Wireless telecommunications system architecture supporting...

Details Wireless telecommunications system architecture supporting... Wireless telecommunications system architecture supporting...

1998-02-13

2001-07-10

Maung, Nay (Department: 2681)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S502000

Reexamination Certificate

active

06259910

ABSTRACT:

FILED OF THE INVENTION
The present invention relates to telecomminications in general, and, more particularly, to an architecture for a wireless telecommunications system.
BACKGROUND OF THE INVENTION
FIG. 1
depicts a schematic diagram of a portion of a typical wireless telecommunications system in the prior art, which system provides wireless telecommunications service to a number of wireless terminals (e.g., wireless terminals
101
-
1
through
101
-
3
) that are situated within a geographic region. The heart of a typical wireless telecommunications system is Wireless Switching Center (“WSC”)
120
, which may also be known as a Mobile Switching Center (“MSC”) or Mobile Telephone Switching Office (“MTSO”). Typically, Wireless Switching Center
120
is connected to a plurality of base stations (e.g., base stations
103
-
1
through
103
-
5
) that are dispersed throughout the geographic area serviced by the system and to local and long-distance telephone and data networks (e.g., local-office
130
, local-office
138
and toll-office
140
). Wireless Switching Center
120
is responsible for, among other things, establishing and maintaining calls between wireless terminals and between a wireless terminal and a wireline terminal (e.g., wireline terminal
150
), which is connected to the system via the local and/or long-distance networks.
The geographic area serviced by a wireless telecommunications system is partitioned into a number of spatially distinct areas called “cells.” As depicted in
FIG. 1
, each cell is schematically represented by a hexagon; in practice, however, each cell usually has an irregular shape that depends on the topography of the terrain serviced by the system. Typically, each cell contains a base station, which comprises the radios and antennas that the base station uses to communicate with the wireless terminals in that cell and also comprises the transmission equipment that the base station uses to communicate with Wireless Switching Center
120
.
For example, when wireless terminal
101
-
1
desires to communicate with wireless terminal
101
-
2
, wireless terminal
101
-
1
transmits the desired information to base station
103
-
1
, which relays the information to Wireless Switching Center
120
via wireline
102
-
1
. Upon receipt of the information, and with the knowledge that it is intended for wireless terminal
101
-
2
, Wireless Switching Center
120
then returns the information back to base station
103
-
1
, again via wireline
102
-
1
, which relays the information, via radio, to wireless terminal
101
-
2
.
FIG. 2
depicts a block diagram of the architecture of a typical wireless telecommunications system in the prior art. Typically, each base station is connected to base station controller
201
via a separate and distinct wireline. Base station controller
201
can be, but is not necessarily, co-located with Wireless Switching Center
120
.
For example, base station
103
-
1
is connected to base station controller
201
via wireline
102
-
1
and base station
103
-
3
is connected to base station controller
201
via wireline
102
-
3
. Wirelines
102
-
1
and
102
-
3
can be fabricated from inexpensive and easily installed twisted-pair. In accordance with this architecture, each radio is located near the antennas with which it transmits and receives. In contrast, the emergence of another technology suggests removing the radios from the base stations and centralizing their functionality in a single unit known as a block radio.
A block radio is a digital signal processor that is programmed to multiplex, modulate, channel code, and upconvert one or more information-bearing signals using digital signal processing techniques. A block radio performs the same functionality as one or more traditional radios, but has several characteristics that are different than traditional radios. First, a traditional radio processes a single information-bearing signal. In contrast, a block radio is generally capable of processing a plurality of information-bearing signals simultaneously.
Second, a traditional radio is fabricated from radio-frequency components (e.g., capacitors, inductors, oscillators, etc.) and the processing of the information-bearing signal is performed by, and is largely defined by, the electrical characteristics of the components. In contrast, a block radio principally comprises a digital signal processor and the processing of the information-bearing signals is defined by software and software parameters.
Third, a change in the characteristics of a information-bearing signal (e.g., modulation scheme, bandwidth, etc.) can be implemented in a traditional radio by changing one or more of the radio-frequency components. In contrast, a change in the characteristics of a information-bearing signal can be implemented in a block radio by changing software and/or software parameters controlling the block radio. This enables a block radio to be re-defined and upgraded remotely via a telecommunications link.
Fourth, a block radio is generally less expensive than multiple traditional radios of comparable quality and processing power.
And fifth, because a block radio processes a plurality of information-bearing signals, it is capable of performing inter-information-bearing signal processing (e.g., diversity combining, beamforming, adjacent channel interference reduction, etc.) that a traditional radio, which sees only one information-bearing signal, is incapable of performing. Therefore, a block radio is more flexible, more powerful, less expensive and more-easily upgraded than the traditional radios that is capable of replacing.
FIG. 3
depicts a block diagram of a typical wireless telecommunications architecture in the prior art that incorporates block radio technology and that comprises: wireless switching center
120
, baseband unit
301
, radio heads
303
-
1
and
303
-
2
, and wirelines
304
-
1
and
304
-
2
. In accordance with this architecture, each geographically-dispersed base station of
FIG. 2
is replaced with a radio head and baseband unit
301
, which comprises block radio
302
, is interposed between wireless switching center
120
and radio heads
303
-
1
and
303
-
2
. Furthermore, in accordance with this architecture, block radio
302
interfaces with base station controller
201
and provides the functionality provided by the distributed traditional radios in the architecture of FIG.
2
. Each of radio heads
303
-
1
and
303
-
2
comprises an amplifier and associated antenna.
In addition to the advantages provided by block radio
302
, this architecture is advantageous because of the simple, uniform, and inexpensive design of the radio heads that it affords. The architecture in
FIG. 3
is disadvantageous over the predecessor architecture in
FIG. 2
in that the information-bearing signals transmitted between baseband unit
301
and radio heads
303
-
1
and
303
-
2
are at RF frequencies, which requires that wirelines
304
-
1
and
304
-
2
be fabricated from expensive and difficult-to-install coaxial cables. Furthermore, the fact that the signals transmitted between baseband unit
301
and radio heads
303
-
1
and
303
-
2
are at radio frequency considerably restricts the distance that baseband unit
301
can be from radio heads
303
-
1
and
303
-
2
.
Therefore, the need exists for a wireless telecommunications system architecture that exhibits the advantages of block radio technology without the expense, distance limitation, and implementation difficulty associated with wirelines that are capable of transmitting signals at RF frequencies.
SUMMARY OF THE INVENTION
The present invention is a wireless telecommunications system that has some of the advantages of block radio technology without some of the disadvantages associated with block radio architectures in the prior art. In particular, some embodiments of the present invention comprise a centralized baseband unit, with a block radio, that is connected to multiple, geographically-dispersed radio heads via low-cost, easily-installed wireline (e.g., twisted-pai

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