CARRIER SENSE MULTIPLE ACCESS (CSMA) FOR NON-PACKETIZED WIRELESS DIGITAL VOICE NETWORKS USING INTELLIGENT CONVERSATION BOUNDARY DETECTION

• US 20080181250A1
• Filed: 01/31/2007
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: Harris Global Communications, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Koski, Eric
• Granted Patent: US 7,792,136 B2
• Time in Patent Office: Days
• US Class Current: 370/445
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]

Abstract

A communications system includes a plurality of radios that form a carrier sense multiple access (CSMA) wireless communications network and communicate non-packetized digital voice with each other. Each radio is operative for dividing the period following the end of a transmission into a sequence of time slots and determining whether an end of a conversation has occurred. If an end of a conversation has occurred, the system decides randomly or pseudo-randomly with probability p to start transmitting on the channel in that slot.

Claims

1. A communications system, comprising:

a plurality of radios that form a carrier sense multiple access (CSMA) wireless communications network and communicate non-packetized digital voice with each other;

each radio being operative for dividing the period following the end of a received transmission into a sequence of time slots, and deciding randomly or pseudo-randomly with probability p whether to start transmitting on the channel in each of the successive slots.

2. The communications system according to claim 1, wherein a radio is operative to estimate the likelihood of channel contention that could potentially result in a collision of its forthcoming transmission with one or more transmissions by other radios.

3. The communications system according to claim 2, wherein at least one radio decides whether to apply the time slots and the probability p, or to transmit immediately without waiting for a time slot, based on its estimate as to whether channel contention is likely.

4. The communications system according to claim 2, wherein at least one radio adapts the value of the probability p based on its estimate as to whether channel contention is likely.

5. The communications system according to claim 2, wherein a radio is operative to determine whether its own forthcoming transmission is the start of a new voice conversation, and use this determination to estimate whether channel contention is likely.

6. The communications system according to claim 1, and further comprising a data tag attached to a voice transmission from a radio, indicating that the transmission is a start of a new voice conversation.

7. The communications system according to claim 6, wherein said data tag is attached to a collection of digital voice data.

8. The communications system according to claim 1, wherein said radio is operative to start transmitting only if a new transmission has not been detected on the channel prior to the start of the slot.

9. The communications system according to claim 1, wherein each slot in the sequence of slots has a duration at least equal to an effective end-to-end traffic latency which includes some or all of transmit latency, maximum propagation time, and latency of traffic detection by a receiver, so as to permit a transmission commenced in slot n to be detected prior to a start of slot n+1.

10. The communications system according to claim 9, wherein at least one of said radios is operative for inferring whether channel contention is likely from patterns in a temporal sequence of past transmissions on a communications channel.

11. The communications system according to claim 10, wherein in a temporal sequence of transmissions t(1), t(2), . . . t(n) on a communications channel, a radio about to commence transmission t(n) on a channel determines whether or not it was the radio that transmitted transmission t(n−

2) on the channel.

12. The communications system according to claim 10, wherein in a temporal sequence of transmissions t(1), t(2), . . . t(n) on a communications channel, a radio about to commence transmission t(n) on a channel determines whether or not the transmission t(n−

1) on the channel was the start of a new voice conversation.

13. The communications system according to claim 10, wherein if a radio is about to commence a new voice conversation on a communications channel with a transmission t(n), and the same radio also transmitted a transmission t(n−

2) in a prior conversation, the radio waits until the channel is declared idle after it receives transmission t(n−

1) before it commences transmission of t(n).

14. The communications system according to claim 13, in which the radio provides an indication to the radio operator when the channel is declared idle, so that the operator can delay initiating the first transmission t(n) of a new voice conversation until after the channel is declared idle.

15. A method for communicating digital voice data, which comprises:

receiving within a radio a non-packetized digital voice communications signal over a carrier sense multiple access (CSMA) wireless communications channel;

dividing the period following the end of a received transmission into a sequence of time slots; and

deciding randomly or pseudo-randomly with probability p whether to start transmitting on the channel in each of the successive slots.

16. The method according to claim 15, which further comprises estimating the likelihood of channel contention that could potentially result in a collision of a radio'"'"'s forthcoming transmission with one or more transmissions by other radios.

17. The method according to claim 16, which further comprises deciding at a radio whether to apply the time slots and probability p or to transmit immediately without waiting for a time slot, based on its estimate as to whether channel contention is likely.

18. The method according to claim 16, which further comprises adapting the value of probability p based on the radio'"'"'s estimate as to whether channel contention is likely.

19. The method according to claim 16, which further comprises determining whether a forthcoming transmission is the start of a new voice conversation and using this determination to estimate whether channel contention is likely.

20. The method according to claim 15, which further comprises attaching a data tag to a voice transmission from a radio, indicating that the transmission is a start of a new voice conversation.

21. The method according to claim 20, which further comprises attaching the data tag to a collection of digital voice data.

22. The method according to claim 16, which further comprises inferring whether channel contention is likely from patterns in a temporal sequence of past transmissions on a communications channel.

23. The method according to claim 22, which further comprises determining at a radio about to commence transmission t(n) on a channel within a temporal sequence of transmissions t(1), t(2), . . . , t(n) that it was the same radio that transmitted transmission t(n−

2) on the channel.

24. The method according to claim 23, which further comprises determining at a radio about to commence transmission t(n) on a channel within a temporal sequence of transmissions t(1), t(2), . . . t(n) that transmission t(n−

1) on the channel was the start of a new voice conversation.