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si: Deal with DCS1800 and PCS1900 have overlapping ARFCN ranges 

For PCS1900 the SI1 does not contain the ARFCN of the serving cell.
This is because the arfcn2band method will return GSM_BAND_1800 and
not GSM_BAND_1900. The academic fix would be to set the ARFCN_PCS bit
but this would require increasing the bitvector sizes from 1024/8 to
(0x8000 + 1024) / 8. This would increase the storage size for each
bitvector by three.

It is not possible to have DCS1800 and PCS1900 in one network so we
can avoid increasing the memory usage and check if the ARFCN resolved
to 1800 and then check if the BTS is a 1900 BTS and then claim that
this is compatible.
This commit is contained in:
Holger Hans Peter Freyther 2013-01-17 13:49:39 +01:00
parent 9e1952a901
commit d4d1d5e751
1 changed files with 23 additions and 3 deletions
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26
openbsc/src/libbsc/system_information.c
View File

@ -37,15 +37,35 @@
#include <openbsc/rest_octets.h>
#include <openbsc/arfcn_range_encode.h>
/*
* DCS1800 and PCS1900 have overlapping ARFCNs. We would need to set the
* ARFCN_PCS flag on the 1900 ARFCNs but this would increase cell_alloc
* and other arrays to make sure (ARFCN_PCS + 1024)/8 ARFCNs fit into the
* array. DCS1800 and PCS1900 can not be used at the same time so conserve
* memory and do the below.
*/
static int band_compatible(const struct gsm_bts *bts, int arfcn)
{
enum gsm_band band = gsm_arfcn2band(arfcn);
/* normal case */
if (band == bts->band)
return 1;
/* deal with ARFCN_PCS not set */
if (band == GSM_BAND_1800 && bts->band == GSM_BAND_1900)
return 1;
return 0;
}
static int use_arfcn(const struct gsm_bts *bts, const int bis, const int ter,
const int pgsm, const int arfcn)
{
if (!bis && !ter && gsm_arfcn2band(arfcn) == bts->band)
if (!bis && !ter && band_compatible(bts, arfcn))
return 1;
if (bis && pgsm && gsm_arfcn2band(arfcn) == bts->band && (arfcn < 1 || arfcn > 124))
if (bis && pgsm && band_compatible(bts, arfcn) && (arfcn < 1 || arfcn > 124))
return 1;
if (ter && gsm_arfcn2band(arfcn) != bts->band)
if (ter && !band_compatible(bts, arfcn))
return 1;
return 0;
}