Docstoc

RF and Radio Technology Fundamen

Document Sample
RF and Radio Technology Fundamen Powered By Docstoc
					WAN Basics
Tsunami MP.11 - QB.11 – QuickBridge 60250




      Radio Frequency (RF) and
      Radio Technology Fundamentals




                                            April 2008
                                  Point to Point (PtP)


 One location to one location
 Dedicated access
    Full bandwidth between two locations




                                                   Unwiring the Network
                                  Point-to-Multipoint (PMP)


 One location to many locations;
  Many locations to one location
 Shared access
    Shared bandwidth between multiple locations


                                                   Indoor Wireless LAN




Outdoor Point-to-Multipoint

                                                          Unwiring the Network
                                        The Concept of Line-of-Sight
                                        (LOS)

 No obstructions between each end
    No trees
    No buildings
    No mountains
        Can you go through a window?
             – Probably, but with added losses that are hard to predict:
                  » Plan on 10dB as an initial guess,
                      can be greater for reflective (metallic) tinted glass


    Note: The lower the frequency, the better it will travel through obstacles




                                                                              Unwiring the Network
                                  The Line-of-Sight Issue -
                                  raising one side

 A structure can be erected to establish line-of-sight over obstacles




                                                              Unwiring the Network
                                 The Line-of-Sight Issue –
                                 raising two sides

 Two structures can be erected to establish line-of-sight over obstacles




                                                             Unwiring the Network
                                   The Line-of-Sight Issue –
                                   using a repeater

 A system approach called a “repeater” can establish line-of-sight to go
  around or over obstacles
    Active repeaters (two radio systems back-to-back)
    Passive repeaters (one radio system redirected)




                                                             Unwiring the Network
                                  The Hertz Measurement of
                                  Frequency

 1 Hertz (Hz) = 1 cycle/second
    1,000 Hz = 1 kHz
    1,000,000 Hz = 1 MHz
    1,000,000,000 Hz = 1 GHz




                                                          time



                                    period
                                    (cycle)
                                                 Unwiring the Network
                                  Wavelength


 Inversely proportional to the frequency
 Wavelength = the distance required to complete one cycle at a particular
  frequency
    The distance from Point A to Point B represents one wavelength
    Wavelength is normally measured relative to meters (such as cm, or mm)




                                                        A         B




                                                                Unwiring the Network
                                  Phase


 The location of the traveling wave at a fixed point in time
 Measured in degrees or radians, related to Pi ()
 360 Degrees = 1 Cycle
    2 Radians = 360°
    57.3° = 1 Radian                                      90°




                                                      0°     180°   360°




                                                                 270°

                                                                 Unwiring the Network
                                   Modulation


 Method of sending information over radio wave
    By changing the signal phase over time
     one can send information
    Example QPSK (Quadrature Phase Shift Keying):
        4 decisions points
        2 code bits per symbol




                                                              90
    64 QAM (Quadrature Amplitude Modulation)
        64 decision points
        6 coded bits per symbol                     180               0



                                                             270

                                                      Unwiring the Network
                                   Watts & Decibels:
                                   Measurement of Power

 Watt (W)
 Decibel reference to 1 mW (dBm)
 Decibel (dB) - a ratio or difference in power
    e.g. 20dBm is 3dB less than 23dBm
    +3 dB equals power x2
    +10 dB equals power x10




                 Conversion equations
                    x(dbm) = 10logy(mW)
                    y(mW) = 10x(dBm)/10



                                                  Unwiring the Network
           Watts vs. dBm


  100 W            50 dBm

   10 W            40 dBm
    2W             33 dBm
    1W             30 dBm

100 mW             20 dBm

  1 mW             0 dBm
 100 uW            -10 dBm

0.001 nW           -80 dBm
                             Unwiring the Network
                                   Power and Directivity


 Without obstructions and with high intensity and beam focus, RF can travel
  long distances
    Power is measure of strength
    Gain is measure of amplification




                                                            Unwiring the Network
                                        Microwaves Behave Similar to
                                        Visible Light & Sound

   They propagate in air similar to light and sound
         Reflect off surfaces
         Absorbed by surfaces
         Diffuse and refract through substances




Transmitting source
(e.g., car headlight)
                                                         Signal is more concentrated
                              Point A          Point B   at Point A than at Point B




                                                                  Unwiring the Network
                                  RF Refraction and Scattering


 RF can pass through materials which will change it‟s direction of travel
  (called „refraction‟)
 RF can pass through materials which will diffuse the energy (scatter)
  to a wider beam




                                             Away from
                 Air (medium 1)             Perpendicular

                                                              Observer


            Apparent
            Position
                                               Water (medium 2)
              Actual Position




                                                              Unwiring the Network
                                Reception:RF ~ Vision:Light


 Reception of RF can be affected by “vision-related” components
      “Blinders”
      Angle of attack
      Focus
      Obstructions
      Weather




                                                           Unwiring the Network
                                 Obstructions Will Stop or
                                 Seriously Attenuate Signals

 Some RF can travel easily through
  walls, stone, etc. and some will be
  immediately dampened
 Partial obstructions can dramatically
  reduce wave energy




                                                 Unwiring the Network
                           RF is Attenuated by Rainfall


                                Signals above 11 GHz can be
                                 severely affected
                                Most of Proxim‟s products operate
                                 below 6 GHz and are virtually
             11GHz               unaffected by rainfall in most parts
             Cloudburst          of the world
=7dB/mile
              6GHz
              Cloudburst




                                                   Unwiring the Network
RF Reflection and Multipath


     RF can “bounce” off objects like
      buildings and mountains, water and
      atmosphere
     Different paths of RF will arrive at
      destination at different times - this is
      called „multipath‟




                          Unwiring the Network
                             The Importance of Signal
                             Phase

 Best Case: Even number of ½ Wavelengths

  x
       _

                                        2x
                                              _
  -x
       _

           +                   =
  x
       _
                                        -2x
                                              _

  -x   _

                                                  Unwiring the Network
                            The Importance of Signal
                            Phase

 Worst Case: Odd number of ½ Wavelengths

   x
        _


   -x
        _

            +                  =
   x    _


   -x   _

                                            Unwiring the Network
                                 Fresnel Zone


 The Fresnel zone is additional path clearance that is required to optimize
  radio reception
 There are an infinite number of points where reflected signal arrives exactly ½
  wavelength out of phase for a given frequency




                                                             Unwiring the Network
                                        Earth Curvature and k factor


 One factor for line-of-sight includes earth curvature and the effects of the
  atmospheric refraction due to the curve of the earth‟s surface
    The earth‟s bulge between the end points must be considered when determining if
     LOS and proper path clearance exists, including Fresnel zone
    The k factor (refraction index) is a mathematical figure that will help determine the
     effect on path clearance
          Not much of a factor under 10 miles




                                                                     Unwiring the Network
                                      Polarization


 Polarization describes the orientation of the E (electrical) and H (magnetic)
  components of an RF wave front.
    Linear polarization (horizontal, vertical, slant linear)
    Circular polarization (right-hand, left hand)
 RF can be transmitted (and received) with dominant polarization
    Polarization provides a level of discrimination (attenuation) against different
     polarization signals, especially “opposite” polarization (e.g. horizontal versus
     vertical)
 Weather and multipath can “de-polarize” RF




                                                                      Unwiring the Network
Terrain Effects on RF


     Mountainous terrain is best
        Many multipath reflections will not
         reach the other end, thus reducing
         the potential for out-of-phase
         reflected signals that may have
         degraded the integrity of the direct
         signal
     Flat, smooth terrain is worst
        Many multipath reflections may reach
         the other end, thus increasing the
         potential for out-of-phase reflected
         signals that may degrade the integrity
         of the direct signal




                          Unwiring the Network
                                   Climate Effects on RF


 Humid climate is worst
    More moisture = more ducting and refraction = more attenuation
 Dry climate is best
    Reduced moisture = less ducting and refraction = less attenuation




                                                                  Unwiring the Network
                                     The Concept of Interference


 Interference is the reception of signals from sources
  other than the intended source
    The source of the interference may be from a closer and/or
     stronger signal level compared to the desired signal impacting
     the ability of the system to receive the desired signal properly
 Interference can be caused by energy that is at the same frequency as the
  signal that you wish to receive, or can be at a nearby frequency with enough
  energy to „leak‟ into the receiver
 Interference can also be caused by energy that is a completely different
  frequency from that which you wish to receive. High-powered transmitters can
  radiate „harmonics‟ where they are also inadvertently transmitting energy that
  is a multiple of the intended transmitter frequency




                                                                    Unwiring the Network
                                  The Basics of Interference
                                  Management

 Use opposite antenna polarization to reject nearby interference
 Change frequency plans to steer around interference
    Swap ends of the system so that the receive frequency is changed (where
     possible)
    Change frequency channels or bands (where possible)
 Move antenna to attenuate interference
    Create physical blocks (hide) the antenna from the interference source
    Moving the antenna may create a new angle from the interference, which may
     greater reject the interference
 Use larger or high-performance antennas (where possible)
    Improves off-angle rejection
    Improves gain of on-angle signals




                                                                Unwiring the Network
                                       Methods of Two-Way
                                       Communications

 Frequency Division Duplex (FDD)
    Communications in one direction are at a different frequency than in the other
     direction, transmitting and receiving in both directions at the same time
        Can establish high speeds in both directions (usually equivalent speed)
        No substantial time delays (latency) for communication, as no information is buffered
        The difference in frequency can be small (a few MHz) or large (100‟s of MHz), in the same
         frequency band or different bands altogether

 Time Division Duplex (TDD – or „Ping Pong‟)
    Communications in one direction are at a different time than in the other direction,
     transmitting and receiving at the same frequency but in succession
        Can provide unbalanced communications when desired (e.g. more download than upload,
         or variable to demand)
        Has an impact on latency




                                                                          Unwiring the Network
                                       One-Piece and Two-Piece
                                       Construction

 For Proxim‟s outdoor wireless solutions,
  one end of the radio system is made up
  of one or two distinct boxes
    One-piece radios Indoor
        Are designed for all-indoor mounting
         (or mounting in a weatherproof container)
    One piece radios Outdoor
        Rugged housing
    Two-piece radios                                   2-piece configuration
        give the flexibility of mounting part of the
         system closer to the antenna and part inside




                                                        1-piece configuration


                                                         Unwiring the Network
                                 Connected or Connectorized
                                 Antenna

 Some Proxim products have built-in antennas that cannot be removed or
  bypassed
 Some Proxim products have built-in antennas that can be bypassed and an
  alternate antenna connected instead
 Some Proxim products do not have a built-in antenna
    an “external” antenna must be connected




     Connected Antenna Configurations          Connectorized Antenna Configurations

                                                              Unwiring the Network
                                    Understanding Antennas


 Outdoor systems usually implement directional antennas
    Highly directional (narrow beamwidths) for PTP systems
    „Sector‟ (wide beamwidths) for the central location of PMP systems
    Somewhat directional (medium beamwidths) for the client locations of PMP systems
 The choice of gain and beamwidth is critical to the application
      The larger the antenna (in surface area), the higher the gain
      The lower the gain, the wider the beamwidth
      The wider the beamwidth, the more susceptible to interference
      The higher the gain, the further the distance and/or improved RSL
 The configuration of polarization is important to the system plan
    To optimize communications, both ends of a wireless system should be implemented
     with the same polarization




            Click here to watch the antenna properties video
                                                                   Unwiring the Network
                               Antenna Performance
                               Parameters

 Gain
 Beamwidth/Coverage Pattern
 Polarization




                                             Unwiring the Network
                                 Effective Isotropic Radiated
                                 Power (EIRP)

 The output power of a transmitter, including all cable losses and antenna
  gains
    Transmitter Output Power - Cable Loss + Antenna Gain


                                Antenna
                                 (Gain)




               Transmission
                 Line (Loss)                    EIRP



                           Radio
                       (Output Power)

                                                             Unwiring the Network
                                  What Governs Distance or
                                  Coverage?

 The radio‟s technology (sometimes)
 The “strength” of the transmitted signal
 The radio‟s „threshold‟ specifications
 The radio‟s frequency of operation
 Output power regulations
 Obstacles between the end points
 Climate/Terrain
 The antenna pattern




                                                 Unwiring the Network
                       Basic Distance Planning:
                       a series of Gains and Losses


            Antenna       Path    Antenna
             (Gain)      (Loss)    (Gain)



Transmission                               Transmission
  Line (Loss)                              Line (Loss)
                            RSL

          Radio                        Radio
      (Output Power)                (Threshold)


                                       Unwiring the Network
                                 Understanding “System Gain”
                                 & “Fade Margin”

 System Gain
   The difference between the output
                                            Output
    power and the threshold
                                            Power
 Fade Margin
   The difference between the received
    signal level and the threshold


                                                              System
                                                               Gain


                   Received Signal Level (RSL)
                                                                   Fade
                                                                  Margin
                                          Threshold


                                                      Unwiring the Network
                                     Understanding “Availability”


 The predicted amount of time the system will be operating above threshold
    Availability is the primary design criteria for outdoor wireless systems


 Examples:
    99.999%        = 5.26 minutes/year outage
    99.995%        = 26.28 minutes/year outage
    99.950%        = 262.8 minutes/year outage




                                                                     Unwiring the Network
                                   Overall Spectrum


            AM
          Radio          UHF TV         Remote Controls
      550 - 1700kHz    460-600MHz       100GHz-500THz Medical X-ray



VLF    LF   MF   HF   VHF   UHF   SHF   EHF   Infrared   Visible   UV   X   Gamma   Cosmic



              FM Radio
   Sound     88-108 MHz                              Light
20Hz - 20kHz   VHF TV                           700THz - 1000THz
             54-220 MHz

                        Cellular 800-900 MHz
                            PCS 1.8-2 GHz
                   Terrestrial Microwave 1–18 GHz
                 Indoor Wireless 900 MHz, 2 & 5 GHz

                                                                   Unwiring the Network
                                       Types of Spectrum


 License-exempt
    Anyone can use
    No coordination or registration required
    Opportunity for interference, which the user must work around
 Licensed (or „Leased‟)
    Coordination required
    Registration required
    Interference is better controlled, but not completely eliminated
        Regulatory agency will assist with any interference cases

 Owned
    Purchased spectrum, usually in a given region, usually by auction
    Owner needs to self-coordinate intra-system interference potential
    Some coordination may be needed with neighboring owners




                                                                     Unwiring the Network
                                      Bands and Regulations
                                      USA and Canada

 900 MHz ISM
   902 – 928 MHz
       +36 dBm EIRP. For every dB of antenna gain above 6dBi, Tx must be reduced by 1 dB

 1.8 GHz Federal Government
   1.755 – 1.850 GHz
       +80 dBm EIRP
 2.4 GHz ISM
   2.4000 – 2.4835 GHz
       +36 dBm EIRP. For every 3 dB of antenna gain above 6dBi, Tx must be reduced by 1dB
       +36 dBm EIRP for PMP systems and some PtP systems

 3.6 GHz
   3.650 – 3.700 GHz
       +44 dBm EIRP (per 25 MHz) for fixed station
       +30 dBm EIRP (per 25 MHz) for mobile station
       An unlimited numbers of licenses will be granted,
        but every base station must be registered.
       established circular protection zones around existing station
             – 150 km for Fixed Satellite Service (FSS) earth stations
             – 80 km for Federal Government stations
                                                                         Unwiring the Network
                                        Bands and Regulations
                                        USA and Canada

 4.9 GHz Public Safety
    4.9405 – 4.9895 GHz
       Chanel size (Mhz)      1    5   10 15   20             For every dB of antenna
        Low power (dBm)        7   14   17 18.8 20             gain above 9dBi, Tx must
        High power (dBm)      20   27   30 31.8 33             be reduced by 1 dB
 5.3 GHz U-NII
    5.250 – 5.350 GHz
       +30 dBm EIRP limit for all systems
 5.4 GHz U-NII
    5470 – 5725 GHz
       +30 dBm EIRP limit for all systems, Automatic DFS Required
 5.8 GHz U-NII
    5.725 – 5.825 GHz
       +53 dBm EIRP limit for qualified PTP systems
       +36 dBm for PMP systems
 5.8 GHz ISM
    5.725 – 5.850 GHZ
       No EIRP limit for qualified PTP systems
       +36 dBm EIRP for PMP systems and some PTP systems
                                                                      Unwiring the Network
                                     Bands and Regulations
                                     India

 2.4 GHz
   2.4000 – 2.4835 GHz
       +36 dBm EIRP, + 30 dBm Output Power
       Indoor + outdoor

 3.3 GHz
   3.300 – 3.400 GHz
   Licensed band
 5 GHz
   5.150 – 5.350 & 5.725 – 5.875 GHz
       +23 dBm EIRP
       Indoor (which includes usage within the single contiguous campus
        of an individual, duly recognized organization or institution)
   5.825 – 5.875 GHz
       +36 dBm EIRP, + 30 dBm Output Power
       Outdoor




                                                                           Unwiring the Network
                                        Bands and Regulations
                                        Russian Federation

 Russian Federation defined four geographical zone
      Category I     cities with population exceeding 1 million inhabitant
      Category II    cities with population between 250k and 1 million inhabitant
      Category III   cities with population between 100k and 250k inhabitant
      Category IV    whole Russian Federation area excluding
                      cities with population exceeding 100k inhabitant


 2.4 GHz
    2.4000 – 2.4835 GHz
         Point to Multipoint systems       I     II    III    IV
          BSU and SU max Tx power         -10    -10   -10    -10     dBWatt
          BSU and SU max EIRP              -4      6     6      6     dBWatt
          BSU max range coverage           0,5     4    10     20       km
         Point to Point systems
          Max EIRP                                    30              dBWatt
          Antenna‟s pattern              According to МСЭ-Р F.1336
                                         or F.699 recommendations




                                                                      Unwiring the Network
                                      Bands and Regulations
                                      Russian Federation

 3.5 GHz
   3.400 – 3.450 and 3.500 – 3.550 GHz
       Point to Multipoint systems      I    II     III   IV
        BSU and SU max Tx power        -10   -10    -10     0     dBWatt
        BSU and SU max EIRP             -4     0     10    20     dBWatt
        BSU max range coverage           3     5     10    20       km
       Point to Point systems
        Max EIRP                                   30             dBWatt
        Antenna‟s pattern             According to МСЭ-Р F.1336
                                      or F.699 recommendations

 5.2 GHz
   5.150 – 5.350 GHz
       Point to Multipoint systems     I     II     III    IV
        BSU and SU max Tx power        -10   -10    -10    -10    dBWatt
        BSU and SU max EIRP              0     6     13    13     dBWatt
        BSU max range coverage           3     6     8      8      km
       Point to Point systems
        Max EIRP                                   30             dBWatt
        Antenna‟s pattern             According to МСЭ-Р F.1336
                                      or F.699 recommendations
                                                                  Unwiring the Network
                                      Bands and Regulations
                                      Russian Federation

 5.7 GHz
   5.650 – 5.725 GHz
       Point to Multipoint systems     I     II     III    IV
        BSU and SU max Tx power        -10   -10    -10      0    dBWatt
        BSU and SU max EIRP              0     6     13     23    dBWatt
        BSU max range coverage           3     5     10     20      km
       Point to Point systems
        Max EIRP                                   30             dBWatt
        Antenna‟s pattern             According to МСЭ-Р F.1336
                                      or F.699 recommendations

 6 GHz
   5.725 – 6.425 GHz
       Point to Multipoint systems     I      II    III   IV
        BSU and SU max Tx power        -10   -10    -10     0     dBWatt
        BSU and SU max EIRP            -10    -7      3    10     dBWatt
        BSU max range coverage           3      5    10    20       km
       Point to Point systems
        Max EIRP                                   30             dBWatt
        Antenna‟s pattern             According to МСЭ-Р F.1336
                                      or F.699 recommendations
                                                                  Unwiring the Network
                                     Bands and Regulations
                                     Europe

 2.4 GHz ETSI 301 328
    2.400 – 2.483 GHz (3 channel)
        +20 dBm EIRP, Indoor and outdoor use.
 3.5 GHz ETSI 301 021 v1.6.1 (July 2003)
    3.400 – 3.600 GHz
        Licensed band

 5 GHz ETSI 301 983 v1.3.1 (August 2005)
    5.150 – 5.250 GHz (4 channel)
        +23 dBm EIRP, Indoor use, TPC
    5.250 – 5.350 GHz (4 channel)
        +23 dBm EIRP, Indoor use, TPC, DFS
    5.470 – 5.725 GHz (11 channel)
        +30 dBm EIRP, Indoor and outdoor use, TPC, DFS

 5.8 GHz ETSI 302 502 v1.1.1 (November 2006)
    5.725 – 5.850 GHz (5 channel)
        +36 dBm EIRP, Fixed outdoor use, TPC, DFS, UK, Norway, Germany



                                                                   Unwiring the Network
                                       Extra Regulation Europe


 WEEE
     Waste of Electrical and Electronics Equipment
     Directive 2002/96/EC
     Implementation August 2005


 RoHS
     Restriction of Hazardous Substance
     Directive 2002/95/EC
     Implementation July 2006



 All Proxim ORiNOCO and TSUNAMI MP.11 / MP.16 product
  comply with those two rules




                                                      Unwiring the Network
                                       Outdoor Wireless Systems
                                       Require Engineering

 Determine Line-of-Sight and Path Clearance
    Including Fresnel Zone, k-factor, reflection point
 Determine Antenna System Requirements
    Meet distance, availability and fade margin requirements
 Determine All Cable Types and Lengths
 Analyze Interference Potential
    Including any self-interference
 Plan for Proper Grounding and Lightning Protection
 Plan for Egress of Cables from Outdoor to Indoor


 These statements are true for ANY deployment,
  even across a parking lot!



                                                                Unwiring the Network

				
DOCUMENT INFO