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We investigate the performance of orthogonal frequency division multiplexing (OFDM)-based dual-hop amplify-and-forward (AF) relay networks in the presence of phase noise (PHN). We show that the use of an AF relay may not be beneficial compared to a direct transmission in the presence of PHN. Using outage probability analysis, an upper bound on the allowable PHN level is derived which ensures that...
Distributed uplink power allocation technique as a strategy for maintaining the quality of service (QoS) is described for orthogonal frequency division multiplexing (OFDM) based networks. In proposed algorithm, the power is allocated to subcarriers having large signal-to-interference-plus-noise ratio (SINR) according to the criterion. In order to reduce cochannel interference, we propose the power...
This paper proposes a superimposed training strategy to estimate the individual frequency and channel parameters in an amplify-and-forward (AF) two-way relay network (TWRN). Two efficient suboptimal estimation algorithms and an iterative process to further improve the performance are proposed. The estimation Cramér-Rao Bound (CRB) on the proposed estimation strategy is also derived. The simulations...
The focus of this paper is on the performance of an orthogonal frequency division multiplexing (OFDM) transmission system considering the combined influence of receiver noise, Rayleigh fading and the timing error due to imperfect slot synchronization at the receiver. Performance results are presented in terms of BER, BER improvement and BER-floor in presence of inter-channel interference (ICI) and...
Proportional Fair (PF) algorithm is known to achieve a good trade-off between efficiency and fairness by allocation opportunistically resources to users with good radio conditions, without sacrificing fairness considerations towards the other users of the system. On the other hand, Hierarchical Modulation (HM) is a means to increase the spectral efficiency of a given system by superposing an additional...
For single-carrier systems with frequency domain equalization, decision feedback equalization (DFE) performs better than linear equalization, and has a lower complexity and computational costs than optimum equalizers. The main challenge in DFE is the feedback symbol selection rule. In this paper, we give a theoretical framework for a simple, sparsity based thresholding algorithm. We feedback multiple...
This paper presents a novel adaptive multiuser detection scheme for MIMO OFDM, which we refer to as AMUD MIMO OFDM. It combines the adaptive minimum mean square error multiuser detection scheme with prior information of the channel and interference cancelation in the spatial domain. Simulation results show that joint channel parameters estimation has good performance compared to individual parameter...
Opportunistic scheduling for wireless network coding (OWNC) combines the strategies of opportunistic scheduling and network coding. This paper applies two variants of OWNC on a two-user OFDMA system. Symbol-based OWNC decides a strategy from sum rate of the whole OFDM symbol. Subcarrier-based OWNC decides a strategy from the capacity on a subcarrier level. Novel algorithms are derived for power allocation...
Cooperative decoding is powerful technique for establishing good quality TV broadcasting. In cooperative decoding, some TV receivers, nodes, are cooperated, each other. These share the received information signal and thus obtain good quality information signal. Incremental-Maximum Ratio Combining (I-MRC) is one of the cooperative decoding methods. In I-MRC, the best condition's node and second one...
In the planning of cellular networks, link budget calculation is the first step to get the maximum allowable cell radius that guarantees a target signal to interference plus noise ratio (SINR) with a certain level of outage probability at the cell border. The interference margin as one of key inputs for link budget is used to compensate for co-channel interference. In this paper, a mathematical analysis...
This paper considers the problem of spectrum sensing in cognitive radio networks when the primary user employs Orthogonal Frequency Division Multiplexing (OFDM). We specifically consider the scenario when the channel between the primary and a secondary user is frequency selective. We develop cooperative sequential detection algorithms based on energy detectors. We modify the detectors to mitigate...
OFDM signals possess a high flexibility, which, besides their typical employment for wireless digital communications, makes them also suitable for radar applications. In this paper an OFDM system will be presented that offers communication and radar functions in parallel based on one joint transmit signal. A typical application area would be intelligent transportation systems, which require the ability...
The multicast/broadcast service (MBS) has emerged as a key technology for delivering multimedia contents in wireless networks.The development of orthogonal frequency division multiplexing access (OFDMA) and multiple-input multiple-output (MIMO) communications have provided a high-throughput air interface for delivering the multimedia contents in MBSs. To further improve the spectral efficiency for...
This paper considers the problem of spectrum sensing in cognitive radio networks when the primary user is using Orthogonal Frequency Division Multiplexing (OFDM). For this we develop cooperative sequential detection algorithms that use the autocorrelation property of cyclic prefix (CP) used in OFDM systems. We study the effect of timing and frequency offset, IQ-imbalance and uncertainty in noise and...
In this paper, we propose a new adaptive subcarrier allocation for a multiuser two-way OFDMA relay network. In the proposed algorithm, subcarriers are allocated to the user-pairs and relays to maximize the achievable sum-rate over all user-pairs while satisfying the minimum rate requirement for each user-pair. Simulation results show that the proposed algorithm improves spectral efficiency and fairness.
This paper investigates the impact of carrier frequency offset (CFO) on Single Carrier wireless communication systems with Frequency Domain Equalization (SC-FDE). We show that CFO in SC-FDE systems causes irrecoverable channel estimation error, which leads to inter-symbol-interference (ISI). The impact of CFO on SC-FDE and OFDM is compared in the presence of CFO and channel estimation errors. Closed...
This paper investigates a novel efficient automatic modulation classification (AMC) algorithm in wireless time division duplex (TDD) orthogonal frequency division multiplexing (OFDM) systems with adaptive modulation (AM). Starting from the well-known maximum-likelihood (ML) classification metric for digital quadrature amplitude modulation (QAM) schemes, partial channel reciprocity in TDD-based adaptive...
In this paper, we develop a simple blind channel estimation algorithm for two-way relay network (TWRN) that consists of two terminal nodes and one relay node. We consider the frequency selective channels and adopt the orthogonal frequency-division multiplexing (OFDM) modulation to compensate the inter-symbol interference (ISI). By applying a non-redundant linear precoding at both terminals, we propose...
We consider a wireless relay network with one source, one relay and one destination, where communications between nodes are preformed over N orthogonal channels. This, for example, is the case when orthogonal frequency division multiplexing is employed for data communications. Since the power available at the source and relay is limited, we study optimal power allocation strategies at the source and...
We maximize the minimum rate among sources in a multi-source, multi-relay, single destination cooperative network. The relays use the decode-and-forward protocol while all transmissions use orthogonal frequency division multiplexing. The key to our approach is fractional cooperation: there may be fewer relays than sources and not all source subcarriers are relayed. Optimal matching of the sources...
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