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SDMA basics and Types of SDMA

• RF Terminology
• Satellite Terminology
• VSAT system overview
• FDMA versus TDMA versus CDMA
• VSAT SCPC
• VSAT MCPC
• RF Transceiver basics
• C band RF Transceiver Design and Development
• Design of RF frequency converter
• RF Power Amplifier
• what is modulation
• satellite Modem design
• RF Link Budget

SDMA stands for Space Division Multiple Access. It is a technique by which access of satellite resources can be enhanced. Satellite bandwidth is one of the resource which is very scarse and depends on number of transponders in a satellite and their distribution.

Another resource on satellite is antenna which need to be effectively used. Let us see how we can make use of antenna effectively by utilizing different polarization and by means of spot beams with narrower beamwidth.

If satellite will have two antennas one vertically polarised and the other horizontally polarised than two electro-magnetic signals with same RF carrier frequency can be transmitted to the same satellite. This concept of frequency re-use helps in effective use of satellite bandwidth.

Similarly, if smaller antennas are mounted on the satellite then these antennas individually capture EM waves in their line of sight from the stations on the earth. Similarly suppose there are more than one satellites in the line of sight of one earth station/VSAT, in this case VSAT station can access each individual satallite by way of changing the beam direction or changing the RF carrier frequency.

All the above techniques are used to provide special separation and they are associated with frequency or time or code. Hence following are types of SDMA.

•  SDMA with FDMA
•  SDMA with TDMA
•  SDMA with SS and FDMA
•  SDMA with SS and TDMA/FDMA
•  SDMA with BH or TH with TDMA
•  SDMA with SS or FH with CDMA

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