Apple, Inc. v. Motorola, Inc. et al

Filing 93

Declaration of Christine Saunders Haskett filed by Plaintiffs Apple, Inc., NEXT SOFTWARE, INC. re: 90 Motion Requesting Claims Construction (Attachments: # 1 Ex. 21 IEEE Dictionary, # 2 Ex. 22 '575 file history, # 3 Ex. 23 '486 file history, # 4 Ex. 24 Order No. 18, # 5 Ex. 25 '705 file history, # 6 Ex. 26 '647 file history, # 7 Ex. 27 Brad Cox, # 8 Ex. 28 Microsoft Press Dictionary, # 9 Ex. 29 '002 file history, # 10 Ex. 30 Dictionary of Computer Words, # 11 Ex. 31 Computer Dictionary, # 12 Ex. 32 Academic Press Dictionary, # 13 Ex. 33 IBM Dictionary, # 14 Ex. 34 Black's Law Dictionary, # 15 Ex. 35 About 3GPP, # 16 Ex. 36 '919 patent, # 17 Ex. 37 '713 provisional application) (Haslam, Robert)

EXHIBIT 36

111111

1111111111111111111111111111111111111111111111111111111111111
US007173919Bl

United States Patent

(10)

Dabak

(12)

(45)

(54)

RANDOM ACCESS PREAMBLE CODING
FOR INITIATION OF WIRELESS MOBILE
COMMUNICATIONS SESSIONS

(75)

Inventor:

(73)
( *)

6,088,347
6,154,486
6,175,587
6,466,566

Anand G. Dabak, Plano, TX (US)

A
A
Bl
Bl

*
*
*
*

7/2000
11/2000
112001
1012002

Minn et al. .................
Scott et al. .................
Madhow et al. ............
De Gaudenzi et al. .....

370/342
375/142
375/148
370/342

FOREIGN PATENT DOCUMENTS

wo

Assignee: Texas Instruments Incorporated,
Dallas, TX (US)
Notice:

Patent No.:
US 7,173,919 Bl
Date of Patent:
Feb. 6,2007

WO
WO
WO

Subject to any disclaimer, the tenn of this
patent is extended or adjusted under 35
U.S.c. 154(b) by 1264 days.

WO 98118280
WO 98 1 49857
WO 98/45961
WO 99121375

411998
5/1998
10/1998
4/1999

OTHER PUBLICATIONS
"Further clarification of Nokia's RACH preamble proposal", TSG-

(21)
(22)

Filed:

RAN Working Group meeting No.5, TSGRI-599199 (Nokia, Jun.

Appl. No.: 09/591,888

1-4, 1999).

Jun. 9, 2000

(Continued)

Related U.S. Application Data
(60)

(51)
(52)
(58)

Primary Examiner-Huy D. Vu
Assistant Examiner-Daniel Ryman
(74) Attorney, Agent, or Firm-Ronald O. Neerings; W.
James Brady, III; Frederick J. Telecky, Jr.

Provisional application No. 601142,889, filed on Jul.
8, 1999, provisional application No. 60/139,334, filed
on Jun. 15, 1999, provisional application No. 60/138,
713, filed on Jun. 11, 1999.

(57)

Int. Cl.
H04B 7/216
(2006.01)
U.S. Cl. ....................... 370/335; 370/342; 370/441
Field of Classification Search ................ 370/203,
370/208,209,328,335,342,441,479
See application file for complete search history.

A method of operating a wireless communications unit (UE)
to request a counection with a base station (10) is disclosed.
The wireless unit (UE) receives a signal from the base
station (10) indicating at least one time slot within which a
preamble may be transmitted by the wireless communications unit (UE). The wireless unit (UE) selects one of a
plurality of orthogonal codes (h,) for the preamble and
generates a spread code using the selected orthogonal code.
The spread code (70) is arranged as a symbol (h,) of the
selected code, repeated a selected number of repetitions. The
wireless unit (UE) transmits the preamble signal corresponding to the spread code to the base station (10).

References Cited

(56)

U.S. PATENT DOCUMENTS
5,237,586
5,353,352
5,608,722
5,790,537
5,828,662

A
A
A
A
A

*
*
*
*
*

811993
1011994
311997
811998
1011998

ABSTRACT

Bottomley .................. 3701206
Dent et al. .................... 380/37
Miller ........................ 370/320
Yoon et al. ................. 370/342
Jalali et al. ................. 370/335

39 Claims, 6 Drawing Sheets

LONG (4096 CHIPS) SCRAMBLING CODE Cn

x
hi

I

hi

16 CHIPS--+-16 CHIPS

I
~I...

hi

I

16 CHIPS---1

hi

000

I

f.-16

1 4 - - - - - - - - - - 256 SYMBOLS - - - - - - - - - - + 1

70

US 7,173,919 Bl
Page 2
OTHER PUBLICATIONS
"Technical Specification", TS 25.213, V2.1.0 (3,d Generation Partnership Project (3GPP); Technical Specification Group (TSG);
Radio Access Network (RAN); Working Group 1 (WG 1); Spreading
and modulation (FDD» (1999), pp. 1-22.
"Comparison of Detection Methods for RACH Preamble Signatures", TSG-RAN Working Group 1 meeting No.3,
TSGRl#3(99)140 (InterDigital Comm. Corp., Mar. 22-26, 1999).
3GPP TSG RAN WGl: "TS 25.214 Vl.O.O: Third Generation
Partnership Project (3GPP); Technical Specification Group (TSG);
Radio Access Network (RAN); Working Group 1 (WG 1); Spreading

and Modulation (FDD) Physical Layer Procedure" 3GPP Technical
Specification, 'Online! Apr. 1999, pp. 1-31, XP0021S0S96,
Retrieved from the Internet: URL:http://www.3gpp.org, retrieved
on Oct. IS, 2001!, * p. IS-p. 19 *.
3GPP TSG RAN WGl: "TS 25.213 V2.0.0: Third Generation
Partnership Project (3GPP); Technical Specification Group (TSG);
Radio Access Network (RAN); Working Group 1 (WG 1); Spreading
and Modulation (FDD)" 3GPP Technical Specification, Apr. 1999,
pp. 1-26, XP0021S0S97 *p. 15, paragraph 4.3.3-p. IS*.

* cited by examiner

u.s. Patent

Feb. 6,2007

US 7,173,919 Bl

Sheet 1 of 6

FIG.

M

S
A

---,
AUDIO
INTERFACE

I
I
I
I
I
I

RF
INTERFACE

DSP

I
I
I
MODULATOR
27
L....-_----' L _____________ '; __

FLASH
MEMORY

JLCONTROLLER

36

BATIERY INTERFACE AND
POWER CONTROL

22

\

33

o
35

37

31

FIG. 2
38

(AMENDED)

~UE·J

:

J

u.s. Patent

Feb. 6,2007

55

56

US 7,173,919 Bl

Sheet 2 of 6

10

r---------------------,

~

.---...l......-""':""'----.

PHY

NETWORK
INTEFACE

INTEFACE
SYMBOL DECODE

52

SYMBOL USER
DETECTION COMBINING

TO/FROM
E1/T1 OR
PACKET
NETWORK

50

ENCODE
AND
MODULATE

CHIP-RATE
DEMODULATE
AND DE -SPREAD

40.../"l

FIG. 3

BSA

I
I
I
I

48
CHANNEL
: _____________________
ESTIMATION
46
L....-_,--.------'
L
~

~

h(k)
x{k}

FIG. 4

I

(a)

68

LONG (4096 CHIPS) SCRAMBLING CODE Cn

x

h_i_~I--h-i--I-I--h·-1_~I"'I

!--_ _

16 CHIPS-/-16 CHIPS

.+.

t 4 - - - - - - - - 256 SYMBOLS

FIG. 5

hi

I

70

u.s. Patent

Feb. 6,2007

US 7,173,919 Bl

Sheet 3 of 6

FIG. 6
72

RECEIVE CELL -SPECIFIC
SCRAMBLING CODE Cn
RECEIVE BROADCAST OF
TIME SLOTS FOR REQUEST

74

NO

r

•

RECE IVE REQUEST
PREAMBLE

..,.,,-

86

+

78
80

DE -INTERLEAVE
SYMBOL BITS

RANDOMLY SELECT TIME
SLOT AND WALSH CODE hm

+

DE -SPREAD INTO WALSH
CODE SYMBOL

GENERATE WALSH CODE
SPREAD SYMBOL hm X256

"'- 90

+

82

SCRAMBLE USING
CELL -SPECIFIC
SCRAMBLING CODE en

CORRELATE OUTPUT
SYMBOLS WITH m WALSH
CODES TO RESOLVE
PREAMBLE SOURCE

84

SEND REQUEST PREAMBLE
TO BASE STATION

INITIATE CONNECTION
TO WIRELESS UNIT

"'- 94

+

--1

v

AT WIRELESS
UNIT UE

V- 88

AT BASE
STATION 10

r- 96

e
•

48
98

7Jl
•

~

FIG. 7

~
~

~

~

--1

r----------------------------~
I
I
16*n
I
I
i
, I
"
I
n
I
I
~
I

100 0

i
L

=

LENGTH 4096*n DESCRAMBLING MATCHED FILTER

EHD-~~

~-------

--------

~---

r0--1B+
~-------.J

~

100 2' 5

1~O,
DELAY
LINE

( ..

--~

...

""f'j

~
0\

~

--~

DELAY
LINE

N

o
o

-....l

I
rFJ

=-

('D

a
o
....
.j;o.

0\

102 0

LENGTH 256
DESPREADER

LENGTH 256
DESPREADER

!

102,

LENGTH 256
DESPREADER

+

000

LENGTH 256
DESPREADER

\

102 2

LENGTH 16 WALSH HADAMARD TRANSFORM AND CODE CORRELATION

""'-102, 5
d

rJl
-....l
~
-....l
W

\c
\C
"""'"

=
"""'"

e
•

FIG. 8

7Jl
•

(AMENDED)

t
I)

I

I

DELAY LINES (256X16Xn)
T(16)

T(32) T(1008)

T(l)

...

1~2

V(l)

V(O)

-

T(1024)

...

•••

T(2032)

V(15)

1

...

1

I

LENGTH 16
WALSH HADAMARD
124 0----- TRANSFORM

LENGTH 16
WALSH HADAMARD
1241.../ TRANSFORM

J ...

! !...

X(16) X(17)

X(l) X(2)

000

I

...

V(63:

...

•
LENGTH 16
WALSH HADAMARD
~1242
TRANSFORM

J J...

X(33) X(34)
X(31 )

T(4095)

LENGTH 64 DESPREADER

122 16

V(32-47l

V(16-31)

T(3087)

\

IV( 16)
+

1~0
•••

I LENGTH 64 DESPREADER I I LENGTH 64 DESPREADER

LENGTH 64 DESPREADER

fo

...

T(1009)

X(47)

V(48-63)
LENGTH 16
WALSH HADAMARD
TRANSFORM

J J...

X(49) X(50)

~
~

~

~

=
~

I

""f'j

~

3

0\

~

N

o
o

-....l

rFJ

=-

('D

a
o
....

Ul

0\

X(15)
X(32)

X(O)

12~ 1
SEGMENTING LOGIC
126 0----- (POWER SUM)

SEGMENTING LOGIC
(POWER SUM)

X(48)

X(63)

126 2

d

rJl

/

SEGMENTING LOGIC
(POWER SUM)

",-.....1
000

SEGMENTING LOGIC
(POWER SUM) i'-12~

-.....1
"""'"
W

\c
\C
"""'"

=
"""'"

e
•

FIG. 9

7Jl
•

(AMENDED)

~

DELAY LINES (256X16Xn)
T(o)1

T( 16)1

T(32) 1T(1 008)1

T(1009)

IT( 1)

...

...

~

~

T(1024)

T(2032)

100 T(3087)

• ••
LENGTH 64 DESPREADER

LENGTH 64 DESPREADER

~

\

o

0

0

T{4095}

...

=
~

LENGTH 64 DESPREADER
""f'j

1220

V(O)
L..--...

124

-1

o

V(l)
1221
.--------'V(15)

V(16)

LENGTH 16
WALSH HADAMARD
TRANSFORM

LENGTH 16
124 J1 WALSH HADAMARD
1 I TRANSFORM

I

l ...

X(16) X(17)

122 63

0\

~

N
0
0

,V(48-63)

X(15)

LENGTH 16
WALSH HADAMARD
TRANSFORM

I

I

X(32)

\

1'- 1242

LENGTH 16
WALSH HADAMARD
TRANSFORM

+ +...
X(33) X(34)

X(31).

136 1

01

('D

0"

-....l

X(l) X(2)

136

16

V(32-47)i

l l"·

X(O)

122

~

...

V(63)

+
X(47)

SEGMENTING LOGIC
(DIFFERENCE)

SEGMENTING LOGIC
(DIFFERENCE)

t

t

t

=-

('D

+...

0\

0\

X(48)

X(63)

~48"
000

rFJ

a
o
....

X(49) X(50)

136 2
(

SEGMENTING LOGIC
(DIFFERENCE)

1'-1243

SEGMENTING LOGIC
(DIFFERENCE) t'-136 15

i

d

rJl

",-.....1
-.....1
"""'"
W

\c
\C
"""'"

=
"""'"

US 7,173,919 Bl
1

2

RANDOM ACCESS PREAMBLE CODING
FOR INITIATION OF WIRELESS MOBILE
COMMUNICATIONS SESSIONS

telephone network, and the wireless units themselves may
initiate a connection by placing a call.
In order for a wireless unit to place a call to a particular
telephone number, it must send a request for a connection to
the base station. An initiation sequence is then carried out,
according to conventional systems, in which the channel for
the desired communications is assigned by the base station
and acknowledged by the wireless unit.
For example, in a CDMA system, the base station and
wireless unit must "agree" upon a modulation code to be
used in the communications link between these two stations.
In conventional CDMA systems, the codes are not determined a priori, given the transient nature of wireless units
within a base station coverage area. As such, techniques
have been developed by way of which the wireless units and
base station may communicate prior to the assignment of a
modulation code. According to a widely used technique for
this initialization, the base station periodically broadcasts
signals that indicate the number and position of reserved
time slots within a communications frame for initialization,
to each of the wireless units in its area that are not currently
connected. These broadcast signals are received by each
wireless unit, so that, in one of these time slots, the unit may
send a signal to the base station to request a connection. This
request signal is commonly referred to as a "preamble,"
following which the message part of the transmission is
communicated.
It is quite likely, however, that multiple wireless units may
try to establish communications at the same time, and may
therefore be simultaneously sending preambles within the
same time slot. As such, conventional CDMA wireless
communications systems specify a set of modulation codes
from which the wireless unit selects a code to request a
connection. The codes in the set are orthogonal relative to
one another, in the sense that the base station can resolve the
sources of simultaneously received messages encoded by
different ones of the set of modulation codes. Because the
requesting wireless unit typically selects a modulation code
in a pseudo-random manner, these charmel selection codes
are typically referred to as "random access" codes. These
random access codes greatly reduce the probability of a
collision between two (or more) wireless units in a coverage
area requesting a connection at the same time slot. For
example, if eight time slots are available for requesting a
connection, using one of sixteen available random access
codes, the likelihood of a collision between two wireless
units that request a connection is reduced from one in eight
to one in 128.
An example of this random access approach uses a
256-chip spreading code in the generation of the preamble
part of the transmission. This conventional approach is
described in Technical Specification TS 25.213 V2.1.0:
Spreading and Modulation (3 rd Generation Partnership
Project, 1999). To request a communications session according to this approach, a wireless unit randomly selects one of
sixteen signature symbols for its preamble. The signature
consists of a sixteen-symbol sequence of plus or minus the
complex value A=I+j. One example of a sixteen symbol
signature is [A, A, A, -A, -A, -A, A, -A, -A, A, A, -A, A,
-A, A, A]. Each symbol in this preamble is then spread into
256 consecutive chips, following which the spread preamble
is modulated and transmitted to the base station by the
requesting wireless unit.
The mobile nature of the wireless units presents certain
difficulties to the resolution of simultaneous encoded request
signals, however. Although random access codes, such as
the 256-chip spread coded random access preamble noted

CROSS-REFERENCE TO RELATED
APPLICATIONS
This application claims the benefit, under 35 U.S.c.
§119(e)(1), of U.S. Provisional Applications No. 60/138,713
(TI-29324PS), filed Jun. 11, 1999, No. 60/139,334 (TI29324PSl), filed Jun. 15, 1999, and No. 601142,889 (TI29324PS2), filed Jul. 8, 1999, all incorporated herein by this
reference.
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH OR DEVELOPMENT

10

15

Not applicable.
BACKGROUND OF THE INVENTION
This invention is in the field of mobile wireless communications, and is more specifically directed to the initiation
of multiple access communications sessions.
The popularity of mobile wireless communications has
increased dramatically over recent years. It is expected that
this technology will become even more popular in the
foreseeable future, both in modem urban settings and also in
rural or developing regions that are not well served by
line-based telephone systems. This increasing wireless traffic strains the available communications bandwidth for a
given level of system infrastructure. As a result, there is
substantial interest in increasing bandwidth utilization of
wireless communications system to handle this growth in
traffic.
Modem digital communications technology utilizes multiple-access techniques to increase bandwidth utilization,
and thus to carry more wireless traffic. Under current
approaches, both time division multiple access (TDMA) and
code division multiple access (CDMA) techniques are used
in the art to enable the simultaneous operation of multiple
communications conversations, or wireless "connections".
For purposes of this description, the term "conversations"
refers to either voice communications, data communications, or any type of digital communications. As evident
from the name, TDMA communications are performed by
the assignment of time slots to each of multiple communications, with each conversation transmitted alternately over
short time periods. CDMA technology, on the other hand,
permits multiple communications sessions to be transmitted
simultaneously in both time and frequency, by modulating
the signal with a specified code. On receipt, application of
the code will recover the corresponding conversation, to the
exclusion of the other simultaneously received conversations.
As is fundamental in the art, a single base station in a
wireless communications network conducts communications sessions with multiple mobile wireless transmissions
in an area of coverage, or "cell". In addition, each base
station is aware of the remaining bandwidth available for
new communications sessions that may be initiated relative
to a wireless unit within its cell. In this regard, the base
station is aware of the presence of those mobile wireless
units that are turned on and within its cell, and also of the
identity of those units, regardless of whether the units are
currently connected in a conversation. In this way, wireless
units may be called by another party from anywhere in the

20

25

30

35

40

45

50

55

60

65

US 7,173,919 Bl

3

4

above, provide signatures that are theoretically orthogonal,
this orthogonality presumes simultaneous receipt at the base
station. As noted above, preambles are simultaneously transmitted by mobile units in the time slots specified by the base
station. However, simultaneously transmitted preambles
from widely differing distances in the cell will not simultaneously arrive at the base station. According to the conventional 256-chip spread coded approach, coded signatures are
not necessarily orthogonal when one preamble is significantly time-shifted relative to another. In other words,
time-shifted preambles coded according to this conventional
approach will cross-correlate with one another. As such, in
some circumstances, conventional CDMA base stations may
not always be able to resolve different random access codes
from multiple wireless units.
This cross-correlation of random access codes received
from varying transmission distances has been addressed by
prior techniques. For example, a so-called "long" code has
been developed which uses a real-valued version of the
uplink spreading code to spread the wireless unit signature
over a much longer preamble. The length of the preamble is,
in this approach, selected to be significantly longer than the
greatest time delay expected within a given cell. This long
code is derived simply by spreading each bit of a sixteen-bit
Gold code signature symbol A over a number of chips, for
example 256 chips; in this case, the sixteen-bit symbol
becomes sixteen sequences of 256-chip values, for a total
length of 4096 chips. This longer preamble greatly reduces
the cross-correlation between orthogonal signatures that are
received at the maximum delay (and thus the maximum
differential distance) relative to one another.
However, it has been observed that this long code
approach remains vulnerable to velocity variations between
requesting mobile wireless units. The well-known Doppler
effect refers to the shift in frequency that results for a
moving source of periodic signals. For the case of mobile
wireless units in a moving automobile, train, or especially an
airplane, the Doppler shift causes a phase shift that accumulates over the transmission length of the request. As noted
above, the conventional "long" random access code has a
length of 4096 chips (i.e., sixteen symbols of 256 chips
each), over which the orthogonal signatures are analyzed to
resolve different wireless units. Because of this code length,
the accumulated Doppler phase shift can cause cross-correlation among codes, so that the base station may not be able
to resolve simultaneous transmission requests.
Other approaches for encoding random access channel
preambles have been derived to address the problem of
Doppler shifts on the transmitted signals. One approach
utilizes a differential encoding technique, in which the
signature is determined by the differences between adjacent
symbols in the preamble. Some level of cross-correlation for
time-delayed signals has been observed for this differential
approach, rendering it somewhat vulnerable to differences in
distance between simultaneously-transmitting mobile wireless units. Because of this vulnerability, coherent encoding
over a long (e.g., 4096 chip) preamble has been used for
slowly moving or stationary transmitters to provide adequate
orthogonality for variations in transmission distance, while
rapidly moving mobile units utilize the differential coding.
Of course, the implementation of different random access
channel encoding for mobile units of different velocities
significantly increases the complexity of transmitters and
base stations.
Another approach uses segmented non-coherent decoding
for fast-moving transmitters, in which the receiver decodes
the preamble in shorter segments of symbols, for example

four segments of four symbols each. According to this
technique, however, the segments are not orthogonal relative
to one another.
BRIEF SUMMARY OF THE INVENTION

10

15

20

25

30

35

40

45

50

55

60

65

It is therefore an object of the present invention to provide
a random access channel resolution method that is robust for
mobile wireless transmissions from varying distances within
a cell and also for transmissions from units that are widely
varying in velocity.
It is a further object of the present invention to provide
such a method in which the preamble encoding and decoding can be implemented in a computationally efficient mannero
It is a further object of the present invention to provide
such a method in which quite large frequency offsets due to
moving transmitters may be tolerated in the establishment of
a wireless communications session.
Other objects and advantages of the present invention will
be apparent to those of ordinary skill in the art having
reference to the following specification together with its
drawings.
The present invention may be implemented into a wireless
communications system in which the transmission preamble
is based upon a Walsh Hadamard code. Spreading is accomplished by repeating the code symbol a plurality of times to
create a preamble of a length corresponding to that of a long
code, creating a preamble of orthogonal symbols that are
repeated in a spread fashion. The preamble is multiplied by
a cell-specific long code, and the process is reversed upon
receipt at the base station to recover the preamble.

BRIEF DESCRIPTION OF THE SEVERAL
VIEWS OF THE DRAWING
FIG. 1 is an electrical diagram, in block form, of a cell of
a wireless communications system, according to the preferred embodiment of the invention.
FIG. 2 is an electrical diagram, in block form, of a mobile
wireless telephone in the wireless communications system
of FIG. 1, according to the preferred embodiment of the
invention.
FIG. 3 is an electrical diagram, in block form, of a base
station in the wireless communications system of FIG. 1,
according to the preferred embodiment of the invention.
FIG. 4 is a functional diagram, in schematic form, illustrating data flow in the encoding of wireless communications.
FIG. 5 is an illustration of the arrangement of code
symbols for generating a preamble, according to the preferred embodiment of the invention.
FIG. 6 is a flow diagram illustrating the operation of a
wireless unit and a base station, according to the preferred
embodiment of the invention.
FIG. 7 is an electrical diagram, in block form, of chip-rate
demodulation and despreading circuitry in a base station,
according to a first preferred embodiment of the invention.
FIG. 8 is an electrical diagram, in block form, of chip-rate
demodulation and despreading circuitry in a base station,
according to a second preferred embodiment of the invention.
FIG. 9 is an electrical diagram, in block form, of chip-rate
demodulation and despreading circuitry in a base station,
according to a third preferred embodiment of the invention.

US 7,173,919 Bl
5

6

DETAILED DESCRIPTION OF THE
INVENTION

according to different architectures. As such, the architecture
of the construction of wireless unit VE) shown in FIG. 2 is
provided by way of example only, it being understood that
such other alternative architectures may also be used in
connection with the present invention.
The exemplary architecture illustrated in FIG. 2 corresponds to a so-called "second generation", or "2G" baseband architecture, such as is typically used to carry out
TDMA and CDMA broadband connnunications. Radio subsystem 22 of wireless unit VE) is directly connected to
antenna A, and handles the power amplification and analog
processing of signals transmitted and received over antenna
A. On the transmit side, modulator 27 in radio subsystem 22
receives the signals to be transmitted from RF (radio frequency) interface circuitry 30, and generates a broadband
modulated analog signal, under the control of synthesizer
25. Power amplifier 21 amplifies the output of modulator 27
for transmission via antenna A. On the receive side, incoming signals from antenna A are received by receiver 23,
filtered and processed under the control of synthesizer 25,
and forwarded to RF interface circuitry 30.
RF interface circuitry 30 processes both incoming and
outgoing signals within the analog baseband of wireless unit
VE)" On the transmit side, RF interface circuitry 30 receives
digital signals from digital signal processor (DSP) 32, and
performs the appropriate filtering and phase modulation
appropriate for the particular transmission protocol. For
example, multiple channels of encoded digital bitstreams
may be forwarded to RF interface circuitry 30 by DSP 32.
RF interface circuitry 30 converts these digital data into
analog signals, phase-shifting selected converted bitstreams
to provide both in-phase (1) and quadrature (Q) analog signal
components, and applies analog filtering as appropriate to
the signals as handed off to modulator 27 in radio subsystem
22 described above.
On the receive side, RF interface circuitry 30 converts the
analog signal received by receiver 23 of radio subsystem 22
into the appropriate digital format for processing by DSP 32.
For example, the in-phase (1) and quadrature (Q) components of the received signal are separated and filtered.
Analog to digital conversion is then carried out by RF
interface circuitry 30, so that digital bitstreams corresponding to the separated and filtered components of the received
signal may be received by DSP 32.
DSP 32 executes the appropriate digital signal processing
upon both the signals to be transmitted and those received.
In this regard, DSP 32 is connected to audio interface 34,
which in tum is coupled to microphone M and speaker S for
input and output, respectively. Audio interface 34 includes
the necessary analog-to-digital conversion circuitry and filtering for generating a sampled bitstream digital signal
based upon the sound received by microphone M, and
conversely includes digital-to-analog conversion circuitry,
filtering, and amplification for driving speaker S with an
analog signal corresponding to the received and processed
connnunications.
The digital functions performed by DSP 32 will depend,
of course, upon the connnunications protocol used by wireless unit VE)" On the receive side, DSP 32 will perform such
functions as channel decoding of the data from RF interface
circuitry 30 to retrieve a data signal from the digitally spread
signal received, followed by the decoding of the speech
symbols from the channel decoded data using techniques
such as inverse discrete Fourier transforms (1DFT) and the
like. Equalization, error correction, and decryption processes are also performed upon the received signal as
appropriate. The resulting signal processed by DSP 32 on the

The present invention will be described in connection
with a wireless voice and data connnunications system,
particularly in the case where the wireless units are mobile
within an area of coverage, or "cell". Further, the particular
preferred embodiment of the invention will be described
relative to such a system in which multiple connnunications
of the Code Division Multiple Access (CDMA) type are
handled by a base station in the cell. It is contemplated,
however, that the present invention may also be used with
other connnunications systems, for example mobile wireless
communications using Time Division Multiple Access
(TDMA) or other spread spectrum or broadband technologies, as well as other applications. It is to be understood,
therefore, that the following description is presented by way
of example only, and is not intended to limit the scope of the
present invention as claimed.
An example of a deployment of a wireless connnunications system, according to the preferred embodiment of the
invention, is illustrated in FIG. 1. As shown in FIG. 1, base
station 10 is located somewhat centrally within an area of
coverage, or cell, 14. Base station 10, as is conventional in
the art, is a fixed facility which transmits and receives
broadband, or spread spectrum, wireless connnunications to
and from wireless units VE that are physically located
within cell 14. As shown in FIG. 1, and is typical in the art,
wireless units VE are mobile wireless units, such as digital
cellular telephones. The number of wireless units VE within
cell 14 may vary widely, depending upon the time of day,
day of the week, and other events that can affect wireless
telephone density within cell 14.
Typically, a large fraction of the wireless units VE within
cell 14 are mobile units, and as such may be anywhere
within the transmission area of cell 14 at any given point in
time. For example, wireless unit VE 2 is quite close to base
station 10, while wireless unit VEn is relatively distant from
base station 10, near the edge of cell 14. Furthermore,
wireless units VE may be moving within cell 14. For
example, wireless unit VEl is moving away from base
station 10 at velocity v. These variations in distance among
wireless units VE, and their velocities of travel, present
difficulties in the resolving of preamble codes for connection
requests, according to conventional techniques. As will be
described below, the preamble coding according to the
preferred embodiment of the invention efficiently provides
good resolution of coded preambles transmitted from different distances and at significant velocities.
The connnunications carried out between base station 10
and wireless units VE are, in this example, telephonic
conversations between one of wireless units VE and another
telephone set elsewhere in the telephone network. Base
station 10 therefore includes the appropriate circuitry for
effecting broadband connnunications with wireless units
VE, as will be described in further detail below; additionally,
base station includes switching system 12 that carries out
some level of switching of the connnunications links
between individual wireless units VE and the public
switched telephone network (PSTN).
Wireless units VE, as noted above, correspond to mobile
wireless telephone sets. FIG. 2 is an electrical diagram, in
block form, of the electronic architecture of a typical mobile
wireless unit VE) (the indexj referring generically to one of
the wireless units VE shown in FIG. 1). It is contemplated,
of course, that different ones of the wireless units VE in the
overall system, such as shown in FIG. 1, may be constructed

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receive side is then forwarded to audio interface 34, for
amplification and output over speaker S.
On the transmit side, substantially the converse operations
are applied. The incoming digitally sampled voice input
from microphone M via audio interface 34 is encoded into
symbols, for example by way of a DFT operation, and the
symbols are then encoded into a digital spread spectrum
signal by the application of channel codes. Scrambling or
other encryption processing is then performed, along with
the necessary pre-equalization and other filtering. The
resulting digital signal is then forwarded to RF interface
circuitry 30, as noted above.
According to the preferred embodiment of the present
invention, DSP 32 is operable to generate preamble codes to
be transmitted by wireless unit VE)" These preamble codes
are transmitted over anteuna A to request the initiation of a
communications session, such as a wireless telephone conversation. These orthogonal preamble codes are selected,
according to this preferred embodiment of the invention, to
be resolvable over a wide range of distances of wireless unit
VE) from base station 10 (FIG. 1), and in the event that
wireless unit VE) is being used in a rapidly traveling conveyance such as an automobile, train, or airplane. The
generation of these preambles will be described in further
detail below.
In this regard, DSP 32 preferably has a significant amount
of processing capacity to handle the digital processing
necessary for both the transmit and receive operations. An
example of a suitable digital signal processor for use as DSP
32 is the TMS320c5x family of digital signal processors
available from Texas Instruments Incorporated.
Other support circuitry is also provided within wireless
unit VE) as shown in FIG. 2. In this example, microcontroller 36 handles the control of wireless unit VE) other than the
data path. Such control functions include resource management, operating system control, and control of the human
interface; in this regard, microcontroller 36 operates with
such functions as flash memory 33 (for storage of the
operating system and user preferences), SIM card 35 (for
add-on functionality), keypad 37, and user display 38. In
addition, wireless unit VE) also includes battery interface
and power control subsystem 31, as shown in FIG. 2, for
monitoring the status of the battery for wireless unit VE),
and implementing power saving functions such as sleep
modes, and the like.
Referring now to FIG. 3, the construction of an example
of base station 10 according to a preferred embodiment of
the invention will now be described, for the case of a
second/third generation base transceiver station. It will be
appreciated by those skilled in the art that this particular
architecture is provided by way of example only, and that
other base station architectures may be used according to the
present invention.
As shown in FIG. 3, base station 10 includes amplifiers 42
for driving amplified transmission signals over one or more
base station antennae BSA, and for amplifYing signals
received from those anteunae BSA. RF interface function 44
includes the appropriate transmit and receive formatting and
filtering circuitry. Additionally, RF interface function 44
includes analog-to-digital converters for digitizing the
amplified receive signals, and digital-to-analog converters
for placing the transmitted signals into the analog domain.
As such, RF interface function 44 communicates digitally
with baseband interface 45, which provides the appropriate
signal formatting between RF interface function 44 and
baseband device 40.

Baseband device 40 communicates with the ultimate
network, which may be of the El or Tl class, or a packet
network as shown in FIG. 3, by way of physical layer
interface 55 and network interface adapter 56. Physical layer
interface 55 and network interface adapter 56 are conventional subsystems, selected according to the type of network
and corresponding interface desired for base station 10. In
the implementation of FIG. 1, network interface adapter 56
interfaces with switching system 12.
Baseband device 40 performs the digital signal processing
functions in handling the wireless communications at base
station 10. To perform this function, it is contemplated that
baseband device 40 will be a subsystem including one or
more high-performance digital signal processor (DSP)
devices, such as those of the TMS320c5x and TMS320c6x
class of DSPs available from Texas Instruments Incorporated, along with the appropriate memory and external
functions suitable for handling the digital processing
requirements of base station 10. In FIG. 3, the implementation of baseband device 40 will be described according to
its various functions, rather than by way of its construction,
it being contemplated that those skilled in the art will be
readily able to realize baseband device 40 using such
conventional integrated circuits from this functional description, and according to the capacity desired for base station
10.
On the transmit side, baseband device 40 includes encode
and modulate function 54, which is coupled between physical layer interface 55 and baseband interface 45, as shown
in FIG. 3. Encode and modulate function 54 receives digital
data from physical layer interface 55, and performs the
appropriate digital processing functions for the particular
protocol. For example, encode and modulate function 54
may first encode the received digital data into symbols.
These symbols are then spread, by way of a spreading code,
into a sequence of chips, according to a selected chip rate;
the spreading may also include the spreading of the symbols
into multiple subcharmels. Typically, a cell-specific scrambling code is then applied to the spread symbols, so that the
receiving wireless unit VE can distinguish transmissions
generated by this base station 10, from those of neighboring
cells. Modulation of the spread symbols is then performed;
commonly, the multiple subchaunels are split into in-phase
(1) and quadrature (Q) groups, so that the eventual modulated signal includes both components. The spread spectrum
signal is then applied to baseband interface 45, after the
appropriate filtering and pre-equalization for chaunel distortion, for transmission over anteunae BSA via RF interface
function 44 and amplifiers 42.
On the receive side, baseband device 40 receives incoming digital signals from baseband interface 45, after digitization of the received signals within RF interface function
44. These signals are applied to chip-rate demodulation and
despreading function 48, the construction of which will be
described in further detail below, and which derives the
transmitted symbols from the digitized received data. Considering that base station 10 receives signals over multiple
channels, from multiple wireless units VE in its cell 14,
channel estimation function 46 estimates the random channel variation. Charmel estimation function 46 and chip-rate
demodulation and de spreading function 48 each provide
output to symbol user detection and combining function 50,
in which the demodulated data are associated with their
respective channels, following which symbol decode function 52 decodes the received symbols, for each charmel and
thus each conversation, into a bit stream suitable for com-

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munication to the network via physical layer interface 55
and network interface function 56.
As discussed above, the present invention is directed to
the generation of connection requests by mobile units, such
as wireless telephone units UE in the example of FIG. 1, and
to the receipt and decoding of such requests by the corresponding base station 10. Referring now to FIGS. 4 and 5,
the principle of operation in the generation of preambles for
requesting connection, according to the preferred embodiment of the invention, will now be described.
FIG. 4 illustrates the data flow for a transmitting element,
such as mobile user equipment UE in the system of FIG. 1,
for example configured as shown in FIG. 2. In this example,
a data bitstream x(k) corresponds to the symbol stream that
is to be transmitted, for example as part of the eventual data
message. This bitstream x(k) is multiplied, in operation 58,
by spreading code h(k). Spreading operation 58 spreads each
bit of bit stream x(k) into multiple "chips", as known in the
art. In effect, spreading operation 58 converts each bit of
bitstream x(k) into a series of samples, or chips, modulated
by the particular code h(k) , with the chip rate out of
operation 58 thus being a multiple of the data rate of
bitstream x(k). A gain factor ~ is then applied to the spread
output of operation 58 in gain stage 60, to adjust the power
of the particular channel.
The channel corresponding to bitstream x(k) is an inphase component (1) that is then combined, at adder 62, with
a quadrature component (Q). As known in the art, the
transmission may consist of a single data channel as shown
in FIG. 4, combined by adder 62 with a control channel that
is at 90° phase relative to the data channel; this quadrature
arrangement permits separation of the data and control
information upon receipt. As known in the art, the transmission may also be carried out over multiple data channels,
each channel receiving a different one of a set of orthogonal
spreading codes h(k) to permit separation. The multiple data
channels may be grouped into in-phase and quadrature
groups, with the groups combined prior to adder 62, as
known in the art. Only a single data channel for bitstream
x(k) is shown in FIG. 4, for clarity in this description, it
being understood that those skilled in the art will be readily
able to incorporate the present invention into a multiple
channel transmission.
The combined I and Q components from adder 62 are then
scrambled by a scrambling code c(k) in operation 64.
Scrambling code c(k) is cell-specific, in that all transmissions taking place in the same cell (e.g., cell 14 of FIG. 1)
use the same scrambling code. Scrambling code c(k) thus

allows each system element to resolve incoming communications for its cell from those that may be received from
other cells. Typically, scrambling code c(k) is a "long" code,
for example 4096 chips in length.
Following scrambling operation 64, the scrambled spread
signal is then modulated for transmission by operations 66,
68 into in-phase and quadrature components, respectively.
Given that scrambling code c(k) will generally have complex coefficients, the in-phase and quadrature output components from operations 66, 68 will generally not correspond to the in-phase and quadrature input components to
adder 62.
The coding of FIG. 4 applied to transmission is, of course,
fully reversible upon receipt.
In addition to the voice or data communication payloads,
preambles are generated according to the scheme of FIG. 4
by wireless units UE to request a connection with base
station 10. According to the present invention, the particular
spreading codes h(k) are selected to provide orthogonality
even in situations where simultaneously requesting wireless
units UE are at widely differing distances from base station
10, and moving at significant velocities, such as suggested
by FIG. 1.
According to the preferred embodiment of the invention,
the spreading codes h(k) applied in operation 58 correspond
to repetitions of a selected one of a set of orthogonal Walsh
Hadamard codes. In effect, the input bitstream x(k) is
assumed to be "1", so that the output of operation 58 is a
Walsh Hadamard code symbol itself. This spreading code
output is then multiplied, in operation 64, by the cell-specific
scrambling code. As will become apparent below, the selection of Walsh Hadamard codes is particularly beneficial in
facilitating transform operations upon receipt.
According to an exemplary implementation of the preferred embodiment of the invention, scrambling code c(k) is
a 4096 chip segment of a 2 25 _1 length, real-valued, Gold
code. Preferably, cell-specific scrambling code c(k) is
formed in the same manner as the in-phase dedicated
channel uplink scrambling code, and as such is selected as
one of256 orthogonal4096-chip segments of the orthogonal
Gold code, with the 256 codes determined from different
initial shift register contents in such code generation. The
resulting scrambling code c(k) is then associated with sixteen possible preamble codes h(k), each corresponding to a
different Walsh Hadamard code.
As is well known, length 16 Walsh Hadamard codes
hm(k), for m=O, 1, ... , 15 are specified as:

ho
hI
h2
h3
h4
hs
h6
h7
hs
hg
hlO
hll
hI2
h13
hI4
hIS

-1
-1

-1
-1

-1
-1

-1
-1

-1
-1

-1
-1

-1
-1

-1
-1

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25

30

35

40

45

-1
-1

-1
-1

-1

-1
-1
-1
-1

-1
-1

-1
-1

-1
-1

-1
-1
-1
-1

-1
-1
-1

-1

-1
-1

-1
-1
-1
-1

-1
-1

-1
-1

-1

-1

-1

-1
-1
-1
-1

-1
-1

-1
-1
-1

-1
-1

-1
-1
-1
-1
-1
-1
-1
-1

-1
-1

-1
-1
-1
-1

-1
-1
-1

-1
-1

-1
-1

-1
-1

-1

-1
-1
-1
-1
-1
-1
-1
-1

-1
-1

-1
-1
-1
-1

-1

-1
-1

-1
-1

-1
-1

-1
-1
-1

-1
-1

-1
-1

-1

-1
-1

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-1

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According to this exemplary implementation, the selected
preamble code h(k) is repeated 256 times, in an interleaved
fashion as will now be described.
Of course, altemative combinations of preamble code
length and number of repetitions may equivalently be used.
For example, a Hadamard code of length 32 could be
repeated 128 times, to still correspond to the 4096-chip
scrambling code. Scrambling codes of different length may
also be used, depending upon the application, providing still
more combinations of code length and number of repetitions.
Consider the set of sixteen Walsh Hadamard codes hm(k),
m=O, 1, ... , 15, and the set of 256 scrambling codes cn(k),
n=O, 1, ... , 255, where each code h m is sixteen chips long,
and each code Cn is 4096 chips long. The mth preamble Smn
output by operation 64 of FIG. 4, corresponding to the nth
scrambling code, may be expressed:

UE into cell 14 serviced by base station 10. This cell-specific
scrambling code cn is used by wireless unit UE for its
transmissions, both the preamble for requesting a connection
and also the eventual payload.
In process 74, wireless unit UE receives a broadcast
message from base station 10 that indicates the particular
periodic time slots within which any wireless unit UE may
transmit a preamble in order to request a connection. As
known in the art, this broadcast by base station 10 is
periodic, so that the wireless nnits UE may receive updates
of the time slots currently available for these requests; of
course, depending upon the instantaneous call traffic within
the cell, the number of available time slots will vary over
time. In decision 76, wireless unit UE decides whether its
user wishes to place a call; if not (decision 76 is NO),
wireless nnit UE returns to process 74 to again receive the
next broadcast of the available time slots for requesting
connections, and repeats decision 76 accordingly.
Upon the user wishing to place a call (decision 76 is
YES), wireless nnit UE selects one of the available time
slots for issuing the request, and selects one of the Walsh
Hadamard codes h m for constructing the preamble, both in
process 78. According to the preferred embodiment of the
invention, the selection of process 78 is performed by way
of a pseudo-random selection algorithm, in order to minimize the likelihood that another wireless unit UE in the same
cell 14 will select the same time slot and same Walsh
Hadamard code for its own request. According to the preferred embodiment of the invention as described above, in
which sixteen Walsh Hadamard codes h m of length sixteen
are available, selection process 78 will thus randomly select
one of the sixteen codes h m listed above.
In process 80, DSP 32 in wireless nnit UE spreads the
selected Walsh Hadamard code h m in an interleaved fashion,
by repeating the code symbol a number of times sufficient to
match the length of the eventual sampling code. For the
present example, in which a 4096-chip scrambling code Cn
is used, the length sixteen Walsh Hadamard code h m is
repeated 256 times (16 times 256 being 4096), effectively
spreading the code symbol in an interleaved fashion as
described above relative to FIG. 5. Process 82 is then
performed by wireless nnit UE to multiply the spread code
symbol according to the cell-specific scrambling code Cn
received from base station 10. Further oversampling of the
scrambled signal may also be applied, as desired. The
resulting preamble is then modulated and transmitted 84 by
wireless nnit UE to base station 10 during the available time
slot that was selected in process 78.
Base station 10 receives the transmitted preamble in
process 86. The received signal corresponding to this preamble is amplified, converted from analog to digital, filtered,
and the like, by circuitry such as amplifiers 42, RF interface
44, and baseband interface 45 of base station 10 for the
exemplary architecture of FIG. 3. The resulting digital signal
is then descrambled, demodulated, and de-spread by chiprate demodulate and despread function 48 of base station 10,
to recover the particular Walsh Hadamard code symbol h m
that was selected and transmitted by wireless unit UE.
According to this implementation, the incoming digitized
signal is first applied to a series of tapped delay lines 100,
for de-interleaving the various interleaved spread code symbols in process 88 according to the preferred embodiment of
the invention, as will now be described in detail. As shown
in FIG. 7, the cell-specific scrambling code is c(k) is
decoded by descrambling matched filter 98, and the resulting bit stream is applied to delay line 1000' As in the
example of delay line 1000' each of delay lines 100 include

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smn(k) = cn(k) ~ hm(k -16i)
i=O

The summation term:

25

255

~ hm'(k -16i)
i=O

30

corresponds to 256 repetitions of the length sixteen Walsh
Hadamard code. As shown in FIG. 5, the arrangement of
preamble symbol 70 according to the preferred embodiment
of the invention consists of one of the sixteen possible Walsh
Hadamard code symbols hm' repeated 256 times to create a
4096-chip preamble. In other words, the first bit is the same
in each of the 256 code symbols hm' the second bit is the
same in each of the 256 code symbols hm' and so on. This
arrangement of preamble symbol 70 is thus in stark contrast
to conventional Gold coded preambles, in which each bit of
the Gold code symbol is repeated over a number of chips,
followed by the next bit repeated for those chips, and so on.
Also as shown in FIG. 5 and as noted above, preamble
symbol 70 is then multiplied by the particular cell-specific
scrambling code Cm prior to transmission.
Of course, the number of repetitions of the Walsh Hadamard code symbol will vary with the length of the "long"
code that is to be applied, and as such the implementation
described above and illustrated in FIG. 5 is by way of
example only. Another example, corresponding to current
standards, utilizes a 3840-chip long code. In this case, the
length sixteen Walsh Hadamard code is repeated 240 times.
Referring now to FIG. 6, the overall operation of wireless
unit UE in combination with base station 10, in requesting
a connection according to the preferred embodiment of the
invention, will now be described. As will be apparent from
the following description, the operations illustrated in FIG.
6 are primarily performed by DSP 32 in the architecture of
wireless unit UE shown in FIG. 2, according to this preferred
embodiment of the invention; of course, the particular
circuit executing the operations of FIG. 6 will depend upon
the specific architecture used to realize wireless nnit UE. As
shown in FIG. 6, this operation begins, in process 72, with
wireless unit UE receiving cell-specific scrambling code c n
from base station 10, for example upon entry of wireless unit

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a series of delay stages D. The length of each delay line 100
is 16n, where n is the overs amp ling factor. Taps are located
prior to the first stage D, and prior to every n delay stages
thereafter. The example of delay line 1000 in FIG. 7 illustrates an overs amp ling factor n=2, such that there are two
delay stages D between taps. The output of delay line 100 0
is applied to the input of delay line 100 1 , which is next in
sequence, and so on. For the present example, in which a
length sixteen Walsh Hadamard code is spread 256 times,
the number of delay lines 100 in chip-rate demodulate and
despread function 48 is 256, as evident by final delay line
100255 in the sequence shown.
The taps from delay lines 100 are routed to appropriate
ones of de spreaders 102. Despreaders 102 constitute circuitry or functionality for combining corresponding bits of
the incoming bitstream back into the bit values for a code
symbol, and in this manner "despread" the number of chips
for each bit back into a single bit value. Additionally,
despreaders 102 apply the appropriate coefficients of the
cell-specific scrambling code to the incoming bits, to reverse
the multiplication of the spread code by scrambling code c n
that was performed in transmission. In this example of
length sixteen Walsh Hadamard codes, sixteen instances of
despreaders 102 (i.e., de spreaders 102 0 through 102 15 ) are
provided, each despreader 102 having a length of 256 as
indicated in FIG. 7. According to this preferred embodiment
of the invention, in which the symbol is repeated, the bits
within the symbol are interleaved among the repetitions, as
described above. De-interleaving process 90 in the flow of
FIG. 6 is thus performed by each despreader 102 receiving
one tap from each of the 256 delay lines 100, from a tap
position corresponding to the position of despreader 102
among the series of despreaders 1020 through 102 1 5" For
example, first despreader 102 0 receives the first tap from
delay line 100 0 as shown, and the first tap from each of the
255 other delay lines 100 1 through 100255 , Second
despreader 102 1 receives the next tap from delay line 1000,
after n delay stages D as shown, as well as the second tap
from each of the 255 other delay lines 100 1 through 100 255
as shown. This arrangement continues for all of the remaining de spreaders 102 2 through 102 15 in this example. The
combination of the input taps to each de spreader 102 is thus
analyzed to generate an output bit, with the combination of
the outputs of de spreaders 102 constituting a sixteen-bit
symbol in this embodiment of the invention.
The outputs of sixteen de spreaders 102 0 through 102 15 are
applied as a sixteen-bit symbol to transform and code
correlation function 104, which compares this symbol, for
example by way of correlation, to each of the possible Walsh
Hadamard codes h min the set, in process 94. In this example,
transform and code correlation function 104 performs a
Walsh Hadamard transform oflength 16, and correlates this
result against the transforms for each of the possible codes
h m. Sixteen outputs are generated, each of which is associated with one of the possible codes hm' and indicating the
extent to which the received bitstream correlates with its
associated code h m. These outputs are then analyzed at base
station 10, for example in symbol user detection and combining function 50 (FIG. 3), to resolve the identity of the
wireless unit UE that forwarded the request corresponding to
the decoded preamble. Assuming that this decoded preamble
is valid, base station 10 then initiates the requested connection to the requesting wireless unit UE, in process 96,
enabling the communication of the voice or data payload
information.
According to this preferred embodiment of the invention,
significant advantages in the resolution of preamble codes

are provided. The interleaving of the spread preamble code,
illustrated by way of example in FIG. 5, provides a short
length over which the coded symbols are coherent, and
remain orthogonal. In the above example, each symbol is
coherent over sixteen chips (times the applied oversampling
factor), repeated 256 times. This short coherency length
allows preambles of rapidly moving mobile units to be
reliably resolved, since the accumulated Doppler phase shift
is insignificant over such a short code length. However, the
repetition of the symbols over the long code length provides
the ability to resolve preambles transmitted by wireless units
at widely varying distances within the cell. In the above
example, the code symbol of length sixteen is repeated 256
times, resulting in a 4096-chip symbol that can be readily
resolved even with significant variations in receipt delay.
Additionally, as described above relative to the example
of FIG. 7, the preamble coding according to the preferred
embodiment of the invention is especially efficient in its
decoding. Referring to FIG. 7, each of the despreaders 102
can operate in parallel with one another, such that the entire
despreading process 90 (FIG. 6) can be done at once. It has
also been calculated that the expected computational complexity for the preamble coding of the preferred embodiment
of the invention is less than that for conventional Gold
coding. As a result, the benefits of the present invention in
providing excellent resolution of preambles over wide distance variations and for rapidly moving transmitters are
obtained at no computational cost, and indeed some
improvement in the computational complexity.
As noted above, the present invention may be implemented in a variety of architectures and arrangements. In
addition, it is contemplated that the coding and decoding
described above may be implemented in combination with
conventional approaches, including the conventional long
coherent code, and segmented code, described above. In
such combinations, it is further contemplated that a base
station may receive and decode preambles according to the
present invention and also according to these conventional
techniques, in which case the base station may use the
approach providing the highest correlation power.
In this regard, referring now to FIG. 8, the construction of
chip-rate demodulate and despread function 48' according to
a second preferred embodiment of the present invention will
now be described in detail. This second preferred embodiment of the invention corresponds to a segmented noncoherent decoding of the incoming preamble; in this particular example, four segments are each sixty-four symbols
long, with each symbol being a Walsh Hadamard code of
length sixteen. Of course, other segment lengths may alternatively be used in combination with different code lengths,
as desired. For the example of a 4096-chip long code and
length sixteen Walsh Hadamard codes, alternative segment
lengths and numbers may include eight segments of thirtytwo symbols each, and two segments of 128 symbols each.
As shown in FIG. 8, the input data stream is again
received by delay lines 100, as in the example of FIG. 7. As
before, delay lines 100 include 256 delay lines 100 0 through
100 255 , each having 16 times n delay stages D therein, where
n is the oversampling factor. Delay lines 100 are tapped
along their length as before, to provide 4096 outputs T(O)
through T( 4095) in this example. These outputs Tare
applied in an interleaved fashion to depsreaders 1220
through 122 63 , each of which is oflength 64 in this embodiment of the invention.
According to this second preferred embodiment of the
invention, the code symbols are considered in segments of
sixty-four symbols each, rather than coherently over the

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entire 4096-chip long code length. As such, de spreaders 122
receive inputs from only a subset of delay lines 100. For
example, first de spreader 1220 receives the first tap (i.e.,
prior to the first delay stage D) from each of the first
sixty-four delay lines 100 0 through 100 63 ; according to the
nomenclature of FIG. 8, these inputs are inputs T(O), T(16),
T(32), ... , up to T(1008). The next de spreader 1221 receives
the second tap from each of the first sixty-four delay lines
1000 through 100 63 , namely inputs T(l), T(17), and so on up
to T(1009). In this marmer, despreaders 1220 through 122 15
receive each of the taps from the first sixty-four delay lines
100, namely the first 1024 taps on lines T(O) through
T(1023). These first sixteen de spreaders thus despread the
interleaved chip samples of the first sixty-four repetitions of
the length sixteen Walsh Hadamard code symbol, and thus
despread the symbols of the first offour segments, according
to this embodiment of the invention.
The next segment of sixty-four repetitions begins with
despreader 122 16 , which receives the first taps from each of
the next group of delay lines 100 (i.e., delay lines 100 64
through 100 127 ; these first taps are presented on lines
T(1024) through T(2032). The remaining despreaders 122 16
through 12263 are thus arranged in three more segments,
similarly as for the first segment of de spreaders 1220 through
122 15 , each de spreader having a length of sixty-four. To the
extent that a segmented cell-specific code was applied in
transmission, to segments of sixty-four symbols, the four
sets of de spreaders 122 applied to these symbols divide out
the cell-specific code from their inputs. According to the
nomenclature of FIG. 8, the output of de spreader 1220 is
presented on line YeO), the output of despreader 1221 is
presented on line V(l), and so on, with the output of the last
despreader 12263 presented on line V(63).
According to this example, the sixty-four outputs YeO)
through V(63) from de spreaders 122 are then applied, in
groups of sixteen to represent a length sixteen Walsh Hadamard code symbol, to one of four Walsh Hadamard transform and code correlation functions 1240 through 1243,
Specifically, first Walsh Hadamard transform and code correlation function 1240 receives outputs YeO) through V(lS),
second Walsh Hadamard transform and code correlation
function 1241 receives outputs V(16) through V(31), Walsh
Hadamard transform and code correlation function 1242
receives outputs V(32) through V(47), and Walsh Hadamard
transform and code correlation function 1243 receives outputs V(48) through V(63). As described above relative to
FIG. 7, Walsh Hadamard transform and code correlation
functions 124 transform the incoming symbol and compare
the transformed symbol against the sixteen possible length
sixteen Walsh Hadamard code values; each function 124
then generates sixteen outputs X, each indicative of the
degree to which the incoming symbol matches the code
value corresponding to the output.
According to this second preferred embodiment of the
invention, outputs X from Walsh Hadamard transform and
code correlation functions 124 are applied to segmenting
logic functions 1260 through 126 15 , to determine the correspondence to the respective symbol values. Segmenting
logic functions 126 number sixteen in this embodiment,
because the number of possible Walsh Hadamard code
values for a code of sixteen length is sixteen. In this regard,
segmenting logic function 126 0 corresponds to Walsh Hadamard code value ho indicated above in the table, and in
general segmenting logic function 126m corresponds to
Walsh Hadamard code value h m • As shown in FIG. 8,
segmenting logic function 126 0 receives output X(O) from
Walsh Hadamard transform and code correlation function
1240, output X(l) from Walsh Hadamard transform and code
correlation function 124u output X(2) from Walsh Had-

amard transform and code correlation function 124 2, and
output X(3) from Walsh Hadamard transform and code
correlation function 124 3, Each of these outputs X(O)
through X(3) provide an indication of the degree to which
the symbol applied to the corresponding Walsh Hadamard
transform and code correlation function 124 matches Walsh
Hadamard code symbol value h o. Similarly, the other fifteen
segmenting logic functions 126 1 through 126 15 receive their
corresponding inputs from each of the Walsh Hadamard
transform and code correlation functions 124, for their
corresponding symbol.
According to this second preferred embodiment of the
invention, segmenting logic functions 126 each perform a
power summation of the amplitude of their input signals.
Specifically, for the example of segmenting logic function
126 0, the power summation corresponds to:

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IX(0)12+IX(16)12+IX(32)12+IX(48)12

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The summation presented by segmenting logic functions
126, for each of their corresponding Walsh Hadamard code
symbols h, provide a good indication of which symbol was
transmitted by wireless unit UE as its preamble. The segmented nature of the decoding, according to this embodiment of the invention, provides additional immunity to
Doppler shift effects, as the duration over which coherency
is required is limited to sixty-four symbols, while each of the
segments contributes to the code resolution operation.
Referring now to FIG. 9, the construction of chip-rate
demodulation and de spreading function 48" according to a
third preferred embodiment of the invention will now be
described. Common elements in function 48" as in function
48' of FIG. 8 are referred to in counection with the same
reference numeral, and as such no additional description will
be provided for these elements.
According to this third preferred embodiment of the
invention, however, segmenting logic functions 136 detect
differentially encoded code symbols, also arranged into
segments of sixty-four symbols in this example. In this
embodiment of the invention, the preamble corresponds to a
sequence of differences that are maximized for the symbol
from segment to segment.
The signal paths in chip-rate demodulation and despreading function 48" shown in FIG. 9 are identical to those in
FIG. 8 for function 48', in this example. This similarity
includes segmenting logic function 136 0 receiving output
X(O) from Walsh Hadamard transform and code correlation
function 1240, output X(16) from Walsh Hadamard transform and code correlation function 124u output X(32) from
Walsh Hadamard transform and code correlation function
124 2, and output X( 48) from Walsh Hadamard transform
and code correlation function 1243, Similarly, the other
fifteen segmenting logic functions 136 1 through 136 15
receive their corresponding inputs from each of the Walsh
Hadamard transform and code correlation functions 124, for
their corresponding symbol.
The function performed by segmenting logic function
136 0, in deriving a difference value according to this preferred embodiment of the invention, corresponds to:
IX(16)X(0)*+X(32)X(16)*+X(48)X(32)*1

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where the * indicates complex conjugate. The same difference operation is performed by each of the other segmenting
logic functions 136 1 through 136 15 upon their respective
inputs. In this mauner, the one of segmenting logic functions
136 generating the highest amplitude output based on its
difference function will indicate the preamble value transmitted, as differentially encoded.
It is contemplated that these, and other coding and decoding alternative embodiments, may be used in connection

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with the present invention, while still attaining the benefits
of efficient computation and realization, with good performance over varying transmission distances and mobile unit
velocities.
While the present invention has been described according
to its preferred embodiments, it is of course contemplated
that modifications of, and altematives to, these embodiments, such modifications and altematives obtaining the
advantages and benefits of this invention, will be apparent to
those of ordinary skill in the art having reference to this
specification and its drawings. It is contemplated that such
modifications and altematives are within the scope of this
invention as subsequently claimed herein.

8. A method of operating a base station to recover a
preamble code transmitted by a wireless unit, comprising the
steps of:
receiving a signal corresponding to a preamble;
arranging the signal into a bitstream having a scrambling
code with a length corresponding to a length of the
preamble code;
de-interleaving bits from the bitstream, to group corresponding bits from each of a plurality of repetitions of
a symbol length into a plurality of groups;
de spreading the bits of each of the plurality of groups to
recover a plurality of symbol bits in a sequence, the
sequence having a length corresponding to the length of
the preamble code; and
correlating the sequence to identifY a code the code
corresponding to one of a set of orthogonal codes.
9. The method of claim 8, wherein the de-interleaving step
comprises:
applying the bitstream into a sequence of tapped delay
lines; and
grouping corresponding taps from each of the tapped
delay lines.
10. The method of claim 8, further comprising:
responsive to the correlating step identifYing a code,
initiating a connection with a wireless unit that transmitted the preamble.
11. The method of claim 8, wherein the number of groups
generated by the de-interleaving step corresponds to the
length of the preamble code times a number of segments in
the bitstream;
wherein the de spreading step recovers the plurality of
symbol bits into a sequence having a length corresponding to the length of the preamble code times the
number of segments;
and wherein the correlating step comprises:
correlating each of the corresponding symbol bits from
each of the plurality of segments to identifY the code.
12. The method of claim 11, wherein the correlating step
comprises summing the power of the corresponding symbol
bits from each of the plurality of segments.
13. The method of claim 11, wherein the correlating step
comprises deriving a difference value of the corresponding
symbol bits from each of the plurality of segments.
14. The method of claim 11, wherein the number of
segments is four, with each segment having sixty-four
symbols.
15. The method of claim 11, wherein the number of
segments is eight, with each segment having thirty-two
symbols.
16. The method of claim 11, wherein the number of
segments is two, with each segment having one hundred
twenty-eight symbols.
17. A wireless communications unit, comprising:
an antenna for transmitting and receiving signals;
a radio subsystem coupled to the antenna for amplifying
and processing of signals transmitted and received at
the antenna;
circuitry, coupled to the radio subsystem, for converting
received signals into digital form, and for converting
digital signals into a form transmittable over the
antenna;
a progranlillable digital circuit, for performing digital
operations upon signals to be transmitted and received,
the programmable digital circuit programmed to
request a connection with a base station by performing
operations comprising:

I claim:
1. A method of operating a wireless communications unit
to request a connection with a base station, comprising the
steps of:
receiving, from the base station, a signal indicating at
least one time slot within which a preamble may be
transmitted by the wireless communications unit;
selecting one of a plurality of orthogonal codes for the
preamble;
generating a spread code using the selected orthogonal
code repeated a selected number of repetitions;
multiplying the spread code by a scrambling code associated with the base station, wherein the spread code
has a length equal to a length of the scrambling code;
and
transmitting, to the base station, a preamble signal corresponding to the multiplied spread code.
2. The method of claim 1, wherein the set of orthogonal
codes consists of a set of Walsh Hadamard codes having a
length of sixteen;
wherein the generating step repeats a symbol of the Walsh
Hadamard code 256 times; and wherein the length of
the scrambling code is 4096 chips.
3. The method of claim 1, wherein the set of orthogonal
codes consists of a set of Walsh Hadamard codes having a
length of sixteen;
wherein the generating step repeats a symbol of the Walsh
Hadamard code 240 times;
and wherein the length of the scrambling code is 3840
chips.
4. The method of claim 1, wherein the plurality of
orthogonal codes corresponds to a set of Walsh Hadamard
codes.
5. The method of claim 1, wherein the selecting step
comprises executing a pseudo-random selection algorithm.
6. The method of claim 1, wherein the receiving step
receives a signal indicating a plurality of time slots within
which the preamble may be transmitted by the wireless
communications unit;
and further comprising:
selecting one of the plurality of time slots for transmission
of the preamble.
7. The method of claim 1, further comprising:
operating a base station to process the transmitted preamble, comprising the steps of:
receiving the transmitted preamble;
de-interleaving bits from the spread code, to group corresponding bits from each of the repetitions of the
symbol;
de spreading the grouped bits to recover a symbol;
correlating the recovered symbol to identify the selected
orthogonal code.

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recelvmg, from the base station, a signal indicating at
least one time slot within which a preamble may be
transmitted by the wireless communications unit;
selecting one of a plurality of orthogonal codes for the
preamble;
generating a spread code using the selected orthogonal
code repeated a selected number of repetitions;
multiplying the spread code by a scrambling code associated with the base station, wherein the spread code
has a length equal to a length of the scrambling code;
and
transmitting, to the base station, a preamble signal corresponding to the multiplied spread code.
18. The unit of claim 17, wherein the plurality of orthogonal codes corresponds to a set of Walsh Hadamard codes.
19. A base station for a wireless communications network,
comprising:
at least one base station anteuna, for receiving and transmitting communications signals;
radio frequency interface circuitry, coupled to the
antenna, for transmit and receive formatting and filtering signals received from or to be transmitted from the
antenna;
baseband circuitry, coupled between the radio frequency
interface circuitry and a telephone network, for performing digital operations upon received data and data
to be transmitted by the base station, the baseband
circuitry comprising:
circuitry for encoding and modulating digital data
received from the telephone network and to be transmitted from the base station via the antenna;
demodulating and de spreading circuitry, for recovering a
preamble code having a predetermined length and
transmitted by a wireless unit, the preamble code
including a scrambling code having the predetermined
length, comprising:
a sequence of delay lines for receiving a bitstream including a plurality of bit symbols having the predetermined
length corresponding to a received signal including the
preamble code;
a plurality of de spreader functions, each coupled to a tap
position in each of the sequence of delay lines, for
receiving corresponding bits from corresponding positions in each of the delay lines, and for generating a bit
of a symbol of the plurality of bit symbols therefrom;
and
a code correlation function, for comparing the symbol
presented by each of the plurality of despreader functions against a set of orthogonal codes, and for generating a signal indicating the correlation of the presented
symbol with each of the orthogonal codes in the set.
20. The base station of claim 19, wherein the plurality of
orthogonal codes corresponds to a set of Walsh Hadamard
codes.
21. A method of using a preamble, comprising the steps
of:
selecting a first code from a plurality of orthogonal codes;
repeating the first code a plurality of times to produce a
spread code having a predetermined length;
multiplying the spread code by a second code having the
predetermined length;
transmitting the preamble to a remote unit; and
receiving an acknowledgement from the remote unit.
22. A method as in claim 21, wherein the orthogonal codes
are Walsh Hadamard codes corresponding to users in a
wireless cell.
23. A method as in claim 22, wherein the second code is
a scrambling code corresponding to a wireless cell.

24. A method as in claim 21, wherein a product of the
plurality of orthogonal codes and the plurality of times the
first code is repeated is equal to the predetermined length.
25. A method as in claim 21, wherein plurality of orthogonal codes is 16, the plurality of times the first code is
repeated is 256, and the predetermined length is 4096.
26. A method of decoding a preamble, comprising the
steps of:
detecting a scrambling code in a received signal, the
scrambling code having a predetermined length;
extracting a first number of repeated groups of signals
having a second number of signals in each group from
the received signal;
applying one signal from each repeated group to each
respective despreader circuit of the second number of
de spreader circuits, each de spreader circuit producing a
respective output signal; and
comparing the second number of output signals to a
plurality of codes.
27. A method as in claim 26, wherein a product of the first
and second numbers is equal to the predetermined length.
28. A method as in claim 27, wherein the first number is
256, the second number is 16, and the predetermined length
is 4096.
29. A method as in claim 26, wherein the plurality of
codes are Walsh Hadamard codes.
30. A method as in claim 26, comprising producing a
signal corresponding to a match between the second number
of output signals and one of the plurality of codes.
31. A method of using a preamble from a remote transmitter, comprising the steps of:
receiving a first number of repeated groups of signals
having a second number of signals in each group from
a received signal having a predetermined length, the
received signal comprising a scrambling code having
the predetermined length;
correlating the first number of repeated groups of signals
with a code having the second number of signals, the
code corresponding to the remote transmitter; and
acknowledging the preamble to the remote transmitter to
establish communications.
32. A method as in claim 31, wherein a product of the first
and second numbers is equal to the predetermined length.
33. A method as in claim 32, wherein the first number is
256, the second number is 16, and the predetermined length
is 4096.
34. A method as in claim 31, wherein the code is a Walsh
Hadamard code.
35. A method as in claim 31, wherein the received signal
is a preamble having the predetermined length transmitted
from a wireless transmitter to a wireless receiver in a cell,
and wherein one of the plurality of codes corresponds to the
wireless transmitter, and wherein the scrambling code corresponds to the cell.
36. A method as in claim 35, wherein the code is a Walsh
Hadamard code, and wherein the scrambling code is a part
of a Gold code.
37. A method as in claim 31, wherein each group of the
first number of groups is substantially identical.
38. A method as in claim 31, comprising de spreading the
first number of groups of signals, thereby producing a
plurality of despread signals.
39. A method as in claim 38, comprising correlating the
despread signals with the code having the second number of
signals repeated the first number of times.

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