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This paper introduces the concept of virtual cells in Time-Division Long Term Evolution (TD-LTE) systems, which enables users residing in overlapping cells' coverage regions to utilize resources from multiple base stations. The benefits of virtual cells are realized by the efficient resource utilization, via adapting the network resource availability with the traffic demand taking also into account...
With uplink inter-site carrier aggregation (CA), it is possible to configure a user equipment (UE) to transmit on multiple layers (macro and small cells) simultaneously, each of which may exhibit different radio channel characteristics. This introduces new challenging issues such as how to configure the UEs with CA and how to assign UEs on different layers. In this paper, we propose an uplink inter-site...
This paper considers Universal Terrestrial Radio Access (UTRA) High Speed Packet Access (HSPA) Heterogeneous Networks (HetNet). A problem of the downlink-uplink (DL-UL) imbalance is explored which consists in serving the UL transmission by the strongest Node B in DL not being the strongest one in UL. This causes UL system capacity degradation as well as gives rise to potential problems with inter-cell...
Heterogeneous networks (Hetnets) introduce an imbalance between downlink and uplink because the downlink transmit powers of the macro and pico eNodeBs can differ by as much as 16 dB. However, the user equipment(UE)'s maximum uplink transmit power is the same regardless of whether the UE is connected to the macro or the pico eNodeB. The uplink throughput performance depends both on the SINR that the...
In Heterogeneous Network (HetNet), reasonable resource allocation has attracted extensive attention. To allocate the resource more effectively, we propose a novel algorithm from the perspective of both time domain and power domain. On the one hand, we propose an adaptive Almost Blank Subframe (ABS) configuration scheme to dynamically match the network resources with the real-time load. On the other...
In 3GPP LTE-Advanced Release-12, the feature of dual connectivity (DC) has been introduced to enhance small cell networks from the aspects of higher layer architecture and physical layer procedures, which can improve mobility robustness and per-user throughput as well as avoid frequent hard handover among small cells. To guarantee the UE maximum transmit power is not exceeded, the conventional power...
We investigate the energy-efficient resource allocation problem for the downlink in long-term evolution heterogeneous networks through maximizing the energy efficiency (EE) under the per-user throughput and per-eNB power constraints in this paper. We demonstrate that EE is an increasing function in channel gain, and that EE is continuously differentiable and strictly quasiconcave in transmit power...
This paper proposes a joint control method for cell association and transmission power control of the pico base stations (BSs) in heterogeneous networks (HetNet) with inter-cell interference coordination (ICIC). The optimization criterion is proportionally fairness. The proposed method employs an iterative algorithm that alternately repeats the cell association for a given transmission power for all...
Traditional macro-cellular wireless networks are not capable of delivering even throughputs to all the users due to large variations in slow fading and inter-cell and inter-user interferences, and the throughputs for cell edge users are necessarily sacrificed to achieve an acceptable level of cell spectral efficiency. We show that this is not the case for large-scale antenna systems (LSAS, also known...
Pico eNodeBs (PeNB) are deployed in 3GPP LTE-A networks to improve the overall performance. However, the inter cell interference may become severe without suitable coordination. In this paper, a dynamic distributed power control scheme is proposed. First, each PeNB gathers information about pico user equipments (PUE) in this cell and macro user equipments (MUE) this PeNB is interfering. Then, in power...
Inserting attenuators between transceivers and antennas is proposed to improve spatial channel reuse in carrier sense multiple access with collision avoidance based WLANs. Using attenuators enables the access points or stations to decrease the powers of transmission signals and received signals, which equivalently results in the increase of the carrier sense threshold. Thus, the attenuation value...
As traditional wireless cellular networks are facing a rapid growth of traffic demand, future networks may consist of a large number of small cells which are densely deployed. However, networks in dense environment is exposed to strong inter-cell interference problem which is critical to networks capacity. To solve the problem, we use the Graph Coloring Algorithm (GCA) to divide the small cells into...
Femtocell networks have emerged as an important means of offloading traffic from today's LTE cellular networks. However, deploying LTE femtocells increases the interference in the network, as they share licensed spectrum with the macro-cellular network. Consequently, a wide range of interference mitigation techniques have been proposed to enable coexistence of femtocells and macrocells. Techniques...
As traditional wireless cellular networks are facing a rapid growth of traffic demand, the future networks may consist of a large number of small cells which are densely deployed. However, a large number of small cell Base Stations (BSs) will consume a lot of energy, which is not conductive to improve the network Energy Efficiency (EE). The purpose of our research is to optimize the dense small cell...
Recently green communications in Heterogeneous Networks has attracted extensive attention. To improve Energy Efficiency (EE) in the premise of maintaining the throughput, we propose an energy-efficient time-power domain resources allocation algorithm. From the aspect of time domain, we propose an adaptive Almost Blank Subframe (ABS) configuration scheme to provide each sector a proper ABS ratio. From...
Device-to-device (D2D) communication is a promising technique of future cellular networks which can improve the system throughput and extend the battery lifetime of user equipments. However, enabling D2D communications in a cellular network causes interference because of spectrum sharing. In this paper, to mitigate the interference and make full use of the advantage of D2D communications, we propose...
Hierarchical layering of cells with macrocells coexisting with low-power small cells has been investigated as a promising technique to enhance coverage extension and reduce power consumption, which has emerged as a candidate for green communications. Due to the challenging interference scenarios, Cell Range Extension (CRE) and enhanced inter-cell interference coordination (eICIC) are the key technologies...
In this paper, we propose a dynamic decentralized scheme, namely, the Multi-Objective Harmony Search (MO-HS). The proposed scheme improves on the conventional single-objective HS scheme by attempting to optimize two objective functions simultaneously. In particular, the MO-HS scheme attempts to minimize the use of the same channels by edge users in neighboring cells, and the average cell interference...
In LTE, the Interference over Thermal Noise (IoT) level is useful for operator to determine the link budget for coverage optimization. However, it is difficult to achieve the desired IoT operating point with the inter-cell power control solution in LTE. In this paper, a novel dynamic inter-cell power control scheme is proposed with enhanced X2 signaling to achieve the desired IoT operating point,...
This paper discusses methods for improving the effectiveness of delivering voice traffic over High-Speed Downlink Packet Access (HSDPA) network by employing transmission diversity with Single-Frequency Dual-Cell (SF-DC) Aggregation that is part of the Multiflow specification. SF-DC Aggregation allows the user to be served at the same time by two different cells. The enhancements discussed in the paper...
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