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.

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.

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.

Latency:

• 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.

Mobility:

• 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.

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

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.

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%.

read more

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 (K_ASME) and identified with a key identifier (KSI_ASME).
• The eNB key (K_eNB) 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 K_ASME. Thus, as a result of an AKA run, the EPC and the UE share K_ASME.

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

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