RAN mechanisms to avoid CN overload due to MTC

Machine-to-Machine (M2M) is the future and Machine-type communications (MTC) will be very important once we have billions of connected devices. I have talked in the past about the 50 Billion connected devices by 2050 and the Internet of Things.

One of the challenges of today's networks is to handle this additional signalling traffic due to MTC. One of the very important topics being discussed in 3GPP RAN meetings is 'RAN mechanisms to avoid CN overload due to MTC'. Even though it has not been finalised, its interesting to see the direction in which things are moving.

The above figure from R2-106188 shows that an extended wait time could be added in the RRC Connection Reject/Release message in case if the eNodeB is overloaded. The device can reattempt the connection once the wait time has expired.

In R2-110462, another approach is shown where Core Network (CN) is overloaded. Here a NAS Request message is sent with delay tolerant indicator a.k.a. low priority indicator. If the CN is overloaded then it can reject the request with a backoff timer. Another approach would be to send this info to the eNodeB that can do a RRC Connection Reject when new connection request is received.

All Documents from 3GPP RAN2 #72-bis are available here. Search for NIMTC for M2M related and overload related docs.

SI on Signalling and procedure for interference avoidance for in-device coexistence

In order to allow users to access various networks and services ubiquitously, an increasing number of UEs are equipped with multiple radio transceivers. For example, a UE may be equipped with LTE, WiFi, and Bluetooth transceivers, and GNSS receivers. One resulting challenge lies in trying to avoid coexistence interference between those collocated radio transceivers. Figure 4-1 below shows an example of coexistence interference.

3GPP initiated a Study Item (SI) in Release-10 timeframe to investigate the effects of the interference due to multiple radios and signalling. This study is detailed in 3GPP TR 36.816 (see link at the end).

Due to extreme proximity of multiple radio transceivers within the same UE, the transmit power of one transmitter may be much higher than the received power level of another receiver. By means of filter technologies and sufficient frequency separation, the transmit signal may not result in significant interference. But for some coexistence scenarios, e.g. different radio technologies within the same UE operating on adjacent frequencies, current state-of-the-art filter technology might not provide sufficient rejection. Therefore, solving the interference problem by single generic RF design may not always be possible and alternative methods needs to be considered. An illustration of such kind of problem is shown in Figure 4-2 above.

The following scenarios were studied:

- LTE coexisting with WiFi

- LTE coexisting with Bluetooth

- LTE Coexisting with GNSS

Based on the analysis in SI, some examples of the problematic coexistence scenarios that need to be further studied are as follows:

- Case 1: LTE Band 40 radio Tx causing interference to ISM radio Rx;

- Case 2: ISM radio Tx causing interference to LTE Band 40 radio Rx;

- Case 3: LTE Band 7 radio Tx causing interference to ISM radio Rx;

- Case 4: LTE Band 7/13/14 radio Tx causing interference to GNSS radio Rx.

In order to facilitate the study, it is also important to identify the usage scenarios that need to be considered. This is because different usage scenarios will lead to different assumption on behaviours of LTE and other technologies radio, which in turn impact on the potential solutions. The following scenarios will be considered:

1a) LTE + BT earphone (VoIP service)

1b) LTE + BT earphone (Multimedia service)

2) LTE + WiFi portable router

3) LTE + WiFi offload

4) LTE + GNSS Receiver

The SI also proposes some ways of reducing the interference and is work in progress at the moment.

Reference: 3GPP TR 36.816 : Study on signalling and procedure for interference avoidance for in-device coexistence; (Release 10).

LTE-Advanced (Rel-10) UE Categories

I blogged about the 1200Mbps of DL with LTE Advanced earlier and quite a few people asked me about the bandwidth, etc. I found another UE categories table in Agilent lterature on LTE-Advanced here.

The existing UE categories 1-5 for Release 8 and Release 9 are shown in Table 4. In order to accommodate LTE-Advanced capabilities, three new UE categories 6-8 have been defined.

Note that category 8 exceeds the requirements of IMT-Advanced by a considerable

margin.

Given the many possible combinations of layers and carrier aggregation, many configurations could be used to meet the data rates in Table 4. Tables 5 and 6 define the most probable cases for which performance requirements will be developed.

eICIC: Enhanced inter-cell interference coordination in 3GPP Release-10

Inter-cell interference coordination (ICIC) was introduced in Release-8/9 of the 3GPP LTE standards. The basic idea of ICIC is keeping the inter-cell interferences under control by radio resource management (RRM) methods. ICIC is inherently a multi-cell RRM function that needs to take into account information (e.g. the resource usage status and traffic load situation) from multiple cells.

Broadly speaking, the main target of any ICIC strategy is to determine the resources (bandwidth and power) available at each cell at any time. Then (and typically), an autonomous scheduler assigns those resources to users. Thus, from the Radio Resource Control perspective, there are two kind of decisions: (a) which resources will be allocated to each cell? and, (b) which resources will be allocated to each user?. Clearly, the temporality of such decisions is quite different. Whereas resources to users allocation is in the order of milliseconds, the allocation of resources to cells take much longer periods of time or can be fixed.

Static ICIC schemes are attractive for operators since the complexity of their deployment is very low and there is not need for new extra signaling out of the standard. Static ICIC mostly relies on the fractional reuse concept. This means that users are categorized according to their Signal-to-Noise-plus-Interference Ratio (SINR), that means basically according to their inter-cell interference, and different reuse factors are applied to them, being higher at regions with more interference, mostly outer regions of the cells. The total system bandwidth is divided into sub-bands which are used by the scheduler accordingly.

A simple way to explain ICIC is based on picture above. The users are divided into two categories, one is Cell Center User (CCU), and the other one is Cell Edge User (CEU). CCUs are the users distributed in the gray region of above figure, and CEUs are the users distributed in the above red, green and blue areas. CCU can use all the frequencypoints to communicate with the base station, while CEU must use corresponding specified frequency points to ensure orthogonality between different cells.

CEUs can be assigned a higher transmissionpower for the frequency reuse factor is greater than 1. The frequency points are not overlapped at the edges so the adjacent cell interference is small. CCU’s frequency reuse factor is 1; for the path loss is small and transmission power is low. Therefore the interference to the adjacent cells is not high either.

Dominant interference condition has been shown when Non-CSG/CSG users are in close proximity of Femto, in this case, Rel8/9 ICIC techniques are not fully effective in mitigating control channel interference, and hence, Enhanced interference management is needed At least the following issues should be addressed by any proposed solutions:

o Radio link monitoring (RLM)

o Radio Resource Management (including detection of PSS/SSS and PBCH)

o Interference from CRS

oo To PCFICH/PHICH/PDCCH

oo To PDSCH

o CSI measurement

o Interference from PDCCH masked with P-RNTI and SI-RNTI (for SIB-1 only) and associated PCFICH

As a result, from Release-10 onwards eICIC work was started. In Rel-10, two eICIC or Enhanced inter-cell interference coordination (also incorrectly referred to as Enhanced Inter-Cell Interference Cancellation) were being actively discussed. They are Time domain eICIC and autonomous HeNB power setting. More advanced ideas are being thought of beyong Rel-10 including Interference management techniques on carrier resolution ( optimally exploiting available Networks frequency assets (carriers in same or different bands) , combination with Carrier Aggregation; interference management schemes proposed both during LTE-Advanced Study Item phase, and during Rel-10 HetNet eICIC work.

From an earlier presentation in SON Conference:

eICIC:

- Effectively extends ICIC to DL control - time domain

- Requires synchronization at least between macro eNB and low power eNBs in its footprint

- No negative impact on legacy Rel 8 Use

Range Extension(RE)

- Refers to UE ability to connect and stay connected to a cell with low SINR

- Achieved with advanced UE receivers - DL interference cancellation (IC)

RE + eICIC technique:

– Eliminates coverage holes created by closed HeNBs

– Improves load balancing potential for macro network with low power eNBs and leads to significant network throughput increase

–Enables more UEs can be served by low power eNBs, which can lead to substantially higher network throughput

More details on eICIC is available in 3GPP CR's and TR's listed below:

• R1-105081: Summary of the description of candidate eICIC solutions, 3GPP TSG-WG1 #62, Madrid, Spain, August 23rd – 27th, 2010.
• R1-104942: Views on eICIC Schemes for Rel-10, 3GPP TSG RAN WG1 Meeting #62, Madrid, Spain, 23-27 August, 2010.
• R1-104238: eICIC Chairman’s note, 3GPP TSG RAN WG1 Meeting #61bis, Dresden, Germany, 28th June – 2nd July 2010.
• R1-103822: Enhanced ICIC considerations for HetNet scenarios, 3GPP TSG RAN WG1 #61bis Meeting, Dresden, Germany, June 28 – July 2, 2010.

You can also check out NTT Docomo's presentation on LTE Enhancements and Future Radio Access here.

An Intellectual Property Rights Primer

Page 5-8 is a very good starting point to understand the IPR issues surrounding LTE.

The Essentials of Intellectual Property - Sep 2010

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An accompanying video and download information is available on Ericsson's website here.

What are Heterogeneous Networks (HetNets)?

HetNets are hot. I hear about them in various contexts. Its difficult to find exactly what they are and how they will work though. There is a HetNets special issue in IEEE Communications Magazine coming out next year but that's far away.

I found an interesting summary on HetNets in Motorola Ezine that is reproduced below:

“The bigger the cell site, the less capacity per person you have,” said Peter Jarich, research director with market intelligence firm Current Analysis. “If you shrink coverage to a couple of blocks, you are having that capacity shared with a fewer number of people, resulting in higher capacity and faster data speeds.”

This is a topic the international standards body, the Third Generation Partnership Project (3GPP), has been focusing on to make small cells part of the overall cellular network architecture.

“What we’re seeing is a natural progression of how the industry is going to be addressing some of these capacity concerns,” said Joe Pedziwiatr, network systems architect with Motorola. “There is a need to address the next step of capacity and coverage by introducing and embracing the concepts of small cells and even looking at further advances such as better use of the spectrum itself.”

As such, discussion regarding this small-cell concept has emerged into what is called heterogeneous networks, or Het-Net, for short. The idea is to have a macro wireless network cooperating with intelligent pico cells deployed by operators to work together within the macro network and significantly improve coverage and augment overall network capacity. Small cells can also be leveraged to improve coverage and deliver capacity inside buildings. Indoor coverage has long been the bane of mobile operators. Some mobile operators are already leveraging this concept, augmenting their cellular service offering with WiFi access to their subscriber base in order to address the in-building coverage and capacity challenges facing today’s cellular solutions.

Pedziwiatr said this Het-Net structure goes far beyond what is envisioned for femtocells or standard pico cells for that matter. Introducing a pico cell into the macro network will address but just one aspect of network congestion, namely air interface congestion. The backhaul transport network may become the next bottleneck. Finally, if all this traffic hits the core network, the congestion will just have shifted from the edge to the core.

“This requires a system focus across all aspects of planning and engineering,” Pedziwiatr said. “We’re trying to say it goes beyond that of a femto. If someone shows up at an operator and presents a pico cell, that is just one percent of what would be needed to provide true capacity relief for the macro network.”

Femtocells, otherwise known as miniature take-home base stations, are obtained by end users and plugged into a home or office broadband connection to boost network signals inside buildings. A handful of 3G operators worldwide are selling femtocells as a network coverage play. For the LTE market, the Femtocell Forum is working to convince operators of the value of a femtocell when it comes to better signal penetration inside buildings and delivering high-bandwidth services without loading the mobile network. This is possible, because the backhaul traffic runs over the fixed line connection. However, this femtocell proposition largely relies on end user uptake of them—not necessarily where operators need them, unless they install femtocells themselves or give end users incentives to acquire them.

As with any new concept, there are challenges to overcome before Het-Nets can become reality. Het-Nets must come to market with a total cost of ownership that is competitive for an operator to realize the benefit of providing better capacity, higher data speeds, and most of all, a better end-user experience said Chevli.

“The level of total cost of ownership has to be reduced. That is where the challenge is for vendors to ensure that any new solution revalidates every existing tenet of cellular topology and evolve it to the new paradigm being proposed,” Chevli said. “You can’t increase the number of end nodes by 25X and expect to operate or manage this new network with legacy O&M paradigms and a legacy backhaul approach.”

One of the issues is dealing with interference and Het-Net network traffic policies. “How do you manage all of these small cell networks within the macrocell network?” asked Jarich. “Right now if you have a bunch of femtocells inside a house, there is this concept that the walls stop the macrocell signals from getting in and out. You get a separation between the two. Go outdoors with small cells underlying bigger cells and you get a lot more interference and hand-off issues because devices will switch back and forth based on where the stronger signal is.”

Pedziwiatr said for a Het-Net to work, it would require a change in node management, whereby an operator isn’t burdened with managing big clusters of small cells on an individual basis. “We see elements of SON (self organizing networks), self discovery and auto optimization that will have to be key ingredients in these networks. Otherwise operators can’t manage them and the business case will be a lot less attractive,” he said.

Fortunately, the industry has already been working with and implementing concepts of SON in LTE network solutions. In the femtocell arena also, vendors have been incorporating some elements and concepts of SON so that installing them is a plug-and-play action that automatically configures the device and avoids interference. But even then, Het-Nets will require further SON enhancement to deal with new use cases, such as overlay (macro deployment) to underlay (pico deployments) mobility optimization.

When it comes to LTE, SON features are built into the standard, and are designed to offer the dual benefit of reducing operating costs while optimizing performance. SONs will do this by automating many of the manual processes used when deploying a network to reduce costs and help operators commercialize their new services faster. SON will also automate many routine, repetitive tasks involved in day-to-day network operations and management such as neighbor list discovery and management.

Other key sticking points are deployment and backhaul costs. If operators are to deploy many small cells in a given area, deploying them and backhauling their traffic should not become monumental tasks.

Chevli and Pedziwiatr envision Het-Nets being deployed initially in hot zone areas – where data traffic is the highest – using street-level plug-and-play nodes that can be easily installed by people with little technical know-how.

“Today, macro site selection, engineering, propagation analysis, rollout and optimization are long and expensive processes, which must change so that installers keep inventories of these units in their trucks, making rollout simple installations and power-ups,” said Pedziwiatr. “These will be maintained at a minimum with quick optimization.”

The notion of backhauling traffic coming from a large cluster of Het-Net nodes could also stymie Het-Nets altogether. Chevli said that in order to keep costs down, Het-Net backhaul needs to be a mix of cost-effective wireless or wired backhaul technology to aggregate traffic from what likely will be nodes sitting on lamp posts, walls, in-building and other similar structures. The goal then is to find a backhaul point of presence to aggregate the traffic and then put that traffic on an open transport network in the area.

Backhaul cost reductions may also be a matter of finding ways to reduce the amount of backhaul forwarded to the core network, Pedziwiatr said. These types of solutions are already being developed in the 3G world to cope with the massive data traffic that is beginning to crush networks. For traffic such as Internet traffic, which doesn’t need to travel through an operator’s core network, offloading that traffic as close to the source as possible would further drive down the cost of operation through the reduction of backhaul and capacity needs of the core network.

In the end, with operators incorporating smaller cells as an underlay to their macro network layer rather than relying on data offloading techniques such as femtocells and WiFi that largely depend on the actions of subscribers and impacted by the surrounding cell operating in the same unlicensed frequency, Het-Nets in licensed spectrum will soon become the keystone in attacking the ever-present congestion issue that widely plagues big cities and this is only likely to get worse over time.

Image Source: Dr. Daichi Imamura, Panasonic presentation.

Presentation: Further Enhancements for LTE-Advanced

Further Enhancements for LTE-Advanced

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Presentation: Smart Antennas and SON

Smart Antennas and SON

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Presented by Kevin Linehan, VP, CTO Antennas, Andrew Solutions in the 4G World, Oct. 2010

Carrier aggregation deployment scenarios for Release-10 LTE-A

One of the important aspects to consider is that carrier aggregation should allow aggregation of not only the existing bands, but also bands that are introduced in future, e.g., 3.5 GHz band, etc. While existing bands already have certain deployments, new deployments can be considered for new bands that are introduced. Since introduction of new bands is done in a release independent fashion, considerations for such future bands are essential already in Rel-10. When higher frequencies such as 3.5 GHz are considered, path loss can be significant (e.g., 4-10 dB difference in link budget) when compared to 2 GHz. Hence, the most efficient deployment may not be to stick with the traditional macro-overlaying approach. Carrier aggregation should allow more flexible use of such new bands, since coverage and mobility can be ascertained by the existing band deployments, e.g., 2 GHz.

Picture below shows some of the potential deployment scenarios for carrier aggregation. Note that the scenarios listed are non-exhaustive. For example, other scenarios using repeaters and femto cells may be considered. Also note that F2 > F1.

Scenario 1

* F1 and F2 cells are co-located and overlaid, providing nearly the same coverage

* Both layers provide sufficient coverage and mobility can be supported on both layers.

* Likely scenario when F1 and F2 are of the same band, e.g., 2 GHz, 800 MHz, etc.

* It is expected that aggregation is possible between overlaid F1 and F2 cells.

Scenario 2

* F1 and F2 cells are co-located and overlaid, but F2 has smaller coverage due to larger path loss

* Only F1 provides sufficient coverage and F2 is used to provide throughput. Mobility is performed based on F1 coverage.

* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.

* It is expected that aggregation is possible between overlaid F1 and F2 cells.

Scenario 3

* F1 and F2 cells are co-located but F2 antennas are directed to the cell boundaries of F1 so that cell edge throughput is increased

* F1 provides sufficient coverage but F2 potentially has holes, e.g., due to larger path loss. Mobility is based on F1 coverage.

* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.

* It is expected that F1 and F2 cells of the same eNB can be aggregated where coverage overlap.

Scenario 4

* F1 provides macro coverage and on F2 Remote Radio Heads (RRHs) are used to provide throughput at hot spots

* Mobility is performed based on F1 coverage.

* Likely scenario when F1 and F2 are of different bands, e.g., F1 = {800 MHz, 2 GHz} and F2 = {3.5 GHz}, etc.

* It is expected that F2 RRE cells can be aggregated with the underlying F1 macro cells.

Scenario 5

* Similar to scenario #2, but frequency selective repeaters are deployed so that coverage is extended for one of the carrier frequencies

Scenarios supported in Rel-10 time frame

* For DL, all scenarios are supported in Rel-10

* For UL, scenario 4 and 5 are not supported in Rel-10

Source: R2-100531 CA deployment scenario NTT DOCOMO

Carrier Aggregation Concepts for LTE Rel-10

Carrier Aggregation Concepts for LTE Rel-10

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CA (Carrier Aggregation) Scenarios in LTE-Advanced

CA (Carrier Aggregation) may be used in three different spectrum scenarios as follows.

Intraband Contiguous CA — This is where a contiguous bandwidth wider than 20 MHz is used for CA. Although this may be a less likely scenario given frequency allocations today, it can be common when new spectrum bands like 3.5 GHz are allocated in the future in various parts of the world. The spacing between center frequencies of contiguously aggregated CCs (Component Carriers) is a multiple of 300 kHz to be compatible with the 100 kHz frequency raster of Release 8/9 and preserving orthogonality of the subcarriers with 15 kHz spacing.

Intraband Non-Contiguous CA — This is where multiple CCs belonging to the same band are used in a non-contiguous manner. This scenario can be expected in countries where spectrum allocation is non-contiguous within a single band, when the middle carriers are loaded with other users, or when network sharing is considered.

Interband Non-Contiguous CA — This is where multiple CCs belonging to different bands (e.g., 2 GHz and 800 MHz are aggregated). With this type of aggregation, mobility robustness can potentially be improved by exploiting different radio propagation characteristics of different bands. This form of CA may also require additional complexity in the radio frequency (RF) front-end of UE. In LTE Release 10, for the UL the focus is on intraband CA, due to difficulties in defining RF requirements for simultaneous transmission on multiple CCs with large frequency separation, considering realistic device linearity. For the DL, however, both intra and interband cases are considered in Release 10, while specific RF requirements are being developed.

Text Source: Carrier Aggregation Framework in 3GPP LTE-Advanced - Mikio Iwamura et al. in IEEE Communications Magazine August 2010

Picture Source: http://www.catr.cn/tecm/dxwjs/201006/t20100610_1143968.htm

The Path to 4G: LTE and LTE-Advanced

The Path to 4G: LTE and LTE-Advanced

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The Path to 4G: LTE and LTE-Advanced presented by James Seymour, Alcatel Lucent in 4G World, 20th Oct. 2010.

3GPP Green activities / Energy Saving initiatives

3GPP has been working on Energy saving initiatives for Release-10 and Release-11. Here is a very quick summary of some of these items.

Telecommunication management; Study on Energy Savings Management (ESM)

Most mobile network operators aim at reducing their greenhouse emissions, by several means such as limiting their networks' energy consumption.

In new generation Radio Access Networks such as LTE, Energy Savings Management function takes place especially when mobile network operators want e.g. to reduce Tx power, switch off/on cell, etc. based on measurements made in the network having shown that there is no need to maintain active the full set of NE capabilities.

By initiating this Work Item about Energy Savings Management, 3GPP hopes to contribute to the protection of our environment and the environment of future generations.

The objective of this technical work is to study automated energy savings management features. Usage of existing IRPs is expected as much as possible, e.g. Configuration Management IRP, etc. However, this technical work may identify the need for defining a new IRP.

The following operations may be considered in this study item (but not necessarily limited to):
• Retrieval of energy consumption measurements
• Retrieval of traffic load measurements
• Adjust Network Resources capabilities


OAM aspects of Energy Saving in Radio Networks

There are strong requirements from operators on the management and monitoring of energy saving functions and the evaluation of its impact on the network and service quality. Therefore an efficient and standardized Management of Energy Saving functionality is needed. Coordination with other functionalities like load balancing and optimization functions is also required.

The objectives of this work item are:
• Define Energy Savings Management OAM requirements and solutions for the following use cases,
• eNodeB Overlaid
• Carrier restricted
• Capacity Limited Network
• Define OAM requirements and solutions for coordination of ESM with other functions like
• Self-Optimization
• Self Healing
• Traditional configuration management
• Fault Management
• Select existing measurements which can be used for assessing the impact and effect of Energy Saving actions corresponding to above Energy Saving use cases.
• Define new measurements which are required for assessing the impact and effect of Energy Saving actions, including measurements of the energy consumption corresponding to above Energy Saving use cases.


Study on impacts on UE-Core Network signalling from Energy Saving

Energy Saving (ES) mechanisms are becoming an integral part of radio networks, and consequently, of mobile networks. Strong requirements from operators (for reasons of cost and environmental image) and indirectly from authorities (for the sake of meeting overall international and national targets) have been formulated. With the expected masses of mobile network radio equipment as commodities, in the form of Home NB/eNBs, this aspect becomes even more crucial.

It is necessary to ensure that ES does not lead to service degradation or inefficiencies in the network. In particular:
• the activation status of radio stations (on/off) introduces a new scale of dynamicity for the UE and network;
• mass effects in signalling potentially endanger the network stability and need to be handled properly.

It is unclear whether and how currently defined procedures are able to cope with, and eventually can be optimized for, ES conditions; thus a systematic study is needed.

The study aims, within the defined CT1 work areas, at:
• analysing UE idle mode procedures and UE-Core Network signalling resulting from frequent switch on/off of radio equipment in all 3GPP accesses, including home cell deployment and I-WLAN;
• performing a corresponding analysis for connected mode UEs;
• analysing similar impacts from activation status of non-3GPP access networks;
• documenting limitations, weaknesses and inefficiencies in these procedures, with emphasis on mass effects in the UE-Core Network signalling;
• studying potential optimizations and enhancements to these procedures;

The study shall also evaluate and give recommendations on potential enhancements to 3GPP specifications (whether and where they are seen necessary).


Study on Solutions for Energy Saving within UTRA Node B

Due to the need to reduce energy consumption within operators’ networks, and considering the large amount of UMTS network equipment deployed in the field around the world, the standardisation of methods to save energy in UMTS Node Bs is seen as an important area of study for 3GPP.There has not been a large amount of focus on energy-saving in UMTS networks so far in 3GPP, although some solutions have been agreed in Release 9. Therefore it is proposed to start an initial study phase to identify solutions and perform any initial evaluation, such that a subset of these proposals can be used as the basis for further investigation of their feasibility.

The objective is to do an initial study to identify potential solutions to enable energy saving within UMTS Node-Bs, and do light initial evaluation of the proposed solutions, with the aim that a subset of them can be taken forward for further investigation as part of a more focused study in 3GPP.

The solutions identified in this study item should consider the following aspects:
• Impacts on the time for legacy and new UEs to gain access to service from the Node B
• Impacts on legacy and new terminals (e.g. power consumption, mobility)

Some initial indication of these aspects in relation to the proposed solutions should be provided.


Study on Network Energy Saving for E-UTRAN

The power efficiency in the infrastructure and terminal should be an essential part of the cost-related requirements in LTE-A. There is a strong need to investigate possible network energy saving mechanisms to reduce CO2 emission and OPEX of operators.

Although some solutions have been proposed and part of them have been agreed in Release-9, there has not been a large amount of attention on energy saving for E-UTRAN so far. Many potential solutions are not fully shown and discussed yet. Therefore, it is proposed to start an initial study phase to identify solutions, evaluate their gains and impacts on specifications.

The following use cases will be considered in this study item:
• Intra-eNB energy saving
• Inter-eNB energy saving
• Inter-RAT energy saving

Intra-eNB energy saving, in EUTRAN network, a single cell can operate in energy saving mode when the resource utilization is sufficiently low. In this case, the reduction of energy consumption will be mainly based on traffic monitoring with regard to QoS and coverage assurance.

A lot of work on Inter-eNB energy saving has already been done for both LTE and UTRA in Rel-9. This Study Item will investigate additional aspects (if any) on top of what was already agreed for R9.

Inter-RAT energy saving, in this use case, legacy networks, i.e. GERAN and UTRAN, provide radio coverage together with E-UTRAN. For example E-UTRAN Cell A is totally covered by UTRAN Cell B. Cell B is deployed to provide basic coverage of the voice or medium/low-speed data services in the area, while Cell A enhances the capability of the area to support high-speed data services. Then the energy saving procedure can be enabled based on the interaction of E-UTRAN and UTRAN system.

The objective of this study item is to identify potential solutions for energy saving in E-UTRAN and perform initial evaluation of the proposed solutions, so that a subset of them can be used as the basis for further investigation and standardization.

Energy saving solutions identified in this study item should be justified by valid scenario(s), and based on cell/network load situation. Impacts on legacy and new terminals when introducing an energy saving solution should be carefully considered. The scope of the study item shall be as follows:
• User accessibility should be guaranteed when a cell transfers to energy saving mode
• Backward compatibility shall be ensured and the ability to provide energy saving for Rel-10 network deployment that serves a number of legacy UEs should be considered
• Solutions shall not impact the Uu physical layer
• The solutions should not impact negatively the UE power consumption

RAN2 will focus on the Intra-eNB energy saving, while RAN3 will work on Inter-RAT energy saving and potential additional Inter-eNB energy saving technology.


Study on Solutions for GSM/EDGE BTS Energy Saving

There has not been a large amount of focus on energy-saving in GSM/EDGE networks so far in 3GPP, although some solutions have been agreed in previous Releases, notably MCBTS. Therefore it is proposed to start an initial study phase to identify solutions and perform any initial evaluation, such that a subset of these proposals can be used as the basis for further investigation of their feasibility.

The objective is to study potential solutions to enable energy saving within the BTS (including MCBTS and MSR), and evaluate each proposed solutions in detail. These potential solutions shall focus on the following specific aspects
• Reduction of Power on the BCCH carrier (potentially enabling dynamic adjustment of BCCH power)
• Reduction of power on DL common control channels
• Reduction of power on DL channels in dedicated mode, DTM and packet transfer mode
• Deactivation of cells (e.g. Cell Power Down and Cell DTX like concepts as discussed in RAN)
• Deactivation of other RATs in areas with multi-RAT deployments, for example, where the mobile station could assist the network to suspend/minimise specific in-use RATs at specific times of day
• And any other radio interface impacted power reduction solutions.

The solutions identified in this study item shall also consider the following aspects:
• Impacts on the time for legacy and new mobile stations to gain access to service from the BTS
• Impacts on legacy and new mobile stations to keep the ongoing service (without increasing drop rate)
• Impacts on legacy and new mobile stations implementation and power consumption, e.g. due to reduction in DL power, cell (re-)selection performance, handover performance, etc.
• Impacts on UL/DL coverage balance, especially to CS voice

Solutions shall be considered for both BTS energy saving non-supporting and supporting mobile stations (i.e. solutions that are non-backwards compatible towards legacy mobile stations shall be out of the scope of this study).

Recap of MIMO Technologies in 3GPP LTE and LTE-Advanced

MIMO Technologies in 3GPP LTE and LTE-Advanced

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1200Mbps DL with LTE-Advanced

I blogged last year about the LTE-A UE categories but then the categories were still under discussion. In the 3GPP RAN WG1#62 LTE-Advanced UE Categories were discussed based on NTT DoCoMo proposal and the data rates are as summarised in the picture above.

Note that category 8 has 1200Mbps DL and 600Mbps UL speed.

The complete report is available here.

Via: WirelessMoves.

LTE will be known as 4G!

I have been mentioning since 3 years that LTE is 3.9G and its not 4G. In fact I have brought it up in many posts and discussions so that we do not dilute the term 4G. From my recent visit to the LTE World Summit and from the news, etc. it seems that the marketing guys won and LTE would be known as 4G.

In the picture above you can clearly see that the press releases by well known companies as well as Samsung's dongle has 4G for LTE stamped. It may be very difficult to reverse this '4G' means LTE term.

So I have now started thinking about what LTE-Advanced will be known as. Here is my attempt:

• 5G - Not sure if people will buy this. Assuming that LTE-Advanced specs are ready by March 2011 (as is predicted) then people wont be ready to jump from 4G to 5G this soon.
• 4G+ - Not sure if this sounds sexy enough
• Super 4G - Boring
• Turbo 4G - reminds me of F1

Suggestions welcome.

Home Relays for LTE-Advanced

If you look at the Home eNodeB (Femtocell) architecture, the HeNB is connected to its gateway which in turn is connected to MME/S-GW. There is a considerable amount of technology investment in this approach. The HeNB consists of complete protocol stack, the HeNB-GW is an expensive piece of equipment and there is lots of other things including the management software, etc.

Now in LTE-A, there is a concept of Relays which we have talked about. The Relays do not contain the complete stack (generally just L1 and L2). If capacity is not an issue but coverage, then we may be able to use Home Relays.

The backhaul for Femtocell is Internet whereas for Relay its generally the same Radio resources within the cell. I guess the main thing for Relay is the requirement of reasonably good channel (Line of sight maybe). Home Relays can use the Internet connection but rather than connection terminating in some kind of gateway, it can terminate at the actual eNB.

There are already many advanced antenna techniques that can handle the transmission and reception without much interference and maybe the SON algorithms may need some additional improvements.

The main thing is that if this technology becomes reality then it may cost less than $50 per Home relay and would become really a commonplace.

Coordinated Multi-Point (CoMP) transmission and reception

The industry’s first live field tests of Coordinated Multipoint Transmission (CoMP), a new technology based on network MIMO, were conducted in Berlin in October 2009. CoMP will increase data transmission rates and help ensure consistent service quality and throughput on LTE wireless broadband networks as well as on 3G networks. By coordinating and combining signals from multiple antennas, CoMP, will make it possible for mobile users to enjoy consistent performance and quality when they access and share videos, photos and other high-bandwidth services whether they are close to the center of an LTE cell or at its outer edges.

The following is from the 3G Americas report on CoMP:

Coordinated Multi-Point transmission/reception (CoMP) is considered by 3GPP as a tool to improve coverage, cell-edge throughput, and/or system efficiency.

The main idea of CoMP is as follows: when a UE is in the cell-edge region, it may be able to receive signals from multiple cell sites and the UE’s transmission may be received at multiple cell sites regardless of the system load. Given that, if the signaling transmitted from the multiple cell sites is coordinated, the DL performance can be increased significantly. This coordination can be simple as in the techniques that focus on interference avoidance or more complex as in the case where the same data is transmitted from multiple cell sites. For the UL, since the signal can be received by multiple cell sites, if the scheduling is coordinated from the different cell sites, the system can take advantage of this multiple reception to significantly improve the link performance. In the following sections, the CoMP architecture and the different CoMP schemes will be discussed.

CoMP communications can occur with intra-site or inter-site CoMP as shown in Figure 7.7.


With intra-site CoMP, the coordination is within a cell site. The characteristics of each type of CoMP architecture are summarized in Table 7.1.



An advantage of intra-site CoMP is that significant amount of exchange of information is possible since this communication is within a site and does not involve the backhaul (connection between base stations). Inter-site CoMP involves the coordination of multiple sites for CoMP transmission. Consequently, the exchange of information will involve backhaul transport. This type of CoMP may put additional burden and requirement upon the backhaul design.



An interesting CoMP architecture is the one associated with a distributed eNB depicted in Figure 7.8. In this particular illustration, the Radio Remote Units (RRU) of an eNB are located at different locations in space. With this architecture, although the CoMP coordination is within a single eNB, the CoMP transmission can behave like inter-site CoMP instead.

DL COMP

In terms of downlink CoMP, two different approaches are under consideration: Coordinated scheduling, or Coordinated Beamforming (CBF), and Joint Processing/Joint Transmission (JP/JT). In the first category, the transmission to a single UE is transmitted from the serving cell, exactly as in the case of non-CoMP transmission. However, the scheduling, including any Beamforming functionality, is dynamically coordinated between the cells in order to control and/or reduce the interference between different transmissions. In principle, the best serving set of users will be selected so that the transmitter beams are constructed to reduce the interference to other neighboring users, while increasing the served user’s signal strength.

For JP/JT, the transmission to a single UE is simultaneously transmitted from multiple transmission points, across cell sites. The multi-point transmissions will be coordinated as a single transmitter with antennas that are geographically separated. This scheme has the potential for higher performance, compared to coordination only in the scheduling, but comes at the expense of more stringent requirement on backhaul communication.

Depending on the geographical separation of the antennas, the coordinated multi-point processing method (e.g. coherent or non-coherent), and the coordinated zone definition (e.g. cell-centric or user-centric), network MIMO and collaborative MIMO have been proposed for the evolution of LTE. Depending on whether the same data to a UE is shared at different cell sites, collaborative MIMO includes single-cell antenna processing with multi-cell coordination, or multi-cell antenna processing. The first technique can be implemented via precoding with interference nulling by exploiting the additional degrees of spatial freedom at a cell site. The latter technique includes collaborative precoding and CL macro diversity. In collaborative precoding, each cell site performs multi-user precoding towards multiple UEs, and each UE receives multiple streams from multiple cell sites. In CL macro diversity, each cell site performs precoding independently and multiple cell sites jointly serve the same UE.

UL COMP

Uplink coordinated multi-point reception implies reception of the transmitted signal at multiple geographically separated points. Scheduling decisions can be coordinated among cells to control interference. It is important to understand that in different instances, the cooperating units can be separate eNBs’ remote radio units, relays, etc. Moreover, since UL CoMP mainly impacts the scheduler and receiver, it is mainly an implementation issues. The evolution of LTE, consequently, will likely just define the signaling needed to facilitate multi-point reception.

INTER-CELL INTERFERENCE COORDINATION

Another simple CoMP transmission scheme which relies on resource management cooperation among eNBs for controlling inter-cell interference is an efficient way to improve the cell edge spectral efficiency. The Inter-Cell Interference Coordination (ICIC) enhancement currently being studied for LTE-Advanced can be classified into dynamic Interference Coordination (D-ICIC) and Static Interference Coordination (S-ICIC). In D-ICIC, the utilization of frequency resource, spatial resource (beam pattern) or power resource is exchanged dynamically among eNBs. This scheme is flexible and adaptive to implement the resource balancing in unequal load situations. For S-ICIC, both static and semi-static spatial resource coordination among eNBs are being considered.

More information coule be found in:

• Coordinated Multipoint Trials in the Downlink - Fraunhofer Heinrich Hertz Institute
• 3GPP TR 36.814: Further Advancements for E-UTRA Physical Layer Aspects

3.9G (LTE) to 4G

Yesterday I blogged about the LTE-Advanced workshop. There are loads of documents that a lot of you will probably find it useful. You can also check the latest whitepapers and presentations on the 3g4g website here.

Last month Nomor published a whitepaper titled 'The way of LTE towards 4G'. The paper is good summary of the progress in standardisation. The following is summary from that paper with regards to LTE-A standardisation:

3GPP already agreed on the schedule for Release 10 where LTE Advanced will be standardized with:

• functional freeze in December 2010

• ASN.1 freeze in March/June 2011

In practice this means that the Physical Layer specification will have to be completed around September 2010, which leaves just about 9 months time. The protocol, interface and test

specification are to be completed by December 2010.

According to the major LTE-A functional enhancements, the following work items have been approved for Release 10:

• Carrier aggregation for LTE

• Enhanced downlink multiple antenna transmission for LTE

• Uplink multiple antenna transmission for LTE

• Latency reductions for LTE

A presentation introducing LTE-A technologies has been published early this year in [4].

The work on Cooperative Multipoint Transmission (CoMP) is still part of the downlink multiple

antenna work item. It is stated that the standardization impact of downlink CoMP will be assessed and a decision will be done in March 2010 if downlink CoMP will be standardized as part of this work item.

LTE Advanced will be fully built on the existing LTE specification Release 10 and not be defined as a new specification series. Stage 2 (architecture and functional description) will for instance be added to TS 36.300 in Release 10.

Please keep in mind that there are a large number of other work items within Release 10. Remarkably 3GPP also approved a Work Item on LTE Advanced Relays to improve coverage and improve cell edge throughput. The Work Item was supported by key operators.

You can read the complete paper here.

3GPP IMT-Advanced Workshop in Beijing

3GPP technical experts have attended the recent IMT-Advanced workshop, in Beijing, China, hosted by the China MIIT Institute of Communication Standards Research (CATR) and China Mobile.

The workshop was chaired by the 3GPP TSG RAN chairman, Takehiro Nakamura, with the first day given over to 3GPP RAN working group presentations and the second to the twelve IMT-Advanced evaluation groups.

3GPP Presentations:

• LTE technologies (Takehiro Nakamura: TSG-RAN Chair, NTT DOCOMO)
• Physical layer aspects (Matthew Baker: RAN WG1 Chair, Alcatel-Lucent)
• Layer 2 and 3 aspects (Magnus Lindström: RAN WG2, Ericsson)
• RAN architecture aspects (Dino Flore: RAN WG3 Chair, Qualcomm)
• RF aspects (Takaharu Nakamura: RAN WG4 Chair, Fujitsu)
• 3GPP Self evaluation methodology and results (Tetsushi Abe: RAN WG1 Vice-Chair, NTT DOCOMO)

Status reports from the IMT-Advanced Independent Evaluation Groups (IEG):

• ARIB
• ATIS WTSC Evaluation Group
• CEG
• ChEG (Part I) (Part II)
• ETSI
• REG
• TCOE India
• TR 45 (Presentation not available)
• TTA PG707
• WFEG
• WINNER+ (Part I)(Part II

You can view the agenda of the workshop here.

You can also check all the documents directly here.