Waheed ur Rehman

On scheduling algorithm for device-to-device communication in 60 GHz networks

The world is witnessing a tremendous increase in data demands which is subject to the new emerging technologies, applications and services. 60 GHz communication network is one of such technology, claiming data rate in multi-gigabits. In this paper, we propose a scheduling algorithm for device-to-device 60 GHz network having directional antennas. The proposed algorithm utilizes the vertex coloring scheme and is optimized to improve system throughput. A threshold minimum distance between conflicting flows is used to keep the accumulative interference limited. Also, when there are conflicts among different flows, those with better data rate prospects will be scheduled priorly. Simulation results show that our scheme has brought significant improvement to system throughput almost by 19% and average flow number per slot is improved by 12%, as compared to other scheduling algorithms.

Tradeoff between energy efficiency and spectral efficiency in two-way relay network

Energy efficiency (EE), which is an important performance indicator as well as spectral efficiency (SE), has drawn increasing attention for the future wireless network design due to the explosive growth of energy consumption. In this paper, we investigate the relationship between EE and SE in two-way multiple relays system with analog network coding. Considering the quality-of-service (QoS) of two transceivers and transmit power constraints of each node, a fundamental EE-SE tradeoff relationship is set up for the first time in two-way multiple relay network. Then we prove that EE is a strictly quasi-concave function, which will have a global maximum. Besides, the iterative algorithm is proposed to search the optimal bidirectional SE for the maximum EE with all condition constraints. In practical system, other factors will also change the fundamental tradeoff relationship between EE and SE, which is also analyzed in this paper. The Monte-Carlo simulation is provided to demonstrate the validity of our theoretical analysis.

Capacity Enhancement in 60 GHz Based D2D Networks by Relay Selection and Scheduling

Millimeter-wave or 60 GHz communication is a promising technology that enables data rates in multigigabits. However, its tremendous propagation loss and signal blockage may severely affect the network throughput. In current data-centric device-to-device (D2D) communication networks, the devices with intended data communications usually lay in close proximity, unlike the case in voice-centric networks. So the network can be visualized as a naturally formed groups of devices. In this paper, we jointly consider resource scheduling and relay selection to improve network capacity in 60 GHz based D2D networks. Two types of transmission scenarios are considered in wireless personal area networks (WPANs), intra and intergroup. A distributed receiver based relay selection scheme is proposed for intragroup transmission, while a distance based relay selection scheme is proposed for intergroup transmission. The outage analysis of our proposed relay selection scheme is provided along with the numerical results. We then propose a concurrent transmission scheduling algorithm based on vertex coloring technique. The proposed scheduling algorithm employs time and space division in mmWave WPANs. Using vertex multicoloring, we allow transmitter-receiver () communication pairs to span over more colors, enabling better time slot utilization. We evaluate our scheduling algorithm in single-hop and multihop scenarios and discover that it outperforms other schemes by significantly improving network throughput.

Relay selection schemes in millimeter-wave WPANs

Relay devices can significantly overcome signal blockage and propagation loss characteristics of millimeter wave based wireless personal area networks (WPANs). In this paper, we consider inter and intra-group communication scenarios and proposed two relay selection schemes for each case. Furthermore, outage probability analysis is provided and is utilized to compare our proposed schemes with direct transmission and fixed node relay scheme. Simulation results show that our proposed schemes significantly improve outage probability and system throughput.

GA based optimal resource allocation and user matching in device to device underlaying network

Device-to-Device (D2D) communication is expected to play a pivotal role in the next generation of LET/LTE-A network, which is able to improve the system throughput by reusing the cellular resource. However, the caused intra-cell interference is quite a challenging issue in D2D underlaying cellular network. In this paper, we propose a Genetic Algorithm (GA) based joint resource allocation and user matching scheme (GAAM) to minimize the intra-cell interference while maximize the system throughput. With the proposed scheme, we firstly analyze and formulate the user matching scheme in mathematical model, during which resources are allocated to cellular user equipments (CUE) and further be shared by D2D UEs (DUE) in a coordinated manner. Secondly, GA is used to globally search the optimal user matching solution to maximize the system throughput. Furthermore, with some innovations, the more efficient GAAM can be applied to a much wider scope in D2D underlying network. Simulation results show that GAAM achieves nearly the same system throughput comparing to the exhaustive method, which is 30 Mbps bigger than the traditional greedy algorithm based allocation and matching scheme (GreedyAM).

Vertex multi-coloring scheduling algorithm for concurrent transmission in 60-GHz networks

Communication in 60-GHz frequency exhibits unique characteristics that are unavailable in traditional lower frequencies. Tremendous propagation loss together with oxygen absorption characteristics helps localize interference and encourages concurrent transmission. It is observed that in short-range, high-speed communication network, (Tx, Rx) pair tends to come close to each others. The network can be seen as naturally formed group of devices, which shared mutual interests. In Such networks, it is argued that throughput mainly depends on scheduling algorithms rather than transmission power control. In this paper, we proposed a concurrent scheduling algorithm based on vertex coloring technique. The proposed algorithm employs time and space division in scheduling in 60-GHz networks. Using vertex multi-coloring, we allow (Tx - Rx) communication pairs to span over more colors, enabling better time slot utilization. Since we use directional antennas, we extend distance based space division between two flows by considering angel between them. Since, data rate in 60-GHz mainly depends on transmission links, distance based relay selection algorithm is also proposed. We evaluate our scheduling algorithm in single-hop and multi-hop scenarios and discover that it outperforms traditional TDMA and greedy algorithm by significantly improving network throughput.

Opportunistic relay selection and outage performance analysis for 60GHz wireless system

In this paper, we investigates idle user as a potential relay node to improve performance of system in 60 GHz millimeter wave wireless communication. We analyze the performance of the relay assist dual-hop transmission, and derive a closed form outage probability (OP) solutions. To minimize the OP for relay position selection, we formulate the objective task as a minimization problem. This position is a function of the transmit power, path loss and height of the access point (AP), and it can be obtained numerically. In addition, we compare the performance for different transmission schemes, including optimal user relay node (URN) assisted transmission, dual-hop transmission assisted by a fixed relay node (FRN), and the single-hop direct transmission. The simulation results have demonstrated that the optimal relay position selection transmission can provide significant higher throughput than FRN assisted transmission as well as direct transmission, therefore it is very promising for the future 60 GHz wireless systems.

A dynamic coalition formation framework for interference management in dense small-cell networks

In response to the drastic increase in the traffic loads being served by existing cellular wireless networks, small cells are envisioned as a promising solution to extend the coverage and offload the traffic from the overburdened macrocells. However, the interference management amongst densely deployed small cells remains a technical challenge. In this paper, a neighbourhood cooperation-based interference mitigation scheme is proposed. By forming coalitions, the transmissions of small-cell base stations SBSs within the coalition are coordinated, and the co-tier interference amongst them is thus suppressed. Considering the facts that SBSs are selfish and rational, the cooperative behaviour of the neighbourhood SBSs is formulated as a coalition game in partition form. To achieve a final stable coalition structure, the concept of recursive core is first introduced. Then a simple distributed merge-only algorithm is proposed, and its performance, in terms of stability, convergence and complexity, is theoretically analysed. The dynamic process of the coalition formation is further investigated. Simulation results show that the proposed algorithm can improve the individual throughput of SBS by 5.6% and 27.3%, respectively, when compared with the classical and non-cooperative cases. Copyright

Cooperative Data Aggregation and Dynamic Resource Allocation for Massive Machine Type Communication

The accommodation of massive machine-type communication (mMTC) in cellular networks brings up serious technical challenges due to concurrent massive access of MTC devices. These challenges may further be aggravated by the presence of delay tolerant and intolerant services in an MTC network. This paper proposes a cooperative data aggregation (CDA) scheme by employing fixed data aggregator (FDA) and multiple mobile data aggregators (MDAs) to cater MTC devices having variable quality of service (QoS) requirements. In this vein, a distributed MDA selection algorithm is also proposed to designate appropriate user equipment as aggregator. The proposed CDA scheme effectively caters the massive access and provides ubiquitous availability of the aggregating devices in the MTC network. In addition, the limited channel resources impel an FDA to schedule resources besides data aggregation. Therefore, a resource allocation scheme is also proposed to dynamically allocate channels to the MTC devices subject to their QoS requirements. The proposed resource scheduling scheme ensures that transmission requests from delay intolerant MTC devices are contented on priority basis. The proposed CDA and dynamic resource scheduling schemes are analyzed and compared with the existing data aggregation and resource scheduling schemes, respectively. The numerical results corroborate that our proposed CDA scheme in conjunction with dynamic resource allocation improves the outage probability, energy efficiency, and system capacity by 30%, 25%, and 44%, respectively, as compared to the single FDA scheme.

Receiver based distributed relay selection scheme for 60-GHz networks

Networks based on 60-GHz promise data rates in gigabits and show least tolerance towards signal blockage. In addition to severe propagation loss, signal blockage may result in an attenuation upto 40dB. Distributed relay selection scheme is proposed in this paper to cater for signal attenuation. By maintaining a table containing details about interference measurements and neighboring devices, a receiver device determines an optimal relay for its active transmission. Furthermore, outage probability analysis is provided and is utilized to compare our proposed scheme with direct transmission and fixed node relay scheme. Simulation results show that our proposed scheme significantly improves outage probability and system throughput.