LTE Release 12 and Beyond

2 LTE Release 12 and Beyond

1. Introduction

Living up to what LTE promised, commercial LTE deployments have shown that LTE networks can deliver peak data rates of up to 100 Mbps and average data rates of tens of Mbps as well as latencies below 20 milliseconds. The next step in LTE evolution has already been made, with LTE-Advanced pushing peak data rates beyond 1 Gbps and enhancing multi-band and multi-antenna operation that is compatible with existing deployments.

The continuing demand for ever more capacity is driven largely by video usage. As outlined by Nokia Siemens Networks in its Beyond 4G vision, a 1,000 fold increase in network capacity requires increases in all dimensions:

As the media-intense lifestyle is set to penetrate all social environments, another issue is end users’ continually rising expectations of throughput and service - by 2020, a typical user will consume 1 Gbyte of data per day. Finally, operators need to secure their share of the mobile broadband market by improving their operational efficiency and network robustness, developing new business opportunities, extending their spectrum and by protecting their investment.

LTE Release 12 and beyond will provide the initial enablers of meeting these challenging demands as well as a smooth way into the Beyond 4G era.

10x Performance

10x Spectrum

10x Base stations

1000x capacity

1. Introduction 2

2. Technology enablers coming with Release 12 32.1 Small cell enhancements 32.2 New Carrier Type 42.3 Macro cell enhancements 42.4 Machine-Type Communications 52.5 Further enhancements 6

3. Summary 6

4. Further Reading 7

3LTE Release 12 and Beyond

2. Technology enablers coming with Release 12

Release 12 enhancements focus on the four areas of Capacity, Coverage, Coordination (between cells), and Cost. Improvements in these areas are based on using several technology enablers: small cell enhancements, macro cell enhancements, New Carrier Type (NCT) and Machine-Type Communications (MTC). These enablers are described in this paper.

Customer experience, capacity and coverage will be improved with small cell enhancements, based on inter-site Carrier Aggregation, LTE-WLAN integration and macro cell enhancements. Small cell enhancements are also known as enhanced local access.

NCT helps achieve the required changes in the physical layer and initially provides base station energy savings, flexibility in deployment and ways to reduce interference in heterogeneous networks (HetNets).

Improvements in capacity and a more robust network performance are achieved by 3D Beamforming/MIMO (Multiple Input Multiple Output), advanced user equipment (UE) receivers and evolved Coordinated Multipoint

(CoMP) techniques, as well as through Self-Organizing Networks for small cell deployments.

Finally, new spectrum footprint and new business will be opened up by optimizing the system for Machine-Type Communications, as well as by, for example, using LTE for public safety.

2.1 Small cell enhancementsThe increasing traffic load will require more cells and more capacity to cope with the expected throughput. Release 12 enhancements help small cell deployments in two main areas - reducing mobility signaling in high density cells and improving user data rates by using macro cells and small cells together.

The high number of small cells will increase signaling traffic in the core network as users move frequently from one small cell to another. This situation will be improved by separating the user plane and control plane functions in the Radio Access Network (RAN) architecture, that is, letting the macro layer manage the mobility while offloading high data traffic to the small cells.

Small cell enhancements

New Carrier Type

Macro cell enhancements

Machine-Type Communications

SON, WLAN integration, Public safety

1 GB per day per user everywhere

1000x capacity increase

New business, new spectrum footprint

Efficiency and robustness

Capacity

Coverage

Coordination

Cost

Figure 1: The Focus (a.k.a. The Four Cs), the Enablers, the Benefits

4 LTE Release 12 and Beyond

Inter-site Carrier Aggregation – i.e. carrier aggregation between sites – is an attractive solution for HetNets that do not have an ideal backhaul network. It allows mobility management to be maintained on the macro layer while aggregating small cells to provide extra user plane capacity, increasing the throughput. Inter-site carrier aggregation is one of Nokia Siemens Networks’ innovations in the small cell area. The concept optimizes performance by combining the benefits of macro cell coverage and small cell capacity. Based on increasing the bandwidth through carrier aggregation, inter-site carrier aggregation can provide a cell edge gain of 50%, even in loaded networks.

2.2 New Carrier TypeThe New Carrier Type will allow the optimization of small cells but can also be used in macro cells. Primarily, NCT will reduce common reference signal overhead and allow the operation of downlink control channels to be based on demodulation reference signals, in a stand-alone NCT solution. These generic optimizations are expected to be implemented in LTE Release 12 and will enable base station energy savings, flexibility in deployment and ways to reduce interference in HetNets, as well as performance gains for four transmit antenna and eight transmit antenna macro base station configurations. NCT can optimize

small cell deployments through a significantly shortened latency and an extremely flexible duplex scheme.

The main deployment assumptions and performance benefits of small cell optimization and NCT are shown in Figure 2. The base station power savings and inter-cell interference savings are becoming more important as the number of small base stations increases considerably.

2.3 Macro cell enhancementsWith exponential growth in network traffic, future networks need to continue to evolve both in macro and small cells. There are opportunities to enhance the network capacity and coverage of current LTE macro cell deployment significantly by exploiting multi-antennas, advanced receivers, network architectures and new spectrum. Macro cell enhancements are attractive for operators because they allow further exploitation of the existing base station sites and transport infrastructure.

Base stations such as the Nokia Siemens Networks’ Flexi Multiradio 10 Base Station establish high capacity macro cells with the potential to double the spectral efficiency of existing LTE macro networks. The target is to support LTE and LTE-Advanced technology in the 700-2600 MHz bands, tight coordination with small cells, for example in the 3.5 GHz

Figure 2: Deployment assumptions and benefits of small cell optimization and New Carrier Type

Higher frequency >3 GHz

Power saving during low loading

Flexible uplink: downlink asymmetry

Small cell optimization and New Carrier Type

4-8 antennas

Improved beamforming with 4-8 transmit antennas

Low number of users per small cell

TDD duplexing

Input assumptions for future HetNets

Performance benefits

Minimized reference overhead especially in HetNet

5LTE Release 12 and Beyond

band, and combinations of the following features: • Largenumberoftransmitandreceive

antennas: more than four transmit and receive antennas

• ActiveAntennaSystems(AAS)whereantenna and RF are built together

• AASwithverticalsectorizationanduserspecific elevation beamforming/3D-MIMO

• Advanceduplinkreceivers• CooperativeMultipointTransmissionand

Reception (CoMP)• Advancedradionetworkarchitecture

including on-site resource pooling • Highcapacitybackhaul• AuthorizedSharedAccesstogainaccess

to more spectrum

By increasing the number of transmit and receive antennas at the base stations from two to four and then to eight, a significant gain in network capacity can be achieved. This gain can be further enhanced by using advanced receiver and single-user and multi-user MIMO schemes (SU/MU MIMO) based on dedicated demodulation reference signals.

Using active antennas where the RF components are integrated into the antenna and performing vertical sectorization or sector specific elevation beamforming (using two fixed beams per sector) can give significant improvements in sector capacity compared to a single beam system. Building upon vertical sectorization, Release 12 will be developing two techniques namely a) UE-specific elevation beamforming that adds UE specific vertical beamsteering to existing azimuth-only closed loop SU/MU MIMO methods and b) 3D-MIMO techniques that simultaneously exploit both the azimuth and the elevation dimensions of the multipath channel on a user-specific basis. These techniques are expected to give significant improvements in both the cell edge and sector capacity.

The concept of 3D-MIMO is illustrated in Figure 3.

Next in line for deployment are centralized solutions such as cluster level on-site resource pooling using high capacity and

low latency fiber backhaul (Centralized RAN), where a baseband pool serves the macro site and underlay remote radio heads. Such a radio network architecture allows for further improvements in radio performance.

Last but not least, macro networks evolve by exploiting Authorized Shared Access – a new and complementary way of authorizing spectrum use in addition to exclusive licensed spectrum – which leads to higher spectrum availability and predictable QoS in the shared spectrum, thereby increasing the number of subscribers and the capacity of the network.

2.4 Machine-Type CommunicationsThe number of embedded machine-to-machine modems is expected to increase substantially in the future. While the urban area today can have up to 5,000-10,000 subscribers per base station, the growth of machine-to-machine could see up to 100,000 connected devices per base station, setting new requirements for the mobile network.

In addition to the already specified MTC support in 3GPP, the following areas of optimization are expected to be covered in Release 12:• Networkloadoptimizationswillcontinue:

MTC-specific signaling and connectivity optimizations ensure that a very large number of connected devices can be supported by the LTE radio, with small amounts of data delivered efficiently.

UE-specific elevation BF/3D-MIMO

Figure 3: UE-specific 3D-MIMO

6 LTE Release 12 and Beyond

• ThelowcostMTCdevicestudiesarecompleted. Based on these, MTC device costs can be reduced in various ways. For example, 15% cost savings can be achieved through simplification to a single receive antenna, 5% by accepting reduced peak data rates and 10% by accepting reduced maximum bandwidth.

2.5 Further enhancementsSelf-Organizing Networks (SON) will play a key role in the efficient operation of dense small cells. Mass deployments will introduce new requirements in SON functions to ensure

proper cell identity management and neighbor cell relations, as well as to enhance mobility robustness and load balancing in small cell coverage gaps. Additionally, intelligent solutions to easily switch small cell capacity layers to a power saving mode will be essential.

Furthermore, 3GPP will look for new opportunities to enhance LTE-HSPA integration and LTE-WLAN interworking, as well as to enable device-to-device discovery and communication for commercial and public safety use.

3. Summary

LTE evolution continues strongly in Release 12 and beyond by enhancing LTE and LTE-Advanced operation. In particular, LTE Release 12 addresses coordinated small cell deployments, macro cell enhancements, Machine-Type Communications, discovery in device-to-device communication, enhanced SON, and in particular the New Carrier Type

enabling energy savings, flexible deployment and improved interference management in HetNets.

Release 12 features aim at boosting performance and at entering new areas and spectrum. The following two tables summarize the most promising Release 12 features:

Benefits from 3GPP Release 12 – Boost performance

Rel12 feature Benefit

Small Cell Enhancement based on Inter-site CA

• OptimizedsmallcellmobilitybyreducingRadioAccessNetworkto Core Network signaling

• Improveddataratesbyusingmacroandsmallcellstogether• EfficientuseofTDDspectrum

New Carrier Type (NCT)

• Minimizedinter-cellinterference• Loweredenergyconsumption• Significantoverheadreductionfordownlink4-8antenna

transmission modes, hence resulting in an improved downlink spectral efficiency

UE-specific elevation beamforming / 3D-MIMO

• Significantlyenhancedmacrocellcapacityandcoverage

Advanced receivers • Removinginterferencetoincreaseuplinkanddownlinkcapacity

Enhanced DL Coordinated Multi-Point (DL eCoMP)

• Enhancedcoveragebyexploitingcoordinationincaseof non-ideal backhaul

Enhanced SON • Efficientoperationofdensesmallcelldeployments• Energysavingsinsmallcellcapacitylayers

7LTE Release 12 and Beyond

Benefits from 3GPP Release 12 – Expand to new areas and new spectrum

Rel12 feature Benefit

LTE-WLAN Integration • 10Mbpsminimumdownlinkdatarate• 1000xhotspotcapacityinpresentdecade

LTE-HSPA Integration • Enhancedmulti-technologysupport

Machine-Type Communications (MTC)

• Getpreparedfor50Bnconnecteddevicesor100.000devicespercell

Public Safety • Secureoperator’smarketsharebyexpandingLTEfootprint

Nokia Siemens Network is a leading contributor in 3GPP, driving LTE and LTE-Advanced standards. It is also shaping Beyond 4G through various activities, including participation in the EU FP7 collaborative project METIS and contribution to ITU-R IMT vision work. LTE

Rel-8 and Rel-9

LTE Advanced Rel-10 and Rel-11

LTE Advanced Evolution Rel-12 and Rel-13

Beyond 4G

2010+

2013+

2015+

2020+

Figure 4: The radio evolution in the present decade

4. Further Reading

• LTE-Advanced–TheadvancedLTEtoolboxfor more efficient delivery of better user experience, Nokia Siemens Networks White Paper

• TakingadvantageoftheconvergenceofWi-Fi and 3GPP, Nokia Siemens Networks White Paper

• LongTermHSPAEvolutionmeetsITUIMT-Advanced requirements, Nokia Siemens Networks White Paper

• DeploymentStrategiesforHeterogeneousNetworks, Nokia Siemens Network White Paper

• 2020:Beyond4G–RadioEvolutionfor the Gigabit Experience, Nokia Siemens Networks White Paper

• Release12andbeyondforC4(Cost,Coverage, Coordination of small cells, and Capacity), Nokia Siemens Networks 3GPP presentation

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