HK1175918A - Radio network controller - Google Patents

Abstract

A radio network controller (RNC) for controlling transmission power of a downlink (DL) enhanced uplink (EU) signaling channel, the RNC comprising: a transceiver configured to transmit and receive signals to and from a Node B; and a controller configured to determine EU transmission failure statistics perceived on the downlink EU signaling channel and adjust transmission power offset for at least one of an acknowledge (ACK) message and a non-acknowledge (NACK) message transmitted over the DL EU signaling channel based on the EU transmission failure statistics, wherein the controller is configured to determine the EU transmission failure statistics by subtracting a number of EU media access control (MAC-e) failures of a wireless transmit/receive unit (WTRU) reported by the WTRU from the number of MAC-e failures of the WTRU reported by a Node-B.

Description

Radio network controller

The present application is a divisional application of the chinese patent application having an application number of 200580011540.9, an application date of 27/04/2005, entitled "method and system for controlling transmission power of a downlink signaling channel based on enhanced uplink transmission failure statistics".

Technical Field

The present invention relates to a wireless communication system, which includes a wireless transmit/receive unit (WTRU), at least one node-B and a Radio Network Controller (RNC). More particularly, the present invention relates to a method and system for controlling a Downlink (DL) Enhanced Uplink (EU) signaling channel based on Enhanced Uplink (EU) transmission and scheduling information reception failure statistics reported by the WTRU and/or the node-B to the RNC, making the enhanced dedicated channel (E-DCH) downlink signaling channel more reliable.

Background

Methods to improve Uplink (UL) coverage, throughput, and transmission delay time are currently being investigated in the third generation partnership project (3 GPP) release 6 (R6). To achieve these goals, the node B will take over the responsibility of scheduling and assigning uplink resources to the WTRU, the node B can make more efficient decisions, and it will be better to manage short-term based radio resources than the RNC, even though the RNC maintains universal overall control.

A new Medium Access Control (MAC) function/entity, referred to as MAC-E, Enhanced Uplink (EU), has been designed in WTRUs and node-bs to handle the transmission and reception of E-DCH transmissions, which must be efficiently and reliably transmitted to the WTRU via a DL EU signaling channel in order to properly support the EU, such as channel allocation, transmission feedback (i.e., Acknowledgement (ACK) or Negative Acknowledgement (NACK)), and other feedback information (e.g., power control commands or channel quality).

Power control over the shared DL EU signaling channel, which is essential to support proper operation of the DL EU signaling channel, reduces overall interference and thus makes the use of radio resources more efficient.

Disclosure of Invention

A Radio Network Controller (RNC) for controlling transmission power of a Downlink (DL) Enhanced Uplink (EU) signaling channel, the RNC comprising: a transceiver configured to transmit and receive signals to and from a node B; a controller configured to determine EU transmission failure statistics perceived on the downlink EU signaling channel and adjust a transmission power offset of at least one of Acknowledgement (ACK) messages and non-acknowledgement (NACK) messages transmitted over the DL EU signaling channel based on the EU transmission failure statistics; wherein the controller is configured to determine the EU transmission failure statistics by subtracting a number of EU MAC-e failures for a wireless transmit/receive unit (WTRU) reported by the WTRU from a number of medium access control (MAC-e) failures for the WTRU reported by a node-B.

The invention is a method and system for controlling the transmission power of at least one DL EU signaling channel, such that E-DCH DL signaling is efficiently and reliably sent to a WTRU, the transmission power of the DL EU signaling channel for a particular WTRU-specific DL signaling is based on the current DL-specific control channel power plus a power offset, and for a plurality of WTRUs sharing the used DL signaling, the transmission power of the DL EU signaling channel is based on the power setting of the RNC plus a power offset. The RNC monitors EU transmission failure statistics reported by the node-bs and WTRUs to evaluate NACK-to-ACK misinterpretation statistics.

The node-B reports the EU transmission failure statistics at the node-B to the RNC, and the WTRU reports the EU transmission failure statistics at the WTRU to the RNC. The RNC then adjusts the NACK to ACK power ratio based on the estimated NACK to ACK misinterpretation statistics. When the node-B sends channel allocation information to the WTRU after the WTRU does not initiate EU transmission, or the data rate/frequency of E-DCH transmission is different from that described in the channel allocation information, the node-B calculates the reception statistics of the failed scheduling information (i.e., channel allocation information) by checking.

The WTRU may also check to calculate the reception statistics of failed scheduling information within a specified period of time after the request is sent, if the EU channel allocation request is not responded to. The RNC monitors failed scheduling information reception statistics reported by the WTRU and the node B to evaluate statistics of scheduling information reception errors. The RNC adjusts the power offset for the scheduling information range based on statistics of scheduling information reception failures.

Drawings

The invention may be understood in more detail by reference to the following description of a preferred embodiment, given as an example, and the accompanying drawings, in which:

FIG. l is a block diagram of a wireless communication system in accordance with the present invention;

FIG. 2 is a signal diagram between the system components of FIG. 1 for performing transmit power control according to the present invention on a DL EU signaling channel;

FIG. 3 is a flowchart of a process for performing transmission power control over a DL EU signaling channel in accordance with one embodiment of the present invention; and

FIG. 4 is a flowchart of a process for performing transmission power control over a DL EU signaling channel according to another embodiment of the present invention.

Detailed Description

The term "WTRU" as used herein includes, but is not limited to, a User Equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology "node B" includes but is not limited to a base station, a site controller, an access point, or any other interfacing device in a wireless environment.

The features of the present invention may be integrated into an Integrated Circuit (IC) or may be configured on a circuit comprising a plurality of interconnected components.

Fig. 1 is a wireless communication system 100 in accordance with the present invention. The system 100 includes a WTRU102, at least one node-B104, and an RNC 106. The RNC controls overall EU operation by configuring EU parameters of the node-bs 104 and the WTRUs 102, such as initial transmission power levels, maximum allowed EU transmission power, or spare channel resources per node-B. Between the WTRU102 and the node-B104, a Dedicated Physical Control Channel (DPCCH) 114, an E-DCH108, an UL EU signaling channel 112, and a DL EU signaling channel 110 are established.

For E-DCH transmissions, the WTRU102 sends an E-DCH allocation request to the node-B104 via the E-DCH108 or the UL EU signaling channel 112, and in response, the node-B104 sends channel allocation information to the WTRU102 via a DL EU signaling channel. After EU radio resources are allocated to the WTRU102, which transmits data via the E-DCH108, the node-B104 sends an ACK or NACK of hybrid automatic repeat request (H-ARQ) via the DL EU signaling channel 110 in response to the E-DCH transmission.

When the WTRU102 is configured by the RNC 106 to operate on the E-DCH108, the power offset (e.g., ACK/NACK, scheduling information, etc.) for each information range transmitted via the DL EU signaling channel 110 is also configured by the RNC 106 and sent to the node-B104 via Iub/lur 108, and these initial power offsets are determined by the RNC based on the probability of error required for the information range, which power offset needs to be adjusted during operation of the E-DCH108 on the DL EU signaling channel 110 according to the actual experienced quality of service of the DL EU signaling channel 110.

For DL signals dedicated to a particular WTRU102, the transmission power of the DL EU signaling channel 110 is based on the current DL dedicated control channel power plus a power offset. For DL signaling shared by multiple WTRUs 102, the transmission power of the DL EU signaling channel 110 is based on the power level set by the RNC 106 plus a power offset.

For each WTRU102, the transmission power of the DL EU signaling channel 110 is controlled separately, and the determination of the transmission power of the DL EU signaling channel 110 for a particular WTRU102 is based on the transmission power of the DL Dedicated Physical Control Channel (DPCCH) 114 of the WTRU102 plus a power offset, it is theorized that the DPCCH power is referenced and the transmission power of the DPCCH of the WTRU102 is controlled according to the Universal Mobile Telecommunications Service (UMTS) release 99/4/5 standard.

Different power offsets may be issued by the node B104 based on information (i.e., ACK/NACK, channel quality feedback, scheduling information, etc.). For the ACK/NACK information range, a higher power offset may be used to transmit NACKs instead of ACKs, since NACK-to-ACK misinterpretation may cause a more serious problem than ACK-to-NACK misinterpretation.

Fig. 2 is a process 200 performed by the system 100 for performing transmit power control over the DL EU signaling channel 110 in accordance with the present invention. The RNC 106 sends an initial configuration of a power offset for the DL EU signaling channel 110 to the node B104 (step 202). The RNC 106 monitors the reception statistics of failed MAC-e transmissions and/or failed channel allocation information reported by the WTRU102 and/or the node-B104 to evaluate the probability of errors in reception and transmission over the DL EU signaling channel 110 (steps 204, 206). In step 207, the RNC 106 evaluates NACK-to-ACK misinterpretation statistics based on the reported failed MAC-e transmission statistics, if the NACK-to-ACK misinterpretation statistics are evaluated above a threshold, the RNC 106 adjusts the NACK-to-ACK power ratio (i.e., power offset ratio), and the RNC 106 adjusts the power offset of the scheduling information accordingly based on the received statistics of the failed channel allocation information from the WTRU102 and the node-B104 (step 208). In this way, the EU will remain well functioning and radio resources are not used correctly.

Fig. 3 is a flow chart of a process 300 for controlling the transmission power of a DL EU signaling channel according to an embodiment of the present invention. The WTRU102 is configured for EU operation (step 302), the WTRU determines whether there is data to be transmitted via the E-OCH 108 (step 304), if so, the WTRU102 sends a channel allocation request to the node-B via the E-DCH108 or UL EU signaling channel 112 (step 306), the node-B104 receives the request, and sends channel allocation information to the WTRU102 via the DL EU signaling channel 110 (step 308).

After sending the channel assignment request, the WTRU102 monitors the DL EU signaling channels 110 for channel assignment information, and the node-B also monitors E-DCH transmissions after sending channel assignment information via the DL EU signaling channels 110 (step 310).

The channel allocation information sent to the WTRU102 may not be successfully delivered, and the lower field of a failed transmission of channel allocation information depends on how the allocation is performed. For deterministic allocations, the WTRU102 may not transmit at all, and for statistical allocations, the WTRU may not transmit, or may transmit data at a rate and/or at a sustained level that is different than that recorded by the channel allocation information.

Deterministic allocation is an allocation where the maximum allocated transmission power and/or data rate is specified and the WTRU102 may transmit at any time as long as its transmission power and/or data rate does not exceed the maximum. Statistical allocation is another allocation where the persistence level (probability) is specified in addition to a specified maximum allocated transmission power and/or data rate, and the WTRU102 may continue transmitting based on the persistence level or transmit at a transmission power and/or data rate determined by the persistence level.

If the WTRU102 does not initiate EU transmission after the node-B104 sends the channel assignment, or if the data rate/frequency of the E-DCH transmission is different than what is specified in the channel assignment, the node-B104 calculates and reports a reception statistic for failed scheduling information by checking (step 312), which may be based on a received power threshold. The WTRU102 may also calculate and report failed scheduling information reception statistics by detecting when there is no response to the EU channel allocation request within a specified time period after the transmission of the channel allocation request (step 312).

If the statistics of failed transmissions of channel assignment information is above a predetermined threshold, the RNC 106 increases the transmission power of the scheduling information field on the DL EU signaling channel 110 (step 314), signaling the RNC via Iub/Iur 118 to adjust the power offset.

Fig. 4 is a flowchart of a process 400 for controlling the transmission power of a DL EU signaling channel 110 according to another embodiment of the present invention. After the WTRU102 is configured for EU operation and channel assignment information is received, at step 402, the WTRU102 transmits data via the E-DCH108 (step 404), which the node-B104 receives and decodes. The node-B104 then sends feedback information (i.e., ACK or NACK) to the WTRU102 based on the decoded data (step 406).

The WTRU102 and/or the node-B104 calculate MAC-e failure statistics and report them to the RNC 106 for adjusting the NACK-to-ACK ratio (i.e., power offset ratio) (step 408). According to one embodiment, the WTRU102 reports the number of MAC-e failures on the WTRU102, which is the number of data blocks that could not be successfully transmitted. A MAC-e failure occurs when a data block cannot be transmitted on the MAC-e due to, for example, a maximum amount of retransmission or a maximum delay of the data block. The node-B104 reports the number of MAC-e failures of the WTRU102 on the node-B104, which is the number of data blocks that were not successfully received on the MAC-e in the node-B104.

Sometimes, the WTRU102 interprets a successfully transmitted data block as not actually being successfully received by the node-B104 because a NACK for the data block is misinterpreted as an ACK at the WTRU 102. The RNC 106 determines the number of NACK-to-ACK misinterpretations for the WTRU102, i.e., the number of MAC-e failures of the WTRU102 reported by the node B minus the number of MAC-e failures of the WTRU102 reported by the WTRU 102.

Alternatively, the RNC 106 may utilize the number of Radio Link Control (RLC) recovery requests for the WTRU 102's E-DCH data at the RNC 106 to determine the number of NACK to ACK misinterpretations, which may be collected or calculated internally by the RNC 106. The WTRU102 interprets the successfully transmitted data block as possibly having an RLC recovery request for the data later because NACK to ACK misinterpretation. The RNC 106 determines the number of NACK-to-ACK misinterpretations for the WTRU102, i.e., the number of RLC recovery requests for the E-DCH data of the WTRU102 at the RNC 106, minus the number of MAC-E failures of the WTRU102 reported by the WTRU 102.

The MAC-e failure statistics of the WTRU102 on the WTRU102 are reported to the RNC 106 via RRC procedures, and the MAC-e failure statistics of the WTRU102 on the node-B104 are reported to the RNC 106 via Iub/Iur 118.

If the NACK-to-ACK misinterpretation probability is above a predetermined threshold, the RNC 106 increases the power ratio of the NACK-to-ACK power offset (step 410). Since there is a higher power offset, NACK will be sent to the WTRU more reliably, the RNC 106 sends a signal via Iub/Iur 118 to adjust the ACK and NACK power offsets (or the power ratio between ACK and NACK), and the node-B104 uses the power offsets/ratios to set the transmission power of the EU DL signaling channel.

Although the features and elements of the present invention are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements of the present invention.

Claims (10)

1. A Radio Network Controller (RNC) for controlling transmission power of a Downlink (DL) Enhanced Uplink (EU) signaling channel, the RNC comprising:

a transceiver configured to transmit and receive signals to and from a node B;

a controller configured to determine EU transmission failure statistics perceived on the downlink EU signaling channel and adjust a transmission power offset of at least one of Acknowledgement (ACK) messages and non-acknowledgement (NACK) messages transmitted over the DL EU signaling channel based on the EU transmission failure statistics;

wherein the controller is configured to determine the EU transmission failure statistics by subtracting a number of EU MAC-e failures for a wireless transmit/receive unit (WTRU) reported by the WTRU from a number of medium access control (MAC-e) failures for the WTRU reported by a node-B.

2. The RNC of claim 1, wherein the WTRU MAC-e failure occurs when a number of retransmissions exceeds a predetermined retransmission limit.

3. The RNC of claim 1, wherein the WTRU MAC-e failure occurs when EU transmission data expires before being successfully transmitted.

4. The RNC of claim 1, wherein the controller determines the EU transmission failure statistics by subtracting a number of Radio Link Control (RLC) recovery requests for a wireless transmit/receive unit (WTRU) reported by the WTRU for MAC-e failures of the WTRU.

5. The RNC according to claim 1, wherein the controller sets a transmission power of the NACK message to be higher than a transmission power of the ACK message.

6. The RNC of claim 1, wherein the controller adjusts transmission power of EU channel allocation information.

7. The RNC of claim 6, wherein the controller determines the EU transmission failure statistics as a number of times that no E-DCH transmissions have been received by a node B from a wireless transmit/receive unit (WTRU) within a predetermined time period after the EU channel allocation information is transmitted.

8. The RNC of claim 6, wherein the controller determines the EU transmission failure statistics based on a number of times a node B receives a UE transmission inconsistent with the EU channel allocation information.

9. The RNC of claim 6, wherein the controller determines the EU transmission failure statistics based on a number of times a wireless transmit/receive unit (WTRU) fails to receive channel allocation information from a node-B in response to the channel allocation request within a specified time period.

10. The RNC of claim 1, wherein a transmission power level of a DL EU signaling channel for a particular wireless transmit/receive unit (WTRU) is determined based on a transmission power of a DL Dedicated Physical Control Channel (DPCCH) for the particular WTRU.