Average Cell Spectral Efficiency Research Articles

Probabilistic Analysis of Spectral Efficiency for LTE Based on PDCCH Measurement Data

As the number of mobile subscribers of long-term evolution (LTE) service increases, it becomes important for various parties, such as operators, policymakers, and researchers, to examine how well LTE cells are deployed in terms of actual performance. To this end, we focus on spectral efficiency (SE) with the cell edge user throughput (TP) and average cell SE which can be calculated from the spectrum data of an LTE physical downlink control channel decoding device—Rohde & Schwarz TSME. For these two aspects, crucial probabilities for the performance evaluations are defined using a joint distribution of resource block utilization and cell TP. We derive novel transformation methods that make them approximately follow a joint Gaussian distribution and use it to compute the probabilities. Furthermore, a deep neural network is adopted to analyze not only limited cases but also a wider range.

Downlink Interference Control in Heterogeneous Cellular Networks: Macroscopic and Microscopic Control

In heterogeneous cellular networks that consist of macrocells and small cells, efficient interference management schemes between macrocells and small cells are crucial for overall system performance. To mitigate intercell interference, we propose macroscopic and microscopic interference control schemes. First, as a macroscopic interference control scheme, we propose a dynamic coordinated silencing. This scheme dynamically controls optimal bandwidth silencing between macrocells and small cells. It is carried out from a system quality of service (QoS) perspective on a long-term basis. Second, as a microscopic interference control scheme, we propose a user QoS-based rate splitting. This scheme controls optimal transmit power and rate for the split messages of scheduled users. It works as the complements of the proposed macroscopic control and is carried out on a short-term basis. The performance evaluations with ten small-cell deployment in each macrocell confirm that the proposed macroscopic control offers $28\%$ and $8\%$ enhanced cell-average spectral efficiency when it is compared with soft fractional reuse control and static silencing control, respectively, and $55\%$ and $23\%$ enhanced cell-edge spectral efficiency when it is compared to partitioning-based control and static silencing control, respectively. Further, it is shown that the proposed microscopic control can additionally enhance cell-edge spectral efficiency by preventing users from being interfered in dead-zone area.

Adaptive Pilot Clustering in Heterogeneous Massive MIMO Networks

We consider the uplink of a cellular massive MIMO network. Acquiring channel state information at the base stations (BSs) requires uplink pilot signaling. Since the number of orthogonal pilot sequences is limited by the channel coherence, pilot reuse across cells is necessary to achieve high spectral efficiency. However, finding efficient pilot reuse patterns is non-trivial especially in practical asymmetric BS deployments. We approach this problem using coalitional game theory. Each BS has a few unique pilots and can form coalitions with other BSs to gain access to more pilots. The BSs in a coalition thus benefit from serving more users in their cells, at the expense of higher pilot contamination and interference. Given that a cell's average spectral efficiency depends on the overall pilot reuse pattern, the suitable coalitional game model is in partition form. We develop a low-complexity distributed coalition formation based on individual stability. By incorporating a base station intercommunication budget constraint, we are able to control the overhead in message exchange between the base stations and ensure the algorithm's convergence to a solution of the game called individually stable coalition structure. Simulation results reveal fast algorithmic convergence and substantial performance gains over the baseline schemes with no pilot reuse, full pilot reuse, or random pilot reuse pattern.

이종 이동통신 네트워크에서 셀 확장 편향치에 따른 하향 링크 성능 분석

최근에 폭발적으로 증가하고 있는 모바일 데이터 트래픽을 효과적으로 수용하기 위하여 다중 안테나와 소형 셀과 같은 신기술들이 차세대 이동통신 시스템의 핵심 기술로 제안되었다. 특히, 기존의 매크로 셀과 소형 셀을 동시에 활용하여 공간 재사용율을 높일 수 있는 이종 이동통신 네트워크에 대한 관심이 높아지고 있다. 그러나, 이종 네트워크에서는 단말들이 소형 기지국 대비 상대적으로 송신 출력이 높은 매크로 기지국을 통해서 서비스 받을 가능성이 높기 때문에 소형 기지국의 활용도가 상대적으로 낮아지는 문제점이 있으며, 이러한 문제점은 상향 링크에서 두드러지게 나타난다. 3GPP에서는 이러한 문제점을 해결하기 위하여 셀 확장 편향치 개념을 제안하고 이에 대한 표준화를 진행하고 있다. 본 논문에서는 셀 확장 편향치를 적용한 네트워크 시뮬레이터를 이용하여 이종 이동 통신 네트워크의 하향 링크 성능을 평균 셀 전송 효율 측면에서 분석한다. New technologies such as multi-antenna and small cell were proposed as key technology for the next generation mobile system to cope with the explosively increasing mobile data traffic. In particular, heterogeneous mobile communication network which can improve spatial reuse factor by exploiting macro and small cells simultaneously is attracting attention. However, the heterogeneous network has a problem that the utilization of small cells becomes low because the transmit power of macro base stations is much higher than that of small base stations and then the probability that mobile stations are attached to the macro base stations becomes high. This problem is dominant in uplink. The concept of cell range expansion bias to mitigate the problem was proposed by 3GPP and the corresponding standardization is in progress. In this paper, we analyze the downlink performance of the heterogeneous mobile communication network based on a system level simulator with the cell range expansion bias in terms of average cell spectral efficiency.