Tuesday, 20 October 2015

TDD-LTE-Describe Radio Resource management ( 3G UMTS and LTE)

Describe Radio Resource management ( 3G UMTS and LTE), covering at least the following aspects.



Admission control concepts,
Radio Admission Control makes the admission or rejected decision based on the overall resource situation and QoS requirement.
2        RAC considers the following three kinds of requests: initial service establishment, in-progress service modification and handover service establishment.
2        RAC takes into account the overall resource utilization situation, including: UL/DL PRB, DL power, S1 transmission bandwidth, hardware capability, etc.
2        RAC takes into consideration of the QoS of new service, including GBR of GBR service, prioritized bit rate of NonGBR service, allocation and retention priority, etc.
Based on the above requirements, there are many judgments to be based on before admitting the radio bearer request.
 the maximum RRC connection user number
2        DL PRB resource
2        DL power
2        UL PRB resource
2        UL/DL S1 transmission bandwidth
2        the maximum active E-RAB number
Only when all of the above judgments are passed, the radio bearer request can be admitted. Otherwise, it will be rejected and taken over by Congestion Control module.
Congestion control concepts,
Pre‐emption of existing data calls to accept new voice calls,
One important task of the RRM functionality is to ensure that the system is not overloaded and remains stable.
The possible congestion control actions in order to reduce load are listed below:
Uplink fast load control: Reduce the uplink Eb=N0 target used by the uplink fast power control.
2        Reduce the throughput of packet data traffic.
2        Handover to another carrier.
2        Handover to another RAT.
2        Decrease bit rates of real time UEs.
2        Drop low priority calls in a controlled fashion.
The first one in this list is fast action that is carried out within a Node B. These actions can take place within 5ms. The instantaneous frame error rate of the non-delay sensitive connections can be allowed to increase in order to maintain the quality of those services that cannot tolerate retransmission. These actions only cause increased delay of packet data services while the quality of the conversational services, such as speech and video telephony, is maintained.
The last one in this list is to pre-empt an existing low priority connection which is always a data service to set apart enough resources to let new connection with high priority to access, such as a voice call.
 Load control concepts,
When eNodeB confirms that overload happens at user access and HO, the load balancing function will be triggered. For Inter-RAT load balancing, service capability and UE capability must be considered:
The load balancing is applied to the cells with same coverage or coverage contained, and it includes UL and DL proceeding.
The load balancing algorithm function is in NEM or in RRM.
When NEM confirms to trigger load balancing in accordance with the information such as KPI, Tracing, fault report, etc., i.e. system overload abnormal report generates, and session dropping rate rises dramatically due to inability of access, etc., NEM needs to trigger the load balancing algorithm processing module.
If eNodeB service ability or system load ability reaches to the threshold, then the load balancing processing module inside the eNodeB needs to be triggered.
As for the load balancing function in NEM, it needs to be processed by co-operating with other RRM parameter optimization module, such as load threshold setting, HO parameter setting, neighboring cell list information setting, etc. Therefore, the load balancing performance is more perfect through the re-allocation optimization of the information.
As for the load balancing function in eNodeB, it pays more attention on load balancing algorithm and the implementation of NEM configuration parameter in the algorithm. It alleviates the load problem, realizes the load-sharing, optimizes the network and improves user QoS through the algorithm.
Scheduling strategies,
Prioritization of low traffic users, various types of applications,
For priorities of low traffic services, SPS is configured where possible, to save PDCCH resources. If SPS cannot be configured, this kind of UE should adopt time slicing to avoid assemble in one TTI which results in CCE resources limited very much. EPS system defines 4 different types of QoS: Conversation, Streaming, Interactive and Background. For priority processing strategy, these kinds of services will be queued and distinguished in scheduling algorithm according to their QCI, QoS characteristics (including delay, GBR, MBR, AMBR and ARP, etc.) and History Throughput, and so on.
Type of schedulers supported/configurable by operator,
Support for operator configurable eNB scheduler algorithm based on:
- Subscriber QoS classes (e.g. Gold, Silver, Bronze), as defined above
- non-GBR QCI parameters (Priority, PDB, PER).
- UE-AMBR
- MBR & GBR
Support for max C/I eNB scheduler.
Support for Proportional Fair eNB scheduler allowing trade-off between maximizing sector throughput and fairness amongst user's throughputs.
Support for frequency selective & frequency diverse scheduling in LTE,
Scheduling algorithm, with self-configuring and optimizing adaptation threshold and wideband/narrowband reporting intervals, per UE, is to maximize cell and user throughput.
Frequency selective scheduling is suitable for UE low speed mobility (below 20km/h) and slow channel variation scenarios. UE will adopt narrowband reporting method for the purpose of eNodeB scheduling.
Frequency diverse scheduling is suitable for UE higher speed mobility (above20km/h) scenarios. eNodeB will require UE to adopt wideband reporting method to feedback.
Support for semi‐persistent scheduling,
The principle of SPS is to pre-allocate resources at fixed sub-frames for initial transmission, while dynamic scheduling is still considered for retransmission. SPS is activated by specific PDCCH order. For downlink, PDCCH formats 1/1A/2/2Aare used; and for uplink, PDCCH format 0 is applied. Pre-allocated resources (the allocation of persistent resources such as the number of RB, the location of RB and MCS) are included in PDCCH order. The type of RB allocation is determined by PDCCH format which is used for activating SPS. For example, for downlink, if PDCCH Formats1/2/2A are used to activate SPS, RB allocation type 1 is adopted; if PDCCH Format1Ais used to activate SPS, RB allocation type2 DVRB is adopted.
It will be supported in future, please refer to the latest roadmap.
Support for TTI bundling,
In case of TTI bundling, the same transport block is repeatedly transmitted in four consecutive sub-frames with different RV parameters. The uplink scheduling grant addresses 4 sub-frames with one scheduling grant. PDCCH transmits only addressing the first UL TTI while PHICH only transmits in responding to the last TTI. For the initial transmission, the number of RB allocated to UE is no more than three and only QPSK is used. While for retransmission, the number of RB can be different from the first transmission.
Channel rate switching concepts (multi‐RAB),
We support multi-RAB.
Multi-RAB is related to QoS, and it is defined in TS 23.401. The figure is shown as below.
 
Admission control concepts,
Radio Admission Control makes the admission or rejected decision based on the overall resource situation and QoS requirement.
2        RAC considers the following three kinds of requests: initial service establishment, in-progress service modification and handover service establishment.
2        RAC takes into account the overall resource utilization situation, including: UL/DL PRB, DL power, S1 transmission bandwidth, hardware capability, etc.
2        RAC takes into consideration of the QoS of new service, including GBR of GBR service, prioritized bit rate of NonGBR service, allocation and retention priority, etc.
Based on the above requirements, there are many judgments to be based on before admitting the radio bearer request.
 the maximum RRC connection user number
2        DL PRB resource
2        DL power
2        UL PRB resource
2        UL/DL S1 transmission bandwidth
2        the maximum active E-RAB number
Only when all of the above judgments are passed, the radio bearer request can be admitted. Otherwise, it will be rejected and taken over by Congestion Control module.
Congestion control concepts,
Pre‐emption of existing data calls to accept new voice calls,
One important task of the RRM functionality is to ensure that the system is not overloaded and remains stable.
The possible congestion control actions in order to reduce load are listed below:
Uplink fast load control: Reduce the uplink Eb=N0 target used by the uplink fast power control.
2        Reduce the throughput of packet data traffic.
2        Handover to another carrier.
2        Handover to another RAT.
2        Decrease bit rates of real time UEs.
2        Drop low priority calls in a controlled fashion.
The first one in this list is fast action that is carried out within a Node B. These actions can take place within 5ms. The instantaneous frame error rate of the non-delay sensitive connections can be allowed to increase in order to maintain the quality of those services that cannot tolerate retransmission. These actions only cause increased delay of packet data services while the quality of the conversational services, such as speech and video telephony, is maintained.
The last one in this list is to pre-empt an existing low priority connection which is always a data service to set apart enough resources to let new connection with high priority to access, such as a voice call.
 Load control concepts,
 the load balancing including Intra-LTE and Inter-RAT LB. When eNodeB confirms that overload happens at user access and HO, the load balancing function will be triggered. For Inter-RAT load balancing, service capability and UE capability must be considered:
The load balancing is applied to the cells with same coverage or coverage contained, and it includes UL and DL proceeding.
The load balancing algorithm function is in NEM or in RRM.
When NEM confirms to trigger load balancing in accordance with the information such as KPI, Tracing, fault report, etc., i.e. system overload abnormal report generates, and session dropping rate rises dramatically due to inability of access, etc., NEM needs to trigger the load balancing algorithm processing module.
If eNodeB service ability or system load ability reaches to the threshold, then the load balancing processing module inside the eNodeB needs to be triggered.
As for the load balancing function in NEM, it needs to be processed by co-operating with other RRM parameter optimization module, such as load threshold setting, HO parameter setting, neighboring cell list information setting, etc. Therefore, the load balancing performance is more perfect through the re-allocation optimization of the information.
As for the load balancing function in eNodeB, it pays more attention on load balancing algorithm and the implementation of NEM configuration parameter in the algorithm. It alleviates the load problem, realizes the load-sharing, optimizes the network and improves user QoS through the algorithm.
Scheduling strategies,
Prioritization of low traffic users, various types of applications,
For priorities of low traffic services, SPS is configured where possible, to save PDCCH resources. If SPS cannot be configured, this kind of UE should adopt time slicing to avoid assemble in one TTI which results in CCE resources limited very much. EPS system defines 4 different types of QoS: Conversation, Streaming, Interactive and Background. For priority processing strategy, these kinds of services will be queued and distinguished in scheduling algorithm according to their QCI, QoS characteristics (including delay, GBR, MBR, AMBR and ARP, etc.) and History Throughput, and so on.
Type of schedulers supported/configurable by operator,
Support for operator configurable eNB scheduler algorithm based on:
- Subscriber QoS classes (e.g. Gold, Silver, Bronze), as defined above
- non-GBR QCI parameters (Priority, PDB, PER).
- UE-AMBR
- MBR & GBR
Support for max C/I eNB scheduler.
Support for Proportional Fair eNB scheduler allowing trade-off between maximizing sector throughput and fairness amongst user's throughputs.
Support for frequency selective & frequency diverse scheduling in LTE,
Scheduling algorithm, with self-configuring and optimizing adaptation threshold and wideband/narrowband reporting intervals, per UE, is to maximize cell and user throughput.
Frequency selective scheduling is suitable for UE low speed mobility (below 20km/h) and slow channel variation scenarios. UE will adopt narrowband reporting method for the purpose of eNodeB scheduling.
Frequency diverse scheduling is suitable for UE higher speed mobility (above20km/h) scenarios. eNodeB will require UE to adopt wideband reporting method to feedback.
Support for semi‐persistent scheduling,
The principle of SPS is to pre-allocate resources at fixed sub-frames for initial transmission, while dynamic scheduling is still considered for retransmission. SPS is activated by specific PDCCH order. For downlink, PDCCH formats 1/1A/2/2Aare used; and for uplink, PDCCH format 0 is applied. Pre-allocated resources (the allocation of persistent resources such as the number of RB, the location of RB and MCS) are included in PDCCH order. The type of RB allocation is determined by PDCCH format which is used for activating SPS. For example, for downlink, if PDCCH Formats1/2/2A are used to activate SPS, RB allocation type 1 is adopted; if PDCCH Format1Ais used to activate SPS, RB allocation type2 DVRB is adopted.
It will be supported in future, please refer to the latest roadmap.
Support for TTI bundling,
In case of TTI bundling, the same transport block is repeatedly transmitted in four consecutive sub-frames with different RV parameters. The uplink scheduling grant addresses 4 sub-frames with one scheduling grant. PDCCH transmits only addressing the first UL TTI while PHICH only transmits in responding to the last TTI. For the initial transmission, the number of RB allocated to UE is no more than three and only QPSK is used. While for retransmission, the number of RB can be different from the first transmission.
Channel rate switching concepts (multi‐RAB),
We support multi-RAB.
Multi-RAB is related to QoS, and it is defined in TS 23.401. The figure is shown as below.
 
eNodeB sends measurement configuration to UE with UTRAN/GERAN neighbor cells, and along with related UTRAN/GERAN cell parameters.
eNodeB makes the handover decision to the target cell, upon received measurement report that contains the target UTRAN/GERAN cell information.
The procedure of handover to UTRAN/GERAN is described briefly as follows:
2        eNodeB configured UE with some measure information such as UTRAN Neighbor Cell List, measure report principle, measure value, measure period.
2        UE reports measurement report to eNodeB.
2        eNodeB selects target UTRAN/GERAN cell according to handover algorithm and process handover preparation with target RNC.
2        eNodeB may forward data during the procedure.
2        eNodeB informs UE to process handover by sending handover command.
2        UE handover to new cell and LTE network releases the old resource if handover is completed successfully.
The target RNC may reject the use of Handover procedure in case none of the request RABs could be established. In this case, the UE remains in the source eNodeB/MME.
Inter-RAT Handover with UTRAN/GERAN will be supported in future, please refer to the latest roadmap.
Support for priority based inter‐RAT cell‐reselection,
eNB provides different systems/bands priorities for UE, and differentiations of systems/bands are taken when UE looking for suitable cell to camp.
Power control concepts,
Downlink power control determines the energy per resource element (EPRE).
LTE uplink power control includes:
2        Open-loop power control: set a basic value based on UE initialized to revise uplink power.
2        Close-loop power control: eNodeB measures SINR of PUCCH/PUSCH/SRS and compared with SINRtarget, informs UE to revise uplink power through PDCCH with TPC command.
2        Outer-loop power control: dynamic revise SINRtarget which is an important parameter of close-loop power control.
Downlink power allocation only includes the open loop power allocation.
Besides, power control needs to cooperate closely with the adaptive modulation and coding scheme, as well as the ICIC.
Positioning support concepts (cell ID, GPS assisted)
Positioning based on Cell ID will be supported in Version V2.0, and Positioning based on GPS will be supported in future.
Support for 5.9 AMR,
eNB is not concerned about concrete voice format. It can process various AMR rates which are assigned by CN.
Support for AMR‐WB,


Budi Prasetyo

About Budi Prasetyo

All About LTE

Subscribe to this Blog via Email :