interview electronics communications interview questions and answers

7/27/2019 Interview Electronics Communications Interview Questions and Answers

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1. What is GSM? Short form of Global System for Mobile Communications, is a wireless network

system A standard for digital cellular mobile communications International roaming arrangements are enabled among mobile network operators, by

providing the subscribers to use their personal mobile phones anywhere in the world. GSM is considered as second generation mobile, as signaling and speech channels are

digital The carriers can be replaced without replacing mobile phones. The ubiquity of GSM implementations is also enabling the switching between

network operators, who can choose equipment from many GSM equipment vendors. GSM pioneered low cost SMS implementation The GSM standard includes a worldwide emergency telephone number feature.2. Explain the services offered by GSM. The services offered by GSM are ISDN compatible GSM allows synchronous data and asynchronous data to be transported as bearer

service, one of the telecommunication services offered by GSM, and forms ISDN

terminal The data could be either transparent service or nontransparent service Telephony is one of the services offered by GSM, which an emergency and the

service provider is notified by dialing 3 digits By using appropriate fax adaptor, G3 fax service is supported One of the features of GSM is Short Messaging Service Certain services, namely supplementary services are provided on top of teleservices

or bearer services by GSM, such as, caller identification, call forwarding, multipartyconversations, barring outgoing calls and call waiting.

GSM services are categorized in three teleservices, bearer, and supplementaryservices.

A. Teleservices (communicate with other subscribers). B. Bearer service (provides the under laying network capacity necessary for

transmission to occur between two points in the same or different networks). The

bearer services describe what the network can offer (e.g. speech, data and fax). C. Supplementary service is optional which subscriber can subscribe for free. Ex: call

forwarding, call waiting,

3. What is the maximum data rate supported by a GSM system? The maximum data rate supported by a GSM system is 9.6 kbps. However there are extensions to GSM standard to improve throughput. GPRS is one of the extended GSM service. The extended standard of GSM allows theoretical data rates on the order of 114

Kbit/s, but with throughput closer to 40Kbit/s in practice.

4. Explain the foll owing: a.) Equali zation b.) I nterleaving c.) Speech coding d.)Channel coding

a.) Equalization:An adaptive equalizer is employed by a GSM receiver for overcoming the impact of non-idealchannel characteristics which are caused by multipath propagation.Adaptive equalizer is required because the channel characteristics are often changing fast.Tuning the for each time slot is done by the equalizer.

b.) Interleaving: Time diversity in a signal communication system is obtained by using Interleaving. The possibility of losing whole bursts will be decreased by interleaving Total 456 bits from convolution encoder, including 20ms of speech, is subdivided

into eight blocks. Each block consists of 57 bits. All these blocks are transmitted in consecutive time slots. Enough information is available in 7 blocks, in case one of the blocks is lost due to

burst errors. This enables whole segment recovery by using error correction.


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c.) Speech coding: Speech coding is all about turning voice into digital form Speech is inherently analog, as GSM is a digital system. The digitization is employed by ISDN, and the current telephone systems that are

used for multiplexing voice lines, with high speed trunks, optical fiber lines is doneby Pulse Code Modulation(PCM)

The PCM output is 64 kbps, which is too high over a radio link in feasibility The 64kbps signal is redundant The algorithm used in conventional cellular is Vector Sum Excited Linear Predictive

speech compression.

d.) Channel coding The data rate for the radio channel is 270 kbps The data rate is split into 8 full rate or 16 half rate traffic channels, along with

signaling channels In order to have the maximum chance for detecting and correcting errors, the code is

complex in a typical propagation path Forward Error Correction is applied in order to get the speech coder encryption,

coding and interleaving in a sophisticated way The data is sent as bursts in 577 mus time slots. Each contains 116 encrypted bits Every TDMA frame consists of 8 or 16 time slots Transmit time slots are staggered, so that at some instant the mobile station will not

receive the same instants while transmitting, which enables the simplifying thefiltering requirements

At least one spare slot between transmit and receive is available with this scheme.5. What do you mean by ARFCN? Absolute Radio Frequency Channel Number, a code to specify a pair of physical

radio carriers and channels within the spectrum that is allocated for cellular mobilecommunications

ARFCN is used for transmitting and receiving on the UM Interface, one to uplinksignal and one to downlink signal

ARFCNs bandwidth is 270.833 kHz; channel spacing is 200 kHz in a given GSMband

The uplink-downlink spacing is generally 45 / 50 MHz If Frequency Division Duplex is operated in the system, then the channel number is

associated with both uplink and downlink radio channels ARFCN is 1-124 within GSM900 spectrum, 512-885 within GSM1800, 512-810

within GSM1900, are used

6. Explain: a.)FDD b.)TDDa.)FDD

Frequency Division Duplex is one of the techniques, in which one frequency band isutilized for transmitting and another used for receiving.

To uplink the carrying data from mobile phones to the base station, oneelectromagnetic block spectrum is allocated

Various blocks of spectrum is allocated to downlink carrying data from the basestation to the mobile telephone hand sets

b.)TDD Time Division Duplexing, a 3GPP standardized version of Universal Mobile

Telecommunications System networks. The designated mobile sends the data in a stipulated time and receives data from the

BTS in another time The time is divided into various time slots and user sends data in few time slots and

receives the data in the rest of the time slots Alternative downlink and uplink directions are used.7. Explain GPRS Short form of General Packet Radio System


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GPRS is the next generation of GSM, and the basis of the 3G networks A packet oriented data service available to users of GSM and IS-136 type mobile

phones It complements the existing services like circuit-switched cellular phone connections

and the SMS Shortest set-up time is added for ISP connections An optimized mobile service for sending and receiving information across a mobile

telephone network, with less cost GPRS provides data rates of mobile telephony and moderate speed data transfer,

using unused TDMA channels GPRS does not need dial-up modem connection Sending and receiving e-mails, surfing internet are among the features of GPRS8. Di fferenti ate between GSM and GPRS.

The differences between GSM and GPRS are depicted in the following table

GSM GPRS

Uses one among 7 slots Uses as many as 4+1 time slots

Connecting resources to each unit from remotelocation to the back office is done through adirect dial up

Does not claim any resources until somedata is sent. The information is divided intopackets

Circuit switched mode of operations Packet switched mode of operations

Dedicated channel all the way to the destinationis provided to the customer

One or more dedicated channels areassigned by the operator specifically forshared use

9. What is handover and what are its types?Handover in mobile communication refers to the process of transferring a call from onenetwork cell to another without breaking the call.There are two types of handover which are as follows:

Hard Handoff: hard handoff is the process in which the cell connection is disconnected fromthe previous cell before it is made with the new one.

Soft Handoff: It is the process in which a new connection is established first beforedisconnecting the old one. It is thus more efficient and smart.

10.What is CDMA?CDMA stands for Code Division Multiple Access which uses digital format. In CDMA

systems several transmissions via the radio interface take place simultaneously on the samefrequency bandwidth. User data is combined at the transmitters side with a code, and then

transmitted. On air, all transmission gets mixed. At the receiver's side the same code is usedas in the transmitters side. The code helps the receiver to filter the user information of the

transmitter from incoming mixture of all transmissions on the same frequency band and sametime.

11.Explain the concept of f requency re-use.The whole of the geographical area is divided into hexagonal shape geometrical area calledcell and each cell having its own transceiver. Each BTS (cell site) allocated different band offrequency or different channel. Each BTS antenna is designed in such a way that i cover cellarea in which it is placed with frequency allotted without interfering other cell signals. Thedesign process of selecting and allocating channel groups for all of the cellular base stationwithin system is called frequency reuse.

12.Explain Bluetooth.Bluetooth is designed to be a personal area network, where participating entities are mobileand require sporadic communication with others. It is Omni directional i.e. it does not have

line of sight limitation like infra-red does. Ericsson started the work on Bluetooth and named


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it after the Danish king Harold Bluetooth. Bluetooth operates in the 2.4 GHz area of spectrumand provides a range of 10 meters. It offers transfer speeds of around 720 Kbps.

13.What are GPRS services?GPRS services are defined to fall in one of the two categories:- PTP ( Point to point)- PTM ( Point to Multipoint)Some of the GPRS services are not likely to be provided by network operators during earlydeployment of GPRS due in part to the phased development of standard. Market demand isanother factor affecting the decision of operators regarding which services to offer first.

14.What are the advantages of CDMA?Advantages of CDMA are as follows:

1. Frequency diversity: Transmission is spread out over a large bandwidth due to that lessaffected by noise. If bandwidth is increased S/N ratio increases, which means noise will bereduced.2. Multiplication Resistance: Chipping codes used for CDMA not only exhibit low correlationbut also low autocorrelation. Hence a version of the signal that is delayed by more than one

chip interval does not interfere with dominant signal as in other multipath environments.3. Privacy: Due to spread spectrum is obtained by the use of noise like signals, where each

user has a unique code, so privacy is inherent.4. Graceful Degradation. In CDMA, more users access the system simultaneously ascompared to FDMA, TDMA.

15.What is the dif ference between CDMA and GPRS? Which of them is better? Why?The Differences:

CDMA is one of the types of mobile connections for making calls whereas GPRS is atechnology for internet connections through a mobile phone.

GPRS enables to surf the internet from a mobile phone. GPRS technology is used inother gadgets apart from mobile phones.

W-CDMA technology is faster than GPRS, since the user cares about the technologythat is applied for air interface.

Average latency on GPRS is around 1.3 seconds, whereas on CDMA is around 400mill second

GPRS supports only User Datagram Protocol, whereas CDMA supports both UDPand TCP

GPRS relies on Network Address Translation and a private IP address is assigned toit. On the other hand CDMA assigns a public IP address CDMA is better because:

E-mail is pretty light, until you enter MS-Office. Pocket PCs support for office documents with similar functionality which can be had

on Palm OS and Symbian Upon availability of APIs, a software developer could write various applications, like

voice transfer, data transfer to clients account, integrating billing amount etc. Web services could be utilized.16.What do you mean by Extended Cell ? Does it have any impact on the system? I f

yes, what?

Extended cell feature enables the operators for extending the coverage withoutinstalling new cell cites

Extended cell feature is designed specifically for providing covering in rural areas,where density of population is low and installation of additional cell sites

New features can be deployed in coastal areas for providing GSM coverage inoffshore waters

Its impact is :The cell radius could be double or even more, based on the antenna, type of terrainand timing advanceIndoor coverage is supported by GSM and could be achieved with the usage of Picocell base station or an indoor repeater along with distributed indoor antennas


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17.What are the advantages of spread spectrum?Spread spectrum has the following advantages:

1. No crosstalk interference.2. Better voice quality/data integrity and less static noise.3. Lowered susceptibility to multipath fading.4. Inherent security.5. Co-existence.6. Longer operating distances.7. Hard to detect.8. Hard to intercept or demodulate.9. Harder to jam than narrow bands.10. Use of ranging and radar.

18.Explain the steps involved in demodulating a signal.Once the signal is coded, modulated and then sent, the receiver must demodulate the signal.This is usually done in two steps:1. Spectrum spreading (e.g., direct sequence or frequency hopping) modulation is removed.

2. The remaining information bearing signal is demodulated by multiplying with a localreference identical in structure and synchronized with received signal.

19.What are the drawbacks of Walsh codes?Walsh codes have the following drawbacks:

1. the codes do not have a single, narrow autocorrelation peak.2. The spreading is not over the whole bandwidth; instead the energy is spread over a number

of discrete frequency components.3. Although the full sequence cross correlation is identically zero, this does not hold for apartial sequence cross correlation function. Thus advantage of using orthogonal codes is lost.4. Orthogonally is also affected by channel properties like multi path.

20.Explain radio environment in buil ding.Building penetration: Building penetration depends on the material used for construction andarchitecture used. This varies building to building and is based on building construction.

Building Height Effect: The signal strength is always higher at top floor and generally floorgain height is about 2.7dB/floor which is not dependent on building construction.Building Floor Reception: The signal isolation between floors in a multi floor building is onthe average about 20dB. Within a floor of 150 * 150 feet, the propagation loss due to interiorwalls, depending on the wall materials is about 20 dB between the strong and the weak areas.

21.L ist some advantages of GSM.Here are some advantages of GSM:1. GSM is mature, this maturity means a more stable network with robust features.2. Less signal deterioration inside buildings.3. Ability to use repeaters.

4. Talk time is generally higher in GSM phones due to pulse nature of transmission.5. The availability of Subscriber Identity Modules allows users to switch networks and

handset at will.6. GSM covers virtually all parts of world so international roaming is not a problem.

22.What are the various types of numbers for network identi ty?Various types of number for network identity are as follows:1. MSISDN (Mobile station ISDN) Number: It is international mobile subscriber numberwhich is normally called mobile number. It is unique worldwide.2. MSRN (Mobile Subscriber Routing Number): MSRN is used during mobile terminatetrunk call to provide location of mobile subscriber.3. HON (Hand over Number): HON is used for providing information required to transfer callfrom one BSC to another BSC or to another MSC.4. ISMI (International Mobile Subscriber Identity Number): Purpose of ISMI is for locationupdate and authentication.


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5. TMSI (Temporary Mobile Subscriber Identity): TMSI is used instead of IMSI to improvesecurity efficiency of network.6. IMEI: International Mobile Equipment Identity.

23.What are the functions of Base Station System (BSS)?Functions of BSS are as follows:1. Radio path control.2. BTS and TC control.3. Connection establishment with MS-NSS.4. Mobility management, speech transcoding.5. Connection of statistical data.

24.What are the parts of Network M anagement System (NMS)?Following are the parts of network management system:1. OMC: Operation and maintenance center - Computerized monitoring center.2. NMC: Network Management Center - Centralized control of a network is done here.3. OSS: Operation and support system - Used for supporting activities performed in an OMCand/or NMC.

25.What are applications of DSP?Some selected applications or digital signal processing that are often encountered in daily lifeare listed as follows:

1. Telecommunication: Echo cancellation in telephone networks.2. Military Radar signal processing3. Consumer electronics Digital Audio/TV4. Instrumentation and control5. Image processing image representation, image compression

6. Speech processing speech analysis methods are used in automatic speech recognition7. Medicine Medical diagnostic instrumentation such as computerized tomography (CT)8. Seismology DSP techniques are employed in geophysical exploration for oil and gas.9. Signal Filtering Removal of unwanted background noise.

26.Explain the fol lowing two types of hand off in CDMA system: a.) Soft handoff b.)Softer handoff

a.) Soft handoff Soft handoff is a feature in which a cellular phone is simultaneously connected to two

or more cellular phones during a single call It is he overlapping of repeater coverage ones, which enables every cell phone set is

always well within the range of a specific repeater. More than one repeater can send and receive signals to transmit signals to and from

mobiles. All repeaters are used with the same frequency channel for each mobile phone set. Practically no dead zones and as result, the connections seldom interrupted or

dropped.

b.) Softer handoff Softer handover is a significant soft handover in which the added and removed links

belong to the same node Macro diversity with maximum ratio combining could be performed in the same node The movement of handoff, when a user can be served in another cell more efficiently

(less power emission, less interference), is the most obvious cause for betterperformance.

27.Br ief descri be the advantages and disadvantages of soft handover? Advantages:

Overcome fading through macro diversity. Reduced Node B power which in turn decreases interference and increases capacity. Reduced UE power (up 4dB), decreasing interference and increasing battery life.

Disadvantages: UE using several radio links requires more channelization codes, and moreresources on the Iub and Iur interfaces.


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28.What are fast fading and slow fading? Fast fading is also called multi-path fading, as a result of multi-path propagation.

When multi-path signals arriving at a UE, the constructive and destructive phasescreate a variation in signal strength.

Slow fading is also called shadowing. When a UE moves away from a cell the signalstrength drops down slowly.

29.During a handover, i f one cell sends a power down request and two cel ls send apower up request, shal l the UE power up or power down?

Power down. As long as a good link can be maintained it is not necessary to power upin order to maintain multiple links. Maintaining unnecessary multiple links increasesnoise rise and shall be avoided.

30.What is cell breathing and why?The cell coverage shrinks as the loading increases, this is called cell breathing.In the uplink, as more and more UE are served by a cell, each UE needs to transmit higher

power to compensate for the uplink noise rise. As a consequence, the UE with weaker link(UE at greater distance) may not have enough power to reach the NodeBtherefore coverageshrinkage.In the downlink, the NodeB also needs to transmit higher power as more UE are being served.As a consequence UE with weaker link (greater distance) may not be reachable by theNodeB.

31.What are the major dif ferences between GSM and UMTS handover decision?GSM: Time-based mobile measures of RxLev and RxQualmobile sends measurement reportevery SACH period (480ms). BSC instructs mobile to handover based on these reports.

UMTS: Event-triggered reportingUE sends a measurement report only on certain event triggers. UE plays more part in the handover decision.

32.What are the possibl e causes for a Drop Call on a UMTS network? Poor Coverage (DL / UL)

Pilot Pollution / Pilot Spillover Missing Neighbor SC Collisions

Delayed Handovers No resource availability (Congestion) for Hand in

Loss of Synchronization Fast Fading Delayed IRAT Triggers Hardware Issues

33.What are the possibl e causes for an Access Fail ur e in UM TS? Missing Neighbors

Poor Coverage Pilot Pollution / Spillover Poor Cell Reselection Core Network Issues Nonavailability of resources. Admission Control denies Hardware Issues

Improper RACH Parameters External Interference


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34.What is Admission Control? Admission Control is an algorithm which controls the Resource Allocation for a new calland additional resource allocation for an existing call. In case, if a cell is heavily a loaded andenough resources in terms of power, codes or CEs are not available, admission control deniespermission for the additional resource requirement.

35.What i s Congestion Control? Congestion Control monitors the dynamic utilization of specific cell resources and insuresthat overload conditions do not occur. If overload conditions do occur,Congestion Control will immediately restrict Admission Control from granting additionalresources. In addition, Congestion Control will attempt to resolve the congestion by eitherdown switching, or terminating existing users. Once the congestion is corrected, thecongestion resolution actions will cease, and Admission Control will be enabled.

36.What i s DTX? Why is it used?Discontinuous Transmission (DTX) is a mechanismwhich allows the radio transmitter to be switched off most of the time during speechpauses.

DTX may be applied independently to each direction, so that the control of DTX must takeinto account two components:

The uplink mode The downlink mode.

DTX can be enabled or disabled for the uplink and/or downlink mode on a per-cell basis.Reasons for DTX When DTX is applied, actual transmission on the radio path is reduced.This will cause a decrease of the interference level in co-channel cells (using the samefrequency). Another advantage will appear when using DTX in the uplink mode: it savesbattery power for the mobile station. However, a disadvantage of the DTX mode is that it

slightly deteriorates the quality of transmission. Note that transmitting in DTX mode does notsave timeslots on the air-interface.

37.What is DRX? Why do we need it?Discontinuous reception is method used toconserve power at the MS. The paging channel, used by the BTS to signal anincoming call, is structured into sub channels.

Each MS is assigned one of these sub-channels and needs to listen only to its own sub-channel. In the time between successive paging sub-channels, the mobile can go into sleep

mode, when almost no power is used.

38.What is TA? Why do we need TA?Time advance (alignment) process The RFcommunication experiences a propagation delay over the distance between the BTSand the MS. In order to synchronize the MS to the BTS, a timing advance is used toalign the time slots arriving at the BTS receiver:

1. The BTS measures the reception time of the incoming MS burst2. The BTS requests the MS to advance its transmission to compensate for the delay over thedistance. A 6-bit number indicates how many bits the MS must advance its transmission.3. The time advance value TA can have a value between 0 and 63 bit lengths, which

corresponds to a delay of between 0 and 233 ms.4. This leads to a maximum mobile range of 35 km, which is rather determined by the TA

than by the signal strength.

39.What is meant by IM SI , TMSI , IMEI and MS-ISDN? Why they are needed?IMSI= International Mobile Subscriber Identity

TMSI = Temporary Mobile Subscriber IdentityIMEI = International Mobile Equipment IdentityMS-ISDN =Mobile Station ISDN NumberA. the MSISDN is the directory number allocated to the mobile subscriber. It is dialed tomake a telephone call to the mobile subscriber.B. A MS is identified by its IMSI. The IMSI is embodied in the SIM of the mobileequipment. It is provided by the MS anytime it accesses the network.


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C. the TMSI is an identity alias which is used instead of the IMSI when possible. The use of aTMSI ensures that the true identity of the mobile subscriber remains confidential byeliminating the need to transfer an IMSI code enciphered over a radio link.

A VLR allocates a unique TMSI code to each mobile subscriber that is operating in its area.This code, which is only valid within the area supervised by the VLR, is used to identify thesubscriber in messages to and from the MS. When a change of location area also involves achange of VLR area, a new TMSI code is allocated and communicated to the MS. The MSstores the TMSI on its SIM.D. IMEI codes that identify the mobile equipment deployed in the GSM system.

40.Why do we use Mu lt ipl e Access Schemes? What is the dif ference between FDMA,TDMA and CDMA?Multiple Access schemes allow for many users to access thenetwork.

FDMA= Users access the network through frequency division (separation between users ismade through frequency). (1G cellular systems)TDMA= Users access the network through time division (separation between users is madethrough time). (2G cellular systems)

CDMA= Users access the network through code division (separation between users is madethrough code). (3G cellular systems)

41.Whi ch channel(s) i s used for SMS?Either SDCCH or SACCH.42.Which channel i s used by MS to request access to the network?RACH = random

access channel.43.What is AGCH?AGCH (Access Grant Channel) assigns a signaling channel

(SDCCH) to the MS.44.Why do we need SDCCH?The BTS switches to the assigned SDCCH. The call set-

up procedure is performed in idle mode. The BSC assigns a TCH. (SDCCH is also

used to transmit text messages).

45.What is a physical channel? H ow do we dif ferenti ate between physical and logicalchannels?Each timeslot on a TDMA frame is called a physical channel. Therefore,there are 8 physical channels per carrier frequency in GSM.

Physical channels can be used to transmit speech, data or signaling information. A physical

channel may carry different messages, depending on the information which is to be sent.

These messages are called logical channels. For example, on one of the physical channels

used for traffic, the traffic itself is transmitted using a Traffic Channel (TCH) message, while

a handover instruction is transmitted using a Fast Associated Control Channel (FACCH)

message.

46.Why do we need FCCH, SCH and BCCH? FCCH: Identifies BCCH carrier by thecarrier frequency and synchronizes with the frequency.

Synchronization Channel (SCH): Transmits information about the TDMA frame structure

in a cell (e.g. frame number) and the BTS identity (Base Station Identity Code (BSIC)).BCCH: Broadcasts some general cell information such as Location Area Identity (LAI),maximum output power allowed in the cell and the identity of BCCH carriers for neighboringcells.

47.Why do we need SACCH?Instructs the MS the transmitting power to use and givesinstructions on timing advance.

48.What is the purpose of PCH and CBCH? Paging Channel (PCH): Transmits apaging message to indicate an incoming call or short message. The paging messagecontains the identity number of the mobile subscriber that the network wishes tocontact.

Cell Broadcast Channel (CBCH): BS uses this logical channel to transmit short message

service cell broadcast.

49.What is VSWR? Why do we need it?


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Standing wave ratio (SWR) is the ratio of the amplitude of a partial standing wave at anantinode (maximum) to the amplitude at an adjacent node (minimum), in an electricaltransmission line. The SWR is usually defined as a voltage ratio called the VSWR, forvoltage standing wave ratio. SWR is used as an efficiency measure for transmission lines,electrical cables that conduct radio frequency signals, used for purposes such as connectingradio transmitters and receivers with their antennas, and distributing cable television signals.A problem with transmission lines is that impedance mismatches in the cable tend to reflect

the radio waves back toward the source end of the cable, preventing all the power from

reaching the destination end. SWR measures the relative size of these reflections. An ideal

transmission line would have an SWR of 1:1, with all the power reaching the destination and

no reflected power. An infinite SWR represents complete reflection, with all the power

reflected back down the cable. The SWR of a transmission line is measured with an

instrument called an SWR meter, and checking the SWR is a standard part of installing and

maintaining transmission lines.

50.Explain various types of Antenna Diversity?Antenna diversity increases the received signal strength by taking advantage of the natural

properties of radio waves. There are two primary diversity methods: space diversity andpolarization diversity.Space Di versity:Increased received signal strength at the BTS may be achieved by mountingtwo receiver antennae instead of one. If the two Rx antennae are physically separated, theprobability that both of them are affected by a deep fading dip at the same time is low. At 900MHz, it is possible to gain about 3 dB with a distance of five to six meters between theantennae. At 1800 MHz the distance can be shortened because of its decreased wavelength.

By choosing the best of each signal, the impact of fading can be reduced. Space diversityoffers slightly better antenna gain than polarization diversity, but requires more space.Polari zation Diversity:With polarization diversity the two space diversity antennae arereplaced by one dual polarized antenna. This antenna has normal size but contains twodifferently polarized antenna arrays. The most common types are vertical/horizontal arrays

and arrays in 45 degree slant orientation. The two arrays are connected to the respective Rxbranches in the BTS. The two arrays can also be used as combined Tx/Rx antennas. For most

applications, the difference between the diversity gain for space diversity and polarizationdiversity is negligible, but polarization diversity reduces the space required for antenna.

Explain Frequency Diversity.

By using frequency hopping sequence.Explain Time Diversity.By using code interleave technology.

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