US20160174260A1 - Method and system for carrier sense multiple access with collision avoidance (csma/ca) with directional transmission - Google Patents
Method and system for carrier sense multiple access with collision avoidance (csma/ca) with directional transmission Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access
- H04W74/08—Non-scheduled access, e.g. ALOHA
- H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
- H04W74/0816—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA] with collision avoidance
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
- H04W16/28—Cell structures using beam steering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
Definitions
- Certain embodiments of the invention relate to data communication. More specifically, certain embodiments of the invention relate to a method and system for CSMA/CA with directional transmission.
- IEEE 802.15 describes a communication architecture, which may enable communicating devices (DEVs) to communicate via wireless personal area networks (WPANs).
- DEVs wireless personal area networks
- Many DEVs utilized in WPANs are small or handheld devices, such as personal digital assistants, portable computers, or consumer electronics devices such as digital video recorders or set top boxes.
- IEEE 802.15 is a short-range wireless communications standard that enables connection between consumer and computer equipment while eliminating wires.
- IEEE 802.15 WPAN DEVs may utilize frequencies in the 57 GHz to 66 GHz range for communication.
- a plurality of communicating DEVs in a WPAN environment may comprise a network known as a piconet.
- One of the DEVs in a piconet may function as a piconet coordinator (or controller), or PNC.
- the PNC may provide overall coordination for the communication between DEVs in a piconet.
- the piconet may comprise the PNC and DEVs, which are associated with the PNC.
- the DEVs may communicate through the transmission and/or reception of protocol data units (PDU) referred to as frames.
- a frame may correspond to a PDU that is associated with a physical (PHY) layer protocol in a protocol reference model (PRM).
- the frame may comprise a physical layer convergence procedure (PLCP) preamble field, a PLCP header field and a physical layer service data unit (PSDU) field.
- PLCP physical layer convergence procedure
- PSDU physical layer service data unit
- the PLCP header field is utilized by a receiver of the PDU to determine the length of the PSDU field, typically measured in octets, and to determine a data rate for data contained within the PSDU field.
- the PSDU field may be referred to as a payload field.
- the payload field may comprise data that are being communicated from a source DEV to a destination DEV.
- Radio frequency (RF) communications between communicating devices via the wireless communication medium within the 60 GHz frequency range are typically directional in nature.
- transmitting DEVs may transmit RF signal energy from a given antenna in a given direction while not transmitting RF signal energy in other directions from the given antenna.
- a potential recipient DEV which is in the direction of RF signal energy transmission may receive signals from the transmitting DEV while the other potential recipient DEV may not.
- one or more destination DEVs identified in the RTS frame may send a clear to send (CTS) frame to the source DEV.
- CTS clear to send
- the source DEV and destination DEV(s) may communicate by sending frames via the wireless communication medium.
- Deafness is a phenomenon, which is observed at a transmitting DEV, in which a plurality of transmitting DEVs concurrently transmit signals via the wireless communication medium, wherein because of the directional nature of each transmitting signal, each transmitting DEV may not detect the signals being transmitted by the other transmitting DEVs.
- the CCA performed at each transmitting DEV may indicate that the wireless communication medium is available for signal transmission.
- Capture effect is a phenomenon, which is observed at a receiving DEV. Because the various transmitted signals may be received at the respective destination DEVs with differing signal-to-interference plus noise ratios (SINR), PDUs received via signals with higher SINR values may be successfully received at the corresponding destination DEV(s) while PDUs received via signals with lower SINR values may not be successfully received at the corresponding destination DEV(s).
- SINR signal-to-interference plus noise ratios
- FIG. 1 is diagram of an exemplary wireless communication system with directional transmission, which may be utilized in connection with an embodiment of the invention.
- FIG. 3 is a diagram illustrating exemplary signal transmission for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention.
- FIG. 4 is a diagram, which illustrates an exemplary direct data transfer sequence, in accordance with an embodiment of the invention.
- FIG. 5 is a diagram, which illustrates an exemplary control guided data transfer sequence, in accordance with an embodiment of the invention.
- FIG. 8 is a diagram, which illustrates an exemplary control guided data transfer sequence with block acknowledgment, in accordance with an embodiment of the invention.
- FIG. 9 is a diagram of an exemplary transceiver comprising a plurality of transmitting antennas and a plurality of receiving antennas, which may be utilized for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission, in accordance with an embodiment of the invention.
- CSMA/CA carrier sense multiple access with collision avoidance
- FIG. 11 is a flowchart that illustrates exemplary steps for collision backoff in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention.
- FIG. 12 is a flowchart that illustrates exemplary steps for control guided data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention.
- Certain embodiments of the invention may be found in a method and system for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission.
- Various embodiments of the invention comprise a method and system by which a communicating device (DEV) may transmit a portion of a protocol data unit (PDU) utilizing omnidirectionally transmitted signals and a subsequent portion of the PDU utilizing directionally transmitted signals.
- the communicating DEV may transmit a frame, which represents a physical layer PDU.
- the frame may comprise a PLCP preamble that is transmitted via omnidirectional signals (omni preamble), a PLCP header that is transmitted via omnidirectional signals (omni header), a PLCP preamble that is transmitted utilizing directionally transmitted signals (directional preamble) and a physical layer service data unit (PSDU) field, or data, field, which is transmitted utilizing directionally transmitted signals (directional data).
- omni preamble a PLCP preamble that is transmitted via omnidirectional signals
- omni header a PLCP header that is transmitted via omnidirectional signals
- directional preamble a PLCP preamble that is transmitted utilizing directionally transmitted signals
- PSDU physical layer service data unit
- the omni header field may comprise a network allocation vector (NAV) value.
- the NAV value may be utilized by recipient DEVs, which receive the transmitted frame, to determine a soonest time instant at which the recipient DEV may attempt to access the wireless communication medium.
- a communicating DEV may compute a NAV value based on a determined maximum data field length (MAX_PAYLOAD), a minimum data rate (MIN_DATA_RATE) and a maximum transmission opportunity time duration for the wireless communication medium (MAX_TXOP).
- Various embodiments of the invention may be practiced for direct data transfers (DDT), in which the transmitting DEV attempts to access the wireless communication medium by transmitting frames, or for control guided data transfers (CGDT), in which the transmission of frames is preceded by an RTS/CTS frame exchange.
- DDT direct data transfers
- CGDT control guided data transfers
- the transmitting DEV may transmit PDUs utilizing directional signal transmission.
- FIG. 1 is diagram of an exemplary wireless communication system with directional transmission, which may be utilized in connection with an embodiment of the invention.
- a plurality of communicating DEVs 112 , 114 , 122 and 124 and a plurality of RF coverage areas 152 and 154 there is shown a plurality of communicating DEVs 112 , 114 , 122 and 124 and a plurality of RF coverage areas 152 and 154 .
- the DEV 112 and the DEV 114 are engaged in a communication and the DEV 122 and the DEV 124 are engaged in a separate communication.
- the DEV 112 transmits directional signals within coverage area 152 and the DEV 122 transmits directional signals within coverage area 154 .
- Signals transmitted by the DEV 112 may be received by the DEV 114 and/or the DEV 124 .
- Signals transmitted by the DEV 122 may also be received by the DEV 114 and/or the DEV 124 .
- the DEV 112 is not located within the coverage area 154 and the DEV 122 is not located within the coverage area 152 . Consequently, the DEV 112 may not receive signals transmitted by the DEV 122 and the DEV 122 may not receive signals transmitted by DEV 112 .
- the DEV 112 may attempt to communicate with the DEV 114 while the DEV 122 is concurrently attempting to communicate with the DEV 124 .
- the DEV 114 and the DEV 124 may each concurrently receive signals transmitted by the DEV 112 and the DEV 122 .
- the concurrent reception of a plurality of transmitted signals is referred to as a collision.
- a signal level for signals received at the DEV 124 and transmitted from the DEV 122 may be higher than a signal level for signals received at the DEV 124 and transmitted from the DEV 112 .
- the signal to interference plus noise ratio (SINR) for signals transmitted by the DEV 122 is sufficiently high to enable the receiving DEV 124 to detect the data transmitted by DEV 122 (where DEV 124 is the destination DEV) via the received signals, the concurrent transmission of signals by the DEV 112 and the DEV 122 does not impair the ability of the DEV 122 and the DEV 124 to communicate via the wireless communication medium. Accordingly, there is no capture.
- SINR signal to interference plus noise ratio
- a signal level for signals received at the DEV 114 and transmitted from the DEV 122 may be higher than a signal level for signals received at the DEV 114 and transmitted from the DEV 112 .
- the concurrent transmission of signals by the DEV 112 and the DEV 122 may impair the ability of the DEV 122 and the DEV 124 to communicate via the wireless communication medium.
- the DEV 114 may receive data transmitted from a source DEV, DEV 122 , for which the destination DEV is DEV 124 . This illustrates an example of capture by the DEV 114 .
- deafness and capture may result in impairment of the ability of at least a portion of the DEVs to communicate via a wireless communication medium.
- FIG. 2 is a diagram of an exemplary frame for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention.
- a frame 200 comprises an omni-directional (omni) preamble field 202 , an omni header field 204 , a directional preamble field 206 , and a directional data field 208 .
- omni omni-directional
- FIG. 3 is a diagram illustrating exemplary signal transmission for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention.
- a plurality of communicating devices DEV 312 , DEV 314 , DEV 322 and DEV 324 an omnidirectional RF coverage area 352 and a directional RF coverage area 354 .
- the directional coverage area 354 may be characterized by a coverage angle ⁇ .
- the coverage area 354 and its position relative to coverage area 352 is presented in FIG. 3 for illustrative purposes and is not intended to limit the practice of various embodiments of the invention.
- the DEV 312 may be operable to transmit signals omnidirectionally within the coverage area 352 and may transmit signals directionally within the coverage area 354 .
- the DEV 314 , the DEV 322 and the DEV 324 are located within the coverage area 352 . Consequently, the DEV 314 , the DEV 322 and the DEV 324 may receive signals that are transmitted within the coverage area 352 .
- the DEV 314 is located within coverage area 354 . Consequently, the DEV 314 may receive signals transmitted within the coverage area 354 while the DEV 322 and the DEV 324 may not receive signals transmitted within the coverage area 354 .
- the DEV 312 may transmit a portion of frame 200 within the coverage area 352 and may transmit a subsequent portion of frame 200 within coverage area 354 .
- the DEV 312 may transmit the omni preamble field 202 and the omni header field 204 within coverage area 352 .
- the DEV 312 may transmit the directional preamble field 206 and the directional data field 208 within coverage area 354 .
- the DEV 314 , the DEV 322 and the DEV 324 may detect the transmitted preamble field 202 and/or header field 204 , thereby addressing the deafness phenomenon. Receipt of the preamble field 202 and/or header field 204 may enable the DEV 322 and the DEV 324 to detect that the DEV 312 is attempting to access the wireless communication medium. Accordingly, the DEV 322 and the DEV 324 may refrain from attempting to access the wireless communication medium in accordance with the CSMA/CA protocol. Consequently, the DEV 322 and/or the DEV 324 may not transmit signals via the wireless communication medium concurrently with signal transmissions from DEV 312 . This, in turn, reduces the likelihood of collisions, thereby addressing the capture phenomenon.
- the header field 204 may comprise a network allocation vector (NAV) value.
- the NAV value may be utilized by a recipient DEV to determine the next time instant at which that the recipient DEV may attempt to access the wireless communication medium.
- the DEV 322 may determine a NAV value based on a received omni header 204 , which was transmitted by the DEV 312 . Based on the determined NAV value, the DEV 322 may determine a time duration during which the DEV may refrain from attempting to access the wireless communication medium.
- a DEV 322 which attempts to access the wireless communication medium, may determine that a collision occurred during the access attempt.
- the DEV may compute a NAV value. Based on the computed NAV value, the DEV may refrain from attempting to make a subsequent attempt to access the wireless communication medium until the expiration of a time duration, which is based on the computed NAV value. This time duration is referred to as a backoff interframe spacing (BaIFS) interval.
- a BaIFS value may be computed as follows:
- BaIFS max ⁇ ( MAX_PAYLOAD MIN_DATA ⁇ _RATE , MAX_TXOP )
- MAX_PAYLOAD represents the maximum length (as measured in octets, for example) of a payload portion of a PDU
- MIN_DATA_RATE represents the minimum data rate (as measured in bits per second, for example) at which data may be transmitted via a wireless communication medium
- MAX_TXOP represents a maximum transmission opportunity (TXOP), or maximum time duration (as measured in seconds, for example) for which a DEV may reserve continuous access to the wireless communication medium for signal transmission.
- Values for MAX_PAYLOAD, MIN_DATA_RATE and/or MAX_TXOP may be specified, for example, in a standards document or other specifications document.
- FIG. 4 is a diagram, which illustrates an exemplary direct data transfer sequence, in accordance with an embodiment of the invention.
- a source DEV 312 FIG. 3
- a destination DEV 314 a plurality of other DEVs 322 and 324 .
- the source DEV 312 and the dest DEV 314 may be engaged in a communication.
- the source DEV 312 may transmit frames 200 as shown in FIG. 2 .
- Communications between DEVs may be based on direct data transfers (DDT).
- the transmitting DEV may commence transmission of a frame 200 comprising a data field 208 , via the wireless communication medium, without transmitting preceding frames, such as request to send (RTS) frames.
- DDT direct data transfers
- the source DEV 312 transmits an omni preamble field 402 using omnidirectional signal transmission. Signals transmitted by the DEV 312 using omnidirectional signal transmission may be transmitted within coverage area 352 .
- the transmitted omni preamble field 402 is received as preamble field 412 by the dest DEV 314 and as preamble field 422 by the DEV 322 and the DEV 324 .
- the source DEV 312 transmits an omni header field 404 using omnidirectional signal transmission.
- the transmitted omni header field 404 is received as header field 414 by the dest DEV 314 and as header field 424 by the DEV 322 and the DEV 324 .
- the transmitted header field 404 may comprise a NAV value.
- the other DEVs, DEV 322 and/or DEV 324 may utilize the received NAV value to determine a time during after which the wireless communication medium may become available for an access attempt. This time duration is indicated in FIG. 4 by the bracket labeled NAV.
- the source DEV 312 transmits a directional preamble field 406 using directional signal transmission. Signals transmitted by the DEV 312 using directional signal transmission may be transmitted within coverage area 354 .
- the transmitted directional preamble field 406 is received as preamble field 416 by the dest DEV 314 .
- the transmitted directional preamble field 406 may not be received by either the DEV 322 or the DEV 324 .
- the source DEV 312 transmits a directional data field 408 using directional signal transmission.
- the transmitted directional data field 408 is received as data field 418 by the dest DEV 314 .
- the dest DEV 314 may acknowledge successful receipt of a frame 200 from the source DEV 312 by transmitting an acknowledgment (ACK) frame.
- ACK acknowledgment
- the dest DEV 314 transmits an omni preamble field 432 using omnidirectional signal transmission.
- the minimum time duration is referred to as a short interframe spacing (SIFS) interval.
- SIFS interval is indicated in FIG. 4 as T SIFS .
- the transmitted omni preamble field 432 is received as preamble field 442 by source DEV 312 and as preamble field 452 by DEV 322 and DEV 324 .
- the dest DEV 314 transmits an omni header field 434 using omnidirectional signal transmission.
- the transmitted omni header field 434 is received as header field 444 by the source DEV 312 and as header field 454 by the DEV 322 and the DEV 324 .
- the dest DEV 314 transmits a directional ACK field 436 using directional signal transmission.
- the transmitted directional ACK field 436 is received as ACK field 446 by the source DEV 312 .
- the transmitted directional ACK field 436 may not be received by either the DEV 322 or the DEV 324 .
- FIG. 5 is a diagram, which illustrates an exemplary control guided data transfer sequence, in accordance with an embodiment of the invention.
- a source DEV 312 FIG. 3
- a destination DEV 314 a plurality of other DEVs 322 and 324 .
- the source DEV 312 and the dest DEV 314 may be engaged in a communication.
- the source DEV 312 may transmit frames 200 as shown in FIG. 2 .
- Communications between DEVs may be based on control guided data transfers (CGDT).
- CGDT control guided data transfers
- the transmitting DEV may transmit an RTS frame to a recipient DEV to request reservation of the wireless communication medium.
- the time duration for the reservation may be referred to as a TXOP time duration.
- the transmitting DEV may commence transmission of a frame 200 comprising a data field 208 , via the wireless communication medium, after receiving a response to the transmitted RTS frame from the recipient DEV, such as a clear to send (CTS) frame.
- CTS clear to send
- the source DEV 312 transmits an omni RTS frame 502 using omnidirectional signal transmission.
- the transmitted omni RTS frame 502 is received an RTS frame 522 by the dest DEV 314 and as RTS frame 542 by the DEV 322 and the DEV 324 .
- the dest DEV 322 transmits an omni CTS frame 524 using omnidirectional signal transmission.
- the transmitted omni CTS frame 524 is received as CTS frame 504 by dest DEV 314 and as CTS frame 544 by DEV 322 and DEV 324 .
- the transmitted RTS frame 502 may comprise a NAV value.
- the other DEVs, DEV 322 and/or DEV 324 may utilize the received NAV value to determine a time during after which the wireless communication medium may become available for an access attempt. This time duration is indicated in FIG. 5 by the bracket labeled NAV_ 1 .
- the transmitted CTS frame 524 may comprise a NAV value.
- the DEV 322 and/or the DEV 324 may utilize the NAV value received in a CTS frame to determine a time duration, which is indicated in FIG. 5 by the bracket labeled NAV_ 2 .
- the source DEV 312 transmits a directional preamble field 506 using directional signal transmission. Signals transmitted by the DEV 312 using directional signal transmission may be transmitted within coverage area 354 .
- the transmitted directional preamble field 506 is received as preamble field 526 by the dest DEV 314 .
- the transmitted directional preamble field 506 may not be received by either the DEV 322 or the DEV 324 .
- the source DEV 312 transmits a directional header field 408 using directional signal transmission.
- the transmitted directional header field 508 is received as header field 528 by the dest DEV 314 .
- the source DEV 312 transmits a directional data field 510 using directional signal transmission.
- the transmitted directional data field 510 is received as data field 530 by dest DEV 314 .
- the dest DEV 314 may acknowledge successful receipt of a frame 200 from the source DEV 312 by transmitting an ACK frame 532 .
- the transmitted directional ACK frame 532 is received as ACK frame 512 by the source DEV 312 .
- the transmitted directional ACK frame 532 may not be received by either the DEV 322 or the DEV 324 .
- one or more subsequent frames 200 may be transmitted by the source DEV 312 and/or by the dest DEV 322 , substantially as described above, during the current TXOP time duration.
- a transmitting DEV may transmit frames by utilizing any of a plurality of methods, or efficiency modes.
- the transmitting DEV may receive an ACK frame for each transmitted frame.
- the transmitting DEV which seeks to transmit a plurality of frames to a recipient DEV, may transmit a single frame 200 to the recipient DEV and wait to receive an ACK frame before transmitting a subsequent frame.
- FIG. 6 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and omnidirectional preamble transmission, in accordance with an embodiment of the invention.
- a sequence of transmitted frames and received frames from the perspective of a single transmitting DEV, such as the DEV 312 .
- the transmitting DEV may transmit a frame comprising an omni preamble field 602 using omnidirectional signal transmission, a directional preamble field 604 using directional signal transmission, and a directional data field 606 using directional signal transmission.
- the transmitting DEV may receive an ACK frame 612 in response to the previously transmitted frame.
- the transmitting DEV may transmit a subsequent frame comprising an omni preamble field 622 , a directional preamble field 624 and a directional data field 626 .
- the transmitting DEV may receive a subsequent ACK frame 632 in response to the subsequent transmitted frame. Succeeding frames may be transmitted and acknowledged as described above.
- the transmitting DEV may receive an ACK frame for each transmitted frame.
- the transmitting DEV may transmit a frame comprising an omni preamble field using omnidirectional signal transmission for the first frame transmitted during a TXOP interval, while subsequent frames, which are transmitted by the transmitting DEV during the TXOP interval, may be transmitted without an omni preamble field.
- FIG. 7 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and without omnidirectional preamble transmission, in accordance with an embodiment of the invention.
- a sequence of transmitted frames and received frames from the perspective of a single transmitting DEV, such as DEV 312 .
- the transmitting DEV may transmit a frame comprising an omni preamble field 702 using omnidirectional signal transmission, a directional preamble field 704 using directional signal transmission, and a directional data field 706 using directional signal transmission.
- the transmitting DEV may receive an ACK frame 712 in response to the previously transmitted frame.
- the transmitting DEV may transmit a subsequent frame comprising a directional preamble field 724 and a directional data field 726 .
- the transmitting DEV may receive a subsequent ACK frame 732 in response to the subsequent transmitted frame. Succeeding frames transmitted by the transmitting DEV during a current TXOP interval may be transmitted without an omni preamble field and acknowledged as described above.
- the transmitting DEV may receive a single ACK frame after transmission of a plurality of frames.
- the single ACK frame which acknowledges receipt by the recipient DEV of a plurality of frames, is referred to as a block acknowledgment (block ACK).
- FIG. 8 is a diagram, which illustrates an exemplary control guided data transfer sequence with block acknowledgment, in accordance with an embodiment of the invention.
- the transmitting DEV may transmit a frame comprising an omni preamble field 802 using omnidirectional signal transmission, a directional preamble field 804 using directional signal transmission, and a directional data field 806 using directional signal transmission.
- the transmitting DEV may transmit a succeeding frame comprising a directional preamble field 814 and a directional data field 816 .
- the transmitting DEV may transmit a subsequent frame comprising a directional preamble field 824 and a directional data field 826 .
- the transmitting DEV may receive a subsequent ACK frame 842 in response to the plurality of transmitted frames.
- Succeeding frames transmitted by the transmitting DEV during a current TXOP interval may be transmitted without an omni preamble field and acknowledged, either by single ACK frames and/or by block ACK frames, as described above.
- FIG. 9 is a diagram of an exemplary transceiver comprising a plurality of transmitting antennas and a plurality of receiving antennas, which may be utilized for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission, in accordance with an embodiment of the invention.
- CSMA/CA carrier sense multiple access with collision avoidance
- FIG. 9 there is shown a transceiver system 900 , a plurality of receiving antennas 922 a, . . . , 922 n and a plurality of transmitting antennas 932 a, . . . , 932 n.
- the transceiver system 900 may be exemplary of any of the DEVs 312 , 314 , 322 , and/or 324 .
- the transceiver system 900 may comprise at least a receiver 902 , a transmitter 904 , a processor 906 , and a memory 908 . Although a transceiver is shown in FIG. 9 , transmit and receive functions may be separately implemented.
- the receiver 902 may perform receiver functions that may comprise, but are not limited to, the amplification of received RF signals, generation of frequency carrier signals corresponding to selected RF channels, for example uplink channels, the down-conversion of the amplified RF signals by the generated frequency carrier signals, demodulation of data contained in data symbols based on application of a selected demodulation type, and detection of data contained in the demodulated signals.
- the RF signals may be received via one or more receiving antennas 922 a, . . . , 922 n.
- the data may be communicated to the processor 906 .
- the transmitter 904 may perform transmitter functions that may comprise, but are not limited to, modulation of received data to generated data symbols based on application of a selected modulation type, generation of frequency carrier signals corresponding to selected RF channels, for example downlink channels, the up-conversion of the data symbols by the generated frequency carrier signals, and the generation and amplification of RF signals.
- the data may be received from the processor 906 .
- the RF signals may be transmitted via one or more transmitting antennas 932 a, . . . , 932 n.
- one or more of the receiving antennas 922 a . . . 922 n may be operable for directional and/or omnidirectional reception of signals.
- One or more of the transmitting antennas 932 a, . . . , 932 n may be operable for directional and/or omnidirectional transmission of signals.
- the memory 908 may comprise suitable logic, circuitry, interfaces and/or code that may enable storage and/or retrieval of data and/or code.
- the memory 908 may utilize any of a plurality of storage medium technologies, such as volatile memory, for example random access memory (RAM), and/or non-volatile memory, for example electrically erasable programmable read only memory (EEPROM).
- RAM random access memory
- EEPROM electrically erasable programmable read only memory
- the memory 908 may enable storage of code for the determining when to transmit frame fields using omnidirectional signal transmission and when to transmit frame fields using directional signal transmission, for example.
- the memory may also enable the storage of received NAV values and/or computed BaIFS values.
- the memory 908 may enable storage of training sequences utilized in preamble fields.
- the processor 906 may configure a transmitter 904 for transmission of omnidirectional signals and/or directional signals, for example.
- the configuration of the transmitter 904 may enable the transmitter 904 to select transmitting antennas, among the plurality of transmitting antennas 932 a, . . . , 932 n, to enable omnidirectional signal transmission and/or to enable directional signal transmission in a determined direction and/or with a determined coverage angle ⁇ .
- the processor 906 may enable determination of when to utilize DDT communication and/or CGDT communication, for example.
- the processor 906 may enable determination of when a transmitting DEV is to utilize single ACK frame transmission and/or when to utilize block ACK frame transmission.
- the processor 906 may also enable the transmission and processing of RTS frames, CTS frames, training sequences, data frames comprising NAV values and/or the transmission and processing of other PDUs transmitted by the transceiver 300 .
- the processor 906 may enable selection of transmitting antennas 932 a, . . . , 932 n and/or receiving antennas 922 a, . . . , 922 n for directional (or sectorized) signal transmission and/or reception.
- the processor 906 may configure the transmitter 904 to concurrently transmit omnidirectional signals and directional signals.
- a transceiver system 900 which utilizes orthogonal frequency division multiplexing (OFDM)
- the processor 906 may configure the transmitter to select frequency carriers within an OFDM RF channel bandwidth that are to be utilized for omnidirectional signal transmission. Remaining frequency carriers within the OFDM RF channel bandwidth may be utilized for directional signal transmission.
- the processor 906 may compute channel estimates, which characterize the wireless communication medium. The computed channel estimates may be utilized to determine a coherence bandwidth for the wireless communication medium.
- the processor 906 may select individual frequency carriers within the OFDM RF channel bandwidth wherein the frequency difference between each such selected frequency carrier is greater than the computed coherence bandwidth. These selected frequency carriers may be utilized for omnidirectional signal transmission while the remaining frequency carriers are utilized for directional signal transmission.
- the processor 906 may configure the transmitter 904 to select one or more transmitting antennas, among the plurality of transmitting antennas 932 a, . . . , 932 n, for transmission of omnidirectional signals while a subsequent one or more transmitting antennas, selected among the plurality of transmitting antennas 932 a, . . . , 932 n, may be utilized for directional signal transmission.
- the processor 906 may configure the transmitter 904 to transmit omnidirectional signals via the selected frequency carriers, while the transmitter 904 is transmitting a data field 208 using directional signal transmission via at least a portion of the remaining frequency carriers.
- FIG. 10 is a flowchart that illustrates exemplary steps for direct data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention.
- a processor 906 which is utilized in connection with a transmitting DEV 312 , may determine a network allocation value (NAV).
- the processor 906 may determine the NAV value based on a determined value, or based on signals received from other DEVs via receiving antenna(s) 922 a, . . . , 922 n and the receiver 902 .
- Examples of other DEVs, as shown in FIG. 3 comprise the DEV 314 , the DEV 322 and/or the DEV 324 .
- the processor 906 may send data comprising the determined NAV value to the transmitter 904 .
- the processor 906 may configure the transmitter 904 to transmit an omni preamble field 202 and/or an omni header field 204 using omnidirectional signal transmission.
- the transmitted omni header field 204 may comprise the determined NAV value.
- the transmitter 904 may select one or more transmitting antennas, among the plurality of transmitting antennas 932 a, . . . , 932 n, for the omnidirectional signal transmission.
- step 1006 prior to the commencement of directional signal transmission to a receiving DEV 314 , the processor 906 , which is utilized in connection with the transmitting DEV 312 , may determine the location of the receiving DEV 314 .
- the processor utilized in connection with the transmitting DEV 312 , may determine the location of the receiving DEV 314 based on a neighborhood map (step 1005 ).
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may generate the neighborhood map based on communications with the DEVs, DEV 314 , DEV 322 and/or DEV 324 .
- the generated neighborhood map may be stored in memory 908 , which is utilized in connection with the transmitting DEV 312 .
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may configure the transmitter 904 to transmit a directional preamble field 206 and/or directional data field 208 using directional signals, which may be transmitted in the direction of the receiving DEV 314 .
- the transmitter 904 may utilize one or more transmitting antennas 932 a, . . . , 932 n, to transmit signals within coverage area 354 .
- the receiver 902 may receive an ACK frame, from the receiving DEV 314 , via one or more receiving antennas 922 a, . . . , 922 n.
- the receiver 902 may communicate the received ACK frame to the processor 906 , which is utilized in connection with the transmitting DEV 312 .
- step 1012 the processor 906 , which is utilized in connection with the transmitting DEV 312 , may determine whether there is additional data to transmit to the receiving DEV 314 . In instances where there is additional data to transmit, step 1004 may follow step 1012 .
- FIG. 11 is a flowchart that illustrates exemplary steps for collision backoff in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention.
- a transmitting DEV 324 may transmit a protocol data unit (PDU) to a receiving DEV 322 .
- the PDU comprises a frame 200 .
- the processor 906 which is utilized in connection with the transmitting DEV 324 , may determine whether an ACK frame has been received from the receiving DEV 322 . In instances where an ACK frame has been received, step 1012 ( FIG. 10 ) may follow step 1104 .
- the processor 906 utilized in connection with the transmitting DEV 324 , may determine that a collision has occurred during transmission of the frame 200 .
- the processor 906 which is utilized in connection with the transmitting DEV 324 , may compute a BaIFS value, as shown in equation [1] above, based on determined values MAX_PAYLOAD, MAX_DATA_RATE and/or MAX_TXOP (step 1105 ).
- the processor 906 which is utilized in connection with the transmitting DEV 324 , may configure the transmitter 902 to refrain from transmitting signals until the expiration of a time duration, which is determined based on the computed BaIFS value.
- a NAV value may be determined based on the computed BaIFS value.
- the processor 906 which is utilized in connection with the transmitting DEV 324 , may determine whether the NAV-determined time duration has expired. In instances where the NAV-determined time duration has not expired, the transmitter 902 may continue to refrain from transmitting signals from the transmitting DEV 324 . In instances where the NAV-determined time duration has expired, the processor 906 , which is utilized in connection with the transmitting Dev 324 , may configure the transmitter 904 to transmit signals. Step 1102 may follow step 1108 .
- FIG. 12 is a flowchart that illustrates exemplary steps for control guided data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention.
- a processor 906 which is utilized in connection with a transmitting DEV 312 , may configure a transmitter 904 to transmit an RTS frame, using omnidirectional signal transmission, to a receiving DEV 314 .
- the transmitted RTS frame may comprise a NAV value and/or a requested TXOP interval time duration.
- the processor 906 may determine whether a CTS frame has been received from the receiving DEV 314 .
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may receive a CTS frame from the receiving DEV 314 based on signals received via receiving antenna(s) 922 a, . . . , 922 n and the receiver 902 .
- a received CTS frame may comprise an indicated TXOP interval time duration.
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may configure the transmitter 904 to transmit a directional preamble field 206 and/or directional data field 208 using directional signals, which may be transmitted in the direction of the receiving DEV 314 .
- the transmitter 906 which is utilized in connection with the transmitting DEV 312 , may determine the location of the receiving DEV 314 based on the received CTS frame.
- the transmitter 904 may utilize one or more transmitting antennas 932 a, . . . , 932 n, to transmit signals within coverage area 354 .
- additional frames may be transmitted at step 1206 .
- the receiver 902 may receive an ACK frame, from the receiving DEV 314 , via one or more receiving antennas 922 a, . . . , 922 n.
- the receiver 902 may communicate the received ACK frame to the processor 906 , which is utilized in connection with the transmitting DEV 312 .
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may determine whether the current TXOP interval has expired.
- step 1214 the processor 906 , which is utilized in connection with the transmitting DEV 312 , may determine whether there is additional data to transmit to the receiving DEV 314 . In instances where there is additional data to transmit, step 1206 may follow step 1214 .
- the processor 906 may determine that a collision has occurred.
- the processor which is utilized in connection with the transmitting DEV 312 , may configure the transmitter 904 to refrain from attempting to transmit signals until a NAV-based time duration has expired.
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may determine whether a frame has been received, which comprises a NAV value.
- the processor 906 may compute a BaIFS value, for example as shown in equation [1].
- a NAV value may be determined based on the computed BaIFS value.
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may set a NAV value based on the NAV value contained in the received frame.
- the processor 906 which is utilized in connection with the transmitting DEV 312 , may determine whether the NAV-based time duration has expired. In instances where the NAV-based time duration has not expired, the transmitter 904 , which is utilized in connection with the transmitting DEV 312 , may continue to refrain from transmitting signals. In instances where the NAV-based time duration has expired, step 1202 may follow step 1222 .
- Another embodiment of the invention may provide a machine and/or computer readable medium, having stored thereon, a computer program having at least one code section executable by a machine and/or computer, thereby causing the machine and/or computer to perform the steps as described herein for CSMA/CA with directional transmission.
- the present invention may be realized in hardware, software, or a combination of hardware and software.
- the present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited.
- a typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein.
- the present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods.
- Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.
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Abstract
Description
- This application is a continuation of U.S. application Ser. No. 12/423,589 filed Apr. 14, 2009 which makes reference to, claims priority to, and claims the benefit of U.S. Provisional Application Ser. No. 61/045,276 filed Apr. 15, 2008, the entire contents of both of which are incorporated herein by reference.
- This Application makes reference to:
- U.S. patent application Ser. No. 12/401,222 filed Mar. 10, 2009; and
- U.S. patent application Ser. No. 12/397,435 filed on Mar. 4, 2009.
- Each of the above stated applications is hereby incorporated herein by reference in its entirety.
- Certain embodiments of the invention relate to data communication. More specifically, certain embodiments of the invention relate to a method and system for CSMA/CA with directional transmission.
- IEEE 802.15 describes a communication architecture, which may enable communicating devices (DEVs) to communicate via wireless personal area networks (WPANs). Many DEVs utilized in WPANs are small or handheld devices, such as personal digital assistants, portable computers, or consumer electronics devices such as digital video recorders or set top boxes. IEEE 802.15 is a short-range wireless communications standard that enables connection between consumer and computer equipment while eliminating wires. IEEE 802.15 WPAN DEVs may utilize frequencies in the 57 GHz to 66 GHz range for communication.
- A plurality of communicating DEVs in a WPAN environment may comprise a network known as a piconet. One of the DEVs in a piconet may function as a piconet coordinator (or controller), or PNC. The PNC may provide overall coordination for the communication between DEVs in a piconet. The piconet may comprise the PNC and DEVs, which are associated with the PNC.
- The DEVs may communicate through the transmission and/or reception of protocol data units (PDU) referred to as frames. A frame may correspond to a PDU that is associated with a physical (PHY) layer protocol in a protocol reference model (PRM). The frame may comprise a physical layer convergence procedure (PLCP) preamble field, a PLCP header field and a physical layer service data unit (PSDU) field. The PLCP preamble field is utilized by a receiver of the PDU to detect a potentially receivable signal and to establish frequency and/or timing synchronization with the received PDU. The PLCP header field is utilized by a receiver of the PDU to determine the length of the PSDU field, typically measured in octets, and to determine a data rate for data contained within the PSDU field. The PSDU field may be referred to as a payload field. The payload field may comprise data that are being communicated from a source DEV to a destination DEV.
- Radio frequency (RF) communications between communicating devices via the wireless communication medium within the 60 GHz frequency range are typically directional in nature. Thus transmitting DEVs may transmit RF signal energy from a given antenna in a given direction while not transmitting RF signal energy in other directions from the given antenna. Thus, given two potential recipient DEVs located at, for example, equal distances in opposite physical directions relative to a transmitting DEV, a potential recipient DEV which is in the direction of RF signal energy transmission may receive signals from the transmitting DEV while the other potential recipient DEV may not.
- Prior to attempting to transmit signals via the wireless communication medium, a communicating DEV, which utilize the CSMA/CA protocol, typically attempts to determine whether there are any DEVs that are transmitting signals via the wireless communication medium. This determination is referred to as a clear channel assessment (CCA). When the CCA indicates that there are no other DEVs, which are transmitting signals, the communicating DEV may determine that the wireless communication medium is available for transmission of signals. The communicating DEV may attempt to reserve the wireless communication medium for signal transmission for a given time duration by transmitting a request to send (RTS) frame. The RTS frame may identify the communicating DEV as a source DEV and may also identify one or more destination DEVs. In response, one or more destination DEVs identified in the RTS frame may send a clear to send (CTS) frame to the source DEV. After completing the RTS/CTS frame exchange, the source DEV and destination DEV(s) may communicate by sending frames via the wireless communication medium.
- Because of the directional nature of 60 GHz signal transmission, the effectiveness of CSMA/CA protocol in achieving collision avoidance may be impaired due to capture effect and/or deafness. Deafness is a phenomenon, which is observed at a transmitting DEV, in which a plurality of transmitting DEVs concurrently transmit signals via the wireless communication medium, wherein because of the directional nature of each transmitting signal, each transmitting DEV may not detect the signals being transmitted by the other transmitting DEVs. In other words, because of the inability to detect the energy from signals transmitted by other transmitting DEVs, the CCA performed at each transmitting DEV may indicate that the wireless communication medium is available for signal transmission.
- Capture effect is a phenomenon, which is observed at a receiving DEV. Because the various transmitted signals may be received at the respective destination DEVs with differing signal-to-interference plus noise ratios (SINR), PDUs received via signals with higher SINR values may be successfully received at the corresponding destination DEV(s) while PDUs received via signals with lower SINR values may not be successfully received at the corresponding destination DEV(s).
- Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.
- A method and system for CSMA/CA with directional transmission, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
- These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
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FIG. 1 is diagram of an exemplary wireless communication system with directional transmission, which may be utilized in connection with an embodiment of the invention. -
FIG. 2 is a diagram of an exemplary frame for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention. -
FIG. 3 is a diagram illustrating exemplary signal transmission for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention. -
FIG. 4 is a diagram, which illustrates an exemplary direct data transfer sequence, in accordance with an embodiment of the invention. -
FIG. 5 is a diagram, which illustrates an exemplary control guided data transfer sequence, in accordance with an embodiment of the invention. -
FIG. 6 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and omnidirectional preamble transmission, in accordance with an embodiment of the invention. -
FIG. 7 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and without omnidirectional preamble transmission, in accordance with an embodiment of the invention. -
FIG. 8 is a diagram, which illustrates an exemplary control guided data transfer sequence with block acknowledgment, in accordance with an embodiment of the invention. -
FIG. 9 is a diagram of an exemplary transceiver comprising a plurality of transmitting antennas and a plurality of receiving antennas, which may be utilized for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission, in accordance with an embodiment of the invention. -
FIG. 10 is a flowchart that illustrates exemplary steps for direct data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. -
FIG. 11 is a flowchart that illustrates exemplary steps for collision backoff in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. -
FIG. 12 is a flowchart that illustrates exemplary steps for control guided data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. - Certain embodiments of the invention may be found in a method and system for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission. Various embodiments of the invention comprise a method and system by which a communicating device (DEV) may transmit a portion of a protocol data unit (PDU) utilizing omnidirectionally transmitted signals and a subsequent portion of the PDU utilizing directionally transmitted signals. In an exemplary embodiment of the invention, the communicating DEV may transmit a frame, which represents a physical layer PDU. The frame may comprise a PLCP preamble that is transmitted via omnidirectional signals (omni preamble), a PLCP header that is transmitted via omnidirectional signals (omni header), a PLCP preamble that is transmitted utilizing directionally transmitted signals (directional preamble) and a physical layer service data unit (PSDU) field, or data, field, which is transmitted utilizing directionally transmitted signals (directional data).
- The omni header field may comprise a network allocation vector (NAV) value. The NAV value may be utilized by recipient DEVs, which receive the transmitted frame, to determine a soonest time instant at which the recipient DEV may attempt to access the wireless communication medium. In another aspect, a communicating DEV may compute a NAV value based on a determined maximum data field length (MAX_PAYLOAD), a minimum data rate (MIN_DATA_RATE) and a maximum transmission opportunity time duration for the wireless communication medium (MAX_TXOP).
- Various embodiments of the invention may be practiced for direct data transfers (DDT), in which the transmitting DEV attempts to access the wireless communication medium by transmitting frames, or for control guided data transfers (CGDT), in which the transmission of frames is preceded by an RTS/CTS frame exchange. In the CGDT case, the transmitting DEV may transmit PDUs utilizing directional signal transmission.
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FIG. 1 is diagram of an exemplary wireless communication system with directional transmission, which may be utilized in connection with an embodiment of the invention. Referring toFIG. 1 , there is shown a plurality of communicatingDEVs RF coverage areas FIG. 1 , theDEV 112 and theDEV 114 are engaged in a communication and theDEV 122 and theDEV 124 are engaged in a separate communication. As shown inFIG. 1 , theDEV 112 transmits directional signals withincoverage area 152 and theDEV 122 transmits directional signals withincoverage area 154. Signals transmitted by theDEV 112 may be received by theDEV 114 and/or theDEV 124. Signals transmitted by theDEV 122 may also be received by theDEV 114 and/or theDEV 124. As shown inFIG. 1 , theDEV 112 is not located within thecoverage area 154 and theDEV 122 is not located within thecoverage area 152. Consequently, theDEV 112 may not receive signals transmitted by theDEV 122 and theDEV 122 may not receive signals transmitted byDEV 112. - The CSMA/CA protocol may not be operable to prevent concurrent signal transmission by the
DEV 112 and theDEV 122 because signals transmitted by theDEV 112 may not be detected by theDEV 122 and signals transmitted by theDEV 122 may not be detected by theDEV 112. This is an example of deafness. - Due to the deafness phenomenon, there is a possibility that the
DEV 112 may attempt to communicate with theDEV 114 while theDEV 122 is concurrently attempting to communicate with theDEV 124. Thus, theDEV 114 and theDEV 124 may each concurrently receive signals transmitted by theDEV 112 and theDEV 122. The concurrent reception of a plurality of transmitted signals is referred to as a collision. In an exemplary signal transmission, a signal level for signals received at theDEV 124 and transmitted from theDEV 122 may be higher than a signal level for signals received at theDEV 124 and transmitted from theDEV 112. In instances where the signal to interference plus noise ratio (SINR) for signals transmitted by theDEV 122 is sufficiently high to enable the receivingDEV 124 to detect the data transmitted by DEV 122 (whereDEV 124 is the destination DEV) via the received signals, the concurrent transmission of signals by theDEV 112 and theDEV 122 does not impair the ability of theDEV 122 and theDEV 124 to communicate via the wireless communication medium. Accordingly, there is no capture. - In an exemplary signal transmission, a signal level for signals received at the
DEV 114 and transmitted from theDEV 122 may be higher than a signal level for signals received at theDEV 114 and transmitted from theDEV 112. In this case, the concurrent transmission of signals by theDEV 112 and theDEV 122 may impair the ability of theDEV 122 and theDEV 124 to communicate via the wireless communication medium. In instances where the SINR for signals transmitted by theDEV 122 is sufficiently high to enable the receivingDEV 114 to detect the data transmitted by the DEV 122 (where theDEV 124 is the destination DEV) via the received signals, theDEV 114 may receive data transmitted from a source DEV,DEV 122, for which the destination DEV isDEV 124. This illustrates an example of capture by theDEV 114. - As described above in connection with the exemplary
FIG. 1 , deafness and capture may result in impairment of the ability of at least a portion of the DEVs to communicate via a wireless communication medium. -
FIG. 2 is a diagram of an exemplary frame for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention. Referring toFIG. 2 , there is shown aframe 200. Theframe 200 comprises an omni-directional (omni)preamble field 202, anomni header field 204, adirectional preamble field 206, and adirectional data field 208. - In an exemplary embodiment of the invention, the
frame 200 corresponds to a physical layer PDU. Theomni preamble field 202 comprises a frame preamble field, which is transmitted by a transmitting DEV, for example theDEV 122, using omni-directional signal transmission. Theomni header field 204 comprises a frame header field, which is transmitted by a transmitting DEV using omni-directional signal transmission. Thedirectional preamble field 206 comprises a frame preamble field, which is transmitted by a transmitting DEV using directional signal transmission. In various embodiments of the invention, the contents of the omni preamble field 202 (as represented by a plurality of binary values, for example) may be identical to the contents of thedirectional preamble field 206, but various embodiments of the invention are not so limited. Thedirectional data field 208 comprises a data field, which is transmitted by a transmitting DEV using directional signal transmission. Thedata field 208 may correspond to a payload, or service data unit (SDU), portion of theframe 200. In various embodiments of the invention, thedirectional data field 208 comprises data which are being communicated from a source DEV, for example theDEV 122, to a destination DEV, forexample DEV 124, via a wireless communication medium. -
FIG. 3 is a diagram illustrating exemplary signal transmission for CSMA/CA with directional signal transmission, in accordance with an embodiment of the invention. Referring toFIG. 3 , there is shown a plurality of communicatingdevices DEV 312,DEV 314,DEV 322 andDEV 324, an omnidirectionalRF coverage area 352 and a directionalRF coverage area 354. Thedirectional coverage area 354 may be characterized by a coverage angle θ. Thecoverage area 354 and its position relative tocoverage area 352 is presented inFIG. 3 for illustrative purposes and is not intended to limit the practice of various embodiments of the invention. - The
DEV 312 may be operable to transmit signals omnidirectionally within thecoverage area 352 and may transmit signals directionally within thecoverage area 354. As shown inFIG. 3 , theDEV 314, theDEV 322 and theDEV 324 are located within thecoverage area 352. Consequently, theDEV 314, theDEV 322 and theDEV 324 may receive signals that are transmitted within thecoverage area 352. As shown inFIG. 3 , theDEV 314 is located withincoverage area 354. Consequently, theDEV 314 may receive signals transmitted within thecoverage area 354 while theDEV 322 and theDEV 324 may not receive signals transmitted within thecoverage area 354. - In various embodiments of the invention, the
DEV 312 may transmit a portion offrame 200 within thecoverage area 352 and may transmit a subsequent portion offrame 200 withincoverage area 354. For example, theDEV 312 may transmit theomni preamble field 202 and theomni header field 204 withincoverage area 352. TheDEV 312 may transmit thedirectional preamble field 206 and thedirectional data field 208 withincoverage area 354. - By transmitting the
omni preamble field 202 and theomni header field 204 withincoverage area 352, theDEV 314, theDEV 322 and theDEV 324 may detect the transmittedpreamble field 202 and/orheader field 204, thereby addressing the deafness phenomenon. Receipt of thepreamble field 202 and/orheader field 204 may enable theDEV 322 and theDEV 324 to detect that theDEV 312 is attempting to access the wireless communication medium. Accordingly, theDEV 322 and theDEV 324 may refrain from attempting to access the wireless communication medium in accordance with the CSMA/CA protocol. Consequently, theDEV 322 and/or theDEV 324 may not transmit signals via the wireless communication medium concurrently with signal transmissions fromDEV 312. This, in turn, reduces the likelihood of collisions, thereby addressing the capture phenomenon. - In various embodiments of the invention, the
header field 204 may comprise a network allocation vector (NAV) value. The NAV value may be utilized by a recipient DEV to determine the next time instant at which that the recipient DEV may attempt to access the wireless communication medium. For example, theDEV 322 may determine a NAV value based on a receivedomni header 204, which was transmitted by theDEV 312. Based on the determined NAV value, theDEV 322 may determine a time duration during which the DEV may refrain from attempting to access the wireless communication medium. - A
DEV 322, which attempts to access the wireless communication medium, may determine that a collision occurred during the access attempt. In various embodiments of the invention, upon determining that a collision may have occurred, the DEV may compute a NAV value. Based on the computed NAV value, the DEV may refrain from attempting to make a subsequent attempt to access the wireless communication medium until the expiration of a time duration, which is based on the computed NAV value. This time duration is referred to as a backoff interframe spacing (BaIFS) interval. In various embodiments of the invention, a BaIFS value may be computed as follows: -
- where MAX_PAYLOAD represents the maximum length (as measured in octets, for example) of a payload portion of a PDU, MIN_DATA_RATE represents the minimum data rate (as measured in bits per second, for example) at which data may be transmitted via a wireless communication medium, and MAX_TXOP represents a maximum transmission opportunity (TXOP), or maximum time duration (as measured in seconds, for example) for which a DEV may reserve continuous access to the wireless communication medium for signal transmission. Values for MAX_PAYLOAD, MIN_DATA_RATE and/or MAX_TXOP may be specified, for example, in a standards document or other specifications document.
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FIG. 4 is a diagram, which illustrates an exemplary direct data transfer sequence, in accordance with an embodiment of the invention. Referring toFIG. 4 , there is shown a source DEV 312 (FIG. 3 ), a destination (dest)DEV 314 and a plurality ofother DEVs source DEV 312 and thedest DEV 314 may be engaged in a communication. Thesource DEV 312 may transmitframes 200 as shown inFIG. 2 . Communications between DEVs may be based on direct data transfers (DDT). In a DDT communication, the transmitting DEV may commence transmission of aframe 200 comprising adata field 208, via the wireless communication medium, without transmitting preceding frames, such as request to send (RTS) frames. - As shown in the exemplary
FIG. 4 , thesource DEV 312 transmits anomni preamble field 402 using omnidirectional signal transmission. Signals transmitted by theDEV 312 using omnidirectional signal transmission may be transmitted withincoverage area 352. The transmittedomni preamble field 402 is received aspreamble field 412 by thedest DEV 314 and aspreamble field 422 by theDEV 322 and theDEV 324. Thesource DEV 312 transmits anomni header field 404 using omnidirectional signal transmission. The transmittedomni header field 404 is received asheader field 414 by thedest DEV 314 and asheader field 424 by theDEV 322 and theDEV 324. - In various embodiments of the invention, the transmitted
header field 404 may comprise a NAV value. The other DEVs,DEV 322 and/orDEV 324, may utilize the received NAV value to determine a time during after which the wireless communication medium may become available for an access attempt. This time duration is indicated inFIG. 4 by the bracket labeled NAV. - The
source DEV 312 transmits adirectional preamble field 406 using directional signal transmission. Signals transmitted by theDEV 312 using directional signal transmission may be transmitted withincoverage area 354. The transmitteddirectional preamble field 406 is received aspreamble field 416 by thedest DEV 314. The transmitteddirectional preamble field 406 may not be received by either theDEV 322 or theDEV 324. Thesource DEV 312 transmits adirectional data field 408 using directional signal transmission. The transmitteddirectional data field 408 is received asdata field 418 by thedest DEV 314. - The
dest DEV 314 may acknowledge successful receipt of aframe 200 from thesource DEV 312 by transmitting an acknowledgment (ACK) frame. As shown inFIG. 4 , thedest DEV 314 transmits anomni preamble field 432 using omnidirectional signal transmission. There may be a minimum time duration between the receipt of thedata field 418 and the transmission of thepreamble field 422. In an exemplary embodiment of the invention, the minimum time duration is referred to as a short interframe spacing (SIFS) interval. The SIFS interval is indicated inFIG. 4 as TSIFS. The transmittedomni preamble field 432 is received aspreamble field 442 bysource DEV 312 and aspreamble field 452 byDEV 322 andDEV 324. Thedest DEV 314 transmits anomni header field 434 using omnidirectional signal transmission. The transmittedomni header field 434 is received asheader field 444 by thesource DEV 312 and asheader field 454 by theDEV 322 and theDEV 324. - The
dest DEV 314 transmits adirectional ACK field 436 using directional signal transmission. The transmitteddirectional ACK field 436 is received asACK field 446 by thesource DEV 312. The transmitteddirectional ACK field 436 may not be received by either theDEV 322 or theDEV 324. -
FIG. 5 is a diagram, which illustrates an exemplary control guided data transfer sequence, in accordance with an embodiment of the invention. Referring toFIG. 5 , there is shown a source DEV 312 (FIG. 3 ), a destination (dest)DEV 314 and a plurality ofother DEVs source DEV 312 and thedest DEV 314 may be engaged in a communication. Thesource DEV 312 may transmitframes 200 as shown inFIG. 2 . Communications between DEVs may be based on control guided data transfers (CGDT). In a CGDT communication, the transmitting DEV may transmit an RTS frame to a recipient DEV to request reservation of the wireless communication medium. The time duration for the reservation may be referred to as a TXOP time duration. The transmitting DEV may commence transmission of aframe 200 comprising adata field 208, via the wireless communication medium, after receiving a response to the transmitted RTS frame from the recipient DEV, such as a clear to send (CTS) frame. - As shown in the exemplary
FIG. 5 , thesource DEV 312 transmits anomni RTS frame 502 using omnidirectional signal transmission. The transmittedomni RTS frame 502 is received anRTS frame 522 by thedest DEV 314 and asRTS frame 542 by theDEV 322 and theDEV 324. Following at least a SIFS interval, subsequent to the receipt ofRTS frame 522, thedest DEV 322 transmits anomni CTS frame 524 using omnidirectional signal transmission. The transmittedomni CTS frame 524 is received asCTS frame 504 bydest DEV 314 and asCTS frame 544 byDEV 322 andDEV 324. - In various embodiments of the invention, the transmitted
RTS frame 502 may comprise a NAV value. The other DEVs,DEV 322 and/orDEV 324, may utilize the received NAV value to determine a time during after which the wireless communication medium may become available for an access attempt. This time duration is indicated inFIG. 5 by the bracket labeled NAV_1. In various embodiments of the invention, the transmittedCTS frame 524 may comprise a NAV value. TheDEV 322 and/or theDEV 324 may utilize the NAV value received in a CTS frame to determine a time duration, which is indicated inFIG. 5 by the bracket labeled NAV_2. - Following at least a SIFS interval, the
source DEV 312 transmits adirectional preamble field 506 using directional signal transmission. Signals transmitted by theDEV 312 using directional signal transmission may be transmitted withincoverage area 354. The transmitteddirectional preamble field 506 is received aspreamble field 526 by thedest DEV 314. The transmitteddirectional preamble field 506 may not be received by either theDEV 322 or theDEV 324. Thesource DEV 312 transmits adirectional header field 408 using directional signal transmission. The transmitteddirectional header field 508 is received asheader field 528 by thedest DEV 314. Thesource DEV 312 transmits adirectional data field 510 using directional signal transmission. The transmitteddirectional data field 510 is received asdata field 530 bydest DEV 314. - Following at least a SIFS interval, the
dest DEV 314 may acknowledge successful receipt of aframe 200 from thesource DEV 312 by transmitting anACK frame 532. The transmitteddirectional ACK frame 532 is received asACK frame 512 by thesource DEV 312. The transmitteddirectional ACK frame 532 may not be received by either theDEV 322 or theDEV 324. - Following the receipt of the
ACK frame 512, one or moresubsequent frames 200 may be transmitted by thesource DEV 312 and/or by thedest DEV 322, substantially as described above, during the current TXOP time duration. - In various embodiments of the invention as applied to CGDT communication, a transmitting DEV may transmit frames by utilizing any of a plurality of methods, or efficiency modes. In an exemplary embodiment of the invention, the transmitting DEV may receive an ACK frame for each transmitted frame. In other words, the transmitting DEV, which seeks to transmit a plurality of frames to a recipient DEV, may transmit a
single frame 200 to the recipient DEV and wait to receive an ACK frame before transmitting a subsequent frame. -
FIG. 6 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and omnidirectional preamble transmission, in accordance with an embodiment of the invention. Referring toFIG. 6 , there is shown a sequence of transmitted frames and received frames from the perspective of a single transmitting DEV, such as theDEV 312. The transmitting DEV may transmit a frame comprising anomni preamble field 602 using omnidirectional signal transmission, adirectional preamble field 604 using directional signal transmission, and adirectional data field 606 using directional signal transmission. The transmitting DEV may receive anACK frame 612 in response to the previously transmitted frame. Subsequent to receipt of theACK frame 612, the transmitting DEV may transmit a subsequent frame comprising anomni preamble field 622, adirectional preamble field 624 and adirectional data field 626. The transmitting DEV may receive asubsequent ACK frame 632 in response to the subsequent transmitted frame. Succeeding frames may be transmitted and acknowledged as described above. - In another exemplary embodiment of the invention, the transmitting DEV may receive an ACK frame for each transmitted frame. In this case, however, the transmitting DEV may transmit a frame comprising an omni preamble field using omnidirectional signal transmission for the first frame transmitted during a TXOP interval, while subsequent frames, which are transmitted by the transmitting DEV during the TXOP interval, may be transmitted without an omni preamble field.
-
FIG. 7 is a diagram, which illustrates an exemplary control guided data transfer sequence with single acknowledgment and without omnidirectional preamble transmission, in accordance with an embodiment of the invention. Referring toFIG. 7 , there is shown a sequence of transmitted frames and received frames from the perspective of a single transmitting DEV, such asDEV 312. The transmitting DEV may transmit a frame comprising anomni preamble field 702 using omnidirectional signal transmission, adirectional preamble field 704 using directional signal transmission, and adirectional data field 706 using directional signal transmission. The transmitting DEV may receive anACK frame 712 in response to the previously transmitted frame. Subsequent to receipt of theACK frame 712, the transmitting DEV may transmit a subsequent frame comprising adirectional preamble field 724 and adirectional data field 726. The transmitting DEV may receive asubsequent ACK frame 732 in response to the subsequent transmitted frame. Succeeding frames transmitted by the transmitting DEV during a current TXOP interval may be transmitted without an omni preamble field and acknowledged as described above. - In another exemplary embodiment of the invention, the transmitting DEV may receive a single ACK frame after transmission of a plurality of frames. The single ACK frame, which acknowledges receipt by the recipient DEV of a plurality of frames, is referred to as a block acknowledgment (block ACK).
-
FIG. 8 is a diagram, which illustrates an exemplary control guided data transfer sequence with block acknowledgment, in accordance with an embodiment of the invention. Referring toFIG. 8 , there is shown a sequence of transmitted frames and received frames from the perspective of a single transmitting DEV, such as theDEV 312. The transmitting DEV may transmit a frame comprising anomni preamble field 802 using omnidirectional signal transmission, adirectional preamble field 804 using directional signal transmission, and adirectional data field 806 using directional signal transmission. Subsequent to transmission of the frame, the transmitting DEV may transmit a succeeding frame comprising adirectional preamble field 814 and adirectional data field 816. Subsequent to transmission of the succeeding frame, the transmitting DEV may transmit a subsequent frame comprising adirectional preamble field 824 and adirectional data field 826. The transmitting DEV may receive asubsequent ACK frame 842 in response to the plurality of transmitted frames. Succeeding frames transmitted by the transmitting DEV during a current TXOP interval may be transmitted without an omni preamble field and acknowledged, either by single ACK frames and/or by block ACK frames, as described above. -
FIG. 9 is a diagram of an exemplary transceiver comprising a plurality of transmitting antennas and a plurality of receiving antennas, which may be utilized for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission, in accordance with an embodiment of the invention. Referring toFIG. 9 , there is shown atransceiver system 900, a plurality of receivingantennas 922 a, . . . , 922 n and a plurality of transmittingantennas 932 a, . . . , 932 n. Thetransceiver system 900 may be exemplary of any of theDEVs transceiver system 900 may comprise at least areceiver 902, atransmitter 904, aprocessor 906, and amemory 908. Although a transceiver is shown inFIG. 9 , transmit and receive functions may be separately implemented. - The
receiver 902 may perform receiver functions that may comprise, but are not limited to, the amplification of received RF signals, generation of frequency carrier signals corresponding to selected RF channels, for example uplink channels, the down-conversion of the amplified RF signals by the generated frequency carrier signals, demodulation of data contained in data symbols based on application of a selected demodulation type, and detection of data contained in the demodulated signals. The RF signals may be received via one ormore receiving antennas 922 a, . . . , 922 n. The data may be communicated to theprocessor 906. - The
transmitter 904 may perform transmitter functions that may comprise, but are not limited to, modulation of received data to generated data symbols based on application of a selected modulation type, generation of frequency carrier signals corresponding to selected RF channels, for example downlink channels, the up-conversion of the data symbols by the generated frequency carrier signals, and the generation and amplification of RF signals. The data may be received from theprocessor 906. The RF signals may be transmitted via one ormore transmitting antennas 932 a, . . . , 932 n. - In various embodiments of the invention, one or more of the receiving
antennas 922 a . . . 922 n may be operable for directional and/or omnidirectional reception of signals. One or more of the transmittingantennas 932 a, . . . , 932 n may be operable for directional and/or omnidirectional transmission of signals. - The
memory 908 may comprise suitable logic, circuitry, interfaces and/or code that may enable storage and/or retrieval of data and/or code. Thememory 908 may utilize any of a plurality of storage medium technologies, such as volatile memory, for example random access memory (RAM), and/or non-volatile memory, for example electrically erasable programmable read only memory (EEPROM). In the context of the present application, thememory 908 may enable storage of code for the determining when to transmit frame fields using omnidirectional signal transmission and when to transmit frame fields using directional signal transmission, for example. The memory may also enable the storage of received NAV values and/or computed BaIFS values. Thememory 908 may enable storage of training sequences utilized in preamble fields. - In operation, the
processor 906 may configure atransmitter 904 for transmission of omnidirectional signals and/or directional signals, for example. The configuration of thetransmitter 904 may enable thetransmitter 904 to select transmitting antennas, among the plurality of transmittingantennas 932 a, . . . , 932 n, to enable omnidirectional signal transmission and/or to enable directional signal transmission in a determined direction and/or with a determined coverage angle θ. Theprocessor 906 may enable determination of when to utilize DDT communication and/or CGDT communication, for example. Theprocessor 906 may enable determination of when a transmitting DEV is to utilize single ACK frame transmission and/or when to utilize block ACK frame transmission. Theprocessor 906 may also enable the transmission and processing of RTS frames, CTS frames, training sequences, data frames comprising NAV values and/or the transmission and processing of other PDUs transmitted by the transceiver 300. Theprocessor 906 may enable selection of transmittingantennas 932 a, . . . , 932 n and/or receivingantennas 922 a, . . . , 922 n for directional (or sectorized) signal transmission and/or reception. - In an exemplary embodiment of the invention, the
processor 906 may configure thetransmitter 904 to concurrently transmit omnidirectional signals and directional signals. In atransceiver system 900, which utilizes orthogonal frequency division multiplexing (OFDM), theprocessor 906 may configure the transmitter to select frequency carriers within an OFDM RF channel bandwidth that are to be utilized for omnidirectional signal transmission. Remaining frequency carriers within the OFDM RF channel bandwidth may be utilized for directional signal transmission. Based on signals received by thereceiver 902, theprocessor 906 may compute channel estimates, which characterize the wireless communication medium. The computed channel estimates may be utilized to determine a coherence bandwidth for the wireless communication medium. Theprocessor 906 may select individual frequency carriers within the OFDM RF channel bandwidth wherein the frequency difference between each such selected frequency carrier is greater than the computed coherence bandwidth. These selected frequency carriers may be utilized for omnidirectional signal transmission while the remaining frequency carriers are utilized for directional signal transmission. Theprocessor 906 may configure thetransmitter 904 to select one or more transmitting antennas, among the plurality of transmittingantennas 932 a, . . . , 932 n, for transmission of omnidirectional signals while a subsequent one or more transmitting antennas, selected among the plurality of transmittingantennas 932 a, . . . , 932 n, may be utilized for directional signal transmission. For example, theprocessor 906 may configure thetransmitter 904 to transmit omnidirectional signals via the selected frequency carriers, while thetransmitter 904 is transmitting adata field 208 using directional signal transmission via at least a portion of the remaining frequency carriers. -
FIG. 10 is a flowchart that illustrates exemplary steps for direct data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. Referring toFIG. 10 , instep 1002, aprocessor 906, which is utilized in connection with a transmittingDEV 312, may determine a network allocation value (NAV). Theprocessor 906 may determine the NAV value based on a determined value, or based on signals received from other DEVs via receiving antenna(s) 922 a, . . . , 922 n and thereceiver 902. Examples of other DEVs, as shown inFIG. 3 , comprise theDEV 314, theDEV 322 and/or theDEV 324. Theprocessor 906 may send data comprising the determined NAV value to thetransmitter 904. Instep 1004, theprocessor 906 may configure thetransmitter 904 to transmit anomni preamble field 202 and/or anomni header field 204 using omnidirectional signal transmission. The transmittedomni header field 204 may comprise the determined NAV value. Thetransmitter 904 may select one or more transmitting antennas, among the plurality of transmittingantennas 932 a, . . . , 932 n, for the omnidirectional signal transmission. - In
step 1006, prior to the commencement of directional signal transmission to a receivingDEV 314, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine the location of the receivingDEV 314. In an exemplary embodiment of the invention, the processor, utilized in connection with the transmittingDEV 312, may determine the location of the receivingDEV 314 based on a neighborhood map (step 1005). Theprocessor 906, which is utilized in connection with the transmittingDEV 312, may generate the neighborhood map based on communications with the DEVs,DEV 314,DEV 322 and/orDEV 324. The generated neighborhood map may be stored inmemory 908, which is utilized in connection with the transmittingDEV 312. - A method and system for generation of neighborhood maps is described in U.S. patent application Ser. No. 12/397,435, which is hereby incorporated herein by reference in its entirety.
- In
step 1008, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may configure thetransmitter 904 to transmit adirectional preamble field 206 and/ordirectional data field 208 using directional signals, which may be transmitted in the direction of the receivingDEV 314. In an exemplary embodiment of the invention, thetransmitter 904 may utilize one ormore transmitting antennas 932 a, . . . , 932 n, to transmit signals withincoverage area 354. - In
step 1010, thereceiver 902, which is utilized in connection with the transmittingDEV 312, may receive an ACK frame, from the receivingDEV 314, via one ormore receiving antennas 922 a, . . . , 922 n. Thereceiver 902 may communicate the received ACK frame to theprocessor 906, which is utilized in connection with the transmittingDEV 312. - In
step 1012, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine whether there is additional data to transmit to the receivingDEV 314. In instances where there is additional data to transmit,step 1004 may followstep 1012. -
FIG. 11 is a flowchart that illustrates exemplary steps for collision backoff in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. Referring toFIG. 11 , instep 1102, a transmittingDEV 324 may transmit a protocol data unit (PDU) to a receivingDEV 322. In an exemplary embodiment of the invention, the PDU comprises aframe 200. Instep 1104, theprocessor 906, which is utilized in connection with the transmittingDEV 324, may determine whether an ACK frame has been received from the receivingDEV 322. In instances where an ACK frame has been received, step 1012 (FIG. 10 ) may followstep 1104. - In instances where an ACK frame has not been received, the
processor 906, utilized in connection with the transmittingDEV 324, may determine that a collision has occurred during transmission of theframe 200. Instep 1106, theprocessor 906, which is utilized in connection with the transmittingDEV 324, may compute a BaIFS value, as shown in equation [1] above, based on determined values MAX_PAYLOAD, MAX_DATA_RATE and/or MAX_TXOP (step 1105). Theprocessor 906, which is utilized in connection with the transmittingDEV 324, may configure thetransmitter 902 to refrain from transmitting signals until the expiration of a time duration, which is determined based on the computed BaIFS value. A NAV value may be determined based on the computed BaIFS value. Instep 1108, theprocessor 906, which is utilized in connection with the transmittingDEV 324, may determine whether the NAV-determined time duration has expired. In instances where the NAV-determined time duration has not expired, thetransmitter 902 may continue to refrain from transmitting signals from the transmittingDEV 324. In instances where the NAV-determined time duration has expired, theprocessor 906, which is utilized in connection with the transmittingDev 324, may configure thetransmitter 904 to transmit signals.Step 1102 may followstep 1108. -
FIG. 12 is a flowchart that illustrates exemplary steps for control guided data transfer communication in a transmitting system for CSMA/CA with directional transmission, in accordance with an embodiment of the invention. Referring toFIG. 12 , instep 1202, aprocessor 906, which is utilized in connection with a transmittingDEV 312, may configure atransmitter 904 to transmit an RTS frame, using omnidirectional signal transmission, to a receivingDEV 314. The transmitted RTS frame may comprise a NAV value and/or a requested TXOP interval time duration. Instep 1204 theprocessor 906 may determine whether a CTS frame has been received from the receivingDEV 314. Theprocessor 906, which is utilized in connection with the transmittingDEV 312, may receive a CTS frame from the receivingDEV 314 based on signals received via receiving antenna(s) 922 a, . . . , 922 n and thereceiver 902. A received CTS frame may comprise an indicated TXOP interval time duration. In instances where a CTS frame has been received atstep 1204, instep 1206, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may configure thetransmitter 904 to transmit adirectional preamble field 206 and/ordirectional data field 208 using directional signals, which may be transmitted in the direction of the receivingDEV 314. Thetransmitter 906, which is utilized in connection with the transmittingDEV 312, may determine the location of the receivingDEV 314 based on the received CTS frame. In an exemplary embodiment of the invention, thetransmitter 904 may utilize one ormore transmitting antennas 932 a, . . . , 932 n, to transmit signals withincoverage area 354. In instances in which the transmittingDEV 312 utilizes block acknowledgment, additional frames may be transmitted atstep 1206. - In
step 1208, thereceiver 902, which is utilized in connection with the transmittingDEV 312, may receive an ACK frame, from the receivingDEV 314, via one ormore receiving antennas 922 a, . . . , 922 n. Thereceiver 902 may communicate the received ACK frame to theprocessor 906, which is utilized in connection with the transmittingDEV 312. In step 1212, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine whether the current TXOP interval has expired. In instances where the current TXOP interval has not expired, instep 1214, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine whether there is additional data to transmit to the receivingDEV 314. In instances where there is additional data to transmit,step 1206 may followstep 1214. - In instances where a CTS frame has not been received at
step 1204, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine that a collision has occurred. The processor, which is utilized in connection with the transmittingDEV 312, may configure thetransmitter 904 to refrain from attempting to transmit signals until a NAV-based time duration has expired. Instep 1216, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine whether a frame has been received, which comprises a NAV value. In instances where a frame comprising a NAV value has not been received atstep 1216, instep 1218, theprocessor 906 may compute a BaIFS value, for example as shown in equation [1]. A NAV value may be determined based on the computed BaIFS value. In instances where a frame comprising a NAV value has been received atstep 1216, instep 1220, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may set a NAV value based on the NAV value contained in the received frame. Atstep 1222, theprocessor 906, which is utilized in connection with the transmittingDEV 312, may determine whether the NAV-based time duration has expired. In instances where the NAV-based time duration has not expired, thetransmitter 904, which is utilized in connection with the transmittingDEV 312, may continue to refrain from transmitting signals. In instances where the NAV-based time duration has expired,step 1202 may followstep 1222. - Another embodiment of the invention may provide a machine and/or computer readable medium, having stored thereon, a computer program having at least one code section executable by a machine and/or computer, thereby causing the machine and/or computer to perform the steps as described herein for CSMA/CA with directional transmission.
- Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein.
- The present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.
- While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.
Claims (19)
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US12/397,435 US9019985B2 (en) | 2008-03-12 | 2009-03-04 | Method and system for scheduling multiple concurrent transmissions during a contention access period in a wireless communications network |
US12/401,222 US8553659B2 (en) | 2008-03-12 | 2009-03-10 | Method and system for optimal beamforming in wireless networks |
US12/423,589 US9301320B2 (en) | 2008-04-15 | 2009-04-14 | Method and system for method and system for carrier sense multiple access with collision avoidance (CSMA/CA) with directional transmission |
US15/049,294 US20160174260A1 (en) | 2008-04-15 | 2016-02-22 | Method and system for carrier sense multiple access with collision avoidance (csma/ca) with directional transmission |
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US20160073434A1 (en) * | 2013-05-20 | 2016-03-10 | Huawei Technologies Co., Ltd. | Channel access method and access point |
US20230171753A1 (en) * | 2011-09-30 | 2023-06-01 | Interdigital Patent Holdings, Inc. | Device communication using a reduced channel bandwidth |
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US20090175257A1 (en) * | 2008-01-04 | 2009-07-09 | Motorola, Inc. | Method and device for dynamically changing preamble duration |
WO2012172156A1 (en) * | 2011-06-16 | 2012-12-20 | Nokia Corporation | Method and apparatus for wireless medium access |
WO2014179575A2 (en) * | 2013-05-03 | 2014-11-06 | Interdigital Patent Holdings, Inc. | Methods for wifi sectorization mac enhancement |
US9769848B2 (en) | 2014-09-03 | 2017-09-19 | Samsung Electronics Co., Ltd. | Method and apparatus to achieve collision-free random access |
WO2016040837A1 (en) * | 2014-09-11 | 2016-03-17 | Interdigital Patent Holdings, Inc. | Method and apparatus for spatial sharing in wireless local area network (wlan) systems |
EP3375108A4 (en) * | 2015-11-11 | 2019-10-23 | Ruckus Wireless, Inc. | Selectivewlan |
US10972324B2 (en) | 2016-01-28 | 2021-04-06 | Qualcomm Incorporated | Dual receiver for millimeter wave communications |
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KR100586886B1 (en) * | 2004-08-13 | 2006-06-08 | 삼성전자주식회사 | Method and apparatus for wireless local area network communication |
US8175532B2 (en) * | 2006-06-06 | 2012-05-08 | Qualcomm Incorporated | Apparatus and method for wireless communication via at least one of directional and omni-direction antennas |
US7822440B2 (en) * | 2006-12-23 | 2010-10-26 | Intel Corporation | Method and apparatus for operating a communication station |
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US20230171753A1 (en) * | 2011-09-30 | 2023-06-01 | Interdigital Patent Holdings, Inc. | Device communication using a reduced channel bandwidth |
US20160073434A1 (en) * | 2013-05-20 | 2016-03-10 | Huawei Technologies Co., Ltd. | Channel access method and access point |
US9924547B2 (en) * | 2013-05-20 | 2018-03-20 | Huawei Technologies Co., Ltd. | Channel access method and access point |
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