Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-12-10
2001-11-06
Kincaid, Lester G. (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S078000, C455S083000, C455S138000, C342S373000
Reexamination Certificate
active
06314305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cellular communications base station that combines adaptive array processing and fixed beam switching within a common antenna set and within a common array.
2. Description of the Related Art
The cellular industry has enjoyed phenomenal growth in the United States and the rest of the world. In a cellular system, large geographical areas are divided into cells. At the center of each cell is a base station. The base station is the one common location within the cell through which all mobile units communicate, therefore, it is extremely important that there be sufficiently strong signals for both the uplink (base station receive) and the downlink (base station transmit) signal paths.
Each cell is also often further divided into sectors. Typically, three or six sector configurations are employed. In a typical three sector cell, each sector covers a 120 degree wide radius of the cell.
Current wireless base station receivers use two branch antenna diversity for the uplink and a single antenna for the downlink. Many systems, however, are now migrating to adaptive antenna array processing for the uplink, as well as to four branch antenna receiver systems.
It should be noted that inasmuch as any given antenna beam pattern (e.g., such as that depicted in
FIG. 1
) is achievable with many different antenna element configurations using different numbers of antenna elements, the invention will be described with reference to antenna ports which are the common input and output nodes connected to an antenna configuration, the latter of which is capable of transmitting or receiving signals using a particular antenna beam pattern.
FIG. 1
depicts a conventional beam pattern for an adaptive antenna array. It is well understood in the art that adaptive antenna arrays are optimal for a receiver uplink as they increase a receiver's effective sensitivity. This can be achieved by increasing the number of separate branches used in diversity processing and/or by increasing the number of antenna elements that are combined together in order to achieve array gain. In
FIG. 1
, four concurrent sector beams
10
a,
10
b,
10
c,
10
d
are shown. It is well known in the art that optimum performance is achieved when the sector of interest is covered by n separate antennas, where each one of n antennas concurrently covers the entire sector. Therefore, while
FIG. 1
depicts the use of four concurrent beams, respectively associated with four antenna ports, any number of antenna ports, and correspondingly, any number of concurrent beams may be used in order to practice conventional adaptive array processing.
With reference to
FIG. 2
, a block diagram for a conventional adaptive array receiver is shown. Each of four antenna ports
20
a,
20
b,
20
c
20
d
,one for each
FIG. 1
beam, is coupled to a respective one of four adaptive array/diversity receiver branches
22
a,
22
b,
22
c
,
22
d.
Each of the receiver branches
22
a,
22
b,
22
c
,
22
d
is further coupled to an adaptive array processor
25
. Typically, the adaptive array processor
25
will perform an adaptive array algorithm in which signals from the receiver branches
22
a,
22
b,
22
c
,
22
d
are weighted against each other to determine relative signal strengths. The spectrum of relative strengths can run between the two extremes of severe Rayleigh fading, where signals received on all ports
20
a,
20
b,
20
c
,
20
d
are of very different amplitude levels, and no Rayleigh fading, where all of the signals received from all four antenna ports
20
a,
20
b,
20
c
,
20
d
are of substantially equal amplitude. Those receiver branches with the strongest uplink signals are weighted more heavily in the array processor
25
in order to increase the effective signal-to-noise ratio of the final result which is then passed through for processing by the receiver
26
.
Referring now to
FIG. 3
, a conventional beam pattern for a switched fixed multi-beam array (hereinafter “fixed beam switching”) is shown. As is well known in the art, fixed beam switching is desirable for a downlink (i.e., base station transmit).
FIG. 3
shows four sub-sector beams
30
a,
30
b
,
30
c,
30
d
which form a transmit antenna array beam pattern. As is well known in the art, the transmitter array performs more optimally if energy can be steered into a narrow beam pointing in the direction of interest. This is achieved by smaller, more compact antenna arrays allowing &lgr;/2 spacing between antenna elements whereby a cell sector is divided into a number of smaller sub-sectors thus allowing for the transmitter to form well defined, tightly controlled beams with no lobing effects. While
FIG. 3
shows four sub-sector beams
30
a,
30
b
,
30
c
,
30
d,
it should be well understood that a given sector may contain any number of sub-sector beams.
Referring now to
FIG. 4
, a block diagram for a conventional beam switching transmitter is shown. A transmitter signal source
40
is coupled to a transmit switch
41
which selects from one of four lines
41
a,
41
b,
41
c,
41
d.
Each of the lines
41
a,
41
b,
41
c,
41
d
is coupled to a transmitter
44
. The transmitter
44
is coupled to a beamformer network
46
, the composition of which is well known in the art. The beamformer
46
is coupled to each of four antenna ports
47
a,
47
b,
47
c,
47
d.
One of the antenna ports
47
a,
47
b,
47
c,
47
d
at a time is selected by switch
41
to serve the downlink function and transmit RF signals from a cellular base station.
As the state of the art currently exists, the use of two separate arrays of beam patterns (e.g., an array of concurrent beams for the uplink function, and an array of sub-sector beams for the downlink function) requires a very complex cellular base station signal processing system because the signal processing for the two separate arrays is also separate. Therefore, the transmitter must decide which sub-sector beam(s) it will radiate without the benefit of any positional information gathered by the receiver during the uplink function. That is to say, little has been done to simplify the downlink function, up to this point, other than simple sub-sectorization of the downlink beams.
While the use of sub-sectorization for the downlink function provides for near optimum transmission of the RF signals, there is currently no efficient way to process the uplink RF signals in such a way as to further optimize the downlink function, through fixed beam switching, in a cost effective way.
SUMMARY OF THE INVENTION
The present invention provides a transmitter/receiver system which interactively combines adaptive array processing, favored for the uplink, and fixed beam switching, favored for the downlink. This is achieved by combining both concurrent beam patterns and sub-sector beam patterns for the passage of uplink RF signals followed by the processing of the received RF signals. The transmitter/receiver system of the invention then decides through which of the available sub-sector beams it will radiate downlink RF signals to a mobile unit.
The transmitter/receiver system of the invention combines both types of distinct beam patterns (i.e., concurrent whole sector beams, and sub-sector beams) in such a way as to allow adequate spatial separation for the uplink function. As is well known in art, spatial separation is required for adequate beam independence in diversity processing of uplink RF signals. The transmitter/receiver system of the invention also allows for sub-sector beam patterns to be employed for the transmission of downlink RF signals.
The invention provides a transmitter/receiver system which uses at least four antenna ports, each associated with a respective antenna configuration which has an associated one of a full sector beam and a sub-sector beam. The at least four antenna ports, with simple cabling and simple duplexing, are employed in the transmitter/receiver system of the invention to support both adaptive array processing for the uplink and fixed beam s
Benning Roger D.
Solondz Max
Dickstein , Shapiro, Morin & Oshinsky, LLP
Kincaid Lester G.
Lucent Technologies - Inc.
LandOfFree
Transmitter/receiver for combined adaptive array processing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmitter/receiver for combined adaptive array processing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmitter/receiver for combined adaptive array processing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2588537