Data　communication　in　GPU　systems　exhibits　asymmetric　patterns　that　create　congestion　hotspots.　Due　to　their　large　number　of　cores　and　big　die　sizes,　GPUs　also　demand　highly　scalable　NoC　designs.　In　this　work,　we　propose　hybrid　NoC　architectures　that　employ　on-chip　integrated　antennas　to　build　overlaid　wireless　networks　on　top　of　conventional　metal/dielectric-based　networks.　We　use　low-power　high-bandwidth　wireless　links　as　express　channels　to　transmit　long　distance　packets　and　use　metal　links　to　deliver　local　packets.　The　hybrid　architecture　can　effectively　alleviate　congestion　near　traffic　hotspots　and　improve　the　throughput　and　scalability　of　GPU　NoCs.　We　propose　solutions　for　design　challenges　in　such　hybrid　NoC　architectures,　such　as　MAC　protocol,　router　microarchitecture,　load　balancing　and　deadlock　free　routing.　To　efficiently　utilize　on-chip　wireless　bandwidth,　we　also　propose　a　novel　scheme　that　adaptively　allocates　bandwidth　to　wireless　channels　based　on　their　usage　needs.　Our　evaluation　results　show　that　for　a　GPU　with　256　cores,　the　proposed　hybrid　architecture　can　improve　performance　by　2.4　times　on　average.