5G Standards on Non-Terrestrial Networks:
NTN uplink time synchronization
L. Ma, C. Park, X. Wang, P. Gaal, A. R. Alvarino, "Uplink Time Synchronization for Non-Terrestrial Networks," IEEE Communications Magazine, July 2023.
This paper summarizes my contribution to the NTN uplink time synchronization in 5G standards, including the solution to the double correction issue and the redefinition of the feeder link delay parameter - the "Common TA".
The above paper was the first to identify the double correction issue in the uplink time synchronization in NTN. Unlike a terrestrial network, NTN employs closed-loop control (network feedback for timing correction) and open-loop control (devices using their GPS locations and the satellite location to calculate and compensate for the propagation delays). I discovered that when the GPS location was updated, the open loop would correct the error already corrected by the closed loop, increasing rather than decreasing synchronization errors.
This paper gave a solution to the double correction issue, which was subsequently adopted by 3GPP TS38.133 for NR and 3GPP TS36.133 for LTE.
L. Ma et al., "Timing Advance Adjustment," US Patent Application #18/069,097, Feb 2022.
Direct-to-Cell
"BWP operation and other issues for NTN," R1-2101467, 3GPP RAN1 #104-e meeting, January 2021.
This was the first paper in 3GPP meetings to show the feasibility of direct communication between smartphones and satellites.
This and prior internal work were the driver for the adoption of OCC for uplink data transmission as a main subject in the NTN Rel-19 standards for both NR and IoT.
5G Standards on Multimedia Systems:
End-to-end delay provisioning for mixed networks (3GPP plus non-3GPP) and precise delay measurement
S4-221319, "Key Issue #1: Latency Aspects for Smartly Tethered AR Glasses (SmarTAR)", 3GPP SA4 #121 meeting, Toulouse, France, Nov 2022.
This paper presented an innovative technique, allowing a 3GPP 5G network to provision the desired end-to-end delay by compensating for the total delay in non-3GPP networks. This is accomplished by measuring end-to-end delay and inferring the cumulative non-3GPP network delay.
S4-231927, "RTP header extension for in-band end-to-end delay measurement", 3GPP SA4 #126 meeting, Chicago, Nov 2023.
L. Ma, et al., "Real-time Transport Protocol Header Extension for In-band Delay Measurement," US Patent Application 18/347,977, July 2023.
The above paper and patent proposed novel RTP header extensions for in-band end-to-end delay measurements. Adopted by 3GPP TS26.522 “5G Real-time Media Transport Protocol Configurations”, these extensions are crucial to low-latency applications, particularly XR. They enable the precise measurement of delays, including one-way, round-trip, and processing delays experienced by the media.
In contrast to conventional methods utilizing control packets like ICMP ping, these extensions focus on capturing delays seen by the media. This distinction allows for more accurate delay compensation by a 3GPP 5G network and facilitates better adaptation of multimedia codecs to dynamic network conditions.
Other Selected Publications:
Physical (PHY) Layer
L. Ma, T. Xu, G. Sternberg, "Computational Complexity of Interference Alignment for Symmetric MIMO Networks", IEEE Communications Letters, Vol. 17, No. 12, Dec 2013.
L. Ma, Y. Li and A. Demir, "Matched Filtering Assisted Energy Detection for Sensing Weak Primary User Signals", IEEE ICASSP 2012.
L. Ma, W. Liu and A. Zeira, "Making Overlay Cognitive Radios Practical", IEEE ICASSP 2012.
MAC Layer
Multimedia Systems
L. Ma, T. Xu, G. Sternberg, A. Balasubramanian, and A. Zeira, "Model-based QoE Prediction to Enable Better User Experience for Video Teleconferencing", IEEE ICASSP 2013.
L. Ma, D. Veer, W. Chen, G. Sternberg, Y. Reznik and R. Neff, "User Adaptive Transcoding for Video Teleconferencing", International Conference on Image Processing (ICIP) 2015.
T. Xu and L. Ma, "Predictive Prefetching for MPEG DASH over LTE Networks", International Conference on Image Processing (ICIP) 2015.
L. Ma, W. Chen, D. Veer, G. Sternberg, W. Liu and Y. Reznik, "Early Packet Loss Feedback for WebRTC-based Mobile Video Telephony over Wi-Fi", IEEE Globecom 2015. Demo links: with EPLF turned off, with EPLF turned on.
T. Xu, L. Ma and G. Sternberg, "QoE-based MAC Layer Optimization for Video Teleconferencing over WiFi", arXiv:1611.00869
Congestion Control
L. Ma, K. Barner and G. Arce, “Statistical Analysis of TCP’s Retransmission Timeout Algorithm”, IEEE/ACM Transactions on Networking, Vol. 14, No. 2, April 2006.
L. Ma, K. Barner and G. Arce, "TCP Retransmission Timeout Algorithm Using Weighted Medians", IEEE Signal Processing Letters, Vol. 11, No. 6, June 2004.
Machine Learning
