Multiplex communications – Communication over free space – Combining or distributing information via frequency channels
Reexamination Certificate
1996-11-25
2001-03-20
Marcelo, Melvin (Department: 2739)
Multiplex communications
Communication over free space
Combining or distributing information via frequency channels
C375S219000
Reexamination Certificate
active
06205133
ABSTRACT:
BACKGROUND
The present invention relates to radio communications and, more particularly, to a distributed wideband architecture for use in radio communications systems.
Today, indoor cellular systems, as well as many small-cell, or pico-cell, outdoor systems, use relatively unintelligent, centralized base stations in conjunction with distributed analog transceivers to transmit and receive communication signals to and from local mobile users operating within the systems. Communication signals are allocated to, and modulated on, frequency division multiplexed (FDM) carriers, or channels, within an overall frequency bandwidth designated for use by the systems. Channel selection and allocation is typically performed using relatively costly, narrowband analog filters located within the analog transceivers or within the base station. The analog filters are tuned to a pre-selected and fixed frequency bandwidth and are capable of supporting only a single air-interface standard. Thus, current systems are inflexible in terms of protocol and, for a given number of transceivers, are limited with respect to the overall number of users which can be simultaneously accommodated in an overall geographic coverage area.
The inflexible nature of current system design also yields fixed user capacity within each single-transceiver coverage area and makes extremely inefficient use of transceiver hardware. As a result, available FDM channels may lie dormant even as potential users are denied access to the system. Empirical data suggest that usage efficiency in these systems is typically less than 30%. Such inefficiency often requires that a large number of analog transceivers be used to obtain only modest system capacity and sometimes leads to overly complex and overly costly base station design. Also, due to the fixed-protocol nature of current systems, system designers must practice careful pre-installation frequency planning and coordination with respect to existing, comparatively powerful, outdoor systems. This can result in high installation and operations costs and may further limit the capacity of the installed system. Thus, there is a real need for an improved radio system architecture.
SUMMARY
The present invention fulfills the above-described and other needs by providing an improved wideband digital architecture which significantly increases overall hardware usage efficiency as compared to conventional systems. The present invention centralizes, shares, and re-uses key system resources, incorporates programmable frequency bandwidths, and adaptively supports a variety of air-interface standards in order to maximize system capacity and flexibility and to minimize the need for careful frequency planning and coordination with respect to existing systems. For example, by monitoring call traffic conditions at multiple distributed radio transceivers, a radio system constructed in accordance with the teachings of the present invention can adaptively allocate what would otherwise be idle system resources to heavy traffic areas on an as needed basis. Additionally, by measuring prevailing signal strengths on available frequency channels, such a radio system can automatically develop a frequency allocation plan which does not conflict with surrounding systems.
In brief, the present invention teaches a digital radio system architecture based on an intelligent wideband radio base station, or hub, controlling streamlined, distributed radio transceivers, or radio heads. The scaled-down radio heads are linked to the central hub station through high speed digital data transports and are designed to perform relatively little signal processing (e.g., multi-carrier RF power amplification, frequency upconversion and downconversion, wideband low-noise amplification, digital-to-analog and analog-to-digital conversion, etc.). The central hub, on the other hand, is designed to perform more computationally intensive signal processing tasks (e.g., signal modulation and demodulation, channel selection and allocation, channel coding and decoding, air-frame synchronization, etc.). By centralizing and adaptively allocating system resources in accordance with actual system usage, the present invention teaches an extremely flexible architecture which combines high system capacity with low overall system cost.
The radio heads are designed to be very small, unobtrusive units which are readily installed, for example, in the ceilings and corners of office buildings, manufacturing facilities, shopping malls, sports arenas, etc. Because the radio heads need perform only minimal signal processing tasks, their cost and overall power consumption is significantly lower as compared to the analog radio transceivers of conventional systems. Additionally, the hub station of the present invention cost effectively consolidates, or pools, many of the required signal processing resources at a single central location. As described below, a resource manager within the hub station can be programmed to dynamically allocate system resources among the radio heads, as necessary, based on changing call traffic conditions. Thus, system usage efficiency is dramatically improved, and tremendous savings in terms of system cost, size, and complexity are possible. These and other features and advantages of the present invention are explained hereinafter with reference to the illustrative examples shown in the accompanying drawings.
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Burns Doane Swecker & Mathis L.L.P.
Ericsson Inc.
Marcelo Melvin
Nguyen Phuongchau Ba
LandOfFree
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