1 What is LTE

Long Term Evolution (LTE) is new wireless technology, all packet-based for voice/video (multimedia) services.

It combines new radio access methods with all-IP environment. It will coexist with legacy circuit switched networks such as

GSM, to allow operators roll-out advanced, new data-centric services alongside key lagacy services (mainly voice).

2 What's the difference between 3G & LTE

From infrastructure point of view, EPS (E-UTRAN + EPC) is simplified & realized with less number of network elements.

In comparison with 3G, eNodeB and UE are in charge of more functions; there is no more RNC and its role is mainly being taken

care of by e-NodeB, whereas e-NodeBs are syncronized via X2 i/f.

On the performance side, EPS (LTE) supports higher throughput in UL & DL. There is a versatility to implement LTE in different

frequency bands (i.e. discrete bands from 1.4 MHz up to 20MHz). LTE also benefits from advanced antenna techniques such as

MIMO, Rx-Div & beamforming.

3 What's the benefit of LTE

It support higher data rates in UL/DL, lower latency and packet-switching using IP.

4 What's technology applied in LTE (both in UL and DL)

For DL, OFDMA (Orthogonal Frequency Division Multiple Access) is used, whereas in UL SC-FDMA (Single Carrier FDMA) is used.

SC-FDMA is also a coded version of OFDM (DFTS-OFDM) which benefits from lower Pick to Average Power Ratio (PAPR) which helps for Lower terminal cost and improved battery life (Efficient transmitter and improved cell-edge performance)

5 What's the max throughput we can achieve from LTE

With 4*4_MIMO scheme (i.e. 4 Tx antenna for eNodeB and UE), we can achive up to 300Mbps in DL and 75Mbps in UL, using

20MhZ band width.

With SISO, throughput is as high as 100Mbps for DL and 50Mbps in UL, with 20MhZ band width.

6 In the market, which type/categ of UE are available now

7 Do you have any experience in LTE dimensioning/planning and drivetesting?

If so, please kindly answer the following questions:

8 what is main frequency band for LTE

While different frequency bands (17 for LTE-FDD) is recognized for LTE usage, it is mainly implemented around 2.5GHz.

LTE frequency band consists of IMT-2000 core frequency band (1.9-2GHZ), and IMT-extended bands (2.5GHZ) and 850-900 MHZ,

1800 MHZ, AWS spectrum (1.7-2.1GHZ) and portions of UHF band.

9 In coverage planning, what are the most influence factors

RSRP (Reference Symbol Received Power) and RSRQ (Reference Symbol Received Quality) are the main factors to achieve sufficent coverage for each service type.

10 In 3G, RSCP and Ec/Io are used to determined in coverage planning, How's about in LTE And why?

11 What are the range of SINR, RSRP, RSRQ, MCS and CQI values

12 What is the typical cell range of LTE

13 How do you understand RB and how does RB impact on Throughput

14 What is the typical value of latency

15 What are the type of HO? If so, pls explain me a bit of best cell HO and coverage HO?

16 For HO, pls explain me the difference between HO via X2 and S1

17 Do we still need Scraming code planning in LTE? If not, why?

18 Please explain me about eNodeB, MME and core network layout

19 For capacity planning, do we still need Channel element (CE) dimensioning? If not, why?

20 Have you experience in Atoll and Momentun

21 Have you expereince in XCAL and Agilent NiXT

22 Please explain me about QoS and Scheduling in LTE

23 Pls explain me about MIMO, SIMO and TxDiV configuration

24 How's about those configuration and expected throughput

25 If you can answer above questions, you will be in short list

MISO

(Multiple Input, Single Output)

SIMO

(Single Input, Multiple Output)

With multiple antennas at the transmitter and only single antenna at

the receiver (referred to as MISO) it is possible to obtain so called

Beamforming. With this method the transmission signal is steered in a beneficial direction (typically towards

the UE). This is accomplished by adjusting the phase (and sometimes amplitude) of the different antenna

elements by multiplying the signal with complex weights. This method increases the SNR (Signal to Noise

Ratio) and thus the capacity.

With this configuration it is also possible to achieve Transmit

Diversity. This is done by transmitting time-shifted copies of the

signal and thus achieving diversity in the time-domain. This

method also increases the SNR.

With multiple antennas at the receiver (SIMO or MIMO), it is

possible to use receive diversity. A combining method (typically

MRC Maximum Ratio Combining) is applied to increase the

SNR of the received signal.

With multiple antennas at both transmitter and receiver, it is

possible to use all of the above mentioned methods.

However, with multiple antennas at both transmitter and receiver, it

is also possible to achieve spatial multiplexing, also referred to as

MIMO. This method creates several layers, or data pipes in the

radio interface. The maximum number of layers that can be created

depends on the radio channel characteristics and the number of tx

and rx antennas. The maximum number of layers that the radio

channel can support is equal to the channel rank. The maximum

number of layers that effectively can be used is equal or less than

the minimum number of antenna elements at the tx or rx side or the

channel rank.

The data rate can at optimal circumstances be multiplied by the

number of layers.

Antenna Config (Example) eNodeB Termianl Device

MISO

(Multiple Input, Single Output) 2*1 2 Tx Ant 1 Rx Ant

SIMO

(Single Input, Multiple Output) 1*2 1 Tx Ant 2 Rx Ant

MIMO

(Multipel Input, Multiple Output) 2*2 2 Tx Ant 2 Rx Ant

Benefits

Transmit Diversity

Beamforming

Receive Diversity

All of the above + Spatial Multiplexing

LTE Downlink Physical Resource

1 RB (Resource Block) is equivalent to 180KhZ in frequency and 0.5 ms in Time domain

1 SB (scheduling Block) corresponds to 180kHz in frequency and 1 ms in Time domain.

Resourec Blocks and Scheduling Blocks are compromised by Resource Elements.

Therefore, Basic DL physical resource of LTE is Resourec Element, which corresponds to One OFDM Subcarrier using One OFDM Symbole length (=66.7microSec=1/15KHz).

It means, each RB corresponds to 12 OFDM sub-carriers during one 0.5ms slot.

A Resource Block corresponds to twelve OFDM sub-carriers during one 0.5 ms slot.

The smallest unit that can be allocated by the scheduler is two consecutive Resource Blocks (12 sub-carriers

during 1ms).

LTE can be impelemented with min 1.4Mhz (6RBs of each 180kHz + some req overhead) or maximum with 20MHz (100 RBs and some overhead).

Active Resource Elements are used to carry the following traffic types:

. Downlink Reference Signals

. Downlink L1/L12 Control Signalling

. Synchronization Signals (SS)

. Broadcast Control Channels (BCH)

. User Plane Data

Therefore, Basic DL physical resource of LTE is Resourec Element, which corresponds to One OFDM Subcarrier using One OFDM Symbole length (=66.7microSec=1/15KHz).

LTE can be impelemented with min 1.4Mhz (6RBs of each 180kHz + some req overhead) or maximum with 20MHz (100 RBs and some overhead).

Cyclic Prefix InsertionThe LTE symbole length is 1/15000=66.7microSec. Each symbole is followed by a 4.7 microSec "Cyclic Prefix (CP)" which is a copt of the last part of the symbole used to preserve the subcarrier orthogonality and improve its robustness in time dispersive channels. This means that each subcarrier can carry 1/(0.0667+0.007)=14 modulation symboles during one TTI (=1ms?).

The 12 subcarriers that make up an RB can thus carry 12.14=168 modulation symbols with 1 Antenna port or (12.14).2=336 with 2 Antenna ports.

The LTE symbole length is 1/15000=66.7microSec. Each symbole is followed by a 4.7 microSec "Cyclic Prefix (CP)" which is a copt of the last part of the symbole used to preserve the subcarrier orthogonality and improve its robustness in time dispersive channels. This means that each subcarrier can carry 1/(0.0667+0.007)=14 modulation symboles during one TTI (=1ms?).

The 12 subcarriers that make up an RB can thus carry 12.14=168 modulation symbols with 1 Antenna port or (12.14).2=336 with 2 Antenna ports.

The LTE symbole length is 1/15000=66.7microSec. Each symbole is followed by a 4.7 microSec "Cyclic Prefix (CP)" which is a copt of the last part of the symbole used to preserve the subcarrier orthogonality and improve its robustness in time dispersive channels. This means that each subcarrier can carry 1/(0.0667+0.007)=14 modulation symboles during one TTI (=1ms?).

The LTE symbole length is 1/15000=66.7microSec. Each symbole is followed by a 4.7 microSec "Cyclic Prefix (CP)" which is a copt of the last part of the symbole used to preserve the subcarrier orthogonality and improve its robustness in time dispersive channels. This means that each subcarrier can carry 1/(0.0667+0.007)=14 modulation symboles during one TTI (=1ms?).

LTE DL Physical Resources

Scheduling Techniques:

Time domainRound-robin

Max C/I

Proportional fair

Frequency domainConsecutive

Random

Measurement based

Link adaptationLayer 1 feature

Time Domain (/user)Modulation scheme

Channel coding

LTE DL peak rate

20 MHz and 4x4 MIMO AND 64

QAM

LTE 3GPP Rel 10Higher peak rates

Delay/latency User plane RTT:

CQI

The US estimates the quality in the downlink and signals it back to eNodeB in the Channel Quality Indicator. The range for CQI is from 0 to 15.

RSRP

The RSRP measurement provides a cell-specific signal strength metric. This measurement is

used mainly to rank different LTE candidate cells according to their signal strength and is

used as an input for handover and cell reselection decisions. RSRP is defined for a specific

cell as the linear average over the power contributions (in Watts) of the Resource Elements

(REs) which carry cell-specific RS within the considered measurement frequency bandwidth

RSRQ

This measurement is intended to provide a cell-specific signal quality metric. Similarly to

RSRP, this metric is used mainly to rank different LTE candidate cells according to their

signal quality. This measurement is used as an input for handover and cell reselection

decisions, for example in scenarios for which RSRP measurements do not provide sufficient

information to perform reliable mobility decisions. The RSRQ is defined as the ratio

N RSRP/(LTE carrier RSSI), where N is the number of Resource Blocks (RBs) of the LTE

carrier RSSI measurement bandwidth.

UMTS FDD CPICH Received Signal Code Power (RSCP)

UTRA FDD CPICH RSCP is a UMTS measurement equivalent to LTE RSRP. This

measurement is used mainly to rank different UMTS FDD candidate cells according to

their signal strength and is used as an input for decisions on handover and cell reselection

to UMTS. It is defined as the received power measured on the P-CPICH [11]. If transmit

diversity is applied on the P-CPICH, the received code power from each antenna is measured

separately and summed together in Watts to a total received code power.

UMTS FDD CPICH Ec/N0

The UTRA FDD CPICH Ec/N0 measurement is defined as the received energy per chip

(Ec) on the P-CPICH of a given cell divided by the total noise power density (N0) on the

UMTS carrier [11]. CPICH Ec/N0 is used mainly to rank different UMTS FDD candidate

cells according to their signal quality and is used as an input for handover and cell reselection

decisions. If receive diversity is not in use by the UE, the CPICH Ec/N0 is identical to CPICH

RSCP divided by UMTS Carrier RSSI. If transmit diversity is applied on the P-CPICH the

received Ec from each antenna must be separately measured and summed together (inWatts)

to a total received energy per chip on the P-CPICH, before calculating the Ec/N0.

GSM Carrier RSSI

GSM RSSI is the wideband received power within the GSM channel bandwidth. This

measurement is performed on a GSM BCCH carrier (i.e. a beacon carrier frequency).

MCS

As already known in 2G or 3G systems, link adaptation (different

modulation and coding scheme MCS) based on UE-reported CQI (Channel Quality Indicator)

is also possible.

The US estimates the quality in the downlink and signals it back to eNodeB in the Channel Quality Indicator. The range for CQI is from 0 to 15.