In today's virtualized cloud, containers and virtual machines (VMs) are prevailing methods to deploy applications with different tenant requirements. However, these requirements are at odds with the resource allocation capabilities of conventional networking stacks in wide-area networks (WANs). In particular, existing WAN traffic engineering (TE) systems at the granularity of aggregated traffic flows are not designed to cater to each individual flow. In this paper, we advocate for a radical new approach to extend TE systems to involve millions of virtual instance endpoints. We propose and implement a first-of-its-kind system, called MegaTE, to satisfy the needs of each fine-grained traffic flow at the virtual instance level. At the core of the MegaTE system is the paradigm shift from the top-down centralized control to the bottom-up asynchronous query in the TE control loop, combined with eBPF-based segment routing on the data plane and TE optimization contraction on the control plane. We evaluate MegaTE using flow-level simulations with production traffic traces. Our results show that MegaTE supports 20× more endpoints with the similar algorithm run time compared to prior work. MegaTE has been adopted by large-scale public cloud providers. Notably, Tencent rolled out MegaTE in its cloud WAN since December 2022. Our production analysis shows that MegaTE reduces the packet latency of real-time applications by up to 51%.

The classical Schalkwijk-Kailath (SK) scheme, which achieves the capacity of the additive white Gaussian noise (AWGN) channel with noiseless feedback, is also shown to be an excellent secure finite blocklength (FBL) coding scheme for the AWGN wiretap channel with noiseless feedback. In this paper, the dirty tape channel (AWGN channel with Gaussian state interference causally known by the transmitter) with noiseless/noisy feedback is investigated. First, SK-type feedback schemes are proposed for this model by introducing a lattice-based strategy into the classical SK scheme, and it is shown that this strategy helps to eliminate the impact of the state interference and the feedback channel noise on the performance of the SK scheme. Then, we analyze the security performance of the proposed schemes, in particular, for the dirty tape channel with noisy feedback and eavesdropper, we give a lower bound on the normalized eavesdropper’s equivocation by establishing a novel inequality about the differential entropy of the Gaussian modulo-lattice function. Finally, performances of our proposed schemes are further explained by numerical examples.

The two-user Gaussian broadcast wiretap channel with common message and feedback (GBC-WTC-CM-F) is revisited. Traditionally, achievable secrecy rate of this model is achieved by combining Marton’s coding scheme for the two-user broadcast channel (BC) and the secret-key based feedback scheme, where both of the two feedback links are used to transmit secret keys shared between the transceivers. Recently, it has been shown that for the Gaussian wiretap channel with feedback, the Schalkwijk-Kailath (SK) feedback scheme achieves its secrecy capacity. Then it is natural to ask: can we do better when applying the SK-type scheme to the GBC-WTC-CM-F? In this paper, we answer this question by proposing two kinds of SK-type schemes. Specifically, first, we propose a hybrid scheme where one feedback link is used to transmit a secret key, and the other one is used for SK-type coding. We show that this hybrid scheme may perform better than the existing one in some cases. Next, we show that Ozarow’s extended SK scheme for the two-user Gaussian BC with feedback, where both feedback links are used for SK-type coding, is self-secure (satisfying perfect weak secrecy constraint by itself) and may perform the best. We further show that Ozarow’s scheme is in fact a secure finite blocklength coding scheme, and extend it to the static fading SISO and SIMO cases. Finally, the results of this paper are further explained by numerical examples.

For the point-to-point additive white Gaussian noise (AWGN) channel with eavesdropper and feedback, it has already been shown that the secrecy capacity can be achieved by a secret key based feedback scheme, where the channel feedback is used for secret sharing, and then encrypting the transmitted message by the shared key, any capacity-achieving coding scheme for the AWGN channel without feedback is secure by itself, which indicates that the capacity of the same model without secrecy constraint is also an achievable secrecy rate of the AWGN channel with eavesdropper and feedback. Then it is natural to ask: is the secret key based feedback scheme still an optimal scheme for the AWGN multiple-access channel (MAC) with external eavesdropper and channel feedback (AWGN-MAC-E-CF), namely, achieving the secrecy capacity region of the AWGN-MAC-E-CF? In this paper, we show that the answer to the aforementioned question is no, and propose an optimal feedback coding scheme for the AWGN-MAC-E-CF, which combines an existing linear feedback scheme for the AWGN MAC with feedback and the secret key scheme in the literature. The study of this paper provides a way to find optimal coding schemes for AWGN multi-user channels in the presence of external eavesdronner and channel feedback.

Ultra-reliable low-latency communication (URLLC) and reconfigurable intelligent surface (RIS) aided communication are two key technologies in future wireless communications. However, secure URLLC over RIS-adied communication channels receives little attention in the literature. In this paper, we propose finite blocklength (FBL) coding schemes for RIS aided SISO/SIMO/MIMO systems in the presence of an eavesdropper (no direct link between the transceiver), which are based on an existing coding scheme for the point-to-point white Gaussian channel with noiseless feedback. Then, we show that the proposed schemes are self-secure when the blocklengths are larger than certain thresholds. Finally, numerical results show that for given decoding error probability and secrecy level, the required coding blocklengths of our proposed schemes are extremely short, and the secrecy capacities of the RIS-aided systems without channel feedback are significantly enhanced by our feedback schemes.

In this paper, the dirty-tape channel (the white Gaussian channel with causal state interference at the trans-mitter) is revisited by considering a noisy feedback link between the transmitter and receiver. A finite blocklength (FBL) coding scheme is proposed for this model, which is based on the classical Schalkwijk-Kailath (SK) scheme and an existing lattice-based interference canceling scheme. Based on the proposed scheme, an achievable rate for given blocklength and decoding error probability is obtained, and the results of this paper are further illustrated via numerical examples.

In this paper, the two-way full-duplex Gaussian channel (TW-FD-GC) is revisited by considering Gaussian state interference non-causally known by the corresponding transmitter, which is also called the two-way full-duplex dirty paper channel (TW-FD-DPC). We propose a novel coding scheme for the TW-FD-DPC, which perfectly eliminates the effect of the state interference. Numerical result shows that for a fixed decoding error probability, the encoding-decoding complexity of this scheme is extremely low.

In this paper, the role of feedback in two-way full-duplex Gaussian channel (TW-FD-GC) is revisited. First, we propose a practical coding scheme for the TW-FD-GC, which is based on the noisy type of the well-known Schalkwijk-Kailath (SK) feedback scheme. We show that though this scheme cannot achieve the capacity of the TW-FD-GC, the codeword length that achieves desired decoding error probability is extremely short. Then, we further prove that the proposed scheme is secure by itself, i.e., the achievable rate region of the proposed scheme is also an achievablesecrecyrate region of the two-way full-duplex Gaussian wiretap channel (TW-FD-GWTC). In addition, for the TW-FD-GWTC, numerical result shows that thesecrecysum rate of our proposed scheme can be as large as those achieved by existing schemes in the literature for some cases. Next, we extend the proposed scheme to the TW-FD-GC with Gaussian state interference non-causally known by the corresponding transmitter. We show that the interference can be perfectly canceled by this extended scheme. Finally, we prove that this extended scheme is also secure by itself, and numerical result shows that this extended scheme may perform better than the existing ones in the literature.

Recently, induced by incorporating the ubiquitous data collected by AI application, there are more and more demand for transferring data to cloud servers due to the restriction of computing resources of devices. To transfer image data efficiently, neural network (NN) codec can be a wise choice, which can result in higher ratio of compression with similar image quality compared with conventional codec methods. However, when the NN codec is employed in the communication system, it is likely that it can be disturbed by channel distortions. In this paper, we innovatively propose a norm method to measure the NN codec's robustness for certain tasks. And with the aid of this method, we develop a greedy algorithm using gradients to find adversarial samples of certain tasks considering communication system distortions, i.e. channel distortions during compressed image or video transferring to cloud server systems. Aided by the adversarial samples, the NN codec has been proved to have better tolerance of communication distortions that the Top-1 accuracy of the image classification can be improved 1.8%.

The existing finite-rate feedback methods for multiuser MIMO systems suffer from significant performance degradation as well as multiuser diversity loss when users are in moderate mobility. To achieve multiuser diversity for users even in fast mobility, a lower bound for the ergodic signal to interference and noise ratio (SINR) is derived, which serves as a near optimal prediction of the future channel condition. Numerical results show that the proposed scheme far surpasses conventional methods and what is more important, multiuser diversity can be maintained.