Systems and methods for communicating to a disassociated station in a protected network
View Patent ↗Stations in standby mode in a wireless local area network (WLAN) become disassociated with their access point. In the event traffic is intended for the station in standby mode, a wakeup message needs to be communicated to the station. Typically, a wakeup message could be broadcast on a broadcast or multicast address, and when the station checks for broadcasts, the station can determine whether it needs to wake up. However, in a protected network, a disassociated station cannot decrypt messages from the access point without reassociating. However, the cost of reassociating in time and power can be significant, so reassociating should not be performed unless the station needs to wake up, leading to a vicious cycle as the station does not know it must wake up unless it can decrypt the message. To address this issue, in one embodiment the access points do not encrypt messages on a select multicast address, whereby messages such as wakeup message can be transmitted. In another embodiment, the messages are still encrypted. However, the identification of which station must wake up is encoded as the length of the encrypted payload. These methods allow a general message of communicating to disassociated stations in a protected WLAN environment.
1. A method comprising:
receiving a broadcast/multicast message having a destination address and a payload from an external source; comparing the destination address with a reserved multicast address; broadcasting an unencrypted message comprising the payload to all nearby stations if the destination address matches the reserved multicast address; and if the destination address does not match the reserved multicast address, encrypting the payload into an encrypted payload and broadcasting an encrypted message comprising the encrypted payload.
2. The method of claim 1 , wherein the payload comprises a station identification.
3. The method of claim 1 , wherein encoding of the unencrypted message includes:
mapping the unencrypted message to a number;
generating one or more dummy payloads having lengths that cumulatively correspond to the number; and
incorporating each payload into a separate protected frame.
4. The method of claim 3 , wherein the generating comprises:
generating a payload having a length equal to the number plus a predetermined minimum payload length.
5. The method of claim 3 , wherein the generating comprises:
if the number is greater than an encoding range, generating a dummy payload having a length equal to a predetermined minimum payload length and decrementing the number by the encoding range;
repeating the previous step until the number is less than the encoding range; and
generating a dummy payload having a length equal to the number plus the predetermined minimum length plus one;
wherein the encoding range is equal to a predetermined maximum payload length minus the predetermined minimum payload length minus one.
6. The method of claim 3 , wherein the generating comprises:
using a predetermined numeric base to divide the number into N pieces, each having a value less than the predetermined numeric base;
generating a dummy payload having a length equal to N plus a predetermined minimum length; and
generating N additional dummy payloads corresponding to the N pieces, each having a length equal to a value representing each piece plus the predetermined minimum length.
7. The method of claim 3 , wherein the generating comprises:
using a predetermined numeric base to divide the number into N pieces, each having a value less than the predetermined numeric base;
generating a dummy payload having a length equal to a reserved value that is reserved as a start of message symbol; and
generating N dummy payloads corresponding to the N pieces, each having a length equal to a value representing each piece plus a predetermined minimum length.
8. An access point comprising:
a processor, a wireless network interface device; and a memory comprising instructions, said instructions causing the processor and the wireless network interface device to perform: receiving a broadcast/multicast message having a destination address and a, payload from an external source; comparing the destination address with a reserved multicast address; broadcasting ml unencrypted message comprising the payload to all nearby stations if the destination address matches the reserved multicast address; and if the destination address does not match the reserved multicast address, encrypting the payload into an encrypted payload and broadcasting an encrypted message comprising the encrypted payload.
9. The access point of claim 8 , wherein the payload comprises a station identification.
10. The access point of claim 8 , wherein encoding of the unencrypted message includes:
mapping the unencrypted message to a number;
generating one or more dummy payloads having lengths that cumulatively correspond to the number; and
incorporating each payload into a separate protected frame.
11. The access point of claim 8 , wherein the generating comprises:
generating a payload having a length equal to the number plus a predetermined minimum payload length.
12. The access point of claim 8 , wherein the generating comprises:
if the number is greater than an encoding range, generating a dummy payload having a length equal to a predetermined minimum payload length and decrementing the number by the encoding range;
repeating the previous step until the number is less than the encoding range; and
generating a dummy payload having a length equal to the number plus the predetermined minimum length plus one;
wherein the encoding range is equal to a predetermined maximum payload length minus the predetermined minimum payload length minus one.
13. The access point of claim 8 , wherein the generating comprises:
using a predetermined numeric base to divide the number into N pieces, each having a value less than the predetermined numeric base;
generating a dummy payload having a length equal to N plus a predetermined minimum length; and
generating N additional dummy payloads corresponding to the N pieces, each having a length equal to a value representing each piece plus the predetermined minimum length.
14. The access point of claim 8 , wherein the generating comprises:
using a predetermined numeric base to divide the number into N pieces, each having a value less than the predetermined numeric base;
generating a dummy payload having a length equal to a reserved value that is reserved as a start of message symbol; and
generating N dummy payloads corresponding to the N pieces, each having a length equal to a value representing each piece plus a predetermined minimum length.