Relay-Induced Error Propagation Reduction for Decode-and-Forward Cooperative Communications

An attractive hybrid method of mitigating the effects of error propagation that may be imposed by the relay node (RN) on the destination node (DN) is proposed. We selected the most appropriate relay location for achieving a specific target Bit Error Ratio (BER) at the relay and signalled the RN-BER to the DN. The knowledge of this BER was then exploited by the decoder at the destination. Our simulation results show that when the BER at the RN is low, we do not have to activate the RN-BER aided decoder at the DN. However, when the RN-BER is high, significant system performance improvements may be achieved by activating the proposed RN-BER based decoding technique at the DN. For example, a power-reduction of up to about 19dB was recorded at a DN BER of 10-4

Commutator estimates in W∗W^*-algebras

Let $\mathcal{M}$ be a $W^*$-algebra and let $LS(\mathcal{M})$ be the algebra of all locally measurable operators affiliated with $\mathcal{M}$. It is shown that for any self-adjoint element $a\in LS(\mathcal{M})$ there exists a self-adjoint element $c_{_{0}}$ from the center of $LS(\mathcal{M})$, such that for any $\epsilon>0$ there exists a unitary element $u_\epsilon$ from $\mathcal{M}$, satisfying $|[a,u_\epsilon]| \geq (1-\epsilon)|a-c_{_{0}}|$. A corollary of this result is that for any derivation $\delta$ on $\mathcal{M}$ with the range in a (not necessarily norm-closed) ideal $I\subseteq\mathcal{M}$, the derivation $\delta$ is inner, that is $\delta(\cdot)=\delta_a(\cdot)=[a,\cdot]$, and $a\in I$. Similar results are also obtained for inner derivations on $LS(\mathcal{M})$.Comment: 30 page

On the Exact BER of Bit-Wise Demodulators for One-Dimensional Constellations

The optimal bit-wise demodulator for M-ary pulse amplitude modulation (PAM) over the additive white Gaussian noise channel is analyzed in terms of uncoded bit-error rate (BER). New closed-form BER expressions for 4-PAM with any labeling are developed. Moreover, closed-form BER expressions for 11 out of 23 possible bit patterns for 8-PAM are presented, which enable us to obtain the BER for 8-PAM with some of the most popular labelings, including the binary reflected Gray code and the natural binary code. Numerical results show that, regardless of the labeling, there is no difference between the optimal demodulator and the symbol-wise demodulator for any BER of practical interest (below 0.1)

On the BER of Multiple-Input Multiple-Output Underwater Wireless Optical Communication Systems

In this paper we analyze and investigate the bit error rate (BER) performance of multiple-input multiple-output underwater wireless optical communication (MIMO-UWOC) systems. In addition to exact BER expressions, we also obtain an upper bound on the system BER. To effectively estimate the BER expressions, we use Gauss-Hermite quadrature formula as well as approximation to the sum of log-normal random variables. We confirm the accuracy of our analytical expressions by evaluating the BER through photon-counting approach. Our simulation results show that MIMO technique can mitigate the channel turbulence-induced fading and consequently, can partially extend the viable communication range, especially for channels with stronger turbulence

General BER Expression for One-Dimensional Constellations

A novel general ready-to-use bit-error rate (BER) expression for one-dimensional constellations is developed. The BER analysis is performed for bit patterns that form a labeling. The number of patterns for equally spaced M-PAM constellations with different BER is analyzed.Comment: To appear in the Proceedings of the IEEE Global Communications Conference (GLOBECOM) 2012. Remark 3 modifie

BER of MRC for M-QAM with imperfect channel estimation over correlated Nakagami-m fading

In this contribution, we provide an exact BER analysis for M-QAM transmission over arbitrarily correlated Nakagami-m fading channels with maximal-ratio combining (MRC) and imperfect channel estimation at the receiver. Assuming an arbitrary joint fading distribution and a generic pilot-based channel estimation method, we derive an exact BER expression that involves an expectation over (at most) 4 variables, irrespective of the number of receive antennas. The resulting BER expression includes well-known PDFs and the PDF of only the norm of the channel vector. In order to obtain the latter PDF for arbitrarily correlated Nakagami-m fading, several approaches from the literature are discussed. For identically distributed and arbitrarily correlated Nakagami-m channels with integer m, we present several BER performance results, which are obtained from numerical evaluation and confirmed by straightforward computer simulations. The numerical evaluation of the exact BER expression turns out to be much less time-consuming than the computer simulations