Early ending of frame reception
An additional cyclic redundancy check (CRC) is inserted in IEEE 802.11 beacon or data frames prior to the end of the frame, at a location following information sufficient for the receiving station to determine whether the frame is from an overlapping basic service set or intended for a different station and to extract other necessary or useful information such as a time of the next full beacon. Upon detecting the CRC, the receiving STA can terminate reception of the frame early to conserve power, and then enter a low power operational mode to further conserve power.
1. A wireless device, comprising:
a controller operable in a wireless local area network (WLAN) configured to:
generate content for fields up to a predetermined location from a start of frame field within a frame that conforms to a WLAN protocol, the WLAN protocol defining a beacon frame, wherein the predetermined location is before a last field of the frame, wherein the fields up to the predetermined location from the start of the frame include for the beacon frame, fields up to and including one of a Traffic Indication Map (TIM) field, if a TIM is to be included in the beacon frame, and a field immediately preceding a location at which the TIM field would be inserted, if no TIM is to be included in the beacon frame, and for a data frame, a last field within a data frame header for the data frame,
generate a cyclic redundancy check (CRC) value on the content generated for the fields, and
insert the generated CRC value into the frame at the predetermined location; and
a transmitter configured to transmit the frame.
2. The wireless device according to claim 1 , wherein the controller is configured to generate content for additional fields within the frame concurrently with generating content for the fields.
3. The wireless device according to claim 1 , wherein the controller is configured to generate content for the entire beacon frame.
4. The wireless device according to claim 1 , wherein, for a beacon frame, the controller is configured to insert a bit in the beacon frame indicating whether the TIM is included in the beacon frame.
5. The wireless device according to claim 1 , wherein the CRC value is one octet in the beacon frame.
6. The wireless device according to claim 1 , wherein the frame that conforms to the WLAN protocol conforms to an IEEE 802.11 protocol.
7. A wireless device, comprising:
a receiver operable in a wireless local area network (WLAN) configured receive a portion of a frame from an access point, wherein the frame conforms to a WLAN protocol; and
a controller configured to
determine whether the received frame portion includes a cyclic redundancy check (CRC) value at a predetermined location from a start of the frame, wherein the predetermined location is before a last field of the frame, and
responsive to determining that the received frame portion includes a CRC value, cause the receiver to terminate reception of a remaining portion of the frame if the frame is either for a basic service set with which the station is not associated or for another station.
8. The wireless device according to claim 7 , wherein, for a beacon frame, the predetermined location comprises at least one of immediately following a Traffic Indication Map (TIM) field, if the beacon frame includes a TIM, and immediately preceding optional information elements within the beacon frame.
9. The wireless device according to claim 7 , wherein, for a data frame, the predetermined location comprises a field immediately following the data frame header.
10. The wireless device according to claim 7 , wherein the CRC value comprises a CRC generated on content preceding the CRC within the frame.
11. The wireless device according to claim 7 , wherein the controller is configured, responsive to determining that the received frame portion does not include any CRC value, to cause the receiver to receive all of the frame.
12. The wireless device according to claim 7 , wherein the receiver is configured to store content from the frame as the content is received for processing by the controller to detect a CRC value.
13. The wireless device according to claim 7 , wherein the controller is configured, after causing the receiver to terminate reception of the remaining portion of the frame, to cause the station to enter a low power operational mode.
14. The wireless device according to claim 7 , wherein the frame from the access point conforms to an IEEE 802.11 protocol.
15. A method, comprising:
receiving, in a receiver within a wireless device operating in a wireless local area network (WLAN), a portion of a frame from an access point, wherein the frame conforms to a WLAN protocol; and
determining with a controller within the wireless device whether the received frame portion includes a cyclic redundancy check (CRC) value at a predetermined location from a start of the frame, wherein the predetermined location is before a last field of the frame; and
responsive to determining that the received frame portion includes a CRC value, causing the receiver to terminate reception of a remaining portion of the frame if the frame is for a basic service set with which the wireless device is not associated or for another wireless device.
16. The method according to claim 15 , wherein, for a beacon frame, the predetermined location comprises at least one of immediately following a Traffic Indication Map (TIM) field, if the beacon frame includes a TIM, and immediately preceding optional information elements within the beacon frame.
17. The method according to claim 15 , wherein, for a data frame, the predetermined location comprises a field immediately following the data frame header.
18. The method according to claim 15 , wherein the CRC value comprises a CRC generated on content preceding the CRC within the frame.
19. The method according to claim 15 , further comprising:
responsive to determining that the received frame portion does not include any CRC value, causing the receiver to receive all of the frame.
20. The method according to claim 15 , further comprising:
storing content from the frame within memory within the wireless device as the content is received for processing by the controller to detect a CRC value.
21. The method according to claim 15 , further comprising:
after causing the receiver to terminate reception of the remaining portion of the frame, causing the wireless device to enter a low power operational mode.
22. The method according to claim 15 , wherein the portion of the frame received from the access point conforms to an IEEE 802.11 protocol.