Friday, November 13, 2009

Local IP access to home based network & Internet via HNB/HeNB

3GPP specfications has specified requirements for Local IP access via femtocell access nodes ie. 3G HNB & LTE HeNB. HNB and eHNB are Customer-premises equipments (femtocell) that connect a 3GPP UE over UTRAN and EUTRAN wireless air interface respectivly to a mobile operator’s network using a broadband IP backhaul.

This is an added advantage and driver for end users to have a femtocell in home. Users would be able to access local IP devices and Internet without going through operator's network.

As per specifications Local IP Access to the home based network provides access for a directly connected (i.e. using H(e)NB radio access) IP capable UE to other IP capable devices in the home.

Further 3GPP adds that it would be possible to access Internet using local IP network also.

Traffic for local IP access is expected to not traverse the operator’s network except H(e)NB.

A logical diagram is shown below for Local IP access

A summary of requirements set by 3GPP for HNB & HeNB to support Local IP Access are as below

  • Support of simultaneous access from a UE to both the operator’s core network and Local IP Access to the home based network/Internet
  • Support of Local IP Access to the home based network/Internet without traversing the operator’s network except H(e)NB
  • The operator or the H(e)NB Owner, within the limits set by the operator would be able to enable/disable Local IP Access to the home based network/Internet per H(e)NB.
  • It would be possible to collect and make available to the operator statistics information (e.g. regular reporting of Local IP traffic volume) for each user on the use of the Local IP Access to the home based network/ Internet.
  • Local IP access to home based network/ Internet would not compromise the security of the operator’s network.

Local IP access to home based network would also be possible through the H(e)NB E-UTRAN/UTRAN-interface as well however It will only be granted to UE with valid subscription.

For further readings 3GPP specification 22.220 can be referred.

Sunday, November 1, 2009

Femtocell - News, Video & Whitepapers

LteWorld has recently added a new page with Femtocell news, videos & whitepapers. Page is available here.

A Femtocell is a device used to improve mobile network coverage in small areas. Femto cells connect locally to mobile phones and similar devices through their normal GSM, GPRS, or UMTS connections, and then route the connections over a broadband internet connection back to the mobile network, bypassing the normal cell towers.

Saturday, October 24, 2009

Voice over LTE via Generic Access (VoLGA) Architecture

LteWorld has recently published a short tutorial about VoLGA architecture as shown below.

For more details click here.

Sunday, October 11, 2009

Self-configuring and self-optimizing Networks in LTE

Self-configuring, self-optimizing wireless networks is not a new concept but as the mobile networks are evolving towards 4G LTE networks, introduction of self configuring and self optimizing mechanisms is needed to minimize operational efforts. A self optimizing function would increase network performance and quality reacting to dynamic processes in the network.

This would minimize the life cycle cost of running a network by eliminating manual configuration of equipment at the time of deployment, right through to dynamically optimizing radio network performance during operation. Ultimately it will reduce the unit cost and retail price of wireless data services.

As per 3GPP standards, a typical operational objective is to optimize the network according to coverage and capacity.

Providing optimal coverage requires that in the area, where LTE system is offered, users can establish and maintain connections with acceptable or default service quality, according to operator’s requirements. Coverage and capacity are linked, a trade-off between the two of them may also be a subject of optimization.

To achieve these objectives, 3GPP suggests to implement following functions
  • Detection of unintended holes in the coverage (planned by the operator)
  • Perform coverage optimization, including DL/UL channel coverage a
  • Ability to balance the trade-off between coverage and capacity

Once solution is implemented, it would result in
  • Continuous, optimized and matched UL and DL coverage
  • Optimized DL and UL capacity of the system
  • Balanced tradeoff between coverage and capacity
  • Interference reduction
  • Controlled cell edge performance
  • Minimized human intervention in network management and optimization tasks
  • Energy savings

Implementing self configuration and self optimization under multi vendor environment is challenging task. For this purpose, It is of importance that measurements and performance data of different vendors follow same standard. Especially when the interaction between self configuring/optimizing networks and O&M has to be considered.

Sunday, September 27, 2009

Understanding CS Fallback in LTE

LTE technology supports packet based services only however 3GPP does specifies fallback for circuit switched services as well. To achieve this LTE architecture and network nodes require additional functionality, this blog is an attempt to provide overview for same.

In LTE architecture, the circuit switched (CS) fallback in EPS enables the provisioning of voice and traditional CS-domain services (e.g. CS UDI video/ SMS/ LCS/ USSD). To provide these services LTE reuses CS infrastructure when the UE is served by E UTRAN.

A CS fallback enabled terminal, connected to E UTRAN may use GERAN or UTRAN to connect to the CS domain. This function is only available in case E UTRAN coverage is overlapped by either GERAN coverage or UTRAN coverage.

The figure above provides architecture for CS fallback in EPS.

CS Fallback and IMS based services can co-exist in the same operator’s network. Although its not very straight forward to support CS fallback, all participating elements i.e UE, MME, MSC & E-UTRAN needs to support additional functionalities.

The support CS fallback in EPS a new interface SGs is added in LTE architecture. SGs interface is the reference point between the MME and MSC server. SGs interface is used for the mobility management and paging procedures between EPS and CS domain, and is based on the Gs interface procedures.

The SGs reference point is also used for the delivery of both mobile originating and mobile terminating SMS.

The CS fallback enabled network elements need to support the following additional functions:

  • supports access to E-UTRAN/EPC as well as access to the CS domain over GERAN and/or UTRAN.
  • Combined procedures for EPS/IMSI attach, update and detach.
  • CS fallback and SMS procedures for using CS domain services.

  • Deriving a VLR number and LAI from the GUTI received from the UE or from a default LAI.
  • Maintaining of SGs association towards MSC/VLR for EPS/IMSI attached UE.
  • Initiating IMSI detach at EPS detach.
  • Initiating paging procedure towards eNodeB when MSC pages the UE for CS services.
  • Support of SMS procedures
  • Rejecting CS Fallback call request (e.g. due to O&M reasons)
  • Use of the LAI and a hash value from the IMSI to determine the VLR number when multiple MSC/VLRs serve the same LAI.

  • Maintaining SGs association towards MME for EPS/IMSI attached UE.
  • Support of SMS procedures as provided in 3GPP specification

  • Forwarding paging request and SMS to the UE.
  • Directing the UE to the target CS capable cell.

At MME - MSC Server interface a new protcol SGsAP is being added to support CS fallback. SGsAP protocol is based on the BSSAP+. Stream Control Transmission Protocol (SCTP) is used to transport SGsAP signaling messages.

A CS Fallback and IMS capable UE would follow the procedures for domain selection for UE originating session/calls according to 3GPP specification 23.221.

If a UE is configured to use SMS over IP services and it is registered to IMS then it would send SMS over IMS, even if it is EPS/IMSI attached.

The home operator has option to activate/deactivate the UE configuration to use SMS over IP by means of device management in order to allow alignment with HPLMN support of SMS over IP.

When UE is performing CS fallback procedure for Mobile Originating Call for the purpose of emergency call, it needs to indicate to the MME that this CS fallback request is for emergency purpose. MME also indicates to the E-UTRAN via the appropriate S1-AP message that this CS fallback procedure is for emergency purpose.

Contents of this blog are mostly derived from 3GPP specification 23.272, for better and detailed understanding same should be referred.

Although there had been talks about another approach for CS Fallback by VoLGA which does not require any enhancement in existing CS elements like MSC but for VoLGA another set of additional nodes are needed. to know more about VoLGA refer one of our earlier blog LTE needs VoLGA.

Saturday, September 19, 2009

LTE : The Global Opportunity

The UMTS Forum has came out with a report - LTE Mobile Broadband Ecosystem: the Global Opportunity. This is available for free download.

The report considers relationship in between LTE & othe mobile technologies; the new services, devices and applications which will drive LTE. Report presents a positive picture of LTE’s transformation of the global market for mobile broadband.

According to report, it is based on over 30 interviews by Ovum with operators, vendors, regulators and standards bodies, plus end user research with 550 respondents in the US, Korea, Japan, Germany, France, Italy, the UK and Spain. It considers both consumer and enterprise market segments, as well as vertical markets that will benefit from the deployment of LTE.

Report further suggests that Offering major enhancements in speed, capacity and support for new services, LTE will dominate the global market for mobile broadband over the next few years. Designed for all-IP traffic, LTE supports a flatter, more efficient network architecture that allows operators to reduce their long term capex and opex. In parallel with this, LTE allows operators to deliver a more compelling, service-rich mobile broadband user experience for consumers and business customers alike.

LTE will enhance many existing services while enabling new ones. In this new environment, non-voice mobile services – including real-time video, P2P content sharing and social networking – will be increasingly important. This evolution from a ‘traditional’ mobile ecosystem to embrace new internet-based applications, devices and content delivery mechanisms will see the emergence of a broader ecosystem than for any previous mobile technology.

Sunday, August 30, 2009

UMTS/LTE in 800 MHz for Europe

800MHz band (also known as 790-862 MHz, channels 61 to 69 in UHF Bands IV and V) was previously used by analog broadcasting, and is particularly suitable for delivery of high-bandwidth services and indoor coverage.

UK regulator Ofcom is pushing to clear the 800MHz band of existing and previously planned users and align the upper band of the UK’s digital dividend with the spectrum being identified for release by an increasing number of other European countries. The reason behind this move is that this spectrum is likely to be particularly suitable for the provision of a new generation of mobile broadband services.

A 3GPP work item is currently under works to provide specification for "UMTS/LTE in 800 MHz for Europe" to provide support for LTE and UMTS with paired channel arrangement in the band 790-862 MHz.

Based on 3GPP work item the 790-862 MHz band is arranged as 2x30 MHz with 11 MHz duplex gap:
  • FDD Uplink: 832 – 862 MHz
  • FDD Downlink: 791 – 821 MHz

The tasks identified by 3GPP in this work item includes, study of UMTS/LTE in upper UHF band for a potential deployment in ITU Region 1, generate a new technical report based on study results and develop channel arrangement in line with the pending ECC decision.

The target date set by the EC for analog switch-off in EU member countries is 2012. Finland, Sweden, France, Switzerland, Germany, Spain and Denmark have already decided to release the whole of the 800 MHz band, with others likely to follow. More speed is both necessary and desirable to fully realize the benefits.

Saturday, August 22, 2009

The State of 3G and LTE in India

With wireless subscription having reached to 441.66 Million, India has yet to catchup with other countries in 3G and LTE (Long Term Evolution) deployments. India's state-run mobile operators BSNL and MTNL have already launched commercial 3G services after getting access to spectrum last year. BSNL and MTNL have set sights on adding between 200,000 and 300,000 subscribers during the first year of operations.

DoT and finance ministry recently indicated to limit the number of slots to just four blocks of 5 MHz each in the 2.1 GHz band for 3G auctions with a view to maximizing revenue per block of spectrum. These four new entrants will be in addition to BSNL/MTNL, taking the total 3G operators per circle to five.

Even as the policy for auctioning spectrum for 3G mobile services is yet to be finalized, the Department of Telecom is already thinking about the introduction of 4G technologies such as LTE. It says some spectrum must be retained to accommodate the future needs of these operators as well as to provide for 4G technology (LTE) which will require a minimum channel of 10 MHz for the launch of service.

However telecom operators RCOM, Tata, Systema and equipment vendor Qualcomm strongly are opposing the government’s move to restrict 3G spectrum auctions to four blocks per circle. These companies want all spectrum to be put on the block so that the demand-supply equation pushes down its price.

The final decisions will be made by Empowered Group of Ministers (EGoM) in the next few weeks, based on which 3G auctions are expected either by early December or after January 2010.

It is still not clear how many operators could get 3G & LTE spectrum. Similar to 3G, LTE may come in India in 2.1 Ghz band, as 2.5 Ghz (EU LTE spectrum) is mostly used for satellite-based networks. In India most operators are looking to move to this technology by 2011, once they start making money on 3G services. MTNL & BSNL may again lead LTE deployments.

Friday, August 14, 2009

LTE Advanced: Evolution of LTE

LTE standards are in matured state now with release 8 frozen. While LTE Advanced is still under works. Often the LTE standard is seen as 4G standard which is not true. 3.9G is more acceptable for LTE. So why it is not 4G? Answer is quite simple - LTE does not fulfill all requirements of ITU 4G definition.

Brief History of LTE Advanced: The ITU has introduced the term IMT Advanced to identify mobile systems whose capabilities go beyond those of IMT 2000. The IMT Advanced systems shall provide best-in-class performance attributes such as peak and sustained data rates and corresponding spectral efficiencies, capacity, latency, overall network complexity and quality-of-service management. The new capabilities of these IMT-Advanced systems are envisaged to handle a wide range of supported data rates with target peak data rates of up to approximately 100 Mbit/s for high mobility and up to approximately 1 Gbit/s for low mobility.

In order to meet this new challenge, 3GPP widened its scope to include systems beyond 3G. LTE Advanced would fulfil the 4G requirements as set by ITU. In 2008 3GPP held workshops on IMT Advanced, where the “Requirements for Further Advancements for E-UTRA” were gathered. The resulting Technical Report 36.913 has been now published.

Let us see some requirements which differentiate LTE & LTE Advanced.

Peak data rate:

  • LTE - DL: 100 Mbps, UL: 50 Mbps
  • LTE Advanced - DL: 1 Gbps, UL: 500 Mbps

Transmission bandwidth:

  • In comparison to LTE, LTE Advanced is wider than approximately 70 MHz in DL and 40 MHz in UL.


  • LTE - C-plane from Idle (with IP address allocated) to Connected in <100>
  • LTE Advanced - C-plane from Idle (with IP address allocated) to Connected in <50>

Peak spectrum efficiency:

  • LTE - DL 3 to 4 times Release 6 HSDPA , UL - 2 to 3 times Release 6 Enhanced Uplink
  • LTE Advanced - DL 30 bps/Hz and UL 15 bps/Hz.

C-plane capacity:

  • LTE - At least 200 users per cell should be supported in the active state for spectrum allocations up to 5 MHz.
  • LTE Advanced - At least 300 active users without DRX in a 5 MHz bandwidth.


  • LTE - Support mobility across the cellular network for various mobile speeds up to 350km/h (or perhaps even up to 500km/h depending on the frequency band).
  • LTE Advanced - Same as that in LTE, System performance shall be enhanced for 0 to 10km/h

LTE Advanced would operate in spectrum allocations of different sizes including wider spectrum allocations than those of Release 8 to achieve higher performance and the target peak data rate, e.g. up to 100 MHz.

Friday, August 7, 2009

3GPP Extended UMTS/LTE 800 Technical Report

3GPP has recently published a technical report of the Extended UMTS/LTE 800 which provides UTRA and E-UTRA specification support for FDD in the Extended 800 MHz band in Japan.

As a frequency re-arrangement plan in 800MHz band of Japan before and beyond year of 2012, the lower part of the band (UL:815 - 830 MHz / DL:860 - 875 MHz) was allocated to cdma2000 and the upper part of the band (UL:830 - 845 MHz / DL:875 - 890 MHz) was allocated to UMTS. To take it into account the latest frequency arrangement above 3GGP has proposed to introduce a new frequency band for UMTS.

3GPP Technical Report indicates that there is high possibility that not only UMTS but also LTE would be introduced in Japan in the band near future in order to enhance frequency efficiency. To accommodate it corresponding necessary work to introduce new bands for LTE is proposed by 3GPP.

The tasks included in proposed work item are to study of Extended UMTS/LTE 800 for a potential deployment in Japan, generate a new technical report based on study results and
study signalling issues related to Extended UMTS/LTE 800.

The specific bands studied by 3GPPare:

Band 18 for LTE:
  • 815 - 830 MHz: UL
  • 860 - 875 MHz: DL
Band XIX for UMTS/ Band 19 for LTE:
  • 830 - 845 MHz: UL
  • 875 - 890 MHz: DL

Tuesday, July 28, 2009

3GPP Technology Approaches for Maximizing Fragmented Spectrum Allocations

In a recently published white paper 3G Americas has offered key recommendations for utilizing non-standard spectrum bands to accommodate the growing bandwidth demands of consumers.

Whitepaper provides a overview of global spectrum allocations for 3GPP based technologies and illustrates some of the key challenges for optimal spectrum utilization when allocations differ either on a country- or region-specific basis.

While covering widely held tenets considered fundamental for sound spectrum policy it discusses current approaches to addressing fragmented spectrum challenges.

In concluding remarks 3G Americas states that that there is a significant impact of fragmented spectrum allocations on the cost and performance of mobile devices. These impacts hold true in virtually every corner of the globe.

Regulators have an important and challenging role in obtaining addition spectrum and bringing it to market to meet the demands of consumers.

3G Americas offered regulators to consider following while working on obtaining addition spectrum:

1. Spectrum should be harmonized and coordinated to the maximum extent feasible;
2. New spectrum should facilitate access by new technologies of all stripes;
3. At the same time, appropriate protections should be established for incumbent and/or adjacent service providers to protect against interference;
4. Spectrum policy should foster as far as possible the efficient use of spectrum; and
5. The rules covering the allocation, auction and deployment of spectrum should be predictable and transparent, prior to auctions.

For further reading download whitepaper.

Thursday, July 23, 2009

MIMO Transmission Schemes for LTE and HSPA Networks

3G Americas has recently published an report: MIMO Transmission Schemes for LTE and HSPA Networks. The report is intended increases awareness and helps guide the deployment of MIMO technology in HSPA and LTE networks.

Multiple-input multiple-output (MIMO) technology is commonly defined as, the use of two or more unique radio signals, in the same radio channel, where each signal carries different digital information, or two or more radio signals that use beam forming, receive combining and spatial multiplexing (SM).

This report provides the principles behind smart antenna technologies such that the reader will be able to understand the fundamental tradeoffs. Report inludes many antenna configurations that can support a wide range of MIMO algorithms at the base station as well as extensively treat the issues behind the antenna configurations at the terminal. Report addresses the specific schemes selected by 3GPP to provide smart antenna capabilities in HSPA and LTE Rel-8.

Further it focuses on the expected standardization outcome in Rel-9 and Rel-10 and more specifically, in enhancements behind clustered linear arrays (CLA) and collaborative multipoint transmission/reception (CoMP) schemes. In addition it provides performance results for a wide variety of channel conditions, and antenna configurations for both DL and UL.

Based on simulation results presented in this report, it was shown that the relatively simple MIMO transmission scheme based on 2x2 CL SM, at low user equipment (UE) speeds can increase by 20% the DL sector spectral efficiency relative to a single antenna transmission, as well as increase the cell edge efficiency by approximately 35%.

Saturday, July 18, 2009

LTE Security Principles

The following are some of the principles of 3GPP E-UTRAN security based on 3GPP Release 8 specifications:

  • The keys used for NAS and AS protection shall be dependent on the algorithm with which they are used.
  • The eNB keys are cryptographically separated from the EPC keys used for NAS protection (making it impossible to use the eNB key to figure out an EPC key).
  • The AS (RRC and UP) and NAS keys are derived in the EPC/UE from key material that was generated by a NAS (EPC/UE) level AKA procedure (KASME) and identified with a key identifier (KSIASME).
  • The eNB key (KeNB) is sent from the EPC to the eNB when the UE is entering ECM-CONNECTED state (i.e. during RRC connection or S1 context setup).
  • Separate AS and NAS level security mode command procedures are used.
  • Keys stored inside eNBs shall never leave a secure environment within the eNB (except when done in accordance with this or other 3GPP specifications), and user plane data ciphering/deciphering shall take place inside the secure environment where the related keys are stored.
  • Key material for the eNB keys is sent between the eNBs during ECM-CONNECTED intra-E-UTRAN mobility.

The figure above depicts simplified key derivation.

The MME invokes the AKA procedures by requesting authentication vectors to the HE (Home environment) if no unused EPS authentication vectors have been stored.

The HE sends an authentication response back to the MME that contains a fresh authentication vector, including a base-key named KASME. Thus, as a result of an AKA run, the EPC and the UE share KASME.

From KASME, the NAS keys, (and indirectly) KeNB keys and NH are derived. The KASME is never transported to an entity outside of the EPC, but KeNB and NH are transported to the eNB from the EPC when the UE transitions to ECM-CONNECTED.

From the KeNB, the eNB and UE can derive the UP and RRC keys.

Tuesday, July 14, 2009

3GPP Release 10 Features

3GPP Release 10 Features detailed in 3GPP description document "Overview of 3GPP Release 10; Summary of all Release 10 Features (Release 10)" are as following
  • Network Selection for non-3GPP Access
  • Registration in Densely-populated area
  • Enhanced Home NodeB / eNodeB continuation of Rel-9
  • IMS aspects of Architecture for Home NodeB - moved from Rel-9
  • IMS Service Continuity – Inter Device Transfer enhancements (EHNB)
  • GTP-based S8 chaining - moved from Rel-9
  • Multi Access PDN Connectivity - moved from Rel-9
  • EEA3 and EIA3 (new Encryption & Integrity EPS security algorithms)
  • Study on Mobile Haptic Services
  • Study on advanced requirements for IP interconnect - moved from Rel-9
  • Study on Unauthenticated PS Emergency Calls - moved from Rel-9
  • Study on Study on Personal Broadcast Service - moved from Rel-9
  • Study on LCS support in SAE for non-3GPP accesses - moved from Rel-9
  • Study on System enhancements for the use of IMS services in local breakout and optimal routing of media - moved from Rel-9
  • Study on Intra Domain Connection of RAN Nodes to Multiple CN Nodes - moved from Rel-9
  • Study on IMS Evolution - moved from Rel-9
  • Study on enhancements to IMS border functions for IMS Interconnection of services - moved from Rel-9
  • Study on Policy solutions and enhancements
  • Study on IPv6 Migration
  • Study on SR-VCC Enhancements

Tuesday, July 7, 2009

Value-added services in LTE

Mobile value-added services (VAS) are those services that are not part of the basic voice offer and are availed off separately by the end user. They are used as a tool for differentiation and allow the mobile operators to develop another stream of revenue.

Once operator start migrating towards LTE then what will be the shape of VAS? It would be interesting to see how current VAS infrastructure will be reused. VoLGA seems to be a bridging the gap during migration but what would be final implementation?

read more at LteWorld

LTE needs VoLGA

LTE (Long Term Evolution) is a data only technology but it seems that we can not live without voice or SMS services. VoLGA forum claims that VoLGA specifications fill this gap. A number of telecom companies (including Ericsson, Alcatel-Lucent, Huawei) are showing interest in VoLGA and are part of VoLGA forum.

According VoLGA stage 1 specification, The aim of VoLGA is to make traditional GSM/UMTS circuit switched (CS) services available to UEs accessing the EPS network via E-UTRAN.

The lack of native SMS over LTE support is a show-stopper for LTE dongle service. Mobile operators rely on SMS for back office customer care, provisioning and management of HSPA-dongle services. Clearly those systems need to be available to an LTE-based terminal service at launch.

read more at LteWorld

What is LTE

Nicole talks to James Orr from Fujitsu and learns about LTE. Visit LteWorld to know more about LTE.

About LteWorld

Long Term Evolution (LTE) is one of the leading next-generation wireless technologies. LTE is initiated by 3GPP to improve the mobile phone standard to cope with future technology evolutions and needs. LteWorld is created for a one-stop online destination for everything about LTE.

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