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“A blank page is no empty space.

It is brimming with potential...

It is a masterpiece in waiting

-- yours.”

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 whileyour 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

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,

AT&T, 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

[email protected] 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

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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• 5MHzThere are 25 Resource Blocks and 300 subcarriers

• 10MHz There are 50 Resource Blocks and 600 subcarriers

• 20 MHzThere are 100 Resource Blocks and 1200 subcarriers

What Maximum LTE throughput canbe 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 phonei.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, downloadingdata, receiving active services requests etc.

Question 6


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 takeplace. 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 asRedirection.

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


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 isfixed, 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


What is difference between X2 andS1 HO? Answer:

In this handover, the signaling associated with 1) X2 Handover:preparation phase of handover is done via X2 interface.

In this handover, the signaling associated with 2) 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 neighboringcells. 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


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 beforedata 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


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 willbe 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 informationis needed, then also PUSCH channel is used to send CQI report in theUplink.

Question 16

What is purpose of SIB19?Answer: SIB19 is used to prioritize LTE over 3G in Idle mode. If UE iscamping 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


What is UE disconnection Timer?Answer: The amount of time, after which RRC connection for the UE isreleased 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


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 placein different, non-overlapping time slots. Thus, TDD can operate in unpaired spectrum, whereas FDD requires paired spectrum.

Question 21

How is downlink power control usedin 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


What is the meaning of the RandomAccess Back-Off Procedure?Answer: For the event of Random Access overload, a Random AccessBack-Off procedure is supported. This procedure prevents immediatenew 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+ LTE1G 2G 3G 4G


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