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The degrees of freedom (DoF) has been recognized as a powerful metric to characterize the capacity of interference channels in the high signal-to-noise (SNR) region. In this paper, by utilizing linear interference alignment, we investigate the DoF of multiple-input and multiple-output (MIMO) interference relay channels without symbol extensions. An innovative algorithm is presented to align the interference,...
This work focuses on the admission of new (secondary) users in a network where existing (primary) users are interference aligned. One of the challenges in this scenario is to achieve the promised degrees of freedom for the secondary users with limited available dimensions. We design a secondary admission network to achieve interference alignment as in equivalent general peer-peer networks, even when...
In this paper, we develop linear interference alignment (IA) approach for multi-input-multi-output interference broadcast channel (MIMO-IBC). Since multiple data streams from each base station (BS) to multiple mobile stations (MSs) experience identical channel, it is hard to ensure the rank constraint to the intended MSs in the desired cell meanwhile ensure the interference aligned at the unintended...
We consider the application of interference alignment (IA) to the cellular case with constant MIMO channel coefficients. Neglecting the weakest interferers in the network, we introduce an algorithm to obtain a partially connected (in particular, L-interfering) network, over which the feasibility of IA can be analyzed simply. We consider the application of IA over the obtained L-interfering network,...
In this paper, we propose a new technique to reduce the interference caused by high OFDM sidelobes to the primary users in MIMO-OFDM cognitive systems. The proposed technique does not affect the rate of the system and has very low complexity. We also analyze the performance of the technique for a class of flat fading channels and show that the analytical results agree with simulations. Furthermore,...
In this paper, we present two optimal resource allocation schemes that maximize throughput and symbol correct rate (SCR). The throughput and SCR are derived. The derived throughput and SCR are optimized with respect to the sensing time, the source transmission power and the relay transmission power. Numerical results show that the optimal sensing time is dependent on the primary user's signal-to-noise-ratio...
This paper considers the resources allocation problem in decode-and-forward (DF) relayed OFDM based cognitive radio (CR) system. The subcarrier matching and power allocation are optimized jointly under the individual power constraints in source and relay so that the sum rate is maximized while the interference induced to the primary system is kept below a pre-specified interference temperature limit...
This paper investigates the resource allocation problem in a relay-aided cognitive radio (CR) system under the orthogonal frequency division multiplexing (OFDM) transmission. Different from the conventional CR resource allocation problem, the relay node here is capable of performing subcarrier permutation over two hops such that the signal received over a particular subcarrier is forwarded on a different...
In this paper, spectrum-sensing based resource allocation for a cognitive radio network that contains multiple secondary users (SUs) and a primary user (PU) is investigated. Each SU firstly performs the individual spectrum sensing and forwards the result to a fusion center to make the global decision. If PU is determined absent, then SUs access the primary band with their regular transmit power. Otherwise...
We consider a cognitive radio (CR) scenario where the signals transmitted by a secondary user are relayed using an amplify-and-forward cooperation protocol. A distributed strategy for power allocation is derived that minimizes the outage probability of the cooperative CR communication system, under the constraint that the interference power experienced by the primary receiver does not exceed a given...
We present a predictor for real Body-Area-Network (BAN) channels that is accurate for up to 2 seconds, even with a nominal channel coherence time of 500 ms. The predictor utilizes the partial-periodicity of measured BAN channels using the previous 4 seconds of channel gain values. We demonstrate use of this predictor for power control with open-access and private channel measurements. When used under...
Characterization of cooperative communications, for the ‘everyday’ body-area-network (BAN) wireless channel is presented. Performance analysis is given based on many hours of empirical data measured on five adult subjects. A decode-and-forward protocol is chosen for the cooperative BAN. Three typical locations for on-body relays/hubs are considered, along with seven typical on-body sensor locations...
Research into localization has produced a wealth of algorithms and techniques to estimate the location of wireless network nodes, however the majority of these schemes do not explicitly account for non-line of sight conditions. Disregarding this common situation reduces their accuracy and their potential for exploitation in real world applications. This is a particular problem for personnel tracking...
In this short paper we describe an approach and primary results for obtaining bounds on mutual information between release times and capture times for a set of M identical quanta traveling from a source to a target. The first-passage times are assumed independent and identically distributed and the launch times are constrained. One major application of area is intercellular molecular signaling in...
This paper focuses on throughput and efficiency of molecular communication between a pair of sender and receiver nanomachines. In the molecular communication considered in this paper, the sender transmits molecules at a fixed rate, the molecules propagate in the environment, and the receiver captures and processes the molecules following simple enzyme kinetics. We define throughput as the average...
Spectrum sensing is considered as the first and main step for cognitive radio systems to achieve an efficient use of spectrum. Cooperation and clustering among cognitive radio users are two techniques that can be employed with spectrum sensing in order to improve the sensing performance by reducing miss-detection and false alarm. In this paper, within the framework of a clustering-based cooperative...
Efficient decision fusion technique for cooperative spectrum sensing based on the logical OR-rule is considered for dynamic spectrum sharing between primary users (PUs) and secondary users (SUs). Due to the use of the OR-rule, the fusion center (FC) only needs to know if any of the local decisions was ”1”. Therefore, it can be a waste of resources to communicate each local decision in an orthogonal...
We consider a time-slotted primary system where both the primary channel and primary activity are modeled as two independent two-state Markov chains. The primary transmitter can be idle or busy, whereas the channel can be in erasure or not. Moreover, the sensing channel between the primary transmitter and secondary transmitter is modeled as a two-state Markov chain to represent two levels of sensing...
In the recent past considerable research has been performed on blind signal detection techniques that exploit the covariance matrix of the signals received at a cognitive radio (CR). These techniques overcome the noise uncertainty problem of the energy detection (ED) method and can even perform better than ED for correlated signals. Contrary to the previous work where the main evaluation technique...
Detection of cyclostationary primary user (PU) signals in colored Gaussian noise for cognitive radio systems is considered based on looking for a cycle frequency at a particular time lag in the cyclic autocorrelation function (CAF) of the noisy PU signal. We explicitly exploit the knowledge that under the null hypothesis of PU signal absent, the measurements originate from colored Gaussian noise with...
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