ches the lower limit, data flow over the lub is allowed. This protects the MAC-hs buffers from overflow. The credit based flow control mechanisms can further smooth the HSDPA traffic over the lub interface, resulting in a reduction of the burstiness of the total lub traffic. The credit based flow control introduces two new aspects with respect to the ON/OFF flow control algorithm. Firstly, the lub allocation message shall be sent periodically from Node B to RNC. Secondly, Appendix the credit allocation algorithm is based on the Provided Bit Rate (PBR) of the per-user priority queues in the Node B. The HS-DSCH PBR measurement is defined 3GPP: for each priority class the MAC-hs entity measures the total number of MAC-d PDU bits whose transmission over the radio interface has been considered successful by MAC-hs in Node B during the last measurement period (cycle time), divided by the duration of the measurement period. The PBR based Flow Control mechanism has an advantage over the simple ON/OFF flow control mechanism that it has a smoothing effect on the data flow over the lub as it considers the instantaneous rates of the Node B priority queues. Whereas, the ON/OFF flow control mechanism is based on the threshold levels of the Node B priority queues filling level. Congestion Control (CC) In the HSPA network when the user traffic over the air interface is greater than the available lub capacity, the congestion occurs at the lub interface. Due to lub congestion, the packet loss probability increases significantly, causing more retransmissions at higher layers such as RLC and TCP. Hence the offered load is further staggered leading the system into congestion collapse and wasting the radio as well as transport resources. To avoid such circumstances, a proper congestion control scheme is required in addition to the flow control mechanism. The basic concept of the lub congestion control is to reduce the user data rate in case of congestion. The data rate should be reduced adaptively according to the available bandwidth 