TRANSMISSION OF PACKETS IN A CSMA WIRELESS NETWORK

Abstract

A wireless device containing a physical layer (in a transceiver) which generates multiple status signals indicating the status of the wireless medium at different time instances. The status signals are examined to determine a time instance after which the medium is available to transmit the packets. In an embodiment, one status signal indicates whether valid preamble bits are being received on (before end of the preamble) the wireless medium consistent with the 802.11a standard and another status signal indicates similar status but for 802.11b standard. The embodiment further includes a qualification logic, which determines a time instance after which the availability of medium is determined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the following accompanying drawings, which are described briefly below.

FIG. (FIG.) 1 is a block diagram illustrating an example environment in which various aspects of the present invention can be implemented.

FIG. 2 is a timing diagram illustrating a transmit sequence in one prior embodiment.

FIG. 3 is a flowchart illustrating the manner in which packets are transmitted according to an aspect of the present invention.

FIGS. 4 a and 4b are example timing diagrams illustrating an improved transmit sequence in an embodiment of the present invention.

FIG. 5 is a block diagram illustrating the details of a wireless device in an embodiment of the present invention.

FIG. 6 is a block diagram illustrating the details of a decision block in an embodiment.

FIG. 7 is a timing diagram illustrating the retransmit sequence in a prior embodiment.

FIG. 8 is a state transition diagram illustrating the sequence of states in determining channel status in one embodiment.

FIGS. 9A and 9B are example timing diagrams illustrating an improved retransmit sequence according to an aspect of the present invention.

Claims

1. A method of determining an optimal time instance to transmit packets on a wireless network, said method being performed in a wireless device, said method comprising: forming packet for transmission on said wireless network;commencing a preparation procedure for transmission of said packet;receiving a plurality of status signals, each status signal indicating a status of a channel at a corresponding time instance on said wireless network;determining a degree of certainty with which said channel is free for transmission by examining said plurality of status signals; andtransmitting said packet at an end of said transmission procedure if said degree exceeds a desired threshold.

2. The method of claim 1, wherein said plurality of status signals comprise a first signal indicating whether a medium signal on said wireless network at a first time instance represents a valid preamble of a packet transmitted by another device in said wireless network, wherein said degree of certainty is enhanced if said first signal indicates that said valid preamble is not detected.

3. The method of claim 2, wherein said plurality of status signals further comprises a second signal indicating whether energy level on said wireless network where said wireless device is located exceeds a second threshold at a second time instance, a third signal indicating whether energy level within a band of interest on said wireless where said wireless device is located exceeds a third threshold at a third time instance, wherein said second time instance is before said third time instance and said third time instance is before said first time instance.

4. The method of claim 3, further comprising examining a plurality of qualifying signals, which respectively tie said first time instance to a specific time instance in time domain.

5. The method of claim 4, further comprising providing a configuration data which can be configured by a user, wherein said configuration data specifies the specific ones of said plurality of status signals which are to be ignored or considered by said determining, and a manner in which the considered status signals are to be processed by said determining in forming said degree.

6. The method of claim 4, wherein said wireless device and said wireless network operated according to 802.11 standard, and wherein said first signal indicates whether said medium signal represents a preamble according to 802.11a, wherein said plurality of status signals further comprises a fourth signal indicating whether said medium signal on said wireless network at a fourth time instance represents a valid preamble of a packet according to 802.11b, wherein said degree of certainty is enhanced if said fourth signal indicates that said valid preamble is not detected according to 802.11b.

7. The method of claim 1, wherein said determining determines a second degree of certainty with which a medium signal on said channel does not represent a valid acknowledgment to said packet by examining said plurality of status signals, said method further comprising: retransmitting said packet if said second degree of certainty exceeds a second threshold.

8. A transceiver to transmit and receive packets on a wireless network, said transceiver comprising: a timer block designed to count a time interval;a transmit block to form a packet for transmission on said wireless network, said transmit block causing said timer block to start counting said time interval;a receive block to generate a plurality of status signals, each status signal indicating a status of a channel at a corresponding time instance on said wireless network; anda decision block examining said plurality of status signals to determine a time instance after which to transmit said packet, wherein said transmit block transmits said packet at an end of said time interval after said time instance.

9. The transceiver of claim 8, wherein said decision block determines a degree of certainty with which said channel is free for transmission by examining said plurality of status signals and indicates said time instance when said degree of certainty exceeds a desired threshold.

10. The transceiver of claim 9, wherein said decision block comprises: a mapping table receiving said plurality of status signals and performing a logical operation of said plurality of status signals to generate a value representing whether said degree of certainty exceeds said threshold.

11. The transceiver of claim 10, wherein said decision block further comprises: a qualification selection logic which generates a signal representing a time instance after which the result of said logical operation is to be represented as said value.

12. The transceiver of claim 11, wherein each of said mapping table and said qualification selection logic is configurable by a user.

13. The transceiver of claim 11, wherein said qualification selection logic comprises a multiplexer which receives from said receive block a plurality of qualifying signals each with a different level of phase shift, and forwards the selected on of the plurality of qualifying signals as a selected qualifying signal, said transceiver further comprising: an AND logic performing a logical AND operation of said selected qualifying signal and an output of said mapping table to generate said value.

14. The transceiver of claim 13, further comprising: an OR logic performing a logical OR operation of said selected qualifying signal and said output of said mapping table to generate an enable signal which starts count of said time interval.

15. The transceiver of claim 11, wherein a protocol underlying said wireless network requires a retransmission of said packet if an acknowledgment packet is not received in a pre-specified interval after transmission of said packet, wherein said mapping table generates a second value indicating whether a second degree of certainty with which a medium signal on said channel does not represent a valid acknowledgment to said packet exceeds a second threshold by examining said plurality of status signals; wherein said transmit block retransmits said packet if said value indicates that said second degree of certainty exceeds a second threshold.

16. The transceiver of claim 11, wherein said plurality of status signals comprise a first signal indicating whether a medium signal on said wireless network at a first time instance represents a valid preamble of a packet transmitted by another device in said wireless network, wherein said degree of certainty is enhanced if said first signal indicates that said valid preamble is not detected.

17. The transceiver of claim 16, wherein said plurality of status signals further comprises a second signal indicating whether energy level on said wireless network where said wireless device is located exceeds a second threshold at a second time instance, a third signal indicating whether energy level within a band of interest on said wireless where said wireless device is located exceeds a third threshold at a third time instance, wherein said second time instance is before said third time instance and said third time instance is before said first time instance.

18. The transceiver of claim 17, wherein said wireless device and said wireless network operate according to 802.11 standard, and wherein said first signal indicates whether said medium signal represents a preamble according to 802.11a, wherein said plurality of status signals further comprises a fourth signal indicating whether said medium signal on said wireless network at a fourth time instance represents a valid preamble of a packet according to 802.11b, wherein said degree of certainty is enhanced if said fourth signal indicates that said valid preamble is not detected according to 802.11b.

19. A wireless device for operation in conjunction with a wireless network, said wireless device comprising: a host unit generating data for transmission on said wireless network; anda transceiver to transmit said data on said wireless network, said transceiver comprising: a transmit block to form a packet for transmission on said wireless network;a receive block to generate a plurality of status signals, each status signal indicating a status of a channel at a corresponding time instance on said wireless network; anda decision block examining said plurality of status signals to determine a time instance after which to transmit said packet,wherein said transmit block transmits said packet after said time instance.

20. The wireless device of claim 19, wherein said transceiver further comprises: a timer block designed to count a time interval, wherein said decision block determines a degree of certainty with which said channel is free for transmission by examining said plurality of status signals,wherein said transmit block transmits said packet at an end of said time interval if said degree exceeds a desired threshold

21. The wireless device of claim 20, wherein said decision block comprises: a mapping table receiving said plurality of status signals and performing a logical operation of said plurality of status signals to generate a value representing whether said degree of certainty exceeds said threshold; anda qualification selection logic which generates a signal representing a time instance after which the result of said logical operation is to be represented as said value.

22. The wireless device of claim 19, wherein said wireless network operates according to 802.11 protocol.