Wednesday, October 29, 2014

RF Planning and Optimisation Questionaire

RF Planning and Optimisation Questionaire



Pls Note: More than one option may be correct. Pls take time to answer


1) For HSN = 0 what is the type of Hopping ?
            i)Pseudo Random Hopping
            ii)Cyclical Hopping
            iii)Circular Hopping
            iv)No Hopping

2) What is the code used for distinguishing 2 BTS having Co-Channels ?
            i)IMSI
            ii)MSISDN
            iii)BSIC
            iv)IMEI
            v)None of the above

3) What is the type of fading generally encountered in a dense urban environment.
            i)Slow and long term fading
            ii)Fast and short term fading
            iii)Both
            iv)None of the above
           
4) Channel Coding at the Air Interface consists of
            i)Block Coding
            ii)Short PN Coding
            iii)Convolutional Coding
            iv)Long PN Coding
            v)None of the above


5) Full Rate Speech Coding is at
            i)9.6 Kbps
            ii)13 Kbps
            iii)6.5 Kbps
            iv)4.8 Kbps
            v)None of the above

6) BSIC – Base Station Identity Code is found in which Logical Channel ?
            i)AGCH
            ii)PCH
            iii)BCCH
            iv)SCH
            v)None of the above


7) For Intercell handovers which is the channel used during handover ?
            i)SDCCH
            ii)SACCH
            iii)TCH
            iv)FACCH
            v)None of the above


8) What is the modulation method used in GSM at Air interface ?
            i)Pulse Code Modulation
            ii)Quadrature Amplitude Modulation
            iii)GMSK Modulation
            iv)PSK Modulation    
            v)None of the above


9) What is the kind of antenna generally used for coverage in GSM ?
            i)Horn Antenna
            ii)Panel Antenna
            iii)Parabolic Antenna
            iv)Yagi Antenna
            v)None of the above


10) Dynamic Power Control in MS is used for
            i)To overcome the effects of path loss
            ii)To resolve near and far problem
            iii)To save battery power
            iv)To reduce uplink interference
            v)All of the above
            vi)None of the above

11) What is the duration of a SACCH Multiframe measurement period?
            i)120 ms
            ii)235 ms
            iii)480 ms
            iv)4.615 ms
            v)None of the above

12) What is the maximum no of bit durations used for the timing advance?
            i)35
            ii)63
            iii)156.25
            iv)26
            v)None of the above


13) Which is the entity involved for deciding an intercell handover ?
            i)MS
            ii)BTS
            iii)BSC
            iv)MSC
v)None of the above

           

14) The TRAU Frame is between which network elements
            i)MS to BTS
            ii)MS to BSC
            iii)BTS to BSC
            iv)BTS to Transcoder
            v)None of the above

15) What is the name of the interface between BSC and Transcoder ?
            i)A Interface
            ii)Abis Interface
            iii)Um Interface
            iv)Ater Interface
            v)None of the above

16) The date rate of the TRAU Frame is
            i)13 Kbps
            ii)22.8 Kbps
            iii)16 Kbps
            iv)270.833 Kbps
            v)None of the above

17) Transcoder belongs logically to which network element
            i) BSC
            ii)MSC
            iii)BTS
            iv)MS
            v)All of the above
vi)None of the above


18) Name the logical Channel which is used by GPRS in dedicated mode.
            i) SDCCH
            ii)PDCCH
            iii)TCH
            iv)SACCH
            v)None of the above


19) When doe an MS needs to do a Location Update
            i)On changing LAC
            ii)On a period basis
            iii)On doing a Power ON
            iv)Logging to the network after no coverage
            v)All of the above
            vi)None of the above

20) The C / I “Co Channel Interference Ratio for a non Hopping GSM Network is
            i) – 9
            ii) 9
            iii)12
            iv) -12
            v) None of the above

21) Discontinuous Transmission helps in
            i)Increasing Battery life
            ii)Increasing Interference
            iii)Decreasing Interference
            iv)None of the above

22) The minimum separation to be kept in the same cell and site during frequency planning

i)200 Khz
ii)400Khz
iii)600Khz
iv)800Khz
v)100Khz

23) Multipath Fading is also called as
i) Lognormal Fading
ii) Shadow fading
iii) Rayleigh Fading
iv) Rician Fading
v) None of the above

24) In GSM Adaptive Equalisation can be maximum up to
i) 1µs
ii)8µs
iii)16µs
iv)32µs
v)None of the above

25) Electrical Tilt of an Antenna is given to the
i) Horizontal Pattern
ii)Vertical Pattern
iii)Both
iv)None of the above


Source: From Google

Monday, May 5, 2014

-DUAL IMEI Number in One MS (Dual International Mobile station Equipment Identity)

Dual International Mobile station Equipment Identity (IMEI)


When we think of mobile telephones we mostly think in terms of them of having a singleInternational Mobile station Equipment Identity number. For two decades, whether for an analogue or digital mobile 'phone, we have often associated, to assist in showing importance of, and drawing anology about, that mobile 'phone serial numbers are alike to vehicle chassis numbers - in essence IMEIs are intended to be unique numbers.
.
Because of that unique numbering scheme, it follows that each mobile phone should only have one IMEI. That has changed and mobile 'phone manufacturers can include two IMEIs. The two IMEIs can be viewed via the label under the battery pack (see photo below Samsung SGH-D888), or by entering *#06# (asterisk, octothorp, 0, 6, octothorp).
.


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Having reviewed the Standards and other documentation and found no definitive statement about the requirement for a dual IMEI numbering scheme, I put out some enquiries and I am grateful to those who assisted. I am told it would appear the occurrence of the dual IMEIs are due to there being two radio chipsets in some handsets. As I understand it, also, I won't find anything in the Standards about this matter - just yet. Moreover, it does not automatically follow that a handset having Dual SIM/USIM slots implies or infers that the handset has two radio chipsets, thus two IMEIs.
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Source: From Google

Thursday, May 1, 2014

Optical Fiber Questions

1

Describe what bend loss is and steps that can be taken to minimise it in the context of optical fibre.


2

Describe what type of fibre cable (loose tube or tight jacket) would usually be used in an outdoor cabling installation stating a reason why.


3

An indoor fibre cable is to be used to connect two floors of a building and is to be installed vertically in a congested maintenance shaft. What types of protection would you expect the cable to have?


4

Discuss in detail the advantages / disadvantages of the three main types of fibre connection, fusion splice, mechanical splice and connectorisation.


5

Give two advantages or disadvantages of a singlemode fibre over a multimode fibre.


6

Describe what type of fibre cable (loose tube or tight jacket) would usually be used in a building cabling installation stating a reason why.


7

An outdoor fibre cable is to be used to connect two buildings on a campus and is to be directly buried, what types of protection you would expect the cable to have.


8

Optical fibre cables use two main techniques to protect the optical fibres within them, describe one of them.



10

List 6 advantages and disadvantages of optical fibre and briefly describe.


11

In optical fibre telecommunications systems three wavelength windows are typically used. What are they and in what advantages and disadvantages do they bring to their respective systems.


12

Show how a loss measurement is taken between two patch panels. Use diagrams to support your answer.


13

Describe 3 safety issues in relation to optical fibre systems.


14

850nm and 1330nm light sources are typically used in optical fibre building cabling systems. Why are 1550nm sources typically not used?


15

Name three common areas that optical communications are used.


16

Describe in brief how ‘Total internal reflection’ allows light to be guided down an optical fibre.


17

The refractive index of the glass in an optical fibre is an important parameter. What does refractive index mean?


18

If the input power of an optical fibre link is 3mW and the output power is 0.01mw, what in the attenuation of the fibre link in dB?


20

Name one type of fibre attenuation processes and discuss how it works.


21

What steps can be taken to reduce Absorption loss in an optical fibre link?


22

What types of protection will an optical fibre cable have, to protect the fibres enclosed from moisture?


23

Describe the typical steps required to terminate an optical connector to an optical fibre.


24

What is Fresnel loss?


25

Describe one form of fibre core misalignment.


26

What advantages do ‘high density’ building cabling connectors bring to an installation?


27

How is an optical fibre cleaved? Use diagrams to support your answer.


28

What is the main difference between a high end (expensive) cleaver and a low end (cheap) cleaver?


29

Describe the steps in detail in carrying out a fusion splice.


30

What is the purpose in a V-groove in a fusion splicer?


31

Discuss the advantages and disadvantages between a fusion splice and a mechanical splice.


32

Describe in brief using a diagram to support your answer how an OTDR operates.


33

What safety precaution should be taken when working with scrap fibre?









2
(a)
A loose tube cable would usually be used in an outdoor installation. Loose tube cables allow a cable to stretch without damaging the fibre within. Also loose tube cables usually have a water blocking gel in the tube that will pour out in a vertical installation.

[10 Marks]


3
(a)
Any 2

Tensile strength – A strength member to stop the cable being stretched while installed
Moisture ingress – maintenance shaft could have water systems or be humid. No water blocking gel.
Crush resistance – Weight if other cables. Protection from cable ties.



4
(a)

Essay type comparison of details in table below.

Advantages
Disadvantages
Splice
Low loss
Initial high cost of fusion splicer
Low cost per splice
Permanent


Mechanical splice
Semi permanent
Higher loss than fusion splice
Lower loss than connector
Higher cost per splice
Low equipment cost

Connector
Removable
Highest loss

High cost per connector


[10 Marks]

5
(a)
Any two of the below.

Advantages
-Higher bandwidth
-Lower dispersion
-Better upgrade potential

Disadvantages
-Difficult to couple light
-Connectorisation, splicing more difficult and expensive
-Connecting equipment more expensive


6
(a)
A tight jacket cable would usually be used in a building installation. Tight jacket cables are capable of tighter bend radii than loose tube cables. Also loose tube cables usually have a water blocking gel in the tube that will pour out in a vertical installation.



7
(a)
Tensile strength – A strength member to stop the cable being stretched while installed
Crush resistance – To stop the weight of the soil damaging the fibre.
Moisture ingress – To stop water coming in contact with the fibre and causing it to fail.



8
(a)
Loose tube or tight jacket.




9
(a)
Any 2
Tensile strength – A strength member to stop the cable being stretched while installed
Moisture ingress – Has an aluminium foil jacket. As it is loose tube will also have moisture blocking gel.
Crush resistance – Has a wire braid jacket just below the first layer of the cables outer jacket.



Source: From Google

Wednesday, April 30, 2014

GSM Protocols

GSM Protocol is divided into mainly three Layers:

Layer-1 Protocol:-          MTP
Layer-2 Protocol:-          LAPDm
-          LAPD
Layer-3 Protocol:-          RR
-          MM
-          CM
-          BSSMAP
-          DTAP
-          MAP

 Layer-1 Protocol:
        MTP-Message Transfer Part:
        The Message Transfer Part (MTP) is part of the Signaling System 7(SS7) used for communication in Public Switched Telephone Networks.
        MTP is responsible for reliable, unduplicated and in-sequence transport of SS7 messages between communication partners.
        The MTP provides a mechanism giving reliable transfer of signaling messages
        The Media Transfer Protocol (MTP) is an extension to the Picture Transfer Protocol (PTP) communications protocol that allows media files to be transferred atomically to and from portable devices.
 Layer-2 protocols:
LAPDm-Link Access Protocol D Channel Mobile
LAPDm:
        LAPDm stands for Link Access Procedure on D channel (modified). This is a modified version of LAPD and is optimized for the GSM Air interface.
        It is said to be a lightweight LAPD protocol as it does not handle error correction/detection.
        It handles:
        Segmentation and reassembly of data and  
        Acknowledges/unacknowledged data transfer
         Re-sequencing of data frames and flow control!
The LAPD protocol is used for A and A-bis interface.
LAPDm is a data link layer protocol used in GSM cellular networks. LAPDm forms Layer 2 of the Um interface between the Base Transceiver Station and Mobile station which is to say that it is used in the radio link between the cellular network and the subscriber handset

     Functions:
– Organization of Layer 3 information into frames
        Data flow Control
        Acknowledged/Unacknowledged data transmission
        Segmentation
        Data re-assembly
– Peer-to-peer transmission of signaling data in defined frame formats
– Recognition of frame formats
– Establishment, maintenance, and termination of one or more (parallel) data links on signaling channels
Layer-3 Protocols:
  • A number of mechanisms needed to establish, maintain and terminate a mobile communication session
  • Layer III implements the protocols needed to support these mechanisms
  • A signaling protocol, the registration process, is composed of a sequence of communication events or messages
RR: Radio Resource Management
MM-Mobility Management
CM-Connection Management
BSSMAP-Base Station Subsystem Mobile Application Part
DTAP-Direct Transfer Application Part
MAP-Mobile Application Part

MM:
-          Responsible for
-           location management and
-           Security
·         Location management involves the procedures and signaling for location updating, so that the mobile’s current location is stored at the HLR, allowing incoming calls to be properly routed.
·         Security involves the authentication of the mobile, to prevent unauthorized access to the network, as well as the encryption of all radio link traffic.
·         The protocols in the MM layer involve the SIM, MSC, VLR, and the HLR, as well as the AuC (which is closely tied with the HLR).
CM:
The CM functional layer is divided into three sub layers.
             - Call Control (CC)
             - Supplementary Services
             - Short Message Service
                Call Control (CC) sub layer
- manages call routing, establishment, maintenance, and release, and is closely related to ISDN call control.
Supplementary Services sub layer
 - manages the implementation of the various supplementary services (Call Forwarding/waiting/hold), and also allows users to access and modify their service subscription.

Short Message Service sub layer
 - handles the routing and delivery of short messages, both from and to the mobile subscriber.
     BSSMAP:
        BSSMAP Support all of the procedure between the MSC & BSS that require interpretation and processing of information related to single call and Resource management
        BSSAP includes all messages exchanged between the BSC and the MSC that the BSC actually processes—examples include PAGING, HND_CMD, and the RESET message. More generally, BSSAP comprises all messages that are exchanged as RR messages between MSC and BSC, and messages that are used for call-control tasks between the BSC and the MSC.
        The BSS Management Application sub-Part (BSSMAP) supports other procedures between the
MSC and the BSS related to the MS (resource management, handover control), or to a cell within the BSS, or to the whole BSS.
   DTAP:
        The Direct Transfer part is used to transfer call control and Mobility management message between the MSC & MS.The DTAP information in these message is not interpreted by the BSS.
MAP:
          It pprovides basic communication between HLR and other MSC
          MAP functions:
        Updating of location information in VLRs
        Storing routing information in HLRs
        Updating and supplementing user profiles in HLRs
        Handoff of connections between MSCs


Source: From Google