Search

In this correspondence, multiuser relay systems with amplify and forward relaying protocol are considered. To make transmission delays as short as possible, the concept of complex field network coding is applied. The relays transmit for all users simultaneously instead of using conventional relaying transmissions over orthogonal channels such as time-division multiplexing for each user. Three transmission schemes with two or three time-slot delays and symbol rates 1/2, 2/3, and 1 are examined. Based on the derived pairwise error probability expressions, optimal precoders achieving the maximum diversity and best coding gains are designed without changing the original ergodic capacity regions. Simulation results are provided to verify the proposed designs. [ABSTRACT FROM AUTHOR]

A response by Nizar Tayem and Hyuck M. Kwon to a letter to the editor about their article "L-Shape Two-Dimensional Arrival Angle Estimation With Propagator Method" that was published in the previous issue is presented.

In this paper, we present an algorithm to estimate the direction of the arrival angles (DOAs) from noncoherent one-dimensional (1-D) signal sources such as binary phase shift keying (BPSK) and M-ary amplitude shift keying (MASK) The proposed algorithm can provide a more precise DOA estimation and can detect more signals than we D-known classical subspace.methods MUSIC and ESPRIT for the 1-D signals. The complexity is the same as that of ESPRIT since the proposed algorithm uses the same array geometry and subarray processing that ESPRIT does. The main differences between the proposed algorithm and the ESPRIT algorithm are as follows: 1) the number of overlapping array elements between two subarrays is equal to M in the proposed algorithm, while in ESPRIT the maximum number of overlapping elements is M - 1, where M denotes the total number of array elements, and 2) the proposed algorithm employs the conjugate of rotation matrix (CRM) V while ESPRIT uses 1 with no conjugate for the second subarray geometry. [ABSTRACT FROM AUTHOR]

An inter-carrier interference (ICI) occurs in an orthogonal frequency division multiplexing (OFDM) system when a channel is rapidly time-varying. The proposed scheme employs a polynomial cancellation code (PCC) to suppress this ICI, and uses a linear complex field (LCF) code as a transmit-diversity technique to make the transmission rate compatible up to {n_T} / {(n_T+1)}, where n_T is the number of transmit antennas used. The conventional orthogonal code (OC), such as the Alamouti code, with accompanying PCC cannot achieve this rate. Both analysis and simulation results verify that the proposed scheme can achieve higher channel capacity as well as lower bit error rate (BER) than the other schemes in rapidly time-varying channels, even with a linear receiver and inaccurate channel estimation. [ABSTRACT FROM PUBLISHER]