LTE Band Landscape

Today, LTE spectrum is extremely fragmented, with over twenty five defined 3GPP FDD bands and over ten TDD bands, leaving a wide range of bands that LTE chipsets need to be able to provide coverage for. This fragmentation has the potential to both significantly increase total cost of ownership for operators as well as negatively impact user experience.

Already today, numerous countries around the world, including the U.S., Europe and China, operate LTE spectrum across both FDD and TDD bands. Additionally, as LTE continues its global deployment, end-users will want the ability to use the same device at home and on the road without incurring roaming expenses, whether they are in a TDD region or FDD region, making smooth handover capabilities a baseline requirement for any device they may consider purchasing. While this demand will require manufacturers to ramp up efforts on building "Handover-Ready" devices, as of today, there are very few field proven devices that have the inherent capability of operating on both duplexing technologies, and there are even less that have the capability of providing consumers with real time HO capabilities.

TDD/FDD-LTE Handover Scenarios

There are various scenarios in which the ability to handover between TDD-LTE and FDD-LTE is required. We will quickly outline a few of these scenarios below:

When traveling between different countries, operators are likely to deploy different networks (TDD and FDD) with a different PLMN, necessitating a device that can support both networksTraveling to a different country does not automatically mean that you will be working with a different operator, however operators (even those with cross-border services), use a different PLMN, meaning that you most likely will be on a different network. Even while traveling domestically within a country, if that country has numerous operators that work over both TDD and FDD-LTE networks, you will be forced to pay roaming charges when transitioning from one network to the other. Additionally, there are also scenarios in which operators deploy two different networks in the same geographical regionHandover capabilities are also very important in situations of co-site and hotspot deployments, in which the operator installs two networks (the same PLMN) in the same region - one used for nation-wide coverage and the other as a hotspot. Additionally, in cases of Macro and HeNB operations, in which the operator deploys one network (the same PLMN) in the same region (where the TDD-LTE duplexing technology is used for indoor-HeNB operation), handover capabilities will allow end-users to seamlessly transfer between the different networks

As outlined above, in the numerous instances in which customers must move between different duplexing technologies, handover capable devices maintain uninterrupted coverage while also giving customers the ability to move between the networks without incurring steep roaming fees.

While LTE technology is becoming the de-facto standard for mobile operators around the world, there are numerous technological challenges that still need to be overcome for it to truly become a global technology. One of the most challenging hurdles presented by LTE is that it supports two different duplexing technologies, TDD and FDD, which can coexist in the same geographic region. Therefore, customer devices must be capable of offering dynamic, real-time handover between the two duplexing technologies. In order to fully leverage the continuous and uninterrupted experience that LTE can provide, mobile operators and device manufacturers should build devices that have the ability to seamlessly transition (or handover) between TDD and FDD without experiencing a drop-off in service. Without this capability, effective spectrum utilization and true global roaming will not be possible.In order to achieve such capabilities in the end device, it is required that the core communications engine - the LTE modem - supports the seamless handover between FDD and TDD-LTE. In other words, devices must be equipped with a smart chipset that has built-in handover capabilities, eliminating the need for software reload or device reset when transitioning between the two duplexing technologies.This paper will examine the industry's first such chipset, produced by Altair Semiconductor, as well as explore some of the underlying technology and challenges that it helps overcome.

Altair Semiconductor6 Ha’harash street, Hod Hashron 45240, Israel, +972-74-780-0800 www.altair-semi.com

Altair's Chipset

Altair is the first chipset manufacturer to achieve live TDD/FDD LTE handover in commercially available devices. The chipset supports all 3GPP Release 9 bands and is commercially used in many LTE markets around the world. By allowing the two LTE duplex modes to operate interchangeably on the same device, Altair's chipset enables true global LTE roaming, an achievement with significant market implications. This achievement is made possible due

to Altair's unique technology package, including the following:A single chipset for both duplexing technologiesSingle L1 and protocol stack software running both technologies. Unlike other chip companies that initially focused on a single duplexing technology and today are forced to port their solution to support the other duplexing technology, Altair's solution was designed from day-one for optimized interworking between FDD and TDD modes and has therefore gained more than 3 years of actual field experience over such companies in mixed-duplex applicationsFull handover capabilities compliance (i.e. different trigger-based handover such as A3, A5 triggers, blind FDD/TDD handover using A2)Low latency (less than 30msec for handover C-plane latency)

Altair has been cooperating with multiple Tier1 eNBs and test equipment vendors performing FDD/TDD handover interoperability testing and field trials for over a year. All major test cases have already been verified, including:

RRC Connection Release with Redirection between TDD and FDDIdle mode inter-band cell reselection (from TDD to FDD & FDD to TDD) TDD to FDD and FDD to TDD Inter-Frequency handover (X2 & S1) with traffic

Different triggers-based handover Blind FDD/TDD handover

FDD/TDD inter BW handover (e.g. 20MHz ' 10MHz ' 5MHz)Test cases passed with parameters (e.g. latency) same as observed for intra-duplexing HO (~30msec for HO C-plane latency)

To summarize, Altair's chipset and software solution supports: UE RRC Connection Release with Redirection procedure with target eNB measurementFull support for handover between FDD and TDD LTE if UE capabilities are identicalFull support for handover between FDD and TDD LTE if UE capabilities are different

Below, we will provide a number of examples of the field-proven handover capabilities of the Altair chipset.

Altair-Ericsson

In June 2012, Ericsson performed live bidirectional LTE FDD/TDD handover in China Mobile Hong Kong's network on a commercial Altair chipset, providing a seamless end-user experience in a converged LTE FDD/TDD network. This was the first public LTE FDD/TDD handover performed on a CMCC live network.

China Mobile Hong Kong's LTE network is an FDD-LTE network built by Ericsson. The handover capabilities provided by Ericsson and Altair will allow China Mobile Hong Kong to provide service and devices that can be operational both on its FDD-LTE network and on China Mobile's TDD-LTE network.

Altair-Rohde & Schwarz

Also in June 2012, Altair and Rohde & Schwarz, the leading global manufacturer of wireless communications and EMC test and measurement equipment performed the world's first live LTE handover demonstration. The demonstration setup is described as follows:

RF

Laptop

Altair Semiconductor6 Ha’harash street, Hod Hashron 45240, Israel, +972-74-780-0800 www.altair-semi.com

R&S CMW Protocol Tester

Altair Semiconductor6 Ha’harash street, Hod Hashron 45240, Israel, +972-74-780-0800 www.altair-semi.com

1 UE is in FDD-LTE, B7 at 10MHz bandwidth. It is camped at cell #1 and channel conditions are good2 Channel conditions deteriorate and event A2 (serving cell RSRP is below TH) is reported.3 As a result the UE is requested to measure different frequency and a different cell (B40, 20MHz bandwidth) is

reported by event A3 (relative RSRP report)4 Due to channel conditions HO command is given resulting with RACH transmission to the target cell and RACH

response (RAR) 5 Real time HO procedure from FDD to TDD band (with different bandwidth) occurs successfully with < 40msec

latency allowing session continuity 6 New serving cell with good channel conditions is maintained

Message log in R&S CMW500 shows the handover from between TDD B40 and FDD B7:

Conclusion

Native support of both TDD-LTE and FDD-LTE duplexing technologies is a challenging technological obstacle and the ability to perform real-time handover between different duplexing technologies is needed for enabling worldwide LTE usage. Complicating this scenario is the dearth of chipset manufacturers actively working to overcome this challenge. Devices with an Altair chipset can inherently utilize both duplexing technologies and perform dynamic handover using the same software and the same chipset. This capability is field proven and has been tested against numerous infrastructure vendors. The chipset is available in commercial devices in numerous global markets.