09 - Ltend - Lte Advanced

7/29/2019 09 - Ltend - Lte Advanced

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Labs S.r.l. all right reserved

LTE Advanced Featur

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This solution is aimed at addressing the LTE-Advanced requirements for the 100 MHz of spectrum

needed to support 1 Gbps peak data rates. It is expected that this required 100 MHz will be created by

the aggregation of non-contiguous channels from different bands in a multi-transceiver mobile device.

The proposal to extend aggregation up to 100 MHz in multiple bands raises questions about the viability

of solutions due to the added cost and complexity to the UE.

Contiguous aggregation of two 20 MHz channels may be a more achievable goal provided the spectrum

can be found.


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LTE Advanced Featur

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The potential reception gains from MIMO systems and from beamsteering are a function of the number

of antennas, and proposals are being considered that would increase this number for systems up to 8x8.

Although the theoretical potential of such systems can be simulated, practical considerations make

commercial deployment more challenging. At the eNB, such an increase could require the use of tower-

mounted radio heads to avoid the need to run 8 sets of expensive and lossy cables up the tower. The

increased power consumption of MIMO systems must also be considered. There is a trade-off between

number of antennas per sector and the number of sectors per cell, so it may be preferable to use a six

sector cell with four antennas per sector rather than a three-sector cell with eight antennas per sector.

At the UE, the main issue with higher order MIMO is the physical space required for the antennas.

Laptop data-only systems clearly have an advantage over handheld devices in terms of size, power

handling, and throughput requirements.

Moreover, it is very hard in a small device to achieve the necessary spatial separation of the antennas in

order to exploit spatial beamforming in the channel.


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Co-operative MIMO allows physically separate transmitters belonging to different UEs to be linked and

to share playload data, thus obtaining the full benefit of closed-loop performance using precoding. This

scenario is possible only in the downlink, and it presents new challenges for inter-eNB communication

over the X2 interface.

In some ways co-operative MIMO is a more advanced form of the macro diversity used to enable soft

handovers. The advantage over soft handovers is that the transmission of two streams over what is

likely to be uncorrelated channel conditions will lead to a higher probability of increased data rates for

cell-edge users. Both techniques, however, reduce overall system capacity due to the scheduling of

downlink resources in more than one cell, though co-operative MIMO will be more efficient. The impact

of co-operative MIMO therefore could be some rise or fall in system capacity depending on the fairness

criteria of the scheduler.


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LTE Advanced Featur

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Co-operative MIMO allows physically separate transmitters belonging to different UEs to be linked and

to share playload data, thus obtaining the full benefit of closed-loop performance using precoding. This

scenario is possible only in the downlink, and it presents new challenges for inter-eNB communication

over the X2 interface.

In some ways co-operative MIMO is a more advanced form of the macro diversity used to enable soft

handovers. The advantage over soft handovers is that the transmission of two streams over what is

likely to be uncorrelated channel conditions will lead to a higher probability of increased data rates for

cell-edge users. Both techniques, however, reduce overall system capacity due to the scheduling of

downlink resources in more than one cell, though co-operative MIMO will be more efficient. The impact

of co-operative MIMO therefore could be some rise or fall in system capacity depending on the fairness

criteria of the scheduler.


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Long Term Evolutio

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The LTE air interface also supports the multimedia broadcast and multicast service (MBMS), a relatively

new technology for broadcasting content such as digital TV to UE using point-to-multi-point

connections. The 3GPP specifications for MBMS first appeared for UMTS in Release 6. LTE will specify a

more advanced evolved MBMS (eMBMS) service, which operates over a Multicast/Broadcast over

single-frequency network (MBSFN) using a time-synchronized common waveform that can be

transmitted from multiple cells for a given duration.

The MBSFN allows over-the-air combining of multi-cell transmissions in the UE, using the cyclic prefix

(CP) to cover the difference in the propagation delays. To the UE, the transmissions appear to come

from a single large cell.

This technique makes LTE highly efficient for MBMS transmission. The eMBMS service will be defined in

Release 9 of the 3GPP specifications.

LTE allows for multicast/broadcast and unicast on the same carrier as well as dedicated

multicast/broadcast carrier


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LTE Advanced Featur

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Another method of improving coverage in difficult conditions is the use of relaying.

The concept of relaying is not new but the level of sophistication continues to grow. The most basic

relay method is the use of a repeater, which receives, amplifies and then retransmits the downlink and

uplink signals to overcome areas of poor coverage. Repeaters can improve coverage but do not

substantially increase capacity. More advanced relays can in principle decode transmissions before

retransmitting them. This gives the ability to selectively forward traffic to and from the UE local to the

relay station thus minimizing interference. The relay station can also be applied in low density

deployments where a lack of suitable backhaul would otherwise preclude use of a cellular network. The

use of in-band or in-channel backhaul can be optimized using narrow point-to-point connections to

avoid creating unnecessary interference in the rest of the network.

Multi-hop relaying is also possible.


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LTE Advanced Featur

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The introduction of OFDMA to cellular systems has significantly changed the nature of cell edge

interference. In OFDMA the potential for frequency-selective scheduling within the channel opens up

new possibilities for optimizing intracell performance, but the inter-cell co-channel interference created

is far more dynamic. Work is ongoing to better understand the effect this interference may have on

operational performance. In particular the behavior of subband CQI and PMI reporting will be

influenced by the narrowband statistical nature of the interference. In OFDMA systems that employ

frequency-selective scheduling, for example, from the time of CQI reporting to the impact on the next

scheduled transmission the interference conditions may have changed from being present to absent or

vice versa.

The interference protection between cells offered in CDMA by whitening of noise is not available in

narrowband OFDMA transmissions, which increases the vulnerability of narrowband signals to

narrowband interference. Techniques to overcome such interference include making transmissions

more robust by repeating (spreading) information across a wider allocation. A technique known as block

repeat OFDM is being considered as a backward compatible enhancement to LTE to mitigate the impact

of interference. The downside is that there is a reduction in system capacity. Other methods for

controlling interference are still being researched.


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LTE Advanced Featur

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LTE Advanced Featur

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Todays cellular systems are very much centrally planned and the addition of new nodes to the network

involves expensive and time-consuming work, site visits for optimization, etc. One of the enhancements

being considered for LTEAdvanced is the self-optimizing network (SON) concept. The intent is to

substantially reduce the effort required to introduce new nodes to the network. There are implications

for radio planning as well as for the operations and maintenance (O&M) interface to the eNB. Some

limited SON capability will be introduced in Release 8 and will be further elaborated in Release 9 and

Release 10.

With the innovation of a flatter all-IP network and the deployment of greater bandwidth in the core

backhaul network, it is now possible to automate many of the configuration, optimization and healing

functions of wireless networks.

SONs offer a vision in which base stations automatically interact with each other and with the core

network to perform self-organizing functions.


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LTE Advanced Featur

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From the moment a SON base station is first powered up, it will have the ability to automatically

configure itself, installing and adjusting its initial parameters before joining the network. This would

apply to macrocell base stations, which are installed in soaring towers with extensive RF ranges;

picocells, which have more limited reach; and even the new femtocell base stations for homes and

small businesses. As a part of the self-configuration process, the base station would have the ability to

configure its physical cell identity, including its IP address, and to authenticate its software and

configuration data.

Once these steps are completed, the base station would initialize its radio configuration. This involves

setting up the stations relationships with base stations in neighboring cells, configuring the stations

neighbor list. An automated configuration process takes on even greater importance as more base

stations are deployed to improve network coverage and capacity. Moreover, 4G networks will not be

homogenous with regards to the types of base stations that make up the network. To date, the

mainstay of the wireless infrastructure has always been the large macrocell, but moving forward, more

and more of the smaller femtocells and picocells will dot the wireless landscape.

Femtocells that automatically configure themselves will be imperative for cost-conscious operators.

Features like the ability to automatically configure the cells physical ID and construct its neighbor

relation table will enable plug-and-play capabilities in a SON; this will support the rapid deployment of

femtocells and picocells.


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LTE Advanced Featur

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Following its initial self-configuration, a SON base station will begin optimizing its operating procedures, including the processwhereby it dynamically prunes and selects the base stations on its neighbors list.The optimization phase strives for maximum efficiencies based on a number of criteria, including energy consumption,interference conditions, range requirements, random access channel (RACH) utilization, mobility optimizations and others.Measurements from the base station itself, as well as cellular handsets within its range, form the basis for an auto-tuning processthat brings the base station to its optimum operating state for any particular moment in time. Of course, conditions can changedramatically from one moment to the next. A SON base station must be able to automatically sense spatial and temporal changesin the network and adapt its operations accordingly.

Operating criteria critical to a SON include:Energy savings. The cost of electricity to power base stations represents a larger portion of service providers operating expensesevery year. For example, at the Base Station Conference in 2006, European service provider Orange acknowledged that basestation power consumption had grown to approximately 75 percent of its networks total power consumption. With non-SON 3Gequipment, the only way operators could curb these expenses was to manually turn cells on or off based on the load conditionspresent in the network.In addition to the low-power components that will be implemented in 4G equipment, SONs will automatically power down cellsor simply reduce the transmit power output of certain base stations. For example, during the middle of the night when there islittle traffic on the network, certain cells can reduce their power output or turn off completely. To maintain coverage, a SONoperations and management system might compensate for turning off a cell by slightly increasing the power output of aneighboring cell. Energy reduction will be critical with the deployment of base stations in new form factors, such as residentialfemtocell and mid-size picocell base stations.Interference. SONs address two aspects of signal interference among cells: Interference reduction (IR) refers to slower low-frequency signals such as power control signals, while intercell interference coordination (ICIC) concerns interference that arisesat a finer time scale than IR interference. SONs IR and ICIC techniques choose the appropriate time and frequency resources tomitigate both types of interference. For example, frequency management, beam forming, transmit power reductions and othertechniques could be deployed automatically.Interference will become increasingly critical because 4G networks will inevitably employ a greater number of access points toincrease capacity, coverage and bandwidth, and many of these new base stations will be nested within larger cells. For example,SONs might dynamically adjust the transmit output power of a femtocell in a home to limit any potential interference it mightcause for the larger macrocell where it is located.Random access channel (RACH) success. Automatically setting up RACH configuration parameters such as the number ofpreambles on a packet and ramp-up power can optimize a SON base stations RACH performance, reducing synchronizationtimes, call setup times and handover delays while improving other aspects of RACH performance.Coverage and capacity maximization. A wireless networks coverage and capacity are optimized by monitoring channel quality toidentify base station coverage holes and to eliminate unnecessary overlapping coverage areas. SON base stations can dynamicallymanipulate parameters such as antenna tilt and reference power offsets to compensate for lapses in coverage and to ensureadequate capacity where and when it is needed.Mobility optimizations. The mobility features of a SON can be optimized in terms of the robustness of mobile services, likehandoffs from one cell to the next and by balancing load traffic among contiguous cells. Robustness is measured by the numberof handoffs that can be processed, the elapsed time needed for handoffs, radio link failures, access failures and others. Byobserving these factors, SON base stations can dynamically adapt certain parameters to improve performance.Balancing call loads in cells can have salutary effects on cell call capacity. SON base stations exchange information on theirrespective call loads and distribute call traffic accordingly. As a result, the handoff success rate improves while QoS increases.


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LTE Advanced Featur

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Once operational and initially optimized, a SON base station is sure to encounter conditions that will

require automatic self-healing mechanisms. In the case of network failures, the station must be able to

detect a wide variety of failure conditions and automatically launch actions that would be appropriate

to each condition. The intent of these alternative self-healing processes and procedures is to guarantee

a certain GoS and QoS to subscribers.

A base stations self-healing processes are often intertwined with self-optimizing procedures. For

example, a station might automatically increase its power output and extend its range in order to

offload a neighboring cell that is overloaded with traffic and failing to connect an unacceptably high

number of calls. This automatic expansion of a cells borders is sometimes referred to as breathing

because the base station will pushed outside its borders to alleviate the congested conditions

experienced by a neighboring cell. At the same time, the overloaded base station will contract its

borders to better serve the highly concentrated number of users within its range.

With SON technology, this automatic breathing process can be particularly beneficial to subscribers

during peak traffic conditions throughout the course of a typical day. For example, many people stuck in

rush hour traffic along a freeway corridor might all want to call home at the same time, increasing the

automatic deployment of resources along this corridor. During off-peak hours when few subscribers are

driving on this highway, some of cells might be turned off. Without SON technology, many wireless

operators have had to deploy technicians to manually manipulate base station energy output, channel

utilization and other operating parameters in their networks.


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LTE Advanced Featur

From the moment a SON base station is first powered up, it will have the ability to automatically

configure itself, installing and adjusting its initial parameters before joining the network. This would

apply to macrocell base stations, which are installed in soaring towers with extensive RF ranges;

picocells, which have more limited reach; and even the new femtocell base stations for homes and

small businesses. As a part of the self-configuration process, the base station would have the ability to

configure its physical cell identity, including its IP address, and to authenticate its software and

configuration data.

Once these steps are completed, the base station would initialize its radio configuration. This involves

setting up the stations relationships with base stations in neighboring cells, configuring the stations

neighbor list. An automated configuration process takes on even greater importance as more base

stations are deployed

to improve network coverage and capacity. Moreover, 4G networks will not be homogenous with

regards to the

types of base stations that make up the network. To date, the mainstay of the wireless infrastructure

has always

been the large macrocell, but moving forward, more and more of the smaller femtocells and picocells

will dot

the wireless landscape.

Femtocells that automatically configure themselves will be imperative for cost-conscious operators.

Features

like the ability to automatically configure the cells physical ID and construct its neighbor relation table

will enable

plug-and-play capabilities in a SON; this will support the rapid deployment of femtocells and picocells.

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09 - Ltend - Lte Advanced