Apparatus, and associated method, for effectuating power control to maintain desired QoS levels in the performance of a communication service

Apparatus, and an associated method, for initiating gain control in a radio communication system. Determinations are made as to a required range of gains at which gain elements of a transmitter must be operated to ensure that a communication service is performed at a selected QoS level. The range of channel gains is sent pursuant to service negotiations as part of an offered gain message. Gain control is effectuated therefrom.

FIELD OF THE INVENTION 
The present invention relates generally to performance of a communication 
service at a desired QoS (quality of service) level in a cellular, or 
other radio, communication system. More particularly, the present 
invention relates to apparatus, and an associated method, to effectuate 
power control in the radio communication system to ensure the performance 
of the communication service at the desired QoS level. Appropriate gain 
levels by which to amplify signals to be transmitted to effectuate the 
communication system at the desired QoS level are determined and requested 
pursuant to service request negotiations in the form of an offered gain 
request by a transmitting station. 
BACKGROUND OF THE INVENTION 
A communication system permits the communication of information between two 
or more communication stations. The communication stations are connected 
by a communication channel upon which a communication signal is 
transmitted. The communication signal includes the information which is to 
be communicated between the communication stations. In a two-way 
communication system, a communication station includes both a transmitter 
portion and a receiver portion operable to transmit and to receive, 
respectively, communication signals. 
A radio communication system is a communication system in which the 
communication channel formed between the communication stations is a radio 
channel defined upon a portion of the electromagnetic spectrum. When a 
communication station operable in such a communication system includes 
both a transmitter portion and a receiver portion, the communication 
station forms a radio transceiver, capable of two-way, radio communication 
with another communication station. Because communication signals can be 
transmitted between radio transceivers on radio channels, wire line 
connections are not required to effectuate communications in a radio 
communication system. Thereby, communications are possible by way of a 
radio communication system when formation of a wire line connection 
between the communication stations would be impractical. 
A cellular communication system is an exemplary radio communication system. 
Cellular communication systems, constructed according to various 
standards, have been installed throughout significant portions of the 
world. A subscriber to a cellular communication system is able to 
communicate telephonically by way of a radio transceiver, typically 
referred to as a mobile station, when the mobile station is positioned 
within an area encompassed by the communication system. Telephonic 
communication of both voice information and data information is permitted 
in such networks. 
Advancements in digital communication techniques have facilitated the 
implementation of new cellular, and other, communication systems capable 
of communicating increased amounts, and types, of data. For instance, a 
proposed cellular communication system set forth in the specification of a 
CDMA2000 standard provides for the performance of multi-media 
communication services. Multi-media communications pertain, generally, to 
the communication of two, or more, separate types of information, such as 
voice and data information. 
QoS (quality of service) level parameters are defined in the specification 
of the proposed CDMA2000 standard. QoS level parameters are analogously 
also defined in standards pertaining to other cellular communication 
systems. QoS level parameters define standards by which to measure, or 
ensure, minimum communication quality levels. A QoS level parameter can be 
used in service initiation and service modification. A QoS level parameter 
can be used during service negotiations in the initiation of performance 
of a communication service as well as to modify service levels during 
performance of a communication service. A QoS level parameter defines a 
communication service in terms, e.g., bit-error rates, service delays, as 
well as other types of performance measures. Performance of a 
communication service at a level at least corresponding to a selected 
performance measure by which a QoS level parameter is defined ensures that 
the communication service is performed at a communication quality level 
associated therewith. The QoS level parameter, therefore, is a 
quantifiable parameter associated with a communication quality level. 
Different communication services might necessitate different levels of 
communication qualities to ensure their performance. And, different 
subscribers to a communication system might be willing to subscribe to 
different levels of service. For instance, one subscriber might require 
that a communication service be performed at a greater data transmission 
rate than another subscriber. A subscription for service at a QoS level 
ensuring performance of the communication service at the greater 
transmission rate can be selected to meet the requirements of the 
subscriber. 
The amount of gain applied to a communication signal at a transmitter 
portion of a communication station is, in part, determinative of a 
performance measure associated with a QoS level parameter. To ensure that 
a communication service is performed at a selected QoS level, the gain by 
which the communication signal transmitted to perform such communication 
service must be selected to be at least great enough to perform the 
communication service at the desired QoS level. However, the level of gain 
at which a communication signal is transmitted in a CDMA (code-division 
multiple-access) communication system cannot merely be increased without 
constraint. A communication signal of an inordinately high level of gain 
interferes with concurrently-generated communication signals by other 
communication stations operable in the CDMA communication system. 
Permitted levels of gain by which a communication station can amplify a 
communication signal must therefore be controlled. In the proposed 
CDMA2000 communication system, the gain is selected pursuant to service 
negotiation. That is to say, control apparatus of the proposed CDMA2000 
system controls whether a request to perform a communication service at a 
desired QoS level shall be permitted. 
While channel gains associated with dedicated data channels are defined in 
CDMA2000 standard proposals, a manner by which to use feedback power 
control to adjust the levels of gain has not been set forth. A manner by 
which to effectuate power control by which to control the levels of gain 
by which communication signals are amplified would advantageously improve 
system efficiency. 
It is in light of this background information related to communications in 
a radio communication system that the significant improvements of the 
present invention have evolved. 
SUMMARY OF THE INVENTION 
The present invention, accordingly, advantageously provides an apparatus, 
and an associated method, by which at least to initiate effectuation of 
power control at a radio transceiver. Effectuation of power control 
ensures that appropriate QoS (quality of service) levels are maintained 
pursuant to performance of a communication service. 
Determinations are made of a range of gain levels by which communication 
signals must be amplified to ensure performance of a communication 
service, such as performance of a multi-media application, at a selected 
QoS level. During service negotiation procedures in which service is 
requested to perform the communication service, indications of the range 
of gain levels are used in the determination of whether to grant 
permission to perform the communication service and to allocate 
appropriate levels of communication system resources to perform the 
communication service. 
In one implementation, the range of gain levels by which signals to be 
transmitted on various channels by a mobile station are determined at the 
mobile station, either by calculations performed at the mobile station, or 
by external inputs thereto, such as by way of a user interface. 
Indications of the range of gain levels is transmitted to network 
infrastructure of the communication system subsequent to a channel request 
message sent to the network infrastructure. In one implementation, the 
message transmitted to the network infrastructure forms part of an offered 
gain request, sent to the network infrastructure during service 
negotiations subsequent to transmission of the channel request. 
In a further implementation, determinations are made at the network 
infrastructure to determine whether to grant access to the mobile station 
to the communication system to perform the communication service 
therethrough. When service is granted, system resources are allocated to 
permit the performance of the communication service. Signals generated by 
the network infrastructure and transmitted to the mobile station control 
the levels of gain by which the communication signals generated by the 
mobile station are amplified. 
In one implementation, closed-loop gain control is effectuated and the 
network infrastructure transmits to the mobile station channel gain 
messages to adjust channel gain, as appropriate, during performance of the 
communication service. 
In another implementation, the mobile station is instructed in manners by 
which to operate responsive to the network infrastructure transmission of 
NAK (no acknowledgement) indications responsive to generation by the 
mobile station of RLP (radio link protocol) data frames, formatted in 
conventional manner of the RLP. The mobile station is provided, either as 
a user-specific message, or as a system parameter, an NAK interval, an NAK 
limit, and a QoS step value. Responsive to such values, the mobile station 
determines in what manner to adjust levels of gain of amplifier circuitry 
of the mobile station. For instance, the mobile station counts NAK 
indications during the interval defined by the NAK interval value, and, 
when the count exceeds the NAK limit value, the level of gain is stepped, 
up or down, according to the step size of the QoS step value. 
A manner is thereby provided by which to ensure that the gain levels at 
which communication signals are generated to perform a communication 
service are great enough to perform the communication service at a 
selected QoS level. If, during performance of the communication service, 
signal conditions warrant a reduction in the gain level, the gain levels 
are appropriately altered. Thereby, system capacity can be better 
utilized. 
In these and other aspects, therefore, the present invention provides 
apparatus, and an associated method, for initiating effectuation of power 
control of signals generated by a radio device operable in a communication 
system to perform a communication service. Signals generated by the radio 
device are transmitted upon a radio channel to a receiving station to 
perform the communication service. A channel gain range determiner is 
coupled at least to receive indications of the communication service to be 
performed by the radio device. The channel gain range determiner 
determines a range of channel gains within which signal levels of the 
signals generated by the radio device permit performance of the 
communication service. A message generator is coupled to receive 
determinations of the channel gain range determiner. The message generator 
generates a message for transmission to the receiving station requesting 
allocation of channel capacity upon the radio channel to transmit signals 
upon the radio channel to perform the communication service. 
A more complete appreciation of the present invention and to the scope 
thereof can be obtained from the accompanying drawings which are briefly 
summarized below, the following detailed description of the 
presently-preferred embodiments of the present invention, and the appended 
Claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1, a portion of a cellular communication system, 
shown generally at 10, is installed throughout a geographical area. The 
network infrastructure of the cellular communication system provides for 
wireless communications with mobile stations, of which an exemplary mobile 
station 12 is shown in the Figure. 
The system 10 includes a plurality of spaced-apart radio base stations 14 
which are positioned at spaced locations throughout the geographical area 
to be encompassed by the communication system. In the implementation shown 
in the figure, sets of three radio base stations are co-located. Each base 
station 14 defines a cell, and the cells 16 together collectively cover 
the area encompassed by the communication system. In the exemplary 
implementation in which sets of three base stations are co-located, each 
radio base station defines a sector cell in conventional manner. 
Groups of the radio base stations 14 are coupled to a BSC (base station 
controller) 18. A BSC is operable to control operation of radio base 
stations coupled thereto. Groups of BSCs 18, in turn, are coupled to an 
MSC (mobile switching center) 22. An MSC is operable, amongst other 
things, to perform switching operations. The MSC is coupled to a PSTN 
(public-switched telephonic network) 24. And, the PSTN is coupled to 
communication stations, such as the communication station 28. 
The apparatus forming the network infrastructure, its operation, and the 
operation of the mobile stations 12 operable therein, conform with a 
cellular standard. An exemplary implementation of an embodiment of the 
present invention shall be described with respect to a proposed CDMA2000 
cellular standard proposed as a 3G (third generation) cellular 
communication system standard. It should be understood, however, that in 
alternative implementations, an embodiment of the present invention is 
similarly operable in other types of cellular, as well as other radio, 
communication systems. 
Various types of communication services are proposed to be provided for in 
a CDMA2000 cellular communication system. Multi-media communication 
services, for instance, are provided for in such a system. QoS (quality of 
service) level parameters are also defined in the proposed CDMA2000 
system. QoS level parameters are representative of performance measures of 
communication of signals in the communication system. Performance measures 
include, for instance, target bit rates, bit-error rates (BERs), service 
delays or any of various other parameters. When communication services are 
performed at a particular QoS level, the communication service is 
effectuated at a quality level at least as good as the performance 
measures associated with the QoS level. Proposals have been made to permit 
subscribers to the communication system to subscribe for service at a 
particular QoS level for a particular subscription rate. The subscription 
rate would, for instance, be related to the QoS level pursuant to which 
subscription is made. And, subscription could be made for different levels 
of QoS for different services. That is to say, subscription could be made 
for voice service at a first QoS level, and a different QoS level for a 
type of data service. 
The following description shall be described with respect to a QoS level 
which is defined in terms of minimum BER (bit error rate) performance. BER 
is measured in terms of any of various terms. For instance, BER can be 
measured in terms of a physical layer BER, an effective BER due to 
automatic repeat requests (ARQ) schemes, or effective receive E.sub.b 
/N.sub.o for a particular service. By maintaining a target received 
E.sub.b /N.sub.o using power control as described below, an effective BER 
may be maintained using existing ARQ protocols. 
FIG. 2 illustrates a mobile station 12 operable pursuant to an embodiment 
of the present invention. The mobile station 12 receives forward-link 
signals transmitted thereto by a radio base station and generates 
reverse-link signals for transmission to a radio base station. Two-way 
communication is thereby effectuated by way of the mobile station to 
perform communication services, such as multi-media applications. 
The mobile station 12 includes a transmit portion having an information 
source 34 at which information to be transmitted is generated. The 
information is provided to an encoder 36 which is operable to encode the 
information provided thereto according to an encoding scheme. The encoder 
provides encoded signals to a modulator 38 which is operable to modulate 
the encoded signals provided thereto and to provide modulated signals, 
once converted into analog form by a digital-to-analog converter (DAC) 40, 
to a VGA (variable gain amplifier) 42. The VGA is operable to amplify the 
modulated signals provided thereto at a selected level of gain and to 
provide amplified signals to an up-converter 44. The up-converter is 
operable to up-convert in frequency the signals provided thereto to be of 
a transmission frequency. Up-converted signals generated by the 
up-converter 44 are then amplified by a power amplifier 46. The amplified 
signals are then applied to an antenna transducer 48 to be transduced 
thereat into electromagnetic form. 
The receive portion of the mobile station includes a down-converter 52 
coupled to the antenna transducer 48. Forward-link signals detected by the 
antenna transducer 48 are converted into electrical form and provided to 
the down-converter. The down-converter is operable to down-convert in 
frequency the signal provided thereto and to provide down-converted to an 
I/Q demodulator 54. The demodulator generates the demodulated signals 
which are provided to an A/D (analog-to-digital) converter 56 to convert 
the signals into digital form. Digitized signals are provided to a rake 
receiver 58 which detects multi-path representations of the same symbols 
and combines such detected symbols. The signals formed by the rake 
receiver 58 are provided to a decoder 62 which decodes the signals into 
decoded form and provides such decoded signals to an information sink 64. 
The mobile station 12 further includes a controller 68 operable pursuant to 
an embodiment of the present invention. In addition to conventional 
control functions performed by control circuitry of the mobile station, 
the controller 68 is here also operable to initiate and to effectuate gain 
control to ensure that communications services performed by the mobile 
station are effectuated at an appropriate QoS level. With respect to a QoS 
level parameter of a BER, the level of gain at which a signal is amplified 
is related to the related BER of the transmitted signals. Various elements 
of the controller are shown as functional blocks. When the controller is 
implemented as a processing device having algorithms executable therein, 
various functions performed by various of the functional blocks are 
effectuated by algorithms executed by the processing device. 
The controller 68 is coupled to a user interface 72 to receive 
user-generated inputs. Inputs generated by way of the user interface are 
provided, amongst other places, to a channel gain range determiner 74 
which functionally forms a portion of the controller. Here, the determiner 
is coupled to receive indications of a communication service which is to 
be performed by the mobile station. The channel gain range determiner is 
operable to determine a range of channel gains within which communication 
signals generated pursuant to a communication service must be amplified to 
ensure that an appropriate level of QoS is maintained during effectuation 
of the communication service. The range of channel gains includes a lower 
boundary value of a channel gain value beneath which maintenance of a 
selected QoS cannot be ensured. 
While various factors are determinative of the lower boundary value, 
including levels of network loading and service rate negotiations, the 
architecture, viz., the components, of the mobile station form critical 
factors as the architecture of the base band components of a mobile 
station typically supports only a limited dynamic range of signal values. 
For instance, a digital to analog converter, such as the DAC 40 shown in 
the Figure, is of a limited dynamic range. Due to pulse shaping and 
emission requirements, signals applied to the DAC 40 must be scaled to 
"fit" the various channels, i.e., signals, into the dynamic range of the 
DAC. Truncation of signals may also be employed, however, with a resultant 
spectral distortion. The RF front-end of a mobile station is also 
sometimes a critical factor in the level of achievable E.sub.b /N.sub.o 
for a particular channel. An analysis of whether the mobile can meet its 
emissions and wave form quality requirements given a particular bearer 
service profile is based, for instance, upon the number of bits assigned 
by a mobile station to a particular channel to implement the channel gain. 
The quantity of the number of bits assigned to a particular channel may 
include implementation of a pulse-shaping filter. Assuming that a mobile, 
during a particular instance in time, assigns a maximum of B bits to a 
particular channel the effective SNR (signal-to-noise ratio) of the 
channel due to quantization error can range anywhere from very low to a 
maximum achievable SNR using B bits. Although B bits have been allocated 
by the mobile to a particular physical channel, there is an effective 
range of SNR in practice as the mobile station may allocate less than this 
number at any time due to QoS constraints. 
Assuming that the quantization noise variants may be represented as 
.sigma..sub.q.sup.2, such noise can be treated as an additional source of 
white noise. If the power at a base station receiver is I.sub.orx 
I.sub.oc, and the processing gain is P.sub.g and the individual physical 
channel chip-to-power ratio is designated as CHAN E.sub.o /I.sub.or, then 
the effective E.sub.b /N.sub.o is represented as: 
##EQU1## 
By defining a received pilot E.sub.b /N.sub.o as (E.sub.b /N.sub.o).sub.PI, 
the value can be represented in terms of G.sub.chan as follows: 
##EQU2## 
A typical DAC, such as the DAC 40, utilized by mobile stations is 
preferably operated by providing uniformly-spaced, output voltage levels 
according to uniformly-spaced input levels based upon the number of bits 
driving the DAC. Analysis of the quantization noise can be made by 
modeling the data flowing over a physical channel, after spreading impulse 
shaping, to be Gaussian. An effective QoS range offered by the mobile 
station is determined in terms of deviation from E.sub.b /N.sub.o on a 
pilot channel. For instance, the minimum normalized quantization noise 
variance for a Gaussian random process is 0.3634, 0.1188, 0.03744, and 
0.01154 for 1, 2, 3 and 4 bits, respectively, of a uniform quantizer. The 
corresponding deviation from G.sub.chan -adjusted E.sub.b /N.sub.o is 
1.346, 0.487, 0.159, and 0.049 dB respectively. Assuming that at least 
three bits are allocated to a particular channel, then the quantization 
noise degradation is less than 0.2 dB. An acceptable range for G.sub.chan 
is obtained such that the QoS range is maximized under the constraints of 
the DAC. In a pedagogical, two-channel example, tradeoffs are shown to be 
evident in the determination of the acceptable range. A pilot channel and 
another channel designated as C, forming a fundamental, supplemental, or 
control channel, are the two channels of the exemplary two-channel 
example. Assuming that the DAC has D bits of useable linear range and that 
the pilot channel has allocated P bits by the mobile station, that the 
minimum number of bits allocated by the mobile station to the channel C is 
C.sub.b and C.sub.b is less than D and P is less than C.sub.b, then the 
following equation applies: 
##EQU3## 
In the above equation, when D=8, P=3, and C.sub.b =5, the maximum value of 
G.sub.c is 7.75. Therefore, as much as 17.78 dB of gain may be added to 
the channel C over the minimum gain. 
The aforementioned manner of determining channel gain is exemplary, and, in 
other implementations, the channel gain range is determined in other 
manners. Indications of the channel gain range determined by the 
determiner 74 are provided to an offered gain message generator 76. The 
offered gain message generator is operable to generate an offered gain 
message including information of the determinations made by the channel 
gain range determiner 74. Messages generated by the generator are provided 
by way a line 78 which is connected to the transmit portion of the mobile 
station. In conventional manner, the message is interleaved or otherwise 
formatted in a selected manner and then modulated by the modulator 38. The 
offered gain message is transmitted by the mobile station during service 
negotiations by which mobile station requests service, that is, allocation 
of a supplemental channel, to perform a communication service. The network 
infrastructure decides whether to grant service to the mobile station and 
to allocate the appropriate amount of channel resources to permit 
effectuation of the communication service at the selected QoS level. 
When the network infrastructure grants service to the mobile station to 
perform the communication service, a service grant message is broadcast as 
a forward-link signal which is detected by the antenna transducer 48 and 
processed by the receive portion of the mobile station. A channel gain 
message is also broadcast by the network infrastructure indicating to the 
mobile station at what gain level signals generated by the mobile station 
are to be amplified to perform the communication service. A channel gain 
message detector 82 is coupled to the receive portion of the mobile 
station. The detector 82 is operable to detect indications of the channel 
gain message received at the mobile station 12 and processed by the 
receive portion thereof. 
Indications detected by the channel gain message detector 82 are provided 
to a gain controller 84. The gain controller is operable to control the 
amplification levels at which the VGA 42 amplifies signals applied 
thereto. Thereby, close-loop gain control is effectuated to control the 
gain levels at which signals are generated at the mobile station to 
perform a communication service while ensuring that an appropriate level 
of QoS is maintained. 
FIG. 3 illustrates a sequence diagram, shown generally at 92, which 
illustrates the signaling between the mobile station 12 and the network 
infrastructure, including a radio base station 14, during operation of an 
embodiment of the present invention. When a communication service is to be 
performed by a mobile station, resources of the communication system must 
be allocated to the mobile station to permit the effectuation of the 
communication service. First, a supplemental channel request, indicated by 
the line 94, is generated by the mobile station and transmitted to the 
network infrastructure. The supplemental channel request is a request for 
the network infrastructure to allocate to the mobile station channel 
resources so that the communication service can be effectuated. Then, as 
indicated by the line 96, an offered gain message generated by the 
generator 76, shown in FIG. 2, is generated by the mobile station and 
transmitted to the network infrastructure. As described above, the offered 
gain message includes indications of a range of channel gains required to 
ensure that the communication service can be effectuated at a selected QoS 
level. 
The network infrastructure grants service to the mobile station to perform 
the communication service by issuing a service grant, indicated by the 
line 98. The service grants includes power control transmissions to select 
an initial level of gain by which the communication signals generated by 
the mobile station are to be amplified. And, during performance of the 
communication service, a channel gain message, indicated by the line 102, 
is transmitted by the network infrastructure to the mobile station to 
adjust the mobile's supplemental channel power levels. That is to say, the 
channel gain message indicates at what level of gain signals should be 
amplified at the mobile station. 
FIG. 4 illustrates the reverse-link channel structure which forms a portion 
of mobile station 12. The reverse-link channel structure shown in the 
Figure is exemplary of the structure of portions of the receive portion of 
the mobile station constructed according to the proposals set forth in the 
proposed CDMA2000 standards proposal. A plurality of channels are 
provided, here shown to include a fundamental channel 104, supplemental 
channels 106, a dedicated control channel 108, and a pilot channel 112. 
Gain elements 114 are associated with the channels 104-108. Walsh coding 
is performed by providing Walsh codes to the mixers 116 which are utilized 
to form Walsh-encoded sequences. The Walsh-encoded sequences are amplified 
by the gain elements 114. The levels of gain at which individual ones of 
the gain elements amplify the signals applied thereto are controlled in 
manners as described above with respect to FIG. 2 or, alternately, as 
shall be described below with respect to FIG. 6. 
The illustrated portion of the mobile station is further shown to include 
summing elements 118 as well as a complex multiply section 122 including a 
plurality of mixers 124 and summing elements 126. Base band filters 128, 
additional gain elements 132, mixers 134 and a summer 136 are further 
shown in the Figure. Additional details related to the reverse-link 
channel structure shown in FIG. 6 can be found in appropriate portions of 
the CDMA2000 standard proposal. Elements of the structure shown in FIG. 4 
correspond to functionally equivalent portions of the mobile station 12 
shown in FIG. 2. 
FIG. 5 illustrates forward link channel structure which forms a portion of 
the transmit portion of a mobile station, such as the mobile station 12 
shown in FIG. 2. Structure shown in the Figure includes a long code 
generator 142, a bit selector 144, a mixer 146, a multiplexer 148, gain 
elements 152, puncture symbols 154, and mixers 156 are used for Walsh 
encoding purposes. 
FIG. 6 illustrates the mobile station 12 of another embodiment of the 
present invention. The mobile station is again shown to include an 
information source 34, encoder 36, modulator 38, DAC 40, VGA 42, 
up-converter 44, and power amplifier 46. Signals generated by the transmit 
portion of the mobile station are again applied to an antenna transducer 
48 to be transduced into electromagnetic form thereat. And, the mobile 
station again includes a receive portion including a down-converter 52, an 
I/Q demodulator 54, an A/D converter 56, a rake receiver 58, a decoder 62, 
and an information sink 64. 
In this embodiment, the controller 68 effectuates gain control even without 
the detection of a channel gain message transmitted thereto by the network 
infrastructure of the communication system. The controller 68 is, however, 
shown to be coupled to receive indications of user-generated inputs 
generated by way of the user interface 72. And, a channel range determiner 
74 is again operable to determine a range of channel gains to permit 
effectuation of performance of a communication service at a selected QoS 
level. Determinations made by the determiner are applied again to an 
offered gain message generator 76 which forms an offered gain message 
which is provided to the transmit portion of the mobile station on line 78 
and used during service negotiations by the mobile station. An RLP (radio 
link protocol) formatting scheme is utilized to format data which is 
communicated to perform the communication service. In conventional manner, 
ACK (acknowledge) or NAK (no acknowledge) indications are sent back to the 
mobile station by the network infrastructure to indicate receipt or 
non-receipt of the RLP frames. The mobile station is provided with 
information pertaining to an NAK interval, a time period in which to sum 
NAK indications received at the mobile station, information related to an 
NAK limit, the maximum number of NAKs permitted during the NAK interval, 
and information related to a QoS step level, the nominal power step size 
in a dB, to alter channel gain on the channels upon which the signals are 
transmitted to perform the communication service. In an exemplary 
implementation, such information is sent to the mobile station by the 
network infrastructure in the form of RLP-related, layer three messages. 
The NAK interval and the NAK limit may be combined into a single message. 
In one implementation, the values of the NAK interval, the NAK limited, 
and the QoS step size are user-specific, in another implementation, such 
values are, instead, system parameters and transmitted to the mobile 
station over a common control channel. 
Here, the controller 68 is further shown to include a step-size detector 
172 coupled to the receive portion of the mobile station to detect 
indications of the QoS step transmitted to the mobile station. An NAK 
detector 174 is also coupled to the receive portion of the mobile station 
to detect the NAK information, i.e., the NAK interval and the NAK limit, 
transmitted to the mobile station. Indications of the NAK interval are 
provided to an NAK timer 176, and indications of the NAK limit are 
provided to a counter 178. 
During operation, the counter is operable to count the number of NAKs 
within the time interval of the NAK interval and timed by the NAK timer. 
If the counter counts-out, an indication is provided to a gain controller 
84. The gain controller is also coupled to receive indications of the QoS 
step size detected by the detector 172. Responsive thereto, the gain 
controller generates signals to control the amplification of the VGA 42. 
Thereby, a rule-of-thumb gain control is effectuated at the transmit 
portion of the mobile station upon receiving negative acknowledgment for a 
selected number of RLP data frames within a selected time. 
FIG. 7 illustrates a sequence diagram, shown generally at 182, listing the 
signaling between the mobile station 12 and the network infrastructure, 
including a radio base station 14, during operation of an embodiment of 
the present invention. When a communication service is to be performed by 
the mobile station, the mobile station generates a supplemental channel 
request, indicated by the line 184, which is transmitted to the network 
infrastructure in which additional system resources are requested to be 
allocated to perform the communication service. An offered gain request, 
including the offered gain message generated by the offered gain message 
generator 76, shown in FIG. 6 to form a portion of the mobile station, is 
also sent, as indicated by the line 186, by the mobile station to the 
network infrastructure. 
The network infrastructure, responsive to the requests, grants service by 
way of a service grant indicated by the line 188, granting service to the 
mobile station to perform the communication service. An NAK information 
message, including the NAK interval and the NAK limit, is also transmitted 
by the network infrastructure to the mobile station as indicated by the 
line 192. And, the network infrastructure sends a message containing the 
QoS step size, indicated by the line 194 to the mobile station. 
Thereafter, during communication of the RLP formatted frames of data, NAK 
information, indicated by the line 196, is provided by the network 
infrastructure to the mobile station. Gain control is effectuated 
therefrom. 
FIG. 8 illustrates a sequence diagram 198 representative of exemplary 
operation of a further embodiment of the present invention. The embodiment 
represented by the sequence diagram 198 provides RLP-based power control 
used to improve the reliability of retransmissions in an RLP (radio link 
protocol) application of a CDMA2000 cellular communication system. During 
operation of the power control effectuated in this embodiment, RLP 
retransmissions on a reverse link extending from the mobile station to the 
network infrastructure are power-controlled by adjusting a traffic channel 
gain by a specified step-size so as to improve the signal-to-noise ratio 
(SNR) of retransmissions received at the network infrastructure. Operation 
of the embodiment provides a manner by which to effectuate outer loop 
power control for a CDMA2000, or other radio communication, system. 
An existing manner provides an algorithm by which to effectuate outer loop 
power control by selectively causing a step-size increase or decrease in 
subsequently-transmitted RLP data frames responsive to whether a 
previously-transmitted data frame is in error. One existing proposal, for 
instance, attempts to ensure that signal-to-noise ratios of RLP data 
frames received at a base station is of a level such that a required FER 
(frame error rate) is maintained. However, such existing power control 
method does not adequately account for values of FER which do not equal 10 
(exp)--L where L is an integer greater than zero. 
An embodiment of the present invention provides a manner by which better to 
effectuate power control in which amplification levels of which RLP data 
frames are amplified at levels responsive to the receipt of indications at 
the mobile station as to whether a previously-transmitted RLP data frame 
was, or was not, received in error at the network infrastructure. Such 
operation is stated in an algorithmic form as follows: 
##EQU4## 
wherein: 
For frame j, j=0,1, . . . , adjust target E.sub.b /N.sub.t, denoted as 
Traffic (E.sub.b /N.sub.t).sub.T, using fixed step-size .DELTA. 
1. If the frame is in error, (E.sub.b /N.sub.t).sub.T (j+1)=(E.sub.b 
/N.sub.t).sub.T (j)+(10.sup.T -round (10.sup.T F)).DELTA. 
2. If the frame is not in error, (E.sub.b /N.sub.t).sub.T 
(j+1)=(E.sub.b/N.sub.t).sub.T (j)-round(10.sup.T F).DELTA.; and 
T is an integer; 
F is a target frame error rate (FER); and 
.DELTA. is a value of a step-size. 
When RLP-based power control is used, retransmissions of data frames 
usually arrive at a slightly better FER than the target F. However, outer 
loop power control should maintain a target FER for regular transmission 
frames in the presence of RLP retransmissions. To minimize the need to 
modify normal outer loop power control operation, operation of this 
embodiment of the present invention utilizes an algorithm as follows: 
For frame j, j=0,1, . . . , adjust target Traffic E.sub.b /N.sub.t, denoted 
as (E.sub.b/N.sub.t).sub.T, using fixed step-size .DELTA. 
1. If frame in error, (E.sub.b /N.sub.t).sub.T (j+1)=(E.sub.b 
/N.sub.t).sub.T (j)+(10.sup.T -round(10.sup.T F)).DELTA. 
2. If frame not in error and frame is not an RLP retransmission, (E.sub.b 
/N.sub.t).sub.T (j+1)=(E.sub.b /N.sub.t).sub.T (j)-round(10.sup.T F).DELTA 
. 
3. If frame not in error and frame is an RLP retransmission, (E.sub.b 
/N.sub.t).sub.T (j+1)=(E.sub.b /N.sub.t).sub.T (j) 
The sequence diagram 198 indicates that first, an RLP data frame, the jth 
data frame, is communicated by the mobile station to the network 
infrastructure, indicated by the line segment 202. Then, as indicated by 
the segment 204, an acknowledgment and error indication is returned from 
the network infrastructure to the mobile station. Then, the gain at which 
a subsequent, the j+1, data frame is communicated by the mobile station to 
the network infrastructure is selectively modified by the above-noted 
algorithm, the subsequent transmission of the data frame is indicated by 
the line segment 206. Thereby, operation provides a power control scheme 
in which, if an RLP retransmission is successfully received at the network 
infrastructure, an outer loop sub-point is not adjusted. Otherwise, 
adjustment is made, as indicated in the algorithm. The calculations of the 
algorithm can be carried out by a gain controller, such as that which 
forms portions of the mobile station shown in preceding Figures. A gain 
control signal generated by the gain controller is then utilized by a 
variable gain amplifier of the transmit portion of the mobile station to 
effectuate the power control. 
FIG. 9 illustrates a method, shown generally at 212, of an embodiment of 
the present invention. The method initiates effectuation of power control 
over signals generated by a radio device operable in the communication 
system. The signals are transmitted upon a radio channel to a receiving 
station to perform a communication service. 
First, and as indicated by the block 214, a range of channel gains is 
determined within which signal levels of the signals can be generated by 
the radio device to permit performance of the communication service at a 
selected QoS level. Then, and as indicated by the block 216, a message is 
generated for transmission to the receiving station requesting allocation 
of channel capacity upon the radio channel to transmit signals upon the 
radio channel to perform the communication service. By determining the 
channel gain required to effectuate the communication service at a 
selected QoS level, maintenance of communications at the selected QoS 
level is better assured. 
The previous descriptions are of preferred examples for implementing the 
invention, and the scope of the invention should not necessarily be 
limited by this description. The scope of the present invention is defined 
by the following claims: