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标题: 网络知识 [查看完整版帖子] [打印本页]

时间: 2011-6-19 17:38

作者: 成斌 标题: 网络知识

T200：

BSS20854, BSS20866 Modifiable T200 timer

It is now possible to modify the Link Access Protocol on the Dm channel (LAPDm) T200 values in the BSC to ensure that the message transfer in the air interface is not stopped too early. Previously, the LAPDm T200 values were defined in the BTS SW configuration file, which required a new SW build. The values are modifiable for full rate, half rate and SDCCH channels. The downloaded FACCH T200 is used for both full rate and half rate, and the one downloaded SDCCH T200 value is used for both SAPI0 and SAPI3 messages.

BSS9060 TRX test

The total performance of the TRX is tested with a multi-purpose TRX test. The test covers digital and RF parts and includes:

Tx Level
Bit error Rate (BER) for Main and Diversity Rx
Estimate (Rx Result) of the Rx level needed by single receiver for good quality decode of Full Rate speech, based on measured Noise + Interference level of the (idle) radio channel, for main and diversity Rx

The TRX test time is about 15 seconds.

When the TRX test is carried out according to a regular schedule it can be used in TRX performance supervision.

Both RX branches are tested separately during the same TRX test. If diversity is not configured, only the main branch is tested.

The power level during the TRX test is the same as the BCCH power level. To avoid unwanted disturbances to the TRXs the training sequence is not the same as the one normally used.

The figure below shows the TRX Test window.

Figure 15:

TRX Test window

All TRXs in a BTS can be tested either remotely from the BSC or NMS/2000 or locally with BTS Manager.

The TRX test can be performed only in TCH timeslots. Two free timeslots are needed for the test.

TRX test is not possible at all when baseband hopping is used. When IDD with RF hopping is used then RTSL 0, 1 and 2 cannot be tested for most TRX.

Dynamic SDCCH allocation

BSS7036 Dynamic SDCCH allocation

Dynamic Stand-alone Dedicated Control Channel (SDCCH) allocation allows the SDCCH resources to be configured according to the actual SDCCH traffic situation of a cell. When the BTS temporarily needs greater SDCCH capacity than normal, the idle Traffic Channel (TCH) resources are configured for SDCCH use by the BSC. An example of this is shown in the figure below. A maximum of two additional SDCCH/8 can be configured. When the SDCCH congestion situation is over, the extra SDCCH resources are configured back to TCH resources. This feature can be used with both combined and non-combined Broadcast Control Channel (BCCH).

The operator is only required to configure the BTS to the minimum static SDCCH capacity sufficient to handle the normal SDCCH traffic.

Figure 24:

Dynamic SDCCH allocation

Extra SDCCH resource is allocated only when the existing SDCCH is fully loaded. When the dynamic SDCCH radio resource is totally free again, it is immediately reconfigured for TCH use. Thus, the maximum number of TCHs is always in use depending on the actual need of the SDCCH resources at each moment.

The feature benefits traffic cases in which signalling is the only transmission to the network, for example Short Message Service (SMS) traffic and location updates. In some special places, such as airports and stations, the location updates can produce sudden short-term SDCCH congestion. This can now be handled without any need to configure extra permanent SDCCH capacity.

CCCH improvements

BSS7048 CCCH improvements

The Common Control Channel (CCCH) scheduling algorithm has been improved to allow priority for access grant messages over paging messages when there are no BTS access grant resources available. The paging channel (PCH) throughput is improved, especially for combined BCCH/CCCH channels. This is achieved by allowing a block reserved for access grant messages to be used for paging messages when there are no current access grant messages. The feature has altered the paging buffer so that pages are deleted because they cannot be transmitted to air within the defined maximum paging delay. Even though the pages are deleted, there may be sufficient buffer space.

The performance of the CCCH can be monitored with several new counters provided by the BTS. These counters are sent to the BSC in the message 'CCCH_LOAD_IND'. The number of paging messages that had to be deleted because of excessive paging load is calculated and reported. The average and maximum occupation of paging buffers is then reported as percentages.

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