Wednesday, February 26, 2014

Blueprint: Impending ITU G.8273.2 to Simplify LTE Planning

By Martin Nuss, Vitesse Semiconductor

Fourth-generation wireless services based on long-term evolution (LTE) have new timing and synchronization requirements that will drive new capabilities in the network elements underlying a call or data session. For certain types of LTE networks, there is a maximum time error limit between adjacent cellsites of no more than 500 nanoseconds.

To enable network operators to meet the time error requirement in a predictable fashion, the International Telecommunications Union is set to ratify the ITU-T G.8273.2 standard for stringent time error limits for network elements. By using equipment meeting this standard, network operator will be able to design networks that will predictably comply with the 500-nanosecond maximum time error between cellsites.

In this article, we look at the factors driving timing and synchronization requirements in LTE and LTE-Advanced networks and how the new G.8273.2 standard will help network operators in meeting those requirements.

Types of Synchronization

Telecom networks rely on two basic types of synchronization. These include:
Frequency synchronization
Time-of-day synchronization, which includes phase synchronization

Different types of LTE require different types of synchronization. Frequency division duplexed LTE (FDD-LTE), the technology that was used in some of the earliest LTE deployments and continues to be deployed today, uses paired spectrum. One spectrum band is used for upstream traffic and the other is used for downstream traffic. Frequency synchronization is important for this type of LTE, but time-of-day synchronization isn’t required.

Time-division duplexed LTE (TD-LTE) does not require paired spectrum, but instead separates upstream and downstream traffic by timeslot. This saves on spectrum licensing costs but also allows to more flexible allocate bandwidth flexibly between upstream and downstream direction, which could be valuable for video.  Time-of-day synchronization is critical for this type of LTE. Recently TD-LTE deployments have become more commonplace than they were initially and the technology is expected to be widely deployed.

LTE-Advanced (LTE-A) is an upgrade to either TD-LTE or FDD-LTE that delivers greater bandwidth. It works by pooling multiple frequency bands, and by enabling multiple base stations to simultaneously send data to a handset. Accordingly adjacent base stations or small cells have to be aligned with one another – a requirement that drives the need for time-of-day synchronization. A few carriers, such as SK Telecom, Optus, and Unitel, have already made LTE-A deployments and those numbers are expected to grow quickly moving forward.

Traditionally wireless networks have relied on global positioning system (GPS) equipment installed at cell towers to provide synchronization. GPS can provide both frequency synchronization and time-of-day synchronization. But that approach will be impractical as networks rely more and more heavily on femtocells and picocells to increase both network coverage (for example indoors) and capacity. These devices may not be mounted high enough to have a line of sight to GPS satellites – and even if they could, GPS capability would make these devices too costly.  There is also increasing concern about the susceptibility of GPS to jamming and spoofing, and countries outside of the US are reluctant to exclusively rely on the US-operated GPS satellite system for their timing needs.

IEEE 1588

A more cost-effective alternative to GPS is to deploy equipment meeting timing and synchronization standards created by the Institute of Electrical and Electronics Engineers (IEEE).

The IEEE 1588 standards define a synchronization protocol known as precision time protocol (PTP) that originally was created for the test and automation industry. IEEE 1588 uses sync packets that are time stamped by a master clock and which traverse the network until they get to an ordinary clock, which uses the time stamps to produce a physical clock signal.

The 2008 version of the 1588 standard, also known as 1588v2, defines how PTP can be used to support frequency and time-of-day synchronization. For frequency delivery this can be a unidirectional flow. For time-of-day synchronization, a two-way mechanism is required.

Equipment developers must look outside the 1588 standards for details of how synchronization should be implemented to meet the needs of specific industries. The ITU is responsible for creating those specifications for the telecom industry.

How the telecom industry should implement frequency synchronization is described in the ITU-T G.826x series of standards, which were ratified previously. The ITU-T G.8273.2 standard for time-of-day synchronization was developed later and is expected to be ratified next month (March 2014).
Included in ITU-T G.8273.2 are stringent requirements for time error. This is an important aspect of the standard because wireless networks can’t tolerate time error greater than 500 nanoseconds between adjacent cellsites.

ITU-T G.8273.2 specifies standards for two different classes of equipment. These include:
Class A- maximum time error of 50 ns
Class B- maximum time error of 20 ns

Both constant and dynamic time errors will contribute to the total time error of each network element, with both adding linearly after applying a 0.1Hz low-pass filter. Network operators that use equipment complying with the G.8273.2 standard for all of the elements underlying a network connection between two cell sites can simply add the maximum time error of all of the elements to determine if the connection will have an acceptable level of time error. Previously, network operators had no way of determining time error until after equipment was deployed in the network, and the operators need predictability in their network planning.

Conforming to the new standard will be especially important as network operators rely more heavily on heterogeneous networks, also known as HetNets, which rely on a mixture of fiber and microwave devices, including small cells and femtocells. Equipment underlying HetNets is likely to come from multiple vendors, complicating the process of devising a solution in the event that the path between adjacent cell sites has an unacceptable time error level.

What Network Operators Should Do Now

Some equipment manufacturers already have begun shipping equipment capable of supporting ITU-T G.8273.2, as G.8273.2-compliant components are already available. As network operators make equipment decisions for the HetNets they are just beginning to deploy, they should take care to look for G.8273.2-compliant products.

As for equipment already deployed in wireless networks, over 1 million base stations currently support 1588 for frequency synchronization and can be upgraded to support time-of-day synchronization with a software or firmware upgrade.

Some previously deployed switches and routers may support 1588, while others may not. While 1588 may be supported by most switches and routers deployed within the last few years, it is unlikely that they meet the new ITU profiles for Time and Phase delivery.  IEEE1588 Boundary or Transparent Clocks with distributed time stamping directly at the PHY level will be required to meet these new profiles, and only few routers and switches have this capability today.  Depending where in the network a switch or router is installed, network operators may be able to continue to use GPS to provide synchronization, gradually upgrading routers by using 1588-compliant line cards for all new line card installations and swapping out non-compliant line cards where appropriate.

Wireless network operators should check with small cell, femtocell and switch and router vendors about support for 1588v2 and G.8273.2 if they haven’t already.

About the Author

Martin Nuss joined Vitesse in November 2007 and is the vice president of technology and strategy and the chief technology officer at Vitesse Semiconductor. With more than 20 years of technical and management experience, Mr. Nuss is a Fellow of the Optical Society of America and a member of IEEE. Mr. Nuss holds a doctorate in applied physics from the Technical University in Munich, Germany. He can be reached at nuss@vitesse.com.

About Vitesse
Vitesse (Nasdaq: VTSS) designs a diverse portfolio of high-performance semiconductor solutions for Carrier and Enterprise networks worldwide. Vitesse products enable the fastest-growing network infrastructure markets including Mobile Access/IP Edge, Cloud Computing and SMB/SME Enterprise Networking. Visit www.vitesse.com or follow us on Twitter @VitesseSemi.

Deutsche Telekom Tests LTE Direct with Qualcomm

Deutsche Telekom is working with Qualcomm on the first LTE Direct operator trial in Germany.

LTE Direct is a new device-to-device proximity technology that enables discovering thousands of devices and their services in the proximity of ~500m.  The platform would be owned by the mobile operator.  It uses licensed spectrum, allowing mobile operators to employ it as a way to offer a range of differentiated applications and services to users. It relies on the LTE physical layer to provide a scalable and universal framework for discovery and connecting proximate peers. Qualcomm Research, along with other 3GPP participants are leading the standardization of this feature in R-12.

Qualcomm said LTE Direct will function in a privacy-sensitive and battery-efficient way, allowing the discovery to be “Always ON” and autonomous, without drastically affecting the device battery life. Qualcomm predicts that LTE Direct will be the basis of many new services from from advertising, to SNS, Gaming, Education and more.

"The LTE Direct trial will be an excellent opportunity for the application developer community to demonstrate a number of unique applications and services working on LTE Direct," stated Matt Grob, Qualcomm's Chief Technology Officer.

The trial with Deutsche Telekom will use prototype devices from Qualcomm, Samsung, and LTE Direct enabled base stations. Standardization of LTE Direct in a 3GPP Release 12 is expected to be completed at the end of this year.

http://www.qualcomm.com
http://www.telekom.com

Huawei and China Mobile Demo Virtualized EPC

Huawei and China Mobile jointly demonstrated a virtualized Evolved Packet Core (vEPC) and virtual IMS this week at Mobile World Congress (MWC) in Barcelona. Both solutions are a part of Huawei’s CloudEdge solution, which has four parts:

  • Mobile: Focused on continued LTE build outs, virtual EPC and simplification of Gi-LAN by introducing service chaining
  • Service: The introduction of MANO (Management and Orchestration)in NFV related to operation management, automation and network services orchestration. MANO avoids siloed point deployment of NFV, including integration and migration with existing backend OSS/BSS.
  • IP: Huawei’s SDN controller for IP RAN backhaul is designed to ease OPEX complexity through automation and simplified management of complex IP backhaul. IP and optical devices under the SDN controller improve traffic engineering and optimization for overall cost reduction and backhaul improvement
  • Home: Virtualized set-up box and virtual EPC to address the home network environment.


Huawei also noted that it is currently conducting more than 20 PoC (proof of concept) CloudEdge projects and is in trials with leading operators around the world, with a planned first commercial product in the third quarter of 2014.

http://www.huawei.com

SK Telecom to Offer Tracking Service via Mobile Sensors, Patterns

SK Telecom has developed a "Context Platform" that seeks to know more about the user by leveraging a smartphone's camera, sensors, GPS and Wi-Fi, along with usage patterns in calls, SMS, SNS, scheduling, and applications.  The carrier says it is using the data to offer a "Life Log" service to help its users automatically track their lives.

"Along with Big Data, Context Platform is an important pillar of the newly emerging field of ICT intelligence," said Park Jin-hyo, Senior Vice President and Head of Network Technology R&D Center at SK Telecom. "With Context Platform, smartphones will truly become an indispensable life partner for customers."

SK Telecom's "Context Platform" could, for instance, detect the user's movements while walking, automatically open a mapping application, guess his likely destination, make suggestions, develop a health profile, etc.

http://www.sktelecom.com

BTI Wireless Builds TD-FEMTOs for China Mobile with Radisys

BTI Wireless, which supplies TD-FEMTO end-to-end solutions providing 3G and 4G Small Cell and Gateway System products, has selected Radisys’ Trillium software for deployment of an advanced LTE-TDD solution for China Mobile.

Specifically, BTI Wireless will leverage Radisys’ Trillium TOTALeNodeB software and protocol stacks and commercial-off-the-shelf (COTS) ATCA platforms to provide dual-mode TD-SCDMA and LTE-TDD small cells and gateways,  achieving successful circuit switched (CS) fallback and a seamless 3G to 4G migration path for China Mobile.

BTI Wireless will begin LTE-TDD network trial deployments next quarter in the Chinese market, and will also deploy LTE-FDD (Frequency Division Duplex) in markets outside of China.

“This customer win signifies another key success for our solutions in the Chinese LTE-TDD market and further substantiates our position as a global leader in LTE,” said Todd Mersch, general manager, Software and Solutions, Radisys. “Not only do we supply award-winning small cell software, but our delivery of the gateway software allows our customers to extend to the core, providing a true one-stop, end-to-end LTE solution.”

http://www.radisys.com


DragonWave Intros 70-80 GHz EBand Radios

DragonWave introduced its Harmony Eband, a compact, lightweight radio that operates in the 70-80 GHz spectrum with low-energy consumption and designed for fronthaul, macro backhaul and small cell deployments.

The Harmony Eband delivers a complete, all-outdoor solution and delivers the industry’s first uncompressed CPRI transport mode that enables wireless fronthaul. The radio comes equipped with an integrated switch, multiple ports and a proprietary mechanical design for self-weatherization that simplifies installation and saves on deployment cost. Additional features include a reach comparable at 23-38 GHz, higher capacity and a lower OPEX expansion solution.

Performance is demonstrated by operation up to 64 QAM to achieve throughput of 2.6 Gbps full duplex in 500 MHz mode. Spectral efficiency is further enhanced by DragonWave’s Bandwidth Accelerator+, which delivers capacity of up to 4 Gbps. Additionally, Harmony Eband features the DragonWave Reach Extender, leveraging Waveform and Modulation Adaptivity (WMA) and MIMO to extend the radio’s reach and deliver 3-7 KM links with high availability.

“The Harmony Eband truly rounds out the DragonWave product portfolio and its addition allows operators a product choice addressing nearly every possible spectrum, while also providing long-term viability and easy redeployment options in evolving network environments,” said Greg Friesen, vice president, Product Management, DragonWave. “Because it meets the capacity and latency requirements required to support fronthaul, macro backhaul and small cell aggregation, and is LTE synchronization ready, we view the Harmony Eband as an extremely viable and cost effective transport option for today’s networks, with future-proof capabilities that will carry over to support tomorrow’s networks, as well.”

http://www.dragonwaveinc.com

TIM Brasil Deploys Juniper's SRX5600 for LTE Security

Telecom Italia Mobile Brasil (TIM) has deployed Juniper's SRX5600 and 5800 Series Services Gateway for improved performance, scalability and integrated security services across its new LTE network. Financial terms were not disclosed.

Juniper noted that its SRX5600 and 5800 support 450,000 connections per second, up to an industry record-breaking 100 million concurrent user sessions and 300 Gbps throughput. The SRX line cards provide TIM zero downtime performance upgrades by offering both in-service software and hardware upgrades reducing the need for planned downtime.

http://www.juniper.net

Saudi Telecom to Launch TDD LTE-A with Huawei

Saudi Telecom has succeeded Huawei to deploy TDD LTE-Advanced technology in its network.  network to the advanced 4th generation LTE-A network. Financial terms were not disclosed.

"Saudi Arabia is considered as the largest telecom market in the Middle East. Therefore, launching the first quad systems network in the world (GSM/ UMTS/ LTE TDD/ LTE FDD), and upgrading the network to the advanced 4th generation LTE-A, enhances the Internet service in the Kingdom significantly, and offers a new experience for the STC's customers in the field of mobile wireless broadband services," stated Dr. Khaled Albayari, Senior Deputy of STC Group for Technology & Operations.

http://www.huawei.com

Saudi Telecom Picks Ericsson's Evolved Packet Core

STC has selected Ericsson's evolved packet core (EPC) solution.

The deployment includes the Ericsson Blade System, MKVIII for SGSN-MME and Ericsson SSR 8020 for GGSN/EPG. The solution handles the growing demand for mobile broadband through common high-capacity multi-access platforms. The new core elements act as a common platform supporting 2G, 3G and 4G/LTE network technologies, providing additional capacity and throughput to cater for surging demand. Financial terms were not disclosed.

http://www.stc.com.sa
http://www.ericsson.com

See also