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. -

Ans:-Fade Margin is an expression for how much margin - in dB - there is between the received signal strength level and the

receiver sensitivity of the radio.

The figure below describes the term fade margin. Site A is transmitting with 33dBm (2W) power. After the distance to the

site B, the signal level has dropped to -100dBm. This gives a margin of -10 dBm since the receiver sensitivity of the radio at

site b is -110 dBm.

In very noisy environments, the level of the noise floor can be higher than the receiver sensitivity. (For example greaterthan -110 dBm in the above example). In this case, it does not help to increase the receiver sensitivity or using a higher gain

receiving antenna. The only solution if the source of the noise can not be eliminated is then to increase the power of the

transmission so that signal strength at the receiving radio is higher than the noise. However, in some cases, moving the

. -

Ans:-In wireless communications, fadingis deviation of the attenuation that a carrier-modulated telecommunication signal

experiences over certain propagation media. The fading may vary with time, geographical position and/or radio frequency,

and is often modelled as a random process. A fading channelis a communication channel that experiences fading. In

wireless systems, fading may either be due to multipath propagation, referred to as multipath induced fading, or due to

shadowing from obstacles affecting the wave propagation, sometimes referred to as shadow fading. Strong destructive

interference is frequently referred to as a deep fade and may result in temporary failure of communication due to a severe

drop in the channel signal-to-noise ratio.

The terms slow and fast fading refer to the rate at which the magnitude and phase change imposed by the channel on the

signal changes. The coherence time is a measure of the minimum time required for the magnitude change of the channel to

become uncorrelated from its previous value.

Slow fading:-It arises when the coherence time of the channel is large relative to the delay constraint of the channel. In

this regime, the amplitude and phase change imposed by the channel can be considered roughly constant over the period of

use. Slow fading can be caused by events such as shadowing, where a large obstruction such as a hill or large building

obscures the main signal path between the transmitter and the receiver. The amplitude change caused by shadowing is

often modeled using a log-normal distribution with a standard deviation according to the log-distance path loss model.

Fast fading:- Itoccurs when the coherence time of the channel is small relative to the delay constraint of the channel. In

In flat fading, the coherence bandwidth of the channel is larger than the bandwidth of the signal. Therefore, all frequency

components of the signal will experience the same magnitude of fading.

In frequency-selective fading, the coherence bandwidth of the channel is smaller than the bandwidth of the signal.

Different frequency components of the signal therefore experience decorrelated fading.

Ans:- 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.

. :- y ere s an ver ga n

Ans:- Handover gain- Soft or Hard gives a gain against slow fading by reducing the required fade margin. This is because slow

fading is partly uncorrelated between base stations, and by making an handover a mobile can select a better base station.

Soft handover gives an additional macro diversity gain against fast fading by reducing the required Eb/No relative to a single

radio link due to the effect of macro diversity combining. Soft handover gain is assumed to between 2db to 3db.

In Brief Soft handover gain comes from the following:

Macro diversity gain over slow fading.

Micro diversity gain over fast fading.

Downlink load sharing over multiple RF links. By maintaining multiple links each link could transmit at a lower power,

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. :- ow oes o o er an o wor

Ans:-Soft/softer handover downlink: UE rake receiver performs maximum ratio combining, i.e. UE combines multi-path

signals and form a stronger signal.

Soft handover uplink: RNC performs selection combining, i.e. RNC selects the better signal coming from multiple NodeB.

. -

Ans:-As the subscriber load increases, additional interference is generated from both inside and outside of a cell. With

increased interference,the coverage area shrinks and some calls are dropped.The expansion/contraction of the coverage

area is a phenomenon

known as cell breathing.

We introduce an interference degradation margin into the linkbudget to eliminate cell breathing.

To account for the maximum interference degradation, we reduce the maximum allowable path loss by an interference

margin. To increase the loading larger Interference Margin needed in Reverse link and coverage area reduced.(Exp: For

coverage limited cases smaller interference margin suggested and for Capacity limited cases larger Interference margin

should use. Typical value for coverage limited cases 1db t0 3 db correspond to 20-50% Loading.

Interference Margin = Process Gain - (Required SNR + System Losses)

Required Signal to Noise Ration is typically about 5 dB

Q.7:- What is Pole Capacity of CDMA Reverse Link?

It is convenient to rewrite the capacity equation in terms of a dimensionless load parameter. Start from the reverse link

capacity equation

Eb/(No+Io)=(W/R)/[(NoW/Ps)+F.v.(N-1)]

Eb/(No+Io)=SNR set point

W/R=Processing Gain=21.1 db(9.6 kbps) or 19.3 db(14.4 Kbps)

Frequency Reuse factor(F)=Total Interference Power/Own-Cell Interference Power=1.6

v=Voice activity factor=0.5

N=Number of active users in this cell and sector.

The pole capacity is the loading which is the solution to this equation when the user station power approaches infinity.

Npole =(W/R)/[Eb/(No+Io)Target x (F) x (v)]

The pole capacity for Eb/N0 = 6 dB and the 9.6 kbps rate set, other parameters as above, is about Npole = 40.

The relationship between loading and power takes a particularly simple form if we make the substitutions

Dimensionless power Z=(NoW+NPsFv)/NoW

and Dimensionless load L=N/Npole

The capacity equation, in terms of these dimensionless parameters, becomes

Z=1/(1-L)

There are two important observations from these equations:

1. The pole capacity depends only on the target Eb/N0, the processing gain, the voice activity factor and the effective

frequency reuse F. It does not depend on the receiver noise figure.

2. The receiver noise figure sets the sensitivity of the receiver, and hence the spatial scale of the system. It does not affect

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Q.8:- What is Pole Capacity Of WCDMA ?

Ans:- The uplink noise increases with the loading exponentially. When the uplink noise approaches infinity then no more

users can be added to a cell and the cell loading is close to 100% and has reached its pole capacity.

Mathematically, to calculate the uplink pole capacity we need to know:

Pole Capacity = (W/R) / [(1+f) * AF * 10^(EbNo/10)] = 120.6W: chip rate (for UMTS 3,840,000 chips per second)

R: user data rate (assuming 12,200 kbps for CS-12.2k)

f: other-cell to in-cell interference ratio (assuming 65%)

EbNo: Eb/No requirement (assuming 5dB)

AF: Activity factor (assuming 50%)

To calculate the downlink pole capacity we also need to know:

Pole Capacity = (W/R) / ((1- +f) * 10^(EbNo/10)) = 64.06

: downlink channels orthogonality factor (assuming 55%)

Typical pole capacity for CS-12.2, PS-64, PS-128 with same assumptions as above:

CS-12.2k: 120.6 (UL) & 64.1 (DL).

PS-64k: 34.8 (UL) & 12.8 (DL).

PS-128k: 16.2 (UL) & 8.4 (DL).

PS-384k: 16.2 (UL) & 2.8 (DL).

PS-384k has only 128k on the uplink, therefore the uplink capacity is the same for both.

Q.9:- What is Radio Bearer Setup ?

Ans:-Radio Bearer Setup is always initiated by network.It involves radio resources.If UE requires with particular conf. RB it

should send through RRC.

There are 4 ways.

1) Radio Bearer setup with dedicated channel activation - A straight forward procedure

-> UTRAN RRC configures Physical Layers in Both RNC and NodeB

-> After the above RB Setup msg send to UE

-> Once UE receives the above message, it configures its RRC with receied parameters and try to do L1 Synchronization (ULand DL)

-> UE sends Radio Bearer Setup Complete to UTRAN

2) Radio Bearer Setup with unsynchronized channel modification

-> This is like modify current physical channel to meet new bearer requirements.

-> Unsynchronized implies: Both old and new RBs can co-exists. Such that UTRAN can use one and UE can use another

-> But while modifying L1 similary through Comm.Phy.RL.Modify.Req, if any error occurs this will be acknowledged to RRC as

error as Negative.

3) Radio Bearer Setup with Synchronized Channel Modification:

-> This is when physical channels can't be reconfigured as per the need

-> So the old and new RBs can't co-exists and only new RB only exists.

-> Before modifying RRC queries NodeB whether Node B Supports this configuration

-> While Modifying after if no error from Nodeb:

RRC includes activation time in RB Setup message and signal to UE. UE intern informs the same to lower layers. At activation

time all entitles starts with new configuration. At end UE responds with RB Setup Complete to Network.

4) Radio Bearer Setup without dedicated channel

-> Here new bearer does not need a permanent DCH

-> So this does not involve an h sical channel modifications. But ust RLC and MAC confi uration.

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Q.10:- What are modulation Techniques used in UMTS ?

Ans:- UMTS Modulation Technique:-Uplink vs. Downlink

Downlink uses QPSK

Uplink uses Dual BPSK

Q.11:- What is Maximum O/P Power of Node B & UE in UMTS ?

Ans:- 1.The maximum NodeB output power is usually 20W or 40W, that is, 43dBm or 46dBm.

2.Maximum UE Transmit Power limit is 21dBm.

Q.12:- What is sensitivity of Node B & UE in UMTS ?

Ans:- 1.The service and load determines the NodeB sensitivity; in general, in a no-load condition, the sensitivity is between -

115dBm to -125dBm. For Ericsson, the NodeB sensitivity level is calculated at around:

CS12.2: -124 dBm

PS-64: -119 dBm

PS-128: -115 dBm

PS-384: -115 dBm

2.The service and load determines the UE sensitivity; in general, in no-load condition, the sensitivity is between -105dBm

and -120dBm. For Ericsson, the UE sensitivity level is calculated at around:

CS12.2: -119 dBm

PS-64: -112 dBm

PS-128: -110 dBm

PS-384: -105 dBm

HSDPA: -95 dBm

Ans:- The maximum path loss is dependent on the service and vendor recommendations; typically it is in between 135 to

140dB for urban areas and between 150 to 160dB for rural areas.

Ans:-A TMA reduces system noise, improves uplink sensitivity and leads to longer UE battery life.

Sensitivity is the minimum input power needed to get a suitable signal-to-noise ratio (SNR) at the output of the receiver. It

is determined by receiver noise figure, thermo noise power and required SNR. Thermo noise power is determined by

bandwidth and temperature, SNR is determined by modulation technique, therefore the only variable is noise figure.

The cascading noise figure can be calculated by Friis equation (Herald Friis):

NFt = NF1 + (NF2-1)/G1 + (NF3-1)/(G1*G2) + ... + (NFi-1)/(G1*G2*...*Gi)As the equation shows, the first block imposes the minimum and the most prominent noise figure on the system, and the

following blocks imposes less and less impact to the system provided the gains are positive. Linear passive devices have

noise figure equal to their loss. A TMA typically has a gain of 12dB.

There are typically top jumper, main feeder and a bottom jumper between antenna and BTS. A TMA placed near antenna

with a short jumper from antenna provides the best noise figure improvement the noise figure will be restricted to the top

jumper loss (NF1) and TMA ((NF2-1)/G1), and the remaining blocks (main feeder and bottom jumper) have little effect.

. :- a s ga n o a va age an sa va age o

Ans:- 1.TMA typically has a 12 dB gain; however, the effective gain comes from noise figure reduction and the gain is close

or equivalent to the feeder loss

2.On the upside, a TMA reduces system noise, improves uplink sensitivity and leads to longer UE battery life. On the

downside TMA im oses an additional insertion loss t icall 0.5dB on the downlink and increases site installation andQ.16:-Describe fast & slow fading and their margin in short ?

Ans:-Fast fadingis also called multi-path fading, as a result of multi-path propagation. When multi-path signals arriving at a

UE, the constructive and destructive phases create a variation in signal strength.

Slow fading is also called shadowing. When a UE moves away from a cell the signal strength drops down slowly.

To factor in the fast fading and slow fading, we need to have a margin in the link budget and they are called fast fading

margin and slow fading margin.In link budget, the fast fading margin is usually set to 2-3; slow fading margin is set to 7-10.

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Q.17:- What is Processing Gain?

Ans:- Processing gain is the Ratio of Chip Rate over Data Bit Rate, usually represented in decibel (dB) scale. For example,

with 3.84MHz chip rate and 12.2k data rate, the processing gain is:

PG12.2k = 10 * log (3,840,000 / 12,200) = 25dB

Service Type

CS12.2: 25dB

PS-64: 18dB

PS-128: 15dB

PS-384: 10dB

HSDPA: 2dB. -

Ans:-A Pseudo-random Noise (PN) sequence is a sequence of binary numbers, e.g. 1, which appears to be random; but is in

fact perfectly deterministic. The sequence appears to be random in the sense that the binary values and groups or runs of

the same binary value occur in the sequence in the same proportion they would if the sequence were being generated based

on a fair "coin tossing" experiment. In the experiment, each head could result in one binary value and a tail the other value.

The PN sequence appears to have been generated from such an experiment. A software or hardware device designed to

produce a PN sequence is called a PN generator.IS-95 uses two PN generators to spread the signal power uniformly over the

physical bandwidth of about 1.25 MHz. The PN spreading on the reverse link also provides near-orthogonality of and; hence,

minimal interference between, signals from each mobile. This allows universal reuse of the band of frequencies available,

. :- at s p ate, t ate, ym o ate

Ans:- Chip:-In digital communications, a chip is a pulse of a direct-sequence spread spectrum (DSSS) code, such as a pseudo-

noise code sequence used in direct-sequence code division multiple access (CDMA) channel access techniques.

In a binary direct-sequence system, each chip is typically a rectangular pulse of +1 or 1 amplitude, which is multiplied by a

data sequence (similarly +1 or 1 representing the message bits) and by a carrier waveform to make the transmitted

signal.The chips are therefore just the bit sequence out of the code generator; they are called chips to avoid confusing them

with message bits.

Chip Rate:- The chip rate of a code is the number of pulses per second (chips per second) at which the code is transmitted

(or received). The chip rate is larger than the symbol rate, meaning that one symbol is represented by multiple chips.

Symbol Rate :-In digital communications a symbol is a waveform, a state or significant condition of the communication

channel that persists for a fixed period of time. Each symbol can represent or convey one or several bits of data.

Symbol rate (also known as baud or modulation rate) is the number of symbol changes (waveform changes or signalling

events) made to the transmission medium per second using a digitally modulated signal or a line code. The Symbol rate is

measured in baud (Bd) or symbols/second.

If N bits are conveyed per symbol, and the gross bit rate is R, inclusive of channel coding overhead, the symbol rate can be

calculated as:

fs= (R/N)x(FEC)The Forward Error Correction (FEC)is usually expressed as a fraction, i.e., 1/2, 3/4, etc. In the case of 3/4 FEC, for every

3 bits of data, you are sending out 4 bits, one of which is for error correction.

For example,M=2^N (M different Voltage leves's & N= no of bit use for modulation),For example, in a QPSK,16QAM,64QAM

modem, M=64 & N=6,M=16 & N=4,M=4 & N=2 respectivily.

Gross Bit Rate:-In digital communication systems, the gross bitrate or uncoded transmission rate is the total number of

h sicall transferred bits er second over a communication link includin useful data as well as rotocol overhead.

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. -

Ans:- Spreading Factor (SF):-The chip rate is larger than the symbol rate, meaning that one symbol is represented by

multiple chips. The ratio is known as the spreading factor (SF) or processing gain: SF=Chip Rate/Symbol Rate

Orthogonal variable spreading factor (OVSF)is an implementation of Wideband Code division multiple access (WCDMA)

where before each signal is transmitted, the signal is spread over a wide spectrum range through the use of a user's code.

User's codes are carefully chosen to be mutually orthogonal to each other.

These codes are derived from an OVSF code tree, and each user is given a different, unique code. An OVSF code tree is a

complete binary tree that reflects the construction of Hadamard matrices.

WCDMA has 3.84 Mcps (chip per second).

One 10-ms radio frame is divided into 15 slots.1000 ms has 3.84 10^6 chips so 10 ms has 3.84 10^4 chips.15 slots have 3.84

10^4 chips so 1 slot has 38400/15 = 2560 chips

Downlink spreading factor from 4 to 256

Uplink spreading factor from 4 to 512

With spreading factor 4,

1 slot has 2560/4 = 640 symbols

15 slot has 640 * 15 = 9600 symbols

10 ms has 9600 symbols

1000 ms has 9600 * 100 = 960K symbols

In QPSK, 1 symbol has 2 bits.

Thus, the answer is 1.92MbpsNote that this is only for one channel (i.e., code)! One user may have several channels simultaneously.

Q.21:- Why smaller Spreading Factor can achieve higher data rate ?

Ans:-First, think about the definition of spreading factor (SF): the number of chips for each symbol.

Second, remember that a chip duration is fixed.

Third, what is symbol? Each symbol can represent some amount of bits. e.g., QPSK, each symbol represents 2 bits.

SF: 2 SF vs. 512 SF

Time: 2*delta vs. 512*delta

Data: 1 symbol vs. 1 symbol

where delta is chip duration.

With 2 SF, you are sending symbol fast (my wife cooks very fast, so she can make lots of food)

With 512 SF, you are sending symbol slow (I cook very slow, so I can can make less amount of food than my wife)

Q.22:- What is Orthogonal Variable Spreading Factor OVSF code tree ?

Ans:-

Q.23:- How to calculate maximum user in a cell in UMTS ?

Ans:- To calculate the maximum number of users (M) on a cell, we need to know:

W: chip rate (for UMTS 3,840,000 chips per second)

EbNo: Eb/No requirement (assuming 3dB for CS-12.2k)

i: other-cell to in-cell interference ratio (assuming 60%)

R: user data rate (assuming 12,200 kbps for CS-12.2k)

: loading factor (assuming 50%)

Take 12.2kbps as example:

M = W / (EnNo * (1 + i) * R) * = 3,840,000 (3 * (1 + 0.6) * 12,200) * 0.5 = 32.8

The number of users could also be hard-limited by OVSF code space. Take CS12.2k for example:

A CS-12.2k bearer needs 1 SF128 code.

Total available codes for CS-12.2k = 128 2 (1 SF64) 2 (4 SF256) = 124.

Consider soft-handover factor of 1.8 and loading factor of 50%: 124 / 1.8 *.05 = 34 uers/cell.

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Ans:-There are in all 512 Scrambling codes in Downlink, they are divided in 64 groups with each group containing 8 codes.

When UE does the initial access to the cell, it first finds out the correct group out of 64 groups by using Primary and

Secondary sysnchronizations channels, once it finds the correct group then it applies all the 8 PSC of that group to pilot bits

of CPICH to get the correct PSC. Thus the overall process becomes quicker in comparison to applying all the 512 codes to.

Ans:- Channel Used for power control

Uplink: RACH, CPCH in used for open loop power control // Downalink: DPCCH is used for closed loop Power Control.

Need of power control-

1. All the user are operating in same frequency band so signals should be transmitted with the lowest possible power level,

which maintains the required signal quality.

2. To over-come Near-far effect: - The mobile stations far away from the base station should transmit with considerably

higher power than mobiles close to the base station.

3. There are two basic types of power control(a. Open loop power control,b. Closed loop power control).

Open loop power control

1. The open-loop power control technique requires that the transmitting entity measures the channel interference and

adjusts its transmission power accordingly.

2. The problem is that the interference estimation is done on the received signal, and the transmitted signal probably uses a

different frequency.

3. In TDD mode both the uplink and downlink use the same frequency and thus their fading processes are strongly

correlated.

Closed loop power control1. The quality measurements are done on the other end of the connection in the base station, and the results are then sent

back to the mobiles transmitter so that it can adjust its transmission power.

2. This method gives much better results than the open loop method, but it cannot react to quick changes in channel

conditions.

3. In this method the received signal-to interference ratio (SIR) is measured over a 667-microsecond period (i.e., one time

slot), and based on that value, a decision is made about whether to increase or decrease the transmission power in the other

end of the connection.

4. The transmit power control (TPC) bits are sent in every time slot within the uplink and the downlink

Closed loop power control is of two type

A. Inner loop power control (or fast closed-loop power control). B. outer loop power control

Inner loop power control

dBm = 10 * log(W*1000) where W is the power in WattsdB is not a unit, it is the difference in dBm.

.

Ans:- RSSI It is the combination of all signals received on the downlink frequency ( in fdd mode ) of the WCDMA system. As

such it is also refered to as the total noise on the downlink . It is the equivalent of rtwp on the uplink. However RSCP is the

code power of the cpich after dE-coding.

RSSI is Rx level before descrembling. Its just RxLev of UARFCH. CPICH_RSCP is Rx level after descrembling.

CPICH_Ec/No is result of filtering after dechanalization.

Simply we can say RSCP=RSSI+Ec/No.

So Your RSSI will have good value compare to RSCP.More RSSI, less Ec/Io, low throughput, high BLER..

Ans:- Congestion = Time when all resources are occupied (no free TCH available) Blocking = Rejected (blocked) attempts over all attempts in %.

Also there is different formulas for TCH blocking. For example in subscriber perceived TCH Blocking all successful directed

retries to another cell are removed from the nominator.

Blocking gives you the non served calls & Congestion gives the time when no resource are available (it is possible that

nobody needs them so no blocks) there is a possiblity to have high blocking and low congestion - this means that you have a

peak of the attempts.

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.

Ans:-The reason for different source rates on AMR is that the different source codec rates will perform differently in relation

to effective BER; as the gross bitrate is the same for all full rate codecs and half rate codecs respectively. This means that a

higher source rate has less redundancy than a lower source rate; hence the BER on a higher source rate will be worse than a

lower source rate on same C/I level.

So; there is a need to optimize the codec rate versus C/I, as the speech quality of a lower source rate is generally better on

worse C/I than a higher source rate within a certain window. If the C/I is very good, the source rate can be increased and

the audible speech quality is improved related to a lower source rate.

Q.30 What are Major KPI of UMTS ?

Ans:-1)R99

-CS Voice RAB CSSR, %

-CS Video RAB CSSR, %

-PS NRT RAB CSSR, %

-CS Voice DCR, %

-CS Video DCR, %

-PS NRT DCR, %

2)HSDPA

-HDPA Accessibility, %

-HSDPA Retainability, %

3)Inter-System Handover Success Rate

-Inter-System Handover Success Rate for RT, %

-Inter-System Handover Success Rate for NRT, %

4)Soft Handover Success Rate

-Soft Handover Success Rate for RT, %

-Soft Handover Success Rate for NRT, %

*** Radio Access Bearrer(RAB), Real Time(RT), Non Real Time(NRT)

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. n ro u on o ven s n

Ans:-Intra-frequency measurements

Reporting event 1A: A Primary CPICH enters the reporting range, Reporting event 1B: A primary CPICH leaves the reporting range

Reporting event 1C: A non-active primary CPICH becomes better than an active primary CPICH, Reporting event 1D: Change of best cell

Reporting event 1E: A Primary CPICH becomes better than an absolute threshold

Reporting event 1F: A Primary CPICH becomes worse than an absolute threshold Intra-frequency reporting events for TDD, Reporting event

1G: Change of best cell (TDD)

Reporting event 1H: Timeslot ISCP below a certain threshold (TDD)

Reporting event 1I: Timeslot ISCP above a certain threshold (TDD)

Inter-frequency measurements

Event 2a: Change of best frequency.

Event 2b: The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used

frequency is above a certain threshold

Event 2c: The estimated quality of a non-used frequency is above a certain threshold

Event 2d: The estimated quality of the currently used frequency is below a certain threshold

Event 2e: The estimated quality of a non-used frequency is below a certain threshold

Event 2f: The estimated quality of the currently used frequency is above a certain threshold

Inter-RAT measurements

Event 3a: The estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the other

system is above a certain threshold

Event 3b: The estimated quality of other system is below a certain threshold

Event 3c: The estimated quality of other system is above a certain threshold

Event 3d: Change of best cell in other systemUE internal measurements

Reporting event 6A: The UE Tx power becomes larger than an absolute threshold

Reporting event 6B: The UE Tx power becomes less than an absolute threshold

Reporting event 6C: The UE Tx power reaches its minimum value

Reporting event 6D: The UE Tx power reaches its maximum value

Reporting event 6E: The UE RSSI reaches the UE's dynamic receiver range

Reporting event 6F: The UE Rx-Tx time difference for a RL included in the active set becomes larger than an absolute threshold

Reporting event 6G: The UE Rx-Tx time difference for a RL included in the active set becomes less than an absolute threshold

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.

Ans:- Spreading and Scrambling-Spreading term means increasing the signal bandwidth. Spreading is a two step procedure

as mentioned below:

Channelization it is used to increase signal bandwidth using orthogonal codes.

Scrambling it does not affect signal bandwidth and is implemented by using pseudo noise code. (In two different cells it is

allowed to reuse orthogonal codes, hence interference is possible, scrambling codes are used to avoid such interference).

Channelization- Channelization is a performed though Spread Spectrum. Spread-spectrum transmission is a technique in

which the users original signal is transformed into another form that occupies a larger bandwidth than the original signal

would normally need.The ratio between the transmission bandwidth and the original bandwidth is called spreading

factor.The spreading-factor values can be between 4 and 512 for Rel99 and 16 fixed for HSDPA. HSUPA Uses Variable

spreading-factor.

Channelization codes are orthogonal codes, based on Orthogonal Variable Spreading Factor (OVSF) technique.The codes are

fully orthogonal, i.e., they do not interfere with each other, only if the codes are time synchronized thus; channelization

codes can separate the transmissions from a single source.

In the downlink, it can separate different users within one cell/sector.Limited orthogonal codes must be reused in every cell

Benefits of Spreading- 1-Each user has its own spreading code at the cell level. 2-Spreading codes have low cross-correlation with other

spreading codes. 3-Several wideband signals can coexist on the same frequency without severe mutual interference. 4-Multiple access

capability. 5-Protection against multipath interference. 6-Good jamming resistance. 7-Privacy.

Scrambling-In the scrambling process the code sequence is multiplied with a pseudorandom scrambling code. The scrambling

code can be a long code (a Gold code with 10 ms period) or a short code (S(2) code).Typically, each Node B has only one

scrambling code for UEs to separate base stations.Problem: Interference if two cells use the same code or two mobiles in uplink using same code

Solution: In downlink Scrambling codes to reduce inter-base-station interference

In the uplink scrambling codes are used to separate the terminals, it can only separate the physical channels/services of one

user because the mobiles are not synchronized in time.

In brief preading procedure in the UTRAN consists of two separate operations:

1. Channelization:-Channelization uses orthogonal codes. 2. Scrambling:-Scrambling uses PN (Pseudo-Noise) codes.

Downlink:.

Ans:-This procedure takes place when the power is turned on in the UE.

The synchronization procedure starts with downlink SCH synchronization.

The UE knows the SCH primary synchronization code, which is common to all cells.

The slot timing of the cell can be obtained by receiving the primary synchronization channel (P-SCH) and detecting peaks in

the output of a filter that is matched to this universal synchronization code.The slot synchronization takes advantage of the fact that the P-SCH is only sent during the first 256 chips of each slot. The

whole slot is 2,560 chips long.

The UE can determine when a slot starts, but it does not know the slot number yet (there are 15 slots in each frame), and

thus it does not know where the radio frame boundary may be.

Thereafter the UE correlates the received signal from the secondary synchronization channel (S-SCH) with all secondary

synchronization codes (SSC), and identifies the maximum correlation value.

The S-SCH is also only sent during the first 256 chips of every slot.

Each code group identifies eight possible primary scrambling codes, and the correct one is found by correlating each

candidate in turn over the CPICH of that cell.

Once the correct primary scrambling code has been identified, it can be used to decode BCH information from the primary

common control physical channel (P-CCPCH), which is covered with the cells unique primary scrambling code.The primary synchronization code is common to all cells, and it is used to gain slot synchronization from the P-SCH.

The primary scrambling code is unique to a cell; it is gained from the CPICH and used to demodulate common control

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.

Ans:- The PDH (plesiochronous Digital Hierarchy) has 2 primary communication systems as its foundation.

These are,

T1 system based on 1544kbit/s that is recommended by ANSI &

E1 system based on 2048kbit/s that is recommended by ITU-T.

Common Characteristics :-

Both are having Same Sampling Frequency i.e. 8kHz.

In both (E1 & T1) Number of samples/telephone signal = 8000/sec.

In both (E1 & T1) Length of PCM Frame = 1/8000s = 125s.In both (E1 & T1) Number of Bits in each code word = 8.

In both (E1 & T1) Telephone Channel Bit Rate = 8000/s x 8 Bit = 64 kbit/s.

Differing Characteristics :-

In E1 Encoding/Decoding is followed by A-Law while in T1 Encoding/Decoding is followed by -Law.

In E1 - 13 Number of Segments in Characteristics while in T1 - 15Number of Segments in Characteristics.

In E1 - 32 Number of Timeslots / PCM Frame while in T1 - 24 Number of Timeslots / PCM Frame.

In E1 - 8 x 32 = 256 number of bits / PCM Frame while in T1 - 8 x 24 + 1* = 193 number of bits / PCM Frame. (* Signifies an

additional bit).

In E1 - (125s x 8)/256 = approx 3.9s is the length of an 8-bit Timeslot while in T1 - (125s x 8)/193 = approx 5.2s is the

length of an 8-bit Timeslot.

In E1 - 8000/s x 256 bits = 2048kbit/s is the Bit Rate of Time-Division Multiplexed Signal while in T1 - 8000/s x 193 bits =, ,

retransmission will be requested. If the retransmission is also erroneous, another retransmission will be requested.

Using HARQ, an erroneous package will be stored at the receiver and a retransmission will be requested. Even if the

retransmission is faulty, the receiver attempts to combine the two erroneous packages to reproduce the original package.

Hybrid Automatic Repeat Request (HARQ):

In case of ARQ, the receiving system on receipt of data checks the CRC. If the CRC is the same as that received in the

message ACK is sent back to the sender. In case if CRC does not match then NACK is sent back and the packet discarded. In

case of HARQ, this method of CRC checking is improved based on the following two things.

Chase Combining:In this when an error is detected in CRC, NACK is sent back but the packet is not discarded. It is stored. In

case the re-transmitted packet is again erroneous then the previous and current poacket is combined in an attempt to

recover from errors. Each time the packet is resent, the same scheme is applied. Eventually the error will be either resolved

or maximum number of retries is reached. In that case higher layer protocols will deal with the error.

Incremental Redundancy (IR):IR is similar to Chase combining but the redundant information that was not transmitted earlier

is also included to improve the chances of reception without errors or with enough errors removed so as to allow combining

with the previously stored packet and resolve the errors.

Ans:-1)After every TTI the resources can be redistributed among the users. Therefore, the resource usage is more efficient.

2) TTI for HSDPA is 2ms & HSUPA 10ms/2ms(Optional)

3)each UE reports about the channel quality after every TTI by sending the CQI.

4)CQI is sent after the very short period of time of 2 ms, it is possible to effectively perform link adaptation even in rapidly

changing conditions.

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.

Ans:- 1.Low Availability

Action: Check SDCCH Availability. Check if the channels are manual, control or automatic blocked.

2.Increasing Traffic Demand:-The high traffic could be related to an occasional event or due to a long term growth.

Action: Check if short term traffic growth. Make trend comparisons. Check if combined SDCCH is used. Check SDCCH

dimensioning.

3.Bad use of Adaptive configuration of Logical Channels:-By using the Adaptive configuration of logical channels feature, the

basic SDCCH configuration in a cell will be under-dimensioned. If this feature is not used correctly, it will cause SDCCH

congestion.Action: Check if ACSTATE is on. Check parameters related to Adaptive configuration of logical channels

4.Long Mean Holding Time:-If the mean holding time is long, this generates a higher traffic load.

Action: Check SDCCH Mean Holding Time

5.Too Frequent Periodic Registration

Action: Check Random Access Distribution. Check the timer T3212 in the BSC and the parameters

6.BTDM and GTDM in the MSC

Solution: Decrease the periodic registration.

7.Location Area Border Cell:-If the cell is situated on a misplaced Location Area border, this means that unnecessary many

normal LUs are performed.

Action: Check site position and location area border. Check Location Update Performance. Check parameter CRH etc.

8.Extensive SMS Usage:-Extensive SMS usage increases the SDCCH traffic and could cause congestion if badly dimensioned

SDCCH channels.Action: Check SMS activity.

9.Cell Broadcast Used

Action: Check if Cell Broadcast is active. .If active, check if it is used by the operator.

10.IMSI Attach/Detach in Use:-An introduction of IMSI attach/detach will increase the traffic on SDCCH. However, the

benefits are that the paging success rate will increase. The recommendation is to use Attach/Detach.

11.Cell Software File Congestion

Action: a)Check SAE setting. High Ratio of Random Accesses.

Q. What are the main reason for SDCCH Drop ?

Ans:- 1)High intreference of freq.,like co-channel

2)SDCCH time slot faulty

3)Poor TRX DL quality

4)Hardware fault like antenna or duplexer malfunction5)May be feeder cable and connectors are faulty.

6)Site taking calls from a very far distance.

Ans:-Let us consider the case of spreading factor 256.

Remember that each slot has 2560 chips.

2560/256 = 10 symbol can be sent in each slot.

For uplink case, remember that DPDCH and DPCCH are code multiplexed. Here 1 symbol is divided into I and Q component.

Thus, 1 symbol can convey 1 bit for uplink case (with QPSK).

Thus, uplink DPDCH has 10 bit data in a slot with 256 SF.

For downlink case, DPDCH and DPCCH are time multiplexed.

Thus, 1 symbol can still convey 2 bits.

Thus, downlink has 20 bit data in a slot with 256 SF. However, remember that some of bits are allocated to DPCCH control

information.

Q. What is physical layer?

Ans:- The physical layer is taking care of the entire physical layer processing functions across the Uu interface.

Functions include

1. RF processing

2. chip rate processing

3. symbol rate processing

4. transport channel combination

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Q. Layer 2 consists of what protocol entities?

Ans:-Layer 2 comprises of 4 protocol entities.

1. MAC protocol

2. RLC protocol

3. PDCP (packet data convergence protocol)

4. BMC (broadcast and multicast control) protocol

Q. What does MAC protocol do?Ans:-The MAC is responsible for dynamic resource allocation under the control of RRC layer.

Using relative priorities betweeservices, MAC does

1. mapping between logical and the transport channels

2. transport format selection

3. priority handling of data flow

4. UE identification management to facilitate transactions such as random access and the use of downlink common channels

5. data ciphering when RLC is operating in transparent mode

6. traffic volume measurement (monitor the buffer levels for the different RLC instances)

Q. How many instance of MAC ?

Ans:-In UE, there is only one instance of MAC.

In the network, there is a MAC instance for each UE that is active within the RNC.

In some cases, multiple MAC instances for a single UE, e.g., at CRNC and SRNC.Q. How many RLC instances?

Ans:-In general, RLC instance exists per service.

(there are some few exceptions such as speech and signaling where multiple RLC entities per service.)

The configuration or the RLC depend on the specific QoS for the service.

Q. What does RLC do?

Ans:-RLC provides 3 different mode:

1. transparent

2. unacknowledged

3. acknowledged mode

Each mode provides a different set of services to the higher layers.

Some of them are1. segmentation and reassembly

2. concatenation

3. reliable transfering data

4. flow control

5. in-sequence delivery

6. Error correction by ARQ(automatic repeat request)

Q. What does PDCP do?

Ans:-PDCP is defined only for PS domain. It does

1. header compression (HC)

2. support for lossless SRNS relocation

Q.What does BMC do?

Ans:-BMC supports the cell broadcast SMS.

BMC messages are delivered via common physical channel.

Those messages are periodic and the periodicity is indicated at SIB5 and SIB6.

The UE will filter and select BMC messages based on user setting.

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Q. What does RRC protocol do?

Ans:-RRC is the main AS control protocol.

RRC performs

1. establishment, modification and release of RRC conncetions

RRC connections are used to transfer RRC signal messages and be used to transport higher layer NAS protocol messages.

2. establishment, modification and release of RAB (radio access bearer ), user plane data connection.

3. radio mobility functions, etc.

Q.How many RRC instance?

Ans:-In UE, a single RRC instance exists.

In the network, multiple instances of RRC, but one per UE.

The RRC entity in the UE receives its configuration from the RRC entity in the UTRAN.

Q. What is the main difference between idle and connected mode?

Ans:-In Connected mode RRC connection exist.

In idle mode, there is no RRC connection.. _

Ans:-Cell_DCH is One of states in connected mode.

The UE is assigned a dedicated physical channel (DPCH) either in response to the RRC connection request or via some UTRAN

controlled bearer reconfiguration procedure.

If UE releases (or asked to release by the network) dedicated channel, the UE can move to any other states in RRC

connected mode (Cell_FACH, Cell_PCH, URA_PCH).If UE releases the RRC connection, it moves to idle.

UE location in Cell_DCH:- In the Cell_DCH, the UE location is known to

1. cell level by the UTRAN. _

Ans:-Cell_FACH is one of states in RRC connected mode.

The UE is assigned to use common channels.

This state is triggered as either part of RRC connection request or some RB reconfiguration process.

The UE can move to any of other connected states as commanded by the network.

UE location in Cell_FACH:-In the Cell_FACH, the UE location is known to the cell level.

If the UE detects the change in cell identity, it performs a cell update procedure.

The UE is addressed by the C-RNTI(cell radio network temporary identifier) from the RNC that controls the cell which the UE

is in.

. _

Ans:-Cell_PCH is one of states in RRC connected mode.

In Cell_PCH, the UE has no uplink resources. The UE monitors the paging channel using the assigned discontinous reception

(DRX) parameters.

The UE will entern into Cell_FACH

1. when it detects the cell change, it performs cell update in Cell_FACH

2. when it is paged by the UTRAN.

UE location in Cell_PCH:-The UE location is known to the level of the cell in Cell_PCH.

The purpose of this state is to save power (performing DRX like idle mode)

but allow rapid network access to the UE by knowing that only one cell needs to be paged (and no RRC connection setup

Q.What is URA_PCH?

Ans:-URA_PCH is one of states in RRC connected mode.

This is similar to the Cell_PCH except that the location of the UE is known to the URA level.

The URA is the collection of cells.

When the UE detects the change in URA, the UE needs to perform URA updates.

UE location in URA_PCH :-In URA_PCH, the UE location is known to the URA level.

The URA_PCH state is used by UEs that are moving fast.

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Q. Area (LA vs. RA vs. URA) updates in UMTS?

Ans:-LA: location area

RA: routing area

URA: UTRAN routing area

The aboves are the collections of cells.

LA and RA are for CN to track the movement of the UE to facilitate the paging of the mobile when an active radio

connection is not available.

A cell can be in up to eight different URAs.

URA size depends on the UEs velocity. Fasting moving UEs should be in a large URA to make less URA update.

Area identifier:-LAI: Location Area Identifier: PLMN id + LAC(location area code) = 24+16=40 bits

RAI: Routing Area Identifier:LAI + RAC (routing area code) =40+8 = 48 bits

URA: UTRAN Routing Area: URA = 16 bits

UTRAN cell id: UC id= RNC id + cell id = 12+16 = 28 bits

Q. What is IMSI, TMSI, P-TMSI ?

Ans:-The IMSI identifies the subscriber (USIM) within the network.

This is the permanent address stored in HLR.

IMSI =MCC (mobile country code) + MNC (mobile network code) + MSIN (mobile subscriber identification number) 15 bits

MCC + MNC is PLMN id.

TMSI (temporary IMSI) together with LAI uniquely identifies the subscriber.

TMSI is assigned by the network and is 32 bits.

It is used to mask the identity of the subscriber and hide the subscribers true identity (IMSI).

P-TMSI (packet TMSI) is similar to TMSI except that it is for PS domain.

P-TMSI is 32 bit number and used as a temporary id within the PS domain.

Q. What are the types of UTRAN address?

Ans:-There are three types of UTRAN addresses:

1.C-RNTI is allocated by the CRNC when a UE access a new cell.

It is only valid within the cell to which the UE is in.

It is 16 bits and used as the main identity while the UE is in a cell and not using DPCHs.

If the UE leaves the clee, then it needs to use a u-RNTI.

2.S-RNTI is assigned by the SRNC.

It is uniquely identified within the SRNC, It is 20 bits,this id is used by UE, SRNC, DRNC.

3.The U-RNTI is assigned by the SRNC and uniquely identifies the UE within the UTRAN.

It is used when a UE cannot be identified in the UTRAN, e.g.,

first access after a UE did cell change (cell update or URA update) or for UTRAN originated paging.

U-RNTI: RNC id + S-RNTI

32 bits.

Ans:-In Cell_DCH (using DPCHs), UE is addressed explicitly using the physical layer parameters such as the frequency

channelization code, scrambling code etc.

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Q. What are various UMTS address?

Ans:-UMTS address can be classified

1. CN address

- IMSI

-TMSI

-P-TMSI

2. UTRAN address

- S-RNTI

- U-RNTI

- C-RNTI

3. UE ID dedicated channels

Ans:-MIB (Master Information Block) is the main index for system information. It contains scheduling information on SIBs and

up to two scheduling blocks.

Scheduling block 1 and 2 are optional block used to provide scheduling information on SIBs.

a) SIB 1 contains NAS information (CN specific info) as well as information on timers for use in idle or connected mode.

b) SIB 2 contains information on the available URAs. There can be up to eight URAs in a cell.

c) SIB 3 contains information on the cell selection and reselection parameters that the UE need to use in idle mode. If SIB4 is

not present it can be also be used for UEs in connected mode.

d) SIB 4 contains information on the cell selection and reselection parameters that the UE need to use in connected mode. If

SIB3 is not present it can be also be used for UEs in idle mode.e) SIB 5 contains information on the common physical channels in the cell (PICH, AICH, PCCPCH, PRACH, SCCPCH) for a UE in

idle mode. If SIB6 is not present it can also be used for UEs in connected mode.

f) SIB 6 contains information on the common physical channels in the cell (PICH, AICH, PCCPCH, PRACH, SCCPCH) for a UE in

connected mode. If SIB5 is not present it can also be used for UEs in idle mode.

g) SIB 7 contains information on fast changing cell parameters such as the uplink interference levels (used for open loop

power control for the PRACH) and the dynamic persistence value ( also used for PRACH).

h) SIB 8 contains static information for CPCH. Only for FDD.

i) SIB 9 contains dynamic information for CPCH. Only for FDD.

j) SIB 10 contains information relevant to the DRAC procedure.For FDD mode only, sent via FACH and the SCCPCH.

k) SIB 11 contains measurement control information for a UE in idle mode. If SIB 12 is not present it can also be used for UEs

in connected mode.

l) SIB 12 contains measurement control information for a UE in connected mode. If SIB 11 is not present it can also be usedfor UEs in idle mode.

m) SIB 13-13.4 contains information on ANSI-41 parameters used with ANSI-41 core network.

n) SIB 14 contains outer loop power control information applied to dedicated and common physical channels, TDD mode

only.

o) SIB 15-SIB15.4 contains information for UE positioning methods such as GPS or OTDOA.

p) SIB 16 contains information on channel configuration (physical, transport and RB) to be stored in the UE for use during

Ans:- The paging occasion is the SFN of the frame of which the UE must monitor the PICH to see whether a paging message is

being sent to the UE.

For FDD,

paging occasion (SFN) = (IMSI div K) mod (DRX cycle length) + n* DRX cycle length

where n=0, 1, 2, up to a maximu such that SFN is valid (i.e.

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.

Ans:- DRX cycle defines the periodicity of the DRX process.

The longer the DRX cycle, the longer the UE is in a sleep state, but the longer the delay before the UE can respond to a

paging message.

DRX cycle length = 2^k frames for FDD mode, where k is DRX cycle length coefficient.

DRX cycle coefficient is different depending on the state of the UE.

In idle, CN domain has a value for it.

In Cell_PCH, URA_PCH, UTRAN has a value for it.

UTRAN DRX cycle length coefficient: values 3-9: cycle length 80 ms 5.12 sec

CN domain DRX cycle length coefficient: values 6-9: cycle length 640 ms 5.12 sec

Q. UTRAN originated page vs. CN originated page

Ans:-Page can be originated

1. UTRAN or 2. CN

If the UE is in idle mode, then CN will originate the page.

If the UE is in Cell_PCH or URA_PCH, then UTRAN will originate the page..

Ans:- MIB value tag, BCCH modification time

Paging record list: a list of paging record up to 8 records.

For each paging record:

for UTRAN originated: u-RNTI, CN-ORIGINATEDPAGE-CONNECTEDMODE-UE, paging cause, CN domain id, paging record type

[IMSI, TMSI, P-TMSI]for CN originated: paging cause, CN domain id (CS or PS), CN paged UE identities (IMSI, TSMI, P-TMSI + value)

Paging causes: Conversational, streaming, interactive, background, high priority signaling, low priority signaling, cause

Q. What are Various radio and data connections in UMTS?

Ans:- There are Various types of connections that the UE will have with the network:

1. RL

2. RB

3. RAB

4. SRB

5. PDP

6. RRC connection

RL (UE-Node B)RB (UE-Node B-RNC)

RAB (UE-Node B-RNC-SGSN)

PDP context (UE-Node B-RNC-SGSN-GGSN)

Q. What is Radio Link (RL)?

Ans:- 1.RL (Radio Link) represents the physical connection between the UE and Node B.

Each RL is defined by its RF frequency, channelization code and scrambling code.

2.RB (Radio Bearer) is a layer 2 connection between the UE and the RNC. It is used for both control signaling and user data.

RB used for signaling is called an SRB.

3.RAB (Radio Access Bearer) is created to provide user plane data transfer. RAB comprises

a) RB and

b) Connection from the SRNC to the SGSN (Iu bearer).

The RAB is created on reequest from the SGSN with a specific QoS request.For a given UE, there can be multiple RABs per NAS service (speech or PS data service).

4.PDP context is for PS service. It consists of

1. RAB

2. CN bearer (bearer between SGSN and GGSN)

The PDP context is created with a defined QoS that is requested by the UE and granted by the network.

5. RRC connection exists when a UE went through the connection establishment procedure and has been allocated resources

in the UTRAN and a U-RNTI.

With RRC connection, some SRBs are allocated.

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Q. What is the distinct difference between Cell_DCH and other states' measurements?

Ans:-In Cell_DCH, the UE makes measurements and reports them to the UTRAN for action by the UTRAN.

However, in other states, the measurements are not reported to the UTRAN and the UE takes action based on the

measurements. (though Cell_FACH measurement has some common things with Cell_DCH)

Ans:- PI Pag ng n cat on s a s ort n cator t at s transm tte on t e PICH to te t e UE t at t ere s a pag ng message

on an associated paging channel carried by the SCCPCH.

The number of PIs per radio frame (Np) can be 18, 36, 72 or 144.

Once the UE knows paging occasion (SFN), then the UE needs to know which PI to look for in the SFN.The equation is

PI = DRX index mod Np

where

DRX index = IMSI div 8192

If the PI bits are set in the paging occasion (SFN), the UE reads the paging message on the PCH transmitted on the associated

SCCPCH.

Q. What is RAB?

Ans:-RAB (Radio Access Bearer) is created to provide user plane data transfer.

RAB comprises

1. RB and

2. Iu Bearer connection from the SRNC to the SGSN .

The RAB is created on reequest from the SGSN with a specific QoS request.For a given UE, there can be multiple RABs per NAS service (speech or PS data service).

RB (Radio Bearer)

is a layer 2 connection between the UE and the RNC.

It is used for both control signaling and user data.

RB used for signaling is called an SRB.

RB is for both user data and signaling.

Especially for signaling purpose RB, we call it SRB: In the control plane, the signalling information is transfered through the

Signaling Radio Bearer (SRB).

However, RAB consists of Iu bearer and user data RB (not SRB).

Ans:-RRC connection exists when a UE went through the connection establishment procedure and has been allocated

resources in the UTRAN and a U-RNTI.With RRC connection, some SRBs are allocated.

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In general, coherence time is inversely

relatedto Doppler spread, typically expressed as

where Tc is the coherence time, Ds is the

Doppler spread, and k is a constant taking

on values in the range of 0.25 to 0.5.

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CSV Access

Success Rate

(%)

98.67%CSV Call

Drop rate(%)0.63%

CS IRAT HO

successful

rate(%)

97.79%

CS Call

Attempts114927.33

Call

Attempts113535.67

CS IRAT HO

Attempts11272.33

CSD Access

Success Rate

(%)

98.20% CSD CallDrop rate(%)

0.00% SHO SuccRate (%)

99.96%

HSDPA

Access

Success

Rate(%)

98.68%

HSDPA Call

Drop rate

(%)

0.51%SHO

Attempts########

HSDPA

Attempts117915.67

RRC

Establishmen

t Fail Rate

(%)

1.01%

CSV Access

Failure

Rate(%)

CSV Drop

Rate(%)

CSV Quality

(UL) (for 2%

BLER)(%)

CSD Access

Failure

Rate(%)

CSD Drop

Rate(%)

CSD Quality

(UL) (for 1%

BLER)(%)

HSDPA +

HSUPA + PS

Access

Failure

Rate %

HSDPA +HSUPA + PS

Drop

Rate(%)

0.06% 0.35% 99.88% 0.00% 0.00% 99.85% 0.40% 0.51%

BBH KPI

3G Accessibility 3G Retainability 3G Integrity 3G Trafficability

Traffic Voice

(Erlang)2,631.81

NQI-BBH

Traffic Video

(Erlang)14.01

HSDPA

Attempts_D119655.33

HSDPA cell

average

throughput

(Kbps)

836.72

Payload

HSDPA

(GByte)

61.97

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Total Sites 1221

Total RNC 3

Total Clust 41

RNC-1 468

RNC-2 446

RNC-3 290

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1Explain Ec/Io and RSCP; on what channel are they

measured on?

Ec/Io = energy of carrier over all noise. RSCP = Receive Signal Code Power

is the sum of all interference: thermal/bg noise + interferers + own cell a

2 What does channelization codes do and function? Channelization codes are used for spreading and despreading of the signathey know that they have an associated Spreading Factor and are allocate

3 What does the scrambling code do and function?Scrambling Code makes it possible for the UE to distinguish the transmiss

broken up to 64 groups of 8 codes each.

4Explain the concept of Cell Breathing. How is the

accounted for in the link Budget?

o or o e n er erence par o c o an o ncrease as e ra c

BTS needs to use more power to maintain the same Eb/No or Ec/Io. When

edge are usually the first to lose service, hence the service area of a cell

5 Explain the different Handover types in UMTS

o er an over: connec e o more an one ce on e same requen

when Ue moves from one cell in one RNC to a cell in another RNC and the

frequency to another frequency (usually due to traffic layer management

6 What is an active set, monitor set and detected set?

Active Set: the set of cells with which the UE is currently connected/com

the UE has detected and is monitoring and are known to the network, theknown to the network as yet (missing neighbor likely).

7What is the major difference in link budgets between

UMTS and GSM/TDMA?

n you genera y ave a n u ge or eac serv ce vo ce, a a, v

consider the target traffic load you will have and add a noise-rise margin,

(like voice) will show up as uplink limited but other services (like HSDPA,

8In the Link Budget, what is a Shadow Fade Margin for

and what factors does it depend on?

The shadow fade margin is dependent on the target percentage area cove

model's standard deviation if the fast fading effects are removed). The Sh

offered "in the worst case"

9What is the typical maximum active set size and what

needs to be consider when setting this?3 to 4 cells, the larger the active set size the more likely it is that Iub link

10

What is typically the requirements (criteria) for a cell

to be added/removed/replaced to/from/in the active

set?

For addition (Event 1a), candidate cell needs to have an Ec/Io value that

removal (event 1b), cell needs to have Ec/Io lower than T_DROP margin f

the active set by the T_REPLACE and for a specific time hysteresis.

11 What would you define as a pilot polluter?Many definitions: A cell that has a high signal strength at a location but is

because the active set is full.

12How would you find such cells from a planning tool and

from a drive test tool?

, -

candidate for pilot polluters. Looking at cells that have a high noise rise,

strength for the (Active Set Size + 1) best pilot (like the 4th best pilot if A

13What would the call flow be for a Mobile Originated

Call (major RRC messages)?

RRC Connect Request -> RRC Connection Setup -> RRC Setup Complete ->

Bearer Setup Complete -> ALERT -> CONNECT -> CONNECT ACK ->DISCONN

14 What are the general triggers for an iRAT handover? Ec/Io of best cell below a certain threshold (usually around -16 to -18 dB

15What is compressed mode, what is it's function, and

what impact does it have on the network?

ompresse mo e s w en e mo e goes n o a s o e ransm mo e w

The impact is that to maintain the same bitrate, it halves the SF, and the

bitrate of the bearer decreases. If they seem knowledable, ask them if th

16Name the 4 RRC Connected Modes (states) and

describe the characteristics of each.

e - : as een a oca e a e ca e p ys ca c anne n

uplink and downlink.

Cell-FACH: UE listens to RACH channel (DL) and is allocated a FACH chann

17

If a UE is on a data call (CELL-DCH state) and there is

in no activity for awhile what would you expect to see

occur?

UE should go from CELL-DCH to CELL-FACH then if still no activity to eithe

from CELL-DCH straight to CELL-PCH or URA-PCH, that is also possible. Bo

18

In Release '99, how does the network manage the

throughput on the Radio Interface for a

user/connection?

This question is a little harder to ask, so you may need to work it differen

the air interface What you are trying to hear from the candidate is that t

service maximum bit rate.

19What is the typical/most common bitrate that a voice

call uses?

They should say 12.2kbps but may be different if they start talking about

for the radio bearer should be 128

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22Explain Inner and Outer loop power control and who

controls them.

If they start talking about Open and Closed Loop PC, tell them you want I

UE and BTS to compensate for signal variations due to fading or pathloss

the target SIR based on the required BER/BLER for the requested services

23 In what cases is Open Loop Power Control used? 1) Idle to Cell-DCH state, when a connection is setup. When UE goes into

24Explain the concept of a Monte Carlo Simulation for

UMTS Design

s s a s mu a or a ran om y s r u es erm na s users geograp ca

connect or not. The simulator modifies parameters such has UE Tx Power

checking if a connection can be made. In every snapshot the simulator run

25In pre-launch optimization, how are missing neighbors

usually detected?

Usually you use a scanner and compare the best pilots in Ec/Io from the s

nearby cell that appears on the scanner but not on the UE, there is a poss

26 LA UPDATE,CELL UPDATE THRU WHICH CHANNEL RACH

27 OPTIMAL SHO OVERAHEAD LESS THAN 30%

28 HSDPA CHANNELS HS-DSCH CARRIES USER DATA IN DL,SPEED UPTO 21MBPS USING 64 QAM(W

HS-SCCH CARRIES PHY LAYER INFO TO DECODE HS-DSCH,SF=256

HS-DPCCH CARRIES FEEDBACK I.E CQI AND ACK/ANACK TO REQUEST RETRA

29 CQI(CHANNEL QUALITY INDICATOR FEEDBACK MECHANISM TO ESTIMATE TRANSPORT BLOCK SIZE,NO OF PARA

30 SF OF RB IN UL SPEECH 12.2-64,VIDEO CALL 64KBPS-16,384KBPS RAB-4,128 KBPS AND 144

31 SF OF RB IN DL SPEECH 12.2-128,VIDEO CALL 64KBPS-32,384KBPS RAB-8,128 KBPS AND 14

32 ZTE NODE B 192 CE/NODE B UL,DL

34 SC DL-511,UL 2 TO POWER 24-1

35 RADIO RESOURCE MANAGEMENT PC,HO CONTROL,AC,LC,PACKET SCHEDULING

36 SCH,CPICH,AICH CARRY INFO RELEVANT TO PHY LAYER ONLY THEREFORE NOT VISIBLE TO H

37 FRAME STRUCTURE OF TC 10 MS RADIO FRAME,BUT FOR PAGING AND RACH >10 FOR CORRECT RECOG

38 DIFF B/W HSDPA AND HSUPA HSDPA-VARIABLE SF=NO,PC =NO,AM=Y,HARQ=Y,SHO=N,NON SCHEDULED T

HSUPA-VARIABLE SF=Y,PC =Y,AM=N,HARQ=Y,SHO=Y,NON SCHEDULED TRAN

39 TTI TOTAL TIME INTERVAL HSDPA=2MS,HSUPA=10MS OR 2MS

40 PSC PLAN 512 AVAILABLE DO NOT REPEAT IN A RNC

41 SPEED DEPENDS ON NO OF CODES UE/DATA CARD SUPPORTS,RADIO CONDITIONS OF UE(CQI VA

42 IRAT-COMPRESSED MODE HO TO GSM BASED ON COVERAGE OR CAPACITY IS IMPLEMENTED USING CO

43 CS12.2,CS64,PS CS12.2 AND CS64 CIRCUIT SWITCHED,PS PACKET SWITCHED

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N BIEGN SENT

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Q.1 What is fundamental principle of spread spectrum?

Ans:-1. Binary XOR operation allows the original symbol reconstruction.

Do spread:

symbol sequence X (XOR) some code Y => some signal Z

Do despread:

some signal Z (XOR) some code Y => symbol sequence X

Fig(1)2. Lets assume there are 10 users who want to send its data X1, X2, , X10.

Lets assume they have their own codes Y1, Y2, ., Y10.

Lets assume they send data at the same time.

Let Z be all summation of Xi (XOR) Yi .

Im only interested in X1 signal. But, how can I extract X1 from all summed signal Z ?

If Yi are othogonal (i.e., Yi XOR Yj => all zero if i and j are different), then

Z (XOR) Y1 => X1

Fig(2)

This is the fundamental concept of spread spectrum.

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