By this Document ou will able to understand basics of LTE Quickly.

1. LTEMINUTES
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BasicLTEBasicLTEBasicLTEInterviewQuestionsInterviewQuestionsInterviewQuestions
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2. “A blank page is no empty space.
It is brimming with potential...
It is a masterpiece in waiting
-- yours.”

3. LTE in 10 Minutes:
When it comes to technology, there is way too much noise out there
and less actual content which solves the problems of professionals. The
reason I call this cheat sheet as LTE in 10 minutes is: Because when it
comes to learning technical stuff, you can spend your whole career in
understanding a particular technology and still the next project or
assignment you worked on may not require the insights you learned in
the past.
This is where this book comes in handy. You can use it whenever and
wherever you want to brush up your LTE knowledge to know the basics.
The questions I have added in here, are an aggregate of typical
questions asked by the interviewees. These questions have been
collected from various industries which are using LTE technology in
one or the other.
The book will help you to focus so that you can :
Because you have only so
much time in the day while
your freedom and life awaits!!!
Ace up your interviews
Impress your co-workers by showing your knowledge
Get answers to all your technical questions in no time.
Finish up your projects on time.
Impress your teachers
and professors
Get more raises, promotions
and bonuses at work

4. Who's Behind This?
I am Azar Taufique
and I use the skills of training,
sales and persuasion to teach technology.
In the last 5 years, I have taught more than
2500+
technical professional,
engineers and
executives from companies such as
Ericsson,
ATT, Sprint,
Verizon,
MetroPCS,
T-Mobile,
US Cellular etc.
If you find any question related to LTE,
which are not given in here or a question
you will
liked to be answered?
Not a problem,
just send me an email at
azar@techtrained.com
and I will get back to you.
Enjoy the next 10 minutes
of your life while you explore
LTE in 10 minutes.
Yours in
Technology Training,
Azar

5. What are the Bandwidths used for
LTE deployment?
Answer: The definitions of the channel bandwidth and transmission
configuration are the same as for the Base Station. For the UE,
however, it is not the same case. I will discuss about it some other.
The bandwidths used for LTE deployment are 1.4 MHz, 3 MHz,
5 MHz, 10 MHz, 15 MHz and 20 MHz
How Many subcarriers/RBs are there
in 5/10/20 MHz channel ?
Answer:
What is Subcarrier Bandwidth in
LTE?
Answer: One Subcarrier Bandwidth is 15 Khz
in LTE as specified in 3 GPP standard.
Question 1
Question 2
Question 3
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•5MHz
There are 25 Resource Blocks and 300 subcarriers
•10MHz
There are 50 Resource Blocks and 600 subcarriers
•20 MHz
There are 100 Resource Blocks and 1200 subcarriers

6. What Maximum LTE throughput can
be achieved in the field?
Answer: In theory, the maximum throughput, for 20 MHZ bandwidth.
LTE can achieve up to 100.3 Mbps, without MIMO.
In field, for 20 MHz bandwidth, the maximum achievable throughput
is 75 Mbps without MIMO.
Question 4
How many states a UE can have?
Answer: In LTE, UE can be in 2 states. Idle and Connected.
Please note that UE Idle/Connected and RRC Idle/Connected means
the same
Question 5
What is difference between Idle
Connected Mode?
Answer:
IDLE MODE: UE is not actively running any end user specific session.
UE will receive only paging and broadcast related information. From
end user perspective, it is the state when you are not using your phone
i.e., requesting any service, such as browsing, making a phone
call, download etc.
CONNECTED MODE: From end user perspective, it is the mode when
you are busy using your smart phone, making phone calls, downloading
data, receiving active services requests etc.
Question 6
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7. What is difference between HO,
Redirection, Cell Selection /
Re-Selection?
Answer:
i.HO:
When the user moves out of coverage of one cell to another cell. For
smooth operation and to avoid call drop, a handover needs to take
place. HO happens only in case of connected user.
ii.Redirection:
When a particular service and coverage is not available to one cell, the
UE is redirected by the eNodeB to other cells for better coverage
and /or respective service requested. This phenomenon is termed as
Redirection.
iii.Cell Selection:
In Idle mode, when UE is not RRC connected to any particular cell, but it
camps on a cell instead. In idle mode, the procedure / process of
camping on a cell is called cell selection.
iv.Cell Re-selection:
In idle mode, when your smart phone (UE) moves out of coverage of
one cell to another cell. UE has to camp from one camp to another
cell. This process of reselecting a new cell, while UE is already camping
on an existing selected cell is called Cell Re-Selection.
Question 7
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8. What is Difference between MIB
and SIB?
Answer: System information is transmitted via Broadcast channel.
System information comes in two parts
1. Static 2. Dynamic
1.Static System information is called Master Information Block (MIB).
MIB carries information like number of antennas, bandwidth etc. It is
fixed, therefore called as Static and is sent every 40 msec.
2.Dynamic information comes as System Information Blocks (SIBs).
There are a number of SIBs for different purposes.
Question 8
Handover types in LTE?
Answer: In LTE, there are two mainly two types of handovers. Intra
LTE and Inter LTE.
These two types can be further classified into the following:
•Intra LTE
Intra eNodeB
Inter eNodeB
Inter MME
Intra MME
Inter SGW
Intra SGW
Intra Frequency
Inter Frequency
•Inter LTE
Handover to WCDMA
Handover to GERAN
Handover to CDMA
Question 9
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9. What is difference between X2 and
S1 HO?
Answer:
In this handover, the signaling associated with1) X2 Handover:
preparation phase of handover is done via X2 interface.
In this handover, the signaling associated with2) S1 Handover:
preparation phase of handover is done via S1 interface.
Explain Events measurements
in LTE?
Answer: UE can perform measurements either by reading RSRP or
RSRQ. The preference either UE should do measurement on RSRP or
RSRQ can be configured accordingly.
In LTE, UE is expected to do measurement on all 504 PCI neighboring
cells. UE is not given a specific neighbor cell list for intra frequency
LTE cells. However, for Inter frequency LTE or inter technology cells,
UE can be provided a list, to identify which neighbors UE has to
perform measurements on.
After measurements when a certain event criterion is fulfilled ONLY
then the UE will send measurement for that specific cell measured to
the serving cell. Otherwise no measurements are sent.
Question 10
Question 11
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10. What is the purpose of Contention-
Free Random Access Procedure?
Answer: For cases where the network knows, in advance, that a
particular UE will perform a Random Access Procedure to acquire
uplink synchronization, a dedicated preamble is reserved and assigned
to the UE under consideration. Dedicated Preamble assignment for
HO is handled by RRC whereas preamble assignment for DL data arrival
is handled by MAC. When the UE transmits the dedicated preamble in
Phase 1, the network knows to which UE this preamble was assigned
and can already at the time of detection of this determine the identity
of the UE. Thus no contention resolution is needed and the delay before
data transmission can be resumed is reduced.
What is ANR?
Answer: It stands for Automatic Neighbor Relationship. It is a
Self-Organizing Network Function (SON )function. Due to ANR, LTE
can form neighbor relationships with other cells, when required. It can
also remove relationships which are no longer needed anymore.
What is QCI?
Answer: QCI stands for Quality of Service (QoS) Class identifier. To
provide various types of QoS for the subscribers, in LTE we have 256
QCI values. Among these 256 QCI values, 9 QCI values have been
standardized by 3GPP. Remaining QCI values are configuration
dependent.
Question 12
Question 13
Question 14
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11. Which channel carries CQI
information to enodB?
Answer: CQI information can be carried on PUSCH or PUCCH channel.
If there is no data to transmit in the Uplink, then CQI information will
be send on PUCCH.
However, if there is data to be transmitted in the Uplink, and CQI
transmission is scheduled at the same time then PUSCH channel is
used for CQI transmission to the eNodeB. If detailed CQI information
is needed, then also PUSCH channel is used to send CQI report in the
Uplink.
Question 16
What is purpose of SIB19?
Answer: SIB19 is used to prioritize LTE over 3G in Idle mode. If UE is
camping on 3G in idle mode. During cell reselection phase, in idle
mode SIB19 is used to give priority to LTE over 3G, so that UE can
come back to LTE with high priority than 3G.
Question 15
What other info PUCCH carries?
Answer: Uplink Control signaling is sent on PUCCH, for example
such as scheduling request, ACK/ NACK, CQI reports etc
Question 17
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12. What is UE disconnection Timer?
Answer: The amount of time, after which RRC connection for the UE is
released and UE is moved from connected (active) mode into idle mode.
What is the Location of PUCCH in
the UL Spectrum?
Answer: PUCCH location is usually at the edges of the Uplink Spectrum.
What is the difference between FDD
and TDD mode in LTE?
Answer: The LTE standard specifies two different duplex modes; FDD
and TDD.
1) In Frequency Division Multiplex (FDD) mode the uplink and downlink
are using separate frequencies.
2) In Time Division Multiplex (TDD) mode the uplink and downlink use
the same frequency but are separated in time.
Question 18
Question 19
Question 20
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13. How is the FDD/TDD flexibility is
employed in paired /unpaired
spectrum deployment?
Answer: One important part of the LTE requirements in terms of
spectrum flexibility is the possibility to deploy LTE-based radio-access
in both paired and unpaired spectrum, i.e., LTE should support both
FDD and TDD based duplex arrangements. Frequency Division Duplex
(FDD), implies that downlink and uplink transmission take place in
different, sufficiently separated, frequency bands. Time Division
Duplex (TDD), implies that downlink and uplink transmission take place
in different, non-overlapping time slots. Thus, TDD can operate in
unpaired spectrum, whereas FDD requires paired spectrum.
Question 21
How is downlink power control used
in LTE?
Answer: Downlink power control, or power boosting, can be used on
both the data channel(PDSCH) and control channels (PBCH, PDCCH,
PCFICH, and PHICH).
As a default solution, the data channel power is distributed uniformly
over the scheduled resource blocks (i.e. no power control is used). More
sophisticated strategies include e.g.
(i) Allocating relatively high power, but few resource blocks to power
limited users and vice versa for bandwidth-limited users, and
(ii) Allocating more power to resource blocks with Good channel quality.
Question 22
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14. What is the meaning of the Random
Access Back-Off Procedure?
Answer: For the event of Random Access overload, a Random Access
Back-Off procedure is supported. This procedure prevents immediate
new Random Access attempts.
How is link adaptation used in LTE?
Answer: For unicast traffic, link adaptation is used and is controlled by
the eNodeB. A common modulation and channel code is used in the
frequency domain per UE and codeword. The modulation and coding
scheme (MCS) is selected based on CQI feedback and buffer content.
Rapid interference variations make it difficult to predict the link quality
accurately, and select MCS based on such knowledge. Instead,
preliminary, MCS selection is based on averaged link quality.
Question 23
Question 24
What reference signals are defined
for LTE uplink transmission?
Answer: There are two types of uplink reference signals in LTE, reference
signals for channel estimation to support coherent uplink transmission
and so-called sounding reference signals.
Question 25
TACS GSM/GPRS/EDGE WCDMA/HSPA/HSPA+ LTE
1G 2G 3G 4G
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