this ppt about the basics of microwave communications & new techniques as E-band & Non LOS MW

1. Microwave Basics
• Contents :
• What is transmission ?
• MW advantages & spectrum allocation
• Radio wave propagation
• Free space propagation & Fresnel Zone
• Fading problem & counter measures
• Fade Margin & path loss calculation
• MW Hardware parts & configuration
• MW Techniques
• E-Band MW introduction

2. What is Transmission ?
• Transmission :
• A process where traffic is transferred over a medium
between the source and the destination
• Transmission Media types:
1- wired (optical fiber-copper cables)
2-wireless(microwave)

3. Microwave Radio advantages
• Advantages over optical fiber and copper
cable system
• Rapid deployment in areas where cables are not
feasible (only terminal works)
• low start up & operational coast
• Easier to implement (no disruption to roads)

9. Free space propagation
• Microwave propagation in free space is
governed by the law of optics
• Like any optical wave microwave also
undergoes
– Reflection
– Refraction

10. Free space propagation—Reflections
• Microwaves are reflected over
- smooth surfaces
- water bodies
• Reflected signals are 180 out of phase

12. Free space propagation--Refraction
• Ray pending due to layers of different
densities in the atmosphere

13. Diffraction
• Diffraction will occur when the beam is partially
obstructed, this may be by the ground or a building.
The effect of this is to scatter the energy of the beam.
The degree of scattering increases as the radius of the
obstruction decreases

14. Fresnel Zone
• The Fresnel zone is the area of space between
the two antennas which the radio signal
travels
• For clear Line of sight Fresnel zone should be
clear of obstacles
• It depends on the distance and frequency

15. • there must be sufficient clearance around the line of sight
for the link to perform correctly
• This is known as “0.6 x 1st Fresnel Zone” clearance

17. Fading
• Phenomenon of attenuation of signal due to
Atmospheric & propagation conditions is
called Fading
• Fading Can occur due to
–Reflections
–Refractions
–Atmospheric anomalies

18. Fading
• Fading types are:
– Multipath Fading
– Frequency selective fading
– Rain Fading

19. Multipath Fading
• Multipath fading is caused due to
Reflected/Refracted signals arriving at receiver
• Reflected signals arrive with
– Delay
– Phase shift
Result in degradation of intended signal

20. Frequency selective fading
• Frequency selective fading
– Due to atmospheric anomalies different
frequencies undergo different attenuation levels

21. Rain Fading
• Frequency band>10 GHz are affected due to
rain as droplet size is comparable to
wavelengths
• Rain Fading occur over and above multipath
fading and frequency selective fading
• Horizontal polarization is more prone to rain
fades

23. Interference
• interference is anything which modifies, or
disrupts a signal as it travels along
a channel between a source and a receiver. Or
it is the addition of unwanted signals to a
useful signal
• Interference types:
– Co-channel interference
– Adjacent-channel interference
– Inter symbol interference

24. Anti Fading Technologies
• Automatic power control (ATPC)
– The output power of the transmitter automatically
traces and changes with the received level of the
receiver within the control range
– Effects of ATPC :
oReduces the interference to adjacent systems
ocounteract against severe up fading
oReduces DC power consumption

25. Anti Fading Technologies
• Space diversity
– Using 2 or more suites of antennas at different
altitudes to receive the signals at the same
frequency
Advantages :
- The frequency resources are saved
Disadvantages:
- The equipment is complicated

26. Anti Fading Technologies
• Space diversity
– The separation between the antennas should be
around 200 wave length

27. Anti Fading Technologies
• Frequency diversity
– We use two or more frequencies to reduce the
influence of fading
 Advantages:
- only one antenna is required
 Disadvantages:
- the utilization ratio of frequency bands is low

28. Receiver Sensitivity
• Lowest possible signal which can be detected
by receiver is called receiver sensitivity or
threshold
• Higher (-ve) value indicates better sensitivity

29. Fade Margin
• The amount by which the Received Signal Level
exceeds the Receiver Threshold is known as the
“Fade Margin” and provides protection against
fading.
• Higher fade margin provide better link reliability

30. • The link budget takes into account all the gains and losses (measured in dB) of the
components of the link to arrive a predicted Receive signal Level (RSL), which should
be greater than the receiver threshold level.

31. Path loss
• We can calculate the free space loss from the
following equation

32. MW parts (split mount MW)
• The split mount MW link consists of :
1- indoor unit (IDU)
process the customer traffic ,multiplex/Demultiplex
and modulation/demodulation for services
2- IF cable
transmitting of IF signal , management signal and
power supply for ODU
3- out door unit (ODU)
RF processing , conversion of IF/RF signals
4- antenna
focuses the RF signals transmitted by ODUs and
increase the signal gain

33. MW parts (split mount MW)

34. MW parts
• There are other MW equipment like:
1- Trunk MW equipment (all indoor except he
antenna is out door)
2-All out door MW equipment

35. 1+0, 1+1, 2+0 Deployments
• Microwave ODUs can be deployed in various
configurations.
– The most common is 1+0 which has a single ODU,
generally connected directly to the microwave
antenna. 1+0 means “unprotected”

36. 1+0, 1+1, 2+0 Deployments
• 1+1 in “Hot Standby” is common and typically
has a pair of ODUs (one active, one standby)
connected via a Microwave Coupler to the
antenna.

37. 1+0, 1+1, 2+0 Deployments
• Other resilient configurations are 1+1 SD
(Space Diversity, using separate antennas, one
ODU on each)
• The other non-resilient configuration is 2+0
which has two ODUs connected to a single
antenna via a coupler. The hardware
configuration is identical to 1+1 FD, but the
ODUs carry separate signals to increase the
overall capacity.

38. Adaptive coding and modulation
• The Goal of ACM
– Adaptive Modulation means dynamically varying
the modulation in order to maximize the
throughput under momentary propagation
conditions

39. XPIC – Cross Polarization Interference
Cancellation
• A Microwave Link using XPIC technology capabilities
effectively doubles the potential capacity of a Microwave
Path.
• XPIC allows the assignment of the same frequency to both the
vertical & horizontal Polarization on a Path

40. XPIC – Cross Polarization Interference
Cancellation
• What is Cross Polar Discrimination (XPD)
• The ratio of the signals (desired) on the
desired polarization to the signals (undesired) signals
on the opposite polarization

41. Introduction--Modulation
• Modulation is the variation one or more
properties( Amplitude—Phase– Frequency) of
an RF signal to represent the information
being transmitted
• Modulation types
• Analog Modulation
• Digital Modulation

42. QAM
• Quadrature Amplitude Modulation or QAM s a form
of modulation which is widely used for modulating
data signals on to a carrier used for radio
communication
• QAM is a signal in which two carriers shifted in phase
by 90 are modulated and the resultant output
consists of both amplitude and phase variations
• High level schemes (such as 64-QAM) are very
bandwidth efficient , but more susceptible to noise

43. Non Line of sight MW
• It is used when there is no direct line of sight
for small cell sites (exists on street level)
• It is working in sub-6 GHz band using
orthogonal frequency division multiplexing
(OFDM) technology, for multipath handling

44. Active &Passive repeaters
Passive repeater :
 are a reflective or sometimes refractive panel or other object that
assists in closing a radio or microwave link, in places where an obstacle
in the signal path blocks any direct, line of sight communication
Active repeaters :
It is a relay station used to extend the transmission distance or to
deflect the transmission direction to avoid obstructions after
regenerating & amplifying the received signal

45. Active & Passive repeaters
• Active repeater• Passive repeater

46. E-Band Millimeter Wave Technology
• Millimeter Wave (MMW) is a technology for high speed high capacity
wireless links Using high frequency microwave in the E-Band (70-80GHz)
and 58GHZ to 60GHz (V-Band) spectrum
• Why use E-Band MMW Technology?
– The 71…76 GHz and 81…86 GHz allocations allow 5 GHz of full-duplex
transmission bandwidth; enough to easily transmit a full-duplex
gigabit Ethernet (GbE) signal even with the simplest modulation
schemes

47. Thank you