aclc

After any reconfiguration (added or removed SDCCH/8s) that leads to a

configuration consisting of more SDCCHs than the basic SDCCH configuration in the cell a supervision routine is started. The purpose is to determine whether the added SDCCH/8 is in use or if it should be reconfigured to a TCH again. In this way, the feature is actively trying to reconfigure “back” to the basic SDCCH configuration. The time it will take to reach the basic SDCCH configuration depends on the number of SDCCH/8s previously added by the feature, the value of parameter STIME and the SDCCH traffic level. Parameter STIME defines the minimum time it will take before a reconfiguration of an SDCCH/8 to a TCH is started.

当SDCCH增加或减少的操作进行之后，一个由于比原来配置更多的SDCCH监控将开始，目的在于决定增加的SDCCH是否在用，是否需要再变换成TCH。这样就出现了一个SDCCH变换成TCH的操作，这个过程的时间由STIME决定，在STIME时间内不能进行SDCCH变换成TCH的操作。

The criterion to remove one SDCCH/8 is in the form of a leaky bucket algorithm with the following attributes:

要减少一条SDCCH/8的操作遵循木桶定理。

A counter is initiated with a value equal to the value of parameter STIME. Thereafter, a check is made every third second to see how many idle SDCCH subchannels that are left in the cell. The counter is then decreased or increased according to the following:

一个设置为=STIME的COUNTER将开始，然后每3S去计算小区里的空闲SDCCH信道数，计数器根据以下条件增加和减少



if the total number of idle SDCCH subchannels in the cell is more than 8+SLEVEL (indicating that the SDCCH traffic load is below the level that initiated the last reconfiguration and that one SDCCH/8 could be removed) the counter is decreased with 3. (If parameter SLEVEL has the value CONG, it is interpreted as zero in the decrease condition.) The value 3 originates from the fact that the check only is made every third second. Parameter STIME is thus given in seconds. The idle SDCCH subchannels does not have to be on the same timeslot for this condition to be fulfilled. 

当一次扫描得到的空闲SDCCH/8数量大于8+SLEVEL（表明SDCCH的话务量在最后一次信道转变以下，一条SDCCH信道可以被清除），计数器将减3，（当SLEVEL=CONG时，在减少SDCCH时，SLEVEL被视为0），减3是因为检查每3S进行一次，STIME的单位为S，SDCCH的空闲信道不需要在同改一个TS。 

if the total number of idle SDCCH subchannels in the cell is less than 8+SLEVEL (indicating that the SDCCH traffic load is above the level

that initiated the last reconfiguration) the counter is set to the initial value, that is STIME. 

if the total number of idle SDCCH subchannels in the cell is exactly 8+SLEVEL the counter is not stepped at all.

When the counter reaches zero, a reconfiguration of an SDCCH/8 to a TCH is initiated.

当计数器的值为0时，将执行SDCCH/8转换成TCH。 The increase criterion

A timeslot holding a TCH is reconfigured immediately to an SDCCH/8 when the increase criterion is fulfilled. The criterion is made up of three sub-conditions that all have to be fulfilled before an SDCCH/8 can be added in the cell:

1. the number of idle SDCCH subchannels in the whole cell (UL and OL)

must be equal to or below the value of parameter SLEVEL . (Parameter SLEVEL can also have the value CONG. This means that this sub-condition is fulfilled any time a connection fails to allocate an SDCCH subchannel due to congestion. The connection may instead allocate a TCH for signalling if the Immediate assignment on TCH feature is enabled, see Reference [4]) Parameter SLEVEL defines the number of remaining idle subchannels when an attempt to reconfigure a TCH to an SDCCH/8 is initiated.

2. the number of idle TCHs in the whole cell (UL and OL) must be more

than four, or more than the total number of TRXs in the cell (if the number of TRXs is three or less).

The number of TRXs is calculated from the number of Basic Physical Channels (BPC) in the cell. The number of BPCs is defined by NUMREQBPC .

3. the number of already defined SDCCH/8s must be less than the

maximum number of SDCCH/8s allowed to be configured in the cell, for details please see Reference [1].

If all these sub-conditions are fulfilled a reconfiguration of a TCH to an SDCCH/8 is initiated. The same criterion must be fulfilled for each SDCCH/8 to be added in the cell. The SDCCH/8s are added one at a time up to the maximum number of SDCCH/8s in the cell (see sub-condition three).

增加SDCCH信道的标准

当满足增加算法的条件时，TCH变成SDCCH的操作将会马上执行。增加算法由三个在增加SDCCH信道之前都必须满足的子条件组成：

1、 整个小区（包括OL跟UL）里的SDCCH/8也就是SDCCH的子信道必须等于或者少于SLEVEL

的参数值，（SLEVEL还可以等与CONG，当等于CONG时表示当一个SDCCH信道请求因为信道拥塞而失败时这个子条件将满足，如果CHAP功能打开，以上操作将代替在TCH上进行立即指派），SLEVEL定义的是当TCH变成SDCCH时剩余的SDCCH/8的数量。 2、 小区里剩余的TCH的数量必须大于4，或者当小区载波数小区或者等于3时，大于小区

载波数。小区的载波数通过NUMREQBPC来计算。

3、 小区已经定义的SDCCH/8必须少于小区可以配置的SDCCH/8的最大值。

（MAXNOSDCCHTRX）

总而言之，增加是必须符合以上条件，SLEVEL，TCH>4或者TRXnum，SDCCH/8少于MAXNOSDCCHTRX*TRXnum。

SDCCH重新转换成TCH的条件是计数器为0，类似RLINKT，STIME定义的是初始值，每3秒扫描SDCCH数量，如果SDCCH子信道少于8+SLEVEL时，设置为初始值；大于8+SLEVEL时减3；等于8+SLEVEL时不跳转。

SDCCH占用时长:

1、 正常位置更新：2.7S 2、 IMSI ATTACH: 2.7S 3、 IMSI DEATTACH: 2.1S 4、 周期性登记：2.7S 5、 MS 主叫：2.7S 6、 MS被叫：2.9S 7、 SMS P2P：5.9S

CGI/TA, E-CGI and U-TDOA: 3 seconds

A-GPS, MS based Holding time: ~20 seconds

A-GPS, MS based with Fine Timing Assistance Holding time: ~20 seconds

A-GPS, MS assisted Holding time: ~20 seconds

A-GPS, MS assisted with Fine Timing Assistance Holding time: ~20 seconds

8、FAX

MS originated call Holding time: 2.7 seconds

MS terminated call Holding time: 2.9 seconds

When a timeslot, currently holding a TCH, is reconfigured to hold an SDCCH/8 it is done without disturbing ongoing traffic. This means that any TCH traffic on the timeslot chosen to hold the SDCCH/8 is handed over to an idle TCH on another timeslot. In the same manner is a reconfiguration of an SDCCH/8 to a TCH also done without disturbing ongoing traffic. Any SDCCH traffic on a timeslot to be

reconfigured to hold a TCH is therefore handed over to idle SDCCH subchannels on other timeslots. This will be done regardless of if the Intra-cell handover feature is enabled or not (see Reference [5] ).

要转换TCH为SDCCH时，时隙上的通话将要切换到其他的空闲信道，同样的，SDCCH转变成TCH时，该SDCCH下面的子信道上的话务也要切换到其他空闲信道，这时将不关注小区内切的功能开启与否。

When an SDCCH/8 is to be removed, the feature will remove an SDCCH/8 from the channel group where the latest added SDCCH/8 were configured. A reconfiguration of a timeslot will take no more than a couple of seconds, depending on if the timeslot to be reconfigured currently is carrying traffic or not.

SDCCH转换成TCH的的过程一般不会超过2秒，得看这个将被转换的时隙当时是否承载话务。

The configuration/reconfiguration of an SDCCH/8 is rather quick and does not affect ongoing traffic due to reconfiguration, that is there is no downtime in the cell. At each configuration a small time period is lost due to the non-enabled state of the configured time slot (TS) as seen in Table 1 . This will correspond to a theoretical traffic loss since no SDCCH/8 nor TCH is configured on the TS. This traffic loss is minor but depends heavily on the reconfiguration frequency (see Example 1). Since the configuration/reconfiguration in the BTS can take up to 10 seconds, in the case of a very large BTS, it is not recommended to set STIME lower than 40 seconds.

Table 1 Typical time values for the TS in neither TCH nor SDCCH/8 state, at adaptive configuration, including time for any intra-cell handovers. TS configuration TCH to SDCCH/8 SDCCH/8 to TCH Time for blocked TS [s] 3 - 10 4 - 10 虽然SDCCH/8的转换过程很快，不会影响正在通话的话务，小区没有停工期，但是转换的时隙将有一个短暂的时间处于NON-ENABLED的状态，这将与该时隙没有配置为UNUSE状态。一个高配置小区在配置该时隙的频率时将有可能用到10S钟的时间，因此以上转换造成的话务丢失是较小的，建议STIME不小于40秒。

The more frequent a configuration can occur the more optimized the SDCCH/TCH channel distribution will be and as a result more traffic can be carried in the cell. Though, if the configurations are too frequent, the traffic gained from optimized channel distribution may be lost to some extent.

ACLC可以使得小区承载更多话务，但是如果转换频繁将会导致时隙分配某种程度上丢失。

Since the feature prioritizes TCH capacity, the down-configuration leaky bucket algorithm (see Section 6 Appendix ) can in some cases be very fast and return the cell to its original SDCCH configuration almost immediately. If the operator finds it unpleasant to have constant up- and down configurations of an SDCCH/8 the number of configurations can be decreased by increasing STIME or decreasing SLEVEL. Increased STIME delays the reconfiguration back to the original SDCCH configuration. Decreased SLEVEL means that more SDCCH capacity can be used before a new SDCCH/8 is automatically configured. Increased STIME will lower the SDCCH congestion while decreased SLEVEL will raise it.

During a reconfiguration, when an SDCCH/8 is added in a cell, it is possible that additional requests for SDCCH subchannels arrives. Some of these connections may then experience congestion. To overcome the problem with congestion on SDCCH in those cases, the Immediate Assignment on TCH feature can with advantage be used as it enables the TCHs to be used also for signalling. This means that the connections experiencing congestion on SDCCH, before another SDCCH/8 have successfully been added to the cell, may use an idle TCH for the call setup signalling. The Immediate assignment on TCH feature may also be useful if there is congestion on SDCCH and no new SDCCH/8 is allowed to be configured (for instance if maximum number of SDCCH/8s already is configured in the cell or too few idle TCH channels exist). For more information see Reference [4] .

当没有完成TCH到SDCCH的转换之前，可以优先通过CHAP来让通话信令建立。当SDCCH/8已经配置为最大，或者小区的TCH也空闲数量太少，CHAP也可以起作用。

这说明了，CHAP比ACLC具有更加高的优先级，而且不受MAXNOSDCCHTRXU的限制;此外,CHAP的速度极快，而ACLC因为要闭塞时隙和配置频率，所以速度较慢而且恢复较慢。而CHAP只能将一条TCH转变成一条SDCCH，利用率低。而且，CHAP变换TCH为SDCCH后，在该SDCCH上的掉话将在TFNDROP和THNDROP上跳转，从而导致无线掉话增多，影响网络指标。