Showing papers in "IEEE Communications Letters in 2012"
TL;DR: Simulation results show that CA-SCL/SCS can provide significant gain over the turbo codes used in 3GPP standard with code rate 1/2 and code length 1024 at the block error probability (BLER) of 10-4.
Abstract: CRC (cyclic redundancy check)-aided decoding schemes are proposed to improve the performance of polar codes. A unified description of successive cancellation decoding and its improved version with list or stack is provided and the CRC-aided successive cancellation list/stack (CA-SCL/SCS) decoding schemes are proposed. Simulation results in binary-input additive white Gaussian noise channel (BI-AWGNC) show that CA-SCL/SCS can provide significant gain of 0.5 dB over the turbo codes used in 3GPP standard with code rate 1/2 and code length 1024 at the block error probability (BLER) of 10-4. Moreover, the time complexity of CA-SCS decoder is much lower than that of turbo decoder and can be close to that of successive cancellation (SC) decoder in the high SNR regime.
722 citations
TL;DR: This work represents the first effort that synergizes software-defined networking and WSN, and proposes a Software-Defined WSN architecture and addresses key technical challenges for its core component, Sensor OpenFlow.
Abstract: While it has been a belief for over a decade that wireless sensor networks (WSN) are application-specific, we argue that it can lead to resource underutilization and counter-productivity. We also identify two other main problems with WSN: rigidity to policy changes and difficulty to manage. In this paper, we take a radical, yet backward and peer compatible, approach to tackle these problems inherent to WSN. We propose a Software-Defined WSN architecture and address key technical challenges for its core component, Sensor OpenFlow. This work represents the first effort that synergizes software-defined networking and WSN.
460 citations
TL;DR: An optimal switching policy that incorporates a-priori knowledge of the channel coefficients is proposed and solved by a mixed-integer linear programming formulation.
Abstract: This letter deals with a three-node cooperative network where the relay node harvests energy from radio frequency (RF) radiation. The source node is the only available RF generator and introduces a fundamental switching between energy harvesting and data relaying. A greedy switching (GS) policy where the relay node transmits when its residual energy ensures decoding at the destination is investigated. The GS policy is modeled as a Markov chain for a discretized battery; the stationary distribution and the outage probability of the system are derived in closed form expressions. In addition, an optimal switching policy that incorporates a-priori knowledge of the channel coefficients is proposed and solved by a mixed-integer linear programming formulation.
324 citations
TL;DR: In this paper, an adaptive SC-List decoder for polar codes with CRC was proposed, which iteratively increases the list size until at least one survival path can pass CRC.
Abstract: In this letter, we propose an adaptive SC (Successive Cancellation)-List decoder for polar codes with CRC. This adaptive SC-List decoder iteratively increases the list size until at least one survival path can pass CRC. Simulation shows that the adaptive SC-List decoder provides significant complexity reduction. We also demonstrate that polar code (2048, 1024) with 24-bit CRC decoded by our proposed adaptive SC-List decoder with very large maximum list size can achieve a frame error rate FER ≤ 10-3{-3} at Eb/No = 1.1dB, which is about 0.25dB from the information theoretic limit at this block length.
316 citations
TL;DR: This letter focuses on baseline multi-user systems, namely multiple access and multi-hop channels, and demonstrates that energy transfer constraints call for additional coordination among distributed nodes of a wireless network.
Abstract: The problem of joint transfer of information and energy for wireless links has been recently investigated in light of emerging applications such as RFID and body area networks. Specifically, recent work has shown that the additional requirements of providing sufficient energy to the receiver significantly affects the design of the optimal communication strategy. In contrast to most previous works, this letter focuses on baseline multi-user systems, namely multiple access and multi-hop channels, and demonstrates that energy transfer constraints call for additional coordination among distributed nodes of a wireless network. The analysis is carried out using information-theoretic tools, and specific examples are worked out to illustrate the main conclusions.
220 citations
TL;DR: A distributed CH selection algorithm that takes into account the distances from sensors to a base station that optimally balances the energy consumption among the sensors is proposed.
Abstract: Central to the cluster-based routing protocols is the cluster head (CH) selection procedure that allows even distribution of energy consumption among the sensors, and therefore prolonging the lifespan of a sensor network We propose a distributed CH selection algorithm that takes into account the distances from sensors to a base station that optimally balances the energy consumption among the sensors NS-2 simulations show that our proposed scheme outperforms existing algorithms in terms of the average node lifespan and the time to first node death
217 citations
TL;DR: This work improves the achievable DoF in this setting by incorporating additional private messages, and provides a tight information theoretic DoF outer bound, thereby identifying the DoF optimal use of mixed CSIT.
Abstract: We consider a multiple-input-single-output (MISO) broadcast channel with mixed channel state information at the transmitter (CSIT) that consists of imperfect current CSIT and perfect outdated CSIT. Recent work by Kobayashi et al. presented a scheme that exploits both imperfect current CSIT and perfect outdated CSIT and achieves higher degrees of freedom (DoF) than possible with only imperfect current CSIT or only outdated CSIT individually. In this work, we further improve the achievable DoF in this setting by incorporating additional private messages, and provide a tight information theoretic DoF outer bound, thereby identifying the DoF optimal use of mixed CSIT. The new result is stronger even in the original setting of only delayed CSIT, because it allows us to remove the restricting assumption of statistically equivalent fading for all users.
202 citations
TL;DR: The well-known virtual network embedding problem (VNE) is extended to energy awareness and a mixed integer program (MIP) which provides optimal energy efficient embeddings is proposed which shows energy gains over the existing cost-based VNE approach.
Abstract: Waste of energy due to over-provisioning and over-dimensioning of network infrastructures has recently stimulated the interest on energy consumption reduction by Internet Service Providers (ISPs). By means of resource consolidation, network virtualization based architectures will enable energy saving. In this letter, we extend the well-known virtual network embedding problem (VNE) to energy awareness and propose a mixed integer program (MIP) which provides optimal energy efficient embeddings. Simulation results show the energy gains of the proposed MIP over the existing cost-based VNE approach.
197 citations
TL;DR: It is shown by simulations that by using multiple antennas at the CRs, it is possible to significantly improve reliability of spectrum sensing with extremely low interference levels to the PU at very low signal-to-noise ratio of the PU-CR link.
Abstract: Performance of cooperative spectrum sensing with multiple antennas at each cognitive radio (CR) is discussed in this paper. The CRs utilize selection combining of the decision statistics obtained by an improved energy detector for making a binary decision of the presence or absence of a primary user (PU). The improved energy detector uses an arbitrary positive power p of amplitudes of samples of the PU's signals. The decision of each CR is orthogonally forwarded over imperfect reporting channels to a fusion center, which takes the final decision of a spectrum hole. We derive expressions of the probabilities of false alarm and missed detection of the proposed cooperative spectrum sensing scheme. By minimizing the total error rate (sum of the probability of missed detection and the probability of false alarm) we derive a closed-form solution of the optimal number of CRs required for cooperation. It is shown by simulations that by using multiple antennas at the CRs, it is possible to significantly improve reliability of spectrum sensing with extremely low interference levels to the PU at very low (much less than 0 dB) signal-to-noise ratio of the PU-CR link.
181 citations
TL;DR: This analysis demonstrates that the channel capacity is largely affected by the life expectancy of molecules, and indicates that the extended modulation scheme can achieve nearly one bit per slot at the expense of extra molecules under optimal conditions.
Abstract: In this paper, we analyze the capacity of a molecular communication channel in a one dimensional environment where information is represented with molecules that are released by a transmitter nanomachine, propagate via Brownian motion, degrade over time, and stochastically reach the receiver nanomachine. The channel is modeled as a time slotted binary channel, and two modulation schemes are proposed: a naive modulation scheme and an extended modulation scheme with a redundant number of molecules. Our analysis demonstrates that the channel capacity is largely affected by the life expectancy of molecules. Our analysis also indicates that the extended modulation scheme can achieve nearly one bit per slot at the expense of extra molecules under optimal conditions.
180 citations
TL;DR: It is shown via computer simulations that the derived upper bound becomes very tight with increasing signal-to-noise ratio (SNR) and the SM scheme is quite robust to channel estimation errors.
Abstract: This work investigates the negative effects of channel estimation errors on the performance of spatial modulation (SM) when operating over flat Rayleigh fading channels. The pairwise error probability of the SM scheme is derived in the presence of channel estimation errors and an upper bound on the average bit error probability is evaluated for M-PSK and M-QAM signalling. It is shown via computer simulations that the derived upper bound becomes very tight with increasing signal-to-noise ratio (SNR) and the SM scheme is quite robust to channel estimation errors.
TL;DR: Security analysis shows that RAPP achieves the functionalities of the authentication protocol and is resistant to various attacks, and performance evaluation illustrates that R APP uses fewer resources on tags in terms of computation operation, storage requirement and communication cost.
Abstract: One of the key problems in RFID is security and privacy. The implementation of authentication protocols is a flexible and effective way to solve this problem. This letter proposes a new ultralightweight RFID authentication protocol with permutation (RAPP). RAPP avoids using unbalanced OR and AND operations and introduces a new operation named permutation. The tags only involve three operations: bitwise XOR, left rotation and permutation. In addition, unlike other existing ultralightweight protocols, the last messages exchanged in RAPP are sent by the reader so as to resist de-synchronization attacks. Security analysis shows that RAPP achieves the functionalities of the authentication protocol and is resistant to various attacks. Performance evaluation illustrates that RAPP uses fewer resources on tags in terms of computation operation, storage requirement and communication cost.
TL;DR: In this article, the authors adopt a stochastic-geometry model of the downlink cellular network and analyze the mobile outage probability, which is shown to diminish inversely with the increasing ratio between the BS and mobile densities.
Abstract: The performance of a cellular network can be significantly improved by employing many base stations (BSs), which shortens transmission distances. However, there exist no known results on quantifying the performance gains from deploying many BSs. To address this issue, we adopt a stochastic-geometry model of the downlink cellular network and analyze the mobile outage probability. Specifically, given Poisson distributed BSs, the outage probability is shown to diminish inversely with the increasing ratio between the BS and mobile densities. Furthermore, we analyze the optimal tradeoff between the performance gain from increasing the BS density and the resultant network cost accounting for energy consumption, BS hardware and backhaul cables. The optimal BS density is proved to be proportional to the square root of the mobile density and the inverse of the square root of the cost factors considered.
TL;DR: A novel approach for ensuring confidential wireless communication is proposed and analyzed from an information-theoretic standpoint and a new concept of outage secrecy region is proposed to evaluate the secrecy performance from a geometrical perspective.
Abstract: A novel approach for ensuring confidential wireless communication is proposed and analyzed from an information-theoretic standpoint. In this approach, the legitimate receiver generates artificial noise (AN) to impair the intruder's channel. This method is robust because it does not need the feedback of channel state information (CSI) to the transmitter and does not assume that the number of Eve's antennas should be smaller than that of Bob. Furthermore, we propose a new concept of outage secrecy region to evaluate the secrecy performance from a geometrical perspective. This should be useful if we need to know what zone should be protected (or militarized). Analysis and simulation results in practical environments show that the proposed method has a good performance.
TL;DR: In this paper, the problem of secure connection in cooperative wireless communication with two relay strategies, decode-andforward (DF) and randomize-and-forward (RF), was considered.
Abstract: This work studies the problem of secure connection in cooperative wireless communication with two relay strategies, decode-and-forward (DF) and randomize-and-forward (RF). The four-node scenario and cellular scenario are considered. For the typical four-node (source, destination, relay, and eavesdropper) scenario, we derive the optimal power allocation for the DF strategy and find that the RF strategy is always better than the DF to enhance secure connection. In cellular networks, we show that without relay, it is difficult to establish secure connections from the base station to the cell edge users. The effect of relay placement for the cell edge users is demonstrated by simulation. For both scenarios, we find that the benefit of relay transmission increases when path loss becomes severer.
TL;DR: It is proved that E-SRS-PA scheme is the optimal energy-efficient RS and PA (OE- RS-PA) scheme in ANC-based TWRC and thus the optimal number of relay nodes to be selected in energy efficiency sense is equal to one.
Abstract: In this letter, we consider a two-way relay channel (TWRC) with two end nodes and k relay nodes, where end nodes have the full channel-state information (CSI) and relay nodes only have the channel-amplitude information (CAI). With the objective of minimizing transmit power consumption at required end-to-end rates, energy-efficient relay selection (RS) and power allocation (PA) scheme is studied for TWRC based on analog network coding (ANC). Firstly, we propose an energy-efficient single RS and PA (E-SRS-PA) scheme, where the best relay node is selected to minimize total transmit power. Then, we prove that E-SRS-PA scheme is the optimal energy-efficient RS and PA (OE-RS-PA) scheme in ANC-based TWRC, and thus the optimal number of relay nodes to be selected in energy efficiency sense is equal to one. In addition, the closed-form expressions of optimal power allocation of E-SRS-PA scheme are derived. Numerical simulations confirm the optimality of proposed E-SRS-PA and demonstrate the energy efficiency of ANC-based TWRC compared with the other relaying schemes.
TL;DR: Two novel dynamic duty-cycle scheduling schemes (called DSR and DSP) are proposed in order to reduce sleep latency, while achieving balanced energy consumption among sensor nodes in wireless sensor networks (WSNs) with energy harvesting capability.
Abstract: In this letter, we propose two novel dynamic duty-cycle scheduling schemes (called DSR and DSP) in order to reduce sleep latency, while achieving balanced energy consumption among sensor nodes in wireless sensor networks (WSNs) with energy harvesting capability. In DSR, each sensor node is allowed to adjust its duty-cycle according to the current amount of residual energy only. Since the residual energy of nodes in energy-harvesting WSNs can increase over time due to their harvesting opportunity, the estimation of prospective increase in their residual energy is useful to achieve our goal. Hence, DSP allows each of sensor nodes to reduce its duty-cycle more aggressively in proportion to such an increase. Through NS-2 simulations, we verified that our proposed schemes outperform the duty-cycle scheduling scheme used in a representative existing MAC protocol such as RI-MAC.
TL;DR: It is shown that the proposed switching algorithm provides substantial performance gain over individual algorithms in the multiuser detection of CDMA downlink.
Abstract: In this paper, we consider a multiuser detection technique when the signal sparsity is changing over time. The key ingredient of our method is a clever switching between the CS reconstruction algorithm and classical detection depending on the sparsity level of the signals being detected. Since none of these approaches is uniformly better in a situation where the sparsity level is varying, proposed switching algorithm can effectively combine the merits of both. We show that the proposed switching algorithm provides substantial performance gain over individual algorithms in the multiuser detection of CDMA downlink.
TL;DR: Results demonstrated that the proposed approach apparently achieves more accurate location estimation than the compared methods including the gradient-based search, linear squares approximation, multidimensional scaling, fingerprinting method, and a multi-expert system.
Abstract: This paper presents a framework for ZigBee indoor positioning with an ensemble approach. This approach exploits the complementary advantages of various algorithms, weights the estimation results, and combines them to improve accuracy. This is achieved by dynamically analyzing the diverse patterns of inputs and combining base positioning algorithms with spatial dependent weights. The experiments were conducted in a realistic ZigBee sensor network. Results demonstrated that the proposed approach apparently achieves more accurate location estimation than the compared methods including the gradient-based search, linear squares approximation, multidimensional scaling, fingerprinting method, and a multi-expert system.
TL;DR: This letter proposes two novel algorithms for the identification of quadrature amplitude modulation (QAM) signals that are robust with respect to timing, phase, and frequency offsets, and phase noise.
Abstract: This letter proposes two novel algorithms for the identification of quadrature amplitude modulation (QAM) signals. The cyclostationarity-based features used by these algorithms are robust with respect to timing, phase, and frequency offsets, and phase noise. Based on theoretical analysis and simulations, the identification performance of the proposed algorithms compares favorably with that of alternative approaches.
TL;DR: This work proposes a novel random access scheme based on its fixed TA information for M2M communications at a large number of fixed-location machine devices in future orthogonal frequency division multiple access (OFDMA)-based cellular systems like Long Term Evolution (LTE) system.
Abstract: Machine-to-machine (M2M) communications typically exhibit features such as a large number of devices, low data-rates, small-sized packets, and low or no mobility, while human-to-human (H2H) communications typically support a small number of users, high data-rates, large-sized packets, and high mobility. To support M2M communications in future cellular systems, one of the most challenging problems is to resolve a collision problem in random access because of access attempts from a large number of devices. For a large class of fixed-location M2M services such as smart metering and remote sensing, each machine device has fixed uplink timing alignment (TA) due to a fixed distance between the machine device and its eNodeB. We propose a novel random access scheme based on its fixed TA information for M2M communications at a large number of fixed-location machine devices in future orthogonal frequency division multiple access (OFDMA)-based cellular systems like Long Term Evolution (LTE) system. The proposed random access scheme yields significantly lower collision probability, shorter access delay, and higher energy-efficiency, compared with the conventional random access scheme.
TL;DR: A novel two-population genetic algorithm to optimize the routing, modulation and spectrum assignments (RMSA) in optical orthogonal frequency-division multiplexing networks and incorporates a migration operation to exchange individuals between them.
Abstract: We propose a novel two-population genetic algorithm (MPGA) to optimize the routing, modulation and spectrum assignments (RMSA) in optical orthogonal frequency-division multiplexing (O-OFDM) networks. The proposed MPGA makes two populations evolve in parallel with different selection and mutation strategies, and incorporates a migration operation to exchange individuals between them. Performance evaluations show that the MPGA outperforms several existing algorithms.
TL;DR: This letter investigates the energy-efficient power allocation for orthogonal frequency division multiplexing (OFDM) based cognitive radio networks (CRNs) and proposes an optimal iterative algorithm based on convex optimization theory and parametric programming.
Abstract: This letter investigates the energy-efficient power allocation for orthogonal frequency division multiplexing (OFDM) based cognitive radio networks (CRNs). The problem is to maximize the energy-efficiency measured using the "throughput per Joule" metric subject to the total transmit power and interference constraints. It is then transformed into an equivalent convex problem using parametric programming. Furthermore, an optimal iterative algorithm based on convex optimization theory and parametric programming is proposed. The numerical results show that the proposed optimal algorithm can achieve higher energy-efficiency than that obtained by solving the original problem directly because of its non-convexity. Energy-efficiency maximization can also achieve a good tradeoff between capacity and energy in CRNs.
TL;DR: Simulation results show that the proposed algorithm can achieve almost the same sum-rate as RBD, substantial bit error rate (BER) performance gains and a simplified receiver structure, while requiring a lower complexity.
Abstract: By employing the regularized block diagonalization (RBD) preprocessing technique, the MU-MIMO broadcast channel is decomposed into multiple parallel independent SU-MIMO channels and achieves the maximum diversity order at high data rates. The computational complexity of RBD, however, is relatively high due to two singular value decomposition (SVD) operations. In this letter, a low-complexity lattice reduction-aided RBD is proposed. The first SVD is replaced by a QR decomposition, and the orthogonalization procedure provided by the second SVD is substituted by a lattice-reduction whose complexity is mainly contributed by a QR decomposition. Simulation results show that the proposed algorithm can achieve almost the same sum-rate as RBD, substantial bit error rate (BER) performance gains and a simplified receiver structure, while requiring a lower complexity.
TL;DR: This paper proposes a collaborative watchdog based on contact dissemination of the detected selfish nodes, and introduces an analytical model to evaluate the detection time and the cost of this collaborative approach.
Abstract: Mobile ad-hoc networks (MANETs) are composed of mobile nodes connected by wireless links without using any pre-existent infrastructure. MANET nodes rely on network cooperation schemes to properly work, forwarding traffic unrelated to its own use. However, in the real world, most nodes may have a selfish behavior, being unwilling to forward packets for others in order to save resources. Therefore, detecting these nodes is essential for network performance. Watchdogs are used to detect selfish nodes in computer networks. A way to reduce the detection time and to improve the accuracy of watchdogs is the collaborative approach. This paper proposes a collaborative watchdog based on contact dissemination of the detected selfish nodes. Then, we introduce an analytical model to evaluate the detection time and the cost of this collaborative approach. Numerical results show that our collaborative watchdog can dramatically reduce the overall detection time with a reduced overhead.
TL;DR: An analytical model is proposed for 3-channel-based neighbor discovery in Bluetooth Low Energy networks and can be used to determine some important performance metrics, such as average latency or average energy consumption during the course of discovering neighbors.
Abstract: In this letter, an analytical model is proposed for 3-channel-based neighbor discovery in Bluetooth Low Energy (BLE) networks. The model can be used to determine some important performance metrics, such as average latency or average energy consumption during the course of discovering neighbors. Since intermittent connections are frequently encountered in practical scenarios of BLE, the modeling results can provide a beneficial guidance to customize advertising or scanning behavior towards user desired performance.
TL;DR: This letter investigates the performance of a dual-hop free space optical link with an all-optical amplify-and-forward relay and demonstrates that semi-blind relaying (which depends only on statistical CSI) provides nearly identical performance to its full-CSI counterpart.
Abstract: In this letter, we investigate the performance of a dual-hop free space optical link with an all-optical amplify-and-forward relay. We employ photon counting methodology and derive closed form expressions for the end-to-end signal-to-noise ratio and the outage probability. In our derivations, we consider either full or partial channel state information (CSI) at the relay and take into account practical limitations such as amplifier noise and filtering effects. Our results indicate significant performance improvements over direct transmission and furthermore demonstrate that semi-blind relaying (which depends only on statistical CSI) provides nearly identical performance to its full-CSI counterpart.
TL;DR: In the presence of the primary user's interference, the outage probability of a dual-hop decode-and-forward (DF) cognitive relay network (CRN) over Rayleigh fading channels is investigated.
Abstract: In the presence of the primary user's interference, the outage probability of a dual-hop decode-and-forward (DF) cognitive relay network (CRN) over Rayleigh fading channels is investigated. We first derive the exact expression for the outage probability, using which the impact of different system parameters on the outage performance is presented in the asymptotic regimes. In addition, the asymptotic outage probability is also derived in the high signal-to-noise ratio (SNR) regime.
TL;DR: In this article, the effect of interference correlation on the diversity in Poisson networks with multi-antenna receivers has been analyzed, and it is shown that interference correlation significantly reduces the probability of successful reception over SIMO links.
Abstract: Interference in wireless systems is both temporally and spatially correlated. Yet very little research has analyzed the effect of such correlation. Here we focus on its impact on the diversity in Poisson networks with multi-antenna receivers. Most work on multi-antenna communication does not consider interference, and if it is included, it is assumed independent across the receive antennas. Here we show that interference correlation significantly reduces the probability of successful reception over SIMO links. The diversity loss is quantified via the diversity polynomial. For the two-antenna case, we provide the complete joint SIR distribution.
TL;DR: This letter proposes a very simple iterative decoding technique, accumulator-assisted distributed turbo code (ACC-DTC) using 2-state (memory-1) convolutional codes (CC), where the correlation knowledge between the source and the relay is estimated and exploited at the destination.
Abstract: In relay systems, the probability of errors occurring in the source-relay (S-R) link can be viewed as representing correlation between the source and the relay. This letter proposes a very simple iterative decoding technique, accumulator-assisted distributed turbo code (ACC-DTC) using 2-state (memory-1) convolutional codes (CC), where the correlation knowledge between the source and the relay is estimated and exploited at the destination.