7/5/2023 0 Comments Rsrp dbmAs such, RSRP measurement bandwidth is the equivalent of only a single subcarrier. Remember those aforementioned and depicted 100 subcarriers that contain reference signals? To calculate RSRP, the power in each one of those subcarriers is averaged. RSRP, on the other hand, is an LTE specific metric that averages the RF power in all of the reference signals in the passband. If we take the above RF sweep of a Sprint 5 MHz bandwidth downlink, RSSI measures the RF power effectively of what is highlighted in yellow: In other words, for LTE, RSSI measurement bandwidth is all active subcarriers. Now, RSSI is the more traditional metric that has long been used to display signal strength for GSM, CDMA1X, etc., and it integrates all of the RF power within the channel passband. So, the sector depicted here exhibits no data traffic it is transmitting only the periodic reference signals on 100 subcarriers, which you can clearly count in the graph: The LTE downlink graph comes from a Sprint site in the Kansas City area in late April, well before Sprint stopped blocking devices from live LTE sites. To illustrate, I captured this power vs frequency sweep with a spectrum analyzer. In other words, of the 300 subcarriers, 100 transmit periodic reference signals. And of those subcarriers, one in three carry LTE reference signals. A 5 MHz bandwidth downlink, which is the configuration that Sprint is deploying, contains 300 subcarriers. To understand why, we need to learn the differences between two types of signal measurement: Received Signal Strength Indicator (RSSI) and Reference Signal Received Power (RSRP).įirst, an LTE downlink is divided into subcarriers. But -102 dBm is actually relatively healthy LTE signal level. ![]() If this were measuring CDMA1X or EV-DO, then, yes, -102 dBm would be nearing the margin of usable signal.
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