HSDPA UMTS Rate maintenance Based on UMAT V0.20

www.finetopix.com mon3em .

HUAWEI TECHNOLOGIES CO., LTD.

It is all based on the logical relation between RLC_Buffer, Assigned rate by RNC, & the allocated bandwidth for the services, & from this three relations you can clearly anticipate which & where is your problem.

RNC CDT L2 statistics

Track Set

To start the CDT at the RNC LMT, the proposed parameters configurations are as follows:

CDT L2 statistics tracking configuration

Ensure that the abnormal rate & the problematic beheaviour has occurred, process for one minute or around it & stop the CDT tracking.

Rate View: L2 is the RNC L2 statistics reflect the true situation, what directly reflect the rate changes in the statistics is RB.ulDlPduNum (L2 PDU sent down the number), and RB.usDlRetranRate (L2 downlink retransmission rate), RB.ulDlNasPktThroughput (L2 downlink throughput of data received) as below illustration

statistics, the rate case View.

Determine the approximate cause of problems A number of reasons can lead to abnormal rate, For the downlink rate analysis of the different interfaces you have to determine whether the problem is IU, RNC or IUB. The following judgments are based on UMAT for "HSDPA throughput curves Open the CDT, the straight on the toolbar

Then click the icon

Right click on the graph to see the legend :

RLC BO: Rlc buffer with green color

Allocated HSDPA bandwidth with blue color

RB rate issued by RNC with red color

Retransmission rate in black color

When the problem is in IU interface or the application layer (such as TCP), the amount of data sent to RNC through IU is inadequate & the rate will naturally be not ideal & RLC BO will fluctuate

RLC BO full circumstances of the curve (VDF test)

Green curve in the figure is RLC BO case,

RLC BO key is to have or not (0 or non-0), if the RLC BO Has a non-0 value, it means that those data can be sent to RNC

The following is an RLC BO abnormality curve:

Figure 2-1 RLC BO shortfall curve

In this graph, four-fifths of the beginning part, RLC BO (green curve) is basically 0, indicating that during this period (because of the low rate of downlink), lack of IU. The last part of fifth, RLC BO increased significantly, when the rate of abnormalities is decreased.

When problem is functionally related

The rate of abnormal performance in the data is:

1) RLC BO has data,

2) RB issued a rate lower than the allocated HSDPA bandwidth by NodeB .

The following is a lack of performance of the UE, UE L2 led the initiative to inform the RNC to reduce the receive window, which affects the RNC issued a rate of speed caused by exception:

UE rate issue

The green for the RLC BO, red for the RNC issued data, blue for the HSDPA bandwidth allocation situation. From this figure we can see, RLC BO (green) has been very full, HSDPA bandwidth allocation (blue) is also adequate, while the RNC issued a rate (red) has been maintained at a very low position.

IUB Interface problems:

IUB interface issues, NodeB problem, UU interface problems, the IUB interface to determine what the problem principle is: RNC issued rate and the volatility of HSDPA bandwidth allocation agreement. The following is an Iub packet loss rate caused by fluctuations:

IUB packet loss rate caused by fluctuations

It can be seen from the figure, HSDPA bandwidth allocation (blue) has been cyclically fluctuated , while the RNC issued a rate (red) which showed with similar fluctuations in bandwidth allocation.

The following is a NodeB HSDPA Path of the lack of SCR configuration caused by the low rate of cases:

IUB rate caused by fluctuations in bandwidth allocation

Retransmission case

IUB RLC retransmission, Right in the throughput of the map, select the legend, hook in the "downlink RLC retransmission rate, " this indicator:

IUB retransmission index configuration

retransmission rate

Retransmission rate of less than 1% is generally considered to be received at this time retransmission rate curve is coincident with the axis, like the figure above the retransmission rate often reaches 30% of the cases,

IUB flow control mode:

Another distinction between Iub problem or empty-case an important means is by changing the NodeB by configuring the flow control algorithm switch (command: SET HSDPAFLOWCTRLPARA, parameters: SWITCH), at different flow control algorithms under the action of View NodeB allocation of HSDPA bandwidth,

NodeB currently supports three different flow control algorithms NodeB list of supported flow control algorithm

No Chinese Name English Name Features

1 AUTO_ADJUST_FLOW_CTRL

Consider the packet loss and delay IUB, Consider the available bandwidth IUB Consider the empty case

2 SIMPLE_FLOW_CTRL Consider the available bandwidth IUB Consider the empty case

3 NO_FLOW_CTRL Consider the empty case

As the three flow control algorithm in bandwidth allocation, consider the factors characteristic of a ladder, by comparing the different flow control mode bandwidth allocation between HSDPA, changes in bandwidth allocation is most likely to handle the problem occurred.

If the L2 retransmission rate, is continue relatively in simple & auto-adjust : * If the adaptive flow control and simple flow control of the HSDPA bandwidth allocation are resulted in very different trend, the retransmission is due to the existence of IUB loss.

* If the adaptive flow control and simple flow control of the HSDPA bandwidth allocation results are consistent, the reasons for retransmission most likely UU mouth.

If the L2 retransmission rate, continue in the three algorithms: * If the three kinds of flow control mode are resulted similar (there are exceptions), current problem is mainly lies in the air interface.

* If no-flow-control has better result, and the remaining two have exceptions, the current problem mainly lies in the IUB transmission configuration.

* If auto-adjust flow control is only abnormal, this is possibly due to existence IUB-order packets which cause NodeB FP negative positives, or trigger a larger delay jitter at adaptive bandwidth adjustment of flow control.

IUB interface,

There are two main IUB interface checks: 1) HSDPA Path RCR configured correctly. 2) IUB involved in the transmission device configuration is correct. If the NodeB is the V18 version of the software, you can also download it via NodeB LMT's "HSDPA MONITOR" to observe the distribution of the bandwidth of the situation at this time in NodeB:

HSDPA monitoring of start position

The following is a list of monitoring results:

Figure 3-1 HSDPA in the form of monitoring

The results include five columns of data, meaning that five were:

1. Total Bandwidth (bps) port the total available bandwidth is calculated as: IUB port physical port bandwidth

2. R99 Allocated Bandwidth (bps) on the physical port bandwidth R99,

3. Hsdpa Remain Bandwidth (bps) HSDPA available bandwidth is calculated as: min (HSDPA RT Path allocation of bandwidth + HSDPA NRT bandwidth allocation,

4. Hsdpa Allocated Bandwidth (bps): refers to the HSDPA on the distribution of all the DSP bandwidth.

5. Hsdpa Used Bandwidth (bps): refers to all DSP operations on the actual use of HSDPA bandwidth.