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www.awe-com.com 2012 by AWE Communications GmbH

LTE Network Planning

by AWE Communications GmbH 2

Overview Air Interface

Frequencies and Bandwidths

Deployment & Coverage

Interference with other systems

Network Planning Module Air Interface

Cell Load

Interference

Network Simulation

Simulation Results

Comparison

Contents


LTE Networks

LTE Long Term Evolution: Overview I Latest standard in mobile communications defined by 3GPP

Peak data rates of at least 100 Mbps downlink and 50 Mbps uplink

Support of MIMO for higher data rates (single stream, 2x2, 4x4)

RAN round trip times less than 10 ms

Scalable carrier bandwidths between 1.4 MHz and 20 MHz

Both frequency division duplex (FDD) and

time division duplex (TDD) supported

Main advantages High throughput, low latency

Higher spectral efficiency

E-UTRA single evolution path for GSM/EDGE, UMTS/HSPA, CDMA2000/EV-DO and TD-SCDMA

Simple all IP flat architecture low operational costs Further evolution towards LTE Advanced in 3GPP Release 10 incl. carrier aggregation, relaying


LTE Networks

LTE Long Term Evolution: Overview II Features

Peak download rates of 326.4 Mbps for 4x4 antennas,

172.8 Mbps for 2x2 antennas (20 MHz),

Peak upload rates of 86.4 Mbps for every 20 MHz of spectrum

using a single antenna

Increased spectrum flexibility supports slices

as small as 1.4 MHz and as large as 20 MHz

Supporting an optimal cell size of 5 km (rural areas),

and up to 100 km cell sizes with acceptable performance,

in urban areas cell sizes less than 1 km

Good support for mobility, i.e. high performance mobile data

is possible at speeds of up to 350 km/h

Support for MBSFN

(Multicast Broadcast

Single Frequency Network)

for provision of Mobile TV


LTE Networks

LTE Long Term Evolution: Air Interface I Downlink

LTE uses OFDM for the downlink

Cyclic prefix of 4.7s to compensate multipath (extended cyclic prefix of 16.6s)

Radio frame in time domain 10 ms long and consists of 10 sub frames of 1 ms each

Every sub frame consists of 2 slots where each slot is 0.5 ms

The sub-carrier spacing in the frequency domain is 15 kHz

12 sub-carriers together (per slot) form a resource block, i.e. one resource block is 180 kHz

6 Resource blocks fit in a carrier of 1.4 MHz and 100 resource blocks fit in a carrier of 20 MHz

In the downlink there are three main physical channels:

Physical Downlink Shared Channel (PDSCH) is used for all the data transmission Physical Multicast Channel (PMCH) is used for broadcast transmission using a SFN Physical Broadcast Channel (PBCH) is used to send most important system information

Supported modulation formats on the PDSCH are QPSK, 16QAM and 64QAM

For MIMO operation either single user MIMO (higher data rate) or

multi user MIMO (higher cell throughput)


LTE Networks

LTE Long Term Evolution: Air Interface II Uplink

LTE uses a pre-coded OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA)

To compensate the high peak-to-average power ratio (PAPR) of OFDM

Reduces the need for linearity of power amplifier, and so power consumption

In the uplink there are three physical channels:

Physical Random Access Channel (PRACH) used for initial access Physical Uplink Shared Channel (PUSCH) carries the data Physical Uplink Control Channel (PUCCH) carries control information

Same modulation formats as in downlink: QPSK, 16QAM and 64QAM

Uplink

Downlink

Frequency

User 1 User 2 User 3

Up to 20 MHz

SC-FDMA

OFDMA


LTE Networks

LTE Long Term Evolution: Frequencies and Bandwidths

E-UTRA Band Uplink Band Downlink Band Duplex Mode Bandwidths [MHz] Alias Regions

1 1920 to 1980 MHz 2110 to 2170 MHz FDD 5, 10, 15, 20 UMTS IMT 2100 Japan, EU, Asia

2 1850 to 1910 MHz 1930 to 1990 MHz FDD 1.4, 3, 5, 10, 15, 20 PCS 1900 CAN, US, Latin A.

3 1710 to 1785 MHz 1805 to 1880 MHz FDD 1.4, 3, 5, 10, 15, 20 DCS 1800 Finland,Hongkong

4 1710 to 1755 MHz 2110 to 2155 MHz FDD 1.4, 3, 5, 10, 15, 20 AWS CAN, US, Latin A.

5 824 to 849 MHz 869 to 894 MHz FDD 1.4, 3, 5, 10 UMTS 850 CAN, US, AUS

6 830 to 840 MHz 875 to 885 MHz FDD 5, 10 UMTS 800 Japan

7 2500 to 2570 MHz 2620 to 2690 MHz FDD 5, 10, 15, 20 IMT-E 2600 EU

8 880 to 915 MHz 925 to 960 MHz FDD 1.4, 3, 5, 10 GSM, UMTS900 EU, Latin America

9 1750 to 1850 MHz 1845 to 1880 MHz FDD 5, 10, 15, 20 UMTS1700 CAN, US, Japan

10 1710 to 1770 MHz 2110 to 2170 MHz FDD 5, 10, 15, 20 UMTS IMT2000 South America

11 1428 to 1448 MHz 1476 to 1496 MHz FDD 5, 10 PDC Japan

12 698 to 716 MHz 728 to 748 MHz FDD 1.4, 3, 5, 10

13 777 to 787 MHz 746 to 756 MHz FDD 5, 10 Verizon 700 MHz US

14 788 to 798 MHz 758 to 768 MHz FDD 700 MHz US (FCC)

17 704 to 716 MHz 734 to 746 MHz FDD AT&T 700 MHz US

20 832 to 862 MHz 791 to 821 MHz FDD 5, 10, 15, 20 Digital Dividend EU


LTE Networks

LTE Long Term Evolution: Frequencies in Germany


LTE Networks

LTE Long Term Evolution: Deployment Options I

Depending on available carrier frequencies in rural areas optimal cell size of 5 km, up to 100 km cell sizes with acceptable performance

in urban areas cell sizes less than 1 km, down to few tens of meters

(hot spots, pico cells, femto cells)

reduce co-channel interference on cell edge by using

appropriate frequency assignment:

frequency reuse 1 implies co-channel interference at cell borders

frequency reuse 3 reduces interference

but limits each cell to a third of the total bandwidth

frequency reuse 1 at cell centers and

reuse 3 for cell borders (partial frequency reuse)f

ff

f f

f2

32

1 3

1

f2f1

f3


LTE Networks

LTE Long Term Evolution: Deployment Options II

Depending on available carrier frequencies and individual scenario F1 and F2 cell are co-located and overlaid, with same coverage and

mobility supported on both layers

(when F1 and F2 of same band)

F1 and F2 cell are co-located and overlaid, F2 with smaller coverage,

full coverage and mobility supported by F1 only, F2 used to provide

throughput (when F1 and F2 of different bands)

F1 provides macro coverage and F2 provides throughput at hot spots

by using remote radio heads. Full coverage and mobility by F1 only.

Likely scenario when F1 and F2 are of different bands


Air Interface (1/5): Overview

Multiple Access (e.g. OFDM/SOFDMA)

Duplex separation mode (FDD / TDD)

MIMO technology

Carriers defined

Transmission Modes- MCS- Priority- Data Rate DL and UL

Cell assignment- Highest received power

(of all carriers/received carriers)- Highest SNIR

(of all carriers/received carriers)- Min. required SNIR in DL Definition of air interface

Network Planning Module


Orthogonal Frequency Division Multiple Access (as example)

Tx Power Settings Split between sub-carriers Back-off possible e.g. for pilot

Sampling Rate (e.g. 384/250 for LTE)

Cell Load controls Tx power in DL or nr. of used sub-carriers

Sub-carriers FFT order guard sub-carriers

Air Interface (2/5): Multiple Access



Orthogonal Frequency Division Multiple Access (as example)

Symbols Split of resource elements Frequency and time domain See figure below

Resource Blocks Nr. of sub-carriers per RB Fractional load (RB level)

Air Interface (3/5): Multiple Access



Specification of an arbitrary number of transmission modes Name: MCS - code rate

Priority: Impacts filling of resources (overall throughput)

Transmission direction Bidirectional, DL only, UL only

Modulation BPSK, QPSK, 16-QAM, 64-QAM

Code Rate 1/3, 1/2, 3/4, 4/5,

Number of resource blocks

Data rate incl. overhead

Min. required SNIR target

Min. required received signal level at BTS and SS Power back-off

Air Interface (4/5): Transmission Modes



Duplex Mode: TDD or FDD mode can be selected

(identical for all BTS in network) FDD

Specification of carrier separation of UL and DL (identical for all carriers)

TDD Definition of switching type

Definition of transmission blocks with number and length

Ratio inside each block

Resulting overall ratios for DL and UL automatically computed and considered in network simulation

Air Interface (5/5): Duplex Mode



Definition of Cell Load (Interference)

Definition of relative transmit power if no traffic is considered

Interference (SNIR) calculation influenced by this parameter

Value indicates how much of the data transmission power should be considered for the interference calculation

50% means 50% of the linear data transmission power (in Watts)

Data transmission power is calculated based on total transmit power, the power split (data/reference/control) and the power backoff value

Controls either Tx power or number of sub-carriers used

Cell load can be defined globally or individually for each transmitter

LTE Networks Cell Load


LTE Networks - Interference

Interference (1/3): Two Types of Interference

Type 1: Multipath Interference (only if delays between paths > guard interval)

Signal contributions arriving after the guard interval are interference

Propagation model must be able to predict multiple paths and path delays (i.e. channel impulse response)

Symbol duration incl. Guard period

Interference

C(t)1

0 Tg Ts

I(t) Different weighting functions available for separating

multi-path contributions in signal and interference power

Channel Impulse Response


Guard interval influences multi path interference

Figures: Effect of guard interval on SNIR (frequency reuse = 1)SNIR

Useful: 224 s

Guard: 1 s

SNIR

Useful: 224 s

Guard: 5 s

SNIR

Useful: 224 s

Guard: 10 s

SNIR

Useful: 224 s

Guard: 28 s

Interference (2/3): Effect of guard interval



Interference (3/3): Inter-cell Interference

Type 2: Inter-cell interference (other cells using the same carrier)

Interference computation based on cell assignment

Tx power of interfering BS is specified relative to max. Tx power of the BS (e.g. 80% of max. power)

- For all BTS in the network homogenously

- For each BTS individually

- Especially important if frequency reuse factor is equal to 1 (or 3)

- Sub-channelization can be modeled (if adjacent cells use different sub-carriers to reduce the interference)

Cell load by relative Tx power of interfering cells is suitable to define typical and/or worst case scenario (sufficient for network planning)

Actual traffic (load) of BTS depending on the number of users in the cell is not considered to determine Tx power because

- Actual Tx power depends on transmission modes

- Resource management must be included in simulator to decide which user/traffic is transmitted in which transmission mode

typically resource management is operator dependent and cannot be handled in an external planning tool



LTE Scenario with Interference Assignment of Rx to cell with highest signal level (RSRP)

Computation of the signal and interference power (SNIR)

Consideration of traffic by individual load factor for each cell

LTE network simulation provides the key performance indicators: RSRP, RSSI, RSRQ, max. data rate per user, max. throughput, ...

LTE Networks - Simulation


LTE Network Planning Results Different channels for transmission of reference, control, data signals

Transmission power depends on allocated resource blocks

RSRP with constant power of one subcarrier (e.g. 1/600 for 10 MHz BW)

RSSI influenced by variable transmission power depending on the throughput (allocated resource blocks)

RSRQ gives difference between RSRP and RSSI


Uplink

Downlink

Frequency

User 1 User 2 User 3

Up to 20 MHz

SC-FDMA

OFDMA


LTE Network Planning Results in Urban Scenario

Reference Signal Received Power (DL) Max. data rate (DL)



LTE Network Planning Results in Urban Scenario

Reference Signal Strength Identifier (DL) Reference Signal Received Quality (DL)



Impact of the Traffic on the Feasible Throughput

Cell Load 80% Cell Load 30%



Impact of Cell Areas on Feasible Handovers

Possible Handover to Site 4 Antenna 1 Possible Handover to Site 6 Antenna

1



Computation with ProMan Measurement

Comparison MIMO Capacity vs. Measurements

Office scenario: MIMO data rate for antenna pair


Further Information

Further information: www.awe-com.com

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