Approximation to the symmetric capacity of Rayleigh fading channels with multi-level signals

A simple approximation for the symmetric capacity of Rayleigh fading channels with finite input alphabet and ideal channel state information is proposed in this letter. This approximation is quite tight over all SNR ranges and can be considered as a good alternative for estimating the symmetric channel capacity for both AWGN and Rayleigh fading channels.     

On the capacity of log-normal fading channels

In this letter we provide an analytical expression for the moments of the capacity for the log-normal fading channel. Since the developed expression involves infinite series, we show that the error that results from the truncation of these series is insignificant. We also analyze in more details the ergodic capacity by giving a simpler expression for the remainder of the truncated series. Relying on the fact that the sum of log-normal Random Variables (RV) is well approximated by another lognormal RV, we further utilize the obtained results to approximate the capacity of diversity combining techniques in correlated lognormal fading channels. The results that we provide in this letter are an important tool for measuring the performance of communication links in a log-normal environment.     

Space-time block codes: a capacity perspective

Space-time block codes are a remarkable modulation scheme discovered recently for the multiple antenna wireless channel. They have an elegant mathematical solution for providing full diversity over the coherent, flat-fading channel. In addition, they require extremely simple encoding and decoding. Although these codes provide full diversity at low computational costs, we show that they incur a loss in capacity because they convert the matrix channel into a scalar AWGN channel whose capacity is smaller than the true channel capacity. In this letter the loss in capacity is quantified as a function of channel rank, code rate, and number of receive antennas     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Tight closed-form approximation for the ergodic capacity of orthogonal STBC

In this letter we derive a simple and tight closed-form approximation for the ergodic capacity of orthogonal space-time block coding in arbitrary fading channels. The expression is an analytical function of the power covariance matrix of the channel. In the case of uncorrelated channels the expression only depends on the variances of the channel power gains. These channel statistics can be easily obtained from both analytical and physical fading channel models. Simulations results show the accuracy of the proposed expression     

Influence of source-drain series resistance on MOSFET field-effect mobility

A simple but general model for explaining the series resistance dependence of transconductance and field-effect mobility is developed in the letter. This model, which enables a quantitative analysis of series resistance effects on the maximum mobility and the corresponding gate voltage, has been successfully tested on short-channel MOSFETs with various channel lengths and external series resistances.     

On the capacity growth of opportunistic single-relay selection using quality-based feedback in fixed-gain amplify-and-forward relaying

In this letter, the capacity of simple opportunistic single-relay selection (OSRS) is addressed for a dual-hop cooperative network with a source, destination, and lots of possibly cooperative relays. We provide asymptotic lower and upper bounds on the capacity of OSRS. Quality-based channel state reporting (QBR) is used to avoid increases in the feedback load, especially when the number of relays is large. The numerical results show that QBR does not degrade the capacity while it successfully reduces feedback.     

A simple detect-and-forward scheme in fading channels

In this letter, we introduce and analyze a Detect-and- Forward scheme for cooperative communications over fading channels based on the transmission of partial source-relay channel state information. The proposed scheme is simple to implement and its efficiency is demonstrated through constrained capacity calculation and throughput evaluation based on practical coding schemes.     

Information-guided channel-hopping for high data rate wireless communication

In this letter, we introduce information-guided channel-hopping, a new scheme for high data rate communication over Rayleigh fading channel using multiple transmit antennas. This scheme is proposed based on the fact that the independence character of multi-channel can be used as an additional information transmitting channel, and the maximum likelihood decoding can be achieved in a simple way by decoupling of the signals conveyed by different methods. The analysis results prove that the capacity behavior of this scheme is better than that of the space-time block coding for more than two transmit antennas.     

Opportunistic orthogonal writing on dirty paper

A simple scheme that achieves the capacity and the reliability function of the wideband Costa dirty-paper channel is proposed. The scheme can be interpreted as an opportunistic version of pulse position modulation (PPM). This interpretation suggests a natural generalization of the scheme which we show to achieve the capacity per unit cost of Gel'fand-Pinsker channels with a zero-cost input letter.     

Closed-form approximation for the outage capacity of orthogonal STBC

In this letter we derive a tight analytical approximation for the outage capacity of orthogonal space-time block codes (STBC's). The proposed expression is a simple closed-form function of the power covariance matrix of the channel. In the case of uncorrelated channels, the expression only depends on the variances of the channel power gains that can be expressed analytically for the most common fading distributions: Rayleigh, Rice, Nakagami, Weibull, etc. Furthermore, the approximation encompasses different fading distributions and gains between different pairs of transmit and receive antennas, which can occur in distributed STBC networks.     

Capacity regions and optimal power allocation for groupwise multiuser detection

In this letter, optimal power allocation and capacity regions are derived for groupwise successive interference cancellation (GSIC) systems operating in multipath fading channels, under imperfect channel estimation conditions. It is shown that the impact of channel estimation errors on the system capacity is two-fold: It affects the receiver performance within a group of users, as well as the cancellation performance (through cancellation errors). An iterative power allocation algorithm is derived, based on which it can be shown that that the total required received power is minimized when the groups are ordered according to their cancellation errors, and the first detected group has the smallest cancellation error. Performance/complexity tradeoff issues are also discussed by directly comparing the system capacity for different implementations: GSIC with linear minimum-mean-square error (LMMSE) receivers within the detection groups; GSIC with matched filter (MF) receivers; multicode LMMSE systems; and simple all MF receivers systems.     

VoIP capacity analysis in cognitive radio system

In this letter, we analyze a voice over IP (VoIP) capacity in a cognitive radio system. We formulate the system as a two-dimensional discrete time Markov chain (DTMC). The VoIP traffic and wireless channel in the cognitive radio system are described as a Markov modulated Poisson process (MMPP) model and a Markov channel model, respectively. We demonstrate various numerical and simulation results, such as packet dropping probability and VoIP capacity.     

On the Performance of the MIMO Zero-Forcing Receiver in the Presence of Channel Estimation Error

By employing spatial multiplexing, multiple-input multiple-output (MIMO) wireless antenna systems provide increases in capacity without the need for additional spectrum or power. Zero-forcing (ZF) detection is a simple and effective technique for retrieving multiple transmitted data streams at the receiver. However the detection requires knowledge of the channel state information (CSI) and in practice accurate CSI may not be available. In this letter, we investigate the effect of channel estimation error on the performance of MIMO ZF receivers in uncorrelated Rayleigh flat fading channels. By modeling the estimation error as independent complex Gaussian random variables, tight approximations for both the post-processing SNR distribution and bit error rate (BER) for MIMO ZF receivers with M-QAM and M-PSK modulated signals are derived in closed-form. Numerical results demonstrate the tightness of our analysis     

Efficient Multiplexing Scheme of Stereoscopic Video Sequences for Digital Broadcasting Services

This letter introduces a stereoscopic video broadcasting system that provides 3D visual service and has full backward compatibility with legacy digital television (DTV) service in the same channel capacity. The proposed stereoscopic video broadcasting system in this letter is composed of both a hybrid codec and a multiplexer with a newly defined stereoscopic‐related signaling method. In conclusion, the proposed method can be effectively applied for 3D broadcasting services without major changes in legacy broadcasting platforms.     

Mobility Influences on the Capacity of Wireless Cellular Networks

Capacity has always been a major concern in wireless networks. This letter studies the impact of mobility on the overall system capacity in wireless cellular networks. In this letter, we present a simple system model which we developed to capture the inherent relationships among system capacity, new call blocking probability, handoff dropping probability, call terminating probability, and bandwidth utilization rate. We investigate the complex relationship between mobility and capacity‐related parameters. Through simulation, we demonstrate that mobility has a significant impact on capacity and is reversely proportional to the bandwidth reserved for handoff traffic.     

A novel in-situ SOI characterization technique: the intrinsicpoint-probe MOSFET

This letter presents a novel, simple yet powerful method, called the intrinsic point-probe MOSFET technique, dedicated to accurate in situ evaluation of SOI material electrical parameters. The proposed method is free of parasitic series resistances and is particularly adapted for both static and dynamic investigations. It is essentially based on the inspection of the intrinsic conductance of the inversion channel induced by the substrate bias acting as a gate. Analytical models of the intrinsic conductance and related parameter extraction procedures are presented and validated on state-of-the-art Unibond wafers     

A Rigorous Proof of MIMO Channel Capacity’s Increase with Antenna Number

It is well known that adding more antennas at the transmitter or at the receiver offers larger channel capacity in the multiple-input multiple-output communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receive antennas. The proof is based on the famous capacity formula of Foschini and Gans and uses matrix theory.

发射分集中空时编码及其性能的研究

介绍了发射分集技术中用于抗信道衰落和提高系统容量的空时分组码的基本特点,并对它进行了性能分析和仿真。     

Source-and-drain series resistance of LDD MOSFET's

The introduction of n- regions makes an LDD MOSFET behave differently from a conventional MOSFET. The source-and-drain series resistance, which consists of the n+-and-n-regions, shows a strong dependence on the gate bias. Also, the apparent effective length can vary with gate bias. These special features cause the traditional method to determine effective channel length and series resistance inapplicable. In this letter, we propose a method to determine the "intrinsic" channel length and gate-voltage-dependent source-and-drain series resistance of an LDD MOSFET and a modal for the LDD device current at small drain-source voltage.