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A multi-hop wireless transmission system employing both half duplex and imperfect full duplex relays is proposed. In this scheme, which uses Ksub-channels for transmission and reception over Rayleigh fading channels, we aim to mitigate the most dominant source of interference in each node by allocating different sub-channels to various groups of nodes. The outage probability of the proposed scheme...
This paper proposes a space division multiplexing aided opportunistic spectrum access (SDM-OSA) scheme for cognitive radio networks by exploiting the spatial signal processing ability provided by multiple antennas. With the scheme, cognitive transmission could be carried out using SDM even though there is no idle spectrum resource available. We make further discussion about antenna requirements for...
Kolmogorov-Smirnov (K-S) test-a non-parametric method to measure the goodness of fit, is applied for automatic modulation classification (AMC) in this paper. The basic procedure involves computing the empirical cumulative distribution function (ECDF) of some decision statistic derived from the received signal, and comparing it with the CDFs of the signal under each candidate modulation format. The...
Uplink scheduling for relay stations in mobile multi-hop relay network has not been widely addressed in the literature under common belief that downlink traffic overwhelms uplink traffic. Recently, data traffic from user created content (UCC) is rapidly growing with a potential to create a huge amount of uplink (UL) traffic. Overlapped resource allocation in uplink transmission allows MSs attached...
This paper addresses the design of optimal and near-optimal detectors in an interference channel with fading and with additive white Gaussian noise (AWGN), where the transmitters employ discrete modulation schemes as in practical communication scenarios. The conventional detectors typically either ignore the interference or successively detect and then cancel the interference, assuming that the desired...
This paper focuses on the coexistence problem of multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) systems and current radio systems such as IEEE802.11a. Aiming at improving the performance of MB-OFDM UWB, we attempt to avoid interferences from IEEE802.11a systems. The cognitive radio (CR) technology is introduced to detect the distribution of co-channel interferences...
We introduce an opportunistic interference mitigation (OIM) protocol for cellular networks, where a user scheduling strategy is utilized in uplink K-cell environments with time-invariant channel coefficients and base stations (BSs) having M receive antennas. In the OIM scheme, each BS opportunistically selects a set of users who generate the minimum interference to the other BSs. We consider two OIM...
In current wireless standards like 3GPP LTE or IEEE 802.16 / WiMAX multiple access is based on orthogonal signalling using single-carrier frequency-division multiple access (SC-FDMA) or orthogonal frequency-division multiple access (OFDMA). Links between a base station and different terminals use mutually orthogonal radio resources. This paper studies potential gains in average cell throughput by...
In this paper, we propose a novel low-complexity, multiple feedback successive interference cancellation (SIC) strategy for uncoded multiple-input multiple output (MIMO) spatial multiplexing systems. Since the complexity of the ML and the existing near ML algorithms such as the sphere decoder (SD) is still high in systems with bad channel conditions and/or low signal-noise ratio (SNR), there is a...
This paper proposes a fast frequency-hopping M-ary frequency-shift keying dynamic multiple-access (FFH/MFSK DMA) scheme for application in cognitive radios (CRs). For characterising the performance of the FFH/MFSK DMA systems, primary users (PUs) are assumed to become active according to a Poisson process. In our FFH/MFSK DMA system, the noncoherent majority vote assisted single-user detector (MV-SUD)...
We consider distributed Inter-Cell Interference Coordination based on rate splitting and interference cancellation. Link adaptation is performed based on Channel Quality Information both on the desired link and on links towards interference victims. A transmitted message is split into a private and a public part. The private part is decodable only by the intended receiver, whereas the public part...
In this paper, our aim is to use a Kerdock codebook-based precoding scheme for a multi-user MIMO broadcast channel with channel state information at the base station and limited feedback. The main reason for applying a Kerdock code in place of optimal precoding is to reduce VLSI implementation complexity. The proposed scheme exploits the scheduling and precoding methods with a view to maximizing system...
In this paper, adaptive beamforming scheme which employs GA was proposed in the downlink of the cognitive radio networks to minimize maximum interference power to the primary users subject to QoS constraints of the secondary users. Performance of the proposed scheme was investigated by some numerical simulation results.
Transmission power plays a crucial role in the design and performance of wireless networks. The issue is therefore complex since an increase in transmission power implies that a high quality signal is received at the receiver and hence an increase in channel capacity. Conversely, due to the shared nature of the wireless medium an increase in transmission power also implies high interference in the...
Cognitive radios are efficient techniques to improve the utilization of the spectrum. Spectrum sensing is the key functionality to improve the spectrum efficiency and avoid harmful interference to the licensed users. By exploiting the spatial diversity of the different secondary users, cooperative sensing can achieve better sensing performance compared to the local sensing, thereby, receiving much...
To avoid inter-cell interference effectively and to improve the performance of cell-edge users, a novel cellular architecture, termed Cellular Architecture Based on Sector Relay (CASR), is proposed in this paper, and two frequency planning schemes based on CASR are investigated. In CASR, fixed relays equipped with directional antennas are located at the vertex of the hexagonal cell for sectorization,...
This paper presents a new space-time two-stage receiver with the assistance of soft information for the Alamouti space-time block code (STBC) and spatially multiplexing (SM) combined systems. The first stage of the receiver consists of a set of soft generalized sidelobe canceller (GSC)-based detectors, each for every STBC group and is intended to yield a more precise initial estimate of the transmitted...
This work presents a novel approach for the avoidance of cross-tier interference in two-tier networks comprised of Orthogonal Frequency Division Multiple Access (OFDMA) macrocells and femtocells. This new technique is based on the use of Intracell HandOvers (IHOs), and it makes possible that either a macrocell or a femtocell can reassign its sub-channel or power allocation upon the detection of cross-tier...
This paper investigates the impact of femtocell interference on existing macrocells with fractional frequency reuse (FFR). Instead of using complicated transmission techniques by coordinating multiple base stations (BSs), this paper adaptively configures FFR pattern to avoids interference caused by femtocells, depending on density and locations of femtocells. Simulation results show that the proposed...
We investigate the use of a timing synchronization technique within cooperative multi-hop networks with and without direct transmission between the source and destination nodes. In particular, we employ a parallel interference cancellation (PIC) technique to combat the effect of timing misalignment of the received signal at both the relay and the destination nodes. We compare the advantage in using...
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