Application And Research Of Enhanced Cell Re-Selection In GPRS Network

GPRS (EDGE)is a transitional technology from 2G mobile telecommunication to 3G mobile telecommunication.Now,for some reasons,our country still have not release 3G license.GPRS(EDGE) becomes the preferred mobile telecommunication technology.But GPRS meets many problems.One of them is that the transmission rate is slow.So we should enhance the performance of GPRS.The thesis will discuss the application and impact of enhanced cell re-selection in GPRS (EDGE) network.Cell re-selections create an outage in the data transfer that varies between 2 and 6 seconds, 4 seconds being a typical value. However these figures correspond to the interruption at the radio interface only. The interruption at radio level creates an interruption at application level which may be much longer.As an example, a TCP based application may suffer quite much from a long cell re-selection. Timers at TCP level expire, and when data are transmitted again, they are transmitted with a low speed; this is known as the"slow-start"phase.In order to ensure that TCP performances are not degraded by the cell re-selection, a minimum interruption has to be provided on the radio interface. Most of the time, TCP layer will not be degraded if the radio interruption is less than 2 seconds.Enhanced cell re-selection (including PACKET (P)SI STATUS and NACC) is able to improve the performance of cell re-selections in GPRS network. PACKET (P)SI STATUS procedure allows the mobile station to make an access to the target cell without having to first acquire the full set of Packet System Information.Indeed the mobile station is only required to read the information really needed to perform GPRS operations in the new cell. The Network Assisted Cell Change takes place in the serving cell and consists in 2 independant procedures: The first independent procedure is called CCN (Cell Change Notification). The MS, in packet transfer and in NC0 mode (autonomous cell re-selection), notifies the network when it has decided to perform a cell reselection.The second procedure is the Cell System Information distribution procedure, performed by the BSS. The BSS sends to the MS system information related to the target cell. This information is sent to the MS in the serving cell and before the cell change is performed. The time needed to send this information is much reduced, compared to the acquisition of the same System Information on the (P)BCCH of the target cell.If both NACC and Packet (P)SI Status procedures are supported, the gain is maximum : the mobile has only to retrieve the partial System Information about the target cell in the initial cell, and can immediately perform its packet access in the target cell.The thesis will discuss the procedure and solution of the enhanced cell re-selection technology.I test the enhanced cell re-selection feature in the ALCATEL BSS B9 software.I will analyze the test case here.Conclusion, based on the fact that GPRS (EDGE) is still the preferred mobile telecommunication technology and will be the effective supplement of 3G mobile telecommunication technology. Developing enhanced cell re-selection technology is very active.