Below, aspects of the invention are explained referring to the drawings. However, these aspects do not limit the technical scope of the invention.
In this invention, when user equipment UE which is performing HSDPA communication using a HS-DSCH changes from the current communication area (cell) to another cell, a base station control device (hereafter “control device”) RNC checks whether there exists, in the wireless base station device (hereafter “base station”) BTS which is the cell change origin, accumulated data to be transmitted to the user equipment UE (transmit-wait data); if there exists accumulated data, the accumulated data is transmitted, via the control device RNC, to the base station BTS at the change destination. By this means, even upon movement between HSDPA cells requiring an interruption for movement between cells, the user equipment UE can change cells without the occurrence of data loss.
In addition to the processing of the prior art, in an aspect of this invention, when the control device RNC initiates cell change processing, an accumulated data check request is transmitted to the base station BTS1 of the cell change origin via the existing channel with the base station BTS1 (S110). The base station BTS1 checks its own buffer for the existence of accumulated data to be transmitted to the user equipment UE which has changed cells (S112), and if accumulated data exists, transfers the accumulated data to the control device RNC (S116). User equipment units UE are identified from the HS-DSCH RNTI and Mac-d Flow IDs. The control device RNC establishes a new channel with the base station BTS2, and after disconnecting the channel with the base station BTS1 transfers the accumulated data to the base station BTS2. The base station BTS2 transmits the accumulated data thus sent to the user equipment UE by means of communication with the user equipment UE using the newly established Mac-hs layer. After accumulated data transmission, the control device RNC transmits the next data group to the base station BTS2.
The base station BTS1 is the cell change origin base station BTS, and the base station BTS2 is the cell change destination base station BTS. A HS-DSCH channel connecting the user equipment UE and the control device RNC via the base station BTS1 is established. The protocol used between the user equipment UE and base station BTS1 is Mac-hs, and the protocol used between the base station BTS1 and the control device RNC is Mac-d Flow.
The user equipment UE receives CPICH from each base station BTS and monitors the base station BTS with the most favorable radio wave state (best cell) (S200). When the base station BTS with the most favorable radio wave state changes from base station BTS1 to base station BTS2, the user equipment UE transmits to the control device RNC a RRC (Radio Link Control Protocol) Measurement Report Event message giving notification of this fact (S202). RRC is a communication protocol between user equipment UE and a control device RNC providing for straight-through transfer via base stations BTS.
When the relevant message is received by the control device RNC, the control device RNC transmits to base station BTS2 a NBAP (Node B Application Part Protocol) Radio Link Reconfiguration Prepare message requesting establishment of a new HS-DSCH channel (S204). In parallel with this, the control device RNC transmits to base station BTS1 a NBAP (Node B Application Part Protocol) Radio Link Reconfiguration Prepare message requesting deletion of the current HS-DSCH channel (S206).
Upon receiving a Radio Link Reconfiguration Prepare message from the control device RNC, base station BTS2 establishes a new HS-DSCH channel to the user equipment UE, and transmits to the control device RNC a NBAP Radio Link Reconfiguration Ready message providing notification of the fact of this establishment (S214). When the new HS-DSCH channel with base station BTS2 is established, the control device RNC uses an RRC Physical Channel Reconfiguration message to notify the user equipment UE of the change to the new HS-DSCH channel (S216). The user equipment UE responds to the RRC Physical Channel Reconfiguration message with a Physical Channel Reconfiguration Complete response message (S218). By this means, processing for the cell change from base station BTS1 to base station BTS2 is completed.
On the other hand, upon receiving the Radio Link Reconfiguration Prepare message from the control device RNC, base station BTS1 deletes the current HS-DSCH channel.
At this time, the control device RNC adds a “Piling up Mac data confirm request” IE (Information Element), to check for the presence of accumulated data for the user equipment UE, to the NBAP Radio Link Reconfiguration Prepare message for transmission to the change origin base station BTS1. The term “piling up” is used as same meaning of “accumulating”, and the term “confirm” is used as same meaning of “checking” in the present application.
Upon receiving the RADIO LINK RECONFIGURATION PREPARE message (with “Piling up Mac data confirm request” IE), the change origin base station BTS1 performs processing to delete the HS-DSCH channel to the user equipment UE, and checks whether there is accumulated data for the user equipment UE. In order to identify the user equipment UE, HS-DSCH RNTI (an identifier for each user equipment unit UE) and the Mac-d Flow ID (an ID added to data flow) are employed.
Upon completion of the HS-DSCH channel deletion processing, the change origin base station BTS1, when returning a RADIO LINK RECONFIGURATION READY message which is a response to the RADIO LINK RECONFIGURATION PREPARE message, adds to the message a “Piling up Mac data confirm response” IE, to report the presence or absence of accumulated data. The “Piling up Mac data confirm response” IE comprises a “Buffer size information” IE indicating the size (in bytes) of the accumulated data (S208).
When there is accumulated data for the user equipment UE (S209 in
Having received all the accumulated data, the control device RNC stores the data (S212), establishes a HS-DSCH channel with the change destination base station BTS2, and monitors for the completion of cell change processing (S219 in
When the accumulated data size in the “Buffer size information” IE is 0, there is no accumulated data for the user equipment UE, and so the control device RNC continues subsequent processing without monitoring the accumulated data reception state. Moreover, the change origin base station BTS1 does not transmit accumulated data.
In this way, in this aspect of the invention the transmit-wait data (untransmitted data) for a user equipment UE which has changed cells is acquired by the control device RNC from the cell change origin base station BTS1 and is transferred via the control device RNC to the cell change destination base station BTS, so that even when there exists accumulated data (transmit-wait data) which has already been transmitted by the control device RNC to the cell change origin base station BTS but has not yet been transmitted to the user equipment UE, the accumulated data can be transferred to the change destination base station BTS, and so HSDPA communication can be performed without data loss even during cell changes.
Further, because the change origin base station BTS is queried as to the existence of accumulated data, it is sufficient merely to add an information element (IE) for confirmation of the presence of accumulated data to an existing message (NBAP protocol signal) used for deletion of the channel with the change origin base station BTS, without adding a new message; hence existing message communication can be used to effect transfer of accumulated data, without the need for complex message communication.
Moreover, after transmitting the accumulated data of the change origin base station BTS to the user equipment UE, the change destination base station BTS then transmits to the user equipment UE any data addressed to the user equipment UE and transmitted to the change destination base station BTS, so that data is transmitted in the correct order even during cell changes.
Number | Date | Country | Kind |
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2006-167950 | Jun 2006 | JP | national |