LTE Interview Question and Answer ( QA)

1. What is LTE?
2. What's the difference between 2G, 3G & LTE?
3. What's the benefit of LTE?
4. What's technology applied in LTE? (Both in UL and DL).
5. What is LTE Architecture?
6. What is the EUTRAN?
7. What is LTE Network Interface?
8. What is LTE Network Element?
9. What's the maximum Throughput we can achieve from LTE?
10. In the market, which type/category of UE is available now?
11. Do you have any experience in LTE dimensioning/planning and Drive-testing?
12. What is main frequency band for LTE?
13. In coverage planning, what are the most influence factors?
14. In 3G, RSCP and Ec/Io are used to determine in coverage planning. How's about in LTE? And why?
15. What are the range of SINR, RSRP, RSRQ, MCS and CQI values?
16. What is the typical cell range of LTE?
17. How do you understand RB and how does RB impact on Throughput?
18. What is the typical value of latency?
19. Do we still need Scraming code planning in LTE? If not, why?
20. Please explain me about eNodeB, MME and core network layout.
21. For capacity planning, do we still need Channel element (CE) dimensioning? If not, why?
22. Have you experience in Atoll and Momentun?
23. Have you experience in XCAL and Agilent NiXT?
24. Please explain me about QoS and Scheduling in LTE?
25. Pls. explain me about MIMO, SIMO and TxDiV configuration?
26. How's about those configuration and expected throughput?
27. What are the types of HO? If so, pls. explain me a bit of best cell HO and coverage HO?
28. What is ANR in LTE?
29. What is SON and how does work in LTE?
30. How does Timing advance(TA) works in LTE?


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Remote OMT





The Remote OMT Over IP is used to remotely perform OMT functionality from a TCP/IP network connecting BSCs.
The Remote OMT Over IP is mainly used for:
  • Getting detailed information about an RBS 2000 - The information can be used to remotely verify that an RBS 2000 is correctly configured and to perform preventive maintenance.
  • Fault localization of an RBS 2000 - Experts can use the Remote OMT Over IP to perform fault localization and to guide service personnel at site
  • Restart of a whole RBS 2000 or a part of an RBS 2000 - The same type of restart that is achieved by pushing a reset button in an RBS 2000 can be performed with the Remote OMT Over IP. This may be useful in situations with abnormal RBS behavior
  • Retrieve detailed information about an RBS 2000 remotely from a TCP/IP network connecting BSCs.
  • Perform fault localization of an RBS 2000 remotely from a TCP/IP network connecting BSCs. This means that it will be easier to prepare for a site visit and it will be possible for experts to remotely guide service personnel at site.
  • It is possible for a BSC to simultaneously handle four Remote OMT Over IP sessions. (Only one Remote OMT Over IP can simultaneously be connected to one specific RBS).
  • Perform "hardware reset" of an RBS 2000 remotely from a TCP/IP network connecting BSCs
  • The signalling is embedded in the LAPD signalling. A whole time slot does not have to be allocated for the OMT signalling as for Remote OMT.
  • It is much easier to establish a connection for the OMT signalling as it is not needed to setup a path in the transmission network. Just an access to the IP network connected to the BSC is needed.
  • The Remote OMT Over IP does not have to be equipped with any special hardware equipment as for Remote OMT which have to be equipped with a special communication board to emulate an E1/T1 transmission link.

The Remote OMT Over IP is an optional feature activated by the BSC.
The Remote OMT Over IP user is required to make an authentication by providing a password to be able to make a connection to the RBS. The password is defined by the BSC operator at the setup of the feature. It is also possible to define how long time the feature shall be activated and also to define the IP-address which the calling Remote OMT Over IP is supposed to have.

Benefits
Remote OMT Over IP makes it possible to:
Benefits with Remote OMT Over IP compared to Remote OMT:

what is Wimax

WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems are expected to deliver broadband access services to residential and enterprise customers in an economical way.
Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies (such as Cable Modems, DSL and T1/E1 links) to provide broadband access to customer premises.


More strictly, WiMAX is an industry trade organization formed by leading communications, component and equipment companies to promote and certify compatibility and interoperability of broadband wireless access equipment that conforms to the IEEE 802.16 and ETSI HIPERMAN standards.
WiMAX would operate similar to WiFi but at higher speeds over greater distances and for a greater number of users. WiMAX has the ability to provide service even in areas that are difficult for wired infrastructure to reach and the ability to overcome the physical limitations of traditional wired infrastructure.
WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz IEEE 802.16 specifications. WiMAX is to 802.16 as the WiFi Alliance is to 802.11.
WiMAX is:
·         Acronym for Worldwide Interoperability for Microwave Access.
·         Based on Wireless MAN technology.
·         A wireless technology optimized for the delivery of IP centric services over a wide area.
·         A scaleable wireless platform for constructing alternative and complementary broadband networks.
·         A certification that denotes interoperability of equipment built to the IEEE 802.16 or compatible standard. The IEEE 802.16 Working Group develops standards that address two types of usage models:
o    A fixed usage model (IEEE 802.16-2004).
o    A portable usage model (IEEE 802.16e).

What is 802.16a ?

WiMAX is such an easy term that people tend to use it for the 802.16 standards and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMAX Forum.
The 802.16a standard for 2-11 GHz is a wireless metropolitan area network (MAN) technology that will provide broadband wireless connectivity to Fixed, Portable and Nomadic devices.
It can be used to connect 802.11 hot spots to the Internet, provide campus connectivity, and provide a wireless alternative to cable and DSL for last mile broadband access.

WiMax Speed and Range:

WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless channel for both fixed and portable applications, depending on the particular technical configuration chosen, enough to support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity. WiMAX can support voice and video as well as Internet data.
WiMax will be to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas. It can also be used to connect WLAN hotspots to the Internet. WiMAX is also intended to provide broadband connectivity to mobile devices. It would not be as fast as in these fixed applications, but expectations are for about 15 Mbps capacity in a 3 km cell coverage area.
With WiMAX users could really cut free from today's Internet access arrangements and be able to go online at broadband speeds, almost wherever they like from within a MetroZone.
WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz, 2.5GHz, 3.5GHz, and 5.8GHz

Why WiMax ?

·         WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, WiFi and cellular backhaul, providing last-100 meter access from fibre to the curb and giving service providers another cost-effective option for supporting broadband services.
·         WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. >10 MHz) are desired using existing infrastructure keeping costs down while delivering the bandwidth needed to support a full range of high-value multimedia services.
·         WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding their existing infrastructure investments because it has the ability to seamlessly interoperate across various network types.
·         WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay-sensitive voice-over-IP (VoIP) to real-time streaming video and non-real-time downloads, ensuring that subscribers obtain the performance they expect for all types of communications.
·         WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-area third-generation (3G) mobile and wireless and wireline networks allowing it to become part of a seamless anytime, anywhere broadband access solution.
Ultimately, WiMAX is intended to serve as the next step in the evolution of 3G mobile phones, via a potential combination of WiMAX and CDMA standards called 4G.

WiMAX Goals:

A standard by itself is not enough to enable mass adoption. WiMAX has stepped forward to help solve barriers to adoption, such as interoperability and cost of deployment. WiMAX will help ignite the wireless MAN industry by defining and conducting interoperability testing and labeling vendor systems with a "WiMAX Certified™" label once testing has been completed successfully.


What is Wi-Fi


Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the Institute of Electrical and Electronics Engineers' (IEEE) 802.11 standards Wi-Fi has become the defacto standard for last feet broadband connectivity in homes, offices, and public hotspot locations. systems can typically provide a coverage range of only about 1,000 feet from the access point.



Wi-Fi offers remarkably higher peak data rates than do 3G systems, primarily since it operates over a larger 20MHz bandwidth, but Wi-Fi systems are not designed to support high-speed mobility.
One significant advantage of Wi-Fi over WiMAX and 3G is the wide availability of terminal devices. A vast majority of laptops shipped today have a built-in Wi-Fi interface. Wi-Fi interfaces are now also being built into a variety of devices, including personal data assistants (PDAs), cordless phones, cellular phones, cameras, and media players.
The WiFi standards define a fixed channel bandwidth of 25 MHz for 802.11b and 20 MHz for either 802.11a or g networks. 
All Wi-Fi networks are contention-based TDD systems, where the access point and the mobile stations all vie for use of the same channel. Because of the shared media operation, all Wi-Fi networks are half duplex.
There are equipment vendors who market Wi-Fi mesh configurations, but those implementations incorporate technologies that are not defined in the standards.

Range:
Wi-Fi networks have limited range. A typical wireless access point using 802.11b or 802.11g with a stock antenna might have a range of 35 m (115 ft) indoors and 100 m (330 ft) outdoors



LTE Advanced Key Features

LTE refers to the advanced version of LTE that is being developed by 3GPP to meet or exceed the requirements of the International Telecommunication Union (ITU) for a true fourth generation radio-communication standard known as IMT-Advanced. 4G LTE, whose project name is LTE-Advanced, is being specified initially in Release 10 of the 3GPP standard, with a functional freeze targeted for March 2011.
Following is the Key Features for LTE Advanced:
§  Peak data rates: Downlink – 1 Gbps and  Uplink – 500 Mbps.
§  Spectrum efficiency: 3 times greater than LTE.
§  Peak spectrum efficiency: Downlink – 30 bps/Hz; Uplink – 15 bps/Hz.
§  Spectrum use: the ability to support scalable bandwidth use and spectrum aggregation where non-contiguous spectrum needs to be used.
§  Latency: from Idle to Connected in less than 50 ms and then shorter than 5 ms one way for individual packet transmission.
§  Cell edge user throughput to be twice that of LTE.
§  Average user throughput to be 3 times that of LTE.
§  Mobility: Same as that in LTE
§  Carrier Aggregation
§  Higher order MIMO
§  Relay nodes and Heterogeneous networks
§  Enhanced Inter-Cell Interference Coordination
§  Coordinated Multipoint (CoMP) Transmission – Formalized in 3GPP Release 11


Liquid Radio

Liquid Radio
Liquid Radio - Making radio networks active, adaptive and aware





Liquid Radio architecture shares resources such as antenna information across a broad area of the network, as well as balances traffic evenly over different bandwidths. It allows radio coverage and capacity to flow to wherever users need it most. Liquid Radio also enables operators to seamlessly integrate 3GPP radio access with Wi-Fi to use unlicensed spectrum.  Liquid Radio improves network efficiency by boosting capacity, balancing loads, enhancing QoS, raising uplink capacity for smartphones, and identifying and avoiding smartphone signaling. It also adds small cell capacity and unifies heterogeneous networks, as well as implementing award-winning self-organizing network (SON) functions to simplify network operations. High energy efficiency is achieved by low power consumption, integration of Rf to the antenna, minimized Rf losses and by an adaptive and cognitive radio network that can proactively align the ‘active’ cells with user demand to save energy.

Nokia Siemens Networks has also announced its innovative Flexi Multiradio Antenna System as part of the Liquid Radio architecture. Nokia Siemens Networks Liquid Radio adapts the capacity and coverage of your networks to match fluctuations in user demand. It maximizes network performance and minimizes operating costs by automating operations. It includes built on Software Suites, Single RAN Active Antenna Systems, Baseband Pooling and Unified and SON-enabled Heterogeneous Networks.

Nokia Siemens Networks Liquid Radio Software Suites
>  Liquid Radio LTE Software Suite
>  Liquid Radio WCDMA Software Suite
>  Liquid Radio GSM Software Suite

Single RAN Active Antenna Systems
Baseband Pooling Unified and SON-enabled Heterogeneous Networks





Active Antenna system (AAS)

An active antenna is an antenna that contains active electronic components.remote radio head (RRH) or antenna-integrated radio designs place the Rf module next to the passive antenna to reduce cable losses

Active Antenna system is developed by Nokia Siemens Network (NSN) to reduce network cost and increase network efficiency. It’s a smart antenna and beam is driven by software.

Active Antenna does not need to be merely passive elements. With intelligent integration, active antenna technology transforms traditional antenna to contribute to base station efficiency. This enables operators to significantly increase the capacity and coverage targets set for their network.
Active Antennas are highly flexible and can meet the needs of many scenarios. They also support rising feature complexity including higher-order MIMO and receiver diversity, while retaining a simple and compact form factor.
§  Carrier-specific tilting
§  System-specific tilting
§  Multi-operator network sharing
§  Boosting performance with SON
§  Lower overall site costs
§  Improved network availability
§  Higher energy efficiency and RF performance
§  Reduced network evolution costs



The benefits to be gained include boosted capacity and coverage, higher energy efficiency, lower site rental fees, lower wind loading and reduced investments as new radio technologies come on line and additional spectrum bands become available. As a result,
active antenna systems enable operators to not only cut site costs substantially, but to also more cost effectively meet the dynamic demands of their mobile customers.

It is clear that active antenna systems will bring about a step-change in the evolution of radio networks. Leading the field is the Nokia Siemens Networks Flexi Multiradio Antenna System, which is a vital part of Liquid Net. This radical new architecture helps operators to cost-effectively address unpredictable demand by creating networks that adapt instantly to changing customer needs, using existing capital investments more efficiently and generating entirely new revenue opportunities. It does this by unleashing frozen network capacity into a reservoir of resources that can flow to fulfill demand, wherever and whenever broadband is used.
AAS BENEFITS
The benefits of active antenna architecture over RRH based site architecture are many. First, there is a potential to significantly reduce the site footprint. Second, the distribution of radio functions within the antenna results in built-in redundancy and improved thermal performance, which can result in higher system availability (lower failure rates). Third, distributed transceivers can support a host of advanced electronic beam-tilt features that can enable improvements in network capacity and coverage; hence, it has the potential to lower capital and operational costs. Each of these features shall now be described in the following sections.

WCMDA Paging

Paging process in WCMDA or HSDPA system is called WCMDA Paging. The Paging Channel (PCH) is a downlink transport channel. The PCH is always transmitted over the entire cell. The transmission of the PCH is associated with the transmission of physical-layer generated Paging Indicators, to support efficient sleep-mode procedures.

Paging Channel selection
System information Block Type 5 (SIB 5) defines common channels to be employed in Idle mode. The UE may use Discontinuous Reception (DRX) in idle mode in order to reduce power consumption. When DRX is used the UE needs only to monitor one Page Indicator, PI, in one Paging Occasion per DRX cycle.
The Paging Indicator Channel (PICH) is a fixed rate (SF=256) physical channel used to carry the paging indicators.
Paging Procedure:

Basically two types of Paging Procedures in WCMDA Paging.

1) Idle Mode Paging
2) Dedicated Mode Paging
Idle mode paging is used when UE is in idle mode so we can say UE is in Cell PCH or URA PCH.PAGING TYPE 1 message on an appropriate paging occasion on the PCCH.

UE dedicated paging procedure is used to transmit dedicated paging information to one UE in connected mode in CELL_DCH or CELL_FACH state. PAGING TYPE 2 message on the DCCH using AM RLC.

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