Radio Frequency Operations

Embed Size (px)

Citation preview

  • 7/27/2019 Radio Frequency Operations

    1/50

    Radio Frequency Operations

    and

    TechnologyMobile Device Investigations Program

    Senior Instructor

    Technical Operations DivisionDHS - FLETC

  • 7/27/2019 Radio Frequency Operations

    2/50

    RF Operation and Technology

    Radio propagation the eletromagnetic phenomenomdiscovered by Henrich Hertz in the late 1880s. Itshow energy travels through a given medium.

    The medium can be air, water, aired cable, fiber opticsand the like. Radio signals travel at the speed oflight through the air 186,282 miles per second.

    The only significant difference cellular systems andconventional landlines is the radio link that connectsthe wireless network to the cell base station.

  • 7/27/2019 Radio Frequency Operations

    3/50

    RF Operation and Technology

    Different radio signals have different properties, i.e.

    High frequencies and Low frequencies

    Signal Refraction - signals bend through theatmosphere

    Signal Diffraction - signals bend around obstructions

    Signal Reflection - signals bounce off obstructions orsolid objects

  • 7/27/2019 Radio Frequency Operations

    4/50

    RF Operation and Technology

    Examples of radio signal actions

    Diffraction Air careens over a moving car andoff the back end

    Reflection Light bouncing off a mirror

    Radio Frequency propagation refers to howwell radio signals radiates or travels in freespace.

  • 7/27/2019 Radio Frequency Operations

    5/50

    RF Operation and Technology

    Wireless signals are basically omnidiriectional

    Omnidirectional; all directions, propagation isoften described as waves.

    Pebble In Water - size of pebble, water andenegey

  • 7/27/2019 Radio Frequency Operations

    6/50

    RF Operation and Technology

    Radio Frequency coverage from any basestation is determined by three factors;

    1. The height of the antenna

    2. The type of antenna used

    3. The Radio Frequency Power Level emitted.

    This is true no matter where the antenna isplaced

  • 7/27/2019 Radio Frequency Operations

    7/50

    There are a number of things that may interferwith the propagation of a radio signal.

    Some of the ongoing issues wireless carriershave to deal with are;

    1. Ducting

    2. Signal Fading

    Signal Fading and Ducting

  • 7/27/2019 Radio Frequency Operations

    8/50

    Ducting

    Ducting is defined as the trapping of RF in theboundary area between two air masses.

    Ducting of RF is an atmospheric anomaly knownas temperature inversion

    Ducting is unavoidable because it is a naturalmeteorological phenomenon.

    Downtilting or directing the RF toward the ground

    may compensate for ducting.

  • 7/27/2019 Radio Frequency Operations

    9/50

    Absorption

    Absorption describes how a radio signal isabsorbed by objects

    The greater the amount of absorption the lessgeographical area can be covered.

    Organic material absorbs more wireless signalsthan in non-organic.

  • 7/27/2019 Radio Frequency Operations

    10/50

    Absorption

    Absorption can be compensated for in thefollowing ways:

    1. By using higher-gain antennas

    2. By using higher RF power levels in order

    to cover the same geographic area3. By decreasing the distance between

    Base Stations

  • 7/27/2019 Radio Frequency Operations

    11/50

    Free-space Loss or Path Loss describes the attenuationof a radio signal over a given distance.

    The higher the frequency the greater the free space loss.PCS carriers operating at 1.9MHz will have greaterloss than wireless carriers operating at 850 MHz.

    Power Levels of a Base Station signal and antenna gainwill determine when a wireless signal will fade

    Free Space Loss

  • 7/27/2019 Radio Frequency Operations

    12/50

    Multipath or Rayleigh Fading; how thetransmitted base signal reacts to physicalfeatures or structures creating multiple signal

    paths.

    Using the pebble in the water analogy, think of

    rocks, sticks or other objects in the water.

    Mutlipath/Rayleigh fading will occur in bothdirections.

    Multipath/Rayleigh Fading

  • 7/27/2019 Radio Frequency Operations

    13/50

    Multipath/Rayleigh Fading

  • 7/27/2019 Radio Frequency Operations

    14/50

    Obviously strongest signal will always be thesignal directly from the mobile unit to the

    Base Station.

    The indirect signals will arrive at the base either

    in phase or out of phase with the directsignal.

    Multipath/Rayleigh Fading

  • 7/27/2019 Radio Frequency Operations

    15/50

    Wireless Frequency Bands

    The radio frequency assigned to the earlycellular industry was the mostly unused 850MHz UHF television spectrum.

    The 850 MHz radio propagation is beneficial forthe following reasons;

  • 7/27/2019 Radio Frequency Operations

    16/50

    Wireless Frequency Bands

    It has a very short wavelength, about 12 inches

    It tends to be line of sight, unlike shortwave radio

    signals

    It is easily reflected off objects.

    It is easily absorbed by foliage, which can be goodor bad. It can help with frequency reuse or incertain urban areas or highways it can degrade thesignal.

  • 7/27/2019 Radio Frequency Operations

    17/50

    Wireless Frequency Bands

    The 1.9 MHz signal used by PCS carriers isgood for wideband services, but haspenetration problems as it relates to buildings

    and the like.

    The 1.9 MHz signal does not propagate as well

    as the 850 MHz signal because it has aneven shorter wavelength.

  • 7/27/2019 Radio Frequency Operations

    18/50

    Wireless Frequency Bands

    It has a very short wavelength, less than12inches

    It tends to be line of sight, unlike shortwaveradio signals

    It is easily reflected off objects.

  • 7/27/2019 Radio Frequency Operations

    19/50

    Due to the nature of building construction and structure itis often difficult receive and maintain RF inside.

    In-Building Coverage

  • 7/27/2019 Radio Frequency Operations

    20/50

  • 7/27/2019 Radio Frequency Operations

    21/50

    Frequency Coordination is the effort by carrierRF Engineers to place base stations in aorderly fashion to minimize interference.

    This is done by adhering to the Distance toReuse ratio within their own system.

    RF Engineers from the various carriers oftencoordinate with each to comply with theFCC mandates.

    Frequency Coordination

  • 7/27/2019 Radio Frequency Operations

    22/50

    System Interference

    Interference is defined as any adverseinteraction between two or more radio signalsthat cause noises or cancels out each other.

    This generally occurs when transmitting RF toclose to each other or on the same

    frequency.

  • 7/27/2019 Radio Frequency Operations

    23/50

    Cochannel Interference

    4

    2

    3

    4

    3

    2

    1

    2

    3

    4

    3

    1

    2

    4

  • 7/27/2019 Radio Frequency Operations

    24/50

    Cochannel Interference

    The RF Engineer considers the following whenplanning cell placement

    1. RF power levels at cochannel cell sites

    2. Geographic distance between cochannel cells

    3. Types of antennas used at cochannel cells

  • 7/27/2019 Radio Frequency Operations

    25/50

  • 7/27/2019 Radio Frequency Operations

    26/50

    Channel Interference

    Other types of Channel Interference are;

    Adjacent Channel Interference the inability of a

    mobile unit to filter signals of adjacent channelsassigned to nearby cells

    Intermodulation Interference or IM IM describes theeffect of several signals mixing together toproduce unwanted signals or no signals.

  • 7/27/2019 Radio Frequency Operations

    27/50

  • 7/27/2019 Radio Frequency Operations

    28/50

    Paired Channels

    All wireless conversations require paired channels tofunction.

    Mobile or portable phones conduct simultaneous two-way transmissions. This is known as Full Duplex.

    One channel is used for transmitting and one channelis used to receive.

    Depending on the technology, the frequency may bethe same or they maybe different.

  • 7/27/2019 Radio Frequency Operations

    29/50

  • 7/27/2019 Radio Frequency Operations

    30/50

  • 7/27/2019 Radio Frequency Operations

    31/50

  • 7/27/2019 Radio Frequency Operations

    32/50

  • 7/27/2019 Radio Frequency Operations

    33/50

    Control Channels

    1. Setup wireless calls, mobile originated or terminated(destined), locating mobile phones to make contactwith them.

    2. Collecting information for billing operations

    3. Collecting traffic measurements on base stations

    4. Autonomous mobile registration, registering thephones on the system (both home and roaming)

    5. Initiating and assisting with call handoff

  • 7/27/2019 Radio Frequency Operations

    34/50

    Control Channels

    Each channel set in a wireless network has a ControlChannel.

    When a mobile unit is powered on it seeks out the

    Control Channel.

    The carrier sets one of its strongest frequencies as theControl Channel when they launch.

    The mobile unit re-tunes to the Control Channelperiodically to maintain a strong connection with theControl Channel.

  • 7/27/2019 Radio Frequency Operations

    35/50

  • 7/27/2019 Radio Frequency Operations

    36/50

  • 7/27/2019 Radio Frequency Operations

    37/50

  • 7/27/2019 Radio Frequency Operations

    38/50

    RF Technologies

    Ultra-Wideband Wireless or UWB UWB is adigital pulse technology designed to transmitlarge amounts of data over a wide spectrumof frequency bands.

    UWB carries large amounts of data in distancesup to 230 feet at very low power levels.

    The digital pulses produced by UWB are timedprecisely over the very wide spectrum at thesame time.

  • 7/27/2019 Radio Frequency Operations

    39/50

  • 7/27/2019 Radio Frequency Operations

    40/50

    RF Technologies

    UWB can also be defined as wireless communicationstechnology that can transmit data at speedsbetween 40 megabits and 60 megabits persecond.

    The two main difference between UWB and othernarrowband or wideband systems;

    1. The bandwidth of UWB is greater than any other current

    technology used for communication2. UWB is typically implemented in a carrierless fashion,

    meaning it is not constricted by the RF allotmentschemes.

  • 7/27/2019 Radio Frequency Operations

    41/50

  • 7/27/2019 Radio Frequency Operations

    42/50

    RF Technologies

    UWB advantages are;

    1. High throughput

    2. Effectiveness in environments with high levels ofmultipath fading

    3. Short range high data rate

    4. Carries a large amount of data with low powerconsumption

    5. Impressive accuracy measuring positions of objectsand people

  • 7/27/2019 Radio Frequency Operations

    43/50

  • 7/27/2019 Radio Frequency Operations

    44/50

  • 7/27/2019 Radio Frequency Operations

    45/50

  • 7/27/2019 Radio Frequency Operations

    46/50

    RF Technologies

    UWB pulse technology has proven effective in theareas of radar and sensor technology. It can beadapted for use in;

    1. Motion Detection

    2. Radar imaging for objects buried underground or behindwalls

    3. Radar imaging in the medical field

    4. 5. 6. Rescue application

  • 7/27/2019 Radio Frequency Operations

    47/50

    RF Technologies

    Current wireless carrier protest the use of UWB basedon that argument that because they transmit onall frequencies, they may cause interference withintheir wireless networks.

    UWB proponents argue because it transmit acrosssuch a wide spectrum and at such low power rates

    it will be impossible for it to interfere with currentwireless networks

  • 7/27/2019 Radio Frequency Operations

    48/50

    RF Technologies

    UWB seeks to replace Bluetooth as a short rangeconnection technology, as well as;

    1.

    Code Division Multiple Access (CDMA)

    2. Global System for Mobile Communication (GSM)

    3.

    General Packet Radio Service (GPRS)

    4. Enhanced Data GSM Environment (EDGE)

    5.

    Wideband-CDMA (W-CDMA)

  • 7/27/2019 Radio Frequency Operations

    49/50

    RF Technologies

    Two other RF technologies are Software DefinedRadio (SDR) and Cognitive Radio (CR).

    Software Defined Radio uses a software package toadminister the all the functions used in wirelesscommunication.

    Everything from RF and channel selection, to handoffand logging is handled independently by thesoftware program.

  • 7/27/2019 Radio Frequency Operations

    50/50