E-UTRA

EUTRAN architecture as part of aLTEandSAEnetwork

E-UTRAis theair interfaceof 3rd Generation Partnership Project (3GPP)Long Term Evolution(LTE) upgrade path for mobile networks. It is an acronym forEvolved UMTS Terrestrial Radio Access,also known as theEvolved Universal Terrestrial Radio Accessin early drafts of the 3GPP LTE specification.E-UTRANis the combination of E-UTRA,user equipment(UE), and aNode B(E-UTRAN Node B or Evolved Node B,eNodeB).

It is aradio access network(RAN) meant to be a replacement of theUniversal Mobile Telecommunications System(UMTS),High-Speed Downlink Packet Access(HSDPA), andHigh-Speed Uplink Packet Access(HSUPA) technologies specified in 3GPP releases 5 and beyond. Unlike HSPA, LTE's E-UTRA is an entirely new air interface system, unrelated to and incompatible withW-CDMA.It provides higher data rates, lower latency and is optimized for packet data. It usesorthogonal frequency-division multiple access(OFDMA) radio-access for the downlink andsingle-carrier frequency-division multiple access(SC-FDMA) on the uplink. Trials started in 2008.

Features

EUTRAN has the following features:

• Peak download rates of 299.6 Mbit/s for 4×4 antennas, and 150.8 Mbit/s for 2×2 antennas with 20 MHz of spectrum.LTE Advancedsupports 8×8 antenna configurations with peak download rates of 2,998.6 Mbit/s in an aggregated 100 MHz channel.
• Peak upload rates of 75.4 Mbit/s for a 20 MHz channel in the LTE standard, with up to 1,497.8 Mbit/s in an LTE Advanced 100 MHz carrier.
• Low data transfer latencies (sub-5 ms latency for small IP packets in optimal conditions), lower latencies forhandoverand connection setup time.
• Support for terminals moving at up to 350 km/h or 500 km/h depending on the frequency band.
• Support for bothFDDandTDDduplexes as well as half-duplex FDD with the same radio access technology
• Support for all frequency bands currently used byIMTsystems byITU-R.
• Flexible bandwidth: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz are standardized. By comparison, UMTS uses fixed size 5 MHz chunks of spectrum.
• Increasedspectral efficiencyat 2–5 times more than in 3GPP (HSPA) release 6
• Support of cell sizes from tens of meters of radius (femtoandpicocells) up to over 100 km radiusmacrocells
• Simplified architecture: The network side of EUTRAN is composed only by theeNodeBs
• Support for inter-operation with other systems (e.g.,GSM/EDGE,UMTS,CDMA2000,WiMAX,etc.)
• Packet-switchedradio interface.

Rationale for E-UTRA

AlthoughUMTS,withHSDPAandHSUPAand theirevolution,deliver high data transfer rates, wireless data usage is expected to continue increasing significantly over the next few years due to the increased offering and demand of services and content on-the-move and the continued reduction of costs for the final user. This increase is expected to require not only faster networks and radio interfaces but also higher cost-efficiency than what is possible by the evolution of the current standards. Thus the 3GPP consortium set the requirements for a new radio interface (EUTRAN) and core network evolution (System Architecture Evolution SAE) that would fulfill this need.

These improvements in performance allowwirelessoperators to offerquadruple playservices – voice, high-speed interactive applications including large data transfer andfeature-richIPTVwith full mobility.

Starting with the 3GPP Release 8, E-UTRA is designed to provide a single evolution path for theGSM/EDGE,UMTS/HSPA,CDMA2000/EV-DOandTD-SCDMAradio interfaces, providing increases in data speeds, and spectral efficiency, and allowing the provision of more functionality.

Architecture

EUTRAN consists only of eNodeBs on the network side. The eNodeB performs tasks similar to those performed by thenodeBsandRNC (radio network controller)together in UTRAN. The aim of this simplification is to reduce the latency of all radio interface operations. eNodeBs are connected to each other via the X2 interface, and they connect to thepacket switched (PS)core network via the S1 interface.

EUTRAN protocol stack

EUTRAN protocol stack

The EUTRANprotocol stackconsists of:

• Physical layer:Carries all information from the MAC transport channels over the air interface. Takes care of thelink adaptation (ACM),power control,cell search (for initial synchronization and handover purposes) and other measurements (inside the LTE system and between systems) for the RRC layer.
• MAC:The MAC sublayer offers a set of logical channels to the RLC sublayer that itmultiplexesinto the physical layer transport channels. It also manages the HARQ error correction, handles the prioritization of the logical channels for the same UE and the dynamic scheduling between UEs, etc..
• RLC:It transports the PDCP'sPDUs.It can work in 3 different modes depending on the reliability provided. Depending on this mode it can provide:ARQerror correction, segmentation/concatenation of PDUs, reordering for in-sequence delivery, duplicate detection, etc...
• PDCP:For the RRC layer it provides transport of its data withcipheringand integrity protection. And for the IP layer transport of the IP packets, withROHC header compression,ciphering, and depending on the RLC mode in-sequence delivery, duplicate detection and retransmission of its own SDUs during handover.
• RRC:Between others it takes care of: the broadcast system information related to theaccess stratumand transport of thenon-access stratum(NAS) messages, paging, establishment and release of the RRC connection, security key management, handover, UE measurements related to inter-system (inter-RAT) mobility, QoS, etc..

Interfacing layers to the EUTRAN protocol stack:

• NAS:Protocol between the UE and theMMEon the network side (outside of EUTRAN). Between others performs authentication of the UE, security control and generates part of the paging messages.
• IP

Physical layer (L1) design

E-UTRA usesorthogonal frequency-division multiple xing(OFDM),multiple-input multiple-output(MIMO) antenna technology depending on the terminal category and can also usebeamformingfor the downlink to support more users, higher data rates and lower processing power required on each handset.

In the uplink LTE uses bothOFDMAand a precoded version of OFDM calledSingle-Carrier Frequency-Division Multiple Access (SC-FDMA)depending on the channel. This is to compensate for a drawback with normal OFDM, which has a very highpeak-to-average power ratio (PAPR).High PAPR requires more expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. For the uplink, in release 8 and 9 multi user MIMO / Spatial division multiple access (SDMA) is supported; release 10 introduces alsoSU-MIMO.

In both OFDM and SC-FDMA transmission modes acyclic prefixis appended to the transmitted symbols. Two different lengths of the cyclic prefix are available to support differentchannel spreadsdue to the cell size and propagation environment. These are a normal cyclic prefix of 4.7 μs, and an extended cyclic prefix of 16.6 μs.

LTEResource Blockin time and frequency domains: 12subcarriers,0.5 ms timeslot (normal cyclic prefix).

LTE supports bothFrequency-division duplex(FDD) andTime-division duplex(TDD) modes. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD splits one frequency carrier into alternating time periods for transmission from the base station to the terminal and vice versa. Both modes have their own frame structure within LTE and these are aligned with each other meaning that similar hardware can be used in the base stations and terminals to allow for economy of scale. The TDD mode in LTE is aligned withTD-SCDMAas well allowing for coexistence. Single chipsets are available which support both TDD-LTE and FDD-LTE operating modes.

Frames and resource blocks

The LTE transmission is structured in the time domain in radio frames. Each of these radio frames is 10 ms long and consists of 10 sub frames of 1 ms each. For non-Multimedia Broadcast Multicast Service(MBMS) subframes, theOFDMAsub-carrier spacing in the frequency domain is 15 kHz. Twelve of these sub-carriers together allocated during a 0.5 ms timeslot are called a resource block.A LTE terminal can be allocated, in the downlink or uplink, a minimum of 2 resources blocks during 1 subframe (1 ms).

Encoding

All L1 transport data is encoded usingTurbo C odingand a contention-freequadratic permutation polynomial(QPP) Turbo C ode internalinterleaver.L1HARQwith 8 (FDD) or up to 15 (TDD) processes is used for the downlink and up to 8 processes for the UL

EUTRAN physical channels and signals

Downlink (DL)

In the downlink there are several physical channels:

• The Physical Downlink Control Channel (PDCCH) carries between others the downlink allocation information, uplink allocation grants for the terminal/UE.
• The Physical Control Format Indicator Channel (PCFICH) used to signal CFI (control format indicator).
• The Physical Hybrid ARQ Indicator Channel (PHICH) used to carry the acknowledges from the uplink transmissions.
• The Physical Downlink Shared Channel (PDSCH) is used for L1 transport data transmission. Supported modulation formats on the PDSCH areQPSK,16QAMand64QAM.
• The Physical Multicast Channel (PMCH) is used for broadcast transmission using a Single Frequency Network
• The Physical Broadcast Channel (PBCH) is used to broadcast the basic system information within the cell

And the following signals:

• The synchronization signals (PSS and SSS) are meant for the UE to discover the LTE cell and do the initial synchronization.
• The reference signals (cell specific, MBSFN, and UE specific) are used by the UE to estimate the DL channel.
• Positioning reference signals (PRS), added in release 9, meant to be used by the UE forOTDOApositioning(a type ofmultilateration)

Uplink (UL)

In the uplink there are three physical channels:

• Physical Random Access Channel (PRACH) is used for initial access and when the UE loses its uplink synchronization,
• Physical Uplink Shared Channel (PUSCH) carries the L1 UL transport data together with control information. Supported modulation formats on the PUSCH areQPSK,16QAMand depending on theuser equipmentcategory64QAM.PUSCH is the only channel which, because of its greater BW, usesSC-FDMA
• Physical Uplink Control Channel (PUCCH) carries control information. Note that the Uplink control information consists only on DL acknowledges as well as CQI related reports as all the UL coding and allocation parameters are known by the network side and signaled to the UE in the PDCCH.

And the following signals:

• Reference signals (RS) used by the eNodeB to estimate the uplink channel to decode the terminal uplink transmission.
• Sounding reference signals (SRS) used by the eNodeB to estimate the uplink channel conditions for each user to decide the best uplink scheduling.

User Equipment (UE) categories

3GPP Release 8 defines five LTE user equipment categories depending on maximum peak data rate and MIMO capabilities support. With 3GPP Release 10, which is referred to asLTE Advanced,three new categories have been introduced. Followed by four more with Release 11, two more with Release 14, and five more with Release 15.

User equipment Category	Max. L1 data rate Downlink (Mbit/s)	Max. number of DLMIMO layers	Max. L1 data rate Uplink (Mbit/s)	3GPP Release
NB1	0.68	1	1.0	Rel 13
M1	1.0	1	1.0
0	1.0	1	1.0	Rel 12
1	10.3	1	5.2	Rel 8
2	51.0	2	25.5
3	102.0	2	51.0
4	150.8	2	51.0
5	299.6	4	75.4
6	301.5	2 or 4	51.0	Rel 10
7	301.5	2 or 4	102.0
8	2,998.6	8	1,497.8
9	452.2	2 or 4	51.0	Rel 11
10	452.2	2 or 4	102.0
11	603.0	2 or 4	51.0
12	603.0	2 or 4	102.0
13	391.7	2 or 4	150.8	Rel 12
14	3,917	8	9,585
15	750	2 or 4	226
16	979	2 or 4	105
17	25,065	8	2,119	Rel 13
18	1,174	2 or 4 or 8	211
19	1,566	2 or 4 or 8	13,563
20	2,000	2 or 4 or 8	315	Rel 14
21	1,400	2 or 4	300
22	2,350	2 or 4 or 8	422	Rel 15
23	2,700	2 or 4 or 8	528
24	3,000	2 or 4 or 8	633
25	3,200	2 or 4 or 8	739
26	3,500	2 or 4 or 8	844

Note: Maximum data rates shown are for 20 MHz of channel bandwidth. Categories 6 and above include data rates from combining multiple 20 MHz channels. Maximum data rates will be lower if less bandwidth is utilized.

Note: These are L1 transport data rates not including the different protocol layers overhead. Depending on cellbandwidth,cell load (number of simultaneous users), network configuration, the performance of the user equipment used, propagation conditions, etc. practical data rates will vary.

Note: The 3.0 Gbit/s / 1.5 Gbit/s data rate specified as Category 8 is near the peak aggregate data rate for a base station sector. A more realistic maximum data rate for a single user is 1.2 Gbit/s (downlink) and 600 Mbit/s (uplink).Nokia Siemens Networks has demonstrated downlink speeds of 1.4 Gbit/s using 100 MHz of aggregated spectrum.

EUTRAN releases

As the rest of the3GPPstandard parts E-UTRA is structured in releases.

• Release 8, frozen in 2008, specified the first LTE standard
• Release 9, frozen in 2009, included some additions to the physical layer like dual layer (MIMO) beam-forming transmission orpositioningsupport
• Release 10, frozen in 2011, introduces to the standard severalLTE Advancedfeatures like carrier aggregation, uplinkSU-MIMOor relays, aiming to a considerable L1 peak data rate increase.

All LTE releases have been designed so far keeping backward compatibility in mind. That is, a release 8 compliant terminal will work in a release 10 network, while release 10 terminals would be able to use its extra functionality.

Frequency bands and channel bandwidths

Main article:LTE frequency bands § Frequency bands and channel bandwidths

Deployments by region

Main article:LTE frequency bands § Deployments by region

Technology demos

• In September 2007, NTT Docomo demonstrated E-UTRA data rates of 200 Mbit/s with power consumption below 100 mW during the test.
• In April 2008, LG and Nortel demonstrated E-UTRA data rates of 50 Mbit/s while travelling at 110 km/h.
• February 15, 2008 – Skyworks Solutions has released a front-end module for E-UTRAN.

See also

• 4G(IMT-Advanced)
• List of interface bit rates
• LTE
• LTE-A
• System Architecture Evolution(SAE)
• UMTS
• WiMAX

External links

• EARFCN calculator and band reference
• S1-AP procedures E-RAB Setup,modify and release
• 3GPP Long Term Evolution page
• LTE 3GPP Encyclopedia
• 3G Americas - UMTS/HSPA Speeds Up the Wireless Technology Roadmap. 3G Americas Publishes White Paper on 3GPP Release 7 to Release 8. Bellevue, WA, July 10, 2007