nsn_load_balancing_white_paper_for_lg_u+.pdf

Page: 1 of 17

Private / Proprietary / Lock Contains Private and / or Confidential Information

May not be used or disclosed outside the LG U+ and Supplier companies except pursuant to a written agreement. Must be stored in locked files when not in use.

Nokia Siemens Networks Load balancing and overload control solution for LTE layer of Pico cell

Page: 2 of 17



The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended solely for the use of Nokia Siemens Networks customers only for the purposes of the agreement under which this document is submitted, and no part of it may be used, reproduced, modified or transmitted in any form or by any means without the prior written permission of Nokia Siemens Networks. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes customer comments as part of the process of continuous documentation development and improvement. Nokia Siemens Networks has made reasonable efforts to ensure that the instructions contained in this document are adequate and free of material errors and omissions. Nokia Siemens Networks will correct errors as soon as reasonably possible. The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products are given AS IS and liability, if any, of Nokia Siemens Networks arising in connection with such hardware or software products shall be defined only in a separate written agreement between Nokia Siemens Networks and its customer. IN NO EVENT SHALL NOKIA SIEMENS NETWORKS BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL OR ANY MONETARY LOSSES, INCLUDING BUT NOT LIMITED TO LOSS OF PROFIT, REVENUE, DATA, GOODWILL, OR OPPORTUNITY,THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION IN IT. This document and the products it describes are protected by copyright and other intellectual property rights according to law. Nokia Siemens Networks will vigorously pursue any breach of its rights hereunder. The Wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark of Nokia Corporation. Siemens is a registered trademark of Siemens AG. Other product names mentioned in this document may be trademarks of their respective owners, and they are mentioned for identification purposes only. Copyright Nokia Siemens Networks 2012. All rights reserved.

Page: 3 of 17



1. Objective ................................................................................................................................................ 4 2. Introduction ............................................................................................................................................ 5

2.1 Overload criteria ............................................................................................................................ 5 2.2 Overload handling ......................................................................................................................... 6

3. Load balancing and pre-emptive strategies ........................................................................................... 6 4. Initial Carrier Preferences ...................................................................................................................... 7 5. Carrier Load Criteria and Imbalance Recognition................................................................................ 10 6. Mechanism for Idle UE Balance Across Carriers ................................................................................. 11

6.1 Priorities for Idle Mode mobility - Cell Reselection ...................................................................... 11 6.2 Change priority of carrier selection in Active to Idle transition .................................................... 11

7. Mechanism for Active UE Balance Across Carriers (including overflow) ............................................ 12 7.1 Load balancing through redirections ........................................................................................... 12 7.2 Load balancing through Inter-frequency Load based HO ........................................................... 14 7.2 Load balancing through Intra- Frequency Load based handovers ............................................. 15

8. eICIC for macro/micro scenarios ......................................................................................................... 15 9. ICIC and overload handling ................................................................................................................. 16 10. Smart Admission Control for Overload Situation.............................................................................. 16 11. Final considerations ......................................................................................................................... 17

1. References ....................................................................................................................................... 17

Page: 4 of 17



1. Objective This document is being used to document topics related to load balancing and Overload Solution for NSNs Pico Cell as requested in the RFI from LG U+. This document represents NSNs current point of view and implementation. NSN is willing to continue the dialogue with LG U+, share view points and adapt our functionalities and features as required by LG-U+. The details for those new functionalities are to be discussed with LG-U+ and, therefore, might not be covered in this document.

Page: 5 of 17



2. Introduction Load balancing has been a hot topic in the past years. As traffic volume increased and QoS became more important, there has always been a concern about how to efficiently use resources for the right type of traffic. This was particularly important in situations where the resources were limited (such as the first releases of HSPA), were the amount of simultaneous users per carrier was low. It is NSNs line of thought that Load balancing will become more important as the LTE systems become more loaded and heavy traffic with QoS needs become a predominant factor. In NSN system the overload situations are tackled primarily by the admission control, the scheduler and mobility mechanisms. Overload handling can be managed on User traffic level and as well on the control plane.

The admission control will have to decide how to behave in overload situations when new requests are received. Therefore, the overload criterias will have to be linked to the admission criterias.

The scheduler will have to strategize the resource allocation depending on traffic priorities to optimize the user experience.

The mobility mechanisms will have to seek the help of surrounding cells to off load part of the traffic and reduce the overload situation whenever possible. These functionalities can also be used before the overload situation is reached.

2.1 Overload criteria As indicated in the introduction, the overload criteria should be linked to the admission control criteria. In theory, the overload should be identified when the admission control criteria has reached a limit. In that situation, the performance can suffer degradation. Therefore, from the conceptual point of view, it is not possible to talk about the overload handling strategy without talking about the pre-emptive strategy that tries to reduce to probability of reaching overload. The admission control will define the criteria or limit for admitting a new request. A margin under that limit will define the pre-emption stage when the pre-emption techniques should be applied. Once the admission control limit is reached, the overload stage will apply.

Page: 6 of 17



2.2 Overload handling Initially, the network will carry only non-GBR traffic. Since this traffic is best effort, there are no constraints in terms of minimum throughput to be provided (except for the behavior of NSNs performance enhancements of a smart scheduler that may try to warranty a minimum throughput at the cell edge). In this case, the admission control will admit new users as long as the maximum amount of simultaneous users is not reached. Then, it is the scheduler job to assign the resources in an efficient way to maximize both the user and the cell throughput. For new users attempting admission, the radio overload conditions will cause RRC connection rejects. This mechanism is further improved to include automatic access class barring for mobile originated signaling based on load. In a later scenario, where GBR is needed, the capability of scheduling the GBR requirements of the new user becomes an important factor. In case of overload due to GBR limitations, the GBR throughput requirements depending on the QCIs will reject new GBR bearers taking in to account the new call and handover differentiation. Please refer to the Smart Admission Control for more details on GBR needs estimations. NSN is planning the implementation of a configurable margin in the Smart Admission Control to allow an additional amount of users even when the GBR limits are met (in practice, this could mean a violation of the GBR requirements and a degradation of active GBR users, but more users will be granted service in the cell). The automatic access class barring for mobile originated calls will based on load. In addition we could also admit GBR bearer and trigger redirect afterwards For overload due to active users, initially we start with capability to reject new users at admission control for new call and handover differentiation as well. Later this will be enhanced to have automatic access class barring for mobile originated calls based on load along with admitting the bearer and triggering redirect afterwards. Transport overload condition will cause packet drop in the initial release. This will be enhanced to have GBR throughput based QCI usage to reject packets during overload.

3. Load balancing and pre-emptive strategies Overload handling can be better utilized in combination with Load balancing features/functionalities during or before overload situations (pre-emptive strategies). Load balancing can encompass a wide area of techniques that involve handover to less loaded cell, access class barring, redirection, fallback mechanism, etc NSN considers that the best way to trigger the load balancing and pre-emptive functionalities is to use the same criteria used for admission control (which will lead to overload scenarios) and apply a margin to the pre-emptions strategies. Please refer to the previous section of this document, where the admission control thresholds are broken down. As a summary the main strategies to be considered are:

Initial carrier preference control

Imbalance recognition

Mechanisms for load balancing of idle users

Mechanisms for load balancing of active users

Inter-carrier overflow mechanisms

Load based Handover.

Additionally, the scheduler is an important factor for load handling. The scheduler should not be part of direct pre-emption strategies. The scheduler should do time and frequency allocations to decide which users will get resources. These decisions will be based on QCI, GBR requirements, traffic weights; fair allocation formulas (please refer to the scheduler white paper for more details). The scheduler will have to

Page: 7 of 17



decide how to best allocate the resources to obtain the best performance when the load is high and try to overcome the overload situation. In high load scenarios, the GBR users will be allocated over the non-GBR ones.

4. Initial Carrier Preferences The PLMN selection and initial carrier selection is described in 3GPP 23.122 and 36.304. Both processes are controlled by the UE and, therefore, are UE dependent. The network can only broadcast the cell reselection parameters needed for the UE to make the appropriate decision. Even if the network could adapt the cell selection parameters depending on the amount of load in the cell; it is still not clear the benefit that this could provide. There is not an obvious way to quantify the amount of idle users camping in the cell. Incorrect parameter settings may even force the majority of the idle users (if not all) to select other cells. This could potentially produce the opposite of the desired effect: some cells will have low amount of camping UEs while others will have the majority of them. Additionally, it is not possible to predict the kind of traffic that those idle users will end up producing if they ever become active. Therefore, it is not clear that balancing the amount of idle users between carriers can actually benefit the network. In other words, even if the amount of users could be balanced, still few amount of high volume GBR UEs can produce imbalance in the actual load carried by the network. With all the considerations above, NSN line of thought is that the best approach for initial carrier preference is to use the priority broadcasted in the cell and let the UE decide where to camp. Therefore, if there is a preference to have most of the users in carrier A (which, for example, could have more BW than carrier B), then the priorities could be higher for carrier A. The figures below show the steps of the mechanisms defined in 3GPP for PLMN selection and Cell selection.

Page: 8 of 17



PLMN Selection mechanism (3GPP 23.122)

Null Switch on, SIM not available

Switch on with SIM

Yes SIM available Select registered

PLMN

Is there a

RPLMN ?

No SIM

No

Trying RPLMN

C Registration success Registration failure

A B

Indicate selected PLMN

LR response "Roaming not allowed"

E A Trying PLMN

On VPLMN and timeout occurs

D

A Yes

Any allowable PLMNs

available ?

On PLMN

C Loss of radio coverage of

selected PLMN **

Select first * PLMN in list

Select next * PLMN in list

User re-selection

Registration successful

Registration failure, more in list

B Registration failure, no more in list D

Move last selected PLMN temporarily into

list No

Any PLMNs

& allowable ?

available Select RPLMN or HPLMN or EHPLMN if

No RPLMN***

Higher priority PLMN PLMN search

G

PLMN background

search

Higher priority PLMN not PLMN found

E A

Yes

C

Select first available and

allowable PLMN in list

A G

No

Wait for PLMNs

to appear

PLMN available and allowable

PLMN available and allowable, which is not RPLMN

E A

* "List" consists of points i) to v) as defined in section 4.4.3.1.1 except in case of a user re-selection in which case "list" consists of points i) to vi) as defined in section 4.4.3.2.1 ** Includes effective loss of coverage due to LAs/TAs being forbidden in all potentially suitable cells *** HPLMN (if the EHPLMN list is not present or is empty) or EHPLMN (if the list is present)

Registered

Switch Off

SIM not available or invalid SIM

User reselection

Higher priority

found

Page: 9 of 17



Cell Selection Mechanism (3GPP 36.304)

Initial Cell Selection

Any Cell Selection

go here when no USIM in the UE

USIM inserted

Camped on any cell

go here whenever a new PLMN is

selected

1 no cell information

stored for the PLMN cell information

stored for the PLMN

Stored information

Cell Selection no suitable cell found

no suitable cell found

Cell Selection when leaving

connected mode

suitable cell found 2

suitable cell found Camped normally

suitable cell found no suitable cell found

leave idle mode

return to idle mode

Connected mode Cell Reselection

Evaluation Process

suitable cell found

trigger

no suitable cell found

1

Cell Selection when leaving

connected mode

no acceptable cell found

acceptable cell found


suitable cell found 2

leave idle mode

return to idle mode

Connected mode

(Emergency calls only)

Cell Reselection Evaluation Process


trigger

no acceptable cell found

NAS indicates that registration on selected

PLMN is rejected (except with cause

#12, #14 or #15 [5][16])

Page: 10 of 17



5. Carrier Load Criteria and Imbalance Recognition Based on the information indicated in the previous section, it is NSN opinion that the best way to identify load is based on the actual traffic. The load balancing mechanisms should work together with the admission control and the scheduler. Initially, the network will carry only non-GBR traffic. Since this traffic is best effort, there are no constraints in terms of minimum throughput to be provided (except for the behavior of NSNs performance enhancements of a smart scheduler that may try to warranty a minimum throughput at the cell edge). In this case, the admission control will admit new users as long as the maximum amount of simultaneous users is not reached. Then, it is the scheduler job to assign the resources in an efficient way to maximize both the user and the cell throughput. In this kind of scenario, it is expected that the load criteria for load balancing will follow the criteria used by the admission control (number of users), as all the users will have similar performance needs. It would also be expected that an equal distribution of users could improve the performance, although it is also true that additional factors such as the RF conditions of those users can skew the fairness of that distribution. In a later scenario, where GBR is needed, scheduler becomes an important factor. The same way that admission control will have to adapt to this needs as part of the admission decision, load balancing will have to consider those factors as well. Therefore, a good way to define the load criteria is to set a threshold before the overload scenario to trigger the load balancing mechanisms.

Page: 11 of 17



6. Mechanism for Idle UE Balance Across Carriers It is still possible to use cell reselection priorities that are broadcasted in the cell to favor certain carriers. This decision is done in the UE.

6.1 Priorities for Idle Mode mobility - Cell Reselection TS36.304 defines the priorities of different E-UTRAN frequencies or inter-RAT frequencies as described below.

Absolute priorities of different E-UTRAN frequencies or inter-RAT frequencies may be provided to the UE in the system information or in the RRC message releasing the RRC connection,

UE shall only perform reselection evaluation for E-UTRAN frequencies and inter-RAT frequencies that are given in system information and for which the UE has a priority provided. UE shall not consider any black listed cells as candidate for reselection.

The UE shall apply the following rules for E-UTRAN inter-frequencies and inter-RAT frequencies which are indicated in system information and for which the UE has priority provided

6.2 Change priority of carrier selection in Active to Idle transition In addition to the method indicated in the previous section, it is possible to use the RRC connection release mechanism to favor the reselection to a particular carrier. This way, the UE gets an indication of which carrier the UE should camp on. So it could be possible to apply an internal mechanism to alternate the carrier indication. This is still under evaluation (e.g. Ping-pong effects with speed dependent cell reselections needs to be considered). The figure below shows the signaling related to the Active to Idle transition. As part of the RRC Connection Release, it could be possible to change idle mode priority setting via dedicated signaling.

Active to Idle transition RRCConnectionRelease-r8-IEs ::= SEQUENCE { releaseCause ReleaseCause,

eNBUE MME S-GW

S1AP: UE Context Release Command

S1AP: UE Context Release CompleteRRC: RRC Connection Release

Release all UE related resources,

remove UE context

Set UE to RRC-IDLE

Set UE to ECM-IDLE

Detect user inactivityor other eNB trigger

S1AP: UE Context Release Request

S11 interaction to inform S-GWabout connection release

UE inRRC-CONNECTED

L2 ACK

Page: 12 of 17



redirectionInformation RedirectionInformation OPTIONAL, - Need ON idleModeMobilityControlInfo IdleModeMobilityControlInfo OPTIONAL, - Need OP nonCriticalExtension SEQUENCE {} OPTIONAL - Need OP }

It is possible to use idlemodibilitycontrolinfo which is OP idleModeMobilityControlInfo Provides dedicated cell reselection priorities. Used for cell reselection as specified in TS 36.304 [4]. cellReselectionPriority Absolute priority of the associated carrier frequency (0 means: lowest priority).

7. Mechanism for Active UE Balance Across Carriers (including overflow) Load balancing of active users seem to be a better approach since the balancing decision can be made with the knowledge of the amount of traffic that the user needs from the network (or, at least, an approximation).

7.1 Load balancing through redirections

The first option that it is being considered is the use of redirection during the admission of a new active user. In a normal call, the UE radio capabilities are known after the RRC message UE Capability Information is received at the eNB (see first of the two figures below). This information is important to know, for example, whether the UE supports the frequency layer. At that point, instead of sending the RRC message RRC Connection Reconfiguration to continue with the call establishment, it could be possible to use the RRC message Connection Release with Redirect to establish the call in a different carrier. There must be further discussion about the redirection strategy between different bands. There is a potential risk that a UE that is capable of starting the call establishment process in one carrier, might not have enough coverage to finish the process in the second carrier if the second carrier is in a higher frequency band. This redirection mechanism could be particularly useful in case of overload (when admission control is going to deny the access to the new bearer). In a case where load balancing is being done based on Load based HO, it is still under evaluation if this type of redirection should be used for load balancing as well. After all, load balance could be achieved through the HOs without risking redirection during call establishment.

Page: 13 of 17



Normal call signaling

Redirected call signaling

UE eNB MME

S 1 AP : INITIAL CONTEXT SETUP REQUEST

S 1 AP : INITIAL CONTEXT SETUP RESPONSE

RRC : RRCConnectionReconfiguration

User Plane Configuration

RRC : RRCConnectionReconfigurationComplete

RRC : SecurityModeCommand

RRC : SecurityCommandComplete

Security Establishment

RRC : UECapabilityEnquiry

RRC : UECapabilityInformation UE radio capabilities available

S 1 AP : UE CAPABILITY INFO INDICATION

UL NAS Transfer

RRC: Connection release w. redirect

S1AP: INITAL CONTEXT SETUP FAILURE

Page: 14 of 17



7.2 Load balancing through Inter-frequency Load based HO Besides the redirection during call establishment, it is also possible to apply Load based HO for the purpose of load balancing between unequally loaded neighbor cells on different frequency layers. This feature applies to following inter frequency use cases: 1) macro/macro 2) macro/small cell 3) Small cell / small cell If the eNB reaches a state of Load balancing needed, the eNB will start the following procedure:

Identify Load balance needed between carriers

Identify which users should be moved to a different carrier

Send measurement commands to those UEs

Evaluate the responses of the measurement commands vs. the list of candidates to be moved a different carrier

Send the HO commands to those users that should be moved to a different carrier

Note that HO with measurements is perceived as a better option than blind HO. That way, the networks can know that there is enough coverage in the target carrier before forcing the UE to perform a HO.

Load based HO procedure Conceptual idea under discussion

It is important to highlight that these kinds of procedures have been important in cases like early stages of WCDMA/HSPA deployments with multiple carriers. In those cases, the amount of simultaneous HSPA users was impacted by R99 voice users and was so low (

Page: 15 of 17



In LTE, the limitations will be less restrictive in terms of amount of users or throughput available. Therefore, it is expected that this kind of load balancing techniques will become more important as GBR becomes a restrictive factor. This should not happen at the early stage of the deployment.

7.2 Load balancing through Intra- Frequency Load based handovers The load balancing through Intra frequency load based Handovers is achieved by applying Cell Individual HO Offsets and is applicable for the following scenarios;

Macro - Macro Load Balancing Macro Micro Load Balancing

Where Micro is for maximizing capacity and as well for closing coverage holes Micro Micro

The intra-frequency load balancing algorithm is triggered once the source cell load is above a threshold and stopped once the source cell load is below a threshold. The load balancing algorithm shifts the handover thresholds between cells with different load conditions, i.e. shrink loaded cells and expand unloaded cells. The allowed handover parameter range is configurable per cell. The load balancing algorithm uses the mobility change procedure via X2 to align the handover thresholds between neighbor cells. The changed handover parameters are applied for e.g.

all new UEs entering the RRC Connected state and UE with heavy resource consumption

Configuration change triggered by this feature are reported to NetAct

8. eICIC for macro/micro scenarios

With 3GPP Rel 10 we get Time domain based eICIC to improve load balancing and interference handling in co-channel deployment scenarios to improve end-user experience in macro/micro network deployments.

The basic idea of the feature is to reduce the downlink inter-cell interference generated by a macro cell to a UE in a micro cell by introducing 'almost blank subframes' (ABS) in the macro cell.

The ABS subframe contains:

Common reference symbols (CRS) Positioning reference symbols (PRS), if configured Primary synchronization channel (PSS) Secondary synchronization channel (SSS) PCFICH PHICH PBCH but no PDSCH or PDCCH.

Pre-condition for the eICIC operation is that all cells are frame synchronized.

The macro eNode B uses the composite available capacity (CAC) parameter which is exchanged via the X2 interface between the macro cell and its X2 micro cell neighbors to decide whether to increase or

Page: 16 of 17



decrease the number of ABS subframes in the macro cell.

The ABS pattern of the macro cell (the number of max ABS subframes and the subframe number) is operator configurable.

The macro cell informs the micro cell via X2 about changes of its ABS allocation.

The micro cells are using this information for uplink and downlink scheduling, i.e. preferably use certain subframes for scheduling.

The introduction of the ABS subframes introduces some variation in the RSRP and RSRQ UE measurements. Accordingly, measurement muting pattern are supported for 3GPP Rel. 10 UEs. 3GPP R8/R9 UE is treated by own measurement configurations.

The following performance counters are provided, e.g.

ABS distribution, i.e. number of frames with no, with one, with two, ABS The feature can be enabled per eNode B by O&M setting.

9. ICIC and overload handling It is NSN current understanding that the current 3GPP Rel8 and 9 based ICIC, the information provided through the X2 interface refers to the usage of PRBs, not the actual load situation of the cell. There is a standardized overload message over X2, but it is used to solve interference issues since it indicates the power received in UL in different PRBs. Still, a cell could be using all the PRBs (scheduler decision to maximize the allocation for peak rates) and still not be overloaded. Even if that information was to be used to overload considerations, those measurements would only be useful for a very concentrated traffic when the same PRBs are allocated systematically to the same users. If the allocation changes dynamically, the information provided over X2 would be less useful and trying to provide that information to the neighbor cells on a regular basis might even increase the load in the eNB. In an overload situation, it is expected that the eNB will need to use as many PRBs as possible to serve traffic. In that scenario, letting the neighbor eNBs know about it will not produce any benefit. NSN relies on the Dynamic (Channel Aware) Scheduler to choose the best PRBs for each user based on UE measurements regardless the level of load of the neighbors. If the neighbors are overloaded, that will be reflected in the measurements taken by the UEs.

10. Smart Admission Control for Overload Situation Smart Admission Control is an enhancement related to the support of QoS as part of Admission Control. The QoS aware Admission Control grants or denies access to a new radio bearer depending on whether the required QoS of the new radio bearer will be fulfilled while guaranteeing the required QoS of the in-progress sessions. Note that these QoS aware Admission Control must work together with a QoS aware scheduler that allocates the dynamically shared data channels to the active radio bearer so as to fulfill their required QoS. The proposed AC algorithm checks if the current resource allocation can be modified so as to admit the new user and satisfy the GBR requirements of all the active users and the new user. Hence, the admission criterion for the new user is that the sum of the required number of physical resource blocks (PRBs) per TTI (Ni) by the new user requesting admission and existing users is less than or equal to the

Page: 17 of 17



total number of PRBs in the system bandwidth (Ntot) e.g. 50 PRBs in 10 MHz and this can be expressed as the formula below.

Where, k is the number of existing users in the cell. Hence, the AC calculates the required number of PRBs per TTI of a user while satisfying its GBR requirement and UL transmitting power constrains. The Ni of the existing users can be estimated at the eNB by using the average scheduled throughput per PRB information, while Nnew needs to be estimated using the pathloss (PL) and required GBR information. The pathloss of a user can be estimated at the eNB by using the downlink reference signal received power (RSRP) measurement signaled by the user over the radio resource control (RRC). Additionally, if the power needed in UL for the new UE is higher than the Pmax available for the new user is denied admission since it is power limited.

11. Final considerations NSN has done extensive analysis on Load Balancing algorithms and how to manage Overload situations at the Admission stage and as well during idle and active mobility scenarios. Current findings are that for LTE deployments where the GBR requirements thresholds are going to be low (such as VoIP), it is sufficient to base the Admission Control decision on the maximum amount of users that the cell can handle or comparing the sum of GBR to some reference GBR in cell threshold. Then, it is up to the Packet Scheduler to make sure that the GBR is met. Once other traffic classes with higher GBR requirements are introduced, a Smart Admission Control, where the radio conditions of the UE are checked, becomes more important. NSN proposes the use of 3GPP and idle mobility and dedicated signaling at RRC connection release to control the distribution of users in different carriers. Admission control criterias (plus certain offset) can be used to identify the situations where the load is getting higher. This way, it will be possible to change the camping preferences of idle UEs. In case of active users, it is understood that active users have already gone through the admission control process. Nevertheless, as part of the handover scenarios, an admission control procedure is applied in the target cell. The admission control for handovers is different from the one used for new calls. In case of load based HO, the load of the target cell will be considered before admitting an in-coming HO.

1. References

[1] NSN_RAN_6_7_10_11_14_27_WP_Scheduler related topicsV1.0

[2] NSN_RAN_16_17_33_Admission Control_WP_v1.0

[3] 3GPP TS 36.331

[4] 3GPP TS 36.304

1. Objective2. Introduction2.1 Overload criteria2.2 Overload handling

3. Load balancing and pre-emptive strategies4. Initial Carrier Preferences5. Carrier Load Criteria and Imbalance Recognition6. Mechanism for Idle UE Balance Across Carriers6.1 Priorities for Idle Mode mobility - Cell Reselection6.2 Change priority of carrier selection in Active to Idle transition

7. Mechanism for Active UE Balance Across Carriers (including overflow)7.1 Load balancing through redirections7.2 Load balancing through Inter-frequency Load based HO7.2 Load balancing through Intra- Frequency Load based handovers

8. eICIC for macro/micro scenarios9. ICIC and overload handling10. Smart Admission Control for Overload Situation11. Final considerations1. References

nsn_load_balancing_white_paper_for_lg_u+.pdf

Documents