Frequency Hopping SS on Interference Issue in Satellite Communication

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Frequency Hopping SS on Interference Issue in
Satellite Communication

• Ozgur YURUR
• U43878201
• 04/08/09

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Outline

• What is Satellite?
• Basic Information
• Propagation Impairments
• Unintentional Interference
• Intentional Interference
• Interference Mitigations
• Frequency Hopping SS

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Satellite

• The word satellite originated from the Latin word
  Satellit- meaning an attendant, one who is
  constantly hovering around attending to a
  master or big man

• Earth Stations antenna systems on earth
• Uplink transmission from an earth station to a
  satellite
• Downlink transmission from a satellite to an
  earth station
• Transponder electronics in the satellite that
  convert uplink signals to downlink signals

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Basic Transmission

• When using a satellite for long distance
  communications, the satellite acts as a repeater.
• An earth station transmits the signal up to the
  satellite (uplink), which in turn retransmits it
  to the receiving earth station (downlink).
• Different frequencies are used for
  uplink/downlink.

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Satellite Categorization

• Coverage Area
• Global, Regional, National
• Service Type
• Fixed Service Satellite (FSS)
• Example Point to Point Communication
• Broadcast Service Satellite (BSS)
• Example Satellite Television/Radio
• Also called Direct Broadcast Service (DBS).
• Mobile Service Satellite (MSS)
• Example Satellite Phones
• General Usage
• Commercial, Military, Amateur, Experimental

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Satellite Orbits

• Geostationary Earth Orbit (GEO)
• in orbit 35,863 km above the earths surface
  along the equator
• revolve around the earth at the same speed as the
  earth rotates
• large coverage area, a 24 hour view of a
  particular area
• Low Earth Orbit (LEO)
• range from 500 to 1,500 km above the surface
• dont stay in fixed position relative to the
  surface, and are only visible for 15 to 20
  minutes each pass
• Medium Earth Orbit (MEO)
• in orbit somewhere between 8,000 km and 18,000 km
  above the earths surface
• visible for between 2 to 8 hours
• High Altitude Platforms (HAPs)
• One of the newest ideas in satellite
  communication
• A blimp or plane around 20 km above the earths
  surface is used as a satellite
• HAPs would have very small coverage area, but
  would have a comparatively strong signal

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Frequency Bands

• Different kinds of satellites use different
  frequency bands.
• LBand 1 to 2 GHz, used by MSS
• S-Band 2 to 4 GHz, used by MSS, NASA, deep space
  research
• C-Band 4 to 8 GHz, used by FSS
• X-Band 8 to 12.5 GHz, used by FSS and in
  terrestrial imaging, ex military and
  meteorological satellites
• Ku-Band 12.5 to 18 GHz used by FSS and BSS
  (DBS)
• K-Band 18 to 26.5 GHz used by FSS and BSS
• Ka-Band 26.5 to 40 GHz used by FSS
• V Band 47.2-47.5 GHz and 47.9-48.2 GHz used by
  FSS for HAPs

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Radio PropagationEarths atmosphere
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Propagation Impairments

• Different types of atmospheric losses can perturb
  radio wave transmission in satellite systems
• Atmospheric absorption
• Energy absorption by atmospheric gases, which
  varies with the frequency of the radio waves
• Example 22.3 GHz from resonance absorption in
  water vapour (H2O) or 60 GHz from resonance
  absorption in oxygen (O2)
• Atmospheric attenuation
• Rain is the main cause of atmospheric attenuation
• Traveling ionospheric disturbances
• Traveling ionospheric disturbances are clouds of
  electrons in the ionosphere that provoke radio
  signal fluctuations which can only be determined
  on a statistical basis
• Atmospheric effects are variations in the
  amplitude, phase, polarisation, or angle of
  arrival of radio waves, caused by irregularities
  in the ionosphere which change over time.
• Depolarisation can cause interference where
  orthogonal polarisation is used to provide
  isolation between signals, as in the case of
  frequency reuse

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Interference

• Satellite systems encounter some challenges
  during their transmission process.
• affects quality and reliability
• Interference means that everything affects the
  desired signal shape on purpose or by mistake
• Types
• Unintentional Interference
• Intentional Interference

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Unintentional Interference

• adjacent beam
• adjacent channel interference
• inter-modulation noise
• Due to filters, mixers, amplifiers

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Intentional Interference

• Interference being done on purpose, called
  jamming, electronic attacks.
• Jamming can be considered radiated power in high
  level or directed energy to damage adversary
  communication
• The main purpose of jamming is to transmit an
  interfering signal to be accompany with desired
  signal in an adversary receiver side

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Interference Mitigations

• Spread Spectrum Techniques
• Direct Sequence SS
• Frequency Hopping SS
• Adaptive Nulling Antenna
• Burst communications
• Multi-Beam Antennas
• Filtering techniques with using multiple receiver
  antennas
• Boosting up radiated power to satisfy link margin

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Frequency Hopping

• Narrow band message signal is modulated with a
  carrier frequency which is rapidly shifted.
• The hop frequency is indicated by a spreading
  function.
• This spreading function is also available at the
  receiver and enables it to retune to the correct
  channel for each hop.

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FH Design
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Hopping Rates in FH

• Fast Frequency Hopping
• Data symbol spread over several hop frequencies
• Symbol diversity
• Very resistant to jamming and interference, often
  used in military systems
• Slow Frequency Hopping
• Several data symbols on each hop frequency
• Codeword diversity with interleaving
• More likely to have successful retransmission
  with ARQ
• Less complex
• Frequency shifted every Tc secs
• Duration of signal is Ts secs
• Slow FHSS has Tc Ts
• Fast FHSS has Tc lt Ts

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FH system with interference sources
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In the Report

• Simulations will be completed while taking
  consider that desired signal has a constant
  power, and there are one or more interference
  sources with different powers
• Objective
• minimum Hopping Rate Selection
• probability of symbol error rate Ps for mostly
  used modulation type, M-FSK
• SINR ratios for different fraction of BW
  (interfered/total)
• Influence of fraction
• Influence of hopping slot number
• Influence of interference power