Patent Application
20240314851
The present invention is related to a 5G/B5G transmission mechanism system and a method thereof, and more particularly to a 5G/B5G transmission adaptive extended keeping reservation threshold probability function with resource watching window and dynamic back-off for contention-based 5G/B5G sidelink system and a method thereof.
The sensing-based semi-persistent scheduling in 5G/B5G sidelink semi-persistent scheduling of the random contention mechanism of 5G/B5G sidelink does not specify different collision areas for different types of flow, so the contention collision probability caused by various types of flows (such as the same type of flows or different types of flows) is significantly increased and the access delay may be degraded. The non-real time (NRT) type of flow has a longer resource reservation interval to effectively differentiate the collision area, and this is because the longer interval range has more time slots, the contention collision probability can be reduced. On the contrary, the real time (RT) type of flow has a shorter resource reservation interval and easily causes contention collision. When contention collision has already occurred, the 5G/B5G sidelink sensing-based semi-persistent scheduling may neglect the back-off mechanism to avoid further contention collision.
According to above-mentioned contents, what is needed is to develop an improved solution to solve the problem that there is no effective mechanism for Vehicle-to-Everything communication of unicasting or groupcasting (V2X) in 5G/B5G sidelink semi-persistent scheduling in Internet of Vehicles (IoV) to avoid contention collision.
An objective of the present invention is to disclose an adaptive extended keeping reservation threshold probability function with resource watching window and dynamic back-off for contention-based 5G/B5G sidelink system and a method thereof, to solve the problem that there is no effective mechanism for Vehicle-to-Everything communication of unicasting or groupcasting (V2X) in 5G/B5G sidelink semi-persistent scheduling in IoV to avoid contention collision.
In order to achieve the objective, the present invention provides an adaptive extended keeping reservation threshold probability function with resource watching window and dynamic back-off for contention-based 5G/B5G sidelink system, the adaptive extended mechanism system is adapted to a user equipment communicating via 5G/B5G and includes a flow differentiating module, a flow guarantee module, a resource estimation module and a collision differentiating module.
The flow differentiating module is configured to differentiate different types of flows in collision domains based on key parameters of collision probability. The flow guarantee module is configured to provide and guarantee access probability for a high type of flow and a flow with low contention collision probability, to formulate an adaptive extended Sigmoid. A 5G/B5G sidelink semi-persistent scheduling of the user equipment determines a range of a sensing window, which is configured to sense and monitor, for a sender, and the resource estimation module estimates an available random contention resource within the sensing window, to prevent the contention collision probability from being high to reduce a resource reservation efficiency. The collision differentiating module is configured to apply a truncated binary exponential (TBE) back-off algorithm to differentiate the collision domains based on an amount of collisions, to reduce an amount of contention collisions and improve a usage rate of a semi-persistent scheduling resource.
In order to achieve the objective, the present invention provides an adaptive extended keeping reservation threshold probability function with resource watching window and dynamic back-off for contention-based 5G/B5G sidelink method, the adaptive extended mechanism method is adapted to a user equipment communicating via 5G/B5G and includes steps of: differentiating different types of flow in collision domains based on key parameters of collision probability, by the user equipment; providing and guaranteeing access probability for a high type of flow and a flow with a low contention collision probability to formulate an adaptive extended Sigmoid, by the user equipment; determining a range of a sensing window, which is configured to sense and monitor, for a sender, by a 5G/B5G sidelink semi-persistent scheduling of the user equipment, and estimating an available random contention resource within the sensing window to prevent the contention collision probability from being high to reduce a resource reservation efficiency; applying the dynamic truncated binary exponential (TBE) back-off algorithm to differentiate the collision domains based on an amount of collisions, to reduce number of contention collision and improve usage rate of the semi-persistent scheduling resource, by the user equipment.
According to the above-mentioned system and method of the present invention, the difference between the present invention and the conventional technology is that the adaptive extended Sigmoid mechanism of the present invention can be applied to reduce the contention collision probability for the different types of flows contending a usage resource; the watching window can be applied to guarantee certain probability and reserve resource for the high priority (that is, more urgent) flow; applying dynamic truncated binary exponential (TBE) back-off mechanism can stagger the flows occurring resource collision to avoid the same consecutive collision, so as to effectively reduce contention collision probability, and improve resource usage rate and the probability of successful flow transmission.
Therefore, the above-mentioned solution of the present invention is able to achieve the effect of minimizing collision probability and access delay and maximizing successful probability and throughput.
The structure, operating principle and effects of the present invention will be described in detail by way of various embodiments which are illustrated in the accompanying drawings.
The following embodiments of the present invention are herein described in detail with reference to the accompanying drawings. These drawings show specific examples of the embodiments of the present invention. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is to be acknowledged that these embodiments are exemplary implementations and are not to be construed as limiting the scope of the present invention in any way. Further modifications to the disclosed embodiments, as well as other embodiments, are also included within the scope of the appended claims.
These embodiments are provided so that this disclosure is thorough and complete, and fully conveys the inventive concept to those skilled in the art. Regarding the drawings, the relative proportions and ratios of elements in the drawings may be exaggerated or diminished in size for the sake of clarity and convenience. Such arbitrary proportions are only illustrative and not limiting in any way. The same reference numbers are used in the drawings and description to refer to the same or like parts. 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. As used herein, the term “or” includes any and all combinations of one or more of the associated listed items.
It will be acknowledged that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present.
In addition, unless explicitly described to the contrary, the words “comprise” and “include”, and variations such as “comprises”, “comprising”, “includes”, or “including”, will be acknowledged to imply the inclusion of stated elements but not the exclusion of any other elements.
The adaptive extended keeping reservation threshold probability function with resource watching window and dynamic back-off for contention-based 5G/B5G sidelink system of the present invention will be illustrated in the following paragraphs. Please refer to
As shown in
The flow differentiating module 11 is configured to differentiate different types of flows in collision domains based on key parameters of collision probability. The flow guarantee module 12 is configured to provide and guarantee access probability for a high type of flow and a flow with low contention collision probability, to formulate an adaptive extended Sigmoid. A 5G/B5G sidelink semi-persistent scheduling of the user equipment determines a range of a sensing window, which is configured to sense and monitor, for a sender, and the resource estimation module 13 estimates an available random contention resource within the sensing window, to prevent the contention collision probability from being high to reduce a resource reservation efficiency. The collision differentiating module 14 is configured to apply a truncated binary exponential (TBE) back-off algorithm to differentiate the collision domains based on an amount of collisions, to reduce an amount of contention collisions and improve a usage rate of a semi-persistent scheduling resource.
In order to realize the Internet of Vehicles (IoV) in 5G/B5G mobile communication, the direct communication between vehicles via the enhanced-Vehicle-to-Everything (eV2X) has become a key technology. The 5G/B5G new radio (NR) frequency band 1 (FR1) in the PC5 interface is operated in the 5.9 GHz licensed spectrum (2570 to 2620 MHz and 5855 to 5925 MHz). Therefore, 5G/B5G standard specifies sidelink (SL) eV2X mode 4 mechanism to enable V2V communicating directly without a generation node B (gNB) controlling and operating not in the gNB service range, even though 5G/B5G SL needs the radio frequency spectrum for realizing different functional radio channels in physical, transport and logical layers, e.g., physical SL shared channel (PSSCH) with RBs and physical SL control channel (PSCCH) with 2 RBs.
In 5G/B5G SL eV2X, in a condition that type k flow data packets arrive at a transmitter Vi of vehicle i (or user equipment UE), and requests the resource pool state Vi of receiver vehicle. Then, vehicle i (or denoted by Vi) randomly reserves for transport block (TB) via physical SL shared channel(PSSCH) by sending the SL Control Information (SCI) to the receiver vehicle j (or Vj) through 5G/B5G physical SL control channel (PSCCH) in prior, and reserves SCI in the transmission block (TB). It should be noted that the SL eV2X defines two multiplexing types of physical channels including an adjacent type and a non-adjacent type. The resource pool is split into several sub-channels, in which the first 2 sub-channel RBs are allocated for PSCCH and more than 1 sub-channel RB are allocated for PSSCH. For efficiently utilizing RBs and avoiding using non-adjacent type data in resource pool, PSSCH for data can overlap PSCCH. In PSCCH, the 32-bit SCI format includes priority value, resource reservation value, resource indication value, time gap, modulation and coding scheme (MCS), retransmission index and reserved information. In PSSCH, a TB of RBs with different MCSs are allowed to be allocated for flow data transmissions.
Diverse applications with different QoS/KPI services in delay, reliability, loss, data rate, etc. contend the limited capacity of the receiver's resource pool before flow data transmissions. Based on the 5G/B5G SL eV2X specifying the sensing-based semi-persistent scheduling (SPS) in the contention-based random access, after the sender obtains the receiver's resource pool state, the sender randomly determines two random parameters including a resource reservation interval (RRI) and a resource reservation counter (RRC). The sender randomly contends TB by sending the sidelink control information (SCI) to the receiver in prior, and the randomly selecting RRI in 4-bit set in SCI's resource reservation field to receiver's resource pool; at the same time, the sender additionally randomly generates RRC for the sender itself to check whether to randomly keep the reserved TB. Furthermore, for supporting different QoS for different types of flows, 5G/B5G SPS specifies various RRC ranges for different RRIs; particularly, for RT with short delay such as 20 (ms), the RRI range is [25, 75]; for NRT with long delay such as 100 (ms), the RRI range is set as [5, 15]; however, these examples are merely for exemplary illustration, and the scope of the present invention is not limited thereto. When the resource reservation field of SCI randomly determined by the sender is ‘1011’, it means that “RRI=20 (nm)” is set to the corresponding SCI in the receiver's resource Pool. When there are more than two senders (or vehicles) set individual RRI value to the same SCI, it may cause contention collision because the receiver cannot obviously identify the SCI content; otherwise, the sender wins the contention, and then the receiver replies the sender with the allocated TB. Next, the sender sends flow data packets to the allocated TB every RRI (ms) and decreases RRC by one (that is, RRC←RRC−1). When RRC=0, 5G/B5G SL SPS mechanism allows the sender to initialize the randomly conditional piggyback-based resource reservation. Specifically, when the randomly-determined probability P is less than the keeping-reservation-threshold probability Prk (that is, P≤Prk), the sender successfully keeps the right to transmit data in the same TB(s); otherwise, the sender releases the reserved TB(s) and randomly reselects (or reserves) for new TB(s).
These vehicles broadcast and exchange the basic safe message (BSM), and the sender determines the communication in type of either unicasting or groupcasting. Due to the distributed (not a centralized) mechanism, the sender first senses resource usage state within the sensing window of [tn−1000sf,tnsf], for example, the sensing window can be the immediate past 1000 sub-frame time (sft) before selecting the resource. The sender randomly determines RRI that is for booking in the receiver's resource pool, and RRC that will be kept in the sender. The sender sends the SCI with RRI to the receiver to reserve TB(s) within the selection window of RRI length. Furthermore, after a successful transmission, the value of RRC is decreased by one and the sender checks whether the value of RRC becomes zero. When RRC is not zero, the sender is allowed to send flow data to the receiver with the interval of RRI (in time); otherwise, when the RRC is zero, the randomly conditional piggyback-based resource reservation is performed. In other words, the sender randomly generates the reservation probability P, and then checks whether the generated reservation probability P is larger than the keeping reservation threshold probability Prk. When P≤Prk, the sender keeps the original reserved TB(s) for further flow data transmission; otherwise, when P>Prk, the sender re-selects new resource of TB(s).
In a condition that two or more numbers of sender vehicles reserve the same TB resource, the receiver detects whether contention collision occurs in 4 (ms). When no contention collision occurs, the receiver sends a HARQ_ACK message to notify the senders; otherwise, the receiver sends HARQ_NAK message to the senders for further resource contention again.
In order to solve above mentioned conventional problem of IoV Vehicle-to-Everything (V2X) communication of unicasting or groupcasting in 5G/B5G SL SPS, the present invention discloses an adaptive extended Sigmoid-based resource reservation (eSRR) mechanism for 5G/B5G SL accesses, so as to minimize access delay, delay jitter and contention collision probability as well as to maximize transmission reliability and stability.
In the randomly distributed contention mechanism of 5G/B5G SL SPS, for increasing goodput, 5G/B5G SPS adopts the static keeping reservation threshold probability, i.e. Prk=0.8, for all senders to keep the original reserved TBs for further ADAS message transmissions. Such static threshold probability Prk suffers from dynamic contentions of different priorities of flows. That is, these senders randomly reserve the same TB, and it results in contention collision because the receiver cannot certainly identify the collided SCI information. As a result, the 5G/B5G SL SPS easily causes high contention collision and long access delay.
The adaptive extended Sigmoid-based resource reservation mechanism differentiates the collision domains of different types of flows (such as uRLLC-dangerous, or uRLLC-safe) based on the key parameter of collision probability. When RRC becomes zero, the sender initializes the randomly conditional piggyback-based resource reservation. for guaranteeing the access probability for the higher type flow and the flow with lower contention collision probability, and the keeping reservation threshold probability Prk of them should be a larger value. The keeping reservation threshold probability of type k flow with collision probability pck is formulated as an extended Sigmoid function, as shown below:
pc denotes the total contention collision probability; δk denotes the fine tune-up factor based on the collision probability pck of type k flow.
The network utilization is denoted as U(t), 0<U(t)≤1, and δk is formulated as shown below:
In a range of 0.01<δk<10, when δk=1, the above-mentioned extended Sigmoid function
becomes a general Sigmoid function.
For dynamically determining Prk in different collision probabilities, the adaptive keeping reservation threshold probability function Prkk(⋅) is formulated as an extended Sigmoid function 21. Please refer to
Please refer to
For differentiating the collision domains (the collision domain 22 and the collision domain 23) of different types of flows, the fine tune-up factor, the collision probability of type flow, and network utilization are applied. For a higher type of flow, δk is increased clearly and then results in a large for keeping the resource reservation. Conversely, for a lower type of flow, δk is decreased, and then leads to a low δk for keeping the resource reservation.
In addition, to justify the efficient and correct performance of the dynamic fine tune-up factor for different types of flows, the high type (priority) of flow for Real-Time uRLLC-dangerous ADAS slicing are adopted and set as RRI=20 ms and RRCE[25, 75], under the evaluation parameters based on the specified parameters in 5G SL SPS. The shortest RRI set as 20 (ms) contributes to the least transmission delay, and a large RRC range contributes to continuous large transmissions of uRLLC-dangerous and uRLLC-warning ADAS slicing. Conversely, for the low type (priority) of flow for non-real-time uRLLC-safe ADAS or mMTC slicing are adopted and set as RRI=100 (ms) and RRC∈[5, 15]. The higher type of flow always yields a higher δk and a significant lower contention collision probability, such as the collision probability 24 shown in
The 5G/B5G SL SPS specifies the sensing window of [tn−1000sf, tnsf] for the sender to sense and to monitor, and then estimates available resource in the selection window of [tn−1000sf, tnsf] for randomly contending resource. In a condition that the sender with RRC=0 will execute either the keeping resource reservation (in case of p≤Prk) or re-selecting new resource (in case of p>Prk). The sensed resource state WSensing in sensing window easily leads to the inconsistent resource state in selection window WSelection. The randomly contending of resource in 5G/B5G SL SPS suffers from the inconsistent states for contention, and thus easily yields high contention collision probability and leads to inefficient resource reservation. The present invention proposes the resource watching window WWatching, for the sender to request a receiver's resource pool state within the period of tnsf, tn+
In the randomly contention-based SL SPS, 5G/B5G specification neglects the processing after contention collision. For example, when the contention is successful, the sender vehicle receives a HARQ_ACK message as a positive notification for flow data packets transmission; otherwise, when receiving a HARQ NACK message, the sender definitely realizes that the contention is collided and then executes resource contention again. As a result, for instance, these collided senders may contend TB immediately or at another time, and it leads to collision again. The next contention time is determined based on three factors: 1) the number of consecutive contention collisions of type k sender vehicle Vi, denoted by nik, 2) the virtual slot time, denoted by ts, and 3) a random contention window range ri←rand( ) of [CWi,mink, CWi,maxk]. The dynamic truncated binary exponential back-off algorithm is shown as below:
The back-off waiting delay tiBackoff of type k sender vehicle, is determined, as follows:
The virtual slot time is set to 8 (ms) because of the round trip delay between two UEs requiring the collision detection time of 4 (ms). In order to avoid the sender vehicle with a large number of consecutive collisions yielding an extremely long contention delay, the maximum contention window CWi,maxk is limited by 23+5 when 5<nik≤10, particularly, for example, a collided sender with nik=3, the waiting back-off time becomes:
As a result, the possible range of the waiting back-off time of this sender is 0, 8, 16, 24, . . . , or 248 (ms). Thus, after waiting for the back-off time, the sender is allowed to contend the resource TB within the resource selection time Wselection of RRI again, so that contention collisions are decreased to improve usage rate of the semi-persistent scheduling resource. It should be noted that in the worst case of the dynamic TBE algorithm (e.g. nik=6), the back-off waiting delay is increased to (23+5−1)*8 or 2040 (ms).
The collided senders may contend TB immediately or use the TB resource at a distributed time, but the collision easily occurs because the senders are in the same collision domain. In the other hand, with the TBE back-off mechanism, the collision domains are differentiated differentially according to the number of consecutive collisions nik, flow type, and the randomly exponential function rand(•), so contention collision probability is certainly decreased obviously.
In summary, applying the extended Sigmoid-based adaptive keeping reservation threshold probability function Prkk(•), the watching window WWatching, and the dynamic TBE back-off algorithm is able to efficiently achieve several objectives for improving the randomly contention-based 5G/B5G SL SPS specification. Differentiating collision domains for different types of flows by using the extended Sigmoid-based adaptive function is able to decrease the contention collision probability efficiently. Based on the dynamic collision probability, the proposed adaptive keeping reservation threshold probability function Prkk(•) is determined adaptively for individual vehicle, while the individual vehicle enters in the randomly conditional piggyback-based resource reservation when RRC=0. By using the sensing window with watching window, the sender vehicle clearly knows the allocated usage resource from the sensing window period as well as accurately knows the resource pool state in the watching window period. As a result, the above-mentioned solution can effectively reduce the contention collision due to blindly random resource reservation. Moreover, differentiating collision domains for vehicles with different number of collisions by using the TBE back-off is able to reduce the contention collision probability efficiently.
The operation of the method of the present invention will be illustrated in detailed in the following paragraphs. Please refer to
As shown in
In a step 101, the user equipment differentiates different types of flow in collision domains based on key parameters of collision probability. In a step 102, the user equipment provides and guarantees access probability for a high type of flow and a flow with a low contention collision probability to formulate an adaptive extended Sigmoid. In a step 103, a 5G sidelink semi-persistent scheduling of the user equipment determines a range of a sensing window, which is configured to sense and monitor, for a sender, and estimates an available random contention resource within the sensing window to prevent the contention collision probability from being high to reduce a resource reservation efficiency. In a step 104, the user equipment applies the dynamic truncated binary exponential (TBE) back-off algorithm to differentiate the collision domains based on an amount of collisions, to reduce number of contention collision and improve usage rate of the semi-persistent scheduling resource.
According to above-mentioned contents, the difference between the present invention and the conventional technology is that the adaptive extended Sigmoid mechanism of the present invention can be applied to reduce the contention collision probability for the different types of flows contending a usage resource; the watching window can be applied to guarantee certain probability and reserve resource for the high priority flow; applying dynamic truncated binary exponential (TBE) back-off mechanism can stagger the flows occurring resource collision to avoid the same consecutive collision, so as to effectively reduce contention collision probability, and improve resource usage rate and the probability of successful flow transmission.
Therefore, the above-mentioned solution of the present invention is able to solve the problem that there is no effective mechanism for IoV Vehicle-to-Everything (V2X) communication of unicasting or groupcasting in 5G/B5G sidelink semi-persistent scheduling to avoid contention collision, so as to achieve the effect of minimizing collision probability and access delay and maximizing successful probability and throughput.
The present invention disclosed herein has been described by means of specific embodiments. However, numerous modifications, variations and enhancements can be made thereto by those skilled in the art without departing from the spirit and scope of the disclosure set forth in the claims.
