lte advanced part3(22052015(24 slides))

LTE-Advanced Part 3: Coordinated multipoint transmission and extended MIMO

Jyri Hmlinen, 2015 Department of Communications and Networking

Contents

Part 3: Coordinated multipoint transmission (CoMP), Rel.11 and extended MIMO 3.1 CoMP: Idea and benefits 3.2 CoMP scenarios 3.3 CoMP categories and schemes 3.4 LTE-Advanced extended MIMO

3.1 CoMP: Idea and benefits

2/19/2010 Word template user guide

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Idea of CoMP

Coordinated Multi-Point Transmission is one of the most important technical improvements of LTE Rel.11 CoMP improves to some extent macrocell network performance In case of Heterogeneous Network (HetNet) composed by macrocells,

microcells and picocells, CoMP is especially useful In all network deployment strategies (macrocell only and HetNet)

cell edge users are experiencing the inter-cell interference. Downlink: Inter-cell interference occurs due to parallel transmissions from

adjacent base stations Uplink: Intercell interference occurs due to simultaneous transmission (on

the same time-frequency resources) by users in adjacent cells. The goal of the CoMP is to further minimize inter-cell interference

for cells that are operating on the same frequency


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Benefits of CoMP

CoMP allows the optimization of transmission and reception from multiple TX/RX points, which could be either base stations or Remote Radio Heads (RRH).

In addition to inter-cell interference mitigation CoMP will help to Improve the network performance Increase rates on cell edges Improve load balancing between the cells


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3.2 CoMP scenarios


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Rel.11 CoMP scenarios

3GPP Rel.11 standardization is based on four different CoMP scenarios.

All scenarios assume Ideal Backhaul The first two scenarios focus on homogeneous (macrocell)

network deployment, Scenario 1: A single eNodeB is serving multiple sectors (Intra-site

CoMP) Scenario 2: Multiple high-transmit power Remote Radio Heads

(RRHs) connected to eNodeB (Inter-site CoMP) The other two scenarios focus on HetNet:

Scenario 3: Macro cells and small cells are jointly deployed using different cell identities

Scenario 4: Macro cells and small cells all employ the same cell ID


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Rel.11 CoMP scenarios (ideal backhaul)


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eNB

Coordination area

High Txpower RRH

Assume high Tx power RRHas same as eNB

Optical fiber

Low Tx power RRH(Omni-antenna)

eNB

Optical fiber

Scenario 1: Homogeneous network with intra-site CoMP

Scenario 2: Homogeneous network with high Tx power RRHs

Scenario 3/4: Network with low power RRHs within the macrocell coverage

Rel.12 CoMP scenarios

3GPP Rel.12 extension will introduce three additional CoMP scenarios

New scenarions (on top of Rel.11) assume non-ideal Backhaul Scenario 5: CoMP used among cells belonging to different

macro eNBs Scenario 6: CoMP used between a macro cell and one of

its small cells (small cell eNBs) Scenario 7: CoMP used among small cells (small cell eNBs) in a

macro cell (macro cell and small cells use different channel, but small cells share the same channel)


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CoMP terminology

CoMP Cooperating Set The CoMP Cooperating Set is determined by higher layers. It is

a set of geographically separated TX/RX points that are directly or indirectly involved in data transmission to a device in a time-frequency resource

The CoMP cooperating set defines the coordination area CoMP Measurement Set

The CoMP Measurement Set is a set of points, in which channel state information (CSI) or statistical data related to their link to the mobile device is measured and/or reported


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3.3 CoMP categories and schemes


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General CoMP categories

Joint processing: Joint processing occurs where there is coordination between multiple TX/

RX entities that are simultaneously transmitting or receiving to or from UEs. Coordinated scheduling or beamforming:

This category is often referred to as CS/CB (coordinated scheduling / coordinated beamforming). It is a form of coordination where a single TX/RX point operates at the time. However the communication is made assuming an exchange of control data among several coordinated entities.

To apply either of these modes, fast channel feedback is required so that the transmission parameter changes can be made.

The techniques used for CoMP are different for the uplink and downlink. This results from the fact that the eNBs are in a network, connected to other

eNBs, whereas the handsets or UEs are individual elements


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Downlink CoMP


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DL CoMP

Joint Processing Coordinated scheduling/beamforming

Joint Transmission Dynamic Point Selection

Downlink CoMP

The applied downlink CoMP schemes can be divided as follows:

Joint processing schemes for transmitting in the downlink: In this scheme data is transmitted to the UE simultaneously from a

number of different transmission points. Joint Transmission (JT): Transmission executed from multiple

points at a time (within CoMP cooperating set) Dynamic Point Selection (DPS): Transmission executed from

one point at a time (within CoMP cooperating set) The aim is to improve the received signal quality and strength.

Another goal can be to actively cancel the interference from transmissions that are intended for other UEs.

This form of CoMP places a high demand onto the backhaul network because the data needs to be sent to each transmission point that will be transmitting it to the UE.


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Downlink CoMP

Coordinated scheduling and or beamforming: When using this concept, data to a UE is transmitted from one

transmission point. The scheduling decisions as well as transmission beams are

coordinated to control the interference The advantage of this approach is that the backhaul

requirements are reduced since only scheduling decisions and details of beams needs to be coordinated between multiple transmission points


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Uplink CoMP


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UL CoMP

Joint Reception Coordinated scheduling/beamforming

Receiver processing in centralized reception point

Uplink CoMP

Joint reception and processing: In this approach antennas at different reception points are utilized. By coordinating between the different reception points it is possible

to form a virtual antenna array. The signals received by the reception points are then combined and processed to produce the final output signal.

The main disadvantage with this technique is that large amounts of data needs to be transferred between the reception points

Coordinated scheduling: This scheme coordinates the scheduling decisions amongst the

reception points to minimize interference This scheme provides a reduced load in the backhaul because only

the scheduling data needs to be transferred between the different reception points that are coordinating with each other.


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3.4 LTE-Advanced extended MIMO


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Downlink MIMO

Downlink MIMO schemes are extended/enhanced from Rel.8 LTE

Single-user MIMO operation is extended to support 8 TX antennas, (instead of 4TX supported by Release 8 LTE). Is eight layer operation practical?

Multi-user MIMO is enhanced by Improved spatial interference suppression

at transmitter side; improved feedback and precoding.

Interference awareness at receiver side, enabling interference cancellation.

Improved flexibility in frequency domain packet scheduling.

Spectral efficiency improved by MIMO

0

5

10

15

20

25

30

-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Spec

tral

effi

cien

cy [b

its/s

/Hz]

SINR [dB]

SIMO (1x2)

MIMO (2x2)

MIMO (4x4)

MIMO (8x8)

Max SE

Max SE

Max SE

Example: impact of extended MIMO

Consider the previous problem with parameters below 4 PRBs used, target rate is 2 Mbit/s and 5Mbit/s on 10 MHz

band Examine the impact of extended MIMO


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Radio Communication Systems II, Exercise 3, 2014 Problem 1. LTE downlink RLB (excel in Noppa): Assume the following link budget parameters 2.1GHz carrier, 25 meter base station antenna height and 1.5 meter UE height:

Parameter Value BS TX power 40W BS antenna gain 18dBi BS cable loss 2dB UE noise figure 7dB Interference margin 4dB RX antenna gain 0dBi RX body loss 0dB Control channel overhead 1dB Indoor penetration loss 20dB Shadow fading margin 7dB BS antenna configuration 2x2/4x4 MIMO

(a) Compute the coverage (large city, rural area) for 5Mbps service when BS allocates 10 PRBs for the user. What happens to the service coverage if BS can allocate all available 48 PRBs for this user (target rate being the same 5 Mbps)?

(b) Increase the user rate 10Mbps and compute solve a) (large city, rural area)? (c) In remote rural area LTE is used on 800MHz to provide mobile broadband for single

houses (e.g. farms). If user is applying simple directive antenna with 5dBi gain on house rooftop (5 meters height) and LTE receiver is connected to WiFi (through cable) that provides indoor connectivity, what is then maximum cell range for 5Mbps service if user can apply 10 PRBs? What happens if rate requirement is increased to 10Mbps?

Assess in all cases a)- c) the impact of MIMO. Does 4x4 MIMO provide significant gain over 2x2 MIMO? Problem 2. LTE downlink RLB. In problem 1 a): write down all computations that excel does when computing allowed propagation loss. Make sure that you understand all phases in link budget calculations of problem 1. Problem 3. In Figure 1 the LTE link spectral efficiency is given as a function of Signal to Interference and Noise ratio. The curve with crosses (x) is related to 2x2 MIMO transmission while curve marked by circles (o) is related to 4x4 MIMO transmission. The LTE bandwidths and number of resource blocks for different band options are given in Table below.

(a) Using Figure 1 define what is the maximum data rate (in bits/s) for 2x2 and 4x4 MIMO in 3MHz and 10MHz deployments.

(b) User with 5 RBs and 4x4 MIMO is served. What is the minimum required SINR when user data rate should be at least 10Mbit/s?

(c) Scheduler allocates for the user 3 RBs. What is the data rate of the user with 4x4 MIMO if SINR=12.5dB. How much rate is decreased if 2x2 MIMO is used instead of 4x4 MIMO?

Example: Range results for 2 Mbit/s case With 2x2 MIMO:

With 4x4 MIMO:

With 8x8 MIMO:


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Example: Range results for 5 Mbit/s case With 2x2 MIMO:

With 4x4 MIMO:

With 8x8 MIMO:


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Uplink MIMO

Uplink single-user MIMO is being introduced in order to increase average user throughput and, in particular, user throughput at the cell edge

UL SU-MIMO was considered already for Rel.8 LTE, but compared to the added benefit, it was found too expensive for the terminals due to need of multiple power amplifiers.

Up to 4 TX antenna transmission can be used in LTE-Advanced uplink.

lte advanced part3(22052015(24 slides))

Documents

benefits of comp comp

idea of comp

comp categories

different comp scenarios

comp scenarios ideal

multipoint transmission

comp cooperating set

macro cell macro cell