LEVEL II TECHNICAL ANALYSISQOS Department

5 Major RAN Complaint Heads• Coverage Outdoor / Indoor • Congestion • Distortion• Call Drop • GPRS / EDGE

CONGESTION / COVERAGE / DISTORTION ANALYSIS & ACTIONS

Day 02

CONGESTIONIntroduction and Analysis

Traffic is total number of incoming and outgoing CS or PS calls per unit time.

Unit of Traffic is Earlings.

Introduction to Traffic

Congestion• When Traffic increase more than what number of resources can

support then it is called congestion.• Congestion can be Temporary and Permanent both have

different scope of analysis and solution.• Temporary Congestion is sometimes called Soft Congestion• Permanent Congestion is sometimes called Hard Congestion

Soft Congestion• Sudden increase in traffic due to some unseen incident,

hardware failure, fluctuations, outage or any unforeseen circumstances causes congestion that is called soft congestion.

• Soft congestion is temporary so there is no need to perform any expansion or parametric change as it will die down.

• Any emergency situation, match, political marches can cause extra load on our network and cause soft congestion.

Soft Congestion

Hard Congestion• When increase in Traffic becomes permanent and our

existing network is not able to support the Traffic then it is called Hard Congestion.

• All decisions regarding Hard Congestion is taken upon Busy Hour Trend of at least 7 days.

• Hard Congestion can be catered through Network Expansion and Capacity Sites Induction.

Hard Congestion

SDCCH & TCH Blocking• As we already know SDCCH Channel is responsible for

preliminary signaling.• SMS in idle mode are also delivered on SDCCH channel.• However we have limited number of resources so

sometimes we face SDCCH congestion.• Because of SDCCH congestion TCH cannot be allocated

and blocking occurs.• SDCCH blocking can be catered either by adding static or

dynamic SDCCH or through other methods.

SDCCH Blocking

TCH Blocking• TCH Blocking is different from SDCCH Blocking. TCH

blocking is actually called CALL BLOCK.• TCH Blocking can be from variety of reasons such as

Hard Blocking, Soft Blocking and Low TCH availability.• Apart from Hard Blocking none other types are in domain

of RAN.

Statistical Analysis• Step 1

• Extraction of stats from INSPUR.

• Step 2• Identification of the problem.

• Step 3• Suggest appropriate action.

Network Limitations• In Hard Congestion we can propose network expansion

but we have limitations such as on one cell only S_444 configuration is currently being used.

• On half rate, one TRx can carry 9E traffic at most theoretically. This means one cell is able to carry 36E of traffic at Half rate during BH.

• If a cell is carrying more than 36E traffic during BH and has congestion trend (more than 2%) for at least 1 week than expansion is not possible. For this we need a new capacity site.

Capacity Sites• Capacity sites are planned especially for congestion.• The criteria of capacity site is that site is at maximum

configuration.• When no further Hardware Expansion can be performed

than we plan new site called Capacity Sites

Case Studies

Case A

Customer is facing Congestion from yesterday.

Case B

Customer is facing Congestion from last one week

Case C

Customer is facing congestion from last one year

Case D

Customer is facing congestion indoor but not outdoor

Case E

Customer is facing congestion indoor but only in some parts of house

COVERAGE INDOOR / OUTDOORIntroduction and Analysis

Radiation Pattern• Radiation Pattern is the pattern of Antenna’s Radiations• Horn Antennas have directional Radiation Pattern and

High Antenna Gain• Gain of Horn Antenna often increases and Beam Width

decreases as the frequency of operation increases• GSM Antennas are Horn Antennas

Radiation Pattern of Horn Antenna

Theoretical Pattern

Types of Fading

• Fast Fading Fast fading occurs if the channel impulse response changes rapidly within the symbol duration. Fast fading occurs when the coherence time of the channel TD is smaller than the symbol period of the

transmitted signal

Fast Fading is due to reflections of local objects and the motion of the objects relative to those objects.

• Slow Fading Slow fading is the result of shadowing by buildings, mountains, hills, and other objects. Slow fading arises when the coherence time of the channel is large relative to the delay constraint of the channel The average within individual small areas also varies from one small area to the next in an apparently random manner .

Signal Strength

(dB)

Distance

Path Loss

Slow Fading (Long-term fading)

Fast Fading (Short-term fading)

Two independent fading issues

Doppler Effect• When a wave source and a receiver are moving towards each other, the

frequency of the received signal will not be the same as the source.• When they are moving toward each other, the frequency of the received signal is

higher than the source.• When they are opposing each other, the frequency decreases.

Thus, the frequency of the received signal is

where fC is the frequency of source carrier,

fD is the Doppler frequency.• Doppler Shift in frequency:

where v is the moving speed, is the wavelength of carrier.

cosv

fD

DCR fff

MS

Signal

Moving speed v

θ

Null Zone • The area between two main lobes where EM field

intensity is negligible due to slow fading is called null zone.

Shadowing• Shadowing is the effect that the received signal power

fluctuates due to objects obstructing the propagation path between transmitter and receiver. These fluctuations are experienced on local-mean powers, that is, short-term averages to remove fluctuations due to multipath fading.

Tunnel effect• The ability of a particle to pass through a region of finite

extent in which the particle's potential energy is greater than its total energy; this is a quantum-mechanical phenomenon which would be impossible according to classical mechanics. Also known as tunneling. 

Case StudyCASE A

Customer is in service area but has indoor coverage issue.CASE B

Customer is in guaranteed coverage area but has weak outdoor coverage.CASE C

Customer has no service outdoor.CASE D

Customer is far away from operational site.

DistortionA distortion is the alteration of the original shape (or other characteristic) of an object, image, sound, waveform or other form of signal

DISTORTIONIntroduction and Analysis

Power ControlRF power control is a process of adjusting the power level of a mobile radio as it moves closer and further away from a base station. RF power control is typically accomplished by the sensing of the received signal strength level and the relaying of power control messages from a transmitter to the mobile device with commands that are used to increase or decrease the mobile device's output power level. GSM RF power adjustments occur in 2 dB steps.

Power Control & Distortion• Distortion may occur due to power control as we have limited band so if mobile

or BTS transmits at full power it may become interferer for some other cell.• Distortion can also occur due to low battery of mobile station because with low

battery mobile may or may not transmit at full power as required.

Case StudyCASE A

Customer located near a frequency jammer.CASE B

Customer is located in congested area.CASE C

Customer’s mobile battery is unstable.

Thank You