What are the possible causes for a Drop Call on a UMTS network?

What are the possible causes for a Drop Call on a UMTS network?

             Poor Coverage (DL / UL)

 Pilot Pollution / Pilot Spillover

 Missing Neighbor

 SC Collisions

 Delayed Handovers

 No resource availability (Congestion) for Hand in

 Loss of Synchronization

 Fast Fading

 Delayed IRAT Triggers

 Hardware Issues

 External Interference

What are the possible causes for an Access Failure in UMTS?

What are the possible causes for an Access Failure in UMTS?      

·         Missing Neighbors

·         Poor Coverage

·         Pilot Pollution / Spillover

·         Poor Cell Reselection

·         Core Network Issues

·         Non – availability of resources. Admission Control denies

·         Hardware Issues

• Improper RACH Parameters
• External Interference

What are the processing gains for CS and PS services

What are the processing gains for CS and PS services?

CS12.2:    25dB

PS-64:      18dB

PS-128:    15dB

PS-384:    10dB

HSDPA:     2dB

3G Basic Parameter

Basic Parameters of WCDMA

Frequency Band                                     :           2100 MHz

1920-1980MHz (UL) &2110-2170 MHz (DL)

Duplex Space                                         :           190 MHz

Channel bandwidth                                 :           5 MHz

Coding Spacing                                      :           200 KHz (RASTER)

UARFCN Range                                       :           10562-10838 (Total ARFCN – 276)

Duplex mode                                          :           FDD and TDD

Downlink RF channel structure                 :           Direct spread

Chip rate& Chips                                    :           3.84 Mcps& It is pulse of spreading spectrum n 

                                                                        It’s in rectangular shape of +1 & -1

Frame length                                         :           10 ms (38400 chips) = 15Slots, & 1slot = 2650chips

Superframe                                           :           A Superframe has a duration of 720ms and consists

                                                                        Of 72 radio frames. The super frame boundaries are

Defined by the System Frame Number (SFN)

Spreading modulation                             :           Balanced QPSK (downlink)

Dual-channel QPSK (uplink)

Complex spreading circuit

Data modulation                                   :           QPSK (downlink) & BPSK (uplink)

Channel coding                                     :           Convolution (Voice) and turbo (data) codes

Coherent detection                               :           User dedicated time multiplexed pilot (DL and UL), 

Common pilot in the downlink

Channel multiplexing in downlink            :           Data and control channels time multiplexed

Channel multiplexing in uplink                :           Control and pilot channel time multiplexed

I&Q multiplexing for data and control channel

Spreading factors                                  :           4–256 (uplink), 4–512 (uplink)

Power control                                        :           Open and fast closed loop (1.6 kHz)

Power control period                              :           1500Hz

Power control step size                          :           0.5, 1, 1.5 and 2db

Power control range

Handover                                              :           Soft HO, softer HO, Inter frequency and IRAT HO

About Us

About Us  Telecomstudy18

Hello Guys, Thanks for landing on “About Page” at Telecomstudy18

Telecomstudy18 was launched on 14-Febuarary- 2013 with a dream to provide every possible guides and tutorials related to Fresher and Experience Telecom. The main goal of starting this blog is to build an active community of Telecom Engineer so that they can learn every aspect of technology GSM, WCDMA and LTE in a better way.

Telecomstudy18 constantly tries to bring quality tutorials for Telecom domain Engineer  to help them make their knowledge  more better gradually. Our unique and detailed posts will surely help you to be an independent successful.

Tutorials to make a successful improve telecom domain skill  :)

This blog mainly focus on below categories:

GSM

WCDMA

CDMA

LTE 

SIR, Ec/Io, RTWP, RSCP, and Eb/No in WCDMA

What is SIR?

SIR is the Signal-to-Interference Ratio – the ratio of the energy in dedicated physical control channel bits to the power density of interference and noise after dispreading.

What is RSCP?

RSCP stands for Received Signal Code Power – the energy per chip in CPICH averaged over 512 chips.

What is Eb/No?

By definition Eb/No is energy bit over noise density, i.e. is the ratio of the energy per information bit to the power spectral density (of interference and noise) after dispreading.

Eb/No = Processing Gain + SIR

For example, if Eb/No is 5dB and processing gain is 25dB then the SIR should be -20dB or better.

What are the Eb/No targets in your design?

The Eb/No targets are dependent on the service:

 on the uplink, typically CS is 5 to 6dB and PS is 3 to 4dB – PS is about 2dB lower.

 on the downlink, typically CS has 6 to 7dB and PS is 5 to 6dB – PS is about 1dB lower.

Why is Eb/No requirement lower for PS than for CS?

PS has a better error correction capability and can utilize retransmission, therefore it can afford to a lower Eb/No.  CS is real-time and cannot tolerate delay so it needs a higher Eb/No to maintain a stronger RF link.

What is Ec/Io?

Ec/Io is the ratio of the energy per chip in CPICH to the total received power density (including CPICH itself).

Sometimes we say Ec/Io and sometimes we say Ec/No, are they different?

Io = own cell interference + surrounding cell interference + noise density

No = surrounding cell interference + noise density

That is, Io is the total received power density including CPICH of its own cell, No is the total received power density excluding CPICH of its own cell.  Technically Ec/Io should be the correct measurement but, due to equipment capability, Ec/No is actually measured.  In UMTS, Ec/No and Ec/Io are often used interchangeably.

What is RTWP? What is the significance of it?    

 Received Total Wide-band Power

         It gives the Total Uplink Power (Interference) level received at NodeB

WCDMA Handover Parameter

Handover Parameter

maxActiveSet: Maximum number of cells allowed in the Active Set.

IndividualOffset:

Offset value which can be assigned to each cell. It is added to the measurement quantity before the UE evaluates whether or not an event has occurred. It can either be positive or negative value.

measQuantity1:

Defines the measurement quantity for intra-frequency reporting evaluation. Default is Ec/No.

hsQualityEstimate:

Indicates whether Ec/No or RSCP should be used for indicating "best cell" for HS-DSCH Cell Change. Default is RSCP.

reportingRange1a:

Relative threshold referred to the CPICH of the best cell in the Active Set used as evaluation criteria for event 1a (a primary CPICH enters the reporting range).

reportingRange1b:

Relative threshold referred to CPICH of the best cell in the Active Set used as evaluation criteria for event 1b (a primary CPICH leaves the reporting range).

reportingInterval1a:

Time between periodic reports at event-triggered periodic reporting for event 1a

timeToTrigger1a:

If event 1a condition is fulfilled during at least a time greater than or equal to timeToTrigger1a milliseconds, then event 1a occurs.

timeToTrigger2dEcno:

If event 2d condition is fulfilled during at least a time greater than or equal to timeToTrigger2dEcno milliseconds, then event 2d occurs