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We consider wireless femtocell networks where scheduling of transmissions is coordinated across multiple cells to mitigate interference and deliver fairness and quality of service (QoS). Coordination across multiple cells entails (i) exchange of (serving and interfering) channel information and traffic priority (which is a function of packet delays, average rate, queue length), and (ii) signalling...
Single-radio mesh routers operating on a single channel suffer from low throughput due to collisions. Equipping mesh routers with multiple radios operating on non-overlapping channels can significantly improve the throughput. However, the assignment of channels to radios in a multi-radio mesh network is a challenging task. In this paper, we propose a channel assignment algorithm, TICA (Topology-controlled...
We consider a multicell random beamforming scheme where a cooperative base station (BS) can simultaneously beamform to its served (local) user via utilizing perfect channel state information and randomly beamform to its neighboring users. The rationale behind this scheme is to curtail channel information feedback in a multicell MIMO system. By sharing antenna degree of freedom and transmit power at...
Femtocells promise to increase the number of users served in a given macrocell by creating indoor hotspots connected to the mobile operator network via cheap backhaul links (i.e., the Internet). However, the interference created by the femtocell transmissions may critically impair the performance of the macrocell users. This effect can be potentially alleviated via so called open-access home base...
A common concept to mitigate the effects of spectrum scarcity is to allow opportunistic dynamic spectrum access (DSA) to licensed frequency bands. In this context, the license holder may experience a decrease in the performance of its network. For cellular networks this may lead to unwanted coverage holes at locations where the secondary-induced interference is too strong. In this paper we propose...
Considering a video/audio server deployed on the gateway node of a wireless mesh network, a large amount of clients distributed on various mesh routers may wish to receive multimedia streams from the server simultaneously. A multicast tree would be a suitable mechanism to deliver subscribed streams to all the destinations. For multi-radio and multi-channel wireless networks, however, it is better...
This paper deals with the use of jamming transmission for physical layer security in wireless networks with power constraints. An approach that incorporates a dirty-paper coding (DPC) design with the jamming process under a total power constraint is investigated. The proposed scheme enables both the source and the jammer nodes to create intentional interference on the eavesdropper node and significantly...
This paper is concerned with the game-theory approach in designing the multiuser downlink beamformers in multicell systems. Sharing the same physical resource, the base station of each cell wishes to minimize its transmit power subject to a set of target signal-to-interference-plus-noise ratios (SINRs) at the multiple users in the cell. In that process, each base station determines its optimal downlink...
With the active evolvement of 3GPP long term evolution (LTE) system, advanced multi-user multiple-input multiple-output (MU-MIMO) transmission schemes attract more and more interests in engineering field. However, in order to bring advanced MU-MIMO techniques from theory to practice, there are two major obstacles to overcome, i.e., how to obtain accurate channel state information at the transmitter...
Power control is an important concern in cognitive radio networks in which secondary users opportunistically compete to access spectrum allocated to primary users. However, most existing studies in this regard have ignored the impact of primary users and only considered the interactions between secondary users. In this study the novel primary-secondary game-theoretic scheme in is extended to realistic...
Cooperative awareness is established by vehicles exchanging their status frequently. In situations where a high number of vehicles access the communication channel with high frequency, communication and cooperative awareness suffer from increased packet loss. So far, forwarding of beacons focuses on extending the range of V2V communication which is not necessarily needed in most scenarios. In this...
We consider a relay network with multiple users and propose a signal-to-interference and noise-ratio (SINR) balancing based relay signal forwarding scheme. Each relay receives a combined signal from multiple sources and processes it using a complex valued scalar and transmits towards the destinations so that the SINR at the receiver of each user is maximised. We solve this problem using semidefinite...
Frequency agility is considered as an indispensable feature of next-generation wireless sensor networks (WSNs), which will have to cope with highly interfered environments due to the increasing diffusion of wireless devices operating in unlicensed bands. In this paper we investigate some design aspects related to spectrum sensing in “cognitive” WSNs, relating the duration of sensing time to the probability...
In the next generation mobile communication systems, high speed data services are expected. However, an unacceptably high transmit power is required. Multi-hop technique can solve this problem. To reduce the transmit power, while increasing the transmission data rate, we have proposed a wireless multi-hop virtual cellular network (VCN). In this paper, we introduce the multi-hop VCN for high speed...
The effect of the head size on the ear-to-ear radio-propagation channel as a part of a body-centric wireless network is examined. The channel quality is evaluated at 2.45 GHz in terms of path gain (|S21|) between two monopole antennas that are placed normal to the surface of the head. The investigation is done by measurements and HFSS simulations. It is found that the characteristics of the head may...
Inter-cell interference is a main reason for performances degradation in cellular systems due to usage of same frequency channels in neighbouring cells. OFDMA and SC-FDMA, used as multiple access techniques in LTE, enables fractional frequency reuse as one of the methods for Inter-cell interference cancellation. Several papers are already treating influence of fractional frequency reuse on performances...
Load balancing in wireless mesh networks (WMNs) is one of the major design goals for any routing protocol. In this paper, we propose AntMesh, an efficient data forwarding scheme, specifically designed for load balancing in multi-radio infrastructure WMNs. As the foundation of AntMesh, we use Ant Colony Optimization (ACO) in which artificial ants (agents) perform the routing and data forwarding to...
Recently, several multi-channel MAC protocols have been proposed for wireless sensor networks (WSNs) to improve network capacity and boost energy efficiency. In addition, cooperative multiple-input multiple-output (MIMO) technique has been shown to be able to significantly enhance the energy efficiency of WSNs if properly configured. However, these two promising techniques have not been jointly utilized...
Receive beamfoming techniques play an important role in MIMO communications systems as means to mitigate interference and enhance the link quality. Multipoint receive beamforming methods are expected to provide additional gains in systems employing advanced coordinated multipoint processing. Due to its importance, receive beamforming has been studied extensively in the literature. The optimal detection...
A prototype of an interference rejection system for OFDM communication was implemented. It comprises a four antennas adaptive receive beam-former with null steering capability and a turbo coded OFDM communication link, both implemented as Globally Asynchronous Locally Synchronous (GALS) system in FPGA, and the analog and radio frequency modules. The system performed well in a radio-frequency laboratory...
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