"No-Edge Networks" and Multi-Stream Aggregation (MSA)

The following is from Huawei press release:


The LTE-Advanced Multi-Stream Aggregation (MSA) technology standard is capable of increasing data rates at the cell's edge. A key component of Huawei's "No-Edge Networks" concept, MSA technology coordinates macro cells to improve user data rates at the cell's edge and also between heterogeneous networking scenarios to improve peak rates and simplify mobile management to ensure a consistent user experience.

With the development of mobile broadband, operators are mostly concerned about user experience. With mobile coverage, should able to enjoy the same quality of services no matter where they are. However, with mobile communication systems, the most challenging issue is system performance at the cell's edge.

The concept behind Huawei's MSA technology is that the user is always able to receive downlink data and aggregate downlink data streams from a cell or cell group with the best signal quality. A similar method applies to uplink data, where the user always transmits uplink data to a cell or cell group with the best signal quality. The uplink data streams are aggregated on the network side.

Huawei's MSA technology reduces the number of handovers, lowering device power transmission and increasing device standby time. These advantages are in accordance with the concept of delivering a "borderless network" and "green" wireless communications. It's expected that MSA technology will improve system performance at the cell's edge by almost 30%.

MSA technology is especially suitable for macro-micro HetNets. In hotspot area, macro cells provide basic LTE coverage while the micro cells provides capacity enhancement. The use of MSA technology allows users to receive controlled signaling from macro cells and services from best quality HetNet cell. Users at any location within the network can then enjoy fast and stable data services with ultra broadband, zero waiting and ubiquitous connectivity. MSA technology brings users high speeds and high quality as well as a simple service experience.

The advanced MSA technology proposed by Huawei is set to become a key feature of the evolution to 3GPP LTE-Advanced standards. Huawei has contributed 293 core standards to the 3GPP LTE/LTE-Advanced standardization process, 20% of the global total and the most of any other company.

I wasnt able to find much information but there is this couple of slides that were submitted in Rel-12 workshop that is embedded below:

Views on Rel-12 and onwards for LTE and UMTS from Zahid Ghadialy

What do you think of this feature?

New Carrier-Aggregation Proposed Bands

Carrier Aggregation (CA) the promised feature of LTE-A that will make it compatible to IMT-A is not fully exploited in Rel-10. There are only 2 bands supported for CA in Rel-10 and the same for Rel-11. The following are the bands for Rel-10

And the following for Rel-11

Unfortunately these are not enough for all the operators launching LTE/LTE-A. As a result there is currently a study on lots of other bands ongoing within 3GPP. Here is my understanding of the bands that would be needed and the region where they would be needed. Interested in knowing if there are other operators/regions where other bands need to be included.
 

LTE, LTE-A and Testing

Some months back R&S held a technical forum where there were many interesting talks and presentations. They have now uploaded video of all these presentations that can be viewed on their website (no embedding allowed).

Available to be viewed here.

Heterogeneous Networks 3G and 4G / LTE-A

There is an excellent presentation and video on Hetnets by Qualcomm that is embedded below:

Heterogeneous Networks 3G and 4G from Zahid Ghadialy

3GPP Release-12 and beyond

3GPP Recently held a workshop on "Release 12 and Onward" to identify common requirements for future 3GPP radio access technologies. The goal of the workshop is to investigate what are the main changes that could be brought forward to evolve RAN toward Release 12 and onward. It is recommended that presentations in the workshop include views on:
- Requirements
- Potential technologies
- Technology roadmap for Releases 12, 13 and after

The discussions from the workshop should be used to define the work plan for Release 12 and onward in TSG-RAN.

The list of presentations and links, etc. are below and I have also embedded the Summary and Draft report, both of which can be downloaded from 3GPP website or slideshare. Here is a list of different topics and the presentations that covered them:

AdHoc Networks
AdHoc Networks - RWS-120035


Antennas, Beamforming, Transmitters, Receivers
3D-beamforming - RWS-120002
Vertical sectorization/3D beamforming via AAS - RWS-120005
Advanced receivers and joint Tx/Rx optimisation - RWS-120005
Network assistance for IC receivers - RWS-120005
Support of Active Antenna Systems - RWS-120006
Advanced transmitter beamforming - RWS-120010
Advanced receiver cancellation - RWS-120010
Vertical and 3D beamforming - RWS-120011
MIMO Enhancements - RWS-120014
New antenna configurations and 3D MIMO - RWS-120014
UE AAS (Active Antenna System) [Detailed] - RWS-120015 / RWS-120049
Cloud of Antennas (CoA) Concept - RWS-120016
Support of Massive MIMO Technology - RWS-120016
Full Dimension MIMO (FD-MIMO) System [Detailed] - RWS-120021 / RWS-120046
Cloud-RAN: Benefits and Drawbacks - RWS-120021 / RWS-120046
Further Enhanced Receivers - RWS-120022
Multiple antenna evolution - RWS-120025
3D beamforming - RWS-120026
Vision of 3D MIMO - RWS-120029
Massive MIMO & 3D MIMO - RWS-120034
Potential MIMO Enhancements - RWS-120035
Advanced Antenna Technology - RWS-120035
DL MIMO Enhancement - RWS-120037
Performance Requirement for 8Rx at eNB - RWS-120037
UE Receiver Enhancements - RWS-120039
DL MU-MIMO Enhancement - RWS-120039
Enhancement of MIMO, CoMP - RWS-120040
Advanced MIMO - RWS-120040
MIMO and COMP - RWS-120041
Role of Advanced Receivers - RWS-120041
Advanced Interference Handling - RWS-120041
Interference Suppression Subframes (ISS) and IRC Receiver [Detailed] - RWS-120051


Applications (Apps)
Efficiency for diverse small data applications - RWS-120011
Device Service/Application Awareness - RWS-120018
I-Net:”I”-centric mobile network design philosophy - RWS-120024
Application Aware Comm - RWS-120036 / RWS-120050


Backhaul and Relay
Relay backhaul enhancement - RWS-120011
LTE Backhaul - RWS-120013
Relay - RWS-120025
CoMP, backhaul and X2 interface - RWS-120027 / RWS-120048
Mobile Relay And Relay Backhaul Enhancement - RWS-120029


Baseband
Baseband resource pooling and virtualization - RWS-120011


Capacity and Coverage
Higher system capacity - RWS-120010
Capacity for Mobile Broadband: Requirements and Candidate technologies - RWS-120012
Increase N/W capacity by 1000 times - RWS-120020
Coverage Enhancement - RWS-120037
Capacity Enhancement - RWS-120038 / RWS-120047
Cell-edge Throughput Improvement - RWS-120038 / RWS-120047


Carrier Aggregation, Flexible Bandwidths and Multiflow
LTE multiflow / Inter-site CA - RWS-120002
LTE/HSDPA Carrier Aggregation - RWS-120002
Multiflow Enhancements - RWS-120002
Multi-Stream Aggregation - RWS-120006
Provide mechanisms for Flexible Bandwidth Exploitation - RWS-120008
Carrier aggregation enhancement - RWS-120019
Inter-eNB Carrier Aggregation - RWS-120021 / RWS-120046
Evolution of Carrier Aggregation - RWS-120036 / RWS-120050
CA of Alternative Spectra - RWS-120042


Cells, Carriers, C/U Planes
C/U plane split & Phantom cell - RWS-120010
Phantom cell by single/separate nodes - RWS-120010
Phantom cell: Other topics - RWS-120010
New Carrier Type for Primary Component Carrier - RWS-120011
Flexible/Reconfigurable Cells - RWS-120023
New carrier-type (NCT) enhancements - RWS-120026
Amorphous cells - RWS-120034
New Carrier Types - RWS-120035
Non-Orthogonal Access - RWS-120039
Dynamic Area Construction for UE - RWS-120040


Cognitive Radio
Cognitive radio - RWS-120034
Cognitive Networking - RWS-120036 / RWS-120050


Coordinated MultiPoint (CoMP)
CoMP Enhancements - RWS-120014
CoMP/ICIC enhancement - RWS-120019
CoMP Enhancements - RWS-120023
CoMP enhancements - RWS-120026
CoMP Technologies - RWS-120027 / RWS-120048
Enhanced CoMP - RWS-120029
Potential CoMP Enhancements - RWS-120035
CoMP - RWS-120037
CoMP Enhancement for Indoor Environment - RWS-120040
Overhauling DL CoMP - RWS-120042


Device, Handsets, UE's
Additional UE Enhancements - RWS-120018
Coordination : Multi-mode UE - RWS-120024


D2D / Device-to-Device
Device-to-Device - RWS-120003
LTE Device to Device - Proximity Based Services - RWS-120004
LTE device to device - RWS-120007
LTE direct communication - RWS-120007
Device-to-Device Communications - RWS-120014
D2D Discovery/Communication - RWS-120016
3GPP Proximity Services (ProSe) / D2D - RWS-120022
Device-to-Device communications - RWS-120026
Device-to-Device communication - RWS-120036 / RWS-120050


Data Rates and Throughputs
Higher data rate and user-experienced throughput - RWS-120010
Fairness of user throughput - RWS-120010


Deployments
LTE in Local Area Deployments & Enhancements - RWS-120004
Energy Efficient Local Area Deployments - RWS-120004
Scaling for Mass Deployment - RWS-120008
Flexible and cost-efficient NW deployments - RWS-120010
Considerations on dense NW deployment - RWS-120019


Energy Consumption, Efficiency and Savings
Energy efficiency - RWS-120005
Reduce energy consumption - RWS-120008
Energy Saving - RWS-120014
UE Power Saving - RWS-120036 / RWS-120050
NB Power Saving - RWS-120036 / RWS-120050
Energy Saving Enhancements with CoMP - RWS-120040
Energy Saving with Centralized eNB - RWS-120040


Herogeneous Networks (HetNets)
Optimisation of Het Nets performance - RWS-120005
Improved Support for Heterogeneous Networks - RWS-120006
Network hyper-densification: LTE HetNet2.0 - RWS-120007
Multi-layer HetNet Deployments - RWS-120016
HetNet for HSPA - RWS-120017
HetNet Enhancements - RWS-120023
HetNet Mobility - RWS-120029
Small cells & HetNet - RWS-120031
HetNet - RWS-120037
HetNet Enhancements for HeNB - RWS-120040


HSDPA / HSUPA / HSPA+ Enhancements
HSPA UL Enhancements - RWS-120003
Uplink Enhancements - RWS-120006
UMTS evolution: enhancing CS voice on DCH - RWS-120007
High Speed Packet Access - RWS-120012
HSPA RRM enhancement - RWS-120024
HSPA+ further evolution - RWS-120034


Interworking (HSPA, LTE)
Coordination : HSPA/LTE e-interworking - RWS-120024
Inter-RAT Coordination/CA - RWS-120037


Local-Area Access (Small Cells)
Local-Area Access - RWS-120003
LTE in Local Area Deployments & Enhancements - RWS-120004
LTE Local Area Enhancements - RWS-120004
LTE Local Area Enhancement Areas - RWS-120004
enhanced Local Area (eLA) - RWS-120010
Local Area Enhancements - RWS-120022
Improved Local Area Mobility - RWS-120022


LTE
LTE for Nomadic and Fixed Use - RWS-120018
E-PDCCH enhancement - RWS-120019
Efficiency : Paging Optimization - RWS-120024


LTE Hotspot and Indoor Enhancements (LTE-Hi)
Hotspot and Indoor Enhancements (LTE-Hi) - RWS-120006
Hotspot/indoor Scenario (LTE-Hi) - RWS-120025
Indoor & Hotspot Enhancements (LTE-Hi) [Detailed] - RWS-120029
Possible Study Items for Indoor Environment - RWS-120040


M2M / Machine Type Communications (MTC)
Machine Type Communications - RWS-120003
Improved Support for MTC - RWS-120006
Machine-to-Machine: The Internet of Things - RWS-120014
Machine Type Communications: a new ecosystem - RWS-120014
Wireless MTC and RAN optimizations for MTC - RWS-120016
Low-Cost MTC UE - RWS-120017
MTC + eDDA (enhanced Diverse data application) - RWS-120019
Further Enhancements to Support MTC - RWS-120023
MTC - RWS-120025
MTC enhancements - RWS-120026
M2M - RWS-120029
MTC and migration of traffic from 2G - RWS-120031
Machine Type Communications enhancements - RWS-120034
Machine Type Communications - RWS-120035
Extension triggered by growing M2M traffic - RWS-120038 / RWS-120047
LTE-based M2M - RWS-120041


MBMS / eMBMS
eMBMS Enhancements - RWS-120007
eMBMS - RWS-120013
UHD Multimedia Broadcast/Multicast Service - RWS-120036 / RWS-120050


Mesh Networks
Mesh Networks - RWS-120018


Network Density
Network density: Scenarios - RWS-120010


Network Architecture and Operation
Easier network operation, tolerance to failure - RWS-120005
System Architecture - RWS-120032
Evolution of LTE Networks - RWS-120034


Positioning
Positioning Enhancements - RWS-120006


Public Safety
Public Safety - RWS-120030
Operation of Public Safety System via LTE - RWS-120031
Public safety’s future in LTE [Detailed] - RWS-120033


Self Organising Networks (SON) and Minimisation of Drive Testing (MDT)
SON Evolution - RWS-120002
Enhanced MDT - RWS-120011
Network Self-Optimisation - RWS-120014
SON and MDT - RWS-120017
HetNet SON - RWS-120029
MDT & Energy Saving - RWS-120029
Autonomous Interference Coordination - RWS-120029
Large scale multi-layer centralized cooperative radio - RWS-120034
MDT Enhancement - RWS-120036 / RWS-120050
SON Enhancements - RWS-120036 / RWS-120050
MDT and eDDA - RWS-120041


Small Cells (HNB/HeNB)
UMTS evolution: small cells - RWS-120007
Wide & Local area enhancements - RWS-120010
Small Cells - RWS-120014
Small Cell Enhancement in Rel-12 - RWS-120021 / RWS-120046
HeNB Enhancement - RWS-120036 / RWS-120050
Efficient Usage of Macro and Small Cells - RWS-120038 / RWS-120047
Low-cost Low Power Nodes (LC-LPN) - RWS-120038 / RWS-120047
Small-Cell Improvements: System Aspects - RWS-120041


Spectrum
Enhanced spectrum efficiency - RWS-120005
Spectrum efficiency: eLA topics - RWS-120010
Scenarios for spectrum extension - RWS-120010
Spectrum and spectrum usage - RWS-120012
Wider Spectrum Utilization - RWS-120016
Spectral efficiency for LTE - RWS-120017
New Spectrum for Mobile Broadband Access - RWS-120021 / RWS-120046
Enabling Technologies for New Spectrum - RWS-120021 / RWS-120046
Radio Propagation - RWS-120021 / RWS-120046
Opportunistic Use of Unlicensed Spectrum for D2D Local Traffic - RWS-120023
Flexible Spectrum Utilization - RWS-120024
Spectrum Related: New Bands And CA Band Combinations - RWS-120029
Spectrum - RWS-120032
Hybrid access scheme - RWS-120034
Spectrum - RWS-120035
Spectrum and Transmission Efficiency - RWS-120039
Spectrum-Agile LTE - RWS-120041


TDD / TD-LTE
TD-LTE - RWS-120014
TDD-specific aspects - RWS-120014
TDD adaptive reconfiguration - RWS-120034
Efficient Usage of Dual Duplex Modes - RWS-120038 / RWS-120047
LTE TDD Small-Cell versus WiFi - RWS-120041


Testing
Testing and Certification - RWS-120022


Traffic and Signalling Overhead
Efficient support of diverse traffic characteristics - RWS-120005
Efficient support for variety of traffic types - RWS-120010
Enhancements for variety of traffic types - RWS-120010
Very high traffic (and signalling) scenarios - RWS-120017
Control Plane Overhead Reduction - RWS-120021 / RWS-120046
Further Enhancements to Support Diverse Data Applications - RWS-120023
Efficiency : Small data services in high mobility - RWS-120024


User Experience
Improve User experience - RWS-120009
User Challenges - RWS-120032


Video streaming, call
RAN Enhancements for Video Streaming QoE - RWS-120023
RAN Enhancements for Internet Video Call - RWS-120023


WiFi / WLAN
Cooperation between LTE/HSPA and WiFi - RWS-120005
Unlicensed spectrum: LTE & WLAN - RWS-120007
LTE integration with other RATs - RWS-120014
WiFi integration: For Beyond Rel-12 - RWS-120017
LTE-WLAN Interworking - RWS-120023
Coordination With WiFi - RWS-120029
Smarter opportunistic usage of Wi-Fi - RWS-120031
LTE TDD Small-Cell versus WiFi - RWS-120041


Others
Other identified techniques for LTE - RWS-120005
Efficient Transactions - RWS-120035
Link Enhancement Considerations - RWS-120035
Intra-RAT cooperation / Inter-RAT cooperation - RWS-120036 / RWS-120050

Here is the summary from the workshop:

Summary of 3GPP TSG-RAN Workshop on Release 12 and Onward

View more PowerPoint from Zahid Ghadialy

Complete list of Presentations

RWS-120002	Release 12 and beyond for C^4 (Cost, Coverage, Coordination with small cells and Capacity)	NSN
RWS-120003	Views on Rel-12	Ericsson & ST-Ericsson
RWS-120004	LTE evolving towards Local Area in Release 12 and beyond	Nokia Corporation
RWS-120005	Views on Release 12	Orange
RWS-120006	Views on Rel-12 and onwards for LTE and UMTS	Huawei Technologies, HiSilicon
RWS-120007	3GPP RAN Rel-12 & Beyond	Qualcomm
RWS-120008	New Solutions for New Mobile Broadband Scenarios	Telefonica
RWS-120009	Telecom Italia requirements on 3GPP evolution	Telecom Italia
RWS-120010	Requirements, Candidate Solutions & Technology Roadmap for LTE Rel-12 Onward	NTT DOCOMO, INC.
RWS-120011	Where to improve Rel-12 and beyond: Promising technologies	NEC
RWS-120012	Deutsche Telekom Requirements and Candidate Technologies	Deutsche Telekom
RWS-120013	Release 12 Prioritization Concepts	Dish Networks
RWS-120014	Towards LTE RAN Evolution	Alcatel-Lucent
RWS-120015	UE AAS (Active Antenna System)	Magnolia Broadband
RWS-120016	Requirements and Technical Considerations for RAN Rel.12 & Onwards	Fujitsu Limited
RWS-120017	Operator requirements on future RAN functionality	TeliaSonera
RWS-120018	AT&T View of Release 12 in the North America Marketplace	AT&T
RWS-120019	Major drivers, requirements and technology proposals for LTE Rel-12 Onward	Panasonic
RWS-120020	Efficient spectrum resource usage for next-generation N/W	SK Telecom
RWS-120021	Technologies for Rel-12 and onwards	Samsung Electronics
RWS-120022	LTE Rel-12 and Beyond	Renesas Mobile Europe
RWS-120023	LTE Rel-12 and Beyond: Requirements and Technology Components	Intel
RWS-120024	Considerations on further enhancement and evolution of UMTS/LTE network in R12 and onwards	China Unicom
RWS-120025	Views on LTE R12 and Beyond	CATT
RWS-120026	A proposal for potential technologies for Release 12 and onwards	ETRI
RWS-120027	A view on requirements on Rel-12 and onwards from an operator’s viewpoint	Softbank Mobile
RWS-120028	India market Requirements for Rel. 12 and beyond	CEWiT
RWS-120029	Views on LTE Rel-12 & Beyond	CMCC
RWS-120030	LTE addressing the needs of the Public Safety Community	IPWireless
RWS-120031	Vodafone view on 3GPP RAN Release 12 and beyond	Vodafone
RWS-120032	An Operator’s View of Release 12 and Beyond	Sprint
RWS-120033	Public Safety Requirements for Long Term Evolution REL-12	U.S. Department of Commerce
RWS-120034	Views on 3GPP Rel-12 and Beyond	ZTE
RWS-120035	Considerations for LTE Rel-12 and beyond	Motorola Mobility
RWS-120036	LG’s view on evolution of LTE in Release 12 and beyond	LG Electronics
RWS-120037	Views on REL-12 and Onwards	China Telecom
RWS-120038	KDDI’s Views on LTE Release 12 onwards	KDDI
RWS-120039	Evolving RAN Towards Rel-12 and Beyond	SHARP
RWS-120040	Views on enhancement of system capacity and energy efficiency toward Release12 and onward	Hitachi
RWS-120041	Beyond LTE-A: MediaTek’s view on R12	MediaTek
RWS-120042	Potential Technologies and Road Map for LTE Release 12 and Beyond	ITRI, HTC
RWS-120043	New concept to maximize the benefit of interference rejection at the UE receiver: interference suppression subframes (ISS)	Broadcom
RWS-120046	Technologies for Rel-12 and onwards	Samsung Electronics
RWS-120047	KDDI’s Views on LTE Release 12 onwards	KDDI
RWS-120048	A view on Rel-12 and onwards from an operator’s viewpoint	Softbank Mobile
RWS-120049	UE AAS (Active Antenna System)	Magnolia Broadband
RWS-120050	LG’s view on evolution of LTE in Release 12 and beyond	LG Electronics
RWS-120051	New concept to maximize the benefit of interference rejection at the UE receiver: interference suppression subframes (ISS)	Broadcom

More technically minded people want to explore the 3GPP website for the workshop links here: http://3gpp.org/ftp/workshop/2012-06-11_12_RAN_REL12/

Draft report that gives more insight into the presentations as follows:

Draft Report of 3GPP RAN Workshop on Release 12 and onwards

View more documents from Zahid Ghadialy

Enhanced Uplink SC-FDMA: PUSCH+PUCCH Simultaneous Transmission

LTE 'Antenna Ports' and their Physical mapping

People who work with LTE Physical layer and maybe higher layers would be aware of this term called 'Antenna Ports'. I have always wondered how these antenna ports are mapped to physical antennas.

The following is from R&S whitepaper:

The 3GPP TS 36.211 LTE standard defines antenna ports for the downlink. An antenna port is generally used as a generic term for signal transmission under identical channel conditions. For each LTE operating mode in the downlink direction for which an independent channel is assumed (e.g. SISO vs. MIMO), a separate logical antenna port is defined. LTE symbols that are transmitted via identical antenna ports are subject to the same channel conditions. In order to determine the characteristic channel for an antenna port, a UE must carry out a separate channel estimation for each antenna port. Separate reference signals (pilot signals) that are suitable for estimating the respective channel are defined in the LTE standard for each antenna port. 

Here is my table that I have adapted from the whitepaper and expanded. 

The way in which these logical antenna ports are assigned to the physical transmit antennas of a base station is up to the base station, and can vary between base stations of the same type (because of different operating conditions) and also between base stations from different manufacturers. The base station does not explicitly notify the UE of the mapping that has been carried out, rather the UE must take this into account automatically during demodulation (FIG 2).

If there is another way to show this physical mappings, please feel free to let me know.

The R&S Whitepaper is available here if interested.

10 Times Beyond LTE-A (5G maybe?)

Recently when I added a presentation by NSN on whats coming after IMT-Advanced, it was very well received and has already had over 8000 views. There seems to be definitely an appetite for the future networks. Here is another such presentation.

10 Times Beyond LTE-A

View more presentations from Zahid Ghadialy

There is also a video of the presentation if you have the patience to sit, watch and learn.

RAN Release 11 Priorities

New Spectrum for LTE-Advanced Carrier Aggregation

Radio relay technologies in LTE-Advanced

The following is from NTT Docomo Technical journal: 

Three types of radio relay technologies and their respective advantages and disadvantages are shown in Figure 1. 

A layer 1 relay consists of relay technology called a booster or repeater. This is an Amplifier and Forward (AF) type of relay  technology by which Radio Frequency (RF) signals received on the downlink from the base station are amplified and transmitted to the mobile station. In a similar manner, RF signals received on the uplink from the mobile station are amplified and transmitted to the base station. The equipment functions of a layer 1 relay are relatively simple, which makes for low-cost implementation and short processing delays associated with relaying. With these  features, the layer 1 relay has already found widespread use in 2G and 3G mobile communication systems. It is being deployed with the aim of improving coverage in mountainous regions, sparsely populated areas and urban areas as well as in indoor environments.


The RF performance specifications for repeaters have already been specified in LTE, and deployment of these repeaters for the same purpose is expected. The layer 1 relay, however, amplifies intercell interference and noise together with desired signal components thereby deteriorating the received Signal to Interference plus Noise power Ratio (SINR) and reducing the throughput enhancement gain.


The layer 2 relay, meanwhile, is a Decode and Forward (DF) type of relay technology by which RF signals received on the downlink from the base station are demodulated and decoded and then encoded and modulated again before being sent on to the mobile station. This demodulation and decoding processing performed at the radio relay station overcomes the drawback in layer 1 relays of deteriorated received SINR caused by amplification of intercell interference and noise. A better throughput-enhancement effect can therefore be expected compared with the layer 1 relay. At the same time, the layer 2 relay causes a delay associated with modulation/demodulation and encoding/decoding processing. In this type of relay, moreover, radio functions other than modulation/demodulation and encoding/decoding (such as mobility control, retransmission control by Automatic Repeat request (ARQ), and user-data concatenation/segmentation/reassembly) are performed between the base station and mobile station transparently with respect to the radio relay, which means that new radio-control functions for supporting this relay technology are needed. 

The layer 3 relay also performs demodulation and decoding of RF signals received on the downlink from the base station, but then goes on to perform processing (such as ciphering and user-data concatenation/segmentation/reassembly) for retransmitting user data on a radio interface and finally performs encoding/modulation and transmission to the mobile station. Similar to the layer 2 relay, the layer 3 relay can improve throughput by eliminating inter-cell interference and noise, and additionally, by incorporating the same functions as a base station, it can have small impact on the standard specifications for radio relay technology and on implementation. Its drawback, however, is the delay caused by user-data processing in addition to the delay caused by modulation/demodulation and encoding/decoding processing.


In 3GPP, it has been agreed to standardize specifications for layer 3 relay technology in LTE Rel. 10 because of the above features of improved received SINR due to noise elimination, ease of coordinating standard specifications, and ease of implementing the technology. Standardization of this technology is now moving forward.


Layer 3 radio relay technology is shown in Figure 2. In addition to performing user-data regeneration processing and modulation/demodulation and encoding/ decoding processing as described above, the layer 3 relay station also features a unique Physical Cell ID (PCI) on the physical layer different than that of the base station. In this way, a mobile station can recognize that a cell provided by a relay station differs from a cell provided by a base station.


In addition, as physical layer control signals such as Channel Quality Indicator (CQI) and Hybrid ARQ (HARQ) can terminate at a relay station, a relay station is recognized as a base station from the viewpoint of a mobile station. It is therefore possible for a mobile station having only LTE functions (for example, a mobile station conforming to LTE Rel. 8 specifications) to connect to a relay station. Here, the wireless backhaul link (Un) between the base station and relay station and the radio access link (Uu) between the relay station and mobile station may operate on different frequencies or on the same frequency. In the latter case, if transmit and receive processing are performed simultaneously at the relay station, transmit signals will cause interference with the relay station’s receiver by coupling as long as sufficient isolation is not provided between the transmit and receive circuits. Thus, when operating on the same frequency, the wireless backhaul-link and radio-access-link radio resources should be subjected to Time Division Multiplexing (TDM) so that transmission and reception in the relay station are not performed simultaneously.

Scenarios in which the introduction of relay technology is potentially useful have been discussed in 3GPP. Deployment scenarios are shown in Table 1. Extending the coverage area to mountainous and sparsely populated regions (rural area and wireless backhaul scenarios) is an important scenario to operators. It is expected that relay technology can be used to economically extend coverage to such areas as opposed to deploying fixed-line backhaul links. Relay technology should also be effective for providing temporary coverage when earthquakes or other disasters strike or when major events are being held (emergency or temporary coverage scenario), i.e., for situations in which the deployment of dedicated fixed-line backhaul links is difficult. In addition, while pico base stations and femtocells can be used for urban hot spot, dead spot, and indoor hot spot scenarios, the installation of utility poles, laying of cables inside buildings, etc. can be difficult in some countries and regions, which means that the application of relay technology can also be effective for urban scenarios. Finally, the group mobility scenario in which relay stations are installed on vehicles like trains and buses to reduce the volume of control signals from moving mobile stations is also being proposed.


In 3GPP, it has been agreed to standardize the relay technology deployed for coverage extension in LTE Rel. 10. These specifications will, in particular, support one-hop relay technology in which the position of the relay station is fixed and the radio access link between the base station and mobile station is relayed by one relay station.



References
[1] 3GPP TS36.912 V9.1.0: “Feasibility study for Further Advancement for E-UTRA (LTE-Advanced),” 2010.
[2] 3GPP TS36.323 V9.0.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification,” 2009
[3] 3GPP TS36.322 V9.1.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control (RLC) protocol specification,” 2010.
[4] 3GPP TS36.321 V9.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification,” 2010.
[5] 3GPP TS36.331 V9.2.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification,” 2010.
[6] 3GPP TS36.413 V9.2.1: “Evolved Universal Terrestrial Radio Access (E-UTRA); S1 Application Protocol (S1AP),” 2010.
[7] 3GPP TR36.806 V9.0.0: “Evolved Universal Terrestrial Radio Access (E-UTRA); Relay architectures for E-UTRA (LTEAdvanced),” 2010.
[8] IETF RFC4960: “Stream Control Transmission Protocol,” 2007.
[9] 3GPP TS29.281 V9.2.0: “General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U),” 2010.

DOCOMO Euro-Labs: LTE/LTE-A Interference Coordination for Femtocells

LTE/LTE‐A Interference Coordination for Femtocells

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