2.
RXTA参数原理2.1 RXTA参数定义NED中RXTA参数定义如下：
This parameter is used to determine whether TCH access is based on downlink RX level.
NOTE:
MML range:
0 = RX level based TCH access is not used
1 = RX level based TCH access is used in call setup
2 = RX level based TCH access is used in call setup and in handovers 2.2 RXTA参数控制半速率原理从RXTA参数定义可知，当RXTA参数设置为1时，RXTA参数在call setup阶段起作用，通过对各种编码方式的C/N、DLN等参数进行设置，就可控制在CALL SETUP时的接入电平，大致原理如下：
In the RX level based TCH allocation method the downlink RX level measured by the MS is used to determine whether the BTS is acceptable for TCH allocation. With the RX level based TCH access (rxta) parameter you can define, if the RX level based TCH allocation method is used. TCH allocation for emergency calls is not restricted because of a too low RX level.
You can define the minimum C/N ratios separately for each call type (AMR FR, AMR HR, EFR/FR, HR and 14.4 data). The minimum allowed RX level per call type is calculated as in the equation 1:
Soft blocking C/N is a group of user-defined BSC level parameters (separate C/N for each call type: SBCNF, SBCNH, SBCNAF, SBCAH, and SBCN), DL noise level (DLN) is a user-defined BTS level parameter, and non BCCH layer offset (NBL) is a user-defined BTS level parameter.
If a downlink RX level measurement is not present, it is assumed that all call types on BCCH BTS are allowed and RX level is calculated by using the highest C/N value as in the equation 2:
The calculated RX level is then compared to the minimum allowed RX level (equation 1) to determine if a TCH can be allocated.
If the serving RX level measured by the MS (or the calculated RX level if the measurement is missing) is equal to or greater than the minimum allowed RX level (equation 1), a TCH is allocated. Otherwise the request is rejected
DLN参数: DL Noise Level, With this parameter you define a BTS-specific downlink noise level. In the BTS the margin between the noise level and the downlink signal level of a connection must be at least the connection type-specific C/N soft blocking limit.
Range: -120...-80 dBm
SBCN系列参数：SBCNF/SBCNH/SBCNAF/SBCNAH，Soft Blocking C/N FR/HR/AMR FR/AMR HR, With this parameter you define the minimum acceptable carrier/noise ratio for FR/HR/AMR FR/AMR HR speech connections.
Range: 0...63 dB