WO2021022564A1

WO2021022564A1 - Achievable sinr set prediction for random access

Info

Publication number: WO2021022564A1
Application number: PCT/CN2019/099846
Authority: WO
Inventors: Haiyou Guo
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2019-08-08
Filing date: 2019-08-08
Publication date: 2021-02-11
Anticipated expiration: 2022-02-08
Also published as: CN114246004B; CN114246004A

Abstract

Embodiments of the present disclosure relate to devices, methods, apparatuses and computer readable storage media of Signal-to-Interference-plus-Noise Ratio (SINR) set prediction for random access. The method comprises receiving a probing signal with a transmission power from a second apparatus in an access process; determining, based on the received probing signal, a set of Signal-to-Interference Ratios (SIRs) for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points; determining, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points; and transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR. In this way, each link can individually predict and refine the knowledge of its own maximal achievable SINR from the observations of local interference dynamic, instead of collecting Channel State Information (CSI). For this reason, it can be readily applied to the distributed random access. Furthermore, the proposed prediction method accelerates the approximation process for maximal achievable SINR, by exploiting the estimate of spectrum radius related to the active links.

Description

ACHIEVABLE SINR SET PREDICTION FOR RANDOM ACCESS

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to devices, methods, apparatuses and computer readable storage media of achievable Signal-to-Interference-plus-Noise Ratio (SINR) set prediction for random access.

BACKGROUND

Random access is an indispensable ingredient of communication network. It is widely applied not only to requesting and establishing connection but also to transmitting transport blocks. Random access is designed as a bootstrap process to activate a communication network. For example, in LTE and NR system, a device in idle/inactive state employs the random process to request the set-up of a connection prior to any Physical Shared Control Channel (PSCCH) or Physical Uplink Control Channel (PUCCH) transmission. In which, the Physical Random Access Channel (PRACH) is designed for random access to carry out initial access, uplink time alignment, cell search and initial beam establishment etc.

In general, multiple users are allowed to transmit the preamble signals respectively and contend the common channel in random access. For example, NR adopts four-step random access, the steps 3 and 4 of which aim at resolving the potential collisions by exchanging messages (uplink “Message 3” and subsequent downlink “Message 4” ) between device and network. If successful, Message 4 also transfers the device to connected state.

SUMMARY

In general, example embodiments of the present disclosure provide a solution of achievable SINR set prediction for random access.

In a first aspect, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first apparatus at least to receive a probing signal with a transmission power from a second apparatus in an access process; determine, based on the received probing signal, a set of Signal-to-Interference Ratios, SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points; determine, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points; and transmit, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.

In a second aspect, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second apparatus at least to transmit, to a first apparatus, a probing signal with a transmission power in an access process; receive, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and determine the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.

In a third aspect, there is provided a method. The method comprises receiving a probing signal with a transmission power from a second apparatus in an access process; determining, based on the received probing signal, a set of SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points; determining, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points; and transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.

In a fourth aspect, there is provided a method. The method comprises transmitting, to a first apparatus, a probing signal with a transmission power in an access process; receiving, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and determining the accessibility of the communication link based on the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR of the communication link.

In a fifth aspect, there is provided an apparatus comprises means for receiving a probing signal with a transmission power from a second apparatus in an access process; means for determining, based on the received probing signal, a set of SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points; means for determining, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points; and means for transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.

In a sixth aspect, there is provided an apparatus comprises means for transmitting, to a first apparatus, a probing signal with a transmission power in an access process; means for receiving, from the first apparatus, a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and means for determining the accessibility of the communication link based on the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR of the communication link.

In a seventh aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the third aspect.

In an eighth aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fourth aspect.

Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

FIG. 1 shows an example communication network in which example embodiments of the present disclosure may be implemented;

FIG. 2 shows a schematic diagram illustrating a process 200 of achievable SINR set prediction for random access according to example embodiments of the present disclosure;

FIG. 3 shows a flowchart of an example method 300 of achievable SINR set prediction for random access according to some example embodiments of the present disclosure;

FIG. 4 shows a flowchart of an example method 400 of achievable SINR set prediction for random access according to some example embodiments of the present disclosure;

FIG. 5A-5C show diagrams of performance comparison between the embodiments of the present disclosure and the conventional method;

FIG. 6 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

Fig. 7 shows a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

The subject matter described herein will now be discussed with reference to several example embodiments. It should be understood these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein, rather than suggesting any limitations on the scope of the subject matter.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a, ” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises, ” “comprising, ” “includes” and/or “including, ” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two functions or acts shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future.

Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system. For the purpose of illustrations, embodiments of the present disclosure will be described with reference to 5G communication system.

The term “network device” used herein includes, but not limited to, a base station (BS) , a gateway, a registration management entity, and other suitable device in a communication system. The term “base station” or “BS” represents a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR (New Radio) NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.

The term “terminal device” used herein includes, but not limited to, “user equipment (UE) ” and other suitable end device capable of communicating with the network device. By way of example, the “terminal device” may refer to a terminal, a Mobile Terminal (MT) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) .

The term “circuitry” used herein may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with

software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. ”

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

FIG. 1 shows an example communication network 100 in which embodiments of the present disclosure can be implemented. The network 100 includes transmitting devices 110-1, 110-2 and 110-3 (hereinafter may be collectively referred to as transmitting devices 110 or individually referred to as a second apparatus 110) and receiving devices 120-1, 120-2 and 120-3 (hereinafter may be collectively referred to as receiving devices 120 or individually referred to as a first apparatus 120) , the receiving device 120-1 may communicate with the transmitting device 110-1 via the communication channel 101, the receiving device 120-2 may communicate with the transmitting device 110-2 via the communication channel 102 and the receiving device 120-3 may communicate with the transmitting device 110-3 via the communication channel 103. All the communication channels may be configured over the same physical resource and interferer with each other. It is to be understood that the number of transmitting devices and receiving devices is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of transmitting devices and receiving devices adapted for implementing embodiments of the present disclosure. It should be understood that the transmitting devices and the receiving devices may be any form of network device or terminal device.

The communications in the network 100 may conform to any suitable standards including, but not limited to, Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols.

As mentioned above, random access is an indispensable ingredient of communication network. It is widely applied not only to requesting and establishing connection but also to transmitting transport blocks. Random access is designed as a bootstrap process to activate a communication network. For example, in LTE and NR system, a device in idle/inactive state employs the random process to request the set-up of a connection prior to any PSCCH or PUCCH transmission. In which, the PRACH is designed for random access to carry out initial access, uplink time alignment, cell search and initial beam establishment etc.

In general, multiple users are allowed to transmit the preamble signals respectively and contend the common channel in random access. Due to the limit resource of preambles, many users may make the simultaneous transmissions of the same preamble within a cell, which inevitably leads to unexpected collisions. For example, NR adopts four-step random access, the steps 3 and 4 of which aim at resolving the potential collisions by exchanging messages (uplink “Message 3” and subsequent downlink “Message 4” ) between device and network. If successful, Message 4 also transfers the device to connected state. The collision resolution is essentially resolved with the help of the orthogonal design in preambles, which is restricted by the bandwidth of the random access channel. Such access reservation protocol can result in around 20 ms delay.

Such a random access with orthogonally-based collision resolution becomes inapplicable as the number of devices scales up, since it is impossible to assign the most of users with mutual orthogonal preambles. The throughput of access reservation protocol is severely degraded due to the lack of collision resolution in the Physical (PHY) and Medium Access Control (MAC) layer. Furthermore, the fail access causes inevitable retransmissions and an endless cascade of signalling exchange between device and BS. Consequently, delay is prolonged dramatically. These issues become more challenging for delay-sensitive massive connection. This scenario comprises diverse use cases, such as environment sensing, event detection, surveillance, and industrial control etc. It is characterized by a massive number of connected devices (totally on the order of 10^5～10^6/km^2) typically transmitting a sporadic (with access probability of 5%) and relatively low volume of delay-sensitive data (in the millisecond range) . Moreover, the devices are required to be low cost and have a very long battery life (10+ years) . Therefore, the future NR release calls for a sophisticated random access scheme accommodating massive devices with advanced collision avoidance.

The issues caused by the conventional access procedure will be explained as follow. NR and LTE just use random access to establish and maintain connection state via PRACH, upon which the data (transport block, TB) transmission is then carried out by network-triggered PUSCH or PDSCH scheduling. PRACH is isolated from PUSCH and PDSCH, completely avoiding the collision between data signal and random-access sequence. However, such separation in access and transmission becomes a barrier to delay-sensitive massive access. The connection state must be always kept for massive devices to pursue low latency. Nevertheless, it is impossible to support massive devices in connection state at the same time, owing to the unsustainable control signalling cost which is very higher relative to a small packet a device intends to send. For this reason, the current NR and LTE systems are incapable for delay-sensitive massive access.

A desired delay-sensitive massive access attempts to fast establish as more successful communication links as possible. To making full use of radio spectrum, massive devices prefer to send preamble or data signal over the common time-frequency resource, allowing for the device-triggered communication with lower latency and control signalling. This give rise to sever random physical-layer collisions, in terms of preamble-preamble, preamble-data, and data-data, that are unable to resolve through orthogonal separation. This is a new arising problem unsolved by the conventional access scheme in LTE and NR.

Although the collision cannot be prevented completely, the interference level caused by collision can be regularized and mitigated via power control. If the collisions are mild and can be tolerated by a successful communication links, then it can always maintain its operational SINR at the required level. Adaptive control of transmitter powers allows successful communication links to achieve their expecting SINRs reflecting given quality of service (QoS) levels. SINR-target tracking power control seems to be a proper choice to avoid unredeemable collision. Indeed, the power control means to establish a set of policies by which all participant links play a game of power competition. Endowing random access procedure with the power-control rule still confronts the following open issues, namely (1) feasibility and compatibility check, (2) non-invasive competition and access and (3) process control of SINR.

For the issue (1) , the random access procedure essentially serves as a bootstrap process, there is less/no Channel State Information (CSI) used to get the right decision on whether the SINR targets of the competitive links are feasible and compatible, especially for the burst arrivals. Power control tracking the infeasible SINR targets necessarily leads to unredeemable collisions with unstable power war. Compatibility verification is a prerequisite for an integrated procedure of power control and random access. The knowledge about the maximal achievable SINR set (of all inactive links) or/and the estimation of spectrum radius of interfering matrix is necessary to make an effective compatibility verification.

For the issue (2) , the devices contends the channel in a burst nature, the resulted and unpredictable interferences cause sharp drop in the reception quality of the always successful links. It perhaps gives rise to an ineligible transmission that eventually incurs the degradation in throughput and packet delay. This is because that the additional retransmissions should be attached to restore the transmission failures. Therefore, non-invasive access is desired for successful communication links to maintain the operational SINRs always exceeding their targets. On the other hand, non-invasive access provides the reliable QoS for the active links, so that it has opportunity to rapidly finish the data delivery, releasing more channel margin from busy links to the new arrivals.

For the issue (3) , although some power-control procedure can converge to a desired and stable SINR state (for a feasible system) eventually, the operational SINR of all participant links may undergoes the unexpected fluctuation during the power competition process. Some already qualified links may decline to being unqualified, even some of them may no long go back to the qualified status when the system is infeasible. Such a power competition procedure without process control not only degrades the reliability and availability of transmission channel, but also introduces the artificial inconveniences for delay-sensitive traffic. In addition to ensuring the ultimately stable state for a power-control process, the dynamic behaviour of the power competition should be appropriately regulated and managed for random access. The related process control should be designed to maintain the eligible trajectory of SINR based on the results of process monitoring. Power coordination with controllable and robust process should entail a continuously improving procedure for interference mitigation and performance improvement. Every single-step updating of power always brings the incremental gain in return, and then the network performance can be continuously promoted in a step-by-step way. A desired power control is expected to regulate the SINR evolution of all participant links along an upgrading or non-decreasing way, the strategy of continuous improvement can increase the access chance for random arrival devices.

For example, the issues have been raised may be reflected in the network 100 shown in FIG. 1. For the case that the link of channel 101 between the transmitting device 110-1 and the receiving device 120-1 and the link of channel 102 between the transmitting device 110-2 and the receiving device 120-2 have already established, and the link of channel 103 between the transmitting device 110-3 and the receiving device 120-3 is to be established, the maximal achievable SINR for the link of channel 103 should be determined. The links of

channels

101 and 102 herein may be referred to as active links and the link of channel 103 may be referred an inactive link. The maximal achievable SINR of link of channel 103 may be determined based on all the channels among transmitting devices 110 and receiving device 120, including the interfering channels associated with other transmitting devices, i.e.

channels

106 and 107 associated with the transmitting device 110-1 and

channels

104 and 108 associated with the transmitting device 110-2,

channels

105 and 109 associated with the transmitting device 110-3. Meanwhile, the transmission of the link of channel 103 to be established should not affect the quality of the links of

channels

101 and 102.

Therefore, the present disclosure proposes a method for random access based on the maximal achievable SINR. In this solution, a prediction of the maximal achievable SINR at a predetermined future time point may be determined by the receiving device. The receiving device may generate an indication for transmission power regulation and accessibility for the transmitting device based on the determined prediction of the maximal achievable SINR at a predetermined future time point. Thus, the transmitting device may control the transmission power to ensure that the target SINR is achieved for the link and meanwhile maintain the quality of the established links.

Principle and implementations of the present disclosure will be described in detail below with reference to FIG. 2, which shows a schematic diagram of a process 200 of SINR set prediction for random access. For the purpose of discussion, the process 200 will be described with reference to FIG. 1. The process 200 may involve the transmitting device 110 and the receiving device 120 as illustrated in FIG. 1.

As shown in FIG. 2, the transmitting device 110 may determine 210 whether the buffer contains data packet to be transmitted. If the transmitting device 110 determines that the buffer contains data packet to be transmitted, the transmitting device 110 may initial an access process. In other words, the transmitting device 110 starts to contend for the transmission resource.

Some of the data packet in the buffer may be new arrival data and the others may be a back-off data packet, which means that the data packet has been transmitted but unsuccessful. For the new arrival data packet, the transmitting device 110 may initial the transmission immediately. For the back-off data packet, the transmitting device 110 may determine whether the back-off timer of the data packet expires, if so, the transmitting device 110 may start to transmit the data packet.

Each access procedure may have a preconfigured period. If the duration of the access procedure performed exceeds the preconfigured period, the access procedure will be suspended. Before the access procedure, the transmitting device 110 may set the initial transmission power and the initial access horizon. For example, the transmitting device 110 and receiving device 120 of link l are labelled by Tx l and Rx l, respectively. The initial transmission power p _l (t) may be set to be p _l, 0 and the initial access horizon may be set to be T _l=0.

The transmitting device 110 transmits 320 a probing signal with a transmission power p _l (t) to the receiving device 120. The access horizon may be updated to be T _l= T _l+1.

The receiving device 120 may determine 330 a prediction of maximal achievable SINR based on the measurement of the probing signal. The principle and process for determining the prediction of the maximal achievable SINR of the receiving device 120 may be described in detail as below.

Assuming that the transmitting device 110 and the receiving device 120 of link l are labelled by Tx l and Rx l, respectively. The receiving device 110 determines a set of SIRs for the link l at a predetermined number of successive time points.

In some example embodiments, the receiving device 120 may measure a set of transmission powers at the predetermined number of the time points based on the probing signal. The receiving device 120 may also determine a set of interference powers associated with at least one further communication link at the predetermined number of the time points. The at least one further communication link may be referred to the interfering links associated with other transmitting device, for example, if the link of channel 103 shown in FIG. 1 is the inactive link l, the links of

channels

104 and 105 may be the interfering links to the link of channel 103.

Specifically, the set of SIRs for the link l may be determined as following Equations. To make full use of spectrum resource, all links attempt to send data or preamble signal over the common channel and interfere with each other. Let G _lm denote the channel gain from Tx m to Rx l. Tx l is assigned with transmit power p _l (t) [W] at time t. Link l attempts to pursue its SINR target γ _l for reliably and fast packet delivery. Then, the observed SINR and SIR at Rx l can be written as:

and

respectively, where

denotes the background power received at Rx l accounting for the total effect of the outside interference and thermal noise.

That is, based on the measurement for the probing signal, the receiving device 120 may determine SINR and SIR at current time point t. The receiving device 120 may also determine SINRs and SIRs at the certain number of previous time point before the current time point t. For example, the SINR and SIR at time point t-1, t-2 etc.

Then the receiving device 120-3 determines a prediction of the achievable SINR, i.e., a prediction of a maximal achievable SINR of inactive link of channel 103 at a future time point. In this case, the future time point may be referred to a time point later than the above-mentioned predetermined number of successive time points. More specifically, the future time point may be consider as any time point later than the current time t.

The process for predicting the maximal achievable SINR will be described in detail as below. Let β _l denote the maximal non-invasive achievable SINR for inactive link

where

denotes the set of inactive links at time point t. The amount of β _l is restricted by the set of active links and their SINR targets. β _l represents the maximal SINR can be achieved by an inactive link

while keeping all active links at their SINR targets (SINR _j≥γ _j holds for j∈Q (t) , where Q (t) denotes the set of active links at time point t. The maximal achievable SINR set of

is the social (Pareto) optimal SINR assignment from which it is impossible to reallocate so as to make any one individual better off without making at least one individual worse off. Obviously, the maximal achievable SINR is higher than the current experiencing SINR, that is β _l≥SINR _l (t) .

reflects the ultimate admitted transmission capacity for all inactive links, which is helpful for designing compatibility verification and drop-out mechanism.

In practice, it is impossible to get the exact knowledge about

without the aggregated CSI of {G _lm|l, m=1, 2, …, L} . Fortunately, for a distributed network endowed with the power updating rule mentioned later, it exhibits some favourable properties that can be exploited to predict

In what follows, single-step and multi-step prediction methods are proposed to continuously approximate β _l just by a small set of the historical observations of local SIR. Moreover, the predictor can be further refined by updating the observation set.

It can be theoretically proved that SIR of an inactive link

is strictly increasing with respect to time, that is, for

and

always have

SIR _l (t) ＜SIR _l (t+1) (3)

In additional, the SIR _l (t) is equal to β _l as t →∞. The gap of SIR _l (t) -β _l can be continuously reduced as t increases. This fact shows that SIR _l (t) provides an effective approximation process on β _l, which is more accurate than the current experiencing SINR. Moreover, this approximation process can be accelerated by predicting the value of SIR _l (t+K) at time t+K for K≥1.

In some embodiments according to the present disclosure, the estimation of spectrum radius for charactering interfering channels associated with at least one further communication link, i.e. the spectrum radius of the interfering matrix of the active links may be considered as an important parameter for determining the maximal achievable SINR.

The estimation sequence of spectrum radius at a future time point t+1 may be represented by the historical SIR sequence, that is:

it follows

It can also be theoretically proved that

for any

where ρ is a constant amount to the spectrum radius of the interfering matrix of the active links B. For a network comprising M active links, labelled by Links 1, 2, …, M, the interfering matrix B is an M×M matrix that can be written as

ρ _l (t+1) ≈ρ _l (t) holds true as t→∞. Thus, the SIR of link l at the future time point t+1 may be represent as:

This means that the future SIRSIR _l (t+1) can be predicted at time t from 3 last SIR observations of {SIR _l (t) , SIR _l (t-1) , SIR _l (t-2) } .

That is, the receiving device 120 may determine the estimation of spectrum radius at time point t based on the set of SIRs at time point t, t-1 and t-2. The receiving device 120 may also select an excepted future time point on which the maximal achievable SINR may be obtained.

If the maximal achievable SINR at time point t+1 is expected to predict, the available SIR at the future time point t+1 may be determined by the set of SIRs, i.e., SIR _l (t) , SIR _l (t-1) and SIR _l (t-2) and the spectrum radius at time point t, which may be represented as below:

Since the active links forms a feasible system with their SINR targets, ρ＜1 must holds. Furthermore, the single-step predictor of maximal non-invasive achievable SINR can be improved as:

which is comply with the monotone property of SIR _l (t+1) > SIR _l (t) . The predicted value can be continuously refined with updating observations of local SIR, until

exactly converges to β _l (as t→∞) .

In general, the estimated spectrum radius ρ _l (t) converges faster than SIR _l (t) , since the former is derived from a difference sequence of the latter. For certain small time t, ρ _l (t) becomes stable such that ρ _l (t) ≈ρ _l (t+K) for K≥1. Such stability of ρ _l (t) can be exploited to carried out a multi-step prediction by repeating the single-step prediction with the updated prediction values. The multi-step prediction converges faster than single-step prediction, allowing for a more accurate estimator for the maximal achievable SINR. The multi-step prediction method will be described as below.

Since

is the predicted value of SIR _l (t+1) , both are approximately equivalent, i.e.

Furthermore, a two-step prediction for SIR _l (t+2) can be made by repeating a single-step predictor with

that is

Analogously, a three-step predictor for SIR _l (t+3) can be carried out by

Thus, multi-step prediction involves an extrapolation process by iteratively repeating the single-step prediction. In general, a multi-step predictor for SIR _l (t+K) at time t can be written by a recursive equation as below

The predictions of the maximal achievable SINR at the future time point t+K may approximate to the maximal SINR for a sufficient large t+K. Accordingly, the receiving device 120 may select any future time point t+K and determine the the maximal achievable SINR at that time based on the corresponding set of SIRs at three time point before the selected future time point t+K.

Then the receiving device 120 may cause the transmitting device 110 to determine an accessibility of the link l at least based on the predicted maximal achievable SINR. Herein, a more rigorous admission condition for the accessibility checking is applied, by replacing SINR _l (t) ≥γ _l with

which ensures the network consisting of the active links are feasible with the raised SINR targets {Δγ _l} .

That is, the receiving device 120 may determine a measured SINR at the time point t based on the probing signal and update the predicted maximal achievable SINR _l (t+K) based on the measured SINR at the time point t and a raising margin for the predicted maximal achievable SINR _l (t+K) , where the raising margin Δ>1 is a constant protection parameter.

Then, the receiving device 120 transmits 340 the checking result associated with the accessibility, the measured SINR and the prediction of the achievable SINR to the transmitting device 110.

The transmitting device 110 further determines an accessibility of the link l. By receiving the checking result from the receiving device 120, the transmitting device 110 may determine the accessibility of the communication link based on the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.

Let the active-link and inactive-link sets at time t be Q (t) = {l=1, 2, …, L|SINR _l (t) ≥γ _l} and

respectively, the mechanism for adjusting the transmission power may be represented as below:

where the raising margin Δ＞1 is the constant protection parameter.

If the result indicating that the predicted maximal achievable SINR _l exceeds the target SINR γ _l, which means the link l is an active link, the transmitting device 110 may adjust the transmission power by

If the result indicating that the predicted maximal achievable SINR _l exceeds the target SINR γ _l, the transmitting device 110 may determine whether the duration of the access process T _l exceeds than the expiry time of the access process. The expiry time of the access process may be represented as below:

If the transmitting device 110 determines that the duration of the access process does not exceed the expiry time, the transmitting device 110 may adjust the transmission power by Δp _l (t) . If the transmitting device 110 determines that the duration of the access process exceeds the expiry time, the transmitting device 110 may suspend the access process.

For a distributed random access network, maximum achievable SINR set is a key metric for all inactive links to make right access decision. In practice, it is impossible to get the exact knowledge about them without the aggregated CSI of the whole network. To overcome this problem, the present disclosure proposed a distributed method to continuously predict the maximal achievable SINR set for a distributed network endowed with DPC/ALP (Distributed Power Control with Active Link Protection) . The proposed method leverages the inherent dynamic of interference regulated by the specific power control rule. Instead of collecting CSI beforehand, each link can individually predict and refine the knowledge of its own maximal achievable SINR from the observations of local interference dynamic. At the heart of the predictor, the spectrum radius related to the active links is estimated to design predictor for the maximal achievable SINR sets. The estimate of spectrum radius exhibits good stability with faster convergence rate, which can be exploited to make multi-step prediction and accelerate the approximation process to the maximal achievable SINR. In particular, the prediction error can be continuously reduced during the whole access procedure. The proposed prediction method can be applied to further improve the DPC/ALP, by introducing compatibility verification function while retaining the favourable technical features of SINR protection and improvement. With help of predicting the maximal achievable SINR, a more rigorous feasibility condition can be established to carry out compatibility verification function. Moreover, a more effective drop-out criterion based on future state can be designed to increase the access chance and hence reduce the packet delay. Simulation results shows that the proposed prediction method can reduce the probing time by around 43%compared with the prior art. Such performance improvement can be translated into the corresponding gain in delay reduction for random access protocol.

In this way, each link can individually predict and refine the knowledge of its own maximal achievable SINR from the observations of local interference dynamic, instead of collecting CSI. For this reason, it can be readily applied to the distributed random access. Furthermore, the proposed prediction method accelerates the approximation process for maximal achievable SINR, by exploiting the estimate of spectrum radius related to the active links. In particular, the prediction can be continuously refined during the access procedure.

FIG. 3 shows a flowchart of an example method 300 of SINR set prediction for random access according to some example embodiments of the present disclosure. The method 300 can be implemented at the receiving device 120 as shown in FIG. 1. For the purpose of discussion, the method 300 will be described with reference to FIG. 1.

As shown in FIG. 3, at 310, the receiving device 120 receives a probing signal with a transmission power from a transmitting device 110 in an access process.

At 320, the receiving device 120 determines, based on the received probing signal, a set of SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points.

At 330, the receiving device 120 determines, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points.

In some example embodiments, the receiving device 120 may determine a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points based on the set of SIRs and select the future time point. The receiving device 120 may further determine the prediction of the achievable SINR at the future time point at least based on the set of SIRs, the estimation of spectrum radius and the future time point.

In some example embodiments, the estimation of spectrum radius may be determine by:

wherein SIR _l (t) , SIR _l (t-1) and SIR _l (t-2) represents SIRs at time points t, t-1 and t-2 of the predetermined number of successive time points t, t-1 and t-2, respectively, and ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points.

In some example embodiments, the future time point t+1 is selected, and wherein the prediction of the achievable SINR is determined by

wherein

represents the achievable SINR at the future time point t+1 next to the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and SIR _l (t) and SIR _l (t-1) represent the measured SIRs at time points t and t-1 of the predetermined number of successive time points, respectively.

In some example embodiments, the receiving device 120 may determine, based on the set of SIRs, an estimation of a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points. The receiving device 120 may also determine the prediction of the achievable SINR at the future time point at least based on the set of SIRs and the estimation of spectrum radius. The receiving device 120 may select a further future time point later than the future time point. The receiving device 120 may determine a prediction of an achievable SINR at the further future time point based on the set of SIRs, the prediction of the achievable SINR at the future time point, the estimation of spectrum radius and the further future time point.

In some example embodiments, the further future time point t+K is selected, and wherein the prediction of the achievable SINR at the further future time point is recursively determined by:

wherein

represents the achievable SIR at the further future time point t+K beyond the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and

represents the prediction of the achievable SINR at the future time point t+K-1 or the one of the set of SIRs at the time point t+K-1 of the predetermined number of successive time points, and

represents the prediction of the achievable SINR at the future time point t+K-2 or the one of the set of SIRs at the time point t+K-2 of the predetermined number of successive time points.

At 340, the receiving device 120 transmit, to the transmitting device 110, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.

In some example embodiments, the receiving device 120 may determine the measured SINR at the last time point of the predetermined number of successive time points based on the probing signal and check the condition associated with the accessibility based on the measured SINR, the prediction of the achievable SINR and the target SINR.

In some example embodiments, the condition is checked by

wherein

represents a prediction of an achievable SIR at the future time point t+K, SINR _l (t) represents the measured SINR at time point t of the predetermined number of successive time points, Δ represents the raising margin, and γ _l represents the desried SINR target.

FIG. 4 shows a flowchart of an example method 400 of SINR set prediction for random access according to some example embodiments of the present disclosure. The method 400 can be implemented at the transmitting device 110 as shown in FIG. 1. For the purpose of discussion, the method 400 will be described with reference to FIG. 1.

As shown in FIG. 4, at 410, the transmitting device 110 transmits, to a receiving device 120, a probing signal with a transmission power in an access process.

At 420, the transmitting device 110 receives, from the receiving device 120, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points.

At 430, the transmitting device 110 determines the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.

In some example embodiments, if the result indicating that the prediction of the achievable SINR exceeds the target SINR, the transmitting device 110 may determine that the communication link is accessible.

In some example embodiments, the transmitting device 110 may decrease the transmission power based on the measured SINR, the target SINR and a raising margin.

In some example embodiments, if the result indicating that the prediction of the achievable SINR is lower than the target SINR, the transmitting device 110 may determine an expiry time for the access process based on the prediction of the achievable SINR and the target SINR and compare the expiry time with duration of the access process. If the duration of the access process is less than the expiry time, the transmitting device 110 may further determine that the communication link is accessible.

In some example embodiments, the transmitting device 110 may increase the transmission power based on a raising margin.

In some example embodiments, if the duration of the access process exceeds the expiry time, the transmitting device 110 may suspend the access process.

FIG. 5A-5C show diagrams of performance comparison between the embodiments of the present disclosure and the conventional method.

The simulation considers a distributed network consisting of 8 links, the matrix of channel gain is listed in Table as below. The network adopts the DPC/ALP for random access. At time t=0, links 1-5 are always active links, all of them pursue the same SINR target of 10 dB, while Links 6-8 are inactive. Fig. 5A shows the convergence process of ρ _l (t) for l=6, 7, 8, respectively. For example purposes, only the prediction processes and the precision of the prediction process for Link 6 are shown in FIGs. 5B and 5C, respectively.

Table 1: Matrix of channel gain.

From FIG. 5A, curves (501-503) of ρ _l (t) converge faster than the sequence of SIR _l (t) shown by the curve (511) in FIG. 5B. This observation justifies the reasonability and effectiveness of multi-step prediction method shown by curves (513-515) . FIG. 5B compares the different prediction methods by showing the estimated value for maximal achievable SINR. The prior art 511 reaches an accurate estimation of maximal achievable SINR at least using 35 iterations, where one iteration corresponds to one unit of probing time (slot) . In contrast, the proposed prediction methods arrive at an accurate estimation using smaller time. We note that the time cost can be significantly reduced by a predictor with long step size. In particular, the 7-step 514 and 20-step 515 predictions obtain an accurate estimation just costing 20 iterations, saving around 43%probing time. These observations can be also verified by FIG. 5C that evaluate the prediction precision in terms of relative error, by comparing the corresponding curves (522-525) with the prior art (521) .

In some example embodiments, an apparatus capable of performing the method 300 (for example, implemented at the receiving device 120) may comprise means for performing the respective steps of the method 300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for receiving a probing signal with a transmission power from a second apparatus in an access process; means for determining, based on the received probing signal, a set of SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points; means for determining, based on the set of SIRs, a prediction of an achievable SINR for the communication link at a future time point later than the predetermined number of successive time points; and means for transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.

In some example embodiments, an apparatus capable of performing the method 400 (for example, implemented at the transmitting device 110) may comprise means for performing the respective steps of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for transmitting, to a first apparatus, a probing signal with a transmission power in an access process; means for receiving, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and means for determining the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.

FIG. 6 is a simplified block diagram of a device 600 that is suitable for implementing embodiments of the present disclosure. The device 600 may be provided to implement the communication device, for example the receiving device 120 and the transmitting device 110 as shown in FIG. 1. As shown, the device 600 includes one or more processors 610, one or more memories 640 coupled to the processor 610, and one or more transmitters and/or receivers (TX/RX) 640 coupled to the processor 610.

The TX/RX 640 is for bidirectional communications. The TX/RX 640 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 610 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 600 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 620 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 624, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 622 and other volatile memories that will not last in the power-down duration.

A computer program 630 includes computer executable instructions that are executed by the associated processor 610. The program 630 may be stored in the ROM 620. The processor 610 may perform any suitable actions and processing by loading the program 630 into the RAM 620.

The embodiments of the present disclosure may be implemented by means of the program 630 so that the device 600 may perform any process of the disclosure as discussed with reference to FIGs. 2 to 5. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 630 may be tangibly contained in a computer readable medium which may be included in the device 600 (such as in the memory 620) or other storage devices that are accessible by the device 600. The device 600 may load the program 630 from the computer readable medium to the RAM 622 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 7 shows an example of the computer readable medium 700 in form of CD or DVD. The computer readable medium has the program 630 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the

methods

300 and 400 as described above with reference to FIGs. 2-5. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first apparatus comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first apparatus at least to:

receive a probing signal with a transmission power from a second apparatus in an access process;

determine, based on the received probing signal, a set of Signal-to-Interference Ratios, SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points;

determine, based on the set of SIRs, a prediction of an achievable Signal-to-Interference-plus-Noise Ratio, SINR for the communication link at a future time point later than the predetermined number of successive time points; and

transmit, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.
The first apparatus of Claim 1, wherein the first apparatus is caused to determine the prediction of the achievable SINR by:

determining, based on the set of SIRs, an estimation of a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points;

selecting the future time point; and

determining the prediction of the achievable SINR at the future time point at least based on the set of SIRs, the estimation of spectrum radius and the future time point.
The first apparatus of Claim 2, wherein the estimation of spectrum radius is determined by:

wherein SIR _l (t) , SIR _l (t-1) and SIR _l (t-2) represents SIRs at time points t, t-1 and t-2 of the predetermined number of the successive time points t, t-1 and t-2, respectively, and ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of the successive time points.
The first apparatus of Claim 2, wherein the future time point t+1 is selected, and wherein the prediction of the achievable SINR is determined by:

wherein
represents the achievable SINR at the future time point t+1 next to the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and SIR _l (t) and SIR _l (t-1) represent the measured SIRs at time points t and t-1 of the predetermined number of successive time points, respectively.
The first apparatus of Claim 1, wherein the first apparatus is caused to determine the prediction of the achievable SINR by:

determining, based on the set of SIRs, an estimation of a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points;

determining the prediction of the achievable SINR at the future time point at least based on the set of SIRs and the estimation of spectrum radius;

select a further future time point later than the future time point; and

determine a prediction of an achievable SINR at the further future time point based on the set of SIRs, the prediction of the achievable SINR at the future time point, the estimation of spectrum radius and the further future time point.
The first apparatus of Claim 5, wherein the further future time point t+K is selected, and wherein the prediction of the achievable SINR at the further future time point is recursively determined by:

wherein
represents the achievable SIR at the further future time point t+K beyond the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and
represents the prediction of the achievable SINR at the future time point t+K-1 or the one of the set of SIRs at the time point t+K-1 of the predetermined number of successive time points, and
represents the prediction of the achievable SINR at the future time point t+K-2 or the one of the set of SIRs at the time point t+K-2 of the predetermined number of successive time points.
The first apparatus of Claim 1, wherein the first apparatus is further caused to:

determine the measured SINR at the last time point of the predetermined number of successive time points based on the probing signal; and

checking the condition associated with the accessibility based on the measured SINR, the prediction of the achievable SINR and a target SINR.
The first apparatus of Claim 7, wherein the condition is checked by:

wherein
represents a prediction of an achievable SINR at the future time point t+K, SINR _l (t) represents the measured SINR at time point t of the predetermined number of successive time points, Δ represents the raising margin, and γ _l represents the desried SINR target.
A second apparatus comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the second apparatus at least to:

transmit, to a first apparatus, a probing signal with a transmission power in an access process;

receive, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and

determine the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.
The second apparatus of Claim 9, wherein the second apparatus is caused to determine the accessibility by:

in response to the result indicating that the prediction of the achievable SINR exceeds the target SINR, determining that the communication link is accessible.
The second apparatus of Claim 10, wherein the second apparatus is further caused to:

decrease the transmission power based on the measured SINR, the target SINR and a raising margin.
The second apparatus of Claim 9, wherein the second apparatus is caused to determine the accessibility by:

in response to the result indicating that the prediction of the achievable SINR is lower than the target SINR, determining an expiry time for the access process based on the prediction of the achievable SINR and the target SINR;

comparing the expiry time with duration of the access process; and

in response to a determination that the duration of the access process is less than the expiry time, determining that the communication link is accessible.
The second apparatus of Claim 12, wherein the second apparatus is further caused to:

increase the transmission power based on a raising margin.
The second apparatus of Claim 12, wherein the second apparatus is further caused to:

in response to a determination that the duration of the access process exceeds the expiry time, determine that the communication link is inaccessible; and

suspend the access process.
A method comprising:

receiving a probing signal with a transmission power from a second apparatus in an access process;

determining, based on the received probing signal, a set of Signal-to-Interference Ratios, SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points;

determining, based on the set of SIRs, a prediction of an achievable Signal-to-Interference-plus-Noise Ratio, SINR for the communication link at a future time point later than the predetermined number of successive time points; and

transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.
The method of Claim 15, wherein determining the prediction of the achievable SINR comprises:

determining, based on the set of SIRs, an estimation of a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points;

selecting the future time point; and

determining the prediction of the achievable SINR at the future time point at least based on the set of SIRs, the estimation of spectrum radius and the future time point.
The method of Claim 16, wherein the estimation of spectrum radius is determined by:

wherein SIR _l (t) , SIR _l (t-1) and SIR _l (t-2) represents SIRs at time points t, t-1 and t-2 of the predetermined number of the successive time points t, t-1 and t-2, respectively, and ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of the successive time points.
The method of Claim 16, wherein the future time point t+1 is selected, wherein the prediction of the achievable SINR is determined by

wherein
represents the achievable SINR at the future time point t+1 next to the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and SIR _l (t) and SIR _l (t-1) represent the measured SIRs at time points t and t-1 of the predetermined number of successive time points, respectively.
The method of Claim 15, wherein determining the prediction of the achievable SINR comprises:

determining, based on the set of SIRs, an estimation of a spectrum radius for charactering interfering channels associated with at least one further communication link at the last time point of the predetermined number of successive time points;

determining the prediction of the achievable SINR at the future time point at least based on the set of SIRs and the estimation of spectrum radius;

select a further future time point later than the future time point; and

determine a prediction of an achievable SINR at the further future time point based on the set of SIRs, the prediction of the achievable SINR at the future time point, the estimation of spectrum radius and the further future time point.
The method of Claim 19, wherein the further future time point t+K is selected, and wherein the prediction of the achievable SINR at the further future time point is recursively determined by:

wherein
represents the achievable SIR at the further future time point t+K beyond the predetermined number of the successive time points, ρ _l (t) represents the estimation of spectrum radius at time point t of the predetermined number of successive time points, and
represents the prediction of the achievable SINR at the future time point t+K-1 or the one of the set of SIRs at the time point t+K-1 of the predetermined number of successive time points, and
represents the prediction of the achievable SINR at the future time point t+K-2 or the one of the set of SIRs at the time point t+K-2 of the predetermined number of successive time points.
The method of Claim 15, further comprising:

determining the measured SINR at the last time point of the predetermined number of successive time points based on the probing signal; and

checking the condition associated with the accessibility based on the measured SINR, the prediction of the achievable SINR and a target SINR.
The method of Claim 21, wherein the condition is checked by:

wherein
represents a prediction of an achievable SINR at the future time point t+K, SINR _l (t) represents the measured SINR at time point t of the predetermined number of successive time points, Δ represents the raising margin, and γ _l represents the desried SINR target.
A method comprising:

transmitting, to a first apparatus, a probing signal with a transmission power in an access process;

receiving, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and

determining the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.
The method of Claim 23, wherein determining the accessibility comprises:

in response to the result indicating that the prediction of the achievable SINR exceeds the target SINR, determining that the communication link is accessible.
The method of Claim 24, further comprising:

decreasing the transmission power based on the measured SINR, the target SINR and a raising margin.
The method of Claim 23, wherein determining the accessibility comprises:

in response to the result indicating that prediction of the achievable SINR is lower than the target SINR, determining an expiry time for the access process based on the achievable SINR and the target SINR;

comparing the expiry time with duration of the access process; and

in response to a determination that the duration of the access process is less than the expiry time, determining that the communication link is accessible.
The method of Claim 26, further comprising:

increasing the transmission power based on a raising margin.
The method of Claim 26, further comprising:

in response to a determination that the duration of the access process exceeds the expiry time, determining that the communication link is inaccessible; and

suspending the access process.
An apparatus comprising:

means for receiving a probing signal with a transmission power from a second apparatus in an access process;

means for determining, based on the received probing signal, a set of Signal-to-Interference Ratios, SIRs, for a communication link between the first apparatus and the second apparatus at a predetermined number of successive time points;

means for determining, based on the set of SIRs, a prediction of an achievable Signal-to-Interference-plus-Noise Ratio, SINR for the communication link at a future time point later than the predetermined number of successive time points; and

means for transmitting, to the second apparatus, at least one of a checking result for a condition associated with an accessibility of the communication link, a measured SINR at last time point of the predetermined number and the prediction of an achievable SINR.
An apparatus comprising:

means for transmitting, to a first apparatus, a probing signal with a transmission power in an access process;

means for receiving, from the first apparatus, at least one of a checking result for a condition associated with an accessibility of a communication link between the first apparatus and the second apparatus, a measured SINR at last time point of a predetermined number of successive time points and a prediction of an achievable SINR at a future time point later than the predetermined number of the successive time points; and

means for determining the accessibility of the communication link based on at least one of the checking result, the measured SINR and the prediction of the achievable SINR and a target SINR.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 15-22.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 23-28.