LTE BIBLE

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LTE BIBLE

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1. Definitions and Benefits

PING PONG HANDOVER:

- Ping-pong handovers occur when the MS is handed over from one cell to another but is quickly handed back to the original cell. This causes unnecessary signalling and can give an indication of incorrect handover

parameter settings or a dominance problem in the area.

TDD 20MHz BANDWIDTH:

- Channel Bandwidth is supported for LTE-TDD with maximum Resource blocks of 100.

Frame Structure Type 2:

Frame structure type 2 is used for LTE-TDD. Radio frame structure is same as frame structure type 1, but subframes are timely multiplexed with a specific DL/UL ratio in a radio frame. eNB supports uplink-downlink configuration.

Special Subframe:

The special subframes defined for DL/UL switching in frame structure type 2 consist of the three fields DwPTS (Downlink Pilot Timeslot), GP (Guard Period), and UpPTS (Uplink Pilot Timeslot). eNB supports special subframe configuration #7 of DwPTS: GP:UpPTS = 10:2:2 for TD-LTE.

Normal Cyclic Prefix:

Addition of redundant bits to avoid data loss. Normal CP (cyclic prefix) of 4.7us is

appended to each transmitted OFDM symbols.

Benefits: Operator can provide LTE service without being affected by inter-symbol interference In normal cell coverage environment.

End User Benefits: End-user can receive LTE service without being affected by inter-symbol interference In normal cell coverage environment.

Downlink QPSK, 16QAM and 64QAM Support:

UE can be configured to report CQI (Channel Quality Indicator) to assist the eNodeB in selecting an appropriate MCS to use for the downlink transmissions. Support

QPSK,16QAM and 64QAM modulation in DL. eNB selects among QPSK, 16-QAM and 64-QAM schemes in response to the CQI feedback from UE.

Benefits: Operator can dynamically change modulation order according to the downlink channel environment.

Uplink QPSK, 16QAM and 64QAM Support

For UL transmissions, the link adaptation process is similar to that for DL, with the selection of modulation and coding

schemes also being under the control of the eNB. eNB estimates the supportable uplink data rate by channel sounding and selects appropriate modulation for the result of estimated UL channel quality. Support QPSK and 16QAM modulation in UL.

Benefits: Operator can dynamically change modulation order according to the downlink channel environment.

Cell Specific Reference Signals:

Cell-specific reference signal

(CRS) is transmitted in all DL subframes in a cell supporting PDSCH transmission. CRS is transmitted on one or several of antenna ports 0 to 3. It is used for both

demodulation and channel

estimation purpose in DL. This CRS is also used for LTE-Advanced UEs to detect PCFICH, PHICH, PDCCH, PBCH, and PDSCH. Operator Benefits: Operator can provide

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End User Benefits: LTE user can estimate downlink channel and demodulate control and traffic channel data.

Positioning Reference Signal:

Positioning reference signals shall only be transmitted in resource blocks in downlink subframes configured for positioning reference signal transmission. Positioning reference signals for OTDOA, which is one of UE Positioning methods.

Operator Benefits: Operator can provide an OTDOA based location service to LTE user using positioning reference signal.

Synchronization Signal:

Synchronization signal is composed of primary and secondary synchronization signals. The synchronization signals always occupy the 72 sub-carrier (6RBs) of the channel, which make a same cell search procedure regardless of channel bandwidth. Primary Synchronization Signal (PSS)

detection to obtain the physical layer cell ID (within a group of three) and slot

synchronization. Secondary Synchronization Signal (SSS) detection to obtain the Cyclic Prefix (CP) length, the physical layer cell group ID and the frame synchronization. Benefits: Operator can make a time

synchronization with LTE UE by using synchronization signal.

End User Benefits: UE can find out a physical cell ID of serving cell by resolving

synchronization signal.

•UE can find out frame and slot starting time by resolving synchronization signal.

Demodulation Reference Signal:

Demodulation reference signal is used for channel estimation in the eNodeB receiver in order to demodulate control and data channels. It is located on the 4th symbol in each slot (for normal cyclic prefix) and

spans the same bandwidth as the allocated uplink data.

Operator Benefits: eNB can demodulate uplink data and control information by the channel estimate from this signal.

Sounding Reference Signal:

Sounding reference signal provides uplink channel quality information as a basis for scheduling decisions in the base station. The UE sends a sounding reference signal in different parts of the bandwidths where no uplink data transmission is available. The sounding reference signal is transmitted in the last symbol of the subframe. The configuration of the sounding signal, e.g. bandwidth, duration and periodicity, are given by higher layers.

Operator Benefits: eNB can estimate uplink channel response from receiving this signal. •The channel estimate is utilized in next

uplink scheduling.

Random Access Procedure Types:

Random Access Procedure are of two types; contention-based and non-contention operation.

Operator Benefits: eNB support contention based and contention free operation of random access procedures. And also, Helps in minimizing the chance of collision. End user Benefits: Contention-free random

access procedure helps UE minimize the chance of collision.

Variable Number of OFDM Symbols:

The number of resources (OFDM symbols) used in each sub frame for PDCCH shall be dynamic based on the requirement of the CCE (control channel element) by the load of control signaling. There shall be

dynamically varying CFI (control format indicator) within the range specified in the standards for different bandwidths.

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4 Operator Benefits: Cell capacity is increased

in cases where not all available PDCCH resource are needed.

End User Benefits: Subscribers may

experience higher throughput in downlink in typical scenarios with low load on PDCCH and high utilization of PDSCH

CCE Aggregation for PDCCH:

Each PDCCH is transmitted using one or more so-called Control Channel Elements (CCEs), where each CCE corresponds to nine sets of four physical resource elements known as Resource Element Groups (REGs). The number of CCEs used for transmission of a particular PDCCH is determined by the eNB according to the channel conditions.CCE aggregation for PDCCH: 1, 2, 4, and 8 CCEs. Operator Benefits: Cell capacity is increased

in cases where not all available PDCCH resource are needed.

End User Benefits: Subscribers may

experience higher throughput in downlink in typical scenarios with low load on PDCCH and high utilization of PDSCH.

Basic DCI Formats

In order to minimize the signalling overhead it is therefore desirable that several different message formats are available, each containing the minimum payload required for a particular scenario. For this motivation, several DCI (Downlink Control Information) formats are defined in standard. DCI formats 0 (PUSCH grants), 1 (PDSCH assignments with a single

codeword), 1A (PDSCH assignments using a compact format), 2 (PDSCH assignments for closed-loop MIMO operation), 2A (PDSCH assignments for open-loop MIMO

operation).

Operator Benefits: In order to minimize the signalling overhead it is desirable that several different message formats are available, each containing the minimum

payload required for a particular scenario. For this motivation, several DCI (Downlink Control Information) formats are defined in standard.

PDSCH Resource Allocation:

PDSCH resource allocation types 0, 1 and 2 Operator Benefits: Enable to enhance a

flexibility in spreading the resources across the frequency domain to exploit frequency diversity.

PUCCH Format

The PUCCH supports different formats depending on the information to be

signalled. The mapping between the PUCCH format and the Uplink Control Information (UCI) supported in LTE. PUCCH format 1,1A, 1B, 2, 2A, 2B.

Operator Benefits: minimize the resources needed for transmission of control signaling.

HARQ in DL and UL: MAC Layer Hybrid ARQ

uses Incremental redundancy technique to discard erroneously received packets and request retransmission providing

robustness against transmission errors. Operator Benefits: Achieve reliable data

transmission by sending a message of ACK/NACK.

Basic Link Adaption

MCS adaptation based upon channel information and error statistics.

Operator Benefits: Match the transmission parameter such as modulation and coding scheme (MCS) as well as MIMO

transmission rank and precoding to the channel condition on resource allocated by the scheduler.

•Serve the best resource allocation under the restriction of limited resource pool

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CQI correction performs CQI adaptation in order to compensate possible non-idealities of the link adaptation in LTE. e.g. CQI estimation error of the UE, CQI quantization error.

Operator Benefits: Enable the better link adaptation from facilitating this feature •Enable downlink radio resource scheduling

to serve the best resource allocation

Scheduling with QoS Support:

Based on the QoS profile of the user, the MAC scheduler will be aware of the priority GBR and AMBR requirements of the users. Accordingly, the scheduler can prioritize the users, ensure guaranteed bit rate and also control the Maximum Aggregate Bit rate allowed for the user. Operator Benefits: Operator can differentiate

traffic data according to the QoS class of LTE user.

End User Benefits: LTE users can be served the better QoS with their priority in the system.

Frequency Selective Scheduling

Frequency selective Scheduling allows eNB to select the best subband for resource allocation on downlink based on the subband CQI feedback from UE. Similarly the best subband selection can be done based on the SRS information.

Operator Benefits: Exploiting available channel knowledge to schedule a UE to transmit using specific Resource Blocks (RBs) in the frequency domain where the channel response is good.

•Maximizing radio resource utilization

Power Control

In uplink, eNB supports closed loop power control by providing TPC, Transmit Power Commands to UE. eNB also provides open loop power control parameters for the UE to perform open loop power control based on the RSRP measurements

Operator Benefits: It can provide the improvement of performance or the expansion of coverage according to the operation environment through Close-loop power control.

End User Benefits: It can prevent the

unnecessary power consumption of UE and provide the stablization of reception performance.

DL Power Allocation

Relative PDSCH power for reference symbols defined by two different parameters: ρA and ρB.

End-User Benefits: Optimized downlink power allocation will have an impact on the performance of an LTE UE.

Paging DRX:

Paging DRX refers to the discontinuous operation of the UE in idle mode, where in UE periodically wakes up from sleep mode to monitor the control channels for Paging operation.

End User Benefits: Enabling this feature results in longer battery life times.

Active DRX:

When Active DRX mode is used, even in RRC Connected state, UE sleeps during inactive periods and monitors PDCCH only during certain wake periods. This functionality improves battery life while UE is in

connected state. This feature includes both Short DRX and Long DRX.

End User Benefits: Enabling this feature results in longer battery life time

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IRC – Interference Rejection Combining:

Receiver supports interference rejection combining based on MMSE criterion. Operator Benefits: Achieve the better quality

of signal and improve system performance by cancelling the interference at eNB receiver.

DL SU 2x2 MIMO

DL single user 2x2 MIMO supported in TM3 and TM4.

Operator Benefits: Provide improvement in cell capacity and throughput as UEs with good channel conditions can benefit from the multiple streams transmission. End User Benefits: Served the improved

throughput or reliable communication due to the multiple streams transmission.

2Rx Diversity:

Rx diversity with 2 antenna

Operator Benefits: Enable to facilitate receiving diversity to select one better qualified path or combine two paths. •Enable to communicate the more reliable

transmission condition.

4Rx Diversity:

Rx diversity with 4 antenna

Operator Benefits: Enable to facilitate receiving diversity to select one better qualified path or combine two paths. •Enable to communicate the more reliable

transmission condition.

MIB & SIB Broadcast(SIB1~4)

eNB broadcasts MIB and SIB type 1, type 2, type 3 and type 4 for PLMN selection, cell selection and intra-frequency cell

reselection.

End User Benefits: Users can perform PLMN selection and cell selection, then access to a cell within E-UTRAN. Also they can perform intra-frequency cell reselection.

SIB Broadcast(SIB5)

eNB broadcasts SIB type 5 for Inter-frequency cell reselection.

End User Benefits: Users can perform inter-frequency cell reselection

eNB broadcasts SIB type 6 for cell reselection to UTRAN

End User Benefits: Users can perform cell reselection from E-UTRAN to UTRAN.

eNB broadcasts SIB type 7 for cell reselection to GERAN

End User Benefits: Users can perform cell reselection from E-UTRAN to GERAN.

RRC Connection Management

eNB performs RRC connections management procedures such as RRC Connection

Establishment, RRC Connection Reconfiguration, RRC Connection Re-establishment and RRC Connection Release. Operator Benefits: Operator can provide

radio connectivity to its subscribers within LTE network.

End User Benefits: LTE users can have a radio connection with an eNB for LTE service.

UE Context Management:

eNB maintains UE contexts while the UEs are in RRC_CONNECTED state, and supports Initial Context Setup, UE Context Release and Modification according to requests from MME.

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Operator Benefits: Operator can maintain UE context for its subscribers in

RRC_CONNECTED state.

E-RAB Setup and Release

eNB supports handling of E-RAB allocation, configuration, maintenance and release. Operator Benefits: Operator can provide EPS

bearer service to its subscribers and manage E-RAB resources for user data transport.

End User Benefits: Users can obtain EPS bearer service within E-UTRAN.

E-RAB Modification

eNB supports handling of E-RAB modification. This is used for QoS modification of one or serveral E-RABs.

Operator Benefits: Operator can modify E-RAB QoS of ongoing session.

S1 Interface Management

S1 interface management procedure is to manage the signaling associations between eNBs, surveying S1 interface and recovering from errors, i.e. Error indication and Reset procedures.

Operator Benefits: manage the signaling associations between eNBs, surveying S1 interface and recovering from errors.

NAS Signaling Transport

eNB supports transfer of NAS signaling messages between MME and UE.

Operator Benefits: This feature allows eNB to transfer NAS signaling messages between MME and UE.

MME Overload Control

eNB cooperates with MME to handle the overload situation of the MME. S1 overload control procedure is used as defined in the 3GPP standard. Overloaded MME sends S1

Overload Start message to eNB with ‘Overload Action’ IE, then eNB restricts RRC connection requests towards the

overloaded MME.

Operator Benefits: Signaling load reduction toward overloaded MME.

MME Selection and Load Balancing

When eNB receives a RRC connection request message from a UE, eNB searches and selects a MME that has served the UE before. The selection is based on S-TMSI information in the message. Otherwise, eNB performs load-based MME selection

function for a new call that has no S-TMSI information in the message.

Operator Benefits: UE can keep the same MME while it moves around even in idle mode, so that the UE can use the same IP address.

•Load is distributed over multiple MMEs. Operator can control relative load of a specific MME by adjusting Relative MME Capacity at each MME.

eNB Configuration Update

X2 eNB Configuration Update procedure is to update application level configuration data needed for two eNBs to interoperate correctly over the X2 interface.

Operator Benefits: Update application level configuration data needed for two eNBs to interoperate correctly over the X2 interface.

RIM Procedure:

RAN Information Management(RIM) procedures exchange the arbitrary RAN information (e.g., SIB) between RAN nodes belonging to different RATs. The RAN information is transparently transferred via core network nodes (MME and SGSN). End User Benefits: eNB can provide 3G

system information for UEs so that they can attach to 3G network quickly. This will help

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8 UEs reduce connection setup time during

CSFB or handover

X2 Interface Management:

X2 interface management procedure is to manage the signalling associations between eNBs, surveying X2 interface and recovering from errors, i.e. Error indication and Reset procedures.

Operator Benefits: This feature enables operatoir to manage the signalling associations between eNBs, surveying X2 interface and recovering from errors. •Efficient usage of the radio resources with

the help of X2 interface management.

Paging:

When eNB receives a paging message from MME, the eNB transmits the paging message to the UE in RRC_IDLE state based on the idle mode DRX configuration cycle. Operator Benefits: Operator can provide

mobile terminating service to its subscribers. End User Benefits: LTE users can receive a

notification for mobile terminating call in RRC_IDLE state.

•Save on battery power and signaling

Idle Mobility Support:

To support UE's idle mobility in E-UTRAN, eNB broadcasts relevant cell reselection information in SIB messages so that the UE can perform intra-LTE cell reselection when needed.

Operator Benefits: Operator can provide idle mobility to its subscribers within E-UTRAN. End User Benefits: LTE users in idle state can

be moving within E-UTRAN.

Intra-eNB Handover:

Intra-eNB handover is mobility control functionality between cells that belong to

the same eNB. UEs can move between the cells without any message exchange with MME.

Operator Benefits: Operator can provide connected mobility to its subscribers between cells in same eNB.

End User Benefits: Users in connected state can be moving within E-UTRAN, with change of serving cell.

S1 Handover:

S1 handover is mobility control functionality between two adjacent eNBs using the S1 interface with MME. S1 handover is used when there is no available direct interface with target eNB, or target eNB belongs to other MME group.

Operator Benefits: Operator can provide connected mobility to its subscribers between cells in different eNBs.

X2 Handover

X2 handover is mobility control functionality between adjacent eNBs. X2 based handover is used when there is an available direct interface with target eNB and target eNB belongs to same MME group.

Operator Benefits: Operator can provide connected mobility to its subscribers between cells in different eNBs.

Data Forwarding:

During handover, source eNB forwards PDCP SDUs in sequence to target eNB. Direct data forwarding is used when a direct path between source eNB and target eNB is available. Otherwise indirect data

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forwarding is used, where PDCP packets are delivered to target eNB through S-GW. End User Benefits: Users can obtain session

continuity during handover within E-UTRAN, with almost no interruption.

Inter-Frequency Handover:

Inter-frequency handover is mobility control functionality between cells that use

different frequency band. eNB provides UEs with measurement gap information in order for the UEs to perform inter frequency search. Measurement Gap avoids

scheduling of data for the UE during inter frequency scan periods

Operator Benefits: Operator can provide connected mobility to its subscribers between cells which have a different center frequency.

Handover to CSG/Hybrid Cells:

To support inbound mobility toward CSG/Hybrid cell, macro eNB performs CSG/Hybrid cell specific measurement control and handover signaling.

Operator Benefits: Operator can provide connected mobility to its subscribers from macro cells to CSG/Hybrid cells.

End User Benefits: LTE users in connected

state can be moving from macro cells to its own CSG cells or Hybrid cells.

Multi-target Preparation:

Multi Target preparation allows eNB to trigger handover procedure to more than one target eNodeB for improving user experiences. Handover preparation

message is sent to multiple candidate target eNBs based on the measurement report received from the UE. Only one target is chosen for the UE to handover. If the UE

fails handover to the above target, the UE can re-establish the connection successfully with the source eNB or other target eNBs that already have the UE context. If the handover is successful, then the source eNB cancels the handover preparation with the other candidate target eNBs.

End User Benefits: Users can obtain session continuity with fast recovery of ongoing sessions though handover failure has been experienced during handover.

Intra-LTE Redirection:

This is intra-LTE mobility functionality towards different LTE carriers from serving carrier.

Operator Benefits: Operator can provide connected mobility to its subscribers between LTE carriers, though not inter-frequency handover.

Idle Mobility to CDMA Network (HRPD/1xRTT).

To support UE's idle mobility to CDMA network (HRPD or 1xRTT), eNB broadcasts relevant cell reselection information in SIB8 message so that the UE can perform cell reselection towards CDMA network when needed.

Operator Benefits: Operator can provide idle mobility to its subscribers to CDMA network. End User Benefits: Users in idle state can

move to CDMA network.

Optimized Handover to HRPD

Optimized PS handover to CDMA2000 eHRPD is outbound mobility control functionality to eHRPD network, in case of the UE has pre-registered to the target eHRPD network and optimized handover can be possible. When mobility event to eHRPD is occurred, eNB initiates optimized handover by sending a request message for handover preparation to the UE. After handover preparation

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10 between the UE and HRPD network, the UE

handovers towards eHRPD network. Operator Benefits: Operator can provide

connected mobility to its subscribers from E-UTRAN to CDMA2000 HRPD.

End User Benefits: Users in connected state can move from E-UTRAN to CDMA2000 HRPD, remaining the connected state.

CSFB to CDMA2000 1xRTT

CS fallback to CDMA2000 1xRTT enables the delivery of CS-domain services when a UE is being served by the E-UTRAN. When eNB receives CSFB indicator from MME, then performs a procedure of redirection to CDMA2000 1xRTT.

Operator Benefits: Operator can provide CS service to its subscribers from E-UTRAN to CDMA2000 1xRTT.

End User Benefits: Users can do a CS call while staying in E-UTRAN, by transition to legacy CS network (1xRTT).

Idle Mobility to UTRAN

To support UE’s idle mobility to UTRAN, eNB broadcasts relevant cell reselection

information in SIB6 message so that the UE perform cell reselection towards UTRAN when needed.

Operator Benefits:

•Operator can provide idle mobility to its subscribers to UTRAN.

End User Benefits:

•Users in idle state can move to UTRAN.

PS Handover to UTRAN

UTRAN PS handover is mobility control functionality between E-UTRAN and UTRAN PS domain.

Operator Benefits:

•Operator can provide connected mobility to its subscribers from E-UTRAN to UTRAN. End User Benefits:

•Users in connected state can move from E-UTRAN to E-UTRAN, remaining in the connected state.

PS Handover from UTRAN

UTRAN PS handover is mobility control functionality between E-UTRAN and UTRAN PS domain.

Operator Benefits:

•Operator can provide connected mobility to its subscribers from UTRAN to E-UTRAN. End User Benefits:

•Users in connected state can move from UTRAN to E-UTRAN, remaining in the connected state.

Redirection to UTRAN without SI

This is outbound mobility control

functionality to UTRAN. When mobility event to UTRAN is occurred, eNB redirects the UE towards UTRAN.

Operator Benefits:

•Users in connected state can move from E-UTRAN to E-UTRAN.

Redirection to UTRAN with SI

This is outbound mobility control

functionality to UTRAN. When mobility event to UTRAN is occurred, eNB redirects the UE towards UTRAN and transfers system information of neighboring UTRAN cells.

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•Users in connected state can move from E-UTRAN to E-UTRAN.

CSFB to UTRAN with Redirection without SI

CS fallback to UTRAN enables the delivery of CS domain services when a UE is being served by the E-UTRAN. When eNB receives CSFB indicator from MME, then performs a procedure of redirection without system information.

Operator Benefits:

•Operator can provide CS service to its subscribers by using legacy CS network (UTRAN)

End User Benefits:

•Users can do a CS call while staying in E-UTRAN, by transition to legacy CS network (UTRAN)

CSFB to UTRAN with Redirection with SI

CS fallback to UTRAN enables the delivery of CS domain services when a UE is being served by the E-UTRAN. When eNB receives CSFB indicator from MME, then performs a procedure of redirection with system information.

Operator Benefits:

End User Benefits:

CSFB to UTRAN with PS Handover

CS fallback to UTRAN enables the delivery of CS domain services when a UE is being served by the E-UTRAN. When eNB receives CSFB indicator from MME, then performs a procedure of PS handover to WCDMA. Operator Benefits:

End User Benefits:

Capacity based Call Admission Control

Capacity-based CAC determines whether to admit or reject the establishment requests (e.g. idle to active transition, handover, additional E-RAB establishment) for new radio bearers, based on maximum number of calls and bearers supported by

eNodeB/Sector. New calls are allowed only if the pre-configured maximum number of calls and bearers allowed for that sector and for that eNB are not exceeded. In case of no resources, emergency calls are allowed by preempting existing calls. Operator Benefits:

•By limiting the maximum number UEs or bearers per cell and per eNB, considering radio and backhaul bandwidth, operator can control the minimum QoS level provided for UEs.

•Operator can protect the system from being shutdown due to overload or congestion

QoS based Call Admission Control

QoS-based CAC determines whether the eNB accepts a new bearer based on the current resource utilization and the QoS

requirements of the new bearer. Operator Benefits:

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12 •Operator can provide QoS guaranteed

service to UEs.

•Operator can configure how much resources(PRB, backhaul bandwidth, number of GBR bearers) can be used for GBR services.

Preemption

In case of no resource available, eNB admits a new bearer by preempting existing bearers. The decision is based on ARP (Allocation and Retention Priority) information of new bearer(s) and existing bearer(s).

Operator Benefits:

•Operator can provide UEs with

differentiated service based on service or based on UE class.

•Operator can design a high-priority service which is always available even in network congestion.

Cell Barring

When eNB is overloaded or a cell is used for testing, operator can configure eNB to transmit cell barring message via BCCH(SIB type1). Accordingly, UEs will not camp on the cell but test UEs can access.

Operator Benefits:

•Operator can prohibit UEs from camping on a specific cell, which enables operator to test the cell for the commissioning of base stations without any interference of commercial UEs.

Access Class Barring

In order to limit UE's access to a cell, operator can manually configure the access class barring information via LSM. eNB broadcast this information in SIB type 2 message. Operator can control how many UEs to be allowed and how long time period it is valid and which type of UE behaviors are

restricted.

Operator Benefits:

•Operator can reduce the amount of incoming calls per call type.

AM, UM and TM Data Transfer at RLC Layer:

eNB supports three different data transfer modes at RLC layer; Acknowledged Mode(AM), Unacknowledged Mode(UM) and Transparent Mode(TM). TM is used to transfer RRC signaling messages without RLC overhead. AM, which allows

retransmission, is used for reliable data transfer and UM is used for delay sensitive data transfer. Operator can configure a transfer mode AM or UM per QCI.

•RLC AM provides a reliable data transfer between eNB and UE.

•RLC UM allows a simple data transfer for delay sensitive packets.

•RLC TM removes RLC overhead to save radio resources.

Header Compression ROHCv1(RTP, UDP, IP)

eNB and UE compress the IP header part of user data packets for transmission over the air. The compression algorithm is

RoHCv1(Robust Header Compression) defined in IETF RFC3095 and other related RFCs. RoHC Profiles 0,1,2 and 4 are supported.

Operator Benefits:

•eNB increases user data throughput by applying RoHC to user data transmitted over the radio link.

•When this feature is enabled for VoLTE, eNB can accommodate more VoLTE users at the same time.

End User Benefits:

•UE can enhance throughput.

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Control plane data integrity protection using security algorithms between eNB and UE. •Per compliance of the data integrity

discipline of communication, eNB shall ensure the data is not modified during the transmission.

•Integrity protection, and replay protection, shall be provided to RRC-signalling.

Ciphering: Null/SNOW3G/AES

eNB supports SNOW 3G/AES as an encryption algorithm to protect user plane data and control plane data transferred between eNB and UE.

Operator Benefits:

•Confidentiality of software transfer towards the eNB shall be ensured

•Sensitive parts of the boot-up process shall be executed with the help of the secure environment.

•Prevent UE tracking based on cell level measurement reports

End User Benefits:

•Support privacy protection for user information

Standard QCI Support

eNB supports standardized QCI(QoS Class Identifier) as defined in 3GPP TS 23.203, which is characterized by priority, packet delay budget and packet error loss rate. eNB handles scheduling of the bearer based on its QCI information.

Operator Benefits:

•This feature enables operator to plan a variety of premium services; end-to-end QoS differentiated services in 9 different levels as per defined in 3GPP standard. •Operator can provide high-quality VoLTE

service by using guaranteed bit rate bearers.

•Operator can provide different user classes for different quality of services.

End User Benefits:

•Users can use a premium service that provides better quality even in congestion.

Operator Specific QCIs Support

eNB supports extended QCIs that are defined by operator.

Operator Benefits:

•Operator can define a customized QCI for a specific service, where QoS characteristics of the extended QCIs may be different from those of standard QCIs in terms of priority, resource type, packet delay budget. End User Benefits:

•UE can receive a customized network service that is suitable to a specific application.

QCI to DSCP Mapping

eNB marks uplink packets with a DSCP value so that intermediate nodes can support QoS for packets heading to EPC. DSCP value is determined depending on QCI. For this, operator can configure QCI to DSCP mapping table according to its service and QoS policy.

Operator Benefits:

•Operator can manage traffic from eNB to SGW for end-to-end QoS service.

•In addition to bearer traffic, operator can setup appropriate DSCP values to signaling traffic and OAM traffic for system

optimization. For example, setting a high priority on signaling message will reduce call setup time while a DSCP value for regularly generated OAM ftp traffic needs to set not to affect user traffic.

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14 eNB reserves radio resource to support

GBR(Guaranteed Bit Rate), and eNB limits the throughput not to exceed

MBR(Maximum Bit Rate). For this, QoS based call admission control and QoS aware scheduling algorithm are used. GBR and MBR are bearer associated parameters and MME sends eNB these parameters during E-RAB setup or modification procedure. Operator Benefits:

•Operator can provide high-quality QoS services by using GBR bearers.

End User Benefits:

•UEs that connect a GBR bearer can achieve at least the guaranteed bit rate that system allows even in cass of congestion.

•By configuring MBR, operator can prevent GBR UEs from overusing data and

monopolizing radio resources. •Efficient usage of the radio resources

UE-AMBR Support

eNB limits the total bit rate(UE-AMBR) that a UE can achieve through its non-GBR bearers. MME sends eNB UE-AMBR parameter during UE Context Setup or Modification procedure

Operator Benefits:

•By controlling UE-AMBR, operator can prevent a UE from overusing data over Non-GBR bearers and monopolizing radio resources.

•Operator can differentiate subscribers by setting UE-AMBR differently per user classes.

Max 8 Bearers per UE

eNB supports up to 8 data bearers for a UE, including default and dedicated bearers regardless of their resource types Operator Benefits:

•Operator can provide a UE with 8 different kind of services at the same time, where each service has different QoS

characteristics such as QCI or ARP. End User Benefits:

•A UE may have maximum 8 different kind of bearers at the same time. Each bearer has different QoS characteristics such as QCI or ARP. This ensures better user experience and fair allocation of radio resources to UE

QCI-based Throughput Differentiation for Non-GBR Bearers

Operator can configure "weight factor" for each different GBR QCIs. Then, Non-GBR bearers can achieve throughput in proportion to the ratio of weight factor between them. This takes effect only in case of resource limitation. When there are enough resources, each bearers are able to transmit all of its own data.

Operator Benefits:

• Operator can support differentiated throughput for non-GBR OCI. Thus ithis feature enable an operator to implement various accounting plan according to QoS (even for the same service).

(For example, normal download vs. high speed download, normal video streaming vs. HD video streaming)

End User Benefits:

• User can enjoy premium service with fast speed in network congestion state

Load Balancing between Carriers

In the LTE network with multiple carriers, the load balancing algorithm selects UEs from a high-loaded carrier and hands them over to a co-located and low-loaded carrier. The UE selection algorithm is designed to guarantee QoS after handover to another carrier.

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Operator Benefits:

•This feature distributes the amount of traffic on multiple carriers and provide even QoS on each carrier.

End User Benefits:

•The bad QoE due to overload will be reduced

Load Balancing between Sectors (Mobility Load Balancing)

Load balancing within an intra-carrier occurs between cells of intra-eNB or inter-eNB. UEs in the boarder area are selected and handed over to the low-loaded neighbor cells. The load balancing algorithm considers serving/target cells' signal

strength at UE. The algorithm is designed to balance the average per-UE non-GBR resources among cells.

Operator Benefits:

•This feature relieves the overload state of a cell.

End User Benefits:

•The bad QoE due to overload will be reduced.

Idle UE Distribution

In multi-carrier network, Idle UE distribution algorithm makes idle UEs distributed over carriers by giving a different priority of frequency to each UE via

IdleModeMobilityControlInfo in the RRCConnectionRelease message. Idle-to-active transition UEs will be distributed over multiple carriers when they camp on. For this feature, Operator should configure the parameters, which control the idle UE ratio among carriers.

Operator Benefits:

•This feature distributes the amount of traffic on multiple carriers and provide even QoS on each carrier.

SPID based Dedicted Priority SPID based Dedicted Priority SPID based Dedicted Priority

eNB supports dedicated signaling with cell reselection priorities based on SPID 254, 255 and 256.

Operator Benefits:

•Operator can control idle mode camping RAT and carriers of a UE based on absolute priorities determined by subscription information.

Load Distribution over Backhaul Links

When eNB has two backhaul Ethernet links alive, eNB distribute load between two links.

Operator Benefits:

•By monitoring one backhaul link, operator can monitor all the traffic of a specific UE.

DL Flow Control between SGW and eNB

When downlink radio link of a cell is congested due to the limited bandwidth, eNB sends XOFF message to SGW so that it stop sending packets in downlink. eNB sends XON message to resume data transmission at SGW. This flow control scheme works per UE or bearer or QCI. Operator Benefits

•This feature enables for SGW to count packets that are actually delivered to UEs, which prevents overbilling for packets overflowed and dropped at eNB due to air congestion.

•This flow control feature reduces the number of packets dropped due to air congestion because both eNB and SGW can buffer packets.

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16

eNB Overload control(Adaptive Access Barring)

eNB periodically monitors the load status of CPU processor. When CPU overload is detected, eNB performs automatically adjustment of the access barring control parameters based on CPU overload level(Minor/Major/Critical).

Operator Benefits:

•Operator can reduce the number of call attempts to an overloaded eNB, which can prevent the eNB from shutting down due to overload.

End User Benefits:

•LTE users can avoid access to an eNB under congestion

Multi-PLMN Support

In a shared cell, eNB periodically broadcasts a SIB1 message which includes supporting PLMN id list up to 6. According to the selected PLMN id included in RRC

Connection Setup Complete message, eNB routes the control message to an

appropriated MME to make a connection to the network.

Operator Benefits:

•Operator can reduce CAPEX.

Flexible Configuration for Radio Resource Sharing eNB allocates the radio

resources(PRB, active UE capacity, bearer capacity) to each PLMN id according to the radio sharing ratio configured by operator. Operator can configure some portion of the resources dedicated to each operator and remaining resources to be commonly Operator Benefits:

•Operator can wholesale a portion of spectrum by configuring some portion of radio resources dedicated to a specific PLMN id.

•In MOCN, operator can highly utilize radio resources between different PLMNs by configuring som portion of radio resources shared between them. shared between operators.

Inter-PLMN Handover

Inter-PLMN handover is mobility control functionality between cells that served PLMN is different from each other. Operator Benefits:

•Operator can provide connected mobility to its subscribers within a shared network. End User Benefits:

•LTE users can obtain EPS bearer service in other network operators’ area which is not the subscribed network operator.

Load Balancing between Multi-operator Frequencies

To support traffic management for the network with both carriers only for a specific operator and shared carriers for multiple operators, eNB provides the concept of carrier-group. Load balancing using the carrier-group concept has two operations: load equalization within the same carrier-group and offloading the overloaded traffic between carrier-gro Operator Benefits:

•Operators can distribute the amount of traffic on shared multiple carriers. End User Benefits:

•The bad QoE due to overload will be reduced. ups.

Usage Report per PLMN

eNB provides usage data per PLMN to LSM. PRB usage, user data usage, number of UEs, number of bearers, and signaling messages will be counted per PLMN.

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•Host operator can figure out how much data is consumed by each partner operator. •The usage data can be utilized for the

purpose of settlement among partner operators

IMS based Emergency Call Support

To support IMS emergency call, eNB performs emergency call specific admission control, security handling and mobility control. Operator Benefits:

•Operator can provide Emergency service to its subscribers while they are staying in E-UTRAN.

End User Benefits:

•LTE users can do an emergency call while staying in E-UTRAN, as well as in legacy CS network.

Emergency Call via CSFB to CDMA2000

This is CSFB to CDMA2000 1xRTT functionality for emergency call

Operator Benefits:

•Operator can provide Emergency service to its subscribers by using legacy CS network (CDMA2000 1xRTT).

End User Benefits:

•LTE users can do an emergency call while staying in E-UTRAN, by transition to legacy CS network (CDMA2000 1xRTT).

Emergency Call via CSFB to UTRAN

This is CSFB to UTRAN functionality for emergency call

Operator Benefits:

•Operator can provide Emergency service to its subscribers by using legacy CS network (UTRAN).

End User Benefits:

•LTE users can do an emergency call while staying in E-UTRAN, by transition to legacy CS network (UTRAN).

CMAS (Commercial Mobile Alert Service)

CMAS is a public warning system developed for the delivery of warning notifications. The CMAS warning notifications are short text messages (CMAS alerts). The CMAS warning notifications are broadcasted via SIB messages.

Operator Benefits:

•Operator can provide public warning notifications to its subscribers while they are staying in E-UTRAN.

End User Benefits:

•Users can be notified for public warning messages from network, and then they can avoid some disasters or accidents.

ETWS (Earthquake and Tsunami Warning System)

ETWS is a public warning system for warning notifications related to earthquake and/or tsunami events. ETWS warning notifications can be either a primary notification (short notifications delivered within 4 seconds) or secondary notification (providing detailed information). The ETWS primary and secondary notifications are broadcasted via SIB messages.

Operator Benefits:

•Operator can provide public warning notifications to its subscribers while they are staying in E-UTRAN.

End User Benefits:

•Users can be notified for public warning messages from network, and then they can avoid some disasters or accidents.

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18 In the Cell ID (CID) positioning method, the

position of an UE is estimated with the knowledge of its serving eNodeB and cell. The information about the serving eNodeB and cell may be obtained by paging, tracking area update, or other methods. Enhanced Cell ID (E CID) positioning refers to techniques which use additional UE and/or E UTRAN radio resource such as TA (Timing Alignment), UE measurement reports to improve the UE location estimate. Operator Benefits:

•additional UE and/or E UTRAN radio measurement reports to improve the UE location estimate.

OTDOA

The downlink (OTDOA) positioning method makes use of the measured timing of downlink signals received from multiple eNode Bs at the UE. The UE measures the timing of the received signals using assistance data received from the positioning server, and the resulting measurements are used to locate the UE in relation to the neighboring eNodeBs. Operator Benefits:.

• to improve UE location estimate using by both UE's received signals from several eNBs and assistance information from eNB.

Intra-LTE ANR

ANR allows automatic discovery and setup of neighbor relations when a UE moves from a serving eNB to target eNB. ANR also

automatically sets up the LTE unique X2 interface between eNBs, primary used for handover.

Operator Benefits:

•ANR minimize the manual handling of neighbor relations when establishing new eNBs and when optimizing neighbor lists.

•This will increase the number of successful handovers and lead to less dropped connections due to missing neighbor relations.

RACH optimization

During self-configuration phase, EMS supports RSI(root sequence index) auto-configuration using location information. Subsequently, during the operational phase, each eNodeB collects the information pertaining to any RSI conflicts and informs EMS about conflict information for

reconfiguring. For RACH optimization, eNB collects the statistics of the dedicated preamble allocation attempt/success and optimizes the number of dedicated

preambles. eNB also collects the statistics of the preamble transmission during RA and optimizes the PRACH Configuration Index, Preamble Initial Received Target Power, Power Ramping Step.

Operator Benefits:

•In the SON framework, as soon as the eNodeB is powered up during the auto-configuration phase, it is allocated to a RSI(Root Sequence Index). Such a RSI is determined using a RSI auto-configuration algorithm that uses the location information with neighbors. Thus, SON ensures that each eNodeB has a RSI value at the time of installation without requiring explicit human intervention.

•In operation phase, SON ensures that each eNB and LSM supports RSI

collision/confusion detection and RSI reconfiguration without human

intervention. In addition, RACH optimization will reduce the amount of manual processes involved in the RACH related optimizations like the number of dedicated preambles, PRACH configuration index, preamble initial received target power and power ramping step.

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eNB supports power amplifier bias control by adjusting PA bias for low RF load without a specified carrier shutdown. Two types of PA bias control mechanisms are supported: Predefined Time schedule based and Traffic load based.

Operator Benefits:

•PA bias control provides high power efficiency with low RF load.

•PA bias control saves about 6.7% of consumed DC power in 800MHz.

Test of VSWR

The functionality of VSWR(Voltage Standing Wave Ratio) test is used to measure return loss in transmitting antenna of power amp unit.

Operator Benefits:

•This feature provides an efficient method for measuring return loss in transmitting antenna of power amp unit.

Packet Loss Detection over S1

eNB counts and provide statistics about lost packets and out-of sequence packets occurred during delivery from SGW to eNB. This feature can be enabled only when eNB interworks with EPC.

Operator Benefits:

•Operator can decide the quality of backhaul network.

Difference between CCO – Cell change Order and Redirection:

CCO from LTE (only possible towards GSM) differs from the LTE->GSM redirection mainly such that with CCO if the UE can't successfully camp and access the given target GSM cell, it has to return to LTE, whereas the redirection can have multiple target cells/frequencies and the UE can attempt to find service in any of them.

With Rel-9 redirection also the system

information messages for the target GSM cell (or, in fact, up to maximum of 32 GSM cells) the performance can be equal (or even better in case the single target cell with CCO cannot be found or access fails) that the CCO with NACC (network assisted cell change, which means the system information for the target GSM cell is provided with the CCO).

In practise the above means that redirection typically would perform equally well and in many cases (esp. if the redirection or CCO is made blindly, i.e. without UE reporting GSM cells) better than CCO, and therefore it is typically used with CS fallback.

Cell reselection

Cell reselection is the process of changing the

mobile's serving cell (either in idle mode or while actively transmitting data). Cell reselections can be initiated by the mobile or network. When the network initiates a cell reselection, it sends a Packet Cell Change Order (GPRS/EGPRS) or a Cell Change Order (W-CDMA/HSPA), which provides the parameters necessary for the mobile to find and synchronize to the destination cell. If the mobile was actively transferring data at the time of the cell reselection, any subsequent allocation of traffic channel resources to continue the packet data transfer are handled by signaling between the mobile and destination cell, and does not involve the origination cell.

Handover

Handover refers to a cell transition that occurs

when a circuit-switched (CS) connection is in place (such as CS voice, CS data, or Dual Transfer Mode). Handovers can only be initiated by the network. During a handover, the network sends the mobile a Handover command, which provides information about the destination cell, including the traffic channel configuration.

The procedure for mobility from LTE to another RAT supports both handover and Cell Change Order (CCO).The CCO

procedure is applicable only for mobility to GERAN. In case of handover (as opposed to CCO), the source eNodeB requests the target RAN node to prepare for the handover. As part of the ‘handover preparation request’ the source eNodeB

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20 provides information about the applicable

inter-RAT UE capabilities as well as

information about the currently-established bearers. In response, the target RAN

generates the ‘handover command’ and returns this to the source eNodeB.

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- LTE is abbreviated as Long term Evolution.

- LTE is successor of not only UMTS but also CDMA 2000.

- LTE is introduced to get higher data rates of 300Mbps peak downlink and 75Mbps peak uplink in 20MHz Carrier for FDD.

- LTE is an ideal technology to support higher data rates for the services VoIP, streaming media, video conferencing.

- LTE uses both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). - In FDD, both uplink and downlink uses different frequencies. Uplink and downlink uses same

frequency in TDD.

LTE – FDD LTE – TDD - LTE supports bandwidths from 1.4MHz, 5MHz, 10MHz and 20MHz.

- LTE devices have to support MIMO, for the base station to transmit several data streams over the same carrier simultaneously.

- The entire interfaces between the nodes are IP based including the backhaul, connection to the base stations.

- Quality of service mechanism have been standardized on all the interfaces to ensure the requirement of voice calls for constant delay and bandwidth

Advantages of LTE:

- High Throughput: High downlink and uplink throughput can be achieved.

- Low Latency: Time required to connect to the network in the range of few hundreds milli

seconds.

- FDD and TDD in the same platform: Frequency Division Duplex – FDD and Time Division

Duplex –TDD.

- Superior End user Experience: Optimized signaling for connection establishment and other air

interface and mobility management procedures have further improved user experience. - Seamless Connection: LTE supports seamless connection to the existing networks such as

GSM, CDMA and WCDMA.

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22 - LTE uses OFDM transmission schemes., it uses OFDMA in Downlink and SC-FDMA in uplink. - A Resource block is a basic entity in the LTE terminology which when modulated using OFDM

sub-carriers becomes Resource Elements – which is the smallest unit of the LTE spectrum. - A Physical Resource Block (PRB) is defined as smallest unit used by the scheduling algorithm. - TTI : Transmission Time Interval is the duration of the transmission on the radio link. TTI is

related to the size of the data blocks passed from the higher network layer to the radio link layer.

- Link Adaptation or Adaptive Modulation Coding: It is the ability to adapt the modulation

scheme and the coding rate of the error correction according to the radio link. If the condition of the radio link are good, a high level efficient modulation scheme and a small amount of error correction is used.

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3. Resource Blocks in LTE

Resource Element: RE is the smallest unit of transmission resources in LTE, in uplink and downlink.

RE consists of 1 subcarrier in the frequency domain for duration of 1 symbol (OFDM in the downlink and SC-FDMA in the uplink).

- Subcarrier Spacing: It is the space between the individual carriers, in LTE 15KHz. There is no

guard band between these subcarrier frequencies , rather Guard period is called as Cyclic prefix is used in the time domain to help prevent multipath Inter Symbol Interference (ISI) between subcarriers.

- Cyclic Prefix: A set of samples which are duplicated from the end of transmitted symbol and

appended cyclically in the beginning of the symbol. This can form a type guard interval to absorb Inter symbol interference (ISI).

- Time Slot: 0.5ms time period of the LTE frame corresponding to 7 OFDM symbols (7CPs)

when normal CP=5usec used. And 6 symbols(CP=6) when Extended CP = 17usec is used.

-

- Resource Block

- Resource Block: A unit of transmission resource consisting of 12 subcarriers in the frequency

domain and 1 time slot (0.5ms) in the time domain.

- 1 RB = 12(Subcarriers) x 7 (Symbols ) = 84 Resource Elements. (For Normal CP :- 7 symbols) - 1 RB = 12(Subcarriers) x 6 (Symbols ) = 72 Resource Elements (For Extended CP:- 6 symbols) - LTE Subframe or TTI = two slots i.e.. 1ms in time

- LTE frame – 10ms or 10 subframes or 20 slots.

- Bandwidths directly affects the throughput. Different Bandwidths have different number of RB.

- 10% of the total bandwidth is used for the Guard band. This is not valid of 1.4MHz bandwidth. - For 20MHz Bandwidth, 10% of 20MHz = 2MHz is used for Guard band and 18MHz is effective

bandwidth.

- Number of subcarriers = 18MHz/15KHz = 1200

- Number of Resource blocks = 18MHz/180KHz = 100RB

- -

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24 -

- Resource Blocks in Frequency Bands.

Resource Blocks (RB):

- Basic unit of resource for the LTE air-interface.

- eNodeB scheduler allocates RBs to UE to allow data transfer. - Defined in both time and frequency domains.

In Time Domain:

- Occupies 0.5 ms slot in time domain.

- Consists of 7 OFDMA symbols when using Normal Cyclic Prefix. - Consists of 6 OFDMA symbols when using Extended Cyclic Prefix.

In Frequency Domain: - Consists of 12 subcarriers.

- Each subcarrier is of 15 KHZ.

- Each RB occupy 12*15 = 180 KHZ in frequency domain.

- The GRID generated by One Sub-Carrier in the Frequency Domain and One Symbol in the Time Domain defines a RESOURCE ELEMENT (RE).

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- RB consists of 72 (12*6) REs when using Extended Cyclic Prefix.

- A single RE can carry a Single Modulation Symbol (2 bits when using QPSK, 4 bits when using 16QAM, and 6 bits when using 64QAM).

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26

4. Resource Allocation & Management Unit

Reading various LTE specification, you will see many terms which seems to be related to resource allocation but looks very confusing. At least you have to clearly understand the following units.

i) Resource Element(RE) : The smallest unit made up of 1 symbol x 1 subcarrier.

ii) Resource Element Group (REG) : a group of 4 consecutive resource elements. (resource elements for reference signal is not included in REG)

iii) Control Channel Element (CCE) : a group of 9 consective REG iv) Aggregation Level - a group of 'L' CCEs. (L can be 1,2,4,8)

v) RB (Resource Block) : I think everybody would know what this is. This is a unit of 72 resource elements which is 12 subcarrier by 6 symbols.

vi) RBG (Resource Block Group) : This is a unit comprised of multiple RBs. How many RBs within one RBG differs depending on the system bandwidth. (Refer to RB Size allocation for each System Bandwidth for the details)

We use these units in hierachical manner depending on whether it is for control channel or data channel.

For PDCCH, the hierachy would be : RE --> REG --> CCE --> Aggregation Level ==> I think a couple of example would give you more practical understanding.

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i) The CCE index for a certain subframe = 4 ii) Aggregation Level is 2

iii) The subframe is sending DCI1 only

Resource Allocation : Network would allocate the DCI 1 spreaded over CCE4, CCE5.

Example 2 > a PDCCH transmission

iii) The subframe is sending DCI1, DCI 0

Resource Allocation : Network would allocate the DCI 1 spreaded over CCE4, CCE5 and allocate the DCI 0 spreaded over CCE6, CCE7.

Example 3 > a PDCCH transmission

iii) The subframe is sending DCI1, DCI 0 and DCI 3 (power control)

Resource Allocation : Network would allocate the DCI 1 spreaded over CCE4, CCE5 and allocate the DCI 0 spreaded over CCE6, CCE7 and allocate two CCE for DCI 3 but DCI 3 would be allocated to a common search space (not to a user specific search space).

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28

5. LTE Throughput Calculation

Throughput calculation for LTE – TDD

- For any system, throughput is calculated as symbols per second.

- For 20MHz Bandwidth, there are 100 Resource Blocks and each resource block have 12 x 7 x 2 = 168 symbols per ms in case of normal CP.

- 168 symbols per ms = 168000 symbols per second = 16.8Msymbols/sec - For 64QAM, there are 6 bits per symbols.

- The Throughput will be 6bits per symbol x 16.8 M symbols per sec = 100.3 Mbps - For LTE MIMO ( 4Tx and 4Rx) the throughput will be calculated as 403.2Mbps - Many simulations indicate that 25% overhead is used for signaling and controlling. - The effective throughput is 300Mbps.

- 300Mbps is valid for downlink and is not valid for uplink.

- In uplink there is single antenna on UE, so with 20MHz we get maximum of 100Mbps, after considering 25% overhead, 75Mbps throughput is achieved in uplink.

- Throughput Calculation for LTE – FDD

- FDD is a paired spectrum has the same bandwidth for the downlink and the uplink. - 20MHz FDD system has 20MHz for downlink and 20MHz for Uplink.

- For Throughput Calculation: - Bandwidth – 20MHz

- UE Category 3

- For Cat 3, TBS index 26 for (75376 for 100RB) and 21 for (UL 51024 for 100RB). - Throughput = Number of chains x TB size

- DL Throughput = 2 x 75376 = 150.752Mbps - UL Throughput = 1 x 51024 = 51.024Mbps

PEAK CAPACITY

- To consider the peak capacity, let us consider 2x5Mhz system

- The number of resource elements in one subframe of 1ms = 12subcarriers x 7OFDM symbols x 25 Resource blocks x 2 slots = 4200 Resource elements.

- Calculating the data rate assuming 64 QAM with no coding (64QAM is highest modulation used in downlink LTE)

- 6 bits per 64QAM symbol x 4200 RE/1ms = 25.2Mbps - MIMO data rate for 2 x 2 MIMO = 2 x 25.2 = 50.4Mbps

- Subtracting the overhead related to control signaling such as PDCH and PBCH, reference and synchronization signals and coding which are estimated as follows

- PDCCH can take 1 to 3 symbols out of 14 in a sub-frame. Assuming that on average 2.5 symbols amount of overhead due to PDCCH becomes 2.5/14 = 17.86%.

- Downlink RS uses 4 symbols in every third subcarrier resulting in 16/336 = 4.76% overhead for 2 x 2 MIMO configuration.

- Other channels (PSS, SSS, PBCH, PCFICH, PHICH) added together upto 2.6% overhead. - The total approximate overhead for the 5 MHz channel is 17.86% + 4.76% + 2.6% = 25.22%. - The peak data rate is then 0.75 x 50.4 Mbps = 37.8 Mbps.

- Note that the uplink would have lower throughput because the modulation scheme for most device classes is 16QAM in SISO mode only.

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- There is another technique to calculate the peak capacity which I include here as well for a 2×20 MHz LTE system with 4×4 MIMO configuration and 64QAM code rate 1:

- Downlink data rate:

- Pilot overhead (4 Tx antennas) = 14.29%

- Common channel overhead (adequate to serve 1 UE/subframe) = 10% - CP overhead = 6.66%

- Guard band overhead = 10%

- Downlink data rate = 4 x 6 bps/Hz x 20 MHz x (1-14.29%) x (1-10%) x (1-6.66%) x (1-10%) = 298 Mbps.

- Uplink data rate:

- 1 Tx antenna (no MIMO), 64 QAM code rate 1 (Note that typical UEs can support only 16QAM)

- Pilot overhead = 14.3%

- Random access overhead = 0.625% - CP overhead = 6.66%

- Guard band overhead = 10%

- Uplink data rate = 1 * 6 bps/Hz x 20 MHz x (1-14.29%) x (1-0.625%) x (1-6.66%) x (1-10%) = 82 Mbps.

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30

6. Frequency Bands

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7. LTE Frame Structure

DOWNLINK FRAME STRUCTURE:

- Frame structure type 1

- 1 Frame = 10 ms = 10 subframes (1ms subframe each) - 1 Frame = 10ms i.e.. 1 subframe = 1ms

- Applicable to FDD and half duplex FDD.

-

- Frame structure

- The duration of one LTE radio frame is 10 ms. One frame is divided into 10 subframes of 1 ms each, and each subframe is divided into two slots of 0.5 ms each. Each slot contains either six or seven OFDM symbols, depending on the Cyclic Prefix (CP) length. The useful symbol time is 1/15 kHz= 66.6 mircosec. Since normal CP is about 4.69 microsec long, seven OFDM symbols can be placed in the 0.5-ms slot as each symbol occupies (66.6 + 4.69) = 71.29 microseconds. When extended CP (=16.67 microsec) is used the total OFDM symbol time is (66.6 + 16.67) = 83.27 microseconds. Six OFDM symbols can then be placed in the 0.5-ms slot. Frames are useful to send system information. Subframes facilitate resource allocation and slots are useful for synchronization. Frequency hopping is possible at the subframe and slot levels.

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32

-

- In LTE, radio resources are allocated in units of Physical Resource Blocks (PRBs). Each PRB contains 12 subcarriers and one slot. If the normal Cyclic Prefix is used, a PRB will contain 12 subcarriers over seven symbols. If the extended CP is used, the PRB contains only six symbols. The UE is specified allocation for the first slot of a subframe. There is implicit allocation for the second slot of the subframe. For example, if the eNB specifies one RB as the resource allocation for the UE, the UE actually uses two RBs, one RB in each of the two slots of a subframe. When frequency hopping is turned on, the actual PRBs that carry the UE data can be different in the two slots. In a 10 MHz spectrum bandwidth, there are 600 usable subcarriers and 50 PRBs.

- LTE - TDD Subframe Configuration

-

- Frame structure Type 2 is applicable to TDD is as shown in the figure. Each radio frame of 10 ms in length consists of two half-frames of 5 ms in length. Each half-frame consists of eight slots of the length Ts=5 ms and three special fields DwPTS, GP, and UpPTS of 1 ms in length.

- Different configurations, numbered zero to six, are defined in the standard for the subframe number allocated for the uplink and downlink transmission. Subframe 1 in all

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configurations and subframe 6 in configurations 0, 1, 2 and 6 consist of DwPTS, GP and UpPTS. All other subframes are defined as two slots.

- Switch-point periodicities of 5 ms and 10 ms are supported. The standard defines the table for the uplink and downlink allocations for switch-point periodicity. In the case of a 5-ms switch-point periodicity, UpPTS and subframes 2 and 7 are reserved for uplink transmission. - In the case of a 10-ms switch-point periodicity, UpPTS and subframe 2 are reserved for

uplink transmission and subframes 7 to 9 are reserved for downlink transmission.

- Subframe 0 and 5 are always for the DL. The subframe following the special SF is always for the UL. The DwPTS field carries synchronization and user data as well as the downlink control channel for transmitting scheduling and control information. The UpPTS field is used for transmitting the PRACH and the Sounding Reference Signal (SRS

- Each subframe is divided into two time slots.

For 1 Frame (10ms) = 10 sub-frames (1ms) = 20 Time slots (0.5ms) 1 sub frame = TTI = 2 Time Slots = 14 symbols ( 1 Time slot = 7 symbols)

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34 LTE- TDD SUBFRAME DETAILED:

Special Subframe Length >

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Switching Points

PRACH Preamble Format

Refer to 36.211 5.7 Physical random access channel for the details.

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36

Special Slot Usage

< RB Allocation on Special Subframe >

Refer to 36.213 7.1.7 Modulation order and transport block size determination for the details.

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HARQ Timing

< ACK/NACK from UE for PDSCH >

Following table shows the Ack/Nack Transmission Timing from UE for the PDSCH it recieved.

Problem is how to interpret this table. Following shows how to interpret each raw of the table.

Case 1 : UL/DL Configuration 0

In case of UL/DL Configuration 0, Ack/Nack response timing for the PDSCH that is received by UE is transmitted according to the following rule.

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38 How do you interpret this table and DL/UL correlation ?

It says

 UE transmit Ack/Nack at subframe 2,4,7,9

 At subframe 2, UE transmit Ack/Nack for PDSCH it received at subframe 6 in previous SFN

 At subframe 4, UE transmit Ack/Nack for PDSCH it received at subframe 0 in current SFN  At subframe 7, UE transmit Ack/Nack for PDSCH it received at subframe 1 in current SFN  At subframe 9, UE transmit Ack/Nack for PDSCH it received at subframe 5 in current SFN

How do you interpret this table and DL/UL correlation ?

It says

 UE transmit Ack/Nack at subframe 2,3,7,8

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SFN

 At subframe 3, UE transmit Ack/Nack for PDSCH it received at subframe 9 in previous SFN  At subframe 7, UE transmit Ack/Nack for PDSCH it received at subframe 0,1 in current SFN  At subframe 8, UE transmit Ack/Nack for PDSCH it received at subframe 4 in current SFN

How do you interpret this table and DL/UL correlation ?

It says

 UE transmit Ack/Nack at subframe 2,7

 At subframe 2, UE transmit Ack/Nack for PDSCH it received at subframe 4,5,6,8 in previous SFN

 At subframe 7, UE transmit Ack/Nack for PDSCH it received at subframe 9 in previous SFN and 0,1,3 in current SFN

< ACK/NACK from eNB for PUSCH >

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40