Hierarchical cell structure

About: Hierarchical cell structure is a research topic. Over the lifetime, 127 publications have been published within this topic receiving 1928 citations.

Performance of Macro- and Co-Channel Femtocells in a Hierarchical Cell Structure

Abstract: In this paper, the feasibility of user deployed femtocells in the same frequency band as an existing macrocell network is investigated. Key requirements for co-channel operation of femtocells such as auto-configuration and public access are discussed. A method for power control for pilot and data that ensures a constant femtocell radius in the downlink and a low pre-definable uplink performance impact to the macrocells is proposed, and the theoretical performance of randomly deployed femtocells in such a hierarchical cell structure is analysed for one example of a cellular UMTS network using system level simulations. The resulting impact on the existing macrocellular network is also investigated.

Expanded carrier capacity in a mobile communications system

Abstract: A mobile communications system includes a plurality of cell segments each allocated primary carriers to carry circuit-switched traffic and packet data carriers for carrying packet-switched traffic. The packet data carriers include two sets of carriers, a main set of carriers and a secondary set of carriers. The main packet data carriers are allocated to corresponding cell segments. The secondary carriers are allocated to high capacity segments, which may be segments having high bursty traffic or segments in which a hierarchical cell structure is implemented. For high bursty cell segments, the main carriers are used to carry control signaling for performing selection or reselection. However, in such high bursty cell segments, the secondary carriers are not used for performing cell segment selection or reselection.

Mobile communications in a hierarchical cell structure

Abstract: A hierarchical cell structure (HCS) cellular communications system includes a macro cell encompassing a smaller micro cell that employ the same frequency band. The macro cell includes a macro cell base station, and the micro cell includes a micro cell base station. An uplink communication cell boundary between the macro cell and the micro cell is established, and a downlink communication cell boundary between the macro cell and the micro cell is established. A radio network controller determines whether a condition exists in the HCS system which indicates that the uplink and downlink micro cell boundaries should be unbalanced. If the condition is met or exists, the power and/or antenna beam tilt of a downlink transmission from the micro cell base station is reduced to unbalance the uplink and downlink micro cell boundaries. Alternatively, the radio network controller may employ an offset value to mathematically reduce mobile detected pilot power levels associated with the micro base station.

Method for carrying out handoff between macrocell and microcell in hierarchical cell structure

Abstract: A method for carrying out an idle handoff from a macrocell to a microcell (picocell) in a hierarchical cell structure includes the steps of: a) allocating different frequency assignments (FA) to the macrocell and the microcell in a same service band, to construct the hierarchical cell structure; b) transmitting cell structure information of neighbouring base stations and pseudo noise (PN) code from base station to mobile station; c) checking whether the mobile station is in the hierarchical cell by using the cell structure information of neighbouring base station; and d) checking whether a value of the pseudo noise (PN) code is greater than T_ADD and greater than Ec/Io of the macrocell by periodically searching the pseudo noise (PN) code of the microcell, to carrying out an idle handoff to the microcell, wherein the T_ADD represents a value of base station pilot strength required for the base station of neighbouring set to be included in a candidate set, the Ec represents a pilot energy accumulated during one pseudo noise (PN) chip period, and the Io represents a total power spectrum density within a reception bandwidth.

A novel hierarchical approach for proximity effect correction in electron beam lithography

Abstract: An efficient CAD pattern processing algorithm based on dose modulation technique is proposed for proximity effect correction calculation in electron beam (EB) lithography. The algorithm resolves a costly and lengthy computation during the pattern processing. First, the original pattern data with multiple-level cell hierarchy is reduced to pattern data with two-level cell hierarchy. Then, a zoning algorithm with dual-frame technique is introduced for realizing the hierarchical proximity correction calculation. Here, the zone is a region of pattern assembly to be proximity-corrected and the frame is a pattern reference region to incorporate the backscattering effects of electrons exposed on the frame into the zone data. The algorithm is applied to typical design layers of 64-Mb DRAM pattern data. The final EB data volume is greatly compacted by a factor of 22-150 compared with a conventional hierarchy-flattened method. The hierarchical approach is indispensable to the accurate proximity correction for next-generation high-density VLSIs. >