Sri Tech

Showing posts with label Telecommunication. Show all posts

Sunday, November 9, 2014

What is the dBm or dBmW

A unit of measure used to reference signal strength level. unlike dB, this is relative measure, dBm is an absolute measure.

dBm ( Decibel-milliwatts ) or dBmW is a short from for the power ratio in decibels (dB) of the measured power referenced to one milli watt (mW). Most communication systems human speech, microwave and fiber optic networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a short form. The baseline reference relationship is 1mW = 0 dBm. A doubling of signal power yields an increase of approximately 3 dBm eg: (2mW = 3 dBm).

GSM Network Components Lesson 2

2:34 PM GSM, Telecommunication No comments

GSM network consists of several functional entities.Those functions and interfaces are defined. The GSM network can be divided into following network components.

Mobile Station ( MS )
Base Transceiver Station ( BTS )
Base Station Controller ( BSC )
Mobile Switching Center ( MSC )
Authentication Center ( AUC )
Home Location Registers ( HLR )
Visitor Location Registers ( VLR )
Equipment identity Register ( EIR )

1) Mobile Station ( MS )

Mobile Station (MS) is the user equipment in GSM System. Mobile station consists of the physical equipment and hardware related software. such as the radio transmitters, display, digital signal processors, and the SIM card. It provides the air interface to the user in GSM networks.

Mobile Station consists of following components

Mobile Termination ( MT )

Mobile termination offers common functions, such as Radio signal Transmission and receiving, handover, speech encoding and decoding, Error detection and correction,signalling and access to the SIM card. The IMEI code is attached to the MT.

Terminal Equipment (TE)

Any device connected to the MS offering services to the user.

Terminal Adapter (TA) This is provides access to the MT. Communication between the TE and MT over the TA takes place using AT commands.

Subscriber Identity module (SIM)
This is a removable subscriber identification ( SIM card ) token storing the IMSI a unique key shared with the mobile network operator. SIM Card provides personal mobility so that the user can have access to all subscribed services irrespective of both the location of the terminal and the use of a specific terminal.

2) Base Transceiver Station (BTS)

BTS is a telecommunication infrastructure used to facilitate wireless communication between subscriber device ( MS ) and Base Station Controller (BSC).

BTS consists of following parts

Transceiver (TRX)
Transceiver (TRX) which handles transmission and reception of signals sending and reception of signals to or from higher network entities.

Combiner

Combines feeds from several TRX so that they could be sent out through a single antenna. Allows for a reduction in the number of antenna and feeders used.

Power amplifier (PA)

Power amplifier which aids in signal amplification from TRX for transmission through the antenna.

Combiner

Duplexer which is used for separating transmitting and receiving signals from the antenna and an Antenna which is an external part of the BTS.

Sector Antenna

Transmitting and reserving signals

Alarm extension system
Collects working status alarms and external alarm (door,main power ,rectifier alarm ) of various units in the BTS and extends them to operations and maintenance (O&M) monitoring stations.

Base band receiver unit (BBxx)

This functions are frequency hopping, handover and signal DSP.

3) Base Station Controller (BSC)

BSC manages the radio resources for BTS. BSC handles Radio channel setup, Frequency hopping, and handovers. The BSC is the connection between the BTS and the MSC. BSC transmit the data to the BTS using Abis interface. BSC assigns frequencies and time slots for the Mobile Station (MS). The BSC also handles intercell handover. It controls the power transmission of the BSS and Mobile Station (MS) in its area. The function of the BSC is to allocate the necessary time slots between the BTS and the MSC. It is a switching device that handles the radio resources.

BSC Function

BTS is connected to BTS and MSC
Radio resource management
Reallocation of frequencies
Control of frequency Hopping
Power control
Inter-cell handover
Time delay measurement of the received signals from MS with respect to BTS clock
Performs traffic concentration to reduce the number of lines from BSC to MSC
BSC performs call processing
TRAU are generally located at the site of MSC
BTS configurations as per requirement
Data from OMC and can be down loaded to BSC

Introduction of Global system for Mobile communications ( GSM ) Lesson 1

1:36 AM GSM, Telecommunication 1 comment

GSM is a Digital wireless Mobile telephony system that is widely used in the world. GSM use a combination of both the FDMA ( frequency division multiple access ) and TDMA ( Time division multiple access ). using this both combination can be transmit more channel of same time.

How to install and align free to Air satellite Dish Without a Meter

6:12 PM Satellite, Telecommunication 52 comments

Buy below Equipment

Ku Band or C band satellite Dish
Ku Band or C Band LNB
Free to Air Satellite Receiver (MPEG 4/DVB-S2 is better )
RG6 Cable ( Antenna coaxial cable )
Taper seal F connector 2 ( connector for coaxial cable )
Find a Drill Machine, Screw drive , Spanner wrench , Compass

Select a your Satellite

Visit a www.lyngsat.com select your favorite satellite. I'm select G-Sat 15 for the continue lesson. write down transponder frequency, Symbol Rates and polarization ( vertical or Horizontal )

My selection details

Transponders 10990,11070,11150, 11490,11570

Symbol Rate 27500

Polarization V

Find your reception details and Dish size

Visit a www.satbeams.com/footprints find your reception details. you have to write down Elevation Angle,Magnetic Azimuth, LNB tilt and recommend dish size.

My selection data for G-Sat 15 for Sri Lanka

Elevation Angle 73°
Magnetic Azimuth 119°
LNB Tilt 60
Dish size For Ku Band 70 cm

Assemble Dish

Assemble dish using manual. and connect F connector for coaxial cable.

Select a location for your Dish

selection location should be direct line of sight in the direction of the satellite and free of obstruction. Generally high location such as a rooftop or side of wall are used. The dish should be fixed at the mounting point. connect LNB and receiver using Coaxial Cable.

Configure your Receiver

Turn on the Receiver and TV. Enter the receiver setup mode and find Transponder edit menu and enter Transponder Frequency , symbol rate and Polarization. Again enter the receiver setup mode and navigate the menu option until you find the signal strength screen.

Dish align method

Keep your partner in front of the TV. keep communication both of you until finish the dish alignment. obtain correct elevation azimuth and LNB Angle setting for your Dish from www.satbeams.com/footprints web site.

Locate the Dish correct Azimuth using compass. Aline the Dish physically very show arc. until it is pointed
in approximately the correct direction. Ask your partner to call when the signal strength indicator begins to move. Turn the dish in one direction just a degree at a time and wait for your partner to respond after each movement. Repeat until the signal strength peaks and then begins to fade again.
Move the dish slowly back in the other direction, until your partner tells you the signal has once again peaked. Tighten the bolts on the mount to finalize the azimuth. Loosen the elevation bolts slightly so you can angle the dish and repeat the process until you have got the elevation fine tuned. Your signal strength should be at least at 80. Now you are dish align completed.

Dish align video this video helps that how to align Satellite dish

Useful web site
www.satbeams.com

www.n2yo.com

www.lyngsat.com