LTE (LONG TERM EVOLUTION) BY.ENG.KHALID ABDEEN ALI

MOHAMMEDMAY 2016

ENG.KHALID ABDEEN ALI MOHAMMED00249120120486

4G (LTE)

LTE stands for Long Term Evolution Next Generation mobile broadband technology Promises data transfer rates of 100 Mbps Based on UMTS 3G technology Optimized for All-IP traffic

History of LTE LTE is a standard for wireless data communications technology and an evolution of

the GSM/UMTS standards. The goal of LTE was to increase the capacity and speed of wireless data networks

using new DSP (digital signal processing) techniques and modulations. A further goal was the redesign and simplification of the network architecture to an

IP-based system with significantly reduced transfer latency compared to the 3G architecture.

The LTE wireless interface is incompatible with 2G and 3G networks, so that it must be operated on a separate wireless spectrum.

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Requirements and Targets for the Long Term Evolution

the requirements for LTE Release 8 were refined and crystallized, being finalized in June 2005. They can be summarized as follows: • reduced delays, in terms of both connection establishment and transmission latency; • increased user data rates; • increased cell-edge bit-rate, for uniformity of service provision; • reduced cost per bit, implying improved spectral efficiency; • greater flexibility of spectrum usage, in both new and pre-existing bands; • simplified network architecture; • seamless mobility, including between different radio-access technologies; • reasonable power consumption for the mobile terminal.

Figure 1.1: Approximate timeline of the mobile communications standards landscape

Network Architecture Requirements LTE is required to allow a cost-effective deployment by an improved radio access network architecture design including: • Flat architecture consisting of just one type of node, the base station, known in LTE as

the eNodeB • Effective protocols for the support of packet-switched services • Open interfaces and support of multivendor equipment interoperability; • efficient mechanisms for operation and maintenance, including self-

optimizationfunctionalities • Support of easy deployment and configuration, for example for so-called home base stations (otherwise known as femto-cells)

Network Architecture and Protocols

Differences between and Evolved NodeB and a Node BAir Interface :-eNB uses the E-UTRA protocols OFDMA (downlink) and SC-FDMA (uplink) on its LTE-Uu interface. By contrast, NodeB uses the UTRA protocols WCDMA or TD-SCDMA on its Uu interface.

Control Functionality:-eNB embeds its own control functionality, rather than using an RNC (Radio Network Controller) as does a Node B.

Network Interfaces:-eNB interfaces with the System Architecture Evolution (SAE) core (also known as Evolved Packet Core (EPC)) and other eNB as follows:[1]eNB uses the S1-AP protocol on the S1-MME interface with the Mobility Management Entity (MME) for control plane traffic.eNB uses the GTP-U protocol on the S1-U interface with the Serving Gateway (S-GW) for user plane traffic. Collectively the S1-MME and S1-U interfaces are known as the S1 interface, which represents the interface from eNB to the EPC.eNB uses the X2-AP protocol on the X2 interface with other eNB elements.

The 3GPP evolution for the 3G mobile system defined the UTRAN Long Term Evolution (LTE) and System Architecture Evolution (SAE) network (LTE Core Network)

1-eNodeB:- is the base station in the LTE/SAE network. Its main functions are (Radio resource management, IP header compression and encrypting of user data stream , Selection of an MME at UE attachment, Routing of user plane data towards SAE gateway, and measurement reporting configuration for mobility and scheduling)

2-SAE gateway :- consists two different gateways; Serving SAE gateway and Public Data Network k (PDN) SAE gateway. Serving SAE gateway is the contact point to the actual network when Public Data Network (PDN) SAE is the counterpart for external networks.

3-PCRF :-(Policy and Charging Rules Function )The PCRF 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 bit rates) that decides how a certain data flow will betreated in the PCEF and ensures that this is in accordance with the user’s subscriptionprofile.  Policy and Charging Rules Function PCRF is the node designated to determine policy rules and charging rules .Its functions are administrary in nature mainly.4-GMLC:- (Gateway Mobile Location Center)The GMLC contains functionalities required to support Location Services (LCS). After performing authorization, it sends positioning requests to the MME and receives the final location estimates.5-Home Subscriber Server (HSS):- The HSS contains users’ SAE subscription data such as the EPS-subscribed QoS profile and any access restrictions for roaming . It also holds information about the PDNs to which the user can connect. This could be in the form of an Access Point Name (APN) (which is a label accordingto DNS2 naming conventions describing the access point to the PDN), or a PDNAddress (indicating subscribed IP address(es)). In addition, the HSS holds dynamicinformation such as the identity of the MME to which the user is currently attachedor registered. The HSS may also integrate the Authentication Centre (AuC) whichgenerates the vectors for authentication and security keysThe HSS is a central database that contains user-related and subscription-related information. Similar to HLR +AuC in the older architectures

6-P-GW. The P-GW is responsible for IP address allocation for the UE, as well as QoSenforcement and flow-based charging according to rules from the PCRF. The P-GW isresponsible for the filtering of downlink user IP packets into the different QoS-basedbearers. This is performed based on Traffic Flow Templates (TFTs) .The P-GW performs QoS enforcement for Guaranteed Bit Rate (GBR) bearers. It alsoserves as the mobility anchor for inter-working with non-3GPP technologies suchas CDMA2000 and WiMAX networks. The PDN Gateway provides connectivity from the UE to external packet data networks It can be considered as the point of exit and entry of traffic for the UE. It is the mobility anchor during handover between LTE and non3GPP technologies7-S-GW. All user IP packets are transferred through the S-GW, which serves as the localmobility anchor for the data bearers when the UE moves between eNodeBs. It alsoretains the information about the bearers when the UE is in idle state (known as EPSConnection Management IDLE (ECM-IDLE), and temporarily buffers 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 GPRS3 and UMTS4. S-GW is in the user plane of LTE CN . It routes and forwards user data packets, It is the mobility anchor for the user plane during inter-eNodeB handovers and as the anchor for mobility between LTE and other 3GPP technologies. S-GW interfaces with P-GW through S5 interface.It may interface with SGSN also for handover support.

8-MME. The MME is the control node which processes the signaling between the UEand the CN. The protocols running between the UE and the CN are known as theNon-Access Stratum (NAS) protocols.MME is the key control node of LTE core network. Major functions done by the MME are registration ,mobility ,paging ,authentication. S1-MME interface connects MME to eNodeb. 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.Functions related to inter-working with other networks. This includes handing over of voice calls to legacy networks9-E-SMLC.( Evolved Serving Mobile Location Centre) The E-SMLC manages the overall coordination and scheduling of resources required to find the location of a UE that is attached to E-UTRAN. It also calculates the final location based on the estimates it receives, and it estimates the UE speed and the achieved accuracy.

The Core NetworkThe CN (called the EPC in SAE) is responsible for the overall control of the UE and theestablishment of the bearers. The main logical nodes of the EPC are:• PDN Gateway (P-GW);• Serving GateWay (S-GW);• Mobility Management Entity (MME) ;• Evolved Serving Mobile Location Centre (E-SMLC).

In addition to these nodes, the EPC also includes other logical nodes and functions such asthe Gateway Mobile Location Centre (GMLC), the Home Subscriber Server (HSS) and thePolicy Control and Charging Rules Function (PCRF). Since the EPS only provides a bearerpath of a certain QoS, control of multimedia applications such as VoIP is provided by theIMS which is considered to be outside the EPS itself.

The Access Network.The eNodeBs are normally inter-connected with each other by means of an interfaceknown as X2, and to the EPC by means of the S1 interface – more specifically, to the MMEby means of the S1-MME interface and to the S-GW by means of the S1-U interface.The protocols which run between the eNodeBs and the UE are known as the AccessStratum (AS) protocols. The E-UTRAN is responsible for all radio-related functions, which can be summarized briefly as:• Radio Resource Management. This covers all functions related to the radio bearers,such as radio bearer control, radio admission control, radio mobility control, schedulingand dynamic allocation of resources to UEs in both uplink and downlink.• Header Compression. This helps to ensure efficient use of the radio interface bycompressing the IP packet headers which could otherwise represent a significantoverhead, especially for small packets such as VoIP • Security. All data sent over the radio interface is encrypted • Positioning. The E-UTRAN provides the necessary measurements and other data tothe E-SMLC and assists the E-SMLC in finding the UE position • Connectivity to the EPC. This consists of the signalling towards the MME and the bearer path towards the S-GW.

On the network side, all of these functions reside in the eNodeBs, each of which canbe responsible for managing multiple cells. Unlike some of the previous second- and thirdgenerationtechnologies, LTE integrates the radio controller function into the eNodeB. Thisallows tight interaction between the different protocol layers of the radio access network, thusreducing latency and improving efficiency. Such distributed control eliminates the need fora high-availability, processing-intensive controller, which in turn has the potential to reducecosts and avoid ‘single points of failure’. Furthermore, as LTE does not support soft handoverthere is no need for a centralized data-combining function in the network.One consequence of the lack of a centralized controller node is that, as the UE moves, thenetwork must transfer all information related to a UE, i.e. the UE context, together with anybuffered data, from one eNodeB to another. mechanisms aretherefore needed to avoid data loss during handover. An important feature of the S1 interface linking the access network to the CN is known asS1-flex. This is a concept whereby multiple CN nodes (MME/S-GWs) can serve a commongeographical area, being connected by a mesh network to the set of eNodeBs in that areaAn eNodeB may thus be served by multiple MME/S-GWs, as is the casefor eNodeB#2 in Figure 2.3. The set of MME/S-GW nodes serving a common area is calledan MME/S-GW pool , and the area covered by such a pool of MME/S-GWs is called a poolarea. This concept allows UEs in the cell(s) controlled by one eNodeB to be shared betweenmultiple CN nodes, thereby providing a possibility for load sharing and also eliminatingsingle points of failure for the CN nodes. The UE context normally remains with the sameMME as long as the UE is located within the pool area.

Protocol Architecture :-The radio protocol architecture for LTE can be separated into control plane architecture and user plane architecture as shown below: At user plane side, the application creates data packets that are processed by protocols such as TCP, UDP and IP, while in the control plane, the radio resource control (RRC) protocol writes the signaling messages that are exchanged between the base station and the mobile. In both cases, the information is processed by the packet data convergence protocol (PDCP), the radio link control (RLC) protocol and the medium access control (MAC) protocol, before being passed to the physical layer for transmission.

User PlaneAn IP packet for a UE is encapsulated in an EPC-specific protocol and tunneled between theP-GW and the eNodeB for transmission to the UE. Different tunneling protocols are usedacross different interfaces. A 3GPP-specific tunneling protocol called the GPRS TunnelingProtocol (GTP) is used over the core network interfaces, S1 and S5/S8.6The user plane protocol stack between the e-Node B and UE consists of the following sub-layers:

1-PDCP (Packet Data Convergence Protocol) 2-RLC (radio Link Control) 3-Medium Access Control (MAC)

Packets received by a layer are called Service Data Unit (SDU) while the packet output of a layer is referred to by Protocol Data Unit (PDU) and IP packets at user plane flow from top to bottom layers.

The control plane includes additionally the Radio Resource Control layer (RRC) which is responsible for configuring the lower layers.The Control Plane handles radio-specific functionality which depends on the state of the user equipment which includes two states: idle or connected The protocol stack for the control plane between the UE and MME is shown below. The grey region of the stack indicates the access stratum (AS) protocols. The lower layers perform the same functions as for the user plane with the exception that there is no header compression function for the control plane

Mode DescriptionIdle The user equipment camps on a cell after a cell selection

or reselection process where factors like radio link quality, cell status and radio access technology are considered. The UE also monitors a paging channel to detect incoming calls and acquire system information. In this mode, control plane protocols include cell selection and reselection procedures

Connected The UE supplies the E-UTRAN with downlink channel quality and neighbour cell information to enable the E-UTRAN to select the most suitable cell for the UE. In this case, control plane protocol includes the Radio Link Control (RRC) protocol.

The protocol stack for the control plane between the UE and MME is shown in Figure 2.6.

Control Plane

The Radio Resource Control (RRC) protocol is known as ‘Layer 3’ in the AS protocolstack. It is the main controlling function in the AS, being responsible for establishing theradio bearers and configuring all the lower layers using RRC signalling between the eNodeBand the UE.

NAS Security: The purpose of NAS security is to securely deliver NAS signaling messages between a UE and an MME in the control plane using NAS security keysAS Security: The purpose of AS security is to securely deliver RRC messages between a UE and an eNB in the control plane and IP packets in the user plane using AS security keys

UMTS Architecture

SD

Mobile Station

MSC/VLR

Base StationSubsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

GGSNSGSN

BTS BSC

NodeB

RNC

RNS

UTRAN

SIM ME

USIMME

+

PSTN

PLMN

Internet

Gateway GPRS support node (GGSN)[ The gateway GPRS support node (GGSN) is a main component of the

GPRS network. The GGSN is responsible for the internetworking between the GPRS network and external packet switched networks, like the internet

From an external network's point of view, the GGSN is a router to a "sub-network", because the GGSN ‘hides’ the GPRS infrastructure from the external network.

When the GGSN receives data addressed to a specific user, it checks if the user is active. If it is, the GGSN forwards the data to the SGSN serving the mobile user, but if the mobile user is inactive, the data is discarded. On the other hand, mobile-originated packets are routed to the right network by the GGSN.

The GGSN is the anchor point that enables the mobility of the user terminal in the GPRS/umts networks

The GGSN converts the GPRS packets coming from the SGSN into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network

Serving GPRS support node (SGSN) A serving GPRS support node (SGSN) is responsible for the delivery of

data packets from and to the mobile stations within its geographical service area.

Its tasks include packet routing and transfer, mobility management (attach/detach and location management), authentication and charging functions. The location register of the SGSN stores location information.

Major LTE Radio Technogies Uses Orthogonal Frequency Division Multiplexing (OFDM) for downlink Uses Single Carrier Frequency Division Multiple Access (SC-FDMA) for uplink Uses Multi-input Multi-output(MIMO) for enhanced throughput Reduced power consumption A salient advantage of SC-FDMA over OFDM is the low

Peak to Average Power (PAP) ratio : Increasing battery life

multiple input / multiple output (MIMO) To minimize the effects of noise and to increase the spectrum

utilization and link reliability LTE uses MIMO technique to send the data. The basic idea of MIMO is to use multiple antennas at receiver end and use multiple transmitters when sending the data

LTE Release 8 Key FeaturesOFDMA & SC-FDMA Compatibility and interworking with earlier 3GPP Releases FDD and TDD within a single radio access  technology Efficient Multicast/Broadcast it can achieve the targeted high data rates with simpler implementations involving

relatively low cost and power-efficient hardware High spectral efficiency

OFDM in Downlink Single‐Carrier FDMA in Uplink

Very low latency Short setup time & Short transfer delay Short hand over latency and interruption time

Support of variable bandwidth 1.4, 3, 5, 10, 15 and 20 MHz

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Evolution of LTE-Advanced (4G) Advanced Multi-cell Transmission/Reception Techniques Enhanced Multi-antenna Transmission Techniques Support of Larger Bandwidth in LTE-Advanced LTE-A helps in integrating the existing networks, new networks,

services and terminals to suit the escalating user demands LTE-Advanced will be standardized in the 3GPP specification Release

10 (LTE-A) and will be designed to meet the 4G requirements as defined by ITU

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LTE-Advanced (4G)

Peak data rates up to 1Gbps are expected from bandwidths of 100MHz. OFDM adds additional sub-carrier to increase bandwidth

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UMTS Universal Mobile Telecommunications System (UMTS) UMTS is an upgrade from GSM via GPRS or EDGE The standardization work for UMTS is carried out by Third

Generation Partnership Project (3GPP) Data rates of UMTS are:

144 kbps for rural 384 kbps for urban outdoor 2048 kbps for indoor and low range outdoor UMTS Band

1920-1980 and 2110-2170 MHz Frequency Division Duplex (FDD, W-CDMA) Paired uplink and downlink, channel spacing is 5 MHz and raster is 200 kHz. An Operator needs 3 - 4 channels (2x15 MHz or 2x20 MHz) to be able to build a high-speed, high-capacity network.1900-1920 and 2010-2025 MHz Time Division Duplex (TDD, TD/CDMA) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency.1980-2010 and 2170-2200 MHz Satellite uplink and downlink.

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Frequencies are in use for LTE in the UKThree different frequency bands are used for 4G LTE in the UK. • 800MHz, • 1.8GHz , • 2.6GHz band.

LTE Downlink Channels

The LTE radio interface, various "channels" are used. These are used to segregate the different types of data and allow them to be transported across the radio access network in an orderly fashion.

Physical channels: These are transmission channels that carry user data and control messages.

Transport channels: The physical layer transport channels offer information transfer to Medium Access Control (MAC) and higher layers.

Logical channels: Provide services for the Medium Access Control (MAC) layer within the LTE protocol structure.

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LTE Downlink Channels

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Paging Channel

Paging Control Channel

Physical Downlink Shared Channel

LTE Downlink Logical Channels

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LTE Downlink Logical Channels

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LTE Downlink Transport Channel

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LTE Downlink Transport Channel

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LTE Downlink Physical Channels

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LTE Downlink Physical Channels

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LTE Uplink Channels

Random Access Channel

Physical Radio Access ChannelPhysical Uplink Shared Channel

CQI report

LTE Uplink Logical Channels

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LTE Uplink Transport Channel

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LTE Uplink Physical Channels

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LTE Uplink (SC-FDMA)

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Multi-Antenna Techniques

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Generic Frame Structure Allocation of physical resource blocks (PRBs) is handled by a

scheduling function at the 3GPP base station: Evolved Node B (eNodeB)

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Frame 0 and frame 5 (always downlink)

Generic Frame Structure

DwPTS field: This is the downlink part of the special subframe and its length can be varied from three up to twelve OFDM symbols.

The UpPTS field: This is the uplink part of the special subframe and has a short duration with one or two OFDM symbols.

The GP field: The remaining symbols in the special subframe that have not been allocated to DwPTS or UpPTS are allocated to the GP field, which is used to provide the guard period for the downlink-to-uplink and the uplink-to-downlink switch.

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Resource Blocks for OFDMA One frame is 10 ms consisting of 10 subframes One subframe is 1ms with 2 slots One slot contains N Resource Blocks (6 < N < 110)

The number of downlink resource blocks depends on the transmission bandwidth.

One Resource Block contains M subcarriers for each OFDM symbol The number of subcarriers in each resource block depends on the

subcarrier spacing Δf The number of OFDM symbols in each block depends on

both the CP cyclic prefix length and the subcarrier spacing.

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W-CDMA Parameters

Main Features in LTE-A Release 10Support of wider bandwidth (Carrier Aggregation)

• Use of multiple component carriers (CC) to extend bandwidth up to 100 MHz• Common L1 parameters between component carrier and LTE Rel-8 carrier Improvement of peak data rate, backward compatibility with LTE Rel-8

Advanced MIMO techniques• Extension to up to 8-layer transmission in downlink (REL-8: 4-layer in downlink)• Introduction of single-user MIMO with up to 4-layer transmission in uplink• Enhancements of multi-user MIMO Improvement of peak data rate and capacity

Heterogeneous network and eICIC (enhanced Inter-Cell Interference Coordination)

• Interference coordination for overlay deployment of cells with different Tx power Improvement of cell-edge throughput and coverage

Relay• Relay Node supports radio backhaul and creates a separate cell and appears

as Rel. 8 LTE eNB to Rel. 8 LTE UEs Improvement of coverage and flexibility of service area extension

Minimization of Drive Tests• replacing drive tests for network optimization by collected UE measurements Reduced network planning/optimization costs

100 MHz

fCC

Relay NodeDonor eNB

UE

UE

eNB

macro eNB

micro/pico eNB

LTE/LTE-A REL-11 features Coordinated Multi-Point Operation (DL/UL) (CoMP):

cooperative MIMO of multiple cells to improve spectral efficiency, esp. at cell edge Enhanced physical downlink control channel (E-PDCCH): new Ctrl channel

with higher capacity Further enhancements for

Minimization of Drive Tests (MDT): QoS measurements (throughput, data volume) Self Optimizing Networks (SON): inter RAT Mobility Robustness Optimisation (MRO) Carrier Aggregation (CA): multiple timing advance in UL, UL/DL config. in inter-band CA TDD Machine-Type Communications (MTC): EAB mechanism against overload due to MTC Multimedia Broadcast Multicast Service (MBMS): Service continuity in mobility case Network Energy Saving for E-UTRAN: savings for interworking with UTRAN/GERAN Inter-cell interference coordination (ICIC): assistance to UE for CRS interference reduction Location Services (LCS): Network-based positioning (U-TDOA) Home eNode B (HeNB): mobility enhancements, X2 Gateway

RAN Enhancements for Diverse Data Applications (eDDA): Power Preference Indicator (PPI): informs NW of mobile’s power saving preference

Interference avoidance for in-device coexistence (IDC): FDM/DRX ideas to improved coexistence of LTE, WiFi, Bluetooth transceivers, GNSS receivers in UE

High Power (+33dBm) vehicular UE for 700MHz band for America for Public Safety Additional special subframe configuration for LTE TDD: for TD-SCDMA interworking In addition: larger number of spectrum related work items: new bands/band combinations

Optical fiber

Coordination

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What is the difference between LTE and 4G?4G: 100Mbp/s while on moving transport and 1Gbp/s when stationary. While LTE is much faster than 3G, it has yet to reach the International Telecoms Union's (ITU) technical definition of 4G. LTE does represent a generational shift in cellular network speeds, but is labelled 'evolution' to show that the process is yet to be fully completed.

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TREND MARKET76 Countries with LTE18 LTE scheduled

Australia (24.5Mbps) Fastest Country With LTEClaro Brazil (27.8Mbps) Fastest Network With LTEJapan (66% LTE improvement) Most Improved country for LTE SpeedTele2 Sweden (93% coverage) Network With Best CoverageSouth Korea (91% average coverage) Country with Best Coverage

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Feb 2013; htt://opensignal.com/reports/state-of-lte/

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Feb 2014; http://opensignal.com/reports/state-of-lte-q1-2014/

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On average LTE is the fastest wireless technology worldwide, representing a real increase in speed on both 3G and HSPA+. 4G LTE is over 5x faster than 3G and over twice as fast as HSPA+ and represents a major leap forward in wireless technology.