Застосування нейронних мереж для визначення місцеположення мобільної станції

An efficient direct feedback method from coordinated base stations (BSs) to a mobile station (MS) for an uplink (UL) coordinated multipoint (CoMP) reception with supporting hybrid automatic-repeat-request (H-ARQ) transmission is proposed. Acknowledgement (ACK)/negative acknowledgement (NACK) feedback based on local detection at each BS in the CoMP set is directly transmitted from the BSs using shared-feedback resources. Therefore, an MS can obtain global ACK/NACK information without experiencing extra backhaul delay with a small feedback overhead, and we can reduce the H-ARQ retransmission latency for the inter-cell UL-CoMP operation. To minimize the ACK/NACK detection error at the MS, we investigate the optimized design methods for shared-feedback resources. We derived the analytical detection error probability of the proposed feedback method and the optimum sub-block size to minimize misdetection probability for a fixed overhead and false alarm rate. Based on the analytical and computer simulation results, we have verified that the proposed feedback method can provide a reliable detection performance with a small feedback overhead. In addition, system level simulation results show the proposed fast feedback based inter-cell UL-CoMP system increases the system throughput compared to the conventional intra-cell UL-CoMP without increasing the feedback latency.

Positioning of users or mobile station (MS) in cellular systems becomes an interesting topic since the related number of applications for the location information is growing rapidly. The decision to make the locating of mobile phones under the US Federal Communications Commission (FCC) mandatory is one of the driving forces to research and provide solutions to it. Deploying such applications would require a proper method for positioning the MS that are simple and accurate especially in urban area. There are many research papers addressing this issue based on timing method that calculate the timing delay for signal sent from MS to base station (BS) or vise versa, and other method based on signal strength. In this paper, we present a new calculation method to locate the mobile phone in urban district. This technique is based on hybrid method that uses signal strength to estimate the timing delay and comparing it with the measured time of arrival of the signal. The minimum timing value of the two results would be accepted and averaged for n samples. This will improve the accuracy and reduce the effect of multi-path signaling that both timing signaling and signal strength methods suffer from. In addition, a new calculation method has been presented to find the location of MS based on the BSs coordinates.

Cell selection is the process of determining the cell(s) that provide service to each mobile station. Optimizing these processes is an important step toward maximizing the utilization of current and future cellular networks. We study the potential benefit of global cell selection versus the current local mobile SNR-based decision protocol. In particular, we study the new possibility available in OFDMA-based systems, such as IEEE 802.16m and LTE-Advanced, of satisfying the minimal demand of a mobile station simultaneously by more than one base station. We formalize the problem as an optimization problem, and show that in the general case this problem is not only NP-hard but also cannot be approximated within any reasonable factor. In contrast, under the very practical assumption that the maximum required bandwidth of a single mobile station is at most an r-fraction of the capacity of a base station, we present two different algorithms for cell selection. The first algorithm produces a (1-r)-approximate solution, where a mobile station can be covered simultaneously by more than one base station. The second algorithm produces a 1-r/2-r-approximate solution, while every mobile station is covered by at most one base station. We complete our study by an extensive simulation study demonstrating the benefits of using our algorithms in high-loaded capacity-constrained future 4G networks, compared to currently used methods. Specifically, our algorithms obtain up to 20 percent better usage of the network's capacity, in comparison with the current cell selection algorithms.

In traditional cellular networks with fixed base stations, the channel reuse pattern is static and deterministic. When the cell layout is dynamic, due to the mobility of base stations, the cluster of cells within cochannel interference range changes with time. Consequently, the channel reuse pattern is highly dynamic. Moreover, base stations also need wireless channels to communicate amongst themselves. A communication session between a pair of nodes may have to switch channels due to the movement of other nodes into the neighborhood. None of the existing dynamic channel allocation algorithms for cellular networks works in such a system. Hence, there is a need for new wireless channel allocation algorithms for virtual cellular networks with mobile base stations. In this paper, principles of mutual exclusion pertaining to distributed computing systems are employed to develop such an algorithm. The inter-base-station wireless links are referred to as backbone links, while the base station to mobile node links are referred to as short-hop links. The proposed algorithm is distributed, dynamic, and deadlock-free. Disjoint sets of channels are used for backbone and short-hop links. The distributed nature of the channel allocation scheme leads to scalability and robustness, as the responsibility is no longer centralized at the mobile telecommunications switching office (MTSO). Instead, it is shared among all the mobile base stations. In addition, the issue of channel rearrangement is addressed. Channel rearrangement is the switching of channels, performed to prevent cochannel interference, when mobile base stations using the same channels, hitherto not in interference range, come within the range of each other. If multiple channels are available to support a communication session, the channel selection policy can have a significant impact on performance. A random selection from the set of available channels yields better performance at low to moderate channel demand. This is in contrast to ordered channel selection (from one end of the spectrum), which always yields the best performance for cellular networks. Results obtained by simulating the algorithm are consistent with the theoretically obtained values.

As for radio channel control of a cellular mobile communication system, location measurement is an important technique for determining the base station to be Connected with the mobile station. This paper describes the radio zone selection characteristic when a part of the control channel is time‐shared by base stations and the reception level of each base station is measured at mobile stations. MSSC (Multitransmitter Simul/Sequential Casting) of control channels is proposed, which improves the location measurement and is suitable for a high‐capacity system. The MSSC channel consists of simul‐cast parts and sequential‐cast parts. Its speech connection control sequence when applied to the cellular mobile communication system is shown. Next, the relation between the reception level variation characteristic in land mobile communication and the average reception level measurement accuracy when burst signals are received several times is studied. Both analytical results and laboratory experimental simulation results are shown. Finally, the zone selecting rate of a mobile station is calculated and the effect of the proposed control channel configuration is clarified.

Achieving maximum network throughput while providing fairness is one of the key challenges in wireless cellular networks. This goal is typically met when the load of base stations (BSs) is balanced. In a recent study, it was confirmed that the preamble sequence, which is mainly used for cell identification and synchronization, can be used as an implicit load indicator for long term load balancing in cellular networks. In this paper, we further explore its viability as an implicit information indicator, and present distributed load balancing schemes based on the properties of the preamble sequence. These schemes empower the mobile stations (MSs) to implicitly obtain information about the load status of BSs for intelligent cell-site selection. By utilizing the two characteristic and important properties of preamble sequences, which are high auto-correlation and low cross-correlation, we propose both network and user side algorithms that work together to enable the MSs to associate with BSs with relatively low load in the long term. We evaluate our algorithms for fairness to the MSs in terms of resources and throughput, and confirm through simulations that the preamble sequence can indeed be used as a leverage for better cell-site selection leading to a high degree of fairness in the system.

Base station coordination is considered as a promising technique to mitigate inter-cell interference and improve the cell-edge performance in cellular orthogonal frequency division multiple-access (OFDMA) networks. The problem to design an efficient radio resource allocation scheme for coordinated cellular OFDMA networks incorporating base station coordination has been only partially investigated. In this contribution, a novel radio resource allocation algorithm with universal frequency reuse is proposed to support base station coordinated transmission. Firstly, with the assumption of global coordination between all base station sectors in the network, a coordinated subchannel assignment algorithm is proposed. Then, by dividing the entire network into a number of disjoint coordinated clusters of base station sectors, a reduced-feedback algorithm for subchannel assignment is proposed for practical use. The utility function based on the user average throughput is used to balance the efficiency and fairness of wireless resource allocation. System level simulation results demonstrate that the reduced-feedback subchannel assignment algorithm significantly improves the cell-edge average throughput and the fairness index of users in the network, with acceptable degradation of cell-average performance.

Network base station (BS) requires specific measurement reports from mobile station (MS) user equipment for MS localization in 3GPP cellular network. Multiple techniques have implemented at Network side with a performance of the localization, while MS-based localization is inadequate. This paper proposed a method for an MS to estimate BS and MS location based on received signal strength (RSS) and received signal quality (RSQ) in 3GPP UMTS cellular network. Suitable approximations used and formulate the localization problem based on Long-distance Path Loss model with consideration of signal strength and signal quality affected by noise and interference. Simulation results show a promising performance for the proposed method, is the solely MS-based method.

Modern cellular communication networks are already being perturbed by large and steadily increasing mobile subscribers in high demand for better service quality. To constantly and reliably deploy and optimally manage such mobile cellular networks, the radio signal attenuation loss between the path lengths of a base transmitter and the mobile station receiver must be appropriately estimated. Although many log-distance-based linear models for path loss prediction in wireless cellular networks exist, radio frequency planning requires advanced non-linear models for more accurate predictive path loss estimation, particularly for complex microcellular environments. The precision of the conventional models on path loss prediction has been reported in several works, generally ranging from 8–12 dB in terms of Root Mean Square Error (RMSE), which is too high compared to the acceptable error limit between 0 and 6 dB. Toward this end, the need for near-precise machine learning-based path loss prediction models becomes imperative. This work develops a distinctive multi-layer perception (MLP) neural network-based path loss model with well-structured implementation network architecture, empowered with the grid search-based hyperparameter tuning method. The proposed model is designed for optimal path loss approximation between mobile station and base station. The hyperparameters examined include the neuron number, learning rate and hidden layers number. In detail, the developed MLP model prediction accuracy level using different learning and training algorithms with the tuned best values of the hyperparameters have been applied for extensive path loss experimental datasets. The experimental path loss data is acquired via a field drive test conducted over an operational 4G LTE network in an urban microcellular environment. The results were assessed using several first-order statistical performance indicators. The results show that prediction errors of the proposed MLP model compared favourably with measured data and were better than those obtained using conventional log-distance-based path loss models.

In this paper, we study the degrees of freedom (DoF) of cellular networks in which a base station with full-duplex operation simultaneously communicates to multiple half-duplex mobile stations. The half-duplex mobile stations are assumed to either communicate with the base station in the uplink or downlink. For such networks, inter-terminal interference needs to be taken into account to achieve the potential gain that doubles the throughput of conventional half-duplex cellular networks. We provide an achievable total DoF for such networks and show that having full-duplex operation at the base station only can indeed double the DoF when the number of mobile stations is sufficiently greater than the number of antennas at the base station. The key idea is to utilize the full DoF for the uplink transmission, while minimizing the inter-terminal interference via interference alignment. The downlink communication rate is then carefully chosen to occupy the remaining DoF at the receiving mobile stations.

Orthogonal frequency division multiplexing (OFDM) has been widely regarded as an effective modulation technique for mitigating the effects of ISI in a frequency selective fading channel and for providing reliable high data rate transmission over wireless links. Adaptive antenna arrays at the base and mobile stations can achieve further increases in system's capacity and bandwidth efficiency, as well as in QoS improvement in conventional OFDM systems. The conventional adaptive antenna arrays based OFDM systems always use the sub-carriers characterized by the first largest eigenvalues to transmit the OFDM block symbols. In this paper and in contrast to previous work, we propose dynamic sub-channel allocation with adaptive beamforming for broadband OFDM wireless transmission systems. The proposed system adaptively selects the eigenvectors associated with the relatively large sub-channel eigenvalues to generate the beamforming weights at the mobile and base stations and then dynamically assigns the corresponding best sub-channels to transmit the OFDM block symbols. It is shown by simulation that, without adding much complexity, the proposed system can achieve a better performance than an adaptive antenna arrays based OFDM system without dynamic sub-channel allocation over multipath fading channels. Simulation results also reveal that the proposed system is not too sensitive to channel estimation errors.

It is well known that Multiple-Input Multiple-Output (MIMO) system provides both spatial and diversity gains by using multiple antennas at both mobile and base stations. However, the mobile station cannot effort multiple antennas due to small and limited dimension. Therefore, the MIMO technique cannot be successfully operated. In this light, the cooperative MIMO technique enables a mobile user with single antenna to realize a virtual multiple antennas by using the antennas of neighboring users. As a result, the mobile user can experience the full benefits of MIMO system. In literatures, the cooperative MIMO technique using Space-Time Block Codes (STBC) is created by the relay capability of neighbor users. However, the devices of all users have the same potential to detect symbols. Therefore, this paper proposes the STBC scheme by changing the symbol order from source to relay in order to be easily performed as MIMO at the destination. The simulation results reveal that it is possible to obtain a better error performance as well as a higher channel capacity by using the proposed scheme for mobile cellular networks.

The Internet protocol (IP) can potentially become the universal network-layer protocol over all wireless systems as it already is for wireline packet networks. Such an all-IP wireless and wireline network can bring the proven advantages of IP networking to mobile users. However, realizing an all-IP wireless network introduces many challenges, among which is soft handoff. Two major problems need to be solved in order to support soft handoff. First, multiple streams of the same IP traffic have to be distributed via multiple base stations to a mobile station. Second, pieces of data arriving at the mobile station at the same time from different base stations need to be copies of the same data in order for the mobile station's radio system to correctly combine these different pieces into a single copy. A similar problem also needs to be resolved in the reverse direction from mobile stations to base stations. Solving these problems in a distributed all-IP wireless network remains a challenge. Although solutions exist for today's circuit-switched wireless systems. This article presents a new approach for soft handoff in distributed all-IP wireless networks. It consists of two main parts. First, a new design of IP-based distributed base stations enables mobile stations in multiple cells to be on the same IP subnet and multiple streams of the same data to be distributed via multiple base stations to a mobile without broadcasting/multicasting and with minimal signaling. Second, a novel IP-layer procedure performed by the base stations ensures that the data coming simultaneously from multiple base stations to a mobile station are copies of the same data.

We investigate the degrees of freedom (DoF) of the downlink of a cellular relay network. In this network, two base stations transmit to two mobile stations via relays due to the absence of a direct communication link. Each base station and mobile station is equipped with $M$ antennas. Each base station has two messages; one to each mobile station, and uses two relays to transmit to the mobile stations. The relays are half duplex, decode-and-forward and equipped with $N$ antennas each. We consider two configurations of the relays; shared and dedicated relays. In the shared relays configuration, the system has two relays that are used by both base stations. Whereas, in the dedicated relays configuration, each base station has two dedicated relays, i.e., the system has four relays. We consider all possible relaying schemes where the base stations can use the relays either simultaneously or alternately. We derive an upper bound on the DoF achievable by each relaying scheme as a function of the ratio between $N$ and $M$ . Furthermore, we propose an achievable scheme that uses interference alignment to achieve the upper bound on the DoF for the shared relays configuration, and for all values of $M$ and $N$ except for $1 in the dedicated relays configuration.

MIMO downlink with base station coordination in a cellular network is considered. In centralized coordinated transmission from a cluster of base stations, the channel state information (CSI) of users needs to be sent to a central processor for precoding and resource allocation. Real time CSI feedback from the users to their home base station and from the base stations to the central processor is a serious challenge from a practical point of view. CSI feedback schemes based on user channel strength and distance of a user to its home base station are proposed that reduce feedback overhead while having not much affect on system throughput. Numerical results show the effectiveness of the proposed schemes.