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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.

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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

What are the events 1a, 1b, 1c, etc.?

 e1a – a Primary CPICH enters the reporting range, i.e. add a cell to active set.

 e1b – a primary CPICH leaves the reporting range, i.e. removed a cell from active set.

 e1c – a non-active primary CPICH becomes better than an active primary CPICH, i.e. replace a cell.

 e1d: change of best cell.

 e1e: a Primary CPICH becomes better than an absolute threshold.

 e1f: a Primary CPICH becomes worse than an absolute threshold.

Brief describe the advantages and disadvantages of soft handover?

Advantages:

  Overcome fading through macro diversity.

  Reduced Node B power which in turn decreases interference and increases capacity.

  Reduced UE power (up 4dB), decreasing interference and increasing battery life.

Disadvantages:

  UE using several radio links requires more channelization codes, and more resources on the Iub and Iur interfaces

What are the major differences between GSM and UMTS handover decision?

GSM:

 Time-based mobile measures of RxLev and RxQual – mobile sends measurement report every SACH period (480ms).

 BSC instructs mobile to handover based on these reports.

UMTS:

 Event-triggered reporting – UE sends a measurement report only on certain event “triggers”.

 UE plays more part in the handover decision.

WCDMA Handover

Handover: call transfer one cell to another cell without disconnecting

There are three types of handover used in WCDMA.

1.    Intra frequency Handover (Soft & Softer )

2.    Inter frequency handover

3.    IRAT Handover

Soft Handover:

            WhenHandover between two NodeB within same carrier frequency and add in active set.

Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN. Soft handover is performed by means of macro diversity, which refers to the condition that several radio links are active at the same time.

Softer Handover:

                        When Handover between two cells within same NodeB and ADD in active set.

IRAT Handover:

                        When handover between WCDMA to GSM and GSM to WCDMA.

What are the three sets in handover?

The 3 sets in handover are:

§ Active set – the list of cells which are in soft handover with UE.

§ Monitored set – the list of cells not in active set but RNC has told UE to monitor.

§ Detected set – list of cells detected by the UE but not configured in the neighbor list.

 

4 events associated with soft (or softer) handover: UE view

•           1A  Add

•           1B  Remove

•           1C  Replace

•           1D  Change of best cell

•          1E   A Primary CPICH becomes better than an absolute threshold

•          1F   A Primary CPICH becomes worse than an absolute threshold Intrafrequency reporting events for TDD