By reusing channels in multiple cells, the system can grow without geographical limits.

F2 F1 F3 F4 F5 F6 F7

Figure 1.5 Frequency Reuse Pattern-7 Frequency Reuse Pattern-1

CDMA assigns one distinct spreading code to each user. As long as the codes are orthogonal or almost orthogonal all users can send and receive their signal through the same wide band channel. Other users signals appear like noise. A CDMA system allows multiple access using a single CDMA channel. The same channel can be used in adjacent cells. Thus CDMA allows a universal reuse pattern, or reuse of one. Because of spread spectrum nature of signals all co-channel interference appear like noise to intended user. Since different base stations or users use different codes with almost zero correlation, the receivers can reject co-channel interference as part of De-spreading.

1.5CDMA BENEFITSWhen implemented in a cellular telephone system, CDMA technology offers numerous benefits to the cellular operators and their subscribers. The following is an overview of the benefits of CDMA. Capacity increases of 8 to 10 times that of an AMPS analog system and 4 to 5 times that of a GSM system. Improved call quality, with better and more consistent sound as compared to AMPS systems. Simplified system planning through the use of the same frequency in every sector of every cell. Enhanced privacy. Improved coverage characteristics, allowing for the possibility of fewer cell sites.1.6CDMA CODESAs the technology, it is known as spread spectrum technology so for spreading the information we have to consider some points, they are as followed: A CDMA signal uses many chips to convey just one bit of information. Each user has unique pattern, in fact a code channel. To receive or recover a bit, integrate a large number of chips known by the code pattern. Other users code pattern appears random and integrates in a self-canceling fashion; dont disturb the decoding decision being made with the proper code pattern.Uplink IdentificationOn the uplink, the base station uses the long code to identify the mobile unit that is using a particular CDMA channel. The long code also provides spreading and encryption. The uplink signal uses the short code for quadrature spreading and to allow the base station to obtain bit synchronization. The Walsh functions are used on the uplink to provide for better signal reception through spreading gain.Downlink IdentificationNow consider downlink identification. On the downlink, the mobile unit must identify the base station as well as the call itself. The following are used on the downlink: Long code for encryption Short code for base station identification Walsh functions for channel assignment

1.7PN CODESForward link of IS-95 CDMA has pilot and sync channels to aid synchronization, but the reverse link does not have pilot and sync channels. Thus, Walsh codes cannot be used on the reverse link. The incoherent nature of the reverse link calls for the use of another class of codes, PN codes, for Channelization. PN codes have very sharp autocorrelation.

Generation of PN CodesPN code sets can be generated from linear feedback shift registers. Binary bits are shifted through the different stages of the register. The output of the last stage and the output of one intermediate stage are combined and fed as input to the first stage. The register starts with an initial sequence of bits, or initial state, stored in its stages. Then the register is clocked, and bits are moved through the stages. This way, the register continues to generate output bits and feed input bits to its first stage. The output bits of the last stage form the PN code. Here we show the code generation using the register Figure 1.6. Let initial state is [1, 0, 1] for register. The output of stage 3 is the output of the register.

Figure 1.6 PN code generation through shift registers

1.8HANDOFF IN CDMAThe act of transferring support of a mobile from one base station to another is termed Handoff. Handoff occurs when a call has to be handed off from one cell to another as the user moves between cells. Figure 1.7 Handoff between two cells

Types of Handoff Hard Handoff Soft HandoffHandover occurs when a call has to be passed from one cell to another as the user moves between cells. The connection to the current cell is broken, and then the connection to the new cell is made. This is known as a "break-before-make" handover. This is also known as hard hand over. Since all cells in CDMA use the same frequency, it is possible to make the connection to the new cell before leaving the current cell. This is known as a "make-before-break" or "soft" handover. Soft handovers require less power, which reduces interference and increases capacity. Mobile can be connected to more than two BTS at the time of handover. This is sometimes called "softer" handover.

HARD HANDOFFFigure 1.8 SOFT HANDOFFBreak before make (a) Make-before-break (b)One of the main advantages of CDMA systems is the capability of using signals that arrive in the receivers with different time delays. This phenomenon is called multi path. FDMA and TDMA, which are narrow band systems, cannot discriminate between the multi path arrivals, and resort to equalization to mitigate the negative effects of multi path.Due to its wide bandwidth and rake receivers, CDMA uses the multi path signals and combines them to make an even stronger signal at the receivers. CDMA subscriber units use rake receivers. This is essentially a set of several receivers. One of the receivers constantly searches for different multi paths and feeds the information to the other three fingers. Each receiver then demodulates the signal corresponding to a strong multi path. The results are then combined together to make the signal stronger. Figure 1.9 Use of Rake receiverSoft Handoff This handoff requires the mobile to constantly search for multi paths from different base stations even while actively receiving and sending traffic. Soft handoff can be costly for network capacity if not implemented properly, as each base station that the mobile is in simultaneous contact with must allocate resources for the communications link.To make Handoff Mobile Station maintains four types of different sets. Active Set: It contain pilot offset of sector whose channel is currently monitored by mobile. Candidate Set: It contain pilot that are not in the active set, but have sufficient signal strength for demodulation. Neighbor Set: It contain pilot of base station of neighboring cell that are indicated by network through paging channel. Remaining Set: This set contains all pilot offset in system excluding active and neighbor set.The active set is the set of base stations that the mobile may be in simultaneous contact. The base station based on measurement information relayed by the mobile controls this set. The candidate set entails pilots that are not in the active set but can be successfully demodulated by the mobile. The maximum number of pilots in either the active or candidate sets is 6.The neighbor set is based on predetermined pilots that are in the vicinity of the base station or base stations the mobile is currently in contact with. This may have as many as 20 pilots in it. The remaining set covers all other pilots.The base station must drop pilots from the active set whose strength has dropped below a certain threshold, T_DROP. This is also another event that can trigger the mobile to send a PSMM. Threshold comparisons to drop a pilot are timer based, meaning that the pilot must be below T-DROP for a certain amount of time (given by T_TDROP) before the pilot is demoted. In addition, the mobile may search for multi paths at certain PN offsets given the network deployment. For instance, if the base station knows the PN offsets of neighboring base stations, it may provide the mobile with search windows. Hard HandoffThe third is the hard handoff. The CDMA system uses two types of hard handoffs. CDMA-to-CDMA handoff occurs when the mobile is transitioning between two CDMA carriers (i.e., two spread-spectrum channels that are centered at different frequencies). This hard handoff can also occur when the mobile is transitioning between two different operators systems. CDMA-to-CDMA handoff is sometimes called D-to-D handoff. On the other hand, CDMA-to-analog handoff occurs when a CDMA call is handed down to an analog network. This can occur when the mobile is traveling into an area where there is analog service but no CDMA service. CDMA-to-analog handoff is sometimes called D-to-A handoff.Other CDMA HandoffCDMA uses soft handoff whenever possible because the performance is very much superior to other forms of handoff. However, there are several forms of handoff that cannot be done softly.Inter Frequency HandoffIf there are multiple CDMA carrier frequencies active, then handoffs between them must be hard. Inter-frequency hard handoffs are probably best accomplished by doing so within one geographical site, rather than trying to handoff to a neighboring site. The inter-frequency handoff can first be executed intra-site, where the mobiles timing is already known, followed immediately by a soft handoff to the neighbor without frequency change on the new frequency.

Softer HandoffEach BTS sector has unique PN offset & pilot. If multiple sectors of one BTS simultaneously serve a handset, this is called Softer Handoff.CDMA Handoff Advantage over AMPS Handoff It is soft meaning that communication is not interrupted by the handoff. This means fewer dropped calls for users and higher customer satisfaction for operators. The handoff is not abrupt, but rather it is a prolonged call state during which there is communication via two or more base stations. The multi-way communication diversity improves the link performance during the handoff, the diversity gain partially compensates for the large path loss at the cell boundary.

CHAPTER 2DIGITAL TRANSMISSION2.1 TRANSPORT NETWORKThe network that carries communication and information signals from one place to another is called the Transport Network.TABLE 2.1Comparison between Early & Modern Transmission NetworkEarly Transmission Network

Modern Transmission Network

1. Supports Voice only

2. Analog3. Covered short distances4. Operate at very slower speed5. Could only accommodate few users. 6. Network availability is not ensured.

1. Provide multiple services like digital voice, video and data.2. digital3. Cover long distances4. Operate at very high speed5. Accommodate millions of users

6. Ensure 99.999% network availability.

Modern definition of Transmission network:The purpose of a transmission network is to multiplex together multiple low bit rate digital traffic streams into higher bit rate traffic streams for efficient transport between access points. Medium: Carries signals from one place to another. Eg. air, copper, optical fiber, etc.

2.2 EVOLUTION OF DIGITAL TRANSMISSION NETWORKSMain principles:1. Pulse Code Modulation2. Time Division Multiplexing 3. Standard Multiplexing Hierarchies (E.g. PDH, SDH).

2.2.1 Pulse Code Modulation PCM is the method to convert analog signals into digital signals by means of sampling according to Nyquist criteria , quantizing and then encoding analog signal and transmitting it at a bit rate of 64 Kbit/s. A transmission rate of 2.048 Mbit/s (known as E1) results when 30 such coded channels are collected together into a frame along with the necessary signaling information. This so-called primary rate is used throughout the world. Only the USA, Canada and Japan use a primary rate of 1.544 Mbit/s, formed by combining 24 channels (known as T1 carrier system) instead of 30.

2.2.2 Time Division MultiplexingMultiplexing is the assembly of a group of lower bit rate individual channels into a higher bit rate aggregate. 32 channels x 64Kbps = 2048 Kbps = 2 Mbps

2.2.3 Introduction to E1 InterfaceA communication line that was developed by European standards is, that multiplexes thirty voice channels and two control channels onto a single communication line. The E1 line uses 256 bit frames and transmits at 2.048 Mbps. The E1 interface is independent standardized TDM technology. This technology enables transmission of several (multiplexed) voice/data channel simultaneously on the same transmission facility. The E1 standard is mostly deployed in Europe.

Fig 2.1 E1 frame structure

PhoneSystemPhoneSystem

FAXFAX

PCPC Figure 2.2 A communication network without E1

Phone SystemPhoneSystem

MUX MUX E1 Link

FAXFAX

PC

PC

Figure 2.3 A communication network with E1

Suppose we have 32 channels, each with a rate of 64Kbs that we wish to transfer to the other end. The multiplexing takes from each of the 32 lines a single byte and sends then one after the other. After doing so; it takes the next byte from every channel, and so on. The multiplexer must be able to send all the 32*8 bits from the 32 channels without the second byte of the first channel getting lost.This implies that output rate of the multiplexer should be at least 32*64 Kbps or 2048Kbps. This method is called Time Division Multiplexing (TDM). Because the multiplexer took there 1/8000 second for transferring a single byte of a single channel, and divided it between the 32 channels by increasing the rate so that each byte of a channel will take 1/ (8000*32) second to send.

2.2.4 Multiplexing HierarchiesTraffic over the past decade has demanded that more and more of these basic E1s be multiplexed together to provide increased capacity.PDH (Plesionchronous Digital Hierarchy):As bandwidth demand grew, the technology called Plesionchronous Digital Hierarchy (PDH) was developed by ITU-T G.702, whereby the basic primary multiplexer 2.048 Mb/s trunks were joined together by adding bits (bit stuffing) which synchronized the trunks at each level of the PDH. This hierarchy is based on multiples of 4 E1s.E2, 4 x E1 - 8Mb/s E3, 4 x E2 - 34Mb/s E4, 4 x E3 - 140Mb/s E5, 4 x E4 - 565Mb/s Figure 2.4 PDH (Plesionchronous Digital Hierarchy)Limitations of PDH:Data sources are nominally synchronous. Tributary signals can only be accessed at the level from which they were multiplexed. The use of Justification bits (added bits which tell the multiplexers which bits are data and which are spare) at each level at PDH, means that identifying the exact location of the frames from a single 2 Mb/s line within a 140 Mb/s channel is impossible. In order to access a single 2 Mb/s line, the 140 Mb/s channel must be completely de-multiplexed to its 64 constituent 2 Mb/s lines via 34 and 8Mb/s. Once the required 2 Mb/s has been identified and extracted, the channels must be then be re-multiplexed back up to 140 Mp/s for onward transmission. SDH (Synchronous Digital Hierarchy):As management in PDH is very inflexible, SDH was developed. Synchronous Digital Hierarchy (SDH) originates from Synchronous Optical Network (SONET) in the US. Telecommunications technologies are generally explained using so called layer models. SDH can also be depicted in this way. SDH networks are subdivided into various layers that are directly related to the network topology.The lowest layer is the physical layer, which represents the transmission medium. This is usually a glass fiber or possibly a radio-link or satellite link. The regenerator section is the path between regenerators. Part of the overhead (RSOH, regenerator section overhead) is available for the signaling required within this layer.The remainder of the overhead (MSOH, multiplex section overhead) is used for the needs of the multiplex section. The multiplex section covers the part of the SDH link between multiplexers.

Fig 2.5 SDH layer modelThe carriers (VC, virtual containers) are available as payload at the two ends of this section. The two VC layers represent a part of the mapping process. Mapping is the procedure whereby the tributary signals, such as PDH and ATM signals are packed into the SDH transport modules. VC-4 mapping is used for 140 Mbit/s or ATM signals and VC-12 mapping is used for 2 Mbit/s signals. 2.3 SDH FRAME STRUCTURESTM-1 frameIn SDH the basic rate is 155.52 Mb/s. This is called the Synchronous Transport Module Level 1(STM-1). Higher rates are designated by STM-M where values of M by the ITU-T recommendations are M=1, 4, 16 and 64. Overheads bytes (first 3*3 columns of frame) carry Network Management Information such as: Trail Trace - misconnection of the physical media most common Error Monitoring Automatic Protection Switching Framing, Multiplexing

Fig 2.6 SDH STM-1 Frame Format

Synchronous Payload Envelope (SPE) (261(87*3) columns) carry User Data i.e. PDH frames plus 27(9*3) bytes of path overhead.Path overheadIn transmission, a path is defined as a circuit joining two nodes that may pass trough a number of intermediate nodes. In SDH, extra capacity is reserved to carry monitoring and management information associated with the path. This extra information associated with the path is called Path Overhead.It allows the checking of aspect such as, Quality of the overall end to end transmission. Existence of path between two termination points.Section OverheadA section can be considered as one stage of an end path. It is defined as node to node transmission. A path may be a number of sections .One section may be a path. The SDH also reserves some extra capacity within the defined bit rates to carry information relating to the section. This extra information associated with a section is called Section Overhead.It contains data to control node-to-node transmission. Protection switching Error monitoring Network management

Fig 2.7 Logical mapping of signals

How Is The Frame Composed ? PDH Payload=Container (C)

Container + Path Overhead (POH)=Virtual Container (VC)

Virtual Container + TU Pointer=Tributary Unit (TU)

more than 1 Tributary Unit=Tributary Unit Group (TUG)

biggest Tributary Unit Group=Administrative Unit (AU)Tributary Unit Group + AU Pointer=Administrative Unit (AU)

more than 1 Administrative Unit =Administrative Unit Group

Administrative Unit Group + Section Overhead (SOH)=SDH Frame

TABLE 2.2 SDH denominationsPDH Standard (Bit rates) SDH Denomination SDH Transport Capacity Corresponding SDH Bit rate

64 kbpsVC-0 -

1.5 mbpsVC-1 -

2 mbpsVC-1 -

6 mbpsVC-2 -

34/45 mbpsVC-3 -

140 mbpsVC-4STM-1155 mbps

VC-4x4STM-4620 mbps

VC-4x16STM-162500 mbps

VC-4x64STM-6410 gbps

Figure 2.8 SDH Hierarchy - TUG Structure

2.4 BENEFITS OF SDH TRANSMISSION

High transmission rates Transmission rates of up to 10 Gbit/s can be achieved in modern SDH systems. SDH is therefore the most suitable technology for backbones. Simplified add & drop functionCompared with the older PDH system, it is much easier to extract and insert low-bit rate channels from or into the high-speed bit streams in SDH. It is no longer necessary to de-multiplex and then re-multiplex the plesiochronous structure, a complex and costly procedure at the best of times. High availability and capacity matchingWith SDH, network providers can react quickly and easily to the requirements of their customers. For example, leased lines can be switched in a matter of minutes. The network provider can use standardized network elements that can be controlled and monitored from a central location by means of a telecommunications network management (TNM) system.

ReliabilityModern SDH networks include various automatic back-up and repair mechanisms to cope with system faults. Failure of a link or a network element does not lead to failure of the entire network which could be a financial disaster for the network provider. These back-up circuits are also monitored by a management system. Future-proof platform for new servicesRight now, SDH is the ideal platform for services ranging from POTS, ISDN and mobile radio through, to data communications (LAN, WAN, etc.), and it is able to handle the very latest services, such as video on demand and digital video broadcasting via ATM that are gradually becoming established. InterconnectionSDH makes it much easier to set up gateways between different network providers and to SONET systems. The SDH interfaces are globally standardized, making it possible to combine network elements from different manufacturers into a network. The result is a reduction in equipment costs as compared with PDH.

CHAPTER 3 NETWORK MANAGEMENT

3.1 NETWORK TOPOLOGIESBasic topologies possible in SDH are shown in figure below.

Figure 3.1 Possible topology in SDH architecturePoint-to-point:The simplest topology is a permanent link between two endpoints. Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is the value of guaranteed, or nearly so, communication between the two endpoints. This topology doesnt provide redundancy. If the path is broken then the communication will be over.

Ring:The type of network topology in which each of the nodes of the network is connected to two other nodes in the network and with the first and last nodes being connected to each other, forming a ring all data that is transmitted between nodes in the network travels from one node to the next node in a circular manner and the data generally flows in a single direction only. But if any fault occurs in the transmission, then data will flow through the reverse direction and provide redundancy.Dual-ringThe type of network topology in which each of the nodes of the network is connected to two other nodes in the network, with two connections to each of these nodes, and with the first and last nodes being connected to each other with two connections, forming a double ring the data flows in opposite directions around the two rings, although, generally, only one of the rings carries data during normal operation, and the two rings are independent unless there is a failure or break in one of the rings, at which time the two rings are joined (by the stations on either side of the fault) to enable the flow of data to continue using a segment of the second ring to bypass the fault in the primary ring.

Mesh In this topology each node is connected to every node in the network. This topology gives redundancy path but the network becomes very complex as the no. of nodes increases.

3.2 OPTICAL ADD DROP MULTIPLEXERThe main function of optical multiplexers is to couple two or more wavelengths into the same fiber. It is clear that if a de-multiplexer is placed and properly aligned back to back with a multiplexer, one could remove an individual wavelength and also insert an individual wavelength. Such a function is called an optical add-drop multiplexer (OADM.).The OADM selectively removes (drops) a wavelength from a multiplicity of wavelength in the fiber, and thus traffic on this channel. It then adds in the same direction of dataflow the same wavelengths, but with different data content.

Fig 3.2 OADM

OADMs are classified as fixed wavelength and as dynamically wavelength selectable OADMs. In a fixed wavelength OADM, the wavelength has been selected and remains the same until human intervention changes it. In dynamically selectable wavelength OADM, the wavelengths between the optical de-multiplexer/multiplexer may be dynamically directed from the outputs of the de-multiplexer to any of the inputs of the multiplexer.

3.3 COMPONENTS OF A SYNCHRONOUS NETWORK

Figure 3.3 Components of Synchronous network

Figure shows a schematic diagram of a SDH ring structure with various tributaries. The mixture of different applications is typical of the data transported by SDH. Synchronous networks must be able to transmit plesionchronous signals and at the same time, be capable of handling future services such as ATM. Current SDH networks are basically made up from four different types of network element. 3.3.1 Regenerators

Fig 3.4 RegeneratorsRegenerator regenerates the clock and amplitude relationships of the incoming data signals that have been attenuated and distorted by dispersion. They derive their clock signals from the incoming data stream. Messages are received by extracting various 64 Kbit/s channels (e.g. service channels E1) in the RSOH (regenerator section overhead). Messages can also be outputed using these channels.

3.3.2 Terminal MultiplexersTerminal multiplexers are used to combine plesionchronous and synchronous input signals into higher bit rate STM-N signals.

Fig 3.5 Terminal multiplexers

3.3.3 Add/Drop Multiplexers (ADM)Plesionchronous and lower bit rate synchronous signals can be extracted from or inserted into high speed SDH bit streams by means of ADMs. This feature makes it possible to set up ring structures, which have the advantage that automatic back-up path switching is possible using elements in the ring in the event of a fault.

Fig 3.6 ADM

3.3.4 Digital Cross Connects (DXC)This network element has the widest range of functions. It allows mapping of PDH tributary signals into virtual containers as well as switching of various containers up to and including VC-4.

Fig 3.7 DXC The telecommunications management network (TMN) is considered as a further element in the synchronous network. All the SDH network elements mentioned so far are software-controlled. This means that they can be monitored and remotely controlled, one of the most important features of SDH.

3.4 PROTECTION IN RING ARCHITECTURE Two basic types of protection architecture are distinguished in APS (Automatic Protection Switching). One is the linear protection mechanism used for point-to-point connections. The other basic form is the so-called ring protection mechanism which can take on many different forms. Both mechanisms use spare circuits or components to provide the back-up path. Switching is controlled by the overhead bytes K1 and K2.

3.4.1 Linear ProtectionThe simplest form of back-up is the so-called 1 + 1 APS. Here, each working line is protected by one protection line. If a defect occurs, the protection agents in the network elements at both ends switch the circuit over to the protection line. The switchover is triggered by a defect such as LOS. Switching at the far end is initiated by the return of an acknowledgment in the backward channel. 1+1 architecture includes 100% redundancy, as there is a spare line for each working line. Economic considerations have led to the preferential use of 1: N architecture, particularly for long-distance paths. In this case, several working lines are protected by a single back-up line. If switching is necessary, the two ends of the affected path are switched over to the back-up line.The 1+1 and 1: N protection mechanisms are standardized in ITU-T Recommendation G.783.The reserve circuits can be used for lower-priority traffic, which is simply interrupted if the circuit is needed to replace a failed working line.

Fig 3.8 1:3 Linear Protection

3.4.2 Ring ProtectionThe greater the communication bandwidth carried by optical fibers, the greater the cost advantages of ring structures as compared with linear structures. A ring is the simplest and most cost-effective way of linking a number of network elements. Various protection mechanisms are available for this type of network architecture, only some of which have been standardized in ITU-T Recommendation G.841. A basic distinction must be made between ring structures with unidirectional and bi-directional connections.

Unidirectional rings Figure shows the basic principle of APS for unidirectional rings. Let us assume that there is an interruption in the circuit between the network elements A and B. Direction y is unaffected by this fault. An alternative path must, however, be found for direction x. The connection is therefore switched to the alternative path in network elements A and B.The other network elements (C and D) switch through the back-up path. This switching process is referred to as line switched. A simpler method is to use the so-called path switched ring. Traffic is transmitted simultaneously over both the working line and the protection line. If there is an interruption, the receiver (in this case A) switches to the protection line and immediately takes up the connection.

Fig 3.9 Two fiber unidirectional path switched ring

Bi-directional rings

Fig 3.10 Two fiber bi-directional line switched ring

In this network structure, connections between network elements are bi-directional. This is indicated in the figure by the absence of arrows when compared with above figure. The overall capacity of the network can be split up for several paths each with one bi-directional working line, while for unidirectional rings, an entire virtual ring is required for each path. If a fault occurs between neighboring elements A and B, network element B triggers protection switching and controls network element A by means of the K1 and K2 bytes in the SOH.Even greater protection is provided by bi-directional rings with 4 fibers. Each pair of fibers transports working and protection channels. This results in 1:1 protection, i.e. 100 % redundancy. This improved protection is coupled with relatively high cost.

Retentive and Non Retentive Switch

Retentive Switch: Automatically takes its original path after recovery of the path in case of breakup.Non Retentive Switch: In case of break up alternate path will work and it will continue to work in spite of original path is now ready to work.

CHAPTER 4STRUCTURE OF BTS

4.1 BTS (BASE TRANSCEIVER STATION)The Base Transceiver (BTS) belongs to the radio part of a base station system. Controlled by BSC, it serves the radio transceiving equipment of a certain cell, implements the conversion between BSC and radio channels, radio transmission through air interface between BTS and MS and related control, and communicates with BSC through the Abis interface.4.1.1 Overview of the HUAWEI BTS3900A cellular Base Transceiver Subsystem (BTS) is one part of a cellular infrastructure system. The Basic functions of cellular infrastructure equipment are to provide the fixed end of the Radio interface to subscribe cellular phones and to route voice and data traffic up to the Public Switched Telephone Network (PSTN). The BTS3900 is an indoor macro base station developed by Huawei. The BTS3900 mainly consists of the BBU3900 and the RFUs. Compared with traditional BTSs, the BTS3900 features simpler structure and higher integration.The BTS3900 has the following features:1. It is developed on the basis of the unified BTS platform for Huawei wireless products and enables the smooth evolution from 2G to 3G.2. It supports the Abis IP/FE interface in hardware and enables Abis over IP through software upgrade if required.3. It shares the BBU3900 sub rack, which is the central processing unit, with the DBS3900 to minimize the number of spare parts and reduces the cost.4. It can be flexibly installed in a small footprint and can be easily maintained with low cost.5. It supports 2-way and 4-way RX diversity (not supported by the GRFU) to improve the uplink coverage.6. It supports the GPRS and the EGPRS.7. It supports Omni directional cells and directional cells.8. It supports multiple topologies, such as star, tree, chain, ring, and hybrid topologies.9. It supports the cell broadcast SMS and point-to-point SMS.4.1.2 Structure of the BTS CabinetThe BTS3900 cabinet adopts the module structure. It consists of the BBU3900, CRFU, FAN, DCDU-01, and SLPU (optional). A space is reserved at the bottom of the cabinet for the installation of user devices such as the transmission equipment.

Figure 4.1 Internal structure of the BTS3900 cabinet

4.1.3 Configuration of the BTS CabinetThe BTS3900 cabinet supports the typical configuration with three CRFUs and the full configuration with six CRFUs. The SLPU is an optional component of the BTS3900 cabinet. Typical configuration of BTS 3900 is as shown in figure 4.2 below. Different cards for BTS are as shown below used in BTS configuration.

Figure 4.2 Typical configuration of the BTS3900 cabinet

TABLE 4.1Describes the functions of the main components of the BTS3900 cabinet.

ComponentDescription

CRFUCRFU is the CDMA RF unit of the BTS3900. It receives and sends radio signals for communication between network system and MS.

FANThe FAN is the fan unit of the BTS3900. It houses fans for heat dissipation in the BTS3900 cabinet.

BBU3900The BBU3900 is the baseband unit of the BTS3900. It performs resource management, operation maintenance, and environment monitoring for the BTS.

DCDU-01The DCDU-01 is the direct current distribution unit of the BTS3900. It supports one DC input and multiple DC outputs.

SLPU (optional)

It is the protection unit of the BTS3900 cabinet, and it houses the UELP and UFLP board for protecting the E1/T1 and FE signals from lightning

4.1.4 Logical Structure of the BTSThis describes the logical structure of the BTS. Logically, the BTS consists of the baseband system, RF system, power system, and antenna system.

Figure 4.3 Logical structure of the BTS3900

4.1.5 Baseband SystemThe baseband system consists mainly of BBU3900s and performs the following functions:1. Providing the physical interface for data exchange between the BTS and the BSC.2. Modulating and demodulating baseband data and CDMA channel signals.3. Providing system synchronization clock signals.4. Implementing resource management, operation and maintenance, and environment monitoring.

4.1.6 RF SystemThe RF system consists mainly of CRFUs and performs the following functions:1. On the forward link, implementing up-conversion and power amplification for modulated transmitted signals and filtering the transmitted signals to make them meet the requirements of the Um interface protocol.2. On the reverse link, filtering the signals received by the antenna to suppress out-band interference and performing low noise amplification, channel division, down-conversion, and channel-selective filtering.4.1.7 Power Supply SystemThe power supply system consists mainly of DCDUs and performs the following functions:1. The DCDU is a DC power distribution unit and provides -48 V DC power input for the components in the cabinet.4.1.8 Antenna SystemThe antenna system consists of the RF antenna system and satellite antenna system. The antenna system performs the following functions: Satellite antenna systemThrough the satellite synchronization antenna, the BTS receives signals from the GPS or GLONASS system and performs wireless synchronization. RF antenna systemThe RF antenna system transmits modulated RF signals and receives the signals from the MS.4.1.9 Clock Synchronization Modes of BTSThe BTS supports various clock sources, such as the GPS clock source, interface clock source, Abis interface clock source, and internal clock source.TABLE 4.2 Clock synchronization modes supported by the BTSClockSynchronizationTypeDescription

GPS clock sourceThe BTS provides the GPS clock input port and obtains clock signals through the external GPS equipment.

Abis interface clockSourceThe BBU3900 supports the extraction of clock signals directly from ports such as the E1/T1 port. The clock module performs frequency division, phase locking, and phase adjustment for the clock signals. In this way, precise 2 MHz and 8 KHz clock signals are obtained and used for frame synchronization and bit synchronization inside the BTS.

Internal clock signalsWhen external clock sources are not available, the crystal oscillators of the BBU3900 boards provides 10 MHz clock signals to guarantee the normal running of the BTS.

4.1.10 Performance Specification of the BTSThis describes the performance specifications of the BTS in terms of transmitter and receiver specifications, CRFU cascading specifications, and BERs on transmission links.Transmitter and Receiver Specifications:The transmitter and receiver specifications refer to the technical parameters of the transceiver of the BTS. The receiver and transmitter specifications of the BTS in different band classes are as follows:

TABLE 4.3 Transmitter specifications (800 MHz)ItemSpecification

Working frequency band869 MHz to 889 MHz

Channel bandwidth1.2288 MHz

Channel precision30 kHz

Frequency tolerance 0.05 ppm

Transmit power 80 W

TABLE4.4 Receiver specifications (800 MHz)

ItemSpecification

Working frequency band824 MHz to 844 MHz

Channel bandwidthChannel bandwidth

Channel precision30 kHz

Signal receiving sensitivityBetter than -130 dBm (main and diversity receiving at RC3)

CHAPTER 5DIFFERENT TYPES OF MULTIPLEXERS

5.1 CLASS OF MUXS USED BY TTSL

Micro SDM BG 20B/E/C XDM 100 XDM 300 XDM 500 XDM 1000 Common Functionality

Most cross-connect, timing, and control functionality is integrated and internal to the main card in BG-20, the MXC20. No separate card is used to control these operational aspects of the unit. Besides this common functionality, the MXC20 also supports various traffic interfaces, such as STM-1/4 aggregates, E1, and FE interfaces.

MXC20 functionality includes:

Integrated cross connection, timing, system control, and overhead processing (including DCC and Clear Channel)

Communication with and control of a daughterboard in the Dslot and extension cards in the BG-20E shelf through the backplane

Control-related functions

Communications and control (by the CPU)

Alarms and maintenance

Fan control

SDH-related functions

SDH timing and synchronization

5.2 SDM-1E

Figure 5.1 MicroSDM MUX

These are third generation Broad gate multiplexers, optimally designed for installation in street cabinets and customer premises locations. This type of equipment enables the implementation of small and simple Access network topologies that are fully managed, flexible, and very cost-effective. With Lights cape Networks new SDM-1E multiplexers, telecom operators can achieve a high level of service and increased revenues, as they benefit from the following advantages: 1. Low cost per line 2. Advanced fiber and copper technologies 3. Integrated management system 4. Support of a wide range of services. 5. Flexible configuration and easy upgradability.The maximum capacity of this mux is 63 E1 and it does not provide Ethernet interface. MAC CARD The MAC card houses one or two O/E modules which are piggyback mounted mini-boards. The O/E modules provide the SDH line interfaces (optical or electrical). An additional card mounted on the MAC is the Timing Module Unit (TMU). The CDB Card The CDB provides control and processing functions to the MAC card and the TEX card (when fitted). It houses the power supply as well as various memory modules (including the NVM, which is mounted on the CDB). The central processing unit is a state-of-the-art PowerPC RISC processor. The TEX Card The TEX card is an optional expansion card fitted into the SDM-1E which provides tributaries interfaces expansion as follows TEX 2_42 support Up to 42 E1.

5.3 BG-20B (BROADGATE-20)

Figure 5.2 BG-20B

ECI Telecoms BG-20 miniature MSPP delivers a cost-effective and affordable mix of Ethernet, SDH, PDH, and PCM services, resulting in new revenue-generating opportunities. It offers a wide variety of features and benefits, including: 1. Ultra-high scalability based on coupling the BG-20E to the BG-20B to make a build-as-you-grow solution.2. Gradual capacity expansion based on service provisioning needs. More STM-1 interfaces can be added very conveniently and ADM-1s can be upgraded to ADM-4s without affecting traffic. This highly adaptable and flexible architecture translates into significant savings in both operational and capital expenditures (OPEX and CAPEX). 3. Provides a carrier class Ethernet-over-WAN/MAN solution (including Ethernet over SDH and Ethernet over PDH) with SDH reliability, security, and management of data services. 4. PCM service interfaces and 1/0 digital cross-connect functions to facilitate the construction and maintenance of various private networks. 5. Multi-ADM and cross-connect functionality, ideal for deployment in flexible network topologies like ring, mesh, and star. 6. Compactness and resiliency, perfectly suited for both indoor and outdoor enclosures. Due to its extended operating temperature range, it is also most suitable for harsh environmental conditions.7. The maximum capacity of BG-20 is STM-4. When the capacity increase beyond the STM-4 than we directly use the XDM-100 MXC20 Card The MXC20 supports the following interfaces: 21xE1, 6 Ethernet port, 2 ports forSTM-1/4, MNG for local login, RS-232, housekeeping alarms. In addition to these interfaces, the MXC20 has LED indicators and one push button. It also consist one D-slot for providing more interface. As the BG-20 is a front-access shelf, all its interfaces, LEDs, and push button are located on the front panel of the MXC20. Now we discuss about the cards that are inserted into the D-slot. ME1_21H cardME1_21H is a D-slot module with 21 x E1 (2.048 Mbps) balanced electrical interfaces. The cabling of the ME1_21H module is directly from the front panel with a twin 68-pin VHDCI female connector. ME1_42H ModuleThe ME1_42 is a D-slot module with 42 x E1 (2.048 Mbps) balanced electrical interfaces. The cabling of the ME1_42 module is directly from the front panel with two twin 68-pin VHDCI female connectors. SMD1H ModuleThe SMD1H is an SDH D-slot module with two STM-1 (155 Mbps) interfaces (either optical or electrical). OMS4H Module The OMS4H is an SDH D-slot module with one STM-4 (622 Mbps) optical interface. MEoP_4 Module The MEoP is an L1 data Dslot module with four 10/100BaseT interfaces on the LAN side and four EoP interfaces on the WAN side. The total WAN bandwidth is 32xE1.

5.4 BG-20E (BROADGATE-20)BG-20E is same as the BG-20B but the only difference is that we expand the cards in the BG-20E. Remaining all the things are same in both cases. Three extension slots are available in the BG-20E to accommodate the various types of extension cards. These cards are: PE1_63 Card The PE1_63 is an electrical traffic card with 63 x E1 (2 Mbps) balanced electrical interfaces. A maximum of three PE1_63 cards can be installed in one BG-20E shelf. The cabling of the PE1_63 card is directly from the front panel with three twin 68-pin VHDCI female connectors. S1_4 Card The S1_4 card is an SDH extension card with four STM-1 (155 Mbps) interfaces (either optical or electrical). ESW_2G_8F_E CardThe ESW_2G_8F_E is an EoS Metro Ethernet L2 switching card with 8 x 10/100BaseT LAN interfaces, 2 x GbE LAN interfaces, and 16 EoS WAN interfaces. The total WAN bandwidth is up to 4 x VC-4. A maximum of three ESW_2G_8F_E cards can be installed in one BG-20E shelf.

5.5 BG-20C (BROADGATE-20)It is same as the BG-20B but the only difference is that it does not have the D-slot and it contains only four Ethernet port.

5.6 XDM-100

Figure 5.3 XDM-100

ECI Telecom's XDM-100 miniature MSPP delivers a cost-effective and affordable mix of Ethernet, SDH and PDH services, resulting in new revenue-generating opportunities. It offers a wide variety of features and benefits, including:1. Gradual in-service capacity expansion based on service provisioning needs. An optical connection operating at a specific STM rate can be upgraded from STM-1 to STM-4/16 without affecting traffic. This high adaptability and "build-as-you-grow architecture means significant savings in both OPEX and CAPEX.2. Multi-ADM and cross-connect functionality makes XDM-100 ideal for deployment in flexible network topologies, such as ring, mesh and star.3. The XDM-100 is compact and resilient, making it perfectly suited for both indoor and outdoor enclosures, as well as for harsh environmental conditions, due to its extended operating temperature range.All electrical connections are located directly in the tributary modules; therefore, the XDM-100 does not need additional electrical interface connections. To support system redundancy, each MXC card contains an integrated xINF (XDM Input Filter) unit with connectors for two input power sources.The xFCU-100 fan control unit at the right side of the shelf provides cooling air to the system. It contains nine separate fans for added system redundancy. Air is drawn in by the fans from the right side of the chassis and exhausted through the horizontally mounted cards and modules and through the left side of the chassis. Redundant controllers, located on the two MXC cards, activate the fans. The xFCU-100 can be extracted and replaced without interrupting the multiplexer operation, provided the replacement does not exceed a few minutes.The basic XDM-100 cage contains slots for I/O interface modules, and dedicated slots for the MXC cards and the ECU. The cages design and mechanical practice conform to international mechanical standards and specifications. The modules and cards are distributed as follows:1. Eight (8) slots, I1 to I8, optimally allocated for I/O interface modules.2. Two (2) slots, A and B respectively, allocated for the MXC cards (main and protection). Each MXC card has two slots (A1 and A2 and B1 and B2) to accommodate SDH aggregate modules.3. One (1) slot allocated for the ECU card.The ECU is located beneath the MXC cards. Its front panel features several interface connectors for management, external timing, alarms, order wire and overhead (future release). It also includes alarm severity colored LED indicators and selectors plus a display for selecting specific modules and ports for monitoring purposes. MXC(MAIN CROSS-CONNECT AND CONTROL) CARDThe basic and expanded versions of the XDM-100 shelf accommodate two identical MXC cards. By default, the MXC-A is the main card and MXC-B is the protection card. Both cards perform the following functions simultaneously in a 1+1 protection configuration: 1. Communications and control2. Alarm and maintenance3. Cross-connect4. Timing and synchronization5. Distribution of power supply to all modules (xINF function)6. Routing and handling of 32 DCC channelsIn addition, the MXC accommodates the NVM compact flash memory card and houses SDH aggregate modules (SAM). The additional MXC card provides 1+1 protection to the cross connect matrix and full 1:1 protection to all other functions, since the standby MXC has an identical database to the active MXC. In case of a hardware failure in the active MXC or its traffic interconnection, the I/O interface modules switch to the protection MXC within 50 ms. Similarly, in case of a hardware failure in the Timing Unit (TMU) of the operational MXC card, the backup TMU takes over the timing control with no disruption in traffic. ECU(EXTERNAL CONNECTION UNIT) CARDThe ECU connects management, alarms, overhead access, and order wire interfaces to the active MXC card. This card also provides the physical connections for these interfaces. Two types of ECU cards are available for the XDM-100: ECU-F and ECU (reduced cost). The ECU-F supports the following management and alarm interfaces and functions: 1. Ethernet interface to XDM element management system2. Ethernet hub for multiple NE connections3. USB interface (future option)4. Synchronization inputs and outputs 5. Alarm severity outputs (Critical, Major, Minor, Warning)6. External alarm outputs and inputs7. Operation and alarms LEDs8. Selection and display of traffic interfaces for monitoring purposes9. Multiplexer reset. AGGREGATE MODULESTwo SDH aggregate modules (SAM) plug into each MXC. The MXC provides the aggregate modules with power and control. The traffic buses of each SAM are connected to both MXC cards. A variety of aggregate modules with electrical, optical and mixed interfaces, and at bit rates from STM-1 to STM-16 are available. I/O MODULESEight slots are available in the XDM-100 shelf to accommodate the various types of I/O modules. Each type of module (PIM, SIM or EIS-M) can be inserted in any of the I1 through I8 positions without limitation (the EIS-M module occupies two slots). PIM and SIM modules, with electrical interfaces, fully supports direct connection to the module without other external connection modules.

TABLE 5.1List of the XDM-100 I/O modules

CHAPTER 6ANTENNAS6.1 PATCH ANTENNA Figure 6.1 Patch AntennaGMS offers variety ofPatch (Panel)antennas in bands from 1.7-6 GHz. They are light-weight and housed in aweather-proof housing. The Messenger Antenna Patch (MAP)is aprecision, high gain antennadesigned for broadband receivers and transmitters where wide bandwidth and high efficiency are key system parameters. They are designed to either output RF directly, or can beconfigured to include an internally-mountedGMS LNA or Block-Down Converter. GMS also supplies this Antenna in a 360degree array configuration called Messenger Antenna Array (MAA)for tracking applications with the Messenger Smart Receiver (MSR).

6.2 OMNI DIRECTIONAL ANTENNAGMS offers variety ofOmni antennas in bands from 1.7-16 GHz. They are light-weight and housed in a strong weather-proof PVC housing.

Figure 6.2 Omni Directional Antenna6.3 HELICAL ANTENNA

Figure 6.3 Helical AntennaGMS Helical (Rod)antennas Right Hand Circular Polarization (RHCP)and range in gain from 6, 12 and 16 dBic. They are lightweight and constructed from strong, gel-coated fiberglass and have an aluminum mounting plate.

6.4 DISK ANTENNAGMSoffershigh accuracy parabolic spun aluminum dishes that are designed with rugged portability in mind. The dishsizes are24 or30 inches in diameter and come with tripod or pole-mount hardware. A wideselection of Linear or Circular feeds that cover 1.7-16 GHz with quick-release option are also available.

Figure 6.4 Disk Antenna6.5 YAGI ANTENNAFigure 6.5 Yagi AntennaGMS offers variety ofYagi antennas in bands from 1.7-5 GHz with typical gain of10 or14 dBic. They are light-weight and housed in aweather-proof radome.

CHAPTER 7DIFFERENT CONNECTERS AND CORDS

7.1 PATCH CORDSApatch cableorpatch cordis anelectricaloropticalcable used to connect ("patch-in") one electronic or optical device to another forsignalrouting. Devices of different types (e.g., a switch connected to a computer, or a switch to a router) are connected with patch cords. Patch cords are usually produced in many different colors so as to be easily distinguishable.Types of patch cords includemicrophonecables,headphoneextension cables,XLR connector,Tiny Telephone (TT) connector,RCA connectorand "TRS connectorcables (as well asmodularEthernetcables), and thicker, hose-like cords (snake cable) used to carryvideoor amplified signals. However, patch cords typically refer only to short cords used withpatch panels.Patch cords can be as short as 3 inches (ca. 8cm), to connect stacked components or route signals through apatch bay, or as long as twenty feet (ca. 6 m) or more in length for snake cables. As length increases, the cables are usually thicker and/or made with more shielding, to prevent signal loss (attenuation) and the introduction of unwanted radio frequencies and hum (electromagnetic interference).Patch cords are often made ofcoaxial cables, with the signal carried through a shielded core, and theelectrical groundor earthed return connection carried through a wire mesh surrounding the core. Each end of the cable is attached to a connector so that the cord may be plugged in. Connector types may vary widely, particularly with adapting cables.Various Patch Cords are: LC SC FC E2000 ST

Figure 7.1 Various Patch Cords

7.2 CONNECTORSAnelectrical connectoris anelectro-mechanicaldevice for joiningelectrical circuitsas aninterfaceusing a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices.There are hundreds of types of electrical connectors. Connectors may join two lengths of flexiblecopperwireor cable, or connect a wire or cable or optical interface to an electricalterminal.In computing, an electrical connector can also be known as aphysical interface(comparePhysical LayerinOSI modelof networking).Cable glands, known ascable connectorsin the U.S., connect wires to devices mechanically rather than electrically and are distinct from quick-disconnects performing the latter.

Figure 7.2 Different types of Connectors

CHAPTER 8WIRELESS LINKS

8.1 MICROWAVE LINK8.1.1 Overview of Microwave LinkMicrowaves in a descriptive term, is used to identify electromagnetic waves in the frequency spectrum ranging from 1 GHz to 30 GHz (telecom). Microwaves frequency characteristics are very similar to light, depending upon propagation in different ways causing attenuation to the original wave. Microwave communication systems require high frequency signals for effective transmission of information. There are several factors that lead to this requirement. For example, an antenna radiates effectively if its size is comparable to the signal wavelength, since the signal frequency is inversely related to its wavelength, antennas operating at higher radiation efficiencies. Further their size is relatively small and hence convenient for mobile communication. Another factor that favours RF and microwaves is that the transmission of broadband information requires high frequency signal. The ionosphere does not reflect microwaves and the signals propagate at line of sight. Hence, curvature of earth limits the range of microwave communication link to less than 50 km. One way of increasing the range of microwave link is to place the repeater intervals. This is known as terrestrial communication.As TTSL communication is using two Types of technology for transportation of data and voice traffic. It is not possible to make OFC network everywhere at city areas because fiber is very costly. Two types of network technology is responsible for making connectivity between one BTS (base transceiver station) to its next BTS. Such a ring connectivity network reaches to MSC (mobile switching centre). Microwave antennas 0.6m to 0.8m are generally used to make point to point connection between two BTS. Figure 8.1 Real time Microwave connectivity

When there is a customer group available in some area out of the radiation coverage then all the times it will not be economical to install another BTS with fiber ring connectivity and use all transport equipment again. In such cases we can install nearby BTS with Microwave connectivity. This will be point to point link provided by drum antennas. It will use appropriate ODU and IDU for conversion from RF signals to E1 lines. Then using this E1s, again we can serve customers as mentioned above.8.1.2 Frequency Allocation 6 and 7 GHz frequency bands are used for intercity backbone routes. Nominal hop distances are 5-50 Kms. 15, 18 and 23 GHz frequency bands are used for access network. Hop distances are 1-10 Kms. Frequency spots in 6 and 7 GHz are extremely crowded. Hence frequency allocation in this band is subjective from place to place. The Tx/Rx separation is fixed at 152 and 154 MHz. The frequency spectrum in 15 GHz is from 14.25 to 15.35 GHz. The frequencies are further classified into various sub bands with channel numbers. In long run OFC would be the right choice, as it will attract no recurring license cost.8.1.3 Pasolink System Features Single chip modulator/ demodulator (fully digital) High reliability Low power consumption Allows smaller antenna and reduced system cost With PASOLINK PDH (QPSK) and PASOLINK PLUS SDH (32 QAM) Forward error correction (FEC) Transmit power controlled in two ways: Automatic transmit power control(ATPC) and Manual transmit power control(MTPC) Common IDU for different RF frequencies. Remote monitoring of ODU operation. Local and remote supervision function on IDU. Local monitor and maintenance using Local Craft Terminal (LCT).8.1.4 IDU (Indoor Unit)

IDU alarmsODU alarmsPower alarmsmaintenance alarmsReset switchRouter connection OptionalEthernet connection optionalEngineering order wire connection ( EOW)Buzzer Wayside optionalIF connection to ODUEarthing PointRed LED Indicates AlarmFigure 8.2 IDUIDU is an Indoor Unit placed inside the shelter and connected to ODU (Outdoor Unit) with help of IF cable, with maximum distance of approx. 300 mts. IDU is connected to electric cable called E1.

PRINCIPLE Principle of IDU is to convert IF signal into optical or electrical signal. There are two types of IDU:1. SDH pasolink IDU2. PDH pasolink IDUIn SDH IDU, we do not get directly electric E1 but first the optical output of IDU is given to MUX which converts optical output to electric and from Mux we get electrical output from DDF (Digital Distribution Frame), then the output is given to customer. So, SDH gives optical output which is converted to electric with help of DDF. In PDH we directly get the electric output and there is no need to use DDF. But the capacity of PDH IDU is less then SDH IDU. It supports up to 16 E1 only, whereas SDH IDU can support upto STM-1 capacity.

8.1.5 ODU (Outdoor Unit)PRINCIPLEPrinciple of ODU is to convert IF (Intermediate Frequency) into RF and vice versa. Its design depends on requirement. Microwave frequency ranges from 6 GHz to 18 GHz.

Figure 8.3 Outdoor UnitThe actual TX frequency of the ODU should be within the TX radio frequency band of the ODU and is entered using the local craft terminal (LCT). The corresponding RX frequency is automatically set after the TX frequency is entered. For 6/7/8 GHz band ODU, the frequency setting should be the same as that written on the ODU label. PASOLINK provides point-to-point wireless solution that fit in a variety of network applications. All the PASOLINK systems feature simple installation and fast rollout, reliable operation, and offer high-speed transmission, scalable future.8.1.6 Antenna (ODU) Alignment During alignment of the antenna always refer NDD for alignment planning and antenna angles. (Latitude, Longitude, Azimuth, Elevation, Height of antenna etc.) Make a short check of adjustability and free rotation in all directions. For the azimuth adjustment of short (urban) distance links, use of a geographic map is most efficient. Use compass for coarse direction finding. If the opposite antenna is not visible, define a remarkable / noticeable object (e.g. building, tree, street-crossing, etc) which is in line with the opposite site and can be found with the above mentioned tools (maps, compass). Install the antenna at proper height for LOS clear visible. Proper route IF cable and check the cable connector connection is proper. Install IDU in Rack and give -48v dc input voltage Connect DDF with IDU if PDH site or with MUX if SDH site.

8.1.7 System ConfigurationSystem protection is required to ensure robustness and survivability of the data link in the case of any radio links problem: Equipment problems (hardware / software failure) Propagation problems (fading / obstruction)The protected configuration would assure the link is up in case of hardware failure and allow maintenance and repair of the redundant (standby) units.

8.1.8 Non Protected System

Figure 8.4 Non-Protected System One IDU with modulation / demodulation channel One ODU One antenna The system has no protection channel (no switching over)8.1.9 Protected System: Single Antenna Configuration

Figure 8.5 Protection by two ODUs One IDU with two modulation / demodulation module Two ODU working at the same spot frequency One antenna On each side only one ODU sends TX power and both ODUs receive the RX power Only one system is selected to carry the traffic and the other system is standby TX & RX switching is available manually and automatically to control switch over function TX & RX switching over does not affect the traffic.8.2 FREE BAND RADIO LINK8.2.1 IntroductionFBR (Free band radio) can be used to provide services like, leased line, PRI etc. Bandwidth up to 8 Mbps (two ways) can be provided using FBR. Varieties of customer services can be provided using FBR. It can also be used for DLC. FBR are actually useful at the place where fiber cannot be deployed and hence communication is required to be done through air interface.

Figure 8.6 Structure of FBRThe free band radio delivers up to 8 Mbps of total data rate for Ethernet and E1/T1 traffic. The system supports a variety of spectrum bands and can be configured to operate in any channel on the band with a carrier step resolution of 20 MHz. The unlicensed band radio employs Time Division Duplex (TDD) transmission. This technology simplifies the installation and configuration procedure. There is no need to plan and to allocate separate channels for the uplink and downlink data streams. Operation over 2.4GHz and 5.8GHz bands is not affected by harsh weather conditions, such as fog, heavy rain etc.

8.2.2 Need of FBR FBR is called free band because we dont have to pay for this band (2.4Ghz and 5.8Ghz). In other words, if one wants, one can start service almost immediately using unlicensed band radios and one need not wait for one year for frequency clearance. This presents great opportunities for service providers. Free Band Radio offers advantages such as Immediate and hassle free deployment of services as no clearance from WPC are required. Radios are very cost effective. Fast realization of revenue (as a result of rapid deployment) Demand-based build-out. Cost shifts from fixed to variable components (with traditional wire-line systems, most of the capital investment is in the infrastructure, while with radio a greater percentage of the investment is shifted to CPE, which means an operator spends money only when a revenue-paying customer signs on) No stranded capital when customers churn Cost-effective network maintenance, management, and operating costs. Limitations Of free band radio Since radio operates in unlicensed band, protection from interference is not guaranteed. Since it is intended to be deployed in very remote areas, where not much interference is expected and also the parabolic antennas have very narrow beam, which provides an additional protection against interference. Lack of standards.8.2.3 Physical Installation of the FBR Installation of antennas. Install ODU at both sites of the link. Install ODU cable and connecting ODU to IDU at both sites. Connect power. Install the management program on the network management station. Run the Installation wizard from the management program. Alignment of the antennas. Connect network and customer equipment to the local and remote IDUs respectively. Proper grounding of all equipments.

8.2.4 IDU (Indoor Unit)Indoor unit is installed in the customer premise. This is the unit, which interfaces with customer equipment, which in most of the cases is a router. This unit receives modulated digital signal over Cat5 cable from ODU. It then de-multiplexes payload, FEC, Management data etc from the digital steam and reconstructs and retimes E1s or similar signals, which are then send to customer equipment. IDU is independent of frequency and hence ODU. IDU can work with any frequency band ODU like 2.4 GHz or 5.8 GHz.

Figure 8.7 IDUDifferent types of IDUs and their applications, 2E1+FE IDUThis IDU provides 2E1 and One Fast Ethernet ports. This can be used where up to 2E1 ports are required. In such cases, FE port at Hub can be used for monitoring. 2E1+2FE IDUThis IDU provides Two E1s and Two Fast Ethernet ports. This IDU will replace the old 2E1+FE for all the new cases. This can be used where up to 2E1+ One FE services are required. 4E1+2FE IDUThis IDU provides Four E1s and Two Fast Ethernet solution. This can be used where up to 4E1+ One FE services are required. Note that more than 2 E1, in normal circumstances is not recommended because of high S/I requirement.

8.2.5 ODU (Outdoor Unit)This is radio frequency unit, which is mounted on a pole on the rooftop of the building or on the tower. This unit receives radio signal, down converts and after demodulation recovers the digital signal. The recovered digital signal is send to IDU over Cat5 cable. In the transmit direction the similar reverse process is done by the ODU. In TTSL network now two type of ODU are deployed:1. 2.4GHz2. 5.8GHz

Figure 8.8 ODU8.2.6 Various Connections CONNECTION BETWEEN THE ODU AND IDUThe ODU-IDU cable is Ultraviolet Proof CAT-5e, 4 twisted-pair 24 AWG FTP. It is terminated with RJ-45 connectors on both ends. It is covered by a cable gland on the ODU side for hermetic sealing. It conducts all the user traffic between the IDU and the ODU and also provides -48 VDC supply to the ODU. The maximum length for one leg of the cable is 100m (328ft) in accordance with10/100BaseT standards.The cable should be clamped directly on the surface with cable ties at 600mm interval. The cable will be laid inside the building through PVC channel. Make sure that some spare length is left for future maintenance purpose. CONNECTION BETWEEN THE ODU AND ANTENNAThe external antenna is connected to the ODU using a co-axial RF cable. An N type RF connector is provided on the ODU for this. Both ends of the RF cable are to be tightly sealed with weather proofing tape. DATA CABLEODU and IDU are connected by Cat5 cable. This cable carries not only the IF signal but also DC Voltage to power ODU. It means that IDU is also used for POE ( Power over Ethernet). Thus a separate power cable for ODU is not required. 8.2.7 How Interface can be Overcome? KEEP THE LINK DISTANCE SMALL IN URBAN AREASSmall link distance is possible in TSL network, as the numbers of CDMA BTS, which are the take-off point for FBR, are large. Thus probability of finding a BTS in reasonable radius, around potential customer site, is very high. C/I will not get affected adversely unless there is very close source interference near the prospective UBR site. EMPLOY HIGH GAIN ANTENNASHigh gain parabolic antennas provide dual protection. By virtue of high gain they increase the signal quality and by small beam width they reject interfering signals.

CHAPTER 9REPEATER9.1INTRODUCTIONRepeaters are bi-directional amplifiers used with highly directional antennas to increase the coverage area of a base station. Repeaters are not designed to increase the base station capacity but will improve signal strength out past the normal operating area for both uplink and downlink traffic. Repeaters are normally located at the outer limit of the base station coverage area and retransmit both the base station downlink signal to mobiles and the mobiles uplink signal back to the base station. Repeaters can also be used to boost signal strength inside a building where mobile users are operating in a highly attenuated area behind coated windows that reflect RF energy or lossy cement and steel walls.What is need of Repeater? Cell enhancing solution with lower cost. Many kinds of cell enhancing applications are available from small room to large coverage. Lower cost cell coverage extension solution than BTS. Flexible cell coverage planning. Easy maintenance of Repeater than BTS

Shrinking Area In Shrinking AreaGood Rx levelWeak Ec/IoNo dominate pilotHigh call drop rateFrequent Hand-offFigure 9.1 shrinking area

Figure 9.2 To remove above Shrinking Area, Repeater installed

9.2 TYPES OF REPEATERS RF Repeaters:RF stands for Radio Frequency as the transmission path between the donor BTS and the Repeater is used in RF Repeater system. No wires are used for this path. RF repeaters can be divided into two types with respect to whether donor link frequency is same to service signal frequency or not, On-frequency and frequency conversion type. On-Frequency Repeaters:A repeater is, in a simplified view, a bi-directional amplifier with filters that amplifies weak signal in both paths, down link and up link. There is no change between input and output frequencies of on-frequency repeater. Type of repeaters are classified as broadband, band selective or channel selective by method of the filtering processes for limiting frequency bandwidth and removing spurious.On-frequency repeater plays a role of extending the outdoor coverage of a Macro-cell. The repeater is installed at the coverage border of the donor BTS cell where the mobile user receives signals close to the acceptable level and re-transmits the amplified signal to additional coverage to extend.

Figure 9.3 Setup of On-frequency repeater:

In the downlink path, an antenna receives signals from a donor BTS. The link antenna is connected to the input of the repeater. The signals are filtered, amplified and transmitted into the service area via a service antenna. The uplink path of the repeater works in the same way. The service antenna takes up signals from mobile stations within the service area and re-radiates the amplified signals through the link antenna to the donor BTS. Broadband RF Repeaters:The filters in a broadband RF repeater are designed to cover the whole actual operating RF band. The filtering and amplification are on the RF band. Band pass filters of RF band are used of which filtering characteristic meets minimum requirements for operating. The broadband RF repeaters are installed in areas with low traffic and where the risk for interference with users directly outside the band is low. The broadband RF repeaters have generally lower gain and lower output power. Propagation delay time in RF band pass filter is short as less than 1 microsecond. Band Selective RF Repeaters:The incoming RF signals are down-converted to an intermediate frequency (IF) with filters that more sharply and effectively blocks signals directly outside the actual band. The band selective RF repeater handles a defined specific band within the total operating band, and any frequency or any numbers of FA can be handled in specific band without changes on hardware. The SAW filter is used as filtering and time delay is generally around 5 microseconds.

Channel Selective RF Repeaters:A channel selective RF repeater is equipped with a number of one channel up-down converter units. The incoming RF signals are down-converted to an intermediate frequency (IF) with filters that more sharply and effectively blocks any signals directly outside the specified channels bandwidth in operating band. IF SAW filter is used as filtering process and time delay is generally around 5 microseconds. The number of channel up-down converter units shall be equal to (or more than) the number of carriers that the operator wants to use.

Example of Repeater solution with low o/p power repeater:

Figure 9.4 Repeater installation for low o/p power

Another type of repeater is low power and low cost repeater. This type of repeater is available with 15 dBm, 17dbm and 27 dBm gains and is employed for providing in-building solutions. Premises such as basement, tunnel, go down, operating rooms in industries and some type of closed offices remain uncovered from coverage of BTS due to the shadow effect.In such type of buildings it is necessary to provide coverage inside the premises by means of low power repeater. Low power repeater receives signals from nearby donor BTS and amplifies it and then provides it inside the building with the help of panel antenna. The panel antenna and repeater module are mounted on the wall inside the structure where the coverage is to be provided. Depending on the area and geographic condition the antenna with suitable gain in selected ex. 15 dBm, 17 dBm.To install the yogi antenna intensity of the coverage is checked on the terrace with CDMA monitor and then yogi is located at proper point. 9.3 FIBER OPTIC REPEATERAnother basic type of repeater is the Fiber Optical repeater. The transmission path between the donor BTS and the repeater is fiber optic cables. Optical repeater first convert RF BTS signal into fiber optic signal & transmit the converted signal afterwards retransmit the RF signal at remote. Fiber Optical repeater system also provides, effective solution for extending cell coverage, Solving multi PN problem and eliminating shadow areas instead of BTS. Seamless service provided into the rural area and on highway.The system consists of Master unit and Slave unit, and installation of fiber optic cable between Master unit and Slave unit is required. The forward link signal of BTS is coupled to the master unit and translated into optic wave in Master Unit. The optic wave goes through optical cable to the Slave unit. Slave unit translates optic signal to service RF signal again and radiates the RF signal to desired service area. Reverse link signal from mobile handset is picked up by service antenna of Slave Unit and translated into optic wave. The optic wave goes through optical cable to the Master Unit. Master unit recovers optic signal to reverse link RF signal and feeds RF signal to Receiver stage of BTS. By using different Medias for service and link signal, RF and optic wave. Fiber optical repeater system can have extreme isolation between input and output stage. Stable and high power of repeater system can be achieved by such a concept of optic conversion. Time delay of optic wave propagation in optic cable is longer than that of air. Consideration should be taken carefully to deploy this type of repeater system.Merits: No limit of FAs Long link distance Not degrade the BTS performance High reliability which has excellent electrical characteristic

Figure 9.5 Set up of optical repeater:

Demerits: High rental cost using Optical FiberFOR Configuration: MU (Master Unit) OFD (Optical Fiber Distributor) SU (Slave Unit)FOR Total Path Connection: Forward PathMU ~ Patch chord ~ OFD ~ Optical Link ~ OF ~Patch chord ~ SU Reveres PathSU ~ Patch chord ~ OFD ~ Optical Link ~ OFD ~ Patch chord ~ MU 9.4 FREQUENCY SHIFT REPEATERFrequency Conversion Repeater system provides effective solution for extending cell coverage, solving multi PN problem and eliminating shadow areas. The system consists of Donor unit and Remote unit, and assignment of additional link channel between Donor unit and Remote unit is required.The down link signal of service channel frequency from BTS is translated to the link channel frequency and transmitted to the Remote unit by Donor Unit. Remote unit translates link channel signal to original service channel frequency and radiates the signal to the mobile handset.The reverse link signal of service channel frequency from mobile station is converted to the link channel frequency and transmitted to the Donor unit by Remote unit. And Donor unit translates link channel signal to service channel frequency and feeds to the BTS coupling port. The empty channel in the Permitted band is used for assigning link channel.By using different frequencies for link and service channel, frequency shifting repeater system can have higher isolation and higher gain than on-frequency repeaters. Stable, longer distance and higher power of repeater system can be achieved by such a concept of frequency conversion. The system handles the signal processing by channel conversion unit and low frequency SAW filter is adapted for filtering channels of which delay time is around 5 to 13 microseconds

Figure 9.6 Set up of frequency Shift Repeater:Merits: Utilize unoccupied FA as link FA High antenna isolation between a link antenna & service antenna is not requiredDemerits: Limited service FA Likely to degrade performance of a BTS due to using adjacent FA

SR Total Path Connection: Forward Path DU ~ Link antenna cable ~ Link antenna (Donor site) ~ RF link ~Link antenna (Remote site) ~ Link antenna able ~ RU. Reverse Path RU ~ Link antenna cable ~ Link antenna (Remote site) ~ RF link ~ Link antenna (Donor sit) ~ Link antenna able ~ RU.

Site Selection condition for FSR:Recommendation to choose installation location as below; Ensure that link loss between Donor Unit site and Remote Unit site is no more than 17kms.Easily installed antenna with proper height Less interference from other BTS Cells Easy access and maintenance of the equipment Avoiding direct sunlight to protect equipment Easy access to electrical powerFigure 9.7 connection between BTS and FSR

9.5IBS (IN BUILDING SOLUTION)Introduction:IBS is stands for IN BUILDING SOLUTION, as the name implies we are using IBS for to recover poor coverage in the congested indoor areas. We are providing IBS service to those service users whose monthly revenue of used service is very much high. So generally, we are providing this service to the small scale and big scale based companies, in which all of the users use mobile phone service, which are provided by us.

Three basic equipments are used for IBS, which are Out Door pick up antenna, Repeater and Indoor antenna. Here Yagi antenna used as outdoor picks up antenna. And Panel antenna, Omni antenna used as an indoor antenna. Panel used for a small cabin while omni antenna used in large hall. IBS connection flow is shown in below diagram.

Figure 9.8 repeater block

Survey: If the company decided to establish the new BTS tower than before that, survey of the particular area is required. In the survey, we use the GPS antenna, by which we can note down the latitude and longitude position of the particular point. We have to determine height of tower, orientation of antenna to be mounted on that tower according to clutter of area. During the survey, we must keep in mind that the distance between the two BTS tower is not too large or to small. If the distance between the two towers is so large than the signal can be weak and coverage might be poor in between and if distance is less than the it will be wastage of resources in addition to interface between two channels can be possible.Equipments used in IBS: Indoor antenna Outdoor antenna Repeater RF cable Connectors Splitter

C

Figure 9.9 Outdoor Yagi antennaFigure 9.10 Omni Directional, Panel antenna

These are the two types of antenna which is used as a indoor antenna: Panel antenna generally used in small cabin or small room type area, Omni antenna used generally used at large hall type area. Above figure shows both type of antenna. For IBS the setup is as shown in below figure. At the field we use following set up. The procedure for the same is as follows:

Yagi AntennarepeaterPanel or Omni Antenana Panel or Omni antenaAntenna spliter

Figure 9.11 Set up Of IBS (In Building Solution)

Procedure:Step1: First by using calibrated CDMA phone we check which are PN we getting at that particular place where we are going to use IBS solution, then we check that which PN giving us better CDMA parameter performance. According to that conclusion we clamp our Yagi pick up antenna on the terrace to fetch that particular PN coverage. Step2: After getting better coverage signals through pick up antenna we route those signals through RF cable to the repeater, here repeater amplifies those signals up to required level and then fed it to the indoor panel antenna.Step3: Here panel indoor antenna