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

Abstract

The invention provides a random access method in smart power grid communication. Under the condition of not increasing additional signaling overheads, the random access collision probability is lowered, and system performance is improved. Due to the fact that multiple smart power grid devices exist and carry out data reporting frequently, the random access collision probability is greatly improved, and the random access process of a common user can be influenced. The random access process for the smart power grid scene is provided. Two different leader sequence sets are generated and used for the common user and a smart power grid respectively. One of MAC RARs is used for reserving bits for marking whether random access is from the common user or the smart power grid. Therefore, under the condition that no additional signaling overhead exists, the random access collision probability of the smart power grid can be reduced, and the random access of the common user cannot be influenced.

Description

A kind of method of random access in intelligent grid communication

Technical field

The present invention relates to random access procedure in intelligent grid radio communication, reduce the probability of random access collision.

Background technology

Intelligent grid is a kind of modern network system that communication network is combined with network system.By the real-time collecting to data in electrical network and analysis, thereby reach the object such as control and demand response to electrical load, can improve efficiency of energy utilization, guarantee supply of electric power safe, reliable, high-quality.In intelligent grid, generating, transmission of electricity, distribution, electricity consumption link all exist a large amount of advanced sensings and measuring technique, equipment, need the support of the network communications technology.But communication in intelligent grid is different from traditional data or voice service, has specific feature and demand.Such as, the terminal equipment features such as (UE) is more, and data volume is less, periodic communication.

LTE can provide spectral efficient, large throughput, and low delay and support IP-based multiple application service, is a kind of comparatively desirable communication technology in intelligent grid.In LTE, in order to obtain uplink synchronous and to be a unique mark C-RNTI of UE distribution, UE need to carry out random access procedure.Only have by random access, UE could obtain uplink synchronous with base station, and for UE distributes a unique mark C-RNTI, and then follow-up communication process just can carry out.Random access is divided into based on competition and non-competing two kinds of modes.Random access procedure based on competition as shown in Figure 1.

Step1) in the time that UE need to be accessed at random by certain Event triggered, first at Physical Random Access Channel (Physical Random Access Channel, PRACH) in resource, send random access guiding to base station, its object is to the random access attempts of eNodeB indication current UE, and makes eNodeB can estimate the propagation delay time between itself and UE.Targeting sequencing has 64, is that UE obtains by the configuration information of resolving eNodeB broadcast.64 parts in leading are kept for based on non-competing random access, and UE selects one leadingly to send to base station at PRACH from remaining at random leading.

Step2) eNodeB sends accidental access response (Random Access Response, RAR) by PDCCH to UE.If eNodeB detects random access guiding on PRACH, will on PDCCH, send accidental access response RAR, comprise random access leader sequence sequence number (RAPID), Timing Advance (Timing Advance Command), T-RNTI (Temporary Radio Network Temporary Identifier), keep out of the way indication, ascending resource distribution etc.After UE has sent preamble, will in RAR time window (RA Response window), monitor PDCCH, to receive the time-frequency determining positions of corresponding RA-RNTI(by PRACH) RAR.If multiple UE send preamble in same PRACH resource (time-frequency position is identical, uses same RA-RNTI), corresponding RAR is multiplexing in same MAC PDU, uses RA-RNTI scrambling, as shown in Figure 2.

If selected same targeting sequencing to initiate the trial of random access in the identical PRACH resource of multiple UE, will bump so.Each UE likely receives same RAR, enters thus competition solution process Step3, Step4.

Step3) in the MAC of last step header, parse the UE of own leading sequence number, on PUSCH, send message 3(Msg3 to eNodeB according to the RAR information parsing).Comprise the T-RNTI decoding in RRC connection request, tracking area update, dispatch request, Step2, and the unique mark (C-RNTI or S-TMSI) of each UE.

Step4) Msg3 of a UE if eNodeB successfully decodes sends competition and solves message (contention resolution) on PDSCH, carries unique mark of this UE to specify the UE winning.And other UE not winning will select a rollback time according to the back off exponent in MAC header (BI), again initiate random access after having postponed the rollback time in conflict solves.

Under typical intelligent grid environment, have that a large amount of transducer, ammeter etc. are measured, reported data.Such as in senior measurement system (AMI), intelligent electric meter will report one time electricity consumption data every 15 minutes.From above-mentioned LTE random access procedure, when multiple ammeters need reported data simultaneously, simultaneously when initiating random access procedure, need to leadingly choose at random one for what compete.Due to ammeter One's name is legion, and reported data periodically frequently, multiple ammeters select same leading probability very large, and while causing random access procedure, collision probability increases greatly, and affects the random access of traditional voice communications versus data communications.Therefore be necessary to propose a kind of method of optimizing random access and go to reduce the collision probability in random access procedure, improve the overall performance of intelligent grid.

Summary of the invention

Based on the above-mentioned analysis to problem, the present invention proposes the method for random access in a kind of intelligent grid communication, and the method can reduce random access collision probability under intelligent grid environment, and does not affect the random access of traditional voice, data service.In addition, the present invention does not need extra signaling consumption, has saved valuable signal resource.

In the Rel.11 of LTE standard, random access guiding is the system configuration information based on base station broadcast and generating by UE.ZC(Zadoff-Chu has finally selected in 3GPP LTE working group) sequence is used for generating random access leader sequence.

ZC sequence is defined as follows:

$x_u\left(n\right)=\exp [-j\frac{\mathrm{\&pi;un}(n+1)}{N_{\mathrm{ZC}}}],0<n\&le;N_{\mathrm{ZC}}-1$

Wherein N _zCfor sequence length, be 839 according to agreement.U is physics root.Exp[] be the exponential function take e the end of as, j is imaginary unit, π is circumference ratio.

Targeting sequencing entered cyclic shift C by ZC sequence _vgenerate:

x _u,v(n)＝x _u((n+C _v)modN _ZC)

Cyclic shift C _vcan obtain by down:

N _cSfor cyclic shift, its value can be obtained by table 1.Offset parameter d _start,

visible [1] is set.

For UE, obtained logic root sequence number and the N of ZC sequence by the configuration information that receives base station broadcast _cSindex, after tabling look-up, obtain physics and take root in u cyclic shift C _v, generate leading according to above formula.If the cyclic shift of system configuration is not enough to too greatly to produce 64 enough derived sequences when needing extra root sequence, only need to add 1 in original logic root sequence index numeral, obtain next u value, thereby generate another one root sequence, by that analogy until root sequence enough produces 64 preamble signature sequences.

Table 1 is for generating leading N _cSvalue

For our typical intelligent grid scene reported data as periodic in a large amount of intelligent electric meters, access at random simultaneously, 64 leading may be not enough to support a large amount of random accesses.First the present invention improves the leading generative process in LTE agreement [1].

Step1) in, 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.

At step2) in process, base station sends accidental access response RAR and distributes ascending resource.As shown in Figure 3, in MAC head, RAPID field is used for representing leading sequence number, 6 bytes can support 64 leading.We use a R territory in MAC RAR, as shown in Figure 4, i.e. and the reserved bit position of 1 bit.We 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, and 1 just represents intelligent electric meter, so just can support two groups 64 leading, and there is no extra signaling consumption.

At step2) in two groups of leading Zu Shi domestic consumers and the random access procedure of intelligent electric meter do not interfere with each other.And due to the increasing of targeting sequencing, select the probability that same preamble sequence sends in same PRACH resource to reduce, thereby reduced step3), step4) in the probability of collision.Promote the performance of system.

Under the environment of intelligent grid, as intelligent electric meter reported data, because terminal equipment is numerous, and the feature of periodicity reported data, the collision probability of traditional LTE random access procedure can be higher, affects the overall performance of system.And accidental access method proposed by the invention, in the case of increasing extra signaling consumption, increase by one group of random access guiding that intelligent grid is special, not only reduce the random access collision probability of system, and allow the random access guiding of common user and intelligent electric meter be separated, the impact on the random access of domestic consumer while having avoided intelligent electric meter periodic report data.

Accompanying drawing explanation

The random access procedure of Fig. 1 based on competition;

Fig. 2 MAC PDU is made up of a MAC head and multiple MAC RAR;

Fig. 3 MAC head;

Fig. 4 MAC RAR.

Embodiment

For example, in a LTE base station range, there are multiple domestic consumers and intelligent electric meter, in the time needing communication service, carry out the random access procedure based on competition.Suppose has 2 domestic consumers and 20 intelligent electric meters to initiate the random access based on competition at a time slot simultaneously.In conventional accidental access method, have 64 leading, suppose based on competition leadingly have 40, the probability that user/intelligent electric meter successfully accesses is:

${\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000475814180000012.png,HDA0000475814180000021.png"\; state="\{\{state\}\}">P</figure-callout>}}_1={(1-\frac{1}{40})}^{22-1}=0.587$

If adopt accidental access method of the present invention, it is leading that 2 domestic consumers are used original based on competition 40, and intelligent electric meter uses next 64 of group leading, and the probability that user successfully accesses is:

${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA0000475814180000012.png"\; state="\{\{state\}\}">P</figure-callout>}}_2={(1-\frac{1}{40})}^{2-1}=0.975$

And the probability that intelligent electric meter successfully accesses is:

$P_3={(1-\frac{1}{64})}^{20-1}=0.741$

As can be seen here, the random access probability of success of domestic consumer and intelligent electric meter is improved, and there is no extra signaling consumption.

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.

Images