What is LIPA?

Local IP Access (LIPA) is the ability for an IP-enabled device to access a consumer’s home-based local area network as well as the broader Internet directly using the air interface of a femtocell, or Home NodeB (HNB). Using LIPA allows for greater performance, innovative services that mesh mobile and home networks, and the off-loading of traffic from the operator’s packet core network which is ultimately destined for the Internet.

 

Why LIPA?
As connected device (i.e., mobiles, laptop data cards, USB dongles, etc.) penetration increases globally, more and more users are using their mobile devices not just for voice but also for data services. Today’s high-speed mobile broadband access technologies—

including Wideband CDMA (WCDMA) and Long Term Evolution (LTE)—are ensuring that users have the dual benefits of high mobility and high speed data access. The ever-increasing content available online via email, social networking sites, blogs, RSS feeds, multimedia calls, streaming video and online music coupled with faster and higher capacity equipment driven by personal digital assistants (PDAs), smartphones and netbooks have led to a boom in the demand for Internet data access using high-speed mobile network infrastructure.

QoS Class Identifier (QCI)

The need for supporting a broader variety of applications requiring higher bandwidth and lower latency led 3GPP to alleviate the existing QoS principles with the introduction for EPS of a QoS Class Identifier (QCI).
LTE provides different QoS for a given application by putting it into the different bearer . each bearer has its own QCI (QoS Class Identifier) which introduce a particular service for a particular application. as far as I know 9 different QCIs have been defined in LTE based on priority,packet loss and delay.

 

Download more on LTE Basics and LTE Optimization

The QoS architecture in EPC enables a number of important capabilities for both operators and users:

VoIP support with IMS: QoS is a crucial element for providing LTE/IMS voice service.
Enhanced application performance:Applications such as gaming or video can operate more reliably.
More flexible business models:With flexible, policy-based charging control, operators and third-parties will be able to offer content in creative new ways. For example, an enhanced video stream to a user could be paid for by an advertiser.
Congestion control: In congestion situations, certain traffic flows (e.g., bulk transfers, abusive users) can be throttled down to provide a better user experience for others.

VoLTE + Wi-Fi = LTE Femto

This week, Kineto announced it now supports the GSMA’s VoLTE profile (IMS voice & SMS) in its Smart Wi-Fi client. Smartphones with the Smart Wi-Fi client will now be able to receive the mobile operator’s voice/SMS service (VoLTE) when attached to Wi-Fi.
I have always believed LTE and Wi-Fi were two sides of the same coin – both are high-speed, low-latency flat IP networks. LTE covers the macro/outdoor world, and Wi-Fi is by far the dominant in-building wireless technology. Marrying the two technologies into a seamless experience delivers a compelling experience for mobile subscribers.
In the move to LTE, mobile operators are adopting VoLTE, an IMS/SIP-based voice and SMS profile that replaces (replicates?) the existing circuit voice/SMS services used in GSM/UMTS networks.

Cyclic Delay Diversity

Cyclic Delay Diversity (CDD) is a simple approach to introduce spatial diversity to an Orthogonal Frequency Division Multiplexing (OFDM) based transmission scheme that itself has no built-in diversity. It also can be regarded as a Space-Time Code (STC).

But in contrast to that there is no additional effort in the receiver necessary, since the different codewords result in a changed channel impulse response in the receiver. They insert virtual echos and thus increase the frequency selectivity of the channel seen by the receiver. Cyclic Delay Diversity (CDD) is a diversity scheme used in OFDM-based telecommunication systems, transforming spatial diversity into frequency diversity avoiding intersymbol interference.

RSRP and RSRQ

In cellular networks, when a mobile moves from cell to cell and performs cell selection/reselection and handover, it has to measure the signal strength/quality of the neighbor cells. In LTE network, a UE measures two parameters on reference signal: RSRP (Reference Signal Received Power) and RSRQ (Reference Signal Received Quality).

RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth. RSRP is applicable in both RRC_idle and RRC_connected modes, while RSRQ is only applicable in RRC_connected mode. In the procedure of cell selection and cell reselection in idle mode, RSRP is used.

RSRQ is a C/I type of measurement and it indicates the quality of the received reference signal. It is defined as (N*RSRP)/(E-UTRA Carrier RSSI), where N makes sure the nominator and denominator are measured over the same frequency bandwidth.

The carrier RSSI (Receive Strength Signal Indicator) measures the average total received power observed only in OFDM symbols containing reference symbols for antenna port 0 (i.e., OFDM symbol 0 & 4 in a slot) in the measurement bandwidth over N resource blocks. The total received power of the carrier RSSI includes the power from co-channel serving & non-serving cells, adjacent channel interference, thermal noise, etc.

The RSRQ measurement provides additional information when RSRP is not sufficient to make a reliable handover or cell reselection decision. In the procedure of handover, the LTE specification provides the flexibility of using RSRP, RSRQ, or both.

What are the functionality of eNodeB?

E-UTRAN consists solely of the evolved Node B (eNB), which is responsible for all radio interface functionality.

eNB is the RAN node in the EPS architecture that is responsible for radio transmission to and reception from UEs in one or more cells.
The eNB is connected to EPC nodes by means of an S1 interface.The eNB is also connected to its neighbor eNBs by means of the
X2 interface. Some significant changes have been made to the eNB functional allocation compared to UTRAN. Most Rel-6 RNC
functionality has been moved to the E-UTRAN eNB. Below follows a description of the functionality provided by eNB.

Good PDF Document on LTE Functionality

UMTS/HSPA to LTE Migration

UMTS/HSPA to LTE Migration- A white Paper from Motorola Maximize the life and value of existing assets while achieving a true 4G network

Download Full lenth Paper from Here

Contents
Abstract
- A Dynamic Industry and Technology Evolution
- LTE Performance
- UMTS " LTE Network Architecture Evolution
- Determine the Business Case for LTE
- Subscriber Device Availability
- Deployment Considerations
- Seamlessly Connected Network
- Spectrum Implications
- Maximize Existing Assets
- UMTS to LTE Upgrade Strategy
- UMTS/LTE Architecture
- Functional Elements
- UMTS / HSPA RAN Site Upgrade to LTE
- Backhaul Site Upgrade to LTE
- LTE Voice
- LTE Video

Download Full lenth Paper from Here

What are the possible causes for an Access Failure in UMTS?

• Missing Neighbors
• Poor Coverage
• Pilot Pollution / Spillover
• Poor Cell Reselection
• Core Network Issues
• Non – availability of resources. Admission Control denies
• Hardware Issues
• Improper RACH Parameters
• External Interference

LTE The Vision Beyond 3G by Nortel
Ericsson Parameters to make Handover Easier