Blogs

I am on vacation in Ahmedabad, India at my parents place. Having arrived last night and up at 3:30 am, I am dealing with jet-lag - and what better way to recover from it than blog about LTE! My attempt at humor for this blog post. The LTE air interface does not define any Dedicated Physical Channels either in the downlink (DL) or the uplink (UL). This has some significant implications on how the UE exchanges information with the eNodeB. I would like to explore this idea from the perspective of the...

Bostonians who rely on telephone and cable TV companies for their high-speed Internet service will soon have a third option. Sometime next month, cellphone carrier Sprint Nextel Corp. will launch the region's first 4G wireless data service, designed to deliver broadband speeds far faster than today's 3G services. The new service, already available in about 50 US cities, can bring the Internet to desktop and laptop computers as well as Sprint's smartphones. "We should launch sometime...

Samsung Electronics Co. Ltd. (Korea: SEC) wants to increase its LTE-on-Android talent pool as it develops pre-4G devices for a US launch. The firm is advertising for an LTE RIL Engineer to work closely with its other Android product development engineers. A radio interface layer (RIL) engineer would be working on connecting the Android OS with the LTE radio in the phone. The location of the position -- in Bridgewater, N.J. -- is also interesting. This means that the right candidate could also work...

During the last few weeks I have been on the road with Ramki (one of the founders of Award Solutions) and this blog is an outcome of one of the many interesting LTE related discussions we have had - as part of our prep-work and research for one of our newer courses on LTE RAN Signaling and Operations. I am hoping to add more related blogs in the future. For now ... In LTE, when a UE wants to communicate with an eNodeB (cell), one of the first things it has to do is get its timing adjusted using PRACH...

LTE system information is one of the key aspects of the air interface. It consists of the Master Information Block (MIB) and a number of System Information Blocks (SIBs). The MIB is broadcast on the Physical Broadcast Channel (PBCH), while SIBs are sent on the Physical Downlink Shared Channel (PDSCH) through Radio Resource Control (RRC) messages. SIB1 is carried by "SystemInformationBlockType 1" message. SIB2 and other SIBs are carried by "SystemInformation (SI)" message. An SI...

By Dr. Nishith Tripathi A Self-Organizing Network (SON) in LTE (Long Term Evolution) is a network that automates various tasks related to network planning, configuration, and optimization. Such automation reduces the amount of "manual" work, thereby reducing the operating expenditure (OpEx) for a service operator. The specific algorithms that implement the SON functionality are not standardized and are product differentiators for SON vendors. We will briefly summarize below the SON architecture...

By Dr. Nishith D. Tripathi While initial commercial deployments have focused on FDD (Frequency Division Duplex) version of LTE (Long Term Evolution), interest in the TDD (Time Division Duplex) version of LTE has been rising. The TDD-based LTE is also known as TD-LTE (Time Division- LTE). We will discuss TD-LTE from the eyes of LTE FDD; the reader is assumed to be familiar with LTE FDD. First and foremost, TD-LTE shares the same channel bandwidth between the uplink (UL) and the downlink (DL). As an...

Long Term Evolution (LTE) networks are now just months away from going live in the USA, so let's run down what you can expect in the way of this proto-4G technology in the coming year. MetroPCS MetroPCS Inc. (NYSE: PCS) has previously claimed that it will have "the first LTE wireless network featuring smartphones" in the US. The operator plans to launch in the "second half of this year." It hopes to have a smartphone that supports both CDMA and LTE ready for the network. So...

Nokia Siemens Networks (NSN), a 50-50 joint venture between Nokia Corp. ( NOK - Analyst Report ) and Siemens AG ( SI - Analyst Report ), won an eight year contract from LightSquared. The deal is worth more than $7 billion. This is closely followed by NSN's announcement just a day before to buy Motorola Inc.'s ( MOT - Analyst Report ) network-equipment business unit for $1.2 billion in cash. As per the terms of the contact, Nokia Siemens will install and maintain a new U.S. 4G LTE mobile broadband...

So far in this ongoing series comparing 1xEV-DO with LTE, I've covered initial system acquisition and the random access process. Although the specific details obviously differ, 1xEV-DO and LTE have some remarkable similarities in these functions. The next step in setting up a call is the actual message exchange between the mobile device and the network. This is where resources are allocated and the radio link is configured for the particular service being requested; this is also where 1xEV-DO...

Yes. There are a number of proposals for LTE voice. They include Circuit Switched (CS) Fallback, Single Radio Voice Call Continuity (SRVCC), and the IP Multimedia Subsystem (IMS). The key stage 2 specs that discuss these topics are 23.272 for CS Fallback, 23.207 for SRVCC, and 23.228 for IMS. A video discussing these options can be found at http://www.lteuniversity.com/media/p/7736.aspx.

LTE provides the following methods to achieve above goals: 1. Transmit Diversity : This method is utilized in the downlink of LTE using 2 or 4 transmit antenna at the eNB. The receiver (UE) may have 1 or more receive antenna. Here, similar modulation symbols are transmitted to improve the signal quality (SINR). Figure 2. SFBC Transmit Diversity in LTE This method does not require any feedback information from the receiver and is effective when the receiver is in a low SINR radio environment. Transmit...

In my previous blog, I compared how 1xEV-DO and LTE devices perform an initial system acquisition. Now I'll continue with the next step in setting up a data call, random access. In virtually every mobile wireless system, mobiles attempting to get on the system have to overcome a Catch-22: they need a radio channel in order to request a radio channel. The usual solution to this is to define a common, or shared, random access channel, which allows devices to transmit their initial messages without...

Hello All, I had a question recently about different types of mobility that I thought might be of interest. The question was about using SIP mobility instead of GTP or MIP in LTE. This is a good question. On the surface both are solving mobility issues so why have different solutions. The problem is that SIP mobility and MIP/GTP are really trying to solve different problems. MIP (or Mobile IP) and GTP (or GPRS Tunneling Protocol) are trying to solve geographical mobility. As a mobile moves through...

LTE (Long Term Evolution) has been designed from the very beginning to provide a natural evolution path for GSM/GPRS and UMTS networks. As a consequence, someone knowledgeable about UMTS will find many aspects of LTE to be familiar. But how does someone used to the unique design of a 1xEV-DO network learn about how LTE works? Earlier blogs and white papers have discussed the different terms used in 1xEV-DO and LTE networks; let me put those into context now, comparing key LTE network operations with...

4G World is the first and only conference and expo covering the entire ecosystem of next-generation technologies that enable the mobile Internet revolution including mobile network infrastructure, advanced devices, applications and content. 4G World delivers a world-class comprehensive four-day conference program that highlights the rapidly evolving interdependencies between operator business models, mobile network technology and architecture, and mobile Internet applications and services. Award...

In my previous blog I had motivated the idea behind the Registered State/Deregistered State and the Connected Mode/Idle Mode. I would like to continue to build on those ideas and briefly talk about five key Identifiers assigned to the UE by different entities during the UEs lifetime. This is not a comprehensive list of all the identifiers but their discussion broadly covers the end to end data connectivity concepts in LTE. The IMSI (International Mobile Subscriber Identity) and IMEI (International...

How many RATs (Radio Access Technologies) can you name? Lets see, there is GSM with 4 billion subscribers and then there is W-CDMA with its released flavors and evolutionary cousin LTE of course, a few still clinch on to their efficient 1xEVDO and its peculiar flavors, then we have the IEEE family from 802.11s and the newly launched mobile versions of those, i.e. WiM... (forbidden word in my blogs) , there are Satellite based RATs, and a few RATs facing the skies mainly aimed at commercial airliners...

“Always On” is a term that has caught on in the industry in the last few years. From the perspective of wireless data access it simply refers to the user device “always being on an IP network”. Why do I call it “The Holy Grail”? Previous generations (2G and 3G) of cellular data technologies have provided this experience of “Always On” to the mobile device but have left it largely to the hosts involved in the end to end connectivity. The hosts periodically...

As I think about mobility in LTE, I always go back to making comparisons with UMTS. I thought t might be good to do a comparison chart of the two. Below is a list of the key mobility terms/concepts and their equivalent terms in UMTS and LTE. Let me know what you think of this and if you have any questions/comments. Thanks, Chris Mobility Concept UMTS Concept LTE Concept Paging Zone Location Area, Routing Area, UTRAN Registration Area Tracking Area Types of Handover Soft, Softer, and Hard Hard Only...

While sitting in a colleague’s class this week we were discussing the UMTS measurement event types. I thought it might be good to do a comparison of UMTS’s measurement events with the measurement events in LTE. There are a couple of key differences between the two. The first is that UMTS supports a soft handover and LTE does not. That is important in looking at this comparison as there is no active set in LTE. The second difference is that LTE does not highlight the differences between...

For those who are too picky on the definition of "true 4G," hold your breath...4G version of LTE is taking shape as LTE-Advanced! LTE-Advanced is a Release 10 feature of 3GPP. Recall that Release 8 defined LTE. Release 9 makes some enhancements to LTE such as support for emergency calls using IMS. We'll summarize below motivating factors behind LTE-Advanced and briefly introduce main features of LTE-Advanced. ITU (International Telecommunication Union) has defined requirements for IMT...

LTE defines an optional sounding reference signal (SRS) in the UL. What is it for? UL channel quality, timing advance, and more. SRS is transmitted by the UE using a known sequence, similar to UL demodulation reference signal (DM RS), so the eNB can use it to estimate the UL channel quality. You may have a question: UL DM RS is already there and the eNB can decode the UL information with its assistance, what's special about SRS? Well, UL DM RS is transmitted together with the UL data and both...

Award Solutions' Senior Consultant John McKeague will be speaking at the pre-conference workshop LTE Essentials at the LTE Forum on Tuesday, April 27, 2010 in Stockholm, Sweden. Join HanseCom Media and Communications and LTE Forum 2010 at this one-day workshop, which provides a comprehensive high-level view of LTE and is intended for those in sales, marketing, product line management, and executives who need to understand LTE and its place in the 4G wireless landscape. The LTE Essentials workshop...

Hello All, Sorry for my lack of blogging lately. Projects can be tough. With the apologies out of the way, I had a colleague ask a couple of questions recently and I thought it would be good to share the answers with LTE-U. His main question was about mobility. Mobility in LTE can be quite tricky. The main point of his question was about the frequency band size. In LTE there is a scalable OFDM channel. The bandwidth can vary from 1.4 MHz to 20 MHz. There are also a number of frequency bands that...