CN103841654A - Random access method in smart power grid communication - Google Patents

Abstract

Translated fromChinese

本发明提出一种智能电网通信中随机接入的方法，在不增加额外信令开销的情况下，降低随机接入碰撞概率，提高系统性能。由于智能电网设备众多、频繁进行数据上报，随机接入碰撞概率大大增加，并且会影响普通用户的随机接入过程。本发明提出一种应对该智能电网场景的随机接入过程。通过生成两组不同的前导序列，分别用于普通用户和智能电网。使用MAC RAR中的一个预留比特位来标识该随机接入来自普通用户或智能电网。因此能在没有额外信令开销的情况下，减少智能电网随机接入碰撞概率，并且不影响普通用户随机接入。

The invention proposes a method for random access in smart grid communication, which reduces the random access collision probability and improves system performance without increasing additional signaling overhead. Due to the large number of smart grid devices and frequent data reporting, the random access collision probability is greatly increased, and it will affect the random access process of ordinary users. The present invention proposes a random access process for the smart grid scenario. By generating two different sets of preamble sequences, they are used for ordinary users and smart grid respectively. A reserved bit in the MAC RAR is used to identify that the random access is from a common user or a smart grid. Therefore, the random access collision probability of the smart grid can be reduced without additional signaling overhead, and the random access of ordinary users is not affected.

Description

Translated fromChinese

一种智能电网通信中随机接入的方法A random access method in smart grid communication

技术领域technical field

本发明涉及智能电网无线通信中随机接入过程，降低随机接入碰撞的概率。The invention relates to a random access process in smart grid wireless communication, which reduces the probability of random access collisions.

背景技术Background technique

智能电网是一种将通信网络与电网系统相结合的现代的电网系统。通过对电网中数据的实时收集与分析，从而达到对电力负载的控制和需求响应等目的，能提高能源利用效率，确保安全、可靠、优质的电力供应。在智能电网中，发电、输电、配电、用电环节都存在着大量的先进传感和测量技术、设备，需要网络通信技术的支撑。然而智能电网中的通信不同于传统的数据或语音服务，有着特定的特点和需求。比如，终端设备（UE）较多，数据量较小，周期通信等特点。Smart grid is a modern grid system that combines communication network and grid system. Through the real-time collection and analysis of data in the power grid, the purpose of power load control and demand response can be achieved, energy utilization efficiency can be improved, and safe, reliable and high-quality power supply can be ensured. In the smart grid, there are a large number of advanced sensing and measurement technologies and equipment in the links of power generation, power transmission, power distribution, and power consumption, which require the support of network communication technology. However, communication in the smart grid is different from traditional data or voice services, and has specific characteristics and requirements. For example, there are many terminal equipment (UE), small amount of data, periodic communication and other characteristics.

LTE可以提供高频谱效率,大吞吐量,低延时以及支持基于IP的多种应用服务，是智能电网中一种较为理想的通信技术。在LTE中，为了获得上行同步并为UE分配一个唯一的标识C-RNTI，UE需要进行随机接入过程。只有通过随机接入，UE才能与基站取得上行同步，并且为UE分配一个唯一的标识C-RNTI，进而后续的通信过程才能进行。随机接入分为基于竞争和非竞争两种方式。基于竞争的随机接入过程如图1所示。LTE can provide high spectral efficiency, high throughput, low delay and support various IP-based application services, and is an ideal communication technology in smart grid. In LTE, in order to obtain uplink synchronization and assign a unique identifier C-RNTI to the UE, the UE needs to perform a random access procedure. Only through random access can the UE obtain uplink synchronization with the base station, and assign a unique identifier C-RNTI to the UE, so that the subsequent communication process can proceed. There are two types of random access based on contention and non-contention. The contention-based random access process is shown in Figure 1.

Step1)当UE由某事件触发需要进行随机接入时，首先在物理随机接入信道(PhysicalRandom Access Channel，PRACH)资源上向基站发送随机接入前导，其目的在于向eNodeB指示当前UE的随机接入尝试,并使得eNodeB能估计其与UE之间的传输时延。前导序列共有64个，是UE通过解析eNodeB广播的配置信息而得到。64个前导中的一部分是预留给基于非竞争随机接入的，UE从剩下的前导中随机选择一个前导在PRACH上发送给基站。Step1) When the UE is triggered by an event and needs to perform random access, it first sends a random access preamble to the base station on the physical random access channel (Physical Random Access Channel, PRACH) resource, the purpose of which is to indicate the random access of the current UE to the eNodeB It enables the eNodeB to estimate the transmission delay between itself and the UE. There are 64 preamble sequences in total, which are obtained by the UE by parsing the configuration information broadcast by the eNodeB. Part of the 64 preambles is reserved for non-contention-based random access, and the UE randomly selects a preamble from the remaining preambles and sends it to the base station on the PRACH.

Step2)eNodeB通过PDCCH向UE发送随机接入响应(Random Access Response，RAR)。若eNodeB在PRACH上检测到随机接入前导,就会在PDCCH上发送随机接入响应RAR,包括随机接入前导序列序号（RAPID）、时间提前量(Timing Advance Command)、T-RNTI(TemporaryRadio Network Temporary Identifier)、退避指示、上行资源分配等。UE发送了preamble之后，将在RAR时间窗（RA Response window）内监听PDCCH，以接收对应RA-RNTI（由PRACH的时频位置决定）的RAR。如果多个UE在同一PRACH资源（时频位置相同，使用同一RA-RNTI）发送preamble，则对应的RAR复用在同一MAC PDU中,用RA-RNTI加扰，如图2所示。Step2) The eNodeB sends a random access response (Random Access Response, RAR) to the UE through the PDCCH. If the eNodeB detects a random access preamble on the PRACH, it will send a random access response RAR on the PDCCH, including the random access preamble sequence number (RAPID), timing advance (Timing Advance Command), T-RNTI (TemporaryRadio Network Temporary Identifier), backoff indication, uplink resource allocation, etc. After the UE sends the preamble, it will monitor the PDCCH within the RAR time window (RA Response window) to receive the RAR corresponding to the RA-RNTI (determined by the time-frequency position of the PRACH). If multiple UEs send preambles on the same PRACH resource (same time-frequency position, using the same RA-RNTI), the corresponding RARs are multiplexed in the same MAC PDU and scrambled with RA-RNTI, as shown in Figure 2.

如果多个UE相同的PRACH资源上选择了同一个前导序列发起随机接入的尝试,那么就会发生碰撞。每个UE都有可能接收到同一个RAR,由此进入竞争解决过程Step3、Step4。If multiple UEs select the same preamble sequence to initiate a random access attempt on the same PRACH resource, a collision will occur. Each UE may receive the same RAR, thus entering the contention resolution process Step3, Step4.

Step3)在上个步骤的MAC header中解析出自己前导序号的UE，根据解析出来的RAR信息在PUSCH上向eNodeB发送消息3（Msg3）。包含RRC连接请求、跟踪区域更新、调度请求、Step2中解码的T-RNTI，以及每个UE唯一的标志（C-RNTI或S-TMSI）。Step3) The UE that parses out its own leading sequence number from the MAC header in the previous step sends a message 3 (Msg3) to the eNodeB on the PUSCH according to the parsed RAR information. Contains RRC connection request, tracking area update, scheduling request, T-RNTI decoded in Step2, and unique flag (C-RNTI or S-TMSI) for each UE.

Step4)若eNodeB成功解码一个UE的Msg3，则在PDSCH上发送竞争解决消息（contention resolution），携带该UE的唯一标志以指定胜出的UE。而其它没有在冲突解决中胜出的UE将根据MAC header中的回退指数（BI）选择一个回退时间，延迟了回退时间后重新发起随机接入。Step4) If the eNodeB successfully decodes the Msg3 of a UE, it sends a contention resolution message (contention resolution) on the PDSCH, carrying the unique identifier of the UE to designate the winning UE. Other UEs that do not win the conflict resolution will select a backoff time according to the backoff index (BI) in the MAC header, and re-initiate random access after delaying the backoff time.

在典型的智能电网环境下，有大量的传感器、电表等进行测量、上报数据。比如在高级量测体系（AMI）中，智能电表每隔15分钟就要上报一次用电数据。由上述的LTE随机接入过程可知，当多个电表同时需要上报数据，同时发起随机接入过程时，需要在用于竞争的前导中随机选取一个。由于电表数量众多，并且频繁的周期性上报数据，多个电表选择同一个前导的概率很大，导致随机接入过程时碰撞几率大大增加，并影响传统的语音和数据通信的随机接入。因此有必要提出一种优化随机接入的方法去减少随机接入过程中的碰撞概率，提高智能电网的整体性能。In a typical smart grid environment, there are a large number of sensors, meters, etc. to measure and report data. For example, in the advanced metering system (AMI), smart meters have to report electricity consumption data every 15 minutes. It can be seen from the above LTE random access process that when multiple meters need to report data at the same time and initiate the random access process at the same time, one needs to be randomly selected from the preambles used for competition. Due to the large number of meters and the frequent and periodic reporting of data, the probability of multiple meters selecting the same preamble is high, which greatly increases the probability of collision during the random access process and affects the random access of traditional voice and data communications. Therefore, it is necessary to propose a method for optimizing random access to reduce the collision probability in the process of random access and improve the overall performance of the smart grid.

发明内容Contents of the invention

基于上述对问题的分析，本发明提出一种智能电网通信中随机接入的方法,该方法能在智能电网环境下降低随机接入碰撞概率，并且不影响传统语音、数据业务的随机接入。另外，本发明不需要额外的信令开销，节约了宝贵的信令资源。Based on the above analysis of the problem, the present invention proposes a random access method in smart grid communication, which can reduce the random access collision probability in the smart grid environment, and does not affect the random access of traditional voice and data services. In addition, the present invention does not require additional signaling overhead, saving precious signaling resources.

在LTE的Rel.11标准中，随机接入前导是由UE基于基站广播的系统配置信息而生成。3GPP LTE工作组最终选择了ZC（Zadoff-Chu）序列用于生成随机接入前导序列。In the Rel.11 standard of LTE, the random access preamble is generated by the UE based on the system configuration information broadcast by the base station. The 3GPP LTE working group finally selected the ZC (Zadoff-Chu) sequence for generating the random access preamble.

ZC序列的定义如下：The ZC sequence is defined as follows:

${\mathrm{<span><span>x</span>x</span>}}_{\mathrm{<span><span>u</span>u</span>}}<span><span>(</span>(</span>\mathrm{<span><span>n</span>no</span>}<span><span>)</span>)</span><span><span>=</span>=</span>\mathrm{<span><span>exp</span>exp</span>}<span><span>[</span>[</span><span><span>-</span>-</span>\mathrm{<span><span>j</span>j</span>}\frac{\mathrm{<span><span>\&pi;un</span>\&pi;un</span>}<span><span>(</span>(</span>\mathrm{<span><span>n</span>no</span>}<span><span>+</span>+</span>\mathrm{<span><span>1</span>1</span>}<span><span>)</span>)</span>}{{\mathrm{<span><span>N</span>N</span>}}_{\mathrm{<span><span>ZC</span>ZC</span>}}}<span><span>]</span>]</span><span><span>,</span>,</span>\mathrm{<span><span>0</span>0</span>}<span><span><</span><</span>\mathrm{<span><span>n</span>no</span>}<span><span>\&le;</span>\&le;</span>{\mathrm{<span><span>N</span>N</span>}}_{\mathrm{<span><span>ZC</span>ZC</span>}}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}$

其中N_ZC为序列长度，根据协议为839。u是物理根值。exp[]为以e为底的指数函数，j为虚数单位，π为圆周率。where N_ZC is the sequence length, which is 839 according to the protocol. u is the physical root value. exp[] is an exponential function with e as the base, j is the imaginary unit, and π is the pi.

前导序列由ZC序列进过循环位移C_v生成：The leading sequence is generated by the ZC sequence through the cyclic shift C_v :

x_u,v(n)＝x_u((n+C_v)modN_ZC)x_u,v (n)＝x_u ((n+C_v )modN_ZC )

循环位移C_v由下可得：The cyclic displacement C_v can be obtained as follows:

N_CS为循环位移，其值可由表1得。偏移参数d_start,

的设置可见[1]。N_CS is the cyclic shift, and its value can be obtained from Table 1. Offset parameter d_start ,

The settings can be seen in [1].

对于UE，由接收基站广播的配置信息得到ZC序列的逻辑根序号和N_CS的索引，经查表后得到物理根植u循环位移C_v，根据上式生成前导。如果系统配置的循环位移太大不足以产生足够的64个衍生序列需要额外的根序列的时候,只需要在原有逻辑根序列索引数字加1,得到下一个u值,从而生成另外一个根序列,以此类推直到根序列足够产生64个前导签名序列为止。For the UE, the logical root number of the ZC sequence and the index of the_NCS are obtained from the configuration information broadcast by the base station, and the physical root u cyclic displacement C_v is obtained after looking up the table, and the preamble is generated according to the above formula. If the cyclic displacement of the system configuration is too large to generate enough 64 derived sequences and an additional root sequence is required, it is only necessary to add 1 to the index number of the original logical root sequence to obtain the next u value, thereby generating another root sequence. And so on until the root sequence is enough to generate 64 leading signature sequences.

表1用于生成前导的N_CS值Table 1 N_CS values used to generate the preamble

对于我们的典型智能电网场景如大量智能电表周期性的上报数据，同时进行随机接入，64个前导可能不足以支持大量的随机接入。本发明首先对LTE协议[1]中的前导生成过程进行改进。For our typical smart grid scenario, such as a large number of smart meters periodically reporting data and performing random access at the same time, 64 preambles may not be enough to support a large number of random access. The present invention first improves the preamble generation process in the LTE protocol [1].

Step1）中，使用传统的语音和数据业务的普通UE仍然按照原先协议中的方式生成第一组共64个前导，而智能电表则从普通UE的64个前导之后另外生成另一组64个专用前导。若普通UE/智能电网需要进行随机接入过程，则分别在对应的前导组中随机选择一个前导序列进行发送。In Step1), ordinary UEs using traditional voice and data services still generate the first set of 64 preambles according to the original protocol, while the smart meter generates another set of 64 dedicated preambles after the 64 preambles of ordinary UEs. leading. If a common UE/smart grid needs to perform a random access process, a preamble sequence is randomly selected in the corresponding preamble group and sent.

在step2）过程中，基站发送随机接入响应RAR来分配上行资源。如图3所示，在MAC子头部中，RAPID字段用来表示前导的序号，6个字节可以支持64个前导。我们使用MAC RAR中的一个R域，如图4所示，即1个比特的预留比特位。我们用这个比特位来标识上述的RAPID来自普通UE的前导组还是智能电表的前导组。如果R位是0，就代表是普通UE，1就代表智能电表，这样就可以支持两组64个的前导，并且没有额外的信令开销。In the process of step2), the base station sends a random access response RAR to allocate uplink resources. As shown in Figure 3, in the MAC subheader, the RAPID field is used to indicate the sequence number of the preamble, and 6 bytes can support 64 preambles. We use an R domain in MAC RAR, as shown in Figure 4, which is a reserved bit of 1 bit. We use this bit to identify whether the above-mentioned RAPID is from the lead group of the common UE or the lead group of the smart meter. If the R bit is 0, it means it is an ordinary UE, and 1 means it is a smart meter, so that two sets of 64 preambles can be supported without additional signaling overhead.

在step2）中的两组前导组使普通用户和智能电表的随机接入过程互不干扰。而且由于前导序列的增多，选择相同前导序列在同一PRACH资源发送的概率降低，从而降低了step3），step4）中的碰撞的概率。提升了系统的性能。The two leading groups in step2) make the random access process of ordinary users and smart meters non-interfering with each other. Moreover, due to the increase of preamble sequences, the probability of selecting the same preamble sequence for transmission on the same PRACH resource is reduced, thereby reducing the probability of collision in step3), step4). Improved system performance.

在智能电网的环境下，如智能电表上报数据，由于终端设备众多，并且周期性上报数据的特点，传统的LTE随机接入过程的碰撞概率会比较高，影响系统的整体性能。而本发明所提出的随机接入方法，在增加额外的信令开销的情况下，增加一组智能电网专用的随机接入前导，不仅减小了系统的随机接入碰撞概率，而且让普通的用户和智能电表的随机接入前导相分离，避免了智能电表周期上报数据时对普通用户随机接入的影响。In the smart grid environment, such as smart meters reporting data, due to the large number of terminal devices and the characteristics of periodic data reporting, the collision probability of the traditional LTE random access process will be relatively high, which will affect the overall performance of the system. However, the random access method proposed by the present invention adds a set of random access preambles dedicated to smart grids in the case of additional signaling overhead, which not only reduces the random access collision probability of the system, but also makes ordinary The random access preamble of the user and the smart meter is separated, which avoids the impact on the random access of ordinary users when the smart meter periodically reports data.

附图说明Description of drawings

图1基于竞争的随机接入过程；Figure 1 is a contention-based random access process;

图2MAC PDU由一个MAC头部和多个MAC RAR组成；Figure 2MAC PDU consists of a MAC header and multiple MAC RARs;

图3MAC子头部；Figure 3 MAC sub-header;

图4MAC RAR。Figure 4MAC RAR.

具体实施方式Detailed ways

例如，在一个LTE基站覆盖范围内有多个普通用户和智能电表，在需要通信服务时进行基于竞争的随机接入过程。假设在一个时隙有2个普通用户和20个智能电表同时发起基于竞争的随机接入。在常规的随机接入方法中，共有64个前导，假设基于竞争的前导有40个，则一个用户/智能电表成功接入的概率为：For example, there are multiple common users and smart meters within the coverage of an LTE base station, and a contention-based random access process is performed when communication services are needed. Assume that in a time slot, 2 common users and 20 smart meters simultaneously initiate contention-based random access. In the conventional random access method, there are 64 preambles in total. Assuming that there are 40 contention-based preambles, the probability of successful access of a user/smart meter is:

${\mathrm{<span><span>P</span><figure-callout\; label="P"\; filenames="HDA0000475814180000012.png,HDA0000475814180000021.png"\; state="\{\{state\}\}">P</figure-callout></span>}}_{\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span>{<span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>40</span>40</span>}}<span><span>)</span>)</span>}^{\mathrm{<span><span>22</span>twenty\; two</span>}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span>\mathrm{<span><span>0.587</span>0.587</span>}$

若采用本发明的随机接入方法，即2个普通用户使用原有的基于竞争的40个前导，而智能电表使用下一组64个前导，则一个用户成功接入的概率为：If the random access method of the present invention is adopted, that is, two ordinary users use the original 40 preambles based on contention, and the smart meter uses the next group of 64 preambles, then the probability of a user's successful access is:

${\mathrm{<span><span>P</span><figure-callout\; label="P"\; filenames="HDA0000475814180000012.png"\; state="\{\{state\}\}">P</figure-callout></span>}}_{\mathrm{<span><span>2</span>2</span>}}<span><span>=</span>=</span>{<span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>40</span>40</span>}}<span><span>)</span>)</span>}^{\mathrm{<span><span>2</span>2</span>}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span>\mathrm{<span><span>0.975</span>0.975</span>}$

而智能电表成功接入的概率为：The probability of successful smart meter access is:

${\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>3</span>3</span>}}<span><span>=</span>=</span>{<span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span>\frac{\mathrm{<span><span>1</span>1</span>}}{\mathrm{<span><span>64</span>64</span>}}<span><span>)</span>)</span>}^{\mathrm{<span><span>20</span>20</span>}<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}}<span><span>=</span>=</span>\mathrm{<span><span>0.741</span>0.741</span>}$

由此可见，普通用户和智能电表的随机接入成功概率均有提高，并且没有额外的信令开销。It can be seen that the random access success probability of ordinary users and smart meters is improved, and there is no additional signaling overhead.

Claims (2)

1. a method for random access in intelligent grid communication, is characterized in that comprising the steps:

Step 1, domestic consumer and intelligent grid equipment generate respectively two groups of targeting sequencings, 64 every group according to the information of eNB broadcast;

Step 2, while needing random access, domestic consumer is selected at random in front 64 targeting sequencings, intelligent grid equipment is selected at random in rear 64 targeting sequencings, thereby carries out random access procedure;

When step 3, eNB return to MAC RAR, indicate domestic consumer or intelligent grid user by a reserved bit position;

Step 4, user complete follow-up random access procedure according to the situation of returning to MAC RAR.

2. the method for random access in intelligent grid communication according to claim 1, is characterized in that:

In step 2, the common UE that uses traditional voice-and-data business still according to the mode in original agreement generate first group totally 64 leading, intelligent electric meter generates in addition 64 Special leaders of another group after 64 of common UE are leading; If common UE/ intelligent grid need to carry out random access procedure, in leading group of correspondence, a targeting sequencing of random selection sends respectively;

In step 3, base station sends accidental access response RAR and distributes ascending resource; In MAC head, RAPID field is used for representing leading sequence number, 6 bytes can support 64 leading; Use a R territory in MAC RAR, the i.e. reserved bit position of 1 bit, identify leading group or leading group of intelligent electric meter of above-mentioned RAPID from common UE with this bit, if R position is 0, just representative is common UE, 1 just represents intelligent electric meter, so just can support two groups 64 leading, and there is no extra signaling consumption.

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