In this letter, we elucidate the ergodic capacity of multiple-input multiple-output (MIMO) systems with M-ary phase-shift keying (MPSK) modulation and time-multiplexed pilots in frequency-flat Rayleigh fading environment. With linear minimum mean square error (LMMSE) channel estimation, the optimal pilots design is presented. For mathematical tractability, we derive an easy-computing closed-form lower bound of the channel capacity. Based on the lower bound, the optimal power allocation between the data and pilots is also presented in closed-form, and the optimal training length is investigated by numerical optimization. It is shown that the transmit scheme with equal training and data power and optimized training length provides suboptimal performance, and the transmit scheme with optimized training length and training power is optimal. With the latter scheme, in most situations, the optimal training length equals the number of the transmit antennas and the corresponding optimal power allocation can be easily computed with the proposed formula.

To obtain large capacity, high quality mobile satellite communication systems in the future, we must use a multi-beam that can cope with extremely high levels of frequency reuse. This paper describes a novel resource allocation algorithm for multi-beam satellite communication systems that can dynamically adapt to maximum communication capacity without compromising quality. The algorithm combines two resource allocation schemes that enable it to contend with the ever-changing user distribution and inter-beam interference conditions. The first scheme optimizes the resources amongst beams. To minimize interference, the optimal constraint conditions are clarified when all clusters share and occupy the same bandwidth completely. These constraints are used in the optimization algorithm. The second scheme manages the various required resources and adapts them to the beam gain and interference levels at various user locations within a single beam. We propose a fixed power adaptive modulation scheme to obtain stable communications. This two-layered scheme can satisfactorily allocate multi-beam satellite resources to contend with the increasing communication capacity and still improve the quality.

This paper deals with a secret key agreement problem from correlated random numbers. It is proved that there is a pair of linear matrices that yields a secret key agreement in the situation wherein a sender, a legitimate receiver, and an eavesdropper have access to correlated random numbers. A relation between the coding problem of correlated sources and a secret key agreement problem from correlated random numbers are also discussed.

Recent work has shown that the usage of multiple antennas at the transmitter and receiver in a flat fading environment results in a linear increase in channel capacity. But increasing the number of antennas induces the higher hardware costs and computational burden. To overcome those problems, it is effective to select antennas appropriately among all available ones. In this paper, a new antenna selection method is proposed. The transmit antennas are selected so as to maximize the channel capacity using the genetic algorithm (GA) which is the one of the general random search algorithm. The results show that the proposed GA achieves almost the same performance as the optimal selection method with less computational amount.

Multiple-input multiple-output (MIMO) systems applying macroscopic selection diversity (MSD) are analyzed in composite fading channels through derived expressions of capacity outage probability. The MSD system uses a maximum capacity MIMO base station (BS) selection algorithm, where the results show a significant improvement in outage capacity.

Feedback-type Adaptive Array Antenna has been proposed for frequency division duplexed (FDD) system, where the mobile station (MS) measures channel characteristics and sends those back to the base station (BS). Using a higher number of feed-back bits provides better performance. However it wastes channel capacity of the up-link. On the other hand, error in feedback signals transmission causes significant performance degradation. To solve these problems, this paper proposes a method that the MS sends back the difference between the optimum weights calculated at the MS and weights which are currently used at the BS. Bit error rate performance of the system is shown under a realistic propagation condition.

The downlink (base-to-mobile) bit error rate (BER) performance for a mobile user with relatively weak received signal in a multicarrier-CDMA (MC-CDMA) cellular system can be improved by utilizing the site diversity reception. With joint use of MMSE-based frequency domain equalization (FDE) and antenna diversity combining, the site diversity operation will increase the downlink capacity. In this paper, an expression for the theoretical conditional BER for the given set of channel gains is derived based on Gaussian approximation of the interference components. The local average BER is then obtained by averaging the conditional BER over the given set of channel gains using Monte-Carlo numerical method. The outage probability is measured from the numerically obtained cumulative distribution of the local average BER to determine the downlink capacity. Results from theoretical computation are compared to the results from computer simulation and discussed.

This paper studies the optimization of the effective channel capacity of wideband code division multiple access (WCDMA) systems under Rayleigh fading environments. Firstly, the results for Shannon capacity of fading channels with channel side information are reviewed, where the capacity is achieved by using an optimal power control scheme. Secondly, an optimal interference threshold is set for a given system outage probability Pout to minimize total interference. Finally, the effective channel capacity of WCDMA is defined and a target SIR level γ* is derived with the Lagrangian multiplier method to maximize the effective channel capacity. It is shown that is dependent on the power control interference ratio (PCIR) ρ, the number of diversity paths identified by the receiver M, and the outage probability of the system. Simulation results are provided to validate the theoretical deductions. We conclude that the total effective channel capacity will be maximized as long as M4, and ρ0.5 for a proper value of .

In this letter, we study the capacity of fading channels with perfect channel side information (CSI) at the receiver and quantized CSI at the transmitter. We present a general algorithm for the joint design of optimal quantization and power control for maximizing the forward link capacity over flat fading channels. Numerical results for Rayleigh fading are given.

An FRPA (frequency reuse power allocation) technique by employing the frequency reuse notion as a strategy for overcoming the ICI (intercell interference) and maintaining the QoS (quality of service) at the cell boundary is described for broadband cellular networks. In the scheme, the total bandwidth is divided into sub-bands and two different power levels are then allocated to sub-bands based on the frequency reuse for forward-link cell planning. In order to prove the effectiveness of the proposed algorithm, a Monte Carlo simulation was performed based on the Chernoff upper bound. The simulation shows that this technique can achieve a high channel throughput while maintaining the required QoS at the cell boundary.

The enormous capacity potential of multiple-input multiple-output (MIMO) is based on some unrealistic assumptions, such as the complete channel state information (CCSI) at the receiver and Gaussian distributed data. In this paper, in frequency-flat Rayleigh fading environment, we investigate the ergodic capacity of MIMO systems with M-ary phase-shift keying (MPSK) modulation and superimposed pilots for channel estimation. With linear minimum mean square error (LMMSE) channel estimation, the optimal pilots design is presented. For the mathematical tractability, we also derive an easy-computing closed-form lower bound of the channel capacity. Furthermore, the optimal power allocation between the data and pilots is investigated by numerical optimization. It is shown that more power should be devoted to the data in low SNR environments and to the pilots in high SNR environments.

This paper clarifies a necessary condition and a sufficient condition for transmissibility for a given set of general sources and a given general broadcast channel. The approach is based on the information-spectrum methods introduced by Han and Verdu. Moreover, we consider the capacity region of the general broadcast channel with arbitrarily fixed error probabilities if we send independent private and common messages over the channel. Furthermore, we treat the capacity region for mixed broadcast channel.

This paper proposes homogeneous neural networks (HNNs), in which each neuron has identical weights. HNNs can realize shift-invariant associative memory, that is, HNNs can associate not only a memorized pattern but also its shifted ones. The transition property of HNNs is analyzed by the statistical method. We show the probability that each neuron outputs correctly and the error-correcting ability. Further, we show that HNNs cannot memorize over the number,, of patterns, where m is the number of neurons and k is the order of connections.

OFDM-based networks utilizing the frequency reuse factor of 1 may produce the severe ICI (intercell interference) at the cell boundary even though overall cell capacity is increased and network deployment is facilitated. In the forward-link, the ICI may rise above a QoS (quality of service) threshold beyond some distance from BSs (base stations). In this paper, we analyze the forward-link capacity of an MC-CDMA system as a function of the ICI according to the distance from a cell. To achieve this goal, a closed form of the outage probability is derived and utilized to obtain the accommodated number of users and system parameters.

A multihop connection scheme, where one or more mobile terminals relay transmission signals using the same access scheme between an end user terminal and its destination base station, is a promising approach to overcome reduction in cell size caused by high bit-rate data transmission. In a general radio communication system, the coverage area and system throughput are closely interrelated. In this paper, the performance of a multihop cellular network employing a CDMA access scheme, which is a promising candidate for beyond the third generation, is studied in terms of the coverage area and system throughput by conducting a link level simulation. The results show that a multihop connection expands the coverage area, especially in the case of light traffic, and also has an advantage in system throughput.

In this paper, we evaluate the effect of space-time coded cooperative relaying technique in multihop inter-vehicle communication (IVC) networks. The IVC systems have an issue that communication links are often blocked by obstacles such as heavy vehicles. The breakage of a radio link in multihop connections may significantly decrease the system throughput in multihop IVC networks. It is demonstrated through system-level evaluations that the cooperative relaying can offer remarkable capacity enhancement by exploiting multi-route diversity and overcoming accidental link breakage resulting from frequent topological changes.

The exact calculation of the ergodic and outage capacity for Rayleigh fading single-input multiple-output (SIMO) channels in the presence of unequal-power Rayleigh fading interferers is mathematically quite challenging due to the complicated distribution of the capacity. In this paper, a SIMO system with M receive antennas and N interferers is considered. Based on some statistical results, the closed-form upper and lower bound for the ergodic and outage capacity are derived respectively. These bounds are shown to be simple to compute and appear to be quite tight.

The effect of antenna correlation on the Multiple-Input Multiple-Output (MIMO) channel capacity in the real propagation environment is a topic of interest. In this paper, we present the results of a measurement campaign conducted in an indoor Line-Of-Sight (LOS) office environment. Channel responses were taken with varying distance in a static indoor environment. Results showed measurements with high received Signal-to-Noise Ratio (SNR) and a high level of correlation among the antenna elements. Further analysis of the results showed that MIMO systems can achieve sufficient channel capacity compared to the Single-Input Single-Output (SISO) system, despite high antenna correlation. Theoretical analysis reveals that when the SNR is sufficiently high, the loss in channel capacity due to high antenna correlation is relatively low. Therefore it is shown that in the indoor LOS environment, MIMO systems can be sufficiently efficient because the MIMO channel is more robust to antenna correlation when the SNR is high.

An essential issue in designing, operating and managing a modern network is to assure end-to-end QoS from users perspective, and in the meantime to optimize a certain average performance objective from the systems perspective. So in the first part of this paper, we address the above issue by using the rerouting approach, where the objective is to minimize the average cross-network packet delay in virtual circuit networks with the consideration of an end-to-end delay constraint (DCR) for each O-D pair. The problem is formulated as a multicommodity network flow problem with integer routing decision variables, where additional end-to-end delay constraints are considered. As the traffic demands increases over time, the rerouting approach may not be applicable, which results in the necessity of capacity augmentation. Henceforth, the second part of this paper is to jointly consider the link capacity assignment and the routing problem (JCR) at the same time where the objective is to minimize the total link installation cost with considering the average and end-to-end delay constraints. Unlike previous research tackling this problem with a two-phase approach, we propose an integrated approach to considering the routing and capacity assignment at the same time. The difficulties of DCR and JCR result from the integrality nature and particularly the nonconvexity property associated with the end-to-end delay constraints. We propose novel Lagrangean relaxation based algorithms to solve the DCR and the JCR problems. Through computational experiments, we show that the proposed algorithms calculate near-optimal solutions for the DCR problem and outperform previous two-phase approach for the JCR problem under all tested cases.

Single cell reuse of the same frequency, which is possible in DS-CDMA cellular systems, yields the option of site diversity to increase link capacity. In this letter, a generalized case of site diversity transmission is considered where multiple base stations (BS's) are involved in weighted transmissions with constant total transmit power to a target mobile station (MS). A general equation of conditional bit error rate (BER) is derived based on the model of weighted transmissions combined with antenna diversity reception and rake combining. It turns out theoretically that the optimum set of weights to maximize forward link capacity makes site selection diversity transmission (SSDT) the best performer. This theoretical analysis is confirmed by performance evaluation based on the Monte-Carlo simulation.