CN102548014B - Network access method of machine-to-machine (M2M) communication terminals - Google Patents

Abstract

The invention discloses a method for M2M terminals to access a network, which includes the following steps: S1: A base station divides multiple M2M terminals into multiple M2M groups, so that the M2M terminals belonging to the same M2M group have the same business category and the same service Quality level; S2: M2M terminals are powered on to obtain initial uplink synchronization and maintain uplink synchronization status; S3: The base station calculates the channel capacity of PRACH and PUCCH in the current system; S4: When M2M terminals generate uplink data waiting to be sent, priority is given to sending scheduling through the PRACH channel request, when the PRACH channel collides, the base station dynamically allocates PUCCH scheduling request resources for the M2M terminal, and the M2M terminal sends the scheduling request through the PUCCH channel. The method of the invention alleviates the congestion of the PRACH channel, and finally meets the service quality requirement of the M2M service terminal.

Description

Method for machine-to-machine communication terminals to access network

technical field

The invention relates to the technical field of wireless communication, in particular to a method for machine-to-machine communication terminals to access a network.

Background technique

In recent years, with the vigorous rise of the Internet of Things technology, machine-to-machine communication (M2M, Machine to Machine) services, such as smart meter reading, smart home appliances, industrial monitoring, environmental testing, etc., have been recognized by the industry due to their wide application prospects of close attention. At the same time, considering the characteristics of M2M services: 1) if the number of terminals is huge, 2) the function is simple, the service is single, and the data volume is small (<100bytes), 3) it can tolerate low transmission rate and is not sensitive to delay, 4 ) does not have mobility or moves regularly, 5) mainly uplink PS services, 6) low-frequency (>5min) large-scale periodic reporting, M2M services and human-to-human communication (H2H, Human to Human) services Therefore, it is particularly necessary to optimize for different M2M service applications combined with actual specific systems.

The Long Term Evolution (LTE, Long Term Evolution) system is a scheduling-based communication system. The H2H service terminal in the uplink synchronization state has uplink services to be sent, and then sends a buffer status report (BSR, Buffer Status Report) to the evolved base station (eNB, evolved NodeB) to report the current buffer size of each logical channel. After receiving the BSR sent by the H2H service terminal, the eNB executes the uplink resource scheduling algorithm, and finally indicates the uplink resource grant (UL Resource Grant) to the H2H service terminal through the Physical Downlink Control Channel (PDCCH, Physical Downlink Control CHannel). After receiving the UL Grant on the PDCCH channel, the H2H service terminal sends data on the corresponding uplink resources. However, since sending a BSR also requires a UL Grant, if a BSR is triggered without a UL Grant, the BSR cannot be sent, which will cause data congestion on the H2H service terminal side. In order to solve this problem, the LTE system allows H2H service terminals that have achieved uplink synchronization to send a scheduling request (SR, Schedule Request) on the physical uplink control channel (PUCCH, Physical Uplink ControlCHannel), requesting at least 4 bytes of uplink resources from the eNB In order to send BSR, as shown in Figure 1. If the H2H service terminal does not obtain uplink synchronization, or obtains uplink synchronization but does not have the PUCCH SR resource allocated by the eNB, or the SR sent on the PUCCH SR resource exceeds the maximum number of transmissions, the H2H service terminal can only be forced to use random access. The channel (PRACH, Physical Random Access CHannel) sends SR, as shown in Figure 2. The basic principle for the H2H service terminal to send SR is that as long as there are PUCCH SR resources, it will not send SR through PRACH.

Combined with the LTE communication system, when a large number of M2M service terminals generate uplink data for some reason at the same time (for example, the power company requires a smart meter in a certain area to report power consumption or adjust a certain power parameter, or when a train passes a certain bridge. All sensors send monitoring data to the system server, or when an earthquake occurs, all earthquake monitors in a certain area send out an alarm), because a large number of M2M service terminals do not have PUCCH SR resources, they can only send SR through PRACH, which is inevitable on PRACH Collision or even congestion occurs, and ultimately the service quality of M2M services cannot be guaranteed (3GPP TR 22.368).

In order to avoid RACH collisions caused by a large number of M2M terminals simultaneously initiating random access and unable to guarantee service access delays, the current candidate solutions proposed by mainstream companies in the world are as follows (3GPP TR 37.868):

Access Class Barring Scheme (ACB, Access Class Barring Scheme). Considering that most M2M services are not sensitive to delay, by defining a special access level for M2M services, the network side independently controls the M2M access probability to achieve the purpose of dispersing RACH load.

Separate backoff strategy (Specific Backoff Scheme). Also considering that most M2M services are not sensitive to delay, a special large backoff time is defined through M2M services to achieve the purpose of dispersing RACH load.

Separate RACH Resources Scheme (Specific RACH Resources Scheme). By allocating different RACH resources for the H2H service and the M2M service, the impact of the M2M service on the common H2H service is avoided. In the UMTS system, different access service classes (ASC, Access Service Class) or random access signatures can be configured for M2M services and H2H services; in the LTE system, different random access signatures can be configured for M2M services and H2H services. The access preamble or the RACH resource in the time-frequency domain.

Dynamic RACH Resources Scheme (Dynamic RACH Resources Scheme). The network side dynamically increases/decreases the RACH resource according to the actual M2M service load to achieve a trade-off between the random access delay and the utilization rate of the RACH resource.

Slotted Access Scheme. The network side allocates dedicated access time slots for various M2M service terminals, and each type of M2M terminal can only initiate a random access process in a specific access time slot, so as to achieve the purpose of dispersing RACH load.

All the above schemes are optimized from the aspects of RACH resource (time slot/preamble sequence) allocation, cell access restriction judgment and backoff strategy in the random access process. Initiate random access to avoid affecting the service quality experience of M2M/H2H users due to RACH congestion.

Existing simulations show (R2-103742) that the access level restriction strategy relieves RACH congestion by prohibiting some M2M terminals from initiating access, but leads to a large access delay; the backoff strategy is only applicable to scenarios with low RACH load ; while the strategy of allocating separate RACH resources for M2M services in heavy RACH load scenarios, the probability of RACH collision remains high. In addition, although the dynamic RACH resource allocation strategy performs well in the above aspects, it must be noted that the dynamic increase of RACH resources will inevitably lead to the reduction of PUSCH resources and affect the overall system throughput. It can be seen that the existing technical solutions cannot fundamentally alleviate the current situation of RACH congestion caused by a large number of M2M service terminals simultaneously initiating random access due to service bursts.

Under the existing technical solution, when a large number of M2M service terminals generate uplink burst data at the same time, since there is no PUCCH SR resource, the uplink data can only be sent if the uplink resource authorization of the eNB is obtained through random access competition. However, because LTE TS 36.211 stipulates that the RACH channel density is limited to a maximum of 6, that is, there are a maximum of 6 RACH resources per 10 ms, the limited RACH resources make the existing technical solutions unable to truly meet the access delay requirements of massive M2M uplink services.

Contents of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is to provide a method for M2M terminals to access the network, so as to alleviate the congestion of the PRACH channel and finally meet the service quality requirements of the M2M service terminals.

(2) Technical solution

In order to solve the above problems, the present invention provides a method for an M2M terminal to access a network, including the following steps:

S1: the base station divides multiple M2M terminals into multiple M2M groups, so that the M2M terminals belonging to the same M2M group have the same service category and the same service quality level;

S2: The M2M terminal is powered on to obtain initial uplink synchronization and maintain the uplink synchronization state;

S3: the base station calculates the PRACH and PUCCH channel capacity of the current system;

S4: When the M2M terminal generates uplink data waiting to be sent, it preferentially sends a scheduling request through the PRACH channel. When the PRACH channel collides, the base station dynamically allocates PUCCH scheduling request resources for the M2M terminal, and the M2M terminal sends a scheduling request through the PUCCH channel.

Preferably, before the step S4, the base station further includes a step of sorting the plurality of M2M groups according to the level of service quality.

Preferably, in step S4, when the PRACH channel collides, the base station dynamically allocates PUCCH scheduling request resources for the M2M terminal, and the steps for the M2M terminal to send the scheduling request through the PUCCH channel are as follows:

The M2M monitors the PDCCH channel, and the base station detects whether the scheduling request sent by the M2M terminal on the PRACH channel exceeds the load threshold of the current system PRACH:

If not exceeded, the base station sends a random access response through the PRACH channel, and the M2M terminal continues to send a scheduling request through the PRACH channel;

If it exceeds, the base station sends downlink control information through the PDCCH channel, and dynamically allocates PUCCH scheduling request resources for the M2M terminal; the M2M terminal monitors the downlink control information sent by the PDCCH, terminates the random access process, and sends a scheduling request on the PUCCH channel allocated by the base station. Request; until the base station detects that the scheduling request sent by the M2M terminal is lower than the load threshold of the current system PRACH, the base station sends downlink control information through the PDCCH channel to reclaim the allocated PUCCH scheduling request resources; the M2M terminal monitors the downlink control sent by the PDCCH information to dynamically release PUCCH scheduling request resources.

Preferably, the base station sends downlink control information through the PDCCH channel, and the step of dynamically allocating PUCCH scheduling request resources for the M2M terminal is specifically as follows:

According to the quality of service priority of the M2M group, the base station defines new downlink control information through the PDCCH channel starting from the M2M group with the highest priority: indicating to each M2M terminal in the M2M group the resource position index that can send the scheduling request; If it is detected that the number of scheduling requests sent by the M2M group is very small during the time that the M2M group occupies the PUCCH scheduling request resources, it indicates that the M2M group does not have burst services, and the allocated resources are recovered through the new downlink control information again. The PUCCH scheduling request resources are then re-allocated for the M2M group with the next quality of service priority.

Preferably, the time for the M2M group to occupy the PUCCH scheduling request resource is determined by the maximum time delay for the M2M terminals in each M2M group to complete uplink service transmission.

Preferably, after the step of calculating the PUCCH channel capacity of the current system, the step S3 further includes the step of reserving scheduling request resources for M2M terminals.

Preferably, the base station transmits downlink control information through a PDCCH channel, and the step of dynamically allocating PUCCH scheduling request resources for M2M terminals further includes: when the PUCCH scheduling request resources to be allocated to the M2M terminals are larger than the PUCCH reserved for M2M When the terminal requests resources for scheduling, expand the number of reserved scheduling request resources.

(3) Beneficial effects

The present invention dynamically configures PUCCH SR resources for M2M service terminals when the PRACH channel collides, relieves the congestion of the PRACH channel, and finally meets the service quality requirements of the M2M service terminals.

Description of drawings

FIG. 1 is a schematic diagram of a terminal (UE) sending a scheduling request to a base station through a PUCCH channel in the prior art;

FIG. 2 is a schematic diagram of the terminal sending a scheduling request to the base station side through the PRACH channel in the current technology;

FIG. 3 is a flowchart of a method for a terminal to access a network according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of the distribution of PUCCH channels in different formats in the frequency domain.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 3, this embodiment records a method for an M2M terminal to access a network, including the following steps:

S1: The base station divides a large number of M2M terminals into multiple M2M groups, so that the M2M terminals belonging to the same M2M group have the same service category and the same service quality level; sort;

After the massive M2M terminals in this embodiment are divided, N M2M groups are formed, and the multiple M2M groups are sorted according to the order of service quality levels from high to low, so that the first M2M group has the highest priority, and the Nth M2M group has the highest priority. Each M2M group has the lowest priority, and the number of M2M terminals in the nth M2M group is NUMn, where n is a natural number from 1 to N.

S2: A large number of M2M terminals are powered on and go through the initial attachment process to obtain initial uplink synchronization; because M2M terminals have low mobility, it is considered that a large number of M2M terminals will always maintain uplink synchronization during the subsequent process of receiving services;

S3: The base station calculates the PRACH channel capacity and the PUCCH channel capacity of the current system; and the PUCCH channel capacity reserves scheduling request resources for the M2M terminal;

The calculation of the PRACH channel capacity is as follows: assuming that the density of PRACH per 10 microseconds configured by the initial system is D _RA , and the number of preambles (preambles) initially reserved for contention random access is n, then the calculated PRACH channel can carry The number of users is n*D _RA ;

The capacity of the PUCCH channel is determined by the number of users that can be carried by PUCCH format 1 (PUCCH Format1, the scheduling request SR is sent on the PUCCH channel in Format 1 format), and the PUCCH format 1 that can be carried by one physical resource block pair (PRB-Pairs) The number of channels is determined. Without considering the mixed physical resource block pairs of PUCCH format 2/2a/2b and PUCCH format 1/1a/1b, as shown in Figure 4, it is assumed that the initial base station eNB allocates the resource starting position for PUCCH format 1a/1b transmission for The number of resources initially allocated to PUCCH format 2/2a/2a transmission is Then the number of PRB-Pairs reserved by the system for PUCCH format 1 is Assuming that in the case of a conventional cyclic prefix, the number of orthogonal spread spectrum sequences is m, and the cyclic shift interval of the supported Zadoff-Chu sequence is Since the transmission of PUCCH format 1 undergoes two code spreading processes of "orthogonal spreading sequence" and "Zadoff-Chu sequence", the number of PUCCH Format1 channels that can be carried by one PRB-Pairs is in is the number of subcarriers contained in a resource block RB.

S4: When the M2M terminal generates uplink data waiting to be sent, it preferentially sends a scheduling request through the PRACH channel, the M2M monitors the PDCCH channel, and the base station detects whether the scheduling request sent by the M2M terminal on the PRACH channel exceeds the current system PRACH load threshold n*D _RA :

If not exceeded, the base station sends a random access response through the PRACH channel, and the M2M terminal continues to send a scheduling request through the PRACH channel;

If it exceeds, it is estimated that one or several M2M groups may trigger a group call or report periodically and there is a large amount of burst uplink data waiting to be sent, then start the dynamic PUCCH SR resource allocation strategy: the base station sends downlink control through the PDCCH channel information, to dynamically allocate PUCCH scheduling request resources for the M2M terminal; the M2M terminal monitors the downlink control information sent by the PDCCH, terminates the random access process, and sends a scheduling request on the PUCCH channel allocated by the base station;

The steps of the base station sending downlink control information through the PDCCH channel and dynamically allocating PUCCH scheduling request resources for the M2M terminal are as follows:

According to the quality of service priority of the M2M group, the base station defines new downlink control information through the PDCCH channel starting from the M2M group with the highest priority: indicating to each M2M terminal in the M2M group the resource position index that can send the scheduling request; If it is detected that the number of scheduling requests sent by the M2M group is very small during the time that the M2M group occupies the PUCCH scheduling request resources, it indicates that the M2M group does not have burst services, and the allocated resources are recovered through the new downlink control information again. The PUCCH scheduling request resources are then re-allocated for the M2M group with the next quality of service priority.

Wherein, the base station estimates the maximum time delay for the M2M terminals in each M2M group to complete the uplink service transmission to determine the time for the M2M group to occupy the PUCCH scheduling request resource.

When the PUCCH scheduling request resource to be allocated to the M2M terminal is greater than the scheduling request resource reserved for the M2M terminal of the PUCCH, expand the number of the reserved scheduling request resource. For example, in this embodiment, according to the number NUMn of M2M terminals in the nth M2M group stored in the base station and the SR period T _n , calculate the number of PRB-Pairs that need to be allocated to the nth M2M group for each transmission time interval TTI for The base station calculates the maximum number of PUCCH PRB-Pairs to be allocated to the M2M terminal as: $\mathrm{Max}\{\frac{1}{T_1}{\mathrm{NUM}}_1/(m*\frac{N_{\mathrm{SC}}^{\mathrm{RB}}}{{\mathrm{\&Delta;}}_{\mathrm{shift}}^{\mathrm{PUCCH}}}),...,\frac{1}{T_{\mathrm{no}}}{\mathrm{NUM}}_{\mathrm{no}}/(m*\frac{N_{\mathrm{SC}}^{\mathrm{RB}}}{{\mathrm{\&Delta;}}_{\mathrm{shift}}^{\mathrm{PUCCH}}})\}.$ If the above-mentioned maximum number of PUCCH PRB-Pairs to be allocated exceeds the number of PRB-Pairs reserved by the base station Then the base station dynamically adjusts the starting position of the resource allocated to PUCCH Format 1a/1b transmission to In order to expand the number of reserved scheduling request resources.

If the base station detects that the scheduling request sent by the M2M terminal is lower than the load threshold of the current system PRACH, it is estimated that one or several M2M groups may have completed the group call or reported periodically, and the base station sends a downlink request through the PDCCH channel. The control information reclaims the allocated PUCCH scheduling request resources; the M2M terminal monitors the reclaimed downlink control information sent by the PDCCH, and dynamically releases the PUCCH scheduling request resources.

The present invention dynamically configures PUCCH SR resources for M2M service terminals when the PRACH channel collides, relieves the congestion of the PRACH channel, and finally meets the service quality requirements of the M2M service terminals.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (5)

1. A method for an M2M terminal to access a network, comprising the following steps: S1: the base station divides multiple M2M terminals into multiple M2M groups, so that the M2M terminals belonging to the same M2M group have the same service category and the same service quality level; S2: The M2M terminal is powered on to obtain initial uplink synchronization and maintain the uplink synchronization state; S3: the base station calculates the PRACH and PUCCH channel capacity of the current system; S4: When the M2M terminal generates uplink data waiting to be sent, it preferentially sends the scheduling request through the PRACH channel. When the PRACH channel collides, the base station dynamically allocates PUCCH scheduling request resources for the M2M terminal, and the M2M terminal sends the scheduling request through the PUCCH channel; In step S4, when the PRACH channel collides, the base station dynamically allocates PUCCH scheduling request resources for the M2M terminal, and the steps for the M2M terminal to send the scheduling request through the PUCCH channel are as follows: The M2M monitors the PDCCH channel, and the base station detects whether the scheduling request sent by the M2M terminal on the PRACH channel exceeds the load threshold of the current system PRACH: If not exceeded, the base station sends a random access response through the PRACH channel, and the M2M terminal continues to send a scheduling request through the PRACH channel; If it exceeds, the base station sends downlink control information through the PDCCH channel, and dynamically allocates PUCCH scheduling request resources for the M2M terminal; the M2M terminal monitors the downlink control information sent by the PDCCH, terminates the random access process, and sends a scheduling request on the PUCCH channel allocated by the base station. Request; until the base station detects that the scheduling request sent by the M2M terminal is lower than the load threshold of the current system PRACH, the base station sends downlink control information through the PDCCH channel to reclaim the allocated PUCCH scheduling request resources; the M2M terminal monitors the downlink control sent by the PDCCH information to dynamically release PUCCH scheduling request resources; Wherein, the base station transmits downlink control information through the PDCCH channel, and the steps of dynamically allocating PUCCH scheduling request resources for the M2M terminal are as follows: According to the quality of service priority of the M2M group, the base station defines new downlink control information through the PDCCH channel starting from the M2M group with the highest priority: indicating the resource location index for sending the scheduling request to each M2M terminal in the M2M group; if During the time that the M2M group occupies the PUCCH scheduling request resources, it is detected that the number of scheduling requests sent by the M2M group is very small, indicating that the M2M group does not have burst services, and the allocated PUCCH is recovered through the new downlink control information again Scheduling request resources, in turn reallocating PUCCH scheduling request resources for the M2M group with the next quality of service priority. 2 . The method for M2M terminals to access the network according to claim 1 , further comprising a step of sorting the plurality of M2M groups by the base station according to the level of service quality before the step S4 . 3 . The method for M2M terminals to access the network according to claim 1 , wherein the time for the M2M groups to occupy PUCCH scheduling request resources is determined by the maximum delay for M2M terminals in each M2M group to complete uplink service transmission. 4 . 4. The method for M2M terminals to access the network according to claim 1, characterized in that the step of calculating the PUCCH channel capacity of the current system in step S3 further includes the step of reserving scheduling request resources for M2M terminals. 5. The method for an M2M terminal to access a network according to claim 4, wherein when the PUCCH scheduling request resource to be allocated to the M2M terminal is greater than the scheduling request resource reserved for the M2M terminal of the PUCCH, Expanding the number of reserved scheduling request resources.