DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] Several preferred embodiments of the present invention will now be described in detail herein below with reference to the annexed drawings. In the drawings, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description, a detailed description of known functions and configurations incorporated herein has been omitted for conciseness.

[0035] The present invention proposes a method for determining a k value, or a Channel Quality Indicator (CQI) report cycle, and transmitting and receiving the determined k value in an High Speed Downlink Packet Access (HSDPA) communication system.

[0036] FIG. 1 schematically illustrates a structure of a wideband code division multiple access (W-CDMA) mobile communication system. Referring to FIG. 1, the WCDMA mobile communication system includes a core network (CN) 100, a plurality of radio network subsystems (RNSs) 110 and 120, and a user equipment (UE) 130. Each of the RNSs 110 and 120 includes a radio network controller (RNC) and a plurality of Node Bs. For example, the RNS 110 includes an RNC 111 and Node Bs 113 and 115, and the RNS 120 includes an RNC 112 and Node Bs 114 and 116. The RNC is classified into a serving RNC (SRNC), a drift RNC (DRNC), and a controlling RNC CRNC) according to its operation. The SRNC is an RNC that manages information on each UE and controls data communication with the CN 100. When data from a UE is transmitted to an SRNC via a particular RNC rather than the SRNC, the particular RNC becomes an DRNC. The CRNC is an RNC that controls each Node B. In FIG. 1, if information from the UE 130 is managed by the RNC 111, the RNC 111 serves as an SRNC for the UE 130, and if data from the UE 130 is received via the RNC 112 due to movement of the UE 130, the RNC 112 becomes a DRNC for the UE 130, and the RNC 111 that controls the Node B 113 in communication with the UE 130 becomes a CRNC for the Node B 113.

[0037] Information necessary for determining a k value includes:

[0038] (info #1) handover state information of a UE,

[0039] (info #2) channel condition change information of a UE,

[0040] (info #3) information on UEs reporting CQI in the same cell, and

[0041] (info #4) state information of neighbor cells.

[0042] A detailed description of the above information will be made herein below.

[0043] First, the “(info #1) handover state information of a UE” represents the number of radio links of a UE, and is recognized by the SRNC. When the UE is in a non-handover state, the UE sets up one radio link with only a Node B currently in service. In contrast, the UE is in a handover state, the UE sets up radio links to multiple Node Bs existing in an active set. That is, if the number of radio links set up by the UE is 1, it indicates that the UE is in a non-handover state, and if the number of radio links set up by the UE is 2 or more, it indicates that the UE is in a handover state.

[0044] Second, the “(info #2) channel condition change information of a ULE” represents a change in the condition of a downlink channel received by a corresponding UE, and can be determined through various measurement reports that a Node B receives from the UE.

[0045] Third, the “(info #3) information on UEs reporting CQI in the same cell” is recognized by a CRNC or a Node B, and represents the number of UEs receiving an HSDPA service in the same cell and a k value, or a CQI report cycle, for each UE.

[0046] Fourth, the “(info #4) state information of neighbor cells” is information on neighbor cells to which the UE will report the CQI, and includes information on the number of UEs existing in the neighbor cells, the number of UEs reporting the CQI in the neighbor cells, and a k value (CQI report cycle) of each UE. The “(info #4) state information of neighbor cells” can be recognized by the CRNC.

[0047] The present invention proposes at least six embodiments for determining a k value, or a CQI report cycle, by the CRNC, and recommending the CRNC the k value by the Node B and the SRNC based on information that can be recognized by Node Bs.

[0048] A brief description will now be made of six embodiments of the present invention.

[0049] (1) In a first embodiment, an SRNC preferentially determines a recommended k value using a Radio Link Setup process and transmits the determined recommended k value to an CRNC. The CRNC then determines the k value based on the recommended k value received from the SRNC and delivers the determined k value to a Node B and a UE.

[0050] (2) In a second embodiment, an SRNC, when it desires to change a previously determined k value, sends a corresponding report to a CRNC using a Radio Link Reconfiguration process. The CRNC then determines a k value according to the received report and delivers the determined k value to a Node B and a UE.

[0051] (3) In a third embodiment, a CRNC, when it desires to change a previously determined k value, delivers a k value determined using a Physical Channel Reconfiguration process to a Node B and a UE via an SRNC.

[0052] (4) In a fourth embodiment, a Node B, when it desires to change a previously determined k value, sends a recommended k value to a CRNC using a Physical Channel Reconfiguration Indication process. The CRNC then determines a k value based on the recommended k value received from the Node B, delivers the determined k value to the Node B, and delivers the determined k value to a UE via an SRNC.

[0053] (5) In a fifth embodiment, a Node B or a CRNC recommend a k value, and an SRNC determines a k value based on the k value recommended by the Node B or the CRNC.

[0054] (6) In a sixth embodiment, a Node B or a CRNC recommend a k value, and an SRNC determines a k value based on the k value recommended by the Node B or the CRNC and at the same time, determines an activation time.

[0055] The first embodiment of the present invention will now be described with reference to FIG. 2.

[0056] FIG. 2 is a flow diagram illustrating a process of determining a CQI report cycle according to a first embodiment of the present invention. Referring to FIG. 2, an SRNC determines a k value to be recommended for a CRNC in Step 101. Herein, the k value to be recommended will be referred to as a “recommended k value” for simplicity. The SRNC determines the recommended k value according to a handover state of a UE. For example, if the number of radio links for a corresponding UE within a range of the k value is large, the SRNC sets the recommended k value to a relatively small value. In contrast, if the number of radio links is small, the SRNC sets the recommended k value to a relatively large value. That is, when the UE is in a handover sate, the SRNC sets the recommended k value to a small value so that CQI report should be performed frequently. When the UE is in a non-handover state, the SRNC sets the recommended k value to a large value to increase a CQI report cycle as compared with when the UE is in a handover state. A range of the k value can become 0, 1, 5, 10, 20, 40, and 80. If the k value is 0, it indicates that CQI report is not performed. If the k value is 1, it indicates that a CQI report cycle is 2 ms, or 3 time slots. In the HSDPA communication system, 1 Transmit Time Interval (TTI) is comprised of 3 time slots, 15 time slots constitute 1 frame, and I frame has a length of 10 ms. Therefore, a CQI report is performed every frame (10 ms) for the k value=5,, every 4 frames (40 ms) for the k value=20, every 8 frames (80 ms) for the k value=40, and every 16 frame (160 ms) for the k value=80. Although a range of the k value is set herein to 0, 1, 5, 10, 20, 40 and 80, the k value range can be changed according to circumstances.

[0057] When the SRNC determines the recommended k value considering the number of radio links set up by the UE, an example of a relationship between a range of the recommended k value and the number of radio links is illustrated in Table 1. 1

[0058] In Table 1, as the number of radio links becomes larger, the SRNC sets the recommended k value to a smaller value for frequent CQI report so that the UE can set up many radio links.

[0059] Another example of a relationship between the range of the recommended k value and the number of radio links is illustrated in Table 2. 2

[0060] In Table 2, during radio link setup, the SRNC separately determines the recommended k value when the number of radio links is two or more (the UE is in a handover state) and when the number of radio links is 1 (the UE is in a non-handover state).

[0061] After determining the recommended k value according to the handover state of the UE, the SRNC transmits the determined recommended k value to the CRNC through a radio network subsystem application part (RNSAP) message of a Radio Link Setup Request message in Step 102. The RNSAP message indicates a message exchanged between RNCs. The Radio Link Setup Request message has a format as illustrated in Table 3 below. 3

[0062] As illustrated in Table 3, the recommended k value is included in HS-DSCH Frequency Division Duplexing (FDD) Information of the Radio Link Setup Request message. In Table 3, “Information Element (IE)/Group Name” represents the name of information to be actually transmitted in the Radio Link Setup Request message, and the recommended k value is represented by “Recommended CQI Cycle k.” In Table 3, “Presence” represents a method in which information is transmitted on the Radio Link Setup Request message, and “M (Mandatory)” represents that the information is continuously transmission. In addition, “IE type and reference” represents a range of information transmitted through the Radio Link Setup Request message, and a range of the “Recommended CQI Cycle k” value, or the recommended k value, becomes 0, 1, 5, 10, 20, 40, and 80. Further, “Semantics description” describes contents of transmission information, and 2 ms set for the Recommended CQI Cycle k indicates that a fundamental unit, i.e., k value 1, for a range of the Recommended CQI Cycle k value is 2 ms.

[0063] Upon receiving the Radio Link Setup Request message, in Step 103, the CRNC detects a recommended k value included in the Radio Link Setup Request message, and determines a k value considering the detected recommended k value, a situation of a cell to which the UE currently belongs, and a situation of neighbor cells. A process of determining the k value by the CRNC will be described herein below. The CRNC can determine a handover state of the UE, i.e., the number of radio links, using the recommended k value. If the k value is 80, the CRNC can determine that the UE is in a non-handover state, i.e., the number of radio links is 1. If the number of UEs receiving an HSDPA service in a cell where the UE belongs is defined as “M,” the number of UEs can be divided into 7 groups as illustrated in Table 4. 4

[0064] If the number of UEs corresponding to each of the 7 groups is defined as Mi (i=0, 1, 2, 3, 4, 5, 6), an amount of uplink resource used for a current CQI report can be calculated by

Resource Amount=80*M1+16*M2+8* M3+4*M4+2*M5+1*M6 Equation (1)

[0065] The SRNC determines the recommended k value considering a maximum resource amount Max_R given to a cell, or a Node B, to which the UE belongs so that a resource amount calculated in accordance with Equation (1) should not exceed the maximum resource amount Max_R. For example, for a UE for which a k value is set to 80, if a recommended k value transmitted to the CRNC by the SRNC is 1, the resource amount is newly calculated.

[0066] If the k value is 80 (k value=80), the resource amount can be calculated by

Existing Resource Amount (k value=80)=80*M1+16*M2+8*M3+4*M4+2*M5+1*M6

[0067] After the k value is changed to 1 (k value=1), the changed resource amount becomes

Changed Resource Amount (k value=1)=80*(M1+1)+1 6*M2+8*M3+4*M4+2*M5+ 1*(M6−1)=Existing Resource Amount+79

[0068] The existing resource amount does not exceed the maximum resource amount Max_R, whereas the changed resource amount can exceed the maximum resource amount Max_R. Therefore, in this case, the CRNC determines a minimum k value not exceeding the maximum resource amount Max_R instead of the recommended k value transmitted by the SRNC.

[0069] That is, the CRNC determines the k value in accordance with Equation (2) below.

k_value=min(k value: Condition #1) Equation (2)

[0070] In Equation (2), Condition #1 1$\left(\mathrm{Exis\; ting}\mathrm{Resource}\mathrm{Amount}\right)+\frac{80}{\mathrm{kvalue}-1}\le \mathrm{Max\_R}.$

[0071] Equation (2) above indicates that a minimum k value must be selected from the k values satisfying Condition #1. Herein, Equation (2) will be called “k value determination algorithm.” A process of determining a k value for a particular UE by a CRNC according to the first embodiment of the present invention will be summarized below.

[0072] If a recommended k value received from an SRNC is defined as k′, the k value is determined by the following algorithm. 2