A lossless algorithm for BSSGP flow control in GPRS and EDGE

In a GPRS or EDGE system, fluctuations in the wireless link rate can cause the buffer in the BSS to either overflow or underflow if the data flow into the BSS buffer from the SGSN is not controlled properly. Currently available algorithms for controlling this data flow rely on imperfect estimates of the wireless link rate and cannot ensure that the BSS buffer will never overflow or underflow. We present a new low-complexity algorithm that ensures that the BSS buffer will never overflow or underflow, without requiring any estimate of the wireless link rate. If there is no feedback delay between the SGSN and BSS, the algorithm is optimal: among all algorithms that ensure that the BSS buffer will never overflow or underflow, it requires the smallest amount of buffering in the BSS. The algorithm also has a fixed point, i.e. if the wireless link rate remains constant, the BSS buffer remains in equilibrium and no flow control updates are required.