Simulate wifi AP + Client with mac80211-hwsim

Hi,
I'm trying to setup a testbed for openwrt with Virtualbox and want to simulate a wifi AP and a client connecting to it.
After installing kmod-mac80211-hwsim I get 2 virtual radios. But I can't enable them via /etc/config/wireless

# cat /etc/config/wireless

config wifi-device 'radio0'
	option type 'mac80211'
	option channel '36'
	option hwmode '11a'
	option path 'virtual/mac80211_hwsim/hwsim0'
	option htmode 'VHT80'
	option disabled '1'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option network 'lan'
	option mode 'ap'
	option ssid 'OpenWrt'
	option encryption 'none'

config wifi-device 'radio1'
	option type 'mac80211'
	option channel '36'
	option hwmode '11a'
	option path 'virtual/mac80211_hwsim/hwsim1'
	option htmode 'VHT80'
	option disabled '1'

config wifi-iface 'default_radio1'
	option device 'radio1'
	option network 'lan'
	option mode 'ap'
	option ssid 'OpenWrt'
	option encryption 'none'
# uci set wireless.@wifi-device[0].disabled="0"
# uci set wireless.@wifi-device[1].disabled="0"
# uci commit wireless
# wifi
# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br-lan state UP qlen 1000
    link/ether 08:00:27:ce:8a:65 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP qlen 1000
    link/ether 08:00:27:35:32:3c brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br-lan2 state UP qlen 1000
    link/ether 08:00:27:bb:9a:33 brd ff:ff:ff:ff:ff:ff
9: br-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether 08:00:27:ce:8a:65 brd ff:ff:ff:ff:ff:ff
10: br-lan2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether 08:00:27:bb:9a:33 brd ff:ff:ff:ff:ff:ff
11: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN qlen 1000
    link/ether 02:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
12: wlan1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 02:00:00:00:01:00 brd ff:ff:ff:ff:ff:ff
13: hwsim0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/[803] 12:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff

Does anybody know the necessary steps to set it up?
Thanks in advance!