Nokia Networks
LTE Release 12 and Beyond
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Nokia Networks white paper LTE Release 12 and Beyond
CONTENTS
1. Introduction
3
2. Technology enablers coming with Release 12
4
2.1 2.2 2.3 2.4 2.5 2.6 2.7
Small Cell enhancements Carrier Aggregation enhancements Macro Cell enhancements Machine-Type Communications (MTC) 3GPP-WLAN radio level interworking LTE Unlicensed Network Assisted Interference Cancellation Cancella tion and Suppression (NAICS) 2.8 Fu Further enhancements
4 6 7 8 9 10 11 11
3. Summary
13
4. Further reading
15
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1. Introduction In 2014 the speed of LTE networks is evolving from 150 Mbps to 300 Mbps, using LTE-Advanced Carrier Aggregation. A further evolution to 450 Mbps has been demonstrated by Nokia Networks at Mobile World Congress 2014. With the upcoming 3GPP releases from Release12 onwards, we will see many more enhancements to the LTE and TD-LTE technology.. This whitepaper aims to provide a concise overview. technology The continuing demand for ever more capacity is driven largely by growing use of video. As outlined by Nokia Networks in its Vision 2020, a 1,000 fold increase in network capacity requires increases in all dimensions – eciency, spectrum and density.
MIMO & adv. receiver
Carrier Aggregation
Advanced macros
Smart Scheduler
New bands
HetNet management
eCoMP
ASA
Flexible small cells
As people from all walks of life start to use media more intensively, another issue is their continually rising expectations of throughput throughput and service - by 2020, a typical user will consume 1 Gbyte of data per day. Operators also need to secure their share of the mobile broadband market by improving the eciency of their operations and the robustness of their networks robustness, developing new business opportunities, extending their spectrum a nd by protecting their investmen investment. t. LTE 3GPP Release 12 and beyond will provide a foundation to meets these challenging demands, as well as smooth the way towards the 4G / 5G era.
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2.
Technology enablers coming with Release 12
Enhancements in 3GPP Release 12 focus on the four areas of Capacity, Coverage, Coordination (between cells) and Cost. Improvements in these areas are achieved ac hieved by several technology technology enablers: small cell enhancements, macro cell enhancements 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. Improvements in capacity and a more robust network performance are achieved by 3D Beam forming/MIMO (Multiple Input Multiple Output), advanced user terminals and evolved Coordinated Multipoint (CoMP) techniques, as well as through Self-Organizing Networks for small cell deployments. New spectrum footprint and new business opportunities will be achieved by optimizing the system for MTC, as well as by, for example, using LTE for Public Safety.
Capacity
Coverage
Small cell enhancements
Macro cell enhancements
1000x capacity increase
1 GB per day per user everywhere
Carrier Aggregation enhancements Coordination
Machine-Type Communications
Cost
SON, WLAN integration, public safety
Efficiency and robustness
New business, new spectrum footprint
Figure 1: The Focus (a.k.a. The Fo Four ur Cs), the Enablers, the Benets
2.11 2.
Small Cell enhancem enhancements ents
Increasing trac load will require more cells and more capacity. Enhancements to Release 12 help small cell deployments in two main areas - reducing mobility signaling in high density cell deployments and improving user data rates by using macro cells and small cells together.
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The high number of small cells will increase signaling trac 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. architecture. This method lets lets the macro layer manage the mobility while ooading high data trac to the small cells. Dual connectivity also known as Inter-site Inter-site carrier aggregation, ag gregation, is used to achieve carrier aggregation between sites. This is an attractive solution for Heterogeneous Networks (HetNets) with no ideal backhaul network. Dual connectivity 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 Networks’ innovations innovations in the small cell area. The concept optimizes performance by combining the benets of macro cell coverage and small cell capacity. Based on increasing the bandwidth through carrier aggregation, inter-site inter-site carrier aggregation can provide a cell edge gain of 50%, even in loaded networks. Figure 2 describes how Dual Connectivity is achieved. The radio protocols of the user plane are split between the Master eNB (MeNB, typically a macro cell) and the Secondary eNB (SeNB, typically a small cell). This gives more exibility to radio bearers carrying user data. They can either use u se resources of the macro cell only (depicted in grey), of the small cell only (depicted in cyan) or aggregate both (depicted in blue), depending on whether coverage, coverage, ooad or throughput is to be favored. In addition to enhancements for the higher layer, Release 12 also improvess physical layer capabilities for small cells. The improve T he introduction of 256 QAM in the downlink enhances the spectrum eciency for terminals experiencing favorable channel conditions. Another improvement area is enhanced small cell discovery, which reduces transition time for dormant cell on/o. This enables further energy savings and reduces Cell-Specic Reference Signals (CRS) interference under varying trac load.
S1
S1
PDCP
PDCP
RLC
RLC
X2
PDCP RLC
RLC
MAC
MAC
MeNB
SeNB
Figure 2: Dual connectivity Page 5
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TDD
FDD
Figure 3. FDD/TDD aggregation ag gregation
2.2
Carrier Aggregation enhancements
The enhanced carrier aggregation ag gregation capabilities in Release 12 will enable the use of FDD/TDD carrier aggregation. Release 10 allows aggregation of either FDD or TDD carriers for intra or inter inter-band -band cases. However, Release 12 will also enable the aggregation of co-located co-locat ed FDD and TDD carriers to a single terminal, as shown in Figure 3. As part of the small cell enhancements, the aggregation will be further extend extended ed to support aggregation between sites, enabling inter-site inter -site carrier aggregation ag gregation between between macro and small cell sites. Work on RF and performance requirements requirements also supports downlink carrier aggregation with three downlink carriers, with up to 60 MHz of total spectrum being aggregated. This will support data rates of up to 450 Mbps, as illustrated in Figure 4. The use of non-backwards compatible compatible New Carrier Type (NCT) was also considered as part of the Release 12 work but it was concluded that the small gains achievable did not justify the resulting market market fragmentation.
20 MHz
150 Mbps
20 MHz
150 Mbps
20 MHz
150 Mbps
450 Mbps
Figure 4. Aggregating 3 downlink carriers with carrier ag gregation.
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2.3
Macro Cell enhancements
With exponential growth in network trac, future networks need to continue to evolve their use of macro and small cells. There are opportunities to enhance the network capacity and coverage of current LTE macro cell deployments signicantly by exploiting multi-antennas, advanced receivers, network architectures and new spectrum. Macro cell enhancements are attractive because they allow further exploitation of existing base station sites and transport infrastructure. Base stations such as Nokia Networks Flexi Multiradio 10 range can be used to build high capacity macro cells with the pot potential ential to double the spectral eciency of existing LTE macro networks. The aim is to support LTE and LTE-Advanced technologies in the 700-2600 MHz bands, achieve tight coordination with small cells, for example in the 3.5 GHz band, and combine the following features: • Large number of transmit and receive antennas: more than four transmit and receive antennas • Active Antenna Systems (AAS) where antenna and RF are built together • AAS with vertical sectorization sectorization and user specic elevation elevation beamforming/3-D beamforming/3 -D MIMO • Advanced uplink receivers receivers • Enhanced Cooperative Multipoint Transmiss Transmission ion and Reception (eCoMP) • Advanced radio network architecture including on-site resource resource pooling • High capacity capacity backhaul • Authorized Shared Access (ASA) to gain access to more IMT spectrum By increasing the number of transmit and receive antennas at the base stations from two to four and then to eight, a signicant 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 specic elevation elevat ion beamforming (using two xed beams per sector) can give signicant improvements improvements in sector capacity compared to a single beam system. Building upon vertical sectorization, Release 12 will be developing develop ing two techniques namely: a) UE-specic elevation elevation beamforming that adds adds UE specic vertical beamsteering to existing azimuth-only closed loop SU/MU MIMO methods Page 7
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UE-specific elevation UE-specific beamforming/3D-MIMO
Figure 5: UE-specic 3D-MIMO b) 3D-MIMO techniques techniques that simultaneously exploit exploit both azimuth and elevation of the multipath channel to suit each user. These techniques are expected to give signicant improvements in both the cell edge and sector capacity. The concept of 3D-MIMO is illustrated in Figure 5. Next in line for deployment are centralized solutions such as cluster level on-site resource resource pooling using high capacity and low latency ber backhaul (Centralized (Centralized RAN), where a baseband pool serves the macro site and underlay remote radio heads. Such a radio network architecture architectur e can also further improve radio performance. Following the study of centralized scheduling with non-ideal backhaul, Following work is also being done on the enhanced CoMP. This has focused on the scenario where benets were identied, namely between a macro and small cell in which the macro cell is used to coordinate the scheduler for small cells in the same coverage area. Last but not least, networks evolve by exploiting Authorized Shared Access / Licensed Shared Access, a new and complementary way of authorizing spectrum use in addition to exclusive licensed spectrum. This leads to higher spectrum availability and a predictable QoS in the shared spectrum, increasing the number of subscribers and network capacity.
2.4
Machine--Type Communications (MTC) Machine
The number of embedded machine-to-machine modems is expect expected ed to increase substantially. substantially. While a typical urban area today can have 5,000-10,000 subscribers per base station, the growth of machineto-machine trac could see up to 100,000 connected devices devices per base station, setting new requirements for the mobile network. Page 8
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In addition to the already specied MTC support in 3GPP, the following areas of optimization are expected to be covered in Release 12: • Network load optimization optimization will continue: MTC-specic MTC-specic signaling and connectivity optimization ensure that a very large number of connected devices can be supported by the LTE radio, with small amounts of data amount delivered eciently. • The low cost MTC MTC device studies are complete. Based on these, 3GPP is dening a new terminal category cost optimized for MTC. 3GPP studies show that for the RF part, signicant savings can be achieved with the terminal using only a single receive antenna antenna and half-duplexx operation. On the baseband side, signicant savings can half-duple be achieved from a single receive antenna, antenna, reduced bandwidth and a lower peak data rate. The studies indicate that combining these measures can achieve a modem cost saving of approximately 60%. Some MTC terminals are installed in the extreme coverage scenario and might have characteristics such as very low data rate and greater tolerance to delays. Release 13 solutions are expected to provide an improvement in LTE coverage equivalent to 15 dB for FDD for terminals operating delay-tolerant MTC applications. This is achieved by techniques such as further repetition, power boosting and simplication simplicatio n of control channel functions.
2.5
3GPP-WLAN 3GPPWLAN radio level interworking
3GPP has made a RAN R AN level study on ways to enhance radio level 3GPP-WLAN interworking. Current ANDSF based methods for access network selection and trac routing do not consider either RAN network conditions or factors such as WLAN load. The mere presence of a WLAN network allowed by ANDSF rules along with an accept acceptable able radio signal strength is used to divert trac from a 3GPP RAN network to a WLAN network. RAN level assistance for 3GPP-WLAN interworking is designed for occasions where typical WLAN selections cannot achieve adequate load balancing between cellular and WLAN, for instance, where legacy device behavior is not sucient. The reason for load balancing or trac steering may be due to a changing load situation in both WLAN and 3GPP radio access networks. With today’s solutions, load is not considered as part of the WLAN selection process. The intention of load balancing is to use the eNB initiative to steer terminal trac onto either the operator controlled controlled WLAN or the RAN, depending on the need. Only RAN has a comprehensive overview of its load situations and resource allocation strategies. Release 12 species a mechanism for 3GPP/WLAN access network selection and trac steering. The solution supports deployments deployments both with and without ANDSF and the co-existence of ANDSF with RAN rules when both are deployed. Page 9
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In the dened mechanism, the RAN assistance parameters are transferred via system broadcast and/or dedicated signaling. In a network without enhanced ANDSF deployment or with terminals without ANDSF support, these RAN assistance parameters parameters are used within RAN rules dened under RAN WG specications. In networks that support ANDSF and which have terminals capable of ANDSF, the RAN assistance parameters parameters are used as part of the ANDSF policies.
2.6
LTE Unl Unlicen icensed sed
A new study area emerging in 3GPP is the use of LTE for unlicensed spectrum, with the Licensed Assisted Access (LAA). Such a solution would complement LTE operation, especially in public hotspots or enterprises, enterp rises, as shown in Figure 6. This would allow the operator to benet from the local extra capacity from the unlicensed spectrum without having to use other technologies with special interworking and admission control arrangements. The solutions are not expected to be standalone but always used with aggregation to the licensed band LTE operation.
Public indoor cells
Home cells to rely on Wi-Fi (or femto)
Outd Ou tdoor oor ho hott sp spot ot Coordinated with macro/micro cells
Figure 6. LAA L AA application environment.
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2.7 Network Assisted Interfer Interference ence Cancellation and Suppression (NAICS) Co-channel interference interference is the major limitation to achieving higher capacity in cellular networks. In addition to various interference interference coordination schemes, interference aware receivers attempting to mitigate co-channel interference have shown promising performance gains compared to receivers considering co-channel interference as AWGN. In Release 11, specifying terminal performance requirements in interference rejection combining (IRC) receivers was the rst step towards increasing the role of the receiver in the system design. The rst steps have also been taken with non-linear interference cancellation receivers. Release 11 specied terminal performance requirements for Cell-Specic Reference Signals (CRS). This focused on how they mitigate interference for heterogeneous deployments where co-channel interference from CRS dominates but is negligible from data, assuming that data resource element muting is in use. Release 12 enhancements to intra-cell and inter-cell interference mitigation at the receiver side (NAICS) are achieved by increasing the degree of knowledge about interfering transmissions with possible assistance in the network. Network assistance enables the use of a more advanced receiver (including non-linear receivers) and improves performance compared to Release 11 IRC that does not require transmission assistance in the network. A specic intra-cell interference scenario part of Release 12 studies is SU-MIMO. Applying advanced receivers to mitigate interstream interference interference with SU-MIMO can be done without additional network assistance. It is enough to just dene new UE performance requirements for this scenario.
2.8
Furt urther her enhanceme enhancements nts
Self Organizing Networks (SON) will play a key role in the ecient 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 Additionally layers to a power saving mode will be essential.
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LTE is also attracting the attention of public safety organizations and authorities, as a strong candidate candidate to enhance their communications. LTE will be optimized to meet service requirements set by missioncritical group communications, including fast and ecient set-up of a low-delay communication path connecting any number of users possibly co-located, co-located, and uncompromise uncompromised d robustness, combined with the mobility of today’s 3GPP systems. Further enhancements to LTE TDD for uplink-downlink interference management and trac adaptation (eIMTA) enable dynamic uplinkdownlink reconguration reconguration according to instantaneous trac statistics while maintaining backwards compatibility. The eIMTA feature to improve TDD capabilities in Release 12 can provide signicant performance benets in a small cells environment. Furthermore, 3GPP will look for new opportunities to enhance LTEHSPA integration and LTE-WLAN interworking, as well as enabling device-to-device device-to-d evice discovery and communication for commercial and public safety use.
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3. Summary LTE development continues strongly in Release 12 and beyond by enhancing LTE and LTE-Advanced. In particular, LTE Release 12 addresses coordinated small cell deployments, macro cell enhancements,, discovery in device-to-d enhancements device-to-device evice communication, enhanced SON, exible deployment and improved interference management in HetNets. Release 12 features aim to boost performance and enter new areas and spectrum. The following two tables summarize the most promising Release 12 features:
Benets from 3GPP Release 12 – Boost Performance Rel12 Feature
Small Cell Enhancement based on Inter-site Inter-sit e CA CA
Beneft
• Optimized small cell mobility by reducing RAN to CN signaling • Improved data rates by using macro and small cells together • More exible TDD spectrum use
UE-specic elevation beamforming/ 3D-MIMO
• Signicantly enhanced macro cell capacity and coverage
Advanced receivers
• Removing interference interference to increase UL and DL capacity
Enhanced Coordinated Multi-Point (eCoMP)
• Enhance coverage by exploiting coordination in case of non-ideal backhaul
Enhanced SON
• Ecient operation of dense small cell deployments • Energy savings in small cell capacity layers
Benets from 3GPP Release 12 – Expand to New Areas and New Spectrum Rel12 Feature
Beneft
LTE-WLAN integration
• 10 Mbps minimum DL data rate rate • 1000x hot spot capacity in present decade
LTE-HSPA integration i ntegration
• Enhanced multi-technology support
Machine-Type MachineType Communication (MTC)
• Get prepared for 50 Bn connected devices or 100.000 devices per cell
Public safety
• Secure operator’s market share by expanding LTE footprint
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Nokia Networks is a leading contributor in 3GPP, driving LTE and LTE-Advanced standards. It is also shaping 5G through various activities, including participation in the EU FP7 collaborative project METIS and is contributing to ITU-R IMT vision work.
2020+
5G 2015+
2013+
2010+
LTE Advanced Evolution Rel-12 and Rel-13
LTE Advanced Rel-10 and Rel-11
LTE Rel-8 and Rel-9
Figure 7: The radio evolution in the present decade
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4.
Furt urther her reading
• Nokia Technology Vision • LTE in Unlicensed Spectrum: European Regulation and Co-existence Considerations, Nokia 3GPP presentation
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Public Nokia is a registered trademark of Nokia Corporation. Other product and company names mentioned herein may be trademarks or trade names of their respective owners. Nokia Nokia Solutions and Networks Oy P.O. Box 1 FI-02022 Finland Visiting address: Karaportti 3, ESPOO, Finland Switchboard +358 71 400 4000 Product code C401-01005 C401-01005-WP-201406-WP-201406-1-EN 1-EN © Nokia Solutions and Networks 2014
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