e-UTRAN or eUTRAN is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. It is the abbreviation for evolved UMTS Terrestrial Radio Access Network, also referred to as the 3GPP work item on the Long Term Evolution (LTE)[1] also known as the Evolved Universal Terrestrial Radio Access (E-UTRA) in early drafts of the 3GPP LTE specification.[1]
It is a radio access network standard meant to be a replacement of the UMTS, HSDPA and 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 with W-CDMA. It provides higher data rates, lower latency and is optimized for packet data. It uses OFDMA radio-access for the downlink and SC-FDMA on the uplink. Trials started in 2008.
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EUTRAN has the following features:
Although UMTS, with HSDPA and HSUPA and their evolution, deliver high data transfer rates, wireless data usage is expected to continue increasing significantly over the next years due to the increase 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 more cost efficient 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.
This improvements in performance allow wireless operators to offer quadruple play services - voice, high-speed interactive applications including large data transfer and feature-rich IPTV with full mobility.
Starting with the 3GPP Release 8, e-UTRA is designed to provide a single evolution path for the GSM/EDGE, UMTS/HSPA, CDMA2000/EV-DO and TD-SCDMA radio interfaces, providing increases in data speeds, and spectral efficiency, and allowing the provision of more functionality.
EUTRAN consists only of enodeBs on the network side. The enodeB performs tasks similar to those performed by the nodeBs and RNC (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 the packet switched (PS) core network via the S1 interface.
The EUTRAN protocol stack consist of [3]:
Interfacing layers to the EUTRAN protocol stack:
E-UTRA uses orthogonal frequency-division multiplexing (OFDM), multiple-input multiple-output (MIMO) antenna technology depending on the terminal category and can use as well beamforming for the downlink to support more users, higher data rates and lower processing power required on each handset.[10] For the UL it uses both OFDM and Single Carrier FDMA (SC-FDMA) depending on the physical channel.
In the uplink LTE uses both OFDMA and a precoded version of OFDM called Single 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 high peak-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 also SU-MIMO.
In both OFDM and SCFDMA transmission modes a cyclic prefix is appended to the transmitted symbols. Two different lengths of the cyclic prefix are available to support different channel spreads due to the cell size and propagation environment. These are a normal cyclic prefix of 4.7µs, and a extended cyclic prefix of 16.6µs.
LTE supports both Frequency-division duplex (FDD) and Time-division duplex (TDD) modes. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD uses the same frequency carrier to, alternatively in time, transmit data from the base station to the terminal and viceversa. Both modes have its 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 with TD-SCDMA as well allowing for coexistence.
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-MBMS subframes the OFDM subcarrier spacing in the frequency domain is 15 kHz. Twelve of these subcarriers together are called a resource block. A LTE terminal can be allocated in the downlink or uplink a minimum of 1 resource block during 1 subframe.
All L1 transport data is encoded using turbo coding and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver.[11] L1 HARQ with 8 (FDD) or up to 15 (TDD) processes is used for the downlink and up to 8 processes for the UL
In the downlink there are several physical channels[12]:
And the following signals:
In the uplink there are three physical channels:
And the following signals:
With 3GPP Release 10, eight LTE user equipment categories are defined[2] depending on the maximum peak data rate and MIMO capabilities support.
| 3GPP Release | User Equipment Category | Maximum L1 datarate Downlink | Maximum number of DL MIMO layers | Maximum L1 datarate Uplink |
|---|---|---|---|---|
| Release 8 | Category 1 | 10.3 Mbits/s | 1 | 5.2 Mbit/s |
| Release 8 | Category 2 | 51.0 Mbits/s | 2 | 25.5 Mbit/s |
| Release 8 | Category 3 | 102.0 Mbits/s | 2 | 51.0 Mbit/s |
| Release 8 | Category 4 | 150.8 Mbits/s | 2 | 51.0 Mbit/s |
| Release 8 | Category 5 | 299.6 Mbits/s | 4 | 75.4 Mbit/s |
| Release 10 | Category 6 | 301.5 Mbits/s | 2 or 4 | 51.0 Mbit/s |
| Release 10 | Category 7 | 301.5 Mbits/s | 2 or 4 | 102.0 Mbit/s |
| Release 10 | Category 8 | 2998.6 Mbits/s | 8 | 1497.8 Mbit/s |
Note: These are L1 transport data data rates not including the different protocol layers overhead. Note: The 3.0 Gbps / 1.5 Gbps 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 Gbps (downlink) and 600 Mbps (uplink).[14]
As the rest of the 3GPP standard parts E-UTRA is structured in releases.
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.
From Tables 5.5-1 "E-UTRA Operating Bands" and 5.6.1-1 "E-UTRA Channel Bandwidth" of 3GPP TS 36.101,[15] the following table lists the specified frequency bands of LTE and the channel bandwidths each listed band supports:
| EUTRAN Operating Band |
Uplink (UL) Operating Band BS Receive UE Transmit |
Downlink (DL) Operating Band BS Transmit UE Receive |
Duplex Mode | Channel Bandwidths (MHz) |
Alias | Region(s) |
|---|---|---|---|---|---|---|
| I (1) | 1920 MHz to 1980 MHz | 2110 MHz to 2170 MHz | FDD | 5, 10, 15, 20 | UMTS IMT, "2100" | Japan, Europe, Asia |
| II (2) | 1850 MHz to 1910 MHz | 1930 MHz to 1990 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | PCS, "1900" | Canada, US, Latin America |
| III (3) | 1710 MHz to 1785 MHz | 1805 MHz to 1880 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | DCS 1800, "1800" | Finland,[16] Hong Kong[17][18], Germany [19] |
| IV (4) | 1710 MHz to 1755 MHz | 2110 MHz to 2155 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | AWS, "1.7/2.1 GHz" | Canada, US, Latin America |
| V (5) | 824 MHz to 849 MHz | 869 MHz to 894 MHz | FDD | 1.4, 3, 5, 10 | Cellular 850, UMTS850 | Canada, US, Australia, Latin America |
| VI (6) | 830 MHz to 840 MHz | 875 MHz to 885 MHz | FDD | 5, 10 | UMTS800 | Japan |
| VII (7) | 2500 MHz to 2570 MHz | 2620 MHz to 2690 MHz | FDD | 5, 10, 15, 20 | IMT-E, "2.6 GHz" | EU, Latin America |
| VIII (8) | 880 MHz to 915 MHz | 925 MHz to 960 MHz | FDD | 1.4, 3, 5, 10 | GSM, UMTS900, EGSM900 | EU, Latin America |
| IX (9) | 1749.9 MHz to 1784.9 MHz | 1844.9 MHz to 1879.9 MHz | FDD | 5, 10, 15, 20 | UMTS1700 | Japan |
| X (10) | 1710 MHz to 1770 MHz | 2110 MHz to 2170 MHz | FDD | 5, 10, 15, 20 | UMTS, IMT 2000 | Uruguay, Ecuador, Peru |
| XI (11) | 1427.9 MHz to 1447.9 MHz | 1475.9 MHz to 1495.9 MHz | FDD | 5, 10 | PDC | Japan (Softbank, KDDI, DoCoMo)[20] |
| XII (12) | 699 MHz to 716 MHz | 729 MHz to 746 MHz | FDD | 1.4, 3, 5, 10 | lower SMH blocks A/B/C | US |
| XIII (13) | 776 MHz to 787 MHz | 746 MHz to 757 MHz | FDD | 5, 10 | upper SMH block C | US |
| XIV (14) | 788 MHz to 798 MHz | 758 MHz to 768 MHz | FDD | 5, 10 | upper SMH block D | US |
| XVII (17) | 704 MHz to 716 MHz | 734 MHz to 746 MHz | FDD | 5, 10 | US | |
| XVIII (18) | 815 MHz to 830 MHz | 860 MHz to 875 MHz | FDD | 5, 10, 15 | ||
| XIX (19) | 830 MHz to 845 MHz | 875 MHz to 890 MHz | FDD | 5, 10, 15 | ||
| XX (20) | 832 MHz to 862 MHz | 791 MHz to 821 MHz | FDD | 5, 10, 15, 20 | EU's Digital Dividend 800 MHz | EU |
| XXI (21) | 1447.9 MHz to 1462.9 MHz | 1495.9 MHz to 1510.9 MHz | FDD | 5, 10, 15 | ||
| XXII (22) | 3410 MHz to 3490 MHz | 3510 MHz to 3590 MHz | FDD | 5, 10, 15, 20 | ||
| XXIII (23) | 2000 MHz to 2020 MHz | 2180 MHz to 2200 MHz | FDD | 1.4, 3, 5, 10 | ||
| XXIV (24) | 1626.5 MHz to 1660.5 MHz | 1525 MHz to 1559 MHz | FDD | 5, 10 | ||
| XXV (25) | 1850 MHz to 1915 MHz | 1930 MHz to 1995 MHz | FDD | 1.4, 3, 5, 10, 15, 20 | ||
| XXXIII (33) | 1900 MHz to 1920 MHz | TDD | 5, 10, 15, 20 | |||
| XXXIV (34) | 2010 MHz to 2025 MHz | TDD | 5, 10, 15 | |||
| XXXV (35) | 1850 MHz to 1910 MHz | TDD | 1.4, 3, 5, 10, 15, 20 | |||
| XXXVI (36) | 1930 MHz to 1990 MHz | TDD | 1.4, 3, 5, 10, 15, 20 | |||
| XXXVII (37) | 1910 MHz to 1930 MHz | TDD | 5, 10, 15, 20 | |||
| XXXVIII (38) | 2570 MHz to 2620 MHz | TDD | 5, 10, 15, 20 | EU | ||
| XXXIX (39) | 1880 MHz to 1920 MHz | TDD | 5, 10, 15, 20 | |||
| XL (40) | 2300 MHz to 2400 MHz | TDD | 5, 10, 15, 20 | IMT-2000 | China, India, Australia | |
| XLI (41) | 2496 MHz to 2690 MHz | TDD | 5, 10, 15, 20 | BRS/EBS | US (Clearwire) | |
| XLII (42) | 3400 MHz to 3600 MHz | TDD | 5, 10, 15, 20 | |||
| XLIII (43) | 3600 MHz to 3800 MHz | TDD | 5, 10, 15, 20 | |||
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