Method and apparatus for cell identification in wireless data networks

• US 8,023,452 B2
• Filed: 12/15/2005
• Issued: 09/20/2011
• Est. Priority Date: 09/30/2003
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Douglas, Bretton Lee, Perahia, Eldad
• Primary Examiner(s): Kizou; Hassan
• Assistant Examiner(s): Shand; Roberta A
• Application Number:
  US11/300,960
• Publication Number:
  US 20060104253A1
• Time in Patent Office: 2,105 Days
• Field of Search: 370/310, 370/328, 370/349, 370/329, 370/338, 455/456.1
• US Class Current: 370/328
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method including wirelessly receiving a packet at a wireless station belonging to a cell of a wireless network, the network for communicating according to a wireless network standard, each transmitting station of the cell able to transmit a packet that includes cell identification information; and ascertaining at the physical layer level whether or not the received packet is from another station of the cell by ascertaining whether or not the received packet includes the cell identification information of the cell.

Claims

1. A method comprising:

wirelessly receiving a packet at a wireless station belonging to a cell of a wireless network, the packet conforming to a wireless network standard according to which a conforming packet includes a portion or portions containing a modulated payload and at least one additional portion distinct from the modulated payload, the modulated payload including at least one specific field and a data portion, the at least one specific field coded according to a predefined code and including a field that specifies how the data portion is coded, such that the at least one field is decodable prior to the data portion, the additional portion and/or at least one specific field being specified in the wireless network standard as being for a purpose or purposes other than including cell indentifying information in the additional portion and/or at least one specific field, each transmitting station of the cell being configured to transmit a packet that includes cell identification information in the packet'"'"'s at least one additional portion and/or in the packet'"'"'s at least one specific field; and

ascertaining without needing to decode any of the data portion whether or not the received packet is from another station of the cell by ascertaining whether or not the received packet'"'"'s at least one additional portion and/or at least one specific field includes the cell identification information of the cell.

2. A method as recited in claim 1, wherein the at least one specific field of a packet according to the network standard includes a particular field that provides information on how the remainder of the packet is encoded, the particular field according to the standard including reserved or empty bits, and wherein some or all of the reserved or empty bits in the particular field of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

3. A method as recited in claim 1, further comprising:

aborting processing the received packet if the ascertaining step ascertains that the received packet does not include the cell identification information of the cell.

4. A method as recited in claim 1, wherein the cell is an infrastructure network having an access point, and wherein the wireless station is an access point, the method further comprising:

transmitting the cell identification information to other stations of the cell such that the other stations can include the cell identification information in packets that the other stations transmit.

5. A method as recited in claim 4, wherein the transmitting of the cell identification information to other stations of the cell uses the MAC layer protocol of the standard.

6. A method as recited in claim 1, wherein the standard is one of the OFDM variants of the IEEE 802.11 standard according to which the at least one specific field of a packet includes a SIGNAL field that provides information on how the remainder of the packet is encoded, the SIGNAL field including reserved or empty bits, and wherein some or all of the reserved or empty bits in the SIGNAL field of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

7. A method as recited in claim 1, wherein the standard is related to one of the OFDM variants of the IEEE 802.11 standard, according to which the at least one specific field of a packet includes a SIGNAL field, and wherein the SIGNAL field provides for a station of the cell to convey at least some of the cell identification information of the cell.

8. A method as recited in claim 1, wherein a packet according to the network standard includes a preamble and a modulated part, wherein the modulated part includes the at least one specific field, including reserved or empty bits, and wherein some or all of the reserved or empty bits in the modulated part of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

9. A method as recited in claim 1, wherein the standard is one of the OFDM variants of the IEEE 802.11 standard according to which the at least one specific field of a packet includes a SERVICE field including reserved or empty bits, and wherein some or all of the reserved or empty bits in the SERVICE field of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

10. A method as recited in claim 1, wherein a first number of bits are provided for the cell identification information of the cell, and wherein the first number of bits are encoded into coded form of a second number of bits greater than the first number of bits according to a coding method to provide for robust communication of the cell identification information.

11. A method comprising:

wirelessly transmitting a packet from a wireless station belonging to a cell of a wireless network, the network for communicating according to a wireless network standard according to which a packet includes a portion or portions containing a modulated payload and at least one additional portion distinct from the modulated payload, the modulated payload including at least one specific field and a data portion, the at least one specific field coded according to a predefined code and including a field that specifies how the data portion is coded, such that the at least one field is decodable prior to the data portion, the additional portion and/or at least one specific field being specified in the wireless network standard as being for a purpose or purposes other than including cell indentifying information in the additional portion and/or at least one specific field, the transmitted packet including cell identification information in the packet'"'"'s at least one additional portion and/or in the packet'"'"'s at least one specific field,

such that another station receiving the transmitted packet can ascertain without needing to decode any of the data portion whether or not the received packet is from a station of the same cell as that of the other station by ascertaining whether or not the received packet'"'"'s at least one additional portion and/or at least one specific field includes the cell identification information of the same cell as that of the other station.

12. A method as recited in claim 11, wherein the at least one specific field includes a particular field that provides information on how the data portion of the packet is encoded, the particular field according to the standard including reserved or empty bits, and some or all of the reserved or empty bits in the particular field of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

13. A method as recited in claim 11, wherein the at least one specific field includes a particular field that provides information on how the data portion of the packet is encoded and that provides for cell identification information, such that the particular field of a packet transmitted by a station of the cell conveys at least some of the cell identification information of the cell.

14. A method as recited in claim 11, wherein a first number of bits are provided for the cell identification information of the cell, and wherein the first number of bits are encoded into coded form of a second number of bits greater than the first number of bits according to a coding method to provide for robust communication of the cell identification information.

15. A wireless station comprising:

a wireless receiver configured to receive a packet from another station of a cell of a wireless network using a wireless network standard for communication, the wireless network standard defining a packet that includes a portion or portions containing a modulated payload and at least one additional portion distinct from the modulated payload, the modulated payload including at least one specific field and a data portion, the at least one specific field coded according to a predefined code and including a field that specifies how the data portion is coded, such that the at least one field is decodable prior to the data portion, the additional portion and/or at least one specific field being specified in the wireless network standard as being for a purpose or purposes other than including cell indentifying information in the additional portion and/or at least one specific field,

wherein each station of the cell is configured to transmit a packet that includes cell identification information in the packet'"'"'s at least one additional portion and/or in the packet'"'"'s at least one specific field,

wherein the wireless receiver is configured to ascertain without needing to decode any of the data portion whether or not a packet received by the receiver packet is from another station of the cell by ascertaining whether or not the received packet'"'"'s at least one additional portion and/or at least one specific field includes the cell identification information of the cell.

16. A wireless station as recited in claim 15, wherein a packet according to the network standard includes a preamble followed by the modulated payload, and wherein the preamble of a packet transmitted by a station of the cell conveys the cell identification information of the cell, and wherein the standard is one of the OFDM variants of the IEEE 802.11 standard according to which the preamble includes a set of short symbols, and wherein at least some of the cell identification information of the cell is conveyed in a plurality of the short symbols encoded such that each cell is given a different sequence.

17. A wireless station as recited in claim 15, wherein a packet according to the network standard includes a preamble followed by the modulated payload, and wherein the preamble of a packet transmitted by a station of the cell conveys the cell identification information of the cell, and wherein a first number of bits are provided for the cell identification information of the cell, and wherein the first number of bits are encoded into coded form of a second number of bits greater than the first number of bits according to a coding method to provide for robust communication of the cell identification information.

18. A wireless station as recited in claim 15, wherein the wireless receiver of the wireless station includes a start-of-packet (SOP) detector that has a settable signal strength threshold such that received signals of received signal strength below the settable threshold do not trigger the start of packet detector, the wireless receiver further comprising a controller that is configured to adjust the settable threshold according to the signal strengths of one or more signals received at the station and ascertained not to be from other stations of the cell.

19. A wireless station as recited in claim 15, wherein a first number of bits are provided for the cell identification information of the cell, and wherein the first number of bits are encoded into coded form of a second number of bits greater than the first number of bits according to a coding method to provide for robust communication of the cell identification information.

20. A non-transitory computer readable storage medium comprising one or more computer readable code segments that when implemented by at least one processor cause carrying out of a method in a wireless station, the method comprising:

wirelessly receiving a packet at a wireless station belonging to a cell of a wireless network, the packet conforming to a wireless network standard according to which a conforming packet includes a portion or portions containing a modulated payload and at least one additional portion distinct from the modulated payload, the modulated payload including at least one specific field and a data portion, the at least one specific field coded according to a predefined code and including a field that specifies how the data portion is coded, such that the at least one field is decodable prior to the data portion, the additional portion and/or at least one specific field being specified in the wireless network standard as being for a purpose or purposes other than including cell indentifying information in the additional portion and/or at least one specific field, each transmitting station of the cell being configured to transmit a packet that includes cell identification information in the packet'"'"'s at least one additional portion and/or in the packet'"'"'s at least one specific field; and

ascertaining without needing to decode any of the data portion whether or not the received packet is from another station of the cell by ascertaining whether or not the received packet'"'"'s at least one additional portion and/or at least one specific field includes the cell identification information of the cell.

21. A non-transitory computer readable storage medium as recited in claim 20, wherein the wireless station uses information of received packets that are ascertained to be not from other stations of the cell to mitigate interference from such stations that are not of the cell.

22. A non-transitory computer readable storage medium as recited in claim 20, wherein the wireless station includes a start-of-packet (SOP) detector that has a settable signal strength threshold such that received signals of received signal strength below the settable threshold do not trigger the start of packet detector, the method further comprising:

adjusting the settable threshold according to the signal strengths of one or more signals received at the station and ascertained not to be from other stations of the cell.

23. A wireless station comprising:

means for receiving a packet from another station of a cell of a wireless network using a wireless network standard for communication, the wireless network standard defining a packet that includes a portion or portions containing a modulated payload and at least one additional portion distinct from the modulated payload, the modulated payload including at least one specific field and a data portion, the at least one specific field coded according to a predefined code and including a field that specifies how the data portion is coded, such that the at least one field is decodable prior to the data portion, the additional portion and/or at least one specific field being specified in the wireless network standard as being for a purpose or purposes other than including cell indentifying information in the additional portion and/or at least one specific field,

wherein each station of the cell is configured to transmit a packet that includes cell identification information in the packet'"'"'s at least one additional portion and/or at least one specific field,

the means for receiving including means for ascertaining without needing to decode any of the data portion whether or not a packet received by the receiver packet is from another station of the cell by ascertaining whether or not the received packet'"'"'s at least one additional portion and/or at least one specific field includes the cell identification information of the cell.

24. A wireless station as recited in claim 23, wherein the at least one specific field includes a particular field that provides information on how the data portion of the packet is encoded, the field according to the standard including reserved or empty bits, and such that some or all of the reserved or empty bits in the particular field of a packet transmitted by a station of the cell convey at least some of the cell identification information of the cell.

25. A wireless station as recited in claim 23, wherein a first number of bits are provided for the cell identification information of the cell, and wherein the first number of bits are encoded into coded form of a second number of bits greater than the first number of bits according to a coding method to provide for robust communication of the cell identification information.