Android - SignalStrength Terminology Explanation

Question

I am looking through the documentation on the SignalStrength class for an app I plan to make, but there is a lot of telecommunications terminology that I'm not very familiar with. I was wondering if anyone could briefly shed some light on some of the methods in this class, specifically these:

int  getCdmaDbm()
Get the CDMA RSSI value in dBm
int  getCdmaEcio()
Get the CDMA Ec/Io value in dB*10
int  getEvdoDbm()
Get the EVDO RSSI value in dBm
int  getEvdoEcio()
Get the EVDO Ec/Io value in dB*10
int  getEvdoSnr()
Get the signal to noise ratio.
int  getGsmBitErrorRate()
Get the GSM bit error rate (0-7, 99) as defined in TS 27.007 8.5
int  getGsmSignalStrength()
Get the GSM Signal Strength, valid values are (0-31, 99) as defined in TS 27.007 8.5

As I understand it, GSM and CDMA are two different protocols for mobile cellular networks, EVDO is the standard by which data is moved through CDMA, and HSPA is the equivalent data standard on GSM. Why then, are there no corresponding HSPA methods, as well as no getCDMASignalStrength() or getCDMABitErrorRate()? I'm also not too clear on what RSSI or Ec/Io are.

Answer 1

Ok, Here we go.

• You got the part that GSM is different than CDMA correctly.
• Also The part that EVDO is the data transport protocols on CDMA while HSPA is the equivalent in GSM.
• The Modulation (data representation in the signal) is completely different between CDMA and GSM. That is why you can't use equivalent units (B.E.R) to calculate the quality of a signal sent by those different protocols.

Now for the measurement values we got:

DBM is a pure signal power measurement unit (in decibel) the more you get the higher reception you have. This covers (getCdmaDbm() and getGsmSignalStrength())

Bit Error Rate: Is a simple quality measurement unit for GSM link, the lower it is the higher the quality of the received signal (independent of signal strength).

EC/IO Represents the ration of Power of signal received to the power of interference signal. the higher this value the higher the quality of the signal you are getting (Regardless of its strength) . in details

RSSI is a signal power measurement unit also.

Now the reason there is two APIS for RSSI and ECIO is that EVDO is carried on part of the CDMA signal so it makes sense that it may have different quality figures than the whole CDMA signal.

hope that helps

Answer 2

RSSI is the raw power measured in the channel. Ec/Io is the Energy of the Carrier relative to the Interference and Noise, so it is a measure of the quality of the signal. dBm is the unit of RF power relative to 1 milliwatt, on the dB (Decibel) scale. EVDO SNR is the Signal to Noise Ratio, which is another representation of the quality of the signal in the presence of interference.

Answer 3

RSSI- received signal strength indicator. It's the amount of power in the signal.
ECIO- it's another ratio of power density.

Why CDMA doesn't have signal strength- my guess is that Dbm is a good enough measure of it, but I can't swear to that.

If you need to use signal strength, you're going to need to do serious research. Unless all you're doing is the equivalent of showing how many bars of signal you have. Even that's non-trivial, the iphone got it wrong for years.