GSM pico cells
Original Publication Date: 2001-May-15
Included in the Prior Art Database: 2001-May-15
Jheroen Dorenbosch: AUTHOR [+2]
AbstractGSM pico cells
GSM pico cells
Jheroen Dorenbosch, Riccardo Fricks.
With the advent of good connectivity into the home and the office, it has become possible to connect each home or office via its own wireless system. These wireless systems can be integrated into a public GSM system in such a way that each home/office becomes a GSM pico cell. A small, low power base station (BTS) can be control the cell. A fast, IP-based line connects the base station with the infrastructure of the GSM system. With the rapid pace of miniaturization, the BTS can be integrated into the hardware of the IP-connection. In particular, it can advantageously be integrated into the broadband set-top box.
The advantage of this approach is that a GSM mobile station (MS) can seamlessly roam between the wide-area public system and the home environment without loosing connectivity and without changing service provider. All wireless services for voice and packet data (circuit switched or via GPRS) would naturally appear on a single bill.
To enable such seamless roaming the home-based pico cell would use its own GSM identifiers. A mobile that roams in and out of the pico cell will then inform the GSM system with the identity of the roamed-to cell, so that paging can be done in the traditional way, without any changes to the infrastructure.
A problem exists, however, with call handover. During handover a GSM unit reports the Base Station Identifier Code (BSIC, also called color code) of the target cell. A BSIC only has a small number of bits. In a system where a large wide-area cell overlaps with a large number of pico cells, many of the pico cells will have to re-use the same BSIC. Hence, when an MS roams from the wide-area cell into a target pico cell, the reported BSIC may be ambiguous.
We propose that in case of ambiguity, the GSM system uses location information. The location of the MS can be determined by well-known methods such as GPS. The system would store the coordinates of each pico cell with an ambiguous BSIC, and search the list for the pico cell that is closest to the MS's location. The system then proceeds to use that pico cell while executing the tradition handover procedures.