|Publication number||US9271307 B2|
|Application number||US 13/720,057|
|Publication date||23 Feb 2016|
|Filing date||19 Dec 2012|
|Priority date||19 Dec 2012|
|Also published as||US9553958, US20140169233, US20160173661, US20170134151|
|Publication number||13720057, 720057, US 9271307 B2, US 9271307B2, US-B2-9271307, US9271307 B2, US9271307B2|
|Inventors||Vaneet Aggarwal, Rittwik Jana, Christopher W. Rice, Nemmara K. Shankaranarayanan|
|Original Assignee||At&T Intellectual Property I, L.P.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Non-Patent Citations (28), Classifications (8), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Technical Field
The present disclosure relates to full-duplex media access control (MAC) timing modification, and more specifically to ensuring that node pairs involved in full-duplex communications do not receive an unfair advantage of capturing the full-duplex channel repeatedly over nodes communicating in a half-duplex mode.
In 802.11 wireless networks, various durations for specific actions and events are defined. The durations often change depending on protocol version (for example, version 802.11(a) versus version 802.11(n)), however the relationships of the defined durations do not change. Examples of durations defined within the 802.11 model are SIFS (short interframe space), DIFS (distributed coordination function interframe space), and EIFS (extended interframe space). The relationships of the exemplary durations, as defined by the 802.11 model, are that a SIFS has a shorter duration than a DIFS, which in turn has a shorter duration than an EIFS. For example, the SIFS can have a duration of 10 μs, the DIFS can have a duration of the SIFS duration+(2×a predetermined slot time), and the EIFS can have a duration of the SIFS duration+the DIFS duration+acknowledgment duration. Alternatively, the SIFS can have a duration determined based on transmission and processing delays built into the system.
A MAC (media access control) layer defines how nodes communicate with other nodes using a specific protocol version. MAC layers for the 802.11 model and other wireless networks specify that nodes will pause for a longer wait time (EIFS), rather than the standard wait time (DIFS), when the nodes receive an erroneous packet. The purpose of the extended wait time upon receiving an erroneous packet is to allow other packet recipient nodes, who received the data correctly, to be able to send an acknowledgment frame in time.
The following disclosure covers two general embodiments that relate to how nodes in a network communication. A first embodiment relates to nodes communicating in a full-duplex mode. A second embodiment focuses on a scenario where a half-duplex node is communicating in a network where other full-duplex nodes are involved in full-duplex communication. In the second embodiment, the half-duplex node ignores what it would normally view as collisions with respect to how it handles the interface spacing. Knowledge about the other nodes being in full-duplex communication can be explicitly communicated or inferred by the half-duplex node.
As noted above, the first embodiment covers full-duplex communication between two nodes. A system, method, computer-readable media, and a computer-readable device reduce the likelihood of monopolization of a frequency channel by full-duplex devices by modifying the MAC layer. In a network where all nodes are configured to be full-duplex capable, the MAC can be modified such that upon termination of the communication between the full-duplex devices, the devices which just finished communicating defer (wait) for an EIFS duration prior to engaging in the next contention round. The other nodes in the network, which were not communicating and which viewed the full-duplex data as collisions, similarly pause for an EIFS. Because all of the nodes in the network pause for an EIFS, the likelihood of channel monopolization by the two communicating full-duplex nodes is reduced.
When full-duplex capable nodes are introduced to a network, data can be transmitted by two separate nodes simultaneously in a single frequency channel. For example, as illustrated in
However, the other nodes 306 in the network, which are either not full-duplex capable or are configured using non-full-duplex MAC layers, see the full-duplex communications as errors. For example, other nodes 306 receive, during the RTS-CTS handshake 310, 314, network allocation vectors (NAVs) 322, 324 indicating the estimated packet sizes the sender 302 and receiver 304 will be communicating. However, upon the full-duplex communications beginning with the transmissions of data 318, 320, the other nodes 306 receive packets intended for two distinct nodes 302, 304, and determine that an error has occurred. Therefore, at time t3, when the sender 302 and receiver 304, have finished communications and begin waiting the standard DIFS 332, 334, which will end at time t4. The other nodes 306 begin, at time t3, to wait for the extended EIFS 336, which will end at time t5. The gap 338 between when the DIFS ends at time t4 and when the EIFS ends at time t5 can produce unfairness in capturing the channel, because the nodes which wait for the DIFS time period can re-capture the channel, never providing the other nodes 306 the opportunity to communicate data. In a network that has both full-duplex and half-duplex nodes, the MAC layer is modified such that the nodes which were transmitting in full-duplex wait, upon completing transmission, for an EIFS duration of time, whereas the other nodes which were detecting “collisions” either immediately begin contending for the next communication round, or alternatively, wait for a DIFS duration before beginning the contention round.
These and other various embodiments are described in detail below. While specific implementations are described, it should be understood that this is done for illustration purposes only. Other components and configurations may be used without parting from the spirit and scope of the disclosure. A brief introductory description of a basic general purpose system or computing device in
With reference to
The system bus 110 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. A basic input/output (BIOS) stored in ROM 140 or the like, may provide the basic routine that helps to transfer information between elements within the computing device 100, such as during start-up. The computing device 100 further includes storage devices 160 such as a hard disk drive, a magnetic disk drive, an optical disk drive, tape drive or the like. The storage device 160 can include software modules 162, 164, 166 for controlling the processor 120. The system 100 can include other hardware or software modules. The storage device 160 is connected to the system bus 110 by a drive interface. The drives and the associated computer-readable storage media provide nonvolatile storage of computer-readable instructions, data structures, program modules and other data for the computing device 100. In one aspect, a hardware module that performs a particular function includes the software component stored in a tangible computer-readable storage medium, or in a computer-readable storage device, in connection with the necessary hardware components, such as the processor 120, bus 110, display 170, and so forth, to carry out a particular function. In another aspect, the system can use a processor and computer-readable storage medium to store instructions which, when executed by the processor, cause the processor to perform a method or other specific actions. The basic components and appropriate variations can be modified depending on the type of device, such as whether the device 100 is a small, handheld computing device, a desktop computer, or a computer server.
Although the exemplary embodiment(s) described herein employs the hard disk 160, other types of computer-readable media which can store data that are accessible by a computer, such as magnetic cassettes, flash memory cards, digital versatile disks, cartridges, random access memories (RAMs) 150, read only memory (ROM) 140, a cable or wireless signal containing a bit stream and the like, may also be used in the exemplary operating environment. Tangible computer-readable storage media, or computer-readable storage devices, expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se.
To enable user interaction with the computing device 100, an input device 190 represents any number of input mechanisms, such as a microphone for speech, a touch-sensitive screen for gesture or graphical input, keyboard, mouse, motion input, speech and so forth. An output device 170 can also be one or more of a number of output mechanisms known to those of skill in the art. In some instances, multimodal systems enable a user to provide multiple types of input to communicate with the computing device 100. The communications interface 180 generally governs and manages the user input and system output. There is no restriction on operating on any particular hardware arrangement and therefore the basic hardware depicted may easily be substituted for improved hardware or firmware arrangements as they are developed.
For clarity of explanation, the illustrative system embodiment is presented as including individual functional blocks including functional blocks labeled as a “processor” or processor 120. The functions these blocks represent may be provided through the use of either shared or dedicated hardware, including, but not limited to, hardware capable of executing software and hardware, such as a processor 120, that is purpose-built to operate as an equivalent to software executing on a general purpose processor. For example the functions of one or more processors presented in
The logical operations of the various embodiments are implemented as: (1) a sequence of computer implemented steps, operations, or procedures running on a programmable circuit within a general use computer, (2) a sequence of computer implemented steps, operations, or procedures running on a specific-use programmable circuit; and/or (3) interconnected machine modules or program engines within the programmable circuits. The system 100 shown in
Having disclosed some components of a computing system, and having discussed
As the sender 402 and receiver 404 exchange data 418, 420 in full-duplex, the other nodes 406 receive two sets of data packets, which is recorded as a collision per previous MAC layer designs. Upon finishing the data transmissions 418, 420, the sender 402 and receiver 404 pause for a SIFS duration 426, and transmit acknowledgements of the data received 428, 430. Following the transmission of acknowledgments, at time t3, the sender 402 and receiver 404 pause an EIFS duration 432, 434 prior to entering a new contention round. The other full-duplex nodes 406, which have been recording collisions during the process, recognize the end of the data exchange, at time t3, and also wait for an EIFS 436. Recognition of the end of the data exchange can occur based on receiving the transmitted acknowledgments 428, 430, or based on the termination of the NAV durations 422, 424 previously received.
In other configurations the other nodes 406 can be half-duplex nodes, or alternatively, a mixture of full-duplex and half-duplex nodes. In addition, the MAC can be modified such that the other nodes 406 wait for a shorter duration than an EIFS, such as a DIFS, an SIFS, or for as short a duration as logistically possible, prior to initiating the next contention round. Because the sender 402 and receiver 404 nodes are configured to wait for an EIFS, these shorter durations can provide an advantage to the other nodes 406 in “winning” the contention round.
The second embodiment disclosed herein covers a configuration where a half-duplex node is communicating in a network where at least one other node is communicating in a full duplex mode.
Upon finishing the data transmissions 518, 520, the sender 502 and receiver 504 pause for a SIFS duration 526, and transmit acknowledgements of the data received 528, 530. Following the transmission of acknowledgments 528, 530, at time t3, the sender 502 and receiver 504 pause an EIFS duration 532, 534 prior to entering a new contention round. The other half-duplex nodes 506, which have been registering collisions during the full-duplex exchange process or ignoring the collisions, recognize the end of the data exchange. The recognition can occur based on receiving the acknowledgments 528, 530 transmitted, or based on the termination of the NAV durations 522, 524 previously received. At time t3, upon recognizing that the data exchange has ended, the other half-duplex nodes 506 do not wait for an EIFS, but instead wait for a DIFS duration 536. After the DIFS duration 536, the other half-duplex nodes 506 can immediately initiate a new contention round, decreasing the likelihood of the nodes which sent and received data 502, 504 in the previous round re-winning the contention round. In certain configurations, at time t3 the other half-duplex nodes 506 do not wait for a DIFS or an EIFS, instead immediately initiating the new contention round.
Having disclosed some basic system components and concepts, the disclosure now turns to the first exemplary method embodiment shown in
The system 100 first determines that a first node and a second node are in full-duplex communication, wherein the first node uses a distributed channel access protocol for contending with other nodes to communicate with the second node (602). For example, the first node uses the distributed channel access protocol to win a contention round. Winning the contention round can be based on strength of signal, priority of data, time since last communication, or other factors having a relative weight higher than factors belonging to other nodes. The system 100, for example, can be the first node or the second node. Examples of the first node and second node can be wireless devices, such as smartphones, tablet computers, laptops, and wireless routers. Therefore, if the system 100, acting as the first node, is a smartphone and the second node is a wireless router, per step 602 the system 100 wins the contention round using a distributed channel access protocol and begins full-duplex communications with the router.
After receiving an acknowledgment of receipt of a successful transmission from the second node, the system 100 defers, or waits, for an extended interframe space (604). The extended interframe space is longer than the standard distributed coordination function interframe space, or DCF interframe space, between rounds of communication. For example, the DCF interframe space could have a duration of 50 μs, whereas the extended interframe space is longer than 50 μs. In certain configurations, the system 100 can receive instructions directing it to wait for the extended interframe space based on the other nodes, whereas in other configurations the MAC layer associated with the system 100 can be permanently modified such that communications the system 100 always defers, after receiving acknowledgment of receipt of data, for an extended interframe space. As an example of a signal that could be used to indicate that an extended interframe space duration should follow, a CTS sender can indicate that it intends to send full-duplex data by re-purposing an unused bit (e.g., the More Data bit in the CTS Frame Control field). The unused bit can indicate that the modified version of the MAC should be used. Another option is for a full-duplex node to use two MAC addresses, one for half-duplex use, and the other for full-duplex use. Having two MAC addresses would allow the RTS sender to adapt its rate based on which MAC address, the full-duplex or half-duplex, is being used, and the new duration using that adapted rate could be set as a NAV duration by the CTS sender.
The other nodes associated with the system 100, which did not win the contention round, can be configured to immediate begin contending for the next round of communications, or can be configured to wait for a DIFS, an EIFS, or another time duration. The interframe spacing durations, such as DIFS, EIFS, or SIFS, used by the system 100 can be set by a standard or model, such as the 802.11 standard.
The system 100, at a first node, determines that a second node and a third node are in full duplex communication, wherein the first node and the second node use a distributed channel access protocol for contending for access to communicate with the third node (702). The nodes can be laptops, smartphones, tablets, base stations, or other wireless devices. Contending for access can take place via a contention round, in which all of the nodes contend for the ability to communicate data with the third node.
After receiving, at the first node, a communication associated with the full-duplex communication between the second node and the third node, the full-duplex communication not intended for the first node, the system 100 defers for a distributed coordination function interframe space period of time (704). In order for the system 100 to defer for a distributed coordination function interframe space duration, the MAC layer of the system 100 can be modified. An exemplary modification can require the distributed coordination function interframe space duration to always be initiated following the reception of non-intended data, or, in other configurations, the signal can indicate that the distributed coordination function interframe space duration should be used.
As an example of a signal that could be used to indicate that a distributed coordination function interframe space duration should follow a communication, a CTS sender can indicate that it intends to send full-duplex data by re-purposing an unused bit (e.g., the More Data bit in the CTS Frame Control field). The unused bit can indicate that the modified version of the MAC should be used. Another option is for a full-duplex node to use two MAC addresses, one for half-duplex use, and the other for full-duplex use. Having two MAC addresses would allow the RTS sender to adapt its rate based on which MAC address, the full-duplex or half-duplex, is being used, and the new duration using that adapted rate could be set as a NAV duration by the CTS sender.
The system 100 can, following the distributed coordination function interframe space duration, enter a new contention round. While the first node defers for a distributed coordination function interframe space period of time, the second and third nodes can be configured to wait for an extended interframe space duration following a communication. The system 100 can initiate the subsequent contention round prior to the second node and the third node completing the extended interframe space “pause,” and thereby prevents unfair monopolization of the frequency channel (used in full-duplex communications) by the second and third nodes. The interframe spacing durations, such as DIFS, EIFS, or SIFS, used by the system 100 can be set by a standard or model, such as the 802.11 standard.
Embodiments within the scope of the present disclosure may also include tangible and/or non-transitory computer-readable storage media for carrying or having computer-executable instructions or data structures stored thereon. Such tangible computer-readable storage media can be any available media that can be accessed by a general purpose or special purpose computer, including the functional design of any special purpose processor as described above. By way of example, and not limitation, such tangible computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of computer-executable instructions, data structures, or processor chip design. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or combination thereof) to a computer, the computer properly views the connection as a computer-readable medium. Thus, any such connection is properly termed a computer-readable medium. Combinations of the above should also be included within the scope of the computer-readable media.
Computer-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Computer-executable instructions also include program modules that are executed by computers in stand-alone or network environments. Generally, program modules include routines, programs, components, data structures, objects, and the functions inherent in the design of special-purpose processors, etc. that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of the program code means for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps.
Other embodiments of the disclosure may be practiced in network computing environments with many types of computer system configurations, including personal computers, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. Embodiments may also be practiced in distributed computing environments where tasks are performed by local and remote processing devices that are linked (either by hardwired links, wireless links, or by a combination thereof) through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices.
The various embodiments described above are provided by way of illustration only and should not be construed to limit the scope of the disclosure. For example, the principles herein apply equally to wireless communications and cellular communications where practical. Various modifications and changes may be made to the principles described herein without following the example embodiments and applications illustrated and described herein, and without departing from the spirit and scope of the disclosure.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US7817641||17 Oct 2006||19 Oct 2010||Amir Keyvan Khandani||Methods for spatial multiplexing of wireless two-way channels|
|US8554237 *||4 Dec 2009||8 Oct 2013||Toshiba America Research, Inc.||Channel partitioning for wireless local area networks|
|US20080240078 *||30 Mar 2007||2 Oct 2008||Pascal Thubert||Path shortening in a wireless mesh network|
|US20090103485 *||4 Jun 2008||23 Apr 2009||Samsung Electronics Co., Ltd.||System and method for wireless data communication having multiple checksums per frame|
|1||A. Sahai, G. Patel, and A. Sabharwal. Asynchronous Full-duplex Wireless. In Proc of IEEE COMSNETS, Bangalore, India, 2012.|
|2||A. Sahai, G. Patel, and A. Sabharwal. Pushing the limits of Full-duplex: Design and Real-time implementation. In arXiv.org:1107.0607, 2011.|
|3||B. Radunovic, D. Gunawardena, P. Key, A.P.N. Singh, V. Balan, and G. Dejean. Rethinking indoor wireless: Low power, low frequency, full duplex. Technical report, Microsoft Technical Report, 2009.|
|4||D.W. Bliss, P. Parker, and A.R. Margetts. Simultaneous transmission and reception for improved wireless network performance. In Proc. of IEEE/SP 14th Workshop on Statistical Signal Processing, pp. 478-482, Aug. 2007.|
|5||David Tse and Pramod Viswanath. Fundamentals of Wireless Communications. Cambridge University Press, 2005.|
|6||*||Design and Characterization of a Full-duplex Multi-antenna System for WiFi networks, Melissa Duarte, Oct. 8, 2012.|
|7||*||Design and Characterization of a Full-duplex Multi-antenna System for WiFi networks, Melissa Durate, Oct. 8, 2012.|
|8||E. Aryafar, M.A. Khojastepour, K. Sundaresan, S. Rangarajan, and M. Chiang. Midu: enabling mimo full duplex. In Proc. of the ACM Mobicom, 2012.|
|9||E. Everett, M. Duarte, C. Dick, and A. Sabharwal. Empowering full-duplex wireless communication by exploiting directional diversity. In IEEE Asilomar Conference on Signals, Systems and Computers, 2011.|
|10||IEEE-802.11. IEEE Std 802.11-2007 and IEEE Std 802.11n-2009.|
|11||J. Choi, M. Jain, K. Srinivasan, P. Levis, and S. Katti. Achieving single channel, full duplex wireless communication. In Proc. of the ACM Mobicom, Illinois, USA, 2010, ACM New York, NY, USA.|
|12||J. Geier. 802.11 Medium Access Methods, Nov. 2002. http://www.wi-fiplanet.com/tutorials/article.php/1548381.|
|13||J.G. Proakis. Digital Communications, McGraw-Hill, 1983. Book.|
|14||L-com Antennas. http://www.1-com.com. 2.4 GHz 7 dBi Desktop Omni Antenna Spec.|
|15||M. Duarte and A. Sabharwal. Full-duplex wireless communications using off-the-shelf radios: Feasibility and first results. In Proc. of Asilomar Conference on Signals, Systems and Computers, Monterey, CA, 2010.|
|16||M. Duarte, C. Dick, and A. Sabharwal. Experiment-driven characterization of full-duplex wireless systems. IEEE Transactions on Wireless Communications Accepted for Publication, Available at http://arxiv.org/abs/1107.1276 2012.|
|17||M. Jain, J. Choi, T.M. Kim, D. Bharadia, S. Seth, K. Srinivasan, P. Levis, S. Katti, and P. Sinha. Practical, Real-time Full Duplex wireless. In Proc. of the ACM Mobicom, Illinois, USA, 2011, ACM New York, NY, USA.|
|18||M.A. Khojastepour, K. Sundaresan, S. Rangarajan, X. Zhang, and S. Barghi. The case for antenna cancellation for scalable full duplex wireless communications. In Proc. of Hotnets, Nov. 2011.|
|19||Melissa Duarte. Full-duplex Wireless: Design, Implementation and Characterization. PhD thesis, Rice University, 2012.|
|20||MIMO. www.mathworks.com, Communications System Toolbox R2011b.|
|21||N. Singh, D. Gunawardena, A. Proutiere, B. Radunovic, H.V. Balan, and P. Key. Efficient and Fair MAC for wireless networks with self interference cancellation. In Proceedings of WiOpt, Princeton, NJ, 2011.|
|22||S. Chen, M.A. Beach, and J.P. McGeehan. Division-free duplex for wireless applications. Electronics Letters, 34(2): 147-148, Jan. 1998.|
|23||S.M. Alamouti. A simple transmit diversity technique for wireless communications. IEEE Journal on Selected Areas in Communications, 16(8):1451-1458, Oct. 1998.|
|24||SMA attenuator. Pasternack Enterprises Data Sheet.|
|25||SMA female power divider PE2014. Pasternack Enterprises Data Sheet.|
|26||T. Riihonen, S. Werner, and R. Wichman. Mitigation of loopback self-interference in full-duplex MIMO relays. IEEE Transactions on Signal Processing, 59(12):5983-5993, Dec. 2011.|
|27||W. Kim, H. Lee, M. Kim, and H.K. Chungl Distribution of eigenvalues for 2×2 mimo channel capacity based on indoor measurements. IEEE Transactions on Wireless Communications, 11(4): 1255-1259, Apr. 2012.|
|28||Wireless Open-Access Research Platform (WARP). http://www.rice.edu/trac.|
|International Classification||H04B1/56, H04W74/08|
|Cooperative Classification||H04L69/28, H04L5/14, H04W72/0446, H04W72/00, H04W74/08, H04W84/12|
|12 Feb 2014||AS||Assignment|
Owner name: AT&T INTELLECTUAL PROPERTY I, L.P., GEORGIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:AGGARWAL, VANEET;JANA, RITTWIK;RICE, CHRISTOPHER W.;AND OTHERS;SIGNING DATES FROM 20140206 TO 20140212;REEL/FRAME:032205/0886