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Lee, and D. Chandrasekhar and J. Andrews, V. Capdevielle, A. Feki, and P. Chu, Y. Wu, L. Benmesbah, W-K. Lee, J-H. Huang, and L-C. Begain, G. Rozsa, A. Pfening, and M. Rahman, H. Yanikomeroglu, and W. Lee, T. Lee, J. Jeong, and J. Juang, P. Ting, H-P. Lin, and D-B. Lee, D-C. Oh, and Y-H. An, X. Zhang, G. Cao, R. Zheng, and L. Chowdhury, Y. Jang, and Z. Guvenc, M-R. Jeong, F. Watanabe, and H. Bai, J. Zhou, L. Liu, L. Chen, and H. Zhou, and L. Li, X. Contact support. Easy, compact solutions. Demanding solutions. Wireless both inside and outside the control cabinet Transfer data wirelessly from the control cabinet, or you can even use our devices with IP65 protection class outside the control cabinet.
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Learn more. Find interesting customer reference stories here. Constellation Brands Inc. Upgrade plant's industrial communication network in line with best practices. Wireless network for laser-guided vehicles avoids interference issues. National Oilwell Varco. With the new network infrastructure and the upgrade of equipment, unplanned stops are eliminated. Detailed process monitoring for seamless quality documentation.
Read the success story. Siemens Wind Power. High-availability network enables totally smooth manufacture of rotor blades for wind turbines. Reliable wireless communication under harsh conditions, even in humid and salty air. Entire network implemented in accordance with strict safety regulations. End-to-end monitoring of materials between manufacture and delivery in Vietnamese steelwork.
Flow of information for warehouse logistics mainly via WLAN infrastructure. Bierbaum Group. Integration of proANT transport robots into the process automation of the Bierbaum factory. The FBS then tunes its transmission power efficiently and enhances the system capacity by mitigating interference. In [ 2 ], the Stochastic Approximation SA algorithm for downlink power control based on the information received through macrocell signalling.
The femtocell then updates its downlink transmission power based on this information. This interference mitigation technique helps to reduce the consumption of power and enhance the throughput of MUE. The MUE exists in the close proximity of HeNB, and receives interference from HeNB, to reduce such interference; a power control scheme proposed in [ 25 ] based on network listening. In [ 26 ], a novel scheme is proposed for interference mitigation in downlink cognitive femtocell networks, which is called joint channel allocation and power assignment. This scheme aims to reduce interference from the femtocell to MUEs and co-tier interference by collaboratively allocating power resources and channels between several femtocells; it depends on the Physical Cluster PC and the Virtual Cluster VC.
The writer also presented subcarrier power allocation and a VC-based power budget adjustment algorithm and Hungarian algorithm to better allocation of resources, minimize both co-tier and cross-tier interference in the femtocell. In [ 27 ], distributed coordination techniques in the DL of macrocells for controlling ICI caused by a femtocell in two-tier networks, where opportunistically reuse resources is an inherent requirement. The technique emphasis is on the autonomous operation of femtocell by self-organizing deployment. In [ 28 ], the downlink power control scheme presented to reduce the interference caused by a femtocell to its neighboring cell users.
The femtocell will adjust the minimum transmit power on the basis of partial path-loss compensation which helps to reduce interference to adjacent cells and its users, that maintain the SINR level and assuages the required Quality-of-Service QoS of femtocell user. This technique identifies the sub-optimal pattern of power allocation in cognitive femtocell networks for increasing femtocell capacity.
P M represents the downlink transmission power of the eNB. We assume that the K PRBs are distributed uniformly among the MUEs in the macro-cell and the same resources are reused within each femtocell. In this paper, we consider an inadequately deployed HeNB in an indoor environment. The HeNB is linked to a macrocell through a broadband Internet backhaul link. The femtocell works in close access mode, where only CSG users can subscribe the services of the femtocell.
The access styles of HeNB plays an important role in dealing with the interference. The interference is much sever in the closed access mode. Therefore, we consider the CSG mode to take the worst interference scenario into account. Figure 1 shows the interference scenario of inter-cell interference ICI between the elements of the primary and secondary systems. In this case, the downlink link transmission of HeNB is the source of interference to MUE existing in its close proximity.
Common approaches to dealing with interference
Similarly, the path loss from the femtocell to MUE and FUE existing in the close proximity indoor and outdoor can be calculated by using the path model as follows:. Similarly, the R 2 is the distance from HeNB to indoor and outdoor users.
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The spectral efficiency can be estimated as:. In a real scenario, the HeNB instructs all the FUE to measure the received signal power from the neighboring interferer BS and send a feedback report [ 35 ]. In 4 , P m i n and P m a x is the minimum and maximum transmission power of the femtocell. The Femtocell can adjust its downlink transmission power by considering the coverage area and the radius of both the macrocell and the femtocell; it also helps to maintain co tier-interference for inadequate deployment and dense femtocell networks [ 36 ].
In 7 , the relationship between eNB downlink transmission power and its coverage area represented by Y. Consequently, it can be utilized to derive HeNB downlink power P i as follows:. Using Equation 8 , Femtocell can adjust its downlink transmission power.
Communications in Interference Limited Networks
Figure 1 shows the ICI scenario between the elements of the primary and the secondary system. The downlink transmission power of femtocell causes interference to the MUE that existing in its coverage area. In such condition, MUE starts the handover or cell re-selection process. Since the femtocell is working in closed access mode, the macro user cannot subscribe to the services of the femtocell.
The IDF determines whether the interference experienced by the macro user is higher or lower than the threshold interference level. The IDF can be expressed as. In 9 , P t i is the transmit power of the femtocell F i. In 10 , I T h r e s h o l d is the interference threshold set for the macro user.
The IDF determines whether the interference experienced by the macro user is higher than the threshold interference to maintain the desired QoS of the MUE or the interference is lower than the threshold level. When the femtocell receives the IM from the macro user via eNB backhaul, it understands that the non-CSG user is getting interference from its downlink transmission.
In the first stage of the active power control technique, we introduced different power levels and time levels to tune the downlink power of the HeNB. The time levels play an important role in the smooth tuning of HeNB transmission power. The same procedure of reducing and increasing transmission power will be carried out based the HeNB receiving a new interference message.
Figure 2 show the femtocell adjusts its transmission power to respond to the IM from the MUE under the active power control technique. Femtocell transmit power tuning P x , P y and P z.
Coping With Interference In Wireless Networks (Signals And Communication Technology) -
The femtocell updates it downlink transmission power based on IM using following formulas. The QoS Indication Function can be expressed as follows:. P r e f is the downlink reference signal transmit power of the HeNB. Using the above-described statement, the femtocell then effectively tunes its downlink power as:.
In 17 , P m a x and P m i n are the maximum and minimum transmit power respectively. P n is the thermal noise density. Comparing with the existing techniques the proposed technique has the following advantages. The femtocell actively tunes its downlink power by using the power levels P x , P y and P z and time levels T L 1 and T L 2 , Hence, the proposed APC approach reduce the unnecessary power consumption to achieve green femtocell network.
Compared with existing power control approaches, the proposed approach offers significantly better performance in terms of downlink throughput CDF of the macro user and the femto user, the average throughput, FBS Power consumption and the green impact and CO 2 emission. The outlines of the proposed method are summarized in the Table 1. Table 2 shows a few summarized parameters. For simplicity, we have considered the widely used full buffer traffic model. It is characterized by the fact that the UE always has data to transmit or receive in the full buffer traffic model.
The simulated interference scenario is shown in Figure 1. The eNB has a maximum transmitting power of 43 dBm. In this simulation, the close access mode is considered, which is the most favorite mode of indoor users, in which the CSG users enjoy higher data rate and capacity and non-CSG users are not allowed to use the femtocell services.
The interference is severe in closed access mode as compared to other access modes. It is a fact that high transmission power of HeNB provides better signal strength, good coverage to the femto users; conversely, the cell edge macro users receive interference from it. Therefore, the interference technique operating in the femtocell should provide a balanced trade-off between the throughput of macrocell and femtocell users.
In the following subsections, we evaluated the performance of proposed and existing power control techniques in-terms of downlink throughput distribution, average throughput distribution, FBS power consumption and green impact and CO 2 emission by conducting numerical experiments. The simulation results in Figure 3 show that the downlink throughput distribution of macro users, which is also called non-CSG users in this case. The downlink throughput of macro user drops severely when there is no power control technique activated in the femtocell.
However, the proposed active power control technique outperforms its counterparts.
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It can be seen from the Figure 3 , the macro user achieve value of CDF of throughput 2. Figure 4 shows the downlink CDF of the femto users. With no power control, the HeNB transmits maximal power. Therefore, the femto users enjoy higher throughput at the cost of MUE performance. It can be seen from Figure 4 that the femto user achieves value of CDF of throughput From the Figure 3 and Figure 4 , we can easily see that the APC technique provide a balanced trade-off between the downlink throughput of macro users and femtocell users.