Packet Ordering in Mobile Network Handovers

The patent introduces a mediator function at the SGSN level that intercepts out-of-sequence packets arriving at the target RNS during handover. This intermediary reorders packets based on their sequence numbers before forwarding them to the mobile station, thereby eliminating TCP retransmissions while maintaining packet forwarding reliability. The mediator acts as a buffer and sorting mechanism between the dual packet paths.

The patent segments the packet handling function by separating the forwarding path from the ordering function. Different packet paths (direct from SGSN and forwarded from source RNS) are allowed to operate independently, with the ordering function applied only at the final delivery stage at the target RNS. This segmentation allows parallel packet transmission while ensuring sequential delivery.

Instead of preventing packet reordering at the RLC layer through strict timing and buffering controls, the patent inverts the approach by allowing reordering to occur naturally during handover and then applying an ordering function at the higher network layer (target RNS). This inversion moves the complexity from the radio access network to the core network, relaxing RLC layer constraints.

The patent introduces an intermediary ordering function at the target RNS that receives packets from multiple sources (direct SGSN path and forwarded RNS path) and reorders them before delivery. This intermediary absorbs the timing and sequencing complexity, allowing the RLC layer to operate with simpler, more flexible timing requirements.