wlan and DSL

Hi, I need to make a DSL connection with my 'wlan-pcmcia' so I modified 'ifcfg-dsl0' and replaced DEVICE='eth0' --> DEVICE='wlan0' ... try to 'ifup dsl0' but I got "unrecognized option 'wlan0'" into /var/log/messages'. Why I cannot use wireless lan to make an dsl connection? or why 'dsl0' doesn't accept different NIC as ethX? Thanks. Andrea