HK1087580A - Wireless multi-cell communication system and method for managing resource power to provide high speed downlink packet access services - Google Patents

Description

Wireless multi-cell communication system and method for managing resource power to provide high speed downlink packet access services

Technical Field

The present invention relates generally to a wireless multi-cell communication system, and more particularly to a wireless multi-cell communication system that controls the transmit power used by a base station when providing High Speed Downlink Packet Access (HSDPA) services.

Background

In the Universal Mobile Telecommunications System (UMTS) versions R99/R4 and R5, the third Generation partnership project (3GPP) wideband code division multiple Access (W-CDMA) system has been outlined. UMTS Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes, version R5, have been incorporated as a feature of High Speed Downlink Packet Access (HSDPA) to improve Downlink (DL) traffic, transmission delay, and spectral efficiency. The principle of HSPDA is to schedule packet transmissions on the air interface to different mobile devices as a function of their instantaneous experienced radio and service status in a dynamic manner (i.e., fast, e.g., 2 ms in FDD or 10 ms in wideband TDD). The key functions of HSPD in both FDD and TDD modes are (i) fast repeat request (Hybrid ARQ) of DL packets received in error over the air interface (Uu), (ii) fast Uplink (UL) notification of DL packets received in error (Acknowledgement)/negative Acknowledgement), (iii) fast channel feedback in the UL in the DL channel state of a wireless transmit/receive unit (WTRU), and (iv) bidirectional bulk (fat-pipe) scheduling to efficiently serve numerous users in the DL. This functionality, i.e., fast, dynamic HSPDA packet scheduler, is located in the base station (node B) and operates in a rather autonomous manner from the Radio Network Controller (RNC).

The RNC in a UMTS network is responsible for network control and Radio Resource Management (RRM). The RNC utilizes a Dynamic Channel Allocation (DCA) algorithm to perform tasks such as user admission control and interface management, and is therefore critical to ensure reliable system operation and maximize efficiency. An efficient method is achieved when a plurality of users can be served or when the total traffic is reached.

In an FDD system, the RNC allocates to each cell a certain number of spreading codes (spreading codes) used by the HSDPA data channel (HS-DSCH). In addition, in the FDD system, the HS-DSCH is transmitted over a Transmission Timing Interval (TTI) (3 × 0.66 ms — 2 ms) of 3 consecutive timeslots. The RNC communicates with the base station, noting that the spreading codes can be used for HSDPA by means of Iub/Iur signaling, and then passes control to the base station as to when to send DL packets in that code. The RNC also signals the WTRU by means of Radio Resource Control (RRC) signaling which physical channels to listen to are HSDPA control channels, i.e., high speed shared control channels (HS-SCCH), which are then used by the base station to dynamically signal to the WTRU that a scheduled DL packet on its HS-DSCH has arrived. The same information is sent from the RNC to the base station that tells the base station which HS-SCCH channel to note to the WTRU when sending HSDPA data to a WTRU. In addition, the base station follows an independent basis to determine when to transmit HSDPA data to a particular WTRU based on its own HSDPA scheduler.

In a TDD system, the RNC allocates a certain number of Timeslots (TS) for the HSDPA data channel (HS-DSCH) to each cell. The RNC communicates with the base station, noting that the TS and spreading codes can be used for HSDPA by means of Iub/Iur signaling, and then passes control to the base station as to when to send DL packets in the TS and codes. The RNC also signals the WTRU by means of RRC signaling as to which physical channels to listen to as HSDPA control channels (i.e., high speed shared control channels (HS-SCCH)), which are then used by the base station to dynamically signal to the WTRU that a scheduled DL packet on its HS-DSCH has arrived. The same information is sent from the RNC to the base station that tells the base station which HS-SCCH channel to note to the WTRU when sending HSDPA data to a WTRU. In addition, the base station follows an independent basis to determine when to transmit HSDPA data to a particular WTRU based on its own HSDPA scheduler.

In any CDMA system, efficient management of the resources "power" is critical to maintaining low interference and maximizing system capacity (i.e., the number of users supported simultaneously, and the total data traffic of all cells in an area).

For interference management, both FDD and TDD employ fast Closed Loop (CL) power control (PL) in the DL of the dedicated channel. Also for the most common FDD and TDD existing releases 99, 4, and 5(R99, R4, and R5) Dedicated Channel (DCH) cases, the CL PC operates within the control power limits of the RNC. Therefore, a dynamic range can be pre-established at DCH setup and the RNC will eventually adjust this range during DCH active lifetime. Since the RNC must make complex decisions to enhance system performance, the RNC signals the node B, the PC dynamic range, in the form of a maximum Tx power that cannot be exceeded, and a minimum Tx power that needs to be maintained. For example, a WTRU that requires excessive power and therefore often reaches the upper limit of the allowable dynamic range may generate an over-proportional (over-proportional) interference level to other users in the system. The RNC may need to transfer or handover (handover) the WTRU's connection. Thus, tight RNC control of power limits while still allowing autonomous base station operators within established power limits would be a key feature of a CDMA system operating in conjunction with power control.

In the common channel for both TDD and FDD systems, tight control of the possible power settings is important to ensure proper coverage and service is available.

In R5, greater autonomy is provided to the base station than in R99 and R4. In particular, the scheduling and transmission of the HS-DSCH is only subject to the reliability of the node B. The RNC can still maintain semi-static control by signaling both the WTRU and the base station the spreading codes and TS used for HSDPA services and to ensure the use of the control channel (HS-SCCH) and the high speed shared information channel (HS-SICH). Once this architecture has been deployed, control is completely passed to the base station, independently scheduling DL packet transmissions autonomously.

In FDD applications, the RNC allocates a maximum amount of DL power that is not exceeded by HSDPA service and is a fraction of the total available base station Tx DL power in a semi-static manner to keep the relatively high level of interference generated by the HSDPA channels within reasonable limits. This can be accomplished by signaling over the RNC base station interface (Iub) when configuring the DL channels in the base station. Otherwise, an HSDPA WTRU at a cell boundary will eventually be served by the node B at a high HSDPA data rate and generate a high level of interference, causing any service in neighboring cells to be severely impacted even detrimentally, and resulting in an unacceptable reduction in overall system capacity or degradation of service for non-HSDPA (R99 and R4) WTRUs. The RNC set maximum HSDPA power fraction per cell then indirectly determines the maximum data rate by which any given WTRU may be served. Another reason this control mechanism exists is that a certain amount of node B DL Tx power needs to be reserved for non-HSDPA channels, e.g., pilot channels, common control channels, or non-HSDPA DCHs.

A method and system for providing HSDPA services using an RNC control mechanism to establish a maximum HSDPA power level for each cell does not exist in TDD. The only way to accommodate this is to dedicate certain timeslots to the HS-DSCH and others to other existing services (dedicated, shared, etc.). However, because the HS-DSCH channels and supporting channels (HS-SCCH or associated dedicated channels) cannot exist in common timeslots, the system does not allow the WTRU to optimize its resource/power usage by minimizing the timeslots a WTRU needs to handle the HS-DSCH channels and supporting channels. This lack of RNC control is a significant obstacle for reliable R5 TDD system operation, and HSDPA-enabled TDD system multi-cell arrangements that co-exist with R99/R4 non-HSDPA WTRUs and even potentially in HSDPA WTRUs when efficient use of HS-DSCH and dedicated to other control channels is required.

The maximum allowed node B Tx power may be allocated by the RNC at the time of cell set-up, but it does not differ between a plurality of time slots of a base station and is applicable to all of the time slots. And there is no difference between non-HSDPA and HSDPA channels.

It is desirable to have a signaling mechanism between the RNC and a plurality of base stations that provides HSDPA services without suffering the drawbacks of the known arrangements.

Disclosure of Invention

A method and wireless multi-cell communication system for providing High Speed Downlink Packet Access (HSDPA) services. The system includes a Radio Network Controller (RNC) and a plurality of base stations in communication with the controller. The RNC transmits a control signal to at least one base station having assigned thereto a plurality of timeslots, such as in a time division duplex (TSS) system, and/or a plurality of frames including Transmission Time Intervals (TTIs), such as in a Frequency Division Duplex (FDD) system, to establish HSDPA channels. The control signal indicates a maximum allowed HSDPA transmit power for each of the timeslots and/or TTIs. The base station may send a feedback signal to the RNC indicating the power measurements of the transmitted HSDPA timeslots and/or TTIs within a given time period.

Drawings

The invention will be understood in more detail by way of the following description of preferred embodiments, given by way of example only, and made apparent in conjunction with the accompanying drawings, in which:

figure 1 is a diagram illustrating a wireless multi-cell communication system for providing HSDPA services in accordance with the present invention;

FIG. 2A is a diagram illustrating downlink transmission power allocation in cells based on timeslots transmitted by a TDD system according to one embodiment of the present invention;

FIG. 2B is a diagram illustrating downlink transmission power allocation among cells based on HS transmission time intervals transmitted by an FDD system, according to one embodiment of the present invention; and

fig. 3 is a flow chart including method steps for providing HSDPA services in the system of fig. 1.

Detailed Description

The present invention is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout.

Although the present invention has been described in connection with TDD and FDD type wireless communication systems, it is important to note that the present invention may be implemented with any type of wireless communication system, including time division-synchronous code division multiple access (TD-SCDMA) and CDMA 2000.

A wireless transmit/receive unit (WTRU) is typically used to establish a communication link. A WTRU includes, but is not limited to, a user terminal equipment, mobile base station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. Such illustrative types of wireless environments include, but are not limited to, wireless local area networks and public mobile communication networks. The WTRU described herein is capable of operating in a time slotted mode or a frequency divided mode, such as TDD and FDD, respectively. A base station includes, but is not limited to, a node B, site controller, access point, or other interfacing device in a wireless environment.

Figure 1 illustrates a wireless multi-cell communication system 100 capable of providing HSDPA services in accordance with the present invention. The system 100 includes a Radio Network Controller (RNC) and a plurality of base stations 110, 115, and 120 operable in cells 125, 130, and 135, respectively. The RNC105 may send a control signal 140A, 140B, 140C to a base station 110, 115, 120, at least one base station having a plurality of timeslots assigned thereto for establishing HSDPA channels, and the control signal 140A, 140B, 140C may indicate a maximum allowed HSDPA transmission power for each timeslot. At least one base station 110, 115, 120 transmits a feedback signal 145A, 145B, 145C to the RNC105, and wherein the feedback signal 145A, 145B, 145C indicates the transmitted HSDPA timeslot power measurements for a given time period. The system 100 may be a TDD system that utilizes an existing Iub interface such that some or all cells/sectors in a deployment area of the system 100 may provide HSDPA service.

In the system 100, the RNC105 may communicate with each base station 110, 115, 120 and inform each timeslot control information regarding the maximum allowed HSDPA TS transmission (Tx) power that cannot be exceeded by the respective HS-DSCH timeslots of a base station 110, 115, 120. The maximum allowed HSDPA Tx power may be set to different values for different HSPDA TS of a particular cell. If the same TS is enabled for HSDPA service in different cells, different maximum allowable HSPDA TS Tx power levels can be allocated for each cell. For example, cell 125 is not allowed to exceed 5dBm in TSm for its HSPDA service, and cell 130 will not exceed 25dBm for its HSDPA service provided in the same TSm.

Figure 2A is a diagram illustrating an exemplary HSDPA TS configuration 200 with various HSDPA power settings for a plurality of timeslots 205 (including timeslot TS)_m、TS_m+1、TS_m+2、TS_m+3、TS_m+4、TS_m+5) Each of the complex cells 125, 130, 135. The maximum possible Radio Frequency (RF) base station power level for each cell, and timeslot, will be depicted by dotted lines 210A, 210B, and 210C, respectively.

Fig. 2A illustrates three different TDD timeslot allocation schemes 220, 230, 240 that may occur. In a TDD, the set of timeslots allocated to HSDPA services per frame varies from cell to cell.

For scheme 220, multiple cells provide HSDPA service in the same TS, whereby a maximum power setting is established to ensure adequate coverage for each TS. Scheme 220 may maximize system-wide HSDPA traffic.

For scheme 230, the multiple cells will use a plurality of TSs as non-HS channels, e.g., to ensure sufficient coverage for the common channel. Scheme 230 may ensure that the non-HSDPA channels are supported simultaneously in the same TS.

For scheme 240, cell 1 provides HSDPA service and cell 2 uses the R99 channel in the same TS. A maximum power setting may be established to guard the R99 channel and to ensure adequate coverage for the TS in cell 1. Scheme 240 may ensure that non-HSDPA channels are supported synchronously in adjacent cells, the same TS.

Control information having the maximum allowed HSDPA TS Tx power setting may be communicated from the RNC105 to the cells 125, 130, 135 at HSDPA resource pool (resource pool) setting in a particular base station 110, 115, 120. Along with this information, the base station will obtain the TS and spreading codes to use in conjunction with an HSDPA resource pool setting sent from the RNC105 to the base station. It is also possible to adjust the value of the maximum allowed HSDPA TS Tx power setting during the period of efficient use of HSDPA resources by a given base station.

The respective base stations 110, 115, 120 may communicate with the RNC105 by means of feedback information 145A, 145B, 145C, preferably, but not exclusively, in the form of measurements such as the effective transmit HSDPA TS Tx power observed over a given time period, such as 100 milliseconds or longer. This may provide Radio Resource Management (RRM) algorithms resident in the RNC105 regarding the efficiency of the HSDPA power allocation and assist in the decision making process.

One or more RRM algorithms resident in the RNC105, such as slow/fast-DCA, congestion/link control, or others, may utilize the WTRU (not shown) and the information regarding the used Tx power/interference level (from HSDPA and non-HSDPA channels) observed by the base stations 110, 115, 120 in the system 100 to maximize the system traffic or user capacity for HSDPA services or non-HSDPA services when HSDPA is present in one or more of the cells 125, 130, 135.

The maximum allowed HSDPA TS Tx power should ideally correspond to the maximum allowed sum of the code powers of all spreading codes in the same TS allowed to be used on one cell HS-DSCH. There may be equivalent versions of the above that are signaled but their functions remain the same in principle.

The feedback information 145A, 145B, 145C sent from the base stations 110, 115, 120 to the RNC105 should ideally correspond to an effective transmit power measurement on the sum of the code powers of all spreading codes in the same TS, and this measurement is averaged over a certain reporting period. Other functionally equivalent measurements or feedback may also be present.

In an FDD system, the allowed HSDPA service power in the DL can be set by the RNC on a per cell basis only. This is no different from the "time domain" one. Thus, for a given FDD cell, the very same power setting will apply to all TTIs available for performing HSDPA services.

Figure 2B illustrates an FDD HSDPA system architecture 270 whereby various HSDPA power settings used by the RNC105 are for each of a plurality of cells 125, 130, 135 that include five TTIs (TTI 1-TTI 5) for each of a plurality of frames (e.g., each 10 ms long), each TTI being 2 ms long. The maximum possible Radio Frequency (RF) base station power level for each cell, and TTI, will be depicted by dotted lines 280A, 280B, and 280C, respectively.

According to one embodiment, different FDD TTIs in a cell are allocated with different maximum Tx power settings. Furthermore, different sets of FDD HS-TTIs in a cell are allocated with different maximum Tx power settings. For example, all 5 HS-TTIs in frame n will share a common maximum power setting, but the 5 HS-TTIs in the next frame n +1 are assigned a different maximum power setting.

The RNC can block one or more HS-TTIs in a cell completely. For example, a cell may be configured to transmit HSDPA not in frame n, frame n +4, frame n +8, etc., but to allow transmission in other frames to support interference management and coverage extension.

Fig. 3 is a flow chart of a process 300 including method steps used by the system 100 in providing HSDPA services. The RNC105 transmits a control signal 140A, 140B, 140C to at least one of the base stations 110, 115, 120 associated with a plurality of timeslots and control signals 140A, 140B, 140C indicating a maximum allowed HSDPA transmission power for each of the timeslots. In step 310, at least one base station 110, 115, 120 sends a feedback signal 145A, 145B, 145C to the RNC indicating the transmitted HSDPA timeslot power measurements within a predetermined time period.

The foregoing is described as an illustrative embodiment of a signaling system between an RNC105 and base stations 110, 115, 120 utilizing the principles of the present invention. While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as described above.

Claims (18)

1. In a wireless multi-cell communication system including a Radio Network Controller (RNC) and a plurality of base stations in communication with the RNC, a method for providing High Speed Downlink Packet Access (HSDPA) services, the method comprising:

(a) the RNC transmitting a control signal to at least one of the base stations, the at least one base station having a plurality of timeslots assigned thereto for establishing a plurality of HSDPA channels, the control signal indicating a maximum allowed HSDPA transmission power for each of the timeslots; and

(b) the at least one base station transmits a feedback signal to the RNC, the feedback signal indicating the transmitted HSDPA timeslot power measurements within a predetermined time period.

2. The method of claim 1 wherein the predetermined time period is at least 100 milliseconds.

3. The method of claim 1 wherein the wireless multi-cell communication system is a time division duplex system wherein the RNC allocates a specified number of timeslots for HSDPA data channels to each cell.

4. The method of claim 1 wherein the maximum allowed HSDPA transmission power for a timeslot of a cell is different from the maximum allowed HSDPA transmission power for the same timeslot in a different cell.

5. A wireless multi-cell communication system for providing High Speed Downlink Packet Access (HSDPA) services, the system comprising:

(a) a Radio Network Controller (RNC); and

(b) a plurality of base stations in communication with the RNC, wherein:

(i) the RNC transmitting a control signal to at least one of the base stations, the at least one base station having a plurality of timeslots assigned thereto for establishing HSDPA channels, the control signal indicating a maximum allowed HSDPA transmission power for each of the timeslots; and

(ii) the at least one base station transmits a feedback signal to the RNC, the feedback signal indicating the transmitted HSDPA timeslot power measurements within a predetermined time period.

6. The system of claim 1 wherein the predetermined time period is at least 100 milliseconds.

7. The system of claim 1 wherein the wireless multi-cell communication system is a time division duplex system wherein the RNC allocates a specified number of timeslots for HSDPA data channels to each cell.

8. The system of claim 1 wherein the maximum allowed HSDPA transmission power for a timeslot of a cell is different from the maximum allowed HSDPA transmission power for the same timeslot in a different cell.

9. A method for providing High Speed Downlink Packet Access (HSDPA) services in a wireless multi-cell communication system, the system including a Radio Network Controller (RNC) in communication with a plurality of base stations, the method comprising:

(a) the RNC transmitting a control signal to at least one of the base stations, the at least one base station establishing a frequency division duplex cell having a plurality of frames, the frames including respective sets of Transmission Time Intervals (TTIs) assigned thereto for establishing HSDPA channels, the control signal indicating a maximum allowed HSDPA transmit power for each of the TTIs; and

(b) the at least one base station transmits a feedback signal to the RNC, the feedback signal indicating the transmitted HSDPA timeslot power measurements within a predetermined time period.

10. The method of claim 9 wherein different sets of TTIs in each frame are allocated different maximum allowed HSDPA transmit power settings.

11. The method of claim 9 wherein the predetermined time period is at least 100 milliseconds.

12. The method of claim 9 wherein the RNC is configured to disable particular ones of the TTIs.

13. The method of claim 9 wherein the RNC is configured to disable particular TTI sets included in the frame.

14. A wireless multi-cell communication system for providing High Speed Downlink Packet Access (HSDPA) services, the system comprising:

(a) a Radio Network Controller (RNC); and

(b) a plurality of base stations in communication with the RNC, wherein:

(i) the RNC transmitting a control signal to at least one of the base stations, the at least one base station establishing a frequency division duplex cell having a plurality of frames, the frames including respective sets of Transmission Time Intervals (TTIs) assigned thereto for establishing a plurality of HSDPA channels, the control signal indicating a maximum allowed HSDPA transmit power for each of the TTIs; and

(ii) the at least one base station transmits a feedback signal to the RNC, the feedback signal indicating the transmitted HSDPA timeslot power measurements within a predetermined time period.

15. The system of claim 14 wherein different sets of TTIs in each frame are allocated different maximum allowed HSDPA transmit power settings.

16. The system of claim 14 wherein the predetermined time period is at least 100 milliseconds.

17. The system of claim 14 wherein the RNC is configured to disable particular ones of the TTIs.

18. The system of claim 14 wherein the RNC is configured to disable particular TTI sets included in the frame.