Array (Smart) Antennas Improve GSM Performance

As wireless data applications over cellular networks become more widespread, the pressure to increase capacity will become even more intense. Capacity in the 800 and 900 MHz bands, where bandwidth is restricted, is already becoming a limiting factor. This paper attempts to address how the application of smart antenna systems has brought about improvements in call quality and increased capacity through reduced Interference in Mobile Communication. The smart antenna may be in a variety of ways to improve the performance of a communications system. Perhaps most importantly is its capability to cancel co-channel interference. It helps in improving the system performance by increasing the channel capacity, spectrum efficiency, extending range coverage, speech quality, enabling tighter reuse of frequencies within a cellular network and economically, feasible increased signal gain, greater, reduced multipath reflection. It has been argued that Smart antennas and the Algorithms to control them are vital to a high-capacity communication system development.

Estimation of co-channel interference between cities caused by ducting and turbulence

With the rapid development of the fifth-generation(5 G)mobile communication technology,the application of each frequency band has reached the extreme,causing mutual interference between different modules.Hence,there is a requirement for detecting filtering and preventing interference.In the troposphere,over-the-horizon propagation occurs in atmospheric ducts and turbulent media.The effects of both ducting and turbulence can increase the probability of occurrence of long-distance co-channel interference(CCI),in turn,severely affecting the key performance indicators such as system access,handover and drop.In the 5 G era,to ensure communication channels and information security,CCI must be reduced.This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries.It combines Hitney’s radio physical optical model and Wagner’s nonuniform turbulent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct.The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments.Finally,as a specific case,the topographical boundaries between several cities in the East China Plain were considered,and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments.The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.

Cluster-Based Interference-Free MAC Protocol with Load Aware in Software Defined VANET

In order to reduce the interference,a novel,cluster-based medium access control(MAC)protocol with load aware for VANETs is proposed in this paper.First,all vehicles on roads are grouped into stable clusters in the light of their direction,number of neighbors,link reliability,and traffic load.By utilizing the advantages of centralized control in software defined VANETs(SDVN),cluster stability can be maintained in real-time.Second,a contention-free MAC mechanism composed of inter-cluster multi-channel allocation and intra-cluster dynamic TDMA frame allocation is proposed to prevent co-channel interference and hidden terminal interference.Simulation results show that the proposed protocol outperforms some existing protocols in cluster stability,delivery ratio,throughput and delay performance.

TDOA estimation of dual-satellites interference localization based on blind separation

The time difference of arrival(TDOA)estimation plays a crucial role in the accurate localization of the satellite interference source.In the dual-satellites interference source localization system,the target signal from the adjacent satellite is likely to be interfered by the normal communication signal with the same frequency.Therefore,the signal to noise ratio(SNR)of the target signal would become too low,and the TDOA estimation through cross-correlation processing would be unreliable or even unattainable.This paper proposes a technique based on blind separation to solve the co-channel interference problem,where separation of the mixed signal can be carried out by the particle filter(PF)algorithm.The experimental results show that the proposed method could achieve more accurate TDOA estimation.The measured data obtained by using the software radio platform at 915 MHz and 2 GHz respectively verify the effectiveness of the proposed method.

Outage Probability Analysis of Relay Systems over K-μ Fading Channels

This paper provides an analytical framework for the outage probability evaluation of dual-hop decode-and-forward relay systems operating over K-μfading channels in the presence of co-channel interference. The interferers are independent non-identically distributed K-μfading. An accurate analytical-form expression for the cumulative distribution function of the received signal power to interference and noise ratio is derived. Various numerical results are compared with Monte Carlo simulation results in order to corroborate the accuracy of the proposed expressions. Our results show that increasing the value of kappa of main links will decrease the outage probability of relay systems. Furthermore, the system performance degrades with the number of interferences.

Generalized Physical Layer Channel Model for RelayBased Super Dense Networks

The κ-μ fading model is an advanced channel model in super dense wireless networks.In this paper,we evaluate the performance of the system over κ-μ fading channel in super dense relay networks with consideration of multiple independent but not necessarily identically distributed(i.n.i.d.) cochannel interference(CCI) under interferencelimited environment.More specifically,we derive a useful and accurate cumulative distribution function(CDF) expression of the end-to-end signal-to-interference plus noise(SINR) ratio.Moreover,we derive novel analytical expressions of the outage probability(OP),average bit error probability(ABEP) and average capacity for binary modulation types and arbitrary positive values of κ-and μ of such system.Furthermore,we propose asymptotic analysis for both the OP and ABEP to give physical insights.A simplified analytical form for the ABEP at high-SNR regimes is provided as well.Finally,the accuracy of the derived expressions is well validated by Monte Carlo simulations.

Low Complexity Multiuser Detection with Recursively Successive Zero-Forcing and SIC Based on Nullspace for Multiuser MIMO-OFDM System

To improve the spectrum efficiency, this paper considers the multiuser detection with the MU-MIMO technology for multiuser MIMO-OFDM system uplink with the same subcarrier shared by multiple users. A low complexity multiuser detection algorithm with recursively successive zero-forcing and successive interference cancellation(RSZF-SIC) based on nullspace is proposed. The RSZF process based on the block diagonalization(BD) technique eliminates the co-channel interference(CCI) by a recursive method based on the nullspace orthogonal theorem. The SIC process detects the user signals respectively with the reasonable user detection sequence based on the results of the RSZF process. The computational complexity of the proposed algorithm is effectively reduced by reducing the total number of singular value decomposition(SVD) operations and the dimension of the SVD matrix in the recursive procedure. The performance of the proposed algorithm is improved in terms of bit error rate and sum capacity of the system, especially in the highSNR regime.

Codebook selected beamforming algorithm for multiuser MIMO systems

For reducing the inter-user interference in multi-user multiple-input multiple-output（MU-MIMO） wireless communication systems,e.g.,MIMO-orthogonal frequency division multiplexing（MIMO-OFDM） systems,it is often desirable to the complex preprocessing at the transmitter.This paper proposes a multi-user beamforming algorithm with sub-codebook selection.Based on the minimal leakage criterion,the codebook selection,limited feed-forward and minimum mean square error（MMSE） detection are combined in the proposed algorithm.This avoids the complex channel matrix decomposition and inversion.Consequently,the computational complexity at the transmitter is significantly reduced.Simulation results show that the proposed algorithm performs better than existing beamforming algorithms.

PERFORMANCE ANALYSIS OF TWO-WAY AMPLIFY-AND-FORWARD RELAYING SYSTEM WITH MULTIPLE INTERFERERS AT THE RELAY

In this paper,we investigate the performance of the two-way Amplify-and-Forward(AF) relaying systems in an interference-limited Rayleigh fading environment.More specifically,assuming the presence of Rayleigh faded multiple interferers at the AF relay and noisy sources,an approximate closed-form expression for the Overall Outage Probability(OOP) and an integral expression for the average Symbol Error Probability(SEP) are derived.The analysis results are verified through com-parison with the Monte Carlo simulation results.

A New Approach for Wireless Cellular Network Design

Wise arrangement of antennas is critical in wireless cellular systems for both reductions of co-channel interference (CCI) and increase the quality of service (QoS). In this paper, a novel architecture for antenna arrangement in CDMA wireless cellular systems is presented. In this architecture that we called Microzone, every cell is divided into three (or more) zones and information transmission in downlink channel is done by an antenna which is placed at the outer region of the related zone. Also, the transmitting signal by the mobile station (MS) in uplink channel is received by all the antennas of the related cell. Analytical calculations of the received signal to noise ratio (SIR) and outage probability for both microzone and used architectures show that proposed architecture has better performance in compared with the used architecture. Also, simulation results confirm lower outage probability in uplink channel for microzone architecture.

Finite Series Representation of Rician Shadowed Channel with Integral Fading Parameter and the Associated Exact Performance Analysis

With the deployment of small cells and device to device communications in future heterogeneous networks,in many situations we would encounter mobile radio channels with partly blocked line of sight component,which are well modeled by the Rician shadowed(RS) fading channel.In this paper,by the usage of Kummer transformation,a simplified representation of the RS fading channel with integral fading parameter is given.It is a finite series representation involving only exponential function and low order polynomials.This allows engineers not only the closed-form expressions for exact performance analysis over RS fading channel,but also the insights on the system design tactics.

SAE-TOPSIS algorithm for vertical handoff decision in heterogeneous wireless networks

An improved technique for order preference by similarity to ideal solution （TOPSIS） algorithm, SAE-TOPSIS, is proposed for the vertical handoff decision in heterogeneous wireless networks. The signal to interference plus noise ratio （SINR） effects, analytic hierarchy process （AHP） and infor- mation entropy （SAE） weight method were introduced into the algorithm. Handoff decision meeting the multi-attribute quality of service （QoS） requirement is made according to an attribute matrix and weight vector using the TOPSIS algorithm. The simulation results have shown that the proposed algo- rithm can provide satisfactory performance fitted to the characteristics of the traffic.

Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

Orthogonal space-time block codes （OSTBCs） are an efficient mean in order to exploit the diversity offered by the wireless multiple-input multiple-output （MIMO） channel. This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out （MISO） Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise, and derives exact expressions of the ergodic capacity and outage probability （capacity distribution） for such OSTBCs. Some numerical examples are given to illustrate the effect of co-channel interference on the ergodic and outage capacity of OSTBCs.

Robust linear receivers for STBC systems with unknown co-channel interference

Focusing on space-time block code （STBC） systems with unknown co-channel interference, an oblique projection-based robust linear receiver is proposed in this paper.Based on the oblique projection, the desired signal subspace and interference-plus-noise subspace are first identified from the received signal.Then the matched filter receiver is used to decode the STBC encoded signals in the desired signal subspace.Simulation results show that the proposed linear receiver obtains significant performance improvement over conventional Capon-type receivers under finite sample-size situations and in the presence of channel estimation errors.

Inter-domain traffic balancing with co-channel interference management in multi-domain heterogeneous network for LTE-A

Heterogeneous network （Het-Net） is part of the long-term evolution advanced （LTE-A） study item and represents cellular deployments with a mixture of cells of different overlapping coverage areas, e.g., a number of relay and pico cells overlaid by a macro cell in the same frequency. Traffic balancing and interference management are required in Het-Net design for LTE-A to maintain system performance. In this paper, we propose an inter-domain cooperative traffic balancing scheme focusing on reducing the effective resource cost and mitigating the co-channel interference in multi-domain Het-Net. We first set up the conception of multi-domain in Het-Net and incorporate the co-channel interference into the proposed traffic balancing scheme. Then we model the traffic balancing issue as a multi-domain traffic resource optimization problem for minimizing the effective resource cost. The detailed implementation for the proposed traffic balancing scheme is designed. In the numerical evaluation, the genetic algorithm （GA） as an optimization method is used to demonstrate that the total effective resource cost is significantly reduced through our proposed inter-domain traffic balancing scheme, comparing with the intra-domain traffic balancing scheme. The 43% of the resource cost is saved. In the system level simulation, the performance results of signal interference noise ratio （SINR） and throughput demonstrate that the proposed scheme has great advantages in interference management in Het-Net.

GSM Co-Channel and Adjacent Channel Interference Analysis and Optimization

Most current Global System for Mobile Communications （GSM） frequency planning methods evaluate the interference and assign frequencies based on measurement reports. Assigning the same or adjacent frequencies to cells close to each other will introduce co-channel and adjacent channel interference which will reduce network performance. Traditionally, man power is used to check and allocate new frequencies which is time consuming and the accuracy is not satisfactory. This paper presents an intelligent analysis method for optimization of co-channel and adjacent channel interference by exploiting cell configuration information. The method defines an interference evaluation model by analyzing various factors such as the base station layer, the azimuth ward relationship, and the cell neighborhood relationships. The interference for each frequency is evaluated and the problem frequencies are optimized. This method is verified by a large number of actual datasets from an in-service GSM network. The results show this method has better intelligence, accuracy, timeliness, and visualization than traditional methods.

Improved Analysis of Co-Channel Interference in Cellular Communications Systems

In terms of the carrier-to-interference-ratio, the performance of co-channel interference in cellular communications systems is studied. The approach is based on an improved analysis, which allows to take into account some area in the desired sector may not be interfered by some co-channel sectors with exact geometrical analysis, instead of the entire sector interfered by some co-channel sectors. Other features, such as power control and the number of interferences are also included.

Optimization of digital multi-beamforming for space-based ADS-B using distributed cooperative coevolution with an adaptive grouping strategy

Space-based Automatic Dependent Surveillance-Broadcast(ADS-B)technology can eliminate the blind spots of terrestrial ADS-B systems because of its global coverage capability.However,the space-based ADS-B system faces new problems such as extremely low Signal-toNoise Ratio(SNR)and serious co-channel interference,which result in long update intervals.To minimize the position message update interval at an update probability of 95%with full coverage constraint,this paper presents an optimization model of digital multi-beamforming for space-based ADS-B.Then,a coevolution method DECCG_A&A is proposed to enhance the optimization efficiency by using an improved adaptive grouping strategy.The strategy is based on the locations of uncovered areas and the aircraft density under the coverage of each beam.Simulation results show that the update interval can be effectively controlled to be below 8 seconds compared with other existing methods,and DECCG_A&A is superior in convergence to the Genetic Algorithm(GA)as well as the coevolution algorithms using other grouping strategies.Overall,the proposed optimization model and method can significantly reduce the update interval,thus improving the surveillance performance of space-based ADS-B for air traffic control.

On Issues about the Application of MIMO in Mobile Cellular Communications

The convenience of mobile communications and the increasing demand for higher data transmitting rate have motivated people to explore more efficient methods of signal transmission because of the limited spectral resource. Multiple-Input and Multiple-Output (MIMO) is a high spectral efficient method and the theoretical capacity of a MIMO channel increases linearly with the number of transmitting/receiving antennas under the ideal conditions. We can adopt MIMO technology in the new generation of mobile cellular communication systems, which is IP based and requires high data rate to support multimedia services. Although much progress has been made in MIMO area recently, there are some problems in its practical application, especially in cellular application. In this paper we will analyze the channel model, the capacity and the technology of MIMO, and then we will focus on the issues of MIMO application in mobile cellular system by the Monte Carlo simulation and give the available solution schemes for the issues.

A New Dynamic Channel Allocation Scheme for Microcellular Systems

A new Distributed Dynamic Channel Allocation (DDCA) algorithm named Combined DDCA is proposed in this paper.In this algorithm, each base station selects channels by learning through past experience of channel usage together with CIR measurement. Computer simulations are used to evaluate system performances. Performances are evaluated in two criteria, blocking probability and interaction probability. Comparisons with other DDCA algorithms have been carried out to validate the proposed algorithm.