HK1134178B - Method of determining signaling overhead and radio resource utilization, base station and user equipment mobile terminal - Google Patents

Description

Method, base station and user equipment mobile terminal for determining signaling overhead and radio resource utilization

RELATED APPLICATIONS

The present application is a divisional application of the chinese patent application entitled "dynamic channel quality measurement for adaptive modulation and coding" with application number 02809876.5.

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to communication stations that use Code Division Multiple Access (CDMA) technology. The present invention relates in particular to determining radio conditions for efficient utilization of radio resource usage and selection of data rates for user services.

Background

In code division multiple access third generation (3G) cellular communication systems, adaptive modulation and coding (AM & C) techniques are applied to transmissions in order to achieve improved radio resource usage and, where appropriate, to provide increased user service data rates. These AM & C techniques take radio transmission conditions into account in advance in order to determine the modulation and coding rates that are beneficial from the current radio propagation conditions using these techniques.

When using these AM & C techniques, a procedure is required to provide physical channel quality measurements from the receiver before each transmission. Based on this quality measure, the transmitter determines the appropriate modulation and coding rate for a particular transmission.

In a CDMA system, as with any wireless system, wireless conditions may change rapidly due to wide variations in both natural and man-made conditions. Since the cqi measurement is used to determine the transmission modulation and coding, and since the channel quality changes rapidly due to changes in the condition of the transmission path, the adaptive transmission process is directly related to the length of the time period between the time the cqi measurement is performed and the time the transmission starts.

The physical or logical control channel is then used to transmit the channel quality measurements from the receiver to the transmitter. Channel quality signaling (signaling) may use a control channel dedicated to each User Equipment (UE) or a common control channel shared by all UEs. The UE may be a cellular phone, PDA (personal data assistant) or other type of wireless device. When a dedicated control channel is used, a continuous signaling channel exists that times out for the propagation of channel quality measurements for each UE. This is an ideal, solution for AM & C because of the constant existence of quality measurements. The transmission may occur at any time, taking into account the persistent quality measure for the appropriate modulation and coding settings. Thus, in a manner that a dedicated control channel is always present in the uplink (uplink), the channel can be used to support low rate uplink data transmission.

The difficulty in using the dedicated control channel method is that physical layer resources are continuously allocated even when there is no data transmission. The main application of AM & C technology is non-real-time high data rate services, such as internet access. For these classes of services, the best quality of service (QoS) is achieved with short, relatively long idle periods between transmissions. These long idle periods result in low efficiency of dedicated resource usage. This limits the number of users that can access the service.

This problem can be minimized by means of a pre-configured periodic dedicated channel. But this results in a periodic availability of quality measurements. If the quality measurements are not continuously available, only some of the UEs will have the most recent channel quality measurements for the UE that generated the transmission at any time, and therefore the selection of the UE transmission will become sub-optimal.

Another approach is the use of common control channels. With the use of a common control channel, there is one continuous signaling channel shared by all UEs within a cell. A procedure is defined for determining access to a common control channel by each UE. UE identification is used to distinguish particular services.

The difficulty with the common control method supporting AM & C is to measure the large amount of signaling overhead required for each UE to access the control channel. As mentioned before, UE identification is required in order to distinguish UE-specific traffic. Thus, to avoid contention-based access to the uplink common control channel, individual allocation of each UE access on the downlink (downlink) common control channel needs to be signaled. Since the uplink is not always predictable, the periodic allocation of uplink control channels must be signaled on the downlink control channel, which results in considerable signaling overhead. Meanwhile, the shared control method does not provide low-rate, uplink data transmission.

In summary, the efficiency of AM & C techniques is based primarily on the benefit of recent physical channel quality measurements from each transmitter of the receiver in advance. Preferably, the measurement exists with a minimum delay for all users with dynamic data transmission. This dedicated control channel solution provides continuous measurements, but because the transmission is discontinuous, it is not efficient to use the radio resources. The periodically designed dedicated control channel minimizes the radio resource requirements, but this increases the delay of the measurement. The common control channel approach may provide measurements on a continuous or periodic basis, but the signaling overhead will result in inefficient use of radio resources.

There is a need to be able to provide methods with low delay and low signaling overhead.

Disclosure of Invention

The present invention provides a method for transmitting downlink data, the method comprising: receiving downlink data destined for a user equipment; transmitting a request for providing a channel quality, CQ, measurement report to the designated user equipment; receiving a CQ measurement report from only the specified user equipment in response to the request; signaling an allocation of radio resources to the designated user equipment in response to the received CQ measurement report, wherein the user equipment is prioritized from highest channel quality to lowest channel quality based on the received CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality; and transmitting the received downlink data to the designated user equipment according to the allocation of the radio resources.

The present invention also provides a base station configured to receive downlink data destined for a user equipment, the base station comprising: a transmitter configured to transmit a request for providing a channel quality, CQ, measurement report to a designated user equipment; a receiver further configured to receive, in response to the request, CQ measurement reports only from the designated user devices; and the transmitter is further configured to signal an allocation of radio resources to the designated user equipment in response to the CQ measurement report, and the transmitter is further configured to transmit the received downlink data to the designated user equipment according to the allocation of radio resources, wherein the user equipments are prioritized from highest channel quality to lowest channel quality based on the CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality.

The present invention also provides a method for receiving downlink data, the method comprising: receiving, at a user equipment, a request to provide a channel quality, CQ, measurement report prior to receiving downlink data allocated only to the user equipment; transmitting a CQ measurement report from the user equipment in response to the request; receiving an allocation of radio resources for the user equipment, the allocation of radio resources being based on the transmitted CQ measurement report; and receiving downlink data according to the allocation of the radio resources, wherein the user equipments are prioritized from highest channel quality to lowest channel quality based on the CQ measurement report and the allocation of the radio resources is prioritized from highest channel quality to lowest channel quality.

The invention also provides a user equipment mobile terminal, the user equipment comprising: a receiver configured to receive a request for providing a channel quality CQ measurement report before receiving downlink data allocated only to a user equipment; a transmitter configured to transmit a CQ measurement report in response to the request; and the receiver is further configured to receive an allocation of radio resources based on the transmitted CQ measurement report, and to receive downlink data according to the allocation of radio resources, wherein the user equipments are prioritized from highest channel quality to lowest channel quality based on the CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality.

Drawings

The objects of the invention will become more apparent based on the detailed description and drawings attached hereto, in which:

fig. 1 is a flow chart of a preferred Dynamic Channel Quality Management Procedure (DCQMP) of the present invention.

Fig. 2 shows another embodiment of the DCQMP of the present invention shown in fig. l.

Detailed Description

The preferred embodiments shown are described below with reference to the attached drawings, wherein like reference numerals refer to like elements throughout.

Fig. l is a flow chart of a dynamic Channel Quality (CQ) measurement procedure 60 of the present invention, which may be implemented by a wireless digital communication system having a base station/node B (hereinafter referred to as base station 12) in communication with at least one UE 30. Although the presented inventive method is intended to support communication between a base station and multiple UEs, for the sake of brevity, the following description will detail the steps performed by a single UE, it being understood that all other UEs will operate in the same manner.

Downlink (DL) data is transmitted to the base station 12 assigned to the particular UE 30 (step Sl).

The base station 12 responds to the receipt of downlink data and requests DL CQ measurements from only UEs 30 with pending downlink transmissions before transmission to the UEs 30 (step S2).

The UE 30 receives the request at step S3 and reports the DL CQ measurements to the base station 12 at step S4.

Based on the CQ measurement report received from each UE (step S5), the base station 12 determines which UEs will have the best radio resource usage efficiency and which slots (slots) to use (step S6). Preferably, the UEs are prioritized by their CQ, so the UE with the highest CQ is transmitted data first, then the UE with the second highest CQ is transmitted its data next, and so on until the data of the UE with the lowest CQ is transmitted last.

Since CQ measurement requests and CQ reports in response are generated only when needed, the signaling overhead required for the common control channel can be greatly reduced. Measurement reports exist for all active transmitting users, similar to dedicated control channels, but avoiding inefficient use of resources in idle periods.

The priority of transmission is determined based on DL CQ measurements and DL physical channel assignments are signaled to the appropriate UEs indicating the particular code rate, modulation type and assigned time slot (step S7). The designated UE receives the code rate, modulation type, and assigned slot (step S8), and sets the parameters for reception (step S9).

After a predetermined but short time after the execution of step S7, the downlink data block is then transmitted by the base station 12 to the designated UE 30 (step S10) to enable the time setting for reception by the UE 30. The UE 30 receives the downlink data at the specific code rate, modulation type, and assigned time slot designated at step S7.

The present invention thus provides the basic requirements needed for AM & C operation while maintaining the most efficient use of radio resources. Because the DL CQ measurement exists with the smallest possible delay for all transmissions, the selection of one or more users to be served in the next transmission time frame may be optimized. Furthermore, the measurements provided by the periodic or continuous mechanism do not provide increased benefit, performance gain or enhancement over the present invention.

Implementation of the present invention also minimizes measurement procedure processing and associated power consumption, which is particularly important for UEs that are typically powered by limited capacity, low power (i.e., a rechargeable battery). Because quality measurements are only requested for a particular active transmission, the number of required measurements can be minimized.

According to the method 70 of fig. 2, according to another embodiment of the present invention, only a certain number of measurements are required, depending on the radio resources used for a particular transmission. For example, in the 3G standard, only CQs for a particular physical slot are requested. Thus, by limiting the need for CQ measurements to active transmissions and, depending on the size of the transmission, only requiring measurements on specific radio resources (i.e., specific timeslots), the number of measurements performed may be reduced. This is shown in FIG. 2, which is similar to FIG. 1 except that modified steps S2A and S3A replace steps S2 and S3, respectively, of FIG. l. In step 2A, the base station 12 requests the UE 30 to perform measurements only on specific radio resources. In response to the request, the UE performs DL CQ measurement on the specific radio resource (step S3A).

The present invention provides a number of advantages over the prior art. First, the present invention provides the most efficient use of the air interface, since only those UEs with outstanding transmissions will need to respond to requests for DL CQ measurements. This allows the signalling overhead to be minimal.

Second, because transmissions are prioritized according to the highest quality DL CQ measurements, the highest data rate allowable per slot or multi-slot will be achieved.

Third, because the UE only needs to respond to the request for DL CQ measurements, measurements not needed by the UE will not be needed, thereby saving UE battery life.

A final advantage of the present invention is the increase in the number of users that can be supported in a cell of the method disclosed herein. The number of users supported is limited by the requirement of dedicated radio resources in the dedicated control channel approach: but limited by the signaling overhead requirements in the common control channel approach. By limiting the measurement signaling procedures for active users, the present invention minimizes the signaling overhead for shared control and supports the maximum number of users in a cell.

While the invention has been described in terms of preferred embodiments, other variations which fall within the scope of the invention as described in the claims will be apparent to those skilled in the art.

Claims (8)

1. A method for transmitting downlink data, the method comprising:

receiving downlink data destined for a user equipment;

transmitting a request for providing a channel quality, CQ, measurement report to the designated user equipment;

receiving a CQ measurement report from only the specified user equipment in response to the request;

signaling an allocation of radio resources to the designated user equipment in response to the received CQ measurement report, wherein the user equipment is prioritized from highest channel quality to lowest channel quality based on the received CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality; and

transmitting the received downlink data to the designated user equipment according to the allocation of the radio resources.

2. The method of claim 1, wherein the allocation of radio resources comprises at least one of a coding rate and a modulation type.

3. A base station configured to receive downlink data destined for a user equipment, the base station comprising:

a transmitter configured to transmit a request for providing a channel quality CQ measurement report to a designated user equipment;

a receiver configured to receive a CQ measurement report only from the designated user equipment in response to the request; and

the transmitter is further configured to signal an allocation of radio resources to the designated user equipment in response to the CQ measurement report, and the transmitter is further configured to transmit the received downlink data to the designated user equipment according to the allocation of radio resources, wherein the user equipment is prioritized from highest channel quality to lowest channel quality based on the CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality.

4. The base station of claim 3, wherein the allocation of radio resources comprises at least one of a coding rate and a modulation type.

5. A method for receiving downlink data, the method comprising:

receiving, at a user equipment, a request to provide a channel quality, CQ, measurement report prior to receiving downlink data destined only to the user equipment;

transmitting a CQ measurement report from the user equipment in response to the request;

receiving an allocation of radio resources for the user equipment, the allocation of radio resources being based on the transmitted CQ measurement report; and

receiving downlink data according to the allocation of radio resources, wherein the user equipments are prioritized from highest channel quality to lowest channel quality based on the CQ measurement reports and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality.

6. The method of claim 5, wherein the allocation of radio resources comprises at least one of a coding rate and a modulation type.

7. A user equipment, the user equipment comprising:

a receiver configured to receive a request for providing a channel quality CQ measurement report before receiving downlink data designated only to a user equipment;

a transmitter configured to transmit a CQ measurement report in response to the request; and

the receiver is further configured to receive an allocation of radio resources based on the transmitted CQ measurement report, and to receive downlink data according to the allocation of radio resources, wherein the user equipments are prioritized from highest channel quality to lowest channel quality based on the CQ measurement report and the allocation of radio resources is prioritized from highest channel quality to lowest channel quality.

8. The user equipment of claim 7, wherein the allocation of radio resources comprises at least one of a coding rate and a modulation type.