Short Pre-RTS Packets for Wireless Collision Avoidance
Improved protocols for wireless networking are disclosed. At low/zero marginal cost, embodiments can provide substantial reduction in collision frequency among nodes in a wireless LAN, including and especially at high traffic density. The reduction in collision rate may result in substantially reduced energy consumption, fewer re-transmission of messages, more efficient use of the available bandwidth, and higher user satisfaction overall. As the wireless traffic density soars in the coming years, embodiments can improve system utility while providing higher message success rates, reducing user frustration, minimizing message delays and message collisions, and eliminating node blocking. An array of embodiments can be implemented on existing and planned equipment with appropriate programming. And of vital importance in emergencies, the likelihood of a blocked 911 call can be significantly reduced.
1 . A system for wireless communication, comprising:
a transmitter configured to transmit wireless messages;
a receiver configured to receive wireless messages;
a processor operably connected to the transmitter and the receiver; and
non-transient computer-readable media operably connected to the processor, containing instructions for causing the processor to perform a method comprising:
transmitting a first wireless message;
receiving a second wireless message;
transmitting a third wireless message which is at least 10 times longer than the first wireless message;
receiving a fourth wireless message;
transmitting a fifth wireless message which is at least 4 times longer than the third wireless message; and
receiving a sixth wireless message.
2 . The system of claim 1 , wherein:
the first wireless message is an AQ message requesting permission to send an RTS message;
the second message is a BQ message granting permission to transmit the RTS message;
the third wireless message is the RTS message requesting permission to send a DAT message;
the fourth message is a CTS message bestowing permission to transmit the DAT message;
the fifth wireless message is the DAT message; and
the sixth message is an ACK message.
3 . The system of claim 2 , wherein the instructions further include instructions for determining that a wireless message was successfully transmitted by receiving a confirmatory reply during a predetermined interval, the confirmatory reply comprising the BQ message or the CTS message or the ACK message, and for determining that the wireless message was not successfully transmitted by failing to receive the confirmatory reply during the predetermined interval.
4 . The system of claim 2 , further including a base station configured to transmit the BQ message, the CTS message, and the ACK message.
5 . The system of claim 4 , wherein the base station is further configured to demark time slots, and wherein the AQ message occupies one or two slots.
6 . The system of claim 5 , wherein the BQ message occupies one or two slots.
7 . The system of claim 4 , wherein the base station is configured to demark bytes of message data, and wherein the AQ message occupies less than four bytes.
8 . The system of claim 7 , wherein the processor is configured to inhibit the transmitter from transmitting during bytes other than the bytes occupied by the AQ message, and wherein the processor is configured to detect a transmission from another node during the bytes not occupied by the AQ message.
9 . The system of claim 7 , wherein the AQ message is positioned randomly within a slot.
10 . The system of claim 7 , wherein the receiver is configured to detect wireless messages or carrier signals during bytes other than the bytes occupied by the AQ message.
11 . The system of claim 4 , wherein the base station is configured to detect and interpret bits of message data in a bitwise sequential manner, and wherein the AQ message occupies one or two bits.
12 . The system of claim 11 , wherein the processor is configured to cause the transmitter to transmit unmodulated carrier signals during times associated with transmission of the bit or bits of the AQ message, and to inhibit the transmitter during bits other than the bits of the AQ message.
13 . The system of claim 11 , wherein the AQ message is positioned randomly within a slot.
14 . The system of claim 11 , wherein the processor is configured to detect carrier signals or wireless messages during times when the AQ bits are not being transmitted.
15 . A method for wireless communication between a node and a base station of a local area network, comprising:
transmitting, by the node, an AQ message;
transmitting, by the base station, a BQ message responsive to the AQ message;
transmitting, by the node, an RTS message responsive to the BQ message;
transmitting, by the base station, a CTS message responsive to the RTS message;
transmitting, by the node, a DAT message responsive to the CTS message; and
transmitting, by the base station, an ACK message responsive to the DAT message.
16 . The method of claim 15 , wherein the base station demarks time in sequential time slots of a predetermined length, and the AQ message has a duration of one slot and the BQ message has a duration of one slot.
17 . The method of claim 15 , wherein the base station demarks time in sequential bytes of a predetermined length, and the AQ message has a duration of two bytes.
18 . The method of claim 15 , further comprising transmitting, by the base station, a beacon message that includes a local identification code of the base station, wherein the local identification code is persistently associated with the base station and has a length of less than four bytes.
19 . The method of claim 18 , wherein the AQ message includes the local identification code of the base station.
20 . The method of claim 19 , wherein the AQ message has the same number of bytes as the local identification code.
21 . The method of claim 18 , wherein the BQ message includes the local identification code of the base station, and one or more symbols indicating that the BQ message is a BQ message.
22 . The method of claim 15 , wherein the AQ message has a duration of less than eight bits.
23 . The method of claim 22 , wherein:
the AQ message comprises one bit of unmodulated carrier signal within a slot;
the slot has no carrier signal therein, other than the one bit comprising the AQ message; and
the base station is configured to transmit a BQ message upon detecting a single bit of unmodulated carrier within a slot having no other carrier signal therein.
24 . The method of claim 15 , wherein the node is configured to receive a BQ message which is not associated with any AQ message transmitted by the node, and to determine that the BQ message is associated with a different node, and if the BQ message is determined to be associated with a different node, then the node is configured to inhibit transmitting for a predetermined time at least equal to a sum of a duration of the RTS message plus a duration of the CTS message, whereby the BQ message is for the node that sent the AQ message, and all other nodes are configured to remain silent for a time equal to RTS+CTS.
25 . A local area network, comprising:
a plurality of nodes, each node comprising a processor, a transmitter, and a receiver; and
a base station comprising a processor, a transmitter, and a receiver; wherein:
each node is configured to initiate wireless communication by transmitting an AQ message to the base station;
the base station is configured to transmit a BQ message responsive to the AQ message;
each node is configured to receive, after transmitting the AQ message, the BQ message, and to transmit an RTS message responsive to the BQ message;
the base station is configured to transmit a CTS message responsive to the RTS message;
each node is configured to receive, after transmitting the RTS message, the CTS message, and to transmit a DAT message responsive to the CTS message;
the base station is configured to transmit an ACK message responsive to the DAT message.
26 . The local area network of claim 25 , wherein each node is configured to begin a backoff delay upon failing to receive a BQ message within a predetermined interval after transmitting an AQ message, or upon failing to receive a CTS message within a predetermined interval after transmitting an RTS message, or upon failing to receive an ACK message within a predetermined interval after transmitting a DAT message.
27 . The local area network of claim 26 , wherein the backoff delay comprises a predetermined waiting interval followed by a randomly selected portion of a predetermined contention window.
28 . The local area network of claim 27 , wherein the AQ message has a duration equal to one slot.
29 . The local area network of claim 28 , wherein the AQ message comprises two bytes.
30 . The local area network of claim 29 , wherein the AQ message comprises a single bit of modulated or unmodulated carrier signal.