Base station, mobile station, and communication method

The present invention relates to a base station that retransmits a transmission packet in response to a retransmission request for a transmission packet of a mobile station, and a mobile station that retransmits a transmission packet in response to a retransmission request for a transmission packet of a base station. The present invention relates to a communication method for retransmitting a transmission packet in response to a retransmission request for the transmission packet of.

As shown in FIG. 1, 3GPP Evolved UTRA and UTRAN defines a protocol stack of wireless interface protocols for transmitting user data between a base station and a mobile station (see Non-Patent Document 1). This protocol stack consists of a PDCP (Packet Data Convergence Protocol) layer, an RLC (Radio Link Control) layer, a MAC (Medium Access Control) layer, and a PHY (Physical) layer. The PDCP layer, RLC layer, MAC layer and PHY layer are terminated at the mobile station and the base station.

The transmission processing flow of user data at the base station in such a protocol stack is shown in FIGS. 2 to 4. Figure 2 shows the functional blocks in each layer. Further, FIG. 3 shows a specific transmission processing flow in the PDCP layer, and FIG. 4 shows a specific transmission processing flow in the RLC layer.

The transmission processing flow of the PDCP layer will be described below with reference to FIGS. 2 and 3. The PDCP layer receives data packets via the Radio Bearer. This data packet is, for example, an IP packet, and is recognized as a PDCP SDU (PDCP Service Data Unit) in the PDCP layer. The PDCP layer performs header compression processing (ROHC) and concealment processing (Ciphering) on this PDCP SDU, and sends the packet to the RLC layer. Depending on the application or operation, header compression processing or concealment processing may not be performed. Packets sent to the RLC layer are recognized as PDCP PDUs (PDCP Protocol Data Units) in the PDCP layer.

The transmission processing flow of the RLC layer will be described below with reference to FIGS. 2 and 4. The RLC layer receives data packets from the PDCP layer or via a wireless bearer. This packet is a PDCP PDU or IP packet, and is recognized as an RLC SDU (RLC Service Data Unit) at the RLC layer. The RLC layer performs segmentation or concatenation on this RLC SDU according to the transport block size of the TTI (Transmission Time Interval) to which the transmission opportunity is assigned, and performs the MAC layer via the logical channel. The segmented / integrated packet is sent to. This split / integrated packet is recognized as an RLC PDU (RLC Protocol Data Unit) at the RLC layer. In the division / integration, the RLC SDU is divided / integrated into RLC PDUs of appropriate size according to the instruction from the scheduling unit (transport format selection unit) of the MAC layer, and sent to the MAC layer via the logical channel. This RLC at the RLC layer Save the PDU and resend ARQ (Automatic Repeat Request) as needed.

The MAC layer receives split / integrated packets via a logical channel. This split / integrated packet is an RLC PDU and is recognized as a MAC SDU (MAC Service Data Unit) at the MAC layer. The MAC layer maps this MAC SDU appropriately to the transport block. At this time, if necessary, multiplex RLC PDUs received via other logical channels. HARQ (Hybrid Automatic Repeat Request) processing is performed on the data mapped to this transport block, and the transport block is sent to the PHY layer. The MAC layer performs HARQ retransmission of the transport block in response to a retransmission request from the mobile station.<nplcit num="1"><text>3GPP TR25.813 v0.8.3</text></nplcit>

<p> The transport block size transmitted from the physical layer to the mobile station is generally determined by the MAC layer scheduling section (transport format selection section) considering the radio quality of the radio link between the base station and the mobile station. Determined adaptively to the appropriate one. The scheduling unit notifies the transport block size (or RLC PDU size commensurate with the transport block size) so that division (or integration) in the RLC layer can be performed appropriately.</p><p> Thus, in 3GPP Evolved UTRA and UTRAN, the transport block size (or RLC PDU size) is adaptively determined according to the radio quality at the time of transmission. Therefore, it is possible to generate the optimum RLC PDU that matches the radio quality. On the other hand, when RLC retransmission is required, there is a time lag between the first transmission of RLC and the retransmission, so the radio quality may fluctuate. That is, the optimum transport block size at the time of initial transmission may be inappropriate at the time of retransmission. If the radio quality is improved, the transport block size at the time of initial transmission will be too small at the time of retransmission. Also, if the radio quality is degraded, the transport block size at the time of initial transmission will be too large.</p><p> Therefore, when the radio quality is improved at the time of retransmission, the transport block size that can be transmitted is larger than that at the time of initial transmission, so that there arises a problem that the radio resources cannot be used up if only the retransmission packet is transmitted.</p><p> On the other hand, in the configuration shown in Figure 2, the MAC layer can multiplex RLC PDUs from different logical channels into one transport block. In this way, it is possible to multiplex other logical channels with unused radio resources. However, for this purpose, the mobile station cannot be multiplexed unless a plurality of logical channels are set. Moreover, even if multiplexing is possible, data on different logical channels have different quality of service (QoS). Multiplexing logical channels with different quality of service into a single transport block necessitates the transmission of packets to the logical channel with the higher quality of service requirement. From the perspective of logical channels with low quality of service requirements, data is transmitted with excessive quality, which wastes radio resources.</p><p> As an example, a case where one of the different logical channels has a strict delay requirement such as VoIP (Voice over Internet Protocol) and the other has a loose delay requirement such as best effort data communication will be described. Since VoIP has strict delay requirements, set the transmission power so that data can reach the receiving side without HARQ retransmission. In addition, since the delay requirement of best effort type data communication is loose, the transmission power is set so that the time diversity gain and the incremental redundancy gain can be obtained by making full use of HARQ retransmission. When multiplexing VoIP data with best effort data, VoIP quality of service requirements must be met. Therefore, transmission power is required so that the multiplexed transport block can reach the receiving side without HARQ retransmission. In this case, the best-effort data cannot obtain the time diversity gain and the incremental redundancy gain (about 2 dB) that would normally be obtained, resulting in waste of transmission power. Further, it leads to deterioration of wireless capacity.</p><p> The present invention has been made in view of such problems of the prior art, and an object of the present invention is to effectively use radio resources at the time of retransmission and to maintain service quality at the time of retransmission.</p>

<p> The base station of the present invention A base station that retransmits a transmitted packet in response to a request to retransmit a transmitted packet from a mobile station: Retransmission control unit that receives the retransmission request from the mobile station;<u style="single">When the wireless quality at the time of resending is better than that at the time of the first transmission</u>Scheduling unit that determines the transport block size that can be transmitted to the mobile station; At the transmission opportunity to retransmit the transmission packet in response to the retransmission request, the scheduling unit has the transmission opportunity to transmit the transmission packet to be retransmitted and a new transmission packet to be newly transmitted on the same logical channel as the transmission packet to be retransmitted. Multiplexing part to multiplex on the transport block of the size determined in; The newly transmitted transmission packet is higher than the layer that generates the newly transmitted transmission packet based on the transmittable transport block size and the size of the retransmission transmission packet determined by the scheduling unit. Division / integration unit generated by dividing / integrating packets in the above layer; Have, One of the features of the multiplexing unit is that when the transport block cannot be filled with the transmitted packet to be retransmitted, the newly transmitted transmission packet is multiplexed with the transport block and the transport block is used up. Let's do it.</p><p> Further, the mobile station of the present invention is A mobile station that retransmits a transmit packet in response to a resend request for a base station's transmit packet: Retransmission control unit that receives a retransmission request from the base station;<u style="single">When the wireless quality at the time of resending is better than that at the time of the first transmission</u>Transmission format determination unit that determines the transport block size that can be transmitted to the base station; At the transmission opportunity to retransmit the transmission packet in response to the retransmission request, the transmission format determination unit determines the transmission packet to be retransmitted and the transmission packet to be newly transmitted on the same logical channel as the transmission packet to be retransmitted. Multiplexing part to multiplex in transport block of size determined by transmission opportunity; and From the layer that generates the newly transmitted transmission packet, the newly transmitted transmission packet is based on the transmittable transport block size determined by the transmission format determination unit and the size of the transmission packet to be retransmitted. Is also a division / integration unit generated by dividing / integrating packets in the upper layer; Have, One of the features of the multiplexing unit is that when the transport block cannot be filled with the transmitted packet to be retransmitted, the newly transmitted transmission packet is multiplexed with the transport block and the transport block is used up. Let's do it.</p><p> Further, the communication method of the present invention In the transmitting device, it is a communication method that retransmits the transmitted packet in response to the retransmission request for the transmitted packet of the receiving device: Steps to receive a resend request from the receiver;<u style="single">When the wireless quality at the time of resending is better than that at the time of the first transmission</u>Steps to determine the transport block size that can be sent to the receiver; At the transmission opportunity to retransmit the transmission packet in response to the retransmission request, the transmission packet to be retransmitted and the transmission packet to be newly transmitted on the same logical channel as the transmission packet to be retransmitted are determined at the transmission opportunity. Multiplexing to a transport block of the size determined in the step; and The newly transmitted transmission packet is a layer higher than the layer that generates the newly transmitted transmission packet based on the determined transmittable transport block size and the size of the retransmission transmission packet. Steps to generate by splitting and consolidating packets in Have, The multiplexing step is characterized in that, when the transport block cannot be filled with the transmitted packet to be retransmitted, the newly transmitted transmission packet is multiplexed with the transport block and the transport block is used up. Let it be one.</p>

<p> According to the embodiment of the present invention, the radio resource can be effectively used at the time of retransmission, and the service quality at the time of retransmission can be maintained.</p>

<figref num="1">Diagram showing the protocol stack of wireless interface protocols</figref><figref num="2">The figure which shows the processing flow of the user data in a base station</figref><figref num="3">Diagram showing the processing flow of the PDCP layer</figref><figref num="4">Diagram showing the processing flow of the RLC layer</figref><figref num="5">A diagram showing the flow of transmitting a retransmission packet from a base station to a mobile station on the time axis.</figref><figref num="6">A diagram showing the amount of information that can be transmitted when the wireless quality improves on the time axis</figref><figref num="7">Block diagram of a base station according to an embodiment of the present invention</figref>

Code description

10 base stations 101 SDU buffer 103 Division / Integration Department 105 PDU buffer 107 Retransmission control unit 109 Scheduling Department 111 Multiple parts 113 Transmitter

Examples of the present invention will be described with reference to the drawings.

FIG. 5 is a diagram showing a flow of transmitting a retransmission packet from a base station to a mobile station on the time axis. Figure 5 shows the radio quality in the vertical direction.

The mobile station measures the radio quality before the base station sends a packet to the mobile station (S101). When the radio quality measurement is completed (S103), the radio quality is reported from the mobile station to the base station (S104). The base station selects the transport block size based on the received radio quality (S105). The packet transmitted at this time has an optimum transport block size adaptively selected based on the measurement result of radio quality. Packets are sent from the base station to the mobile station with this optimum transport block size (S107). When the mobile station detects a transmission error in a packet (S109), it detects which RLC PDU in the packet needs to be retransmitted (S111). The mobile station then sends a retransmission request to the base station (S113). When the base station receives a retransmission request from the mobile station, it reschedules based on the radio quality continuously reported by the mobile station (S115).

Looking at the radio quality at the time of retransmission in this way, it is possible that the radio quality at the time of initial transmission (S107) is improved as shown in FIG. In such a case, since the amount of information that can be transmitted from the base station to the mobile station is large, the transport block size is also large. That is, as shown in FIG. 6, the amount of information that can be transmitted in 1 TTI (Transmission Time Interval) also increases.

When the radio quality is improved in this way, if the same packet as at the time of the first transmission is transmitted at the time of retransmission, unused radio resources will be generated. Therefore, in the base station according to the embodiment of the present invention, the packet of the same logic channel as the retransmission packet is multiplexed with the unused portion of the radio resource. Specifically, when the retransmitted RLC PDU cannot fill the transport block, the transport block is used up by multiplexing the newly transmitted RLC PDU on the same logical channel with the transport block. By doing so, it becomes possible to effectively use the radio resource at the time of retransmission. Further, since the packet of the same logical channel as the retransmitted packet is multiplexed, the packet having the same service quality is multiplexed. Therefore, it is possible to maintain the quality of service at the time of retransmission.

FIG. 7 shows a block diagram of the base station 10 according to the embodiment of the present invention. The base station 10 has an SDU buffer 101, a division / integration unit 103, a PDU buffer 105, a retransmission control unit 107, a scheduling unit 109, a multiplexing unit 111, and a transmission unit 113. Although each block is shown separately for the MAC layer and the RLC layer, it does not necessarily have to be implemented as shown in the figure. For example, the retransmission control unit 107 may exist in the RLC layer.

The SDU buffer 101 is a buffer for storing data (RLC SDU) received from the PDCP layer shown in FIG. 4 at the RLC layer. The division / integration unit 103 corresponds to the division / integration shown in FIG. That is, the division / integration unit 103 divides / integrates the data in the SDU buffer into RLC PDUs of an appropriate size according to the instruction from the scheduling unit 109 of the MAC layer. This divided RLC PDU is stored in the PDU buffer 105.

When the retransmission control unit 107 receives the retransmission request from the mobile station, it refers to the PDU buffer and notifies the scheduling unit 109 of the size of the retransmission packet. The scheduling unit 109 determines the transport block size that can be transmitted from the radio quality that is continuously received from the mobile station. At the time of the first transmission, the scheduling unit 109 instructs the division / integration unit 103 of the transport block size suitable for the first transmission. On the other hand, at the time of retransmission, the scheduling unit 109 divides and integrates the RLC PDU size (RLC PDU size that can be transmitted on the same logical channel as the retransmission packet) obtained by subtracting the size of the retransmission packet from the transport block size that can be transmitted. Instruct.

The multiplexing unit 111 multiplexes the SDU buffer data and the PDU buffer data divided by the dividing / integrating unit 103, and the transmitting unit 113 transmits the multiplexed data to the mobile station. When multiplexing the data in the SDU buffer and the data in the PDU buffer divided by the division / integration unit 103, a logical channel identifier may be added to the header associated with each packet.

When the retransmission control unit 107 receives the retransmission request from the mobile station using the above configuration, the retransmission control unit 107 notifies the scheduling unit 109 of the size of the retransmission packet by referring to the PDU buffer. The scheduling unit 109 instructs the division / integration unit 103 of the RLC PDU size obtained by subtracting the size of the retransmission packet from the transport block size suitable for retransmission based on the radio quality received from the mobile station. If the radio quality is improved, the transport block at the time of retransmission becomes larger than the transport block size at the time of the first transmission. The division / integration unit 103 divides the data in the SDU buffer of the same logical channel into the RLC PDU size specified by the scheduling unit 109. The multiplexing unit 111 multiplexes the retransmission data and the data from the SDU buffer of the same logical channel. The multiplexed data is transmitted to the mobile station by the transmission unit 113.

By doing so , the radio resource at the time of retransmission can be effectively used. Further, the data of the same logical channel can be transmitted to the mobile station with the same quality of service. For example, VoIP data and best effort type can be transmitted to a mobile station with a predetermined service quality for each logical channel without being transmitted in the same transport block.

Although the base station has been described in the above embodiment, the radio resource at the time of retransmission can be effectively used for the mobile station with the same configuration. In the case of a mobile station, the scheduling unit 109 of the base station corresponds to the transmission format determination unit (not shown).

In the case of a mobile station, at the time of retransmission, the mobile station receives the retransmission request and also receives the radio resource allocation information scheduled by the scheduling unit of the base station. At this time, when the radio quality is improved, the same effect as described above can be obtained by transmitting the packet of the same logic channel as the retransmission packet in multiples with the retransmission packet.

This international application claims priority based on Japanese patent application 2006-127997 filed on May 1, 2006, and the entire contents of 2006-127997 are incorporated into this international application.