Abstract
Abstract A 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system uses the concept of two-tier heterogeneous networks (HetNets), where low-power and short-range femtocells are laid under macrocells to fulfill the quality of service (QoS) requirements of users and to boost overall network capacity. However, co-channel interference is one of the major issues that need to be resolved for the successful deployment of HetNets. To overcome this problem, fractional frequency reuse (FFR) schemes have been proposed that can efficiently utilize the available spectrum. Nevertheless, these schemes waste limited frequency resources owing to their static allocation and lack of following QoS requirements, network loading conditions, and service priority of users. In this paper, a QoS-based dynamic FFR (QoS-DFFR) scheme is proposed that efficiently allocates the non-occupied center-zone frequency bands, i.e., bonus bandwidth (BBW), to cell-edge users by considering their QoS requirements. Consequently, the proposed QoS-DFFR scheme can optimize cell-edge user throughput and sector throughput and reduce co-channel interference by dynamically allocating the BBW to the most demanding cell-edge users. The proposed QoS-DFFR scheme improves performance because of its ability to dynamically allocate the limited portion of the frequency bands based on the service priorities of users. The system-level simulation results show that the proposed QoS-DFFR scheme performs remarkably well in a HetNet environment. Compared with the usual FFR schemes, the proposed scheme almost doubles the cell-edge user's throughput and reduces the user's packet loss rate.
Highlights
Conventional cellular systems use a planned homogeneous macrocell-based network architecture where the macrocells, i.e., evolved NodeBs or eNBs, provide services to the users in the network
To solve the issues of quality of service (QoS) and network loading conditions, we propose a QoS-based dynamic fractional frequency reuse (FFR) (QoS-DFFR) scheme for frequency band allocation to fulfill users' QoS requirements and to maximize per-user and per-sector throughput
Because the parameters of the PHY abstraction models such as frequency, symbol duration, and error correcting codes do not depend on the channel models or the multi-antenna techniques employed, the SISOabstracted PHY layer can be used for multiple-input multiple-output (MIMO) configurations in the system-level simulations [21]
Summary
Conventional cellular systems use a planned homogeneous macrocell-based network architecture where the macrocells, i.e., evolved NodeBs or eNBs, provide services to the users in the network. Many uncoordinated schemes such as classical fractional frequency reuse (FFR) [12] have been proposed; a cellular network using a frequency reuse factor of 3 (FRF3) would be an example This type of network reduces co-channel interference and is helpful in improving cell-edge users' throughput by proper cell planning or spectrum management between the eNB and HeNBs, at the cost of system throughput. In the proposed QoS-DFFR scheme, the concept of bonus bandwidth (BBW) is introduced to dynamically allocate the frequency bands to the PR zones according to QoS requirements and service priorities of the users In this way, the QoS of the users can be guaranteed, and the per-user and per-sector throughput can be optimized, according to network loading conditions.
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