LTE INTRODUCTION - Burak · PDF fileLTE INTRODUCTION. C1 ... Provides對 support for...
38
C1 LTE INTRODUCTION
Transcript of LTE INTRODUCTION - Burak · PDF fileLTE INTRODUCTION. C1 ... Provides對 support for...
C1
LTE INTRODUCTION
C1
LTE Network Evolution
LTE Design Aims
LTE Architecture
LTE SAE Key Features
LTE Background
Module Contents
C1
LTE Network Evolution
Presenter
Presentation Notes
LTE (Long Term Evolution) represents the next developmental step for the 3GPP standarts group Role Of 3GPP: 3GPP – the 3rd Generation Partnership Project was originally responsible for developing 3G UMTS networks, and inherited responsibility for 2G GSM from ETSI. (www.3gpp.org). GSM, GPRS, W-CDMA, UMTS, EDGE, HSPA and LTE are all Radio Access Network Technologies specified by 3GPP. Release 99 - UMTS: Enhancements to GSM data (EDGE). Majority of deployments today are based on Release 99. Provides support for GSM/EDGE/GPRS/WCDMA radio-access networks. Release 4: Multimedia messaging support. First steps towards using IP transpot in the core network. Release 5 - HSDPA: First phase of Internet Protocol Multimedia Subsystem (IMS). Full ability to use IP-based transport instead of just Asynchronous Transfer Mode (ATM) in the core network. Release 6 – HSUPA: Enhanced multimedia support through Multimedia Broadcast/Multicast Services (MBMS). Performance soecifications for advanced receivers. Wireless Local Area Network (WLAN) integration option. IMS enhancements. Initial VoIP capability. Release 7 – HSPA+: Higher order modulation and Multiple-Input/Multiple-Output (MIMO) antenna systems. Performance enhacements, improve spectral efficiency, increased capacity and better resistance to interference. Release 8 – LTE: R8 defines the Long Term Evolution (LTE) system, starting the transition to 4G technology. Specifies OFDMA-based 3GPP LTE. Release 9: HSPA and LTE enhancements including HSPA dual-carrier operation in combination with MIMO. Release 10: LTE-Advanced meeting the requirements set by ITU’s IMT-Advanced project (1Gbps).
C1
LTE Design Aims
User Experience
Increase throughput
Reduce Latency
Improve Terminal Power Efficiency
Variety of different services support
Low Costs
Simplify Network Complexity
Scalable Ip based architecture
Re-use of sites & infrastructure
Optimized Spectrum Usage
Frequency flexibility
Bandwidth sclability
Presenter
Presentation Notes
Spectrum efficiency birimi ne
C1
Evolved Packet System (EPS)
Serv
ice
Arc
hite
ctur
e Ev
olut
ion
(SA
E)
LTE ARCHITECTURE
Presenter
Presentation Notes
The EPS architecture goal is to optimize the system for packet data transfer. There are no circuit switched components. SAE (System Architecture Evolution) is the term used to describe the evolution of the core network into EPC The EPS architecture is made up of: EPC: Evolved Packet Core EPC provides access to external packet IP network and performs a number of CN related functions (security, QoS, mobility management) for idle and active terminals eUTRAN: Radio Access Network, also referred as LTE eUTRAN performs all radio interface related functions
C1
LTE Key Features
Presenter
Presentation Notes
Evolved NodeB No RNC is provided, eNodeB take over all radio management functionality. This will make radio management faster&network architecture simpler IP Transport Layer E-UTRAN exclusively uses IP as transport layer UL/DL resource scheduling In UMTS physical resources are eiter shared or dedicated eNodeB handles all physical resource via a scheduler and assigns them dynamically to users&channels QOS awareness The scheduler must handle & distinguish different QoS classes Otherwise RT services would not be possible via EUTRAN The system provides the possibility of differentiated services Self Configuration Currently under investigation To let Evolved NodeBs configure themselves Pacekt Siwtched Domain only No Cs domain is provided CS over IP Only one mobility management for the UE in LTE 3GPP(GTP) or IETF(MIPv6) option The EPC can be based either on 3GPP GTP protocols or on IETF Mobile Ipv6 The EPC will be prepared also to be used by on-3GPP access (LAN, WLAN, WIMAX)
C1
Dec. 2008/Rel.8
2100/1700 bands selected.Rel.9
700,800,2600Mhz.InterRAT MobilityLTE Devices
Network SharingSONRel.10(LTE-Advanced)
LTE Background
C1
LTE Standardization Bodies
C1
LTE Frequency Bands Intended
C1
LTE EPC Network Elements
Evolved NodeB (eNB)
Mobility Management Entity (MME)
Serving Gateway (S-GW)
Packet Data Network (PDN-GW)
Policy and Charging Rules Function (PCRF)
Module Contents
C1
LTE EPC Network Elements
Presenter
Presentation Notes
Basic nodes of the EPC are; MME: Mobility Management Entity S-GW: Serving GateWay PDN- Gateway: Packet data network Gateway PCRF:Policy and Charging Resource Function(Optional Node) HSS: Home Subscriber Server (HLR) The Basic building block of E-UTRAN access network is the eNB plus backhaul
C1
LTE EPC Network Elements
Evolved NodeB (eNB)
Presenter
Presentation Notes
Replaces the old NodeB / RNC combination from 3G Terminates the complete radio interface including physical layer Provides all radio management functions To enable efficient inter-cell radio management for cells not attached to the same eNB, there is a inter-eNB interface X2 specified. It will allow to coordinate inter-eNB handovers without direct involvement of EPC during the proces X2 interface: Handover and provide data forwarding In RRM to provide load info to nei. eNbs to facilitate interference management Logical interface doesn’t need direct site-to-site connection
C1
LTE EPC Network Elements
Mobility Management Entity (MME)
C1
LTE EPC Network Elements
Serving Gateway (S-GW)
C1
LTE EPC Network Elements
PDN Gateway (P-GW)
C1
LTE EPC Network Elements
Handles QoS (Quality of Service)
Bearer Policy enforcement
Charging and rating facilities
Decides whther and when to create additional EPS bearers
If not deployed some of functions be performamed by PDN-GW
Policy and Charging Rules Function (PCRF)
C1
OFDM
OFDM SIGNAL GENERATION
OFDM WEAKNESSES
CYLIC PREFIX
SC-FDMA
MODULATION CODING
LTE CHANNEL STRUCTURE
LTE CHANNEL PARAMETERS
LTE DL/UL TRANSMISSION
MULTIPLE ANTENNA TECHS
LTE SYSTEM FIELD TRIALS
Module Contents
C1
OFDM
18
Transmits hundreds or even thousands of seperately modulated radio signals using orthogonalsubcarriers spread across a wideband channel.
Advantage: High spectrum utilization efficiency due to orthogonal subcarriers need no protect bandwidth.Support frequency link auto adaptation and scheduling. Easy to combine with MIMO.
Disadvantage: Strict requirement of time-frequency domain synchronization. High PAPR.
Presenter
Presentation Notes
Transmits hundreds or even thousands of seperately modulated radio signals using orthogonal subcarriers spread across a wideband channel. Advantage: High spectrum utilization efficiency due to orthogonal subcarriers need no protect bandwidth. Support frequency link auto adaptation and scheduling. Easy to combine with MIMO. Disadvantage: Strict requirement of time-frequency domain synchronization. High PAPR.
C1
OFDM SIGNAL GENERATION
19
OFDM
• OFDM signal generation is based on Inverse Fast Fourier Transform (IFFT) operation on transmitter side.
• On receiver side, an FFT operation will be used.
• In OFDMA, each sub-carrier only carries information related to one specific symbol
Presenter
Presentation Notes
OFDM signal generation is based on Inverse Fast Fourier Transform (IFFT) operation on transmitter side. On receiver side, an FFT operation will be used. Sub-carrier mapping allows flexible allocation of signal to available sub-carriers IFFT and cyclic prefix (CP) insertion as in OFDM –In OFDMA, each sub-carrier only carries information related to one specific symbol –In SC-FDMA, each sub-carrier contains information of ALL transmitted symbols.
C1
OFDM WEAKNESSES
20
One possible cause that introduces frequency errors is a fast moving Transmitteror Receviver (Doppler effect)
Presenter
Presentation Notes
The price for the optimum subcarrier spacing is the sensitivity of OFDM to frequency errors. If the receiver’s frequency slips some fractions from the subcarrier center frequencies, then we encounter not only interference between adjacent carriers, but in principle between all carriers. This is known as Inter-Carrier Interference (ICI) and sometimes also referred to as Leakage Effect in the theory of discrete Fourier transform. One possible cause that introduces frequency errors is a fast moving Transmitter or Receviver (Doppler effect)
C1
CYCLIC PREFIX
21
Having the cyclic prefix longer than thechannel multi-path delay spread prevents ISI.In all major implementations of the OFDMAthe Guard Period is equivalent to the CyclicPrefix CP.
The technique consists in copying the lastpart of a symbol shape for a duration ofquard-time and attaching it in front of thesymbol.
A receiver typically uses the high correlationbetween the CP and the last part of thefollowing symbol to locate the start of thesymbol and begin then with decodiing.
Presenter
Presentation Notes
Having the cyclic prefix longer than the channel multi-path delay spread prevents ISI. In all major implementations of the OFDMA the Guard Period is equivalent to the Cyclic Prefix CP. The technique consists in copying the last part of a symbol shape for a duration of quard-time and attaching it in front of the symbol. A receiver typically uses the high correlation between the CP and the last part of the following symbol to locate the start of the symbol and begin then with decodiing.
C1
PAPR: Peak To Average Ratio in OFDM
22
The transmitted power is the sum of the powersof all the subcarriers. Due to large number of subcarriers, the peak
to average power ratio (PAPR) tends to havea large range.
The higher the peaks, the greater the rangeof power levels over which the transmitter isrequired to work.
Not best suited for use with mobile (battery-powered) devices.
Presenter
Presentation Notes
The transmitted power is the sum of the powers of all the subcarriers. Due to large number of subcarriers, the peak to average power ratio (PAPR) tends to have a large range. The higher the peaks, the greater the range of power levels over which the transmitter is required to work. Not best suited for use with mobile (battery-powered) devices.
C1
SC-FDMA
SC-FDMA SIGNAL GENERATION
DFT “pre-coding” is performed on modulated data symbols to transform them into frequency domain. In SC-FDMA, each sub-carrier contains information of ALL transmitted symbols.
It is a variant of OFDM that reduces the PAPR:− It can reduce the PAPR between 6...9 dB compared to OFDMA
SC-FDMA transmits data spread across a group of radio subcarriers, which ensures that thevariations in transmit power are smaller and that the PAPR of the uplink remains low. ReducesPAPR means lower RF hardware requirements (power amplifier).
Presenter
Presentation Notes
DFT “pre-coding” is performed on modulated data symbols to transform them into frequency domain In SC-FDMA, each sub-carrier contains information of ALL transmitted symbols. It is a variant of OFDM that reduces the PAPR: Combines the PAR of single-carrier system with the multipath resistance and flexible subcarrier frequency allocation offered by OFDM. It can reduce the PAPR between 6...9 dB compared to OFDMA TS36.201 and TS36.211 provide the mathematical description of the time domain representation of an SC-FDMA symbol. SC-FDMA transmits data spread across a group of radio subcarriers, which ensures that the variations in transmit power are smaller and that the PAPR of the uplink remains low. Reduces PAPR means lower RF hardware requirements (power amplifier).
C1
MODULATION and CODING
24
Presenter
Presentation Notes
Digital radio systems convey data by modulating a carrier signal. Simple schemes transmit one bit of data per modulated symbol, higher-order schemes carry greater amounts of data. LTE connections can use QPSK, 16QAM or 64QAM modulation, depending on link quality. The level of error coding employed on a connection has an effect on its overall data throughput potential. LTE employs powerful error coding that can react to changing radio conditions. Key point of this section is that higher order modulation schemes require a better CINR because their decision space between adjacent symbols is smaller.
C1
LTE CHANNEL PARAMETERS
25
FFT Size 128 256 512 1024 1536 2048
Sampling Rate Mhz 1.92 3.84 7.68 15.36 23.04 30.72
Frame Duration: 10ms Subframe Duration (TTI): 1 ms
(composed of 0.5ms slots) Subcarrier spacing: Fixed to 15kHz Sampling Rate: Varies with the bandwidth
but always factor or multiple of 3.84 toensure compatibility with WCDMA by usingcommon clocking.
Channel Bandwith: Bandwidths rangingfrom 1.4 MHz to 20 MHz
A symbol period carries one modulateddata symbol per subcarrier, equivalent to 2bits using QPSK, 4 bits using 16QAM etc.
LTE physical layer supports any bandwidthfrom 1.4 MHz to 20 MHz in steps of 180 kHz(resource block).
Presenter
Presentation Notes
Frame Duration: 10ms Subframe Duration (TTI): 1 ms (composed of 0.5ms slots) Subcarrier spacing: Fixed to 15kHz Sampling Rate: Varies with the bandwidth but always factor or multiple of 3.84 to ensure compatibility with WCDMA by using common clocking. Channel Bandwith: Bandwidths ranging from 1.4 MHz to 20 MHz A symbol period carries one modulated data symbol per subcarrier, equivalent to 2 bits using QPSK, 4 bits using 16QAM etc. LTE physical layer supports any bandwidth from 1.4 MHz to 20 MHz in steps of 180 kHz (resource block). To ensure that all signals are received correctly, the receiver sampling rate must be slightly higher than the bandwidth of the signal used to carry it. The data rate available to individual connections is determined by the number of Resource Blocks assigned to them over time and the modulation and coding schemes that each link can support.
C1
LTE CHANNEL STRUCTURE
26
Presenter
Presentation Notes
The LTE air interface has been designed to follow generic OFDMA principles. Subcarriers are evenly spaced across channels and are grouped into units of twelve covering 180 kHz of spectrum. The center frequency of each channel is known as the DC Carrier and is left un modulated. A varying number of ‘null’ subcarriers at the top and bottom ends of each channel are transmitted at zero power and provide a guard band between adjacent channels. The capacity of each LTE air interface subcarrier is administratively organized into a structure of Frames, Sub frames and Slots. In the most typical configuration a Slot consists of seven consecutive symbol periods. A Sub frame lasts for 1 ms and is created by concatenating two consecutive Slots. Sub frames carry a mix of control channels and user traffic. Ten sub frames are bound together to form a Frame, which lasts for 10 ms. Alternative Slot and Sub frame configurations exist to support other operational modes. LTE capacity allocation is based on a series of Resource Units. A Resource Element consists of the modulated symbol carried by one subcarrier during one symbol period. A Resource Block binds together the capacity of twelve subcarriers, occupying 180 kHz of spectrum, during one Slot period. The minimum scheduling period in LTE is one sub frame (1 ms), which will carry two consecutive Resource Blocks.
C1
LTE DL TRANSMISSION
27
Presenter
Presentation Notes
LTE uses OFDMA to define multiple adjacent subcarriers; different-width radio channels employ different numbers of subcarriers. Transmission across the subcarriers is organized into units of time known as Symbol Periods. During each Symbol Period, all, some, or none of the subcarriers could be assigned to carry traffic for a given user. The greater the number of subcarriers assigned, and the more Symbol Periods the allocation lasts for, the greater the data throughput that a user will achieve.
C1
LTE UL TRANSMISSION
Presenter
Presentation Notes
LTE uplink channels employ an adaptation of OFDMA known as SC-FDMA. This technology employs the same orthogonally spaced subcarriers and Fourier transforms as OFDMA, but encodes data onto the subcarriers using a different technique. The SC-FDMA based uplink offers roughly 50% of the capacity that is available on the downlink, with a 20 MHz wide LTE channel being able to carry around 50 Mbit/s of user traffic. SC-FDMA transmits data spread across a group of radio subcarriers, which ensures that the variations in transmit power are smaller and that the PAPR of the uplink remains low.
C1
Mutiple Antenna Technologies
MISO (Tx diversity)MISO increases the robustness of the signalto poor channel conditions. It does notincrease data rates but increases coverageand therefore cell capacity.
SIMO (Rx diversity)SIMO improves the received SNR bycombining multiple copies of the same signal.Like MISO it does not increase data rates butextends coverage and hence cell capacity.
MIMOMIMO uses multiple data streams to increasecell capacity. The data streams can beallocated to one user to increase single-userdata rates.
Presenter
Presentation Notes
MISO (Tx diversity) MISO increases the robustness of the signal to poor channel conditions. It does not increase data rates but increases coverage and therefore cell capacity. SIMO (Rx diversity) SIMO improves the received SNR by combining multiple copies of the same signal. Like MISO it does not increase data rates but extends coverage and hence cell capacity. MIMO MIMO uses multiple data streams to increase cell capacity. The data streams can be allocated to one user to increase single-user data rates. Multiple antenna techniques are fundamental to LTE and an appreciation of the different methods and their relative advantages and disadvantages is important. There are three main multi-antenna techniques used in LTE. 1. Transmit/receive diversity (TX/RX) 2. Spatial multiplexing – Single User MIMO (SU-MIMO) – Multi-user MIMO (MU-MIMO) 3. Beamforming 2*2 SU-MIMO is mandotary for the downlink and opitonal for the uplink.
C1
Multiple Antenna Technologies
C1 31
NGDI LTE System Field TrialsField Trials
Objective: Global LTE trials program established to understand the end-to-end LTE technology capability, identify weaknesses in vendor’s implementation and drive improvements. NGDI is leading the global LTE trials program to ensure LTE delivers step change in customer
experience and operational efficiency…
Presenter
Presentation Notes
C1 32
NGDI LTE System Field TrialsLTE2600 MHz Trial Network Setup
Presenter
Presentation Notes
C1 33
NGDI LTE System Field TrialsUser Experience Summary
Presenter
Presentation Notes
C1 34
NGDI LTE System Field TrialsDownlink Cell Capacity – MIMO Modes
Presenter
Presentation Notes
C1 35
NGDI LTE System Field TrialsUplink Multi User MIMO
Presenter
Presentation Notes
C1 36
Vodafone Germany Commercial LTE Service
Presenter
Presentation Notes
C1
BACK UP
C1
