TWI676402B - Methods for data transmission and reception of a random access procedure for a user equipment of a wireless communication system - Google Patents

Abstract

The invention discloses a data receiving method for a random access flow of a network of a wireless communication system, which includes: receiving a preamble and data of the random access flow from a message of a user equipment of the wireless communication system; and according to the received preamble Code to obtain timing advance information; and perform channel estimation based on the allocated demodulation reference signal for demodulating the received data and timing advance compensation, where the timing advance compensation is linear in the frequency domain based on the timing advance information Phase rotation operation. Content)

Description

Data sending method for random access flow of network for wireless communication system and Receiving method

The present invention relates to the field of wireless communication technology, and more particularly, to a data sending method and a receiving method for a random access flow of a network for a wireless communication system.

The Random Access Channel (RACH) of the Long Term Evolution (LTE) system is used for initial network access and uplink time synchronization. Different from the traditional 4-step RACH procedure, the 2-step RACH procedure has been discussed in the 3G standard conference of 5G. Note that compared to the 4-step RACH procedure in LTE, the simplified 2-step RACH procedure reduces signaling overhead and transmission latency.

Please refer to Fig. 1, which is a schematic diagram of a 2-step RACH process. In a first step, the user equipment (UE) sends a preamble to the network together with the RACH data (ie, using the message Msg 1). In a second step, the UE receives a RACH response including the detected preamble index, UE identification, and Timing Advance (Timing Advance, TA) from the network (ie, using message Msg 2). In other words, the 2-step RACH procedure allows the UE to send the preamble and information on the RACH, and the 4-step RACH procedure allows the UE to send the preamble only on the RACH. As a result, the 2-step RACH procedure is favorable for small packet uplink transmission.

However, there are no physical channel design specifications for the 2-step RACH procedure. In detail, the LTE specification does not consider demodulation reference signal (Demodulation Reference Signal, DMRS) allocation and parameter set (format) for RACH data transmission in message Msg 1. Therefore, the network cannot extract / decode the RACH data received from the UE in the 2-step RACH procedure.

The following overview is illustrative only and is not intended to be limiting in any way. That is, the following overview is provided to introduce the concepts, gist, benefits, and advantages of the novel and non-obvious technologies described herein. The implementation of selection is further described in the detailed description below. Accordingly, the following summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

The invention provides a data receiving method for a random access flow of a network of a wireless communication system, which includes: receiving a preamble and data of the random access flow from a message of a user equipment of the wireless communication system; and according to the received preamble Code to obtain timing advance information; and perform channel estimation based on the allocated demodulation reference signal for demodulating the received data and timing advance compensation, where the timing advance compensation is linear in the frequency domain based on the timing advance information Phase rotation operation.

The invention provides a data transmission method for a random access process of a user equipment of a wireless communication system, which includes: at least a frequency resource and a time resource in a code division multiplexing manner and a configured demodulation reference signal sequence, and The preamble and data are sent to the network of the wireless communication system in a message entering the process; wherein the configured demodulation reference signal sequence does not consider the propagation delay of the random access channel data transmission.

It can be known from the above that the technical solution of the present invention can implement data transmission and reception of a 2-step RACH procedure in a 5G new radio (NR).

20‧‧‧communication equipment

214‧‧‧Program code

210‧‧‧Memory Unit

200‧‧‧ processing unit

220‧‧‧ communication interface unit

50‧‧‧ flow

500 ~ 540‧‧‧step

Figure 1 is a schematic diagram of a two-step RACH process.

FIG. 2 shows a schematic diagram of an exemplary communication device 20.

Figures 3 to 4 show parameter sets and formats of RACH data according to the present disclosure.

FIG. 5 is a flowchart of a process 50 according to an example of the present disclosure.

FIG. 6 illustrates a DMRS density reduction using a TA compensation operation according to the present disclosure.

Fig. 7 shows a channel estimation procedure used in the present invention.

8 to 9 are diagrams illustrating the configuration principle of the DRMS sequence according to the present disclosure.

FIG. 10 illustrates a parameter set and format of a RACH data according to the present disclosure.

Certain terms are used in the description and the scope of patent applications to refer to specific elements. Those skilled in the art will understand that hardware manufacturers may use different terms to refer to the same component. The scope of this specification and the patent application does not use the difference in names as a way to distinguish components, but rather uses the difference in functions of components as a criterion for distinguishing components. The terms "including" and "including" mentioned throughout the specification and the scope of patent application are open-ended terms and should therefore be interpreted as "including but not limited to". "Substantially" means that within the acceptable error range, those skilled in the art can solve the technical problem within a certain error range, and basically achieve the technical effect. In addition, the term "coupled" includes any direct and indirect electrical connection means. Therefore, if it is described that a first device is coupled to a first device, The two devices represent that the first device can be directly and electrically connected to the second device, or indirectly and electrically connected to the second device through other devices or connection means. The following is the best way to implement the present invention. The purpose is to explain the spirit of the present invention and not to limit the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the scope of the attached patent application.

The following description is the preferred embodiment contemplated by the present invention. These descriptions serve to illustrate the general principles of the invention and should not be used to limit the invention. The protection scope of the present invention should be identified on the basis of the patent application scope of the present invention.

FIG. 2 shows a schematic diagram of an exemplary communication device 20. The communication device 20 may be a network (eg, a base station) or a user equipment (UE), such as a wearable device, an IoT device, a mobile phone, an appliance, a machine type device, and the like, compatible with the LTE or 5G New Radio (NR) specifications. The communication device 20 may include a processing unit 200 such as a processor, an application specific integrated circuit (ASIC), etc., a memory unit 210 and a communication interface unit 220. The memory unit 210 may be any data storage device that can be stored. The program code 214 corresponds to a process for the processing unit 200 to access. The processing unit 200 may be coupled to the memory unit 210 for processing program code 214 to perform processing. Examples of the memory unit 210 include, but are not limited to, read only memory (ROM), flash memory, random access memory (RAM), CD-ROM, magnetic tape, hard disk, and optical data storage devices. The communication interface unit 220 may be a radio transceiver, and may exchange wireless signals according to a processing result of the processing unit 200.

Referring back to FIG. 1, in FIG. 1, the UE not only sends the RACH preamble but also the RACH data through the message Msg 1 of the 2-step RACH procedure. For RACH data transmission, the UE uses the same cyclic prefix (Cyclic Prefix, CP) and guard time (GT) as the RACH preamble. In short, the UE uses the RACH in a Phvsical Random Access Channel (PRACH). The RACH data is sent with the same parameter set and format as the preamble. In addition, the subcarrier spacing (SCS) of the RACH data is the same as or different from the RACH preamble.

Figures 3 to 4 show parameter sets and formats of RACH data according to the present disclosure. In one embodiment, UE1 and UE2 respectively send a RACH preamble and RACH data to the base station BS. UE1 is at the cell center and UE2 is at the cell edge, so the base station BS receives the RACH preamble and RACH data from UE1 earlier than the RACH preamble and RACH data from UE2. As shown in Figure 3, the RACH data has the same SCS, CP, and GT as the RACH preamble to support RACH data transmission in an asynchronous scenario. That is, because the 2-step RACH process has not been completed, that is, the UE has not received a RACH response from the network, the UE and the network are not synchronized. On the other hand, in Fig. 4, the RACH has an SCS different from the RACH preamble, but has the same CP and GT as the RACH preamble.

Please refer to FIG. 5, which is a flowchart of a process 50 according to an example of the present disclosure. The process 50 can be used in the network of FIG. 2 for receiving RACH data. The process 50 can be compiled into program code 214 and stored in the memory unit 210 for processing by the processing unit 200, including the following steps:

Step 500: Start.

Step 510: Receive the RACH preamble and RACH data of the 2-step random access procedure from the UE simultaneously (for example, by detecting a single message).

Step 520: Obtain timing advance information according to the received RACH preamble.

Step 530: Perform channel estimation according to the DMRS allocated for demodulating the received RACH data and timing advance compensation, where the timing advance compensation is a linear phase rotation operation in the frequency domain generated by the timing advance.

Step 540: End.

According to process 50, the network uses not only the DMRS sequence to estimate the channel, but also a timing advance (TA) compensation operation to estimate the channel. In detail, due to the 2-step RACH procedure, the UE sends RACH data in an asynchronous scenario. Therefore, the total channel delay for RACH data transmission includes propagation delay (ie, timing advance) and multipath delay spread. In order to cover the total channel delay for accurate channel estimation, the network needs more DMRS allocations in frequency resources, ie high DMRS density. However, high DMRS density in frequency resources results in overhead. With the TA compensation of the present invention, the timing advance can be recovered, so the total channel delay includes only the multipath delay spread. Therefore, the network needs fewer DMRS allocations in frequency resources for channel estimation in order to reduce DMRS density and uplink DMRS overhead.

Referring to FIG. 6, which illustrates a decrease in DMRS density using a TA compensation operation according to the present disclosure. As shown in Figure 6, the CP length in the asynchronous case is 0.1ms, that is, the maximum multipath delay extension tolerance is 0.1ms. As mentioned above, the total channel delay in an asynchronous scenario includes timing advance plus multipath delay spread, which is a maximum of 4.7us (ie, the CP length is 4.7us in a traditional data transmission synchronization scenario). Due to the longer delay, that is, CP = 100us, the network (that is, the base station) needs a higher DMRS density in frequency resources for channel estimation, which means that frequency resources are occupied by DMRS and cannot be used for RACH data transmission, thus reducing System performance.

On the other hand, the present invention proposes a TA compensation operation to recover a part of the propagation delay, that is, a timing advance part. Therefore, the channel delay only retains the multipath delay extension part, that is, CP = 4.7us. Therefore, the network needs a lower DMRS density in frequency resources for channel estimation. In addition, DRMS overhead can be reduced from 12.5% to 0.5875%. In detail, TA compensation is performed by the accompanying RACH preamble. The network knows the timing advance through the RACH preamble, and then uses the timing advance information to generate a compensated phase for the linear phase rotator in the frequency domain, which is expressed by the following formula: theta (k) = ta_phase * k, where k is the carrier index; ta_phase is estimated from the RACH preamble.

In addition, please refer to FIG. 7, which shows a channel estimation process used in the present invention. The UE sends the RACH preamble and RACH data in the time-frequency resources allocated by the network. After receiving the RACH preamble, the network obtains the TA value of each detected RACH preamble corresponding to the UE. At the same time, the network receives RACH data with DMRS in some subcarriers of the Physical Resource Block (PRB), and then performs minimum mean square error (MMSE) channel estimation to obtain a channel with the allocated DMRS (ie, with a sloped line Labeled channels). After obtaining the channel and TA value, the network performs a TA compensation operation "theta (k)" on the channel of the obtained subcarrier of the RRB. Therefore, a channel without timing advance delay is obtained, and then the network performs frequency-domain channel estimation based on the channel without timing advance delay to obtain an accurate channel estimation result.

In addition, for DMRS design, the present invention provides a code-division multiplexing (CDM), frequency-division multiplexing (FDM), and time-division multiplexing (TDM) Or any combination of these three ways to expand DMRS capacity. In a traditional LTE system, the 12 CDM-based DMRS sequences in a PRB have a maximum of 12 REs (Resource Elements) (that is, the DMRS is multiplexed in a CDM manner by a ZC-type sequence). The network can reuse this structure with the 12 CDM-based DMRS sequences to create an additional 12 DMRS sequences using the EDM approach. As shown in Figure 8, 24 DMRS sequences can be used, so the network can allocate DMRS13 ~ DMRS 24 in the next PRB in the frequency resource. Similarly, as shown in Figure 9, the network can use this structure with 12 CDM-based DMRS sequences to create an additional 12 DMRS sequences using TDM. For example, the network may allocate DMRS13 ~ DMRS24 in the next OFDM symbol in the time resource.

Note that, as shown in FIG. 10, if the UE knows the timing advance information when performing the 2-step RACH procedure, the UE sends through the same parameter set and format as the Physical Uplink Shared Channel (PUSCH) Uplink profile because the UE and the network are synchronized. In other words, data transmission should use the same CP (eg CP = 4.7us), SCS and GT as PUSCH instead of PRACH. In addition, the UE removes the preamble for optimized data transmission.

The above steps including the flow / operation of the recommended steps can be implemented by means of hardware, software, or firmware, which is a combination of hardware devices, computer instructions, and software on a hardware device or electronic system as read-only data. Examples of hardware can include analog, microchip, or silicon chips called analog, parameter sets, and hybrid circuits. Examples of the electronic system may include a system on chip (SOC), a system-in-package (SiP), a computer on a module (COM), and a communication device 20.

In a word, the present invention is directed to the DMRS design of the 2-step RACH process, especially to the DMRS configuration expansion and DMRS density reduction. In addition, the present invention provides a parameter set and format for RACH data transmission. Therefore, the data transmission and reception of the 2-step RACH procedure can be realized in the 5G new radio (NR).

In some embodiments, the terms "about", "about" and "substantially" may be used to indicate within ± 10% of a target value. The terms "about", "about" and "substantially" may include a target value. It should be understood that the terms "about", "about" and "substantially" can be used to refer to a range less than ± 10% of the target value, for example: ± 5% of the target value, ± 1% of the target value of ± 2.5%, ± 1% of target value.

The use of ordinal terms such as "first", "second", "third" in the scope of patent applications to modify elements of the scope of patent applications does not in itself mean that one element of the scope of patent applications has priority over another or any time Right, priority or order. The order in which the method's actions are performed, but only Used as a label to distinguish one patented scope element with a specific name from another element with the same name (but for use of ordinal terms) to distinguish patented scope elements.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the scope of patent application of the present invention shall fall within the scope of the present invention.

Claims (5)

A data receiving method for a random access flow of a network of a wireless communication system, comprising: receiving a preamble and data of the random access flow from a message of a user equipment of the wireless communication system; and acquiring timing based on the received preamble Advance information; and channel estimation based on the allocated demodulation reference signal for demodulating the received data and timing advance compensation, where the timing advance compensation is based on the timing advance information to perform a linear phase rotation operation in the frequency domain . The method according to item 1 of the scope of patent application, wherein performing channel estimation according to the allocated demodulation reference signal and timing advance compensation for demodulating the received data includes: obtaining an estimated channel by using the demodulation reference signal; And estimating the channel carrying data through the estimated channel and the timing advance compensation operation. The method according to item 1 of the scope of patent application, further comprising: configuring a demodulation reference signal sequence allocated to the resource in a code division multiplexing manner at least in the time resource and the frequency resource. The method according to item 1 of the scope of patent application, wherein receiving a preamble and information of the random access procedure from a message of a user equipment of a wireless communication system includes: receiving a parameter set having the same parameter set as the physical random access channel and Data in a format in which the cyclic prefix of the data is the same as the cyclic prefix of the preamble, and the subcarrier interval of the data is the same as or different from the subcarrier interval of the preamble. The method according to item 1 of the patent application scope further comprises: when the user equipment is synchronized with the network, only receiving data having the same parameter set and format as the physical uplink shared channel.