Tight Upper and Lower Bounds to the Information Rate of the Phase Noise Channel

Numerical upper and lower bounds to the information rate transferred through the additive white Gaussian noise channel affected by discrete-time multiplicative autoregressive moving-average (ARMA) phase noise are proposed in the paper. The state space of the ARMA model being multidimensional, the problem cannot be approached by the conventional trellis-based methods that assume a first-order model for phase noise and quantization of the phase space, because the number of state of the trellis would be enormous. The proposed lower and upper bounds are based on particle filtering and Kalman filtering. Simulation results show that the upper and lower bounds are so close to each other that we can claim of having numerically computed the actual information rate of the multiplicative ARMA phase noise channel, at least in the cases studied in the paper. Moreover, the lower bound, which is virtually capacity-achieving, is obtained by demodulation of the incoming signal based on a Kalman filter aided by past data. Thus we can claim of having found the virtually optimal demodulator for the multiplicative phase noise channel, at least for the cases considered in the paper.Comment: 5 pages, 2 figures. Accepted for presentation at ISIT 201

Improved Nyquist pulse shaping filters for generalized frequency division multiplexing

Generalized Frequency-Division Multiplexing (GFDM) is one of the multicarrier modulation schemes currently under study for next generation 5G cellular networks. One of the main characteristics of GFDM is the low out of band emission that is achieved by means of a flexible time-domain pulse shaping of individual subcarriers. In the paper, we propose to use improved Nyquist pulse shaping filters which have been originally introduced in the context of single-carrier modulation schemes for reducing the sensitivity to symbol timing error due to their higher eye opening and smaller maximum distortion. Here we consider their use in GFDM and evaluate their symbol error rate (SER) performance in case of 16-QAM transmission over an additive white Gaussian noise channel. Moreover, we also considered the concept of the wavelet for better time-frequency localization of the pulse shaping filters by using the Meyer auxiliary function. Numerical results are reported to demonstrate the superior SER performance achieved by the proposed improved Nyquist pulse shaping filters in comparison to that achieved with conventional Nyquist pulse shaping filters

Wiener's loop filter for PLL-based carrier recovery of OQPSK and MSK-type modulations

This letter considers carrier recovery for offset quadrature phase shift keying (OQPSK) and minimum shift keying-type (MSK-type) modulations based on phase-lock loop (PLL). The concern of the letter is the optimization of the loop filter of the PLL. The optimization is worked out in the light of Wiener's theory taking into account the phase noise affecting the incoming carrier, the additive white Gaussian noise that is present on the channel, and the self-noise produced by the phase detector. Delay in the loop, which may affect the numerical implementation of the PLL, is also considered. Closed-form expressions for the loop filter and for the mean-square error are given for the case where the phase noise is characterized as a first-order process

Interference alignment for the K-user MIMO X network using time division multiple access

This paper investigates an interference alignment (IA) scheme suitable for a K-user multiple-input multiple-output (MIMO) wireless X network. The K-user MIMO X-network is a communication architecture where each transmitter, equipped with multiple antennas, has independent messages for each of the receivers, also equipped with multiple antennas. Earlier only 2 × N or M × 2 X networks were considered to be achievable. In this paper we remove this restriction by employing time division multiple access scheme. The proposed IA scheme allows each user to achieve a degree of freedom of KA/2K-1 a particular time slot, where A is the number of antennas at each transmitter and receiver. The capacity and bit error-rate (BER) performance of the proposed scheme is compared to that of another scheme recently proposed by Park and Ko. Simulation results are reported to show the BER performance for K-user (for a toy example, K is set equal to 3) and two-user X channel IA in case of transmission over flat-fading Rayleigh channels

Lower Bound Based on Kalman Carrier Recovery below the Information Rate of Wiener Phase Noise Channel

A new lower bound below the information rate transferred through the Additive White Gaussian Noise (AWGN) channel affected by discrete-time multiplicative Wiener’s phase noise is proposed in the paper. The proposed lower bound is based on the Kalman approach to data-aided carrier phase recovery, and is less computationally demanding than known methods based on phase quantization and trellis representation of phase memory. Simulation results show that the lower bound is close to the actual channel capacity, especially at low-to-intermediate signal-to-noise ratio

Pilot-Aided Equalization with a Constrained Noise-Estimation Filter

In this paper we focus on a single carrier pilotassisted transmission scheme where one pilot symbol is periodically inserted in the transmitted sequence on a time-division multiplexing basis. A new equalization scheme, where the knowledge of pilot symbols is exploited by the equalizer to generate an estimate of the noise affecting the symbol to be detected, is introduced and analyzed. The criterion used to compute the equalizer coefficients is the minimization of the mean-square error (MSE). The main new result of our analysis is that the optimal pilot aided equalizer (PAE) can be decomposed as the cascade of an unconstrained minimum MSE (MMSE) linear equalizer (LE) and a data-aided noise estimation filter. This result completes and extends the noise-predictive view of decision feedback equalization to general data-aided equalization. The PAE is compared here to the MMSE-LE and to the MSE decision feedback equalizer on two frequency selective wireless channels

Optimal overhead selection for interference alignment in time-varying two-user MIMO X channel

Channel state information (CSI) at the transmitter and receiver is an essential requirement for interference alignment (IA) schemes. For moving users the channel coefficients vary with time and, therefore, it is required to update CSI both at the transmitter and receiver at regular intervals. Meanwhile it is important to note that frequent updates of CSI will reduce data rate and delayed updates will cause a large variation in CSI. In this context we explore the error performance of IA in two-user multiple-input multiple-output (MIMO) X channel where the channel suffers continuous time-varying fading. The bit error rate (BER) performance of MIMO two-user X channel is evaluated for different Doppler frequencies. We also propose a method for calculating optimal pilot overhead for time-varying channels by setting an upper bound on BER