Qingchun Chen

Design of isotropic orthogonal transform algorithm-based multicarrier systems with blind channel estimation

Orthogonal frequency division multiplexing (OFDM) technique has gained increasing popularity in both wired and wireless communication systems. However, in the conventional OFDM systems the insertion of a cyclic prefix (CP) and the transmission of periodic training sequences for purpose of channel estimation decrease the systems spectral efficiency. As an alternative to OFDM, isotropic orthogonal transform algorithm (IOTA)-based multicarrier system adopts a proper pulse shaping with good time and frequency localisation properties to avoid interference and maintain orthogonality in real field among sub-carriers without the use of CP. In this study, the authors propose linearly precoded IOTA-based multicarrier systems to achieve blind channel estimation by utilising the structure of auto-correlation and cross-correlation matrices introduced by precoding. The results show that the proposed IOTA-based multicarrier systems achieve better power and spectral efficiency compared with the conventional OFDM systems.

Comments on "Distributed Bayesian algorithms for fault-tolerant event region detection in wireless sensor networks"

In this correspondence, several errors related to the distributed Bayesian algorithms for fault-tolerant event region detection in wireless sensor networks in (B. Krishnamachari et al., 2004) are spotted and corrected.

Hypergraph-based data link layer scheduling for reliable packet delivery in wireless sensing and control networks with end-to-end delay constraints

Abstract Many mission-critical and safety-critical applications in networked wireless sensing and control systems have stringent reliability requirements and timing constraints on end-to-end ( E2E ) packet delivery. Late arrivals of packets could severely degrade overall system performance and cause serious problems in system operation. In this paper, we study the data link layer scheduling problem to maximize the reliability of E2E packet delivery in TDMA-based wireless sensing and control networks ( WSCNs ) subject to specified delay constraints. We propose to organize the physical network nodes into logical hypernodes and form a hypergraph for improved scheduling flexibility. Based on the hypergraph, we introduce two data link layer scheduling schemes to maximize the E2E reliability in packet delivery without violating any delay constraints of the packets. The first scheme, named dedicated scheduling , decides how many time slots (TSs) for each hypernode along the path to the destination should be allocated to transmit a packet, and the packets are only transmitted in their scheduled TSs. The second scheme, named shared scheduling , allows the packets to share their scheduled TSs, and thus further improve the E2E reliability. We apply these two schemes in both single-path routing and any-path routing in WSCNs. Asymptotic analysis of the proposed schemes is provided and extensive simulation experiments are performed to illustrate their effectiveness in improving the E2E reliability of packet delivery under different network settings.

Outage Probability of Switch and Stay Combining in Two-Way Amplify-and-Forward Relay Networks

In this letter, a switch-and-stay combining (SSC) in two-way amplify-and-forward (AF) networks with two relays is proposed and analyzed. In particular, the closed-form expression of the outage probability for the proposed scheme over Rayleigh fading channels is derived. Asymptotic performance analysis for high signal-to-noise ratio (SNR) is also presented. It is shown that the SSC scheme is capable of realizing full diversity order, and even achieving the same outage performance as the best-relay selection (BRS), when reasonable switching thresholds are set. Simulations are provided to corroborate the theoretical analysis.

On the Average of the Product of Two Gaussian Q-Functions over Nakagami-q (Hoyt) Fading and Its Application

In this letter, the average of the product of two Gaussian Q-functions over the Nakagami-q (Hoyt) distribution with arbitrary parameters is presented in terms of the Lauricella hypergeometric function, which can be evaluated numerically using its integral or converging series representation. The result obtained is then applied to evaluate the symbol error probability (SEP) of general rectangular quadrature amplitude modulation (QAM) constellations over Nakagami-q fading channels. The impact of fading severity (parameter q) on the error performance of the general rectangular QAM system is also investigated.

Optimum Linear Block Precoding for Multi-Point Cooperative Transmission with Per-Antenna Power Constraints

Using cyclic prefix (CP), the transmission schemes, orthogonal frequency-division multiplexing (OFDM), single carrier block transmission, and time reversal, can be unified as linear block precoding. Considering frequency-selective channels, this paper studies linear block precoding for CP-based multi-point transmission with per-antenna power constraints (PAPCs) under capacity maximization and mean-square-error (MSE) minimization criteria. We show that, the optimal precoders for both criteria could be, but not necessarily, in the form of OFDM transmission (i.e., an inverse discrete fourier transformation (IDFT) matrix multiplying a complex diagonal matrix). Based on the optimal precoder structure, the two problems are simplified to two matrix-free optimization problems for which we prove strong duality holds. Moreover, it is shown that the dual problems can be equivalent to two unconstrained convex optimization problems. Efficient optimum precoding algorithms are proposed for both problems. Simulation results show that the maximum capacity (or minimum MSE) in the PAPC case almost coincides with that in the sum power constraint (SPC) case when the power budgets for each antenna are equal, but a capacity (or MSE) gap exists between the two power constraint cases when the power budgets for each antenna are different.

The optimal puncturing pattern design for rate-compatible punctured Turbo codes

In this paper, the puncturing pattern design criteria for rate-compatible punctured Turbo (RCPT) codes are reviewed at first. Then the optimal puncturing pattern design problem for RCPT codes are highlighted for Turbo codes with specific interleaver instead of the uniform interleaver assumption. By employing the constrained subcode algorithm to calculate the low weight spectrum sequence, the optimized weight spectrum sequence (OWSS) criterion is utilized to determine the optimal puncturing pattern. Two algorithms are utilized to realize the OWSS design criterion for both the periodic puncturing pattern design and the non-periodic puncturing pattern design. And simulation results are presented to validate the performance for the long term evolution (LTE) standard Turbo codes. The analysis in this paper unveils that, non-periodic puncturing pattern design will always outperform the periodic puncturing pattern design. However, the performance difference between the periodic puncturing and the non-periodic puncturing will tend to be negligible with the increase in the puncturing period. As a conclusion, when the simplified implementation in practical application is concerned, it seems that the periodic puncturing pattern with long enough puncturing period is recommended.

Complex rotary codes revisited: a low-complexity high-performance decoding approach

In this paper, based on a belief-propagation decoding strategy, a class of generalized parity-check codes called complex rotary codes is investigated. It is shown that, by using iterative sum-product decoding, the complex rotary codes have a much lower decoding complexity than Turbo codes, but have almost the same performance for the high code rate and short frame case (frame length< 500 bits). It is also shown that the prime block size of complex rotary codes is essential to achieve better performance because of its uniform checking characteristic.

A novel parallel turbo coding technique based on frame split and trellis terminating

A new parallel turbo encoding and decoding technique is introduced. In this technique, a long information data frame is first divided into subblocks which are then encoded with trellis terminating and decoded by parallel multiple SISO modules. It is shown that, at a slight increase in hardware complexity and a slight loss in the transmission efficiency due to the extra terminating bits appended, the proposed scheme can effectively reduce the decoding delay, and at the same time achieve noticeably better error performance compared with the regular schemes, especially in high code rate situation.

On the Spatial Error Propagation Characteristics of Cooperative Localization in Wireless Networks

Cooperative localization is an important technique in wireless networks. However, there are always errors in network node localization, which will spatially propagate among network nodes when performing network localization. In this paper, we study the spatial error propagation (EP) characteristics of network localization in terms of Fisher information. First, the spatial propagation function is proposed to reveal the spatial cooperation principle of network localization. Second, the convergence property of spatial localization information propagation (SLIP) is analyzed to shed light on the performance limits of network localization through spatial information propagation. It is shown that 1) the network localization error propagates in the way of Ohms law in electric circuit theory, where the measurement accuracy, node location accuracy, and geometric-resolution information behave like the resistances connected in parallel or series; 2) the network location error gradually diminishes with spatial localization cooperation procedures, due to the cooperative localization information propagation; and 3) the essence of spatial localization cooperation among network nodes is the spatial propagation of localization information.