Embed Size (px)
Citation preview
doc.: IEEE 802.11-13/0765 r1
Submission
Co-time Co-frequency Full Duplex for 802.11 WLAN
July 2013
Hongliang Bian (China Telecom)Slide 1
Date: 2013-07-15
Authors:
Name Affiliations Address Phone emailHongliang Bian China
TelecomNo.118 Xizhimennei Street, Xicheng District, Beijing ,China
86-10-58552955
Yonggang Fang ZTE USA [email protected] Sun ZTE Corp. [email protected] Li Tsinghua Univ. [email protected]
doc.: IEEE 802.11-13/0765 r1
Submission
Abstract
July 2013
Slide 2
HEW aims at improving the transmission efficiency of WLAN.
This presentation briefly introduces a new PHY technology called Co-time Co-frequency Full Duplex (CCFD) transmission. It intends to share the latest research study information and to facilitate further investigation and discussion on full-duplex transmission technology on WLAN.
Hongliang Bian (China Telecom)
doc.: IEEE 802.11-13/0765 r1
Submission
Background (1/2)
July 2013
Slide 3
WLAN has been widely used in indoor and outdoor environment to provide home wireless networking, enterprise and campus wireless networks, cellular offload hotspot networks.
Next generation WLAN network needs to accommodate more users and
provide higher regional data throughput.
WLAN operates on license exempt spectrum, and frequency bands are limited. Therefore it may be necessary to consider some new technologies to further improve spectrum efficiency.
Hongliang Bian (China Telecom)
doc.: IEEE 802.11-13/0765 r1
Submission
Background (2/2)
July 2013
Slide 4
Wireless Communication Mechanisms Include Functions Multiple access to the shared medium. Duplex transmission over the same medium for the pair communicating stations
Duplex Transmission Mechanisms Include Half duplex transmission. In the half duplex transmission, both communicating
stations cannot transmit information at same time, such as walky-talky. Full duplex transmission, on the other hand, allows both communicating stations
to exchange information simultaneously over the same medium. In order to support full duplex communication over half-duplex link, wireless
transmission operates on Frequency division duplexing (FDD) Time division duplexing (TDD)
Hongliang Bian (China Telecom)
doc.: IEEE 802.11-13/0765 r1
Submission
Co-time Co-frequency Full Duplex (CCFD) (1/2)
July 2013
Slide 5
Current 802.11 technologies only use TDD scheme and allows transmission and reception at different time, causing low medium usage efficiency.
CCFD allows transmission and reception simultaneously over the same frequency, which could improve the spectrum efficiency significantly.
Hongliang Bian (China Telecom)
STA1 (bits/s/Hz)
STA2 (bits/s/Hz)
half-duplex
full-duplex
full-duplex limit
STA 1
STA 2
doc.: IEEE 802.11-13/0765 r1
Submission
Co-time Co-frequency Full Duplex (CCFD) (2/2)
July 2013
Key challenge: Self-interference from the transmitter of one station to its own receiver and interference from the transmitter of stations other than the target station is the key issue. Interference cancellation is critical to the full-duplex transmission.
Slide 6 Hongliang Bian (China Telecom)
STA 1 STA 2
doc.: IEEE 802.11-13/0765 r1
Submission
Interference Cancellation
July 2013
Slide 7
There are a quite few full-duplex transmission academic study reports. Current those studies mainly focus on self-interference cancellation specific to the point to point communication.
Three types of self-interference cancellation schemes: Antenna cancellation Analog cancellation Digital cancellation
Hongliang Bian (China Telecom)
doc.: IEEE 802.11-13/0765 r1
Submission
Antenna Cancellation (1/2)
July 2013
Slide 8
1. Asymmetric Antenna Placement
Hongliang Bian (China Telecom)
Distance difference from two transmit antennas to receive antenna is an odd number of λ/2, which provides an inverse phase difference between the two self interferences.
Factors that influence antenna cancellation performance:
Placement accuracy of transmit antennasPower balance of self interferencesSignal bandwidth
Distance mismatch effect on antenna cancellation[1]
Amplitude mismatch effect on antenna cancellation[1]
doc.: IEEE 802.11-13/0765 r1
Submission
Antenna Cancellation (2/2)
July 2013
Slide 9
2. Symmetric Antenna Placement
Hongliang Bian (China Telecom)
With a π phase inversion between two symmetric Rx/Tx antennas, self interference can be cancelled at Tx/Rx antenna.
The main factor needs to be considered is distance mismatch of the pair of Rx/Tx antennas.
Benefits of symmetric placement compared to asymmetric placement:
Receive cancellation and transmit cancellation can be combined with placement of both symmetric Rx antennas and symmetric Tx antennas. Symmetric antenna placement can be extended to support MIMO easily.
Double antenna cancellation with receiving cancellation plus transmitting cancellation[2]
doc.: IEEE 802.11-13/0765 r1
Submission
Analogy Cancellation
July 2013
Slide 10 Hongliang Bian (China Telecom)
Take the known interference and received signals as input and outputs the received signal with the suppressed self interference.
Noise cancellation ASIC can be used to adjust the amplitude and phase of the interference reference signal to match the self interference.[3]
Factors that influence analogy cancellation performance: Accuracy of adjustment of the amplitude and phase of the interference reference signal is key issue. Adaptive adjustment of the interference reference signal according to the output signal may need to be considered.
doc.: IEEE 802.11-13/0765 r1
Submission
Digital Cancellation
July 2013
Hongliang Bian (China Telecom)
Given that the input signal from the RF receiver module doesn't saturate the ADC, the digital cancellation can be performed to further remove the residual of self-interference from the transmitter. Digital interference reference signal is derived from transmitting signal, then it is subtracted in the output of the baseband so that the self interference can be removed.
Factors that influence digital cancellation performance: ADC dynamic range SINR of the output of ADC Quantification method
RX PHY
TX PHY
TX MACRX MAC
DACADC
Digitalfeedback
-
Slide 11
doc.: IEEE 802.11-13/0765 r1
Submission
Summary
July 2013
Slide 12 Hongliang Bian (China Telecom)
Full-duplex creates a new promising for improving medium efficiency. But some challenges in the full-duplex transmission need further investigation before the technology becomes feasible in the real world.
Performance of antenna cancellation is very sensitive to the AP placement. It needs to improve the self-interference cancellation performance of individual AP which can’t be managed professionally.
Multi-path signal will degrade the performance of self-interference cancellation, especially for indoor scenario.
Digital cancellation performance is limited by the dynamic range and quantification method of ADC. For some amplitude sensitive modulation/demodulation schemes such as OFDM, it needs higher dynamic range and specific quantification method of ADC.
Since the analog cancellation and digital cancellation can be performed together, it may need to coordinate the analog cancellation and digital cancellation to improve and optimize the performance.
doc.: IEEE 802.11-13/0765 r1
Submission
Conclusion
July 2013
This presentation proposes a Co-time Co-frequency Full Duplex technology for improving the spectrum efficiency.
• Proposal 1: The full-duplex transmission needs to be considered in HEW.
• Proposed 2: Self interference cancellation performance and algorithms for full-duplexer should be further studied.
• Proposal 3: Impacts to the current WLAN should be investigated and backward compatibility to legacy WLAN needs to be careful considered.
Slide 13 Hongliang Bian (China Telecom)
doc.: IEEE 802.11-13/0765 r1
Submission
References
July 2013
Slide 14 Hongliang Bian (China Telecom)
• [1] Choi J I, Jain M, Srinivasan K, et al.. Achieving single channel, full duplex wireless communication [C]. Proceedings of the 16th Annual International Conference on Mobile Computing and Networking (MobiCom '10), New York, 2010: 1–12.
• [2] Khojastepour M A, Sundaresan K, Rangarajan S, et al.. The case for antenna cancellation for scalable full-duplex wireless communications [C]. 10th ACM Workshop on Hot Topics in Networks (HOTNETS '11), Massachusetts, USA, 2011: 17-17.
• [3] Jain M, Choi J I, Kim T M, et al.. Practical, real-time, full duplex wireless [C]. Proceedings of the 17th Annual International Conference on Mobile Computing and Networking (MobiCom '11), New York, 2011: 301-312.
doc.: IEEE 802.11-13/0765 r1
Submission
Thank You!
July 2013
Slide 15 Hongliang Bian (China Telecom)
