WO2010020078A1

WO2010020078A1 - Method and system for implementing harq retransmission using unicast link

Info

Publication number: WO2010020078A1
Application number: PCT/CN2008/001516
Authority: WO
Inventors: 朱孝龙; 杨红卫; 汪勇刚
Original assignee: 上海贝尔阿尔卡特股份有限公司; 阿尔卡特朗讯
Priority date: 2008-08-22
Filing date: 2008-08-22
Publication date: 2010-02-25
Also published as: CN102067499A; CN102067499B

Abstract

A method for implementing hybrid automatic repeat request HARQ retransmission in enhanced multimedia broadcast multicast service E-MBMS using unicast link is disclosed. The method includes the following steps: a user terminal detects the E-MBMS packets transmitted from at least one base station; when the user terminal cannot restore the E-MBMS packets, the user terminal selectively reports a negative acknowledge NACK for the E-MBMS packets to its service base station using unicast uplink; after the service base station receives the negative acknowledge NACK for the E-MBMS packets from the user terminal, the service base station selectively retransmits the E-MBMS packets to the user terminal using unicast downlink.

Description

Method and system for realizing HARQ retransmission using unicast link

The present invention relates to the field of mobile communications, and more particularly, to a method, system, and method for implementing enhanced multimedia broadcast multicast service (E-MBMS) hybrid automatic repeat request (HARQ) retransmission using a unicast link. The user terminal, and the base station, implement HARQ retransmission of the E-MBMS packet by using the unicast link, improving the radio resource utilization for the E-MBMS transmission and being suitable for the single cell arrangement and the multi-cell arrangement. Background technique

Enhanced Multimedia Broadcast and Multicast Service (E-MBMS) is an important topic for many standardization organizations including 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) / LTE+ and IEEE 802.16e/m.

For E-MBMS, the base station (BS) serves multiple users at the same time, and different users may experience completely different channel conditions, so it is necessary to reasonably select the modulation and coding scheme (MCS) of the E-MBMS packet to ensure that Most users offer E-MBMS services. Typically, E-MBMS can be deployed in two scenarios: multi-cell E-MBMS (also known as "single frequency network") and single cell E-MBMS. The existing multi-cell E-BMS does not support hybrid automatic repeat request (HARQ) because there is no reverse link of the E-MBMS to report the user's positive acknowledgement (ACK) / negative acknowledgement (NACK). Since the selected MCS only ensures coverage for most users, the system often cannot provide E-MBMS services for users with poor channel conditions. On the other hand, the MCS level employed by the E-MBMS service is generally conservative, which results in relatively low spectral efficiency. For the layout of a single-cell E-MBMS, the current HARQ retransmission is possible only when there is an uplink for the E-MBMS, and the BS determines whether to retransmit based on the ACK/NACK report from all users. E-MBMS grouping. For example, if only an individual user cannot recover the E-MBMS packet, the BS does not perform the child transmission. That is, the BS will discard those users with poor channel conditions. In this case, the E-MBMS service cannot be provided to these users. In an alternative scenario, the BS chooses to retransmit the E-MBMS packet to all users even if very few users are not able to correctly detect these packets. In this case, resource waste is unavoidable because the BS transmits redundant information to a large number of users with better channel conditions. Summary of the invention In order to overcome the above drawbacks of the prior art, the present invention has been made. The object of the present invention is to provide a method, system, user terminal, and base station for implementing enhanced multimedia broadcast multicast service E-MBMS hybrid automatic repeat request HARQ retransmission using a unicast link, by utilizing a unicast link To implement HARQ retransmission, the radio resource utilization for E-MBMS transmission is improved and at the same time suitable for single cell arrangement and multi-cell arrangement.

In order to achieve the above object, according to the present invention, a method for implementing hybrid automatic repeat request HARQ retransmission using a unicast link is proposed, the method comprising the steps of: detecting, by a user terminal, enhanced multimedia transmitted from at least one base station Broadcasting a multicast service E-MBMS packet; when the user terminal is unable to recover the E-MBMS packet, the user terminal selectively reports a negative acknowledgement NACK for the E-MBMS packet to its serving base station in a unicast uplink And after the serving base station receives the NACK for the E-MBMS packet from the user terminal, the serving base station selectively retransmits the E-MBMS packet to the user terminal through the unicast downlink.

Advantageously, the step of the user terminal selectively reporting a NACK for the E-MBMS packet to its serving base station in a unicast uplink comprises: if the E-MBMS packet has a priority above a preset threshold and When there is an idle unicast uplink, the user terminal reports the NACK for the E-MBMS packet to the serving base station in a unicast uplink, otherwise, the user terminal does not report the E-MBMS packet to the serving base station. NACK.

Preferably, the step of the serving base station selectively retransmitting the E-MBMS packet to the user terminal by using the unicast downlink comprises: if the E-MBMS packet has a priority higher than a preset threshold and there is a free ticket When the downlink is broadcast, the serving base station retransmits the E-MBMS packet to the user terminal, otherwise the serving base station does not retransmit the E-MBMS packet to the user terminal.

Preferably, the serving base station further requests other base stations to perform joint retransmission or suppress interference to the user terminal in the unicast downlink.

Preferably, the method is simultaneously suitable for a single cell arrangement and a multi-cell arrangement of an enhanced multimedia broadcast multicast service E-MBMS communication system 6

According to the present invention, there is also provided a system for implementing an enhanced multimedia broadcast multicast service E-MBMS hybrid automatic repeat request (HARQ) retransmission using a unicast link, the system comprising: a user terminal, configured to detect a slave base station The enhanced multimedia broadcast multicast service E-MBMS packet transmitted; and when the user terminal cannot recover the E-MBMS packet, the user terminal selectively reports the E-MBMS packet to its serving base station in a unicast uplink Negative acknowledgement NACK; and at least one base station including the serving base station, wherein After the serving base station receives the NACK for the E-MBMS packet from the user terminal, the serving base station selectively retransmits the E-MBMS packet to the user terminal through the unicast downlink.

Preferably, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink, the user terminal reports to the serving base station for the E-MBMS in a unicast uplink. The NACK of the packet, otherwise, the user terminal does not report the NACK for the E-MBMS packet to the serving base station.

Preferably, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink, the serving base station retransmits the E-MBMS packet to the user terminal, otherwise the serving base station does not The E-MBMS packet is retransmitted to the user terminal.

Preferably, the system is simultaneously suitable for single cell placement and multi-cell placement of an enhanced multimedia broadcast multicast service E-MBMS communication system.

According to the present invention, a user terminal is provided, including: receiving means for receiving an enhanced multimedia broadcast multicast service E-MBMS packet transmitted from a base station; and detecting means for detecting the received E-MBMS packet; And a negative acknowledgement NACK reporting means for selectively reporting a NACK for the E-MBMS packet to its serving base station in a unicast uplink when the detecting means is unable to recover the E-MBMS packet.

Preferably, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink, the negative acknowledgment NACK reporting device reports the unicast uplink to the serving base station for the The NACK of the E-MBMS packet, otherwise, the negative acknowledgement NACK reporting device does not report a NACK for the packet to the serving base station.

According to the present invention, there is also provided a base station, comprising: a packet transmission and retransmission apparatus, configured to transmit and retransmit an enhanced multimedia broadcast multicast service E-MBMS packet; and a negative acknowledgement NACK receiving apparatus, configured to receive from a user terminal a NACK for the unrecoverable E-MBMS packet; and a retransmission control device for selectively controlling the packet transmission and retransmission device after the negative acknowledgement NACK receiving device receives the NACK for the E-MBMS packet from the user terminal The E-MBMS packet is retransmitted to the user terminal over a unicast downlink.

Preferably, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink, the retransmission control device controls the packet transmission and retransmission device to retransmit the packet to the user terminal. E-MBMS packet, otherwise the retransmission control device controls the packet transmission and retransmission device not to retransmit the E-MBMS packet to the user terminal. DRAWINGS

The above objects, advantages and features of the present invention will become apparent from the <RTIgt;

1 is a block diagram of a system for implementing HARQ retransmission using a unicast link in the case of a single frequency network in accordance with the present invention;

2 is an operational sequence diagram of a method for implementing HARQ retransmission using a unicast link in the case of a single frequency network according to the present invention;

Figure 3 is a block diagram of a user terminal in accordance with the present invention;

4 is a block diagram of a terminal in accordance with the present invention. detailed description

The basic idea of the invention is to utilize a unicast link to assist E-MBMS retransmission. This is feasible for single cell based arrangements and multi cell based arrangements, but requires the user terminal to be able to receive unicast services in addition to the E-MBMS. Specifically, the user terminal selectively reports the NACK of the E-MBMS packet to its serving base station using the unicast uplink. The serving base station then selectively retransmits the E-MBMS packet to the user using the unicast downlink. Finally, the user terminal utilizes techniques such as Maximum Likelihood Merging (MRC) to recover the E-MBMS packet. ·

In addition, in addition to ACK/NACK reporting for E-MBMS, the user terminal can also use its unicast uplink to report channel quality indicator (CQI) related information related to its E-MBMS channel. Based on information such as CQI collected from all user terminals, the system can specify a more appropriate MCS level for the E-MBMS service. The solution of the present invention is suitable for both a single cell based arrangement of E-MBMS and a multi-cell based arrangement. Without loss of generality, the HARQ retransmission system of the present invention will be described below by taking the SFN (single frequency network) shown in FIG. 1 as an example. In the SFN shown in FIG. 1, a plurality of base stations are directed to M31 (user terminal 1). Transfer E-MBMS packets. In addition, there is a unicast link between the serving base station BS1 and the user terminal MS1, and the BS1 provides the unicast service and the E-MBMS service to the MS1 in a time division multiplexing (TD) manner or in different working frequency bands.

1 is an example of a HARQ mechanism for unicast transmission assisted E-MBMS transmission for E-MBMS. The E-MBMS service is provided to the MS1 by a plurality of BSs, and the unicast service is provided to the MS1 by the serving base station BS1. When MS1 detects that the E-MBMS cannot be recovered, the MS1 selectively reports the E-MBMS packet to BS1 through its uplink unicast link. NACK. When BS1 receives a NACK from the MSI, the BS1 schedules appropriate unicast downlink resources to retransmit the E-MBMS packet to MS1. Finally, the MS1 uses MRC technology to recover the E-MBMS packet. 2 is an operational sequence diagram of a method of implementing HARQ retransmission using a unicast link in the case of a single frequency network in accordance with the present invention.

as shown in picture 2,

In step 201, the plurality of BSs transmit E-MBMS packets to the MS1 in an E-MBMS subframe, the plurality of BSs including the serving base station BS1.

Step 202: The MS1 detects the E-MBMS packet. If MS1 is unable to recover the E-MBMS packet, Bay ijMSl selectively reports the NACK for the packet to its serving base station BS1 over the unicast uplink. Specifically, it determines whether a NACK for the packet is reported to BS 1 in a unicast uplink. For example, if the current E-MBMS packet has a priority higher than a preset threshold (ie, the current E-MBMS packet is an important packet) and there is an idle unicast uplink resource, the MS1 transmits to the BS1 through the unicast uplink. NACK, otherwise, MS1 does not feed back NACK message to BS 1.

Step 203: After BS1 receives a NACK from MS1, BS1 selectively uses a unicast downlink to

MS 1 retransmits the E-MBMS packet. Specifically, it determines if and how to retransmit the E-MBMS packet to MS1. For example, if the current E-MBMS has a priority higher than a preset threshold (ie, the packet is an important packet), and there is an idle unicast downlink resource, BS1 performs a unicast downlink to perform the packet for the packet. Retransmission. Otherwise, retransmissions for this packet are not performed.

Optionally, when the serving base station BS1 decides to retransmit the E-MBMS packet by using the unicast downlink, the BS1 may adjust (for example, reduce) the original MCS level of the E-MBMS, or adopt an advanced unicast sending technology (such as , multi-antenna MIM0 technology, beamforming technology, etc.) to improve the quality of E-MBMS retransmission.

Optionally, the serving base station BS1 may also request other base stations to perform joint retransmission or suppress interference to the user terminal MS1 in the unicast downlink. Specifically, the former, that is, joint retransmission, means that the serving base station and the other one or more base stations retransmit the same E-MBMS packet to the MS 1 on the unicast downlink in a synchronous manner. The latter interference suppression means that the serving base station retransmits the E-MBMS packet to the MS1 on the unicast downlink (assumed to be the time-frequency resource block A), and the other one or more base stations are idle on the time-frequency resource block A, Or through reasonable scheduling, to avoid or reduce interference to MS1.

After the MS1 receives the retransmitted E-MBMS packet, the packet can be recovered using a technique such as MRC in which a packet originally received from a plurality of BSs and a packet newly received from BS1 are merged. If the MS I still cannot recover the packet, the MS 1 may choose to report another NACK to BS 1 and request retransmission again.

With the HARQ retransmission method for E-MBMS according to the present invention described above, optimal resource utilization is achieved by balanced scheduling between unicast packets and E-MBMS packets. On the other hand, if there are sufficient unicast resources, the MCS level of the E-MBMS can be increased, and the E-MBMS service can be provided to more users by the HARQ retransmission method of the present invention. On the other hand, if the unicast resources are very limited (or have a heavier load), the MCS level of the E-MBMS can be lowered to reduce the use of the unicast channel for E-MBMS retransmission.

2 is an example of implementing HARQ retransmission by unicast transmission in accordance with the present invention. The MS 1 receives the unicast service and the E-MBMS service in a time division multiplexing (TDM) manner or in different working frequency bands. The following points should be noted: U In addition to the BS 1, other BSs can simultaneously transmit the same to the MS1. E-MBMS packets, such as other BSs in the SFN; 2) ACK/NACK reporting in the unicast uplink is optional. For example, if the E-MBMS packet is not important, or there is no idle unicast uplink resource, or the MS 1 is operating in sleep mode, the MS 1 may choose not to feed back the ACK for the E-MBMS to the BS 1 NACK message; 3) Retransmission of E-MBMS packets in the unicast downlink is also optional, for example, if the E-MBMS packet is not important or there is no idle unicast downlink resource, then the serving base station BS1 does not perform retransmission for this E-MBMS packet. In addition, as described above, in addition to the serving BS1, other BSs may utilize the unicast downlink to perform joint retransmission of E-MBMS packets or to avoid interference with MS1.

The method of the present invention has been described above by taking the case of a multi-cell arrangement as an example. It should be noted that, in the case of a single cell arrangement, the method of the present invention relates only to the interaction between one base station (also a serving base station) and one mobile terminal, and the operation process thereof is the same as the multi-cell described above. The arrangement is exactly the same. Figure 3 is a block diagram of a user terminal in accordance with the present invention.

As shown in FIG. 3, the user terminal includes a receiving device 301, a detecting device 303, and a NACK reporting device 305. The receiving device 301 receives an E-MBMS packet transmitted from a base station. The detecting means 303 detects the received E-MBMS packet. When the detecting device is unable to recover the E-MBMS packet, the NACK reporting device 305 selectively reports the NACK for the E-MBMS packet to its serving base station in a unicast uplink.

Here, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink, the NACK reporting device 305 reports to the serving base station for the E- in a unicast uplink. NACK of the MBMS packet, otherwise, the NACK reporting device does not report to the serving base station for the packet NACK. 4 is a block diagram of a base station in accordance with the present invention.

As shown, the base station 4 comprises: a packet transmission and retransmission apparatus 401, NACK reception device 403 and retransmission control device ^405. The packet transmission and retransmission means 401 transmits and retransmits the E-MBMS packet. NACK receiving apparatus ⁴⁰³ receiving a NACK from the user terminal can not restore the E-MBMS packet. After the NACK receiving apparatus receives the NACK for the E-MBMS packet from the user terminal, the retransmission control apparatus 405 selectively controls the packet transmission and retransmission apparatus 401 to retransmit the E-MBMS to the user terminal through the unicast downlink. Grouping.

Here, if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink, the retransmission control device 405 controls the packet transmission and retransmission device 401 to retransmit to the user terminal. The E-MBMS packet, otherwise the retransmission control device 405 controls the packet transmission and retransmission device 401 not to retransmit the E-MBMS packet to the user terminal. Advantages of the invention include:

1) Suitable for single cell arrangement and multi-cell arrangement of E-MBMS;

2) increasing the spectral efficiency of the E-MBMS link due to the higher MCS than the MCS required by users with poor channel conditions;

3) Extend the coverage of E-MBMS by providing services to users with poor channel conditions;

4) avoiding resource waste by not transmitting redundant E-MBMS packets to users who have correctly detected these packets;

5) Optimize resource utilization through balanced scheduling between unicast services and E-MBMS services. While the invention has been described in terms of the preferred embodiments of the present invention, it will be understood that various modifications, changes and changes may be made to the inventions without departing from the spirit and scope of the invention. Therefore, the present invention should not be limited by the foregoing embodiments, but by the appended claims and their equivalents.

Claims

Rights request

A method for implementing an enhanced multimedia broadcast multicast service E-MBMS hybrid automatic repeat request HARQ retransmission using a unicast link, the method comprising the steps of:

The user terminal detects an E-MBMS packet transmitted from at least one base station;

When the user terminal is unable to recover the E-MBMS packet, the user terminal selectively reports a negative acknowledgement NACK for the E-MBMS packet to its serving base station in a unicast uplink;

After the serving base station receives the NACK for the E-MBMS packet from the user terminal, the serving base station selectively retransmits the E-MBMS packet to the user terminal through the unicast downlink.

2. The method of claim 1, wherein the step of the user terminal selectively reporting a NACK for the E-MBMS packet to its serving base station in a unicast uplink comprises:

If the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink, the user terminal reports a NACK for the E-MBMS packet to the serving base station in a unicast uplink, Otherwise, the user terminal does not report a NACK for the E-MBMS packet to the serving base station.

3. The method according to claim 1 or 2, wherein the step of the serving base station selectively retransmitting the E-MBMS packet to the user terminal through the unicast downlink comprises:

If the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink, the serving base station retransmits the E-MBMS packet to the user terminal, otherwise the serving base station does not forward to the user terminal Retransmit the E-MBMS packet.

4. The method of claim 1, wherein the serving base station further requests other base stations to perform joint retransmission or suppress interference to the user terminal in a unicast downlink.

5. The method of claim 1, the method being simultaneously suitable for a single cell arrangement and a multi-cell arrangement of an enhanced multimedia broadcast multicast service E-MBMS communication system.

6. A system for implementing enhanced multimedia broadcast multicast service E-MBMS hybrid automatic repeat request HARQ retransmission using a unicast link, the system comprising:

a user terminal, configured to detect an E-MBMS packet transmitted from the base station; and when the user terminal cannot recover the E-MBMS packet, the user terminal selectively reports to the serving base station in the unicast uplink for the E - a negative acknowledgement NACK for the MBMS packet;

At least one base station including a serving base station, After the serving base station receives the NACK for the E-MBMS packet from the user terminal, the serving base station selectively retransmits the E-MBMS packet to the user terminal through the unicast downlink.

7. The system according to claim 6, wherein if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink, the user terminal uses a unicast uplink to the location The serving base station reports a NACK for the E-MBMS packet, otherwise the user terminal does not report a NACK for the E-MBMS packet to the serving base station.

8. The system according to claim 6 or 7, wherein the serving base station retransmits the E-MBMS packet to the user terminal if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink E-MBMS packet, otherwise the serving base station does not retransmit the E-MBMS packet to the user terminal.

9. The system of claim 6, wherein the serving base station further requests other base stations to perform joint retransmission or to suppress interference to the user terminal in a unicast downlink.

10. The system of claim 6 wherein said system is simultaneously adapted to a single cell arrangement and a multi-cell arrangement of an enhanced multimedia broadcast multicast service E-MBMS communication system.

1 1. A user terminal, comprising: receiving means, configured to receive an enhanced multimedia broadcast multicast service transmitted from at least one base station

E-MBMS grouping;

a detecting device, configured to detect the received E-MBMS packet;

A negative acknowledgement NACK reporting means for selectively reporting a NACK for the E-MBMS packet to its serving base station in a unicast uplink when the detecting means is unable to recover the E-MBMS packet.

12. The user terminal according to claim 11, wherein the NACK reporting device unicasts uplink if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast uplink The way to report the NACK for the E-MBMS packet to the serving base station, otherwise the NACK reporting device does not report a NACK for the packet to the serving base station.

13. A base station, comprising: a packet transmission and retransmission apparatus, for transmitting and retransmitting an enhanced multimedia broadcast multicast service E-MBMS packet;

a negative acknowledgement NACK receiving means for receiving a NACK for the unrecoverable E-MBMS packet from the user terminal;

a retransmission control apparatus, configured to selectively control, after the NACK receiving apparatus receives a NACK for the E-MBMS packet from the user terminal, to selectively control the packet sending and retransmission apparatus to the user terminal through the unicast downlink Pass the E-MBMS packet.

14. The base station according to claim 13, wherein the retransmission control apparatus controls the packet transmission if the E-MBMS packet has a priority higher than a preset threshold and there is an idle unicast downlink And the retransmission device retransmits the E-MBMS packet to the user terminal, otherwise the retransmission control device controls the packet transmission and retransmission device not to retransmit the E-MBMS packet to the user terminal.