Wireless mesh network (WMN) is a promising technology for building cost-effective and easy-deployable wireless home networking infrastructure. To efficiently utilize limited radio resources in WMNs, packet transmissions (especially, redundant packet transmissions) should be carefully managed. To this end, we introduce a software-defined WMN architecture where the data plane and control plane are separated and packet transmissions over WMNs are controlled by a centralized entity. We also propose a lightweight traffic redundancy elimination (LTRE) scheme in software-defined WMNs to reduce redundant packet transmissions. Preliminary analysis results show that LTRE can significantly reduce the traffic overhead.