Hierarchical cellular radio communication system

Abstract

A hierarchical cellular radio communication system comprises a plurality of pico cells (106) and an umbrella macro cell (102), each cell having a controlling primary station (104, 108). A secondary station (110) has a communication channel with the system split into a control sub-channel (212), for the transmission of control information, and a data sub-channel (214), for the transmission of user data. The control sub-channel connects the secondary station to the primary station serving the macro cell while the data sub-channel connects the secondary station to the primary station serving the pico cell. The control portions of the channel are largely served by the umbrella macro cell to reduce the overheads of frequent mobility management, while the data portions are largely served by the pico cells which can support high data rates and large data density. For a system serving packet data, the pico cell layer can be non-contiguous.

Description

technical field [0001] The present invention relates to a radio communication system, to primary and secondary stations used in such a system, and to a method of operating in such a system. Although this specification describes a system with specific reference to the Universal Mobile Telecommunications System (UMTS), it should be understood that the techniques can be used in other mobile radio systems as well. Background technique [0002] Cellular radio communication systems, such as UMTS and GSM (Global System for Mobile Communications), are well known. In these systems the cells are usually of a certain size, for example smaller in urban areas and larger in suburban areas. Cell capacity usually depends on its size, so smaller cells provide higher data density. Therefore, by reducing the cell size and thus the number of users per cell, it should be possible to provide higher data rates to individual users. However, a disadvantage of smaller cells is the need to switch c...

AI Technical Summary

Problems solved by technology

[0006] However, this situation presents some problems, especially when considering future cellular networks with increasing need for high bit rates for higher mobility

First, the overhead of network signaling supporting handover may limit system capacity, thus wasting expensive spectrum resources

Second, as the terminal moves faster and cells shrink (to increase capacity / data rate), it may cause the terminal to move too fast to successfully handover from one cell to the next before it has already left the next cell. a community

Third, the cost of deploying a fully contiguous picocellular network may increase excessively as cells shrink

Images