Single-user and multi-user MIMO in downlink and uplink

MIMO schemes, including single- user (SU) MIMO to increase peak data rates and multi-user (MU) MIMO to increase the cell capacity, have been further extended.

The downlink direction now sup-ports up to eight layers. The neces-sary modifications include a new reference signal structure (common CSI-RS and dedicated DMRS) to support eight TX antennas. In ad-dition, feedback mechanisms have been enhanced with periodic/aperi-odic reporting (CQI, PMI, RI) and a new precoding type indicator (PTI) reporting to distinguish slow from fast fading environments.

In uplink direction, up to four layers are supported. Modulation symbols associated with each of the trans-port blocks are mapped onto one or two layers according to the same principle as for LTE Release 8 down-link spatial multiplexing. The nec-essary modifications include the introduction of aperiodic sounding reference signals (SRS) and need-based SRS triggering, as well as or-thogonal spread (OCC) DMRS.

UE1

UE2

eNB

eNB

UE3

SU-MIMOmax. 8x8

MU-MIMOe.g. 2x2

Downlink

UE1

UE2

UE3

SU-MIMOmax. 4x4

MU-MIMO

Uplink

Enhanced uplink transmission scheme

Single-carrier frequency division multiple access (SC-FDMA) is main-tained as the basic LTE-Advanced uplink transmission scheme.

New enhancements are control-data decoupling (simultaneous PUCCH and PUSCH transmission) and non-contiguous data transmis-sion.

Uplink transmission is no longer restricted to the use of consecu-tive subcarriers. Instead, two clus-ters of subcarriers can be allocated. This enables frequency-selective scheduling, which will increase link performance.

PUSCH

PUCCH

Frequency

Time

1 subframe = 1 ms = 1 TTI

Clusters of consecutive subcarriers

1 slot

Frequency

Time

1 subframe = 1 ms = 1 TTI

Consecutive subcarrier operation

1 slot

Example of a heterogeneous network

Example of non-contiguous band aggregation

Two to five component carriers are aggregated to support wider trans-mission bandwidths up to 100 MHz. Spectrum deployments can be ei-ther contiguous or non-contiguous.

Initial LTE-Advanced deployments were limited to two adjacent com-ponent carriers in the same fre-quency band or two single compo-nent carriers in different frequency bands. Further product enhance-ments allow multiple carriers to be applied in both downlink and uplink direction.

The existing scheduling mechanism (method 1) is extended to enable cross-carrier scheduling (method 2).

The DCI formats include an addi-tional 1 bit to 3 bit carrier indicator field. The PDCCH on the primary cell now schedules resources for all ag-gregated carrier frequencies. The 3GPP Release 8 PDCCH structure is maintained, i.e. the same coding and CCE-based resource mapping is used.

Frequency band A Frequency band B

Carrier 1 Carrier 2 Carrier 5

Secondary cellPDSCHPDSCH

PDCC

HPD

CCH

PDCC

HPD

CCH

PDSCHPDSCH

Method 2Method 1

Primary cell

1 slot = 0.5 msTime

Freq

uenc

y

1 subframe = 1 ms

MacroeNB

MacroSub-frame for macro eNB transmission

Sub-frame (1 ms)

Almost blank subframe (ABS)

Sub-frame for pico eNB transmission

Pico cells can also serve UEs that receive astronger macro cell signal

Pico cells can reuse the same frequency as macro cells whenthe UE is closer to the pico eNB

Pico

PicoeNB

FemtoeNB

LTE-Advanced (Release 10)Technology OverviewThe International Telecommunication Union (ITU) has coined the term

IMT-Advanced to identify mobile communications systems with capa-

bilities that go beyond those of IMT-2000 (International Mobile Telecom-

munications). IMT-Advanced requirements include compatibility with

IMT-2000 systems, interworking, high-quality service support and in-

creased data rates. To support advanced services and applications,

mobility scenarios – with 100 Mbit/s for high mobility and 1 Gbit/s for

low mobility – must be implemented. The 3GPP partners made a for-

mal sub mission to the ITU proposing that LTE-Advanced, i.e. LTE as of

3GPP Release 10 and beyond, be evaluated as a candidate technology

for IMT-Advanced. LTE-Advanced maintains the basic LTE approach to

a large extent. Enhancements include carrier aggregation, higher order

MIMO schemes in DL and UL, enhanced UL transmission and enhanced

inter-cell interference coordination (eICIC). According to 3GPP, LTE-

Advanced fulfills and partly exceeds the IMT-Advanced requirements.

Therefore, mobile operators running commercial LTE networks are able

to provide an evolutionary path towards a true 4G system.

Rohde & Schwarz test solutions for LTE were the first on the mar-

ket and since then have evolved to a full product portfolio. The

modular and highly flexible solutions can easily be extended to

cover LTE-Advanced testing needs. From GSM to 4G, from R & D

to conformance, from testing chipsets and assembled end-user

devices to infrastructure equipment, Rohde & Schwarz is the right

partner to satisfy your test requirements.

Heterogeneous networks consist of different cell sizes with overlap-ping areas operating at the same frequency, such as femto and pico eNBs applied within the range of a macro eNB. Overlapping areas re-sult in new interference scenarios caused by different path losses and restricted access due to closed sub-scriber groups. This is a challenge for control channel demodulation and UE measurements. eICIC cre-ates DL transmission gaps in the time domain. These almost blank subframes only contain information required for Release 8/9 UEs to en-sure backward compatibility. eICIC also enables UEs, equipped with in-terference cancellation techniques, to stay connected even with low SINR, which effectively increases the range of femto and pico cells.

¸CMW500 wideband radio communication tester ❙ Multi-RAT covering all main cellular communications standards and multiple band support up to 6 GHz ❙ Carrier aggregation up to 4 DL and 2 UL carriers, supporting up to 8x2 MIMO (including fading) in the DL and eICIC ❙ All layers, from RF parametric tests and protocol tests to end-to-end application tests, in one box ❙ Support of wireless connectivity, GNSS and broadcast standards

¸FSW signal and spectrum analyzer ❙ LTE-Advanced FDD and TD-LTE DL and UL signal analysis for terminal and base station transmitter tests, including built-in multistandard radio analyzer (MSRA) function ❙ Support of sequential and parallel carrier aggregation measurements, MIMO signal analysis and simultaneous PUSCH/PUCCH measurements ❙ Up to 500 MHz analysis bandwidth, low phase noise of –137 dBc (1 Hz) at 10 kHz offset (1 GHz carrier) and 88 dB dynamic range (with noise cancellation) for ACLR measurements ❙ Multistandard platform supporting all main cellular communications and wireless connectivity standards

¸SMW200A vector signal generator ❙ LTE-Advanced FDD and TD-LTE DL and UL signal generation for terminal and base station receiver tests, including closed-loop HARQ feedback and UL timing adjustments ❙ Support of all key MIMO modes such as 3x3, 4x4, 8x2 and 2x8, including realtime fading, ABS and enhanced SC-FDMA ❙ Interband and intraband carrier aggregation, including cross carrier scheduling for up to 5 component carriers ❙ Combination of MIMO and carrier aggregation ❙ Multistandard platform supporting all main cellular communications and wireless connectivity standards

Glossary: 3GPP = 3rd Generation Partnership Project, 4G = 4th Generation Mobile Communications Technology, ABS = Almost Blank Subframe, ACLR = Adjacent Channel Leakage Ratio, CCE = Control Channel Element, CQI = Channel Quality Indicator, CSI-RS = Channel State Information Reference Symbols, DCI = Downlink Control Information, DL = Downlink, DMRS = Demodulation Reference Signal, eICIC = Enhanced Inter-Cell Interference Coordination, eNB = Enhanced NodeB, FDD = Frequency Division Duplex, GNSS = Global Navigation Satellite System, GSM = Global System for Mobile Communications, HARQ = Hybrid Automatic Repeat Request, IMT = International Mobile Telecommunications, ITU = International Telecommunication Union, LTE = Long Term Evolution, MIMO = Multiple Input Multiple Output, MU-MIMO = Multi-User MIMO, OCC = Orthogonal Cover Code, PDCCH = Physical Downlink Control Channel, PDSCH = Physical Downlink Shared Channel, PMI = Precoding Matrix Indicator, PTI = Precoding Type Indicator, PUCCH = Physical Uplink Control Channel, PUSCH = Physical Uplink Shared Channel, RAT = Radio Access Technology, RI = Rank Indicator, SC-FDMA = Single-Carrier Frequency Division Multiple Access, SINR = Signal to Interference and Noise Ratio, SRS = Sounding Reference Signal, SU-MIMO = Single-User MIMO, TD-LTE = Time Division – LTE, TTI = Transmission Time Interval, TX = Transmission, UE = User Equipment, UL = Uplink.

Rohde & Schwarz LTE-Advanced test solutions

Carrier aggregation Extended MIMO schemes

Enhanced uplinkEnhanced ICIC

www.rohde-schwarz.com/technology/LTE

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LTE_advanced_po_en.indd 1 22.01.2015 17:08:01