The R&S TSM Instruments can measure the basic RF parameters of any Node B which is transmitting within a range.
For the Primary and Secondary Synchronisation Channels (P-SCH and S-SCH) this includes:
● Correlation result of all P-SCHs found at the requested frequency ● Relative power of detected peaks in dB
● Time delay of detected peaks in us
For each Primary Common Pilot Channel (P-CPICH) found at the requested frequency, this includes:
● Scrambling Code
● Total Power of the CPICH For each Scrambling Code:
● CPICH Channel Impulse Response (CIR) measurements
● Received Signal Code Power (RSCP) and Interference Signal Code Power (ISCP) ● Time drift of C-PICH CIR measurements, giving an indication of Node B timing drift. ● Root Mean Square (RMS) of delay spread related to Chip
● Optionally, frequency (Doppler) drift of the Node B signal
For each peak within the CIR measurement of one Scrambling Code: ● Power of the identified peak
● Relative time of arrival
To support the above measurements, (and when this option is present) the R&S TSM Instruments use the synchronisation channels to synchronise to the Broadcast Chan- nel (BCH) of the same network, and decode System Information Broadcasts (SIBs). SIB information is available across the R&S ViCom Interface, in the measurement result structure. A complete list of information available in each SIB is given in Table 18-3.
● CPICH Channel Impulse Response (CIR) Measurements... 62 ● Peak Information...63
6.1.1 CPICH Channel Impulse Response (CIR) Measurements
The R&S TSM Instruments return a CIR measurement for each Common Pilot Channel (CPICH) that was found during the measurement time, on the requested frequency. This will include the C-PICHs transmitted by different NodeBs belonging to the same network, in the reception area. Each NodeB broadcasts the CPICH with a different scrambling code, as well as with a different delay to the code broadcasts, because the Node Bs are not synchronised.
A channel impulse response is a measurement of the effect on an impulse or sequence of impulses, of transmitting it along a particular channel. The R&S TSM Instruments measure the effect on a sequence of impulses, when a Node B transmits them along the CPICH transmitted by a NodeB at the requested frequency.
From each impulse, the R&S TSM Instruments measure a power delay profile, by sam- pling the power at regular time intervals along the pulse (see the figure).
The R&S TSM Instruments estimate a lower level for the code power that is high enough above the noise floor to be sure that noise measurements are not included in the CIR measurement. Then they get an array of code power measurements sampled from the signal over the discrimination interval (see below).
The maximum delay is the interval between the first code measurement of the CIR and the last one.
The signal is likely to have reached the receiver via several different reflected paths (multipath). The resulting peaks may overlap, leading to a broader peak, possibly with several sub-peaks. Alternatively, there may be adjacent peaks close together, from the same NodeB CPICH transmission.
The signal quality can be estimated by measuring the width of the peak (maximum delay), and the delay to the impulse peak, as well as the code power to inband power ratio Ec / Io.
The RMS delay spread (S) measures the standard deviation of the delay spread. Delay spread is an indication of the average drift of signals. Delay spread is a common prob- lem, and is very important for optimisation. High delay spreads mean that more fingers are needed in a rake receiver to make a connection between a mobile and a NodeB. For each CPICH signal found, the R&S TSM Instruments also return the Received Sig- nal Code Power (RSCP), and the Interference Signal Code Power (ISCP). The RSCP
is the interference on the received signal in the given timeslot that cannot be eliminated by the receiver.
Together with the spreading factor (SF), these two values can be used to calculate the Signal to Interference Ration (SIR).
SIR = (RSCP / ISCP) * SF
The ratio Ec / Io, the average chip energy divided by the total inband energy per chip duration, may be calculated by subtracting the inband power from the absolute code power, both reported in the measurement result structure.
The R&S TSM Instruments return a time drift for each CPICH measurement. They also return a standard deviation for an approximated Gaussian distribution of time drifts of the PDPs. The accuracy of the time drift can be estimated by considering the standard deviation, i.e. if the deviation is low, then the calculated time drift is likely to be accu- rate.
6.1.2 Peak Information
If the signal of one CPICH has reached the scanner via several different paths, there may be several peaks, either overlapping or single peaks. The R&S TSM Instruments separate these peaks and returns a list of structures containing peak information. The information returned includes the time delay of the peak, relative to the start of the measurement, and a measurement of the peak power.
Each time that the R&S TSM Instruments synchronise to a CPICH by using the Pri- mary and Secondary Synchronisation Channels, it also returns the inband power and the code power measurements for the PSCH and SSCH. If the R&S TSM Instruments are reporting a measurement of a CPICH to which it synchronised previously, then these values will not be reported.
In the peak information structure, the R&S TSM Instruments will also report an esti- mate of the frequency drift of the CPICH signal. This frequency drift could be caused by movement of the receiver (if it is mounted in a moving vehicle, for example). How- ever, if the receiver is stationary, then the frequency drift of a Node B can be mea- sured.