WO2001015481A1

WO2001015481A1 - Method and apparatus using a multi-carrier forward link in a wireless communication system

Info

Publication number: WO2001015481A1
Application number: PCT/US2000/023420
Authority: WO
Inventors: William R. Gardner; Edward G. Tiedemann, Jr.
Original assignee: Qualcomm Incorporated
Priority date: 1999-08-25
Filing date: 2000-08-25
Publication date: 2001-03-01
Also published as: KR100870843B1; EP1236369B1; BR0013505A; HK1141385A1; CN101616455B; EP2096891A1; US8064409B1; JP4927980B2; KR20070122561A; CN101616455A; CN1421111A; CN100420330C; AU6939100A; JP2003522446A; DE60042420D1; BRPI0013505B1; KR20020085870A; KR100831190B1; ATE434356T1; EP1236369A1

Abstract

A method and apparatus that allows a telecommunications system using cdma2000 1X to easily migrate to using cdma2000 3X. In other embodiments, the invention provides for better spectrum management, allows concurrent usage of a standard cdma2000 1X reverse link with a cdma2000 1X time-division-duplexing (TDD) reverse link, and provides for hardware supplementation - as opposed to total replacement - when additional services are added to an existing code-division-multiple-access (CDMA) system.

Description

METHOD AND APPARATUS USING A MULTI-CARRIER FORWARD LINK IN A WIRELESS COMMUNICATION SYSTEM

BACKGROUND OF THE INVENTION

1. Field Of the Invention

The present invention relates to communications. More particularly, the

invention concerns a method and apparatus for transmitting information in a

wireless communication system.

2. Description of the Related Art

Figure 1 illustrates a portion of the radio frequency spectrum used in a

common telecommunications system. Frequency range 100 centered around 800

MHz has historically been known as the cellular frequency range and frequency range 102 centered about 1900 MHz is a newer defined frequency range associated with personal communication services (PCS). Each range of

frequencies, i.e., the cellular and PCS, are broken into two portions. In the

cellular frequency range 100, there is a reverse link portion 104 that is used for

communications from a mobile communication device to a base station such as

a cellular base station. Portion 106 of cellular frequency range 100 is used for

forward link communications, that is, communications from a cellular base

station to a mobile communication device. In a similar fashion, portion 108 of

PCS frequency range 102 is used for reverse link communications, that is,

communications from a mobile communication device to a base station. Portion O 01/15481

2

110 of PCS frequency range 102 is used for reverse link communications, i.e.,

communications from a base station to a mobile communication device.

Each of the frequency ranges is broken into bands that are typically

associated with different service providers. In the case of cellular frequency

range 100, frequency bands 112 and 114 are designated band "A" for reverse

link and forward link communications, respectively. A reverse link is the band

connecting a mobile station to a base station, and a forward link is the band connecting a base station with a mobile station. In a particular geographic area,

a cellular service provider is assigned frequency band "A" in order to carry out

mobile communications. Likewise, in the same geographic area another cellular

service provider is assigned frequency bands 116 (for forward link

communications) and 118 (for reverse link communications) which are designated band "B". The transmit and receive frequencies are separated by 45

MHz and with the minimum separation between transmit and receive bands is

20 MHz. This minimum separation is to avoid interference between the

forward and reverse links and to permit diplexers, which separate the forward and reverse link signals in a mobile station to be used.

A few years ago, the US Government auctioned the PCS frequency

spectrum to service providers. As with the cellular frequency range, the PCS

frequency range is broken into several bands where a different service provider

may use a particular frequency band for which it is licensed within a particular

geographical area. The PCS bands are referred to as A, B, C, D, E and F. The A O 01/15481

3 band includes reverse link band 120 and forward link band 122. The B band

includes reverse link band 124 and forward link band 126. Band C includes

reverse link band 128 and forward link band 130. The reverse link and the

forward link band of A, B and C bands are each 15 MHz wide. The D band

includes reverse link band 132 and forward link band 134. The E band includes

reverse link band 136 and forward link band 138. Likewise, band F includes

reverse link band 140 and forward link band 142. The reverse link and forward

link bands of D, E and F are each 5 MHz wide. Each of the different cellular

and PCS bands can support a number of communications carriers in both the

reverse link and forward link direction.

As shown in Figure 1, it is possible to have as many as eight different

wireless communication service providers in a particular area - two cellular

service providers, each having a total allocated bandwidth of 25 MHz (forward and reverse links), and six PCS service providers, each having a total allotted bandwidth of 30 MHz for the A, B, and C blocks or 10 MHz for the D, E, and F

blocks. These providers may employ different technologies for transmitting

and receiving telephone calls, data, control commands, or other types of

information, singularly and collectively referred to in this application as

information signals. For example, a time-division-duplexing technique, a

frequency-division-duplexing technique, or a code-division-multiple-access

(CDMA) technique might be employed by a provider as described below.

Further, if the carrier is using CDMA, then various CDMA releases are available such as IS-95-A and IS-95-B. O 01/15481

Recently, in response to consumers demand for greater service options,

the International Telecommunications Union (ITU) solicited proposals for Third

Generation wireless communications. The Third Generation Proposals strive to

expand the capabilities of the preceding technologies to include wireless e-mail,

Web browsing, and corporate and local network access, as well as

videoconferencing, e-commerce and multimedia. One of the candidate

submissions to the ITU was proposed by subcommittee TR45.5 of the

Telecommunications Industry Association (TIA) and was called cdma2000,

which has since been developed and continues to be developed under the name

of IS-2000. The proposed cdma2000 system includes three modes of operation:

IX, 3X direct spread (DS) and 3X multi-carrier (MC). Each of these modes can

be operated in frequency division duplex (FDD) or time-division duplex (TDD)

manner.

The IX FDDmode operates within a 1.25 MHz bandwidth on both the

forward and reverse links, thereby providing for higher capacity in the 1.25 MHz bandwidth and supporting high-speed data transmissions. The spreading

rate is 1.2288 Mcps on both the forward and reverse links of IX systems. The 3X

FDDmode operates within a 3.75 MHZ band on both forward and reverse links.

The 3X mode forward link employs either a direct spread or a multi-carrier

transmission format. In the 3X direct spread mode, a single forward link carrier

with a chip rate of 3.6864 Mcps is used; in the 3X multi-carrier mode, the

forward link consists of three carriers that are each spread at a spreading rate of 01/15481

5 1.2288Mcρs. The IX TDD mode operates within a single 1.25 MHz bandwidth

for both the forward and reverse links. The 3X direct spread and multi-carrier

TDD modes operates within a single 3.75 MHz for both the forward and reverse

links.

By using the 3X FDD mode and providing a forward link using the

multi-carrier format, a communications system is fully compatible with existing

IS-95 system. That is, the cdma2000 forward link structure may be "over-laid" on existing PCS systems. One attribute that makes the forward link multi-

carrier system compatible with existing systems is that it preserves

orthogonality of signals transmitted in the forward link. The reverse link is not

orthogonal, so cdma2000 systems use a direct spreading to 3.6864 Mcps. When

used, the time-division-duplex (TDD) mode of operation allows both the

forward link and reverse link to be transmitted in a single 1.25 MHz band. The

TDD forward link is transmitted in a first time interval and the TDD reverse

link is transmitted in a non-overlapping second time interval. The

transmissions in both time intervals are direct spread at a 1.2288 Mcps spreading rate.

As mentioned above, Third Generation Systems such as cdma20003X are

designed for transmitting information that may have very high data transfer

requirements, such as email downloading and web browsing. For example, a

mobile station user may send a simple message requesting that a page from

web site be downloaded to his mobile phone. This simple request requires very O 01/15481

6 little bandwidth when transmitted on the reverse link to the base station, but

timely downloading of the web site on the forward link from the base station to

the mobile station will require substantial bandwidth. A request for a page may be in the order of a few hundred bytes, but the response from the web server

can be several tens of thousands of bytes, particularly if it includes graphics or

pictures. However, in the currently proposed Third Generation Systems, the

bandwidth allocated to reverse link transmissions is the same as the bandwidth

allocated for forward link transmissions.

What is needed is a method and apparatus that will allow for the

bandwidth allocated to the forward link to be different than the bandwidth

allocated for the reverse link. One version of the method and apparatus should provide for better spectrum management. Further, the method and apparatus

should allow the user of a technology such as cdma2000 IX to easily transition

to a newer version of the technology, such as cdma20003X.

SUMMARY OF THE INVENTION

Broadly, the present invention relates to wireless communications. More

particularly, the invention concerns forward link and reverse link designs utilized in a wireless telecommunications system. In various embodiments, the

invention allows a system using the IX mode of cdma2000 to easily migrate to

using a 3X mode of cdma2000. In other embodiments, the invention provides

for better spectrum management, and allows the bandwidth used in the O 01/15481

7 forward link to vary from the bandwidth in the reverse link. The invention also

provides for less unwanted emissions, thus permitting more effective utilization

of the bandwidth.

In one embodiment, the present invention provides a method that

improves spectrum use. With the method, a single cdma2000 IX reverse link

(IX RL) is used in conjunction with a cdma20003X forward link (3X FL). The

3X FL has three 1.2288 Mcps carriers and the IX RL uses one 1.2288 Mcps

carrier. The 3X FL carriers may occupy adjacent "frequency bins" as described

below, or the bins might not be adjacent. In an exemplary embodiment where

the 3X carrier bins are adjacent, the IX carrier bin may be located in the center

frequency bin range. In other embodiments, it may be located at anyone of the

three frequencies. In general, it can be located anywhere within a providers

allotted frequency band, or where allowed by multiple providers, anywhere

within the frequency spectrum for the cellular or PCS spectrum. In another embodiment, the 3X FL carrier uses one or more carriers with a chip rate that is

greater than the chip rate used on the IX RL carrier.

In another embodiment, the invention provides an article of manufacture

containing digital information executable by a digital signal-processing device.

In another embodiment, the invention yields an apparatus used to practice the

methods of the invention. The apparatus may comprise a remote station and at least one base station that has, amongst other things, a transceiver used to

communicate information signals to the remote station. Obviously, to receive O 01/15481

8 signals, the remote station also includes a transceiver which transmits and

receives from the base station, and possibly satellites where applicable. The

apparatus will also include at least one digital processing apparatus, such as a

microprocessor, that is communicatively coupled to the network or one of its

component parts.

The invention provides its users with numerous advantages. One

advantage is that it provides better spectrum management to a service provider. Another advantage is that a cdma2000 IX system can be upgraded to cdma2000

3X system services on an incremental basis if desired without having to entirely

replace existing hardware at once. As explained below, additional hardware

can be added to provide particular types of service as demand for those service

types increase. This allows a provider to economically supply only those

services that its users demand. The invention also provides a number of other

advantages and benefits that should become even more apparent after

reviewing the following detailed descriptions of the invention.

01/15481

9 BRIEF DESCRIPTION OF THE DRAWING

The nature, objects, and advantages of the invention will become more

apparent to those skilled in the art after considering the following detailed

description in connection with the accompanying drawings, in which like

reference numerals designate like parts throughout, and wherein:

FIGURE 1 illustrates the frequency spectrum used for wireless

communications;

FIGURE 2 shows a cdma2000 3X multi-carrier forward link and a single cdma2000 IX reverse link used in accordance with the invention;

FIGURE 3 shows a grouping in a band of CDMA reverse links that

allows room in the band for TDD channels used in accordance with the

invention;

FIGURE 4a is a block diagram of a general configuration for a mobile

station used in accordance with the invention;

FIGURE 4b is a block diagram of a general channel structure used in

accordance with the invention;

FIGURE 5a is a block diagram of a portion of the hardware components and

interconnections of a digital signal processing apparatus used in accordance with the invention;

FIGURE 5b shows an exemplary arrangement for a demultiplexer 511

shown in Figure 5a and used in accordance with the invention; O 01/15481

10

FIGURE 5c shows another arrangement for a demultiplexer 511 shown

in Figure 5a and used in accordance with the invention;

FIGURE 5d is a block diagram of the hardware components and

interconnections of a digital signal processing apparatus used in accordance

with the

invention;

FIGURE 5e is a block diagram of the hardware components and

interconnections of the modulator 526 shown in Figure 5d and used in

accordance with the invention; FIGURE 6a is a block diagram of a portion of the hardware components

and intercormections of a digital signal processing base station apparatus used in

accordance with the invention; and

FIGURE 6b is a block diagram of the hardware components and

interconnections of the demodulator 604 shown in Figure 6a and used in

accordance with the invention.

FIGURE 7 is a diagram showing the spectrum of a IX and a 3X reverse link spectrums.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

OPERATION

Figures 2- 6b illustrate examples of various method and apparatus

aspects of the present invention. For ease of explanation, but without any

limitation intended, these examples are described in the context of a digital O 01/15481

11 signal processing apparatus, one example of which is described following the

discussion of the various method embodiments below.

An exemplary embodiment of the present invention is based upon a

CDMA system. CDMA systems are disclosed in TIA/EIA/IS-2000, prepared by

the Telecommunications Industry Association, entitled "SPREAD SPECTRUM

DIGITAL TECHNOLOGY - MOBILE AND PERSONAL COMMUNICAΗONS

STANDARDS," and TIA/EIA/IS-95-x entitled "MOBILE STATION-BASE

STATION COMPATIBILITY STANDARD FOR DUAL-MODE WIDEBAND

SPREAD SPECTRUM CELLULAR SYSTEM", all of which are incorporated by

reference herein. As disclosed in IS-2000, a standard cdma20003X multi-carrier

(MC) forward link (FL) system uses three 1.2288 Mcps carriers paired with a

reverse link (RL) that uses a single 3X carrier. This single carrier provides a direct spread chip rate of 3.6864 Mcps. The present invention improves upon

this normal configuration.

It should be understood that the methods of the present invention as

disclosed below apply to a broad range of services. These services include voice

and data services, but the invention is particularly suitable for data services,

such as email and Web browsing, which typically have a significantly greater

FL load requirement than RL load requirement. O 01/15481

12

Spectrum Management

In one embodiment, the invention uses a cdma2000 MC FL and a single

cdma2000 IX reverse link as illustrated in Figure 2. For a cdma2000 PCS

configuration, each MC FL carrier is separated by 1.25 MHz. In the figure, the

IX RL carrier is shown in a center "frequency bin," wherein the term frequency

bin describes a 1.25 MHz band within a band class. However, in other

embodiments, the IX RL carrier could be located in any one of the three possible frequency bins corresponding to each of the three MC FL frequencies.

In the example of Figure 2, the three possible bins have center frequencies for

each carrier of 1.25 MHz, 2.5 MHz, and 3.75 MHz respectively. The 3X MC FL

is centered at 2.5 MHz. In other embodiments, the IX RL carrier may be in any

frequency bin allocated to a provider.

As is known in the art and discussed below, a mobile station can transmit the IX RL on any frequency within a provider's band. There are a

number of well-known ways that can be used to generate the different RL

frequencies. The small geometries being used for digital signal processing

devices, such as semiconductors, permit the use of high clock rates with

relatively low power consumption. Thus, it is quite practical to generate an RL

waveform that can be varied over the bandwidth allocated to a provider. In

particular, it is quite simple to generate the three bins described above. One

benefit of this invention is that there really isn't any change in the physical layer

structure of the cdma2000 IX technique to implement the invention, wherein O 01/15481

13 physical layer refers to the communication protocol between a mobile station

and a base station that is responsible for the transmission and reception of data.

For example, a power control signal for RL power control can be sent on the

three FL multi-carriers and the power control stream for FL power control can

be sent on a single RL carrier.

By moving the cdma2000 IX RL over a wide frequency range, and the

asymmetric structure that results, the RLs can be grouped in one part of the

frequency band and the FLs in another part of the frequency band. This allows

for novel and previously undiscovered opportunities in spectrum management.

One such arrangement is shown in Figure 3. Here, the RLs are grouped

together, leaving room in the provider's band to use IX and 3X FDD channels and IX time-division-duplexed (TDD) channels. It should be noticed that the

TDD usage is on the RL where interference issues will be less problematic than the other way around, particularly if FDD service is considered the more important service. The separation of frequency bands between the FDD and the

TDD service is sufficient to provide little interference between the FDD and

TDD services. Accordingly, the TDD mobile station transmitter may be using

the same frequency band as the FDD base station transmitter if there is

sufficient frequency separation between the mobile station and the base station.

Figure 7 shows the emissions for both IX and 3X reverse links from a mobile

station. Ideally, the transmitted spectrums would be exactly the bandwidth of

1.2288 MHz for IX or 3.6864 MHz for 3X. However, intermodulation distortion

in the transmitter causes unwanted emissions. As can be seen in Figure 7, the pedestal due to intermodulation distortion in the transmitter is significantly

broader in bandwidth with a 3X reverse link than a IX reverse link. The close in

pedestal is due to 3^rd order intermodulation products; the farther out pedestal is

due to 7^th order intermodulation products. The bandwidth of each pedestal is

approximately equal to the chip rate. Thus, the bandwidth of the 3X reverse

link including the 3^rd order pedestal is approximately three times the chip rate,

or 11.0592 MHz. In contrast, the bandwidth of the IX reverse link including the

3^rd order pedestal is approximately three times the chip rate, or 3.6864 MHz.

The intermodulation distortion can be reduced (and thus the unwanted

emissions can be reduced) by having a more linear power amplifier. However,

a more linear power amplifier in the mobile station requires more battery power for the same power output. Since a design goal of a mobile station is to

have a long battery life, there is a tradeoff between unwanted emissions and

battery life. As is easily understood from the discussion, the 3X waveform has

much broader emissions in terms of bandwidth which results in a greater

guardband to TDD and other systems. While emissions from the base station are also a concern, base stations usually don't use batteries as their main power source. Thus, having a more linear power amplifier is significantly less difficult than in a mobile station.

Forward Link Distribution by Data Type

In one embodiment of the proposed invention using a cdma2000 MC FL

transmission system, each of the channels of information is evenly distributed

across each of the three carriers of the forward link. For example, when transmitting a data signal on the forward link, the symbols for that data signal

are evenly distributed with a third of the symbols transmitted on each of the carriers. The benefit of this method is that is provides maximum frequency

diversity and increases the reliability of the transmission of the signal. This

method minimizes problems caused by frequency dependent propagation

characteristics, such as fading.

However, using this even-distribution embodiment reduces the

flexibility that a multi-carrier forward link can provide. Therefore, in another

embodiment of the present invention, different types of information are

transmitted using different carriers. For example, fundamental channel data

such as speech data may be transmitted on a first carrier while supplemental

channel data such as high-speed digital data is transmitted on a second carrier.

This allows the system to be adapted to the needs of the area that it is serving

and permits a service provider to incrementally increase the services provided

to its customers.

For example, when a provider has a three-carrier FL system, he may elect initially to provide speech services on a IX band. Later, in response to the needs of his customers, a second band can be deployed to carry additional

speech services, or the band may be allocated to the purpose of carrying high¬

speed digital data. Thus, in this embodiment of the present invention, the

bands are allocated to carrying different types of data. In yet another embodiment, three cdma2000 IX FLs are provided on

adjacent frequencies with a single cdma2000 IX RL. Unlike techniques used for

multi-code transmissions, multiple FL code channels are assigned to a mobile

station on different frequencies. Any combination of code channels can be used

on the three frequencies. For example, a 307.2 kbps FL code channel can be

supplied on each of the FL carriers, providing a total data rate of 921.6 kbps. In

another embodiment, the spectrum management methods discussed in the

previous section can be used with this method. In another arrangement, one of the forward link channels coveys power control information for the RL and a fundamental channel. A fundamental channel is generally a channel that

carries voice, low speed rate, such as acknowledgements, and control

information. Other frequencies can be used for supplemental channels that

operate in conjunction with the fundamental channel, and /or possibly other

channels, to provide higher data rate services.

These embodiments have the advantage that existing base station (BS)

hardware may be used and, when necessary, supplemented with additional hardware to increase the forward link transmission rates. Supplementing

existing hardware, as opposed to replacing an entire base station, is less expensive. Further, the methods of the present invention allow a provider to

easily transition from a cdma2000 IX system to a cdma2000 3X system.

However, in order to reuse existing BS hardware, some simplifications may be

needed in various implementations. One such simplification is that fast (800

Hz) forward link power control used for controlling the transmission power on one frequency probably cannot be used to control the transmit power on other

frequencies. This situation arises if a particular BS design uses separate

hardware cards for each frequency. Separate hardware cards would not permit

the transfer of fast power control streams between frequencies in common

configurations.

Further, for high-speed data channels, particularly channels with long

interleavers, fast forward link power control is not always the best technique for controlling power if the goal is to maximize system capacity. Thus, in this

embodiment, a slower form of power control, such as one widely known in the

art, should be used. For example, one way of performing FL power control for

these additional frequencies is to control the transmitted power from a selector,

as is currently done with many IS-95 systems. There, algorithms in a selector

determine when the power transmitted to a mobile station needs to be changed

and sends the gain to the BS every frame. A more detailed description of the

technique may be found in TIA/EIA/IS-634, entitled "MCS-BS INTERFACE (A- INTERFACE) FOR PUBLIC 800 MHZ," published by the Telecommunications Industry Association, and incorporated by reference herein.

As a result, fast forward power control can be used on one FL frequency

which contains the fundamental, control channels, and perhaps some

supplemental channels. Slow power control can be used on other FL

frequencies which contain additional supplemental channels. HARDWARE COMPONENTS AND INTERCONNECTIONS

A digital data processing apparatus used to execute a sequence of

machine-readable instructions as mentioned above may be embodied by

various hardware components and interconnections as described in Figures 4a-

6b.

Figure 4a shows a simple block representation of a mobile station (MS) 401 configured for use in accordance with the present invention. MS 401 receives a signal from a base station (not shown) using a cdma2000 3X MC

forward link. The signal is processed as described below. MS 401 uses a

cdma2000 IX RL to transmit information to the base station.

Figure 4b shows a more detailed block representation of a channel

structure used to prepare information for transmission by MS 401 in accordance

with the present invention. In the figure, information to be transmitted,

hereafter referred to as a signal, is transmitted in bits organized into blocks of

bits. A CRC and tail bit generator (generator) 403 receives the signal. The

generator 403 uses a cyclic redundancy code to generate parity check bits to assist in determining the quality of the signal when received by a receiver.

These bits are included in the signal. A tail bit - a fixed sequence of bits - may

also be added to the end of a block of data to reset an encoder 405 to a known

state.

The encoder 405 receives the signal and builds a redundancy into the

signal for error-correcting purposes. Different "codes" may be used to determine how the redundancy will be built into the signal. These encoded bits

are called symbols. The repetition generator 407 repeats the symbols it receives

a predetermined number of times, thus allowing part of the symbols to be lost

due to a transmission error without affecting the overall quality of the

information being sent. Block interleaver 409 takes the symbols and jumbles

them. The long code generator 411 receives the jumbled symbols and scrambles

them using a pseudorandom noise sequence generated at a predetermined chip

rate. Each symbol is XOR-ed with one of the pseudorandom chips of the scrambling sequence.

The information may be transmitted using more than one carrier

(channel) as explained with regards to the method, above. Accordingly,

demultiplexer (DEMUX) 511, shown in Figure 5a, takes the input signal "a" and splits it into multiple output signals in such a way that the input signal may be recovered. As shown in Figure 5b, in one embodiment the signal "a" is split

into three separate signals, each signal representing a selected data-type, and is

transmitted using one FL channel per data-type signal. In another embodiment,

DEMUX 511 as shown in Figure 5c splits signal "a" into two components per

data-type. Regardless of the arrangement, the present invention contemplates that distinct signals generated from a parent signal can be transmitted using one or more channels.

Further, this technique can be applied to multiple users whose signals

are transmitted using completely or partially the same FL channels. For example, if the signals from four different users are going to be sent using the

same three FL channels, then each of these signals is "channelized" by

demultiplexing each signal into three components, where each component will

be sent using a different FL channel. For each channel, the respective signals

are multiplexed together to form one signal per FL channel. Then, using the

technique described herein, the signals are transmitted. Remrning to Figure 5a,

the demultiplexed signal is then encoded by Walsh encoder 513 and spread into

two components, components I and Q, by multiplier 517. These components are summed by summer 519 and communicated to a mobile station (not shown)

by transmitter 521.

Figure 5d illustrates a functional block diagram of an exemplary

embodiment of the transmission system of the present invention embodied in a

wireless communication device 500. One skilled in the art will understand that

certain functional blocks shown in the figure may not be present in other

embodiments of the invention. The block diagram of Figure 5e corresponds to

an embodiment consistent for operation according to the TIA/EIA Standard IS-

95C, also referred to as IS-2000, or cdma2000 for CDMA applications. Other

embodiments of the present invention are useful for other standards including

Wideband CDMA (WCDMA) standards as proposed by the standards bodies

ETSI and ARIB. It will be understood by one skilled in the art that owing to the

extensive similarity between the reverse link modulation in the WCDMA

standards and the reverse link modulation in the IS-95C standard, extension of

the present invention to the WCDMA standards may be accomplished. In the exemplary embodiment of Figure 5d, the wireless communication

device transmits a plurality of distinct channels of information which are

distinguished from one another by short orthogonal spreading sequences as

described in the U.S. Patent Application Serial No. 08/886,604, entitled "HIGH

DATA RATE CDMA WIRELESS COMMUNICATION SYSTEM," assigned to

the assignee of the present invention and incorporated by reference herein. Five

separate code channels are transmitted by the wireless communication device:

1) a first supplemental data channel 532, 2) a time multiplexed channel of pilot

and power control symbols 534, 3) a dedicated control channel 536, 4) a second supplemental data channel 538 and 5) a fundamental channel 540. The first supplemental data channel 532 and second supplemental data channel 538 carry digital data which exceeds the capacity of the fundamental channel 540

such as facsimile, multimedia applications, video, electronic mail messages or

other forms of digital data. The multiplexed channel of pilot and power control

symbols 534 carries pilots symbols to allow for coherent demodulation of the

data channels by the base station and power control bits to control the energy of transmissions of the base station or base stations in communication with

wireless communication device 500. Control channel 536 carries control

information to the base station such as modes of operation of wireless

communication device 500, capabilities of wireless communication device 500

and other necessary signaling information. Fundamental channel 540 is the

channel used to carry primary information from the wireless communication device to the base station. In the case of speech transmissions, the fundamental

channel 540 carries the speech data.

Supplemental data channels 532 and 538 are encoded and processed for

transmission by means not shown and provided to modulator 526. Power

control bits are provided to repetition generator 522, which provides repetition

of the power control bits before providing the bits to multiplexer (MUX) 524. In

MUX 524 the redundant power control bits are time multiplexed with pilot symbols and provided on line 534 to modulator 526.

Message generator 512 generates necessary control information messages

and provides the control message to CRC and tail bit generator 504. CRC and

tail bit generator 504 appends a set of cyclic redundancy check bits which are

parity bits used to check the accuracy of the decoding at the base station and

appends a predetermined set of tail bits to the control message to clear the

memory of the decoder at the base station receiver subsystem. The message is

then provided to encoder 516, which provide forward error correction coding

upon the control message. The encoded symbols are provided to repetition

generator 518, which repeats the encoded symbols to provide additional time

diversity in the transmission. The symbols are then provided to interleaver 520

that reorders the symbols in accordance with a predetermined interleaving

format. The interleaved symbols are provided on line 536 to modulator 526. Variable rate data source 502 generates variable rate data. In the

exemplary embodiment, variable rate data source 502 is a variable rate speech

encoder such as described in U.S. Patent No. 5,414,796, entitled "VARIABLE

RATE VOCODER," assigned to the assignee of the present invention and

incorporated by reference herein. Variable rate vocoders are popular in

wireless communications because their use increases the battery life of wireless

communication devices and increases system capacity with minimal impact on

perceived speech quality. The Telecommunications Industry Association has codified the most popular variable rate speech encoders in such standards as IS-

96, IS-127, and IS-733. These variable rate speech encoders encode the speech

signal at four possible rates referred to as full rate, half rate, quarter rate or

eighth rate according to the level of voice activity. The rate indicates the

number of bits used to encode a frame of speech and varies on a frame by frame

basis. Full rate uses a predetermined maximum number of bits to encode the

frame, half rate uses half the predetermined maximum number of bits to encode the frame, quarter rate uses one quarter the predetermined maximum number

of bits to encode the frame and eighth rate uses one eighth the predetermined maximum number of bits to encode the frame.

Variable rate date source 502 provides the encoded speech frame to CRC

and tail bit generator 504. CRC and tail bit generator 504 appends a set of cyclic

redundancy check bits which are parity bits used to check the accuracy of the

decoding at the base station and appends a predetermined set of tail bits to the

control message in order to clear the memory of the decoder at the base sta_tion. The frame is then provided to encoder 506, which provides forward error

correction coding on the speech frame. The encoded symbols are provided to repetition generator 508, which provides repetition of the encoded symbol. The

symbols are then provided to interleaver 510 and reordered in accordance with

a predetermined interleaving format. The interleaved symbols are provided on

line 540 to modulator 526.

In the exemplary embodiment, modulator 526 modulates the data channels in accordance with a code division multiple access modulation format

and provides the modulated information to transmitter (TMTR) 530, which

amplifies and filters the signal and provides the signal through duplexer 528 for

transmission through an antenna. In IS-95 and cdma2000 systems, a 20 s

frame is divided into sixteen sets of equal numbers of symbols, referred to as

power control groups. The reference to power control is based on the fact that

for each power control group, the base station receiving the frame issues a power control command in response to a determination of the sufficiency of the received reverse link signal at the base station.

Figure 5e illustrates a functional block diagram of an exemplary

embodiment of modulator 526 of Figure 5d. The first supplemental data

channel data is provided on line 532 to spreading element 542 which covers the

supplemental channel data in accordance with a predetermined spreading

sequence. In the exemplary embodiment, spreading element 542 spreads the

supplemental channel data with a short Walsh sequence (++-). The spread data is provided to relative gain element 544, which adjusts the gain of the

spread supplemental channel data relative to the energy of the pilot and power

control symbols. The gain adjusted supplemental channel data is provided to a

first summing input of summing element 546. The pilot and power control

multiplexed symbols are provided on line 534 to a second summing input of

summing element 546.

Control channel data is provided on line 536 to spreading element 548

which covers the supplemental channel data in accordance with a

predetermined spreading sequence. In the exemplary embodiment, spreading

element 548 spreads the supplemental channel data with a short Walsh

sequence (++++++++ ). The spread data is provided to relative gain

element 550, which adjusts the gain of the spread control channel data relative

to the energy of the pilot and power control symbols. The gain adjusted control data is provided to a third summing input of summing element 546. Summing element 546 sums the gain adjusted control data symbols, the gain adjusted

supplemental channel symbols and the time multiplexed pilot and power

control symbols and provides the sum to a first input of multiplier 562 and a first input of multiplier 568.

The second supplemental channel is provided on line 538 to spreading

element 552 which covers the supplemental channel data in accordance with a

predetermined spreading sequence. In the exemplary embodiment, spreading

element 552 spreads the supplemental channel data with a short Walsh sequence (++--)• The spread data is provided to relative gain element 554,

which adjusts the gain of the spread supplemental channel data. The gain

adjusted supplemental channel data is provided to a first summing input of

summer 556.

The fundamental channel data is provided on line 540 to spreading

element 558 which covers the fundamental channel data in accordance with a

predetermined spreading sequence. In the exemplary embodiment, spreading element 558 spreads the fundamental channel data with a short Walsh sequence

(++++ — ++++ — ). The spread data is provided to relative gain element 560

that adjusts the gain of the spread fundamental channel data. The gain adjusted

fundamental channel data is provided to a second summing input of summing

element 556. Summing element 556 sums the gain adjusted second supplemental channel data symbols and the fundamental channel data symbols and provides the sum to a first input of multiplier 564 and a first input of

multiplier 566.

In the exemplary embodiment, a pseudonoise spreading using two

different short PN sequences (PN, and PN_Q) is used to spread the data. In the

exemplary embodiment the short PN sequences, PN, and PN_Q, are multiplied by

a long PN code to provide additional privacy. The generation of pseudonoise

sequences is well known in the art and is described in detail in U.S. Patent No.

5,103,459, entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL

WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM," assigned to the assignee of the present invention and incorporated by reference herein. A

long PN sequence is provided to a first input of multipliers 570 and 572. The

short PN sequence PN, is provided to a second input of multiplier 570 and the

short PN sequence PN_Q is provided to a second input of multiplier 572.

The resulting PN sequence from multiplier 570 is provided to respective

second inputs of multipliers 562 and 564. The resulting PN sequence from

multiplier 572 is provided to respective second inputs of multipliers 566 and 568. The product sequence from multiplier 562 is provided to the summing

input of subtractor 574. The product sequence from multiplier 564 is provided

to a first summing input of summing element 576. The product sequence from

multiplier 566 is provided to the subtracting input of subtractor 574. The

product sequence from multiplier 568 is provided to a second summing input of summing element 576.

The difference sequence from subtractor 574 is provided to baseband

filter 578. Baseband filter 578 performs necessary filtering on the difference

sequence and provides the filtered sequence to gain element 582. Gain element

582 adjusts the gain of the signal and provides the gain-adjusted signal to

upconverter 586. Upconverter 586 upconverts the gain adjusted signal in

accordance with a QPSK modulation format and provides the unconverted

signal to a first input of surrvming element 590. O 01/15481

28

The sum sequence from summing element 576 is provided to baseband

filter 580. Baseband filter 580 performs necessary filtering on difference

sequence and provides the filtered sequence to gain element 584. Gain element

584 adjusts the gain of the signal and provides the gain-adjusted signal to

upconverter 588. Upconverter 588 upconverts the gain adjusted signal in

accordance with a QPSK modulation format and provides the upconverted

signal to a second input of summing element 590. Summing element 590 sums

the two QPSK modulated signals and provides the result to a transmitter (not

shown).

Turning now to Figure 6a, a functional block diagram of selected portions of a base station 600 in accordance with the present invention. Reverse

link RF signals from the wireless communication device 500 (Figure 5e) are

received by receiver (RCVR) 602, which downconverts the received reverse link

RF signals to an baseband frequency. In the exemplary embodiment, receiver

602 down converts the received signal in accordance with a QPSK

demodulation format. Demodulator 604 then demodulates the baseband signal.

Demodulator 604 is further described with reference to Figure 6b below.

The demodulated signal is provided to accumulator 606. Accumulator

606 sums the symbol energies of the redundantly transmitted power control

groups of symbols. The accumulated symbol's energies are provided to de-

interleaver 608 and reordered in accordance with a predetermined de-

interleaving format. The reordered symbols are provided to decoder 610 and 01/15481

29 decoded to provide an estimate of the transmitted frame. The estimate of the

transmitted frame is then provided to CRC check 612 which determines the

accuracy of the frame estimate based on the CRC bits included in the

transmitted frame.

In the exemplary embodiment, base station 600 performs a blind

decoding on the reverse link signal. Blind decoding describes a method of

decoding variable rate data in which the receiver does not know a priori the rate of the transmission. In the exemplary embodiment, base station 600

accumulates, deinterleaves and decodes the data in accordance with each

possible rate hypothesis. The frame selected as the best estimate is based on quality metrics such as the symbol error rate, the CRC check and the Yamamoto metric.

An estimate of the frame for each rate hypothesis is provided to control

processorβ>16_]and a set of quality metrics for each of the decoded estimates is

also provided. Quality metrics that may include the symbol error rate, the

Yamamoto metric and the CRC check. Control processor selectively provides

one of the decoded frames to the remote station user or declares a frame erasure.

An expanded functional block diagram of an exemplary single

demodulation chain of demodulator 604 is shown in Figure 6b. In the preferred

embodiment, demodulator 604 has one demodulation chain for each information channel. The exemplary demodulator 604 of Figure 6b performs

complex demodulation on signals modulated by the exemplary modulator 604

of Figure 6a. As previously described, receiver (RCVR) 602 downconverts the

received reverse link RF signals to a baseband frequency, producing Q and I

baseband signals. Despreaders 614 and 616 respectively despread the I and Q

baseband signals using the long code from Figure 5d. Baseband filters (BBF)

618 and 620 respectively filter the I and Q baseband signals.

Despreaders 622 and 624 respectively despread the I and Q signals using the PN, sequence of Figure 5e. Similarly, despreaders 626 and 628 respectively despread the Q and I signals using the PN_Q sequence of Figure 5e. The outputs

of despreaders 622 and 624 are combined in combiner 630. The output of

despreader 628 is subtracted from the output of despreader 624 in combiner

632. The respective outputs of combiners 630 and 632 are then Walsh- uncoverers in Walsh-uncoverers 634 and 636 with the Walsh code that was used

to cover the particular channel of interest in Figure 5e. The respective outputs

of the Walsh-uncoverers 634 and 636 are then summed over one Walsh symbol by accumulators 642 and 644.

The respective outputs of combiners 630 and 632 are also summed over

one Walsh symbol by accumulators 638 and 640. The respective outputs of

accumulators 638 and 640 are then applied to pilot filters 646 and 648. Pilot

filters 646 and 648 generate an estimation of the channel conditions by

determining the estimated gain and phase of the pilot signal data 534 (see , .„, O 01/15481

31

Figure 5d). The output of pilot filter 646 is then complex multiplied by the

respective outputs of accumulators 642 and 644 in complex multipliers 650 and

652. Similarly, the output of pilot filter 648 is complex multiplied by the

respective outputs of accumulators 642 and 644 in complex multipliers 654 and

656. The output of complex multiplier 654 is then summed with the output of

complex multiplier 650 in combiner 658. The output of complex multiplier 656

is subtracted from the output of complex multiplier 652 in combiner 660.

Finally, the outputs of combiners 558 and 660 are combined in combiner 662 to

produce the demodulated signal of interest.

Figure 7 compares the spectrum of a IX reverse link spectrum to a 3X reverse link spectrum.

Despite the specific foregoing descriptions, ordinarily skilled artisans

having the benefit of this disclosure will recognize that the apparatus discussed

above may be implemented in a machine of different construction without

departing from the scope of the present invention. Similarly, parallel methods may be developed. As a specific apparatus example, one of the components such as summing element 622, shown in Figure 6b, may be combined with

summing element 626 even though they are shown as separate elements in the

functional diagram.

OTHER EMBODIMENTS

While there have been shown what are presently considered to be

preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departing

from the scope of the invention as defined by the appended claims.

* * * * *

WHAT IS CLAIMED IS:

Claims

1. A method to allocate a reverse link within a band class, said reverse link

communicatively coupling a base station and a mobile station, comprising:

transmitting first information on a multi-carrier forward link comprising

multiple frequencies;

receiving said first information at said mobile station;

transmitting second information on said reverse link at one of said multiple frequencies; and

receiving said second information at said base station.

2. The method in accordance with claim 1, wherein said multiple

frequencies support any combination of code channels.

3. The method in accordance with claim 2, wherein one of said code channels on said forward link is used to communicate power control

information for said reverse link and a fundamental channel.

4. The method in accordance with claim 3, wherein a channel other than said one of said code channels is used for a supplemental channel.

5. The method in accordance with claim 1, wherein said reverse link is

varied over said band class allocated to said mobile station. O 01/15481 34

6. The method in accordance with claim 5, wherein said multiple

frequencies consist of three frequencies.

7. The method in accordance with claim 6, wherein said multiple

frequencies are adjacent frequencies.

8. The method in accordance with claim 6, wherein said multiple

frequencies are adjacent frequencies separate from another frequency

supporting another type of channel, said another type of channel being different

than channels supported by said adjacent frequencies.

9. The method in accordance with claim 8, wherein said another type of

channel is a time-division-duplexing channel, and said channels are frequency-

division-duplexing channels.