Hamidreza Bagheri

Novel concepts for device-to-device communication using network coding

Device-to-device communication is currently a hot research topic within 3GPP. Even though D2D communication has been part of previous ad hoc, meshed and sensor networks proposals, the main contribution by 3GPP is that the direct communication among two devices is carried out over a dynamically assigned, licensed spectrum; thus, it is under full control of the cellular network. D2D communication creates a market potential for new services, new approaches to efficient spectrum use, and security concepts. This is especially true if D2D communication is extended to larger communication groups organized in meshed clusters. In this article, we discuss the potential and shortcomings of D2D communication as proposed today, advocating for the use of network coding as an enabling technology for enhanced security and communication efficiency using the PlayNCool and CORE protocols as key examples to deliver smarter D2D systems.

Mobile clouds: Comparative study of architectures and formation mechanisms

In this paper, we investigate cooperative architectures and cloud formation mechanisms within the concept of mobile clouds, where multi-standard multi-radio devices in close proximity communicate to each other over short-range radio links while preserving connectivity to the overlay cellular network. Four architecture approaches are considered, namely a central cellular controlled, a cloud leader based as well as two novel hybrid schemes. We develop models and derive analytical expressions for the performance of the studied architectures. The performance of cloud formation mechanisms for these architectures is then compared. We show that the proposed hybrid mechanisms outperform the basic approaches in terms of control message overhead, cloud formation latency and energy consumption.

D2D-Based Mobile Clouds for Energy- and Spectral-Efficient Content Distribution

Over the recent years, the rapid development and penetration of the new and powerful mobile device generation (e.g., smart phones and tablets) have unsurprisingly increased mobile data traffic to new heights, nearly doubling it each year. As reported by Cisco, the overall mobile data traffic will grow to 11.2 Exabyte per month by 2017 [1].

A resource allocation mechanism for enhancing spectral efficiency and throughput of multi-link D2D communications

In this paper, we consider downlink resource allocation of a cellular user to group of device-to-device (D2D) communication pair to enhance the overall system throughput and achieve higher spectral efficiency in mobile cloud. A mobile cloud can be defined as an opportunistic cooperative cluster of wireless devices in close proximity which are capable to communicate to other devices while preserving their connection to an overlay cellular access network (i.e., eNB), simultaneously. Thus this study considers D2D communications from a novel and wider perspective, assuming that multiple D2D communication links are simultaneously supported. We model, formulate and analyze the overall throughput of the mobile cloud as the function of distance between communication devices when the D2D pairs communicate in cellular, dedicated and reuse modes. In cellular and dedicated modes there is no severe intra-cell interference but for the reuse mode we propose an innovative and practical downlink resource allocation mechanism to coordinate the interferences and maximize the system sum-rate when several D2D pairs communicate by reusing the resources of a cellular user. In fact, the eNB as the centralized decision-maker selects a cellular user equipment (UE) and group of D2D pairs to communicate by reusing the downlink resources of the selected cellular UE while it guarantees the SINR at both the cellular and D2D receivers. Numerical results show that by exploiting the proposed mechanism we can achieve the aforementioned goals.

Energy and delay efficient strategies for content distribution using mobile-to-mobile cooperation

In this paper we consider the content distribution to a set of mobile users interested in the same content. We use the concept of mobile clouds, which exploits cooperation between mobile terminals over the low-power short-range links. We propose, formulate and investigate the energy efficiency and delay of four realistic cooperative content delivery strategies. The derived results, through analysis of mathematical models and simulations, demonstrate around 65% to 95% energy saving gain in mobile cloud strategies compared to conventional multicasting. We also show that using mobile clouds, content distribution delay can be reduced for up to 85%.

A self-organizing approach to malicious detection in leader-based mobile ad-hoc networks

Task-based self-organizing algorithms have been proposed as a solution for the management of mobile ad-hoc networks (MANETs). Such algorithms assign tasks to nodes by sequentially selecting the best nodes as leaders. Since the correct functionality of such algorithms depends on the truthfulness of participant nodes, any misbehavior can disrupt the operation of the network due to absence of a centralized monitoring unit. In this paper, we consider the problem of malicious behavior in leader-based MANETs. Current solution analyzes the behavior of the leader by means of some checker nodes. This approach is vulnerable since a malicious checker can ruin the character of a normal behaving leader, and declare it as a malicious one. We propose an efficient self-organizing mechanism which can detect a malicious behaving leader, while protecting a normal behaving leader from being declared as a malicious node. In addition, our mechanism is designed with no constraints on leader selection algorithm, which makes it applicable to any kind of leader-based network. We also provide several simulation results, showing that our proposed mechanism is efficient and effective even for large MANETs.

An energy-efficient leader selection algorithm for cooperative mobile clouds

In this paper, we propose and study a context-aware leader selection algorithm within the concept of mobile clouds. We deploy a dedicated Cooperative Control Server (CCS) to assist and manage the process of leader selection more efficiently. The proposed algorithm collects data regarding instantaneous conditions of Mobile Terminals (MTs) and their radio environment; and then computes and assigns a rank to each MT. The ranks calculated based on a combination of different context-related parameters and corresponding weighting factors, allow selecting the leader. Furthermore, the energy efficiency and stability of the selected leaders is investigated for different parameter values through simulations. The results indicate that the proposed algorithm can achieve great energy saving in cooperative scenarios through proper leader selection.

Energy and delay efficient cooperative media content download

The advent of smartphones has brought about a new change in the traffic pattern of mobile users, for instance, there is a growing demand for high quality media content. In this paper, we consider a group of users within proximity of each other, who are interested in downloading the same content. Instead of the conventional cellular method of downloading the same content independently from the base station (BS), the group of users can exploit cooperative downlink strategies in a framework that involves both cellular and short-range communications. A few of such two-stage cooperative downlink strategies are studied in this paper. The results show that a significant energy saving of approximately 60% and a maximum possible delay reduction of 57% on an average, can be achieved by the proposed cooperative strategies.

An incentive-based leader selection mechanism for mobile ad-hoc networks (MANETs)

In this paper, we study the problem of leader selection in the presence of selfish nodes in mobile ad-hoc networks (MANETs). In order to encourage selfish nodes to assume the leadership role, some form of incentive mechanism is required. We present an incentive-based leader selection mechanism in which incentives are incorporated in the form of credit transfer to the leader, which motivates nodes to compete with each other for assuming the leadership role. The competition among nodes is modeled as a series of one-on-one incomplete information, alternating offers bargaining games. Furthermore, we propose an efficient algorithm in order to reduce the communication overhead imposed on the network for selecting a new leader, in case the current leader is disconnected from the network due to reasons such as mobility and battery depletion. Simulation results show that the proposed mechanism not only increases the overall lifetime of a network, but also decreases the amount of imposed communication overhead on the network in comparison with the traditional leader selection algorithms.

A low‐complexity QoS aware resource allocation algorithm for multi pair device‐to‐device (D2D) communications

Device-to-device (D2D) communication underlaying cellular networks is considered a promising technology to enhance network throughput, spectral efficiency, and performance of next generation networks. However, these potential gains hinge on the exploiting mechanism for resource sharing between cellular users (CUs) and D2D pairs. In this paper, we analytically formulate the problem of resource sharing as an optimization problem to maximize network throughput while guaranteeing the required quality-of-service (QoS) for both cellular and D2D users. We propose a low-complexity four-step resource allocation algorithm to address the optimization problem. We exploit a distance-based method to derive a resource reuse candidacy graph (RCG) and three exclusive regions (ERs) to evaluate the suitability of resource sharing between each CU and D2D pair. Then, we use a paring mechanism to find the optimal set of D2D pairs for spectrum sharing with each CU to maximize network throughput. The performance of the proposed algorithm is investigated in terms of network throughput, outage probability, and computational complexity. Numerical results show that the proposed algorithm provides high throughput and spectrum utilization with low complexity while efficiently guaranteeing QoS for CUs and D2D pairs.