A network system having two layers is proposed. This system uses radio as a transmission medium for the lower layer and uses a conventional LAN for the upper layer. The users of a wireless network enjoy complete freedom from frequent relocation of existing terminal arrangements. However, office buildings present a harsh environment for radio transmission because of numerous reflections from walls, furniture and even people. A dynamic channel assignment scheme with no host computers is described. The system performance was analyzed through computer simulations. The results show that the number of channels assigned to each base station can be reduced without loss of performance under the condition that a 10-Mb/s carrier sense multiple access with collision detection (CSMA/CD) network is used as the upper layer and a 32 kb/s CSMA packet radio network is used as the lower layer.