Adaptix, Inc. v. T-Mobile USA, Inc.

Filing 1

COMPLAINT against T-Mobile USA, Inc. ( Filing fee $ 350 receipt number 0540-3620802.), filed by Adaptix, Inc.. (Attachments: # 1 Civil Cover Sheet, # 2 Exhibit A - U.S. PATENT NO. 7,146,172, # 3 Exhibit B - U.S. PATENT NO. 6,870,808, # 4 Exhibit C - U.S. PATENT NO. 7,573,851, # 5 Exhibit D - U..S. PATENT NO. 6,904,283, # 6 Exhibit E - U.S. PATENT NO. 7,072,315)(Hill, Jack)

EXHIBIT C

111111111111111111111111111111111111111111111111111111111111111111111111111
US007573851B2

United States Patent

(10)

Xing et al.

(12)

(45)

(54)

METHOD AND SYSTEM FOR SWITCHING
ANTENNA AND CHANNEL ASSIGNMENTS
IN BROADBAND WIRELESS NETWORKS

(75)

Inventors: Guanbin Xing, Bellevue, WA (US);
Manyuan Shen, Bellevue, WA (US);
Hui Liu, Sammamish, WA (US)

(73)

Assignee: Adaptix, Inc., Bellevue, WA (US)

( *)

Notice:

(21)

Appl. No.: 11/007,064

(22)

Filed:

Patent No.:
US 7,573,851 B2
Date of Patent:
Aug. 11, 2009

7,062,246
7,062,295
7,072,315
7,116,944
200210006120
200210188723
2003/0003937
2005/0064908
2005/0185733

B2 * 6/2006 Owen ...................... 455/277.1
B2 * 6/2006 Yoshii et aI . ............. 455/562.1
Bl* 7/2006 Liu et al. .................... 370/329
B2 * 1012006 Das et al. ...................... 455/69
Al
112002 Suzuki et al.
Al
1212002 Choi et al.
Al
112003 Ohkubo et al.
Al * 3/2005 Boariu et al. ............ 455/562.1
Al * 8/2005 Tolli et aI .................... 375/285

OTHER PUBLICATIONS
Subject to any disclaimer, the term of this
patent is extended or adjusted under 35
U.S.c. 154(b) by 659 days.

Primary Examiner-Brenda Pham
(74) Attorney, Agent, or Firm-Fulbright & Jaworski L.L.P.

A method and apparatus for anteuna switching, grouping, and
channel assigmnents in wireless communication systems.
The invention allows multiuser diversity to be exploited with
simple antenna operations, therefore increasing the capacity
and perfonnance of wireless communications systems. Channel characteristics indicative of signal reception quality for
downlink or bi-directional traffic for each channel/antenna
resource combination are measured or estimated at a subscriber. Corresponding channel characteristic infonnation is
returned to the base station. Channel characteristics infonnation may also be measured or estimated for uplink or bidirectional signals received at each of multiple receive
antenna resources. The base station employs channel allocation logic to assign uplink, downlink and/or bi-directional
channels for multiple subscribers based on channel characteristics measured and/or estimated for the uplink, downlink
and/or bi-directional channels.

Jun. 8,2006

Int. Cl.
H04Q 7/00
(2006.01)
U.S. Cl. ....................................... 370/334; 370/332
Field of Classification Search ................. 370/312,
370/208,203,314,319,320,321,332,333,
370/334,335,337,342,343,347,310,310.2,
370/336,344,329,349,431,464
See application file for complete search history.
References Cited

(56)

U.S. PATENT DOCUMENTS
5,327,576
6,175,550
6,281,840
6,870,808
6,904,283

A *
Bl*
Bl*
Bl*
B2 *

711994
112001
8/2001
3/2005
6/2005

Uddenfeldt et al. .........
van Nee .....................
Miyoshi et aI . .............
Liu et al. ....................
Li et al. ......................

ABSTRACT

(57)

Prior Publication Data
US 2006/0120395 Al

(52)
(58)

* cited by examiner

Dec. 7, 2004

(65)

(51)

International Search Report & Written Opinion issued for PCTI
US05/44156 dated Oct. 26, 2006.

370/333
3701206
342/374
3701203
455/450

31 Claims, 9 Drawing Sheets

INITIAL INPUT
,, - ------ --- -REASSIGNMENT ---- -- --- -- ----,
,
,
,
,
,
,
,

,
,
,
,
,
,
,
,
,
,

~--------------------~c:==~~~====)
ANT 1: AVAILABLE
SUBCHANNEL LIST;

602

FIND THE AVAILABLE
SUBCHANNEL WITH THE
HIGHEST GAIN AMONG ALL
AVAILABLE ANTENNAS: (k,j)

604
'--------UPDATE---------I

610

612

L____________________________________ J

u.s. Patent

Aug. 11, 2009

US 7,573,851 B2

Sheet 1 of9

Fig.l

I
I
I

108

NEW
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I

,.

r='==-'{

...

:::

104

V
#1

114

120A

y-120B
#2

116
102

100

112

u.s. Patent

Aug. 11, 2009

~O8
B

-----

I

US 7,573,851 B2

Sheet 2 of9

104

i

ANT
#2
I

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2

1I11111111

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3

4

5

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6

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M

~10
B

104

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ANT
#1

:<><
2

3

4

5

6

SUBCHANNEL INDEX

Fig. 2

u.s. Patent

US 7,573,851 B2

Sheet 3 of9

Aug. 11, 2009

4

Fig.3a

3
2

2

5

6

ANTENNA # 1
CHANNEL
CHARACTERISTICS
(DOWNLINK)

2

122

\

3

4

ANTENNA # 2
CHANNEL
CHARACTERISTICS
(DOWNLINK)

114

116
102

5

6

u.s. Patent

Aug. 11, 2009

US 7,573,851 B2

Sheet 4 of9

ANTENNA # 1
CHANNEL
CHARACTERISTICS
(UPLINK)

4

Fig.3b

2

2

3

4

ANTENNA # 2
CHANNEL
CHARACTERISTICS

6

5

(UP~INK)

4

2

122

\
2

UPLINK OR
BI-DIRECTIONAL LINK

3

4 /

5

I

\

/
120A #1

120B

BASE STATION

114
102

6

u.s. Patent

US 7,573,851 B2

Sheet 5 of9

Aug. 11, 2009

BROADCAST BEACON SIGNAL COVERING ALL
f..-' 400
(SUB-)CHANNELS FROM EACH ANTENNA
RESOURCE AT BASE STATION

~
TUNE SUBSCRIBER RECEIVER UNIT TO CYCLE
THROUGH CHANNELS WHILE MEASURING
I--' 402
CHANNEL CHARACTERISTICS
(e.g., SINR, CINR, RSSI, BER, OoS, etc.)

~
RETURN CHANNEL CHARACTERISTIC
MEASUREMENT DATA TO BASE STATION

i'--' 404

~
SELECT BEST (AVAILABLE) CHANNEL TO
ASSIGN TO SUBSCRIBER

'-/

406

Fig.4a
SUBSCRIBER PERFORMS RANGING WITH EACH
ANTENNA RESOURCE AT BASE STATION

'-/

450

~
CYCLE THROUGH UPLINK CHANNELS AT
SUBSCRIBER WHILE MEASURING CHANNEL
,
'-" 452
CHARACTERISTICS (e.g., SINR, CINR, RSSI, BER, OoS,
etc.) AT EACH BASE STATION ANTENNA RESOURCE

~
STORE CHANNEL CHARACTERISTIC MEASUREMENT
r---- 454
DATA AT BASE STATION

l
SELECT BEST (AVAILABLE) CHANNEL TO ASSIGN TO
i'--' 456
SUBSCRIBER

Fig.4b

u.s. Patent

Aug. 11, 2009

US 7,573,851 B2

Sheet 6 of9

SWITCHING ANTENNA
WITH OFDMA
N

I

en
:;:,
in

ANTENNA #1
CHANNEL
CHARACTERISTICS

4
3
2

2

3

4

5

6
TRAFFIC CHANNEL INDEX

N

I

en
:;:,
in

ANTENNA #2
CHANNEL
CHARACTERISTICS

4
3
2

2

3

4

5

6
TRAFFIC CHANNEL INDEX

Fig. 5

~

7J).

•

# OF USERS: i = 1:p

•

# OF ANTENNAS: j=1 :Nt
# OF SUBCHANNELS: k=1:N

•

:-----------.REASSIGNMENT ________
I
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MAX # OF SUBCHANNELSI
ANTENNA:M

~

=
~

INITIAL INPUT
--

FOR i=1:P

602

MEASURE SUBSCRIBERS'
CHANNEL PROFILE FOR EACH
OF Nt ANTENNAS

~

~

....
....
N

UPDATE
ANT 1: AVAILABLE
SUBCHANNEL LIST;
ANT M: AVAILABLE
SUBCHANNEL LIST

FIND THE AVAILABLE
SUBCHANNEL WITH THE
HIGHEST GAIN AMONG ALL
AVAILABLE ANTENNAS: (k,j)

INPUT

402,
452

SUBSCRIBERS'
CHANNEL
PROFILE REGISTER

o
o

\0

rFJ

=-

('D
('D

.....

-....l

....

o

604

\0

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ASSIGN SUBCHANNEL k AND
ANTENNA j TO USER i

610

d

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NEXTi

-....l
W

612

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_____ J

00
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,- - i - - - - i. - -

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CHANNEL
CHARACTERISTICS
ESTIMATION!
MEASUREMENT

~

704

1

:

1
1

y: 703
1

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1.

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ONGOING TRAFFIC
REGISTER

OFDM
DEMODULATOR

706

718:

'-'

1
1
I

RECEIVER
L
_____
: _ _ _ _ _ _ _ _ _ _MODULE _

~

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(710

=
~

~

~

II

OFDMA SUBCHANNEL
ALLOCATION LOGIC

H

:

~

SUBCHANNEL
FORMATION

1_ _ _ _ _ _ _ _

....
....

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o

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SUBSCRIBERS'
CHANNEL PROFILE
REGISTER

=-

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MODULATOR

.....

Jv716

QO

....

o

\0

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t712

(608
OFDMA MAC

L-

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BEACON SIGNAL
GENERATOR (e.g.
OFDMA PILOT
SYMBOLS)

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(714

Fig. 7

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UP-CONVERTERS 1---722

1

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DOWNCONVERTERS

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INFORMATION
STREAMS

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-....l

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tit

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=

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~

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INFO BITS FOR
USER # 1

~

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MODEM AND
SUB-CHANNEL
ALLOCATION

=
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FFT

ADDCP

PIS

1

~

810 1

P_1

~

....
....

N

806 1

o
o

808 1

\0

MAC DYNAMIC
CHANNEL
ALLOCATION

rFJ

=-

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.....

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....

o

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\0

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INFO BITS FOR I MODEM AND
USER # P • SUB-CHANNEL
ALLOCATION

Fig. 8

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=
N

US 7,573,851 B2
1

2

"Multiuser OFDM with Adaptive Subcarrier, Bit and Power
Allocation," IEEE J. Select. Areas Connnun., Vol. 17(10), pp.
1747-1758, October 1999.
Within one cell, the subscribers can be coordinated to have
different subcarriers in OFDMA. The signals for different
FIELD OF THE INVENTION
subscribers can be made orthogonal and there is little intracell
interference. However, with an aggressive frequency reuse
The present invention relates to the field of connnunicaplan, e.g., the same spectrum is used for multiple neighboring
tions systems; more particularly, the present invention relates
cells, the problem of intercell interference arises. It is clear
to techniques for switching channel and antenna assignments
10 that the intercell interference in an OFDMA system is also
in wireless networks.
frequency selective and it is advantageous to adaptively allocate the sub carriers so as to mitigate the effect of intercell
BACKGROUND OF THE INVENTION
interference.
One approach to subcarrier allocation for OFDMA is a
Spatial processing with antenna arrays is one of the most
15 joint optimization operation, not only requiring the activity
used techniques in wireless connnunications. Among many
and channel knowledge of all the subscribers in all the cells,
schemes developed to date, multiple-input multiple-output
but also requiring frequent rescheduling every time an exist(MIMO) and beamforming are often studied and have been
ing subscribers is dropped off the network or a new subscribproved to be effective in increasing the capacity and perforers is added onto the network. This is often impractical in real
mance of a wireless network (see, e.g., Ayman F. Naguib,
Vahid Tarokh, Nambirajan Seshadri, A. Robert Calderbank, 20 wireless system, mainly due to the bandwidth cost for updating the subscriber information and the computation cost for
"A Space-Time Coding Modem for High-Data-Rate Wireless
the joint optimization.
Connnunications", IEEE Journal on Selected Areas in ComExisting approaches for wireless traffic channel assignmunications, vol. 16, no. 8, October1998 pp. 1459-1478). On
ment are subscriber-initiated and single-subscriber (point-tothe other hand, realization of MIMO or beamforming often
means higher complexity and cost on the system side. In 25 point) in nature. Since the total throughput of a multipleaccess network depends on the channel fading profiles, noiseparticular, MIMO operations entail complicated signal proplus-interference levels, and in the case of spatially separately
cessing and decoding, while beamforming involves hardware
transceivers, the spatial channel characteristics, of all active
calibrations and multi-dimensional data processing.
subscribers, distributed or subscriber-based channel loading
Over the years, orthogonal division multiple-access 30 approaches are fundamentally sub-optimum. Furthermore,
(OFDMA) has become the access scheme of choice for
subscriber-initiated loading algorithms are problematic when
almost all broadband wireless networks (e.g., WiMAX, WiFi,
multiple transceivers are employed as the base-station, since
and 4G cellular systems). In OFDMA, multiple subscribers
the signal-to-noise-plus-interference ratio (SINR) measured
are allocated to different subcarriers, in a fashion similar to
based on an onmi -directional sounding signal does not reveal
frequency division multiple access (FDMA). For more infor- 35 the actual quality of a particular traffic channel with spatial
mation, see Sari and Karam, "Orthogonal Frequency-Diviprocessing gain. In other words, a "bad" traffic channel measion Multiple Access and its Application to CATV Netsured at the subscriber based on the onmi-directional soundworks," European Transactions on Teleconnnunications, Vol.
ing signal may very well be a "good" channel with proper
9 (6), pp. 507-516, November/December 1998 and Noguerspatial beamforming from the base-station. For these two
oles, Bossert, Donder, and Zyablov, "Improved Performance 40 reasons, innovative information exchange mechanisms and
of a Random OFDMA Mobile Connnunication System," Prochannel assignment and loading protocols that account for the
ceedings ofIEEE VTC'98, pp. 2502-2506.
(spatial) channel conditions of all accessing subscribers, as
The fundamental phenomenon that makes reliable wireless
well as their QoS requirements, are highly desirable. Such
transmission difficult to achieve is time-varying multipath
"spatial-channel and QoS-aware" allocation schemes can
fading. Increasing the quality or reducing the effective error 45 considerably increase the spectral efficiency and hence data
rate in a multi path fading channel may be extremely difficult.
throughput in a given bandwidth. Thus, distributed
For instance, consider the following comparison between a
approaches, i.e., subscriber-initiated assignment are fundatypical noise source in a non-multipath environment and mulmentally sub-optimum.
tipath fading. In environments having additive white Gaussian noise (AWGN), it may require only 1- or 2-db higher 50
SUMMARY OF THE INVENTION
signal-to-noise ratio (SNR) using typical modulation and
coding schemes to reduce the effective bit error rate (BER)
A method and apparatus is disclosed herein for antenna
from 10- 2 to 10- 3 . Achieving the same reduction in a multiswitching and channel assignments in wireless communicapath fading environment, however, may require up to 10 db
tion systems. Channel characteristics indicative of signal
improvement in SNR. The necessary improvement in SRN 55 reception quality are obtained for each of multiple channels
may not be achieved by simply providing higher transmit
hosted by each antenna resource at a base station. Channels
power or additional bandwidth, as this is contrary to the
are assigned to subscribers based on the channel characterisrequirements of next generation broadband wireless systems.
tics. base station,
Multipath phenomena causes frequency-selective fading.
BRIEF DESCRIPTION OF THE DRAWINGS
In a multiuser fading environment, the channel gains are 60
different for different subcarriers. Furthermore, the channels
The present invention will be understood more fully from
are typically uncorrelated for different subscribers. This leads
to a so-called "multiuser diversity" gain that can be exploited
the detailed description given below and from the accompathrough intelligent sub carrier allocation. In other words, it is
nying drawings of various embodiments of the invention,
advantageous in an OFDMA system to adaptively allocate the 65 which, however, should not be taken to limit the invention to
subcarriers to subscribers so that each subscriber enjoys a
the specific embodiments, but are for explanation and underhigh channel gain. For more information, see Wong et aI.,
standing only.

METHOD AND SYSTEM FOR SWITCHING
ANTENNA AND CHANNEL ASSIGNMENTS
IN BROADBAND WIRELESS NETWORKS

US 7,573,851 B2

3

4

FIG. 1 shows a base station employing a pair of switched
antennas that are used to communicate with various subscribers, wherein each subscriber is assigned to a channel corresponding to a respective subchannel/antenna combination.
FIG. 2 shows an OFDMA sub channel allocation for the
subscribers shown in FIG. 1 prior to the entry of a new
subscriber.
FIG. 3a shows a beacon signal sent out by each of the
antennas in FIG. 1 that is received by a new subscriber and
contains various channels via which the new subscriber can
measure downlink or bi-directionallink channel characteristics that are returned to the base station.
FIG. 3b shows a ranging signal sent out by the new subscriber and containing test data sent over various channels via
which uplink or bi-directional channel characteristics can be
measured at each of the switched antennas of FIG. 1.
FIG. 4a is a flowchart illustrating operations perfonned to
obtain downlink or bi -directional link channel characteristics
using the beacon signal scheme of FIG. 3a.
FIG. 4b is a flowchart illustrating operations perfonned to
obtain uplink or bi-directional link channel characteristics
using the ranging signal scheme of FIG. 3b.
FIG. 5 depicts exemplary subscriber's channel responses
corresponding to channel characteristics for the switched
antennas of FIG. 1.
FIG. 6 shows a flowchart illustrating operations performed
to assign channels to various users for a base station having
multiple antenna resources, wherein a channel comprising
the best available subchannel/antenna combination is
assigned to a new user based on measured or estimated subchannel characteristics for each antenna.
FIG. 7 is a block diagram of one embodiment of an
OFDMAlSDMA base-station.
FIG. 8 shows an architecture for a OFDMA transmitter
module employing multiple switched antennas.

sion multiple access), OFDMA, and SDMA (space division
multiple access) schemes, as well as combinations of these
multiple-access schemes.
In the following description, numerous details are set forth
to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art, that
the present invention may be practiced without these specific
details. In other instances, well-known structures and devices
are shown in block diagram fonn, rather than in detail, in
order to avoid obscuring the present invention.
Some portions of the detailed descriptions which follow
are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory.
These algorithmic descriptions and representations are the
means used by those skilled in the data processing arts to most
effectively convey the substance of their work to others
skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a
desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily,
these quantities take the fonn of electrical or magnetic signals
capable of being stored, transferred, combined, compared,
and otherwise manipulated. It has proven convenient at times,
principally for reasons of common usage, to refer to these
signals as bits, values, elements, symbols, characters, tenns,
numbers, or the like.
It should be borne in mind, however, that all of these and
similar tenns are to be associated with the appropriate physical quantities and are merely convenient labels applied to
these quantities. Unless specifically stated otherwise as
apparent from the following discussion, it is appreciated that
throughout the description, discussions utilizing tenns such
as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and
processes of a computer system, or similar electronic computing device, that manipulates and transfonns data represented as physical (electronic) quantities within the computer
system's registers and memories into other data similarly
represented as physical quantities within the computer system memories or registers or other such information storage,
transmission or display devices.
The present invention also relates to apparatus for performing the operations herein. This apparatus may be specially
constructed for the required purposes, or it may comprise a
general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a
computer program may be stored in a computer readable
storage medium, such as, but is not limited to, any type of disk
including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random
access memories (RAMs), EPROMs, EEPROMs, magnetic
or optical cards, or any type of media suitable for storing
electronic instructions, and each coupled to a computer system bus.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus.
Various general-purpose systems may be used with programs
in accordance with the teachings herein, or it may prove
convenient to construct more specialized apparatus to perform the required method steps. The required structure for a
variety of these systems will appear from the description
below. In addition, the present invention is not described with
reference to any particular programming language. It will be
appreciated that a variety of programming languages may be
used to implement the teachings of the invention as described
herein.

10

15

20

25

30

35

DETAILED DESCRIPTION OF THE PRESENT
INVENTION
40

The marriage ofOFDMA and spatial processing provides
powerful platfonn for multiuser broadband communications.
The present invention describes a method, apparatus, and
system for easy integration ofOFDMA with antenna arrays of
various configurations. The method and apparatus allows
multiuser diversity to be exploited with simple antenna operations, therefore increasing the capacity and performance of
wireless communications systems. In one embodiment,
Channel characteristics indicative of signal reception quality
for downlink or bi-directional traffic for each channel (e.g.,
OFDMA subchannel/antenna resource combination) are
measured or estimated at a subscriber. Corresponding channel characteristic infonnation is returned to the base station.
Channel characteristics infonnation may also be measured or
estimated for uplink or bi-directional signals received at each
of multiple receive antenna resources. The base station
employs channel allocation logic to assign uplink, downlink
and/or bi-directional channels for multiple subscribers based
on channel characteristics measured and/or estimated for the
uplink, downlink and/or bi-directional channels.
The benefits of the present invention include simpler hardware (much less expensive than beamforming antenna arrays)
and easier processing (much less complicated than MIMO),
without sacrificing the overall system performance. In addition to OFDMA implementation, the general principles may
be utilized in FDMA (frequency division multiple access),
TDMA (time division multiple access), CDMA (code divi-

45

50

55

60

65

US 7,573,851 B2

5

6

A machine-readable medium includes any mechanism for
storing or transmitting infonnation in a fonn readable by a
machine (e.g., a computer). For example, a machine-readable
medium includes read only memory ("ROM"); random
access memory ("RAM"); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical,
acoustical or other fonn of propagated signals (e.g., carrier
waves, infrared signals, digital signals, etc.); etc.

Generally, a base station communicates with a subscriber
in the following manner. Data bursts, such as cellular packets,
IP packets or Ethernet frames, are encapsulated into an appropriate data frame fonnat (e.g., IEEE 802.16 for WiMAX
networks) and forwarded from a network component, such as
a radio access node (RAN), to an appropriate base station
within a given cell. The base station then transmits to a
selected subscriber (identified by the data frame) using a
unidirectional wireless link, which is referred to as a "downlink." Transmission of data from a subscriber to network 1 00
proceeds in the reverse direction. In this case, the encapsulated data is transmitted from a subscriber to an appropriate
base station using a unidirectional wireless link referred to as
an "uplink." The data packets are then forwarded to an appropriate RAN, converted to IP Packets or Ethernet frames, and
transmitted henceforth to a destination node in network 100.
Under some types of broadband wireless networks, data
bursts can be transmitted using either Frequency-DivisionDuplexing (FDD) or Time-Division-Duplexing (TDD)
schemes. In the TDD scheme, both the uplink and downlink
share the same RF (radio frequency) channel, but do not
transmit simultaneously, and in the FDD scheme, the uplink
and downlink operate on different RF channels, but the channels may be transmitted simultaneously. In general, the unidirection wireless downlinks may comprise a point-to-point
(PP) link, a point-to-multiple (PMP), or a MIMO link.
Uplinks typically comprise PP or PMP links, although
MIMO links may also be used.
Multiple base stations are configured to fonn a cellular-like
wireless network, wherein one or more base stations may be
accessible to a given subscriber at any given location using a
shared medium (space (air) through which the radio waves
propagate). A network that utilizes a shared medium requires
a mechanism to efficiently share it. Sharing of the air medium
as enabled via an appropriate channel-based scheme, wherein
respective channels are assigned to each subscriber within the
access range of a given base station. Typical channel-based
transmission schemes include FDMA, TDMA, CDMA,
OFDMA, and SDMA, as well as combination of these multiple access schemes. Each of these transmission schemes are
well-known in the wireless networking arts.
To facilitate downlink and uplink communications with the
various subscribers, base station 102 provides multiple antennas. For illustrative purposes, these are depicted as antenna
120A and antenna 120B (antennas #1 and #2) in FIG. 1.
Signals from two or more of the multiple antennas may be
combined to support beam fonning or spatial multiplexing, or
may be used individually for different groups of subscribers
using well-known techniques. The multiple antennas may
also be configured in one or more clusters. In general, antennas 120A and 120B are representative of various antenna
types employed in wireless broadband network, including
sectorized antennas and onmi-directional antennas.
Under one embodiment, each subscriber is assigned to a
respective channel or sub channel provided by one of the
antennas at a given base station (or antenna resources, when
multiple antennas may be combined to transmit or receive
signals). For example, in the illustrated configuration of FIG.
1, mobile subscriber 104 and fixed subscriber 110 are
assigned to respective channels facilitated by antenna 120A,
while fixed subscriber 108, and mobile subscribers 106 and
112 are assigned to respective channels facilitated by antenna
120B. As described in further detail below, the channel/antenna or subchannel/antenna selection for each subscriber is
based on the best available channel characteristics at the point
at which a new subscriber enters the network via a given base

Overview
Efficient exploitation of spatial diversity in a high-speed
wireless network is a challenging task due to the broadband
nature of spatial channel characteristics. In OFDMA networks, the wide spectrum is partitioned into parallel narrowband traffic channels (commonly referred to as "sub-channels"). The methodology described herein provides a means
for allocating traffic channels through intelligent traffic channel assignment.
In the communication system described herein, channel
allocation logic perfonns "channel-aware" traffic channel
allocation. In one embodiment, the channel allocation logic
provides bandwidth on demand and efficient use of spectral
resources (e.g., OFDMA traffic channels) and spatial
resources (e.g., the physical location of subscribers as it pertains to spatial beamfonning) and performs traffic channel
assignment based on broadband spatial channel characteristics of a requesting subscriber and on-going subscribers. Furthennore, channels are allocated to subscribers based on the
best antenna resources for those subscribers. Thus, the channel allocation provides enhanced performance over a larger
number of subscribers than might be typically obtained using
conventional channel assignment approaches.
In responding to a link request from a new subscriber, or
when the base-station has data to transmit to a standby subscriber, the logic first estimates the channel characteristics of
transmissions received over all, or a selected portion of
OFDMA traffic channels for each antenna resource. As used
herein, an antenna resource may comprise a single antenna, or
a sub-array of antennas (from an array of an antennas for a
given base station) that are collectively used to transmit and/
or receive signals from subscribers. For example, multiple
antennas may be configured to function (effectively) as a
single antenna resource with improved transmission characteristics (when compared with a single antenna) by using one
or more signal diversity schemes (spatial, frequency, and/or
time). In one embodiment, the channel characteristics, along
with channel assignment for on-going subscribers are used to
determine which antenna resource is optimum for each subscriber. The channel characteristic data may be stored in a
register or other type of storage location (e.g., a database, file,
or similar data structure). In one embodiment, traffic channels
corresponding to antenna resources that have the best communication characteristics are assigned to the accessing subscriber to satisfy the service request of the accessing subscriber.
An exemplary portion of a broadband wireless network
100 including a base station 102 that implements the channel
selection techniques described herein is shown in FIG. 1.
Base station 102 includes facilities to support communication
with various subscribers, as depicted by a mobile (phone)
subscribers 104 and 106, fixed (location) subscribers 108 and
110, and a mobile (PDA) subscriber 112. These facilities
include a receive module 114, a transmit module 116, and
channel management component 118, as well as antennas
120A (also referred to herein as antenna #1) and 120B (also
referred to herein as antenna #2).

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station (e.g., base station 102). In addition, channels may be
re-assigned to on-going subscribers based on changes inmeasured channel characteristics.
By way of illustration, the following discussion concems
allocation of channels for an OFDMAnetwork. However, this
is not meant to be limiting, as similar principles may be
applied to wireless networks employing other channel-based
transmission schemes, including FDMA, TDMA, CDMA,
SDMA, and OFDMAlSDMA, as well as other combinations
of these schemes.
In accordance with aspects of the present invention, a channel allocation scheme is now disclosed that allocates downlink and/or uplink or shared (bi-directional) channels for
respective subscribers to selected antenna resources based on
current channel characteristics. The overall approach is to
assign channel/antenna or sub channel/antenna combinations
having the best channel characteristics to new and on-going
subscribers.
FIG. 2 shows an exemplary set of initial OFDMA channel
assignments for the various subscribers shown in FIG. 1. In
the illustrated embodiment, each of antennas #1 and #2 (120A
and 120B) supports N subchannels. Typically, a respective
sub channel for a given antenna or antenna resource is
assigned to each subscriber. In some cases, multiple subchannels may be assigned for the same subscriber. For illustrative
purposes, only a single set of sub channel assignments in FIG.
2 are shown, wherein the single set is illustrative of uplink,
downlink, or shared (same channel for uplink and downlink)
channel assignments. It will be understood that another set of
channel assignments will also exist for transmission schemes
that employ separate channels for downlink and uplink traffic.
Referring to FIGS. 1 and 3a, now suppose that a new
mobile subscriber 122 attempts to initiate service with base
station 102, either by originating a new service request or in
connection with a hand-over from another (currently) serving
base station (not shown) to base station 102. As discussed
above, it is desired to assign a best available channel to the
new user. Accordingly, a mechanism for determining the best
available channel is provided.
With further reference to the flowchart of FIG. 4a, one
embodiment of a process for determining the channel characteristics begins at a block 400, wherein a base station broadcasts a beacon signal covering all sub-channels over the frequency bandwidth allocated to that station from each of its
antenna resources. For example, under an FDMA scheme, the
broadcast signal may comprise a signal that varies in frequency over the allocated bandwidth using a pre-determined
cycle. Under a CDMA scheme, a test signal transmitted over
various CDMA channels that are changed in a cyclic manner
may be used. Under a channel scheme that supports multiple
channels operating on the same frequencies (such as
OFDMA), the broadcast signal will include applicable subchannel/frequency combination per antenna resource. (Further details of one embodiment of an OFDMA beacon signal
scheme are described below.) As a result, the broadcast beacon signal will provide information from which spatial and
frequency channel characteristics may be determined. In one
embodiment, the beacon signal is broadcast over a management channel on an ongoing basis. In the case of some channel schemes based on time slots (e.g., OFDMA, CDMA,
TDMA), it may be necessary to first perform timing synchronization between a base station and subscriber to enable the
subscriber to adequately tune into (e.g., synchronize with) the
broadcast beacon signal.
In response to the beacon signal, the subscriber (device)
tunes its receiving unit to cycle through the various channels
(in synchrony with the channel changes in the beacon signal)

while measuring channel characteristics. For example, in one
embodiment, signal-to-interference plus noise ratio (SINR,
also commonly referred to as carrier-to-interference plus
noise ratio (CINR) for some types of wireless networks)
and/or relative-signal strength indicator (RSSI) measurements are performed at the subscriber to obtain the channel
characteristic measurements or estimates. In one embodiment, the channel characteristic measurement pertains to data
rates that can reliably be obtained for different channels, as
exemplified by the sets of channel characteristic measurement data corresponding to antennas #1 and #2 shown in FIG.
5 (with reduced versions shown in FIG. 3a). For example, it is
common to measure such data rates in Bits per second per
Hertz (Bitls/Hz), as shown in FIG. 5. In another embodiment,
BER measurements are made for each channel/antenna
resource combination. In yet another embodiment, Quality of
Service (QoS) parameters, such as delay and jitter are measured to obtain the channel characteristic data. In still other
embodiments, various indicia of signal quality/performance
may be measured and/or estimated to obtain the channel
characteristic data.
Continuing at a block 404 in FIG. 4a, after, or as channel
characteristic measurements are taken, corresponding data is
returned to the base station. In one embodiment, this information is returned via a management channel employed for
such purposes. In response, a best available channel is
selected to be assigned to the subscriber in view of current
channel availability information and the channel characteristic data. Details of the selection process are described below
with reference to FIG. 6.

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Under one embodiment employed for OFDMA networks,
each base station periodically broadcasts pilot OFDM symbols to every subscriber within its cell (or sector). The pilot
symbols, often referred to as a sounding sequence or signal,
are known to both the base station and the subscribers. In one
embodiment, each pilot symbol covers the entire OFDM frequency bandwidth. The pilot symbols may be different for
different cells (or sectors). The pilot symbols can serve multiple purposes: time and frequency synchronization, channel
estimation and SINRmeasurement for sub channel allocation.
In one embodiment, each of multiple antenna resources
transmits pilot symbols simultaneously, and each pilot symbol occupies the entire OFDM frequency bandwidth. In one
embodiment, each of the pilot symbols have a length or duration of 128 microseconds with a guard time, the combination
of which is approximately 152 microseconds. After each pilot
period, there are a predetermined number of data periods
followed by another set of pilot symbols. In one embodiment,
there are four data periods used to transmit data after each
pilot, and each of the data periods is 152 microseconds in
length.
As the pilot OFDM symbols are broadcast, each subscriber
continuously monitors the reception of the pilot symbols and
measures (e.g., estimates) the SINR and/or other parameters,
including inter-cell interference and intra-cell traffic, for each
sub channel. In one embodiment, the subscriber first estimates
the channel response, including the amplitude and phase, as if
there is no interference or noise. Once the channel is estimated, the subscriber calculates the interference/noise from
the received signal.
During data traffic periods, the subscribers can determine
the level of interference again. The data traffic periods are
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interference level. Specifically, the power difference during
the pilot and traffic periods may be used to sense the (intracell) traffic loading and inter-sub channel interference to
select the desirable sub channel.
In one embodiment, each subscriber measures the SINR of
each subchannel (or a set of sub channels corresponding to
available subchannels) and reports these SINR measurements
to their base station through an access channel. The feedback
of information from each subscriber to the base station contains an SINR value (e.g., peak or average) for each sub channel. A channel indexing scheme may be employed to identify
the feedback data for each subchannel; no indexing is needed
if the order of information in the feedback is known to the
base station in advance.
Upon receiving the feedback from a subscriber, the base
station selects a subchannel to assign to the subscriber in a
manner similar to that described below. After sub channel
selection, the base station notifies the subscriber about the
sub channel assignment through a downlink common control
channel or through a dedicated downlink traffic channel if the
connection to the subscriber has already been established. In
one embodiment, the base station also informs the subscriber
about the appropriate modulation/coding rates. Once the
basic communication link is established, each subscriber can
continue to send the feedback to the base station using a
dedicated traffic channel (e.g., one or more predefined uplink
access channels).
The foregoing scheme determines channel characteristics
for downlink and shared bi-directionallink channels. However, it may be inadequate for predicting uplink channel characteristics. The reason for this is that multipath fading is
generally unidirectional. As a result, a channel that produces
good downlink channel characteristics (as measured at a
receiving subscriber) may not provide good uplink channel
characteristics (as measured at a receiving base station).
With reference to FIGS. 3b and 4b, one embodiment of a
process for determining channel characteristics for uplink
channels (or optionally, bi -directional shared channels)
begins at a block 450 (FIG. 4b), wherein a subscriber performs ranging with each antenna resource at the base station.
The term "ranging" is used by the WiMAX (IEEE 802.16)
standard to define a set of operations used by a subscriber
station to obtain service availability and signal quality information from one or more base stations. During this process, a
subscriber station synchronizes with a base station and a
series of messages are exchanged between the subscriber
station and the base station. Also, signal quality measurements may be obtained by performing CINR and/or RSSI
measurements at the base station and/or the subscriber station.
As used herein, "ranging" generally concerns transmission
activities initiated by a subscriber to enable uplink channel
characteristics to be measured by a base station; thus, ranging
includes the aforementioned ranging operations defined by
the WiMAX specification for WiMAX networks, as well as
other techniques used to obtain uplink channel characteristics. For example, similar operations to those employed during WiMAX ranging may be employed for other types of
broadband wireless networks. In one embodiment, a subscriber and base station exchange information relating to a
channel sequence over which channel characteristic measurements will be made. For example, in some implementations a
base station may only identifY unused uplink channels to
measure, thus reducing the nnmber of measurements that will
be performed. Optionally, the channel sequence may be
known in advance.

Continuing at a block 452, in view of the channel sequence
information, the subscriber cycles through the applicable
uplink channels while transmitting test data to each base
station antenna resource. In general, this may be performed
concurrently for all individual antennas or combined antenna
resources, or may be performed separately for each antenna
resource. In connection with the transmission of the test data
via each uplink channel, channel characteristic measurements are made by the base station in block 452 and stored in
block 454. In general, the channel characteristic measurements performed in block 452 are analogous to those performed in block 402 (FIG. 4a), except now the measurements
are made at the base station rather than at the subscriber. The
best available uplink channel to assign the subscriber is then
selected in a block 456 in the manner now described with
reference to the operations of FIG. 6.
In further detail, FIG. 6 depicts a process for channel
assignment under a generic configuration for a base station
having a variable number of users (subscribers), antennas
(individual antennas or combined antenna resources), and
subchannels for each antenna or combined antenna resource.
Accordingly, a set of data 600 comprising an initial input
defining the number of users, antennas, number of subchannels, and maximum nnmber of sub channels per antenna is
provided to the processing operations depicted below data
600 in FIG. 6.
As depicted by start and end loop blocks 602 and 612, the
operations depicted in the blocks 604, 606, and 610 are performed for each of users 1 to P. First, in block 604, the
available subchannel with the highest gain is selected among
all available antennas (or combined antenna resources, if
applicable). As depicted by input data block 606, the set of
available subchannels for each of antennas is maintained and
updated on an ongoing basis to provide current sub channel
allocation information to block 604. In addition, channel
characteristic profile data measured in blocks 402 and/or 452
(as applicable) is stored in a subscribers' channel profile
register 608 and updated on an ongoing basis. During channel
selection for a particular subscriber, corresponding channel
characteristic profile data is retrieved from subscribers' channel profile register 608 as an input to block 604.
In view of input data from data blocks 606 and 608, a
sub channel k and antenna j are assigned to the user i in block
610. The process then moves to the next user (e.g., user i+ 1)
to assign a channel comprising a subchannel/antenna combination for that user via the operations of block 604 in view of
updated input data from data blocks 606 and 608. In general,
these operations are repeated on an ongoing basis.
These concepts may be more clearly understood from
exemplary channel assignment parameters in accordance
with network participants shown in the figures herein. For
example, FIG. 2 illustrates an initial condition wherein
mobile subscriber 106 and fixed subscriber 110 are respectively assigned channels comprising subchannels 1 and 6 for
antenna #1, while fixed subscriber 108 is assigned a channel
comprising sub channel 2 for antenna #2 and mobile subscribers 104 and 112 are respectively assigned channels comprising subchannels 5 and M-1 for antenna #2. For point of
illustration, these channel assignments are representative of
uplink, downlink, or bi-directionallink channel assignments.
For the following example it is presnmed that corresponding
channel assignment information is present in data block 606.
Now suppose that mobile subscriber 122 (FIGS. 1, 3a, and
3b) attempts to enter the network. First, channel characteristic
measurement data will be collected in accordance with the
operations of the flowcharts shown in FIGS. 4a and/or 4b, as
applicable. This will update subscribers' channel profile reg-

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ister 608. During the processing of block 604, antenna channel characteristic data for each of antennas #1 and #2 will be
retrieved from subscribers' channel profile register 608. As
discussed above, exemplary channel characteristic data are
depicted in FIG. 5. In view of this channel characteristic data
in combination with available sub channel information shown
in FIG. 2 and retrieved from data block 606, a new channel for
mobile subscriber 122 is selected in block 610.
In the view of the exemplary channel characteristic data
and subchannel assignment data in respective FIGS. 5 and 2,
sub channel 3 for antenna #2 should be assigned to mobile
subscriber 122, which represents the available channel with
the highest gain (e.g., available channel with the best channel
characteristics). In one embodiment, this may be determined
in the following manner. First, the channel with the highest
gain is selected for each antenna resource. In the present
example, this corresponds to channel 1 for antenna #1 and
sub channel 3 for antenna #2. Next, a determination is made to
whether that sub channel is available. In the case of subchannell for antenna #1, this subchannel is already assigned, so it
is not available. The channel corresponding to the next best
gain is then selected for antenna #1, which corresponds to
sub channel 5. Likewise, a similar determination is made for
channel 2. In the present example, sub channel 3, which represents the subchannel for antenna #2 with the highest gain, is
available. The gains for sub channel 5 for antenna #1 and
sub channel 3 for antenna #2 are then compared. The sub chan nel/antenna combination with the highest gain is then
selected for assignment to the new subscriber. This results in
the selection of sub channel 3 for antenna #2 as the new
channel to be assigned to mobile subscriber 122.
From time to time, processing logic may perform channel
reassignment by repeating the process described above with
reference to FIG. 6. This channel reassignment compensates
for subscriber movement and any changes in interference. In
one embodiment, each subscriber reports its channel characteristics data. The base station then performs selective reassignment of sub channel and antenna resources. That is, in one
embodiment some of the subscribers may be reassigned to
new channels, while other channel assignments will remain
as before. In one embodiment, retraining is initiated by the
base station, and in which case, the base station requests a
specific subscriber or subscribers to report its updated channel characteristics data. A channel reassignment request may
also be submitted by a subscriber when it observes channel
deterioration.
FIG. 7 is a block diagram of base station 700 that communicates with multiple subscribers through OFDMA and spatial multiplexing. The base-station 700 comprises receiving
antenna array 702, a receiver module 703 including a set of
down-converters 704 coupled to receiving antenna array 700
and an OFDM demodulator 706, a channel characteristics
module 708, an on-going traffic register 710, OFDMA subchannel channel allocation logic 712, a subscribers's channel
profile register 608, an OFDMA medium access controller
(MAC) 714, an OFDM modem 716, a beacon signal generator, an OFDMA transmitter module 718 including a subchannel formation block 720, and a set of up-converters 722
that provide inputs to respective antenna resources in a transmission antenna array 724.
Uplink signals, including the accessing signal from a
requesting subscriber, are received by receiving antenna array
702 and down-converted to the base-band by down-converters 704. The base-band signal is demodulated by OFDM
demodulator 706 and also processed by channel characteristics block 708 for estimation of the accessing subscriber's
uplink channel characteristics using one of the techniques

described above or other well-known signal quality estimation algorithms. The estimated or measured channel characteristics data, along with channel characteristics corresponding to channels assigned to ongoing traffic that is stored in
subscribers channel profile register 608 and on-going traffic
information stored in the on-going traffic register 710, are fed
to OFDMA sub channel allocation logic 712 to determine a
channel assignment for the accessing subscriber, and possibly
partial or all of the on-going subscribers. The results are sent
to OFDMA MAC 714, which controls the overall traffic.
Control signals from OFDMA MAC 714 and downlink
data streams 726 are mixed and modulated by OFDM modulator 716 for downlink transmission. Sub channel formation
(such as the antenna beamforminglswitching operations
described below with reference to FIG. S) is performed by
sub channel formation block 720 using sub channel definition
information stored in the subscribers' channel profile register
608. The output of subchannel formation block 720 is upconverted by the set of up-converters 722, and transmitted
through transmission antenna array 724.
Beacon signal generator 717 is used to generate a beacon
signal appropriate to the underlying transmission scheme. For
example, for an OFDMA transmission scheme, beacon signal
generator 717 generates a signal including OFDMA pilot
symbols interspersed among test data frames.
Details of functional blocks corresponding to one embodiment of an OFDMA transmitter module SOO for a base station
having N antennas are shown in FIG. S. A MAC dynamic
channel allocation block S02 is used to select an appropriate
antenna resource and subchannel for each of P users, as
depicted by selection inputs to modem and sub channel allocation blocks S04 1 _P ' Based on the modem and sub channel
allocation for each user, a corresponding OFDMA baseband
signal is generated, up-converted, and transmitted over an
appropriate antenna using signal-processing techniques that
are well-known in the OFDMA transmission arts. The process is depicted by Fast Fourier Transform (FFT) blocks
S04 1 _N , parallel to serial (P/S) conversion blocks S06 1 _M and
add cyclic prefix (CP) blocks S04 1 _N
OFDMA transmitter module SOO performs antenna
switching operations by adjusting the FFT inputs. For
example, for a given subscriber channel, certain FFT inputs
are set to 1 (meaning use), while other FFT inputs are set to 0
(meaning ignore). OFDMA transmitter module SOO also support channels that are facilitated by concurrently sending
signals over multiple antennas.
In general, the operations performed by the process and
functional blocks illustrated in the figures herein and
described above are performed by processing logic that may
comprise hardware (circuitry, dedicated logic, etc.), software
(such as is nm on a general purpose computer system or a
dedicated machine), or a combination of both.
Whereas many alterations and modifications of the present
invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment
shown and described by way of illustration is in no way
intended to be considered limiting. Therefore, references to
details of various embodiments are not intended to limit the
scope of the claims which in themselves recite only those
features regarded as essential to the invention.
We claim:
1. method for assigning channels to support commnnication between subscribers and a base station in a broadband
wireless network, comprising:
for each of multiple antenna resources configured for communication on multiple channels, at the base station,

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obtaining one or more channel characteristics for each
channel hosted by each antenna resource, the channel
characteristics indicative of reception quality for a corresponding channel; and
assigning, by said base station, one or more channels to
subscribers based on the one or more channel characteristics that are obtained;
wherein said obtaining one or more channel characteristics
is accomplished, at least in part, by ranging operations
performed by said subscribers;
wherein the channel characteristics are measured by performing operations comprising:
performing ranging operations between a subscriber and a
base station over one of an uplink or bi -directional link,
the ranging operations including transmissions sent
from the subscriber station and received by each antenna
resource, the transmissions carried over multiple channels; and
obtaining, at each antenna resource, channel characteristics indicative of signal quality of each of the multiple
channels.
2. The method of claim 1, wherein the one or more channels assigned comprise one or more downlink channels for
use with transmissions sent from the base station to the subscribers.
3. The method of claim 1, wherein the one or more channel
assigned comprise one or more uplink channels for use with
transmissions sent from subscribers to the base station.
4. The method of claim 1, wherein the one or more channel
assigned comprise one or more bi-directionallink channels
employed for both uplink and downlink transmissions
between the base station and the subscribers.
5. The method of claim 1, wherein the channel characteristics are measured by performing operations comprising:
broadcasting a respective beacon signal from each of the
antenna resources at the base station, each beacon signal
including transmissions over multiple channels;
measuring channel characteristics indicative of signal
quality for each of the multiple channels at a subscriber;
and
sending data corresponding to the channel characteristics
that are measured from the subscriber to the base station.
6. The method of claim 5, wherein the respective beacon
signals that are broadcast from each of the antenna resources
comprise orthogonal frequency division multiple access
(OFDMA) signals including OFDMA pilot symbols.
7. The method of claim 6, further comprising the subscriber
using information from pilot symbol periods and data periods
to measure channel and interference information.
B. The method of claim 6, wherein the pilot symbols
occupy an entire OFDM frequency bandwidth.
9. The method of claim 1, wherein the multiple antenna
resources comprises multiple individual antennas.
10. The method of claim 1, wherein at least one antenna
resource comprises a set of antennas that are operated collectively to perform at least one of transmit and receive radio
frequency transmissions.
11. The method of claim 1, wherein the wireless broadband
network supports OFDMA (orthogonal frequency division
multiple access) transmissions, and the channels comprise
combinations of OFDMA subchannels and antenna
resources.
12. The method of claim 11, further comprising switching
antennas by adjusting the inputs to fast Fourier transform
(FFT) blocks in an OFDMA transmitter module at the baseband.

13. The method of claim 11, wherein each subscriber is
assigned to a single OFDMA channel, transmission for the
single channel provided by a single antenna resource.
14. The method of claim 1, wherein the channel assignment
operations are employed to assign respective channels for
downlink and uplink transmissions.
15. The method of claim 1, wherein the channel characteristic measurements comprise at least one of Signal-to-interference plus noise ratio (SINR), carrier-to-interference plus
noise ratio (CINR) and relative-signal strength indicator
(RSSI) measurements.
16. The method of claim 1, wherein the channel characteristic measurements comprise bit error rate (BER) measurements.
17. The method of claim 1, wherein the channel characteristic measurements comprise measurement of Quality ofService (QoS) parameters.
lB. The method of claim 1, wherein the channels comprise
one of channels or sub channels corresponding to at least one
of a FDMA (frequency division multiple access), TDMA
(time division multiple access), CDMA (code division multiple access), OFDMA (orthogonal frequency division multiple access), and SDMA (space division multiple access)
channel schemes.
19. The method of claim 1, further comprising:
periodically updating channel characteristics information
for one or more subscribers; and
reassigning channels for at least one subscriber in view of
changed channel characteristics.
20. A base station, comprising:
multiple antenna resources to support wireless communications system transmissions;
a transmission module to generate signals over various
downlink or bi-directional channels via which data is
transmitted via the multiple antenna resources to multiple subscribers;
a reception module to extract data indicative of reception
quality for a corresponding channel from signals
received at the multiple antenna resources over various
uplink or the bi-directional channels from the subscribers; and
channel allocation logic to assign at least one of uplink,
downlink and the bi-directional channels for the multiple subscribers based at least on channel characteristics
indicative of reception quality obtained for the uplink,
downlink and/or bi-directional channels;
wherein said assigning comprises:
maintaining and updating the set of available sub channels for each of available antennas on an ongoing
basis, and
selecting the available sub channel with the highest gain
among available antennas.
21. The base station of claim 20, wherein the channel
allocation logic assigns one of an uplink channel or bi-directional channel to a subscriber based on channel characteristics measured or estimated at the subscribers in response to
beacon signals broadcast from each of the antenna resources,
the base station further comprising:
a beacon signal generator.
22. The base station of claim 21, wherein the beacon signal
generator generates orthogonal frequency division multiple
access (OFDMA) signals including OFDMA pilot symbols.
23. The base station of claim 22, wherein the pilot symbols
occupy an entire OFDM frequency bandwidth.
24. The base station of claim 20, wherein the multiple
antenna resources comprise multiple individual antennas.

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25. The base station of claim 20, wherein at least one
antenna resource comprises a set of antennas that are operated
collectively to transmit and/or receive radio frequency transmissions.
26. The base station of claim 20, further comprising:
means for measuring and/or estimating channel characteristics in response to ranging signals sent from the subscribers.
27. The base station of claim 20, further comprising:
a subscribers' channel profile register to store channel
characteristics infonnation for the subscribers; and
an ongoing traffic register to store channel assignment
information.
28. A wireless communications system, comprising:
a plurality of subscriber units, each configured to support
wireless communication; and
a base station including, multiple antenna resources,
including transmit antenna resources to transmit wireless communication transmission signals and receive
antenna resource to receive wireless communication
transmission signals;
a transmission module, to generate signals over various
downlink or bi-directional channels via which data is
transmitted via the transmit antenna resources to the
plurality of subscribers;
a reception module, to extract data from signals received at
the receive antenna resources over various uplink or the
bi-directional channels from the plurality of subscribers;
and
channel allocation logic to assign at least one of uplink,
downlink and the bi -directional channels for the plurality of subscribers based on channel characteristics measured and/or estimated for the uplink, downlink and/or

bi -directional channels, each of the plurality of subscribers to measure or estimate channel characteristic information indicative of channel signal quality at the subscriber and provide feedback to the base station
containing the channel characteristic information;
wherein said assigning comprises:
maintaining and updating the set of available sub channels for each of available antennas on an ongoing
basis, and
selecting the available sub channel with the highest gain
among available antennas.
29. The system of claim 28, wherein the base station channel allocation logic assigns one of an uplink channel or bidirectional channel to a subscriber based on channel characteristics measured or estimated at the subscribers in response
to beacon signals broadcast from each of the transmit antenna
resources, the apparatus further comprising:
a beacon signal generator.
30. The system of claim 29, wherein the beacon signal
generator generates orthogonal frequency division multiple
access (OFDMA) signals including OFDMA pilot symbols
occupy an entire OFDM frequency bandwidth.
31. The system of claim 28, wherein at least one of the
subscribers to generate ranging signals to be received at
respective receive antenna resources for the base station, and
wherein the base station further includes means for measuring channel characteristics indicative of signal quality of
ranging signals received at the respective receive antenna
resources, the channel allocation logic to assign one of an
uplink or bi -directional channel for each of said at least one
subscriber based on the channel characteristics that are measured and channel availability.

10

15

20

25

30

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