Average SIR estimation in cellular networks with best server policy

Distributed antenna system (DAS)-aided unity frequency reuse (UFR) and fractional frequency reuse (FFR) transmission scenarios are investigated in this paper, employing the classic multiobjective of nondominated sorting genetic algorithm II (NSGA-II) for maximizing cell throughput and the coverage. More specifically, coordinated multipoint (CoMP) cooperation is invoked among the distributed antennas (DAs) and the base station (BS) in support of the mobile stations (MSs) roaming at the cell edge, while considering a range of practical impairments. We demonstrate that the received signal-to-interference ratio (SIR) of non-CoMP transmissions follows the lognormal distribution by taking into account both fast fading and large-scale shadowing and path-loss effects. Our simulation results demonstrate that DAS-aided cooperation is capable of achieving a fivefold increased throughput over that of the traditional arrangement. Explicitly, an average throughput per channel of 6.61 bits/symbol may be achieved.

Due to its mathematical tractability, the homogeneous Poisson point process (PPP) has been employed to model wireless networks and analyze their performance widely. PPP falls short in modeling the effect of interference management techniques, which typically introduces some form of spatial mutual exclusion among base stations (BSs). Considering the spatial mutual exclusion between macro BSs s (BSs), in this paper, we studies the coverage performance of a two-tier heterogeneous cellular network (HCN) modeled by Poisson hard-core process (PHCP) and PPP. We first provide the approximate expression of coverage probability of the two-tier PHCP-PPP HCN with the use of PT-ASAPPP method, which stands for “per tier approximate signal to interference ratio (SIR) analysis based on PPP. In this method, each tier is approximated to PPP by using SIR gain. The concrete expression of the SIR gain G PHCP for PHCP model is derived through simulation and data fitting. Simulation results verify the correctness of theoretical analysis and the effectiveness of PT-ASAPPP method.

Filter bank multicarrier with pulse amplitude modulation (FBMC-PAM) is a candidate waveform for the fifth generation of wireless networks (5G). It can transmit at the same rate as orthogonal frequency division multiplexing (OFDM) opposed to the conventional FBMC-based systems. It also has a minimum overlapping factor leading to a transmit signal with a shorter ramp-up and ramp-down than the existing FBMC- based systems. However, this brings some shortcomings to the FBMCPAM system in terms of equalization. In this paper, performance of FBMC-PAM is studied in massive multiple-input multipleoutput (MIMO) channels. It is discussed that although in massive MIMO channels, multiuser interference as well as channel noise average out, there remains some residual interference due to the channel distortions even for an infinite number of base station (BS) antennas. Consequently, the signal to interference ratio (SIR) saturates after the number of BS antennas reaches a certain value. To quantify this saturation level, we find an upper bound for the SIR performance of FBMC-PAM in such channels. Then, our theoretical analysis is confirmed through simulations. Moreover, it is shown that by choosing an appropriate number of subcarriers, although the SIR saturates, FBMC-PAM can equalize the channel efficiently and the error floor in the bit error rate (BER) can be completely removed.We have chosen OFDM as a benchmark, because of its infinite SIR in multipath channels. We also show that FBMC-PAM provides even a better BER performance than OFDM due to its higher bandwidth efficiency.

In this article, we propose a network planning algorithm for IEEE802.11g, which minimises the total interferences between access points while maintaining a required quality of service (QoS), measured by users' signal to interference ratio (SIR). Three planning problems are formulated as integer linear programs. (1) A frequency assignment problem, which assigns frequencies to access points while minimising total interferences and ensuring users' SIR higher than a required threshold. (2) Assuming the optimal frequency assignment, a power management problem is modelled to assign five different power levels to access points while reducing the network total interference and ensuring the required QoS is met. (3) Given the frequency and power assignments, a load balancing problem is formulated to minimise the maximum number of users assigned per access point, taking into consideration users' QoS. Once the planning is done, new joining users are dynamically assigned to the less loaded acceptable access point. Based on realistic scenarios analysis, we show that the proposed planning achieves significant improvement in average user SIR and power savings while balancing the network. In fact, for one of the analysed scenarios the algorithm achieved 55% power savings while the SIR increased by 6 dB improving the QoS.

The problem of finding an optimal base station (BS) configuration for CDMA networks given a set of candidate BS sites is investigated. The design is first formulated as an optimization problem. Features which are unique to CDMA, such as power control, intra-cell and other cell interference, etc., are included in our consideration. In particular, the signal-to-interference ratio (SIR) in both uplink and downlink of each MS is taken as the quality of measure. The solution to the problem is simplified by using a heuristic algorithm. The heuristic begins from all candidate BS sites being activated and assignment of each mobile station (MS) to BS is based on smallest path loss. It then proceeds to deactivate the sites one by one until the minimum number of sites needed to serve the traffic is obtained

Cochannel interference is the most important issue in cellular mobile systems. It can be reduced by increasing the frequency re-use distance among the cochannel cells while keeping constant cell radius which improves the quality of a cellular mobile system. But this will decrease the overall network capacity because cluster size, which is inversely proportional to network capacity, also increases. Beamforming using antenna arrays is an effective technique to reduce cochannel interference while cluster size remains the same. Here first we use beamforming technique at the base station to reduce uplink cochannel interference and hence improvement in uplink carrier to interference ratio (CIR). Then we use power control together with the beamforming technique for further improvement in CIR and hence increase in network capacity. Both beamforming and power control parameters are updated iteratively in our proposed algorithm so that they jointly increase the network capacity. There are many other advantages of beamforming and power control such as saving in power of mobile station but here we focus only on CIR Improvement because it is the most common parameter in all access schemes like FDMA, TDMA, CDMA and SDMA.

This paper considers optimization and implementation of the pulse shape for Orthogonal Frequency Division Multiplexing (OFDM) systems over doubly dispersive channel. The proposed pulse shape is expressed as a linear combination of the most localized Hermite waveforms. In our previous works, we have proposed pulses optimization based on an exact expression of the Signal to Interference Ratio (SIR). In order to accelerate the optimization procedure, we propose an approximate expression of the SIR using Taylor series of interference and desired signal mean powers. For a performance evaluation of the optimized OFDM system, we propose an efficient implementation of both the modulator and the demodulator of the system and an efficient method to find out the resulting simulated SIR. Simulations results, obtained for different values of the dispersion factor, show that the SIR computed through system level simulation matches the maximum achievable SIR obtained through numerical optimization.

This paper analyzes the packet error rate (PER) in both mobile networks and cellular systems under interference-limited conditions. The analysis characterizes the time-varying signal-to-interference ratio (SIR) in the fading channels. First, the level crossing rate (LCR) and the average outage duration (AOD) of SIR are derived. The derivation leads to a new Markov model that classifies the propagation conditions into two exclusive states: one represents the condition that SIR is greater than a certain threshold. Next, PER is analytically derived on the basis of the model. The results show that the PER performance of the ad-hoc network is almost the same as that of the cellular system.

In wireless networks, the distances from a user to its desired transmitters and undesired interferers play a critical role in its channel quality. In this letter, we study this location-dependence in a cellular network, where a user is always served by its nearest base station. For any stationary and ergodic base station process, we partition its associated Voronoi cells into the cell centers and the cell boundaries. We show that in Poisson networks, the top fraction ${x}$ of users enjoy a signal-to-interference ratio (SIR) gain of ${-}{5}{\alpha }\text {log}_{{10}}{x}$ dB relative to the typical user for Rayleigh fading and the power-law path loss with the exponent $\alpha $ . For the cell boundary users, we give both the exact and asymptotic form of the SIR distribution. As such, this letter permits the grouping of users and the analysis of different groups of users.

This paper proposes a novel heuristic algorithm that mitigates pilot contamination in Massive MIMO (multiple-input, multiple-output) systems by optimizing the allocation of pilots, which are a shared resource among base stations (BSs). The goal is to minimize the effect of pilot contamination caused by interference from reusing the same pilot sequence from multiple user equipment (UE) in different cells. Specifically, we aim to maximize the minimum uplink signal to interference ratio (SIR) through the network by assigning the same pilot to the UEs in different cells that cause the least amount of interference. For this purpose, the algorithm starts with two cells that have the worst arithmetic mean of the potential SIR between their users. Then the algorithm continues the assignment procedure for the rest of the cells depending on the arithmetic mean of the worst potential SIR of the users of a cell and the users of the already assigned cells. The simulation results showed that our results are very close to the optimal solution where the exhaustive search is feasible, and outperforms the results obtained from recently published related work which served as a benchmark when the exhaustive search could not be applied to the search space size.

The spectral efficiency of cellular networks can be improved when proximate users engage in device-to-device (D2D) communications to communicate directly without going through a base station. However, D2D communications that are not properly designed may generate interference with existing cellular networks. In this paper, we study resource allocation and power control to minimize the probability of an outage and maximize the overall network throughput. We investigate three power control-based schemes: the Partial Co-channel based Overlap Resource Power Control (PC.OVER), Fractional Frequency Reuse based Overlap Resource Power Control (FFR.OVER) and Fractional Frequency Reuse based Adaptive Power Control (FFR.APC) and also compare their performance. In PC.OVER, a certain portion of the total bandwidth is dedicated to the D2D. The FFR.OVER and FFR.APC schemes combine the FFR techniques and the power control mechanism. In FFR, the entire frequency band is partitioned into two parts, including a central and edge sub-bands. Macrocell users (mUEs) transmit using uniform power in the inner and outer regions of the cell, and in all three schemes, the D2D receivers (D2DRs) transmit with low power when more than one D2DRs share a resource block (RB) with the macrocells. For PC.OVER and FFR.OVER, the power of the D2DRs is reduced to its minimum, and for the FFR.APC scheme, the transmission power of the D2DRs is iteratively adjusted to satisfy the signal to interference ratio (SIR) threshold. The three schemes exhibit a significant improvement in the overall system capacity as well as in the probability of a user outage when compared to a conventional scheme.

Heterogeneous cellular networks (HCNs) constitute a necessary step in the evolution of cellular networks. In this paper, we apply the signal-to-interference ratio (SIR) meta distribution framework for a refined SIR performance analysis of HCNs, focusing on K-tier heterogeneous cellular networks based on the homogeneous independent Poisson point process (HIP) model, with range expansion bias (offloading bias) in each tier. Expressions for the b-th moment of the conditional success probability for both the entire network and each tier are derived, based on which the exact meta distributions and the beta approximations are evaluated and compared. Key performance metrics including the mean success probability, the variance of the conditional success probability, the mean local delay and the asymptotic SIR gains of each tier are obtained. The results show that the biases are detrimental to the overall mean success probability of the whole network and that the b-th moment curve (versus the SIR threshold) of the conditional success probability of each tier can be excellently approximated by the horizontal shifted versions of the first moment curve of the single-tier PPP network. We also provide lower bounds for the region of the active probabilities of the base stations to keep the mean local delay of each tier finite.

Spectrum management is one of the key functions needed for opportunistic spectrum access (OSA) to utilize white space without causing harmful interference to incumbent receivers. Geo-location database approaches using radio propagation estimation have been regarded as practical spectrum management methods. However, propagation models inevitably include an estimation error of path loss in actual radio environments, resulting in estimation error of carrier to interference ratio (CIR) of the incumbent receivers. Consequently, an allowable transmit power of the opportunistic system has to be limited to keep the CIR at a required level. This could prevent white space from being efficiently utilized. To improve the accuracy of CIR estimation, we propose monitoring-based spectrum management. In the proposed technology, referred to as Interference Monitoring, a monitoring node located near the incumbent receivers actually measures both the interference signals and the incumbent signals. Using the measurement results, the CIR estimates are compensated based on minimum mean square error (MMSE) criterion. The proposed Interference Monitoring can be extended cooperatively to utilize spatial diversity. Analytical evaluations assuming a simple cellular system model show that the Interference Monitoring can more accurately estimate CIR, and thus it can significantly increase the allowable transmit power. For an urban macro cell, the Interference Monitoring with a single node achieved more than a 4 dB increase of the transmit power; the Cooperative Interference Monitoring with 4 nodes achieved more than a 7 dB increase. Thus, the Interference Monitoring can expand opportunities for white space utilization without increasing the interference to the incumbent system.

In this paper, we study the network average power consumption minimization problem in a two-tier heterogeneous network by optimally tuning the activation ratio of micro base stations (BSs) under the quality of service (QoS) constraints of the network mean queueing delay and the network signal-to-interference ratio (SIR) coverage. With the consideration of dynamic packets arrivals, each BS can either be busy or be idle depending on its queueing status. The network performance is thus critically determined by the traffic intensity of each BS. With the assumption of universal frequency reuse, the average traffic intensity of each tier is characterized by a set of fixed-point equations, which can be solved by a proposed iterative method. By using the approximation that BSs of the same tier have the same SIR coverage, the cumulative distribution function of the traffic intensity of each tier is further obtained. On that basis, the network average power consumption per area, the network mean queueing delay, and the network SIR coverage are characterized. Numerical results demonstrate that if the idle power coefficient is below a certain threshold, then the optimal activation ratio equals the one to minimize the network average power consumption per area; otherwise, the optimal activation ratio can be obtained according to the QoS constraints. It is further shown that universal frequency reuse outperforms spectrum partitioning in terms of both the network average power consumption and the network SIR coverage in the considered scenario.

Soft handoff techniques are generally used in the downlink of CDMA cellular systems. When there is traffic deviation, the communications quality differs between cells. Some methods of equalizing the quality, such as signal-to-interference ratio (SIR)-based power control methods and flexible cell control methods have been developed. The method described in this paper controls the transmission power ratio allocated to the mobile stations in a soft handoff region according to the traffic load. The SIR difference between cells can be reduced by controlling the power transmitted to the soft handoff mobile stations. We calculate an optimum power allocation ratio for minimizing the SIR difference for a given traffic deviation range and the downlink orthogonality factor.