3G品質提昇及技術研討會 (1)有關目前PrxLoadMarginDCH參數設定值為10 dB，為避免上鏈負載成長過高，造成過大的細胞呼吸效應， 網維提出修訂建議。經NSN 測試後建議一併調整PrxTarget/PrxOffset、DeltaPrxMaxUP等參數。NSN change the related parameters of the whole network (Due to network activity, RN291, 28, 281, 61, 611, 411 are not changed yet), find that HSDPA Accessibility Failure due to UL-DCH can be improved while there are the increment of BTS and Iub failure due to higher traffic. Please NSN roll out this setting in remaining RNC. And propose the monitor report in the next meeting after roll-out.
細胞呼吸效應---一旦資料傳輸速率或使用人數增加時，則系統話務負擔增加，因此要降低系統負載，就必須縮小細胞涵蓋 區域，換言之，當細胞間的干擾增大，為維持系統容量，實際的細胞涵蓋區域會需要縮小，也就是細胞呼 吸效應。
PrxLoadMarginDCH
Range
0...30 Step
0.1 Default value 0 dB
For the interference domain, this parameter defines the maximum capacity for the throughput based traffic load that is allowed for the uplink DCH traffic in the cell. The parameter introduces a protection margin against the possible estimation errors in the interference based DCH resource allocation. If the received noise power level is overestimated, and because of that the interference of the DCH users is underestimated, it may result to overload which means possible loss in the uplink coverage and the network stability. When the DCH traffic load exceeds the threshold defined with the parameter, the RNC initiates UL overload control actions to reduce the uplink PS interactive and background DCH traffic.
DCH traffic load threshold
PrxNoise of WCEL - Value of the parameter is defined in the relation to the value of the parameter PrxNoise. , PrxLoadMarginDCH of WCEL Value of the PrxLoadMarginMaxDCH must be higher than or equal to the value of the PrxLoadMarginDCH.
PrxTotal
Interference margin for the minimum UL DCH load
RAB is not admitted
PrxOffset RT RAB is not admitted
DeltaPrxMaxUP NoiseRiseTarget= Prx_target/PrxNoise Prx_Noise
The packet scheduler and the medium access control (MAC) layer together make the decision regarding which type of channel to use in the downlink direction.
The load caused by best effort non real-time traffic is called controllable load. For Non real time traffic real-time traffic + interference from other cell users + noise = non-controllable load For Real time traffic
The amount of scheduled capacity depends on: the UE and BTS capabilities the properties of the radio access bearer the current RNP parameter settings the availability of the capacity in RAN
The packet scheduler takes care of scheduling radio resources for non real-time radio bearers for both the uplink and the downlink directions. Packet access is implemented for dedicated (DCH) as well as common control transport channels (RACH/FACH). The packet scheduler and the medium access control (MAC) layer together make the decision regarding which type of channel to use in the downlink direction. As regards the uplink direction, the UE decides which type of channel to use, on the basis of parameters controlled by the network. The channel type selection is fast and takes into account the amount of data in the buffer and the current radio conditions. Uplink data transmission on dedicated channel is initiated when UE sends a capacity request. In the downlink it is the MAC layer that requests transmission the UE and BTS capabilities ;the properties of the radio access bearer ; the current RNP parameter settings ; the availability of the capacity in RAN
Packet scheduling • To determine the available radio interface resources for non real time radio bearer. • To share the available radio interface resources between non real time radio bearers. • to monitor the allocations for non real time radio bearers. • To initiate transport channel type switching between common, shared and dedicated channels when necessary. • To monitor the system loading. • To perform load control actions for the non-real-time radio bearers when necessary.
HSDPA_BTS transmission power
The principle of the BTS based dynamic power allocation algorithm is illustrated in the following figure:
Figure: BTS based power allocation PMax is the cell maximum output power defined by the minimum of the following two parameters: PtxCellMax and MaxDLPowerCapability. PtxCellMax is the operator adjustable management parameter and MaxDLPowerCapability is the maximum output power capability received from the base station. PtxTargetPS stands for the NRT DCH scheduling target, which is dynamically adjusted by the RNC (it is not an operator adjustable parameter but the name for the parameter internally used and adjusted by the RNC). PtxTargetPSMax and PtxTargetPSMin are the maximum and minimum values for the PtxTargetPS, respectively. Both values can be adjusted by the operator (PtxTargetPSMax and PtxTargetPSMin management parameters). The figure assumes that the WCEL-parameter PtxMaxHSDPA is set to not restrict the HSDPA power allocation in the BTS.
The packet scheduler is located in the Interface Control and Signalling Unit (ICSU) of the serving radio network controller (SRNC). In the drift RNC, non real-time bearers are handled as real-time bearers, and therefore are not taken into account in packet scheduling. The figure below shows the logical working environment of the packet scheduler.
Figure: Logical working environment of the packet scheduler
When the own cell throughput exceeds a particular level, the interference estimations are initiated and the planned interference target is applied in the uplink DCH resource allocations. transport channel; TrCH channel offered by the physical layer to the data link layer for data transport between peer physical layer entities
Maximum bit rate of HS-DSCH MAC-d flow The maximum user bit rate of the HS-DSCH MAC-d flow used in the resource reservation for the HS-DSCH MAC-d flow is the smallest of the following values: The maximum bit rate based on UE capability The value of the MaxBitRateNRTMACdflow management parameter. The parameter does not limit the maximum instantaneous bit rate on the air interface. The value of the parameter is compared to the user bit rate of the HS-DSCH MAC-d flow excluding MAC-hs header, RLC header and padding. The maximum bit rate in RAB parameters. This condition is checked only if the HSDPAPeakRateLimitRABMax management parameter is set to value 1 (Limitation is active).
Call Setup Basic Mobile Originating Call Diagram
MAC 結構
MAC Control
DCCH DTCH DTCH
MAC-d 的架構 Transport Channel Type Switching C/T MUX
Deciphering C/T MUX
To MAC-hs To/from MAC-c/sh
UL: TFC selection MAC-d
Ciphering
DCH
DCH