This traffic class has much lower transport costs. UBR+ is similar to UBR, but bandwidth is guaranteed up to a minimum rate MDCR (Minimum Desired Cell Rate). With UBR+, the HSPA traffic can be guaranteed up to MDCR. A.16 Use of Traffic Separation for Transport of HSPA and Rel99 R99 Data Streams (symmetric) HSDPA Data HSDPA User Data (HS-DSCH) Streams UBR/UBR+ (asymmetric) ASDPA Inband signaling HSUPA Data HSUPA User Data (E-DCH) Streams (asymmetric) UBR/UBR+ HSUPA Inband Signaling ATM Network Node B Node B high priority traffic Figure A.22: Concept of Traffic Separation With the use of traffic separation technique to differentiate the HSPA and Rel99 traffic over different paths with different priorities, the transport of Rel99 traffic is separated from the HSPA traffic and its stringent delay requirements can be guaranteed by using the CBR VP. On the other hand, using the UBR+ VPs for the transport of HSPA traffic can result in cell discards or long delays on the HSPA traffic if the MDCR is exceeded. But since the QoS requirements of the HSPA traffic is usually lower than the Rel99 traffic, some decreased performance of HSPA by using a separated UBR or UBR+ VP can be tolerated. In this way, compared to not using any traffic separation, the overall network cost is reduced at expenses of possible degraded HSPA performance. III. Configuration of HSPA and Rel99 Traffic Separation For setting up a traffic separation scenario, the following ATM parameters need to be configured: PCR (Peak Cell Rate) is the upper limit of the traffic that can be sent to the link. MDCR (Minimum Desired Cell Rate) defines a minimum guaranteed cell rate on UBR VC. It is optionally configured on either a VC or VP connection. PCR is required to configure for both ATM CBR and UBR/UBR+ service categories. Maximum allowed bandwidth can be set different for the uplink and downlink by means of an asymmetric PCR configuration of VPs and VCs. MDCR is only configurable for UBR+ VP/VCs. As the Rel99 traffic consists of a considerable amount of symmetr