WO2015173644A1

WO2015173644A1 - Method and apparatus for implementing device-to-device broadcast communication in a wireless communication network

Info

Publication number: WO2015173644A1
Application number: PCT/IB2015/001122
Authority: WO
Inventors: Yong Liu; Dong Li; Haiyou Guo; Yun DENG
Original assignee: Alcatel Lucent
Priority date: 2014-05-08
Filing date: 2015-05-04
Publication date: 2015-11-19
Also published as: EP3141067A1; CN105101043A; CN105101043B; TW201545596A; TWI565351B; KR101915159B1; KR20160149278A

Abstract

The invention provides a method, in a user equipment in a wireless communication network, of implementing Device-to-Device broadcast communication, the method comprises following steps:- determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix H₁ and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix H₁ and -1;- determining one row from the transmission pattern set; and- implement a Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:- transmitting the broadcast when the element is a first value;- receiving the broadcast when the element is a second value.

Description

METHOD AND APPARATUS FOR IMPLEMENTING DEVICE-TO-DEVICE BROADCAST COMMUNICATION IN A WIRELESS COMMUNICATION NETWORK

Field of the invention

The present disclosure relates to mobile communication technology, and particularly to a method of implementing Device-to-Device broadcast communication in a wireless communication network and a corresponding user equipment.

Background of the invention

Device-to-device (D2D) communication has been introduced as an important enhancement to LTE-Advanced (Long Term Evolution) for cellular networks. The related standardization has been carried out in 3 GPP (Third-Generation Partnership Project) to study both device discovery and direct communication techniques.

For D2D direct communication, broadcast communication in out-of-coverage scenario is prioritized for Release 12 time frame. It is the most critical task for D2D broadcast communication to support VoIP traffic. It's required for a broadcast packet to reach a user equipment (UE) as far as possible. To increase coverage, a narrow band (as low as 2 or 3 RBs) is a suitable choice for transmission of a broadcast VoIP packet. For a large channel bandwidth (50 RBs for 10MHz bandwidth), we need to FDM (frequency domain multiplexing) broadcast transmissions from multiple UEs to fully use available spectral resources. However, it incurs half-duplex constraint and in-band emissions which eventually impact broadcast performance.

Summary of the invention

In view of this, this invention provides a solution for D2D broadcast communication.

According to a first aspect of the invention, there is proposed a method, in a user equipment in a wireless communication network, of implementing Device-to-Device broadcast communication, the method comprises following steps:- determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix Hi and -1 ;- determining one row from the transmission pattern set; and- implement a Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:- transmitting the broadcast when the element is a first value;- receiving the broadcast when the element is a second value.

Advantageously, the transmission pattern set includes the even rows in the Walsh matrix Hi and the first matrix H₂.

Herein, a mechanism to down-select suitable transmission patterns is designed for a narrow band, such as 3MHz and 5MHz, so as to provide additional benefits. Through this mechanism, transmissions of a VoIP packet are spread more uniformly which helps to accomplish time diversity. Further, this mechanism helps to reduce overall transmission latency of a VoIP packet.

According to a second aspect of the invention, there is proposed a user equipment, in a wireless communication network, of implementing Device-to-Device broadcast communication, the user equipment comprises:- unit for determining a transmission pattern set, configured for determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix Hi and -1 ;- unit for determining one row, configured for determining one row from the transmission pattern set; and- broadcasting unit, configured for implementing a Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:- transmitting the broadcast when the element is a first value;- receiving the broadcast when the element is a second value.

In the current invention, a method for constructing a transmission pattern set is proposed. Herein, the total number of transmission patterns is (N-l)*2. N is the order of a Walsh matrix. This will help to reduce the collision probability in resource allocation and increase transmission pattern selection. Meanwhile, the transmission pattern according to the present invention still keep the feature of Walsh based transmission pattern set. By applying the above transmission pattern for D2D broadcast communication, the half-duplex constraint could be resolved and the in-band emission seen at receiving UEs could be alleviated.

The respective aspects of the invention will become more apparent from the following description of particular embodiments.

Brief description of drawings

Other features, objects and advantages of the invention will become more apparent upon review of the following detailed description of non-limiting embodiments taken with reference to the drawings in which:

Fig. l illustrates constructing a Walsh matrix-based transmission pattern set according to an embodiment of the present invention;

Fig.2 illustrates a Walsh matrix-based transmission pattern set according to an embodiment of the present invention;

Fig.3 illustrates a flow chart of a method of implementing D2D broadcast communication according to an embodiment of the present invention; Fig. 4 illustrates a relationship between two corresponding rows in two matrixes in a transmission pattern set according to an embodiment of the present invention;

Fig. 5 illustrates a relationship between two arbitrary rows in two matrixes in a transmission pattern set according to an embodiment of the present invention;

Fig. 6 illustrates a Walsh matrix-based transmission pattern set according to an embodiment of the present invention;

Fig. 7 illustrates a Walsh matrix-based transmission pattern set according to another embodiment of the present invention;

Fig. 8 illustrates a Walsh matrix-based transmission pattern set according to a further embodiment of the present invention;

Fig. 9 illustrates a Walsh matrix-based transmission pattern set according to a further embodiment of the present invention; and

Fig. 10 illustrates a UE according to an embodiment of the present invention.

In the drawings, identical or like reference numerals denote identical or corresponding components or features throughout the different figures.

Detailed description of embodiments

At first, the design for D2D broadcast communication should consider the following factors:

Firstly, LTE frame structure is reused to keep compatibility with legacy cellular communication.

1. In LTE, resources are partitioned in time-frequency plane.

2. In LTE, the minimum scheduling (resource allocation) unit consists of two time-consecutive resource blocks within one subframe, which is referred to as a resource-block (RB) pair. The resource allocation unit for D2D broadcast communication should be multiple of

RB pairs. For D2D communication, it's required for a broadcast packet to reach a UE as far as possible. To increase coverage, the narrow band (as low as 2 or 3 RBs) is a suitable choice for transmission of a broadcast VoIP packet. For a large channel bandwidth (50 RBs for 10MHz bandwidth), we need to FDM (frequency domain multiplexing) broadcast transmissions from multiple UEs to fully use available spectral resources.

Secondly, the design should suit VoIP traffic which is the basic traffic type for the D2D broadcast communication. VoIP traffic has the following properties:

1. VoIP traffic is periodical. The encoder frame length is 20 ms which means a voice encoder generates a voice packet for each 20ms. The mean length of a talk spurt is 2.5s.

2. The voice payload per speech frame is 328 bits with header compression.

3. The requirement of end-to-end latency for VoIP traffic is 200ms. With the deduction of processing time, the tolerable transmission delay of a VoIP packet for D2D broadcast communication (unidirectional transmission) is about 160ms.

Fig. l illustrates constructing a Walsh matrix-based transmission pattern set according to an embodiment of the present invention. In Fig. l, the order N of the Walsh matrix is set as 8 only for illustration.

As shown in Fig. l , one Walsh matrix Hi is selected firstly. It has an order of N.

Secondly, a first matrix H₂ is obtained as the product of the Walsh matrix Hi and - 1.

Lastly, as shown in Fig. 2, the remaining rows in the Walsh matrix Hi and the first Walsh matrix H₂ except the first row in each matrix construct a transmission pattern set.

Each row in this transmission pattern set can be used by a UE. Each element in each row can be used to determine whether the UE performs broadcast transmitting or broadcast receiving in one subframe. For example, for element +1 , the UE can perform broadcast

transmitting, while for element -1 , the UE can perform broadcast receiving.

Fig.3 illustrates a flow chart of a method of implementing D2D broadcast communication at the UE according to an embodiment of the present invention.

As shown in Fig.3, in step S l l , the UE determines a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix Hi and -1.

In one embodiment of the present invention, the UE and the base station can predefine a corresponding transmission pattern set, and preconfigure it in the UE. When the UE needs to perform a broadcast communication, it will use the transmission pattern set.

Alternatively, the base station can determine the transmission pattern set, and transmit the determined transmission pattern set to the UE by a first indication message. The, the UE can determine the transmission pattern set according to the first indication message. This first indication message can be transmitted during the scheduling procedure, for example.

Still refer to Fig.3, in step S I 2, the UE determines one row from the transmission pattern set.

This could be implemented by using the following ways:

For example, the UE receives a second indication message from the base station. This second indication message indicates an associated row. Then, the UE determines the row from the transmission pattern set according to the second indication message. Herein, the base station determines the corresponding row for the respective UE according to the usage in the transmission pattern set, for example, so as to perform the corresponding broadcast. Alternatively, the UE itself can determine the row form the transmission pattern set according to the predefined conditions. Those predefined conditions includes current usage situation of each row in the transmission pattern set; current interested broadcast from other user equipment; and/or the quality of a current channel. For example, when the UE is very interested in the broadcast of another UE, it can select the corresponding suitable row to receive the broadcast in the respective subframe. However, when the UE is not interested in the broadcast of another UE, it can select the corresponding suitable row to transmit the broadcast in the respective subframe.

In step S 13, the UE performs D2D broadcast according to the transmission pattern corresponding to the determined row. As described above, the transmission pattern is: implementing the following procedures based on each element in the determined row successively: - transmitting the broadcast when the element is a first value (+1 , for example);- receiving the broadcast when the element is a second value (-1, for example).

Fig. 4 illustrates a relationship between two corresponding rows in two matrixes in a transmission pattern set according to an embodiment of the present invention. Fig. 5 illustrates a relationship between two arbitrary rows in two matrixes in a transmission pattern set according to an embodiment of the present invention.

With respect to Figs.4 and 5, the property of the transmission pattern set will be described in the following. H(i,:) represents the row i in the matrix H.

1. For any row in the Walsh matrix Hi and the first matrix H₂ except the first row, i.e. Hi(i,:) and H₂(i,:) with i≠ 1, half of elements are + 1 and half of elements are - 1.

2. For any two corresponding rows in the Walsh matrix Hi and the first matrix H₂ except the first row (two 3rd rows marked in Figure 4, for example), i.e. Hi(i,:) and H₂(i,:) with i≠ 1, there are N/2 pairs of { + 1, -1 } and {- 1, +1 } . Herein, since the order of the Walsh matrix is selected as 8 in Fig. 4, there are four pairs of {+1, -1 } and four pairs of {-1 , +1 } .

3. For arbitrary two rows in the Walsh matrix Hi and the first matrix H₂ except the first row, i.e. H_m(i,:) and H_n(j,:) with i≠ j≠ 1, which means those two rows can either come from an identical matrix, or come from two different matrixes. Fig.5 shows four situations: the third and sixth rows in the Walsh matrix H_{1 ?} the third and sixth rows in the first Walsh matrix H₂, the third row in the Walsh matrix Hi and the sixth row in the first Walsh matrix H₂, and the sixth row in the Walsh matrix Hi and the third row in the first Walsh matrix H₂. After

observing Fig. 5, it is apparent that in this situation there are N/4 pairs of {+1, -1 } and N/4 pairs of {-1, +1 }. Since the order of the Walsh matrix in Fig.5 is selected as 8, it exists two pairs of {+1, -1 } and two pairs of {-1, +1 }.

To improve link level performance, retransmissions of a VoIP packet are needed and spread in time domain. The number of potential transmission subframes for a VoIP packet is preconfigured as N. The gaps of sequential potential transmission subframes may also be preconfigured, which can be the same (Np_l=Np_2=...=Np_(N-l)) or different. Based on elements in a certain row of both the Walsh matrix ¾ and the first Walsh matrix H₂ (except two 1st rows), a broadcast UE determines whether to transmit/receive at potential transmission subframes.

Fig. 6 illustrates a Walsh matrix-based transmission pattern set according to an embodiment of the present invention. It is assumed that the UE 1 performs the broadcast transmission based on the 3rd row in the Walsh matrix H_{1 ?} and the UE2 performs the broadcast transmission based on the 6th row in the first Walsh matrix H₂. Based on the feature of the abovementioned two matrixes, the broadcast has the following properties: 1. Each broadcast UE transmits a VoIP packet N/2 times.

2. For any two broadcast UEs using different rows, i.e. different transmission patterns, the UE 1 can receive the broadcast transmissions from the UE 2 at least N/4 times, and vice versa, which resolves half-duplex constraint.

Herein, if the transmission pattern is based on the two

corresponding rows in the different matrixes except the first row, that is Hi(i,:) and H₂(i,:), i≠l, the UE1 can receive broadcast transmissions from the UE2 N/2 times, and vice versa.

Herein, if the transmission pattern is based on the arbitrary two rows in the two matrixes except the first row, that is H_m(i,:) and H_n j,:), i≠j≠l, the UE1 can receive broadcast transmissions from the UE2 N/4 times, and vice versa.

Herein, the number of available transmission patterns doubles to (N- l)*2.

Fig. 7 illustrates a Walsh matrix-based transmission pattern set according to another embodiment of the present invention. If the transmission patterns are based on two corresponding rows in Hi and H₂, all potential transmission subframes can be occupied for

transmission. In the example shown in Fig.7, the UE 1 uses the 3rd row in the matrix H_{1 ?} and the UE 2 uses the 3rd row in the matrix H₂. The UE 3 uses the 6th row in the matrix H_{1 ?} and the UE 4 uses the 6th row in the matrix H₂

By using the transmission pattern set, multiple transmissions of a VoIP packet are randomized in time domain which alleviates in-band emission seen at receiving UEs. Transmission pattern is fixed once the row of Walsh matrix for transmission pattern is chosen. Fixed

transmission pattern facilitates the packet reception/combining at receiving UEs. And it also reduces signaling overhead if transmission pattern information is conveyed in scheduling assignment before data transmission. For narrower channel bandwidths such as 3MHz (15 resource blocks) and 5MHz (25 resource blocks), it is not necessary to use all the rows of the transmission pattern set. Hence for this case, the

transmission pattern set could be reduced further to provide additional benefits.

1. Transmissions of a VoIP packet are spread more uniformly which helps with obtaining time diversity.

2. DRX (discontinuous reception) is realized, the gap between consecutive transmissions (in terms of sub-frames) needs to be set large enough to guarantee sufficient decoding time for a VoIP packet. This mechanism helps to reduce overall transmission latency of a VoIP packet.

Fig. 9 illustrates a Walsh matrix-based transmission pattern set according to a further embodiment of the present invention. Herein, the UE 1 uses the 2nd row in the Walsh matrix H_{1 ?} and the UE 2 uses the 4th row in the first matrix H₂. Herein, Np_l , Np_3, Np_(N-l) can be set as 1 , which means there is no gap between two sequential potential transmission subframes.

Fig. 10 illustrates a UE according to an embodiment of the present invention. As shown in Fig. 10, the UE comprises a unit for

determining a transmission pattern set, a unit for determining one row and a broadcasting unit.

The unit for determining a transmission pattern set is configured for determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix Hi and -1.

Advantageously, the unit for determining a transmission pattern comprises: a preconfiguring unit, configured for preconfiguring the transmission pattern set at the UE.

Alternatively, the unit for determining a transmission pattern comprises: a first receiving unit, configured for receiving a first indication message from a base station, the first indication message indicating the transmission pattern set; and a first determining unit, configured for determining the transmission pattern set according to the first indication message.

The unit for determining one row is configured for determining one row from the transmission pattern set.

Advantageously, the unit for determining one row comprises: a second receiving unit, configured for receiving a second indication message from a base station, the second indication message indicating the row; and a second determining unit, configured for determining the row from the transmission pattern set based on the second indication message.

Alternatively, the unit for determining one row comprises: a third determining unit, configured for determining the row according to a predetermined condition.

The broadcasting unit is configured for implementing a

Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:- transmitting the broadcast when the element is a first value;- receiving the broadcast when the element is a second value.

It shall be appreciated that the foregoing embodiments are merely illustrative but will not limit the invention. Any technical solutions without departing from the spirit of the invention shall fall into the scope of invention, including that different technical features, methods appearing in different embodiments are used to combine to advantage.

Claims

1. A method, in a user equipment in a wireless communication network, of implementing Device-to-Device broadcast communication, the method comprises following steps:

- determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix Hi and -1 ;

- determining one row from the transmission pattern set; and

- implement a Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:

- transmitting the broadcast when the element is a first value;

- receiving the broadcast when the element is a second value.

2. A method according to claim 1 , wherein the step determining the transmission pattern set including:

the transmission pattern set is preconfigured at the user equipment.

3. A method according to claim 1 , wherein the step determining the transmission pattern set including:

receiving a first indication message from a base station, the first indication message indicating the transmission pattern set; and

determining the transmission pattern set according to the first indication message.

4. A method according to claim 1 , wherein the step determining one row from the transmission pattern set including:

receiving a second indication message from a base station, the second indication message indicating the row; and

determining the row from the transmission pattern set based on the second indication message.

5. A method according to claim 1 , wherein the step determining one row from the transmission pattern set including:

determining the row according to a predetermined condition.

6. A method according to claim 5, wherein the predetermined condition comprises at least one of the followings:

i. current usage situation of each row in the transmission pattern set; ii. current interested broadcast from other user equipment; and/or iii. quality of a current channel.

7. A method according to claim 1 , wherein the transmission pattern set includes even rows in the Walsh matrix Hi and the first matrix H₂.

8. A user equipment, in a wireless communication network, of implementing Device-to-Device broadcast communication, the user equipment comprises:

- unit for determining a transmission pattern set, configured for determining a transmission pattern set, which includes all rows except the first row in a Walsh matrix Hi and a first matrix H₂, wherein the first matrix H₂ is a product of the Walsh matrix H_: and -1 ;

- unit for determining one row, configured for determining one row from the transmission pattern set; and

- broadcasting unit, configured for implementing a Device-to-Device broadcast according to a transmission pattern corresponding to the determined row, wherein the transmission pattern is: implementing the following procedures based on each element in the determined row successively:

- transmitting the broadcast when the element is a first value; - receiving the broadcast when the element is a second value.

9. A user equipment according to claim 8, wherein the unit for determining a transmission pattern set comprises:

preconfigurmg unit, configured for preconfigurmg the transmission pattern set at the user equipment.

10. A user equipment according to claim 8, wherein the unit for determining a transmission pattern set comprises: first receiving unit, configured for receiving a first indication message from a base station, the first indication message indicating the transmission pattern set; and

first determining unit, configured for determining the transmission pattern set according to the first indication message.

11. A user equipment according to claim 8, wherein the unit for determining one row comprises:

second receiving unit, configured for receiving a second indication message from a base station, the second indication message indicating the row; and

second determining unit, configured for determining the row from the transmission pattern set based on the second indication message.

12. A user equipment according to claim 8, wherein the unit for determining one row comprises:

third determining unit, configured for determining the row according to a predetermined condition.

13. A user equipment according to claim 12, wherein the predetermined condition comprises at least one of the followings:

14. A user equipment according to claim 8, wherein the transmission pattern set includes even rows in the Walsh matrix Hi and the first matrix H₂.