Uplink (UL) data splits between LTE and WLAN can be go supported in cellular networks. The split can be UE controlled or network controlled. Both UE and network controlled bearer split architectures can be supported. The reporting of Uplink Buffer Status (BSR) and the subsequent data allocation can depend on what option is supported by the network. For UE controlled UL data splits, the UE determines a traffic split ratio between LTE and WLAN. The split can be based on local link conditions. For network controlled UL data splits, the network (e.g. a Link Aggregation Scheduler at the eNB) is responsible for making bearer split decisions. The decisions can be based on link qualities, available traffic and quality of service (QoS) requirements of associated users. The split can be based on a per bearer threshold, an eNB configured ratio, or an implicit inference based on a UL grant.