HK1069488B

HK1069488B - Mobile communication system, wireless base station apparatus and power control method for use therein

Info

Publication number: HK1069488B
Application number: HK05101790.5A
Authority: HK
Inventors: 高木健树
Original assignee: 日本电气株式会社
Priority date: 2003-03-26
Filing date: 2005-03-01
Publication date: 2007-11-09

Description

Mobile communication system, radio base station apparatus, and power control method used therefor

Technical Field

The present invention relates to a mobile communication system, a radio base station apparatus, and a power control method used therein, and more particularly to a power control method used in a mobile communication system of a Code Division Multiple Access (CDMA) system.

Background

In a conventional mobile communication system of CDMA system, a dedicated physical data channel and a dedicated physical control channel for transmitting data of a forward link are time-division multiplexed for transmission to a mobile station terminal.

The dedicated physical data channel is a channel for transmitting user data to the mobile station terminal, and the dedicated physical control channel is a channel for transmitting control information in the physical layer. The control information includes a known form of pilot bits (pilot bits), Transmit Power Control (TPC) commands and Transport Format Combination Indicator (TFCI) used for channel estimation in sync detection. Incidentally, the TFCI is an information item indicating how many transport channels are multiplexed in a received frame of a forward link dedicated physical data channel or which transport channel uses which transport format.

The forward link dedicated physical data channel is encoded in an algorithm with error correction capability such as a Turbo code or convolutional code, but the dedicated physical control channel is not encoded.

For this reason, in the radio base station apparatus, it is necessary to consider the coding gain of the dedicated physical data channel, and to increase the transmission power level of the dedicated physical data channel and the dedicated physical control channel, which are time-division multiplexed, by as much as the coding gain with respect to the transmission power level of the dedicated physical data channel and the dedicated physical control channel.

In particular, when performing outer loop power control of the forward link, it is determined whether the coded dedicated physical data channel satisfies a quality requirement, and a signal-to-interference ratio (SIR) target of the forward link is lowered to achieve convergence at a level satisfying a specific quality requirement.

Signals with the same SIR level may differ in reception quality in different radio propagation environments. Outer loop power control of the forward link refers to control for measuring the block error rate (BLER) of the received signal in this case and determining whether the quality requirements specified by the network and the service are met, i.e. for determining a target SIR level that meets the overall system requirements. For example, in W-CDMAMobile Communication Forma: this control is disclosed in 2-2W-CDMA Basic Transmission technology (in Japan, edition super by KeijiTachkawa, publichedby Maruzen Co., Ltd. on June 25, 2001), p.55.

In this way, when the outer loop power control of the forward link is being performed, the transmission power of the dedicated physical channel from the radio base station apparatus is reduced and converged to a level that can satisfy the quality requirement of the user data unit. As a result, the pilot, TPC command and TFCI of the dedicated physical control channel, which are not encoded, cannot satisfy the quality requirement as much as the coding gain of the dedicated physical data channel.

In order to avoid this problem in a mobile communication system of a currently available CDMA system, there may be a fixed value of the coding gain of the dedicated physical data channel to supplement the transmission power of the dedicated physical control channel. This parameter can only be set when setting the transmission channel and can only have a fixed value, which cannot be changed at any time during the communication.

However, in the conventional mobile communication system of the CDMA system, a difference between the dedicated physical data channel and the dedicated physical control channel affects not only a difference in coding gain (fast code or convolutional code and no coding), but also bit repetition (repetition) or bit reduction (puncturing-out) caused by rate matching.

Where the bit repetition is frequent, the error correction rate is correspondingly increased, resulting in improved reception quality at the mobile station terminal, thereby enabling the mobile station terminal to obtain sufficiently high quality even at low reception power.

On the other hand, where bit reduction is frequent, the error correction rate at the mobile station terminal is lower than in the normal case, resulting in worse reception quality than in the normal case, and thus in higher reception power required by the radio base station apparatus to satisfy the quality requirement.

Disclosure of Invention

An object of the present invention is to avoid the above-mentioned problems and to provide a mobile communication system which enables a mobile station terminal to keep the reception quality of a forward link dedicated physical control channel at a constant level at all times, a power control method and a radio base station apparatus used therein.

Another object of the present invention is to provide a mobile communication system capable of reducing a drop in the total capacity of a mobile station terminal in the system, and a power control method and a radio base station apparatus used therein.

A forward link dedicated physical data channel with error correction and a dedicated physical control channel without error correction are time-division multiplexed and transmitted from a radio base station apparatus to a mobile station terminal by a mobile communication system according to the present invention, the mobile communication system being provided with:

means for correcting transmission power in consideration of a coding gain of the dedicated physical data channel, and means for transmitting the dedicated physical channel of the forward link at the corrected transmission power.

A radio base station apparatus according to the present invention, by which a forward link dedicated physical data channel with error correction and a dedicated physical control channel without error correction are time-division multiplexed and transmitted to a mobile station terminal, is provided with:

According to the power control method of the present invention intended for a mobile communication system by which an error-corrected dedicated physical data channel and an error-uncorrected dedicated physical control channel of a forward link are time-division multiplexed and transmitted from a radio base station apparatus to a mobile station terminal, a step of correcting transmission power in consideration of a coding gain of the dedicated physical data channel and a step of transmitting the dedicated physical channel of the forward link at the corrected transmission power are provided on the radio base station side.

Thus, according to the mobile communication system using the CDMA scheme of the present invention, the coding gain (fixed) of the transmission power obtained by the error correction processing (coding) on the dedicated physical data channel (with error correction) and the dedicated physical control channel (without error correction) of the forward link time-division multiplexed and transmitted is corrected based on the bit repetition/bit reduction caused by rate matching calculated from the change in the amount of data transmitted, the power level of the corrected gain is added to the dedicated physical control channel, and the result as the forward link dedicated physical channel is transmitted from the radio base station apparatus.

In this way, according to the mobile communication system of the present invention, it is possible to maintain the balance of transmission power between the time-division multiplexed dedicated physical data channel and dedicated physical control channel without increasing the received signal-to-interference ratio (SIR) of the mobile station terminal to an unnecessarily high level, so that the dedicated physical control channel can be always maintained at a constant level at which channel estimation can be performed.

To describe in more detail, in a mobile communication system of the CDMA system, a dedicated physical channel is used for communication between a radio base station apparatus and a mobile station terminal, the dedicated physical channel being composed of a time-division-multiplexed dedicated physical data channel and a dedicated physical control channel. In this communication, the original transmission power level set on the dedicated physical data channel is used to set a power level higher than the coding gain power level of the dedicated physical data channel in consideration of the dedicated physical data channel.

Here, the reason why the transmission power of the dedicated physical control channel is set to a level higher than the level of the dedicated physical data channel by the coding gain of the dedicated physical data channel is as follows: when the forward link transmission power level converges such that the dedicated physical data channel having been subjected to the error correction processing under the forward link outer loop power control by the mobile station terminal satisfies the relevant quality requirement, the dedicated physical control channel not subjected to the error correction processing cannot maintain the required quality standard. By setting the transmission power of the dedicated physical control channel to a level higher than the level of the dedicated physical data channel by the coding gain of the dedicated physical data channel, it is made possible to guarantee the mobile station terminal with a certain level of reception quality on both channels.

However, since the amount of data transmitted on the dedicated physical data channel is different at each transmission time interval, user data with different quality of service is mapped to the physical channel. (for example, in the case where voice communication and packet communication coexist, voice communication which does not allow a long delay and packet communication of e-mail or the like which allows a certain delay are different in QoS.) for this reason, bit repetition/bit reduction caused by rate matching to simultaneously satisfy QoS requirements is also different (because different QoS requirements are simultaneously satisfied by changing the data amount ratio).

The result is that the amount of data on the dedicated physical data channel is different at each transmission time interval, resulting in a fluctuation of the reception quality. For this reason, when the power difference reflecting the coding gain can only be set to a fixed value as in the conventional processing, the fluctuation of the bit repetition/reduction may make it impossible to always maintain the reception quality of the mobile station terminal at a certain constant level.

In view of this problem, in the mobile communication system according to the present invention, the bit repetition/bit reduction caused by rate matching in each transmission time interval is considered and the transmission power level to be added to the dedicated physical control channel is corrected. The corrected offset level is added to the power level of the coding gain of the dedicated physical data channel and the transmission of the dedicated physical control channel of the time-division multiplexed forward link occurs at the transmission power level of the dedicated physical control channel.

In the mobile communication system according to the present invention, the power level of the coding gain of the dedicated physical data channel is corrected in consideration of the bit repetition/bit reduction caused by the rate matching in each transmission time interval, and the corrected level is added to the dedicated physical control channel. It is thus possible to provide the mobile station terminal with the reception quality of the forward link dedicated physical control channel which is always at a constant level and does not vary between transmission time intervals.

Since this also prevents the radio base station apparatus from transmitting the dedicated physical control channel with unnecessarily high power, it is possible to reduce a decrease in the total accommodating capacity of the system due to an increase in the transmission power of the radio base station apparatus. Incidentally, the reverse link means transmission from the mobile station terminal to the radio base station apparatus, and the forward link means transmission from the radio base station apparatus to the mobile station terminal.

As described above, according to the mobile communication system, the radio base station apparatus, and the power control method used therein of the present invention, the reception quality of the forward link dedicated physical control channel of the mobile station terminal is always at a constant level.

Further, according to the mobile communication system, the radio base station apparatus, and the power control method used therein of the present invention, it is possible to reduce a decrease in the total capacity of the mobile station terminals of the system.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

fig. 1 is a block diagram of the construction of a mobile communication system of the preferred embodiment of the present invention;

fig. 2 shows a general configuration of the radio base station apparatus of fig. 1;

FIG. 3 illustrates a transmission format of forward link user data in an embodiment of the present invention;

FIG. 4 illustrates bit reduction caused by rate matching of forward link user data in an embodiment of the present invention;

FIG. 5 illustrates bit repetition caused by rate matching of forward link user data in an embodiment of the present invention;

fig. 6 illustrates correction of transmission power on a dedicated physical control channel in an embodiment of the present invention;

fig. 7 is a flowchart illustrating an operation of the mobile communication system of the embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 is a block diagram of the construction of a mobile communication system of a preferred embodiment of the present invention. Referring to fig. 1, a mobile communication system incorporating the present invention uses a Code Division Multiple Access (CDMA) scheme, and includes a radio base station apparatus 1 and a mobile station terminal 2. The radio base station apparatus 1 is provided with a baseband unit 11 which performs a plurality of types of measurement by processing rate matching.

In a conventional mobile communication system of the CDMA system, radio base station apparatuses 1 are arranged at intervals of several kilometers, each constituting an area, and radio links are established between each radio base station apparatus 1 and a plurality of mobile station terminals 2. In fig. 1, it is assumed that a radio link is established between a radio base station apparatus 1 and a mobile station terminal 2.

The forward link dedicated physical channel 100 is constructed by time division multiplexing a dedicated physical data channel 101 and a dedicated physical control channel 102. In this embodiment, an optimal balance of transmission power between the time-multiplexed dedicated physical data channel 101 and dedicated physical control channel 102 is sought.

Typically, the dedicated physical data channel 101 is encoded with an error correction code, such as a turbo code or a convolutional code, and has a high error correction capability. On the other hand, the dedicated physical control channel 102 is not coded and has no error correction capability.

Therefore, when the power is controlled by outer loop power control of the forward link to meet the quality requirement of the dedicated physical data channel 101, the quality requirement on the dedicated physical control channel 102 without error correction capability cannot be met, which would cause call interruption in the worst case.

For this reason, in the present mobile communication system of the CDMA system, it is possible to fix the transmission power difference between the dedicated physical data channel 101 and the dedicated physical control channel 102 (i.e., the power level of the coding gain of the dedicated physical data channel) to the offset level 103.

Fig. 2 shows a general configuration of the radio base station apparatus 1 of fig. 1. In fig. 2, radio base station apparatus 1 includes coding section 12, rate matching section 13, offset power level correcting section 14, dedicated physical data channel generating section 15, dedicated physical control channel generating section 16, and time division multiplexing section 17. The encoding unit 12 handles data encoding of the user data 201 and 202, and the rate matching unit 13 handles rate matching of the encoded data. The offset power level correction unit 14 corrects the offset power level of the control information on the user data 201 and 202.

The dedicated physical data channel generating unit 15 generates a dedicated physical data channel from the data that has undergone rate matching, and the dedicated physical control channel generating unit 16 generates a dedicated physical control channel from the control information whose offset power level has been corrected. The time division multiplexing unit 17 time-division multiplexes these dedicated physical data channels and dedicated physical control channels.

Fig. 3 shows a transmission form of forward link user data in the embodiment of the present invention. Fig. 4 illustrates bit reduction caused by rate matching of forward link user data in an embodiment of the present invention. Fig. 5 illustrates bit repetition caused by rate matching of forward link user data in an embodiment of the present invention. Fig. 6 illustrates a correction of transmission power on a dedicated physical control channel in an embodiment of the present invention.

Referring to fig. 3, forward link user data 301 through 303 are placed in each of transmission time intervals 311 through 313 on a forward link dedicated physical data channel. As a result, the data amounts of the forward link user data 301 to 303 at the transmission time intervals 311 to 313 are different from each other.

To this end, in the forward link user data 301 to 303 in each of the transmission time intervals 311 to 313, a bit reduction 404 by rate matching 402 as shown in fig. 4 or a bit repetition 504 by rate matching 502 as shown in fig. 5 may occur.

In this embodiment, as shown in fig. 6, bit reduction 404 or bit repetition 504 caused by rate matching of the user data portion received by the radio base station apparatus 1 is calculated, and a power level (fixed) 603 set as a coding gain of the dedicated physical data channel 601 is corrected based on the calculated result. (the corrected level is a power level 604 reflecting that bit reduction/repetition caused by rate matching is taken into account, as shown in fig. 6.) then, the corrected power level is added to the transmission power of the dedicated physical control channel 602, and the dedicated physical data channel and the dedicated physical control channel are time-division multiplexed and transmitted to the wireless section. These processing steps are executed by the radio base station apparatus 1 whose configuration is shown in fig. 2.

Since the dedicated physical data channels of the transmission time intervals 311 to 313 shown in fig. 3 are all different from each other in the amount of data transmitted, user data different in quality of service (QoS) is mapped onto the physical channels. (for example, in the case where voice communication and packet communication coexist, voice communication which does not allow a long delay and packet communication of e-mail or the like which allows a certain delay are different in QoS.) for this reason, bit repetition/bit reduction caused by rate matching for satisfying QoS requirements is also different (because different QoS requirements are satisfied at the same time by changing the data amount ratio).

Thus, the amount of data on the dedicated physical data channel of each mobile station terminal 2 is different from each other from the transmission time intervals 311 to 313, and the reception quality fluctuates accordingly. While the power difference reflecting the coding gain can only be set to a fixed value as in the conventional processing, the fluctuation of the bit repetition/reduction makes it impossible to keep the reception quality of the mobile station terminal 2 at a certain constant level at all times.

In view of this problem, in the embodiment of the present invention, the bit repetition 504/bit reduction 404 (see fig. 4 and 5) caused by rate matching in each of the transmission time intervals 311 to 313 is considered as shown in fig. 3, and the transmission power level (coding gain of the dedicated physical data channel 601) to be added to the dedicated physical control channel is corrected as shown in fig. 6.

The corrected offset level (power level 604 reflecting bit reduction/repetition caused by rate matching shown in fig. 6) is added to the power level 603 of the coding gain of the dedicated physical data channel 601, and the dedicated physical control channel of the time-division multiplexed forward link is transmitted at the transmission power level of the dedicated physical control channel 602.

In this embodiment, the bit repetition 504/bit reduction 404 caused by rate matching is considered in each of the transmission time intervals 311 to 313, the power level 603 of the coding gain of the dedicated physical data channel 601 is corrected, and the corrected level is added to the dedicated physical control channel 602. It is thus possible to provide the mobile station terminal 2 with the reception quality of the forward link dedicated physical control channel which is always at a constant level and does not vary between the transmission time intervals 311 to 313.

Since this also prevents the radio base station apparatus 1 from transmitting the dedicated physical control channel with unnecessarily high power, it is possible to reduce a decrease in the total capacity of the system due to an increase in the transmission power of the radio base station apparatus 1. Incidentally, the reverse link means transmission from the mobile station terminal 2 to the radio base station apparatus 1, and the forward link means transmission from the radio base station apparatus 1 to the mobile station terminal 2.

Fig. 7 is a flowchart illustrating an operation of the mobile communication system of the embodiment of the present invention. The operation of the mobile communication system incorporating the present invention will be described with reference to fig. 1 to 7.

First, the radio base station apparatus 1 receives user data 201 and 202 from a host apparatus (not shown) (step S1 in fig. 7). In the radio base station apparatus 1, in order to transmit user data different in QoS on a single channel, the variation in the number of bits (bit repetition 504/bit reduction 404) in the encoded sequence (user data) mapped onto the physical channel in each of the transmission time intervals 311 to 313 is calculated (rate matching) (step S2 in fig. 7).

In the radio base station apparatus 1, since the reception quality of the mobile station terminal 2 differs depending on the bit repetition 504/bit reduction 404 due to rate matching obtained by the above-described processing, the fixed value of the transmission power level 603 set as the coding gain of the forward link dedicated physical data channel is corrected (step S3 in fig. 7).

The radio base station apparatus 1 adds the corrected transmission power level to the transmission power of the dedicated physical control channel, and transmits the dedicated physical data channel and the dedicated physical control channel in a time-division multiplexed form (steps S4 and S5 of fig. 7).

Therefore, in this embodiment of the present invention, the reception quality of the mobile station terminal 2 is changed by the bit repetition 504/bit reduction 404 calculated by rate matching in each of the transmission time intervals 311 to 313. For this purpose, the transmission power difference of the coding gain between the dedicated physical data channel having undergone error correction and the dedicated physical control channel having not undergone error correction is corrected in each of the transmission time intervals 311 to 313 based on the calculated value of the reception quality. This enables the embodiment to keep the reception quality of the forward link dedicated physical control channel of the mobile station terminal 2 at a constant level at all times.

Further, in this embodiment, the reduction of transmission at an unnecessarily high power level by the radio base station apparatus 1 reduces the level of interference to which the mobile station terminal 2 is subjected, prevents the mobile station terminal 2 from making further power demands on the radio base station apparatus 1, and can reduce the reduction of the total accommodation capacity of the mobile station terminal 2 of the system.

As described so far, the mobile communication system according to the present invention, by having the above-described construction and operation, provides an advantage of being able to make the reception quality of the forward link dedicated physical control channel of the mobile station terminal at a constant level at all times.

Further, another mobile communication system according to the present invention provides an advantage of being able to reduce a drop in the total capacity of the mobile station terminals of the system by having the above-described configuration and operation.

Although the present invention has been described with reference to specific preferred embodiments thereof, it should be understood that the subject matter encompassed by way of the present invention is not limited to the particular embodiments. Indeed, the subject matter of the invention is intended to embrace all such alternatives, modifications and equivalents as may be included within the spirit and scope of the following claims.

Claims

1. A mobile communication system by which a forward link dedicated physical data channel with error correction and a dedicated physical control channel without error correction are time-division multiplexed and transmitted from a radio base station apparatus to a mobile station terminal, comprising:

a power correction unit correcting transmission power in consideration of coding gain of the dedicated physical data channel and bit repetition/bit reduction caused by rate matching calculated from variation of the amount of transmitted data, and

a transmission unit that transmits the dedicated physical channel of the forward link at the corrected transmission power.

2. The mobile communication system of claim 1, wherein:

the power correction unit corrects the transmission power at each transmission time interval.

3. The mobile communication system of claim 1, wherein:

the power correction unit corrects a coding gain of transmission power obtained by error correction processing on the dedicated physical data channel and the dedicated physical control channel based on bit repetition/bit reduction caused by rate matching calculated from a change in the amount of transmitted data.

4. The mobile communication system of claim 2, wherein:

5. The mobile communication system of claim 3, wherein:

the rate matching will satisfy the quality of service requirements for both voice communications and packet communications.

6. The mobile communication system of claim 4, wherein:

7. The mobile communication system of claim 1, wherein:

the mobile communication system uses a code division multiple access system.

8. The mobile communication system of claim 2, wherein:

the mobile communication system uses a code division multiple access system.

9. The mobile communication system of claim 3, wherein:

the mobile communication system uses a code division multiple access system.

10. The mobile communication system of claim 4, wherein:

the mobile communication system uses a code division multiple access system.

11. The mobile communication system of claim 5, wherein:

the mobile communication system uses a code division multiple access system.

12. The mobile communication system of claim 6, wherein:

the mobile communication system uses a code division multiple access system.

13. A radio base station apparatus by which a forward link dedicated physical data channel with error correction and a dedicated physical control channel without error correction are time-division multiplexed and transmitted to a mobile station terminal, comprising:

14. The radio base station apparatus of claim 13, wherein:

15. The radio base station apparatus of claim 13, wherein:

16. The radio base station apparatus of claim 14, wherein:

17. The radio base station apparatus of claim 15, wherein:

18. The radio base station apparatus of claim 16, wherein:

19. The radio base station apparatus of claim 13, wherein:

the mobile communication system uses a code division multiple access system.

20. The radio base station apparatus of claim 14, wherein:

the mobile communication system uses a code division multiple access system.

21. The radio base station apparatus of claim 15, wherein:

the mobile communication system uses a code division multiple access system.

22. The radio base station apparatus of claim 16, wherein:

the mobile communication system uses a code division multiple access system.

23. The radio base station apparatus of claim 17, wherein:

the mobile communication system uses a code division multiple access system.

24. The radio base station apparatus of claim 18, wherein:

the mobile communication system uses a code division multiple access system.

25. A power control method for a mobile communication system by which a forward link dedicated physical data channel with error correction and a dedicated physical control channel without error correction are time-division multiplexed and transmitted from a radio base station apparatus to a mobile station terminal, comprising the steps of:

a step of correcting transmission power in consideration of coding gain of the dedicated physical data channel and bit repetition/bit reduction caused by rate matching calculated from variation of the amount of transmitted data, and

transmitting the dedicated physical channel of the forward link at the corrected transmission power.

26. The power control method of claim 25, wherein:

correcting the transmission power at each transmission time interval by the step of correcting the transmission power.

27. The power control method of claim 25, wherein:

correcting, by the step of correcting transmission power, a coding gain of transmission power obtained by error correction processing on the dedicated physical data channel and the dedicated physical control channel based on bit repetition/bit reduction caused by rate matching calculated from a change in the amount of transmitted data.

28. The power control method of claim 26, wherein:

29. The power control method of claim 27, wherein:

30. The power control method of claim 28, wherein:

31. The power control method of claim 25, wherein:

the mobile communication system uses a code division multiple access system.

32. The power control method of claim 26, wherein:

the mobile communication system uses a code division multiple access system.

33. The power control method of claim 27, wherein:

the mobile communication system uses a code division multiple access system.

34. The power control method of claim 28, wherein:

the mobile communication system uses a code division multiple access system.

35. The power control method as claimed in claim 29, wherein:

the mobile communication system uses a code division multiple access system.

36. The power control method of claim 30, wherein:

the mobile communication system uses a code division multiple access system.