Did you set your sights on telecommunication filed? Do you want to work as professional at a high standard organization? Wisdom jobs let you make decisions that benefit your long-life career. LTE or Long Term Evolution is defined as a base for high-speed wireless communications for data terminals and mobile devices that are based on the GSM, CDMA/WCDMA, UMTS/HSPA, and EDGE technologies. By selecting LTE job as your career, you can surpass your limitations. LTE jobs require excellent C programming skills, knowledge of digital communications and RF technologies, and RF testing tools. To gain further knowledge and to get impeccable scores on the interview, access LTE jobs interview questions and answers page designed by Wisdomjobs.com experts. To gather further information on recently posted jobs, visit our jobs portal.
Answer :
LTEi (Long Term Evolution) is initiated by 3GPPi to improve the mobile phone standard to cope with future technology evolutions and needs.
Question 2. What Is Goal Of Lte?
Answer :
The goals for LTE include improving spectral efficiency, lowering costs, improving services, making use of new spectrum and reformed spectrum opportunities, and better integration with other open standards.
Question 3. What Speed Lte Offers?
Answer :
LTE provides downlink peak rates of at least 100Mbit/s, 50 Mbit/s in the uplink and RAN (Radio Access Network) round-trip times of less than 10 ms.
Question 4. What Is Lte Advanced?
Answer :
LTE standards are in matured state now with release 8 frozen. While LTE Advanced is still under works. Often the LTE standard is seen as 4G standard which is not true. 3.9G is more acceptable for LTE. So why it is not 4G? Answer is quite simple - LTE does not fulfill all requirements of ITU 4G definition.
Brief History of LTE Advanced: The ITU has introduced the term IMT Advanced to identify mobile systems whose capabilities go beyond those of IMT 2000. The IMT Advanced systems shall provide best-in-class performance attributes such as peak and sustained data rates and corresponding spectral efficiencies, capacity, latency, overall network complexity and quality-of-service management. The new capabilities of these IMT-Advanced systems are envisaged to handle a wide range of supported data rates with target peak data rates of up to approximately 100 Mbit/s for high mobility and up to approximately 1 Gbit/s for low mobility.
Question 5. What Is Lte Architecture?
Answer :
The evolved architecture comprises E-UTRAN (Evolved UTRAN) on the access side and EPC (Evolved Packet Core) on the core side.
Answer :
The E-UTRAN (Evolved UTRAN) consists of eNBs, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of the X2 interface. The eNBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) by means of the S1-MME and to the Serving Gateway (S-GW) by means of the S1-U.
Question 7. What Are Lte Interfaces?
Answer :
The following are LTE Interfaces : (Ref: TS 23.401 v 841)
Question 8. What Are Lte Network Elements?
Answer :
eNB : eNB interfaces with the UE and hosts the PHYsical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers. It also hosts Radio Resource Control (RRC) functionality corresponding to the control plane. It performs many functions including radio resource management, admission control, scheduling, enforcement of negotiated UL QoS, cell information broadcast, ciphering/deciphering of user and control plane data, and compression/decompression of DL/UL user plane packet headers.
Mobility Management Entity : manages and stores UE context (for idle state: UE/user identities, UE mobility state, user security parameters). It generates temporary identities and allocates them to UEs. It checks the authorization whether the UE may camp on the TA or on the PLMN. It also authenticates the user.
Serving Gateway : The SGW routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and PDN GW).
Packet Data Network Gateway: The PDN GW provides connectivity to the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PDN GW for accessing multiple PDNs. The PDN GW performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening.
Question 9. What Are Lte Protocols & Specifications?
Answer :
In LTE architecture, core network includes Mobility Management Entity (MME), Serving Gateway (SGW), Packet Data Network Gateway (PDN GW) where as E-UTRAN has E-UTRAN NodeB (eNB).
Protocol links are as below
Answer :
VoLGA stands for "Voice over LTE via Generic Access". The VoLGA service resembles the 3GPP Generic Access Network (GAN). GAN provides a controller node - the GAN controller (GANC) - inserted between the IP access network (i.e., the EPS) and the 3GPP core network.
The GAN provides an overlay access between the terminal and the CS core without requiring specific enhancements or support in the network it traverses. This provides a terminal with a 'virtual' connection to the core network already deployed by an operator. The terminal and network thus reuse most of the existing mechanisms, deployment and operational aspects.
Question 11. What Is Cs Fallback In Lte?
Answer :
LTE technology supports packet based services only, however 3GPP does specifies fallback for circuit switched services as well. To achieve this LTE architecture and network nodes require additional functionality, this blog is an attempt to provide overview for same.
In LTE architecture, the circuit switched (CS) fallback in EPS enables the provisioning of voice and traditional CS-domain services (e.g. CS UDI video/ SMS/ LCS/ USSD). To provide these services LTE reuses CS infrastructure when the UE is served by E UTRAN.
Question 12. How Does Lte Security Works?
Answer :
The following are some of the principles of 3GPP E-UTRAN security based on 3GPP Release 8 specifications:
Question 13. What Is Ip Multimedia Subsystem (ims)?
Answer :
The 3GPP IP Multimedia Subsystem (IMS) technology provides an architectural framework for delivering IP based multimedia services. IMS enables telecom service providers to offer a new generation of rich multimedia services across both circuit switched and packet switched networks. IMS offers access to IP based services independent of the access network e.g. wireless access (GPRS, 3GPP’s UMTS, LTE, 3GPP2’s CDMA2000) and fixed networks (TISPAN’s NGN)
IMS defines a architecture of logical elements using SIP for call signaling between network elements and Provides a layered approach with defined service, control, and transport planes. Some of IMS high level requirements are noted below:
The application plane provides an infrastructure for the provision and management of services, subscriber configuration and identity management and defines standard interfaces to common functionality.
The IMS control plane handles the call related signaling and controls transport plane. Major element of control plane is the Call Session Control Function (CSCF) , which comprises Proxy-CSCF (P-CSCF), Interrogating-CSCF (I-CSCF) and Serving-CSCF (S-CSCF). The CSCF (Call/Session Control Function) is essentially a SIP server.
The IMS transport plane provides a core IP network with access from subscriber device over wireless or wireline networks.
Question 14. How Does Measurements Work In Lte?
Answer :
In LTE E-UTRAN measurements to be performed by a UE for mobility are classified as below
Question 15. What Is Automatic Neighbour Relation?
Answer :
According to 3GPP specifications, the purpose of the Automatic Neighbour Relation (ANR) functionality is to relieve the operator from the burden of manually managing Neighbor Relations (NRs). This feature would operators effort to provision.
Question 16. How Does Intra E-utran Handover Is Performed?
Answer :
Intra E-UTRAN Handover is used to hand over a UE from a source eNodeB to a target eNodeB using X2 when the MME is unchanged. In the scenario described here Serving GW is also unchanged. The presence of IP connectivity between the Serving GW and the source eNodeB, as well as between the Serving GW and the target eNodeB is assumed.
The intra E-UTRAN HO in RRC_CONNECTED state is UE assisted NW controlled HO, with HO preparation signalling in E-UTRAN.
Question 17. How Does Policy Control And Charging Works In Lte?
Answer :
A important component in LTE network is the policy and charging control (PCC) function that brings together and enhances capabilities from earlier 3GPP releases to deliver dynamic control of policy and charging on a per subscriber and per IP flow basis.
LTE Evolved Packet Core (EPC) EPC includes a PCC architecture that provides support for fine-grained QoS and enables application servers to dynamically control the QoS and charging requirements of the services they deliver. It also provides improved support for roaming. Dynamic control over QoS and
charging will help operators monetize their LTE investment by providing customers with a variety of QoS and charging options when choosing a service.
The LTE PCC functions include:
Question 18. What Is Son & How Does It Work In Lte?
Answer :
Self-configuring, self-optimizing wireless networks is not a new concept but as the mobile networks are evolving towards 4G LTE networks, introduction of self configuring and self optimizing mechanisms is needed to minimize operational efforts. A self optimizing function would increase network performance and quality reacting to dynamic processes in the network.
This would minimize the life cycle cost of running a network by eliminating manual configuration of equipment at the time of deployment, right through to dynamically optimizing radio network performance during operation. Ultimately it will reduce the unit cost and retail price of wireless data services.
Question 19. How Does Network Sharing Works In Lte?
Answer :
3GPP network sharing architecture allows different core network operators to connect to a shared radio access network. The operators do not only share the radio network elements, but may also share the radio resources themselves.
Question 20. How Does Timing Advance (ta) Works In Lte?
Answer :
In LTE, when UE wish to establish RRC connection with eNB, it transmits a Random Access Preamble, eNB estimates the transmission timing of the terminal based on this. Now eNB transmits a Random Access Response which consists of timing advance command, based on that UE adjusts the terminal transmit timing.
The timing advance is initiated from E-UTRAN with MAC message that implies and adjustment of the timing advance.
Question 21. How Does Lte Ue Positioning Works In E-utran?
Answer :
UE Positioning function is required to provide the mechanisms to support or assist the calculation of the geographical position of a UE. UE position knowledge can be used, for example, in support of Radio Resource Management functions, as well as location-based services for operators, subscribers, and third-party service providers.
Question 22. How Many Operators Have Committed For Lte?
Answer :
List of operators committed for LTE has been compiled by 3GAmericas from Informa Telecoms & Media and public announcements. It includes a variety of commitment levels including intentions to trial, deploy, migrate, etc.
Question 23. What Is Single Radio Voice Call Continuity (srvcc)?
Answer :
Along with LTE introduction, 3GPP also standardized Single Radio Voice Call Continuity (SRVCC) in Release 8 specifications to provide seamless continuity when an UE handovers from LTE coverage (E-UTRAN) to UMTS/GSM coverage (UTRAN/GERAN). With SRVCC, calls are anchored in IMS network while UE is capable of transmitting/receiving on only one of those access networks at a given time.
Question 24. How Does Location Service (lcs) Work In Lte Network?
Answer :
In the LCS architecture, an Evolved SMLC is directly attached to the MME. The objectives of this evolution is to support location of an IMS emergency call, avoid impacts to a location session due to an inter-eNodeB handover, make use of an Evolved and support Mobile originated location request (MO-LR) and mobile terminated location request MT-LR services.
Release 9 LCS solution introduces new interfaces in the EPC:
Question 25. How Does Lawful Interception Works In Lte Evolved Packet System?
Answer :
3GPP Evolved Packet System (EPS) provides IP based services. Hence, EPS is responsible only for IP layer interception of Content of Communication (CC) data. In addition to CC data, the Lawful Interception (LI) solution for EPS offers generation of Intercept Related Information (IRI) records from respective control plane (signalling) messages as well.
Question 26. What Is Carrier Aggregation In Lte-advanced?
Answer :
To meet LTE-Advanced requirements, support of wider transmission bandwidths is required than the 20 MHz bandwidth specified in 3GPP Release 8/9. The preferred solution to this is carrier aggregation.
It is of the most distinct features of 4G LTE-Advanced. Carrier aggregation allows expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. Multiple component carriers are aggregated to form a larger overall transmission bandwidth.
Question 27. What Is Relay Node And How Does Relaying Works In Lte-advanced?
Answer :
For efficient heterogeneous network planning, 3GPP LTE-Advanced has introduced concept of Relay Nodes (RNs). The Relay Nodes are low power eNodeBs that provide enhanced coverage and capacity at cell edges. One of the main benefits of relaying is to provide extended LTE coverage in targeted areas at low cost.
The Relay Node is connected to the Donor eNB (DeNB) via radio interface, Un, a modified version of E-UTRAN air interface Uu. Donor eNB also srves its own UE as usual, in addition to sharing its radio resources for Relay Nodes.
Question 28. What Are The Measurement Events In Lte?
Answer :
Intra/Inter Frequency Events:
Inter RAT Events:
Question 29. When Radio Link Failure Is Detected?
Answer :
Radio link failure to be detected:
Question 30. What Is Srs Used For?
Answer :
UL reference signal used to measure the channel quality over a section of the bandwidth.
Node B use this information for frequency selective scheduling and link adaptation decisions.
Question 31. What Is Dmrs/drs?
Answer :
DMRS/DRS is uplink reference signal.
Used for :
PUSCH DMRS:
PUCCH DMRS:
Question 32. What Is Timing Advance? What Happens If Timing Advance Timer Expires?
Answer :
The timing of UL radio frame is relative to DL radio frame. EnB provides timing advance command to each UE such that all UL transmissions arrive at the eNodeB in synchronous manner.
If TA timer expires UE goes of reestablishment procedure or move to idle.
Question 33. What Is Backoff Indicator? What Is The Use Of Backoff Indicator?
Answer :
Backoff Indicator is a special MAC subheader that carries the parameter indicating the time delay between a PRACH and the next PRACH.
if the Random Access Response contains a Backoff Indicator subheader:
set the backoff parameter value in the UE as indicated by the BI field of the Backoff Indicator subheader
else,
set the backoff parameter value in the UE to 0 ms.
Answer :
The Buffer Status reporting procedure is used to provide the serving eNB with information about the amount of data available for transmission in the UL buffers of the UE.
Question 35. At What Scenario Ue Triggers Bsr?
Answer :
Question 36. When Different Types Of Bsr Are Triggered?
Answer :
For Regular and Periodic BSR:
if more than one LCG has data available for transmission in the TTI where the BSR is transmitted
report Long BSR
else,
report Short BSR.
For Padding BSR: if the number of padding bits is equal to or larger than the size of the Short BSR plus its subheader but smaller than the size of the Long BSR plus its subheader:
if more than one LCG has data available for transmission in the TTI where the BSR is transmitted: report Truncated BSR of the LCG with the highest priority logical channel with data available for transmission;
else
report Short BSR.
else if the number of padding bits is equal to or larger than the size of the Long BSR plus its subheader, report Long BSR.
Question 37. What Is The Content Of Rar?
Answer :
A MAC RAR consists of the four fields
Question 38. In What Are The Scenario Ue Triggers Rrc Connection Reestablishment?
Answer :
UE Triggers RRC Connection Reestablishment procedure on following condition:
Question 39. When Ue Activates Integrity And Ciphering?
Answer :
Question 40. What Is The Difference Between Lte Fdd And Lte Tdd?
Answer :
The difference lies in the LTE frame structure in both the FDD and TDD versions of the LTE. In FDD there will be pair of frequencies assigned in the downlink and uplink directions and hence transmissions from multiple subscribes can happen at the same time but on different frequencies as mentioned. In TDD, one single frequency will be used at different time instants by multiple subscriber terminals (UEs). Both frame versions of LTE will have 1 ms sub-frame duration and 0.5 ms slot duration.
Question 41. What Is Resource Block In Lte?
Answer :
LTE frame is divided based on time slots on time axis and frequency subcarrier on frequency axis. Resource block is the smallest unit of resource allocation in LTE system. It is of about 0.5ms duration and composed of 12 subcarriers in 1 OFDM symbol. One time slot is equal to 7 OFDM symbols in normal cyclic prefix and 6 OFDM symbols in extended cyclic prefix. One full resource block is equal to 12 subcarriers by 7 symbols in normal CP. Hence it consists of total 84 time/frequency elements referred as resource elements in LTE network.
Question 42. What Are The Lte Logical, Transport And Physical Channels?
Answer :
All these channels help LTE UE establish the connection with the eNodeB, maintain the connection and terminate the same. Logical channels are characterized by the information that is transferred. Transport channels are characterized by how the data are transferred over the radio interface. Physical channel corresponds to a set of resource elements used by the physical layer. Channels are further divided into control channel and traffic channel at logical channel stage.
Answer :
Reference signal (RS) is used as pilot subcarrier in LTE similar to other broadband wireless technologies such as WLAN, WIMAX etc. Synchronization signal is used as preamble sequence in LTE for synchronization purpose. RS is used for channel estimation and tracking. SS are of two types viz. P-SS and S-SS. P-SS is used for initial synchronization. S-SS is used for frame boundary determination.
RS are of two types viz.
DRS is used for sync and channel estimation purpose. SRS is used for channel quality estimation purpose. DRS is used in both the uplink and downlink, while SRS is used only in the uplink.
Question 44. What Is The Function Of Lte Physical Broadcast Channel I.e. Pbch?
Answer :
After initial cell synchronization is completed, UE reads MIB (Master information block) on PBCH (Physical channel). Broadcast channel is referred as BCH at transport level and BCCH at logical level. MIB composed of downlink channel bandwidth in units of RBs, PHICH duration, PHICH resource and system frame number.
Question 45. What Is The Advantage Of Using Sc-fdma In The Lte Uplink?
Answer :
The main advantage of SC-FDMA is low PAPR compare to OFDMA used in LTE downlink. This increases the efficiency of power amplifier and hence increases the battery life.
Answer :
RSSI stands for Received Signal Strength Indication. It is used almost in all the RATs to identify power received from the cell in idle as well as connected/dedicated modes. This helps UE always camped on to the best cell all the time. In case of drop in power measured using RSSI, either UE or network initiates the handover or cell re-selection is carried out.
Question 47. Explain Circuit Switch Fall Back I.e. Csfb With Respect To Lte And Gsm?
Answer :
Framework allowing the provisioning of voice services by reuse of legacy GSM served CS infrastructure when the UE is served by E-UTRAN (LTE).To provide voice call support, Circuit Switch Fall Back is carried out to GSM RAT from LTE RAT to facilitate the voice over LTE (VoLTE) feature.
Question 48. Explain Lte Network Architecture And Various Interfaces?
Answer :
There are various entities forming the LTE network architecture, the main interfaces are Uubetween UE and eNB, X2 interface between eNBs and S1 interface between eNB and EPC(Evolved Packet Core).
Question 49. Is Lte A 4g Protocol?
Answer :
The networking industry recognizes LTE a 4G technology along with WiMax and HSPA+. None of these qualified as 4G based on the original definition of the International Telecommunications Union (ITU) standards group, but in December 2010 the ITU redefined 4G to include them.
While some marketing professionals and press have labeled LTE-Advanced as 5G, no widely-approved definition of 5G exists to justify the claim.
Question 50. What Is The Difference Between Lte And Lte Advanced?
Answer :
LTE is specified in 3GPP release 8 and release 9. LTE advanced is specified in 3GPP release 10. The main difference between them is carrier aggregation is introduced in LTE advanced. Number of antennas supported by MIMO has been increased to 8 in LTE advanced.
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