LTE信号相关的调试

RSRP（Reference Singnal Received Power，参考信号接收功率）是终端接收到的Cell-specific Reference Signal（CRS）功率值，数值为测量带宽内单个RE功率的线性平均值，反映的是本小区有用信号的强度。
RSRP levels for usable signal typically range from about -75 dBm close in to an LTE cell site to -120 dBm at the edge of LTE coverage.

RSSI（Received Singnal Strengthen Indicator，接收信号强度指示）接收信号强度指示。是指导频符号上(一个包含有CRS的OFDM符号)总的接收功率在测量周期内的平均值。反应的是整个包含有CRS的OFDM符号的总功率。包括了有用信号，循环前缀，小区内干扰，邻小区干扰，噪声等。在本小区有业务时会增高，因为PDSCH和PDCCH上面有数据在跑。RSSI的正常范围是[-90dBm,-25dBm]

RSRQ（Reference Singnal Received Quality，参考信号接收质量）是N倍的RSRP与RSSI的比值，RSRQ=N*RSRP/RSSI,其中N表示RSRP的测量带宽内包含的RB数目，能反映出信号和干扰之间的相对大小。
The reporting range of RSRQ is defined from -3…-19.5dB

SINR（Signal to Interference&Noise Ratio，信烦躁比）是有用信号功率与干扰和噪声功率之和的比值，直接反映接收信号的质量。

如果要看RS-SNR
Click View --> New --> LTE --> Lower Layer1 --> LTE LL1 SNR CQI/RI MCS Display.

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随机接入的debug如下

服务小区的信号强度和质量可以在下面这个包看
0xB193 LTE ML1 Serving Cell Meas Response
2016 Dec 24 03:32:57.587 [30] 0xB193 LTE ML1 Serving Cell Meas Response
Version = 1
Number of SubPackets = 1
SubPacket ID = 25
Serving Cell Measurement Result
Version = 18
SubPacket Size = 96 bytes
E-ARFCN = 1825
Physical Cell ID = 448
Serving Cell Index = PCell
Is Serving Cell = 1
Reserved = 0
Current SFN = 804
Current Subframe Number = 8
Is Restricted = false
Cell Timing[0] = 39000
Cell Timing[1] = 39000
Cell Timing SFN[0] = 804
Cell Timing SFN[1] = 804
Inst RSRP Rx[0] = -90.38 dBm
Inst RSRP Rx[1] = -84.69 dBm
Inst Measured RSRP = -84.69 dBm
Inst RSRQ Rx[0] = -3.88 dB
Inst RSRQ Rx[1] = -3.56 dB
Inst RSRQ = -3.56 dB
Inst RSSI Rx[0] = -67.75 dBm
Inst RSSI Rx[1] = -62.38 dBm
Inst RSSI = -62.38 dBm
Residual Frequency Error = 0
FTL SNR Rx[0] = 11.40 dB
FTL SNR Rx[1] = 15.40 dB
Projected Sir = 8 dB
Post Ic Rsrq = 4294967266 dB

MSG1 is transmitted by the UE in (SFN, SN)(906, 7) and the response (i.e. MSG2) is expected to be received from the network between (SFN, SN)(907, 0) and (SFN, SN)(908, 0):

1980 Jan 6 00:08:22.903 [58] 0xB167 LTE Random Access Request (MSG1) Report
Version = 5
Preamble Sequence = 27
Physical Root Index = 46
Cyclic Shift = 767
PRACH Tx Power = -28 dBm
Beta PRACH = 242
PRACH Frequency Offset = 0
Preamble Format = 0
Duplex Mode = TDD
f_ra = 0
t_0_ra = Resource reoccurring in all radio frames
t_1_ra = RA resource in second half frame
t_2_ra = 0
Density Per 10 ms = 4
PRACH Timing SFN = 906
PRACH Timing Sub-fn = 7
PRACH Window Start SFN = 907
RACH Window Start Sub-fn = 0
PRACH Window End SFN = 908
PRACH Window End Sub-fn = 0
RA RNTI = 8
PRACH Actual Tx Power = -28

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如果基站有收到上行的包就会在PHICH上给一个HARQ的ACK，如下图的格式，这个图是随便找的，并不是按照上面所描述顺序对应

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the RACH attempt fails:
1980 Jan 6 00:08:22.918 [F9] 0xB062 LTE MAC Rach Attempt
Version = 1
Number of SubPackets = 1
SubPacket ID = 6
SubPacket - ( RACH Attempt Subpacket )
Version = 2
Subpacket Size = 36 bytes
RACH Attempt V2:
Retx counter = 1
Rach result = Failure at MSG2
Contention procedure = Contention Based RACH procedure
Msg1 - RACH Access Preamble[0]
Preamble Index = 27
Preamble index mask = Invalid
Preamble power offset = -90 dB
Msg2 - Random Access Response
Backoff Value = 0 ms
Result = False
TCRNTI = 56048
TA value = Not applicable

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Later, the UE ramps up the PRACH Tx power and sends the MSG1, but still there is no response received from the network resulting in contiuous RACH failures:

1980 Jan 6 00:08:23.219 [62] 0xB062 LTE MAC Rach Attempt
Version = 1
Number of SubPackets = 1
SubPacket ID = 6
SubPacket - ( RACH Attempt Subpacket )
Version = 2
Subpacket Size = 36 bytes
RACH Attempt V2:
Retx counter = 19
**Rach result = Failure at MSG2**
Contention procedure = Contention Based RACH procedure
  Msg1 - RACH Access Preamble[0]
    Preamble Index = 6
    Preamble index mask = Invalid
    Preamble power offset = -54 dB
  Msg2 - Random Access Response
    Backoff Value = 0 ms
    **Result = False**
    TCRNTI = 56048
    TA value = Not applicable