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Arief Hamdani Gunawan
1.1. Introduction to LTEIntroduction to LTE
2.2. OFDMAOFDMA
3.3. SCSC--FDMAFDMA
4.4. LTE Network and ProtocolLTE Network and Protocol
5. LTE Radio Procedures5. LTE Radio Procedures
6. LTE Uplink Physical Channels and 6. LTE Uplink Physical Channels and
SignalsSignals
7. LTE Mobility7. LTE Mobility
8. LTE Test and Measurement8. LTE Test and Measurement
Day Two
Arief Hamdani Gunawan
Session 5: LTE Radio Procedures•LTE Initial Access
•Downlink physical channels and signals
•Cell search in LTE
•Primary Synchronization Signal•Primary Synchronization Signal
•Secondary Synchronization Signal
•Cell search in LTE, reference signals
•Downlink Reference Signals
•Cell Search in LTE, essential system information
•System Information Broadcast in LTE
•Random Access Procedure
•How to derive information in LTE
•Hybrid ARQ in Downlink
•Default EPS Bearer Setup
LTE Initial Access
Downlink physical channels and signals
DL Physical Layer Procedures
• Cell search and synchronization
• Scheduling
– Dilakukan di base station (eNodeB)
– PDCCH (Phy DL Control Channel) menginformasikan alokasi time/freq resource
dan format transmisi yang digunakan kepada user.
– Scheduler mengevaluasi berbagai tipe informasi (parameter QoS, pengukuran
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– Scheduler mengevaluasi berbagai tipe informasi (parameter QoS, pengukuran
dari UE, kapabilitas UE, buffer status)
• Link Adaptation
– Skema modulasi dan coding untuk shared data channel diadaptasi sesuai
dengan kualitas link radio.
– Untuk tujuan ini, UE secara teratur melaporkan Channel Quality Indicator
(CQI) ke eNodeB.
• Hybrid ARQ (Automatic Repeat Request)
Cell Search in LTE
Synchronization & Cell Search
• UE yang ingin mengakses suatu sel LTE, terlebih dahulu harus melakukan
prosedur Cell Search.
• Cell Search terdiri dari serangkaian tahapan sinkronisasi, dimana UE
menentukan parameter waktu & frekuensi yang diperlukan untuk
mendemodulasi sinyal DL dan untuk mengirimkan sinyal UL dengan timing
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mendemodulasi sinyal DL dan untuk mengirimkan sinyal UL dengan timing
yang tepat.
• Tiga kebutuhan sinkronisasi utama:
– Symbol timing acquisition
– Carrier frequency synchronization
– Sampling clock synchronization
Case StudyCase Study
Cell Search for Multiple Bandwidths - Problem
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• LTE offers system flexibility by supporting systems and UEs of multiple bandwidths.
• Challenge in synchronization & bandwidth detection.
• Unbalance traffic loads may result
Case Study Case Study
Cell Search for Multiple Bandwidths - Solution
Step 1:
Cell search using synchronization channel
�detect center 1.25 spectrum
of entire 20-MHz spectrum•The UE first detect the central
part of the spectrum regardless of
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Step 2:
BCH reception
Step 3:
UE shifts to the center of carrier frequency assigned
by the system and initiates data transmission
Source: 3GPP R1-061651, “3GPP TR 25.814 v 1.5.0”
part of the spectrum regardless of
the transmission bandwidth
capability of the UE and that of the
cell site (BTS).
•UE moves to the transmission
bandwidth according to the UE
capability for actual
communication
Synchronization Sequence
Dua prosedur cell search dalam LTE :
• INITIAL SYNCHRONIZATION
– UE mendeteksi suatu sel LTE dan mendekode semua informasi yang
diperlukan untuk registrasi.
– Diperlukan pada saat UE di-ON-kan atau ketika kehilangan koneksi dengan
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– Diperlukan pada saat UE di-ON-kan atau ketika kehilangan koneksi dengan
serving cell.
• NEW CELL IDENTIFICATION
– Dilakukan ketika UE sudah terhubung ke suatu sel LTE dan sedang dalam
proses mendeteksi suatu sel tetangga baru.
– Dalam hal ini UE melaporkan hasil pengukuran yang terkait dengan sel baru ke
serving cell, sebagai persiapan untuk handover.
RS : Reference Signal
PBCH : Physical Broadcast Channel
PSS : non-coherent detection
SSS : non-coherent/coherent detection
Cell Search procedure
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• PSS (Primary Synchronization Signal) dan SSS (Secondary Synchronization Signal) adalah kanal-kanal fisik
yang di-broadcast dalam setiap sel.
• Pendeteksian dua kanal ini :
– memungkinkan dilakukannya sinkronisasi waktu & frekwensi.
– memberikan identitas phy layer dari sel dan panjang cyclic prefix kepada UE.
– memberitahu UE apakah sel menggunakan FDD atau TDD.
Primary Synchronization Signal
Secondary Synchronization Signal
PSS and SSS frame and slot structure in FDD
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PSS and SSS frame and slot structure in TDD
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Cell search in LTE, reference signals
Downlink reference signals
Reference Signals & Channel Estimation
• Berbeda dengan jaringan berorientasi paket, LTE tidak menggunakan PHY Preamble untuk
• Sebaliknya LTE menggunakan sinyal referensi khusus yang disisipkan dalam PRB.
• Sinyal referensi tsb dikirimkan selama simbol OFDM pertama dan kelima dari setiap slot
untuk short CP, dan simbol OFDM pertama dan ke-empat untuk long CP.
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• Simbol-simbol referensi dikirimkan setiap selang 6 subcarrier.
• Dalam LTE downlink, terdapat 3 tipe RS :
– Cell-specific RS
– UE-specific RS
– MBSFN-specific RS
DL Reference Signal Structure for 2 & 4 Antenna Transmission
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RS-aided Channel Estimation
• Problem estimasi kanal berhubungan dengan model kanal yang diasumsikan, yang
ditentukan oleh karakteristik propagasi fisik, termasuk jumlah antena Tx/Rx,
bandwidth transmisi, carrier frequency, konfigurasi sel dan kecepatan relatif antara
eNodeB dan UE.
• Kondisi propagasi mencirikan fungsi korelasi kanal dalam 3-dimensi, yaitu : domain
frekwensi, domain waktu dan domain ruang (spatial).
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frekwensi, domain waktu dan domain ruang (spatial).
• Frequency-Domain Channel Estimation
– menggunakan Linear Interpolation Estimator
– menggunakan IFFT Estimator
• Time-Domain Channel Estimation
– menggunakan Finite & Infinite Length MMSE (Min Mean Squared Error)
– menggunakan Normalized Least-Mean-Square
• Spatial-Domain Channel Estimation
Cell search in LTE, essential system information
P-SCH and S-SCH
Physical Downlink Shared Channel
Physical Downlink Control Channel
Physical Broadcast Channel
Downlink Physical Channels and Signals
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Physical Broadcast Channel
Physical Control Format Indicator Channel
Physical Multicast Channel
Physical Hybrid ARQ Indicator Channel
P-SCH : Primary Synchronization Channel
S-SCH : Secondary Synchronization Channel
LTE Downlink Physical Channels 1
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LTE Downlink Physical Channels 2
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System information broadcast in LTE
Random Access Procedure
How to derive information in LTE?
Indicating PDCCH format
Channel Coding & Link Adaptation
• Prinsip link adaptation menjadi landasan perancangan suatu interface radio yang
efisien untuk trafik data berbasis paket-switched.
• Link adaptation dalam LTE dilakukan dengan mengatur laju data informasi yang
dikirim (skema modulasi dan channel coding rate) secara dinamis, sesuai dengan
kualitas radio link.
• Link adaptation mempunyai hubungan yang sangat erat dengan perancangan
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• Link adaptation mempunyai hubungan yang sangat erat dengan perancangan
skema channel coding yang digunakan untuk FEC.
• Skema channel coding untuk FEC yang digunakan dalam LTE :
– Convolutional Coding
– Turbo Coding
– LDPC (Low Density Parity Check) coding
• Fitur advanced channel coding yang ditambahkan dalam LTE adalah : HARQ
(Hybrid Automatic Repeat Request).
Link Adaptation
• UE: Reports the finest possible
granularity
– The reporting scheme and
granularity depend on the radio
channel quality variation!
• ENB: Receives mobility and
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• ENB: Receives mobility and
quality information
– Incremental feedback
information forms a rough
picture of the radio channel with
the first report (s). The
granularity gets finer and finer
with each report.
Adaptive Modulation
• Adaptive Modulation & Coding
memastikan error rate tetap dibawah
limit yang dapat diterima, dengan
pengaturan modulasi dan coding rate
secara dinamis.
• Level modulasi yang lebih rendah
meningkatkan link budget dan fade
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meningkatkan link budget dan fade
margin.
• Perubahan lingkungan propagasi
menyebabkan perubahan skema
modulasi dan coding.
• Dalam perencanaan kapasitas, variasi
kanal propagasi jangka-panjang harus
diperhitungkan.
Typical SNR Performance of LTE Modulation and Coding
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Adaptive Modulation & Coding
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QoS parameters for QCI
Hybrid ARQ in the downlink
• ACK/NACK for data packets transmitted in the downlink is the same as for HSDPA,
where the UE is able to request retransmission of incorrectly received data
packets,
– ACK/NACK is transmitted in UL, either on PUCCH (Physical Uplink Control Channel) or
multiplexed within PUSCH (Physical Uplink Shared Channel) see description of those UL
channels for details),
– ACK/NACK transmission refers to the data packet received four sub-frames (= 4 ms) – ACK/NACK transmission refers to the data packet received four sub-frames (= 4 ms)
before,
– 8 HARQ processes can be used in parallel in downlink.
Hybrid ARQ Operation
Default EPS bearer setup
Session 6: Uplink Physical Channels and Signals•Scheduling of UL Data
•UL Frequency Hopping
•Demodulation Reference Signal (DRS) in the UL
•Sounding Reference Signal (SRS) in the UL•Sounding Reference Signal (SRS) in the UL
•PUSCH power control & timing relation
•Acknowledging UL data packets on PHICH
•Physical UL Control Channel
Uplink physical channels and signals
Scheduling of uplink data
Physical Random Access Channel
Physical Uplink Shared Channel
Physical Uplink Control Channel
Uplink Physical Channels and Signals
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Physical Uplink Control Channel
• PUSCH (Physical Uplink Shared Channel): used for uplink shared data transmission.
• PUCCH (Physical Uplink Control Channel): used to carry ACK/NACK, CQI for downlink
transmission and scheduling request for uplink transmission.
Uplink Data Transmission
• Pada uplink, data dialokasikan dalam beberapa resource block (RB).
• Ukuran RB untuk uplink sama dengan yang digunakan untuk downlink,
tetapi untuk menyederhanakan disain DFT dalam pemrosesan sinyal
uplink, tidak semua kelipatan bulat digunakan (hanya kelipatan 2, 3 dan 5).
• Interval waktu transmisi uplink adalah 1 ms (sama dengan downlink).
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• User data dibawa pada Physical Uplink Shared Channel (PUSCH), yang
ditentukan oleh BW transmisi dan pola frequency hoping.
• Physical Uplink Control Channel (PUCCH) membawa informasi kontrol
uplink, seperti : laporan CQI dan informasi ACK/NACK, yang terkait dengan
paket-paket data yang diterima pada arah downlink.
UL frequency hopping
Intra- and inter-subframe hopping,
• Intra-subframe hopping. UE hops to another frequency allocation from one slot to another within one subframe,
• Inter-subframe hopping. Frequency allocation changes from one subframeto another one,to another one,
Two types of hopping,
• Type I. Explicit frequency offset is used in the 2nd slot, can be configured and is indicated to the UE by resource block assignment / hopping resource allocation field in DCI format 0,
• Type II. Use of pre-defined hopping pattern, allocated BW is divided into sub-bands, hopping is done from one sub-band to another from one slot or subframe depending on configured frequency hopping scheme.
Screenshots of R&S® SMU200A Vector Signal Generator
Demodulation Reference Signal (DRS) in the UL
Sounding Reference Signal (SRS) in the UL
PUSCH power control & timing relation
Random Access
• Suatu LTE UE (User Equipment) hanya dapat di-scheduled untuk transmisi uplink, apabila uplink transmission timing-nya sinkron.
• Oleh karena itu LTE RACH (Random Access Channel) memainkan peran penting sebagai interface antara non-synchronized UE dan skema transmisi othogonal pada akses radio uplink LTE.
• Prosedur LTE random access mempunyai dua bentuk, yaitu : contention-based atau contention-free.
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based atau contention-free.
• Dalam prosedur contention-based, suatu random access preamble signature dipilih secara acak oleh UE, yang kemungkinan dapat menyebabkan lebih dari satu UE mengirimkan signature yang sama secara simultan.
• Dalam prosedur contention-free, eNodeB memiliki opsi untuk mencegah terjadinya contention dengan mengalokasikan suatu dedicated signature kepada UE.
Contention-based Random Access Procedure
Step 1 : Preamble transmission
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Step 1 : Preamble transmission
Step 2 : Random Access
Response
Step 3 : L2/L3 message
Step 4 : Contention resolution
message
Contention-free Random Access Procedure
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Prosedur contention-free
random access dapat
diterapkan dalam hal
diperlukan low latency, seperti
handover dan new downlink
data.
UL Transmission Procedures
• Uplink scheduling
– Dilakukan oleh base station (eNodeB)
– PDCCH (Phy DL Control Channel) menginformasikan alokasi time/freq resource dan format transmisi yang digunakan kepada user.
– Scheduler mengevaluasi berbagai tipe informasi (parameter QoS, pengukurandari UE, kapabilitas UE, buffer status)
• Uplink Adaptation
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• Uplink Adaptation
– Untuk keperluan adaptasi uplink, dapat digunakan : transmission power control, adaptive modulation & channel coding rate, serta adaptive transmission BW.
• Uplink timing control
– Diperlukan untuk menyelaraskan waktu transmisi dari UE-UE yang berbeda, dengan receiver window dari eNodeB.
• Hybrid ARQ
Acknowledging UL data packets on PHICH
Physical Uplink Control Channel
PUCCH carries Uplink Control Information (UCI), when no PUSCH is available,
• If PUSCH is available, means resources have been allocated to the UE for data transmission, UCI are multiplexed with user data,
UCI are Scheduling Requests (SR), ACK/NACK information related to DL data packets, CQI, Pre-coding Matrix Information (PMI) and Rank Indication (RI) for MIMO,Indication (RI) for MIMO,
PUCCH is transmitted on reserved frequency regions, configured by higher layers, which are located at the edge of the available bandwidth
• Minimizing effects of a possible frequency-selective fading affecting the radio channel,
• Inter-slot hopping is used on PUCCH,
• A RB can be configured to support a mix of PUCCH formats (2/2a/2b and 1/1a/1b) or exclusively 2/2a/2b,
PUCCH
• CQI / PMI / RI are only signaled via PUCCH when periodic reporting is requested, scheduled
– Optional for UE to support– Optional for UE to support
• Multi-user MIMO / collaborative MIMO:– Simultaneous transmission from 2
Ues on same time/frequency resource
– Each UE with single transmit antenna
– eNodeB selects UEs with close-to orthogonal radio channels
Multi User Scheduling
• Scheduler (untuk transmisi unicast) secara dinamis mengontrol resource waktudan frekwensi mana yang akan dialokasikan kepada suatu user pada suatu waktutertentu.
• DL control signalling memberitahu UE, resource dan format transmisi seperti apayang sudah dialokasikan.
• Scheduler dapat secara dinamis memilih strategi multiplexing terbaik daribeberapa metode yang ada, misalnya : localized atau distributed allocation.
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beberapa metode yang ada, misalnya : localized atau distributed allocation.
• Scheduling berinteraksi erat dengan link adaptation dan HARQ.
• Pertimbangan scheduling antara lain didasarkan pada :
– minimum & maximum data rate
– daya yang tersedia untuk di-share
– Persyaratan target BER
– parameter QoS
– laporan CQI (Channel Quality Indicator)
– kapabilitas UE
Channel-Dependent Scheduling
• Shared channel transmission
• Select user and data rate on
instantaneous channel quality
– Time-domain adaptation used
already in HSPA
• Scheduling in time and frequency
domain
– Link adaptation in time domain
only
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already in HSPA
Packet-scheduling framework
• Packet scheduler adalah entitas
pengendali untuk seluruh proses
scheduling.
• Berkonsultasi dengan modul LA (Link
Adaptation) untuk memperoleh estimasi
data rate yang dapat disuport untuk user
tertentu dalam sel.
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• LA dapat menggunakan frequency-
selective CQI feedback dari user, untuk
memastikan estimasi data rate yang sesuai
dengan target BLER tertentu.
• Modul Offset calculation dalam proses
link-adaptation dapat digunakan untuk
menstabilkan performansi BLER dalam
kondisi LA yang tidak pasti.
Session 8: LTE Test and Measurement•LTE RF Testing aspects
•eNB Modulation quality measurements
•ACLR in DL (FDD)
•eNB Performance Requirements
•UE RF Testing Aspects
•Transmit Modulation
•Inband Emission
•IQ Component
•ACLR Measurement
•Receiver characteristics
•LTE Wireless device testing from R&D upto conformance
•Stages of LTE terminal testing
•LTE Terminal Interoperability testing
•Test Scenarios for LTE Terminal IOT
•LTE Conformance Testing
•LTE Terminal Certification
•LTE Field Trials
System architecture for 3GPP access networks
PCRF
• It is responsible for policy control decision-making, as
well as for controlling the flow-based charging
functionalities in the Policy Control Enforcement
Function (PCEF) which resides in the P-GW.
• The PCRF provides the QoS authorization (QoS class
identifier and bitrates) that decides how a certain
data flow will be treated in the PCEF and ensures
that this is in accordance with the user’s subscription
profile.
P-GW
• The P-GW is responsible for IP address allocation for the UE,
as well as QoS enforcement and flow-based charging
according to rules from the PCRF.
• The P-GW is responsible for the filtering of downlink user IP
packets into the different QoS based bearers. This is packets into the different QoS based bearers. This is
performed based on Traffic Flow Templates (TFTs).
• The P-GW performs QoS enforcement for Guaranteed Bit Rate
(GBR) bearers.
• It also serves as the mobility anchor for inter-working with
non-3GPP technologies such as CDMA2000 and WiMAX
networks.
S-GW
• All user IP packets are transferred through the S-GW, which serves as the local mobility anchor for the data bearers when the UE moves between eNodeBs.
• It also retains the information about the bearers when the UE is in idle state (known as ECM-IDLE) and temporarily buffers downlink data while the MME initiates paging of the UE to re-establish the bearers. downlink data while the MME initiates paging of the UE to re-establish the bearers.
• In addition, the S-GW performs some administrative functions in the visited network such as collecting information for charging (e.g. the volume of data sent to or received from the user), and legal interception.
• It also serves as the mobility anchor for inter-working with other 3GPP technologies such as GPRS and UMTS.
MME
• The MME is the control node which processes the signaling
between the UE and the CN.
• The protocols running between the UE and the CN are known
as the Non-Access Stratum (NAS) protocols.
• The main functions supported by the MME are classified as:• The main functions supported by the MME are classified as:
– Functions related to bearer management. This includes the
establishment, maintenance and release of the bearers, and is
handled by the session management layer in the NAS protocol.
– Functions related to connection management. This includes the
establishment of the connection and security between the network
and UE, and is handled by the connection or mobility management
layer in the NAS protocol layer.
HSS
• Home Subscription Server (HSS) is the subscription data repository for all permanent user data. It also records the location of the user in the level of visited network control node, such as MME. It is a database server maintained centrally in the home operator’s premises.
• The HSS stores the master copy of the subscriber profi le, which contains information about the services that are applicable to the user, including information about the allowed PDN connections, and whether roaming to a particular visited network is allowed or not. For supporting mobility between non-3GPP ANs, the HSS also stores the Identities of those P-GWs that are in use. The particular visited network is allowed or not. For supporting mobility between non-3GPP ANs, the HSS also stores the Identities of those P-GWs that are in use. The permanent key, which is used to calculate the authentication vectors that are sent to a visited network for user authentication and deriving subsequent keys for encryption and integrity protection, is stored in the Authentication Center (AuC), which is typically part of the HSS.
• In all signaling related to these functions, the HSS interacts with the MME. The HSS will need to be able to connect with every MME in the whole network, where its UEs are allowed to move. For each UE, the HSS records will point to one serving MME at a time, and as soon as a new MME reports that it is serving the UE, the HSS will cancel the location from the previous MME.
EPS Connection Management
• To reduce the overhead in the E-UTRAN and processing in the UE, all UE-related information in the access network can be released during long periods of data inactivity.
• This state is called EPS Connection Management IDLE (ECM-IDLE). The MME retains the UE context and the information about the established bearers during these idle periods.
• To allow the network to contact an ECM-IDLE UE, the UE updates the network as to its new location whenever it moves out of its current
• To allow the network to contact an ECM-IDLE UE, the UE updates the network as to its new location whenever it moves out of its current Tracking Area (TA); this procedure is called a ‘Tracking Area Update’. The MME is responsible for keeping track of the user location while the UE is in ECM-IDLE.
• When there is a need to deliver downlink data to an ECM-IDLE UE, the MME sends a paging message to all the eNodeBs in its current TA, and the eNodeBs page the UE over the radio interface. On receipt of a paging message, the UE performs a service request procedure which results in moving the UE to ECM-CONNECTED state.
MME connections to other logical nodes
and main functions
S-GW connections to other logical nodes
and main functions
P-GW connections to other logical nodes
and main functions
PCRF connections to other logical nodes
and main functions
Each PCRF may be associated with one or more AF, P-GW and S-GW. There is only
one PCRF associated with each PDN connection that a single UE has.
LTE RF Testing AspectsBase station (eNodeB) according to 3GPP
• Measurements are performed using Fixed Reference Channels (FRC) and EUTRA Test Models (E-TM),
• Tx characteristic (= Downlink)– Base station output power
– Output power dynamics: RE Power Control dynamic range, total power dynamic range,
3GPP TS 36.104: Base Station (BS) radio transmission and reception
eNB modulation quality measurements
• Frequency error– If frequency error is larger than a few subcarrier, demodulation at the UE
might not work properly and cause network interference,
– Quick test: OBW, Limit for frequency error after demodulation 0.05 ppm + 12 Hz (1ms),
• Error Vector Magnitude (EVM),– Amount of distortion effecting the receiver to demodulate the signal properly,– Amount of distortion effecting the receiver to demodulate the signal properly,
Emission Mask (SEM), Adjacent Channel Leakage Power Ratio (ACLR),
• Spurious Emission,
• Transmit Intermodulation,
• Spurious emissions,
Performance requirements
• Demodulation FDD PDSCH (FRC),
• Demodulation FDD PCFICH/PDCCH (FRC)
3GPP TS 36.101: User Equipment (UE) radio transmission and reception
Transmit modulation
According to 3GPP specification LO leakage (or IQ origin offset) is removed from evaluated
signal before calculating EVM and in-band emission.
In-band emission
IQ component
• Also known is LO leakage, IQ offset, etc.,
• Measure of carrier feedthrough present in the signal,
• Removed from measured waveform, before calculating EVM and in-band emission
(3GPP TS 36.101 V8.3.0, Annex F),
• In difference to DL the DC subcarrier in UL is used for transmission, but subcarriers
are shifted half of subcarrier spacing (= 7.5 kHz) to be symmetric around DC are shifted half of subcarrier spacing (= 7.5 kHz) to be symmetric around DC
carrier,
• Due to this frequency shift energy of the LO falls into the two central subcarrier