3G Interview Questions and Answer
Tell Me How Does Soft/softer Handover Work?
- Soft/softer handover down-link: UE rake receiver performs maximum ratio combining, i.e. UE combines multi-path signals and form a stronger signal.
- Soft handover up-link: RNC performs selection combining, i.e. RNC selects the better signal coming from multiple NodeB.
- Softer handover up-link: NodeB performs maximum ratio combining, i.e. NodeB rake receiver combines signals from different paths and forms a stronger signal
·
What Is Pole Capacity?
The
uplink noise increases with the loading exponentially. When the up-link 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.
Explain 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.
·
Rscp Stands For?
RSCP
stands for Received Signal Code Power - the energy per chip in CPICH averaged
over 512 chips.
·
Do You Know How Does Tma Work?
A
TMA reduces system noise, improves up-link 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.
·
Explain Typical Maximum Path Loss?
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.
·
Do You Know What Is A Typical Antenna Gain?
The
antenna gain depends on antenna model; in link budget we use around 17dBi.
·
Tell Me What Is A Typical Nodeb Maximum Output Power?
The
maximum NodeB output power is usually 20W or 40W, that is, 43dBm or 46dBm.
·
What Is A Typical Nodeb Sensitivity Level?
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
·
Explain Several Event In 3g?
- Event 1A:UTRAN will add the new cell in the UE's active cell list and will send an ACTIVE SET UPDATE message.
- Event 1B:UTRAN will send ACTIVE SET UPDATE message to remove the cell from UE's active set.
- Event 1C:UTRAN will send ACTIVE SET UPDATE message that will remove one or more cells and will add one or more cells. The only restriction for 1C is that there should be atleast one radio link that is not affected by the procedure.
·
Tell Me What Is Typical Tma Gain?
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.
·
What Is Soft Handover?
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. Normally soft handover can be used when
cells operated on the same frequency are changed.
·
What Is Hard Handover?
Hard
handover means that all the old radio links in the UE are removed before the
new radio links are established. Hard handover can be seamless or non-seamless.
Seamless hard handover means that the handover is not perceptible to the user.
In practice a handover that requires a change of the carrier frequency
(inter-frequency handover) is always performed as hard handover.
·
What Are The Types Of Hand Over?
- Hard Handover
- Soft Handover
1. A wireless technology for
Motorola
2. It has the capabilities
of digi-cellular phone, 2 way radio, alphanumeric pager and data modem / fax
modem in a single network
3. Operational bands are 800
MHz, 900 MHz and 1.5 GHz
4. iDEN is based on
TDMA(Time Division Multiple Access) and GSM architecture
5. For voice compression it
uses Motorola's Vector Sum Excited Linear Predictors vocoder
6. For delivering 64 KBPS
over a 25 KHz channel, it uses QAM modulation.
7. iDEN is designed to serve
the mobile user for accessing information quickly without carrying several
devices.
·
What Is Hlr (home Location Register)?
1. For GSM and CDMA wireless
networks
2. It's responsibility is to
authenticate and authorize subscribers and their services.
·
Explain Gprs (general Packet Radio Service)?
1. Packet oriented mobile
data service available to the users of 2G cellular systems.
2. It is global system for
communicating through mobile phones using GSM as well as in 3G systems.
3. GPRS data transfer is
charged per MB of traffic transferred, where as in circuit switching, data
transfer is charged per minute of connection time
4. GPRS is better packet
switching service, as opposed to circuit switching.
5. 2G cellular systems are
combined with GPRS and known as 2.5 G.
6. Provides moderate speed
data transfer by using unused TDMA channels, such as GSM.
·
Explain Gsm (global System For Mobile Communications)?
1. Most popular standard for
mobile telephony systems, originated from Group Special Mobile
2. The ubiquity of GSM
enables the international roaming arrangements among mobile phone operators.
3. Both signaling and speech
channels are digital, and thus GSM is considered as 2G mobile phone system.
4. GSM standard benefited
customers the ability to roam and switch carriers without replacing the hand
sets and network operators.
5. GSM implements low-cost
implementation of Short Message Service
·
Can You Please Explain The Difference Between 3g And 2g?
o
Packet
data speed is higher in 3G, and it is up to 384 KBPS
o
Voice
and sms speed is also 384 KBPS in 3G
o
2G
utilizes different switching techniques for voice and data, where as 3G uses
single switching, irrespective of data
o
3G
has at least 2MB of data link of a mobile, where in 2G the data rate is in KBPS
o
3G
has WiMAX facility for faster VOIP and internet
o
2G
uses GSM TDMA technology with narrow band 200 KHz.
o
3G
uses CD-MA technology with broadband 5 MHz, with same frequency carrier and
time.
·
Explain The Disadvantages Of 3g?
o
The
cost of cellular infrastructure , upgrading base stations is very high
o
Needs
different handsets.
o
Roaming
and data/voice work together has not yet been implemented
o
Power
consumption is high
o
Requires
closer base stations and are expensive
o
Spectrum-license
costs, network deployment costs and handset subsidies subscribers are
tremendous.
·
Explain The Advantages Of 3g?
0. Overcrowding is relieved
in existing systems with radio spectrum
1. Bandwidth, security and
reliability are more
2. Provides interoperability
among service providers
3. Availability of fixed and
variable rates
4. Support to devices with
backward compatibility with existing networks
5. Always online devices -
3G uses IP connectivity which is packet based
6. Rich multi media services
are available
·
What Is Evolution-data Optimized?
Evolution-Data
Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and often EV, is
a telecommunications standard for the wireless transmission of data through
radio signals, typically for broadband Internet access. It uses multiplexing
techniques including code division multiple access (CDMA) as well as time
division multiple access (TDMA) to maximize both individual user's throughput
and the overall system throughput. It is standardized by 3rd Generation
Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards.
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