On the Deterministic-Code Capacity of the Two-User Discrete Memoryless Arbitrarily Varying General Broadcast Channel With Degraded Message Sets

An inner bound on the deterministic-code capacity region of the two-user discrete memoryless arbitrarily varying general broadcast channel (AVGBC) was characterized by Jahn, assuming that the common message capacity is nonzero; however, he did not indicate how one could decide whether the latter capacity is positive. Csiszaacuter and Narayan's result for the single-user arbitrarily varying channel (AVC) establishes the missing part in Jahn's characterization. Nevertheless, being based on Ahlswede's elimination technique, Jahn's characterization is not applicable for symmetrizable channels under state constraint. Here, the various notions of symmetrizability for the two-user broadcast AVC are defined. Sufficient non-symmetrizability condition that renders the common message capacity of the AVGBC positive is identified using an approach different from Jahn's. The decoding rules we use establish an achievable region under state and input constraints for the family of degraded message sets codes over the AVGBC     

The Capacity Region of the Gaussian Multiple-Input Multiple-Output Broadcast Channel

The Gaussian multiple-input multiple-output (MIMO) broadcast channel (BC) is considered. The dirty-paper coding (DPC) rate region is shown to coincide with the capacity region. To that end, a new notion of an enhanced broadcast channel is introduced and is used jointly with the entropy power inequality, to show that a superposition of Gaussian codes is optimal for the degraded vector broadcast channel and that DPC is optimal for the nondegraded case. Furthermore, the capacity region is characterized under a wide range of input constraints, accounting, as special cases, for the total power and the per-antenna power constraints     

Closed-Form Solutions to the Pareto Boundary and Distributed Beamforming Strategy for the Two-User MISO Interference Channel

The outer boundary of the achievable rate region for multiple-input single-output (MISO) interference channel (IC) is Pareto boundary, and all points on the Pareto boundary can be obtained by solving weighted sum rate maximization problem. Unfortunately, since the optimization problem is non-convex, it is generally very difficult to obtain the solutions without performing an exhaustive search. In this paper, the achievable rate region of the two-user MISO IC is considered. Firstly, by minimizing the interference power leaked to the other receiver for fixed useful signal power received at the intended receiver, the non-convex optimization problem is converted into a family of convex optimization problems. Secondly, after some conversions, the closed-form solutions to all Pareto optimal points are derived using the Lagrange duality theory, and the only computation involved is to solve a basic quadratic equation. Then, the antenna reduction is performed to further simplify the process of derivation. In order to avoid the exchange of channel state information (CSI) between base stations, a distributed iterative beamforming strategy which can achieve a approximate Pareto optimal outcome with only a few iterations is also proposed. Finally, the results are validated via numerical simulations.     

A Formulation of the Channel Capacity of Multiple-Access Channel

The necessary and sufficient condition of the channel capacity is rigorously formulated for the N -user discrete memoryless multiple-access channel (MAC). The essence is to invoke an elementary MAC where sizes of input alphabets are not greater than the size of output alphabet. The main objective is to demonstrate that the channel capacity of an MAC is achieved by an elementary MAC included in the original MAC. The proof is quite straightforward by the very definition of the elementary MAC. The second objective is to prove that the Kuhn-Tucker conditions of the elementary MAC are sufficient (obviously necessary) for the channel capacity. The latter proof requires two distinctive properties of the MAC: Every solution of the Kuhn-Tucker conditions is a local maximum on the domain of all possible input probability distributions (IPDs), and then particularly for the elementary MAC a set of IPDs for which the value of the mutual information is not smaller than the arbitrary positive number is connected on the domain. As a result, in respect of the channel capacity, the MAC in general can be regarded as an aggregate of a finite number of elementary MACs.     

A New Outer Bound and the Noisy-Interference Sum–Rate Capacity for Gaussian Interference Channels

A new outer bound on the capacity region of Gaussian interference channels is developed. The bound combines and improves existing genie-aided methods and is shown to give the sum–rate capacity for noisy interference as defined in this paper. Specifically, it is shown that if the channel crosstalk coefficient magnitudes lie below thresholds defined by the power constraints then single-user detection at each receiver is sum–rate optimal, i.e., treating the interference as noise incurs no loss in performance. This is the first capacity result for the Gaussian interference channel with weak to moderate interference. Furthermore, for certain mixed (weak and strong) interference scenarios, the new outer bounds give a corner point of the capacity region.      

A New Barankin Bound Approximation for the Prediction of the Threshold Region Performance of Maximum Likelihood Estimators

It is well known that the ML estimator exhibits a threshold effect, i.e., a rapid deterioration of estimation accuracy below a certain signal-to-noise ratio (SNR) or number of snapshots. This effect is caused by outliers and is not captured by standard tools such as the CramÉr-Rao bound (CRB). The search of the SNR threshold value (where the CRB becomes unreliable for prediction of maximum likelihood estimator variance) can be achieved with the help of the Barankin bound (BB), as proposed by many authors. The major drawback of the BB, in comparison with the CRB, is the absence of a general analytical formula, which compels one to resort to a discrete form, usually the Mcaulay–Seidman bound (MSB), requesting the search of an optimum over a set of test points. In this paper, we propose a new practical BB discrete form that provides, for a given set of test points, an improved SNR threshold prediction in comparison with existing approximations (MSB, Abel bound, Mcaulay–Hofstetter bound) at the expense of the computational complexity increased by a factor $leq(P+1)^{3}$ , where $P$ is the number of unknown parameters. We have derived its expression for the general Gaussian observation model to be used in place of existing approximations.      

The Capacity Region of the Degraded Multiple-Input Multiple-Output Compound Broadcast Channel

The capacity region of a compound multiple-antenna broadcast channel is characterized when the users exhibit a certain degradedness order. The channel under consideration has two users, each user has a finite set of possible realizations. The transmitter transmits two messages, one for each user, in such a manner that regardless of the actual realizations, both users will be able to decode their messages correctly. An alternative view of this channel is that of a broadcast channel with two common messages, each common message is intended to a different set of users. The degradedness order between the two sets of realizations/users is defined through an additional, fictitious, user whose channel is degraded with respect to all realizations/users from one set while all realizations/users from the other set are degraded with respect to him.     

A New Union Bound on the Error Probability of Binary Coded OFDM Systems in Wireless Environments

Orthogonal Frequency Division Multiplexing (OFDM) systems are commonly used to mitigate frequency-selective multipath fading and provide high-speed data transmission. In this paper, we derive new union bounds on the error probability of a coded OFDM system in wireless environments. In particular, we consider convolutionally coded OFDM systems employing single and multiple transmit antennas over correlated block fading (CBF) channels with perfect channel state information (CSI). Results show that the new union bound is tight to simulation results. In addition, the bound accurately captures the effect of the correlation between sub-carriers channels. It is shown that as the channel becomes more frequency-selective, the performance get better due to the increased frequency diversity. Moreover, the bound also captures the effect of multi-antenna as space diversity. The proposed bounds can be applied for coded OFDM systems employing different coding schemes over different channel models.     

A New Upper Bound on the Block Error Probability After Decoding Over the Erasure Channel

Motivated by cryptographic applications, we derive a new upper bound on the block error probability after decoding over the erasure channel. The bound works for all linear codes and is in terms of the generalized Hamming weights. It turns out to be quite useful for Reed-Muller codes for which all the generalized Hamming weights are known whereas the full weight distribution is only partially known. For these codes, the error probability is related to the cryptographic notion of algebraic immunity. We use our bound to show that the algebraic immunity of a random balanced m-variable Boolean function is of order ^m/₂(1-o(1)) with probability tending to 1 as m goes to infinity     

Optimality Properties,Closed-Form Parameterizations and Distributed Strategy of the Two-User MISO Interference Channel

In this paper, the closed-form parameterizations to the Pareto boundary for the two-user multiple-input single-output interference channel are studied. Firstly, for the equivalent channel model with each transmitter having only two antennas, the weighted sum-rate maximization (WSRMax) problem is reformulated with newly defined angle variables. Then, a centralized weighted leakage-plus-noise-to-signal ratio minimization (WLNSRMin) algorithm is proposed to find a locally optimal weighted sum-rate point. Each step of the algorithm is solved by evaluating closed-form expressions. A distributed algorithm is also given to avoid the exchange of the channel state information (CSI) between transmitters. Numerical results show that the centralized WLNSRMin algorithm converges to a local optimum of the WSRMax problem after a few iterations and the distributed algorithm achieves a performance very close to that of the centralized algorithm with only local CSI.

     

基于信道编码及空时编码级联的两用户协同分集

传统协同分集通过使网络中各单天线用户共享彼此天线,形成虚拟多天线阵列来实现空间分集,使得体积和功耗受限的网络终端也能获得分集增益,然而这并没有将信道编码和空时编码结合起来以使系统得到编码增益。为了能够获得编码增益来进一步改善系统性能,本文提出了一种基于信道编码和分布式空时分组码级联方式下的两用户协同分集方案,并且在准静态的瑞利衰落信道下对系统误码性能进行了理论推导和系统仿真,给出了误比特率的上限解析表达式。在协同用户间信道存在噪声的情况下,我们分别对CRC-DSTBC和CC-DSTBC级联下的发射方案进行了性能分析和系统仿真。仿真结果表明:即使协同用户间的信道存在噪声,本文所提出的协同分集方案与传统协同分集相比,不但获得了分集增益,同时也得到了编码增益,系统误比特率大大降低,从而显著提高了系统性能,并且这也和理论分析相吻合。     

Capacity Region of a Class of Gaussian Cognitive Degraded Broadcast Channel

This paper studies the cognitive broadcast channel in which the primary user com- municates to the primary receiver, while the secondary user has noncausal knowledge of the primary radio＇s codeword and expects to communicate to two secondary receivers. Comparing with the existing cognitive radio channel which considers only one secondary receiver, cognitive broadcast channel studies the case that there are multiple secondary receivers. To this end, we investigate the fundamental limits of the performance of the Gaussian cognitive broadcast channel from the information theoretic perspective. Specifically, we derive the capacity region of the Gaussian cognitive degraded broadcast channel with weak interference.     

A Constructive Capacity Lower Bound of the Inhomogeneous Wireless Networks

Many research results in the direction of wireless network capacity are based on the homogeneous Poisson node process and random homogeneous traffic. However, most of the realistic wireless networks are inhomogeneous. And for this kind of networks, this paper gives a constructive capacity lower bound, which may be effective on network designing. To ensure significant inhomogeneities, we select both inhomogeneous node process and traffic. We divide the transmission into two parts: intra-cluster transmission and inter-cluster transmission. Within each distinct cluster, a circular percolation model is proposed and the highway system is established. Different with regular rectangle percolation model, the highway in our model is in the radial direction or around the circle. Based on this model, we propose a routing strategy and get the intra-cluster per-node rate. In the following, among these clusters, we set many “information pipes” connecting them. By getting the results of per-node transmission rate of each part, we can find that the bottleneck of the throughput capacity is caused by the difference of the node density all over the network region. Specially, the lower bound interval of the capacity can be easily obtained when the traffic is inhomogeneous.     

A New Closed-Form Expressions of Channel Capacity with MRC,EGC and SC Over Lognormal Fading Channel

In this work, we derive the closed-form expressions of channel capacity with maximal ratio combining, equal gain combining and selection combining schemes under different transmission policies such as optimal power and rate adaptation, optimal rate adaptation, channel inversion with fixed rate (CIFR) and truncated CIFR. Various approximations to the intractable integrals have been proposed using methods such as Holtzman and Gauss–Hermite approximations and simpler expressions are suggested. Moreover, as an application, the channel capacity of lognormally distributed fading channel in the interference-limited environment is discussed. The obtained closed-form expressions have been validated with the exact numerical results.

     

Secrecy Capacity Region of a Multiple-Antenna Gaussian Broadcast Channel With Confidential Messages

Wireless communication is particularly susceptible to eavesdropping due to its broadcast nature. Security and privacy systems have become critical for wireless providers and enterprise networks. This paper considers the problem of secret communication over the Gaussian broadcast channel, where a multiple-antenna transmitter wishes to send independent confidential messages to two users with information-theoretic secrecy. That is, each user would like to obtain its own confidential message in a reliable and safe manner. This communication model is referred to as the multiple-antenna Gaussian broadcast channel with confidential messages (MGBC-CM). Under this communication scenario, a secret dirty-paper coding scheme and the corresponding achievable secrecy rate region are first developed based on Gaussian codebooks. Next, a computable Sato-type outer bound on the secrecy capacity region is provided for the MGBC-CM. Furthermore, the Sato-type outer bound proves to be consistent with the boundary of the secret dirty-paper coding achievable rate region, and hence, the secrecy capacity region of the MGBC-CM is established. Finally, two numerical examples demonstrate that both users can achieve positive rates simultaneously under the information-theoretic secrecy requirement.      

New Models of Prefix Adder Topologies

This paper introduces a variety of approaches for assessing logarithmic-depth parallel prefix adders: a delay model based on a slight modification to the Logical Effort methodology is derived; a simple area model based on wire pitch is described; a new parameter, span(i), is defined that provides a mechanism for determining cell count and whether a prefix tree exhibits idempotency. The models are tested against Knowles Family of Adders and found to give results that are within 5% of those reported by Knowles, as well as allowing a full assessment of the family to be made. Finally, the delay and area models are used to assess the Flagged Prefix Adder, an enhanced adder capable of computing absolute differences.Neil Burgess Ph.D., M.Sc., B.Sc., was awarded a PhD by Southampton University (U.K.) in 1986 for his work on graph theoretic techniques to model failure mechanisms in MOS VLSI circuits. He then spent two years designing DSP VLSI chips at GECs Hirst Research Labs in Wembley, London, before moving to academia to lecture in Microelectronic Systems, first at Brunel University, London, then for 6 years at the University of Adelaide, Australia. In 1996, he was appointed Director of the University of Adelaides Centre for High-Performance Technology and Systems, whose major research activity was centred on the design of high-performance digital microelectronic circuits. In 1999, he returned to the U.K. to take up a Professorial Research Fellowship in the Division of Electronics at Cardiff Universitys School of Engineering. His research activities in these posts have revolved around digital VLSI design in both CMOS and GaAs, and high-speed arithmetic processing, expanding this work to address applications including cryptography, image compression, and DSP. In October 2003, he left the academic sector to join Icera Semiconductor, a silicon start-up company whose design office is in Bristol, UK. He has published over 80 papers and is an associate editor of the IEEE Transactions of Computers. He co-chaired the 14th and 15th IEEE Symposia on Computer Arithmetic (in 1999 and 2001), the 13th IEEE International Conference on Application-Specific Systems Architectures and Processors (2002), and the 37th and 38th IEEE Asilomar Conference on Signals, Systems and Computers (2003 and 2004).     

Signal Design for the Amplitude-Limited Gaussian Channel by Error Bound Optimization

A necessary and sufficient condition is presented for an input signal alphabet to optimize the random coding exponent for a time-discrete channel with signals restricted in amplitude. It is applied to the white noise Gaussian channel for signals in one and two dimensions. By use of this theorem the best input signal quantizafion is determined by numerical optimization. Results are presented on the number of amplitude or envelope levels needed to maximize the error bound parameter R0at different signal-to-noise ratios. For one-dimensional (baseband) signals a binary antipodal configuration is optimum, in the sense of maximizing R0, for signal-to-noise ratios below 6.9 dB. For two-dimensional (passband) signals with limited envelope, phase modulation is shown to be optimum for signal-to-noise ratios below 7.35 dB.     

A Finite-Length Algorithm for LDPC Codes Without Repeated Edges on the Binary Erasure Channel

This paper considers the performance, on the binary erasure channel, of low-density parity-check (LDPC) codes without repeated edges in their Tanner graphs. A modification to existing finite-length analysis algorithms is presented for these codes.      

图像水印的信道容量模型及其估算

运用信息论的基本原理来估计一幅图像中可以嵌入的信息量，就是水印信道的理论容量问题。文章首先给出了水印信道的模型，然后分析了DCT系数的分布特点并从理论上估计了水印信道的容量，最后给出了相应的实验结果。     

An Upper Bound for Limited Rate Feedback MIMO Capacity

We develop a technique to upper bound the pointto- point MIMO limited rate feedback (LRF) capacity under a wide class of vector quantization schemes. The upper bound turns out to be tight and can also be used to obtain an absolute upper bound by using a bounding distribution for Grassmannian beamforming. The bounding technique can be applied to other problems requiring the exact evaluation of the expected value of matrix determinant.