LTE Curs 2 _v2012

LTE for 4G Mobile Broadband
by Ren ANDREESCU

Curs 2

by Ren ANDREESCU

Flat Architecture of LTE and SAE ( System Architecture Evolution )

by Ren ANDREESCU

Flat Architecture of LTE and UMTS

by Ren ANDREESCU

LTE Network Architecture

by Ren ANDREESCU

Ressourec Scheduling of Shared Channels

Dynamic resource scheduler resides in eNB on MAC layer.

Radio resource assignment based on radio condition, traffic volume, and QoS requirements.

Radio resource assignment consists of:

Physical Resource Block (PRB)

Modulation and Coding Scheme (MCS)

by Ren ANDREESCU

Radio Resource Management

Radio bearer control (RBC)

Radio admission control (RAC)

Connection mobility control (CMC)

Dynamic resource allocation (DRA) or packet scheduling (PS)

Inter-cell interference coordination (ICIC)

Load balancing (LB)

by Ren ANDREESCU

Downlink Overview

DL physical channels

Physical Broadcast Channel (PBCH)

Physical Control Format Indicator Channel (PCFICH)

Physical Downlink Control Channel (PDCCH)

Physical Hybrid ARQ Indicator Channel (PHICH)

Physical Downlink Shared Channel (PDSCH)

Physical Multicast Channel (PMCH)

DL physical signals

Reference signal (RS)

Synchronization signal

Available modulation for data channel

QPSK, 16-QAM, and 64-QAM

by Ren ANDREESCU

Downlink Physical Channel Processing

by Ren ANDREESCU

Downlink Reference Signal

Cell-specific 2D RS sequence is generated as the symbol-by symbol product of a 2D orthogonal sequence (OS) and a 2D

pseudo-random sequence (PRS).

3 different 2D OS and ~170 different PRS.

Each cell (sector) ID corresponds to a unique combination of

one OS and one PRS ~510 unique cell IDs.

CDM of RS for cells (sectors)of the same eNodeB (BS)

Use complex orthogonal spreading codes.

FDM of RS for each antenna in case of MIMO

by Ren ANDREESCU

Downlink Reference Signal

Radio Network Planning and Optimization
by Ren ANDREESCU

Example of a European operator with good spectrum resources

by Ren ANDREESCU

Downlink MIMO

Supported up to 4x4 configuration.

Support for both spatial multiplexing (SM) and Tx diversity (TxD)

SM

Unitary precoding based scheme with codebook based feedback

from user.

Multiple codewords

TxD: SFBC/STBC, switched TxD, CDD (Cyclic Delay Diversity)

considered.

MU-MIMO supported.

by Ren ANDREESCU

Uplink Overview

UL physical channels

Physical Uplink Shared Channel (PUSCH)

Physical Uplink Control Channel (PUCCH)

Physical Random Access Channel (PRACH)

UL physical signals

Reference signal (RS)

Available modulation for data channel

QPSK, 16-QAM, and 64-QAM

Single user MIMO not supported in current release.

But it will be addressed in the future release.

Multi-user collaborative MIMO supported.

by Ren ANDREESCU

Uplink Resource Block

by Ren ANDREESCU

Uplink Physical Channel Processing

by Ren ANDREESCU

Uplink Reference Signal

by Ren ANDREESCU

Random Access

by Ren ANDREESCU

LTE Standard Procedures

Synchronization procedures

Radio link monitoring

Inter-Cell synchronization for MBMS

Transmission timing adjustments

Power control for DL and UL

UE procedure for CQI (Channel Quality Indication) reporting

UE procedure for MIMO feedback reporting

UE sounding procedure

by Ren ANDREESCU

Coverage Requirements
For the coverage prediction, it is important to base it on accurate link budgets, which are influenced by both, environment and system specific parameters. The environment specific parameters are based on a threedimensionalray-tracing tool, which takes the topology data.It takes account of antenna patterns, pathloss
and shadowing.

by Ren ANDREESCU

Coverage Requirements
For indoor penetration loss, 20 dB is
assumed and is applied to buildings according to the topography.
The average peak rate is calculated for
the downlink direction.

by Ren ANDREESCU

Current 3G Macro Sites

by Ren ANDREESCU

LTE Link Budget
For coverage the specific parameters can be described by SINR to-data rate mappingsFor the UL coverage link budgets we assume an SNR of 3dB on both the UE and base station access links to be achieved for users with an assignment of 6 simultaneously used LTE resource blocks.This equals to a bandwidth of 1.08 MHz per user if a 10 MHz FDD system with 50 available resource blocks is considered

by Ren ANDREESCU

LTE Link Budget
These assumptions translate into an UL target user data rate of about 400 kbps.User data rates are calculated by assuming a total overhead of 30% for both, up- and downlink.The uplink part has some differences with UMTS: smaller interference margin in LTE, no macro diversity gain in LTE and no fast fading margin in LTE

by Ren ANDREESCU

LTE Link Budget
The link budgets show that LTE can be deployed using existing GSM and HSPA sites assuming that the same frequency is used for LTE as for GSM and HSPA.LTE itself does not provide any major boost in the coverage

by Ren ANDREESCU

Uplink link budget parameters for LTE

by Ren ANDREESCU

Downlink link budgets

by Ren ANDREESCU

Adaptive spatial multiplexing MIMO Requirements

The minimum set of required feedback information from the UE to support downlink adaptive spatial multiplexing MIMO transmission

comprises:

channel state/quality information (CQI): direct (e.g. SINR) or indirect (e.g. MCS) information on the average channel conditions estimated on the physical resources and MIMO codewords;

MIMO rank information: indicates the optimum number of spatial layers (streams) to be used and the corresponding pre-coding vector/matrix index (PMI);

HARQ information: indicates the reception status (ACKnowledged/Not ACKnowledged) of the transmitted data packets on the scheduled MIMO spatial layers.

by Ren ANDREESCU


The first two items above, CQI and PMI, are estimated by the mobile station based on the downlink pilot measurements and are transmitted back to the base station in a quantized form.

The HARQ mechanism has an impact on the freedom of the radio resource management blocks, when link adaptation and optimized packet scheduling has to be performed for single/dual codeword MIMO transmission.

CQI = Channel Quality Information

HARQ = Hybrid Adaptive Repeat and Request

PMI = Precoding Matrix Index

by Ren ANDREESCU


The mobile station feedback information is heavily dependent on the channel/signal estimation performance, which has an upper bound due to the practical system design limitations (reference signals, measurement/estimation time, propagation delays, etc.).

Furthermore, all thise feedback information requires uplink control channel capacity; thus it is desirable to minimize the actual number of information bits used to encode them and converge to a practical tradeoff between the achievable MIMO performance and the required uplink capacity.

CQI = Channel Quality Information

HARQ = Hybrid Adaptive Repeat and Request

PMI = Precoding Matrix Index

by Ren ANDREESCU

Higher Order Sectorization

One of the methods for increasing the performance by using more antennas at the base station is to use higher order sectorization. The use of higher order sectorization is especially considered to be an option for macro cell installations, where antennas are mounted above rooftops.

Typically, three-sector sites are assumed in most of the LTE macro cell performance evaluations, by using three separate panel antennas per site, each with a 3 dB beamwidth of 65 or 70 degrees.

by Ren ANDREESCU

Higher Order Sectorization

A first step could therefore be to increase the sectorization to four sectors per site by simply using six panel antennas with a narrower beamwidth of, for example, 90 degrees.

This provides a simple method for increasing the capacity of the network at the sites with high offered traffic.

by Ren ANDREESCU

Four Sectors Plan

by Ren ANDREESCU

Four Sectors Plan

Performance results for these four cases are presented in next figure, where the average throughput per site is reported.

These results were obtained with a simple full buffer traffic model, assuming two antennas at the terminals, and standard proportional fair time-frequencypacket scheduling.

A signifi cant performance gain is achieved by increasing the sectorization

from three sectors to four sectors: the site capacity is increased by 88%.

by Ren ANDREESCU

Relative spectral efficiency compared to 10 MHz bandwidth in macro cells

The Spectral efficiency for 20 MHz is

1.74 bps/Hz/cell 20 MHz = 35 Mbps,

while for 1.4 MHz

the cell throughput is

1.74 bps/Hz/cell 60% x 1.4 MHz = 1.5 Mbps.

by Ren ANDREESCU

Relative spectral efficiency compared to 10 MHz bandwidth in macro cells

The conclusion is that LTE should be deployed using as large a bandwidth as possible.

The main motivation is to maximize the LTE data rates, but the second motivation is to optimize the spectral effi ciency as well.

The narrowband options are still useful for refarming purposes if it is not possible to allocate larger bandwidths initially.

by Ren ANDREESCU

LTE dimensioning exemple at 20 MHz bandwidth in macro cells

by Ren ANDREESCU

Traffic growth scenarios with 10 times and 50 times more traffic

by Ren ANDREESCU

Example of a European operator with good spectrum resources

LTE Curs 2 _v2012

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Transcript of LTE Curs 2 _v2012