Delay skew packet flow control in wireless systems with dual connectivity

The paper presents a new data flow controller for use in 4G and 5G wireless applications where the incoming internet data flow is split in support of multipoint downlink wireless transmission. The different paths of the data from the node of the split to the wireless transmission nodes and on to the mobile may then result in different travel times. The mobile can cope with small values of this delay skew by means of buffers and reordering protocols. The control objective is therefore to keep the delay skew within a prespecified interval of time, when the packets arrive in the mobile. The proposed algorithm solves the problem by cascade control. The packet dwell time of each wireless transmission node data queue is controlled by an inner loop, with the reference dwell times being determined by an outer delay skew control loop. The delay skew control loop exploits a deadzone to achieve interval control. In a further contribution the L2-stability of the controller is analyzed for the dual connectivity functionality of the coming 5G cellular network deployment. A combined use of the input-output Nyquist-and Popov-criteria is required for the analysis. The performance is also evaluated by a laboratory testbed implementation.