Mai Vu

Tufts University | Tufts · Department of Electrical and Computer Engineering

As next generation cellular networks become denser, associating users with the optimal base stations at each time while ensuring no base station is overloaded becomes critical for achieving stable and high network performance. We propose multi-agent online Q-learning (QL) algorithms for performing real-time load balancing user association and hando...

Intelligent reflecting surfaces (IRSs) are a promising technology for future-generation wireless networks by extending coverage region to blind spots and increasing mmWave propagation paths in non-line of sight environments. User association (UA) in dense millimeter wave (mmWave) networks is vital to characterizing connections among base stations (...

Distributed learning can lead to effective user association with low overhead, but faces significant challenges in incorporating load balancing at all base stations (BS) because of coupling constraints. In this paper, we propose a distributed multi-agent deep Q-learning model for user association to satisfy the load balancing constraint at every BS...

The integration of millimeter wave and higher frequencies into 5G and 6G networks raises concerns about potential conflicts with existing satellite services that operate in the same or adjacent frequency bands. This paper analyzes the co-channel interference and out-of-band (OOB) leakage power from terrestrial networks to satellites, and offers des...

Intelligent reflecting surface (IRS) has recently emerged as a promising technology for Internet-of-Things (IoT) networks to provide massive connectivity. In this paper, we propose IoT user selection methods and beamforming designs in a multi-IRS aided IoT network. Specifically, we aim to jointly optimize the base station (BS) beamforming, IRS refl...

Using a multi-armed bandit technique, we propose centralized and semi-distributed online algorithms for load balancing user association and handover in mmWave-enabled networks. Load balancing at all base stations (BSs) imposes explicit constraints that makes the actions of all user equipment (UEs) co-dependent, a challenging twist to reinforcement...

The wide deployment of IoT sensors has enabled the collection of very big time series across different domains, from which advanced analytics can be performed to find unknown relationships, most importantly the correlations between them. However, current approaches for correlation search on time series are limited to only a single temporal scale an...

Wireless charging coupled with computation offloading in edge networks offers a promising solution for realizing power-hungry and computation intensive applications on user-devices. We consider a multi-access edge computing (MEC) system with collocated MEC server and base-station/access point (AP), each equipped with a massive MIMO antenna array, s...

We consider multi-input convolutional codes with unequal error protection (UEP) among the inputs. Using conventional metrics including the free input distance and free input sum weight as a measure for UEP degree, we design efficient and optimal algorithms to evaluate these metrics for any number of inputs. Next, we discuss several ambiguities aris...

Wireless charging coupled with computation offloading in edge networks offers a promising solution for realizing power-hungry and computation intensive applications on user devices. We consider a mutil-access edge computing (MEC) system with collocated MEC servers and base-stations/access points (BS/AP) supporting multiple users requesting data com...

This paper introduces a low complexity and optimum decoding algorithm for tail-biting codes. The algorithm, called Selective Initialization Viterbi Algorithm (SIVA), performs the Viterbi algorithm (VA) iteratively and assigns at each iteration the initial costs for a selective set of states to satisfy a necessary condition. The process of selecting...

Wireless charging coupled with computation offloading in edge networks offers a promising solution for realizing power-hungry and computation intensive applications on user devices. We consider a multi-access edge computing (MEC) system with collocated MEC server and base-station/access point, each equipped with a massive MIMO antenna array, suppor...

We study distributed user association in 5G and beyond millimeter-wave enabled heterogeneous networks using matching theory. We propose a novel and efficient distributed matching game, called early acceptance (EA), which allows users to apply for association with their ranked-preference base station in a distributed fashion and get accepted as so...

We study distributed user association in 5G and beyond millimeter-wave enabled heterogeneous networks using matching theory. We propose a novel and efficient distributed matching game, called early acceptance (EA), which allows users to apply for association with their ranked-preference base station in a distributed fashion and get accepted as soon...

Using a reinforcement learning multi-armed bandit (MAB) technique, we design a centralized and a semi-distributed online algorithms, for performing load balancing user association in multi-tier heterogeneous cellular networks. The proposed algorithms guarantee user association solutions that satisfy load balancing constraints among the base station...

Wireless charging coupled with computation offloading in edge networks offers a promising solution for realizing power-hungry and computation intensive applications on user devices. We consider a mutil-access edge computing (MEC) system with collocated MEC servers and base-stations/access points (BS/AP) supporting multiple users requesting data com...

We study a wireless edge-computing system which allows multiple users to simultaneously offload computation-intensive tasks to multiple massive-MIMO access points, each with a collocated multi-access edge computing (MEC) server. Massive-MIMO enables simultaneous uplink transmissions from all users, significantly shortening the data offloading time...

We study a wireless edge-computing system which allows multiple users to simultaneously offload computation-intensive tasks to multiple massive-MIMO access points, each with a collocated multi-access edge computing (MEC) server. Massive-MIMO enables simultaneous uplink transmissions from all users, significantly shortening the data offloading time...

We study the distribution of the interference power in a millimeter wave (mmWave) cellular network. Such interference is random and highly dependent on the employed transmission technique, as well as the varying channel conditions and the varying association between users and base stations. Traditional networks at lower frequencies usually employ o...

In this paper we examine the use of matching theory for user association in millimeter wave (mmWave)-enabled cellular heterogeneous networks (HetNets). In a mmWave system, the channel variations can be fast and unpredictable, rendering centralized user association potentially inefficient. We propose an efficient distributed matching algorithm, call...

In this paper we examine the use of matching theory for user association in millimeter wave (mmWave)-enabled cellular heterogeneous networks (HetNets). In a mmWave system, the channel variations can be fast and unpredictable, rendering centralized user association potentially inefficient. We propose an efficient distributed matching algorithm, call...

Recent development in computing, sensing and crowd-sourced data have resulted in an explosion in the availability of quantitative information. The possibilities of analyzing this so-called Big Data to inform research and the decision-making process are virtually endless. In general, analyses have to be done across multiple data sets in order to bri...

Recent development in computing, sensing and crowd-sourced data have resulted in an explosion in the availability of quantitative information. The possibilities of analyzing this so-called "Big Data" to inform research and the decision-making process are virtually endless. In general, analyses have to be done across multiple data sets in order to b...

User association is necessary in dense millimeter wave (mmWave) networks to determine which base station a user connects to in order to balance base station loads and maximize throughput. Given that mmWave connections are highly directional and vulnerable to small channel variations, user association changes these connections and hence significantl...

This paper investigates wireless information and power transfer in a full-duplex MIMO relay channel where the self-sustained relay harvests energy from both source transmit signal and self-interference signal to decode and forward source information to a destination. We formulate a new problem to jointly optimize power splitting at the relay and pr...

We present a novel approach to maximize the transmission rate in a MIMO relay system, where all nodes are equipped with multiple antennas and the relay is self-sustained by harvesting energy using a non-uniform power splitting method. By deriving a closed-form solution for the optimal power splitting ratios for harvesting at the relay and the optim...

We design user-assisted relaying strategies and analyze their performance in a multiple-input multiple-output (MIMO) uplink cellular network. In user-assisted relaying, the base station (BS) serves a user-equipment (UE) using a transmission scheme adaptive between direct and relaying according to a cooperation strategy. The proposed relaying transm...

User association determines which base stations a user connects to, hence affecting the amount of network interference and consequently the network throughput. Conventional user association schemes, however, assume that user instantaneous rates are independent of user association. In this paper, we introduce a new load-aware user association scheme...

User association is necessary in dense millimeter wave (mmWave) networks to determine which base station a user connects to in order to balance base station loads and maximize throughput. Given that mmWave connections are highly directional and vulnerable to small channel variations, user association changes these connections and hence significantl...

User association determines which base stations a user connects to, hence affecting the amount of network interference and consequently the network throughput. Conventional user association schemes, however, assume that user instantaneous rates are independent of user association. In this paper, we introduce a new load-aware user association scheme...

This paper introduces and studies a model in which two relay channels interfere with each other. Motivated by practical scenarios in heterogeneous wireless access networks, each relay is assumed to be connected to its intended receiver through a digital link with finite capacity. Inner and outer bounds for achievable rates are derived and shown to...

We propose analytical models for the interference power distribution in a cellular system employing MIMO beamforming in rich and limited scattering environments, which capture non line-of-sight signal propagation in the microwave and mmWave bands, respectively. Two candidate models are considered: the Inverse Gaussian and the Inverse Weibull, both...

We propose a composite decode-forward (DF) scheme for the two-way relay channel in the fullduplex mode by combining coherent, independent and partial relaying strategies. The relay partially decodes each user’s information in each block and forwards this information coherently with the source user to the destination user in the next block as in blo...

In this paper, we examine message prioritization in terms of both rate and reliability in the two-way relay channel using decode-forward relaying. Each source sends both a low priority message and a high priority message. We design a scheme that routes the high priority messages through the relay but not necessarily the low priority message dependi...

We propose a novel probabilistic model for the interference power distributions in a cellular network employing MIMO beamforming in mmWave spectrum. Considering both line-of-sight (LOS) and non-line-of-sight (NLOS) propagations, we use the Gamma distribution for LOS interference power, and propose a mixture of the Inverse Gaussian and Inverse Weibu...

We establish a novel link-state regime result for a composite decode-forward (DF) two-way relaying scheme with a direct link. During transmission, our scheme combines block Markov coding and an independent coding scheme that resembles network coding at the relay. A developed novel approach optimizes the composite technique by analyzing the dual var...

We consider a composite independent and coherent decode-forward (DF) relaying scheme and analytically evaluate its outage performance over Rayleigh fading channels. We consider the link regimes under which the optimal strategy can be direct transmission, independent DF (IDF), or coherent DF (CDF), depending on the relation among 3 links in a relay...

In this paper, we re-examine the basic relay channel under the decode-and-forward (DF) strategy. Contrary to the established belief that block Markov coding is always the rate-optimal DF strategy, we find that under certain channel conditions (a link regime), independent signaling between the source and relay achieves the same transmission rate wit...

We analyze the impact of user cooperation in the two-way relay channel (TWRC) by letting each user send a quantized version of its received signal in addition to its own message. The proposed scheme is based on quantize-forward (QF) and partial decode-forward (PDF) relaying with sliding window decoding at the relay, and QF relaying with backward de...

In this paper, we analyze a full-duplex composite decode-and-forward scheme for the two-way relay channel in a Rayleigh fading environment. Designed from a link-state perspective, this scheme combines both block Markov and independent coding, and yields relay power savings in some link-state regimes. For a given distance configuration of nodes, we...

We propose composite decode-forward (DF) schemes for the two-way relay channel in both the full- and half-duplex modes by combining coherent relaying, independent relaying and partial relaying strategies. For the full-duplex mode, the relay partially decodes each user's information in each block and forwards this partial information coherently with...

We analyze the outage performance of coherent partial decode-forward (pDF) relaying over Rayleigh fading channels in both half- and full-duplex transmissions. In coherent DF relaying, the relay either partially or fully decodes the source message, then coherently forwards the decoded message with the source to the destination. This coherent transmi...

By relying on a wireless backhaul link, relay stations enhance the performance of cellular networks at low infrastructure cost, but at the same time, they can aggravate the interference issue. In this paper, we analyze for several relay coding schemes the maximum energy gain provided by a relay, taking into account the additional relay-generated in...

We analytically evaluate the outage performance of the half-duplex partial decode-forward (PDF) relaying over Rayleigh fading channels. In PDF relaying, the source splits its information into cooperative and private parts, and the relay decodes only the cooperative information then forwards it to the destination coherently with the source. Assuming...

We propose a time-division uplink transmission scheme that is applicable to future-generation cellular systems by introducing hybrid device-to-device (D2D) and infrastructure cooperation. Compared to existing frequency-division schemes, the proposed time-division scheme achieves the same or better spectral efficiency and outage performance with sim...

In this paper, we analyze a composite decode-and-forward scheme for the two-way relay channel with a direct link. During transmission, our scheme combines both block Markov coding and an independent coding scheme similar to network coding at the relay. The main contribution of this work is to examine how link state impacts the allocation of power b...

We use stochastic geometry to analyze the performance of a partial decode-and-forward (PDF) relaying scheme applied in a user-assisted relaying setting where an active user relays data through another idle user in uplink cellular communication. We present the geometric model of a network deploying user-assisted relaying and propose two geometric co...

Relay-based cellular networks are likely to play an important role in the race for energy efficiency. However, potential gains greatly depend on how relay stations are deployed within the cell. Using a geometrical model for energy-efficient analysis, we investigate the impact of the number and location of relays on energy consumption, and its depen...

Relay-aided cooperative communication is a critical component of next generation cellular networks as it improves coverage and boosts system capacity. In this paper, we use stochastic geometry to study the performance of partial decode-and-forward (PDF) relaying through another idle user in uplink cellular communication. We analytically derive the...

We introduce exhaustive message splitting for partial decode-forward in a single-source single-destination relay network with N relays, in which every relay subset has a private message to decode. We apply this idea to a three-relay network and propose a partial decode-forward scheme based on block Markov encoding with exhaustive message splitting...

We consider the uplink transmission over Rayleigh fading channels of two mobiles cooperating to send their information to a base station. We propose a cooperative transmission scheme, derive its achievable rate region and analyze its outage performance. By dividing each transmission block into 3 phases with variable durations, the two mobiles parti...

We extend the primitive relay channel (PRC) introduced by Cover and Kim to a more general scenario where two Gaussian PRC's cause interference to each other. We show that extended hash-and-forward relaying with proper power allocation can achieve bounded gaps to the capacity region of the Gaussian channel in different regimes of channel parameters.

This paper studies a new model for cooperative communication, the interfering relay channels. We show that the hash-forward scheme introduced by Kim for the primitive relay channel is capacity achieving for a class of semideterministic interfering relay channels. The obtained capacity result generalizes and unifies earlier capacity results for a cl...

The performance of a relay-based cellular network is greatly affected by the relay location within a cell. Existing results for optimal relay placement do not reflect how the radio propagation environment can impact system performance. In this paper, we analyze the impact on uplink relaying performance of node distances, relay height and line-of-si...

The Causal Cognitive Interference Channel (CCIC) models realistic causal cognitive communication between two sender-and-receiver pairs, in which the cognitive sender causally obtains a message from the primary sender and helps forward it to the primary receiver while also sending its own message to the cognitive receiver. We propose a new coding sc...

We consider the impact of destination cooperation on improving the achievable rate region in a multiple access channel with joint source-destination cooperation (MAC-SDC). Such cooperation may be appealing in systems with a more powerful destination than the sources, such as the uplink of cellular networks. We propose a coding scheme in which each...

We study a discrete-memoryless relay network consisting of one source, one destination and N relays, and design a scheme based on partial decode-forward relaying. The source splits its message into one common and N+1 private parts, one intended for each relay. It encodes these message parts using Nth-order block Markov coding, in which each private...

In this paper, we analyze and compare several en- coding and decoding techniques for the interference channel with destination cooperation (IC-DC). For the encoding techniques, we consider standard Han-Kobayashi (HK) techniques at both sources as well as quantize-forward (QF) and compress-forward (CF) relaying at the destinations. For the decoding...

This paper shows that the capacity of the relay chan- nel can be asymptotically achieved by allowing relay-destination cooperation. Consider a scheme with rate splitting and second- order superposition block Markov encoding at the source, partial decode-forward (PDF) relaying and joint decoding over two consecutive blocks at the relay, and quantize...

The causal cognitive interference channel (CCIC) is a four-node channel, in which the second sender obtains information from the first sender causally and assists in the transmission of both. We propose a new coding scheme called Han-Kobayashi partial decode-forward binning (HK-PDF-binning), which combines the ideas of Han-Kobayashi coding, partial...

We propose three energy-optimal distributed schemes for the half-duplex relay channel with block fading to maintain a desired source rate. We consider both network energy consumption and consumption of the relay alone, assuming only local channel knowledge. Then, we combine both into a generalized distributed energy-efficient scheme. In these schem...

We design novel partial decode-forward (PDF) schemes for the Gaussian two-way relay channel with direct link. Different from pure decode-forward, each user divides its message into two parts and the relay decodes only one part of each. The relay then generates its codeword as a function of the two decoded parts and forwards to the two users. We pro...

We propose two coding schemes combining decode-forward (DF) and noisy network coding (NNC) with different flavors. The first is a combined DF-NNC scheme for the one-way relay channel which includes both DF and NNC as special cases by performing rate splitting, partial block Markov encoding and NNC. The second combines two different DF strategies an...

The feasibility of having chaos-based communication in a MIMO system is presented. A promising chaotic symbolic dynamics modulation is chosen, and an Alamouti space-time code scheme is used with 2 transmit and 2 receiver antennas. The diversity technique is combined with chaotic modulation to improve the performance of the system. The performance o...

We derive the optimal resource allocation of a practical half-duplex scheme for the Gaussian multiple access channel with transmitter cooperation (MAC-TC). Based on rate splitting and superposition coding, two users transmit information to a destination over 3 phases, such that the users partially exchange their information during the first 2 phase...

We propose an iterative mode-dropping algorithm that optimizes input signals to achieve the sum capacity of the MIMO-MAC with per-antenna power constraint. The algorithm successively optimizes each user's input covariance matrix by applying mode-dropping to the equivalent single-user MIMO rate maximization problem. Both analysis and simulation show...

A relay channel is one in which a Source and Destination use an intermediate Relay station in order to improve communication rates. We propose the study of relay channels with classical inputs and quantum outputs and prove that a "partial decode and forward" strategy is achievable. We divide the channel uses into many blocks and build codes in a ra...

The causal cognitive relay channel (CRC) has two sender-receiver pairs, in which the second sender obtains information from the first sender causally and assists the transmission of both senders. In this paper, we study both the full- and half-duplex modes. In each mode, we propose two new coding schemes built successively upon one another to illus...

Noisy network coding is recently proposed for the general multi-source network by Lim, Kim, El Gamal and Chung. This scheme builds on compress-forward (CF) relaying but involves three new ideas, namely no Wyner-Ziv binning, relaxed simultaneous decoding and message repetition. In this paper, using the two-way relay channel as the underlining exampl...

We explore the issue of the network energy efficiency in relay channels. We first propose a half-duplex decode-forward coding scheme. We then optimize the power allocation to minimize the total power consumption while maintaining a desired source rate. We show that this scheme significantly outperforms direct and two-hop transmissions. Moreover, it...

We consider the role of Wyner-Ziv binning in compress-forward for relay channels. In the one-way relay channel, we analyze a compress-forward scheme without Wyner- Ziv binning but with joint decoding of both the message and compression index. It achieves the same rate as the original compress-forward scheme with binning and successive decoding. The...

Two distinct, but overlapping, networks that operate at the same time, space, and frequency is considered. The first network consists of n randomly distributed primary users, which form an ad hoc network. The second network again consists of m randomly distributed ad hoc secondary users or cognitive users. The primary users have priority access to...

This paper analyzes the impact and benefits of infrastructure support in improving the throughput scaling in networks of n randomly located wireless nodes. The infrastructure uses multiantenna base stations (BSs), in which the number of BSs and the number of antennas at each BS can scale at arbitrary rates relative to n . Under the model, capacity...

We consider the full-duplex two-way relay channel with direct link between two users and propose two coding schemes: a partial decode-forward scheme, and a combined decode-forward and compute-forward scheme. Both schemes use rate-splitting and superposition coding at each user and generate codewords for each node independently. When applied to the...

This paper provides comprehensive coding and outer bound for the half-duplex multiple access channel with generalized feedback (MAC-GF). Two users communicate with one destination over a discrete memoryless channel using time division. Each transmission block is divided into 3 time slots with variable durations: the destination is always in receive...

We study a cooperative communication system consisting of two users in half duplex mode communicating with one destination over additive white Gaussian noise (AWGN). Cooperation is performed between the two users by partial decode-forward relaying over 3 time slots with variable duration. During the first two slots, each user alternatively transmit...