asset v8 - lte application notes - 2.0
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Copyright 2012 AIRCOM International - All rights reserved. No part of this work, which is protected by copyright, may be
reproduced in any form or by any means - graphic, electronic or mechanical, including photocopying, recording, taping or storage
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ASSETV8.0- LTE Application Notes
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AIRCOM International ASSETV8.0- LTE Application Notes Page 2 of 64
Contents
1 Document Control ............................................................................................................................ 3
1.1 Revision History ..................................................................................................................... 3
2 Introduction ...................................................................................................................................... 4
2.1 LTE Objective and Performance Requirements ...................................................................... 4
2.2 High Level System Architecture ............................................................................................. 4
3 LTE Technology Overview .............................................................................................................. 6
3.1 Frequency Band and EARFCN ............................................................................................... 6
3.1.1 General ............................................................................................................................... 6
3.1.2 LTE Frequency Bands ........................................................................................................ 7
3.1.3 Channel Arrangement ......................................................................................................... 7
3.2 Frame Structure ....................................................................................................................... 8
3.2.1 Type 1- FDD ....................................................................................................................... 9
3.2.2 Type 2- TDD ...................................................................................................................... 9
3.2.3 Basic Time Unit ................................................................................................................ 10
3.2.4 Subcarrier Spacing ............................................................................................................ 11
3.3 Transport Channels ............................................................................................................... 11
3.3.1 Downlink Transport Channels .......................................................................................... 11
3.3.2 Uplink Transport Channels ............................................................................................... 12
3.4 Physical Channels ................................................................................................................. 12
3.4.1 Downlink Physical Channels ............................................................................................ 12
3.4.2 Uplink Physical Channels ................................................................................................. 12
3.4.3 Mapping between transport channels and physical channels (Downlink) ........................ 13
3.4.4 Mapping between transport channels and physical channels (Uplink) ............................. 13
3.5 Physical Signals .................................................................................................................... 13
3.5.1 Downlink Physical Signals-Channels ............................................................................... 13
3.5.2 Uplink Physical Signals .................................................................................................... 14
3.6 Multi-Antenna Transmission ................................................................................................ 15
3.6.1 General on MIMO ............................................................................................................ 15
3.6.2 Downlink .......................................................................................................................... 15
3.6.3 Uplink ............................................................................................................................... 16
3.6.4 MBSFN Transmission ...................................................................................................... 16
3.7 Physical Layer Procedure ...................................................................................................... 16
3.7.1 Link adaptation ................................................................................................................. 16
3.7.2 Cell search ........................................................................................................................ 17
3.8 Physical Layer Measurements and Indicators ....................................................................... 17
3.8.1 Reference Signal Received Power (RSRP) ....................................................................... 17
3.8.2 E-UTRA Carrier RSSI ...................................................................................................... 17
3.8.3 Reference Signal Received Quality (RSRQ) .................................................................... 17
3.8.4 DLRS TX Power .............................................................................................................. 17
3.8.5 Received Interference Power ............................................................................................ 17
3.8.6 Thermal noise power ........................................................................................................ 17
3.8.7 Quality, Precoding & Rank Indicators .............................................................................. 18
3.9 Radio Resource Management and Scheduling ...................................................................... 18
3.9.1 Radio Bearer Priority and Rate Control ............................................................................ 19
3.10 Interference Co-ordination Schemes ..................................................................................... 19
3.11 LTE Devices UE Categories .............................................................................................. 20
4 LTE Technology in ASSET ........................................................................................................... 21
4.1 Introduction ........................................................................................................................... 21
4.2 Frequency bands ................................................................................................................... 22
4.3 LTE Frame Structure ............................................................................................................ 24
4.4 Carriers .................................................................................................................................. 26
4.5 Bearers .................................................................................................................................. 28
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4.6 Services ................................................................................................................................. 29
4.7 eNodeB and Cell parameters ................................................................................................. 32
4.8 LTE Planners ........................................................................................................................ 32
4.8.1 Physical Cell ID Planner ................................................................................................... 32
4.8.2 LTE Frequency Planner .................................................................................................... 33
4.9 Terminal Types ..................................................................................................................... 33
4.9.1 Creating a Traffic Raster .................................................................................................. 34
5 LTE Network Performance- Coverage and Capacity Predictions .................................................. 35
5.1 Basic Coverage (RSRP, RSSI, RSRQ) ................................................................................. 37
5.2 MIMO Schemes .................................................................................................................... 39
5.2.1 SU-MIMO Diversity ...................................................................................................... 40
5.2.2 SU-MIMO Spatial Multiplexing .................................................................................... 41
5.2.3 SU-MIMO Adaptive Switching ..................................................................................... 43
5.2.4 MU-MIMO ....................................................................................................................... 47
5.2.5 SU-MIMO and MU-MIMO .............................................................................................. 49
5.3 ICIC ...................................................................................................................................... 52
5.3.1 Reuse 1 (Prioritisation) ..................................................................................................... 53
5.3.2 Soft Frequency Reuse and Reuse Partitioning .................................................................. 56
5.4 Schedulers ............................................................................................................................. 62
1 Document Control
1.1 Revision History
Revision
Number
Date Name Revision
1.0 05/07/2010 AIRCOM Product Engineering Initial version ASSETv7
2.0 12/03/2012 AIRCOM Product Engineering ASSET v8
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2 Introduction
This document describes a brief overview of how to model, plan and simulate LTE radio networks with
the use of AIRCOMs radio network planning tools, specifically with ASSET. This version of the LTE
application notes has been written to be used alongside V8.0 of the ENTERPRISE suite.
2.1 LTE Objective and Performance Requirements
The main objective behind LTE is the Evolution of the 3GPP radio-access technologies towards high-
data-rate, low-latency and packet-optimised radio-access networks. The performance requirements for
the first phase of LTE deployment include:
Peak Data Rates (for 20MHz Spectrum), DL: 300 Mbps, UL: 75 Mbps
Mobility Support, Up to 500km/h and also optimised for low speeds (0-15km/h)
Reduced Latency with quick response time,
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AIRCOM International ASSETV8.0- LTE Application Notes Page 5 of 64
Evolved-UTRAN: Consists of eNodeBs, X2 interface which connects eNodeBs that need to
communicate with each other e.g. for support of handover of UEs, etc. S1 interface, which
connects eNodeBs to the EPC
MME: responsible for idle mode UE tracking and paging procedure including retransmissions
S-GW: Routes and forwards user data packets, acts as Mobility Anchor during inter-eNodeB
handovers and between LTE and 3GPP technologies
LTE architecture enables Network Sharing solutions by allowing the service providers to have a
separate CN (MME, S-GW, Packet Data Network Gateway (PDN-GW)) while the E-UTRAN
(eNodeBs) is jointly shared. This is achieved by the S1-flex Mechanism that has the following
characteristics:
S1-flex Mechanism:
Allows separate CN (MME, S-GW, PDN-GW) and creates pools of MMEs and S-GWs
Allows each eNodeB to be connected to multiple MMEs and SGWs in a pool
Provides support for network redundancy
Facilitates load sharing of traffic across network in the CN, the MME and the S-GW
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3 LTE Technology Overview
This Chapter provides a brief overview on LTE Technology and it will be used as reference in Chapter
4 where the information presented here is used to model an LTE network in ASSET.
3.1 Frequency Band and EARFCN
3.1.1 General
E-UTRA (or LTE as it is commercially marketed) will support operation in a wide range of spectrum
allocations, achieved by the flexible transmission bandwidths that are part of the LTE specifications.
The main reason for this is that the amount of spectrum available for LTE may significantly vary
between different frequency bands and operators. Furthermore, the possibility to operate in different
spectrum allocations gives the opportunity for gradual migration of the spectrum from other radio
access technologies to LTE. Operation mode can be either Frequency Division Duplex (FDD) or Time
Division Duplex (TDD).
The LTE physical-layer specifications are bandwidth-agnostic and do not make any particular
assumption on the supported transmission bandwidths beyond a minimum value. The basic radio-
access specification, including the physical-layer and protocol specifications, allows for any
transmission bandwidth ranging from around 1MHz up to beyond 20MHz in steps of 180 kHz. At the
same time, radio-frequency requirements are only specified for a limited subset of transmission
bandwidths, corresponding to what is predicted to be relevant spectrum-allocation sizes and relevant
migration scenarios. Thus, in practice, LTE radio access supports a limited set of transmission
bandwidths, but additional transmission bandwidths could be easily supported by simply updating the
RF specifications.
The following frequency spectrum related terminologies and definitions have been used in 3GPP and
will be used throughout this document.
Channel bandwidth: The RF bandwidth supporting a single E-UTRA RF carrier with the transmission
bandwidth configured in the uplink or/and downlink of a cell. The channel bandwidth is measured in
MHz and is used as a reference for the transmitter and receiver RF requirements.
Transmission bandwidth: Bandwidth of an instantaneous transmission from a UE or eNodeB,
measured in Resource Block units.
Transmission bandwidth configuration: The highest transmission bandwidth allowed for uplink or
downlink in a given Channel Bandwidth, measured in Resource Block (RB) units.
NDL Downlink E-UTRA Absolute Radio Frequency Channel Number(E-ARFCN)
NOffs-DL Offset used for calculating downlink E-ARFCN
NOffs-UL Offset used for calculating uplink E-ARFCN
NRB Transmission Bandwidth configuration, expressed in units of resource blocks
NUL Uplink E-ARFCN
BWChannel Channel Bandwidth
BWConfig Transmission Bandwidth configuration, expressed in MHz, BWConfig = NRB x 180
kHz in the uplink and BWConfig = 15 kHz + NRB x 180 kHz in the downlink.
Figure 3-1 shows the relation between the Channel Bandwidth (BWChannel) and the Transmission
Bandwidth Configuration (NRB). The channel edges are defined as the lowest and highest frequencies
of the carrier separated by the channel bandwidth, i.e. at FC +/- BWChannel /2, where FC is the centre
frequency. Also, Table 3-1 summarises the currently supported transmission bandwidth configurations
for the defined Channel Bandwidths.
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Channel bandwidth BWChannel
[MHz]
1.4 3 5 10 15 20
Transmission Bandwidth
Configuration NRB
6 15 25 50 75 100
Table 3-1 Channel Bandwidth and Transmission Bandwidth Configurations
Figure 3-1 Definition of Channel Bandwidth and Transmission Bandwidth Configuration
3.1.2 LTE Frequency Bands
LTE is designed to operate in the frequency bands defined in Table 3-2.
E-UTRA
Band
Uplink Downlink Duplex Mode
FUL_low FUL_high FDL_low FDL_high
1 1920 MHz 1980 MHz 2110 MHz 2170 MHz FDD
2 1850 MHz 1910 MHz 1930 MHz 1990 MHz FDD
3 1710 MHz 1785 MHz 1805 MHz 1880 MHz FDD
4 1710 MHz 1755 MHz 2110 MHz 2155 MHz FDD
5 824 MHz 849 MHz 869 MHz 894MHz FDD
6 830 MHz 840 MHz 875 MHz 885 MHz FDD
7 2500 MHz 2570 MHz 2620 MHz 2690 MHz FDD
8 880 MHz 915 MHz 925 MHz 960 MHz FDD
9 1749.9 MHz 1784.9 MHz 1844.9 MHz 1879.9 MHz FDD
10 1710 MHz 1770 MHz 2110 MHz 2170 MHz FDD
11 1427.9 MHz 1452.9 MHz 1475.9 MHz 1500.9 MHz FDD
12 698 MHz 716 MHz 728 MHz 746 MHz FDD
13 777 MHz 787 MHz 746 MHz 756 MHz FDD
14 788 MHz 798 MHz 758 MHz 768 MHz FDD
...
33 1900 MHz 1920 MHz 1900 MHz 1920 MHz TDD
34 2010 MHz 2025 MHz 2010 MHz 2025 MHz TDD
35 1850 MHz 1910 MHz 1850 MHz 1910 MHz TDD
1930 MHz 1990 MHz 1930 MHz 1990 MHz TDD
37 1910 MHz 1930 MHz 1910 MHz 1930 MHz TDD
38 2570 MHz 2620 MHz 2570 MHz 2620 MHz TDD
39 1880 MHz 1920 MHz 1880 MHz 1920 MHz TDD
40 2300 MHz 2400 MHz 2300 MHz 2400 MHz TDD
Table 3-2 Worldwide standardised LTE Frequency Bands
3.1.3 Channel Arrangement
The channel arrangement depends on the following:
Channel Spacing: The spacing between carriers will depend on the deployment scenario, the size of
the frequency block available and the Channel Bandwidth. The nominal Channel Spacing between two
adjacent LTE carriers is defined as following:
Transmission
Bandwidth [RB]
Transmission Bandwidth Configuration [RB]
Channel Bandwidth [MHz]
Resource block
Channel e
dge
Channel edge
DC carrier (downlink only)Active Resource Blocks
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AIRCOM International ASSETV8.0- LTE Application Notes Page 8 of 64
Nominal Channel Spacing = (BWChannel(1) + BWChannel(2))/2
where, BWChannel(1) and BWChannel(2) are the Channel Bandwidths of the two respective LTE carriers. The
Channel Spacing can be adjusted to optimise performance in a particular deployment scenario.
Channel Raster: The Channel Raster is 100 kHz for all bands, which means that the carrier centre
frequency must be an integer multiple of 100 kHz.
Carrier frequency and E-ARFCN: The carrier frequency in the uplink and downlink is designated by
the E-UTRAN E-ARFCN. The relation between E-ARFCN and the carrier frequency in MHz for the
downlink and uplink is given by the following equations, where FDL_low, NOffs-DL, FUL_low and NOffs-UL are
given in Table 3-3 and NUL \NDL are the uplink\downlink EARFCNs.
FDL = FDL_low + 0.1(NDL NOffs-DL)
FUL = FUL_low + 0.1(NUL NOffs-UL)
E-UTRA
Band
Downlink Uplink
FDL_low [MHz] NOffs-DL Range of NDL FUL_low [MHz] NOffs-UL Range of NUL
1 2110 0 0 599 1920 13000 13000 13599
2 1930 600 600 1199 1850 13600 13600 14199
3 1805 1200 1200 1949 1710 14200 14200 14949
4 2110 1950 1950 2399 1710 14950 14950 15399
5 869 2400 2400 2649 824 15400 15400 15649
6 875 2650 2650 2749 830 15650 15650 15749
7 2620 2750 2750 3449 2500 15750 15750 16449
8 925 3450 3450 3799 880 16450 16450 16799
9 1844.9 3800 3800 4149 1749.9 16800 16800 17149
10 2110 4150 4150 4749 1710 17150 17150 17749
11 1475.9 4750 4750 4999 1427.9 17750 17750 17999
12 728 5000 5000 5179 698 18000 18000 18179
13 746 5180 5180 5279 777 18180 18180 18279
14 758 5280 5280 5379 788 18280 18280 18379
33 1900 26000 26000 26199 1900 26000 26000 26199
34 2010 26200 26200 26349 2010 26200 26200 26349
35 1850 26350 26350 26949 1850 26350 26350 26949
36 1930 26950 26950 27549 1930 26950 26950 27549
37 1910 27550 27550 27749 1910 27550 27550 27749
38 2570 27750 27750 28249 2570 27750 27750 28249
39 1880 28250 28250 28649 1880 28250 28250 28649
40 2300 28650 28650 29649 2300 28650 28650 29649
Table 3-3 E-UTRA Absolute Radio Frequency Channel Number (EARFCN)
3.2 Frame Structure
Downlink and uplink transmissions are organised into radio frames with frame duration of
ms 10307200 sf == TT , where fT is the frame duration and the size of various fields in the time
domain is expressed as a number of time units ( )2048150001s =T seconds. This Base time-unit is explained later in this section. There are two main radio frame structures:
Type 1, applicable to FDD
Type 2, applicable to TDD
In addition, there is a slightly different frame structure for Multi-Media Broadcast over a Single
Frequency Network (MBSFN) support.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 9 of 64
3.2.1 Type 1- FDD
Frame structure Type 1 is applicable to both full duplex and half duplex FDD.
Each radio frame is ms 10307200 sf == TT long and consists of 20 slots of length
ms 5.0T15360 sslot ==T , numbered from 0 to 19. A subframe is defined as two consecutive slots
where subframe i consists of slots i2 and 12 +i . For FDD, 10 subframes are available for downlink
transmission and 10 subframes are available for uplink transmissions in each 10 ms interval. Uplink
and downlink transmissions are separated in the frequency domain. In half-duplex FDD operation, the
UE cannot transmit and receive at the same time while there are no such restrictions in full-duplex
FDD.
Figure 3-2 Type-1 Frame Structure
3.2.2 Type 2- TDD
Frame structure Type 2 is applicable to TDD.
Each radio frame of length ms 10307200 sf == TT consists of two half-frames of length fT =
ms 5153600 s =T each. Each half-frame consists of eight slots of length ms 5.015360 sslot == TT and
three special fields, Downlink Pilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time
Slot (UpPTS).
Figure 3-3 Type-2 Frame Structure for 5ms switch-point periodicity
The length of DwPTS and UpPTS is given by Table 3-4 subject to the total length of DwPTS, GP and
UpPTS being equal to ms 107203 s =T . The supported uplink-downlink allocations are listed in Table
3-5 where, for each subframe in a radio frame, D denotes the subframe is reserved for downlink
transmissions, U denotes the subframe is reserved for uplink transmissions and S denotes a special
subframe with the three fields DwPTS, GP and UpPTS.
Subframe 1 in all configurations and subframe 6 in configurations 0, 1, 2 and 6 in Table 2 consists of
DwPTS, GP and UpPTS. All other subframes are defined as two slots where subframe i consists of
slots i2 and 12 +i . Subframes 0 and 5 and DwPTS are always reserved for downlink transmission. In
case of 5 ms switch-point periodicity, UpPTS and subframes 2 and 7 are reserved for uplink
transmission. In case of 10 ms switch-point periodicity, DwPTS exist in both half-frames while GP and
UpPTS only exist in the first half-frame and DwPTS in the second half-frame has a length equal to
ms 107203 s =T . UpPTS and subframe 2 are reserved for uplink transmission and subframes 7 to 9 are
reserved for downlink transmission.
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Special-subframe Configuration Normal cyclic prefix Extended cyclic prefix
DwPTS GP UpPTS DwPTS GP UpPTS
0 s6592 T s21936 T
s2192 T
s7680 T s20480 T
s2560 T
1 s19760 T s8768 T
s20480 T
s7680 T
2 s21952 T s6576 T
s23040 T
s5120 T
3 s24144 T s4384 T
s25600 T
s2560 T
4 s26336 T s2192 T
s7680 T
s17920 T
s5120 T 5 s6592 T
s19744 T
s4384 T
s20480 T s5120 T
6 s19760 T s6576 T
s23040 T
s2560 T
7 s21952 T s4384 T
- - -
8 s24144 T s2192 T
- - -
Table 3-4 Configuration of Special Subframe (duration of DwPTS, GP and UpPTS)
Uplink-downlink
Configuration
Downlink-to-Uplink
Switch-point periodicity
Subframe number
0 1 2 3 4 5 6 7 8 9
0 5 ms D S U U U D S U U U
1 5 ms D S U U D D S U U D
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 10 ms D S U U U D S U U D
Table 3-5 Uplink Downlink Configurations for Type-2 Frames
The Basic Time Unit as defined below provides a one to one relation with all frame related parameters
3.2.3 Basic Time Unit
To provide consistent and exact timing definitions, different time intervals within the LTE radio access
specification can be expressed as multiple of a basic time unit 30720000/1=sT . Hence, it
influences every parameter in LTE frames, e.g.
Slot Duration: LTE frames consist of 20 slots of 0.5ms each calculated as
sslot TT .2
30720=
Subframe Duration: Two slots make one subframe of duration 1ms calculated as
ssubframe TT .30720=
Frame Duration: LTE frames are 10ms of time length which can be calculated as
sframe TT .307200=
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AIRCOM International ASSETV8.0- LTE Application Notes Page 11 of 64
3.2.4 Subcarrier Spacing
Currently, LTE employs a fixed subcarrier spacing of 15 kHz. However, there is also a reduced
subcarrier spacing of 7.5 kHz. This reduced subcarrier spacing specifically targets MBSFN- based
multicast/broadcast transmissions. Table 3-6 summarises the frame related parameters.
Transmission BW (MHz) 1.4 3.0 5 10 15 20
Slot duration (ms) 0.5 0.5 0.5 0.5 0.5 0.5
Sub-carrier spacing (kHz) 15 15 15 15 15 15
Sampling frequency (MHz) 30.72
/1.92
30.72
/3.84 30.72/7.68
30.72
/15.36
30.72
/23.04
30.72
/30.72
OFDM symbol length (in
time units* and excluding
cyclic prefix,1 time unit =
1/30.72 MHz)
2048/128 2048/256 2048/512 2048/1024 2048/1536 2048/2048
OFDM symbol length (micro
sec) 66.67 66.67 66.67 66.67 66.67 66.67
Number of occupied resource
blocks 6 15 25 50 75 100
Occupied sub-carriers 73 181 301 601 901 1201
OFDM symbols
per slot
Normal
CP 7 7 7 7 7 7
Extended
CP 6 6 6 6 6 6
Cyclic Prefix
(CP) length
where A is the
symbol position
in a slot
Normal CP 160, A = 0
144, A=1-6
160, A= 0
144, A=1-6
160,A = 0
144, A=1-6
160,A = 0
144, A=1-6
160,A= 0
144,A=1-6
160,A= 0
144,A=1-6
Extended
CP 512,A= 0-5 512,A= 0-5 512,A= 0-5 512,A= 0-5 512,A=0-5 512,A=0-5
Cyclic Prefix
(CP) length
where A is the
symbol position
in a slot
Normal CP
(time)micro
sec
5.21, A = 0
4.69, A=1-
6
5.21, A = 0
4.69, A=1-6
5.21, A = 0
4.69, A=1-6
5.21, A = 0
4.69, A=1-6
5.21, A = 0
4.69, A=1-6
5.21, A = 0
4.69, A=1-6
Extended
CP
16.67,A=
0-5
16.67,A= 0-
5 16.67,A= 0-5
16.67,A= 0-
5
16.67,A= 0-
5
16.67,A= 0-
5
Table 3-6 LTE frame structure related parameters
3.3 Transport Channels
3.3.1 Downlink Transport Channels
BCH (Broadcast Channel): It has a fixed transport format, provided by the specifications. It is used
for transmission of the information on the BCCH logical channel. It can be characterised by fixed, pre-
defined transport format and the requirement to be broadcast in the entire coverage area of the cell
DLSCH(Downlink Shared Channel): DL-SCH is the transport channel used for transmission of
downlink data in LTE. It supports LTE features such as dynamic rate adaptation and channel-
dependent scheduling in the time and frequency domain, hybrid ARQ, and spatial multiplexing. It also
supports discontinuous reception (DRX) to reduce mobile-terminal power consumption while still
providing an always on experience, similar to the Continuous Packet Connectivity (CPC) mechanism in
HSPA.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 12 of 64
PCH(Paging Channel): It is used for transmission of paging information on the PCCH logical
channel. The PCH supports DRX to allow the mobile terminal to save battery power by sleeping and
waking up to receive the PCH only at predefined time instants.
MCH (Multicast Channel): It is used to support MBMS. It is characterised by a semi-static transport
format and semi-static scheduling. In case of multi-cell transmission using MBSFN, the scheduling and
transport format configuration is coordinated among the cells involved in the MBSFN transmission
3.3.2 Uplink Transport Channels
UL-SCH (Uplink Shared Channel): It is characterised by the possibility to use beamforming; support
for HARQ, dynamic link adaptation by varying the transmit power and potentially modulation and
coding and also for both dynamic and semi-static resource allocation.
RACH (Random Access Channel(s)): It is characterised by limited control information and collision
risk. The possibility of using open loop power control depends on the physical layer solution.
3.4 Physical Channels
Physical Channels carry information from higher layers including user data and control information.
3.4.1 Downlink Physical Channels
PBCH (Physical Broadcast Channel): The coded BCH transport block is mapped to four subframes
within a 40 ms interval. This 40 ms timing is blindly detected, i.e. there is no explicit signalling
indicating 40 ms timing. Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded
from a single reception, assuming sufficiently good channel conditions.
PCFICH (Physical Control Format Indicator Channel): Informs the UE about the number of
OFDM symbols used for the PDCCHs. It is transmitted in every subframe
PDCCH (Physical Downlink Control Channel): Informs the UE about the resource allocation of
PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH. It also carries the uplink
scheduling grant. The downlink control signalling (PDCCH) is located in the first n OFDM symbols
where n 3 and consists of:
Transport format, resource allocation, and hybrid-ARQ information related to DL-SCH, and
PCH;
Transport format, resource allocation, and hybrid-ARQ information related to UL-SCH;
QPSK modulation is used for all control channels
PHICH (Physical Hybrid ARQ Indicator Channel): Carries Hybrid ARQ ACK/NAKs in response to
uplink transmissions
PDSCH (Physical Downlink Shared Channel): Carries the DL-SCH and PCH
PMCH (Physical Multicast Channel): Carries the MCH
3.4.2 Uplink Physical Channels
PUCCH (Physical Uplink Control Channel): Carries Hybrid ARQ ACK/NAKs in response to
downlink transmission. It also carriers Scheduling Request (SR) and CQI reports.
PUSCH (Physical Uplink Shared Channel): Carries the UL-SCH
PRACH (Physical Random Access Channel): Carries the random access preamble. Used for Call
setup
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AIRCOM International ASSETV8.0- LTE Application Notes Page 13 of 64
3.4.3 Mapping between transport channels and physical channels (Downlink)
Figure 3-4 below depicts the mapping between the downlink transport and physical channels
Figure 3-4 Mapping between downlink transport and physical channels
3.4.4 Mapping between transport channels and physical channels (Uplink)
Figure 3-5 below depicts the mapping between the uplink transport and physical channels
Figure 3-5 Mapping between uplink transport and physical channels
3.5 Physical Signals
Physical Signals handle synchronisation, cell identification and channel estimation.
3.5.1 Downlink Physical Signals-Channels
P-SCH (Downlink Primary Synchronisation Channel): Used for cell search and identification by
the UE. Carries part of the cell ID (one of 3 orthogonal sequences).
S-SCH (Downlink Secondary Synchronisation Channel): Used for cell search and identification by
the UE. It carries the remainder of the cell ID (one of 168 binary sequences).
DL RS (Downlink Reference Signal): To carry out downlink coherent demodulation, the mobile
terminal needs estimates of the downlink channel. A straightforward way to enable channel estimation
in case of OFDM transmission is to insert known reference symbols into the OFDM time-frequency
grid. In LTE, these cell specific reference symbols are jointly referred to as the LTE Downlink
Reference Signals (DL RSs). These downlink reference symbols are inserted within the first and the
third last OFDM symbols of each slot and with a frequency-domain spacing of six subcarriers.
Furthermore, there is a frequency-domain staggering of three subcarriers between the first and second
reference symbols. Thus within each resource block, consisting of 12 subcarriers, there are four
reference symbols. This is true for all subframes except subframes used for MBSFN-based
transmission.
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In case of multi antenna transmission, there is one reference signal transmitted per downlink antenna
port. The number of downlink antenna ports is equal to 1, 2 or 4. The two-dimensional reference signal
sequence is generated as the symbol-by-symbol product of a two-dimensional orthogonal sequence and
a two-dimensional pseudo-random sequence. There are 3 different two-dimensional orthogonal
sequences and 168 different two-dimensional pseudo-random sequences. Each cell identity (ID)
corresponds to a unique combination of one orthogonal sequence and one pseudo-random sequence,
thus allowing for 504 unique cell identities. In the reference-signal structure, the frequency-domain
positions of the reference symbols are the same between consecutive subframes. However, the
frequency-domain positions of the reference symbols may also vary between consecutive subframes,
also referred to as reference-symbol frequency hopping. Thus, the frequency hopping can be described
as adding a sequence of frequency offsets, to the basic reference-symbol pattern, with the offset being
the same for all reference symbols within a subframe, but varying between consecutive subframes. The
reference-symbol positions p in subframe k can thus be expressed as
First reference symbols: p(k) = (p0 + 6 i + offset(k)) mod 6 Second reference symbols: p(k) = (p0 + 6 i + 3 + offset(k)) mod 6
where, i is an integer. The sequence of frequency offsets or the frequency-hopping pattern has a period
of length 10, i.e. the frequency-hopping pattern is repeated between consecutive frames. There are 168
different frequency-hopping patterns defined, where each pattern corresponds to one cell-identity
group. By applying different frequency-hopping patterns to neighbour cells, the risk that reference
symbols of neighbour cells are continuously colliding can be avoided. This is especially of interest
if/when reference symbols are transmitted with higher energy compared to the remaining resource
elements, also referred to as reference signal energy boosting.
3.5.2 Uplink Physical Signals
DM-RS (Uplink Demodulation Reference Signal): It is used for synchronisation to the UE and UL
channel estimation and is associated with transmission of PUSCH or PUCCH
S-RS (Uplink Sounding Reference Signal): It is used to monitor propagation conditions with UE,
however it is not associated with transmission of PUSCH or PUCCH
In Table 3-7 all uplink and downlink Channels and Signals are presented along with their allowable
Modulation options.
Channels Link Modulation Signals Link Modulation
PBCH DL QPSK P-SCH DL One of 3 Zadoff-Chu sequences
PDCCH DL QPSK
S-SCH DL Two 31-bit M-sequences (binary)
- one of 168 Cell IDs plus other info PDSCH DL
QPSK, 16QAM,
64QAM
PMCH DL QPSK, 16QAM,
64QAM RS DL
OS*PRS defined by Cell ID
(P-SCH &S-SCH) PCFICH DL QPSK
PHICH DL BPSK DM-RS UL Uth root Zadoff-Chu
PRACH UL QPSK S-RS UL Zadoff-Chu
PUCCH UL BPSK, QPSK
PUSCH UL QPSK, 16QAM,
64QAM
Table 3-7 Supported modulations for all Physical Channels and Signals
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3.6 Multi-Antenna Transmission
3.6.1 General on MIMO
LTE supports downlink transmission on 1, 2 or 4 cell specific antenna ports corresponding either to 1,
2 or 4 cell-specific reference signals. On their turn each one of the RS corresponds to one antenna port.
The following DL transmission modes are defined for PDSCH
Single antenna port; port 0
Single User MIMO
Transmit diversity
Open loop spatial multiplexing
Closed loop spatial multiplexing
Multi User MIMO
Closed-loop Rank=1 pre-coding
Single antenna port; port 5
3.6.2 Downlink
For the LTE downlink, the following multiple antenna schemes are supported:
Tx diversity: The first and simplest downlink LTE multiple antenna scheme is open-loop Tx diversity.
It is identical in concept to the scheme introduced in UMTS Release 99. The more complex, closed-
loop Tx diversity techniques from UMTS have not been adopted in LTE, which instead uses the more
advanced MIMO, which was not part of Release 99. LTE supports either two or four antennas for Tx
diversity. Space-Frequency Block Coding (SFBC) is used for two antennas while a combination of
SFBC and Frequency Switching Transmit Diversity (FSTD) is employed for four transmit antennas.
Rx diversity: The second downlink scheme, Rx diversity, is mandatory for the UE. It is the baseline
receiver capability for which performance requirements will be defined. A typical use of Rx diversity is
maximum ratio combining of the received streams to improve the SNR in poor conditions. Rx diversity
provides little gain in good conditions
Spatial Multiplexing and SU-MIMO: SU-MIMO (Figure 3-6) includes conventional techniques such
as Delay (cyclic for OFDM) Diversity, Transmit \ Receive (spatial) diversity and Spatial Multiplexing
and Precoded Spatial Multiplexing. It can be implemented as Open (without feedback) and Closed
Loop (with feedback). Diversity techniques improve the signal to interference ratio by transmitting the
same stream of single user data from multiple antennas. On the other hand, Spatial Multiplexing
increases the per-user data rate or throughput by transmitting multiple streams of data dedicated to for a
single user.
Spatial multiplexing and MIMO are supported for two and four antenna configurations. Assuming a
two-channel UE receiver, this scheme allows for 2x2 or 4x2 MIMO. A four-channel UE receiver,
which is required for a 4x4 configuration, has been defined but is not likely to be implemented in the
near future. The most common configuration will be 2x2 SU-MIMO. In this case the payload data will
be divided into the two code-word streams CW0 and CW1 and processed accordingly. Depending on
the pre-coding used, each code word is represented at different powers and phases on both antennas. In
addition, each antenna is uniquely identified by the position of the reference signals within the frame
structure.
Cyclic Delay Diversity: In addition to MIMO pre-coding there is an additional option called cyclic
delay diversity (CDD). This technique adds antenna-specific cyclic time shifts to artificially create
multi-path on the received signal and prevents signal cancellation caused by the close spacing of the
transmit antennas. The CDD system works by adding the delay only to the data subcarriers while
leaving the RS subcarriers alone.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 16 of 64
3.6.3 Uplink
The baseline configuration of the UE has one transmitter. This configuration was chosen to save cost
and battery power, and with this configuration the system can support MU-MIMO (Figure 3-6), i.e.,
two different UE transmitting in the same frequency and time to the eNodeB. This configuration has
the potential to double uplink capacity (in ideal conditions) without incurring extra cost to the UE. MU-
MIMO scheme consists of multiple users separated in spatial domain in both UL and DL sharing the
same time-frequency resources. It uses multiple narrow beams to separate users in the spatial domain
and can be considered as a hybrid of beamforming and spatial multiplexing. It can ultimately serve
more terminals by scheduling multiple terminals using the same resources. This increases the overall
cell capacity and the number of simultaneously served terminals. It is suitable for highly loaded cells
and for scenarios where the number of served terminals is more important than the peak user data rates.
An optional configuration of the UE is a second transmit antenna, which allows the possibility of
uplink Tx diversity and SU-MIMO. The latter offers the possibility of increased data rates depending
on the channel conditions. For the eNodeB, receive diversity is a baseline capability and the system
will support either two or four receive antennas.
Figure 3-6 SU-MIMO and MU-MIMO
3.6.4 MBSFN Transmission
MBSFN is supported for the MCH transport channel. Multiplexing of transport channels using MBSFN
and non-MBSFN transmission is done on a per-sub-frame basis. Additional reference symbols,
transmitted using MBSFN are transmitted within MBSFN subframes.
3.7 Physical Layer Procedure
3.7.1 Link adaptation
Link adaptation (AMC: Adaptive Modulation and Coding) with various modulation schemes and
channel coding rates is applied to the shared data channel. The same coding and modulation is applied
to all groups of resource blocks belonging to the same Layer 2 Protocol Data Unit (PDU) scheduled to
one user within one TTI and within a single stream.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 17 of 64
3.7.2 Cell search
Cell search is the procedure by which a UE acquires time and frequency synchronisation with a cell
and detects the Cell ID of that cell. LTE cell search supports a scalable overall transmission bandwidth
corresponding to 72 sub-carriers and upwards. LTE cell search is based on the primary and secondary
synchronisation signals (see chapter 3.5.1 Downlink Physical Signals), the downlink reference signals
transmitted in the downlink. The primary and secondary synchronisation signals are transmitted over
the central 72 sub-carriers in the first and sixth subframe of each frame. Neighbour-cell search is based
on the same downlink signals as the initial cell search.
3.8 Physical Layer Measurements and Indicators
3.8.1 Reference Signal Received Power (RSRP)
Reference Signal Received Power (RSRP), is determined for a considered cell as the linear average
over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals
within the considered measurement frequency bandwidth. For RSRP determination the cell-specific
reference signals R0 and if available R1 can be used. If receiver diversity is in use by the UE, the
reported value shall not be lower than the corresponding RSRP of any of the individual diversity
branches.
3.8.2 E-UTRA Carrier RSSI
E-UTRA Carrier Received Signal Strength Indicator, comprises the total received wideband power
observed by the UE from all sources, including co-channel serving and non-serving cells, adjacent
channel interference, thermal noise etc.
3.8.3 Reference Signal Received Quality (RSRQ)
RSRQ is defined as the ratio NRSRP / (E-UTRA carrier RSSI), where N is the number of RBs of the
E-UTRA carrier RSSI measurement bandwidth. The measurements in the numerator and denominator
shall be made over the same set of resource blocks.
3.8.4 DLRS TX Power
Downlink Reference Signal transmit power is determined for a considered cell as the linear average
over the power contributions (in [W]) of the resource elements that carry cell-specific reference signals
which are transmitted by the eNodeB within its operating system bandwidth. For DL RS TX power
determination the cell-specific reference signals R0 and if available R1 can be used. The reference point
for the DL RS TX power measurement shall be the TX antenna connector.
3.8.5 Received Interference Power
Received Interference Power is the uplink received interference power, including thermal noise, within
one physical resource blocks bandwidth of RBscN resource elements. The reported value shall contain a
set of Received Interference Powers of physical resource blocks. The reference point for the
measurement shall be the RX antenna connector. In case of receiver diversity, the reported value shall
be the linear average of the power in the diversity branches.
3.8.6 Thermal noise power
The uplink thermal noise power within the UL system bandwidth consisting of ULRBN resource blocks is
defined as (No x W), where No denotes the white noise power spectral density on the uplink carrier
frequency and fNNWRBsc
ULRB = denotes the UL system bandwidth. The measurement is optionally
reported together with the Received Interference Power measurement, it shall be determined over the
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AIRCOM International ASSETV8.0- LTE Application Notes Page 18 of 64
same time period as the Received Interference Power measurement. The reference point for the
measurement shall be the RX antenna connector. In case of receiver diversity, the reported value shall
be the linear average of the power in the diversity branches.
3.8.7 Quality, Precoding & Rank Indicators
The following indicators are reported by the UE back to the eNodeB
CQI (Channel Quality Indicator): It is a 4 bit index pointing into a table of 16 different modulation
and coding schemes. It indicates or suggests a combination of modulation and coding scheme that the
eNodeB should use to ensure that the BLER (Block Error Ratio) experienced by the UE remains less
than 10%.
CQI Modulation Efficiency Actual coding rate Required SINR 1 QPSK 0.1523 0.07618 -4.46 2 QPSK 0.2344 0.11719 -3.75 3 QPSK 0.3770 0.18848 -2.55 4 QPSK 0.6016 308/1024 -1.15 5 QPSK 0.8770 449/1024 1.75 6 QPSK 1.1758 602/1024 3.65 7 16QAM 1.4766 378/1024 5.2 8 16QAM 1.9141 490/1024 6.1 9 16QAM 2.4063 616/1024 7.55 10 64QAM 2.7305 466/1024 10.85 11 64QAM 3.3223 567/1024 11.55 12 64QAM 3.9023 666/1024 12.75 13 64QAM 4.5234 772/1024 14.55 14 64QAM 5.1152 873/1024 18.15 15 64QAM 5.5547 948/1024 19.25
Table 3-8 CQI Table
PMI (Precoding Matrix Indicator): PMI ensures that the correct spatial domain precoding matrix is
applied by the eNodeB so that the transmitted signal matches with the spatial channel experienced by
the UE. It is denoted by the Transmit Precoding Matrix Indicator (TPMI) that consists of 3 bit or 6 bit
information field for 2 or 4 transmit antennas, respectively. It is compulsory for closed loop spatial
multiplexing.
RI (Rank Indicator): RI indicates the number of spatial layers that can be supported by the UE based
on the channel conditions. The transmission rank selected to be used is dependent on RI as well as
other factors (depending on the vendor) such as traffic pattern, available transmission bandwidth etc. RI
is compulsory for both open and closed loop spatial multiplexing.
3.9 Radio Resource Management and Scheduling
There are two schedulers in the eNodeB allocating physical resources, one for uplink and one for
downlink. The schedulers grant the right to transmit on a per UE basis. The resource assignment
consists of Physical Resource Blocks (PRBs) and a Modulation and Coding Scheme (MCS). The
resources are allocated for one or multiple TTIs. A PRB consists of certain subcarriers in the frequency
domain and one TTI in the time domain as explained in LTE Frame Structure section. The baseline for
both uplink and downlink is dynamic scheduling where the PRBs and MCSs can be scheduled for each
TTI via a Cell Radio Network Temporary Identifier (C-RNTI) on the L1/L2 control channels. The UE
always monitor the control channels in order to find any allocation of uplink or downlink resources
when downlink reception is enabled.
Predefined resources can also be allocated which the UE can use if no C-RNTI is found on the control
channels. In downlink this means the UE does blind decoding of the predefined resources unless a C-
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AIRCOM International ASSETV8.0- LTE Application Notes Page 19 of 64
RNTI is found in which case it overrides the predefined allocations for the TTI. In the downlink case
the network decodes the resources predefined to the UEs unless the C-RNTI is present. The scheduler
should consider a number of factors when taking scheduling decisions. These factors include transport
volume, QoS and measurements of the UE radio environment. In both uplink and downlink,
measurement reports need to be reported to the eNodeB.
3.9.1 Radio Bearer Priority and Rate Control
In downlink, the eNodeB enforces the Maximum Bit Rate (MBR) of radio bearers with a Guaranteed
Bit Rate (GBR) and the Aggregate Maximum Bit Rate (AMBR) of groups of Non-GBR bearers. In the
uplink, the Radio Resource Control (RRC) entity controls the uplink rate by giving each bearer a
priority and a Prioritised Bit Rate (PBR). For radio bearers with GBR, a MBR is also provided. The
radio bearers are served in decreasing priority order up to their PBR. For any remaining resources the
bearers are served again in decreasing priority order ensuring that the MBR is not exceeded. If all
bearers have a PBR of 0, the first step is skipped and the bearers are served in strict priority order. The
eNodeB ensures that the AMBR in uplink is not exceeded, by limiting the total amount of granted
resources.
3.10 Interference Co-ordination Schemes
To minimise Inter-Cell Interference the following frequency reuse schemes are considered.
Frequency Reuse-1 with Prioritisation: Each sector divides the available bandwidth into prioritised
(one third) and non-prioritised (two third) sections. The prioritised section is used more often than the
non-prioritised one by each sector in order to concentrate the interference that it causes to other sectors.
Soft Frequency Reuse: The introduction of power difference between the prioritised and non-
prioritised spectrum divides the sector into an inner and outer region. Cell Centre Users (CCU) who are
users in the inner region can be reached with reduced power compared to Cell Edge Users (CEU) who
lie in the outer region. Overall CCUs are assigned with frequency Re-use 1 while CEUs employ
frequency Re-use 3.
Reuse Partitioning: Reuse is similar to the Soft Frequency Reuse scheme. The total channel
bandwidth is divided into two parts and one of the parts uses higher power than the other. The lower-
power-part is the same in all sectors. The higher-power-part is divided between sectors so that each one
of them gets one third of the high power spectrum. Overall the lower-power-part employs frequency
Re-use 1 while the higher-power-part is configured with a frequency Re-use 3.
Figure 3-7 Reuse Partitioning
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3.11 LTE Devices UE Categories
Five different device capability classes have been standardised. The supported data rates range from 5
to 75Mbps in the UL and 10 to 300Mbps in the DL. Category 5 devices support 64QAM in the uplink
while others use QPSK and 16QAM. MIMO transmit and receive diversity are supported by categories
2 to 5. The actual device capabilities also depend on other signalling requirements and not just on these
categories. Table 3-9 presents the nominal characteristic for each one of the 5 UE categories.
Parameters Category 1 Category 2 Category 3 Category 4 Category 5
Peak Data Rate (DL) 10 Mbps 50 Mbps 100 Mbps 150 Mbps 300 Mbps Peak Data Rate (UL) 5 Mbps 25 Mbps 50 Mbps 50 Mbps 75 Mbps Block Size (DL) 10296 51024 102048 149776 299552 Block Size (UL) 5160 25456 51024 51024 75376 Max. Modulation (DL) 64QAM 64QAM 64QAM 64QAM 64QAM Max. Modulation (UL) 16QAM 16QAM 16QAM 16QAM 64QAM RF Bandwidth 20 MHz 20 MHz 20 MHz 20 MHz 20 MHz Transmit Diversity 1-4 Tx 1-4 Tx 1-4 Tx 1-4 Tx 1-4 Tx Receive Diversity Yes Yes Yes Yes Yes Spatial Multiplexing (DL) Optional 2 X 2 2 X 2 2 X 2 4 X 4 Spatial Multiplexing (UL) No No No No No MU-MIMO (DL) Optional Optional Optional Optional Optional MU-MIMO (UL) Optional Optional Optional Optional Optional
Table 3-9 UE Categories
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4 LTE Technology in ASSET
4.1 Introduction
This chapter presents how LTE technology is modelled in ASSET. The relevant Graphical User
Interfaces (GUIs) are explained and suggestions are made on the values to be entered in the various
fields to properly design an LTE network depending on planners objectives. The logical order in
which the LTE elements are presented is as follows:
Frequency bands No dependencies
Frame Structure No dependencies
Carriers Frequency Band and Frame Structure should be decided upon first
Bearers No dependencies
Services Carriers and Bearers should be decided upon first
Terminal Types Services should be decided upon first
E-Node B and Cell parameters Carriers should be decided upon first
Coverage Predictions (RSRP, RSRQ) All of the above are required
Capacity Predictions / Simulation All of the above are required
Figure 4-1 LTE modelling in ASSET
Frequency
Bands
Frame Structure
Carriers Bearers
Services
Terminal Types eNodeB and Cell parameters\Load Levels
Setup
dependencies
Coverage Predictions (RSRP,
RSRQ)
Capacity Predictions
Results
Traffic Raster
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AIRCOM International ASSETV8.0- LTE Application Notes Page 22 of 64
4.2 Frequency bands
An LTE network can consist of eNodeBs with cells configured with same or different carrier
bandwidths (with overlapping start and end frequencies). In addition, FDD and TDD might co-exist.
This overlapping of carriers between different cells can result in co-channel and adjacent-channel
interference. The ASSET GUI for defining and selecting the LTE frequency bands is presented below.
The 3GPP standard E-UTRA bands are already set up for you; these are not modifiable, but you can
rename them. If necessary, you can add customised bands.
Figure 4-2 Definition of LTE frequency bands in ASSET
LTE will operate in a wide range of spectrum with simultaneous deployment in different E-UTRA
bands. The supported modes of operation are Frequency Division Duplex (FDD), Half Duplex FDD
(H-FDD) and Time Division Duplex (TDD). A typical UE would support a certain subset of E-UTRA
bands defining the capability to switch bands, roam between national operators and roam
internationally. Table 4-1 presents the worldwide standardised LTE bands.
The default bands for FDD are 1 to 14 and for TDD 33 to 40. For FDD, the E-ARFCNs are different
for uplink and downlink, but for TDD they are the same.
The channel bandwidth is measured in MHz and is used as a reference for transmitter and receiver RF
requirements. Some E-UTRA bands do not allow operation in the narrow bandwidth modes, i.e. less
than 5 MHz while others restrict operations in the wider channel bandwidths, i.e. more than 15 MHz.
This is summarised in Table 4-2.
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E-UTRA
Band
Bandwidth
UL (MHz)
E-ARFCN
UL
Bandwidth
DL (MHz)
E-ARFCN
DL
Duplex
Mode
1 1920-1980 13000 13599 2110-2170 0 599 FDD
2 1850-1910 13600 14199 1930-1990 600 - 1199 FDD
3 1710-1785 14200 14949 1805-1880 1200 1949 FDD
4 1710-1755 14950 15399 2110-2155 1950 2399 FDD
5 824-849 15400 15649 869-894 2400 2649 FDD
6 830-840 15650 15749 875-885 2650 2749 FDD
7 2500-2570 15750 16449 2620-2690 2750 3449 FDD
8 880-915 16450 16799 925-960 3450 3799 FDD
9 1749.9-1784.9 16800 17149 1844.9-1879.9 3800 4149 FDD
10 1710-1770 17150 17749 2110-2170 4150 4749 FDD
11 1427.9-1452.9 17750 17999 1475.9-1500.9 4750 4999 FDD
12 698-716 18000 18179 728-746 5000 5179 FDD
13 777-787 18180 18279 746-756 5180 5279 FDD
14 788-798 18280 18379 758-768 5280 5379 FDD
...
33 1900-1920 26000 26199 1900-1920 26000 26199 TDD
34 2010-2025 26200 26349 2010-2025 26200 26349 TDD
35 1850-1910 26350 26949 1850-1910 26350 26949 TDD
36 1930-1990 26950 27549 1930-1990 26950 27549 TDD
37 1910-1930 27550 27749 1910-1930 27550 27749 TDD
38 2570-2620 27750 28249 2570-2620 27750 28249 TDD
39 1880-1920 28250 28649 1880-1920 28250 28649 TDD
40 2300-2400 28650 29649 2300-2400 28650 29649 TDD
Table 4-1 E-UTRA Bands
Supported Channels (non-overlapping)
E-UTRA
Band
Downlink
Bandwidth
Channel Bandwidth (MHZ)
1.4 3 5 10 15 20
1 60 - - 12 6 4 3
2 60 42 20 12 6 4* 3*
3 75 53 23 15 7 5* 3*
4 45 32 15 9 4 3 2
5 25 17 8 5 2* - -
6 10 - - 2 1* X X
7 70 - - 14 7 4 3*
8 35 25 11 7 3* - -
9 35 - - 7 3 2* 1*
10 60 - - 12 6 4 3
11 25 - - 5 2* 1* 1*
12 18 12 6 3* 1* - X
13 10 7 3 2* 1* X X
14 10 7 3 2* 1* X X
...
33 20 - - 4 2 1 1
34 15 - - 3 1 1 X
35 60 42 20 12 6 4 3
36 60 42 20 12 6 4 3
37 20 - - 4 2 1 1
38 50 - - 10 5 - -
39 40 - - 8 4 3 2
40 100 - - - 10 6 5
* UE receiver sensitivity can be relaxed
X Channel bandwidth too wide for the band - Not supported
Table 4-2 Supported channel configurations for the LTE bands
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Transmission Bandwidth is defined as the bandwidth of an instantaneous transmission from a UE or
eNodeB, measured in Resource Blocks (RBs). Six different Channel Bandwidths and their
corresponding Transmission Bandwidths have been standardised and are presented in the following
table.
Channel Bandwidth (MHz) 1.4 3 5 10 15 20
Transmission Bandwidth (MHz) 1.08 2.7 4.5 9 13.5 18 Transmission Bandwidth configuration (N
RB) 6 15 25 50 75 100
Bandwidth Efficiency (%) 77 90 90 90 90 90 Table 4-3 Channel Bandwidth and Transmission Bandwidth
The Transmission Bandwidth is contained inside the Channel Bandwidth as indicated in this figure:
Figure 4-3 Channel Bandwidth and Transmission Bandwidth
4.3 LTE Frame Structure
The following figure shows the LTE Frame Structures dialog box:
Figure 4-4 LTE frame structure definition in ASSET
The transmitted signal in one slot is described by a Resource Grid consisting of subcarriers and
symbols in frequency and time domain, respectively. The smallest part of the resource grid is called
Resource Element (RE) and it has dimensions of 1 subcarrier x 1 modulated symbol. A Resource Block
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AIRCOM International ASSETV8.0- LTE Application Notes Page 25 of 64
(RB) consists of N consecutive OFDMA symbols x M consecutive subcarriers. This concept is
demonstrated in Figure 4-5.
Figure 4-5 Definition of the Resource Element and the Resource Block
The standardized RB configurations are given in Table 4-4. Firstly they are separated in three main
types, namely Type-1 which is Frequency Division Duplex (FDD), Type-2 which is Time Division
Duplex (TDD) and Type-3 that is Multi-Media Broadcast over a Single Frequency Network (MBSFN).
Types 1 and 2 can be implemented either with Normal Cyclic Prefix or Extended Cyclic Prefix with a
subcarrier spacing of 15\7.5 kHz while Type 3 is implemented only with Extended Cyclic Prefix with a
reduced subcarrier spacing of 7.5 kHz. In an OFDM symbol the cyclic prefix is a repeat of the end of
the symbol at the beginning. The purpose is to allow multipath to settle before the main data arrives at
the receiver. The receiver is arranged to decode the signal after it has settled because this is when the
frequencies become orthogonal to one another thus CP acts as a guard interval.
Frame
Type Cyclic Prefix
Subcarrier
Spacing (kHz)
Link
Direction # of Subcarriers
# of
Symbols
Type 1 FDD Normal 15 DL 12 7
Extended 15 DL 12 6
Type 2 TDD Normal 15 UL 12 7
Extended 7.5 DL 24 3
Type 3 MBSFN Extended 15 UL 12 6
Table 4-4 Standardized Resource Block configurations
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Default values for LTE Standards Frame Structures
Type-1FDD-
Normal CP
Type-1FDD-
Extended CP
Type-2TDD-
Normal CP
Type-2TDD-
Extended CP
Type3-MBSFN
Duplex mode FDD FDD TDD TDD FDD
Configuration LTE Standards LTE Standards LTE Standards LTE Standards LTE Standards
Frame duration 10 10 10 10 10
Slots/ subframe 2 2 2 2 2
Subframes 10 10 10 10 10
Cyclic Prefix Normal Extended Normal Extended Extended
Subcarrier spacing 15 15 15 15 7.5
TDD frame Config Greyed-Out Greyed-Out 1 1 Greyed-Out
RB Symbols DL 7 6 7 6 3
RB Symbols UL 7 6 7 6 6
Subcarriers DL 12 12 12 12 24
Subcarriers UL 12 12 12 12 12
RS Subcarriers 2 2 2 2 12
Table 4-5 Parameter settings for the Default Frame structures in ASSET
4.4 Carriers
Since the appropriate LTE Frequency Band and LTE Frame Structure have been selected or defined (in
case the default ones are not the appropriate) then the Carriers can be defined. Figure 4-6 and Figure
4-7 show the ASSET GUI for defining LTE Carriers.
Figure 4-6 Definition of the LTE Carriers in ASSET
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Figure 4-7 Definition of the LTE Carriers in ASSET, Overhead
Each LTE Carrier is representing the Channel bandwidth with a certain Transmission Bandwidth
Configuration. The relation between Channel Bandwidth and Transmission Bandwidth is shown in
Table 4-3. One of the pre-defined Frequency Bands and Frame Structures has to be selected for each
one of the carriers. Based on the Frequency Band selection (FDD or TDD according to Table 4-1), only
the respective default and user-defined Frame Structures are available in Frame Structure drop down
list. For example for FDD frequency bands only the FDD frame structures appear in the drop down list.
Then, the available Bandwidth within the specific Frequency Band must be specified keeping in mind
the restrictions implied by Table 4-2 as some Frequency Bands dont support all Bandwidth options.
The next step is to specify the placement of the Bandwidth chunk within the Frequency Band. This is
done by defining the point where the Bandwidth chunk starts (Low point) and then the High Point as
well as the E-ARFCNs are automatically calculated. It is important to place the Bandwidth at the right
place in the Frequency Band as this will affect co-channel and adjacent-channel interference
calculations of overlapping and neighbouring carriers. The number of Resource Blocks, Fast Fourier
Transform (FFT) Size and Sampling Factor are auto-completed based on Table 4-6. The Subcarrier
Spacing used to calculate Sampling Factor is given in Table 4-5.
Channel Bandwidth (MHz) # of Resource Blocks FFT Size
1.4 6 128
3 15 256
5 25 512
10 50 1024
15 75 1536
20 100 2048
Table 4-6 LTE Carrier Parameters
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4.5 Bearers
Bearers represent the air interface connections, performing the task of transporting voice and data
information between cells and terminal types. After bearers have been defined, you can then decide
which ones will be supported by your different services. The following figure presents the ASSET GUI
for the definition of LTE Bearers.
Figure 4-8 Definition of LTE Bearers in ASSET
The Default Uplink and Downlink LTE bearers are defined per CQI providing 15 DL bearers and 4 UL
bearers. CQI is a report sent from the UE to the eNodeB suggesting the appropriate Modulation and
Coding to be used by the eNodeB when transmitting in order to maintain a Block Error Ratio (BLER)
less than 10% at the RLC level. The eNodeB is finally deciding upon MCS depending on CQI and
other (vendor dependent) related measurements. Downlink MCSs are 32. Each default Bearers has
Control & Traffic SINR requirements according to Table 3-8.
Figure 4-9 Bearer SINR requirements
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The following table is a vendor specific mapping of CQIs to MCSs.
MCS Index Modulation Coding rate x 1024 Efficiency Comments Code Rate
0 2 120 0.2344 from CQI table 0.1171875
1 2 157 0.3057 Average Efficiency 0.15332031
2 2 193 0.377 from CQI table 0.18847656
3 2 251 0.4893 Average Efficiency 0.24511719
4 2 308 0.6016 from CQI table 0.30078125
5 2 379 0.7393 Average Efficiency 0.37011719
6 2 449 0.877 from CQI table 0.43847656
7 2 526 1.0264 Average Efficiency 0.51367188
8 2 602 1.1758 from CQI table 0.58789063
9 2 679 1.3262 Average Efficiency 0.66308594
10 4 340 1.3262 overlap 0.33203125
11 4 378 1.4766 from CQI table 0.36914063
12 4 434 1.69535 Average Efficiency 0.42382813
13 4 490 1.9141 from CQI table 0.47851563
14 4 553 2.1602 Average Efficiency 0.54003906
15 4 616 2.4063 from CQI table 0.6015625
16 4 658 2.5684 Average Efficiency 0.64257813
17 6 438 2.5684 overlap 0.42773438
18 6 466 2.7305 from CQI table 0.45507813
19 6 517 3.0264 Average Efficiency 0.50488281
20 6 567 3.3223 from CQI table 0.55371094
21 6 616 3.6123 Average Efficiency 0.6015625
22 6 666 3.9023 from CQI table 0.65039063
23 6 719 4.21285 Average Efficiency 0.70214844
24 6 772 4.5234 from CQI table 0.75390625
25 6 822 4.8193 Average Efficiency 0.80273438
26 6 873 5.1152 from CQI table 0.85253906
27 6 910 5.33495 Average Efficiency 0.88867188
28 6 948 5.5547 from CQI table 0.92578125
29 Implicit TBS signalling with QPSK
30 Implicit TBS signalling with 16QAM
31 Implicit TBS signalling with 64QAM
Table 4-7 CQIs to MCS mapping
4.6 Services
To account for the different services offered to the subscriber, you can set up your own services and
then allocate the services to terminal types. For example, services might have different costs, data rates,
and other requirements such as quality of service (QoS). Some of these factors are determined by the
bearers that you assign to a service. The parameters that you specify will influence how the simulation
(Chapter 5) behaves and will enable you to examine coverage and service quality for individual types
of services.
The standard LTE services correspond to QoS Class Identifier (QCI) values of 1 to 9 and are available
in ASSET by default. The following figure presents the ASSET GUI for the definition of LTE
Services.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 30 of 64
Figure 4-10 Definition of LTE Services in ASSET
QoS differentiation, i.e. prioritisation of different services according to their requirements becomes
extremely important when the system load gets higher. The most relevant parameters of QoS classes
are
Transfer Delay: This represents how delay sensitive the traffic is. For example, the VoIP
class is meant for very delay sensitive traffic while the P2P File Sharing class is delay
insensitive.
Guaranteed Bit rate: Delay sensitive QoS Classes have guaranteed bit rate requirements.
This defines the minimum bearer bit rate that the E-UTRAN must provide and it can be used
in admission control and in resource allocation. Each guaranteed bit rate service also has a
maximum bit rate demand, i.e. it can't exceed this limit.
Allocation and Retention Priority (ARP): Within each QoS class there are different
allocation and retention priorities. The primary purpose of ARP is to decide whether a bearer
establishment / modification request can be accepted or needs to be rejected in case of
resource limitations (typically available radio capacity in case of GBR bearers). In addition,
the ARP can be used (e.g. by the eNodeB) to decide which bearer(s) to drop during
exceptional resource limitations (e.g. at handover).
It is important to remember that pure prioritisation in packet scheduling alone is not enough to provide
full QoS differentiation gains. Users within the same QoS class and ARP class will share the available
capacity. If the number of users is simply too high, then they will suffer from bad quality. In that case it
is better to block a few users to guarantee the quality of existing connections, like streaming videos.
The radio network can estimate the available radio capacity and block an incoming user if there is no
room to provide the required bandwidth without sacrificing the quality of existing connections.
Table 4-8 presents the standard LTE Services per QCI. Gaming, VoIP, Signalling and Web Browsing
are treated as the most delay sensitive Classes while Streaming, E-mail, P2P File Sharing and Chat are
not that delay sensitive. Highest Priority in terms of ARP is given to Signalling followed by VoIP and
lowest to Chat. Packet Error Loss Rate (PELR) requirements vary with values starting from 10-2
down
to 10-6
. The loosest PELR requirements hold for VoIP at 10-2
.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 31 of 64
Name QCI Resource
Type Priority
Packet
Delay
Budget
Packet Error Loss
Rate Example Services
VoIP QCI-1
1 2 100 ms 10-2 Conversational Voice
Video Call QCI-2
2
GBR 4 150 ms 10-3
Conversational Video (Live Streaming)
Gaming
QCI-3 3 3 50 ms 10-3 Real Time Gaming
Streaming
QCI-4 4 5 300 ms 10-6
Non-Conversational Video
(Buffered Streaming)
Signalling
QCI-5 5 1 100 ms 10-6 IMS Signalling
E-mail
QCI-6 6
6
300 ms
10-6
Video (Buffered Streaming) TCP-based (e.g., www, e-mail,
chat, ftp, p2p file sharing,
progressive video, etc.)
Web browsing
QCI-7 7 Non-GBR
7
100 ms
10-3
Voice,
Video (Live Streaming) Interactive Gaming
P2P File Sharing
QCI-8
8
8
300 ms
10-6
Video (Buffered Streaming)
TCP-based (e.g., www, e-mail, chat, ftp, p2p file
Chat QCI-9
9 9 sharing, progressive video, etc.)
Table 4-8 Definition of Default LTE Services
After defining the General Service Parameters one or more Carriers can be related to the Service. Since
a supporting Carrier has been assigned to the Service, all UL and DL Bearers will be available for
selection as the Supporting Bearers. For example in Figure 4-11 all DL Bearers have been assigned to
VoIP Service. A Minimum Bit Rate (Min-GBR) and a Maximum Bit Rate (Max-MBR) have been
specified for the service. If a terminal achieves connection to one or more of the available bearers then
the eNodeB will firstly allocate enough resources to it in order to achieve the Min-GBR. It will keep
allocating more resources to it until the terminal either reaches the Max-MBR ceiling or until there not
more resources available due to cell loading. When many services are competing to get assigned to
resources from the same eNodeB then the services priorities and the eNodeBs scheduling algorithm
(Round Robin, Proportional Fair, Proportional Demand or Max SINR) will determine the proportion of
resources to be allocated to each one of them. The most preferable bearer is DL-CQI-15 and the least
preferable bearer is DL-CQI-1. ASSET sorts the bearers automatically in descending Throughput or
Data Rate.
Figure 4-11 LTE Service, Example of Supporting Bearers
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AIRCOM International ASSETV8.0- LTE Application Notes Page 32 of 64
4.7 eNodeB and Cell parameters
The LTE Radio Access Network consists of eNodeBs. In ASSET eNodeBs can be defined on the GIS
or imported from a spreadsheet using the xml editor. Cell and eNodeB templates may be used to speed
up this procedure. The configuration values for the eNodeBs should normally be taken from vendor
specifications. As a sort check list the following should be set accordingly:
Antennas with propagation models
Carriers, ICIC schemes, schedulers defined and applied on per cell basis
Advanced Antenna Systems (AAS) Settings
Transmit Power and Power Channel Offsets
Figure 4-12 Site Database
4.8 LTE Planners
4.8.1 Physical Cell ID Planner
In LTE, the Primary and Secondary Synchronisation (P-SCH and S-SCH) signals are employed for
initial cell search and detection of Physical Cell Identities (Physical Cell IDs). The LTE Physical Cell
ID Planner in ASSET is designed to assign these Physical Cell IDs automatically to each sector with a
sophisticated (fixed\automatic) reuse distance algorithm, using multiple filters and schemas and
Neighbour relations.
Figure 4-13 PCI Planner
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AIRCOM International ASSETV8.0- LTE Application Notes Page 33 of 64
4.8.2 LTE Frequency Planner
ASSET incorporates an Automatic Frequency Planner (AFP) for the optimum assignment of carriers
(Channel Bandwidths) to LTE sectors. In addition to a simple distance based algorithm, AFP uses the
Interference matrix for minimizing inter-cell interference. Carrier assignments and conflicts can be
visualised and further analysed in an enhanced reporting engine to determine the quality of produced
frequency plans.
Figure 4-14 Frequency Planner
For a detailed description of the LTE planners functionality please refer to ASSET User Reference
Guide.
4.9 Terminal Types
The following figure presents the ASSET GUI for the definition of LTE Terminal Types.
Figure 4-15 Definition of LTE Terminal Types in ASSET
In ASSET, terminal types represent the different types of mobile devices in your network, and their
distribution. In a modern cellular network, subscribers can have different types of terminals with
different characteristics. In ASSET, you can define a variety of terminal types to represent current or
projected distribution profiles of the subscribers in your network. You can associate these terminal
types with specific or multiple services. Importantly, you can then determine how the traffic will be
spread for each service, according to specified distributions in relation to the mapping data.
In summary, a terminal type defines the following key characteristics that will in their turn determine
the accuracy of the Simulations:
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AIRCOM International ASSETV8.0- LTE Application Notes Page 34 of 64
How much traffic will the terminal type generate in total?
How will the traffic be spread geographically?
What is the expected mobile speed distribution for this terminal type?
With which service will the terminal type be associated?
What are the mobile equipment characteristics?
The purpose of master and slave terminal types is so that you can specify geographical distribution
settings on a 'master' terminal type, and then experiment with various scaling factors when you spread
traffic. If you want to do this, you can define separate 'slave' terminal types with appropriate scaling
percentages. Each slave must always be associated with a 'master' terminal type.
4.9.1 Creating a Traffic Raster
This is usually done per clutter type by assigning a terminal density or a relative weight to each one of
the clutters. It is also possible to spread traffic on user defined points, polygons and inside polygons.
The percentage of in-building traffic per clutter type can also be specified.
For in-building terminals a different fading standard deviation, indoor loss and angular spread will be
applied as defined in LTE Clutter Parameters. It is also possible to define the terminals Mean Speed,
Speeds Standard deviation, Minimum and Maximum Speed per clutter type.
To complete the traffic modelling the Traffic Wizard is run to spread the actual terminals in the area
under examination. The Resolution Option for the outcome array should be in alignment with the
lowest resolution of the propagation models in use.
There is an option to Restrict Traffic to Coverage that ensures that traffic will be spread only in areas
where there is coverage. This option should not be used if only initial estimates of the site locations,
equipment and configuration needed for a new or expanding network are required.
The option to Restrict Traffic to Coverage should be used when the 3G available coverage is required
to match that of the LTE network under planning. Having already a set of 2G and 3G sites/cells and
assuming that they have been finely optimised over years to cover and serve all wanted areas and
traffic it may be required that LTE coverage matches the coverage provided by the old technologies. In
this case the coverage predictions for the 2G and 3G cells should be created and the LTE traffic should
be restricted to the contour created by them.
The actual number of terminals to be served should come from the operators OSS statistics and traffic
forecasts also taking into account the churn rates and the 2G/3G to LTE customer conversion predicted
rates.
Figure 4-16 Example of Traffic Raster or Geographical Traffic Distribution
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AIRCOM International ASSETV8.0- LTE Application Notes Page 35 of 64
5 LTE Network Performance- Coverage and Capacity Predictions
LTE network performance using the Monte-Carlo simulator can be performed in two different manners
with regards to how the cell load levels are specified. In the first case they are specified in the Site
Database and specifically under the LTE Parameters tab in the fields of Downlink Load (as a
percentage) and Mean UL Interference Level (in dB). The second option is to create a traffic raster
spreading the defined LTE Terminal Type(s) and then the cell load levels get calculated by running
Simulator Snapshots. In both cases a reference terminal type has to be specified for the calculation
process.
Figure 5-1 LTE Simulator Wizard
Figure 5-2 Selection of Filters and Cells
The decision on what resolution should be used for the simulations is based on what propagation
models are assigned to the cell antennas.
Firstly, it is suggested to use a propagation model at the resolution it has been tuned for.
Secondly, it is suggested to use two propagation models.
o The first one (Primary) should be calculated at high resolution (2-20 meters) and for
a relatively small radius (1-3 km).
o The second one (Secondary) should be calculated at relatively lower resolution (20-
100 meters) and for a larger radius (3-30km).
This setup will provide high accuracy at the expected serving area of the cell which usually doesnt
span farther than 3km (for urban type of environment). It will also provide good enough accuracy for
the calculation of interference caused by the bespoken cell far away from it but and at the same time it
will be computationally effective (relatively fast to calculate as the resolution is low). The number of
covering cells mainly affects the accuracy of the interference based calculations. The more cells taken
into account, the more accurate the interference values are. A typical value would be 6 to 10. The
typical values for Fading Correlation Coefficients are 0.8 for Intra-Site antennas and 0.5 for Inter-Site
antennas.
Figure 5-3 Selection of Terminal Type(s)
Figure 5-4 Line of Sight Settings
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AIRCOM International ASSETV8.0- LTE Application Notes Page 36 of 64
It is also important to consider cells with prediction area within the specified region (2D View) as those
cells will possibly pick up some of the traffic in the specified area and also increase interference.
The Line of Sight Settings allow deactivating certain MIMO schemes based on LOS information.
MIMO schemes rely on a low correlation between the signal paths to the transmit elements of an
antenna; locations that have LOS to an antenna are more likely to have a high correlation, therefore
MIMO gains should not be considered for such locations.
Following, a comprehensive presentation and discussion of the ASSET LTE module is presented. It
will focus on four main areas, namely basic coverage (RSRP, RSSI and RSRQ), MIMO schemes, Inter-
Cell Interference Coordination (ICIC) schemes and Schedulers. An urban area was chosen expanding
6.4 by 4.8 km and covered by 78 eNodeBs bearing 224 cells.
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AIRCOM International ASSETV8.0- LTE Application Notes Page 37 of 64
5.1 Basic Coverage (RSRP, RSSI, RSRQ)
RSRP, RSSI and RSRQ are defined in detail chapter 3.8. An informal definition of these quantities is
given hereby:
Received Signal Reference Power (RSRP) is the indicator of the signal strength coming
from the serving cell experienced by a UE at a certain point and time.
Received Signal Strength Indicator (RSSI) is the indicator of how much power is received
by the UE over its operating bandwidth. The sources of this power include co-channel serving
and non-serving cells, adjacent channel interference, thermal noise and so on.
Reference Signal Received Quality (RSRQ) is the indicator of the quality of the signal. In
this context, quality is expressing how stronger the signal is compared to noise and
interference. It is thereafter proportional to RSRP and diversely proportional to RSSI, however
it is not a ratio of RSRP over RSSI.
From a terminal point of view a pixel is covered if the required RSRP, RSRQ and BCH/SCH SINR are
met.
Figure 5-5 Trial Area
Figure 5-6 LTE Terminal Type
Well examine how cell load levels affect the satisfaction of these requirements. Cell Load Setting live
on the Cell Params. To start with, SU-MIMO as well as MU-MIMO was disabled on both uplink and
downlink at the Cell Params as well as at the Terminal Type.
Figure 5-7 Site DB Settings - Cell Load Levels
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AIRCOM International ASSETV8.0- LTE Application Notes Page 38 of 64
RSRP (Figure 5-8) is not affected by cell loads. This is the reason why a network is usually firstly
dimensioned to provide adequate signal strength at the desired areas.
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