Method and apparatus for synchronizing fast ethernet data packets to radio frames in a wireless metropolitan area network

• US 7,002,941 B1
• Filed: 09/23/1998
• Issued: 02/21/2006
• Est. Priority Date: 10/14/1997
• Status: Expired due to Fees

• Current Assignee: Sparkmotion Incorporated (Quarterhill Inc. (f/k/a Wi-LAN Inc.))
• Original Assignee: Alvarion Israel (2003) limited (Alvarion Limited)
• Inventors: Hamilton, Mike, Treadaway, Kirk, Ngoc, Tho Le, Denton, Darryl
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): HOANG, THAI D
• Application Number:
  US09/159,267
• Time in Patent Office: 2,708 Days
• Field of Search: 3703101-3102, 370313-314, 370328-330, 370/338, 370/350, 370/473, 370/503, 370/507, 370509-514, 370465-466, 455/554.2
• US Class Current: 370/338
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

Method and apparatus for synchronizing Fast Ethernet data packets to radio frames in a wireless metropolitan area network. A method of synchronizing Fast Ethernet data packets to radio frames includes receiving Fast Ethernet data packets, storing packet data in a packet buffer according to a first clock signal wherein the first clock signal is derived from the data packets, retrieving the packet data from the packet buffer according to a second clock signal wherein the second clock signal is asynchronous with the first clock signal, and formatting the retrieved packet data according to radio frames. According to another aspect of the invention, a method of synchronizing radio frames to Fast Ethernet data packets includes recovering packet data for Fast Ethernet data packets from radio frames, storing packet data from the radio frames in a packet buffer according to a first clock signal synchronous with the radio frames, retrieving the packet data from the packet buffer according to a second clock signal wherein a frequency of the second clock signal is lower than a frequency of the first clock signal, and forwarding the data packets reconstructed from the radio frames. The method can also include adjusting a frequency of the second clock signal according to an amount of space available in the packet buffer, adjusting an inter-packet gap for the data packets according to an amount of space available in the packet buffer, or pausing the step of forwarding according to an amount of space available in the packet buffer.

Claims

1. A method of synchronizing Fast Ethernet data packets to radio frames, the method comprising steps of:

a. receiving Fast Ethernet data packets;

b. storing packet data from the Fast Ethernet data packets in a packet buffer wherein the step of storing is performed according to a first clock signal wherein the first clock signal is derived from the Fast Ethernet data packets;

c. retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the step of retrieving is performed according to a second clock signal wherein the second clock signal is asynchronous with the first clock signal; and

d. formatting the retrieved packet data according to radio frames;

wherein the method does not include a step of converting the packet data into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

2. The method according to claim 1 wherein the step of formatting is performed according to the second clock signal.

3. The method according to claim 2 wherein the second clock signal is higher than the first clock signal.

4. The method according to claim 2 wherein the step of formatting includes a step of removing a data valid bit from each four-bit portion of retrieved packet data.

5. The method according to claim 2 wherein the step of storing includes a step of removing a preamble from each Fast Ethernet data packet.

6. The method according to claim 5 wherein the step of storing further includes steps of:

a. determining a length of the packet data for each Fast Ethernet data packet; and

b. storing the length of the packet data in a length buffer.

7. The method according to claim 6 wherein the step of formatting further includes a step of inserting the length of the packet into the radio frame.

8. The method according to claim 7 wherein the step of formatting further includes a step of inserting a check sum for the length into the radio frame.

9. The method according to claim 8 wherein the check sum is a Golay check sum.

10. The method according to claim 2 wherein the step of formatting includes steps of:

a. performing forward error correction on the retrieved packet data thereby forming error corrected packet data; and

b. inserting the error corrected packet data into a data field of a radio frame.

11. The method according to claim 10 wherein the step of formatting further includes a step of randomizing the data field of the radio frame.

12. The method according to claim 10 wherein the radio frames each have a same length and wherein the step of formatting the retrieved packet data is performed such that boundaries for the data packets are not necessarily aligned with boundaries for the radio frames.

13. The method according to claim 10 wherein the step of formatting further includes a step of time-division multiplexing the data packets into the radio frames.

14. An apparatus for synchronizing Fast Ethernet data packets to radio frames, the apparatus comprising:

a. a packet transceiver for detecting Fast Ethernet data packets;

b. a packet buffer coupled to the packet transceiver for temporarily storing packet data from the data packets according to a first clock signal derived from the data packets;

c. a packet retriever coupled to the packet buffer for retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the packet retriever retrieves the packet data according to a second clock signal and wherein the second clock signal is asynchronous with the first clock signal; and

d. a radio framer coupled to the packet retriever for formatting the retrieved packet data into radio frames;

wherein the Packet data is not converted into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

15. The apparatus according to claim 14 wherein the radio framer formats the retrieved packet data in radio frames according to the second clock signal.

16. The apparatus according to claim 15 wherein the second clock signal is higher than the first clock signal.

17. The apparatus according to claim 15 wherein the radio framer removes a data valid bit from each four-bit portion of the retrieved packet data.

18. The apparatus according to claim 15 a preamble is removed from each Fast Ethernet data packet prior to storage of the packet data in the packet buffer.

19. The apparatus according to claim 18 further comprising a length buffer coupled to the radio framer for storing a length of packet data for each Fast Ethernet data packet.

20. The apparatus according to claim 19 wherein the radio framer inserts the length of packet data for each Fast Ethernet data packet from the length buffer into the radio frames.

21. The apparatus according to claim 20 wherein the radio framer inserts into the radio frames a check sum for the length of packet data for each Fast Ethernet data packet.

22. The apparatus according to claim 21 wherein the check sum is a Golay check sum.

23. The apparatus according to claim 15 wherein the radio framer comprises:

a. a forward error corrector for correcting errors in the retrieved packet data thereby forming error corrected data; and

b. a framing apparatus coupled to the forward error corrector for inserting the error corrected data into a data field of a radio frame.

24. The apparatus according to claim 23 wherein the radio framer further comprises a randomizer coupled to the framing apparatus for randomizing the data field of the radio frame.

25. The apparatus according to claim 23 wherein the radio frames each have a same length and wherein the framing apparatus inserts the error corrected data into the data field such that boundaries for the data packets are not necessarily aligned with boundaries for the radio frames.

26. The apparatus according to claim 23 wherein the framing apparatus time-division multiplexes the error corrected data into the radio frames.

27. The apparatus according to claim 14 further comprising a packet counter coupled to the packet buffer for maintaining a count of Fast Ethernet data packets stored in the buffer.

28. The apparatus according to claim 27 further comprising arbitration logic means coupled to the packet buffer and to the packet counter for determining when packet data corresponding to a complete Fast Ethernet packet has been stored in the packet buffer and for determining when the packet data corresponding to a complete Fast Ethernet packet has been retrieved from the packet buffer.

29. The apparatus according to claim 28 further comprising a threshold compare means coupled to the packet counter for determining when the count is equal to or greater than a predetermined threshold number.

30. The apparatus according to claim 29 further comprising a packet reading means coupled to the threshold compare means for providing an initiation signal when the count exceeds the predetermined threshold.

31. The apparatus according to claim 30 wherein the predetermined threshold is one.

32. The apparatus according to claim 30 wherein the radio framer forms a frame enable signal when the radio framer is ready to receive packet data and wherein the apparatus further comprises a logic gate coupled to receive the initiation signal and the frame enable signal, the logic gate for initiating of retrieval of packet data from the packet buffer.

33. An apparatus for synchronizing radio frames to Fast Ethernet data packets, the apparatus comprising:

a. a synchronizer/de-synchronizer for recovering packet data for Fast Ethernet data packets from radio frames received from a wireless link;

b. a packet buffer coupled to the synchronizer/desynchronizer for temporarily storing packet data from the radio frames according to a first clock signal synchronous with the radio frames;

c. a packet retriever coupled to the packet buffer for retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the packet retriever retrieves the packet data according to a second clock signal and wherein a frequency of the second clock signal is lower than a frequency of the first clock signal; and

d. an Ethernet transceiver coupled to the packet retriever for forwarding the Ethernet data packets reconstructed from the radio frames;

wherein the method does not include a means for converting the packet data into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

34. The apparatus according to claim 33 wherein the packet retriever adjusts a frequency of the second clock signal according to an amount of space available in the packet buffer.

35. The apparatus according to claim 33 wherein the packet retriever adjusts an inter-packet gap for the Fast Ethernet data packets according to an amount of space available in the packet buffer.

36. The apparatus according to claim 33 wherein a layer-two switch at an opposite end of the wireless link is selectively paused according to an amount of space available in the packet buffer.

37. An apparatus for synchronizing radio frames to Fast Ethernet data packets, the apparatus comprising:

a. a synchronizer/de-synchronizer for recovering packet data for Fast Ethernet data packets from radio frames received from a wireless link;

b. a packet buffer coupled to the synchronizer/desynchronizer for temporarily storing packet data from the radio frames according to a first clock signal synchronous with the radio frames;

c. a packet retriever coupled to the packet buffer for retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the packet retriever retrieves the packet data according to a second clock signal and wherein at least sufficient packet data for a complete one of the Ethernet data packet is stored in the packet buffer prior to the packet retriever retrieving the packet data; and

d. an Ethernet transceiver coupled to the packet retriever for forwarding the Fast Ethernet data packets reconstructed from the radio frames;

wherein the method does not include a means for converting the packet data into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

38. The apparatus according to claim 37 wherein the packet retriever adjusts a frequency of the second clock signal according to an amount of space available in the packet buffer.

39. The apparatus according to claim 37 wherein the packet retriever adjusts an inter-packet gap for the Fast Ethernet data packets according to an amount of space available in the packet buffer.

40. The apparatus according to claim 37 wherein the a layer-two switch at an opposite end of the wireless link is selectively paused according to an amount of space available in the packet buffer.

41. A method of synchronizing radio frames to Fast Ethernet data packets, the method comprising steps of:

a. recovering packet data for Fast Ethernet data packets from radio frames received from a wireless link;

b. storing packet data from the radio frames in a packet buffer according to a first clock signal synchronous with the radio frames;

c. retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the step of retrieving is performed according to a second clock signal and wherein a frequency of the second clock signal is lower than a frequency of the first clock signal; and

d. forwarding the Fast Ethernet data packets reconstructed from the radio frames;

wherein the method does not include a step of converting the packet data into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

42. The method according to claim 41 further comprising a step of adjusting a frequency of the second clock signal according to an amount of space available in the packet buffer.

43. The method according to claim 41 further comprising a step of adjusting an inter-packet gap for the Fast Ethernet data packets according to an amount of space available in the packet buffer.

44. The method according to claim 41 further comprising a step of initiating a pause to a layer-two switch at an opposite end of the wireless link according to an amount of space available in the packet buffer.

45. A method of synchronizing radio frames to Fast Ethernet data packets, the method comprising steps of:

a. recovering packet data for Fast Ethernet data packets from radio frames received from a wireless link;

b. storing packet data from the radio frames in a packet buffer according to a first clock signal synchronous with the radio frames;

c. retrieving the packet data from the packet buffer thereby forming retrieved packet data wherein the step of retrieving is performed according to a second clock signal and wherein at least sufficient packet data for a complete one of the Fast Ethernet data packet is stored in the packet buffer prior to retrieving the packet data; and

d. forwarding the Fast Ethernet data packets reconstructed from the radio frames;

wherein the method does not include a step of converting the packet data into a telephony communication protocol or into an asynchronous transfer mode (ATM) protocol prior to communication of the radio frames over the wireless link.

46. The method according to claim 45 further comprising a step of adjusting a frequency of the second clock signal according to an amount of space available in the packet buffer.

47. The method according to claim 45 further comprising a step of adjusting an inter-packet gap for the Fast Ethernet data packets according to an amount of space available in the packet buffer.

48. The method according to claim 45 further comprising a step of initiating a pause to a layer-two switch at an opposite end of the wireless link according to an amount of space available in the packet buffer.