UTRAN Cell Identity returned by getCid()

Question

In UMTS I get a large number returned by getCid() (larger than the allowed value). Is this the UTRAN Cell Identity (UC-ID)?

UC-Id = RNC-Id + C-Id

Does someone knows that? How to get the C-Id from the UC-Id?

Thanks and Best, Benny

Answer 1

The RNC id is the first 2 bytes of the 4 byte Cell Id (3GPP 25.401, section 6.1.5), if the network type is UMTS/HSxPA/HSPA+."
I have access to an operator network and I checked in the system and it's true and correct.
Based on that please see my code how you can easily get RNCID + CID:
Convert CID to ByteArray:

    public static byte[] convertByteArray__p(int p_int){
    byte[] l_byte_array = new byte[4];
    int MASK_c = 0xFF;
    for (short i=0; i<=3; i++){
        l_byte_array[i] = (byte) ((p_int >> (8*i)) & MASK_c);
    }
    return l_byte_array;
} 

Get the RNCID and CID:

    public int getRNCID_or_CID__p(byte[] p_bytes, short p_which){
    int MASK_c = 0xFF;
    int l_result = 0;   
    if (p_which == Constants.CID_C) {
        l_result = p_bytes[0] & MASK_c ;
        l_result = l_result + ((p_bytes[1] & MASK_c ) << 8);
    } else if (p_which == Constants.RNCID_C){
        l_result = p_bytes[2] & MASK_c ;
        l_result = l_result + ((p_bytes[3] & MASK_c ) << 8);
    } else { 
        g_FileHandler.putLog__p('E', "getRNCID_or_CID__p invalid parameter");
    }
    return l_result;     
}

Than you can easily call like this:

        byte[] l_byte_array = new byte[4];
        l_byte_array = convertByteArray__p(l_cid);
        int l_RNC_ID   = getRNCID_or_CID__p(l_byte_array,Constants.RNCID_C);
        int l_real_CID = getRNCID_or_CID__p(l_byte_array,Constants.CID_C);

Constants RNCID_C(1) and CID_C(2) are only contants just for me to seperate which parameter will be passed through.

Answer 2

If CID is > 65536, it's not actually the cell-ID, but a linear combination of the real cell-ID and RNC-ID:

UTRAN_CELL_ID = RNCID x 65536 + CellID

To extract the cellID, use the modulo operation:

CellID = UTRAN_CELL_ID % 65536

To extract the RNCID, get the integer part:

RNCID = UTRAN_CELL_ID / 65536

Answer 3

try (cell id % 65536) it worked for me.

Answer 4

This is more simple than this. Cell ID is in the low register of the value getCid() returns, the RNC is the high register of this value (http://developer.android.com/reference/android/telephony/gsm/GsmCellLocation.html#getCid()). So:

getCid() == RNC << 16 | CID

CID = getCid() & 0xffff

RNC = (getCid() >> 16) & 0xffff