U.S. patent application number 10/345557 was filed with the patent office on 2003-07-24 for method and apparatus for transmitting and receiving information about forward channel status in a multi-carrier mobile communication system.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Choi, Ho-Kyu, Kim, Dong-hee, Kim, Youn-Sun, Kwon, Hwan-Joon.
Application Number | 20030137955 10/345557 |
Document ID | / |
Family ID | 19718525 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030137955 |
Kind Code |
A1 |
Kim, Youn-Sun ; et
al. |
July 24, 2003 |
Method and apparatus for transmitting and receiving information
about forward channel status in a multi-carrier mobile
communication system
Abstract
A method and apparatus for transmitting and receiving forward
channel status information in a multi-carrier mobile communication
system. An MS transmits to a BS forward channel status information
representing an average C/I of forward signals with respect to a
plurality of carriers, the maximum of the forward signal C/Is, or
each of the forward signal C/is. The forward channel status
information is absolute C/I information representing a current C/I,
or relative C/I information representing a difference of the
current C/I from a previous C/I.
Inventors: |
Kim, Youn-Sun; (Seoul,
KR) ; Choi, Ho-Kyu; (Songnam-shi, KR) ; Kwon,
Hwan-Joon; (Seoul, KR) ; Kim, Dong-hee;
(Seoul, KR) |
Correspondence
Address: |
Paul J. Farrell, Esq.
DILWORTH & BARRESE, LLP
333 Earle Ovington Blvd.
Uniondale
NY
11553
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
KYUNGKI-KO
KR
|
Family ID: |
19718525 |
Appl. No.: |
10/345557 |
Filed: |
January 16, 2003 |
Current U.S.
Class: |
370/332 ;
370/333 |
Current CPC
Class: |
H04L 27/2647 20130101;
H04L 1/0057 20130101; H04L 1/0029 20130101; H04L 1/0026 20130101;
H04L 1/0073 20130101 |
Class at
Publication: |
370/332 ;
370/333 |
International
Class: |
H04Q 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2002 |
KR |
P2002-2570 |
Claims
What is claimed is:
1. A method of transmitting forward channel status information to a
base station (BS) from a mobile station (MS) in a multi-carrier
mobile communication system, comprising the steps of: measuring
strengths of forward channel signals received from the BS by a
multi-carrier; calculating an average of the strength measurements;
generating forward channel status information representing the
calculated average strength; and transmitting the forward channel
status information to the BS.
2. The method of claim 1, wherein the step of calculating the
average comprises the steps of: compensating the strength
measurements for differences among transmission powers of the
carriers; and calculating an average of the compensated
strengths.
3. The method of claim 1, wherein the steps of generating and
transmitting the forward channel status information comprises the
step of: generating an absolute information representing the
calculated average strength and transmitting the absolute
information in a selected transmission period.
4. The method of claim 3, wherein the steps of generating and
transmitting the forward channel status information further
comprises the step of: generating a relative information
representing a difference from a previously calculated average
strength and transmitting the relative information in a remaining
transmission period other than the selected transmission
period.
5. The method of claim 3, wherein the absolute information is
transmitted if a solution to (T-N-Mobile_Parameter)mod period is 0;
wherein T is system time represented in the number of slots, period
is an absolute information transmission period, N is a time point
when an absolute information is transmitted in the transmission
period, Mobile_Parameter is a MS-specific value for distributing
absolute information transmissions from a plurality of MSs, and mod
represents modulo operation.
6. The method of claim 1, further comprising the step of encoding
the forward channel status information at a coding rate
corresponding to a bit number of the forward channel status
information.
7. A method of receiving forward channel status information from a
mobile station (MS) to a base station (BS) in a multi-carrier
mobile communication system, comprising the steps of: receiving
forward channel status information representing an average of
signal strengths measured with respect to a multi-carrier; and
obtaining the average signal strength from the forward channel
status information in order to control forward packet data
transmission by the multi-carrier.
8. The method of claim 7, wherein the step of obtaining the average
signal strength comprises the steps of: replacing a stored previous
average signal strength with the average signal strength if the
forward channel status information is absolute information
representing the average signal strength; and updating the previous
average signal strength with the average signal strength if the
forward channel status information is relative information
representing a difference from the previous average signal strength
in the average signal strength.
9. A transmitter for transmitting forward channel status
information to a base station (BS) from a mobile station (MS) in a
multi-carrier mobile communication system, comprising: a plurality
of measurers for measuring the strengths of forward channel signals
received from the BS by a multi-carrier; an average calculator for
calculating the average of the strength measurements; and an
information generator for generating forward channel status
information representing the average strength and transmitting the
forward channel status
10. The transmitter of claim 9, wherein the average calculator
compensates the strength measurements for differences among the
transmission power of the carriers and calculates an average of the
compensated strengths.
11. The transmitter of claim 9, wherein the information generator
generates an absolute information representing the calculated
average strength in a selected transmission period and generates a
relative information representing a difference from a previously
calculated average strength in the calculated average strength in a
remaining transmission period other than the selected transmission
period.
12. The transmitter of claim 9, further comprising an encoder for
encoding the forward channel status information at a coding rate
corresponding to a bit number of the forward channel status
information.
13. The transmitter of claim 12, wherein the encoder encodes the
absolute information at a coding rate corresponding to a bit number
of the absolute information in the selected transmission period,
and encodes the relative information at a coding rate corresponding
to a bit number of the relative information in the remaining
transmission period other than the selected transmission
period.
14. A receiver for receiving forward channel status information
from a mobile station (MS) in a base station (BS) in a
multi-carrier mobile communication system, comprising: a decoder
for decoding a received signal at a coding rate corresponding to a
bit number of forward channel status information and outputting the
forward channel status information representing an average of
signal strengths measured with respect to multi-carriers; and a
memory for storing the average signal strength obtained from the
forward channel status information.
15. The receiver of claim 14, wherein the decoder decodes the
received signal at a coding rate corresponding to a bit number of
absolute information if the forward channel status information is
the absolute information, and decodes the received signal at a
coding rate corresponding to a bit number of relative information
if the forward channel status information is the relative
information representing a difference from a previous average
signal strength in the average strength.
16. A method of transmitting forward channel status information to
a base station (BS) from a mobile station (MS) in a multi-carrier
mobile communication system, comprising the steps of: measuring the
strengths of forward channel signals received from the BS by a
multi-carrier; comparing the signal strength measurements and
selecting a maximum of the signal strength measurements; generating
forward channel status information representing the selected
maximum signal strength and carrier selection information
indicating a best carrier having the maximum signal strength; and
transmitting the forward channel status information and the carrier
selection information to the BS.
17. The method of claim 16, wherein the step of selecting the
maximum signal strength comprises the steps of: compensating the
strength measurements for differences among transmission powers of
the carriers; comparing the compensated signal strength
measurements; and selecting a maximum of the compensated signal
strength measurements.
18. The method of claim 16, wherein the steps of generating and
transmitting the forward channel status information comprises the
step of: generating an absolute information representing the
maximum signal strength and transmitting the absolute information
in a selected transmission period
19. The method of claim 18, wherein the steps of generating and
transmitting the forward channel status information comprises the
step of: generating a relative information representing a
difference from a previously maximum signal strength and
transmitting the relative information in a remaining transmission
period other than the selected transmission period.
20. The method of claim 18, wherein the absolute information is
transmitted if a solution to (T-N-Mobile_Parameter)mod period is 0;
wherein T is system time represented in the number of slots, period
is an absolute information transmission period, N is a time point
when an absolute information is transmitted in the transmission
period, Mobile_Parameter is a MS-specific value for distributing
absolute information transmissions from a plurality of MSs, and mod
represents modulo operation.
21. The method of claim 16, further comprising the step of encoding
the forward channel status information at a coding rate
corresponding to a bit number of the forward channel status
information and the carrier selection information.
22. A method of receiving forward channel status information from a
mobile station (MS) in a base station (BS) in a multi-carrier
mobile communication system, comprising the steps of: receiving
forward channel status information representing a maximum of signal
strengths measured with respect to multi-carrier, and carrier
selection information indicating a best carrier having the selected
maximum signal strength; and obtaining the maximum signal strength
from the forward channel status information and the carrier
selection information in order to control forward packet data
transmission by a multi-carrier.
23. The method of claim 22, wherein the step of selecting the
maximum signal strength comprises the steps of: replacing a stored
previous maximum signal strength with the maximum signal strength
if the forward channel status information is absolute information
representing the maximum signal strength; and updating the previous
maximum signal strength with the maximum signal strength if the
forward channel status information is relative information
representing a difference from the previous maximum signal strength
in the maximum signal strength.
24. A transmitter for transmitting forward channel status
information to a base station (BS) from a mobile station (MS) in a
multi-carrier mobile communication system, comprising: a plurality
of measurers for measuring the strengths of forward channel signals
received from the BS by multi-carrier; a selector for comparing the
signal strength measurements and selecting a maximum of the signal
strength measurements; an information generator for generating
forward channel status information representing the selected
maximum signal strength and carrier selection information
indicating a best carrier having the maximum signal strength and
transmitting the forward channel status information.
25. The transmitter of claim 24, wherein the selector compensates
the strength measurements for differences among transmission powers
of the carriers, compares the compensated signal strength
measurements, and selects a maximum of the compensated signal
strength measurements.
26. The transmitter of claim 24, wherein the information generator
generates an absolute value symbol representing the maximum signal
strength in a selected transmission period and generates a relative
value representing a difference from a previously maximum signal
strength in a remaining transmission period other than the selected
transmission period.
27. The transmitter of claim 26, further comprising an encoder for
encoding the absolute information and the carrier selection
information at a coding rate corresponding to a bit number of the
absolute information and the carrier selection information in the
selected transmission period, and encodes the relative information
and the carrier selection information at a coding rate
corresponding to a bit number of the relative information and the
carrier selection information in the remaining transmission
period.
28. A receiver for receiving forward channel status information
from a mobile station (MS) in a base station (BS) in a
multi-carrier mobile communication system, comprising: a decoder
for decoding a received signal at a coding rate corresponding to a
bit number of forward channel status information and carrier
selection information, and outputting the forward channel status
information representing a maximum of signal strengths measured
with respect to multi-carrier and the carrier selection information
representing a best carrier having the maximum signal strength; and
a memory for storing the maximum signal strength obtained from the
forward channel status information.
29. The receiver of claim 28, wherein the decoder decodes the
received signal at a coding rate corresponding to the bit number of
absolute information and the carrier selection information if the
forward channel status information is the absolute information, and
decodes the received signal at a coding rate corresponding to the
bit number of relative information and the carrier selection
information if the forward channel status information is the
relative information representing a difference from a previous
maximum signal strength in the maximum signal strength.
30. A method of transmitting forward channel status information to
a base station (BS) from a mobile station (MS) in a multi-carrier
mobile communication system, comprising the steps of: measuring the
strengths of forward channel signals received from the BS by a
multi-carrier; generating forward channel status information
representing each of the signal strength measurements; and
transmitting the forward channel status information to the BS.
31. The method of claim 30, wherein the steps of generating and
transmitting the forward channel status information comprises the
step of: generating an absolute information of selected carrier and
relative information of other carriers representing a difference
from previously calculated signal strengths respectively and
transmitting the absolute information and relative information in a
selected transmission period.
32. The method of claim 31, wherein the steps of generating and
transmitting the forward channel status information comprises the
step of: generating a relative information representing a
difference from previously calculated signal strengths of
multi-carrier respectively and transmitting the relative
information in a remaining period other than in a selected
transmission period.
33. The method of claim 31, wherein the absolute information for
the carriers is transmitted at an interval determined by 2
tx_interval tx_period - 1 Num_Carrier - 1 where tx_interval
represents an interval between transmissions of the absolute
information of the carriers, tx_period is a transmission period of
the absolute information of each of the carriers, and Num_Carrier
is a number of the carriers.
34. The method of claim 31, wherein the absolute information is
transmitted if a solution to
(T-N-Mobile_Parameter-(carrier_id-1).times.t- x_period)mod
tx_period is 0; where T is system time represented in a number of
slots, tx_period is a transmission period of the absolute
information of each of the carriers, N is a time point when the
absolute information is transmitted in the transmission period,
Mobile_Parameter is a MS-specific value, carrier_id is a carrier
identifier, and tx_interval is a transmission interval between the
absolute information of the carriers.
35. The method of claim 30, further comprising step of encoding the
forward channel status information at a coding rate corresponding
to a bit number of the forward channel status information.
36. A method of receiving forward channel status information from a
mobile station (MS) in a base station (BS) in a multi-carrier
mobile communication system, comprising the steps of: receiving
forward channel status information representing a signal strengths
measured with respect to a multi-carrier; and obtaining the signal
strengths of the carriers from the forward channel status
information in order to control forward packet data transmission by
the multi-carrier.
37. The method of claim 36, wherein the step of obtaining the
signal strength comprises the steps of: replacing a stored previous
signal strength with a signal strength of a carrier if the forward
channel status information for the carrier is absolute information
representing the signal strength of the carrier; and updating the
previous signal strength with the signal strength of the carrier if
the forward channel status information is relative information
representing a difference from the previous signal strength in the
signal strength of the carrier.
38. A transmitter for transmitting forward channel status
information to a base station (BS) from a mobile station (MS) in a
multi-carrier mobile communication system, comprising: a plurality
of measurers for measuring strengths of forward channel signals
received from the BS by a multi-carrier; a plurality of information
generators for generating forward channel status information
representing each of the signal strengths; a multiplexer for
multiplexing the forward channel status information representing
the signal strengths of the multi-carrier respectively and
transmitting the forward channel status information
39. The transmitter of claim 38, wherein each of the information
generators generates an absolute information of selected carrier
and relative information of other carriers representing a
difference from previously calculated signal strengths respectively
in a selected transmission period and generates a relative
information representing a difference from previously calculated
signal strengths of the carriers respectively in a remaining period
other than in a selected transmission period.
40. The transmitter of claim 38, further comprising an encoder for
encoding the forward channel status information at a coding rate
corresponding to a bit number of the forward channel status
information.
41. The transmitter of claim 40, wherein the encoder encodes the
absolute information of the selected carrier and the relative
information of the other carriers at a coding rate corresponding to
a bit number of the absolute information and the relative
information in the selected transmission period, and encodes the
relative information of the carriers at a coding rate corresponding
to a bit number of the relative information respectively in the
remaining transmission period other than the selected transmission
period.
42. A receiver for receiving forward channel status information
from a mobile station (MS) in a base station (BS) in a
multi-carrier mobile communication system, comprising: a decoder
for decoding a received signal at a coding rate corresponding to a
bit number of forward channel status information representing
signal strengths of a multi-carrier, and outputting the forward
channel status information; and a memory for storing a signal
strengths obtained from the forward channel status information.
43. The receiver of claim 42, wherein the decoder decodes the
received signal at a coding rate corresponding to a bit number of
absolute information and relative information if the forward
channel status information includes the absolute information of a
selected carrier and the relative information of the other
carriers, the relative information representing difference from a
previous signal strength of the other carriers in the signal
strengths of the each other carriers, and decodes the received
signal at a coding rate corresponding to a bit number of relative
information of the each carriers if the forward channel status
information includes the relative information.
Description
PRIORITY
[0001] This application claims priority to an application entitled
"Method and Apparatus for Transmitting and Receiving Information
about Forward Channel Status in a Multi-Carrier Mobile
Communication System" filed in the Korean Industrial Property
Office on Jan. 16, 2002 and assigned Serial No. 2002-2570, the
contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a mobile
communication system supporting voice and data services, and in
particular, to a method and apparatus for efficiently transmitting
information about the status of a forward channel from a mobile
station (MS) in a multi-carrier mobile communication system.
[0004] 2. Description of the Related Art
[0005] A typical mobile communication system such as CDMA (Code
Division Multiple Access) provides only a voice service. However,
growing user demand and development of mobile communication
technology have led to mobile communication systems that
additionally provide a data service. One of them is a so-called
1xEV-DV (Evolution-Data and Voice) system.
[0006] In the 1xEV-DV mobile communication system, a plurality of
MSs report to a base station (BS) measurements of the status of a
forward channel from the BS by R-CQICHs (Reverse-Channel Quality
Indicator Channels) and the BS then determines an MS to receive
forward packet data and its related transmission parameters based
on the forward channel status measurements. Here, the forward
channel status is measured as the carrier-to-interference ratio
(C/I) of a forward pilot channel from the BS.
[0007] FIG. 1 is a block diagram of an R-CQICH transmitter in a
typical 1xEV-DV mobile communication system. Referring to FIG. 1, a
C/I measurer 101 measures the C/I of a forward pilot channel signal
and a C/I information generator 102 generates C/I information in a
predetermined number of bits by quantizing the C/I measurement.
Mapping of C/I measurements to C/I information is illustrated in
Table 1 below.
1TABLE 1 C/I measurement of forward pilot C/I information (a4, a3,
a2, a1, a0) NULL 00000 (below -14.5 dB or MS not ready) -14.5 to
-13.1 dB 00001 -13.1 to -11.6 dB 00010 -11.6 to -10.2 dB 00011
-10.2 to -8.8 dB 00100 -8.8 to -7.4 dB 00101 -7.4 to -5.9 dB 00110
-5.9 to -4.5 dB 00111 -4.5 to -3.1 dB 01000 -3.1 to -1.6 dB 01001
-1.6 to -0.2 dB 01010 -0.2 to 1.2 dB 01011 1.2 to 2.6 dB 01100 2.6
to 4.1 dB 01101 4.1 to 5.5 dB 01110 Above 5.5 dB 01111
[0008] In Table 1, one bit in the position of a4 is reserved.
Therefore, the C/I information is represented actually in 4
bits.
[0009] A block encoder 103 encodes the C/I information at a coding
rate of (12, 5). A Walsh coverer 104 covers the 12 code symbols
received from the block encoder 103 with a Walsh code of length 8.
The Walsh code is determined according to a 3-bit best sector
indicator (BSI). The BSI indicates a BS (i.e. sector) in the best
forward channel status in an active set listing BSs (sectors in a
sectored BS) communicating with an MS.
[0010] A Walsh spreader 105 spreads the 96-bit Walsh covered
sequence received from the Walsh coverer 104 with a Walsh code
assigned to an R-CQICH and transmits the spread signal to the
BS.
[0011] The 4-bit C/I information and the one reserved bit are
transmitted in every reverse channel slot of 1.25 ms. The C/I
information is equivalent to 3200 bps and each MS that is to
receive a packet data service transmits C/I information to the BS.
This C/I information transmission uses a large amount of reverse
transmission capacity that might otherwise be used for transmission
of traffic data.
[0012] Moreover, the R-CQICH configuration is applicable only up to
a 2xEV-DV system using a single carrier. An advanced 3xEV-DV system
uses multiple carriers to increase system efficiency and the
multiple carriers are in different forward channel statuses.
Therefore, there is a need for a preferable method of transmitting
forward channel status information in a multi-carrier mobile
communication system.
SUMMARY OF THE INVENTION
[0013] It is, therefore, an object of the present invention to
provide a method and apparatus for effectively transmitting
information about a forward channel status in a multi-carrier
mobile communication system.
[0014] It is another object of the present invention to provide a
method and apparatus for effectively transmitting information about
a forward channel status with minimum reverse transmission capacity
in a multi-carrier mobile communication system.
[0015] To achieve the above and other objects, according to an
aspect of the present invention, an MS transmits to a BS forward
channel status information representing an average C/I of forward
signals with respect to a plurality of carriers. The BS then
controls transmission of forward packet data to the MS based on the
average C/I.
[0016] According to another aspect of the present invention, an MS
transmits to a BS forward channel status information representing a
maximum C/I of forward signals with respect to a plurality of
carriers. The BS then controls transmission of forward packet data
to the MS based on the maximum C/I.
[0017] According to a further aspect of the present invention, an
MS transmits to a BS forward channel status information
representing each C/I of forward signals with respect to a
plurality of carriers. The BS then controls transmission of forward
packet data to the MS based on the individual C/I.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings in which:
[0019] FIG. 1 is a block diagram of an R-CQICH transmitter in a
typical 1xEV-DV mobile communication system;
[0020] FIG. 2 illustrates assignment of three forward carriers and
one reverse carrier;
[0021] FIG. 3 illustrates frequency assignment to three forward
carriers and one reverse carrier;
[0022] FIG. 4 illustrates an R-CQICH slot format for 3xEV-DV
according to an embodiment of the present invention;
[0023] FIG. 5 is a block diagram of an R-CQICH transmitter
according to the embodiment of the present invention;
[0024] FIG. 6 is a block diagram of an R-CQICH receiver in
correspondence with the R-CQICH transmitter illustrated in FIG.
5;
[0025] FIG. 7 is a flowchart illustrating an operation for
transmitting information about a forward channel status in the
R-CQICH transmitter illustrated in FIG. 5;
[0026] FIG. 8 is a flowchart illustrating an operation for
receiving information about the forward channel status in the
R-CQICH receiver illustrated in FIG. 6;
[0027] FIG. 9 illustrates an R-CQICH slot format for 3xEV-DV
according to a second embodiment of the present invention;
[0028] FIG. 10 is a block diagram of an R-CQICH transmitter
according to the second embodiment of the present invention;
[0029] FIG. 11 is a block diagram of an R-CQICH receiver in
correspondence with the R-CQICH transmitter illustrated in FIG.
10;
[0030] FIG. 12 is a flowchart illustrating an operation for
transmitting information about a forward channel status in the
R-CQICH transmitter illustrated in FIG. 10;
[0031] FIG. 13 is a flowchart illustrating an operation for
receiving information about the forward channel status in the
R-CQICH receiver illustrated in FIG. 11;
[0032] FIG. 14 illustrates an R-CQICH slot format for 3xEV-DV
according to a third embodiment of the present invention;
[0033] FIG. 15 illustrates concurrent transmission of R-CQICHs from
a plurality of MSs according to the third embodiment of the present
invention;
[0034] FIG. 16 is a block diagram of an R-CQICH transmitter
according to the third embodiment of the present invention;
[0035] FIG. 17 is a block diagram of an R-CQICH receiver in
correspondence with the R-CQICH transmitter illustrated in FIG.
16;
[0036] FIG. 18 is a flowchart illustrating an operation for
transmitting information about a forward channel status in the
R-CQICH transmitter illustrated in FIG. 16; and
[0037] FIG. 19 is a flowchart illustrating an operation for
receiving information about the forward channel status in the
R-CQICH receiver illustrated in FIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] Preferred embodiments of the present invention will be
described herein below with reference to the accompanying drawings.
In the following description, well-known functions or constructions
are not described in detail since they would obscure the invention
in unnecessary detail.
[0039] The R-CQICH delivers information about a forward channel
status from an MS to a BS, and a 3xEV-DV mobile communication
system uses a plurality of forward carriers spread to 1.2288 Mcps
(Mega chips per second) and one reverse carrier spread to 1.2288 or
3.6864 Mcps for the purpose of efficient packet data transmission
and reception. Exemplary forward and reverse frequency assignments
in the 3xEV-DV system are illustrated in FIGS. 2 and 3.
[0040] FIG. 2 illustrates three forward carriers, each being spread
to 1.2288 Mcps and one reverse carrier spread to 1.2288 Mcps, and
FIG. 3 illustrates three forward carriers, each being spread to
1.2288 Mcps and one reverse carrier spread to 3.6864 Mcps. If two
or more carries are assigned on the forward link as illustrated in
FIGS. 2 and 3, it is necessary to measure the forward channel
states of each carrier and report them. The requirement for this
operation is transmission of accurate forward channel status
information, minimizing R-CQICH-incurred interference.
[0041] In a multi-carrier mobile communication system, each BS (or
each sector) transmits signals by a plurality of carriers. An MS
receives forward pilot channel signals from all possible BSs and
selects the best sector, which has the strongest pilot channel
among them. The best sector can be determined in many methods. One
method is that the MS calculates an average strength of the forward
pilot channel signals received on a plurality of carriers from each
sector and selects a sector having a maximum signal strength as the
best sector. Another method is to select as the best sector a
sector transmitting a strongest pilot channel signal among all
possible sectors, each sector transmitting pilot channels by a
plurality of carriers.
[0042] The MS measures the forward channel status using a plurality
of pilot channel signals from the best sector and generates forward
channel status information based on the measurement. Therefore, it
is to be understood in the following description that the best
sector is a sector from which the MS receives signals to generate
forward status information with respect to a plurality of carriers.
The MS transmits the forward channel status information to all
neighbor sectors including the best sector in order to ensure
continuity of packet data at handoff. However, for clarity of
description, it will be described herein that the MS transmits the
forward channel status information to the best sector.
[0043] First Embodiment
[0044] In a first embodiment of the present invention, an MS
calculates an average of the strengths of forward channel signals
with respect to a plurality of carriers and generates forward
channel status information based on the average strength.
[0045] FIG. 4 illustrates an R-CQICH slot format for 3xEV-DV
according to the first embodiment of the present invention. The
R-CQICH delivers the absolute information and relative information
of the average signal strength. The absolute information and the
relative information will be referred to as an absolute C/I and a
relative C/I, respectively. The absolute C/I is a quantized C/I
measurement of a forward channel signal in the current slot, and
the relative C/I represents a difference in the forward channel
signal strength of the current slot from a previous slot. If
absolute C/I information is formed as illustrated in Table 1, the
absolute C/I information occupies 4 bits and relative C/I
information occupies 1 bit. An increment or decrement represented
by the relative C/I information is preset, for example, to be 1 dB
between the MS and the BS.
[0046] As illustrated in FIG. 4, the MS measures the C/I of the
forward pilot channel signal in every slot #0 and generates 4-bit
absolute C/I information. In each of the other slots #1 to #15, the
MS generates 1-bit relative C/I information by comparing the C/I
measurement of the slot with that of its previous slot. In this
manner, the MS generates absolute C/I information every 16 slots
and relative C/I information in the other slots, and transmits them
in corresponding slots on the R-CQICH. Here, the absolute C/I
information is transmitted with stronger power than the relative
C/I information, for example, twice as much power.
[0047] While the absolute C/I information is transmitted every 16
slots in FIG. 4, its transmission period is determined according to
system parameters set between the MS and the BS. The slot position
of the absolute C/I information is also selected between the MS and
the BS.
[0048] The MS measures the C/I of the forward pilot channel signal
with respect to each of the carriers received from the BS,
calculates an average of the C/I measurements, and generates
absolute C/I and relative C/I information based on the average C/I.
More specifically, the MS averages the forward pilot channel
measurements with respect to the carriers in slot #0 and generates
absolute C/I information by quantizing the average C/I. The MS
operates in the same manner in each of the other slots, and
generates relative C/I information by comparing the absolute C/I of
each of the slots and that of its previous slot. The MS then
transmits the absolute C/I information and the relative C/I
information on the R-CQICH, thereby reporting the channel statuses
of all the carriers to the BS, while minimizing R-CQICH-caused
interference.
[0049] While 64(=4.times.16) bits are used to deliver the forward
channel status information in every 16 slots in the conventional
R-CQICH transmission method illustrated in FIG. 1, only 19
(=4+1.times.15) bits are used in the embodiment of the present
invention.
[0050] In FIG. 4, a single MS transmits forward channel status
information every 16 slots. If two or more MSs transmit forward
channel status information to the same BS, their absolute C/I
information transmissions occur at different times. Since
transmission of absolute C/I information requires greater power
than that of relative C/I information, concurrent transmission of
absolute C/Is from the MSs causes an instantaneous increase in
reverse interference. To prevent this problem, the absolute C/I
transmissions from the MSs are distributed uniformly across a
absolute C/I transmission period.
[0051] FIG. 5 is a block diagram of an R-CQICH transmitter using
three carriers according to the first embodiment of the present
invention. Referring to FIG. 5, three C/I measurers 501A, 501B, and
501C measure the C/Is of forward pilot channel signals received by
three carriers, respectively. An average calculator 503 calculates
an average of the three C/I measurements and a CQICH information
generator 504 generates 4-bit absolute C/I information or 1-bit
relative C/I information under the control of a CQICH transmission
controller (a CQICH Tx controller) 502. The CQICH Tx controller 502
determines whether to generate the absolute C/I or relative C/I
information according to the transmission period and transmission
time of the absolute C/I information selected between a BS and an
MS.
[0052] A block encoder 505 encodes the C/I information at a coding
rate of (n, k). The coding rate varies according to the number of
bits of the C/I information. For the 4-bit absolute C/I
information, the coding rate is (n, 4) and for the 1-bit relative
C/I information, the coding rate is (n, 1). Thus, the block encoder
505 selectively uses the two coding rates under the control of the
CQICH Tx controller 502.
[0053] A Walsh coverer 506 covers the n code symbols received from
the block encoder 505 with a Walsh code of length 8 determined
according to a 3-bit BSI. The BSI indicates a sector in the forward
channel status in an active set listing BSs communicating with the
MS.
[0054] A Walsh spreader 507 spreads the Walsh-covered sequence with
a Walsh code assigned to the R-CQICH. The Walsh-spread signal is
then transmitted to the active set BSs.
[0055] FIG. 6 is a block diagram of an R-CQICH receiver
corresponding to the R-CQICH transmitter illustrated in FIG. 5.
Referring to FIG. 6, a Walsh decoverer 601 decovers a
channel-compensated R-CQICH signal with a Walsh code assigned to
the BS. A block decoder 603 decodes the Walsh-decovered signal at a
coding rate of (n, 1) or (n, 4), thereby recovering C/I
information.
[0056] The coding rate is determined by a CQICH reception
controller (CQICH Rx controller) 602. The CQICH Rx controller 602
selects (n, 4) for a slot transmitting absolute C/I information,
and (n, 1) for a slot transmitting relative C/I information
according to the transmission period and transmission time of the
absolute C/I information selected with the R-CQICH transmitter. A
C/I memory 604 stores the recovered C/I information. If the C/I
information is 4-bit absolute C/I information, the C/I memory 604
discards the previous C/I information and is refreshed with the
absolute C/I information. If the C/I information is 1-bit relative
C/I information, the C/I memory 604 increases or decreases the
previous C/I information by a predetermined level according to the
relative C/I information. The increment or decrement is preset
between the MS and the BS before communication is initiated.
[0057] FIG. 7 is a flowchart illustrating an operation for
transmitting forward channel status information in the R-CQICH
transmitter illustrated in FIG. 5. Referring to FIG. 7, the C/I
measurers 501A, 501B, and 501C measure forward pilot channel C/Is
with respect to three carriers in step 701 and the average
calculator 503 calculates the average of the C/I measurements in
step 702. When averaging the C/I measurements, the MS must consider
whether the power of the forward pilot channel is the same on each
carrier, or different according to the carriers. In the former
case, the MS sums the C/I measurements and simply divides the sum
by the number of the carriers. However, in the latter case, the MS
must compensate the C/I measurements for power differences.
[0058] In step 703, the CQICH Tx controller 502 determines whether
to generate absolute C/I information or relative C/I information
using the average C/I. One of methods of making the determination
is to transmit a absolute C/I when the solution to the following
formula is 0, and a relative C/I when the solution is a value other
than 0.
(T-N-Mobile_Parameter)mod period (1)
[0059] where T is system time represented in the number of slots,
period is a absolute C/I transmission period, N is a time point
when a absolute C/I is transmitted in the transmission period,
Mobile_Parameter is an MS-specific value for distributing absolute
C/I transmissions from a plurality of MSs, and mod represents
modulo operation.
[0060] If the relative C/I information is to be transmitted, the
CQICH information generator 504 generates the relative C/I
information using the average C/I in step 704. To generate the
relative C/I information, the CQICH information generator 504
compares the average C/I of the previous slot with that of the
current slot. If the average C/I of the current slot is greater
than that of the previous slot, the 1-bit relative C/I information
is set to indicate C/I increase. Otherwise, it is set to indicate
C/I decrease. The block encoder 505 encodes the relative C/I
information at a coding rate of (n, 1) in step 705 and the n code
symbols are transmitted in step 708.
[0061] If the absolute C/I information is to be transmitted, the
CQICH information generator 504 generates the absolute C/I
information using the average C/I in step 706. To generate the
absolute C/I information, the CQICH information generator 504 maps
the average C/I to corresponding C/I information referring to Table
1. In Table 1, a4 is reserved and thus the other bits "a3, a2, a1,
a0" are selected as 4-bit absolute C/I information. The block
encoder 505 encodes the absolute C/I information at a coding rate
of (n, 4) in step 707 and the n code symbols are transmitted in
step 708.
[0062] FIG. 8 is a flowchart illustrating an operation for
receiving forward channel status information in the R-CQICH
receiver illustrated in FIG. 6. Referring to FIG. 8, the R-CQICH
receiver receives an R-CQICH signal from the R-CQICH transmitter
illustrated in FIG. 5 in step 801. After despreading, channel
compensation, and Walsh decovering, the CQICH Rx controller 602
determines whether the current slot of the R-CQICH contains
relative C/I information or absolute C/I information in step 802.
As stated before, when the solution to the above formula (Equation
1) is 0, the CQICH Rx controller 602 considers that absolute C/I
information has been received. If the solution is a value other
than 0, the CQICH Rx controller 602 considers that relative C/I
information has been received.
[0063] In the case of relative C/I information, the block decoder
603 decodes the R-CQICH signal at a coding rate of (n, 1) in step
803 and the C/I memory 604 updates stored average C/I of three
carriers according to the recovered 1-bit relative C/I information
in step 804. In the case of absolute C/I information, the block
decoder 603 decodes the R-CQICH signal at a coding rate of (n, 4)
in step 805 and the C/I memory 604 is refreshed with the absolute
C/I in step 806.
[0064] In step 807, the updated or refreshed forward average C/I is
used for forward packet data scheduling and determination of
transmission parameters such as a modulation scheme and a coding
rate.
[0065] Second Embodiment
[0066] In a second embodiment of the present invention, an MS
selects a carrier having the best forward channel status among a
plurality of carriers and measures the C/I of a forward pilot
channel with respect to the selected carrier.
[0067] FIG. 9 illustrates an R-CQICH slot format for 3xEV-DV
according to the second embodiment of the present invention. The
R-CQICH delivers carrier selection information indicating a carrier
in the best forward channel status (hereinafter, referred to as the
best carrier), and the C/I information of the forward pilot channel
with respect to the best carrier.
[0068] The MS selects the best of three carriers received from the
BS and transmits corresponding carrier selection information and
C/I information to the BS. The BS then transmits packet data on the
best carrier, thereby maximizing system capacity.
[0069] The carrier selection information is formed in 2 bits with
which 3 carriers can be identified, and transmitted with the C/I
information in each slot. The C/I information is 4-bit absolute C/I
information or 1-bit relative C/I information. The transmission
period and transmission time of the absolute C/I information are
selected between the MS and the BS.
[0070] In FIG. 9, a single MS transmits forward channel status
information every 16 slots. If two or more MSs transmit forward
channel status information to the same BS, their absolute C/I
information transmissions occur at different times. Since
transmission of absolute C/I information requires greater power
than that of relative C/I information, concurrent transmission of
absolute C/Is from the MSs causes an instantaneous increase in
reverse interference. To prevent this problem, the absolute C/I
transmissions from the MSs are distributed uniformly across a
absolute C/I transmission period.
[0071] FIG. 10 is a block diagram of an R-CQICH transmitter using
three carriers according to the second embodiment of the present
invention. Referring to FIG. 10, three C/I measurers 1001a, 1001b
and 1001c measure the C/Is of forward pilot channel signals
received by three carriers, respectively. A best C/I selector 1003
selects a maximum of the C/I measurements and a CQICH information
generator 1004 generates 2-bit carrier selection information and
one of 4-bit absolute C/I information and 1-bit relative C/I
information using the maximum C/I measurement under the control of
a CQICH Tx controller 1002. The CQICH Tx controller 1002 determines
whether to generate the absolute C/I or relative C/I information in
each slot.
[0072] If the absolute C/I information is to be transmitted, the
CQICH information generator 1004 outputs the 4-bit absolute C/I
information and the 2-bit carrier selection information. If the
relative C/I information is to be transmitted, the CQICH
information generator 1004 outputs the 1-bit relative C/I
information and the 2-bit carrier selection information. Mapping of
C/I information and carrier selection information to bits output
from the CQICH information generator 1004 is illustrated in Table 2
below.
2TABLE 2 C/I information for transmission Bits Absolute C/I
information Bits #0 and #1: carrier selection information Bits #2
to #5: absolute C/I information Relative C/I information Bits #0
and #1: carrier selection information Bit #2: relative C/I
information
[0073] A block encoder 1005 encodes the 6- or 3-bit CQICH
information at a coding rate of (n, k). The coding rate varies
according to the number of bits of the input CQICH information. For
the 4-bit absolute C/I information and the 2-bit carrier selection
information, the coding rate is (n, 6) and for the 1-bit relative
C/I information and the 2-bit carrier selection information, the
coding rate is (n, 3). Thus, the block encoder 1005 selectively
uses the two coding rates under the control of the CQICH Tx
controller 1002.
[0074] A Walsh coverer 1006 covers the n code symbols received from
the block encoder 1005 with a Walsh code of length 8 determined
according to a 3-bit BSI. The BSI indicates a sector in the forward
channel status in an active set listing BSs communicating with the
MS.
[0075] A Walsh spreader 1007 spreads the Walsh-covered sequence
with a Walsh code assigned to the R-CQICH. The Walsh-spread signal
is then transmitted to the active set BSs.
[0076] FIG. 11 is a block diagram of an R-CQICH receiver
corresponding to the R-CQICH transmitter illustrated in FIG. 10.
Referring to FIG. 11, a Walsh decoverer 1101 decovers a
channel-compensated R-CQICH signal with a Walsh code assigned to
the BS. A block decoder 1103 decodes the Walsh-decovered signal at
a coding rate of (n, 6) or (n, 3), thereby recovering C/I
information and carrier selection information.
[0077] The coding rate is determined by a CQICH Rx controller 1102.
The CQICH Rx controller 1102 selects (n, 6) for a slot transmitting
absolute C/I information and carrier selection information, and (n,
3) for a slot transmitting relative C/I information and carrier
selection information according to the transmission period and
transmission time of the absolute C/I information selected with the
R-CQICH transmitter. Mapping of bits output from the block decoder
1103 to C/I information and carrier selection information is
illustrated in Table 3 below.
3TABLE 3 Received information Decoded bits Absolute C/I information
Bits #0 and #1: carrier selection information Bits #2 to #5:
absolute C/I information Relative C/I information Bits #0 and #1:
carrier selection information Bit #2: relative C/I information
[0078] A C/I memory 1104 stores the recovered C/I information. If
the C/I information is 4-bit absolute C/I information, the C/I
memory 1104 discards the previous C/I information and is refreshed
with the absolute C/I information. If the C/I information is 1-bit
relative C/I information, the C/I memory 1104 increases or
decreases the previous C/I information by a predetermined level
according to the relative C/I information. The increment or
decrement is preset between the MS and the BS.
[0079] The recovered carrier selection information indicates a
carrier that the C/I information is about.
[0080] FIG. 12 is a flowchart illustrating an operation for
transmitting forward channel status information in the R-CQICH
transmitter illustrated in FIG. 10. Referring to FIG. 12, the C/I
measurers 1001a, 1001b, and 1001c measure forward pilot channel
C/Is with respect to three carriers in step 1201 and the best C/I
selector 1003 selects a maximum of the C/I measurements in step
1202. When selecting the maximum C/I measurement, the MS must
consider whether the power of the forward pilot channel is the same
on each carrier, or different according to the carriers. In the
former case, the MS simply selects the maximum C/I measurement.
However, in the latter case, the MS must compensate the C/I
measurements for power differences.
[0081] In step 1203, the CQICH Tx controller 1002 determines
whether to generate absolute C/I information or relative C/I
information using the maximum C/I. One of methods of making the
determination is to transmit a absolute C/I when the solution of
Eq. (1) is 0, and a relative C/I when the solution is a value other
than 0.
[0082] If the relative C/I information is to be transmitted, the
CQICH information generator 1004 generates the relative C/I
information using the maximum C/I in step 1204. To generate the
relative C/I information, the CQICH information generator 1004
compares the maximum C/I of the previous slot with that of the
current slot. If the maximum C/I of the current slot is greater
than that of the previous slot, the 1-bit relative C/I information
is set to indicate C/I increase. Otherwise, it is set to indicate
C/I decrease. The CQICH information generator 1004 also generates
2-bit carrier selection information corresponding to the ID of the
best carrier to indicate the best carrier in step 1204. The block
encoder 1005 encodes the 1-bit relative C/I information and the
2-bit carrier selection information at a coding rate of (n, 3) in
step 1205 and the n code symbols are transmitted to the BS in step
1208.
[0083] If the absolute C/I information is to be transmitted in step
1203, the CQICH information generator 1004 generates the absolute
C/I information using the maximum C/I in step 1206. To generate the
absolute C/I information, the CQICH information generator 1004 maps
the maximum C/I to corresponding C/I information referring to Table
1. In Table 1, a4 is reserved and thus the other bits "a3, a2, a1,
a0" are selected as 4-bit absolute C/I information. The CQICH
information generator 1004 also generates the 2-bit carrier
selection information corresponding to the ID of the best carrier
to indicate the best carrier in step 1206. The block encoder 1005
encodes the 4-bit absolute C/I information and the 2-bit carrier
selection information at a coding rate of (n, 6) in step 1207 and
the n code symbols are transmitted to the BS in step 1208.
[0084] FIG. 13 is a flowchart illustrating an operation for
receiving forward channel status information in the R-CQICH
receiver illustrated in FIG. 11. Referring to FIG. 13, the R-CQICH
receiver receives an R-CQICH signal from the R-CQICH transmitter
illustrated in FIG. 10 in step 1301. After despreading, channel
compensation, and Walsh decovering, the CQICH Rx controller 1102
determines whether the current slot of the R-CQICH contains
relative C/I information or absolute C/I information in step 1302.
As stated before, when the solution to Eq. (1) is 0, the CQICH Rx
controller 1102 determines that absolute C/I information has been
received. If the solution is a value other than 0, the CQICH Rx
controller 1102 determines that relative C/I information has been
received.
[0085] In the case of relative C/I information, the block decoder
1103 decodes the R-CQICH signal at a coding rate of (n, 3), thereby
recovering 1-bit relative C/I information and 2-bit carrier
selection information in step 1303. In step 1304, the C/I memory
1104 updates stored maximum of the C/I measurements of three
carriers in the previous slot according to the recovered 1-bit
relative C/I information in the current slot. Even if carrier
selection information received in the previous and current slots
indicates different carriers, the maximum C/I measurement stored in
the C/I memory 1104 is updated.
[0086] In the case of absolute C/I information, the block decoder
1103 decodes the R-CQICH signal at a coding rate of (n, 6),
recovering 4-bit absolute C/I information and 2-bit carrier
selection information in step 1305. The C/I memory 114 is refreshed
with the absolute C/I in step 1306. Even if carrier selection
information received in the previous and current slots indicates
differential carriers, the C/I memory 1104 is refreshed.
[0087] In accordance with the second embodiment of the present
invention, the C/I memory 1104 stores only the C/I measurement of
one carrier irrespective of the number of carriers.
[0088] In step 1307, the updated or refreshed forward maximum C/I
is used for forward packet data scheduling and determination of
transmission parameters such as a modulation scheme and a coding
rate.
[0089] Third Embodiment
[0090] In a third embodiment of the present invention, an MS
generates forward channel status information of a plurality of
carriers using the C/I measurement of a forward channel signal on
each of the carriers.
[0091] With the average C/I measurement of the carriers in
accordance with the first embodiment of the present invention, a BS
cannot optimize transmission parameters for each of the carriers in
different forward channel statuses. If the MS transmits the C/I
information of one carrier in the best forward channel status in
the second embodiment of the present invention, the BS cannot
determine the forward channel statuses of the other carriers except
the best carrier.
[0092] Therefore, the MS transmits the C/I information of each
carrier in the third embodiment of the present invention. The BS
then can determine how many carriers to be used and what
transmission parameters (modulation scheme and coding rate, etc.)
to be used for each carrier for transmission of packet data to the
MS.
[0093] FIG. 14 illustrates an R-CQICH slot format for 3xEV-DV
according to the third embodiment of the present invention. The
R-CQICH delivers the absolute C/I and relative C/I information of
the carriers. The absolute C/I information is transmitted in an
order predetermined between the MS and the BS, with power greater
than the relative C/I information, for example, twice as much
power.
[0094] The absolute C/I information of the carriers is transmitted
in different slots. Otherwise, the MS must use a large amount of
transmission power. The resulting increase in its peak-to-average
power ratio may cause a malfunction of a power amplifier in the MS.
To prevent this problem, the absolute C/I information is arranged
in different slots, #0, #5, and #10.
[0095] The distributed absolute C/I transmission is possible by
maintaining a predetermined interval between the absolute C/I
transmission periods. For example, if the transmission period of
the absolute C/I information is 16 slots and three carriers are
used, 5 slots is a desirable absolute C/I transmission interval. If
the transmission interval is 1 slot, the MS successively transmits
the absolute C/I measurements of the carriers.
[0096] Let the number of carriers transmitted from the BS be
Num_Carrier, the transmission period of the absolute C/I of each
carrier be tx_period, and the transmission interval between the
absolute C/I measurements be tx_interval. Then, 1 tx_interval
tx_period - 1 Num_Carrier - 1 ( 2 )
[0097] where tx_interval represents the transmission interval
between the absolute C/I measurements of carrier 1 and carrier 2
and between the absolute C/I measurements of carrier 2 and carrier
3. tx_period, tx_interval, and Num_Carrier are positive integers,
and tx_period and tx_interval are represented in the number of
slots.
[0098] If Num_Carrier is 3 and tx_period is 16, tx_interval is
between 1 and 7. If tx_interval is 7, the MS transmits the absolute
C/Is of carriers 1, 2, and 3 in Nth, (N+7)th, and (N+14)th slots,
respectively. In an (N+16)th slot, the MS transmits the absolute
C/I of carrier 1.
[0099] In FIG. 14, a single MS transmits forward channel status
information in 16 slots. If two or more MSs transmit forward
channel status information to the same BS, their absolute C/I
information transmissions occur at different times. Since
transmission of absolute C/I information requires greater power
than that of relative C/I information, concurrent transmission of
absolute C/Is from the MSs causes an instantaneous increase in
reverse interference. To prevent this problem, the absolute C/I
transmissions from the MSs are distributed uniformly across a
absolute C/I transmission period.
[0100] Consequently, the MS must transmit the absolute C/I
information of the carriers in a different time period from that
from other MSs. It also must transmit the absolute C/I information
of the carriers in different time periods.
[0101] FIG. 15 illustrates R-CQICH slot formats when a plurality of
MSs transmit forward channel status information simultaneously.
Here, the transmission interval tx_interval between the absolute
C/I measurements of three carriers is 5 slots and the transmission
period tx_period of the absolute C/I of a particular carrier is 16
slots.
[0102] Referring to FIG. 15, each MS transmits absolute C/I
measurements in different time periods from the other MSs. The
absolute C/I measurements are arranged at intervals of 5 slots
across the transmission period of 16 slots.
[0103] To determine a way a plurality of MSs transmit forward
channel status information simultaneously, two transmission
parameters are required. One parameter is the transmission interval
tx_interval between the absolute C/I measurements of multi-carrier
in each MS. The transmission interval tx_interval is achieved by
Eq. (2). The other parameter is a time point N within the absolute
C/I transmission period, when the absolute C/I of a particular
carrier is transmitted. One of methods of determining N is to
transmit the absolute C/I when the solution to the following
formula is 0.
(T-N-Mobile_Parameter-(carrier_is-1).times.tx_period)mod tx_period
(3)
[0104] where T is system time represented in the number of slots,
tx_period is the absolute C/I transmission period of the same
carrier, N is a time point when a absolute C/I measurement is
transmitted in a corresponding absolute C/I transmission period,
and carrier_id is an identifier being a natural number starting
from 1 to identify a carrier. tx_interval is the transmission
interval between the absolute C/I measurements of the carriers, as
determined by Eq. (2). If the solution to Eq. (3) is 0, the MS
transmits the absolute C/I of a carrier corresponding to
carrier_id.
[0105] While Eq. (2) is used to avoid overlap in transmission time
between the absolute C/I measurements of carriers in an MS, Eq. (3)
is used to avoid overlap in absolute C/I transmissions from a
plurality of MSs.
[0106] FIG. 16 is a block diagram of an R-CQICH transmitter using
three carriers according to the third embodiment of the present
invention. Referring to FIG. 16, three C/I measurers 1601a, 1601b,
and 1601c measure the C/Is of forward pilot channel signals
received by three carriers, respectively and provide the C/I
measurements to corresponding CQICH information generators 1603A,
1603B, and 1603C. The CQICH information generators 1603A, 1603B,
and 1603C generate absolute C/I information or relative C/I
information using the received C/I measurements under the control
of a CQICH Tx controller 1602. The CQICH Tx controller 1602
determines whether to generate the absolute C/I or relative C/I
information in the CQICH information generators 1603A, 1603B, and
1603C. A multiplexer (MUX) 1604 multiplexes in time division the
C/I information received from the CQICH information generators
1603A, 1603B, and 1603C.
[0107] If absolute C/I information is to be transmitted, a
corresponding CQICH information generator outputs 4-bit absolute
C/I information. If relative C/I information is to be transmitted,
the CQICH information generator outputs 1-bit relative C/I
information.
[0108] Since absolute C/I transmissions for the three carriers are
distributed, the total bit number of outputs of the CQICH
information generators 1603A, 1603B, and 1603C is 6 when one of
them outputs absolute C/I information, and 3 when all of them
output relative C/I information. Mapping of C/I information to the
output of the MUX 1604 is illustrated in Table 4 below.
4TABLE 4 C/I information for transmission Bits Absolute C/I
information for Bits #0 to #3: absolute C/I information carrier 1
for carrier 1 Bit #4: relative C/I information for carrier 2 Bit
#5: relative C/I information for carrier 3 Absolute C/I information
for Bit #0: relative C/I information for carrier 2 carrier 1 Bits
#1 to #4: absolute C/I information for carrier 2 Bit #5: relative
C/I information for carrier 3 Absolute C/I information for Bit #0:
relative C/I information for carrier 3 carrier 1 Bit #1: relative
C/I information for carrier 2 Bits #2 to #5: absolute C/I
information for carrier 3 Relative C/I information for Bit #0:
relative C/I information for carriers 1, 2, and 3 carrier 1 Bit #1:
relative C/I information for carrier 2 Bit #2: relative C/I
information for carrier 3
[0109] A block encoder 1605 encodes the 6- or 3-bit multiplexed
CQICH information at a coding rate of (n, k). The coding rate
varies according to the number of bits of the input CQICH
information. For the 4-bit absolute C/I information and the 2-bit
relative C/I information, the coding rate is (n, 6) and for the
3-bit relative C/I information, the coding rate is (n, 3). The
CQICH Tx controller 1602 determines whether to transmit absolute
C/I information or relative C/I information for each carrier by Eq.
(2) and Eq. (3) and determines the coding rate correspondingly.
[0110] A Walsh coverer 1606 covers the n code symbols received from
the block encoder 1605 with a Walsh code of length 8 determined
according to a 3-bit BSI. A Walsh spreader 1607 spreads the
Walsh-covered sequence with a Walsh code assigned to the R-CQICH.
The Walsh-spread signal is then transmitted to the active set
BSs.
[0111] FIG. 17 is a block diagram of an R-CQICH receiver
corresponding to the R-CQICH transmitter illustrated in FIG. 16.
Referring to FIG. 17, a Walsh decoverer 1701 decovers a
channel-compensated R-CQICH signal with a Walsh code assigned to
the BS. A block decoder 1703 decodes the Walsh-decovered signal at
a coding rate of (n, 6) or (n, 3), thereby recovering C/I
information. The coding rate is determined by a CQICH Rx controller
1702. The CQICH Rx controller 1702 selects (n, 6) for a slot
transmitting 4-bit absolute C/I information and 2-bit relative C/I
information, and (n, 3) for a slot transmitting 3-bit relative C/I
information according to Eq. (2) and Eq. (3). Mapping of decoded
bits to C/I information is illustrated in Table 5 below.
5TABLE 5 Received C/I information Decoded bits Absolute C/I
information for Bits #0 to #3: absolute C/I information carrier 1
for carrier 1 Bit #4: relative C/I information for carrier 2 Bit
#5: relative C/I information for carrier 3 Absolute C/I information
for Bit #0: relative C/I information for carrier 2 carrier 1 Bits
#1 to #4: absolute C/I information for carrier 2 Bit #5: relative
C/I information for carrier 3 Absolute C/I information for Bit #0:
relative C/I information for carrier 3 carrier 1 Bit #1: relative
C/I information for carrier 2 Bit #2 to #5: absolute C/I
information for carrier 3 relative C/I information for Bit #0:
relative C/I information for carriers 1, 2, and 3 carrier 1 Bit #1:
relative C/I information for carrier 2 Bit #2: relative C/I
information for carrier 3
[0112] A demultiplexer (DEMUX) 1704 demultiplexes the decoded bits
and provides CQICH information for carriers 1, 2, and 3 to C/I
memories 1705a, 1705b, and 1705c, respectively. The C/I memories
1705a, 1705b and 1705c store the demultiplexed C/I information of
the carriers respectively.
[0113] If received CQICH information is 4-bit absolute C/I
information, a corresponding C/I memory discards the previous C/I
information stored therein and is refreshed with the absolute C/I
information. If the CQICH information is relative C/I information,
the C/I memory increases or decreases the previous C/I measurement
by a predetermined level according to the relative C/I information.
The increment or decrement is preset between the MS and the BS.
[0114] FIG. 18 is a flowchart illustrating an operation for
transmitting forward channel status information in the R-CQICH
transmitter illustrated in FIG. 16. Referring to FIG. 18, the C/I
measurers 1601a, 1601b, and 1601c measure forward pilot channel
C/Is with respect to three carriers in step 1801. The CQICH Tx
controller 1602 determines whether to transmit absolute C/I
information or relative C/I information for each carrier by Eq. (2)
and Eq. (3) in step 1802. Eq. (2) determines the transmission
interval between absolute C/I measurements for the carriers and
when the solution to Eq. (3) is 0, absolute C/I information for a
corresponding carrier and relative C/I information for the other
carriers are transmitted.
[0115] If relative C/I information is to be transmitted for the
three carriers, the CQICH information generators 1603A, 1603B, and
1603C generate the relative C/I information using their received
C/I measurements in step 1803. To generate the relative C/I
information, each of the CQICH information generators 1603A, 1603B,
and 1603C compares the C/I measurement of the previous slot with
that of the current slot for a corresponding carrier. If the C/I
measurement of the current slot is greater than that of the
previous slot, the 1-bit relative C/I information is set to
indicate C/I increase. Otherwise, it is set to indicate C/I
decrease. Consequently, 3-bit differential information is output
from the CQICH information generators 1603A, 1603B, and 1603C. The
block encoder 1605 encodes the 3-bit relative C/I information at a
coding rate of (n, 3) in step 1804 and the n code symbols are
transmitted to the BS in step 1807.
[0116] If absolute C/I information is to be transmitted for one of
the three carriers and differential information is to be
transmitted for the other carriers, a CQICH information generator
for the carrier of the absolute C/I information, for example, the
CQICH information generator 1603A generates 4-bit absolute C/I
information by selecting 4-bit C/I information mapped to its
received C/I measurement referring to Table 0.1. In Table 1, a4 is
reserved and thus the other bits "a3, a2, a1, a0" are selected as
4-bit absolute C/I information in step 1805. The CQICH information
generators 1603B and 1603C each generate 2-bit C/I information for
the other carriers in step 1805.
[0117] The block encoder 1605 encodes the 6-bit C/I information at
a coding rate of (n, 6) in step 1806 and the n code symbols are
transmitted to the BS in step 1807.
[0118] In accordance with the third embodiment of the present
invention, the sequence of transmitting C/I information on the
R-CQICH is determined according to the mapping relation illustrated
in Table 4. For example, if absolute C/I information is transmitted
for carrier 1 and relative C/I information is transmitted for
carriers 2 and 3, the MS arranges the absolute C/I for carrier 1 in
bits #0 to #3, the relative C/I for carrier 2 in bit #4, and the
relative C/I for carrier 3 in bit #5.
[0119] FIG. 19 is a flowchart illustrating an operation for
receiving forward channel status information in the R-CQICH
receiver illustrated in FIG. 17. Referring to FIG. 19, the R-CQICH
receiver receives an R-CQICH signal from the R-CQICH transmitter
illustrated in FIG. 16 in step 1901. After despreading, channel
compensation, and Walsh decovering, the CQICH Rx controller 1702
determines whether the current slot of the R-CQICH contains
absolute C/I and relative C/I information or only relative C/I
information in step 1902. As stated above, when the solution to Eq.
(3) is 0, the CQICH Rx controller 1702 determines that absolute C/I
information for a particular carrier and relative C/I information
for the other carriers have been received. If the solution is a
value other than 0, the CQICH Rx controller 1702 determines that
relative C/I information has been received for all the three
carriers.
[0120] In the case of relative C/I information for the three
carriers, the block decoder 1703 decodes the R-CQICH signal at a
coding rate of (n, 3), thereby recovering 3-bit relative C/I
information in step 1903.
[0121] In step 1904, the C/I memory 1705a updates the C/I
measurement of the previous slot for carrier 1 stored therein
according to the recovered 1-bit relative C/I information for
carrier 1 in the current slot, the C/I memory 1705b updates the C/I
measurement of the previous slot for carrier 2 stored therein
according to the recovered 1-bit relative C/I information for
carrier 2 in the current slot, and the C/I memory 1705c updates the
C/I measurement of the previous slot for carrier 3 stored therein
according to the recovered 1-bit relative C/I information for
carrier 3 in the current slot.
[0122] In the case of absolute C/I information for one of the three
carriers and relative C/I information for the other carriers, the
block decoder 1703 decodes the R-CQICH signal at a coding rate of
(n, 6), recovering 4-bit absolute C/I information and 2-bit
relative C/I information in step 1905. In step 1906, a C/I memory
for the carrier corresponding to the absolute C/I information, for
example, the C/I memory 1705a is refreshed with the absolute C/I,
and the C/I memories 1705b and 1705c update the C/I measurements of
the previous slot stored therein according to the relative C/I
information in the current slot.
[0123] The recovered C/I information is mapped to corresponding C/I
information for the carriers according to Table 5. For example, if
absolute C/I information for carrier 2 and relative C/I information
for carriers 1 and 3 are received, the BS concludes that bit #0
indicates the relative C/I information for carrier 1, bits #1 to #4
indicate the absolute C/I information for carrier 2, and bit #5
indicates the relative C/I information for carrier 3.
[0124] In step 1907, the updated or refreshed C/I information for
the three carriers is used for forward packet data scheduling and
determination of transmission parameters such as a modulation
scheme and a coding rate.
[0125] In accordance with the present invention as described above,
an MS measures the forward channel status of each of carriers and
reports the forward channel statuses to a BS in a multi-carrier
mobile communication system. Thus, the BS transmits forward packet
data according to the forward channel status information. The MS
transmits absolute C/I information for each carrier in a
predetermined slot and relative C/I information for the other
carriers in the other slots. Consequently, reverse transmission
capacity is significantly increased.
[0126] While the invention has been shown and described with
reference to certain preferred embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the invention as defined by the appended claims.
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