Channel allocation and handover for the HSCSD service in SDMA systems

In order to increase the traffic capacity of F/TDMA based cellular systems like, e.g. GSM, SDMA techniques can be applied. In such systems the base stations are equipped with antenna arrays and appropriate signal processing capabilities, which enable directional transmission on the downlink as well as directional reception on the uplink. Channels (frequencies/time slots) can then be multiply used within the cell as long as the RRM secures sufficient spatial separability among users sharing a channel. Channel allocation and handover strategies for such systems have been investigated for instance in (C. Hartmann and H.-J Vogel, October 1999) (C. Hartmann, May 2000) (C. Hartmann and J. Eberspacher, September 2001, February 2001). To increase the user data rate in systems like GSM, the high speed circuit switched data (HSCSD) service has been introduced. In HSCSD, several channels can be pooled together for a single user in order to multiply its data rate by means of multi-slot operation. The time slots allocated to a HSCSD user must be allocated on a single GSM carrier. For this purpose we propose new algorithms for HSCSD channel allocation and handover. Specifically the new algorithms consider SDMA operation, i.e. sharing of time slots within the cell. The resulting capacity is investigated by means of multi cell system simulations.