This paper addresses the issues of user association in multi-tier heterogeneous networks (HetNets) to reduce co-channel interference and provide load balancing for proactively offloading users onto mobile personal cells (mPC). Previously, much of the literature discussed the user' association problem for HetNets with conventional fixed small cells. The problem discussed in the existing literature is easy to analyze owing to fix nature of the small cells. In this paper, we focus on the mPC instead of fixed small cells, which complicates the user association problem due to its nature of mobility. In this paper, we propose the public safety (PS) users priority-based mPC user association (PS-UA) scheme for load balancing and interference reduction in highly fluctuating PS long-term evolution systems. The proposed scheme improves the user-association problem by minimizing call blocking probability (CBP) according to the network load conditions and PS user priority. Moreover, it further improves user signal-to-interference-and-noise ratio by implementing enhanced intercell interference coordination scheme to further reduce the interference to the offloaded users. System-level simulations confirmed the validity of the proposed PS-UA scheme, because it convincingly reduces the CBP for PS users as compared with the conventional static user association scheme.
A loss of subchannel orthogonality due to timevariant multipath channels in orthogonal frequency-division multiplexing (OFDM) systems leads to interchannel interference (ICI) which increases the error floor in proportion to the Doppler frequency. In this paper, a simple frequency-domain equalization technique which can compensate for the effect of ICI in a multipath fading channel is proposed. In this technique, the equalization of the received OFDM signal is achieved by using the assumption that the channel impulse response (CIR) varies in a linear fashion during a block period and by compensating for the ICI terms that significantly affect the bit-error rate (BER) performance.
In the Republic of Korea, a Long Term Evolution (LTE)-based public safety (PS)-LTE network is being built using 718~728 MHz for uplink and 773~783 MHz for downlink. However, the same bands are also assigned to the LTE-based high-speed railway (LTE-R) network, so great concerns and practical researches on co-channel interference (CCI) management schemes are urgently required. In this paper, performance is analyzed and evaluated by considering the cases of non-RAN (radio access network) sharing and LTE-R RAN sharing by PS-LTE user equipments (UE). Since a train control signal requires high reliability and low latency in order to fulfill its mission-critical service (MCS) requirements, we give higher priority to LTE-R UE during resource allocation under the LTE-R RAN sharing by PS-LTE UEs. In addition, interference management schemes are more effective for the coexistence of PS-LTE and LTE-R networks under RAN sharing environment. In this paper, we utilize enhanced inter-cell interference coordination (eICIC) and further enhanced ICIC (FeICIC) schemes to mitigate the interference from PS-LTE network to LTE-R network while improving the LTE-R eNodeB (eNB) resource utilization by offloading more PS-LTE UEs to LTE-R network. Moreover, a coordinated multipoint (CoMP) transmission scheme is considered among LTE-R eNBs to enhance LTE-R cell edge user performance. By employing FeICIC along with coordinated scheduling (CS) CoMP, the best throughput performance can be achieved under the case of RAN sharing.
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