Title: Hierarchical Cellular Structures in High-Capacity Cellular Communication Systems
ArXiv ID: 1110.2627
Date: 2023-06-15
Authors: : John Doe, Jane Smith, Michael Johnson
📝 Abstract
In the prevailing cellular environment, it is important to provide the resources for the fluctuating traffic demand exactly in the place and at the time where and when they are needed. In this paper, we explored the ability of hierarchical cellular structures with inter layer reuse to increase the capacity of mobile communication network by applying total frequency hopping (T-FH) and adaptive frequency allocation (AFA) as a strategy to reuse the macro and micro cell resources without frequency planning in indoor pico cells [11]. The practical aspects for designing macro- micro cellular overlays in the existing big urban areas are also explained [4]. Femto cells are inducted in macro / micro / pico cells hierarchical structure to achieve the required QoS cost effectively.
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The provision of capacity for the increasing traffic demand in mobile radio networks comes along with the reduction of the cell size and, hence, stronger traffic fluctuations between the cells. Moreover, improved indoor coverage is required. Hierarchical cellular structures can serve indoor users and hot spots by pico-and micro cell layers, respectively, while providing coverage in the area by the macro cell layer. Moreover, hierarchical cellular structures can compensate traffic fluctuations e.g. by shifting overflow traffic from lower to higher layers. In order to avoid interference between the layers, their frequency allocations have to be coordinated. This can be achieved by incorporating smart antenna / Intelligent antenna in hierarchical structure with adaptive-SDMA approach.
Moreover, hierarchical cellular structures become a regular feature of future mobile radio networks. Although different multiple access techniques may apply, some experiences from GSM can also be useful for the design of other hierarchical cellular networks, where several layers share the same resources [1]. The results of [1], comparative simulation study has been discussed, which aims at network configurations in a dense urban environment where a high additional traffic capacity in the pico cell layer shall be achieved solely by reusing the micro-and/or macro cell frequencies. The results of number of general conclusions for the design of hierarchical cellular networks are also discussed [1].
In order to obtain a useful knowledge about the deployment and operation of macro-micro CDMA cellular overlays, we must deal with the existing conditions of today"s big urban areas, which include spatial and temporal traffic distributions, geographical characteristics, user mobility characteristics, and so on. In [5] a novel algorithmic approach for the joint deployment of macro cells and micro cells over big urban areas having spatially non-uniform traffic distributions has been discussed. Based on a discrete area representation, the proposed algorithm determines the locations, radii and required capacities of macro cells and micro cells, which guarantee the required quality of service (QoS) cost effectively. For the practical design of macromicro CDMA cellular overlays we have to take care of the following issues in depthi) Effect of user"s mobility. ii) In presence of many high mobility users, the undesirable micro cellular coverage holes in hot spot areas incur a critical problem, assuming a significant volume of limited macro-cellular code division multiple access (CDMA) capacity. iii) Even though a macro-micro cellular overlay well accommodates the traffic loads of working hours, it may loose much of its significance if it can not manage a temporal traffic variation during a day. iv) Since only a few wideband CDMA carriers exist in the third generation wireless personal communications, it is quite difficult to fully exploit all the potentials of macromicro cellular overlays. v) If some operating functions, such as cell layer selections or interlayer handovers, are improperly configured, they can degrade the performance of a macro-micro cellular overlay considerably.
Since the number of mobile users is continuously growing, we shrink cell size to increase system capacity. By shrinking cell size, handoff rate is increased. To overcome these problems, hierarchical cell structure is proposed. As efficient use of radio resources is very important, utilization of all resources have to be optimized. Thus, in hierarchical cell structure, how to assign available radio resources to each user is critical question [6]. In order to adapt the changes of traffic, adaptive radio resource management can be considered in CDMA based hierarchical cell structure. The proposed scheme improves call blocking, call dropping and optimal utilization of radio resources. www.ijacsa.thesai.org
II. TECHNOLOGIES FOR ENHANCEMENT OF SPECTRAL DENSITY IN HIERARCHICAL SYSTEM A tractable, flexible and accurate model for downlink heterogeneous cellular networks (fig 1) was developed successfully. The model consist of K tiers of randomly located base stations where each tier may differ in terms of average transmit power, the supported data rate and BS density. This allows elements spanning traditional, micro, pico, and femtocell BSs to be simultaneously considered. Assuming a mobile user connects to its strongest BS, we derive its Signalto-Interference-Ratio (SIR) distribution and use to find the coverage (equivalently outage) probability over the entire network. The accuracy of these analytical results through empirical comparisons with an actual 4G macro cell network verified [7]. Cellular networks are becoming increasingly heterogeneous due to the co-deployment of many disparate infrastructure elements, including micro, pico and femtocells, and distributed antennas. A flexible, accurate and tractable model for a general downlink HCN consisting of K tiers of randomly
